bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent CMS results on soft and small-x QCD physics
Authors: Gupta Rajat
Published: April 2019

We present latest results of soft and small-x QCD measurements with the CMS experiment, such as minimum bias/underlying event physics, and studies on forward jet production.
Convergence properties of Lévy expansions: implications for Odderon and proton structure
Authors: Csörgő T. , Pasechnik R. , Ster A.
Published: April 2019

We detail here the convergence properties of a new model-independent imaging method, the Lévy expansion, that seems to play an important role in the analysis of the diﬀerential cross section of elastic hadron-hadron scattering.We demonstrate, how our earlier results concerning the Odderon eﬀects in the diﬀerential cross-section of elastic proton-proton and proton-antiproton scattering as well as those related to apparent sub-structures inside the protons were obtained in a convergent and stable manner.
The Pierre Auger Observatory status and latest results
Authors: Berat Corinne
Published: April 2019

Ultra-high energy cosmic rays represent the most energetic particles available to scientists. These particles have macroscopic energies, exceeding 1 EeV,but their detectionisa challenge, their flux beingvery weak, around one particle per square kilometer per century for the highest energies. The Pierre Auger Observatory, in Argentina, is the present flagship experiment studying ultra-high energy cosmic rays. The combination of a large array of surface detectors covering 3000 km2 and fluorescence telescopes enhances the performances of the extensive air shower detection and measurements, resulting in both high statistics and unprecedented data quality. Moreover, the operation of a denser sub-array has extended the sensitivity to lower energies. Altogether, these well performing detectors contribute to providing important information on key questions on cosmic rays in the energy range from 0.1 EeV up to 100 EeV, as highlighted in this presentation of the latest results obtained by the Pierre Auger Collaboration. Despite a large number of valuable results, the understanding of the nature and the origin of the highest energy cosmic rays remains an open science case that the Auger Collaboration is willing to address with the AugerPrime project.
Analysis of high energy resolution data of 26Mg(3He,t)26Al reaction
Authors: Win Kalayar , Fujita Yoshitaka , Yeeoo Yee , Fujita Hiro
Published: April 2019

The Gamow-Teller (GT) transition is a powerful tool to study nuclear structure because of its simple form of the operator στ. The structure of 26Al is studied through Gamow-Teller transitions using nuclear charge-exchange reaction. The reaction 26Mg(3He,t)26Al was performed at an incident energy of 140 MeV/nucleon and scattering angle at and near 0˚. The energy resolution of ΔE = 22 keV allowed us to study many discrete states. Most of the prominent states are suggested that they are excited with ΔL = 0 GT transitions. The GT states were studied up to 18.5 MeV. For the extraction of the B(GT) value, the proportionality between cross section and B(GT) was used. The standard B(GT) values were obtained from the 26Si beta decay, where the mirror symmetry of B(GT) was obtained. The T = 2 GT states are expected in the region Ex ≥ 13.5 MeV. By comparing with the results of 26Mg(t, 3He)26Na reactions, the isospin symmetry of T = 2 GT states is discussed. Due to the high-energy resolution, the decay widths Γ for the states in the Ex > 9 MeV region could be studied. The narrow width of the T = 2 states at 13.592 MeV is explained in terms of isospin selection rules.
ElasticppScattering in AdS/CFT
Authors: Agarwal Pulkit , Chan Aik Hui , Oh Choo Hiap
Published: April 2019

This work is geared towards studyingppcollisions using the AdS/CFT correspondence. It is inspired by the work of Richard C. Brower, Joseph Polchinski, Matthew J. Strassler and Chung I Tan (arXiv:1204.0472v1) on particle interactions. A simple extension is provided by calculating the scattering amplitudes ofppcollisions using the BPST Pomeron and comparing it to the well known empirical result of elasticppscattering.
Analysis of a Single-Λ Hypernuclear Event in KEK-PS E373 Nuclear Emulsion Experiment
Authors: Aung Myo Thandar , Wint Thida , Myint Khin Swe , Nakazawa Kazuma
Published: April 2019

The purpose of this research is to identify a single-Λ hypernucleus and its decay products which support to get more information about hyperon-nucleon interaction. Before performing the analysis of a single-Λ hypernucleus, first, we have deduced the density of emulsion by calibrating the range-energy relation using alpha decay events data from thorium series. It is very important for the mass reconstruction of hypernucleus events in nuclear emulsion. And we have reconstructed a single-Λ hypernucleus event by using the kinematical reconstruction for mesonic and non-mesonic decay modes. From the result of our analysis, we can uniquely identify that single-Λ hypernucleus is
$ {}_\Lambda ^9 B $
and decay products are 4He,3He, proton and neutron.
Chou-Yang Model for Forward-Backward Multiplicity Correlations at 7 TeV using Generalized Multiplicity Distribution.
Authors: Phang S.W. , Chan A.H. , Oh C.H. , Yuen E. , Ong Z. , Leong Q.X.
Published: April 2019

The basis of the Chou-Yang model is made up of a stochastic and non-stochastic distribution and has been successful in describing forward-backward multiplicities.[1] This project examines data drawn from CERN’s 7 TeV run where we revist the Chou-Yang model’s components. It also approaches phenomenological descriptions for cluster sizes from forward-backward multiplicaity correlation strength by the E735 collaboration.[6] For the stochastic binomial component, it examines the variance of the charge asymmetry parameter z with regards to fixed total charged multiplicities n. The fitting of the Generalized Multiplicity distribution along with the linear least square fitting of the forward backward multiplicity is analysed. The parameters for the Generalized Multiplicity Distribution is presented along with an investigation on the cluster size r.[3] This serves as an extention to the work done by W.Y Wang’sWeighted GMD model at7TeV, however the nonweighted GMD model is used here.[7]
Photometric Redshift Analysis using Supervised Learning Algorithms and Deep Learning
Authors: Chong De Wei, Kenny , Yang Abel
Published: April 2019

We present a catalogue of galaxy photometric redshifts for the Sloan Digital Sky Survey (SDSS) Data Release 12. We use various supervised learning algorithms to calculate redshifts using photometric attributes on a spectroscopic training set. Two training sets are analysed in this paper. The first training set consists of 995,498 galaxies with redshifts up to z ≈ 0.8. On the first training set, we achieve a cost function of 0.00501 and a root mean squared error value of 0.0707 using the XGBoost algorithm. We achieved an outlier rate of 2.1% and 86.81%, 95.83%, 97.90% of our data points lie within one, two, and three standard deviation of the mean respectively. The second training set consists of 163,140 galaxies with redshifts up to z ≈ 0.2 and is merged with the Galaxy Zoo 2 full catalog. We also experimented on convolutional neural networks to predict five morphological features (Smooth, Features/Disk, Star, Edge-on, Spiral). We achieve a root mean squared error of 0.117 when validated against an unseen dataset with over 200 epochs. Morphological features from the Galaxy Zoo, trained with photometric features are found to consistently improve the accuracy of photometric redshifts.
Dark Energy Constraints from a five-dimensional AdS Black Hole via AdS/CFT
Authors: Jeong Yoobin , Khimphun Sunly , Lee Bum-Hoon , Tumurtushaa Gansukh
Published: April 2019

There are many dark energy models having been investigated with constraint from observational data. The best dark energy candidate is ΛCDM model. In this work, our model has extended to include AdS/CFT correspondent, where the AdS black hole boundary exhibit the FLRW metric foliated with four-dimensional gravity theory, can lead to a modified Friedmann Equation contains extra parameter coming from 5D AdS (hairy) black hole, where such extension to ACDM can be considered. We obtained modified Friedmann equation from both 5D hairless and scalar hair black hole. The eﬀect from extra dimension in hairless black hole solutions can be observed in the form of radiation. Also, it is interesting to see a non-trivial term emerges in scalar hair solution case. However in this study, we only consider Hairless black hole case for data constraint by using a join analysis of Supernovae, CMB and H0 measurement to obtain
$ \chi _{\min }^2 $
. As a result, we compare this particular case with ACDM using AIC and BIC statistics.
From Tsallis Scheme of high-energy pp collisions to Generalized Multiplicity Distribution with Modified Combinants
Authors: Ghaﬀar M. , Ang H. W. , Chan A. H.
Published: April 2019

An analysis of the generalized multiplicity distribution, (GMD), has been made in high energy pp collisions. An attempt is made to reconcile the generating function of GMD with Tsallis statistics in order to find an interpretation of Tsallis parameter,(q). The modified combinants, (Cj’s), for both GMD and NBD are obtained using the generating functions of these distributions. Our results show that single NBD does not lead to the oscillatory behaviour of the observed Cj. However, for GMD the corresponding Cj not only oscillate but also show the fading-down feature of the experimentally observed Cj. This could help in future to analyse the physical process which is responsible for these oscillations.
Unitarity of neutrino mixing matrix
Authors: Nguyen Thi Kim Ha , Nguyen Thi Hong Van , Cao Van Son
Published: April 2019

Neutrinos are neutral leptons and there exist three types of neutrinos (electron neutrinos νe, muon neutrinos νµ and tau neutrinos ντ). These classifications are referred to as neutrinos’s “flavors”. Oscillations between the different flavors are known as neutrino oscillations, which occurs when neutrinos have mass and non-zero mixing. Neutrino mixing is governed by the PMNS mixing matrix. The PMNS mixing matrix is constructed as the product of three independent rotations. With that, we can describe the numerical parameters of the matrix in a graphical form called the unitary triangle, giving rise to CP violation. We can calculate the four parameters of the mixing matrix to draw the unitary triangle. The area of the triangle is a measure of the amount of CP violation.
Rainbow Gravity: Big Bounce in Bianchi Type I Universe
Authors: Wong Wesley , Ching Chee Leong , Ng Wei Khim
Published: April 2019

We will examine the Bianchi Type I universe under the Rainbow Gravity formalism and calculate various quantities like the dynamical equation for the energy density and the negative energy density. Finally, we apply the analysis to a specific Rainbow Gravity model.
Hubble Parameter Measurement Constraints on Holographic Dark Energy
Authors: Lum You Sheng Plato , Ng Shao Chin Cindy
Published: April 2019

We review and attempt to constrain the ΛCDM and XCDM models using 26 Hubble parameter against redshift data points from [1], [2], [3], [4] and [5]. Also known as the cosmic chronometers approach, these constraints are now almost as restrictive as or less than those from Type 1a Supernova (SN1a) apparent magnitude versus redshift data [6]. Then, we attempt to constrain the Holographic Dark Energy model [7] using the aforementioned 26 H(z) measurement. Although interesting, errors for the H(z) could be less well estimated as it is a relatively new measure relative to SN1a data, which has been studied for a much longer time.
A Boltzmann-Tsallis approach towards cell survival curve in Radiobiology
Authors: Tan B.W.Q. , Tan H.Q. , Chan A.H.
Published: April 2019

This paper outlines a phenomenological approach towards cell survival curve at low dose using tools of extensive Statistical Mechanics and nonextensive Statistical Mechanics. An Ising chain model is developed for the cell survival curve and the canonical ensemble formalism based on Boltzmann Gibbs statistic and Tsallis statistic is presented. The resulting cell survival curve shows excellent agreement with the experimental data and the physical parameters from our Tsallis model (N’, q) can be shown to provide clear classification between healthy and cancerous cells. In this paper, we also provides possible biophysical interpretation to the (N’, q) parameters where N’ is representative of the amount of repairable DNA content in the nucleus and q represents the degree of correlation in DNA damage. Overall, this is the first time a Statistical Mechanics approach is used in Radiobiology, and could present a new perspective.
Dynamics of Negative Diffusivity and Uphill Diffusion in Ternary and Single systems
Authors: Vu Ba Dung , Dinh Van Thien , Tong Ba Tuan
Published: April 2019

Negative diﬀusivity and uphill diﬀusion, that contrast with Fick’s laws, however which can occur in multicomponent and single systems. In this paper, authors present studied results about the dynamics of the uphill diﬀusion in ternary and single system. Results have shown that: i) in ternary systems, the dynamics of negative diﬀusivity is high concentration eﬀect and the combina-tion of coupled diﬀusion eﬀect with high concentration eﬀect is the dynamics of uphill diﬀusion; ii) in single systems, the diﬀerence of temperatures in two areas that is the dynamics of negative diﬀusivity and uphill diﬀusion. Keywords: Dynamics of uphill diﬀusion; dynamics of negative diﬀusivity.
Applications of Polymeric Quantisation
Authors: Jia Pern Neville Chen , Chee Leong Ching
Published: April 2019

Polymer quantisation is a background independent quantisation scheme inspired by loop quantum gravity. Under this quantisation scheme, it predicts that space is discretised and changes in multiples of a fundamental length scale λ. As a result, the momentum operator is not well-defined. However, a new operator can be defined such that a Schrödinger-like equation can be retrieved. The solutions give rise to eigenspectra which are similar to the standard counterparts, with an additional correction term due to λ. We present the basic principles of the polymer representation and apply it to the harmonic oscillator to study the phenomenological implications of such solutions. In addition, we consider an ensemble of such oscillators and calculated the thermodynamical properties for systems that safisty the bosonic and fermionic statistics. The results presented may have physical significance at high energy scales or in exotic matter.
Clustering of hotspots in the cosmic microwave background
Authors: Low En Zuo Joel , Yang Abel
Published: April 2019

The physics behind the origin and composition of the Cosmic Microwave Background (CMB) is a well-established topic in the field of Cosmology. Literature on CMB anisotropies reveal consistency with Gaussianity [1], but these were conducted on full multi-frequency temperature maps. In this thesis, we utilise clustering algorithms to specifically conduct statistical analyses on the distribution of hotspots in the CMB. We describe a series of data processing and clustering methodologies conducted, with results that conclusively show that the counts-in-cells distribution of hotspots in the CMB does not follow a Poisson distribution. Rather, the distribution exhibits a much closer fit to both the Negative Binomial Distribution (NBD) and the Gravitational Quasi-Equilibrium Distribution (GQED). From this result, we conclude that structure likely existed in the early universe, from the period of the recombination Epoch, possibly opening new insights in the field of galaxy formation.
Effects of toxic cyanobacterium Microcystis aeruginosa on the morphology of green alga Chlorella vulgaris
Authors: Dong Jing , Li Chenlu , Chang Mengyang , Dai Dujuan , Liu Shiwen , Quan Bingyu , Zhang Yifan , Gao Yunni
Published: April 2019

In eutrophic freshwater lakes, cyanobacteria and green algae are in succession due to abiotic factors. Allelochemical interaction also exists. In this study, we indicated that filtrates of Microcystis aeruginosa can influence the growth rate and photosynthetic pigments of the target alga named Chlorella vulgaris. We also determined the morphological appearance and colony formation of green alga C. vulgaris that were induced by chemicals associated with a competitor cyanobacterium named M. aeruginosa. However, microcystins (MCs) were not the active substances in this study. The morphology changes and growth of C. vulgaris affected by M. aeruginosa filtrates were dependent on the initial cultivation density of the target algae and the cultivation phase of M. aeruginosa. We also assumed that the morphology changes were defensive strategies utilised by C. vulgaris to resist M. aeruginosa. The temporary stress of M. aeruginosa was favourable to the growth of C. vulgaris. By contrast, the continuous induction of colony formation by M. aeruginosa in the field inhibited the growth of C. vulgaris. The present results provided new insights into the interaction between algae and theoretical basis for algae succession in the field.
Modélisation déterministe de l’oued Mekerra pour l’identification de la zone inondable de Sidi Bel-Abbès (Nord-Ouest algérien)
Authors: Benmansour N. , Haddouche D.
Published: April 2019

Cet article présente une méthodologie effective pour l’identification des zones à risques, en prenant comme cas d’étude l’oued Mekerra. Celui-ci a provoqué une dizaine d’inondations depuis 1980. L’insuffisance des mesures de terrain ou leur manque de fiabilité a nécessité de mettre au point une méthode de travail qui pourrait être adaptée à d’autres bassins versants. Cette méthode propose une modélisation hydrologique déterministe pour la définition de la crue de projet et une modélisation hydraulique pour l’étude du comportement de la crue. Cela a permis de cartographier les zones inondables de la ville de Sidi Bel-Abbès située sur la partie aval du bassin versant. La tache inondable obtenue a été validée en comparaison avec celle obtenue par la méthode hydrogéomorphologique et des enquêtes de terrain. Les solutions empiriques adoptées durant cette étude sont parvenues à un taux de validation d’environ 85 %. Ces solutions peuvent servir d’outils d’aide à la décision et être adaptées à d’autres bassins versants se trouvant dans le même contexte.
The Department of Defense Birth and Infant Health Research Program: Assessing the Reproductive Health of U.S. Active-Duty Women
Authors: Khodr Zeina , Bukowinski Anna , Hall Clinton , Gumbs Gia , Wells Natalie , Conlin Ava Marie
Published: April 2019

As the percentage of women serving in the active-duty military continues to grow, and as their roles continue to expand, the importance of monitoring reproductive health in the military community increases. The Department of Defense Birth and Infant Health Research (BIHR) program conducts ongoing epidemiologic studies to assess potential increased risks for adverse reproductive and infant health outcomes in the military population. Military personnel endure unique physical and mental demands as a part of their occupational duties (e.g., extensive preventive care, numerous trainings, and deployments), which require special consideration as parental exposures in reproductive health research that cannot be well assessed in the general population. From 2003 to 2014, the BIHR program captured 250,604 pregnancies among approximately 2.4 million active-duty women of reproductive age when limited to non-cadet Army, Air Force, Navy, and Marine Corps personnel. Approximately 15,000 live births occurred each year, and the live birth rate ranged from 76.9 per 1,000 in 2003 to 71.0 per 1,000 in 2014. Safety of military-unique preventive measures, environmental exposures, and occupational hazards in pregnancy are summarized herein. Reproductive health is important to our service members and their families, and optimizing the health of military families ultimately contributes to force readiness.
The Gynecologic Health Consequences of Chlamydia trachomatis Infection in Military Servicewomen
Authors: Nadeau Christine , Fujii Dennis , Lentscher Jessica , Haney Amanda , Burney Richard
Published: April 2019

Chlamydia trachomatis is the most common sexually transmitted bacterial infection in the United States. Within the U.S. military, the age- and race-adjusted chlamydia infection rates among female service members are consistently higher than civilian rates, with a 20% annual acquisition rate among young active-duty women. The sequelae of chlamydia disproportionately impact women in terms of severity and cost. Untreated chlamydia progresses to pelvic inflammatory disease in 40% of cases, and is a leading cause of fallopian tube damage and pelvic adhesive disease resulting in ectopic pregnancy, tubal infertility, and acute and chronic pelvic pain. Tubal infertility is among the leading indications for in vitro fertilization (IVF) nationally and rates among couples undergoing IVF at military treatment centers are double the national average. Collectively, chlamydia infection represents a significant resource burden to the military health care system and, in view of the serious gynecologic health sequelae, a significant threat to the readiness of servicewomen. In this review, we discuss the gynecologic impact of chlamydia infection within the military, the critical gaps for research funding, and opportunities for intervention.
Preconception Care in the Veterans Health Administration
Authors: Callegari Lisa , Edmonds Stephanie , Borrero Sonya , Ryan Ginny , Cusack Caitlin , Zephyrin Laurie
Published: April 2019

Preconception care (PCC), defined as a set of interventions to help women optimize their health and well-being prior to pregnancy, can improve pregnancy outcomes and is recommended by national organizations including the Centers for Disease Control and Prevention and the American College of Obstetricians and Gynecologists. Women Veterans who use the Department of Veterans Affairs (VA) health care system may face elevated risks of adverse pregnancy and birth outcomes due to a high prevalence of chronic medical and mental health conditions as well as psychosocial stressors including sexual trauma history and intimate partner violence. Many women Veterans of childbearing age experience poverty and homelessness, which are key social determinants of poor reproductive health outcomes. Furthermore, racial/ethnic disparities in maternal and neonatal outcomes are well documented, and nearly half of women Veterans of reproductive age are minority race/ethnicity. High-quality, equitable, patient-centered PCC services to address modifiable risks in this population are therefore a priority for VA. In this article, we provide a brief background of PCC, discuss the health risks of Veterans associated with adverse pregnancy outcomes, and highlight VA initiatives related to PCC. Lastly, we discuss implications and future directions for PCC research and policy within VA and across other health systems.
Intermediate Outcomes after Rapid Deployment Aortic Valve Replacement in Multiple Valve Surgery
Authors: Schlömicher Markus , Bechtel Matthias , Taghiyev Zulfugar , Naraghi Hamid , Haldenwang Peter Lukas , Moustafine Vadim , Strauch Justus T.
Published: April 2019

Background Multiple valve surgery is associated with significant higher operative risks. Reduced cross-clamp and cardiopulmonary bypass times in multiple valve surgery may potentially be beneficial as they can be considered independent risk factors for increased morbidity and mortality following cardiac surgery. We report first intermediate outcomes of the Edwards Intuity valve system (Edwards Lifesciences, Irvine, California, United States) in combined procedures

Methods Fifty-eight patients underwent rapid deployment aortic valve replacement with concomitant mitral valve surgery between January 2014 and November 2017 in our institution. The valve was assessed echocardiographically after 12 months. The median follow-up was 1.7 years with a cumulative follow-up time of 115.3 patient years.

Results The mean age was 73.5 ± 6.2 years and the mean logistic Euroscore was 11.6 ± 3.1%. Concomitant mitral valve repair was performed in 43 cases (74.1%), and mitral valve replacement in 15 cases (19.0%). The mean cross-clamp time was 93 ± 21 minutes along with a mean bypass time of 118 ± 24 minutes. All-cause mortality after 30 days was 8.6%. Overall actuarial survival at 1 year was 87.2 ± 4.5% and after 2 years 82.8 ± 5.3%, respectively.

Conclusions Rapid deployment aortic valve replacement in multiple valve surgery can be performed safely with good intermediate outcomes in elderly, high-risk patients.
AGE–RAGE Stress in the Pathophysiology of Pulmonary Hypertension and its Treatment
Authors: Prasad Kailash
Published: April 2019

Pulmonary hypertension (PH) is a rare and fatal disease characterized by elevation of pulmonary artery pressure ≥ 25 mm Hg. There are five groups of PH: (1) pulmonary artery (PA) hypertension (PAH), (2) PH due to heart diseases, (3) PH associated with lung diseases/hypoxia, (4) PH associated with chronic obstruction of PA, and (5) PH due to unclear and/or multifactorial mechanisms. The pathophysiologic mechanisms of group 1 have been studied in detail; however, those for groups 2 to 5 are not that well known. PH pathology is characterized by smooth muscle cells (SMC) proliferation, muscularization of peripheral PA, accumulation of extracellular matrix (ECM), plexiform lesions, thromboembolism, and recanalization of thrombi. Advanced glycation end products (AGE) and its receptor (RAGE) and soluble RAGE (sRAGE) appear to be involved in the pathogenesis of PH. AGE and its interaction with RAGE induce vascular hypertrophy through proliferation of vascular SMC, accumulation of ECM, and suppression of apoptosis. Reactive oxygen species (ROS) generated by interaction of AGE and RAGE modulates SMC proliferation, attenuate apoptosis, and constricts PA. Increased stiffness in the artery due to vascular hypertrophy, and vasoconstriction due to ROS resulted in PH. The data also suggest that reduction in consumption and formation of AGE, suppression of RAGE expression, blockage of RAGE ligand binding, elevation of sRAGE levels, and antioxidants may be novel therapeutic targets for prevention, regression, and slowing of progression of PH. In conclusion, AGE–RAGE stress may be involved in the pathogenesis of PH and the therapeutic targets should be the AGE–RAGE axis.
Examining Performance on a Process-Based Assessment of Word Learning in Relation to Vocabulary Knowledge and Learning in Vocabulary Intervention
Authors: Kelley Elizabeth Spencer , Goldstein Howard
Published: April 2019

Vocabulary knowledge of young children, as a well-established predictor of later reading comprehension, is an important domain for assessment and intervention. Standardized, knowledge-based measures are commonly used by speech-language pathologists (SLPs) to describe existing vocabulary knowledge and to provide comparisons to same-age peers. Process-based assessments of word learning can be helpful to provide information about how children may respond to learning opportunities and to inform treatment decisions. This article presents an exploratory study of the relation among vocabulary knowledge, word learning, and learning in vocabulary intervention in preschool children. The study examines the potential of a process-based assessment of word learning to predict response to vocabulary intervention. Participants completed a static, knowledge-based measure of vocabulary knowledge, a process-based assessment of word learning, and between 3 and 11 weeks of vocabulary intervention. Vocabulary knowledge, performance on the process-based assessment of word learning, and learning in vocabulary intervention were strongly related. SLPs might make use of the information provided by a process-based assessment of word learning to determine the appropriate intensity of intervention and to identify areas of phonological and semantic knowledge to target during intervention.
Systematic error in conventionally measured Raman spectra of boron carbide—A general issue in solid state Raman spectroscopy
Authors: Werheit Helmut
Published: April 2019

Solid state Raman spectroscopy requires careful attention to the penetration depth of exciting laser radiation. In cases like semiconducting boron carbide and metallic hexaborides, high fundamental absorption above the bandgap and reflectivity R ≈ 1 beyond the plasma edge respectively prevent the excitation of bulk phonons largely. Thus, correspondingly measured spectra stem preferably from surface scattering. For decades, Raman spectra of boron carbide obtained with different equipment were controversially discussed. Now, common features of icosahedral phonons in Fourier transform-Raman spectra of B4.3C and Raman spectra of α–rhombohedral boron evidence their bulk character, while refuting conventionally measured Raman spectra.
Development of a confocal scanning microscope for fluorescence imaging and spectroscopy at variable temperatures
Authors: Hu Yi , Moran Bradley M. , Woehl Jörg C.
Published: April 2019

We developed and tested a confocal scanning optical microscope that fits into a thermally controlled, commercial research cryostat designed for operation from ambient temperature down to below 4 K. The home-built microscope is a fiber-coupled, self-contained instrument based on readily available mechanical and optical components. Its sample module is sealed in a protective stainless steel tube that minimizes vibrations caused by the flow of cryogenic gas. A high numerical aperture microscope objective specifically designed for cryogenic and high-vacuum applications focuses the excitation light onto the sample, while the core of an optical fiber attached to an avalanche photodiode acts as the confocal detection pinhole. The sample is displaced using a piezotube scanner mounted on top of a three-axis, low-temperature nanopositioner assembly for coarse sample positioning. A broadband polarizing cube beam splitter in the emission path allows for polarization-resolved imaging and spectroscopy. Fluorescence excitation scans are acquired with custom-written software that correlates fluorescence photon counts with the output from a high precision wavelength meter, which is part of a narrow-band, tunable dye laser setup. The imaging and spectral data acquisition capabilities of the microscope were confirmed using a variety of samples and excitation wavelengths at temperatures ranging from 5 K to room temperature.
A full additive QM/MM scheme for the computation of molecular crystals with extension to many-body expansions
Authors: Teuteberg Thorsten L. , Eckhoff Marco , Mata Ricardo A.
Published: April 2019

An additive quantum mechanics/molecular mechanics (QM/MM) model for the theoretical investigation of molecular crystals (AC-QM/MM) is presented. At the one-body level, a single molecule is chosen as the QM region. The MM region around it consists of a finite cluster of explicit MM atoms, represented by point charges and Lennard-Jones potentials, with additional background charges to mimic periodic electrostatics. Cluster charges are QM-derived and calculated self-consistently to ensure a polarizable embedding. We have also considered the extension to many-body QM corrections, calculating the interactions of a central molecule to neighboring units in the crystal. Full gradient expressions have been derived, also including symmetry information. The scheme allows for the calculation of molecular properties as well as unconstrained optimizations of the molecular geometry and cell parameters with respect to the lattice energy. Benchmarking the approach with the X23 reference set confirms the convergence pattern of the many-body extension although a comparison to plane-wave density functional theory reveals a systematic overestimation of cohesive energies by 6–16 kJ mol−1. While the scheme primarily aims to provide an inexpensive and flexible way to model a molecule in a crystal environment, it can also be used to reach highly accurate cohesive energies by the straightforward application of wave function correlated approaches. Calculations with local coupled cluster with singles, doubles, and perturbative triples, albeit limited to numerical gradients, show an impressive agreement with experimental estimates for small molecular crystals.
Local well-posedness and blow-up phenomena of the generalized short pulse equation
Authors: Guo Yingying , Yin Zhaoyang
Published: April 2019

In this paper, we investigate the Cauchy problem of the generalized short-pulse equation in periodic domain. We first establish the local well-posedness of the equation in Hs(S),s≥2 by taking advantage of the Kato method and present some useful conservation laws. Then, we obtain the boundedness of the solution by virtue of the conservation laws. Finally, we give a precise blow-up criterion for α > 0 (or α < 0) and get several blow-up results provided the initial data satisfies some certain conditions.
Complex coupling effects and dissipative structure in nonlinear thermodynamic systems
Authors: Wang Xiaomeng , Xiao Changming
Published: April 2019

It is well known that a dissipative structure can only possibly turn out when the nonlinear system is far away from the equilibrium. In this paper, the instability of steady state in an ideal system with two kinds of irreversible processes has been studied. The most important factor in our discussions is that, in the nonlinear range, both the linear and nonlinear items of the generalized thermodynamic forces have been included in the functional relationship between the generalized thermodynamic flows and forces. Our results show that the complex coupling effect plays a very important role in the instability of steady state: if the coefficient related to complex coupling item is very small, the steady state of the system almost does not lose its stability. The dissipative structure is almost impossible, however, if the coefficient about the complex coupling is very large, it is possible for the steady state to lose its stability. Then a dissipative structure is possible. And, this conclusion was verified by the dynamical analyzing about a chemical monomolecular reaction system with strong complex coupling effects. So the dissipative structure can only possibly turn out in a nonlinear non-equilibrium system which is not only far away from the equilibrium but also is strongly coupled.
An atomic view on spall responses of release melted lead induced by decaying shock loading
Authors: Wang Kun , Zhang Fengguo , He Anmin , Wang Pei
Published: April 2019

Knowledge of spallation behaviors of partially melted metals, as well as the ones of solids and liquids, is critical for understanding the complete spall responses of metals to a wide range of loading strengths. However, compared with traditional spallation in solids, the spallation of liquids, especially of partially melted metals, receives considerably less attention despite some advancements in recent years. In the present work, spallation behaviors of partially melted/completely melted Pb under various decaying shock loadings are investigated. The effects of peak free surface velocity on the incipient spall strength of the partially melted Pb are uncovered, which is attributed to the difference of melting degree. Our results suggest that the incipient spall strength decreases with the growing melting degree for the partially melted Pb. Besides, incipient spall criterion, as well as damage evolutions at the later stage, is discussed. It is found that, after the incipient spall takes place, the total void volume linearly increases with time evolutions regardless of the detailed void mechanism for the volume increment. The increasing rate grows with the promoting melting degree even under the same tensile strain rate and initial temperature. For a liquid Pb, the increasing rate is governed by the tensile strain rate. Physical reasons for the different behaviors between partially and completely melted metals are analyzed.
Assessing the performance of trajectory surface hopping methods: Ultrafast internal conversion in pyrazine
Authors: Xie Weiwei , Sapunar Marin , Došlić Nađa , Sala Matthieu , Domcke Wolfgang
Published: April 2019

Trajectory surface hopping (TSH) methods have been widely used to study photoinduced nonadiabatic processes. In the present study, nonadiabatic dynamics simulations with the widely used Tully’s fewest switches surface hopping (FSSH) algorithm and a Landau-Zener-type TSH (LZSH) algorithm have been performed for the internal conversion dynamics of pyrazine. The accuracy of the two TSH algorithms has been critically evaluated by a direct comparison with exact quantum dynamics calculations for a model of pyrazine. The model comprises the three lowest excited electronic states (B3u(nπ*), A1u(nπ*), and B2u(ππ*)) and the nine most relevant vibrational degrees of freedom. Considering photoexcitation to the diabatic B2u(ππ*) state, we examined the time-dependent diabatic and adiabatic electronic population dynamics. It is found that the diabatic populations obtained with both TSH methods are in good agreement with the exact quantum results. Fast population oscillations between the B3u(nπ*) and A1u(nπ*) states, which reflect nonadiabatic electronic transitions driven by coherent dynamics in the normal mode Q8a, are qualitatively reproduced by both TSH methods. In addition to the model study, the TSH methods have been interfaced with the second-order algebraic diagrammatic construction ab initio electronic-structure method to perform full-dimensional on-the-fly nonadiabatic dynamics simulations for pyrazine. It is found that the electronic population dynamics obtained with the LZSH method is in excellent agreement with that obtained by the FSSH method using a local diabatization algorithm. Moreover, the electronic populations of the full-dimensional on-the-fly calculations are in excellent agreement with the populations of the three-state nine-mode model, which confirms that the internal conversion dynamics of pyrazine is accurately represented by this reduced-dimensional model on the time scale under consideration (200 fs). The original FSSH method, in which the electronic wave function is propagated in the adiabatic representation, yields less accurate results. The oscillations in the populations of the diabatic B3u(nπ*) and A1u(nπ*) states driven by the mode Q8a are also observed in the full-dimensional dynamics simulations.
Optimizing multiple beam interferometry in the surface forces apparatus: Novel optics, reflection mode modeling, metal layer thicknesses, birefringence, and rotation of anisotropic layers
Authors: Schwenzfeier Kai A. , Erbe Andreas , Bilotto Pierluigi , Lengauer Maximilian , Merola Claudia , Cheng Hsiu-Wei , Mears Laura L. E. , Valtiner Markus
Published: April 2019

Multiple beam interferometry (MBI) evolved as a powerful tool for the simultaneous evaluation of thin film thicknesses and refractive indices in Surface Forces Apparatus (SFA) measurements. However, analysis has relied on simplifications for providing fast or simplified analysis of recorded interference spectra. Here, we describe the implementation of new optics and a generalized fitting approach to 4 × 4 transfer matrix method simulations for the SFA. Layers are described by dispersive complex refractive indices, thicknesses, and Euler angles that can be fitted, providing modeling for birefringent or colored layers. Normalization of data by incident light intensities is essential for the implementation of a fitting approach. Therefore, a modular optical system is described that can be retrofit to any existing SFA setup. Real-time normalization of spectra by white light is realized, alignment procedures are considerably simplified, and direct switching between transmission and reflection modes is possible. A numerical approach is introduced for constructing transfer matrices for birefringent materials. Full fitting of data to the simulation is implemented for arbitrary multilayered stacks used in SFA. This enables self-consistent fitting of mirror thicknesses, birefringence, and relative rotation of anisotropic layers (e.g., mica), evaluation of reflection and transmission mode spectra, and simultaneous fitting of thicknesses and refractive indices of media confined between two surfaces. In addition, a fast full spectral fitting method is implemented for providing a possible real-time analysis with up to 30 fps. We measure and analyze refractive indices of confined cyclohexane, the thickness of lipid bilayers, the thickness of metal layers, the relative rotation of birefringent materials, contact widths, as well as simultaneous fitting of both reflection and transmission mode spectra of typical interferometers. Our analyses suggest a number of best practices for conducting SFA and open MBI in an SFA for increasingly complex systems, including metamaterials, multilayered anisotropic layers, and chiral layers.
Oocyte orientation selection method based on the minimum strain position in the penetration process
Authors: Liu Yaowei , Cui Maosheng , Sun Yumeng , Feng Zeyang , Bai Yunxiang , Sun Mingzhu , Zhao Qili , Zhao Xin
Published: April 2019

In this paper, we proposed an oocyte orientation selection method based on the minimum strain position in the penetration process in order to maximize the developmental potential of the operated oocytes. Considering the symmetry of an oocyte during the penetration process, we analyzed only the intracellular strain of the lower half of the oocyte (from 3 o’clock to 9 o’clock). Firstly, the strain distribution in the penetration process was calculated using the finite element analysis method. The influences of penetration force, zona pellucida thickness, oocyte radius, Young’s modulus of the cytoplasm, and zona pellucida on the strain distribution were studied. The simulation results showed that the strain values at the 4 o’clock and 9 o’clock areas were significantly smaller than those at the 5 o’clock, 6 o’clock, 7 o’clock, and 8 o’clock areas. Secondly, the experimental strain distribution during penetration was evaluated for the first time using an optical flow method. The experimental strain distribution was strongly positively correlated to the aforementioned simulated results. Finally, the developmental potential of the penetrated porcine oocyte with different orientations was evaluated using the cleavage rate (48 h after penetration and parthenogenetic activation). The cleavage rate was strongly negatively correlated to the intracellular strain. We inferred that a smaller strain on the polar body areas in the penetration process caused less potential damage, which leads to a higher developmental potential of the penetrated oocyte. The optimized oocyte orientations, with the polar body at the 4 o’clock and 9 o’clock areas, are determined based on the minimum strain position in the penetration process.
Enhanced magnetoelectric response in bismuth-deficient BiFeO3-BaTiO3 ceramics
Authors: Pan Qi , Chu Baojin
Published: April 2019

The magnetoelectric response of the bismuth-deficient BiFeO3-BaTiO3 ceramics fabricated using a conventional solid-state reaction method was investigated. We found that a ferromagnetic BaFe12O19 phase is produced as a consequence of bismuth-deficiency (Bi-deficiency) and that the ceramics are 0–3 composites of BaFe12O19 and BiFeO3-based perovskite. An enhanced magnetoelectric response can be achieved in Bi-deficient composites as a consequence of the coupling between magnetostriction in the BaFe12O19 phase and the piezoelectric effect in the BiFeO3-based perovskite phase. In comparison with the composite ceramics prepared using a direct mixing method for the two components, Bi-deficient ceramics have a more uniform distribution of the BaFe12O19 phase in the perovskite matrix and a reduction in dielectric loss and conduction. Thus, the magnetoelectric response of Bi-deficient ceramics is greater than that of ceramics fabricated using a direct mixing method. Our work presents a simple approach for the fabrication of BiFeO3-based composite ceramics with uniformly distributed ferromagnetic particles and enhanced ferromagnetic and magnetoelectric responses.
Reaction-driven oscillating viscous fingering
Authors: Rana C. , De Wit A.
Published: April 2019

Localized oscillations can develop thanks to the interplay of reaction and diffusion processes when two reactants A and B of an oscillating reaction are placed in contact, meet by diffusion, and react. We study numerically the properties of such an A+B→ oscillator configuration using the Brusselator model. The influence of a hydrodynamic viscous fingering instability on localized concentration oscillations is next analyzed when the oscillating chemical reaction changes the viscosity of the solutions involved. Nonlinear simulations of the related reaction–diffusion–convection equations with the fluid viscosity varying with the concentration of an intermediate oscillatory species show an active coupling between the oscillatory kinetics and the viscously driven instability. The periodic oscillations in the concentration of the intermediate species induce localized changes in the viscosity, which in turn can affect the fingering instability. We show that the oscillating kinetics can also trigger viscous fingering in an initially viscously stable displacement, while localized changes in the viscosity profile can induce oscillations in an initially nonoscillating reactive system.
Reconfigurable spin logic device using electrochemical potentials
Authors: Lee Joo-hyeon , Hong Seokmin , Kim Hyung-jun , Chang Joonyeon , Koo Hyun Cheol
Published: April 2019

A reconfigurable spin logic device is realized using an asymmetric quantum well displaying strong Rashba spin splitting. This design is developed to remove the inefficient spin injection process and to utilize the Rashba-effect-induced electrochemical potential shifts. In this logic device, two ferromagnetic electrodes were deposited on two quantum well channels, respectively. The magnetization orientations of the ferromagnetic electrodes determine the function of the logic operation, and the polarity of the charge current is assigned to the logic input. The output voltage corresponds to the difference between potentials of the two ferromagnetic terminals, which read the electrochemical potentials of the individual quantum well channels. The detected signal induced by the Rashba channel is observed to be two orders of magnitude greater than the spin injection signal from the ferromagnetic source into the semiconductor channel. Four logic functions, i.e., the AND, OR, NAND, and NOR operations, are illustrated for a single device up to room temperature.
Single-Hessian thawed Gaussian approximation
Authors: Begušić Tomislav , Cordova Manuel , Vaníček Jiří
Published: April 2019

To alleviate the computational cost associated with on-the-fly ab initio semiclassical calculations of molecular spectra, we propose the single-Hessian thawed Gaussian approximation in which the Hessian of the potential energy at all points along an anharmonic classical trajectory is approximated by a constant matrix. The spectra obtained with this approximation are compared with the exact quantum spectra of a one-dimensional Morse potential and with the experimental spectra of ammonia and quinquethiophene. In all cases, the single-Hessian version performs almost as well as the much more expensive on-the-fly ab initio thawed Gaussian approximation and significantly better than the global harmonic schemes. Remarkably, unlike the thawed Gaussian approximation, the proposed method conserves energy exactly, despite the time dependence of the corresponding effective Hamiltonian, and, in addition, can be mapped to a higher-dimensional time-independent classical Hamiltonian system. We also provide a detailed comparison with several related approximations used for accelerating prefactor calculations in semiclassical simulations.