bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Bernard–Soulier Syndrome Megakaryocytes and Platelets Using Patient-Derived Induced Pluripotent Stem Cells
Authors: Mekchay Ponthip , Ingrungruanglert Praewphan , Suphapeetiporn Kanya , Sosothikul Darintr , Ji-au Wilawan , Maneesri Le Grand Supang , Israsena Nipan , Rojnuckarin Ponlapat
Published: July 2019

Bernard–Soulier syndrome (BSS) is a hereditary macrothrombocytopenia caused by defects in the glycoprotein (GP) Ib-IX-V complex. The mechanism of giant platelet formation remains undefined. Currently, megakaryocytes (MKs) can be generated from induced pluripotent stem cells (iPSCs) to study platelet production under pharmacological or genetic manipulations. Here, we generated iPSC lines from two BSS patients with mutations in different genes (GP1BA and GP1BB: termed BSS-A and BSS-B, respectively). The iPSC-derived MKs and platelets were examined under electron microscopy and stained by immunofluorescence to observe proplatelet formation and measure platelet diameters which were defined by circumferential tubulin. BSS-iPSCs produced abnormal proplatelets with thick shafts and tips. In addition, compared with the normal iPSCs, the diameters were larger in platelets derived from BSS-A and BSS-B with the means ± standard deviations of 4.34 ± 0.043 and 3.88 ± 0.045 µm, respectively (wild-type iPSCs 2.61 ± 0.025 µm, p < 0.001). Electron microscopy revealed giant platelets with the abnormal demarcation membrane system. Correction of BSS-A and BSS-B-iPSCs using lentiviral vectors containing respective GP1BA and GP1BB genes improved proplatelet structures and platelet ultrastructures as well as reduced platelets sizes. In conclusion, the iPSC model can be used to explore molecular mechanisms and potential therapy for BSS.
A Multisite Examination of Everyday Discrimination and the Prevalence of Spontaneous Preterm Birth in African American and Latina Women in the United States
Authors: Fryer Kimberly E. , Vines Anissa I. , Stuebe Alison M.
Published: July 2019

Objective African American women have a higher risk of spontaneous preterm birth than White and Latina women. Although Latina women are exposed to similar social determinants of health, they have lower rates of spontaneous preterm birth. One theory for this difference is the maternal stress biological pathway, whereby lifetime stressors, such as racial discrimination, lead to a premature activation of parturition. We investigated the prevalence of self-reported discrimination and its association with the prevalence of spontaneous preterm birth.

Study Design Using data from the Community Child Health Research Network Study, a multisite cohort study from 2008 to 2012, we conducted a cross-sectional analysis of 1,154 African American women and 578 Latina women.

Results Adjusting for multiple risk factors, African American and Latina women who experienced the highest tertile of discrimination had a higher prevalence of preterm birth compared with those who experienced discrimination less than once per year, adjusted hazard ratio (aHR) = 1.5 (0.7–3.1) and 3.6 (0.9–14.4), respectively.

Conclusion In our cohort, we found a statistically significant association only in the medium discrimination group in Latina women, but we did not find a statistically significant association in African American women. Reduction in experienced discrimination may be an important intervention for reducing adverse pregnancy outcomes.
Team Stress and Adverse Events during Neonatal Tracheal Intubations: A Report from NEAR4NEOS
Authors: Umoren Rachel A. , Sawyer Taylor L. , Ades Anne , DeMeo Stephen , Foglia Elizabeth E. , Glass Kristen , Gray Megan M. , Barry James , Johnston Lindsay , Jung Philipp , Kim Jae H. , Krick Jeanne , Moussa Ahmed , Mulvey Christine , Nadkarni Vinay , Napolitano Natalie , Quek Bin Huey , Singh Neetu , Zenge Jeanne P. , Shults Justine , Nishisaki Akira ,   for the National Emergency Airway Registry for Neonates (NEAR4NEOS) Investigators
Published: July 2019

Objective This study aimed to examine the association between team stress level and adverse tracheal intubation (TI)-associated events during neonatal intubations.

Study Design TIs from 10 academic neonatal intensive care units were analyzed. Team stress level was rated immediately after TI using a 7-point Likert scale (1 = high stress). Associations among team stress, adverse TI-associated events, and TI characteristics were evaluated.

Result In this study, 208 of 2,009 TIs (10%) had high stress levels (score < 4). Oxygenation failure, hemodynamic instability, and family presence were associated with high stress level. Video laryngoscopy and premedication were associated with lower stress levels. High stress level TIs were associated with adverse TI-associated event rates (31 vs. 16%, p < 0.001), which remained significant after adjusting for potential confounders including patient, provider, and practice factors associated with high stress (odds ratio: 1.90, 96% confidence interval: 1.36–2.67, p < 0.001).

Conclusion High team stress levels during TI were more frequently reported among TIs with adverse events.
Methods of Glycemic Control and Neonatal Outcomes after Antenatal Corticosteroid Administration among Women with Pregestational Diabetes
Authors: Battarbee Ashley N. , Anderson Sarah B. , Tita Alan T.N. , Harper Lorie M.
Published: July 2019

Objective The objective of this study was to evaluate the association between the method of maternal glycemic control after antenatal corticosteroid, administration and maternal hyperglycemia and neonatal morbidity among women with diabetes.

Study Design This was a retrospective cohort study of women with pregestational diabetes who received antenatal corticosteroids and delivered in <34 weeks. The primary maternal outcome was adequate glycemic control, defined as <50% of glucose values above goal (fasting <100 mg/dL, 2-hour postprandial <120 mg/dL, or <115 mg/dL on insulin infusion). The primary neonatal outcome was composite morbidity (continuous positive airway pressure, mechanical ventilation, intraventricular hemorrhage, or death). Demographic characteristics and outcomes were compared by the method of glycemic control and neonatal morbidity using chi-square test, Fisher's exact test, Mann–Whitney U-test, and Student's t-test, as appropriate.

Results Of 52 eligible women, only 1 (1.9%) had adequate maternal glycemic control. There was no significant association between the method of glycemic control and maternal hyperglycemia or neonatal morbidity. There was no association between maternal glucose and neonatal morbidity; however, neonates with composite morbidity were more likely to be born to women who received less insulin.

Conclusion Maternal glycemic control among women with diabetes was poor after the antenatal corticosteroid administration, regardless of glycemic control method. Neither the method of maternal glycemic control nor the degree of control was associated with neonatal morbidity.
Liver Organoids Generated from Mice with Necrotizing Enterocolitis Have Reduced Regenerative Capacity
Authors: Miyake Hiromu , Lee Carol , Seo Shogo , Li Bo , Pierro Agostino
Published: July 2019

Introduction Necrotizing enterocolitis (NEC) is one of the most severe gastrointestinal diseases in infancy. NEC can cause metabolic derangements, multi-organ injury including severe liver damage. The mechanism leading to hepatic damage in NEC remains unclear. The aim of this study is to establish and characterize liver organoids from NEC mice.

Materials and Methods Following ethical approval (#44032), we induced experimental NEC from postnatal day 5 (P5) to P9 using C57BL/6 mice pups. NEC was induced by gavage formula feeding, gavage lipopolysaccharide (LPS) administration, and hypoxia. Breastfed pups were used as control. On P9, NEC and control pups were sacrificed and liver tissue was harvested and organoids were generated. Organoid size was recorded daily (day 2–4) by measuring their surface area and organoid growth was calculated. RNA was extracted on day 4 after liver organoid generation.

Results Organoid growth rate was significantly lower in NEC liver organoids compared to control liver organoids. mRNA expression of liver progenitor cells markers of LGR5 and SOX9 was lower in NEC liver organoids compared to control liver organoids. Similarly, expression of proliferation markers of Ki67 and PCNA was lower in NEC liver organoids.

Conclusion We report a novel technique to generate liver organoids during NEC. These organoids are characterized by reduced progenitor cells, reduced proliferation, and overall impaired regenerative capacity. Liver progenitor cells are important targets to prevent liver damage in NEC and promote recovery.
Factors that Influence Longitudinal Growth from Birth to 18 Months of Age in Infants with Gastroschisis
Authors: Nair Nitya , Merhar Stephanie , Wessel Jacqueline , Hall Eric , Kingma Paul S.
Published: July 2019

Objective This study aimed to investigate factors that influence growth in infants with gastroschisis.

Study Design Growth parameters at birth, discharge, 6, 12, and 18 months of age were collected from 42 infants with gastroschisis.

Results The mean z-scores for weight, length, and head circumference were below normal at birth and decreased between birth and discharge. Lower gestational age correlated with a worsening change in weight z-score from birth to discharge (rho 0.38, p = 0.01), but not with the change in weight z-score from discharge to 18 months (rho 0.04, p = 0.81). There was no correlation between the day of life when the enteral feeds were started and the change in weight z-score from birth to discharge (rho 0.12, p = 0.44) or discharge to 18 months (rho −0.15, p = 0.41).

Conclusion Our study demonstrates that infants with gastroschisis experience a significant decline in weight z-score between birth and discharge, and start to catch up on all growth parameters after discharge. Prematurity in gastroschisis infants is associated with a greater risk for weight loss during this time. This information emphasizes the importance of minimizing weight loss prior to discharge in premature infants with gastroschisis and highlights the need for optimal management strategies for these infants.
High Fetal Fraction on First Trimester Cell-Free DNA Aneuploidy Screening and Adverse Pregnancy Outcomes
Authors: Shook Lydia L. , Clapp Mark A. , Roberts Penelope S. , Bernstein Sarah N. , Goldfarb Ilona T.
Published: July 2019

Objective To test the hypothesis that high fetal fraction (FF) on first trimester cell-free deoxyribonucleic acid (cfDNA) aneuploidy screening is associated with adverse perinatal outcomes.

Study Design This is a single-institution retrospective cohort study of women who underwent cfDNA screening at <14 weeks' gestation and delivered a singleton infant between July 2016 and June 2018. Women with abnormal results were excluded. Women with high FF (≥95th percentile) were compared with women with normal FF (5th–95th percentiles). Outcomes investigated were preterm birth, small for gestational age, and hypertensive disorders of pregnancy.

Results A total of 2,033 women met inclusion criteria. The mean FF was 10.0%, and FF >16.5% was considered high (n = 102). Women with high FF had a greater chance of delivering a small for gestational age infant <fifth percentile, with an adjusted odds ratio of 2.4 (95% confidence interval: 1.1–4.8, p = 0.039). There was no significant association between high FF and either preterm birth or hypertensive disorders of pregnancy.

Conclusion Women with a high FF in the first trimester are at increased risk of delivering a small for gestational age infant <fifth percentile. Further investigation into the clinical implications of a high FF is warranted.
Interactions of plasticity and phase transformation under shock in iron bicrystals
Authors: Zhang Xueyang , Chen Jun , Hu Wangyu , Zhu Wenjun , Xiao Shifang , Deng Huiqiu , Cai Mengqiu
Published: July 2019

The interaction of plasticity and martensitic transformation in iron bicrystals under shock has been investigated via nonequilibrium molecular-dynamic simulations with our modified analytic embedded-atom model potential. Our results show that grain boundaries (GBs) can change the kinetics of α → ɛ martensitic transformations. The condition that GBs trigger strain induced transformation (SIT) is revealed, that is, the local structure of GBs can be converted to a hexagonal close packing (HCP) lattice with a lower potential barrier than the BCC → HCP transformation (stress assist transformation, SAT) because the driving energy of transition can be partly provided by the energy of GBs. It can explain why the threshold of the phase transition can be greatly reduced in samples containing some types of GBs. The threshold of SIT is lower than that of SAT, which agrees well with experimental results. Then, the nucleation kinetics of phase transition induced by dislocations are described. The propagation of dislocation provides the driving force for the nucleation of the phase transition. The dislocations can be directly emitted from the GBs under shock, which provides a new view that the phase transition is not always preceded by dislocations near GBs. In addition, dislocations can be induced by pre-existing dislocations under shock, which makes it understandable that GBs can emit dislocations. Our findings have an important significance for experimental studies and macroscopic and mesoscopic scale simulations regarding iron martensitic transformation.
Single-particle relaxation time in doped semiconductors beyond the Born approximation
Authors: Marchetti Gionni
Published: July 2019

We compare the magnitudes of the single-particle relaxation time exactly computed in the variable phase approach with those computed in the first Born approximation for doped semiconductors such as Si and GaAs, assuming that the Coulomb impurities are randomly distributed centers. We find that for typical dopant concentrations in Si, the Born approximation can overestimate the single-particle relaxation time by roughly 40% and underestimate it by roughly 30%. Finally, we show that the strong interference of phase shifts is missing in the strong scattering regime where the Born approximation fails.
Complexity reduction for sign configurations through the KP II equation and its information-theoretic aspects
Authors: Angelelli Mario
Published: July 2019

We provide a combinatorial setting to explore the information content associated with the fulfillment of the Kadomtsev-Petviashvili (KP) II equation. We start from a special family of solutions of KP II, namely, tau-functions of Wronskian type. A solution in this class can be expressed as a sum of exponentials, and we look at combinations of signs (signatures) for the nonvanishing terms in this sum. We prove a characterization of the signatures that return another solution of the KP II equation: they can be represented as choices of signs for columns and rows of a coefficient matrix, so we recover a function satisfying the whole KP hierarchy from this single constraint. The redundancy of this representation for different choices of the initial solution is investigated. Enumerative, information-theoretic, and geometric aspects of this construction are discussed.
Inverse scattering transform for the complex reverse space-time nonlocal modified Korteweg-de Vries equation with nonzero boundary conditions and constant phase shift
Authors: Luo Xu-Dan
Published: July 2019

Recently, the complex reverse space-time (RST) nonlocal modified Korteweg-de Vries equation (mKdV) was introduced and shown to be an integrable infinite-dimensional dynamical system. The inverse scattering transform (IST) for zero boundary condition was studied by Ablowitz and Musslimani in 2016. In this paper, the IST for the complex RST nonlocal mKdV equation with nonzero boundary conditions at infinity is presented. The direct and inverse scattering problems are analyzed. The method to carry out the inverse problem employs two Riemann surfaces associated with square root branch points in the eigenfunctions/scattering data, which is more complicated than that for the zero boundary condition. Four cases are considered, special soliton solutions are discussed, and an explicit 1-soliton and two 2-soliton are found for three cases. In another case, there are no solitons.
Effect of laser illumination on the electrical conductivity of single-crystal diamond needles
Authors: Arnoldi L. , Borz M. , Blum I. , Kleshch V. , Obraztsov A. , Vella A.
Published: July 2019

Herein, we present the results of electrical conductivity studies of single-crystal diamond needles. Pyramid-shaped needles of about hundreds of micrometers in length and about tens of micrometers in thickness were produced by oxidation of polycrystalline diamond films fabricated by chemical vapor deposition. The electrical conductivity of the needles was characterized via current measurements using a field ion microscope in the dark and under laser illumination. Considering the effects of laser intensity and wavelength on the measured current, we determine that the observed conduction regime corresponds to competing Ohmic and Poole-Frenkel conduction mechanisms. The measured values are in good agreement with the values reported previously for bulk and thin film diamond. The model that is proposed explains the electric conduction properties as well as light absorption and subsequent sample heating, with the presence of structural defects and impurities in diamond.
Photoreflectance and photoinduced microwave reflectance studies of surface band bending in Mg-doped InN
Authors: Kudrawiec R. , Janicki L. , Linhart W. M. , Mayer M. A. , Sharp I. D. , Choi S. , Bierwagen O. , Speck J. S. , Walukiewicz W.
Published: July 2019

Photoreflectance (PR) and microwave-reflectance photoconductivity-decay (μ-PCD) have been applied to study the surface band bending in Mg-doped InN layers with various Mg concentrations (∼1 × 1017 to ∼7 × 1019 cm−3) and thicknesses (∼400 to ∼3600 nm). A PR resonance related to the band-to-band transition at the Γ point below the surface electron accumulation is observed for moderately doped samples ([Mg]: 1.3 × 1017 cm−3 to 8.7 × 1017 cm−3). Samples with the Mg doping concentration in the range of ∼5 × 1018 ≤ [Mg] ≤ 7 × 1019 cm−3 are p-type and show very weak or no PR resonance. It is shown that the results correlate with the surface layer depletion thickness. The strongest PR signal is observed for thick depletion layers. The results are confirmed by μ-PCD measurements that show the longest carrier lifetimes for moderately doped samples with the thickest surface depletion layer.
Ground state energy of a dilute two-dimensional Bose gas from the Bogoliubov free energy functional
Authors: Fournais Søren , Napiórkowski Marcin , Reuvers Robin , Solovej Jan Philip
Published: July 2019

We extend the analysis of the Bogoliubov free energy functional to two dimensions at very low temperatures. For sufficiently weak interactions, we prove two term asymptotics for the ground state energy.
Equations of state for polyethylene and its shock-driven decomposition products
Authors: Maerzke Katie A. , Coe Joshua D. , Ticknor Christopher , Leiding Jeffrey A. , Tinka Gammel J. , Welch Cynthia F.
Published: July 2019

We construct new equations of state (EOS) for high density and ultrahigh molecular weight polyethylene and their chemical decomposition products under shock loading. The former were built using the SESAME framework, based in part on new specific heat and thermal expansion data reported here. The products EOS was based on thermochemical modeling under the assumption of full thermodynamic and chemical equilibrium. The products are represented as the ideal mixture of bulk carbon in the form of diamond, H2, H, and CH4. In the process of building a new EOS for the products, we recalibrated our exponential-6 pair potential for methane in order to better agree with data that have appeared since its original parameterization. The polyethylene EOS were calibrated to thermal, thermomechanical, and shock data, and their performance was evaluated in hydrodynamic modeling of deep release experiments reported previously.
A coupled oscillator model for the origin of bimodality and multimodality
Authors: Johnson J. D. , Abrams D. M.
Published: July 2019

Perhaps because of the elegance of the central limit theorem, it is often assumed that distributions in nature will approach singly-peaked, unimodal shapes reminiscent of the Gaussian normal distribution. However, many systems behave differently, with variables following apparently bimodal or multimodal distributions. Here, we argue that multimodality may emerge naturally as a result of repulsive or inhibitory coupling dynamics, and we show rigorously how it emerges for a broad class of coupling functions in variants of the paradigmatic Kuramoto model.
Influence of 3D plasmoid dynamics on the transition from collisional to kinetic reconnection
Authors: Stanier A. , Daughton W. , Le A. , Li X. , Bird R.
Published: July 2019

Within the resistive magnetohydrodynamic model, high-Lundquist number reconnection layers are unstable to the plasmoid instability, leading to a turbulent evolution where the reconnection rate can be independent of the underlying resistivity. However, the physical relevance of these results remains questionable for many applications. First, the reconnection electric field is often well above the runaway limit, implying that collisional resistivity is invalid. Furthermore, both theory and simulations suggest that plasmoid formation may rapidly induce a transition to kinetic scales, due to the formation of thin current sheets. Here, this problem is studied for the first time using a first-principles kinetic simulation with a Fokker-Planck collision operator in 3D. The low-β reconnecting current layer thins rapidly due to Joule heating before the onset of the oblique plasmoid instability. Linear growth rates for standard (ky = 0) tearing modes agree with semicollisional boundary layer theory, but the angular spectrum of oblique (|ky|>0) modes is significantly narrower than predicted. In the nonlinear regime, flux-ropes formed by the instability undergo complex interactions as they are advected and rotated by the reconnection outflow jets, leading to a turbulent state with stochastic magnetic field. In a manner similar to previous 2D results, super-Dreicer fields induce a transition to kinetic reconnection in thin current layers that form between flux-ropes. These results may be testable within new laboratory experiments.
Optical constants and band gap of wurtzite Al1−xScxN/Al2O3 prepared by magnetron sputter epitaxy for scandium concentrations up to x = 0.41
Authors: Baeumler Martina , Lu Yuan , Kurz Nicolas , Kirste Lutz , Prescher Mario , Christoph Tim , Wagner Joachim , Žukauskaitė Agnė , Ambacher Oliver
Published: July 2019

Wurtzite Al1−xScxN thin films with scandium Sc concentrations up to x = 0.41 were prepared by reactive pulsed DC magnetron co-sputtering at heater temperatures between 300 °C and 400 °C on Al2O3 substrates. Spectroscopic ellipsometry was used to determine the dielectric functions of wurtzite Al1−xScxN by modeling the spectra with a three-layer model involving parametric oscillator functions for the Al1−xScxN layers. By combining ellipsometry with transmission spectroscopy, we determined the composition dependence of the optical band gap Eg. For x < 0.25, the experimentally determined band gap follows the theoretical prediction with an offset, which arises from residual sub-band gap absorption. For higher Sc concentrations, for which the band gap is expected to become indirect, the experimental data deviate from the theoretical values for the direct band gap. No absorption that can be attributed to cubic ScN crystallites was observed up to x = 0.41, indicating a high phase purity in line with X-ray diffraction data.
Limiting factors and efficiencies of narrow bandgap single-absorber and multi-stage interband cascade thermophotovoltaic cells under monochromatic light illumination
Authors: Huang Wenxiang , Yang Rui Q.
Published: July 2019

In this work, the factors that limit the conversion efficiency of narrow bandgap thermophotovoltaic (TPV) cells are identified and their impact on device performance is explored through studying their effects on key aspects such as quantum efficiency (QE), fill factor, open-circuit voltage, and voltage efficiency. These factors are closely associated with short carrier lifetime, high dark saturation current density, small absorption coefficient, and the limiting effects of diffusion length on the collection of photogenerated carriers. Calculations are carried out for narrow bandgap InAs/GaSb superlattice materials to illustrate how the conversion efficiency is limited by these factors for specific material parameters such as the product of absorption coefficient α and diffusion length L. We show that the multistage interband cascade (IC) architecture is capable of circumventing the diffusion length limitation to overcome the problem of a low QE in conventional single-absorber TPV cells, thereby enhancing the conversion efficiency by about 10% in wide ranges of αL and bandgaps with the particle conversion efficiency approaching 100%. The enhancement of conversion efficiency with the multistage IC architecture is especially significant with small αL, which is more than double of that in the single-absorber TPV cell. Also, the device performance dependence on the illumination source is investigated, which demonstrates flexibilities and advantage of the multistage IC architecture to achieve its maximum conversion efficiency with the energy of incident photons near the bandgap of absorbers. Finally, the future directions are discussed in terms of what can be further improved or need to be addressed with the remaining issue for the development of narrow bandgap TPV cells.
Single-crystal diffractometer coupled with double-sided laser heating system at the Extreme Conditions Beamline P02.2 at PETRAIII
Authors: Bykova Elena , Aprilis Georgios , Bykov Maxim , Glazyrin Konstantin , Wendt Mario , Wenz Sergej , Liermann Hanns-Peter , Roeh Jan Torben , Ehnes Anita , Dubrovinskaia Natalia , Dubrovinsky Leonid
Published: July 2019

Combination of in situ laser heating with single-crystal X-ray diffraction (scXRD) in diamond anvil cells (DACs) provides a tool to study crystal structures and/or chemistry of materials at simultaneous high pressures and high temperatures. Here, we describe the first dedicated single-crystal X-ray diffractometer coupled with double-sided laser heating (dsLH) system. The scXRD/dsLH setup was developed for the P02.2 Extreme Conditions Beamline at PETRA III and became available for general users in 2017. It enables the collection of reliable scXRD data at simultaneous high pressure and high temperature. We demonstrate the performance of the setup on example of studies of iron and chromium nitrides.
Internal quantum efficiency of radiation in a bulk CH3NH3PbBr3 perovskite crystal quantified by using the omnidirectional photoluminescence spectroscopy
Authors: Kojima K. , Ikemura K. , Matsumori K. , Yamada Y. , Kanemitsu Y. , Chichibu S. F.
Published: July 2019

The internal quantum efficiency (IQE) of radiation for bulk CH3NH3PbBr3 crystals was quantified by using omnidirectional photoluminescence spectroscopy. The angle-resolved photoluminescence revealed that the emission with photon energies higher than the absorption-edge shows a Lambertian distribution and that the light extraction efficiency is determined by the escaping cone. The IQE value strongly depends on the photo-excitation density (P), and a CH3NH3PbBr3 crystal fabricated under the methylammonium-rich conditions gave the maximum IQE of 62.5% under P = 28 W/cm2. A further increase in P gave rise to the decrease in IQE due to the Auger effects.
Universal scaling behavior of resonant absorption
Authors: Yu D. J. , Van Doorsselaere T.
Published: July 2019

Mode conversion and resonant absorption are crucial mechanisms for wave transport and absorption. The scaling behavior of mode conversion or resonant absorption is well-known for electromagnetic and MHD waves in planar geometry. Our recent study showed that such a scaling behavior of resonant absorption could also exist for coronal loop oscillations with cylindrical geometry, but it was only tested for one density profile. Here, we generalize our previous study on the scaling behavior of resonant absorption by considering multiple density profiles. Applying an invariant imbedding method to the ideal MHD wave equations, we show that the scaling behavior also exists for these density models. We thus generalize our earlier results and show that such a universal scaling exists in cylindrical geometry, too. Given these results and the earlier results in planar geometry, we formulate a hypothesis that a universal scaling behavior exists regardless of the type of mode conversion or resonant absorption.
Surface chemistry and reactivity of α-MoO3 toward methane: A SCAN-functional based DFT study
Authors: Zhang Tianyu , Yang Xiaofeng , Ge Qingfeng
Published: July 2019

Molybdenum trioxide (α-MoO3) is a key component in the redox solid catalysts for methane activation. The wide range of interactions including van der Waals interaction and chemical bonding in α-MoO3 as well as between methane and the catalyst surface makes the accurate description of the methane chemistry a challenge. Herein, we performed a strongly constrained and appropriately normed (SCAN)-functional based density functional theory study of the surface chemistry and reactivity of α-MoO3 toward C–H bond activation of methane. With this meta-generalized-gradient approximation functional, we can predict the bulk structure of α-MoO3 more accurately while reproducing the thermal chemistry of MoO3. The results indicate that surface reduction of α-MoO3 (010) occurs preferably through releasing the terminal oxygen atoms, generating oxygen vacancies while exposing reduced Mo centers. These oxygen vacancies tend to be separated from each other at a higher density due to repulsive interactions. Furthermore, the reduced α-MoO3 (010) promotes methane activation kinetically by reducing the activation barrier for the break of the first C–H bond and thermodynamically by stabilizing the product state as compared with those on the stoichiometric surface. There is a synergy between the reduced Mo active site and surface lattice oxygen for C–H bond cleavage. Our results also show that the reactivity based on the Perdew-Burke-Ernzerhof functional is qualitatively consistent with that from the SCAN functional.
New modulation method in acousto-optic spectrometers
Authors: Pustovoit V.I.
Published: July 2019

A new method is proposed for modulating radiation in collinear acousto-optic (AO) spectrometers, which is based on the sequential diffraction of incident polarised optical radiation using two sound packets with the same frequencies and initial phases. A theory of diffraction of optical radiation on two successive packets of sound waves propagating in a crystal is constructed, and the instrumental function of the AO spectrometer is found. It is established that the instrumental function of such a spectrometer becomes time-dependent, and the modulation frequency of this dependence, in turn, depends on the intensity of the sound wave and on the detuning from the phase-matching conditions. The frequency dependence of the measured photocurrent for some finite number of sound packets is obtained explicitly, and it is shown that its measurement allows the spectral composition of the incident optical radiation to be determined with greater accuracy.
Use of heavily doped germanosilicate fibres with a small core diameter in stretchers of ultrashort laser pulses at a wavelength of 1.03 μm
Authors: Khudyakov D.V. , Ganin D.V. , Lyashedko A.D. , Borodkin A.A. , Likhachev M.E. , Salganskii M.Yu. , Vartapetov S.K.
Published: July 2019

The use of a heavily doped germanosilicate fibre with a W-profile refractive index and small core diameter in stretchers of ultrashort laser pulses with their subsequent amplification and compression in all-fibre laser systems is considered. The application of fibres of this type makes it possible to stretch, amplify, and then compress a laser pulse with minimum distortions of its initial shape and width. Due to the dispersion properties of these fibres, which allow the pulse duration to be increased significantly at a small fibre length and the third-order positive dispersion of the diffraction-grating-based output compressor to be compensated for, amplified pulses with an energy of 2 μJ and width of 250 fs, free of a picosecond pedestal, are obtained. Several types of fibres intended for the use in stretchers of ultrashort laser pulses are comparatively analysed from the point of view of their dispersion compatibility with a diffraction-grating-based output compressor.
Fluorescence and lasing in an electric-field-induced periodic structure of a cholesteric liquid crystal
Authors: Shtykov N.M. , Palto S.P. , Umanskii B.A. , Rybakov D.O. , Simdyankin I.V.
Published: July 2019

Fluorescence and lasing in a structure with an electric-field-induced spatially periodic director modulation in the plane of a planar-oriented layer of a cholesteric liquid crystal (CLC) is experimentally investigated. The thickness of the CLC layer is chosen close to the natural pitch of the cholesteric helix, which corresponds to the second Grandjean zone. The electric-field-induced periodic field of the CLC director leads to spatial modulation of the refractive index and the appearance of optical properties typical of 1D photonic crystals, when light propagating in the plane of the CLC layer experiences Bragg reflection. In polarised light, the induced spatial modulation of the refractive index manifests itself in the form of banded domains oriented in the plane of the CLC layer perpendicular to the original (unperturbed electric field) direction of the director in the centre of the layer. For the electric field strengths that correspond to fundamentally different distributions of the field of a CLC director, the fluorescence spectra of the DCM laser dye are studied both for different geometries (including the waveguide regime) and for different levels of optical pumping. In the range of electrical voltages corresponding to the induction of a spatially periodic photonic structure, multimode lasing in the waveguide regime is detected. It is shown that the mode composition of lasing depends on the electric field, which affects the properties of the distributed feedback.
Effect of a magnetic field on polarisation of light in an optical fibre with a random distribution of linear birefringence
Authors: Konyshev V.A. , Lukinykh S.N. , Nanii O.E. , Novikov A.G. , Treshchikov V.N. , Ubaydullaev R.R.
Published: July 2019

A numerical model is proposed to describe the evolution of polarisation of a light wave propagating through a telecommunication fibre with random linear birefringence in a magnetic field. As a result of statistical processing of a set of numerical simulation results, a convenient phenomenological formula is obtained for the first time for the dependence of the average value of the polarisation rotation angle on the magnetic field, the fibre parameters and its length. It is found that the average value of the polarisation rotation angle in a long telecommunication fibre in the representation of the Stokes vectors linearly depends on the applied longitudinal magnetic field (as in the classical Faraday effect for an isotropic medium) but is proportional to the root of the fibre length. It is theoretically shown and experimentally confirmed that the polarisation rotation angle for an extended segment of a telecommunication fibre (50 km) is two orders of magnitude less than that for an isotropic fibre of the same length and material.
Economical generation regime of a supersonic continuous-wave chemical DF laser
Authors: Fedorov I.A.
Published: July 2019

We have performed experimental and computer-aided theoretical studies of the effect of the dilution degree ψ
2 of a secondary fuel (deuterium) by an inert gas (helium) on the output characteristics of a supersonic cw chemical DF laser with a flat nozzle array, constructed in accordance with the nozzle – nozzle reagent mixing scheme. It is shown that an increase in the dilution degree in the range of 0 ⩽ ψ
2 ⩽ 20 leads to a monotonous increase in the lasing zone length (a decrease in the radiation load on the resonator mirrors) and a drop in the laser specific energy output. With an increase in the optical path length (a decrease in the threshold gain), the sensitivity of the laser energy characteristics to the dilution degree decreases. Consequently, for a high-power DF laser (with a long nozzle array) with partial replacement of expensive deuterium with cheaper helium, a potential possibility for the implementation of an economical generation regime with acceptable specific energy output is achieved. The conditions for the implementation of this regime are identified.
Rate equations for the diode laser and their applicability area
Authors: Bogatov A.P.
Published: July 2019

Taking into account spontaneous emission by adding its intensity in the form of a constant term to the laser emission intensity in rate equations is shown to be an inadequate approach. The use of rate equations without equations for phases of waves is limited to problems in which light is characterised by its total intensity, without its spectral composition. Such equations are incapable of adequately modelling the emission spectrum of diode lasers.
Scanning spectrometer/monochromator for a wavelength range of 50 – 330 Å
Authors: Shatokhin A.N. , Vishnyakov E.A. , Kolesnikov A.O. , Ragozin E.N.
Published: July 2019

A flat-field scanning spectrometer/monochromator of the Hettrick – Underwood type is implemented for a wavelength range λ ≈ 50 – 330 Å. The optical arrangement of the spectrograph comprises a focusing spherical (R = 6000 mm) mirror, mounted at a grazing angle of 8.34 °, and a grazing-incidence plane varied line-space (VLS) grating operating for a constant deflection angle of 16.68 °. The entrance and output slits of the instrument are immobile, and the focal distance varies only slightly over its operating spectral range. The short-wavelength boundary of the operating range is determined by the spectral source brightness and the reflection coefficients of the grating and the mirror rather than by defocusing. Laser-produced plasma spectra excited by a focused laser beam (0.5 J, 8 ns, 1.06 μm) are recorded. A spectral resolving power λ/δλ = 1300 is demonstrated at a wavelength of 182 Å. The configuration of the instrument of this type is suited to soft X-ray reflectometry and metrology with the use of laser-plasma and synchrotron radiation sources, and is perfectly compatible with modern CCD detectors.
The impact of the deposition process of the emitting layer on the internal structure of organic light-emitting diodes
Authors: Maderitsch Angelika , Pflumm Christof , Buchholz Herwig , Borchert Holger , Parisi Jürgen
Published: July 2019

Organic light-emitting diodes (OLEDs) continue to attract research interest due to their increasing applications in display and lighting markets. A current field of development is the application of solution-based deposition techniques for the organic layers. However, in general, corresponding devices do not yet reach the performance of OLEDs with vapor deposited materials. In the present work, we have used a model system with a sulfur-containing host material in the emission layer that can either be deposited by thermal evaporation or spin coating. The structure of the corresponding devices was analyzed by a combination of transmission electron microscopy and spatially resolved energy-dispersive x-ray analysis. To investigate the devices’ cross section, wedge shaped, electron transparent lamellas were prepared by focused ion beam milling. Significant differences of the spatial distribution of sulfur have been observed in the devices.
Geometric phase in beating of light waves
Authors: Hannonen Antti , Saastamoinen Kimmo , Leppänen Lasse-Petteri , Koivurova Matias , Shevchenko Andriy , Friberg Ari T , Setälä Tero
Published: July 2019

Beating is a simple physical phenomenon known for long in the context of sound waves but remained surprisingly unexplored for light waves. When two monochromatic optical beams of different frequencies and states of polarization interfere, the polarization state of the superposition field exhibits temporal periodic variation—polarization beating. In this work, we reveal a foundational and elegant phase structure underlying such polarization beating. We show that the phase difference over a single beating period decomposes into the Pancharatnam–Berry geometric phase and a dynamical phase of which the former depends exclusively on the intensities and polarization states of the interfering beams whereas the sum of the phases is determined solely by the beam frequencies. Varying the intensity and polarization characteristics of the beams, the relative contributions of the geometric and dynamical phases can be adjusted. The geometric phase inherent in polarization beating is governed by a compact expression containing only the Stokes parameters of the interfering waves and can alternatively be obtained from the individual beam intensities and the amplitude of the intensity beats. We demonstrate both approaches experimentally by using an interferometer with a fast detector and a specific polarimetric arrangement. Polarization beating has a unique character that the geometric and dynamical phases are entangled, i.e. variation in one unavoidably leads to a change in the other. Our work expands geometric phases into a new domain and offers important novel insight into the role of polarization in interference of electromagnetic waves.
Transport of a colloidal particle driven across a temporally oscillating optical potential energy landscape
Authors: Abbott Joshua L , Straube Arthur V , Aarts Dirk G A L , Dullens Roel P A
Published: July 2019

A colloidal particle is driven across a temporally oscillating one-dimensional optical potential energy landscape and its particle motion is analysed. Different modes of dynamic mode locking are observed and are confirmed with the use of phase portraits. The effect of the oscillation frequency on the mode locked step width is addressed and the results are discussed in light of a high-frequency theory and compared to simulations. Furthermore, the influence of the coupling between the particle and the optical landscape on mode locking is probed by increasing the maximum depth of the optical landscape. Stronger coupling is seen to increase the width of mode locked steps. Finally, transport across the temporally oscillating landscape is studied by measuring the effective diffusion coefficient of a mobile particle, which is seen to be highly sensitive to the driving velocity and mode locking.
Low-lying positive parity yrast bands in Gd, Dy and Er nuclei for N = 96
Authors: Mahdi Mahdi A. , Radhi Fahmi Sh. , Kassim Huda H. , AbedAlJubbori Mushtaq , Sharrad Fadhil I.
Published: July 2019

The interacting boson model has been applied to calculate the low-lying positive parity yrast bands in Gd, Dy and Er nuclei for N = 96 neutrons. The results closed to the SU(3) limit in this model. Reasonable agreement with available energies and B(E2) transition rates. The potential energy surfaces (PESs) to the IBM Hamiltonian have been obtained using the intrinsic coherent state.
A comparison clinical study between Water-Pipe and cigarettes males smokers on serum lipid profile and blood hemoglobin concentration in the Thi-Qar governorate
Authors: Sultan Mohammad Q.
Published: July 2019

20 samples of each non-smoking (group A, as a standard case), smoking cigarette (group B) and smoking water pipe (group C) were studied, respectively at Thi –Qar Governorate between 1st Jan. 2017 till the end of Feb. 2017. The average ages of all groups ranged between 25 and 40 years and all of them do not suffer of any genetic disease (i.e. sugar diabetes and high blood pressure).Both, the blood hemoglobin concentration (Hb) and serum lipid profile were measured for groups A, B and C, respectively. The results indicated the presence of relative increase (p <0.05) of Hb in group B as compared with group A. In order of C > B> C Furthermore, it was found that there was a relative increase (p <0.05) in Hb of group C as compared with both groups A and B.With respect to the serum lipid profile, the result showed the presence of a relative increase (p <0.05) in the concentrations of total cholesterol in group (B) as compared with group (A) while there was a relative increase (p <0.05) in group (C) when its compared with both groups A and B. By considering the concentrations of triglyceraldehyde (TG) in group (B), it was noticed that there is no relative increase (p <0.05) as compared with group (A) while there was an relative increase (p <0.05) of group (C) in comparison with both groups (A and B).In the case of high density lipoprotein (HDL) it was found that there was non-relative decrease (p <0.05) in the human body concentration as compared with group (A) while there was a relative decrease (p <0.05) in the concentration of (HDL) with the group (C) as compared with group (A) but in comparison of such result with group (B), it was found that there was non-relative decrease (p <0.05).As for as the low density lipoprotein (LDL) is concerned, an relative increase (p <0.05) was found with both groups (B and C) as compared with group (A). Also it was noticed that a non-relative increase was indicated with group (C) when it was compared with group (B).Finally, the results showed a non-relative increase (p <0.05) in concentration (vLDL) with both groups (B and C) as compared with group (A). But in comparison between groups (C and B) it was found that there was a relative increase (p <0.05) with group (C).
A Wearable Rehabilitation System to Assist Partially Hand Paralyzed Patients in Repetitive Exercises*
Authors: Naeem Hasan Hussein
Published: July 2019

The main purpose of the paper is development, implementation, and testing of a low cost portable system to assist partially paralyzed patients in their hand rehabilitation after strokes or some injures. Rehabilitation includes time consuming and repetitive exercises which are costly and demotivating as well as the requirements of clinic attending and direct supervision of physiotherapist. In this work, the system consists of a graphical user interface (GUI) on a smartphone screen to instruct and motivate the patients to do their exercises by themselves. Through the GUI, the patients are instructed to do a sequence of exercises step by step, and the system measures the electrical activities (electromyographic signals EMG) of the user’s forearm muscles by Myo armband. Depending on database, the system can tell whether the patients have done correct movements or not. If a correct movement is detected, the system will inform the user through the GUI and move to the next exercise. For preliminary results, the system was extensively tested on a healthy person.
The Effect of Ce-doping Molar Concentration with Silica Xerogel on the Materials Optical Properties
Authors: Abbas Oudh Abdul-Jabbar , Al-Mashhadani Asia H. , Twej Wesam A.A.
Published: July 2019

Ionic cerium-doped pure silica glass with high photoluminescence, has been prepared using the sol–gel technique and densification of the porous xerogel under inert and air atmosphere.The present study shows the effect of densification atmosphere and molar concentrations on the optical properties of ionic cerium-activated silica glasses.Moreover, the PL intensity increased with increasing the molar concentration of ionic Ce+3.The PL is composed of two sub-bandsascribable to tetragonal distortion of the matrix and spin–orbit coupling but these sub-bands arecloser to each other when the core rod is densified under inert atmosphere.