bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-LTE analysis of K I in late-type stars
Authors: Reggiani Henrique , Amarsi Anish M. , Lind Karin , Barklem Paul S. , Zatsarinny Oleg , Bartschat Klaus , Fursa Dmitry V. , Bray Igor , Spina Lorenzo , Meléndez Jorge
Published: June 2019

Context. Older models of Galactic chemical evolution (GCE) predict [K/Fe] ratios as much as 1 dex lower than those inferred from stellar observations. Abundances of potassium are mainly based on analyses of the 7698 Å resonance line, and the discrepancy between GCE models and observations is in part caused by the assumption of local thermodynamic equilibrium (LTE) in spectroscopic analyses.

Aims. We study the statistical equilibrium of K I, focusing on the non-LTE effects on the 7698 Å line. We aim to determine how non-LTE abundances of potassium can improve the analysis of its chemical evolution, and help to constrain the yields of GCE models.

Methods. We construct a new model K I atom that employs the most up-to-date atomic data. In particular, we calculate and present inelastic e+K collisional excitation cross-sections from the convergent close-coupling (CCC) and the B-Spline R-matrix (BSR) methods, and H+K collisions from the two-electron model (LCAO). We constructed a fine, extended grid of non-LTE abundance corrections based on 1D MARCS models that span 4000 < Teff∕K < 8000, 0.50 < log g < 5.00, − 5.00 < [Fe/H] < + 0.50, and applied the corrections to potassium abundances extracted from the literature.

Results. In concordance with previous studies, we find severe non-LTE effects in the 7698 Å line. The line is stronger in non-LTE and the abundance corrections can reach approximately − 0.7 dex for solar-metallicity stars such as Procyon. We determine potassium abundances in six benchmark stars, and obtain consistent results from different optical lines. We explore the effects of atmospheric inhomogeneity by computing for the first time a full 3D non-LTE stellar spectrum of K I lines for a test star. We find that 3D modeling is necessary to predict a correct shape of the resonance 7698 Å line, but the line strength is similar to that found in 1D non-LTE.

Conclusions. Our non-LTE abundance corrections reduce the scatter and change the cosmic trends of literature potassium abundances. In the regime [Fe/H] ≲−1.0 the non-LTE abundances show a good agreement with the GCE model with yields from rotating massive stars. The reduced scatter of the non-LTE corrected abundances of a sample of solar twins shows that line-by-line differential analysis techniques cannot fully compensate for systematic LTE modelling errors; the scatter introduced by such errors introduces a spurious dispersion to K evolution.
Temporal evolution and correlations of optical activity indicators measured in Sun-as-a-star observations
Authors: Maldonado J. , Phillips D. F. , Dumusque X. , Collier Cameron A. , Haywood R. D. , Lanza A. F. , Micela G. , Mortier A. , Saar S. H. , Sozzetti A. , Rice K. , Milbourne T. , Cecconi M. , Cegla H. M. , Cosentino R. , Costes J. , Ghedina A. , Gonzalez M. , Guerra J. , Hernández N. , Li C.-H. , Lodi M. , Malavolta L. , Molinari E. , Pepe F. , Piotto G. , Poretti E. , Sasselov D. , San Juan J. , Thompson S. , Udry S. , Watson C.
Published: June 2019

Context. Understanding stellar activity in solar-type stars is crucial for the physics of stellar atmospheres as well as for ongoing exoplanet programmes.

Aims. We aim to test how well we understand stellar activity using our own star, the Sun, as a test case.

Methods. We performed a detailed study of the main optical activity indicators (Ca II H & K, Balmer lines, Na I D1 D2, and He I D3) measured for the Sun using the data provided by the HARPS-N solar-telescope feed at the Telescopio Nazionale Galileo. We made use of periodogram analyses to study solar rotation, and we used the pool variance technique to study the temporal evolution of active regions. The correlations between the different activity indicators as well as the correlations between activity indexes and the derived parameters from the cross-correlation technique are analysed. We also study the temporal evolution of these correlations and their possible relationship with indicators of inhomogeneities in the solar photosphere like sunspot number or radio flux values.

Results. The value of the solar rotation period is found in all the activity indicators, with the only exception being Hδ. The derived values vary from 26.29 days (Hγ line) to 31.23 days (He I). From an analysis of sliding periodograms we find that in most of the activity indicators the spectral power is split into several “bands” of periods around 26 and 30 days. They might be explained by the migration of active regions between the equator and a latitude of ∼30°, spot evolution, or a combination of both effects. A typical lifetime of active regions of approximately ten rotation periods is inferred from the pooled variance diagrams, which is in agreement with previous works. We find that Hα, Hβ, Hγ, Hϵ, and He I show a significant correlation with the S index. Significant correlations between the contrast, bisector span, and the heliocentric radial velocity with the activity indexes are also found. We show that the full width at half maximum, the bisector, and the disc-integrated magnetic field correlate with the radial velocity variations. The correlation of the S index and Hα changes with time, increasing with larger sun spot numbers and solar irradiance. A similar tendency with the S index and radial velocity correlation is also present in the data.

Conclusions. Our results are consistent with a scenario in which higher activity favours the correlation between the S index and the Hα activity indicators and between the S index and radial velocity variations.
Discrete-time autoregressive model for unequally spaced time-series observations
Authors: Elorrieta Felipe , Eyheramendy Susana , Palma Wilfredo
Published: June 2019

Most time-series models assume that the data come from observations that are equally spaced in time. However, this assumption does not hold in many diverse scientific fields, such as astronomy, finance, and climatology, among others. There are some techniques that fit unequally spaced time series, such as the continuous-time autoregressive moving average (CARMA) processes. These models are defined as the solution of a stochastic differential equation. It is not uncommon in astronomical time series, that the time gaps between observations are large. Therefore, an alternative suitable approach to modeling astronomical time series with large gaps between observations should be based on the solution of a difference equation of a discrete process. In this work we propose a novel model to fit irregular time series called the complex irregular autoregressive (CIAR) model that is represented directly as a discrete-time process. We show that the model is weakly stationary and that it can be represented as a state-space system, allowing efficient maximum likelihood estimation based on the Kalman recursions. Furthermore, we show via Monte Carlo simulations that the finite sample performance of the parameter estimation is accurate. The proposed methodology is applied to light curves from periodic variable stars, illustrating how the model can be implemented to detect poor adjustment of the harmonic model. This can occur when the period has not been accurately estimated or when the variable stars are multiperiodic. Last, we show how the CIAR model, through its state space representation, allows unobserved measurements to be forecast.
Gravel and boulders mining from mountain stream beds
Authors: Radecki-Pawlik Artur , Kidová Anna , Lehotsky Milan , Rusnák Miloš , Manson Russell , Radecki-Pawlik Bartosz
Published: June 2019

Mountain stream gravel is very often legally and illegally mined and gravel is removed from river beds sometimes on the very large scale which is disastrous for fluvial situation of rivers, for river ecology and river engineering works done for flood protection such as river revetments, bridges and all hydraulic structures. This situation makes a big problem for all river managers. Thus gravel mining of the mountain streams in the Polish Carpathians is the subject of many scientific studies when we observe river problems, but also it has a place in Slovakia. This paper deals with such problems additionally showing examples of such bad practices.
Categories of mining areas of closed mines due to limitations of land use for building purposes on selected examples
Authors: Strzałkowski Piotr , Ścigała Roman , Szafulera Katarzyna
Published: June 2019

The paper presents the issue of categorization of mining areas of liquidated coal mines in terms of land development limitations. The authors have presented their observations regarding the determination of hazard zones resulting from the presence of linear and surface discontinuous deformations, excessive subsidence and tilt zones as well as the duration of the final phase of deformation process.
Mechanical behaviour of calcareous waste under consolidated drained triaxial compression testing in saturated conditions
Authors: Zięba Jakub
Published: June 2019

The article presents the mechanical behaviour of calcareous waste under consolidated and drained condition in Triaxial compression test (CD). The host material currently being considered for the construction purpose of several buildings in Poland. One of the location of calcareous waste is in Łagiewniki area (in Cracow) [1,2]. In this work, particular attention has been paid to the to ensure fully saturation for all the tested soil samples and avoid generation of unwanted excess pore water pressure during shearing stage. The saturation level of soil samples was estimated based on Skempton’s law (B>0.95). CD Triaxial test have been conducted in order to derive information on its strength and stiffness properties.
Advantages of suspension structures under seismic effects on the example of the water tank
Authors: Azizov Taliat , Jurkowska Nadzieja , Melnik Oleksiy
Published: June 2019

The paper presents the advantages of suspension buildings and structures in comparison with the traditional buildings. It has been demonstrated, that during an earthquake the strains in the support structures of such buildings and structures are significantly reduced compared to the strains in traditional cantilever buildings. The advantage of the suspension structures is shown by the example of a water tower with a tank of a capacity of 50 m3. Various schemes of the considered construction are given: the construction freely suspended on the bearing frame, the construction with the suspended foundation (prototype). These schemes are compared with the scheme of the cantilever structure. It is proved that the dynamic forces arising from the ground oscillation in the suspended structure are less than the forces in the cantilever structure. The strains depend on the frequency and amplitude of the ground vibrations. The scheme of the forces’ adjustment by means of springs (dampers) is given. It is illustrated that by changing the flexural stiffness of the bearing frame, changing the stiffness of the damper, it is possible to adjust the frequency of oscillations and forces in the suspension building or structure.
Strengthening of masonry and concrete structures working in elevated temperatures and mining tremors area
Authors: Zając Bogusław , Kwiecień Arkadiusz , Gams Matija , Tatara Tadeusz
Published: June 2019

In this paper, comparison of behaviour of composite strengthening bonded to concrete and masonry substrate are presented. Specimens are tested in single lap shear tests under constant load and action of elevated temperatures. Obtained results showed that tested stiff epoxy adhesives are vulnerable to elevated temperatures, changing strain distribution, whereas the tested flexible polyurethane adhesive works stable in the whole tested temperature range. The carried out analysis concerns cracked industrial chimneys working in mining areas, which are strengthened with composite materials and carry thermal and dynamic loads, and can be responsible for the composite strengthening detachment.
Dynamic response of a cable-stayed footbridge to high-energy mining tremors
Authors: Drygała Izabela , Dulinska Joanna M. , Polak Maria Anna , Wazowski Marek
Published: June 2019

In this work an analysis of the dynamic response of a cable-stayed footbridge to mining tremors typical for two main regions of mining activity in Poland, i.e. the Legnica-Glogow Copper District (LGCD) and the Upper Silesian Coal Basin (USCB) is presented. For analysis, a 3-D finite element (FE) model of the structure was created in the ABAQUS/Standard software program. As a final result, the dynamic responses of the footbridge to the typical mining tremors were delivered. For this stage, the numerical simulations were conducted with the non-uniform kinematic excitation as well as with the uniform kinematic excitation. Finally, the evaluation of two calculation approaches was also made for the studied structure.
Structural and Functional Basis of Plasminogen Activation by Staphylokinase
Authors: Jespers L. , Vanwetswinkel S. , Lijnen H. R. , Van Herzeele N. , Van Hoef B. , Demarsin E. , Collen D. , De Maeyer M.
Published: June 2019

Staphylokinase (Sak), a 15.5-kDa bacterial protein, forms a complex with human plasmin, which in turn activates other plasminogen molecules to plasmin. Three recombinant DNA-based approaches, (i) site directed substitution with alanine, (ii) search for proximity relationships at the complex interface, and (iii) active-site accessibility to protease inhibitors have been used to deduce a coherent docking model of the crystal structure of Sak on the homology-based model of micro-plasmin (μPli), the serine protease domain of plasmin. Sak binding on μPli is primarily mediated by two surface-exposed loops, loops 174 and 215, at the rim of the active-site cleft, while the binding epitope of Sak on μPli involves several residues located in the flexible NH2-terminal arm and in the five-stranded mixed β-sheet. Several Sak residues located within the unique μ-helix and the β2 strand do not contribute to the binding epitope but are essential to induce plasminogen activating potential in the Sak:μPli complex. These residues form a topologically distinct activation epitope, which, upon binding of Sak to the catalytic domain of μPli, protrudes into a broad groove near the catalytic triad of μPli, thereby generating a competent binding pocket for micro-plasminogen (μPlg), which buries approximately 2500 Å of the Sak:μPli complex upon binding. This structural and functional model may serve as a template for the design of improved Sak-derived thrombolytic agents. Following the completion and presentation of the present study, the deduced Sak:μPli:μPlg complex was fully confirmed by X-ray crystallography, which further illustrates the power and potential of the present approach.
Differential Inhibition of Thrombin Activity and Thrombin Generation by a Synthetic Direct Thrombin Inhibitor (Napsagatran, Ro 46-6240) and Unfractionated Heparin in Patients with Deep Vein Thrombosis
Authors: Bounameaux Henri , Ehringer Herbert , Gast Alain , Hulting Johan , Rasche Herbert , Rapold Hans J. , Reber Guido , Tschopp Thomas B. ,   ADVENT Investigators
Published: June 2019

Background: Direct thrombin inhibitors belong to a new class of antithrombotic drugs whose effects on blood coagulation in vivo in patients suffering from acute thrombotic conditions have not yet been fully explored. Methods and Results: One hundred and five patients with acute proximal deep-vein thrombosis were randomized to receive a continuous intravenous infusion of napsagatran, a novel synthetic thrombin inhibitor, at a fixed dose of 5 mg/h (n = 36) or 9 mg/h (n = 25) for five days, or APTT-adjusted unfractionated heparin (UFH, n = 44) for the same time. In these patients, thrombin activity and thrombin generation could be assessed by measuring thrombin-antithrombin III complexes (TAT) and prothrombin fragment 1+2 (F1+2), respectively, on three occasions. At baseline, TAT and F1+2 did not differ among the three groups. On Day 2 (steady state), TAT significantly decreased in all groups, and the decrease was significantly more pronounced in the patients given higher-dose napsagatran. F1+2 decreased significantly only in UFH-treated patients. Two hours after cessation of the infusion, the TAT levels increased in the two napsagatran groups but not in the UFH group, whilst F1+2 went back to the baseline levels in the napsagatran-treated patients but remained low in the UFH-treated patients. There was no rebound effect. Conclusions: The data presented suggest that direct thrombin inhibition with napsagatran at 9 mg/h is more potent than UFH in attenuating thrombin activity, but is less potent than UFH in inhibiting thrombin generation. The real significance of these findings will have to be substantiated in further trials with clinically relevant endpoints.
Plasminogen Activator Inhibitor-1 (PAI-1) Promoter 4G/5G Genotype and Increased PAI-1 Circulating Levels in Postmenopausal Women with Coronary Artery Disease
Authors: Grancha S. , Estellés A. , Tormo G. , Falco C. , Gilabert J. , España F. , Cano A. , Segui R. , Aznar J.
Published: June 2019

Increased circulating levels of type 1 plasminogen activator inhibitor (PAI-1) have been associated with coronary artery disease (CAD). However, genetic and environmental determinants of PAI-1 expression are only partially understood. The levels of PAI-1 have been found to relate to 4/5 guanosine (4G/5G) polymorphism in the promoter region of the PAI-1 gene. The 4G allele in this polymorphism has been associated with higher levels of plasma PAI-1 activity, but despite the strong correlation between PAI-1 activity and antigen, no association has been found between PAI-1 antigen levels and the PAI-1 promoter 4G/5G genotype. The aim of the present study was to analyze the influence of the PAI-1 promoter 4G/5G genotype on PAI-1 levels in post-menopause women with coronary disease in comparison with healthy women in pre and postmenopausal status, and the influence of this genotype on variations in PAI-1 levels after hormone replacement therapy (HRT). No differences between 4G/5G allele distribution in the groups studied were observed. The group of postmenopausal women with CAD showed significantly increased PAI-1 antigen and activity levels in comparison with the control groups, and the levels of PAI-1 correlated with the 4G/5G genotype. A multivariate analysis revealed that in the CAD group there was a high correlation between 4G allele dosage and PAI-1 antigen levels, which were also influenced by the triglyceride levels but not by estrogen or glucose levels. After hormone replacement therapy the decrease in PAI-1 levels was correlated with the 4G allele dosage. We conclude that in the group of postmenopausal women with CAD the influence of the PAI-1 promoter 4G/5G genotype on PAI-1 levels is more evident than in the control groups, and that the decrease in PAI-1 levels after HRT in CAD women correlates with the 4G allele dosage.
Procoagulant Activity and Cytokine Expression in Whole Blood Cultures from Patients with Atherosclerosis Supplemented with Omega-3 Fatty Acids
Authors: Seljeflot Ingebjørg , Johansen Odd , Arnesen Harald , Eggesbø Jan-Bertil , Westvik Åse-Britt , Kierulf Peter
Published: June 2019

Omega-3 fatty acids (n-3 FA) may reduce atherogenesis and thrombosis. We investigated the effects of n-3 FAs on procoagulant activity and cytokine expression in whole blood cultures from patients with atherosclerosis. Eleven of the 23 included patients had received 5.1 g n-3 FA daily for 6 months (group I) whereas 12 patients had been on placebo (group II). All patients were then given 5.1g n-3 FA daily for another 4 weeks.

At baseline significantly lower levels of LPS-induced prothrombin fragment1+2 were found in group I (p = 0.010), this difference being eliminated after 4 weeks. Il-6 and TNFαwere significantly higher at baseline in group I and the differences in changes from baseline between the groups were statistically highly significant with increasing values in group II (Il-6 p = 0.001, TNFαp = 0.002).

The present results indicate a reduction in pro-thrombotic potential in patients receiving highly concentrated n-3 FA, whereas some pro-inflammatory responses might be adverse.
Increased Thrombogenic Potential of Human Monocyte-derived Macrophages Spontaneously Transformed into Foam Cells
Authors: Colli Susanna , Lalli Mariagrazia , Risè Patrizia , Mussoni Luciana , Eligini Sonia , Galli Claudio , Tremoli Elena
Published: June 2019

This study investigated whether spontaneous lipid enrichment of human macrophages affects their thrombogenic potential as measured by increased production of tissue factor (TF) and plasminogen activation inhibitor types 1 and 2 (PAI-1 and PAI-2). Macrophages were obtained following a 7-day culture period of monocytes, isolated from the same donor, in autologous serum (HS) or in fetal bovine serum (FBS). Those cultured in HS underwent marked lipid accumulation relative to those cultured in FBS that was accompanied by increased production of TF and PAI-1, but not of PAI-2, and decreased production of interleukin-1β. They also contained more arachidonic and linoleic acid and lower amounts of n-3 polyunsaturated fatty acids, particularly docosahexaenoic acid (22:6). These data indicate that the transformation of macrophages into foam cells results in an increase in their thrombogenic and antifibrinolytic potential and provide a possible explanation of the thrombotic sequelae frequently consequent on plaque fissuring and disruption.
High Prevalence of Factor V Leiden in Healthy Jordanian Arabs
Authors: Awidi A. , Shannak M. , Bseiso A. , Kailani M. A. M. , Kailani M. A. , Omar N. , Anshasi B. , Sakarneh N.
Published: June 2019

The prevalence of APC resistance in healthy Jordanian Arabs was studied. Between October 1996 through September 1997 a total of 400 healthy subjects were studied. There were 212 males and 188 females. APC resistance was studied by functional and DNA methods. There were a total of 52 subjects (13%) who were APC resistant by the functional test. There were 49 subjects (12.25%) who had FV Q506 by DNA test. Of these there were 42 heterozygous and 7 homozygous (allele frequency 0.07). None of the subjects had clinical thrombosis. It is concluded that the prevalence of APC resistance due to FV Q506 is high in Jordanian Arabs.
Nucleotide Structure and Characterization of the Murine Gene Encoding the Endothelial Cell Protein C Receptor
Authors: Liang Zhong , Rosen Elliot D. , Castellino Francis J.
Published: June 2019

The nucleotide sequence of the entire gene encoding the murine endothelial cell receptor for activated protein C (EPCR) has been determined. A total of 5303 bp of DNA was sequenced that included 4 exons and three introns, which constituted the coding region of the gene, as well as 393 bp upstream of the first exon and 841 bp downstream of the last exon. From the locations of the introns in this gene and analysis of the exon structures, it is clear the EPCR gene is a member of the CD1 class of multiple histocompatibility proteins, and its cDNA sequence is nearly identical to that of CCD41, a centrosome-associated protein. All elements needed for RNA polymerase II-based transcription are predicted to exist in the 5’ uncoded region of the gene, and potential 3’ regulatory sequences for efficient polyadenylation have been located at their optimal locations. A variety of highly probable transcription factor binding sites have been located in the 5’ region of the gene. These data suggest that the EPCR gene is under efficient transcriptional control, and support the finding that this gene product may be involved in the inflammatory pathway.
Fibrin-specificity of a Plasminogen Activator Affects the Efficiency of Fibrinolysis and Responsiveness to Ultrasound: Comparison of Nine Plasminogen Activators In Vitro
Authors: Sakharov Dmitry V. , Barrett-Bergshoeff Marrie , Hekkenberg Rob T. , Rijken Dingeman C.
Published: June 2019

In a number of cases, thrombolytic therapy fails to re-open occluded blood vessels, possibly due to the occurrence of thrombi resistant to lysis. We investigated in vitro how the lysis of hardly lysable model thrombi depends on the choice of the plasminogen activator (PA) and is accelerated by ultrasonic irradiation. Lysis of compacted crosslinked human plasma clots was measured after addition of nine different PAs to the surrounding plasma and the effect of 3 MHz ultrasound on the speed of lysis was assessed.

Fibrin-specific PAs showed bell-shaped dose-response curves of varying width and height. PAs with improved fibrin-specificity (staphylokinase, the TNK variant of tissue-type PA [tPA], and the PA from the saliva of the Desmodus rotundus bat) induced rapid lysis in concentration ranges (80-, 260-, and 3,500-fold ranges, respectively) much wider than that for tPA (a 35-fold range). However, in terms of speed of lysis, these three PAs exceeded tPA only slightly. Reteplase and single-chain urokinase were comparable to tPA, whereas two-chain urokinase, anistreplase, and streptokinase were inferior to tPA. In the case of fibrin-specific PAs, ultrasonic treatment accelerated lysis about 1.5-fold. For streptokinase no acceleration was observed. The effect of ultrasound correlated with the presence of plasminogen in the outer plasma, suggesting that it was mediated by facilitating the transport of plasminogen to the surface of the clot.

In conclusion, PAs with improved fibrin-specificity induce rapid lysis of plasminogen-poor compacted plasma clots in much wider concentration ranges than tPA. This offers a possibility of using single-or double-bolus administration regimens for such PAs. However, it is not likely that administration of these PAs will directly cause a dramatic increase in the rate of re-opening of the occluded arteries since they are only moderately superior to tPA in terms of maximal speed of lysis. Application of high-frequency ultrasound as an adjunct to thrombolytic therapy may increase the treatment efficiency, particularly in conjunction with fibrin-specific PAs.
Thrombin Induces Surface and Intracellular Secretion of Amyloid Precursor Protein from Human Endothelial Cells
Authors: Ciallella John R. , Figueiredo Helmer , Smith-Swintosky Virginia , McGillis Joseph P.
Published: June 2019

Thrombin, a major coagulant and inflammatory mediator, was shown to regulate amyloid precursor protein (APP) secretion. APP is the protein from which the amyloid beta peptide (Aß) is derived. Aß forms the core of vascular and cerebral plaques in Alzheimer’s disease (AD). In this study, human umbilical vein endothelial cells (HUVEC) were used to examine the effects of thrombin on APP expression. Cell supernatants from thrombin-treated HUVEC were immunoblotted to measure secreted APP. Thrombin-induced secretion of APP peaks at approximately 30 min post-treatment. Immunohistochemical analysis found that APP is not colocalized with or secreted through the same pathway as coagulation factor VIII. The secretion of APP is thrombin receptor-mediated, since it is inhibited by the thrombin antagonist N-Acetyl-D-Phe-Pro1Amido-4-Guanidino-Butyl-1-Boronic Acid. It also is induced by treatment with a calcium ionophore. Moreover, APP secretion is protein kinase C (PKC)-dependent because it is blocked by the PKC inhibitor bisindolylmaleimide. APP secretion also occurs from the cell surface, possibly through direct cleavage by thrombin. Immunoreactivity on the surface of HUVEC decreased after thrombin treatment but not after treatment with a non-proteolytic thrombin receptor activator. These data suggest that thrombin induces APP secretion through a PKC-dependent mechanism, as well as from the cell surface. Our results are consistent with thrombin playing a role in AD pathology.
The Independence of Maximal Intimal Thickening from Severity of Balloon Injury in the Rabbit Aorta
Authors: Waissbluth Alvaro D. , Schwartz David , Abendschein Dana R. , Eisenberg Paul R.
Published: June 2019

Endothelial injury induces intimal thickening, but whether more extensive injury increases the extent of neointimal proliferation in the rabbit aorta is not well defined. We induced graded injury in the abdominal aortas of rabbits and maximal intimal/medial (I/M) area and thickness ratios were calculated from aortic cross sections harvested 2 weeks after injury. The degree of injury was verified by blinded observers who graded the extent of disruption of the internal elastic laminae. Intimal thickening was not significantly different after severe injury (mean maximal I/M area ratio 0.32 ± 0.02 [SE], n = 16) compared with moderate injury (0.23 ± 0.02, n = 8, p = 0.24), but was greater than that induced by mild injury (0.08 ± 0.01, n = 7, p <0.0001). The ratio of the maximal I/M thickness was similar in all groups (I/M thickness ratio 0.68 ± 0.04, 0.73 ± 0.04, and 0.56 ± 0.04 for severe, moderate, and mild focal injury groups, respectively; p = 0.19). Thus, balloon injury of the rabbit aorta induces reproducible thickening of the intima by 2 weeks. The maximal I/M area ratio is dependent on the extent of injury, while the maximal intimal thickening is independent.
A model study on effects of vanadium ion diffusion through ion exchange membranes in a non-aqueous redox flow battery
Authors: Lee Dohyeon , Ryu Seungbo , Shin Sung-Hee , Kim Jae-Hun , Moon Seung-Hyeon
Published: June 2019

A simple charge-discharge model of a nonaqueous vanadium redox flow battery (VRFB) was introduced in this study to analyze the diffusion coefficients of active materials permeating an electrolyte membrane. Using this model, the effects of diffusion coefficients on the long-term performance, efficiency, and capacity of the system have been studied. Based on a literature review, the diffusion coefficients of approximately 10−7–10−6 cm2 s−1 were applied and the results were analyzed to determine relevant parameters for this study. Through this study, it has been confirmed that the capacity of the system was maintained at 100% under ideal conditions in the long-term operation, whereas that of the system reduced by more than half when only one vanadium species moved and is 10 mAh when all vanadium species moved. In addition, the simulation clarified the effect of diffusion coefficients on coulombic efficiency. In most conditions of the various diffusion coefficients, coulombic efficiency enhanced through cycle had been operated. In the case of voltage efficiency, the value was not largely changed regardless of diffusion coefficients since it was affected more by other factors. One important factor revealed through this model study is that electrolyte membrane performance of the VRFB system was not only affected by the diffusion coefficient of a specific ion, but also by the relationship between the diffusion coefficients of all active ions involved in the reaction. This study provides guidance for the development of an electrolyte membrane to improve the performance of VRFB systems.
Numerical computation of rare events via large deviation theory
Authors: Grafke Tobias , Vanden-Eijnden Eric
Published: June 2019

An overview of rare event algorithms based on large deviation theory (LDT) is presented. It covers a range of numerical schemes to compute the large deviation minimizer in various setups and discusses best practices, common pitfalls, and implementation tradeoffs. Generalizations, extensions, and improvements of the minimum action methods are proposed. These algorithms are tested on example problems which illustrate several common difficulties which arise, e.g., when the forcing is degenerate or multiplicative, or the systems are infinite-dimensional. Generalizations to processes driven by non-Gaussian noises or random initial data and parameters are also discussed, along with the connection between the LDT-based approach reviewed here and other methods, such as stochastic field theory and optimal control. Finally, the integration of this approach in importance sampling methods using, e.g., genealogical algorithms, is explored.
Magnetic mirror metasurface based on the in-phase excitation of magnetic dipole and electric quadrupole resonances
Authors: González-Alcalde Alma K. , G. Mandujano Miguel A. , Salas-Montiel Rafael , Le Cunff Loïc O. , Lerondel Gilles , Méndez Eugenio R.
Published: June 2019

We consider the design of magnetic mirrors that consist of a layer of two-dimensional high-refractive-index dielectric particles. The central idea is to search for conditions for which the electric field of the light backscattered by a single particle has a zero phase difference with respect to the incident field. Employing physical arguments, we conclude that this can occur when the electric dipolar contribution vanishes. Optimizing the form of the cross section, we find a situation in which the vanishing of the dipolar contribution coincides with an in-phase condition for the magnetic dipole and the electric quadrupole contributions. The resulting scattering pattern of the particle resembles that of an electric dipole, with the difference that the forward and backscattered electric fields have opposite signs. Based on these results, we design a metasurface reflector that behaves as a magnetic mirror at a specific wavelength within a wideband spectral response. Subsequently, we extend the results to the design of supported structures where a magnetic mirror condition at a single wavelength is similarly found.
Schrödinger-Poisson system with concave-convex nonlinearities
Authors: Shao Mengqiu , Mao Anmin
Published: June 2019

We consider a class of the Schrödinger-Poisson system with concave-convex nonlinearities. Under some suitable assumptions, we prove the existence of nontrivial solutions and infinitely many negative energy solutions by using the variational method and making accurate analysis on the combined effect of parameters μ and λ. Our results extend that in the related works.
Fourier transform plasmon resonance spectrometer using nanoslit-nanowire pair
Authors: Uulu Doolos Aibek , Ashirov Timur , Polat Nahit , Yakar Ozan , Balci Sinan , Kocabas Coskun
Published: June 2019

In this paper, we present a nanoscale Fourier transform spectrometer using a plasmonic interferometer consisting of a tilt subwavelength slit-nanowire pair on a metallic surface fabricated by the focused ion beam microfabrication technique. The incident broadband light strongly couples with the surface plasmons on the gold surface, and thus, surface plasmon polaritons (SPPs) are generated. The launched SPPs interfere with the incident light and generate high contrast interference fringes in the nanoslit. The transmitted SPPs through the metal nanoslit can decouple into free space and are collected by an objective in the far field. The spectroscopic information of the incidence light is obtained by fast Fourier transform of the fringe pattern of the SPPs. In our design, there is no need for a bulky dispersive spectrometer or dispersive optical elements. The dimension of the spectrometer is around 200 μm length. Our design is based on inherent coherence of the SPP waves propagating through the subwavelength metal nanoslit structures etched into an opaque gold film.
Modulation ferromagnetism in multiferroic BiFeO3 nanocrystals via bandgap engineering
Authors: Zhou Hang , Luo Xingfang , Yuan Cailei , Hong Aijun , He Jun , Lei Wen
Published: June 2019

In addition to electric fields and currents, light can also provide an approach to modulate the ferromagnetism with low energy consumption. BiFeO3, with features of relatively small bandgap and large polarization, provides an opportunity for investigating the optical modulation of magnetism. In this work, pure-phase BiFeO3 nanocrystals embedded in Al2O3 films are synthesized. It is demonstrated that the strain generated and accumulated during the growth process of BiFeO3 nanocrystals can lead to the modification of the atomic structure and thus produce a strain engineered bandgap. A distinguished light-modulated ferromagnetism is observed in BiFeO3 nanocrystals. Contributed by the strain engineered bandgap, the ferromagnetism of BiFeO3 nanocrystals can be modulated and enhanced more efficiently by light irradiation. It paves the way for modulating the ferromagnetic properties of BiFeO3 nanocrystals via bandgap engineering, which has promising applications in modern information technology.
Meso-resolved simulations of shock-to-detonation transition in nitromethane with air-filled cavities
Authors: Mi X. C. , Michael L. , Ioannou E. , Nikiforakis N. , Higgins A. J. , Ng H. D.
Published: June 2019

Two-dimensional meso-resolved numerical simulations are performed to investigate the complete shock-to-detonation transition (SDT) process in a mixture of liquid nitromethane (NM) and air-filled, circular cavities. The shock-induced initiation behaviors resulting from the cases with neat NM, NM with an array of regularly spaced cavities, and NM with randomly distributed cavities are examined. For the case with randomly distributed cavities, hundreds of cavities are explicitly resolved in the simulations using a diffuse-interface approach to treat two immiscible fluids and graphic processing unit-enabled parallel computing. Without invoking any empirically calibrated, phenomenological models, the reaction rate in the simulations is governed by Arrhenius kinetics. For the cases with neat NM, the resulting SDT process features a superdetonation that evolves from a thermal explosion after a delay following the passage of the incident shock wave and eventually catches up with the leading shock front. For the cases wherein mesoscale heterogeneities are explicitly considered, a gradual SDT process is captured. These two distinct initiation behaviors for neat NM and heterogeneous NM mixtures agree with experimental findings. Via examining the global reaction rate of the mixture, a unique time scale characterizing the SDT process, i.e., the overtake time, is measured for each simulation. For an input shock pressure less than approximately 9.4GPa, the overtake time resulting from a heterogeneous mixture is shorter than that for neat NM. This sensitizing effect is more pronounced for lower input shock pressures. A random distribution of cavities is found to be more effective in enhancing the SDT process than a regular array of cavities. Statistical analysis on the meso-resolved simulation data provides more insights into the mechanism of energy release underlying the SDT process. Possible directions toward a quantitatively better agreement between the experimental and meso-resolved simulation results are discussed.
Derivation of renormalized Gibbs measures from equilibrium many-body quantum Bose gases
Authors: Lewin Mathieu , Nam Phan Thành , Rougerie Nicolas
Published: June 2019

We review our recent result on the rigorous derivation of the renormalized Gibbs measure from the many-body Gibbs state in 1D and 2D. The many-body renormalization is accomplished by simply tuning the chemical potential in the grand-canonical ensemble, which is analogous to the Wick ordering in the classical field theory.
State dependent ring polymer molecular dynamics for investigating excited nonadiabatic dynamics
Authors: Chowdhury Sutirtha N. , Huo Pengfei
Published: June 2019

A recently proposed nonadiabatic ring polymer molecular dynamics (NRPMD) approach has shown to provide accurate quantum dynamics by incorporating explicit state descriptions and nuclear quantizations. Here, we present a rigorous derivation of the NRPMD Hamiltonian and investigate its performance on simulating excited state nonadiabatic dynamics. Our derivation is based on the Meyer-Miller-Stock-Thoss mapping representation for electronic states and the ring-polymer path-integral description for nuclei, resulting in the same Hamiltonian proposed in the original NRPMD approach. In addition, we investigate the accuracy of using NRPMD to simulate the photoinduced nonadiabatic dynamics in simple model systems. These model calculations suggest that NRPMD can alleviate the zero-point energy leakage problem that is commonly encountered in the classical Wigner dynamics and provide accurate excited state nonadiabatic dynamics. This work provides a solid theoretical foundation of the promising NRPMD Hamiltonian and demonstrates the possibility of using the state-dependent RPMD approach to accurately simulate electronic nonadiabatic dynamics while explicitly quantizing nuclei.
On the “Born” term used in thermodynamic models for electrolytes
Authors: Simonin Jean-Pierre
Published: June 2019

In the literature, many expressions for the Helmholtz or Gibbs energy of electrolyte solutions have included a term that takes into account the variation of the solution permittivity with the composition of solution (e.g., within the statistical-associated fluid theory formalism). This contribution is often called the “Born” term because it was inspired by the classic expression established by Born to describe the solvation energy of an ion. The present work is an attempt to get more physical insight into this semiempirical “Born” term. The way in which it has been used in the literature is briefly examined, and its typical magnitude is evaluated. Next, it is proposed to use the nonprimitive mean spherical approximation model to calculate the chemical potential of an ion in a solution composed of charged hard spheres (HSs) (the ions) and dipolar HSs (the solvent). The cation and the anion are monovalent monoatomic ions of equal diameter. The dipoles have a different size and mimic water molecules. The theoretical expressions for this model were found to fulfill the Gibbs-Duhem relation, which suggests that they are correct. A rescaled ion-dipole contribution is introduced, in a form that is suitable for inclusion in electrolyte models. It is compared with a “Born” term expressed in the same framework. It is found that the former is in general not well estimated by the latter. The two might even be of opposite signs in the case of ions of sufficiently small size.
Controllable conduction and hidden phase transitions revealed via vertical strain
Authors: Zhao Run , Chen Yu , Ji Yanda , Li Weiwei , Chen Li , He Anpeng , Lu Hao , Zhao Meng , Yao Jinlei , Jiang Yucheng , Liu Guozhen , Gao Ju , Wang Haiyan , Yang Hao
Published: June 2019

The desire for room-temperature multiferroicity has motivated the search for hidden phase transitions at higher temperatures. By means of the imposition of vertical strain in EuTiO3 (ETO)–MgO nanocomposite films, we unveil two hidden phase transitions in the strained ETO phase at around T′ = 80 K and T* = 230 K, and we are able to tune the behavior of the electrical conductivity at these temperatures. Compared with the phase transition temperatures in bulk ETO, T′ remains unchanged and T* is increased owing to stretching of the c-axis lattice. Interface-limited conduction appears at both transitions, in contrast to the bulk-limited mode shown at other temperatures. With regard to the underlying mechanism, it is found that controllable behavior of conduction at the transition temperatures can be achieved by the common effect of vertical strain and oxygen vacancies. Overall, the present work highlights the importance of the effect of vertical strain in revealing and enhancing the tunability of properties at hidden phase transitions.
Coarse-graining of many-body path integrals: Theory and numerical approximations
Authors: Ryu Won Hee , Han Yining , Voth Gregory A.
Published: June 2019

Feynman’s imaginary time path integral approach to quantum statistical mechanics provides a theoretical formalism for including nuclear quantum effects (NQEs) in simulation of condensed matter systems. Sinitskiy and Voth [J. Chem. Phys. 143, 094104 (2015)] have presented the coarse-grained path integral (CG-PI) theory, which provides a reductionist coarse-grained representation of the imaginary time path integral based on the quantum-classical isomorphism. In this paper, the many-body generalization of the CG-PI theory is presented. It is shown that the N interacting particles obeying quantum Boltzmann statistics can be represented as a system of N pairs of classical-like pseudoparticles coupled to each other analogous to the pseudoparticle pair of the one-body theory. Moreover, we present a numerical CG-PI (n-CG-PI) method applying a simple approximation to the coupling scheme between the pseudoparticles due to numerical challenges of directly implementing the full many-body CG-PI theory. Structural correlations of two liquid systems are investigated to demonstrate the performance of the n-CG-PI method. Both the many-body CG-PI theory and the n-CG-PI method not only present reductionist views of the many-body quantum Boltzmann statistics but also provide theoretical and numerical insight into how to explicitly incorporate NQEs in the representation of condensed matter systems with minimal additional degrees of freedom.
Optimized waveguide coupling of an integrated III-V nanowire laser on silicon
Authors: Bissinger Jochen , Ruhstorfer Daniel , Stettner Thomas , Koblmüller Gregor , Finley Jonathan J.
Published: June 2019

The recent integration of III-V semiconductor nanowire (NW) lasers on silicon waveguides marked a key step toward their usage as coherent light sources for future silicon photonics applications. However, the low index contrast between III-V semiconductors and silicon results in a weak modal reflectivity, calling for improved design structures that enable both low-threshold lasing and good in-coupling efficiency into waveguides. Here, we perform numerical simulations to explore how the alternating refractive index of a silicon waveguide with a thin SiO2 interlayer can be used to significantly improve the reflectivity at the III-V–silicon interface to values of up to 83%. We further investigate the frequency dependencies of the end-facet reflectivity and in-coupling efficiency as a function of the nanowire and waveguide dimensions. Our results are kept general by the normalization to the nanowire radius R and show for a waveguide width of 2.75⋅R a maximum coupling efficiency of 50%. Variations in waveguide height or SiO2 interlayer thickness by ±0.1⋅R increase the coupling efficiency by a factor of 2, with little effect on the end-facet reflectivity. Ultimately, a prototypical NW-laser structure consisting of a 1.3-μm emitting InGaAs MQW active region in a core-multishell structure was simulated, showing an optimized low-threshold gain of <500 cm−1 for a TE01 mode with a coupling efficiency of ∼13%. By simplified approximations, we illustrate that these analyses can be adapted to a variety of material systems and serve as guidelines in the construction of optimized nanowire lasers on silicon-on-insulator waveguides for future on-chip optical interconnects.
Signatures of physical aging and thixotropy in aqueous dispersion of Carbopol
Authors: Agarwal Mayank , Joshi Yogesh M.
Published: June 2019

In this work, we investigate signatures of physical aging in an aqueous dispersion of Carbopol that shows yield stress and weak enhancement in elastic modulus as a function of time. We observe that the creep curves, as well as strain recovery, show a significant dependence on waiting time elapsed since shear melting. The corrected strain, which is the strain in excess of the recovered strain, has been observed to show time–waiting time superposition in the effective time domain, wherein time is normalized by time dependent relaxation time that shows a power-law dependence. The corresponding power law exponent, which is close to unity in a limit of small stresses, decreases with stress and tends to zero as stress approaches the yield stress. For a range of stresses, the material shows time–stress superposition suggesting the shape of the evolving relaxation time spectrum to be independent of the time as well as the stress. This work, therefore, suggests the presence of physical aging in an aqueous dispersion of Carbopol even though the elastic modulus shows only a weak enhancement. We also discuss the Andrade type of creep behavior in aqueous Carbopol dispersion.