bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of biscarboxylic acid functionalised EDTA mimicking polymers and their ability to form Zr(iv) chelation mediated nanostructures
Authors: Leiske Meike N. , Walker Julia A. , Zia Aadarash , Fletcher Nicholas L. , Thurecht Kristofer J. , Davis Thomas P. , Kempe Kristian
Published: March 2020

We present a new biscarboxylic acid acrylate, which is used for the synthesis of double hydrophilic EDTA-mimicking block copolymers capable of self-assembly upon zirconium complexation.
Phytomanagement: perspectives of using of phytoremediation technology in Kazakhstan
Authors: Atabayeva Saule , Kenzhebayeva Saule , Alybayeva Ravilya , Аsrandina Saltanatm , Shoinbekova Sabina
Published: March 2020

The content of heavy metals around the metallurgical plants of East Kazakhstan in the soil and plants growing around these plants was studied. It was determined the concentration of heavy metals in soils, plant organs, it was calculated bioconcentration factor and the level of extraction of heavy metals by sunflower and lawn grasses. The study of sunflower plants and lawn grasses showed that the studied species accumulated a significant amount of heavy metals mainly in the roots. Sunflower plants and lawn grasses had high accumulation activity and accumulated a significant amount of heavy metals in their organs. Determination of the content of heavy metals in the soil showed a significant removal of heavy metals from the soil, which indicates a high degree of phytoextraction of heavy metals by the studied plant species.
Research on factors contributing to the development of accommodation facilities in areas with environmental constraints
Authors: Maksanova Lyudmila , Andreeva Alyona , Kaurov Ivan , Budaeva Darima
Published: March 2020

Recently studies of factors affecting the successful operation of small-scale accommodation facilities have expanded significantly. Mandatory classification of hotels and other accommodation facilities is one of the key factors to increase their competitiveness. However, there are few works studying the problems of classifying small-scale accommodation facilities in conditions of infrastructural restrictions in environmentally sensitive areas. Therefore, the factors affecting the functioning of small-scale accommodation facilities in territories with environmental restrictions are discussed in this study in the context of the mandatory classification of hotels and other accommodation facilities in the Russia. The research uses the case of Enkheluk village’s guest houses (Russian Federation, Republic of Buryatia). Primary data obtained during the interviews with local entrepreneurs in 2018 was used in the study. The main infrastructural restrictions influencing the entrepreneurs providing temporary tourists’ accommodation were revealed: in the field of water supply, wastewater disposal, passing an environmental assessment. These problems, having a dynamic and interconnected nature, constrain the passing of mandatory classification by small-scale accommodation facilities. Possible ways of solving these problems are formulated. The study’s results can serve as the basis for further studies of factors affecting entrepreneurial and investment activities in the field of accommodation in environmentally sensitive areas.
Econometric model for forecasting oil production in OECD member states
Authors: Rădulescu Carmen Valentina , Bodislav Dumitru Alexandru , Burlacu Sorin , Bran Florina , Karimova Lyaman
Published: March 2020

In this article we present an econometric model of oil production forecast at OECD member level that will allow decision makers but also other oil product stakeholders to be responsible for oil production in OECD member states. This responsibility can be perceived from several perspectives: economic, social, environmental, political, military etc.

In order to be able to find the ideal formula for our calculation, we went through the specialized literature and brought elements of analysis during the research through several econometric paths traveled by other researchers and who provided us with support for our research. Before proceeding technically, in order to understand the urgency of this approach and of this study, we also discussed how oil and natural gas are explored, exploited and extracted from the underground deposits.

We considered that the proposed model could be improved in the future so as to portray certain geopolitical or economic factors, determinants for oil production, such as embargoes, periods of armed conflict in the main extraction areas or times of financial crisis and the decline of financial markets.
Development of best environmentally avallable rise irrigation technology
Authors: Aldambergenova Gulzinat , Shayanbekova Bakhytzhan , Zhunissov Abaybek , Omarov Kali , Shilmanova Altynay
Published: March 2020

Research is aimed at developing the best environmentally available rice irrigation technology that provides normal physiological indicators of the growth and development of rice plants while maintaining favorable salt and thermal regimes of soil and water. The research study was based on certified methodological guidelines and standards. The agricultural rice production practices in the experimental plots corresponded to the recommendations of the LLP Kazakh Research Rice Institute.According to preliminary calculations, by more than 15-20% of the required amount of water is used for irrigation which leads to a deterioration of ecological and reclamation conditions and a diminished performance of the irrigated hectare.Saving of irrigation water on the recommended option for intensive rice varieties averaged 3,550 m3/ha; it allowed to reduce irrigation water intake by 273 million m3of water per year in the course of the current rice land under cultivation - 77,000 ha.
Overview of actions to strengthen financial stability of companies
Authors: Yerdavletova Fariza , Ermekbaeva Bayan , Zhunissova Gulnar , Mukhametzhanova Zhanar
Published: March 2020

Based on a review of the recommendations of various scientists, the article presents measures to strengthen the solvency and financial stability of companies in various fields of production. These include effective receivables management, accelerated capital turnover, increased profits and cash flow. The article reveals the concept of financial stability as the main criteria of the company’s financial condition. As well the negative aspects of the financial condition of companies are discussed. All negative factors divided into three groups based on their characteristics: general economic factors, state factors, and market factors. The model of accounts receivable management, which includes three stages is presented. It is concluded that a high share of accounts receivable as part of assets can lead any company to loss of solvency. Ways to improve the structure of funding sources, aspects of increasing return on capital are considered. Several recommendations given to reduce the duration of capital turnover in order to increase the company’s solvency. As a factor of increasing profits a possible ways of minimizing costs are investigated. Ways of increasing production volumes are highlighted and described, measures to increase cash flow are analyzed. Considerable attention is paid to the irrational management of cash flows.
Assessing the competitiveness of Kazakhstan regions: creating an index
Authors: Zhidebekkyzy Aknur , Sagiyeva Rimma , Temerbulatova Zhansaya
Published: March 2020

Today there is no single universally accepted method for assessing the competitiveness of the country’s regions. For this reason, the research created a methodology for assessing competitiveness at the regional level for Kazakhstan. The three-factor model of Huggins for ranking the regions of Great Britain by the level of competitiveness was used as the basis, and then the model was expanded on the example of a study assessing the competitiveness of the regions of the European Union countries. All data for assessing the competitiveness of the regions of Kazakhstan were collected from the official website of the Committee on Statistics of the Ministry of National Economy of the Republic of Kazakhstan. In the article, 14 regions and 2 cities of republican significance were ranked in terms of competitiveness. As a result, the most competitive regions of Kazakhstan were Almaty city, Atyrau region and Nur-Sultan city, the worst indicator was found for the North Kazakhstan and Zhambyl regions.
Formation and development trends of self-employment in the Republic of Kazakhstan: applied research
Authors: Ilyashova Guliya , Turarov Dauren , Murabildaeva Riza , Batyr Aiman
Published: March 2020

A lot of the business learning a self-employed must do is actually unlearning many old husbands’ tales that are so often told to unsuspecting indies. Take, for instance, all the dire warnings and urgings to feel sorry for yourself because you are being shafted by the tax code. Oh, big, bad government — does not it give all the tax breaks to national corporations and employees! Moreover, poor little indie gets nothing but headaches and high taxes. Well, right now, as your New Year’s Resolution, throw out those old-fashioned ideas. Take charge. Learn. Pay less tax! Sure, the tax code is written for corporations and employees, not for you, a self-employed. Of course the big boys get advantages that are out of bounds for you. However, in a dynamically developing modern economy, self-employment has its advantages. The aim of the study is to identify criteria that allow defining self-employment among other types of employment, determining the status of self-employment in the national economy, disclosing forms of self-employment, and considering the factors and characteristics of the formation of self-employment in the modern economy of the Republic of Kazakhstan. The researchers propose a methodological approach to the definition of the self-employment concept.
Plankton characterization of alpine ponds: a case of study for the assessment of water quality in Serra da Estrela (Portugal)
Authors: Martins F.S. , Moutinho A. , Espinha Marques J. , Formigo N. , Antunes S.C.
Published: March 2020

Serra da Estrela is Portugal's mainland highest mountain, with distinctive geological, climatic and geomorphological characteristics which play a key role on surface and groundwater resources. These mountains have the largest set of glacial ponds of Portugal and are scarcely studied. Besides, there are concerns of possible impacts of the use of salts in road de-icing on ponds' biotic communities. This research intends to characterize the hydrology of five Mediterranean alpine ponds and assess their planktonic communities. The biotic index proposed by the Water Framework Directive for lentic systems was used to check its applicability to these systems. Sampling was conducted monthly from June to November 2015 alongside with hydrological characterization. Water parameters and nutrients' content were quantified. Phytoplankton and macrozooplankton were identified. Ponds' water level is controlled by precipitation (input) and evaporation, infiltration and streamflow (output). Ponds were in good ecological quality. However, the current ecological assessment tools proposed by the WFD for lentic systems do not fit alpine ponds, showing a gap in the current methods. Salts used for road de-icing did not impact the communities and the ecological state of ponds. Phytoplankton was dominated by Cyanobacteria, Dinophyceae and Bacillariophyceae; Cyclopoida was the most abundant zooplanktonic group. For macrozooplankton, RDA shows association between cladocerans and phosphorus content. Phosphorus changes promoted shifts in zooplankton, what may be of major concern from a conservation point of view, once alpine ponds and its species are still mostly unknown. Efforts should be done to develop tools to classify aquatic ecosystems from harsh environments.
Optimisation des propriétés mécaniques de matériaux polymériques par les mélanges et effet bénéfique du vieillissement thermique
Authors: Djeddi Fadila , Mohellebi Mouloud , Ouibrahim Ahmed
Published: March 2020

On cherche ici les propriétés mécaniques optimales de matériaux polymériques par mélangeage mécanique de deux polypropylènes et leur amélioration sous l’effet du vieillissement thermique. Ces mélanges de polypropylène homopolymère (PPH) et de polypropylène copolymère (PPC) sont élaborés sans additif ni compatibilisant. Leurs températures de fusion et leurs indices de fluidité sont déterminés par caractérisation physico-chimique. Les valeurs trouvées suggèrent l’injection comme procédé d’élaboration. Les caractérisations chimique et mécanique ont mis en évidence d’une part, la miscibilité des deux polymères et, d’autre part, des propriétés mécaniques intéressantes des deux polymères. Le PPH présente une bonne résistance à la traction avec un grand allongement à la rupture, mais une faible résistance aux chocs. Le PPC manifeste une bonne résistance aux chocs avec une faible contrainte limite élastique et un faible allongement à la rupture. L’introduction de 30 % de PPC dans la matrice PPH conduit, relativement au PPH, à accroître de 94 % la résistance aux chocs pour une diminution de 6 % seulement de la contrainte limite élastique et du module d’élasticité, l’allongement à la rupture restant égal à celui du PPH. Le vieillissement thermique accéléré améliore la rigidité et la contrainte limite élastique, mais diminue la résilience et l’allongement à la rupture.
Traduction, adaptation et évaluation psychométrique préliminaire d’une mesure d’engagement et d’une mesure de charge cognitive en contexte d’apprentissage numérique
Authors: Fontaine Guillaume , Cossette Sylvie , Maheu-Cadotte Marc-André , Mailhot Tanya , Lavoie Patrick , Gagnon Marie-Pierre , Dubé Véronique , Côté José
Published: March 2020

Contexte : L’apprentissage numérique chez les professionnels de la santé amène des défis comme le manque d’engagement et l’excès de charge cognitive. Toutefois, il n’existe pas de mesures d’engagement et de charge cognitive validées en français. De telles mesures permettraient de considérer ces variables dans le développement de formations numériques et l’évaluation de leurs effets. Buts : (1) Traduire et adapter la User Engagement Scale – Short Form et le Cognitive Load Index en français ; (2) Effectuer une évaluation psychométrique préliminaire des échelles afin d’examiner leurs caractéristiques, les corrélations entre les sous-échelles et la cohérence interne. Méthode : La traduction et l’adaptation ont été réalisées selon Sousa et Rojjanasrirat (2011). Pour l’évaluation des propriétés psychométriques, des étudiants en sciences infirmières ont répondu en ligne à l’Échelle d’engagement de l’utilisateur – Forme abrégée (EEU-FA) et à l’Indice de charge cognitive (IDCC). Les données ont été analysées par des statistiques descriptives, des coefficients de corrélation de Pearson, des coefficients omega (ω) de McDonald et des coefficients alpha (α) de Cronbach. Résultats : Cinquante-sept participants ont complété l’étude. La majorité des distributions étaient normales. Les corrélations entre les sous-échelles étaient entre 0,03 et 0,64 pour l’EEU-FA, et entre −0,12 à 0,41 pour l’IDCC. Les coefficients ω pour l’EEU-FA (0,77 à 0,89) et α pour l’IDCC (0,70 à 0,96) démontrent une bonne cohérence interne. Conclusions : Cette étude a permis de traduire et d’adapter en français des mesures d’engagement et de charge cognitive en contexte numérique. Les échelles font état de bonnes qualités psychométriques préliminaires.
The effects of acute blood flow restriction on climbing-specific tests
Authors: Saeterbakken Atle Hole , Andersen Vidar , Stien Nicolay , Pedersen Helene , Solstad Tom Erik Jorung , Shaw Matthew Peter , Meslo Mari , Wergeland Are , Vereide Vegard Albert , Hermans Espen
Published: March 2020

The aim of the study was to compare climbing specific performance tests with and without blood flow restriction (BFR). Thirty one climbers (age 26.9 ± 5.5 years, height 177.2 ± 7.5 cm, weight 70.5 ± 8.3 kg, fat percentage 11.9 ± 4.1 %, climbing skill 18.9 ± 4.0 IRCRA scale) performed climbing specific grip tests measuring isometric strength (peak force, rate of force development and maximal voluntary contraction (and dynamic strength (power and peak velocity in pull-up) on a 23-mm campus rung. Further, an intermittent finger endurance (7 seconds work, 3 seconds rest at 60% of maximal voluntary contraction) test to failure was conducted. All tests were performed on two separate occasions (separated by 2–5 days) with and without blood flow restriction (200 mmHg) in a randomized order. The results demonstrated no differences in the isometric strength tests (p = 0.496–0.850, ES = 0.060–0.170), dynamic strength test (p = 0.226–0.442, ES = 0.200–0.330) or the intermittent finger endurance test (p = 0.563, ES = 0.160). In conclusion, no differences were observed in the maximal isometric pull-up test, dynamic pull-up test or finger endurance tests including measurements as peak force, MVC, RFD, power output, peak velocity or time to fatigue at 60% of MVC with and without BFR.
Gastroesophageal reflux disease after peroral endoscopic myotomy is unpredictable, but responsive to proton pump inhibitor therapy: a large, single-center study
Authors: Nabi Zaheer , Ramchandani Mohan , Kotla Rama , Tandan Manu , Goud Rajesh , Darisetty Santosh , Rao G. Venkat , Reddy D. Nageshwar
Published: March 2020

Background Gastroesophageal reflux disease (GERD) is an important concern after peroral endoscopic myotomy (POEM). However, there are limited data on the risk factors for post-POEM GERD and its responsiveness to proton pump inhibitors (PPIs). In this study, we aimed to analyze the variables affecting the occurrence of GERD and its response to PPI therapy.

Methods Consecutive patients with idiopathic achalasia who underwent POEM (December 2016 to January 2018) were evaluated for GERD using 24-hour pH impedance, esophagogastroduodenoscopy (EGD), and symptoms. Multivariate analysis was performed to identify the variables affecting the incidence of post-POEM GERD.

Results A total of 209 patients with esophageal motility disorders, including 194 patients with non-sigmoid achalasia, underwent POEM during the study period. Comprehensive evaluation of GERD was completed on 167 patients (86.1 %): 47.3 % women with a mean (standard deviation) age of 41 (14.42) years and body mass index of 22.2 (3.89) kg/m2; the majority (70.7 %) were treatment naïve. A high DeMeester score (> 14.72), reflux esophagitis, and symptomatic GERD were identified in 47.9 %, 41.9 %, and 29.3 % of patients, respectively. On logistic regression analysis, type of achalasia, technique of POEM (anterior vs. posterior), pre- or post-POEM esophageal manometry variables, and patient characteristics were not associated with post-POEM GERD. Erosive esophagitis responded to PPI therapy in the majority of patients (81.4 %).

Conclusion The incidence of GERD is high after POEM. Most of the reflux esophagitis is mild and responsive to PPI therapy. There are no procedural or patient-related variables that appear to affect the incidence of post-POEM GERD.
Catalytic Asymmetric Aziridination of Benzhydryl Imines and Diazoacetate­ Esters with BOROX Catalysts from 3,3′-Disubstituted VANOL Ligands
Authors: Wulff William D. , Guan Yong , Lu Zhenjie , Yin Xiaopeng , Mohammadlou Aliakbar , Staples Richard J.
Published: March 2020

This work details the synthesis of 22 new chiral VANOL ligands that differ by the nature of the substituent in the 3- and 3′-positions of the ligand. These ligands were incorporated into boroxinate catalysts that were used to screen the catalytic asymmetric aziridination of benzhydryl imines with ethyl diazoacetate. Each catalyst was screened in the reaction of imines generated from benzaldehyde and cyclohexanecarboxaldehyde and some with 4-nitro- and 4-methoxybenzaldehyde. In addition, the first report of the effect of the ester substituent of the diazoacetate ester on the asymmetric induction in these aziridination reactions is presented. The first X-ray structure of a boroxinate catalyst generated from a VANOL-derived ligand is also reported.
An Improved, Versatile, and Easily Scalable Synthesis of Sphingomyelins: Application to Stable Isotope Labeling
Authors: Philippe Nicolas , Pérard Serge , Le Strat Franck , Blankenstein Jörg , Roy Sébastien
Published: March 2020

With a view to make conveniently labeled mass spectrometry standards available, a set of deuterated sphingomyelins were prepared by a new expedient, flexible, robust, scalable, and high-yielding synthetic scheme starting from 2-azido-3-O-benzoylsphingosine as the key intermediate. Unlike previously published procedures, this work emphasizes the benefit arising from the choice of the azido function as a masking group for the reactive primary amine during the troublesome, though crucial, phosphorylation step.
One-Pot Synthesis of α-Halo β-Amino Acid Derivatives via the Difunctional Coupling of Ethyl α-Diazoacetate with Silyl Halides and N,O-Acetals or Aromatic Tertiary Amines
Authors: Sakai Norio , Sasaki Kazuki , Suzuki Hiroki , Ogiwara Yohei
Published: March 2020

The difunctionalization of ethyl α-diazoacetate (EDA) using silyl halides as a nucleophile and N,O-acetals as an electrophile under metal-free conditions is described. This process undergoes a novel three-component coupling (3-CC) reaction using EDA, which leads to a one-pot preparation of α-halo β-amino acid esters. Also, this protocol could be adapted to accept an electrophile composed of aromatic tertiary amines. In both 3-CC reactions, the key reaction intermediate is an iminium intermediate that can be easily and effectively generated either from N,O-acetals or from aromatic tertiary amines.
The Synthesis of 2-Spiroindolin-3-one-(thio)barbiturates from 2,1-Benzisoxazoles: A Rearrangement Promoted by Thermal Conditions
Authors: Almeida Paulo , Soeiro Pedro F. , Serrano João L. , Paixão José A. , Boto Renato E. F. , Silvestre Samuel
Published: March 2020

A new thermal process to prepare spiroindolin-3-ones from 3-substituted 2,1-benzisoxazoles in good yields (70–85%) is described. The highest yields were observed when microwave irradiation was used. The method does not require the use of any additive or catalyst. A possible reaction mechanism involving a nitrene key intermediate is proposed.
Effect of Degree of Arterial Inflow on a Functioning Free Muscle Transplantation in a Rat Gracilis Model
Authors: Sakarya Ahmet Hamdi , Do Nicholas Thu Khoa , Huang Yen-Lin , Lu Johnny Chuieng-Yi , Chang Tommy Nai-Jen , Chuang David Chwei-Chin
Published: March 2020

Background Various surgical effects have previously been studied in an attempt to improve the functional outcome of the functioning free muscle transplantation (FFMT). However, the effect of the recipient arterial inflow on the FFMT has remained uninvestigated. This study was to investigate whether or not high flow versus low flow will affect the functional outcome of FFMT.

Methods Rat's left gracilis FFMT model was devised and the nutrient arterial inflow was modified. Twenty-four Lewis rats were divided evenly into relatively high (0.071 mL/min) and relatively low (0.031 mL/min) blood flow groups (p < 0.001). The unoperated right sides served as the controls. Cases resulting in poor function were additionally grouped as functional failure group for comparison. Regular swimming exercise was implemented at 1 month postoperatively for 3 months. Gracilis muscle functions were then evaluated.

Results Compared groups were: control (n = 13), low blood flow (n = 10), high blood flow (n = 8), and functional failure (n = 5). The control group showed superior functional results over the experimental groups (p < 0.0001). In the experimental group, successful group showed superior over the poor function group (p < 0.01). However, there was no significant difference between the high- and low-flow groups.

Conclusion This is the first study to evaluate the effect of arterial inflow on the FFMT. The rate of blood flow (relatively high vs. low) has little effect on the functional outcome of transferred muscle. Survival of FFMT is the major concern while performing FFMT surgery. Arterial inflow while choosing the recipient artery is not the factor for consideration.
A New Family of Rigid Dienone Musks Challenges the Perceptive Range of the Human Olfactory Receptor OR5AN1
Authors: Wang Quanrui , Riniker Sereina , Kraft Philip , Liu Jie , Hürlimann Vera , Emter Roger , Natsch Andreas , Esposito Carmen , Linker Stephanie M. , Zou Yue , Zhou Lijun
Published: March 2020

A new family of dienone musks was discovered by alkylation of different aldehydes with but-3-en-1-yn-1-yllithium and subsequent domino reaction of a Saucy–Marbet transfer vinylation–Claisen rearrangement with an intramolecular Diels–Alder reaction, and concluding Lewis acid catalyzed double-bond isomerization. The newly synthesized dienone structures possess pleasant musk odors displaying fatty, slightly fruity and green facets. Although the dienone musks were predicted in silico to bind to the OR5AN1 receptor based on QM/MM calculations, they were found to be inactive in the in vitro assay. The latter results suggest that the OR5AN1 receptor is not the prime musk receptor but primarily responsible for the animalic character of certain macrocyclic ketones and nitro musks.
Perinatal Outcomes with Longer Second Stage of Labor: A Risk Analysis Comparing Expectant Management to Operative Intervention
Authors: Ausbeck Elizabeth B. , Jennings Sara F. , Champion Macie , Gray Meredith , Blanchard Christina , Tita Alan T. , Harper Lorie M.
Published: March 2020

Objective The aim of this study is to assess the impact of a prolonged second stage of labor on maternal and neonatal outcomes by comparing women who had expectant management versus operative intervention beyond specified timeframes in the second stage of labor.

Study Design Retrospective cohort including live singletons at ≥36 weeks who reached the second stage of labor. Expectant management (second stage >3, 2, 2, and 1 hour in nulliparas with an epidural, nulliparas without an epidural, multiparas with an epidural, and multiparas without an epidural, respectively) was compared with those who had an operative delivery (vaginal or cesarean) prior to these timeframes. The primary maternal outcome was a composite of postpartum hemorrhage, chorioamnionitis, operative complications, postpartum infections, and intensive care unit admission. The primary neonatal outcome was a composite of cord blood acidemia, 5-minute Apgar's score <5, chest compressions or intubation at birth, sepsis, seizures, birth injury, death, transfer to a long-term care facility, and respiratory support for >1 day.

Results Among 218 women, 115 (52.8%) had expectant management. Expectant management was associated with a significantly increased risk of the maternal composite (adjusted odds ratio [aOR]: 1.99, 95% confidence interval [CI]: 1.09–3.64) but not the neonatal composite (aOR: 1.54, 95% CI: 0.71–3.35).

Conclusion Expectant management of a prolonged second stage was associated with a higher rate of adverse maternal outcomes, but the rate of adverse neonatal outcomes was not significantly increased.
Changes in microbubble dynamics upon adhesion to a solid surface
Authors: Lum Jordan S. , Daeichin Verya , Kienle Daniel F. , Schwartz Daniel K. , Murray Todd W. , Borden Mark A.
Published: March 2020

The interaction between an acoustically driven microbubble and a surface is of interest for a variety of applications, such as ultrasound imaging and therapy. Prior investigations have mainly focused on acoustic effects of a rigid boundary, where it was generally observed that the wall increases inertia and reduces the microbubble resonance frequency. Here we investigate the response of a lipid-coated microbubble adherent to a rigid wall. Firm adhesion between the microbubble and a glass surface was achieved through either specific (biotin/avidin) or nonspecific (lipid/glass) interactions. Total internal reflection fluorescence microscopy was used to verify conditions leading to either adhesion or non-adhesion of the bubble to a glass or rigid polymer surface. Individual microbubbles were driven acoustically to sub-nanometer-scale radial oscillations using a photoacoustic technique. Remarkably, adherent microbubbles were shown to have a higher resonance frequency than non-adherent microbubbles resting against the wall. Analysis of the resonance curves indicates that adhesion stiffens the bubble by an apparent increase in the shell elasticity term and decrease in the shell viscosity. Based on these results, we conclude that surface adhesion is dominant over acoustic effects for low-amplitude microbubble oscillations.
CMOS-coupled NaI scintillation detector for gamma decay measurements
Authors: Bergeson Scott D. , Ware Michael J. , Hawk Jeremy
Published: March 2020

We report an all-solid-state gamma-ray scintillation detector comprised of a NaI(Tl) crystal and a scientific-grade CMOS camera. After calibration, this detector exhibits excellent linearity over more than three decades of activity levels ranging from 10 mCi to 400 nCi. Because the detector is not counting pulses, dead-time correction is not required. Compared to systems that use a photomultiplier tube, this detector has similar sensitivity and noise characteristics on short time scales. On longer time scales, we measure drifts of a few percent over several days, which can be accommodated through regular calibration. Using this detector, we observe that when high activity sources are brought into close proximity to the NaI crystal, several minutes are required for the measured signal to achieve a steady state.
Nanowire crystals of tantalum nitride grown in ammonium halide fluxes at high pressures
Authors: Gaida Nico Alexander , Sasaki Takuya , Liu Zheng , Niwa Ken , Hirozawa Masaki , Ohsuna Tetsu , Hasegawa Masashi
Published: March 2020

Nanowire crystals of a tantalum nitride phase have been grown from epsilon-tantalum nitride and ammonium halide precursors at high pressures exceeding several gigapascals. Synchrotron x-ray diffraction and Transmission Electron Microscopy (TEM) observations revealed that they had crystallized in an unreported hexagonal structure with lattice parameters of a = 3.050(1) Å and c = 2.909(2) Å. The one-dimensional growth orientation was along the crystallographic [001] direction. Scanning TEM–EDX elemental analyses showed that the nanowire crystals were composed of tantalum and nitrogen with small amounts of oxygen. The presence of the melted ammonium halides combined with supercritical ammonia acting as a reactive flux at high pressure and temperature played a significant role in the nanowire crystal growth. Raman spectroscopy performed on several single crystal nanowires pointed toward metallic properties, and the temperature dependence of the magnetization measured by Superconducting Quantum Interference Device magnetometry suggested a superconducting transition about 6.2 K. The analysis of the compression behavior revealed an incompressible nature, and the bulk modulus was determined to be 363(6) GPa.
Inexpensive modeling of quantum dynamics using path integral generalized Langevin equation thermostats
Authors: Kapil Venkat , Wilkins David M. , Lan Jinggang , Ceriotti Michele
Published: March 2020

The properties of molecules and materials containing light nuclei are affected by their quantum mechanical nature. Accurate modeling of these quantum nuclear effects requires computationally demanding path integral techniques. Considerable success has been achieved in reducing the cost of such simulations by using generalized Langevin dynamics to induce frequency-dependent fluctuations. Path integral generalized Langevin equation methods, however, have this far been limited to the study of static, thermodynamic properties due to the large perturbation to the system’s dynamics induced by the aggressive thermostatting. Here, we introduce a post-processing scheme, based on analytical estimates of the dynamical perturbation induced by the generalized Langevin dynamics, which makes it possible to recover meaningful time correlation properties from a thermostatted trajectory. We show that this approach yields spectroscopic observables for model and realistic systems that have an accuracy comparable to much more demanding approximate quantum dynamics techniques based on full path integral simulations.
Director grating and two-beam energy exchange in a hybrid photorefractive cholesteric cell with a helicoidal polymer network
Authors: Reshetnyak V. Yu. , Pinkevych I. P. , McConney M. E. , Evans D. R.
Published: March 2020

We develop a theory describing two-beam energy exchange in a cholesteric liquid crystal (CLC) stabilized in the planar state by a helicoidal polymer network. The CLC layer is placed between photorefractive and non-photorefractive substrates and illuminated by two intersecting coherent light beams. An interference pattern created by the incident beams induces a spatially periodic space-charge electric field in the photorefractive substrate. The field penetrates into the adjacent CLC layer and interacts with the charges trapped on the polymer fibrils forcing the fibrils to move along the helicoidal axis. At new positions, the fibrils reorient the CLC director and, therefore, induce a director grating. The light beams propagating across the cell couple within the grating. We calculate the energy exchange between the coupled beams and the gain of the weak light beam. We analyze the dependence of the gain coefficient on the parameters of the polymer network and the CLC and show that it can reach values greater than those obtained in typical solid photorefractive crystals.
A theory of contact resistance under AC conditions
Authors: Antoulinakis Foivos , Lau Y. Y.
Published: March 2020

Electrical contact is an important issue to high power microwave sources, pulsed power systems, field emitters, thin film devices and integrated circuits, interconnects, etc. Contact resistance and the enhanced ohmic heating that results have been treated mostly under steady state (DC) condition. In this paper, we consider the AC contact resistance for a simple geometry, namely, that of two semi-infinite slab conductors of different thicknesses joined at z = 0, with current flowing in the z-direction. The conductivity of the two planar slabs may assume different values. We propose a procedure to accurately calculate the normalized contact resistance under the assumption σ≫ωϵ, where ω is the frequency, σ is the electrical conductivity, and ϵ is the dielectric constant of the material in either channel. We found that in the low frequency limit, the normalized AC contact resistance reduces to the DC case, which was solved exactly by Zhang and Lau. At very high frequency, we found that the normalized contact resistance is proportional to ω, in which case the resistive skin depth becomes the effective channel width, and the physical origin of the contact resistance is identified. The transition between the high and low frequency limits was explored, where, in some cases, the normalized contact resistance may become negative, meaning that the total resistance is less than the total bulk resistance expected from the two current channels. In other cases, the numerical data suggest that the normalized contact resistance is proportional to ω in the transition region. Other issues are addressed.
Coarse-graining of polyisoprene melts using inverse Monte Carlo and local density potentials
Authors: Shahidi Nobahar , Chazirakis Antonis , Harmandaris Vagelis , Doxastakis Manolis
Published: March 2020

Bottom-up coarse-graining of polymers is commonly performed by matching structural order parameters such as distribution of bond lengths, bending and dihedral angles, and pair distribution functions. In this study, we introduce the distribution of nearest-neighbors as an additional order parameter in the concept of local density potentials. We describe how the inverse-Monte Carlo method provides a framework for forcefield development that is capable of overcoming challenges associated with the parameterization of interaction terms in polymer systems. The technique is applied on polyisoprene melts as a prototype system. We demonstrate that while different forcefields can be developed that perform equally in terms of matching target distributions, the inclusion of nearest-neighbors provides a straightforward route to match both thermodynamic and conformational properties. We find that several temperature state points can also be addressed, provided that the forcefield is refined accordingly. Finally, we examine both the single-particle and the collective dynamics of the coarse-grain models, demonstrating that all forcefields present a similar acceleration relative to the atomistic systems.
Skyrmion bubbles are stable at room temperature and a zero magnetic field
Authors: Mandel Savannah
Published: March 2020

Changing cobalt and ruthenium thickness in the magnetization process of a Pt/Co/Ru/MgO system proves to be a promising method for developing stable skyrmion bubbles with spintronics applications.
Non-local photocurrent in a ferroelectric semiconductor SbSI under local photoexcitation
Authors: Nakamura M. , Hatada H. , Kaneko Y. , Ogawa N. , Sotome M. , Tokura Y. , Kawasaki M.
Published: March 2020

We have investigated the photovoltaic action in a ferroelectric semiconductor SbSI with a potentiometry for a multiterminal device under local laser irradiation. The DC-voltage characteristics indicate that the device characteristics are understood to be equivalent to a series circuit composed of dark-resistances for the unirradiated parts and the parallel circuit of a current source and photo-resistance for the irradiated part. The results clearly guide us toward designing photovoltaic and photodetective devices based on ferroelectric materials.
Theoretical study of kinetics of proton coupled electron transfer in photocatalysis
Authors: Giret Yvelin , Guo Pu , Wang Li-Feng , Cheng Jun
Published: March 2020

Photocatalysis induced by sunlight is one of the most promising approaches to environmental protection, solar energy conversion, and sustainable production of fuels. The computational modeling of photocatalysis is a rapidly expanding field that requires to adapt and to further develop the available theoretical tools. The coupled transfer of protons and electrons is an important reaction during photocatalysis. In this work, we present the first step of our methodology development in which we apply the existing kinetic theory of such coupled transfer to a model system, namely, methanol photodissociation on the rutile TiO2(110) surface, with the help of high-level first-principles calculations. Moreover, we adapt the Stuchebrukhov–Hammes-Schiffer kinetic theory, where we use the Georgievskii–Stuchebrukhova vibronic coupling to calculate the rate constant of the proton coupled electron transfer reaction for a particular pathway. In particular, we propose a modified expression to calculate the rate constant, which enforces the near-resonance condition for the vibrational wave function during proton tunneling.
Acoustic tweezers and motor for living cells
Authors: Zhang Ruoqin , Guo Honglian , Deng Weiyin , Huang Xueqin , Li Feng , Lu Jiuyang , Liu Zhengyou
Published: March 2020

Acoustic waves can act as tweezers to trap and rotate particles without contact, which have promising application in the manipulation of tissues and living cells. Here, we report a realization of acoustic tweezers and motor. The device is fabricated on a silicon chip scaled to manipulate living cells. The silicon chip transfers incident plane ultrasonic waves into a vortex beam, which traps particles in the center of the device and exerts torque on the particles simultaneously. As an illustration, we put living shrimp eggs inside the acoustic vortex and observe the acoustic driving rotation. The rotation frequency of the shrimp egg can be easily controlled, and its relationship between driving voltage and the egg size is established. We anticipate that the acoustic tweezers and motor can find widespread applications in cell manipulation, cell screening, and micro actuator in the future.
Benzene–H2O and benzene–HDO: Fully coupled nine-dimensional quantum calculations of flexible H2O/HDO intramolecular vibrational excitations and intermolecular states of the dimers, and their infrared and Raman spectra using compact bases
Authors: Felker Peter M. , Bačić Zlatko
Published: March 2020

We present a rigorous and comprehensive theoretical treatment of the vibrational dynamics of benzene–H2O and benzene–HDO dimers, where the quantum bound-state calculations of the coupled intra- and intermolecular vibrational states of the dimers are complemented by the quantum simulations of their infrared (IR) and Raman spectra utilizing the computed eigenstates. Apart from taking benzene to be rigid, the methodology for the nine-dimensional (9D) vibrational quantum calculations introduced in this study is fully coupled. The approach yields the intramolecular vibrational fundamentals and the bend (ν2) overtone of H2O and HDO in the complex, together with the low-lying intermolecular vibrational states in each of the intramolecular vibrational manifolds considered. Following the recently introduced general procedure [P. M. Felker and Z. Bačić, J. Chem. Phys. 151, 024305 (2019)], the full 9D vibrational Hamiltonian of the dimer is divided into a 6D intermolecular Hamiltonian, a 3D intramolecular Hamiltonian, and a 9D remainder term. A 9D contracted product basis is constructed from the low-energy eigenstates of the two reduced-dimension Hamiltonians, and the full vibrational dimer Hamiltonian is diagonalized in it. The symmetry present in the dimers is exploited to reduce the Hamiltonian matrix to a block diagonal form. Guided by the findings of our earlier study referenced above, the 6D intermolecular contracted bases for each symmetry block include only 40 eigenstates with energies up to about 225 cm−1, far below the stretch and bend fundamentals of H2O and HDO, which range between 1400 cm−1 and 3800 cm−1. As a result, the matrices representing the symmetry blocks of the 9D Hamiltonian are small for the high-dimensional quantum problem, 1360 and 1680 for the H2O and HDO complexes, respectively, allowing for direct diagonalization. These calculations characterize in detail the H2O/HDO intramolecular vibrations, their frequency shifts, and couplings to the large-amplitude-motion intermolecular vibrational sates. The computed IR spectra of the two complexes in the OH-stretch region, as well as the intermolecular Raman spectra, are compared to the experimental spectra in the literature.
The size and affinity effect of counterions on self-assembly of charged block copolymers
Authors: Jiang Jiadi , Chen Xu , Yang Shuang , Chen Er-Qiang
Published: March 2020

The effect of counterions’ size and affinity on the microphase separated morphologies of neutral-charged diblock copolymers is investigated systematically using a random phase approximation (RPA) and self-consistent field theory (SCFT). The phase diagrams as a function of χAB and fA at different counterion sizes and different affinities to neutral blocks are constructed, respectively. Stability limits calculated using the RPA are in good agreement with the disorder-body-centered cubic phase boundaries from SCFT calculations. It was found that increasing the size of counterions causes the phase diagram to shift upward and leftward, which is attributed to electrostatic interactions and the intrinsic volume of counterions. The domain size of the ordered phase shows an unexpected tendency that it decreases with increasing counterions’ size. The counterions’ distributions in H and G phases demonstrate that it is electrostatic interaction, instead of packing frustration, that plays a leading role in such systems. For finite size counterions, with the increase in affinity between counterions and neutral blocks, the phase diagram shifts upward, indicating the improved compatibility between different blocks. Furthermore, the affinity effect between counterions and neutral blocks can be mapped into an effective Flory parameter χAB′ = χAB + 0.27χBC.
Land managers’ and service providers’ perspectives on the magnitude, impact and management of non-domestic grazing pressure in the southern rangelands of Australia
Authors: Atkinson T. , Hacker R. B. , Melville G. J. , Reseigh J.
Published: March 2020

In the southern rangelands of Australia, the capability of land managers to manage total grazing pressure, with support from their service providers, influences resource condition, livestock production and pastoral business profitability. This study investigated the perspectives of people who face the challenge of managing total grazing pressure. Self-administered surveys were used to collect the perspectives of 220 land managers and 46 service providers to total grazing pressure management and the impacts of grazing animals. Land managers and service providers agreed that, on average, 40 to 50% of the total demand for forage is due to non-domestic animals, that a reduction in this component is required, and that current levels are at least double the desirable level. The majority of respondents (>54%) assessed both livestock and non-domestic animals to have a negative impact on soils and pastures. However, livestock were more frequently assessed to have a positive impact on soils and pastures than non-domestic animals. The respondents commonly suggested that the impact livestock have on soils and pastures depends on management. Non-domestic animals were assessed by the majority of respondents to have a negative impact on livestock production and business profitability, apart from unmanaged goats where opinions were divided. Both land managers and service providers used the ‘large negative’ category to describe the impact on livestock production and business profitability more frequently for kangaroos than for any other herbivore. There were significant differences in the respondents’ perspectives among the States. Respondents in New South Wales and Queensland estimated a higher proportion of demand for forage from non-domestic animals than respondents from other States. The respondents in New South Wales also more frequently assessed unmanaged goats to have a positive impact on business profitability compared with the other States. Total grazing pressure management was rated as a high priority issue by 66% of respondents. ‘Improved kangaroo management’ and ‘fencing’ were the two main factors identified with potential to make a substantial difference to total grazing pressure management in the next ten years.
Deceleration of China’s human water use and its key drivers
Authors: Zhou Feng , Bo Yan , Ciais Philippe , Dumas Patrice , Tang Qiuhong , Wang Xuhui , Liu Junguo , Zheng Chunmiao , Polcher Jan , Yin Zun , Guimberteau Matthieu , Peng Shushi , Ottle Catherine , Zhao Xining , Zhao Jianshi , Tan Qian , Chen Lei , Shen Huizhong , Yang Hui , Piao Shilong , Wang Hao , Wada Yoshihide
Published: March 2020

Increased human water use combined with climate change have aggravated water scarcity from the regional to global scales. However, the lack of spatially detailed datasets limits our understanding of the historical water use trend and its key drivers. Here, we present a survey-based reconstruction of China’s sectoral water use in 341 prefectures during 1965 to 2013. The data indicate that water use has doubled during the entire study period, yet with a widespread slowdown of the growth rates from 10.66 km
3
⋅y
−2
before 1975 to 6.23 km
3
⋅y
−2
in 1975 to 1992, and further down to 3.59 km
3
⋅y
−2
afterward. These decelerations were attributed to reduced water use intensities of irrigation and industry, which partly offset the increase driven by pronounced socioeconomic development (i.e., economic growth, population growth, and structural transitions) by 55% in 1975 to 1992 and 83% after 1992. Adoptions for highly efficient irrigation and industrial water recycling technologies explained most of the observed reduction of water use intensities across China. These findings challenge conventional views about an acceleration in water use in China and highlight the opposing roles of different drivers for water use projections.