bluuebunny/crossref_metadata_2025 huggingface dataset:
The electronic transport properties affected by B/N doping in graphene-based molecular devices
Authors: Deng Xiao-Qing  , Yang Chang-Hu  , Zhang Hua-Lin  ,   School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114, China
Published: December 2020

The electron transport properties of the system consisting of the zigzag graphene nanoflake doped with nitrogen and boron atoms connected to two Au electrodes through S-Au bonds are investigated theoretically. The results show that a nanoflake doped with nitrogen and boron atoms at edges has poor rectifying performance. While the system consisting of two pieces of graphene flakes doped by boron and nitrogen atoms, respectively, and linked with an alkane chain, shows good performance. And the significant effects of the doped sites on the current-voltage characteristics are observed. The mechanisms for these phenomena are explained by the different shifts of transmission spectra, the different spatial distributions of the molecular projected self-consistent Hamiltonian eigenstates. The negative differential resistance behavior results from the biase induced shifts of the energy level and change of the resonance transmission spectra, and the suppression of the relevant channels at some bias voltages.
A class of associated chaotic system, its switching and internal synchronization mechanism
Authors: Zhou Xiao-Yong  , Qiao Xiao-Hua  , Zhu Lei  , Liu Su-Fen  ,   Department of Electric and Information Engineering, Jangsu University of Technology 213001, China
Published: December 2020

A novel class of the associated chaotic systems with switching and synchronization features is proposed in this paper. The system can be switched between the same-dimensional systems, can also be switched between different-dimensional systems, when the system is switched to a four-dimensional system, the synchronization between the system variables can be realized. Basic dynamic properties and the internal synchronization mechanism of the new system are investigated via theoretical analysis, numerical simulation, Lyapunov dimension and Lyapunov exponent spectrum. Finally, the hardware for circuit of the switching chaotic system is designed and realized by using Multisim software; the chaotic system and its synchronization characteristics are simulated and achieved at the same time. The numerical simulation and circuit simulation confirm that the switching chaotic system can be realized physically, and the system has shown rich dynamic properties.
Two-photon excitation in H2X (X=O, S, Se, Te)
Authors: Wang Hong-Bin  , Jiang Gang  , Zhu Zheng-He  , Wan Ming-Jie  ,   Institute of Atomic and Molecular Physics, Chengdu 610065, China
Published: December 2020

The present work is mainly to study two-photon process in H2X (X=O, S, Se, Te) by using the full relativistic theory. For comparison, we also study the single-photon process by SAC-CI method. The transition probability of two-photon excitation is 10-2–10-5 times of the single-photon process; the relativistic effects become more and more obvious with the increase of atomic number. In addition, every molecule observes the selection principles; dipole transition component and oscillator strength of individual symmetrical states are greater than those of other individual states. This is due to the symmetry of molecule and it should be an important basis for selecting transition energy.
Study of data format transform with optical waveguide resonators
Authors: Zhang Li-Bin  , Chen Shao-Wu  , Fei Yong-Hao  , Cao Tong-Tong  , Cao Yan-Mei  , Lei Xun  ,   State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

Based on the linear property of silicon microring resonators, we experimentally observed that such resonator can transform square-wave signal into pulse-wave signal, and the output waveform is strongly dependent on the input wavelength. We then proposed a mathematical model, which utilized linear coupling mode theory, Fourier transform and electro-optical Mach-Zehnder (MZ) intensity modulation functions. The numerical simulation results fit well with the experimental results. Besides, we gave a detailed explanation based on the transfer function of microrings. Furthermore, we have studied the case when the ring resonator is deviated from the critical coupling condition, and found that the coupling state, over coupling or under coupling, can be easily judged through the output waveform.
Martensitic transformation and magnetic properties in Ga-doped MMX alloy MnNiGe1-x Gax (x=00.30)
Authors: Zhang Yu-Jie  , Liu En-Ke  , Zhang Hong-Guo  , Li Gui-Jiang  , Chen Jing-Lan  , Wang Wen-Hong  , Wu Guang-Heng  ,   Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The characteristics of martensitic transformation and magnetostructural coupling have been investigated for MnNiGe1-xGax (x=00.30) alloys. It has been found that the martensitic transformation temperature of the system can be deceased about 400 K by doping a low content of Ga to substitute for Ge. Adding Ga may weaken the hybridization and at the same time enhance the magnetic exchange interaction, which are responsible for the increase of the atomic moment and the Curie temperature in the austenitic phase. The structural and magnetic phase diagram was obtained to show some important points: 1) the decreased transition temperature successively pass through the Neel temperature and the Curie temperature; 2) the Curie temperature window still opens during the doping; 3) the magnetism can effectively affect the transformation behavior. The metamagnetization and the preparation influence on the transformation are also observed. These properties are significantly beneficial to the development of new magnetostructural materials.
Luminescent properties and energy transfer mechanism of CaWO4：Sm3+ phosphors
Authors: Bi Chang-Hong  , Meng Qing-Yu  ,   Key Laboratory for Photonic and Electric Bandgap Materials, Ministry of Education, School of Physics and Electronic Engineering, Harbin Normal University, Harbin 150025, China
Published: December 2020

The scheelite-structured CaWO4 phosphors doped with different concentrations of Sm3+ were prepared by precipitation method. Photoluminescence properties of Sm3+-doped CaWO4 samples were studied. Results indicate that red light emission of Sm3+ with higher color purity in the samples can be excited by 404 nm blue light. There are 4f-4f intrinsic emission of Sm3+ and a strong self-excitation emission of CaWO4 when excited by 240 nm short-wave ultraviolet, and the white light emission can be obtained. Experiments show that the best Sm3+ doping concentration is 2%. The energy transfer type between Sm3+ ions was determined to be the electric dipole-electric dipole interaction and the critical energy transfer distance (Dc) was calculated to be 2.0 nm.
Effects of transverse electromagnetic field distribution in the multipactor discharge on dielectric window surface
Authors: Dong Ye  , Dong Zhi-Wei  , Yang Wen-Yuan  , Zhou Qian-Hong  , Zhou Hai-Jing  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: December 2020

By using a P3D3V PIC code programmed by the authors, the multipactor discharge effects on dielectric inner and outer surface under high-power microwave with TE10 mode in the BJ32 rectangular waveguide are numerically studied. The electron spatial distribution, distribution of electric field in the normal direction of the dielectric surface, and electron density spatial distribution are presented. Numerical results could be concluded as follows. For inner surface, the multipacting first occurs in the area with large electric-field of microwave; for the outer surface, multipacting first occurs in the area with small electric-field of microwave. The above phenomena could be explained as follows. Poynting direction of microwave is the same as the outer surface normal direction and opposite to the inner surface normal direction. So the drift in the area with large electric-field of microwave causes electrons easy to move back to inner surface, and so electrons are easy to leave from outer surface. Compared with 1D3V model, in P3D3V model, we have for inner surface multipactor discharge with long oscillator forming time, small secondary electron number, high average electron energy, low incident power of microwave, and low level deposited power; for outer surface, we have multipactor discharge with short oscillator forming time, small secondary electron number, low average electron energy, low incident power of microwave, and low level deposited power. The deposited power is about 1%–2% of incident microwave power both in 1D3V and P3D3V models; while the ratio between deposited power and incident power of microwave has nothing to do with microwave parameters and inner or outer surface.
An accurate macro-cell-method for extracting dispersion characteristics of 1D reciprocal microwave structures with finite periodicity
Authors: Gong Jian-Qiang  , Liang Chang-Hong  ,   National Laboratory of Science and Technology on Antennas and Microwaves, Xidian University, Xi’an 710071, China
Published: December 2020

A novel macro-cell-method (MCM) has been proposed, which is capable of accurately extracting the dispersion characteristics of 1D reciprocal microwave structures with finite periodicity. In practice a single macro-cell consists of multiple periodic unit cells, therefore the electromagnetic coupling effects among unit cells can be rigorously considered. The eigen transfer factors ξN and 1/ξN corresponding to the forward and backward Bloch waves can be calculated in terms of the Bloch theory. Imposing complex logarithmic operation to ξN, the attenuation constant α can be univocally determined, while multiple integer branches exist in the solution of the phase shift constant β due to the multiroots property of the complex logarithm function. The rational integer branch is uniquely selected by comparing β from the MCM with that extracted from the unwrapping-method (UPM), regarding β from the UPM as the approximate value. Compared to the conventional eigenmode-method, UPM and single-cell-method, the MCM has no requirements to the coupling intensity among unit cells comprising finitely periodic structures, and with such good generality and accuracy, the MCM can be an effective tool for characterizing 1D reciprocal finitely periodic structures, facilitating their wide applications in microwave engineering.
Shielding effectiveness of a metal cavity covered by a material with a medium conductivity
Authors: Niu Shuai  , Jiao Chong-Qing  , Li Lin  ,   State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
Published: December 2020

The electromagnetic shielding effectiveness (SE) of a metal cavity covered by a material of medium conductivity is investigated theoretically by using an equivalent circuit method based on the transmission line and waveguide theory. The validity of the theoretical model is verified by comparison with the electromagnetic simulation software. The position effect and the resonance effect of the SE are calculated. A method for evaluating the SE of materials is suggested. With this method, the influence of the resonance effect and the position effect can be impaired greatly, also the SE of materials against plane wave can be evaluated directly.
Stability study on high sensitive CO monitoring in near-infrared
Authors: Xia Hua  , Wu Bian  , Zhang Zhi-Rong  , Pang Tao  , Dong Feng-Zhong  , Wang Yu  ,   Anhui Institute of Optics & Fine Mechanics, Chinese Academy of Sciences, Anhui Provincial Key Laboratory of Photonic Devices and Materials, Hefei 230031, China
Published: December 2020

CO is an indicative gas of coal spontaneous combustion warning and mine production safety instruction, whose detection process generally requires fiber long-haul transmission. However, currently, the communication fiber windows are mainly in the near-infrared band, so it is very significance to realize highly sensitive CO detection at near-infrared band. Tunable diode laser absorption spectroscopy (TDLAS) technology has advantages of high sensitivity, high resolution, fast response ability and no-contact, which has been widely used in air pollution monitoring, industrial and agricultural production process control, and many other fields. Long-path multi-pass cell can effectively improve the TDLAS detection capabilities, at the same time, the whole system is more compact. In this paper, 1566.64 nm DFB laser and the novel multi-pass cell with an optical path 56.7 m are used to detect different CO concentrations in long-term, while the system stability and linearity are analyzed. In addition, the detection limit is 0.25 ppmv with 30 s integration time by calculating the Allan variance. It means that we have primarily achieved highly sensitive detection of CO in the near-infrared bands.
Effects of surface tension on Rayleigh-Taylor instability
Authors: Xia Tong-Jun  , Dong Yong-Qiang  , Cao Yi-Gang  ,   School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001, China;,   Department of Physics and Hydroelectricity, Gansu National Normal University, Hezuo 747000, China;,   Information College of Electronic-Engineering, Xuchang University, Xuchang 461000, China
Published: December 2020

In this paper, Layzers model which has a simple velocity potential, and Zufirias model are extended to the case of non-ideal fluids, and the effects of surface tension on Rayleigh-Taylor instability are investigated. Firstly, the analytical expressions for the asymptotic bubble velocity and curvature are obtained in the two models. Secondly, the effects of surface tension on Rayleigh-Taylor instability are studied systematically. Finally, the two models are compared with each other and the comparisons with numerical simulation are made as well. The results indicate that the surface tension depresses the bubble velocity, but does not affect the bubble curvature. The Layzers model with the simple velocity potential gives a smaller bubble velocity than that predicted by the Layzers model with a complex velocity potential. But the bubble velocity predicted by the Layzers model with the simple velocity potential is larger than that obtained by Zufirias model. Both Layzers models lead to the same bubble velocity when the Atwood number is A = 1.
The investigation of LED degradation model based on the chemical kinetics
Authors: Guo Chun-Sheng  , Zhang Yan-Feng  , Wan Ning  , Li Rui  , Zhu Hui  , Feng Shi-Wei  ,   College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing 100124, China
Published: December 2020

The degradation of a device can be described by the degradation model in the accelerated tests. Because the degradation is closely related to the degradation mechanism, which reflects the intrinsic physical or chemical reactions, the degradation model can be established based on the temperature effect on the reaction rate and the change of reaction volume concentration in the physical/chemical reactions. Different degradation processes can be studied using the degradation model, including both the monotonic and nonmonotonic degradation processes. Moreover, the accelerated test is carried out for the GaN LED, figuring out the parameters for the degradation model, the ratio of different degradation processes, and the time constant.
All optical quartz-enhanced photoacoustic spectroscopy
Authors: Liu Yan-Yan  , Dong Lei  , Wu Hong-Peng  , Zheng Hua-Dan  , Ma Wei-Guang  , Zhang Lei  , Yin Wang-Bao  , Jia Suo-Tang  ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China
Published: December 2020

A trace gas sensor based on all optical quartz-enhanced photoacoustic spectroscopy (QEPAS) is designed and demonstrated. An extra detection light beam is added to the traditional QEPAS setup to convert the amplitude of vibration of the quartz tuning fork, which is proportional to the concentration of the target gas, into the variation of the detection light intensity. As a result, there are not any electrical components near the measurement position. Such a design makes it immune to electromagnetic interference and provides a compact sensor head, which can be used in a tiny space or an adverse environment. Using the new setup to measure the water concentration in air, the obtained noise equivalent absorption coefficient is 1.13×10-6 cm-1W/√Hz. The approaches to further optimizing the system and improving the sensitivity are also discussed in detail.
Modeling and experimental study of the mechanism of electrification from aero-engine jet
Authors: Zhu Li  , Liu Shang-He  , Zheng Hui-Zhi  , Wei Ming  , Hu Xiao-Feng  , Sorokin Andrey  ,   Institute of Electrostatic and Electromagnetic Protection, Ordnance Engineering College, Shijiazhuang 050003, China;,   People’s Liberation Army of 95, 927 troops, Cangzhou 061000, China;,   Central Institute of Aviation Motors, 2 Aviamotornaya Str., Moscow 111116 Russia
Published: December 2020

To investigate the mechanism of electrification from aero-engine jet and the electrification effect on the overall charging characteristics of vehicle, a simulation model of concentration of charged particles in aero-engine is build based on the equations of fluid motion. And concentration changes of various particles are simulated. To verify the simulation result, a special electrostatic induction sensor for detecting the electrification of engine jet is designed, according to the principle of the Faraday cup, to measure the dynamic potential when the turbofan engine starts, operates steadily, accelerates, decelerates and stops. The simulation and experimental results show that the aircraft is negatively charged by the electrification from aero-engine jet and the mechanism of electrification from aero-engine jet is described specifically. The research may provide a guidance to the further study on analyzing the overall charging characteristics of vehicle during the flight.
Numerical simulation of coupled arc in double electrode tungsten inert gas welding
Authors: Wang Xin-Xin  , Fan Ding  , Huang Jian-Kang  , Huang Yong  ,   State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050, China;,   Key Laboratory of Non-ferrous Metal Alloys, The Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China
Published: December 2020

A three-dimensional quasi-steady state mathematical model for the coupled arc in double electrode tungsten inert gas (TIG) welding is established based on the fluid dynamic equations and Maxwell equations under the reasonable boundary conditions. By solving these equations, the distributions of temperature, velocity, arc pressure and current density of the coupled arc are obtained. The results accord well with previous experimental results. It is found that the maximum temperature and plasma velocity of the coupled arc decrease compared with those of the TIG arc in the similar conditions. The peak value of arc pressure and current density at the anode surface decline sharply. Both the electrode spacing and arc length have significant influences on temperature and flow field, current density, and arc pressure of the coupled arc. Furthermore, coupled arc pressure and current density at the anode cannot be described by Gaussian assumption.
Design and simulation of chaotic circuit for flux-controlled memristor and charge-controlled memristor
Authors: Hong Qing-Hui  , Zeng Yi-Cheng  , Li Zhi-Jun  ,   Department of Photoelectric Engineering, Xiangtan University, Xiangtan 411105, China;,   College of Information Engineering, Xiangtan University, Xiangtan 411105, China
Published: December 2020

In this work,we design a fifth-order chaotic circuit with HP memristors, which consists of a flux-controlled memristor and a charge-controlled memristor. By changing the control parameters, the circuit evolves into different orbits, such as periodic orbits, double-scroll, of single-scroll. In order to ensure the occurrence of chaotic behaviors in the circuit, simulators of the charge-controlled memristor and the flux-controlled memristor are designed with conventional electronic devices, and Pspice simulation is conducted on the resulting circuit. Pspice simulation results verify the correctness of the theorectical analysis.
Study on the temperature modified method for monitoring gas concentrations with tunable diode laser absorption spectroscopy
Authors: Zhang Zhi-Rong  , Wu Bian  , Xia Hua  , Pang Tao  , Wang Gao-Xuan  , Sun Peng-Shuai  , Dong Feng-Zhong  , Wang Yu  ,   Anhui Provincial Key Laboratory of Photonic Devices and Materials, Anhui Institute of Optics & Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

Tunable diode laser absorption spectroscopy (TDLAS) is often used to detect gas concentrations in many fields. But because of the variation of ambient temperature, the measured harmonic signal amplitudes are affected and may lead to the monitoring errors. The impact of temperature on the measurement as well as the temperature compensation method is emphasized. So in order to modify the inversion results and adapt industrial measurement, combustion diagnostics, the numerical fitting empirical modified equation and theoretical modified equation from HITRAN database are discussed and compared in this paper. In experiment, the 21% oxygen as the safety monitoring gas and absorption wavelength at 760.77 nm are employed. Meanwhile, the first harmonic signals are also used to decrease the laser intensity fluctuations. We thus obtained the unmodified and modified results with the tube furnace in the temperature range 300–900 K (interval 50 K). Experimental results show that these two modified methods have some effective influence on the temperature changes and can be applied to gas monitoring correction to improve the accuracy and feasibility of the TDLAS technology. In addition, the methods also provide evidence for the real-time gas monitoring in the application of combustion diagnosis.
Molecular dynamics study on the structure and properties of silicon-graphdiyne
Authors: Yan Xiao  , Xin Zi-Hua  , Zhang Jiao-Jiao  ,   Department of Physics, Shanghai University, Shanghai 200444, China
Published: December 2020

A study to shed light on the existence of silicon-graphdiyne as well as their stability, structural and other properties, has been carried out using an efficient semi-empirical Hamiltonian scheme based on quantum mechanics. Its most stable structure is a single planar structure with a lattice constant of 12.251 Å. The system occurs structural phase transition at 1520 K. When the temperature is above 1520 K, the basic structure will be destroyed, While the temperature is below 1520 K, the system can restore its initial structure. It is found that sp hybridization exists between Si and C atoms in this conjugated structure. The study of pair distribution function shows that sp bond length is about 1.58 Å. The sp hybridization would gradually transform into other forms of hybridization at high temperatures. Our calculation indicates that delocalized π-bonds exist in this system and all the lengths of Si-C bonds tend to be more uniform. The energy gap is 1.416 eV. LUMO and HOMO energy levels are 0.386 eV and –1.03 eV respectively. It is found that the silicon-graphdiyne should be n-type material.
Correlation-based analytical modeling of MIMO systems with hybrid-diversity antenna
Authors: Hai Lin  , Zhang Ye-Rong  , Pan Can-Lin  ,   College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
Published: December 2020

By considering the correlations between cross-polarized sub-channels, the traditional multi-input multi-output (MIMO) channel models are proved to be unable to reflect the effect of antenna polarization on correlation coefficients. To solve the problem, a new modeling theory is proposed to amend the traditional model. Furthermore, the method of calculating correlation coefficients of the MIMO system with hybrid-diversity antennas in traditional channel models is proved to be an inaccurate approximation, and a new method of modeling with statistical data of MIMO systems with hybrid-diversity antennas is presented. The new model is able to replicate the correlation coefficients accurately and meet the high-precision requirements.
Studies on sulpho-selenization of electrodeposited Cu-In-Ga metallic precursor
Authors: Zhang Chao  , Ao Jian-Ping  , Bi Jin-Lian  , Yao Li-Yong  , Sun Guo-Zhong  , Zhou Zhi-Qiang  , He Qing  , Sun Yun  ,   Tianjin Key Laboratory of Photo-Electronic Thin FilmDevices and Technology, Institute of Photo-Electronic Thin FilmDevices and Technique, Nankai University, Key Laboratory of Optoelectronic Information Technology, Ministry of Education (Nankai University Tianjin University), Tianjin 300071, China
Published: December 2020

In this paper, the electrodeposited Cu-In-Ga metallic precursors have been sulpho-selenized by using H2S gas as the sulfur source and Se vapor as selenium source. Through the comparative experiments of selenization, sulfization and sulpho-selenization of the Cu-In-Ga metallic precursor, it has been found that the formations of CuInS2 phase and CuIn(S,Se)2 phase have priority over and restrain the formation of CuInSe2, so that the InSe phase diffuses into the film and weakens the phenomenon of separation into two phases in the film. Then the process of first selenization and sulfization next was made to optimize the preparation of Cu(In,Ga)(S,Se)2 film. At 250 ℃, the pre-selenization temperature, the solar cells with 570 mV open circuit voltage are prepared, while at a higher pre-selenization temperature, the solar cells with a large short-circuit current are prepared. Finally the optimized solar cell with 10.4% efficiency is obtained.
Novel ultra-broadband polarization beam splitter based on dual-core photonic crystal fiber
Authors: Han Bo-Lin  , Lou Shu-Qin  , Lu Wen-Liang  , Su Wei  , Zou Hui  , Wang Xin  ,   School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

A novel broadband polarization beam splitter (PBS) based on dual-core photonic crystal fiber is proposed. With a full-vector finite element method, the effects of structural parameters of fiber on the bandwidth and length of PBS are systematically investigated in detail. Numerical results indicate that an increase in the index of fluorine-doped region can not only broaden the bandwidth but also shorten the length of PBS. An increase in the diameters of air hole and hole pitch in an optical fiber can broaden the bandwidth of PBS, however, lengthen the length of PBS at the same time. Thus, it is necessary to balance the bandwidth and length of PBS when selecting the fiber structure parameters. Through optimizing the fiber structure parameters mentioned above, a kind of ultra-broadband PBS is achieved. When the extinction ratio is greater than 20 dB, the length of PBS is as short as 7.362 mm and its bandwidth is more than 600 nm.
Fetomaternal Outcome in Twin Pregnancies: A Retrospective Analysis from a Tertiary Care Centre
Authors: Kumari Kamlesh , Misra Minakshi , Jhanwar Ambika , Kumari Asha
Published: December 2020

Introduction: Twin pregnancies are among the major challenges faced by obstetricians globally. Increased maternal and foetal morbidity is observed with an increase in the incidence of twin pregnancies. Due to elevated rates of complications, a larger number of caesarean sections are performed in twin pregnancies in comparison to singleton gestation. Aim: The study aimed to find out the incidence of twin pregnancy with associated maternal risk factors and foetal outcome in the study population. Materials and Methods: This retrospective observational study was carried out at JNU Hospital and Medical College, Jaipur for a period of 4 years from December 2015 to December 2019. A total of 70 mothers, who presented with twin pregnancy, were included in this study. Data were collected from hospital records regarding maternal age, parity, whether spontaneous or assisted conception, gestational age, pregestational Body Mass Index (BMI) and family history. Details of maternal and foetal complications that occurred during the antenatal period and labour as well as the mode of delivery were collected and analysed. Statistical significance was considered if the p-value was ≤0.05. Qualitative data were represented as rate and proportions, while quantitative data were represented as mean and standard deviation. Results: A total of 70 mothers with twin births, resulting in 140 babies during the 4 years study period were included. A total of 4240 deliveries overall during the study period, gave a twin pregnancy incidence rate of 16.5 in 1000 deliveries. Preterm labour (25.4%), anaemia (26.8%) and hypertension (22.5%) were common problems. The most common indication for caesarean delivery was foetal malpresentation (37.8%) The mean weight of the first twin was 2.12±0.35 kg while the mean weight of the second twin was 1.97±0.30 kg. Among foetal complications, Intrauterine Growth Restriction (IUGR) was seen in 11.4% and birth weight discordance in 21.4% of children. A low Appearance, Pulse, Grimace, Activity, and Respiration (APGAR) score was noted in 21.4% of babies, while 12.9% of babies died in the early neonatal period. Conclusion: Maternal complications during twin pregnancy were mainly preterm labour, diabetes, hypertension and anaemia. Caesarean section was the main mode of delivery in this study with significant association with hypertension and preterm labour. Foetal complications were in the majority related to IUGR. More vigilance during the antenatal period and labour is needed for proper selection of mode of delivery. Active foetal surveillance and intervention with appropriate neonatal care can improve fetomaternal outcome.
Nicotinamide mononucleotide (NMN) protects bEnd.3 cells against H2O2‐induced damage via NAMPT and the NF‐κB p65 signalling pathway
Authors: Deng Xiujun , Liang Xinghuan , Yang Haiyan , Huang Zhenxing , Huang Xuemei , Liang Chunfeng , Kuang Yaqi , Qin Yingfen , Lin Faquan , Luo Zuojie
Published: December 2020

An increasing number of studies have shown that nicotinamide mononucleotide (NMN) can inhibit not only ageing but also oxidative stress and inflammatory reactions by improving energy metabolism. However, the role of NMN in regulating the anti‐apoptotic, antioxidative stress and inflammatory responses of brain microvascular endothelial cells is still unknown. Therefore, here we studied the effects of NMN on H2O2‐induced oxidative damage of bEnd.3 cells. In this study, we found that NMN could inhibit the NF‐κBp65 inflammatory signalling pathway and increase the expression of the enzymes NAMPT, VEGF and eNOS, alleviating H2O2‐induced apoptosis in bEnd.3 cells. Taken together, these results suggest that NMN reduces H2O2‐induced oxidative stress and apoptosis and improves cell functions by inhibiting the NF‐κBp65 inflammatory pathway and increasing NAMPT expression.
A sustainable approach to enhance fruit shelf‐life: Edible coating from pineapple fruit waste biomass
Authors: Bhattacharjee Satyajit , Haldar Dibyajyoti , Manna Mriganka Sekhar , Gayen Kalyan , Bhowmick Tridib Kumar
Published: December 2020

The quality and commercial value of fruits largely depend on color, texture, appearance, nutritional value, and other factors that cease the growth of the microbes causing food spoilage. Coating with suitable edible material would keep fruits fresh for a considerable time after their harvest till it reaches to the demanding consumers. The nonedible portions (peel, crown) of pineapple are identified as an inexpensive source for the production of such edible coating material. The present work is focused on the extraction and physicochemical analysis of cellulose prepared from waste bio‐mass of pineapple fruit. Physicochemical characterization of the cellulose is performed using X‐ray diffraction, Fourier‐transform infrared spectroscopy and scanning electron microscopy. The extracted cellulose is converted to carboxymethyl cellulose and formulated as a coating film in conjugation with other suitable substances. The formulated coating is applied on banana fruit to check the performance of protection against the natural degradation of the fruit. FTIR analysis of the extracted cellulose has confirmed the removal of lignin and hemicelluloses molecules from the waste biomass of pineapple. X‐ray diffraction analysis has shown the crystal size of extracted cellulose was 3.23 nm with 35.62% crystallinity. Degree of substitution (DS) is estimated 0.523 for carboxymethyl cellulose prepared from the extracted cellulose. Application of coating has shown the increment in shelf‐life period of banana in comparison with control up to 8 days of storage at ambient condition. This study has demonstrated a sustainable process to transform waste biomass into carboxymethyl cellulose based coating for improving storage capacity of banana fruit.
A waterproof and breathable nanofibrous membrane with thermal‐regulated property for multifunctional textile application
Authors: Yi Liqiang , Wang Shuoshuo , Wang Lina , Yao Juming , Marek Jaromir , Zhang Ming
Published: December 2020

In this work, a waterproof and breathable nanofibrous membrane with thermal‐regulated performance and exhibits excellent mechanical property is fabricated by coaxial electrospinning. The fiber shell is consisted of polyvinylidene fluoride (PVDF) and polyvinyl butyral (PVB), and the core is octadecane. First, well‐performed waterproof and breathable membranes are obtained by optimizing its morphology and pore structure. Then octadecane is loaded into the fibers in the form of core by coaxial electrospinning, though it gives the membranes a thermal regulating function, but the drawback is the sacrifice of overall properties. Thus, carbon nanotubes are loaded into the shell and studied, finally, the best membrane has a comprehensive performance with hydrostatic pressure of 59.2 kPa, water vapor transmission rate (WVTR) of 7.846 kg m−2 d−1, latent heat of 50.1 J g−1, as well as excellent tensile strength of 20.2 MPa, which shows its certain reference significance to the synthesis of multifunctional membrane.
Error propagation in constraint‐based modeling of Chinese hamster ovary cells
Authors: Széliová Diana , Iurashev Dmytro , Ruckerbauer David E , Koellensperger Gunda , Borth Nicole , Melcher Michael , Zanghellini Jürgen
Published: December 2020

Chinese hamster ovary (CHO) cells are the most popular mammalian cell factories for the production of glycosylated biopharmaceuticals. To further increase titer and productivity and ensure product quality, rational system‐level engineering strategies based on constraint‐based metabolic modeling, such as flux balance analysis (FBA), have gained strong interest. However, the quality of FBA predictions depends on the accuracy of the experimental input data, especially on the exchange rates of extracellular metabolites. Yet, it is not standard practice to devote sufficient attention to the accurate determination of these rates. In this work, we investigated to what degree the sampling frequency during a batch culture and the measurement errors of metabolite concentrations influence the accuracy of the calculated exchange rates and further, how this error then propagates into FBA predictions of growth rates. We determined that accurate measurements of essential amino acids with low uptake rates are crucial for the accuracy of FBA predictions, followed by a sufficient number of analyzed time points. We observed that the measured difference in growth rates of two cell lines can only be reliably predicted when both high measurement accuracy and sampling frequency are ensured.
Use of Platelet‐Rich Fibrin Membranes With Single Implant Placement for Peri‐Implant Mucosal Thickness Augmentation: A Case Series Study
Authors: Lima Victória Clara da Silva , Miguel Manuela Maria Viana , Ferraz Laís Fernanda Ferreira , Filho Antonio Braulino de Melo , Jardini Maria Aparecida Neves , Santamaria Mauro Pedrine
Published: December 2020

Introduction

The use of platelet‐rich fibrin (PRF) membranes has been evaluated for different purposes. However, few studies aimed to assess the effect of PRF membranes on peri‐implant mucosal thickness augmentation. Thus, the aim was to evaluate whether the use of PRF membranes placed using the same surgical procedure of single implant installation in the anterior area of the maxilla can result in peri‐implant mucosal thickness increase.

Case series

Eight patients received single maxillary implants (anterior area), covered by three PRF membranes (2,500 rpm/12 minutes, RCFmax = 719.71 g). Clinical parameters (baseline and 3 months postoperative) and patient‐centered parameters were evaluated. The buccal peri‐implant mucosal thickness (BMT) and ridge defect (RD) parameters showed a statistically significant difference, with a gain of 0.7 ± 0.3 mm in BMT and reduction of 0.8 ± 0.3 mm in RD. Supracrestal tissue height (STH) was >3 mm after 3 months. Postoperative pain and number of analgesics showed low values (0.95 ± 1.06 and 1.92 ± 2.75), respectively, using a visual analog scale (VAS).

Conclusion

The use of three PRF membranes along with single implant placement in the anterior maxilla led to an increase in the BMT.
Modification of clinoptilolite with dialkylphosphinic acid for the selective removal of cobalt (II) and nickel (II) from hydrometallurgical effluent
Authors: Kabuba John , Banza Musamba
Published: December 2020

This study describes the selective removal of cobalt (II) and nickel (II) from hydrometallurgical effluent using modified clinoptilolite. X‐ray fluorescence (XRF), x‐ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis were used to characterize the natural and modified clinoptilolites with dialkylphosphinic acid. In a batch experiment, the influence of different variables such as initial concentration, pH, particle size, clinoptilolites dosage, temperature, and contact time was evaluated. Higher removal efficiency was obtained at initial concentration of 600 mg/L, pH 6, particles size of 1000‐1400 μm, dosage of 10 g/100 mL, a temperature of 25°C, and contact time of 300 minutes. The experimental data fit satisfactorily to the pseudo‐second order kinetic and to the Langmuir isotherm model. Thermodynamic parameters like Gibb's free energy (ΔGo), enthalpy (ΔHo), and entropy (ΔSo) were also evaluated. The results revealed that modified clinoptilolite with dialkylphosphinic acid could be successfully employed for the selective removal of cobalt (II) and nickel (II) from hydrometallurgical effluent.
Almost‐Rigidity of Frameworks
Authors: Holmes‐Cerfon Miranda , Theran Louis , Gortler Steven J.
Published: December 2020

We extend the mathematical theory of rigidity of frameworks (graphs embedded in d‐dimensional space) to consider nonlocal rigidity and flexibility properties. We provide conditions on a framework under which (I) as the framework flexes continuously it must remain inside a small ball, a property we call “almost‐rigidity”; (II) any other framework with the same edge lengths must lie outside a much larger ball; (III) if the framework deforms by some given amount, its edge lengths change by a minimum amount; (IV) there is a nearby framework that is prestress stable, and thus rigid. The conditions can be tested efficiently using semidefinite programming. The test is a slight extension of the test for prestress stability of a framework, and gives analytic expressions for the radii of the balls and the edge length changes. Examples illustrate how the theory may be applied in practice, and we provide an algorithm to test for rigidity or almost‐rigidity. We briefly discuss how the theory may be applied to tensegrities. © 2020 Wiley Periodicals LLC.
Design, synthesis, in vitro and in silico studies of novel Schiff base derivatives of 2‐hydroxy‐4‐methoxybenzamide as tyrosinase inhibitors
Authors: Iraji Aida , Panahi Zahra , Edraki Najmeh , Khoshneviszadeh Mahsima , Khoshneviszadeh Mehdi
Published: December 2020

Due to the fact that tyrosinase is responsible for biosynthesis and regulation of melanins and browning food products, tyrosinase inhibitors can be favorable agents in cosmetics and medicinal industries. A series of novel 2‐hydroxy‐4‐methoxybenzohydrazide were designed, synthesized, and their new application as tyrosinase inhibitors was also disclosed. Based on in vitro tyrosinase inhibitory assay, 4d as the strongest inhibitor of tyrosinase with an IC50 value of 7.57 μM showed approximately 2.5‐fold better inhibition than kojic acid as positive control followed by two compounds 4b (IC50 = 8.19 ± 0.25 μM) and 4j (IC50 = 8.92 ± 0.016) which displayed preferable tyrosinase inhibitory activity. Detailed investigations on the mechanism of action of the 4d reported mix type of inhibition. More importantly, molecular modeling assessments proposed the ability of 4d for potential interaction with Cu (metal)‐His (residue) within tyrosinase active site. Overall, 4d is a promising candidate for the development of anti‐tyrosinase agents.
Stability region of hydropower plant with surge tank at HVDC sending terminal
Authors: Yang Weijia , Huang Yifan , Zhao Zhigao , Yang Jiandong , Yang Jiebin
Published: December 2020

This paper aims to study the stability region of hydropower plants (HPPs) at high‐voltage direct current (HVDC) sending terminal, to theoretically predict the frequency stability of isolated HPPs under small disturbances. The overall transfer function of the system is derived, and the Hurwitz stability criterion is applied to deduce the stability region. The theoretical analysis of the stability region and time‐domain simulation results of the system show good consistency, and this proves the accuracy of the model. The focus of this paper is mainly on the influence of the hydraulic‐mechanical aspects. Improperly tuned governor parameters and unfavourable design of the surge tank could lead to the frequency instability of HPPs, which appears as divergent oscillations of the frequency of units. A key suggestion of this paper is that the control strategy should consider the factors from not only the electrical side but also hydraulic‐mechanical aspects, for enhancing the stability of the HVDC sending terminal. Besides, the influence mechanism and parameter tuning of frequency limitation controller (FLC) are investigated and the results demonstrate its capability of quick compensation for power disturbances at the HVDC receiving terminal.
Multimodal imaging improves brain age prediction and reveals distinct abnormalities in patients with psychiatric and neurological disorders
Authors: Rokicki Jaroslav , Wolfers Thomas , Nordhøy Wibeke , Tesli Natalia , Quintana Daniel S. , Alnæs Dag , Richard Genevieve , de Lange Ann‐Marie G. , Lund Martina J. , Norbom Linn , Agartz Ingrid , Melle Ingrid , Nærland Terje , Selbæk Geir , Persson Karin , Nordvik Jan Egil , Schwarz Emanuel , Andreassen Ole A. , Kaufmann Tobias , Westlye Lars T.
Published: December 2020

The deviation between chronological age and age predicted using brain MRI is a putative marker of overall brain health. Age prediction based on structural MRI data shows high accuracy in common brain disorders. However, brain aging is complex and heterogenous, both in terms of individual differences and the underlying biological processes. Here, we implemented a multimodal model to estimate brain age using different combinations of cortical area, thickness and sub‐cortical volumes, cortical and subcortical T1/T2‐weighted ratios, and cerebral blood flow (CBF) based on arterial spin labeling. For each of the 11 models we assessed the age prediction accuracy in healthy controls (HC, n = 750) and compared the obtained brain age gaps (BAGs) between age‐matched subsets of HC and patients with Alzheimer's disease (AD, n = 54), mild (MCI, n = 90) and subjective (SCI, n = 56) cognitive impairment, schizophrenia spectrum (SZ, n = 159) and bipolar disorder (BD, n = 135). We found highest age prediction accuracy in HC when integrating all modalities. Furthermore, two‐group case–control classifications revealed highest accuracy for AD using global T1‐weighted BAG, while MCI, SCI, BD and SZ showed strongest effects in CBF‐based BAGs. Combining multiple MRI modalities improves brain age prediction and reveals distinct deviations in patients with psychiatric and neurological disorders. The multimodal BAG was most accurate in predicting age in HC, while group differences between patients and HC were often larger for BAGs based on single modalities. These findings indicate that multidimensional neuroimaging of patients may provide a brain‐based mapping of overlapping and distinct pathophysiology in common disorders.
Benign connective and soft‐tissue neoplasms of the oral and maxillofacial region: Cross‐sectional study of 1066 histopathological specimens
Authors: da Costa Adriana Aparecida Silva , Tavares Thalita Soares , Caldeira Patrícia Carlos , Barcelos Natália Santos , de Aguiar Maria Cássia Ferreira
Published: December 2020

Background

Benign connective and soft‐tissue neoplasms (CSTNs) are unusual in the head and neck region. The aim of the present study was to evaluate the demographic and clinicopathological features of these neoplasms.

Methods

A cross‐sectional study was conducted of cases diagnosed as benign CSTNs, with data collected from biopsy records. The chi‐square test was used. A p‐value <0.05 was considered indicative of statistical significance.

Results

Among the 38 119 specimens, 1066 (2.79%) were benign CSTNs: 369 fibroblastic/myofibroblastic, 250 adipocytic, 179 vascular, 130 neural, 94 osseous/cartilaginous, 19 muscular, and two fibrohistiocytic. Most patients were female (62.8%) and white‐skinned (45.8%). Mean age was 42 years. The tongue (25.2%) was the most affected site for extraosseous neoplasms.

Conclusion

This study had the largest sample of benign oral and maxillofacial CSTNs. Although these tumors have similar clinical features, the characterization and differentiation detailed here may help clinicians with regards to the correct diagnosis.
Comparison of three automatic chemiluminescent immunoassays for monitoring dynamic profile of SARS‐CoV‐2 IgG and IgM
Authors: Dou Xiaowen , Wang Enyun , Hu Jiwen , Zong Zengyan , Jiang Ruiwei , Wang Mengmeng , Kan Lijuan , Zhang Xiuming
Published: December 2020

Background

Seldom performance evaluation and diagnosis comparison studies were reported for different chemiluminescent immunoassay (CLIA) kits approved under an emergency approval program for SARS‐CoV‐2 infection.

Methods

A total of 100 and 105 serum separately from non‐infected populations and COVID‐19 patients were detected with SARS‐CoV‐2 IgM and IgG kits. The characteristics including precision, functional sensitivity, linearity, and accuracy were evaluated for Axceed, iFlash, and Maglumi CLIA kits.

Results

Maglumi and iFlash had the best analytical sensitivity for IgM and IgG, respectively. Axceed kits had a linearity response in the detected concentration. The clinical sensitivity of Axceed, iFlash, and Maglumi was 68.0%, 64.9%, and 63.9% with a specificity of 99.0%, 96.0%, and 100% for IgM, 85.6%, 97.9%, and 94.8% with a specificity of 97.0% for IgG. ROC analysis indicated all kits had a diagnostic power greater than 0.9. Notably, either IgM or IgG kits obtained a poor agreement (Kappa value from 0.397 to 0.713) with others. Among 38 recovered patients, 94.7% had an effective immune response, and both seropositive IgM and IgG accounted for the biggest proportion (medium, 42 days onset), then followed by the single seropositive IgG (medium, 50 days onset) in Ab profile.

Conclusion

The performance of CLIA kits satisfied the diagnosis of SARS‐CoV‐2 infection. Both positive of IgG and IgM contributes to improve the specificity, and a positive one will enhance the sensitivity.