Over the last years, fiber optic sensors have been increasingly applied for applications in environments with a high level of radiation as an alternative to electrical sensors, due to their: high immunity, high multiplexing and long-distance monitoring capability. In order to assess the feasibility of their use, investigations on optical materials and fiber optic sensors have been focusing on their response depending on radiation type, absorbed dose, dose rate, temperature and so on. In this context, this paper presents a comprehensive review of the results achieved over the last twenty years concerning the irradiation of in-fiber Long Period Gratings (LPGs). The topic is approached from the point of view of the optical engineers engaged in the design, development and testing of these devices, by focusing the attention on the fiber type, grating fabrication technique and properties, irradiation parameters and performed analysis. The aim is to provide a detailed review concerning the state of the art and to outline the future research trends. Beyond their typical applications for communications and sensing, optical fibers and fiber sensors have found wide interest in radiation related scenarios, due to their several advantages such as: high sensitivity and resolution measurements, low cost implementation, immunity to electromagnetic interferences, chemical inertness, long distance monitoring and high multiplexing capability ,2,3. Hen15 cm−2 [18 cm−2 whereas the gamma dose can accumulate up to 10 MGy [20 cm−2). Moreover, fiber components are also important in space applications where the main sources of energetic particles are protons and electrons in the Van Allen belts, heavy ions in the magnetosphere, cosmic ray protons and heavy ions, and protons and heavy ions from solar flares. Here, the doses are usually lower than 10 kGy [Radiation can interact with materials in different forms, for example it can be distinguished between purely ionizing radiations such as gamma- and X-rays and particle radiations such as protons, neutrons, and heavy ions. The first kind delivers energy mainly through the creation of secondary electrons (and positrons), whereas the second one interacts with materials both through ionization and non-ionizing energy loss, the latter being associated for example to the displacement or the vibration of an atom . Optical15 cm−2 ,11. Conco 10 MGy ,13, whern 10 kGy ,15. Finan 10 kGy .Three main physical effects can influence the working conditions of fiber-based devices when subjected to irradiation ,16: the Until now, the most part of the studies targeted optical fibers, by mainly focusing on their radiation induced attenuation. Different fiber compositions  were considered in order to assess the dependence of the response upon the dopant ions, and tested under different radiation conditions  and types  ,23,24,25Finally, despite the great interest evinced from the scientific community on the Long Period Grating (LPG) as the sensing platform ,50,51,52L is the grating length. The properties of the LPG rejection bands are dependent on fiber parameters, grating properties, as well es external conditions of temperature, strain, bending and surrounding refractive index [LPG sensors are fabricated by inducing a periodic perturbation in the refractive index and/or geometry of an optical fiber. The period of the perturbation Λ typically ranges from 100–1000 µm and promotes the power coupling between the core mode and several co-propagating cladding modes . As a reve index . Hence, ve index ,50,51,522 lasers [Different techniques are available for their fabrication, the most important being: UV-radiation , CO2 las2 lasers , IR femt2 lasers , mechani2 lasers  and elec2 lasers ,62. MoreIn this section, the analysis concerning the state of the art about radiation effects on LPGs is reported taking into consideration gratings fabricated in different fibers and with different techniques. The results are primarily presented by following a chronological order and they are grouped based on the outcomes of the main research groups working in this field.19 mode) and a thermo-induced LPG in an N-doped fiber by CO-laser . The gratings were exposed to a 60Co gamma source at a dose rate ranging from 5.4–6.6 Gy/s up to a total dose of 1.47 MGy, at 40 °C temperature. Mach–Zehnder interferometers (MZI) [The first report about Long Period Gratings under gamma radiation was provided by Vasiliev et al.  in 1998.rs (MZI)  and FBGs−5 after a 100 kGy dose were also reported, probably due to radiation induced absorption bands of atoms in the UV region affecting the RI via the Kramers–Krönig formula. Finally, the authors stated they found some inconsistencies in their results probably due to some experimental errors.The authors stated that the LPG in the N-doped fiber did not show any change in the resonance wavelength after the irradiation to within an experimental error of ±0.3 nm, the MZI response was also negligible. The same happened for the LPG in the Ge-doped fiber, differently significant phase shifts were observed in the MZI in this case. The authors justified the apparent stability of LPG response with the elimination of the precursors of gamma radiation induced color centers  in the process of grating writing through the UV laser. Induced refractive index changes in the core region up to 2.8∙10We would like to add that the response of LPGs in the Ge-doped fiber found in  was unex60Co gamma source and two dose rates were considered for comparison: 0.87 Gy/s up to a total dose of 100 kGy and 0.1 Gy/s up to 20 kGy dose. Each grating was inserted into a thin quartz capillary, without fixing the fiber to have a strain-free state and mounted onto an aluminum plate.In , HenscheThe attention was mainly focused on the fiber RIA and grating wavelength shift as a consequence of irradiation. Moreover, Another aspect was related to the trends of wavelength shift and RIA as a function of radiation dose. In particular, for low RIA fibers the wavelength shift saturated as the dose approached 10 kGy while the RIA still continued to increase up to 100 kGy. Differently, for high RIA fibers the behavior was the opposite: RIA saturated after 20 kGy and wavelength shift increased up to 100 kGy. Finally, for Nufern 1 (fiber 6) both RIA and wavelength shift showed a steady increase up to 100 kGy, while for Alcatel (fiber 1) they both saturated at 20 kGy. Concerning the comparison between the time dynamics of RIA and wavelength shift recovery, reported in Based on these results, the authors concluded that RIA and wavelength shift shows similarities but also differences; anyway it is not surprising since the RIA of most single mode fibers is primarily due to an attenuation increase of the core material, whereas the wavelength shift is dependent on radiation induced changes of both core and cladding materials (changing core and cladding effective refractive indices) through the phase-matching condition of Equation (1) and maybe also compaction (affecting grating period) has an influence.Another interesting outcome of this research is related to the dependence of wavelength shift upon the dose rate: it was found that for a dose rate of 0.87 Gy/s it was around 1.1 to 1.2 times higher than at 0.1 Gy/s. Finally, concerning the temperature sensitivity of the CPLPGs, the authors stated that it did not change after the irradiation up to 100 kGy.2 laser in a commercial photosensitive B/Ge codoped PS980 fiber by Fibercore UK. The period of the gratings were selected in the range 206–208 µm to achieve the coupling with 11th order cladding mode and different working points in the TAP region. The LPGs were irradiated by a 60Co gamma source  at 1.3 kGy/h dose rate and up to a total dose of 65 kGy and measured off-line. The grating was fixed on a metal plate during irradiation.In ,67 Kher −5.The wavelength shifts observed in this case were the highest reported so far due to the TAP operation: each peak of the double resonance 11th mode experienced a shift (that is positive for left peak and negative for right peak) of about 35 nm after a 6 kGy dose that increased up to 80 nm when the dose reached 65 kGy. The authors attributed the wavelength shift to an increase of the core refractive index in the B/Ge codoped fiber by about 10−4 after a 1.54 MGy dose. This RI change recovered by less than 10−5 after 67 h of room temperature annealing. Finally, the authors predicted a saturation of the RI change at 8.2·10−4 after a 15 MGy dose.The same group deepen their study in  by corre2 laser based setup, with a period of 450 µm and presented high strain sensitivity and negligible temperature response in comparison to LPGs in the standard fiber [Kher et al. ,70 also rd fiber .The device was tested under gamma irradiation up to 75 kGy and no significant changes were observed in spectral properties and sensing characteristics. Such fibers, along with air guiding PCFs (or photonic bandgap fibers-PBGs) have recently attracted interest in this field, as the all silica structure can lead to an improved radiation hardened response ,28,29.2 laser assisted by a micro flame.In ,73,74 Sp02) [60Co industrial gamma source at “Horia Hulubei” institute , resulting in a dose rate of 0.2 kGy/h and up to a total dose of 45 kGy.The F-doped model was a single mode optical fiber with 8.5 µm core diameter and fluorine concentration of 0.2 wt.% in the core and 1.8 wt.% in the cladding; the grating was fabricated by iXblue, France using a 740 µm period which resulted in the coupling with 1st order cladding mode (LP02) . The graA blue shift of 0.7 nm was measured in the resonance wavelength after the irradiation, whereas the recovery was about 0.6 nm after 120 h at room temperature (6.7 pm/h rate). The temperature sensitivity of the grating before and after irradiation was also evaluated: it raised from 27.7 pm/°C to 29.3 pm/°C suggesting some radiation dependence of the response at high total doses.A similar procedure was adopted in ,74 for tIn the first case, the final wavelength shift reached 3.3 nm after 34 kGy, however, the response saturated after the 10 kGy dose as shown in 60Co gamma source at the Radio Isotope Test Arrangement (RITA) irradiation facility  at 37.4 °C temperature, using a rate of 1 kGy/h and up to a total dose of 560 kGy. The gratings were placed into stainless-steel capillary tubes with the fiber fixed at both ends with wax. The authors did not report about wavelength shift explicitly, but they considered changes in amplitude. The experiment showed that the transmission spectra of the gratings written in both fibers remained almost unchanged. Moreover, the temperature and strain sensitivities of LPGs written in the Oxford fiber were also not affected by radiation.One of the first reports about arc-induced LPGs under gamma irradiation was provided by Rego et al.  in 2005.03 or LP04 at 1560 nm. The irradiations were performed at room temperature at the “Horia Hulubei” institute  at 0.2 kGy/h dose rate, whereas the final doses ranged from 26.6–35 kGy. The gratings were kept in plastic frames to fix their strain state during irradiation and put in a thermally insulated box.Over the last years, the authors of this review have performed a systematic investigation about the effects of gamma radiation on arc-induced LPG in standard and different radiation hardened optical fibers ,77,78,79The attention was focused on the real-time resonance wavelength shift and optical transmission of the fiber, as reported in −5 for SMF28, 2.3∙10−5 for Fiber-A and Nufern in the fiber core at the end of the irradiation, whereas for Fiber-B the changes were one order of magnitude lower.By combining the experimental results with full spectrum numerical simulations ,83, the −8 °C−1, whereas for the other fibers it was lower than 10−8 °C−1.Finally, the temperature sensitivity of the gratings was also compared before and after the irradiation. For SMF28 LPG it increased from 50.5 to 53.8 pm/°C (around 6.5% change), whereas smaller variations were observed for Nufern and Fiber-A gratings, where it changed from 49.3 to 49.6 pm/°C and from 48.9 to 49.3 pm/°C, respectively. For Fiber-B LPG, the value of 22.8 pm/°C was not modified. The numerical model was also applied to estimate a change in the core thermo-optic coefficient of the SMF28 fiber of 1.5∙1012 n/(cm2∙s) resulting in a neutron fluence of 9.18∙1015 n/cm2. The gratings were kept in plastic frames to fix their strain state during irradiation and placed on an aluminum alloy plate.The same authors also irradiated a similar set of gratings under a mixed neutron-gamma field by using a TRIGA research nuclear reactor at the Nuclear Research Institute ICN  ,85. The 15 n/cm2 neutron fluence. The wavelength shifts recorded at the end of the irradiation were the following: 6.4 nm for LPG in SMF28, 9.0 nm for Fiber-A, 11.8 nm for Nufern and −0.4 nm for Draka. These trends were in agreement with those observed during gamma irradiation of similar samples reported in [The real-time wavelength shift of the gratings during the irradiation is reported in orted in .−5 for SMF28, 3.5∙10−5 for Fiber-A, 4.1∙10−5 for Nufern in the core of these fibers, whereas in the cladding of Draka the change was equal to 0.2∙10−5.By combining the experimental results with numerical modeling, the following RI changes were estimated by the end of irradiation: 2.6∙10−8 °C−1, for the Nufern fiber it was around 3∙10−8 °C−1, finally it was 6∙10−8 °C−1 in the cladding region of Draka.Finally, the temperature sensitivity of the gratings was also compared before and after the irradiation. For SMF28 and Fiber-A it increased 2% maximum, passing from the value of 50.0 and 50.8 pm/°C before the irradiation to 51.2 and 51.6 pm/°C, respectively, after the irradiation. Concerning the Nufern fiber, a greater increase in the thermal sensitivity was recorded, changing from 49.5 to 57.7 pm/°C (17% increase), whereas for Draka fiber a 10% decrease was found from 29.6 to 26.5 pm/°C. The changes in thermo-optic coefficients were also estimated by numerical analysis: in the core of SMF28 and Fiber-A they were lower than 1008) at 1540 nm. The irradiation was performed at the CERN proton facility named IRRAD, where the grating was exposed to a proton fluence of 4.4∙1015 p/cm2 for about 6 days up to a total high dose of 1.16 MGy (dose rate of 2.36 Gy/s). The grating was mounted on a support to fix the strain conditions during the experiment.Recently, in ,87 the gAs reported in −4 in the core effective refractive index was found at the end of irradiation , while a decrease of 0.93∙10−4 in the grating RI modulation was estimated as well. Finally, no significant change in the temperature sensitivity of the grating was found after the irradiation.Subsequently, the authors combined the experimental results with numerical modeling in order to estimate the changes of the main parameters affecting the grating response during the irradiation. In particular, a variation of about 1.61∙102) layer of about 100 nm. Such a material was selected due to its hygroscopic properties, moreover having a refractive index (n = 1.96) higher than cladding it was used to induce the mode transition phenomenon and enhance the LPG sensitivity [In ,89, the sitivity ,91,92.60Co source up to a dose of 10 kGy. The preliminary results reported a wavelength shift of about 4.4 nm (at 30% RH), whereas the sensor response towards humidity exhibited the same shape (except for some variations around 16%) as a consequence of irradiation.The performance of the sensor was measured in the range 0–75% RH and at −10, 0, 10, 25 °C, to replicate the working conditions required for CERN experiments. The sensor exhibited an exponential-like response with sensitivity changing from 1.4 to 0.11 nm/%RH for humidity levels in the range 0–10% RH (at room temperature) as reported in Figure 17 from . The coaIn this work, we conducted a thorough review of the state of the art concerning the irradiations performed on LPGs over the last twenty years. We considered all the contributions to the topic by the research groups working in this field.2-written LPGs in standard and radiation hardened fibers have been reported in [The first report about gamma irradiation of LPGs can be dated back to 1998 . Since torted in ,73. Thenorted in  and, fororted in . The attorted in .For a comparative analysis, it is worth noting that most of the works attributed the shift in LPG resonance wavelengths to radiation induced refractive index changes, even under different kind of radiations and grating fabrication techniques. The shift is typically towards higher wavelengths, which can be attributed to an increase in the core RI. The amount of shift is, of course, dependent on the radiation type, dose rate, final dose, as well as fiber and grating parameters. Concerning the attenuation band depth, it seems to show trivial changes in most of experiments except for a few cases. In fact, an UV-written LPG showed a significant band decreasing under proton beam . It is rFuture works should focus on the investigation of LPGs fabricated in innovative optical fibers, that have never been tested before in this field, exhibiting unconventional dopants, refractive index profiles and glass structures. In this context, the advancements in grating fabrication techniques could give a further push. Despite the huge efforts done so far and the sustained irradiation costs, there is still demand for a full understanding of the influence of dose rate  and irradiation temperature. Moreover, as most of the literature is focused on gamma radiation (with single reports on neutrons and protons), other kinds of radiations have to be also considered . Finally, as LPG can be integrated with sensitive overlays, the mentioned studies could be extended to coated gratings as well, for the development of different sensing devices to be used in radiation environments. The need of the hour is to develop innovative LPG sensors comprised of new features which can provide further insights into radiation effects.


Also, the Zn(II), Hg(II), Pb(II) and Cu(II) ions interfered moderately on the determination of Cd(II).A poly(acrylic acid-co-itaconic acid) (PAA-co-IA)/NaOH hydrogel containing bamboo-type multiwall carbon nanotubes (B-MWCNTs) doped with nitrogen (PAA-co-IA/NaOH/B-MWCNTs) was synthesized and characterized by SEM, absorption of water, point of zero charges, infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The possible use of the PAA-co-IA/NaOH/B-MWCNT hydrogel as an electrode modifier and pre-concentrator agent for Cd(II) sensing purposes was then evaluated using carbon paste electrodes via differential pulse voltammetry. The presence of the B-MWCNTs in the hydrogel matrix decreased its degree of swelling, stabilized the structure of the swollen gel, and favored the detection of 3 ppb Cd(II), which is comparable to the World Health Organization’s allowable maximum value in drinking water. A calibration curve was obtained in the concentration range of 2.67 × 10 Multiwall carbon nanotubes (MWCNTs) have been used in numerous applications, including biomedicine, energy conversion and storage, as well as in the construction of nanoscale electronic and electrochemical devices such as sensors and biosensors . One of Other composites generated through the reaction of ionic polymers and metals have been successfully used as dynamic sensors, transducers, and actuators. In this regard, these ionic polymer-metal composites (IPMCs) have been studied for various applications such as integration into energy harvesting as systems , for vibRegarding the bamboo-like multiwall carbon nanotubes doped with nitrogen (B-MWCNTs), these are tubes divided into small compartments, which are produced by partial substitutions of carbon atoms by nitrogen atoms as dopants. Their electrical conductivity and chemical reactivity are greatly improved due to the introduction of an unpaired electron pair per nitrogen atom . Among t−1 as the maximum permissible limit in water for human use and consumption  0.01 mol L−1 in KCl 0.1 mol L−1 at pH 6 [6]3−/[Fe(CN)6]4−. However, these responses demonstrated that with the hydrogel as a modifying agent it is possible to obtain an electroactive surface. The resulting pastes were packed into plastic tubes (0.15 cm diameter and 7 cm long). Electrical contact was achieved by inserting a copper wire into the packed plastic tube. The surface was renewed before each experiment by pushing an excess of paste out of the tube and polishing the new surface with filter paper.The CPEs were prepared according to the methodology used by Bejarano-Jimenez et al. . The dri at pH 6 . The cycThe electrochemical analysis was performed in a three-electrode electrochemical cell connected to a potentiostat/galvanostat model VMP3 Bio-Logic SAS coupled to EC-Lab software version 10.23. The working electrode consisted of a carbon paste modified with either PAA-co-IA/NaOH or PAA-co-IA/NaOH/B-MWCNT hydrogel. The Ag/AgCl/KCl (sat.) system was used as a reference electrode and a glassy carbon rod as the auxiliary electrode.−3 M Cd(II) and 0.1 M KNO3 electrolytic solution at pH 5. The solutions were deoxygenated with argon for 10 min before each test. The detection procedure was performed following the next stages: (1) The surface of the modified carbon paste electrode was pre-treated before use in the detection of Cd(II) by applying a cathodic potential of −1.0 V for 20 s followed by an anodic potential scan from −1.0 to 1.3 V at a scan rate of 100 mV s−1 in 0.1 M KNO3 solution; (2) the uptake of Cd(II) was tested at different times  at open circuit potential, under constant stirring in 1 × 10−3 M Cd(II) + 0.1 M KNO3 solution; (3) the electrode with pre-concentrated Cd(II) was transferred to a 0.1 M KNO3 solution free of Cd(II) to perform the DPV, which consisted of reducing the pre-concentrated Cd(II) to Cd(0) on the electrode surface at −0.95 V for 40 s, followed by anodic stripping (oxidation of Cd(0) to Cd(II)) from −0.95 to 0.6 V with a 33.3 mV s−1 scan rate, 40 mV pulse height, 75 ms pulse width, and 5 mV step height. The DPV conditions were optimized according to the voltametric response of the re-dissolved Cd(II) on a modified CPE electrode, which is observed in s is the standard error of the linear regression and m is the slope.The electroanalytical performance of the PAA-co-IA/NaOH/MWCNT hydrogel was studied using differential pulse voltammetry (DPV) in 1 × 10−1. The polymer spectra  show the band associated with the O–H stretching at 3450 cm−1, which is typical for PAA and similar polymers [−1 is consistent with the extension links –CH2– in the polymer chains, as well as the bands at 1394 and 795 cm−1, which indicate C–H bond deformations. On the other hand, it is possible to distinguish bands corresponding to the harmonics and combinations of bands near 1413 and 1248 cm−1 augmented by Fermi resonance [−1, as well as to identify C=O and C–O stretching bonds from carboxylic acid groups at 1697 and 1160 cm−1, respectively. The band at 1540 cm−1 corresponds to carboxylate groups. The spectrum of PAA-co-IA/NaOH/B-MWCNTs shows an additional band located at 1641 cm−1 associated with the C=C bond present in B-MWCNTs. These results confirm the effectiveness of the synthesis process. Additionally, the band around 2400 cm−1 corresponds to the stretching of carbon dioxide (O=C=O), suggesting its presence in the large quantity of pores in hydrogels.polymers . A band esonance  with theThe appearance of the dry and swollen PAA-co-IA/NaOH/B-MWCNT composite hydrogel is shown in The swelling capacity of pure PAA-co-IA/NaOH and modified PAA-co-IA/NaOH/B-MWCNT hydrogels was determined at pH 5 and 6.6. It is interesting to point out that the hydrogels developed in this work have shown a greater degree of swelling in comparison to some PAA/graphene oxide hydrogels developed by Bejarano-Jimenez et al. , which wThe thermal stability of the copolymer was determined through the derivative thermogravimetry (DTG) of individual components of hydrogels. Thermograms of PAA-co-IA/NaOH and PAA-co-IA/NaOH/MWCNT hydrogels, as well as a PAA-co-IA hydrogel without NaOH, are presented in −3 M Cd2+ and 0.1 M KNO3 solution at pH 5. 2+ such as Zn(II), Hg(II), and Ni(II) [The capacity of the carbon paste electrode modified with the PAA-co-IA/NaOH/B-MWCNT hydrogel to pre-concentrate the analyte was studied in a 1 × 10d Ni(II) , and pred Ni(II) , which c−3 M Cd(II) . A longer immersion time would result in an increase of the anodic charge (anodic current) until a maximum was reached. This maximum can be apparently explained by the equilibrium achieved between the Cd(II) bound to the modifier and the one, which is solubilized in solution [The effect of accumulation time of Cd(II) on the surface of CPEs modified with either the PAA-co-IA/NaOH or PAA-co-IA/NaOH/B-MWCNT hydrogel was studied to assess the role of the B-MWCNTs in the polymeric network. The swelling capacity of the hydrogels on the CPEs was expected to have a significant influence on the voltametric response. Therefore, a study was carried out to establish the relationship between the voltametric signal and the accumulation time at the surface of the carbon paste electrode. solution . The elesolution , the incsolution ,46. Thes2+ due to the higher mechanical stability of this hydrogel, which contributed to better reproducibility of the voltametric signal. Therefore, the maximum value of time used for Cd(II) accumulation was 10 min to avoid the excessive swelling. An increase in the size of hydrogel particles on the electrode surface would cause hydrogel fragmentation, which may decrease the overall conductivity of the electrode surface and produce a degradation of Cd signals. These results confirm that accumulation time played a major role in the detection of Cd(II) when these hydrogels were used as modifying agents.On the other hand, at times longer than 12 min, both hydrogels began to fragment at the electrode surface, a situation that was undesirable since it may lead to poor reproducibility of readings. The swelling of the hydrogel causes the formation of structures like a cauliflower that can be seen with the naked eye on the surface of the electrode. Fragmentation was favored due to agitation during the pre-concentration of Cd(II) at open circuit potential and the fragments were seen at the bottom of the cell. In this test, the electrode modified with PAA-co-IA/NaOH/B-MWCNTs presented a significant reduction of the uncertainty of the quantification of CdConcerning the B-MWCNTs, Pérez et al.  reported2+. The calibration plot was found to be linear between 2.67 × 10−8 and 6.23 × 10−7 M  with a slope of 0.15 µC ppb−1 L (R2 = 0.99) and an LOD and LOQ of 19.2 and 58.3 ppb, respectively. The time needed for preconcentration of Cd(II) in this case was longer, 10 min at OCP, since in this case the concentrations were lower than those used to obtain the voltametric responses shown in −3 and 0.13 × 10−3 M  with a slope of 0.02 µC ppb−1 (R2 = 0.99) and a LOD and LOQ of 1800 and 5500 ppb, respectively. Both curves  with a slope of 0.002 µC ppb−1 L (R2 = 0.99)  see , showing−3 and 0.9 × 10−3 M  with a slope of 0.001 µC ppb−1 L (R2 = 0.99), compared with the linear regression for other ranges of concentrations, meaning that this electrode was less sensitive and had less reproducibility than the electrode containing the PAA-co-IA/NaOH/B-MWCNT hydrogel. Further studies will consider the preparation of specific molecular weights of the polymers to improve the degree of uncertainty.On the other hand, −8 M), so it was evidently a competitive adsorption mechanism during the pre-concentration process, causing a recovery of 35% of the voltametric response of Cd(II) in the mixture of all the metal cations. It has been reported that the metal ion binding properties of linear hydrosoluble poly(acrylic acid) with 3 × 106 of average molecular weight increased in the following order: Ni(II) < Cd(II) < Cu(II) < Pb(II) [2+ such as Zn(II), Hg(II), and Ni(II) [The interference of the voltametric response of Cd(II) was also studied in the presence of other metal cations, such as Pb(II), Zn(II), Hg(II), and Cu(II), which could be adsorbed simultaneously under the conditions for adsorption of Cd(II) . Figure < Pb(II) . Also, ad Ni(II) , which eFurthermore, other studies have proven that PAA composite films have great capacities to sense Cu(II) and Pb(II) ,51 due tThe polymeric material containing itaconic acid possessed an increased swelling capacity due to the presence of many carboxylate groups. The swelling capacity was affected by the presence of B-MWCNTs since they acted as crosslinking agents, decreasing the swelling capacity but providing greater mechanical resistance. The electrochemical detection of cadmium by the carbon paste electrodes modified with PAA-co-IA/NaOH/B-MWCNT hydrogel confirmed that such material can pre-concentrate Cd(II), and therefore provided electroanalytical signals derived from its re-oxidation by anodic stripping voltammetry techniques. The electrodes were able to detect 3 ppb of Cd(II) like those stipulated as the maximum permissible limit in water for human use and consumption (3 to 5 ppb). The modified electrode was able to detect Cd(II) in the presence of other metal cations, and therefore further studies to try to better understand the behavior of the composite in the presence of these metals are being carried out, which is very important for future applications. This composite material can be potentially applied for electrochemical detection of other water contaminants, such as disinfection by-products  and alga


I think I am … underweight, normal weight, overweight, obese”). We used the following statistical analysis: Paired sample t-tests, a Bland–Altman plot kappa statistics, chi-squared tests, and a logistic regression. Results: Mean difference of BMI calculated from self-reported and measured data was 0.06  in men, and 0.16  in women, with four participants being outliers of the 95% limits of agreement (Bland-Altman plot). Allowing a difference of 0.5 kg between self-reported and measured weight, we found that 16% reported their weight correctly, 31.2% underreported (−1.89 ± 1.59 kg), and 52.8% overreported (1.85 ± 1.23 kg), with no sex differences (p = 0.870). Further, our results suggest that both sexes may have difficulty recognizing overweight/obesity in themselves, and particularly men are likely to underreport their perceived weight group compared with women. More than half (53.3%) of the overweight men perceived themselves to be normal weight (women: 14%), and only 33.3% of obese men and women correctly classified themselves as being obese. We did not find any difference between participants correctly or incorrectly classifying weight group and fitness club attendance (≥2 times a week) at three months follow-up. Conclusion: Both sexes reported body weight and height reasonably accurately, and BMI based on self-report appears to be valid measure. Still, a large proportion of novice exercisers do not recognise their own overweight or obesity status, which may in part explain why public health campaigns do not reach risk populations.Background: Data from the research project “Fitness clubs—a venue for public health?” provided an opportunity to evaluate the accuracy of self-reported body weight and height, and subsequent Body Mass Index (BMI), as well as the “trueness” of novice exercisers perception of weight status category, which has not been examined in this population. The aims were to examine self-reported body weight, height, and calculated BMI data from an online survey compared with measured data at fitness club start-up, investigate how accurately novice exercisers place themselves within self-classified weight group , and compare this with fitness club attendance at three months follow-up. Methods: Prior to anthropometric measurements, 62 men and 63 women responded to an online questionnaire, including body weight  and height , and self-classified weight group (“ Body Mass Index (BMI) has gradually increased over the past three decades, with 39% and 13% of adults being overweight BMI ≥ 25) or obese (BMI ≥ 30) worldwide 5 or obes,5,6. HenSystematic literature reviews have examined the validity of self-reported body weight and height in different adult populations ,12, conc(1)Examine self-reported weight, height, and calculated BMI data from an online survey compared with measured data in men and women starting a fitness club membership.(2)Investigate how accurately new members place themselves within self-classified weight group .Since the 1990s, the number of fitness and health clubs have increased, reflecting a growing interest of health among the general adult population. To date, this industry has about 185 million members worldwide, representing a 54% increase over the last decade . In fitnThis is a secondary analysis of data collected as part of a prospective study investigating contributing factors that influence exercise involvement, attendance, and drop-out in a fitness club setting .The research project was reviewed by the Regional Committee for Medical and Health Research Ethics (REK 2015/1443 A), who concluded that, according to the act on medical and health research , the study did not require full review by REK. The procedures followed the World Medical Association Declaration of Helsinki, were approved by the Norwegian Social Science Data Service (NSD 44135), and financed and conducted at the Norwegian School of Sport Sciences (NSSS) (October 2015–April 2017). No economic compensation was given to the participants.n = 270) or had cardiovascular disease, hypertension, or asthma (n = 8). Besides, 148 individuals did not respond after the first e-mail, leaving 250 in the original study. Of these, a subgroup of 62 men and 63 women completed anthropometric measurements at the university laboratory. More details of the research project are published elsewhere [New members at 25 fitness clubs in Oslo, Norway were contacted by an e-mail invitation from the fitness club chain (SATS). In this email, the aims and implications of the study were explained. Among those who expressed interest in participating in the study, the eligibility criteria were checked by a follow-up email from our research fellow. The participants had to be healthy novice exercisers (≥18 years), with <four weeks membership. Healthy was defined as no disease considered to hinder physical activity , and novice exercisers were defined as <60 min/week of exercise at moderate or vigorous intensity, or brisk walking <150 min/week, in the last six months . In totalsewhere ,22.What is your height in centimeters (cm)?” and “What is your weight in kilograms (kg)?”. Participants reported their weight and height in whole numbers or decimal number, and all stated their weight or height. The participants were also asked to select a self-classified weight group: “I think I am …” The response options were grouped according to World Health Organization (WHO) BMI classification: “underweight (<18.5 kg/m2)”, “normal weight (18.5 to 24.9 kg/m2)”, “overweight (25 to 29.9 kg/m2)”, and “obese (≥30 kg/m2)”. Since it may be unethical with mandatory questionnaire responses, we included “I do not want to answer” as a response option on all questions. One woman ticked this option for the self-classified weight group, which in the SPSS dataset was treated as a missing value.A standardized, multidimensional electronic questionnaire (SurveyXact) was answered at start-up (52 questions) and after three months (65 questions) of fitness club membership. The questionnaire contained questions about socio-economic status, health, motives and barriers for physical activity, social support to physical activity, perceived quality of life, and body image. All questions were close-ended, and the survey took about 25 min to complete. For the present study, socio-demographic variables  and self-reported weight and height were obtained from an electronic questionnaire (SurveyXact), answered at start-up of fitness club membership: “Are you still a fitness club member?”: “yes” or “no”, (2) “Have you been exercising regularly at the fitness club?”: “yes” or “no” and (3) “How often have you exercised per week on average at the fitness club?”: “once a week”, “twice a week”, “three times a week”, “four times a week”, “five times a week”, “six times a week” or “seven times a week or more”. Based on the latter (question 3), average sessions/week was obtained. In line with definitions suggested by Hawley-Hague, in the analysis, the participants were classified with either high (≥2 times a week) or low exercise attendance (≤1 time a week) [At three months of membership, we collected data on fitness club attendance the last four weeks. Out of 125 initially recruited, 104 responded to these questions: (1) “ a week) . High at a week) .Measures of anthropometrics were carried out by trained staff and after standardized test procedures, in the same week as collection of self-reported body weight and height. We sent out polls to the participants and let them choose the best time to meet (morning to late afternoon). To ensure confidentiality and privacy, we met one participant at a time in a quiet room. Participants were instructed to be in fasting condition for at least two hours before attendance, and they were encouraged to empty the bladder prior to the test for most accurate measurement. Body weight was measured without shoes, socks, and in light clothing using the InBody720  to the nearest 0.1 kg. To compensate for clothing, the instrument was calibrated to subtract 0.5 kg.Body height was measured to 0.1 cm by a portable stadiometer . Participants stood without shoes/socks and were instructed to look straight ahead (head in the Frankfurt plane), as well as to stand in an upright position with a straight back .2) for both self-reported and measured data. Because height was measured in centimeters, we divided height in centimeters by 100 to obtain height in meters. BMI was also classified according to WHO’s adult reference values . A relative difference of ±250 g between measured and self-reported body weight was used as cut-off to investigate proportions who correctly classified body weight [BMI was calculated as the weight in kilograms divided by the square of the height in meters  [All statistics were conducted with SPSS Software V. 24 for Windows, and descriptive data were screened for normality and outliers, including a comparison of the overall curve of the bars of the histograms, and the usage of parametric statistics . The dif. (2020) , a Bland. (2020) . Due to n = 90).Pearson’s chi-squared test was used to determine the distribution of observations in different categories, and concordance between measured BMI categories  and self-classified weight group were assessed using Cohen’s weighted kappa statistic. Finally, a logistic regression analysis was used to investigate five factors  associated with misreporting of self-classified weight group. To examine participants correctly or underreporting weight group in relation with fitness club attendance at three months follow-up, a chi-squared test for proportions was used. In the statistical analysis, only those correctly or underreporting weight group were included (Most participants (76.8%) were of Norwegian descent, with a mean age of 36.8 (±11.0) years. About half (45.6%) reported university education of ≥4 years, 63.2% were employed full-time, and 32.8% had a mean household income classified as “high” . Marriage or cohabitation were reported by 65.6% and 32.8% had children. About 65% had previously been a member at another fitness club.2). For all participants, mean BMI values were 22.5 (±1.4) kg/m2, 26.6 (±1.3) kg/m2, and 33.7 (±4.5) kg/m2 in the normal weight, overweight, and obesity groups, respectively. Those normal weighted were somewhat younger than those measured as overweight or obese , and a higher proportion were women .2, CI −1.0692 to 0.8492, p = 0.206). 2) analyzed by Bland–Altman plot, with four participants being outliers of the 95% limits of agreement.Pearson correlation between self-reported and measured body weight, height, and BMI were 0.98, 0.99, and 0.96 in men, and 0.99, 0.94, and 0.98 in women, respectively. Both sexes slightly overreported body weight (0.442 kg in men and 0.344 kg in women) and men overreported body height with 0.006 m . In all Overall, prevalence of overweight and obesity was marginally underreported by the participants, and four men and two women (4.8%) who were overweight, and one woman (0.8%) who was obese, would be missed using self-reported data.Allowing a difference of 0.5 kg between self-reported and measured weight, among men, 14.5% reported their body weight correctly, 30.6% underreported by an average of −2.01 (±1.91) kg, and 54.8% overreported by an average of 1.93 (±1.27) kg. Among women, 17.5%, 31.8%, and 50.8% reported their body weight correctly, underreported (−1.77 (±1.24) kg), and overreported (1.77 (±1.19) kg), respectively. Further, we observed that in both sexes, significantly more individuals overreported than underreported body weight, with a higher prevalence among normal weight individuals compared with those classified as overweight .A high proportion did not properly classify their weight group . Among np = 0.007).In both sexes, nearly 70% of those measured to be obese considered themselves to be overweight (men: 50% and women: 66.7%) or normal weight (men: 16.7%). In addition, more than half of overweight men (53.3%) perceived themselves to be normal weight, while the corresponding number for women was 14.4%. These results suggest that both sexes may have difficulty recognizing overweight/obesity in themselves, and particularly men are likely to underreport their perceived weight group compared with women (2) compared with normal-weight participants (BMI < 25 kg/m2) .After adjusting for sex, age, educational level, and household income, the odds of underreporting self-classified weight group were nearly three times higher in those with a high BMI (≥25 kg/mWe did not find any difference between participants correctly or incorrectly classifying weight group and fitness club attendance (≥2 times a week) at the three-month follow-up .Due to the social costs and health risks of a high BMI, it is important to examine how well individuals perceive overweight and obesity. To our knowledge, this study is the first to evaluate the accuracy of self-reported body weight, height, and BMI, as well as the “trueness” of novice exercisers perception of weight status group  in a fitness club setting. Although the average difference between self-reported and measured body weight, height, and BMI were marginal, more than 60% of the men and nearly 40% of the women did not correctly classify their weight status category. Especially, a large proportion of men did not recognize their own overweight, and among both sexes, only one in three properly classified themselves as obese. Others have also reported that study participants misclassified perceived weight group compared to measured BMI ,28,29,302) is in our opinion negligible. Our interpretation is therefore that self-reported weight and height in novice exercisers are so close to direct measurements that it can be used as proxy in situations where anthropometric measurements are not feasible. For instance, it may not be possible due to time, logistical, and economic restrictions in large-scale studies. Furthermore, self-report reaches those living in rural and remote regions and allows the investigator to gather data from numerous respondents at the same time [It is commonly reported that body weight is underreported while height is somewhat overreported in the general adult population, leading to misestimates of BMI and proportions classified in the different BMI categories ,12. In aame time .We also found a high sensitivity (about 95%) when self-reported body weight and height were used to identify overweight or obesity. This is in contrast to other studies that have reported that 20–40% of those overweight or obese would be misclassified when relying on self-report, depending on sex and background characteristics of the population ,35,36,37We collected self-reported data before body weight and height were measured, and the elapsed time between the two measurements was about three to seven days. Others have reported an average of nearly 24 days between self-reported and measured data  or lackeAs BMI is the most common method to assess overweight and obesity, adult’s misperception of own weight group may result in little motivation to change lifestyle habits. In the present study, a fitness club setting was chosen, because its members are targets for marketing strategies about weight loss, exercise interventions and diets. Further, studies have shown that weight loss is one common reason why individuals may buy a gym membership ,18,19. Fn = 174,000), concluding that self-perceived BMI group is often incorrect, with underreporting being more prevalent than overreporting [The prevalence of measured overweight or obesity (BMI ≥ 25) was nearly 60% in men and 30% in women, but more than half of those underreported their weight group when asked about this, especially the men . This is consistent with the results from a recent systematic review of more than 50 studies from 25 countries  is now about 26 (overweight category) compared with former 23  [According to the Norwegian Institute of Public Health, overweight and obesity have steadily increased since 1975, and average BMI (kg/mategory) . We founategory) . A seconategory) ,48, makiPerception of body weight status may be a key factor of healthy lifestyle and body weight management. Novice exercisers who are overweight or obese, but fail to see this, may slip back to former habits, and drop out of regular exercise routines. As far as we know, no one investigated this association in fitness club members. We did not find any difference between participants correctly or underreporting weight group and exercise attendance (≥2 a week) at three months follow-up. Research has shown that physical activity and improvements in cardiorespiratory fitness may counterbalance the risks associated with a high BMI and adiposity, regardless of weight loss ,50,51. IThis is the first study to investigate the accuracy of self-reported body weight and height, and self-classified weight group in novice exercisers starting a gym membership. Other aspects were a complete dataset, with no missing values regarding anthropometric measures, and that our participants included an age diverse group of both sexes. We completed data-collection within the same week, which may minimize bias due to possible alterations in body weight, and self-reported data were collected before direct measurements. Body weight and height measurements were also taken by the same research staff using the same equipment and after standardized procedures. Further, the use of a Bland–Altman plot with LOAs provided a robust evaluation of agreement between self-reported and measured BMI, and several socio-demographic variables were investigated as potential predictors of misreporting perceived weight status. Finally, we provided detailed data about exercise involvement and had a high response rate (83%) regarding this question at a three-month follow-up. Hence, we were able to analyze associations between self-classified weight group and fitness club attendance.The limitations are little ethnic diversity and the fact that data were obtained from one fitness club chain, with middle to high monthly costs, limiting the generalizability of findings. Enrollment of other clubs (such as low-cost gyms and CrossFit centers) might have given other results. In addition, we pre-defined high fitness club attendance as a minimum of two sessions a week. This does not reflect whether the participants exercised according to current activity recommendations for adults regarding intensity, duration, and mode of activity (endurance and resistance exercise). In addition, collecting information regarding exercise by self-report may cause social-desirability bias, which could explain why we did not find any differences between participants correctly reporting or underreporting perceived weight status category and fitness club attendance. As such, we recommend future studies in this area to add information about gym statistics (such as membership card swipes). Finally, this study did not investigate why those measured as overweight or obese did not acknowledge having an unhealthy weight. Hence, there is a need for future qualitative studies exploring this in more depth.Novice exercisers reported their body weight and height with reasonable accuracy, and subsequent BMI may be a valid measure of overweight and obesity among both sexes. On the other hand, compared with BMI calculated from either self-reported or measured data, the self-classified weight group is largely flawed, and particularly those with a BMI ≥ 25 may have difficulty recognizing overweight or obesity in themselves. As inaccuracies in weight perception, both underestimation and overestimation, may lead to unhealthy weight control practices, we need additional research examining weight loss history and dieting behavior in fitness club setting with a larger sample size.


Coronavirus disease 2019 (COVID-19) has a significant impact on children, adolescents, and their families. So, the purpose of this study is to investigate the prevalence of children’s psychological problems during the COVID-19 pandemic and their association of COVID-19 infection in children and their risk factors. A cross-sectional study was conducted on 148 children aged 6–12 years old categorized into 2 groups based on COVID-19 infection history. Participants were assessed by the Socioeconomic Scale and the Checklist for Children’s Behavior (CBCL).Children who had COVID-19 had a high percentage of problems regarding family, school, social, financial, and parent problems due to the COVID-19 pandemic. Regarding CBCL, children who had COVID-19 infection had a higher percentage of clinical rating than the other group regarding withdrawal (11.1% vs. 8.9%), anxious/depressed (33.3% vs. 25%), somatic (11.1% vs. 10.7%), internalizing (61.1% vs. 48.2%), externalizing (38.9% vs. 35.7%), and total problems (50% vs. 44.6%). Family history of psychiatric disorder and the presence of three or more offspring were at high risk for internalizing problems, while those with school problems during pandemic were more vulnerable for internalizing and total problems.Children with COVID-19 infection had a higher risk of developing psychological problems, such as withdrawal, anxiety/depression, somatic, internalizing, externalizing, and total problems. Coronavirus disease 2019 (COVID-19) has a significant impact on people all over the world. Isolation, contact limitations, and financial closure would all have a profound effect on the psychological environment of the impacted countries. Children, adolescence, and their families are severely affected by the current circumstances [Children have a less chance of acquiring the severe form of the illness and need less hospitalization and mechanical breathing than adults . HoweverDuring the COVID-19 pandemic, many factors impacted children and adolescents, including the closure of kindergartens and schools, the restriction of social contacts, and outdoor leisure activities. Parents were encouraged to help their children with home education while also working from home. Other family members’ and social support systems’ assistance has declined. Aside from worries and fears about COVID-19, the economic situation has deteriorated, escalating unemployment rates in all countries affected. This has placed a great stress on children, adolescents, and their families, potentially leading to distress, mental health issues, and violence [COVID-19 pandemic consequences could be disastrous. As a child or adolescent’s central nervous system (CNS) is in a susceptible developmental time, any stressful issues during crucial time can cause short- and long-term physiological , 6, cognPeople with COVID-19 infection may have psychiatric problems caused by biological factors other than psychosocial factors , schizopSo, the purpose of this study is to investigate the psychological problems of the COVID-19 pandemic in children aged 6 to 12 years old. Also, the impact of COVID-19 infection and the possible risk factors for these problems.N = 36) as documented with a PCR report, and the second group, who did not have COVID-19 infection (n = 112). Children with a history of mental disorders, a medical or neurological disease, or their intelligence quotient (IQ) below 70 were excluded from the study.From February to May 2021, a cross-sectional study was conducted. A total of 148 children aged 6–12 years old were recruited from three Assiut government primary schools, Egypt. During this time, students were only allowed to attend school for 2 days a week, and most of their education was provided online. So, with the permission of the manager’s school, we distributed an online Google form through school websites to invite parents to participate in our study to assess their children. The parents who accepted our invitation were interviewed with their children at Assiut University’s Child Psychiatry Clinic, the Neurology and Psychiatric Hospital. Furthermore, the children were divided into two groups: the first group who had COVID-19 infection  have a diagnosis as COVID-19 infection? (yes/no), Did any one of the family (first relative degree) die from COVID-19 infection? (yes/no), School problems (academic) due to COVID-19 infection? (yes/no), Social problems (peers) due to COVID-19 infection? (yes/no), Problems in parent relationship due to COVID-19 infection? (yes/no), Increase family expenses due to COVID-19 infection? (yes/no), Decrease family income due to COVID-19 infection? (yes/no).The socioeconomic scale  is a tooThe CBCL  is a quet test was used to assess quantitative variables. Researchers used multivariate logistic regressions to identify possible risk factors for externalizing, internalizing, and total problems in children. Statistical significance was defined as a probability value  of less than 0.05.SPSS was used to conduct the statistical analysis (version 26). As descriptive statistics, frequencies and percentages were reported. The categorical variables were evaluated using the Pearson chi-squared test. To detect the difference in mean values between the two groups, the independent A total of 148 child were assessed and included in this study of them, the majority were males, first birth order, no postpartum problems, no delay in speech or motor development, no family history of psychiatric disorders, and belong to middle socioeconomic level  had delay of speech development compared to children without COVID-19 infection (26.8%). Regarding the socioeconomic (SE) level, middle class was the prevailing in both groups. However, lager proportion of children who had COVID-19 was in the high SE class (22.2%) in comparison to children without COVID-19 infection (7.1%). Subsequently, children without COVID-19 infection had higher percentage of lower class (16.1%) when compared to children with history of COVID-19 infection (11.1%).In Table According to the CBCL scores, the percentage of children who had a clinical rating of the profile of syndromes during the COVID-19 pandemic were 9.5% of withdrawal; 13.5% of somatic complaints; 14.9% of social problems; 27% of anxious/depressed; 18.9% of thought problems; 54.1% of rules breaking behavior; 18.9% of aggressive behavior; 23% of depression problems; 24.3% of anxiety problems; 10.8% of somatic problems; 18.9% of oppositional defiant problems; 17.6% of conduct problems; 51.4% of internalizing problems; 36.5% of externalizing problems; and 45.9% of total problems.There was a significant difference regarding thought problems and rules breaking behavior between the studied groups. Children who had COVID-19 had a higher percentage of clinical rating than children without COVID-19 infection regarding withdrawal (11.1% vs. 8.9%), anxious/depressed (33.3% vs. 25%), internalizing problems (61.1% vs. 48.2%), externalizing problems (38.9% vs. 35.7%), and total problems (50% vs. 44.6%).In addition, the CBCL Profile of DSM-5 scales had a higher percentage of clinical rating in children who had COVID-19 than without COVID-19 infection regarding depression problems (27.8% vs. 21.4%) and somatic problems (11.1% vs. 10.7%) , externalizing problems (38.9% vs. 35.7%), and total problems (50% vs. 44.6%). No identified risk factors were associated with externalizing problems. At the same time, children who had a family history of psychiatric disorder, and the presence of three or more offspring were more vulnerable to internalizing problems while children who had school problems during pandemic were more vulnerable for internalizing and total problems.In the current study, children who had COVID-19 were more frequent in speech development delay, belonged to a high socioeconomic level and more suffered regarding family members who got an infection or died from COVID-19; school, social, and parent problems; increase family expenses; and decrease family income than the other group.Social contact plays a major role in development of cognition, emotions, attachment, and relationships . Also, iFear’s influence on children and adolescents is another major source of concern. During COVID-19 pandemic, a study about fear in the quarantined children and adolescents found a high prevalence of fear among the studied groups. This fear was primarily related to financial concerns, risk of COVID-19 infection, and infecting others . FurtherAlso, school routines are important coping mechanisms for children and adolescent with psychiatric problems . MoreoveRegarding socioeconomic level, low socioeconomic status (SES) has been consistently associated with adverse health outcomes and an increased risk of death –26. AccoIn this study, according to CBCL, half of children with COVID-19 had psychiatric problems and had a higher percentage of clinical rating regarding withdrawal, anxious/depressed, somatic problems, internalizing problems, externalizing problems, and total problems than children who did not have COVID-19.Two previous researches were done in China to evaluate psychiatric problems in children and adolescent, the first one was conducted on the quarantined children and adolescent and found them to have depressions, anxiety, or both while the second study was conducted during the pandemic and found symptoms of inattention, clinging, worry, and irritability , 34. AnoA literature review reported the impacts of COVID-19 pandemic stressors on children and adolescents’ life. The COVID-19 pandemic stressor caused dysregulation in hypothalamic-pituitary-adrenal (HPA) axis by having inflammatory mediators’ synthesis and release, e.g., proinflammatory cytokines, neurotransmitters, hormones, and other molecules that can interfere with different physiological mechanisms during the early stages of life when the child or adolescent is exposed to situations of long-term stress. This imbalance could be linked to immune, endocrine, and nervous system overload and the risk of developing psychiatric disorders later in life. The possible short-term effects of exposure to COVID-19 pandemic stressors at this stage of life were distress and hopelessness, irregular food intake, abuse and trauma, interpersonal and environmental restraint, sensory deprivation, and neglect. In contrast, the possible long-term consequences were underdeveloped brain circuitry, obesity, etc. [This study has a few important implications for policymakers, which may be applied to enhance families’ support with COVID-19 infection, as the infected children suffer more and are at an increased risk of developing psychiatric problems. As a result, psychiatric screening for children should be recommended, especially after infection with COVID-19. Psychoeducational programs are required to raise school, family, and community awareness of those children.The current study had some limitations, including small sample size. As a result, we recommend that future studies with large representative samples to be conducted to confirm our findings. In addition, because most of the children were treated at home, we were unable to investigate the link between the severity of COVID-19 infection according to WHO guidelines  and psycChildren infected with COVID-19 had a higher risk of developing psychological problems, such as withdrawal, anxiety/depression, somatic problems, internalizing problems, externalizing problems, and total problems. Furthermore, they were more affected by the COVID-19 pandemic in terms of family member infection or death from COVID-19; school, social, and parent problems; increased family expenses; and decreased family income than children who did not have with COVID-19. Also, children with a family history of psychiatric disorder, school problems, and the presence of three or more offspring were more vulnerable to internalizing problems while children who had school problems were more vulnerable to total problems.


N correlated sources over an N-user multiple-access channel. For each user, the set of messages is partitioned into classes and codebooks are generated according to a distribution depending on the class index of the source message and under the constraint that the codewords satisfy a set of cost functions. Proper choices of the cost functions recover different coding schemes including message-dependent and message-independent versions of independent and identically distributed, independent conditionally distributed, constant-composition and conditional constant composition ensembles. The transmissibility region of the scheme is related to the Cover-El Gamal-Salehi region. A related family of correlated-source Gallager source exponent functions is also studied. The achievable exponents are compared for correlated and independent sources, both numerically and analytically.This paper studies a generalized version of multi-class cost-constrained random-coding ensemble with multiple auxiliary costs for the transmission of  In information theory, the fundamental problem of communication over a channel is studied from two complementary perspectives. First, one characterizes the transmissibility conditions, namely the circumstances under which the error probability asymptically vanishes as the blocklength goes to infinity. Second, one describes by means of error exponents the speed at which this error probability vanishes; the larger the exponent, the faster the error probability tends to zero. Since finding an exact expression for error probability is very difficult, a large body of work has investigated upper and lower bounds on the average error probability, or equivalently lower and upper bounds for the error exponent. In point-to-point, that is, single-user communication, using separate source-channel random coding ,2, possiFor point-to-point communication, it was shown in ref.  (Prob. 5Many works have been devoted to studying the transmissibility and the error exponent for a two-user multiple-access channel (MAC) ,10,11. SIn contrast to single-user communication, the problem of reliable transmission of two correlated sources has not been solved yet and just the sufficient conditions of a reliable transmission has been derived. In ref. , by applIn this paper, we examine how statistical dependency between the messages and codewords improves the exponent, as well as its impact on the transmissibility region. In view of refs.  (Ch. 7) N correlated sources over an N-input discrete memoryless multiple-access channel and provide the key definitions of error probability, transmissibility, random-coding ensemble, and achievable exponent. In The paper is organized as follows—in N correlated, discrete, memoryless sources over a channel; users are indexed by n symbols drawn from the alphabet We study the simultaneous transmission of n and with symbols drawn from the alphabet W, and the channel is characterized by a conditional probability distributionn.Each user Based on n, namely whether the error probability vanishes and how fast this probability tends to zero as it vanishes. The sources We are interested in the asymptotics of the error probability for sufficiently large n grows. More importantly, it shows the existence of good codes in the ensemble such that their error probability vanishes. For the point-to-point and the multiple-access channels, a number of such random-coding ensembles have been studied in the literature, as reviewed in the following section, where we also present a multi-class cost-constrained ensemble subsuming all these ensembles and characterize the achievable exponent and transmissibility region of this ensemble.Source transmissibility and error-exponent achievability are typically studied by means of random coding. With random coding, one generates and studies sequences of ensembles of codebooks whose codewords are randomly drawn from a distribution n-Cartesian product set of x belongs to a set Sets are usually denoted by calligraphic upper case letter, e.g., N and user indices are typically represented by The number of users is denoted by A may represent sets of user indices Subscripts and superscripts in a quantity X and lowercase letters represent a particular realisation, for example, n, (resp. for symbols) are represented by text-style letters, for example, P, Q, W). Sequences symbols are usually affixed a subscript to indicate a user index; the t-th symbol in the sequence Scalar random variables are denoted by capital letters, for example, P replaced by Q or a respectively replaced by The source-symbol distribution for user iid) [mi-iid) ensemble, since codewords have the same distribution for all source messages and symbols are independent of each other and independent of the source message symbols too. For the mi-iid ensemble, the random-coding distribution is given byThe simplest and oldest random-coding ensemble is the independent, identically distributed (iid) ,12,17,27mi-icd) ensemble, the codewords mi-iid ensemble, the mi-icd ensemble can lead to a larger transmissible region for the multiple-access channel with correlated sources [In the message-independent, independent-conditionally-distributed =∏t=1nQν, sources . An exammd-iid) ensemble [md-iid random-coding distribution is given bymd-iid ensemble can be larger than that of the mi-iid ensemble for joint source-channel coding [Next, we have the message-dependent iid  ensemble, messages in the class md-icd ensemble is thus given byIn the message-dependent, independent conditional symbol distributions (mi-cc) ensemble [mi-cc ensemble, the random-coding distribution is given bymi-cc and mi-iid ensembles lead to identical transmissibility conditions, the former may achieve strictly larger exponents for suboptimal input distributions already in single-user settings [In the message-independent, constant-composition  ensemble combines features of the mi-icd and mi-cc ensembles. For each subsequence a and two cs.The message-independent, conditional constant-composition (md-cc) ensemble combines the features of having different distributions for different messages with constant-composition random coding. For messages in the class The message-dependent, constant-composition (md-ccc) ensemble combines several of the ensembles listed above. For a given message Finally, the message-dependent, conditional constant-composition  For each user, we partition the set of source messages into Equation . Let theEquation , and we Codewords iid and icd ensembles are recovered by setting The multi-class cost-constrained ensemble subsumes all the ensembles described in To recover the constant-composition ensembles, for which constraints force the subcodewords to belong to some set  so thataν,uνiν,ℓEquation  is simplEquation  where QνAgain, choosing the right number of classes Equation  as folloEquation ,(29)Dν,Theorem 1.For the transmission of N correlated memorlyess sources with joint distribution Equation , and encEquation  through where the Gallager function and the functions and implicitly depende on the set of optimization parameters Proof. This result is proved in The random-coding exponent in Equation  depends In this section, we evaluate the generalized Gallager function Equation  for the For the simple mi-iid ensemble, with only one source class and no cost constraints, Equation  gives thmi-icd ensemble, we have a similar set-up as for the mi-iid ensemble, where mi-iid ensemble with a tilted unconditional input distribution and identical exponent. To this end, and for a given conditional input distribution For the Equation  with Qσ=Xν giveRνiν(xν)=Equation ,Eτmi-ccEquation .md-cc ensemble was studied for N users is obtained by combining the derivation of Equation Eτm in ref.  mi-icd case, and similarly to Gallager’s For the function   for each user. First, we consider two correlated discrete memoryless sources, md-iid exponent The optimal achievable exponent   leaEquation . Figure In this example, we obtained the achievable exponent Equation  and optiAlternatively, we may first optimize over Equation  in AppenEquation . We provt(Ωj) asEcost(Ωj)Equation .In the second example, we consider the transmission of two independent discrete memoryless sources with identical source alphabets Equation , given bEquation , and arequations –(69). Foquations  and 74)Uν={0,1} mi-iid ensemble described in Equation  in ref. . Hence, From the numerical results presented in iiid distribution mi-iid and mi-icd ensembles attains the same exponent, after maximization over the input distributions. Similarly, we conclude that md-iid and md-icd-ensembles attain the same exponent.For independent sources, we found in Equation (42) that for a given conditional input distribution Equation  with ideIn ref.  Equation  the Eτ,iEquation  containsEquation . This alEquation  also conEquation , yieldinSummarizing, proper choices of the cost functions recover the different coding schemes considered in


ABCB1/P-glycoprotein is an ATP binding cassette transporter that is involved in the clearance of xenobiotics, and it affects the disposition of many drugs in the body. Conformational flexibility of the protein within the membrane is an intrinsic part of its mechanism of action, but this has made structural studies challenging. Here, we have studied different conformations of P-glycoprotein simultaneously in the presence of ivacaftor, a known competitive inhibitor. In order to conduct this, we used high contrast cryo-electron microscopy imaging with a Volta phase plate. We associate the presence of ivacaftor with the appearance of an additional density in one of the conformational states detected. The additional density is in the central aqueous cavity and is associated with a wider separation of the two halves of the transporter in the inward-facing state. Conformational changes to the nucleotide-binding domains are also observed and may help to explain the stimulation of ATPase activity that occurs when transported substrate is bound in many ATP binding cassette transporters. P-glycoprotein (P-gp) is an ATP-dependent multi-drug transporter of the ATP-binding cassette (ABC) family that is involved in the active efflux of many drugs and xenobiotics from cells . Overexpa of 11 (CHEMBL2010601) and points towards the guanidino group of R933 in the structural model [Recent studies have demonstrated that the novel cystic fibrosis (CF) therapeutic ivacaftor is a competitive inhibitor or transported substrate of P-gp ,23. Thisal model ,27, implIn this study, we examined the P-gp structure in the presence of ivacaftor. In order to minimize non-specific binding of the hydrophobic drug, we employed a concentration likely to be encountered in vivo  and at aP. pastoris harboring the opti-mdr3 gene was kindly provided by Prof. Ina L. Urbatsch, Texas Tech University [abcb1a) was initiated by the addition of methanol, and the expression was prolonged following an optimized procedure [iversity . Cell cuiversity . Overexprocedure . Cell pev/v) glycerol, 50 mM NaCl, 1 mM 2-mercaptoethanol and 2% (w/v) DDM). Solubilized materials were processed through multi-step protein purification, described previously [Cell rupture was conducted using glass bead beating, and microsomal membranes were prepared as described in (4). Microsomal membranes were diluted to 2.5 mg/mL prior to solubilization in detergent-containing buffer  instrument: concentrated P-gp protein (1 µg per sample) was diluted into 10 µL of buffer  containing different concentrations of ivacaftor. The experiments were also repeated with the further addition of 100 ng of CPM dye -4-Methylcoumarin), which acts as a reporter of solvent-exposed cysteine residues ,45,46,47− Å−2 were used over 40 frames spanning 10 s of exposure, and early and late frames were discarded. The magnification was calibrated at 1.043 Å/pixel. A total of 2436 movie stacks were collected, and beam-induced image shift was eliminated using MotionCorr2 [P-gp was initially buffer-exchanged into a detergent/glycerol-free buffer. The protein was diluted to 1.1 mg/mL and incubated with 2 µM Ivacaftor (stock: 100 µM in DMSO) for 30 min on ice. Quantifoil 200 or 400 Au grids with a 1.3-micron spacing pattern were pre-treated prior to protein deposition, as described previously . BrieflyionCorr2 .cisTEM [cisTEM and calculate_fsc routine. Local resolution was also estimated using the program ResMap [matchmaker, color zone/split map, and calculate volume and area functions of Chimera [The data processing of the 2436 images was entirely performed with cisTEM . A totalcisTEM . These mcisTEM , with thm ResMap . Rigid-dm ResMap  with a 5 Chimera  and usin Chimera .D) was estimated at 0.3 μM using a fluorescent dye transport assay with the purified protein [50) of 0.2 μM was estimated using an in-vivo assay [D values of 0.2 μM (static light scattering) and ≅1 μM (tryptophan fluorescence) .Ivacaftor has been identified as a competitive inhibitor of Hoechst 33,342 and digoxin transport by human P-gp ,23. Ivac protein . Similarescence) . The bint 0.2 μM . Hence, Images (2436) were recorded with the Volta phase plate, and after initial rejection of poor quality images by eye, the contrast transfer function (CTF) of each was estimated. A total of 1537 images gave CTF fits that were judged to be reliable whilst 868 were rejected at this stage. A second criterion was applied to eliminate all images affected by excessive defocus values, and a total of 131 further images were eliminated, with a final set of 1406 images . As expeb-initio 3D classes of the final P-gp dataset were generated from a subset of only ~50,000 particles, and these are shown in a and c) were also picked out by the image processing package. For each of the five low-resolution ab-initio maps, a PDB model was derived using Molecular Dynamics Flexible Fitting (see Methods), and results were compared. Utilizing the center of mass of the NBDs as a reference, classes b, d, and e showed a narrower separation of the NBDs (from 56 Å to 53 Å), while both classes a and c were found to have a wider distance (60 Å). A moderate low-pass filter was applied to the ab-initio maps to avoid over-fitting effects. CTF parameters were also further refined at this stage with per-micrograph CTF fits using the dedicated cisTEM functionality for this. Refinement of the full dataset  starting with each of the five cisTEM ab-initio 3D classes was carried out with a combination of auto- and manual-refinement, and an atomic model was generated for each resulting refined 3D map using the PHENIX real space refinement routine [3 are displayed in A routine . The 3D a displayed the lowest resolution of all the maps in the various tests employed, although the overall map-to-model correlation was better  as well as using the Resmap routine, which calculates local resolution in the maps ,55. The s better . The Res micelle . Converslgorithm  and by Fa through e;  between TM helices 1 and 2 was weaker for maps c and e, perhaps representing increased disorder in this loop, which may be core glycosylated in the expression system used. These symmetry-breaking features of P-gp likely aid the image processing via discrimination of projections of alternative 180°-rotated orientations of particles . The density is surrounded by residues contributed by TM helices 6, 10, and 12, and hence is positioned more in one lobe of the aqueous cavity , a local bulging outwards of the transmembrane helices were apparent , the outwards bulging of the TM helices upon ivacaftor accommodation was more noticeable. In both cases, TM helices 1, 2, 7, and 8 move most whilst helices 6 and 12 move little  shift of the Walker A and B regions relative to intracellular loops 1 and 4 that connect NBD1 from the TMD, and in map  in NBD1 d. SimilaStructural data for 3D conformations of P-gp were obtained with the Volta phase plate; and with this methodology the resolution of the 3D information obtained was around 6-4 Ångstrom. Whether these resolution limitations can be overcome with a larger dataset remains to be established. The use of sub-stoichiometric levels of ligand may be a suitable approach in future cryo-EM studies, provided that ligand–protein complexes can be distinguished from ligand-free protein on the basis of different conformational status and/or by a sufficiently large additional density due to the ligand. Clearly, atomic details of ligand binding mode will depend on close to atomic resolution data, but the overall location of the ligand and some modeling of likely binding modes will be possible at intermediate resolution, as described here and in other studies for various other proteins and ligands ,40,41,42Drug and inhibitor binding locations in P-gp have previously been studied for both mouse and human versions of the protein ,15,16,58a that is described here, with root mean squared deviation (rmsd) between the main chain Cα atoms of the models of around 4 Å over 1179 comparisons . When these various atomic models are superimposed (A comparison of murine P-gp models both with and without bound compounds is shown in a is consistent with a single molecule, but again, in this comparison, it would be located closer to the cytoplasmic side of the membrane than the other compounds, with the exception of one of the elacridar molecules (orange stick representation, A comparison of the mouse/ivacaftor P-gp model with human and human/mouse chimera P-gp models in the presence and absence of other small molecules is shown in Taken together, the data for ivacaftor is equivocal: the single density observed would imply that ivacaftor shares P-gp substrate characteristics, whilst its overall location in one lobe and over towards the cytoplasmic leaflet of the bilayer is suggestive of binding characteristics of an inhibitor according to the work of Nosol et al. . It seem


Virtual stenting using vFFR provided an accurate estimation of post-PCI FFR and post-PCI vFFR. Further studies are needed to prospectively validate a vFFR-guided PCI strategy.3D coronary angiography-based vessel fractional flow reserve (vFFR) proved to be an accurate diagnostic alternative to invasively measured pressure wire based fractional flow reserve (FFR). The ability to compute post-PCI vFFR using pre-PCI vFFR virtual stent analysis is unknown. We aimed to assess the feasibility and diagnostic accuracy of pre-PCI vFFR virtual stenting analysis  with post-PCI FFR as a reference. This is an observational, single-center retrospective cohort study including consecutive patients from the FFR-SEARCH registry. We blindly calculated residual vFFR from pre-PCI angiograms and compared them to invasive pressure-wire based post-PCI FFR. Inclusion criteria involved presentation with either stable or unstable angina or non-ST elevation myocardial infarction (NSTEMI), ≥1 significant stenosis in one of the epicardial coronary arteries  and pre procedural angiograms eligible for vFFR analysis. Exclusion criteria comprised patients with ST elevation myocardial infarction (STEMI), coronary bypass grafts, cardiogenic shock or severe hemodynamic instability. Eighty-one pre-PCI residual vFFR measurements were compared to post-PCI FFR and post-PCI vFFR measurements. Mean residual vFFR was 0.91 ± 0.06, mean post-PCI FFR 0.91 ± 0.06 and mean post-PCI vFFR was 0.92 ± 0.05. Residual vFFR showed a high linear correlation (r = 0.84) and good agreement : 0.005 (−0.002–0.012)) with post-PCI FFR, as well as with post-PCI-vFFR ). Residual vFFR showed good accuracy in the identification of lesions with post-PCI FFR < 0.90  0.93 (95% CI: 0.86–0.99),  Functional physiological lesion assessment after angiographically successful percutaneous coronary intervention (PCI) proved to have significant prognostic value ,7,8,9,10Vessel fractional flow reserve (vFFR) has been recently introduced into the armamentarium of catheterization laboratory practice aiming to simplify functional lesion assessment ,16. Its As a next step, the ability to predict the functional outcomes of PCI is gaining increased attention ,28,29,30Here, we present the ‘Virtual stenting’ vFFR study that aimed to assess the diagnostic performance of residual vFFR —performed using the pre-PCI angiogram—against invasively measured post stenting FFR in a consecutive series of patients.The ‘Virtual stenting’ vFFR study is an observational, single-center cohort study aiming to evaluate the diagnostic performance of offline pre-PCI angiogram-based estimation of final functional PCI outcome—namely residual vFFR—against invasively measured post-PCI FFR. A consecutive cohort of the 200 most recent patients enrolled in the FFR SEARCH registry who underwent PCI with stenting were screened for eligibility ,32. The The study was conducted in accordance with the Declaration of Helsinki. The study protocol was approved by the Erasmus University Medical Center ethics committee (MEC-2016-063). All patients provided written informed consent for the procedure and the use of anonymous datasets for research purposes in alignment with the Dutch Medical Research Act.−1·min−1 through an antecubital vein [FFR was measured using a dedicated microcatheter . FFR was defined as the mean distal coronary artery pressure divided by mean aortic pressure during maximum hyperemia induced by continuous intravenous infusion of adenosine at a rate of 140 μg kgtal vein . Post-PCtal vein . Subsequtal vein .Pre- and post-PCI vFFR analysis was conducted offline by trained analysts blinded to the invasive FFR values using dedicated software . The methodology of pre- and post-PCI vFFR calculation has been reported in detail elsewhere ,24,26.Pre- and post-PCI angiograms were used to compute pre- and post-PCI vFFR, respectively. Apart from two angiographic views with ≥30° differences in rotation/angulation to produce a 3D reconstruction of the coronary artery, also the views demonstrating the position of FFR microcatheter were checked upon post-PCI vFFR measurement. All analyses were blinded to the invasive FFR value.Whereas the alignment of the cardiac cycle between the two angiograms was performed automatically based on ECG triggering, manual frame selection was possible . Vessel The concept of residual vFFR  involves computation of vFFR assuming that the diseased segment of the coronary artery has been treated with a successful stent implantation eliminating the drop of vFFR in the selected artery segment . ResiduaCorrelations between residual vFFR and post-PCI FFR and between residual vFFR and post-PCI vFFR were evaluated.In addition, the diagnostic accuracy of residual vFFR to identify post-PCI FFR <0.90 was assessed. The threshold of <0.90 for post-PCI FFR has been selected based on prior reports suggesting more favorable clinical outcomes in case the post PCI FFR values exceeded this threshold ,11.t-test. Continuous variables with non-normal distribution are presented as median (25th–75th percentile), and compared using the Mann–Whitney test. Categorical variables are shown as counts and percentages and compared with the use of chi-square or Fisher exact tests. The correlations between residual vFFR and post-PCI FFR and post-PCI vFFR were evaluated using the Pearson R or Spearman’s rank correlation coefficients, for variables with normal and non-normal distribution, respectively. Agreement between the indices was evaluated by Bland–Altman plots depicting mean differences and corresponding 95% limits of agreement.Variable distributions were evaluated by Kolmogorov–Smirnov tests. Normally distributed continuous variables are displayed as mean ± standard deviation (SD), and compared using the Student’s Receiver–operating curves (ROC) were used to assess the discriminative ability of the residual vFFR to detect a post-PCI microcatheter-based FFR < 0.9 which has been used in previous studies as a cut-off value to predict clinical outcome ,12,13. Sn = 90), lack of two sufficient orthogonal angiographic views > 30 degrees or substantial overlap/foreshortening in pre-PCI (n = 19) or post-PCI (n = 21) angiograms, inadequate pressure waveforms (n = 10) or assessment of bypass grafts (n = 9). Baseline clinical characteristics are summarized in A total of 200 patients who underwent post-PCI evaluation with invasive FFR were screened. Residual ‘virtual stenting’ vFFR and post-PCI vFFR computation were subsequently performed in 81 eligible individuals. Key reasons for screening failure included: presentation with STEMI  were male. Diabetes was present in 20 (24.7%) of the patients. A history of previous myocardial infarction (MI) or prior PCI was present in 18.5% and 30.9% of the patients, respectively. In 49.4% of the patients, the FFR measurement was performed in the left anterior descending artery. Mean 3D QCA-based diameter stenosis pre-PCI was 53 ± 15% with a reference vessel diameter of 2.90 ± 0.65 mm . Mean prp < 0.001) as well as between residual vFFR and post-PCI vFFR   and actual post-PCI FFR value (0.91 ± 0.06). Likewise, no differences were found between estimated residual vFFR (0.91 ± 0.06) and post-PCI vFFR (0.92 ± 0.05). A good linear correlation was observed between residual vFFR and post-PCI FFR  A. Bland < 0.001) B, wherea< 0.001) B.p < 0.001) (There were 31 lesions (38.5%) identified with post-PCI FFR < 0.90. Residual vFFR showed a good accuracy in the identification of lesions with post-PCI FFR < 0.90  0.93 (95% CI: 0.86–0.99), < 0.001) .The present study is the first to evaluate the feasibility of vFFR estimation of post PCI functional outcome. Residual vFFR calculated based on pre-PCI angiograms simulating the effects of coronary stent implantation correlates well with both post-PCI FFR and post-PCI vFFR values. Moreover, discriminative ability for post-PCI FFR < 0.9 was good, without the necessity for an invasive pressure wire or microcatheter and pharmacological induction of hyperemia, before actual stent implantation in patients presenting with either chronic coronary syndrome or non-ST-ACS.Indeed, a considerable proportion of patients after successful PCI still suffer from angina . The latThe presented findings, although preliminary, constitute another step forward in the development of virtual PCI planning tools. Our study extends prior observations from computed tomography coronary angiography (CCTA) based FFRCT PCI planning software  and otheImportantly, virtual stenting vFFR cannot account for heavy calcifications or stent underexpansion; the software used in this study assumes an almost perfect PCI result.Virtual stenting vFFR predicts the physiological response to PCI and is not intended to be a replacement for optical coherence tomography or intravascular ultrasonography in determining procedural success, which is dependent on several procedural factors . As suchThe following limitations of this study need to be noted while interpreting its results. This is a retrospective cohort study with a relatively small sample size. The residual vFFR was compared with post PCI FFR analyzed with a dedicated microcatheter known to slightly overestimate FFR values ,37. ImpoPre-PCI estimation of ‘residual’ vFFR based upon invasive angiographic imaging is feasible, correlates well with post PCI invasive FFR and vFFR measurements and can predict physiological response to stenting with high accuracy. Further studies are needed to evaluate the efficacy and safety of 3D-QCA based FFR-guided coronary interventions.