bluuebunny/crossref_metadata_2025 huggingface dataset:
Variations of seismic activity caused by the Chandler Wobble
Authors: Blagoveshchenskaya Elena , Lyskova Evgenia , Sannikov Konstantin
Published: November 2019

The problem of the correlation of the global dynamic phenomenon “Chandler wobble” with the local dynamics in different parts of the Earth’s crust and lithosphere is wide of the solution. In this study, an attempt was made to approach the solution by analyzing the temporal variations of local seismic activity in the restricted geospace volumes (GSV) within the uniform seismoactive regions. The driver of Chandler wobble is the deep mantle – the most hard and most massive Earth’s layer, whose large inertia tensor value is able to keep up Chandler’s specific rotation of the Earth for a long time. We use the geocentric coordinate system where daily rotation is absent. In this system Chandler wobble is very slow rotation of the Earth around the current equatorial axis (the pole of which is denoted as EP14). Probably, this slow rotation can influence on the seismic events in the GSV. This influence is proposed to determine by the some statistical parameter EP14gsv that indicates the most typical position EP14 on equator when the most part of the earthquakes have occurred in the given GSV. For some geospace volumes the distribution indicates certain longitudes, where the number of seismic events is maximal or minimal.
Diabetische Pneumopathie
Authors: Kopf Stefan
Published: November 2019

Breathlessness or dyspnea is a frequent symptom in patients with diabetes and the first disease which has to be excluded is the coronary heart disease. However, previous epidemiological studies have shown that patients with diabetes mellitus have an increased risk for fibrotic pulmonary diseases, such as the idiopathic pulmonary fibrosis (IPF). Recent studies were able to show that patients with newly diagnosed type 2 diabetes have impaired pulmonary oxygen consumption and over 26 % of patients with long-term type 2 diabetes showed restrictive lung function with fibrotic interstitial lung diseases. Especially patients with type 2 diabetes and nephropathy had an 8-fold higher risk for lung diseases. This is not surprising since the pathomechanisms of pulmonary fibrosis and diabetic complications have much in common: reactive oxygen species induce DNA-damage with consecutive activation of inflammatory cytokines which induce fibrotic remodeling of the tissue. This leads us to the suggestion that patients with diabetes, albuminuria and breathlessness should be examined for interstitial lung disease on regular basis. However, data regarding the natural course of diabetic pneumopathy and therapeutic approaches are still missing. Small intervention studies with IPF-patients could show that sports and physical activity were able to stabilize the disease progression.
Several Circulating Biomarkers for PCOS Diagnosis
Authors: Luo Peiqi , Zhang Cheng , He Yirui , Yang Gangyi , Liu Hua , Li Ling
Published: November 2019

Aims Irisin, Betatrophin and Zinc-α2-glycoprotein (ZAG) have been
shown to be associated with insulin resistance (IR) and polycystic ovary
syndrome (PCOS), respectively. The purpose of this study is to explore the
potential accuracy of this combination of three cytokines in screening
PCOS.

Methods 186 individuals were recruited for this study. Circulating
Irisin, Betatrophin and ZAG concentrations were measured by enzyme-linked
immunosorbent assay. The association between these serum biomarkers and PCOS
was assessed by logistic regression analysis. Receiver operating curve (ROC)
analysis was performed to evaluate the diagnostic value of these biomarkers
for PCOS women.

Results In women with PCOS, serum Irisin and Betatrophin levels were
markedly elevated compared to those in healthy controls (p<0.01), while
ZAG levels were lower (p<0.01). PCOS women with IR (M-value<6.28) had
lower circulating ZAG concentrations, and higher circulating Irisin and
Betatrophin levels relative to PCOS women without IR (M-value ≥ 6.28). ROC
curve analyses showed that the AUC for Irisin, ZAG and Betatrophin for
predicting PCOS were 0.77, 0.83 and 0.85, respectively. In a joint ROC
curves analysis of these serum markers and other parameters, the results
showed that the AUC was 0.93, and the sensitivity and specificity were 82.1
% and 92.3 %, respectively.

Conclusions When compared to using single cytokine, the analysis of
Irisin, ZAG and Betatrophin elevates the accuracy in diagnosing PCOS.
Metal-Free Synthesis 6-Benzylphenanthridines via Radical Addition/Cyclization of 2-Isocyanobiphenyls
Authors: Lu Yuling , Chen Li , Chen Xia , Yao Meng , Luo Zengwei , Zhang Yonghui
Published: November 2019

A simple and practical approach has been established for the synthesis of 6-benzylphenanthridines from benzylic hydrocarbons and 2-isocyanobiphenyls via C(sp3)–H/C(sp2)–H bond functionalization under metal-free condition. The reaction exhibits good functional group tolerance and delivers the target products in moderate to excellent yields. The preliminary mechanistic investigation revealed that a radical intermediate might be involved in this reaction.
Synthesis of N-(Hetero)arylconvolvine Derivatives through a Palladium-Catalyzed Buchwald–Hartwig Cross-Coupling
Authors: Hassine Manel , Jannet Hichem Ben , Ghermani NourEddine , Alami Mouad , Messaoudi Samir
Published: November 2019

The present study describes the isolation of convolvine from the roots of the Tunisian plant Convolvulus dorycnium L. and its synthesis through a four-step sequence starting from tropine. Then, an efficient synthesis of N-(het)aryltropanes derivatives by a sequence of a palladium-catalyzed N-arylationof convolvine has been established. This strategy enabled access to unknown tropane scaffolds of biological interests.
The Reaction of 6-(4-Chloro-5H-1,2,3-dithiazol-5-ylidene)-4-methylcyclohexa-2,4-dien-1-one with Benzene-1,2-diamine: Synthesis and Chemistry of N-(2-Aminophenyl)-2-hydroxy-5-methylbenzimidoyl Cyanide
Authors: Koyioni Maria , Koutentis Panayiotis A.
Published: November 2019

(Z)-6-(4-Chloro-5H-1,2,3-dithiazol-5-ylidene)-4-methylcyclohexa-2,4-dien-1-one, readily prepared from 4,5-dichloro-1,3,4-dithiazolium chloride and p-cresol, reacts with benzene-1,2-diamine to give N-(2-aminophenyl)-2-hydroxy-5-methylbenzimidoyl cyanide. The latter, in acidic media, cyclizes to give, depending on the reaction conditions, 2-methylbenzofuro[2,3-b]quinoxaline, 2-(1H-benzo[d]imidazol-2-yl)-4-methylphenol or 2-(3-aminoquinoxalin-2-yl)-4-methylphenol.
Total Synthesis of (–)-Alstofolinine A: Selected Furan Oxidation/ Cyclization Cascade
Authors: Zhang Ye , Zhang Lei , Qi Xiangbing
Published: November 2019

Indole-fused tetracyclic ring systems containing nitrogen atoms are common core skeletons of many indole alkaloids such as sarpagine, macroline, and ajmaline. Efficient and stereoselective construction of these ring systems can promote the development of the corresponding alkaloid syntheses. In this article, we briefly summarize our current progress toward the application of the aza-Achmatowicz reaction and indole nucleophilic addition reaction cascade for the first asymmetric total synthesis of the macroline-type indole alkaloid (–)-Alstofolinine A. Our synthetic strategy is based on furan oxidation/rearrangement and proceeds from easily accessible materials such as indole and furan derivatives.
Silver-Mediated Intramolecular Friedel–Crafts-Type Cyclizations of 2-Benzyloxy-3-bromoindolines: Synthesis of Isochromeno[3,4-b] indolines and 3-Arylindoles
Authors: Yamashiro Toshiki , Yamada Koji , Yoshida Haruka , Tomisaka Yutaro , Nishi Takahide , Abe Takumi
Published: November 2019

We disclose a silver-mediated intramolecular Friedel–Crafts-type cyclization of 2-benzyloxy-3-bromoindolines to afford an untapped family of isochromeno[3,4-b]indolines and 3-arylindoles, in which deformylative arylation of 2-(4-methoxybenzyloxy)-3-bromoindolines is reported for the first time. The isochromeno[3,4-b]indolines can be readily transformed into other heterocyclic moieties.
Metal-Free 1,2,3-Triazole Synthesis in Deep Eutectic Solvents
Authors: Sebest Filip , Haselgrove Samuel , White Andrew J. P. , Díez-González Silvia
Published: November 2019

The metal-free regioselective preparation of 1,5- and 1,4-disubstituted triazoles is reported through a cycloaddition–elimination sequence. Reactions were carried out in environmentally friendly deep eutectic solvent (DES) and pure products were isolated without the need for chromatographic techniques.
Caecal Herniation through the Foramen of Winslow: A Lesser Known Complication of the Lesser Sac
Authors: Charters Pia , Lowe Andrew , Keogan Richard , Edwards Tom
Published: November 2019

The foramen of Winslow is the omental communication between the greater and lesser sac. An internal hernia through the foramen of Winslow is extremely rare, accounting for <0.1% of abdominal hernias and 8% of internal hernias. The majority of lesser sac hernias contain small bowel only, less commonly cecum or omentum. Diagnostic delay is associated with high morbidity and mortality, and accurate radiological interpretation is invaluable to guide surgical intervention. As such, the recognition of foramen of Winslow herniation on computed tomography (CT) is paramount. We present a case of caecal herniation that was recognized early and reversed within 48 hours of presentation, without the need for bowel resection.
Quantifying Medication Exposure in Very Low Birth Weight Neonates
Authors: Davis Natalie L. , Akinmboni Temitope O. , Mooney Sandra M.
Published: November 2019

Objective Very low birth weight (VLBW) infants are exposed to medications with insufficient evidence describing pharmacokinetics and safety. Objective was to quantify and identify risk factors associated with the highest quartile of medication exposure.

Study Design Retrospective record review of VLBW infants admitted to a level-IV neonatal intensive care unit (NICU). We obtained baseline clinical and demographic characteristics, as well as data on all medications received during admission. Characteristics of patients within the upper quartile of medication use were compared with remaining patients.

Results Identified 106 infants, mean birth weight (BW) = 961 g, gestational age = 27.3 weeks. Infants received a median = 20 medications (range, 4–72). Those in the top quartile of medication use received ≥30 medications while in the NICU and had higher odds of being male sex, lower BW, longer length of hospital stay (LOHS), and bronchopulmonary dysplasia. Sepsis did not affect medication exposure. Antibiotics, opiates, and reflux medications were among the top prescribed.

Conclusion Infants are exposed to a large number of medications during NICU hospitalization, including potentially unnecessary antibiotics and reflux medications. Male sex, the presence of certain comorbidities such as necrotizing enterocolitis, and LOHS, are associated with higher exposure. Increased awareness of this issue may assist in decreasing medication exposure in VLBW populations.
Off-Pump Tricuspid Annuloplasty through a Direct Transatrial Approach: Early Results
Authors: Andreas Martin , Werner Paul , Laufer Guenther , Sauer Jude
Published: November 2019

Severe tricuspid regurgitation constitutes a growing disease burden. Conventional surgery for tricuspid valve disease has an increased risk while several interventional procedures are currently under clinical investigation, yet do not offer comprehensive solutions. We investigated a novel surgical approach for off-pump beating-heart tricuspid annuloplasty in circulating blood through a single port in the right atrium. Early feasibility results in preclinical porcine in vivo studies encourage further development of this approach, combining the proven concept of surgical annuloplasty with the benefits of minimally invasive off-pump procedures in a hybrid setting.
Subfoveal Choroidal Thickness and Associated Changes of Angiogenic Factors in Women with Severe Preeclampsia
Authors: Stern-Ascher Conrad N. , North Victoria S. , Garg Aakriti , Ananth Cande V. , Wapner Ronald J. , Bearelly Srilaxmi
Published: November 2019

Objective Severe preeclampsia complicates roughly 1% of all pregnancies. One defining feature of severe preeclampsia is new onset visual disturbance. The accessibility of the choroid to high-resolution, noninvasive imaging makes it a reasonable target of investigation for disease prediction, stratification, or monitoring in preeclampsia. This study aimed to compare subfoveal choroidal thickness between women with severe preeclampsia and those with normotensive pregnancies, and to investigate associations between such findings and other indicators of disease severity, including gestational age and serum angiogenic factors.

Study Design We designed a case-control study comprised of 36 women diagnosed with severe preeclampsia (cases) matched to 37 normotensive women (controls) by race/ethnicity and parity, all diagnosed in the postpartum period. All patients underwent enhanced depth imaging spectral-domain optical coherence tomography and serum analysis.

Results Cases showed no difference in subfoveal choroidal thickness compared with controls (p = 0.65). Amongst cases, subfoveal choroidal thickness and gestational age at delivery were inversely related (r = 0.86, p < .001). There was a positive association of placental growth factor with subfoveal choroidal thickness amongst cases (r = 0.54, p = 0.002).

Conclusion This study suggests a relationship between the degree of disease severity and the magnitude of choroidal thickening. We also show an association between this index and placental growth factor level in the postpartum period.
Glucose Levels during the First 24 Hours following Perinatal Hypoxia
Authors: Alsaleem Mahdi , Zeinali Lida I. , Mathew Bobby , Kumar Vasantha H.S.
Published: November 2019

Objective Hypoglycemia is a significant risk factor for perinatal brain injury and adverse outcomes, particularly in infants requiring resuscitation following hypoxic ischemic (HI) insult. We aimed to study blood glucose (BG) levels in physiologically stressed infants in the presence or absence of epinephrine (Epi) administration at resuscitation in the first 24 hours after birth.

Study Design A retrospective chart review of all infants with heart rate (HR) < 100/min at 1 minute requiring positive pressure ventilation (PPV) at birth was performed. Infants were classified into two groups as follows: (1) PPV group: infants' HR improved with PPV only at resuscitation, and Epi group: infants received Epi at resuscitation for persistent bradycardia. Serial measurements of BG levels collected and glucose infusion rate (GIR) calculated at 24 hours.

Results By design, infants in the Epi group had lower cord pH and higher base deficit. BG was significantly lower overtime in premature infants ≤32 weeks of gestation in the Epi group. The BG was markedly higher in near-term and term infants in the Epi group compared with the PPV group. Hypoglycemia was more common despite administration of higher GIR in premature infants ≤32 weeks of gestation.

Conclusion In the presence of physiological stress, premature infants are more at risk for hypoglycemia than term infants.
Modelization of Blood-Borne Hypercoagulability in Myeloma: A Tissue-Factor-Bearing Microparticle-Driven Process
Authors: Papageorgiou Loula , Alhaj Hussen Kutaiba , Thouroude Sandrine , Mbemba Elisabeth , Cost Héléne , Garderet Laurent , Elalamy Ismail , Larsen Annette , Van Dreden Patrick , Dimopoulos Meletios A. , Mohty Mohamad , Gerotziafas Grigoris T.
Published: November 2019

Introduction Hypercoagulability is a common blood alteration in newly diagnosed chemotherapy naïve patients with multiple myeloma. The identification of the procoagulant potential of cancer cells, which is principally related to tissue factor (TF) expression, attracts particular interest. The mechanisms by which myeloma plasma cells (MPCs) activate blood coagulation have been poorly investigated.

Aim To identify the principal actors related with MPCs that boost thrombin generation (TG).

Methods TF and annexin V expression by MPCs and MPC-derived microparticles (MPC-dMPs) was analyzed by flow cytometry. TF activity (TFa) and TF gene expression were also determined. TG in the presence of MPCs or MPC-dMPs was assessed with the calibrated automated thrombogram assay (CAT) in normal human PPP and in plasma depleted of factor VII or XII. TG was also assessed in plasma spiked with MPCs and MPC-dMPs.

Results MPC-dMPs expressed approximately twofold higher levels of TF as compared with MPCs. The TFa expressed by MPC-dMPs was significantly higher compared with that expressed by MPCs. MPCs and MPC-dMPs enhanced TG of human plasma. TG was significantly higher with MPC-dMPs compared with MPCs.

Conclusion MPCs indirectly induce blood-borne hypercoagulability through the release of MPC-dMPs rich in TF. Since MPCs, expressing low TFa, represent a weak procoagulant stimulus, the hypercoagulability at the microenvironment could be the resultant of MPC-dMPs rich in TF.
Optical reflectivity of ion-irradiated cerium dioxide sinters
Authors: Costantini Jean-Marc , Lelong Gérald , Guillaumet Maxime , Gourier Didier , Takaki Seiya , Ishikawa Norito , Watanabe Hideo , Yasuda Kazuhiro
Published: November 2019

Reflection spectra of cerium dioxide sintered samples were measured in the UV-visible range after irradiation with various heavy ions (2.4-MeV Cu, 5-MeV W, 10-MeV W, 36-MeV W, 100-MeV Kr, and 200-MeV Xe). Differential reflectance spectra of irradiated samples after subtraction of the reference sample spectrum are fit with six broad Gaussian bands centered at about 1.2, 2.2, 2.8, 4.0, 4.8, and 6.2 eV. The growth curves of most bands show a saturation behavior vs ion fluence. Reflection spectra are consistent with the UV-visible absorption spectra of electron-irradiated ceria single crystals for photon energies lower than 3.2 eV, corresponding to the optical gap. The spectra are tentatively analyzed on the basis of charge transfer bands and the 4f-5d transitions related to the Ce3+ ions in the distorted environment formed by irradiation. More insight into defect formation is given by the reflection spectra rather than the absorption ones due to the limitation in the absorption of the optical gap. These data are also discussed with reference to the radiation damage processes by electronic excitations and nuclear collisions in ceria.
Interactions of laser speckles due to kinetic stimulated Raman scattering
Authors: Winjum B. J. , Tableman A. , Tsung F. S. , Mori W. B.
Published: November 2019

We examine the possible interactions of two laser speckles due to the exchange of electrons and waves generated by stimulated Raman scattering (SRS) using two-dimensional particle-in-cell simulations. By controlling the relative polarization, spatial placement, and timing of two laser speckles, one above-threshold and one below-threshold for SRS, we isolate and characterize SRS growth stimulated in below-threshold speckles. SRS in the below-threshold speckle is shown to be triggered by energetic electrons, scattered light waves, and scattered plasma waves generated from the above-threshold speckle. We show that scattered light or electrons alone can be an intermediary trigger for SRS.
Spatially resolved optical excitation of mechanical modes in graphene NEMS
Authors: Miller David , Alemán Benjamín
Published: November 2019

Emerging applications in nanoelectromechanical systems (NEMS) made from two-dimensional (2D) materials demand simultaneous imaging and selective actuation of the mechanical modes. Focused optical probes to measure and actuate motion offer a possible solution, but their lateral spatial resolution must be better than the size of the resonator. While optical interferometry is known to have excellent spatial resolution, the spatial resolution of the focused, laser-based optical driving is not currently known. Here, we combine separately scanned interferometry and optical drive probes to map the motion and forces on a suspended graphene nanomechanical resonator. By analyzing these maps with a force density model, we determine that the optical drive force has a spatial resolution on the order of the size of the focused laser spot. Using the optical force probe, we demonstrate the selective actuation and suppression of a pair of orthogonal antisymmetric mechanical modes of the graphene resonator. Our results offer a powerful approach to image and actuate any arbitrary high-order mode of a 2D NEMS.
Adaptive chaotic MIMO radar based on DPMM clustering and Kalman filtering technique
Authors: Yao Yu , Li Zeqing , Zhao Junhui , Wu Lenan
Published: November 2019

A novel scheme to optimize the adaptive transmit waveform of chaotic multiple-input multiple-output (MIMO) radar is developed. The main objective of this work is to achieve high ability in target discrimination by using a Dirichlet process mixture model (DPMM)-based clustering method based on nonparametric Bayesian theory and to improve the capability of target detection by minimizing the mean square error of radar channel response via Kalman filtering (KF) technique. The two stages are the discrimination of multiple range-extended targets and the optimization of the adaptive chaos-based waveform for transmission. The adaptive chaotic MIMO waveform optimization scheme overcomes the problem of target discrimination and detection in an intelligent transportation system, where there is a need for extracting the feature of target information achieved from vehicle-mounted sensor. As the number of iterations increases, simulation experiments demonstrate better target discrimination capability provided by the proposed DPMM-KF technique as compared with the traditional waveform design method. In addition, the proposed DPMM-KF technique leads to improved target detection probability and receiver operating characteristics in the interference environment.
Wake transitions and laminar separation bubble in the flow past an Eppler 61 airfoil
Authors: Samuthira Pandi Jawahar Sivabharathy , Mittal Sanjay
Published: November 2019

The flow past an Eppler 61 airfoil at 10° angle to the free-stream is investigated numerically for 100 ≤ Re ≤ 87 000. Vortex shedding is observed beyond Re ∼ 600 and three-dimensionality sets in at Re ∼ 1280.9 via the mode C instability and hairpin vortex structures that grow with an increase in Re. At larger Re, the shear layer vortices, arising from the instability of the separated shear layer, interact with the flow close to the airfoil and cause it to reattach. A Laminar Separation Bubble (LSB) forms at Re ∼ 20 000 and beyond. The airfoil experiences a very significant increase in the lift and a decrease in the drag at the formation of LSB. Although the flow is three-dimensional, the primary mechanism of the formation of LSB appears to be two-dimensional. The length of the LSB decreases with an increase in Re. The variation of the shear layer and primary wake frequency, with Re, is studied. Both follow the power law. However, the variation before and after the formation of LSB is quite different. Unlike the primary wake frequency, the shear layer frequency suffers a jump at the formation of LSB. Wake formation length (Lf), estimated via the spatial distribution of Reynolds stress, exhibits spanwise periodicity at the onset of three-dimensionality.
Sheath oscillations during directional motion of fire tube formation in expanding RF plasma
Authors: Paul Manash Kumar , Chakraborty Shamik
Published: November 2019

Low-frequency sheath oscillations, initiated by the sheath-plasma instability, are observed in connection with the complex structure formations in expanding radio frequency (RF) plasma generation. The temporal variations of the floating potential during the double layer formations, measured using electric and magnetic probe diagnostics, suggest the significant role of sheath-plasma instability in charged particle dynamics in the present operational regime. The burst oscillations of the potential occur due to the oscillations of the electric field associated with the high-gradient plasma source geometry, the sheath field. The initially localized discharge evolves into multiple luminous annular plasma structures with the progressive RF power. Although plasma discharges using additional electrodes immersed in plasma have been investigated extensively in DC plasmas, present experiments are carried out in the absence of any additional plasma source as well as any externally applied magnetic field. In line with our earlier reports, [Chakraborty et al., Phys. Plasmas 25, 033518 (2018); Paul et al., Phys. Plasmas 26, 023516 (2019)], the present work emphasizes the complex sheath structure formations, discharge transition from unstable to stable state, followed by the sheath oscillations through sheath-plasma instability during the expanding radio frequency discharge features that differentiate it in many ways from the earlier experimental investigations.
Secondary ion mass spectrometry to verify the implantation of magnetic ions in nanodiamonds
Authors: Lin Bo-Rong , Wang Chiung-Chi , Chen Chien-Hsu , Kunuku Srinivasu , Hsiao Tung-Yuan , Yu Hung-Kai , Chen Tzung-Yuang , Chang Yu-Jen , Liao Li-Chuan , Chang Chun-Hsiang , Chen Fang-Hsin , Niu Huan , Lee Chien-Ping
Published: November 2019

Ion implantation is used to create nanodiamonds (NDs) with embedded magnetic ions for use in a wide range of biological and medical applications; however, the effectiveness of this process depends heavily on separating magnetic NDs from nonmagnetic ones. In this study, we use secondary ion mass spectrometry to verify the implantation of magnetic ions in NDs and the success of separation. When applied to a series of NDs with embedded iron or manganese ions, the sorting tool used in this study proved highly effective in selecting magnetic NDs. Besides, multienergy ion implantation and precise thickness control of NDs coating on the silicon wafer were suggested to improve this technology.
Plasma formation and relaxation dynamics in fused silica driven by femtosecond short-wavelength infrared laser pulses
Authors: Jürgens P. , Vrakking M. J. J. , Husakou A. , Stoian R. , Mermillod-Blondin A.
Published: November 2019

Laser-induced plasma formation and subsequent relaxation in dielectric solids is the precursor to structural modifications serving as the basis for direct laser writing of functional optical micro- and nanostructures. Based on an experimental arrangement combining a time-resolved transmission measurement with a cross-phase modulation measurement, we isolate the plasma formation and relaxation dynamics in the bulk of amorphous fused silica excited by femtosecond short-wavelength infrared (λ= 2100 nm) laser pulses. Whereas the relaxation time of the generated subcritical electron-hole plasma was so far assumed to be constant, our findings indicate an intensity-dependent relaxation time. We attribute this intensity dependence to vibrational activation of the medium, leading to detrapping of trapped carriers and a reduced trapping probability.
Optimally graded porous material for broadband perfect absorption of sound
Authors: Boulvert Jean , Cavalieri Théo , Costa-Baptista Josué , Schwan Logan , Romero-García Vicente , Gabard Gwénaël , Fotsing Edith Roland , Ross Annie , Mardjono Jacky , Groby Jean-Philippe
Published: November 2019

This article presents a numerical optimization procedure of continuous gradient porous layer properties to achieve perfect absorption under normal incidence. This design tool is applied on a graded porous medium composed of a periodic arrangement of ordered unit cells allowing one to link the effective acoustic properties to its geometry. The best microgeometry continuous gradient providing the optimal acoustic reflection and/or transmission is designed via a nonlinear conjugate gradient algorithm. The acoustic performances of the so-designed continuous graded material are discussed with respect to the optimized homogeneous, i.e., nongraded and monotonically graded material. The numerical results show a shifting of the perfect absorption peak to lower frequencies or a widening of the perfect absorption frequency range for graded materials when compared to uniform ones. The results are validated experimentally on 3D-printed samples, therefore, confirming the relevance of such a gradient along with the efficiency of the control of the entire design process.
Transient probability currents provide upper and lower bounds on non-equilibrium steady-state currents in the Smoluchowski picture
Authors: Copperman Jeremy , Aristoff David , Makarov Dmitrii E. , Simpson Gideon , Zuckerman Daniel M.
Published: November 2019

Probability currents are fundamental in characterizing the kinetics of nonequilibrium processes. Notably, the steady-state current Jss for a source-sink system can provide the exact mean-first-passage time (MFPT) for the transition from the source to sink. Because transient nonequilibrium behavior is quantified in some modern path sampling approaches, such as the “weighted ensemble” strategy, there is strong motivation to determine bounds on Jss—and hence on the MFPT—as the system evolves in time. Here, we show that Jss is bounded from above and below by the maximum and minimum, respectively, of the current as a function of the spatial coordinate at any time t for one-dimensional systems undergoing overdamped Langevin (i.e., Smoluchowski) dynamics and for higher-dimensional Smoluchowski systems satisfying certain assumptions when projected onto a single dimension. These bounds become tighter with time, making them of potential practical utility in a scheme for estimating Jss and the long time scale kinetics of complex systems. Conceptually, the bounds result from the fact that extrema of the transient currents relax toward the steady-state current.
Nanoscale X-ray imaging of spin dynamics in yttrium iron garnet
Authors: Förster J. , Wintz S. , Bailey J. , Finizio S. , Josten E. , Dubs C. , Bozhko D. A. , Stoll H. , Dieterle G. , Träger N. , Raabe J. , Slavin A. N. , Weigand M. , Gräfe J. , Schütz G.
Published: November 2019

Time-resolved scanning transmission x-ray microscopy has been used for the direct imaging of spin-wave dynamics in a thin film yttrium iron garnet (YIG) with sub-200 nm spatial resolution. Application of this x-ray transmission technique to single-crystalline garnet films was achieved by extracting a lamella (13×5×0.185 μm3) of the liquid phase epitaxy grown YIG thin film out of a gadolinium gallium garnet substrate. Spin waves in the sample were measured along the Damon-Eshbach and backward volume directions of propagation at gigahertz frequencies and with wavelengths in a range between 200 nm and 10 μm. The results were compared to theoretical models. Here, the widely used approximate dispersion equation for dipole-exchange spin waves proved to be insufficient for describing the observed Damon-Eshbach type modes. For achieving an accurate description, we made use of the full analytical theory taking mode-hybridization effects into account.
Suppression of the negative effect of abnormal data based on the Hough transform and application to the magnetic compensation of airborne optically-pumped magnetometer data
Authors: Ge Jian , Wang Wenjie , Dong Haobin , Liu Huan , Li Han , Luo Wang , Wang Hongpeng , Yuan Zhiwen , Zhang Haiyang , Zhu Jun
Published: November 2019

A magnetic sensor of the optically pumped magnetometer may enter a dead zone during an aeromagnetic survey, resulting in unavoidable abnormal data and seriously affecting the effect of aeromagnetic compensation. We propose a fast discrimination and culling method based on the Hough transform to prevent abnormal data from participating in the coefficient estimation. In the proposed method, the parameter space is partitioned into small buckets and the most frequently passed region of sinusoidal curves is detected to eliminate abnormal data. Although the conventional method performs similarly to the proposed method when there is only 1% abnormal data, it is theoretically shown that the proposed method has a better goodness of fit of 0.9518, compared with a value of 0.1956 for the conventional method, in the presence of 45% abnormal data. Furthermore, we construct an experimental platform and conduct a flight test in which the proposed method has an improvement ratio of 4.11 compared with a value of 0.34 for the conventional method.
Inter-subsystem charge-transfer excitations in exact subsystem time-dependent density-functional theory
Authors: Tölle Johannes , Böckers Michael , Niemeyer Niklas , Neugebauer Johannes
Published: November 2019

We investigate the ability of projection-based embedding (PbE)/subsystem density-functional theory to describe intersubsystem charge-transfer (CT) excitations. To this end, we derive the corresponding subsystem time-dependent density-functional theory (sTDDFT) working equations including the response kernel contributions for three different popular projection operators currently in use in connection with PbE. We demonstrate that supermolecular electronic excitation spectra can be fully restored with this “exact” sTDDFT. Both intra- and intersubsystem CT excitations can be described correctly, provided that suitable long-range corrected functionals and basis sets of sufficient flexibility are used. In particular, we show that outgoing CT excitations can be described in individual subsystem calculations without intersubsystem response coupling. We introduce efficient techniques to restrict the virtual-orbital space to obtain reasonable CT excitation energies with heavily reduced computational cost. Finally, we demonstrate the ability to extract electronic couplings between CT and local excitations with this new formulation of exact sTDDFT.
Efficient two-color two-step laser ionization schemes of λ1 ∼ 250 nm and λ2 = 307.9 nm for heavy refractory elements—Measurements of ionization cross-sections and hyperfine spectra of tantalum and tungsten
Authors: Hirayama Y. , Mukai M. , Watanabe Y. X. , Oyaizu M. , Jeong S. C. , Kakiguchi Y. , Schury P. , Wada M. , Miyatake H.
Published: November 2019

We demonstrated efficient two-color two-step laser ionization schemes in the combined use of λ1 ∼ 250 nm and λ2 = 307.9 nm, which are applicable to heavy refractory elements with an atomic number in the wide range of Z = 69–78. We investigated newly observed ionization schemes of tantalum and tungsten atoms in an argon-gas-cell-based laser ion source for the efficient ionization of atoms of unstable nuclei through the two-color two-step laser resonance ionization technique. We experimentally determined the ionization cross sections from the measured saturation curves by solving the rate equations for the ground, intermediate, and ionization continuum populations. Hyperfine structures of these elements were also studied to deduce the isotope-shift, pressure-shift, and pressure-broadening in the resonance spectra of the excitation transitions in the argon gas cell. The electronic factor F255 of the excitation transition λ1 = 255.2115 nm between the ground and intermediate states was deduced from the measured isotope shifts of stable 182,183,184,186W isotopes. The ionization schemes investigated here are applicable to extract any isotopes of these elements by considering the measured pressure shift and nuclear isotope shift in optimizing the wavelength λ1.
Exact bound rovibrational spectra of the neon tetramer
Authors: Sarka János , Petty Corey , Poirier Bill
Published: November 2019

Exact quantum dynamics calculations are performed for the bound rovibrational states of the neon tetramer (Ne4) in its ground electronic state, using pair-wise Lennard-Jones potentials and the ScalIT suite of parallel codes. The vibrational states separate into a low-lying group mostly localized to a single potential well and a higher-energy delocalized group lying above the isomerization threshold—with such a structure serving as a testament to the “intermediate” quantum nature of the Ne4 system. To accurately and efficiently represent both groups of states, the phase-space optimized discrete variable representation (PSO-DVR) approach was used, as implemented in the ScalIT code. The resultant 1D PSO effective potentials also shed significant light on the quantum dynamics of the system. All vibrational states were computed well up into the isomerization band and labeled up to the classical isomerization threshold—defined as the addition of the classical energy of a single bond, ϵ = 24.7 cm−1, to the quantum ground state energy. Rovibrational energy levels for all total angular momentum values in the range J = 1–5 were also computed, treating all Coriolis coupling exactly.
Trion dynamics in lead halide perovskite nanocrystals
Authors: Kanemitsu Yoshihiko
Published: November 2019

Metal halide perovskite semiconductors fabricated with simple low-temperature solution processes are a unique class of materials anticipated for use in photonic devices such as solar cells, light-emitting diodes, and light modulators. The metal halide perovskites in the form of nanocrystals are particularly attracting attention as novel functional materials because of their exceptionally high luminescence efficiencies and wide range of possible luminescence wavelengths. By combining different optical characterization techniques, that is, single-dot spectroscopy, photon correlation spectroscopy, femtosecond transient absorption spectroscopy, and time-resolved photoluminescence spectroscopy, we study the dynamics of excitons, trions, and biexcitons in perovskite nanocrystals. Here, we provide a concise review of recent developments in this research field with a focus on trions in lead halide perovskite nanocrystals. A deep understanding of trion dynamics is especially important because they determine the luminescence properties of nanocrystals and are related to the ionization processes of nanocrystals.
Polaronic nature of a muonium-related paramagnetic center in SrTiO3
Authors: Ito T. U. , Higemoto W. , Koda A. , Shimomura K.
Published: November 2019

The hyperfine features and thermal stability of a muonium (Mu)-related paramagnetic center were investigated in SrTiO3 perovskite titanate via muon spin rotation spectroscopy. The hyperfine coupling tensor of the paramagnetic center was found to have prominent dipolar characteristics, indicating that the electron spin density is dominantly distributed on a Ti site to form a small polaron near an ionized Mu+ donor. Based on a hydrogen-Mu analogy, interstitial hydrogen is also expected to form such a polaronic center in the dilute doping limit. The small activation energy of 30(3) meV found for the thermal dissociation of the Mu+-polaron complex suggests that the strain energy required to distort the lattice is comparable to the electronic energy gained by localizing the electron.
Machine learning can be used to distinguish protein families and generate new proteins belonging to those families
Authors: Jin Chi , Cukier Robert I.
Published: November 2019

Proteins are classified into families based on evolutionary relationships and common structure-function characteristics. Availability of large data sets of gene-derived protein sequences drives this classification. Sequence space is exponentially large, making it difficult to characterize family differences. In this work, we show that Machine Learning (ML) methods can be trained to distinguish between protein families. A number of supervised ML algorithms are explored to this end. The most accurate is a Long Short Term Memory (LSTM) classification method that accounts for the sequence context of the amino acids. Sequences for a number of protein families where there are sufficient data to be used in ML are studied. By splitting the data into training and testing sets, we find that this LSTM classifier can be trained to successfully classify the test sequences for all pairs of the families. Also investigated is whether the addition of structural information increases the accuracy of the binary comparisons. It does, but because there is much less available structural than sequence information, the quality of the training degrades. Another variety of LSTM, LSTM_wordGen, a context-dependent word generation algorithm, is used to generate new protein sequences based on seed sequences for the families considered here. Using the original sequences as training data and the generated sequences as test data, the LSTM classification method classifies the generated sequences almost as accurately as the true family members do. Thus, in principle, we have generated new members of these protein families.
The extrudate swell singularity of Phan-Thien–Tanner and Giesekus fluids
Authors: Evans Jonathan D. , Evans Morgan L.
Published: November 2019

The stress singularity for Phan-Thien–Tanner (PTT) and Giesekus viscoelastic fluids is determined for extrudate swell (commonly termed die swell). In the presence of a Newtonian solvent viscosity, the solvent stress dominates the polymer stresses local to the contact point between the solid (no-slip) surface inside the die and the free (slip) surface outside the die. The velocity field thus vanishes like rλ0, where r is the radial distance from the contact point and λ0 is the smallest Newtonian eigenvalue (dependent upon the angle of separation between the solid and free surfaces). The solvent stress thus behaves like r−(1−λ0) and dominates the polymer stresses, which are like r−4(1−λ0)/(5+λ0) for PTT and r−(1−λ0)(3−λ0)/4 for Giesekus. The polymer stresses require boundary layers at both the solid and free surfaces, the thicknesses of which are derived. These results do not hold for the Oldroyd-B fluid.
Understanding downward longwave radiation for cooling buildings
Authors: Mandel Savannah
Published: November 2019

Two scientists fill in gaps in current models for downward longwave radiation in China to include consideration of different weather conditions such as cloud coverage.
Coherent beam combining in optically coupled laser arrays
Authors: Vysotsky D.V. , Napartovich A.P.
Published: November 2019

Phase locking of laser arrays is a promising approach for obtaining high-brightness light. A variety of experimental methods have been employed to ensure phase locking. Concurrently, complex theoretical models were developed and nontrivial physical effects were found. Here we review experimental data on passive phase locking and discuss current views on the potentialities of this method.
Effect of backscattering on nonlinear distortions of the scale factor of a laser gyro with a rectangular bias
Authors: Beketov S.E. , Bessonov A.S. , Petrukhin E.A. , Khokhlov I.N. , Khokhlov N.I.
Published: November 2019

We report the results of measurements of nonlinear scale factor corrections, resulting from the backscattering effect in a laser gyro with a rectangular bias. It is shown that taking conservative and dissipative backscattering components into account allows one to obtain analytical relationships that adequately describe the frequency response of a laser gyroscope over the entire working range of angular velocities. Using these relationships to correct the frequency response of a laser gyroscope makes it possible to reduce the value of nonlinear corrections to 1 – 2 ppm.
Short O–O separation in layered oxide Na
0.67
CoO
2
enables an ultrafast oxygen evolution reaction
Authors: Wang Hao , Wu Jinpeng , Dolocan Andrei , Li Yutao , Lü Xujie , Wu Nan , Park Kyusung , Xin Sen , Lei Ming , Yang Wanli , Goodenough John B.
Published: November 2019

Significance

The development of a low-cost, stable, and more active electrocatalyst for the oxygen evolution reaction (OER) is critical for the practical storage of electric power in hydrogen gas produced by the electrolysis of water. We demonstrate a stable OER of higher rate at a lower voltage with a low-cost oxide that provides, as an alternative to the conventional reaction route, a faster route that is greatly enhanced by an unusually short O–O separation.
Defining the layers of a sensory cilium with STORM and cryoelectron nanoscopy
Authors: Robichaux Michael A. , Potter Valencia L. , Zhang Zhixian , He Feng , Liu Jun , Schmid Michael F. , Wensel Theodore G.
Published: November 2019

Primary cilia carry out numerous signaling and sensory functions, and defects in them, “ciliopathies,” cause a range of symptoms, including blindness. Understanding of their nanometer-scale ciliary substructures and their disruptions in ciliopathies has been hindered by limitations of conventional microscopic techniques. We have combined cryoelectron tomography, enhanced by subtomogram averaging, with superresolution stochastic optical reconstruction microscopy (STORM) to define subdomains within the light-sensing rod sensory cilium of mouse retinas and reveal previously unknown substructures formed by resident proteins. Domains are demarcated by structural features such as the axoneme and its connections to the ciliary membrane, and are correlated with molecular markers of subcompartments, including the lumen and walls of the axoneme, the membrane glycocalyx, and the intervening cytoplasm. Within this framework, we report spatial distributions of key proteins in wild-type (WT) mice and the effects on them of genetic deficiencies in 3 models of Bardet–Biedl syndrome.
Hsp110 mitigates α-synuclein pathology in vivo
Authors: Taguchi Yumiko V. , Gorenberg Erica L. , Nagy Maria , Thrasher Drake , Fenton Wayne A. , Volpicelli-Daley Laura , Horwich Arthur L. , Chandra Sreeganga S.
Published: November 2019

Parkinson’s disease is characterized by the aggregation of the presynaptic protein α-synuclein and its deposition into pathologic Lewy bodies. While extensive research has been carried out on mediators of α-synuclein aggregation, molecular facilitators of α-synuclein disaggregation are still generally unknown. We investigated the role of molecular chaperones in both preventing and disaggregating α-synuclein oligomers and fibrils, with a focus on the mammalian disaggregase complex. Here, we show that overexpression of the chaperone Hsp110 is sufficient to reduce α-synuclein aggregation in a mammalian cell culture model. Additionally, we demonstrate that Hsp110 effectively mitigates α-synuclein pathology in vivo through the characterization of transgenic Hsp110 and double-transgenic α-synuclein/Hsp110 mouse models. Unbiased analysis of the synaptic proteome of these mice revealed that overexpression of Hsp110 can override the protein changes driven by the α-synuclein transgene. Furthermore, overexpression of Hsp110 is sufficient to prevent endogenous α-synuclein templating and spread following injection of aggregated α-synuclein seeds into brain, supporting a role for Hsp110 in the prevention and/or disaggregation of α-synuclein pathology.
POT1-TPP1 differentially regulates telomerase via POT1 His266 and as a function of single-stranded telomere DNA length
Authors: Xu Mengyuan , Kiselar Janna , Whited Tawna L. , Hernandez-Sanchez Wilnelly , Taylor Derek J.
Published: November 2019

Significance

Telomere length homeostasis is an important mechanism for maintaining genomic stability. Telomere length is regulated by numerous events that include protein–DNA interactions, the length and structure of telomere DNA, and recruitment of telomerase. Here we used hydroxyl radical footprinting to identify environmental changes in the telomere end-binding heterodimer, POT1-TPP1, as a function of telomere length. Our data identified a specific residue (histidine 266) of the POT1 protein that reports differences in solvent accessibility as a function of telomere DNA length. We further show that the chronic lymphocytic leukemia-related H266L POT1 mutation disrupts the ability of POT1-TPP1 to negatively regulate telomerase activity in vitro and in cancer cells.