bluuebunny/crossref_metadata_2025 huggingface dataset:
F-element metalated dipyrrins: synthesis and characterization of a family of uranyl bis(dipyrrinate) complexes
Authors: Bolotaulo Duer , Metta-Magaña Alejandro , Fortier Skye
Published: February 2017

Using an improved, chromatography-free dipyrrin synthesis, a new family of actinide dipyrrinate complexes has been synthesized.
Facile synthesis of an ultra-stable metal–organic framework with excellent acid and base resistance
Authors: Zhao Nian , Li Ping , Mu Xin , Liu Chuanfang , Sun Fuxing , Zhu Guangshan
Published: February 2017

A novel ultra-stable metal–organic framework, MCIF-1, [Cu2(DCI)2](MeCN), based on dicyanoimidazole and Cu(i), has been synthesized at room temperature successfully. MCIF-1 shows excellent water stability and can retain crystallinity after soaking in water for about one week. In addition, MCIF-1 also shows exceptional resistance under both acidic and basic conditions within a large pH range from 0 to 13.5. What is more, after modifying the synthesis procedure slightly, we can produce this material in a large scale during a very short time. Mild synthesis conditions, excellent stability and ease of large scale production give MCIF-1 great potential for practical use.
Sustainable sources need reliable standards
Authors: Galkin Maxim V. , Di Francesco Davide , Edlund Ulrica , Samec Joseph S. M.
Published: February 2017

This review discusses the challenges within the research area of modern biomass fractionation and valorization. The current pulping industry focuses on pulp production and the resulting cellulose fiber. Hemicellulose and lignin are handled as low value streams for process heat and the regeneration of process chemicals. The paper and pulp industry have therefore developed analytical techniques to evaluate the cellulose fiber, while the other fractions are given a low priority. In a strive to also use the hemicellulose and lignin fractions of lignocellulosic biomass, moving towards a biorefining concept, there are severe shortcomings with the current pulping techniques and also in the analysis of the biomass. Lately, new fractionation techniques have emerged which valorize a larger extent of the lignocellulosic biomass. This progress has disclosed the shortcomings in the analysis of mainly the hemicellulose and lignin structure and properties. To move the research field forward, analytical tools for both the raw material, targeting all the wood components, and the generated fractions, as well as standardized methods for evaluating and reporting yields are desired. At the end of this review, a discourse on how such standardizations can be implemented is given.
MRI-guided and ultrasound-triggered release of NO by advanced nanomedicine
Authors: Jin Zhaokui , Wen Yanyuan , Hu Yaxin , Chen Wenwen , Zheng Xianfeng , Guo Weisheng , Wang Tianfu , Qian Zhiyong , Su Bao-Lian , He Qianjun
Published: February 2017

A new concept of tumor-targeted gas delivery and imaging-guided and stimuli-triggered gas release is proposed for precision gas therapy.
A vinylic rotaxane cross-linker for toughened network polymers from the radical polymerization of vinyl monomers
Authors: Sawada J. , Aoki D. , Kuzume M. , Nakazono K. , Otsuka H. , Takata T.
Published: February 2017

A [2]rotaxane cross-linker with one vinyl group in each component was synthesized as a vinylic cross-linker for highly toughened network polymers.
Extraction and characterization of anti-oxidative polysaccharide–protein complexes from Corbicula fluminea through three-phase partitioning
Authors: Wang Yao-Yao , Qiu Wen-Yi , Wang Zhen-Bin , Ma Hai-Le , Yan Jing-Kun
Published: February 2017

In this study, a simple, efficient, and green bioseparation technology called three-phase partitioning (TPP) was employed to extract and separate polysaccharide–protein complexes (PSP) from Corbicula fluminea.
Ex situ Cu(0) nanoparticle mediated SET-LRP of methyl methacrylate/styrene-methyl methacrylate in a biphasic toluene–water system
Authors: Bansal Ankushi , Singhal Nikita , Panwar Vineeta , Kumar Arvind , Kumar Umesh , Ray Siddharth S.
Published: February 2017

Cu(0) nanoparticles mediated SET-LRP of methyl methacrylate/styrene-methyl methacrylate in biphasic toluene–water system.
A mild catalytic system for radical conjugate addition of nitrogen heterocycles
Authors: Aycock R. A. , Wang H. , Jui N. T.
Published: February 2017

A catalytic redox system for the direct conjugate addition of pyridines and diazines to Michael acceptors has been developed.
Design and synthesis of porous ZnTiO3/TiO2 nanocages with heterojunctions for enhanced photocatalytic H2 production
Authors: Tian Hao , Wang Songcan , Zhang Chi , Veder Jean-Pierre , Pan Jian , Jaroniec Mietek , Wang Lianzhou , Liu Jian
Published: February 2017

Unique mesoporous ZnTiO3/TiO2 hollow polyhedra with selectively located Pt nanoparticles have been designed and constructed for photocatalytic hydrogen production.
Cyan emissive super-persistent luminescence and thermoluminescence in BaZrSi3O9:Eu2+,Pr3+ phosphors
Authors: Guo Haijie , Wang Yuhua , Li Gen , Liu Jie , Feng Peng , Liu Dongwei
Published: February 2017

We developed a novel long-lasting phosphorescence (LLP) material BaZrSi3O9:Eu2+,Pr3+.
Intramuscular Migration of Venous Catheter as a Rare Complication of Ventriculoatrial Shunt: Case Report and Literature Review
Authors: Hung Cheng-Che , Chuang Hao-Yu , Lin Hung-Lin , Chu Yen-Tse , Cheng Cheng
Published: February 2017

The most common procedure to manage hydrocephalus is a ventriculoperitoneal shunt. Other alternatives include a ventriculoatrial (VA) shunt, ventriculopleural shunt, lumboperitoneal shunt, or ventriculocisternal shunt. The VA shunt is a relatively rare procedure for hydrocephalus. As reported, several complications of VA shunt include obstructions, malposition, shunt infections, endocarditis, heart failure, tricuspid regurgitation, intra-atrial thrombus, and pulmonary hypertension. In this case report and literature review, we discuss a rare case of intramuscular migration of a venous tube 1 year after VA shunt implantation. We also report all the possible locations of migration after placement of VA shunt.
Synchronous Aberrant Cerebellar and Opercular Development in Fetuses and Neonates with Congenital Heart Disease: Correlation with Early Communicative Neurodevelopmental Outcomes, Initial Experience
Authors: Wong A. , Chavez T. , O'Neil S. , Votava-Smith J. , Miller D. , delCastillo S. , Panigrahy A. , Paquette L.
Published: February 2017

Patients with congenital heart disease (CHD) demonstrate multidomain cognitive delays. Cingulo-opercular and cerebellar brain networks are critical to language functions. This is a description of our initial experience aiming to identify an anatomic correlate for CHD patients with expressive language delays. Fetal CHD patients, prospectively enrolled, underwent serial fetal (1.5T), postnatal pre- and postoperative (3T) MRI. Non-CHD patients were enrolled retrospectively from the same epoch. Comparable fetal and neonatal T2 contrast was used for manual linear cross-sectional measurement. Multivariable analysis was used for adjustments and curve fitting. Neurodevelopment was assessed with Battelle Developmental Inventory, 2nd ed. between 9 and 36 months of age. This interim analysis included patients from our longitudinal CHD study who had fetal, postnatal imaging and neurodevelopmental data—yielding a total of 62 mothers (11 CHD fetuses and 51 non-CHD fetuses). Altered brain trajectories were seen in selected cerebellar and opercular measurements in CHD patients compared with the non-CHD group. Smaller inferior cerebellar vermis measurements were associated with multiple communication-related abnormalities. Altered early structural development of the cerebellum and operculum is present in patients with CHD, which correlates with specific neurodevelopmental abnormalities.
Dynamic Alignment Analysis in the Osteoarthritic Knee Using Computer Navigation
Authors: Murillo-Vizuete David , Garcia-Bogalo Raul , Escobar-Anton David , Horna-Castiñeiras Lissette , Peralta-Molero Juan , Larrainzar-Garijo Ricardo
Published: February 2017

The lower limb alignment is influenced by the geometry of the joint surfaces and surrounding soft tissue tension. The mechanical behavior changes in a normal, osteoarthritic, and postoperative knee. The purpose of this study is to determine the dynamic coronal femoral tibial mechanical angle (FTMA) in osteoarthritic knees using computer navigation. The authors hypothesize that there are different varus-valgus patterns between flexion and extension in the osteoarthritic knee. We conducted a transversal observational study and included patients with osteoarthritis who underwent primary navigation TKA (Orthopilot version 4.2; B. Braun Aesculap, Tuttlingen, Germany). In total, 98 consecutive patients with 100 osteoarthritic knee joints, on which total knee arthroplasty was performed in our institution from 2009 to 2010, were enrolled in this prospective study. The FTMA was measured with the patient supine with maximum knee extension possible (considering the value as 0), 30, 60, and 90 degrees. All FMTA data obtained were segmented by hierarchic cluster measuring method. Through the clustering system, five segments were generated for varus patients and three for valgus patients: expected varus, expected valgus, severe varus, severe valgus, structured varus, structured valgus, concave varus, mixed varus-valgus, and mixed valgus-varus. The findings of the present study have demonstrated that there is a well-defined dynamic alignment in osteoarthritic knees, resulting in a wide kinematic variation in the coronal FTMA between flexion and full extension. Further studies will be necessary to determine whether this dynamic approach to FTMA has clinical utility in the surgeon's decision-making process.
Influence of Maternal Factors in Neonatologists' Counseling for Periviable Pregnancies
Authors: Kunkel Melissa , Downs Stephen , Tucker Edmonds Brownsyne
Published: February 2017

Background Neonatologists have varying counseling practices for women with threatened periviable pregnancies. Previous research has suggested this variability may be influenced by social and economic factors of the mother.

Objective The objective of this study was to determine the relative influence of maternal factors in counseling recommendations for periviable pregnancies.

Methods A national cohort of neonatologists was sent a web-based survey. Five maternal characteristics were varied across eight vignettes: age, education, race, parity, and pregnancy “intendedness.” Following each vignette, participants reported their likelihood to recommend full resuscitation versus comfort care. Conjoint analysis was used to assess the relative influence of each factor on respondents' recommendations.

Results Responses from 328 neonatologists were included. Of the five tested maternal characteristics, parity and intendedness had the highest importance scores (40.2 and 35.0), followed by race, education, and age. If parents requested resuscitation, respondents were highly likely to comply with preferences, with little variation across vignettes.

Conclusion Fetal-specific factors such as gestational age and estimated weight are known to influence counseling and decision making for extremely preterm infants. Our results suggest that maternal factors may also influence counseling practices, although physicians are likely to comply with parental preferences regardless of maternal factors. Future research should identify how maternal characteristics impact actual counseling practices.
Analyse von Daten aus der Einschulungsuntersuchung zur Evaluation von Fördermaßnahmen in Kindertageseinrichtungen im Landkreis Biberach
Authors: Hart Ulrike , Wildner Manfred , Krämer Daniela , Crispin Alexander
Published: February 2017

Anhand von Daten der Einschulungsuntersuchung (ESU) sollen die Effekte der Einführung von Fördermaßnahmen im Bereich Sprache, Mathematik und Singen in den 161 Kindertageseinrichtungen des Landkreises Biberach untersucht werden. Es handelt sich nicht um eine geplante Interventionsstudie, sondern um eine Analyse von Gebrauchsdaten.

ESU-Daten der Einschulungsjahrgänge 2011–2014 (Kinder untersucht in den Schuljahren 2009/2010–2012/2013) aus dem Landkreis Biberach werden in Studie 1 (N=7 148 Kinder) durch Mittelwertsvergleiche und mittels multipler linearer Regression analysiert und in Studie 2 (N=3×80 000 Kinder) deskriptiv mit denen des Landes Baden-Württemberg (BW) verglichen. In Studie 3 (N=1 783 Kinder) wird in einer Querschnittsanalyse des Einschulungsjahrganges 2014 im Landkreis Biberach der Zusammenhang zwischen Förderangeboten und Entwicklungsstand mittels einer logistischen Regression untersucht.

In den Entwicklungsbereichen Sprache, frühe Mathematik sowie visuelle Wahrnehmung und Visuomotorik ergeben sich in Studie 1 vom Einschuljahrgang 2011–2014 statistisch signifikante Leistungsverbesserungen, allerdings nicht im Bereich Grobmotorik. Die Landesdaten zeigen in Studie 2 dagegen keine Hinweise für eine ähnliche Leistungsverbesserung. In Studie 3 ist Mathematikförderung mit günstigeren Entwicklungsprofilen verbunden (frühe Mathematik OR 0,72 [0,55–0,94], grammatische Kompetenz 0,75 [0,59–0,95], auditive Merkspanne 0,53 [0,40–0,70]). Kinder mit Singförderung unterscheiden sich nicht von Kindern ohne Singförderung. Kinder in speziellen Sprachfördergruppen, haben nach 6-monatiger Förderung, meist im Umfang von 4×30 min pro Woche, wie zu erwarten, immer noch ein größeres Risiko für Sprachdefizite (OR 3,32 [2,57–4,28] für grammatische Kompetenz). Sie fallen aber auch in anderen Bereichen, insbesondere im Verhalten häufiger auf (Hyperaktivität OR 3,08 [2,12–4,46]). Kinder, die mit einer nichtdeutschen Familiensprache aufwachsen, sind häufiger im Sprachbereich auffällig (OR 2,78 [2,15–3,59]), aber weniger häufig im Bereich Visuomotorik (OR 0,52 [0,36–0,77]) und Hyperaktivität (0,51 [0,34–0,78]).

Die Analysen von Daten aus der Einschulungsuntersuchung zeigen im Verlauf von 4 Jahren signifikante Leistungsverbesserungen für die Kinder aus dem Landkreis Biberach. Aufgrund des Querschnittsdesigns der Studie sind kausale Schlussfolgerungen nicht möglich. Die Ergebnisse deuten auf das positive Einwirken eines „Biberacher Förderfaktors“ hin. Die Effektstärken entsprechen denen, die die aktuelle Forschung für Kindertageseinrichtungen mit hoher pädagogischer Qualität berichtet.
Single-balloon enteroscopy efficacy and degree of concordance with noninvasive evaluation of small bowel
Authors: Marques Margarida , Santos-Antunes João , Coelho Rosa , Cardoso Hélder , Vilas Boas Filipe , Ribeiro Armando , Macedo Guilherme
Published: February 2017

Background and study aims Clinical impact of single-balloon enteroscopy (SBE) is fairly known, as well as its diagnostic yield comparing with other small bowel gastrointestinal investigations. This study represents a contribution to better understand it and is designed to

evaluate SBE efficacy and degree of concordance with previous evaluation of small bowel.

Patients and methods This is a single-center retrospective study of patients that underwent SBE with suspected small bowel disease based on non-invasive imaging. Demographic, clinical, procedural and outcome data were collected for analysis. Agreement beyond positive findings was evaluated using κ-coefficient.

Results A total of 197 SBEs were performed in 168 patients; mainly men (64.3 %) with mean age 53.3±17.6 years. Most SBEs (86.3 %) performed were preceded by a noninvasive evaluation: in 61.4 % (n = 119) of cases, capsule enteroscopy (CE) was performed, in 18.8 % (n = 37), computed tomography was performed, and in 6.1 % (n = 12) magnetic resonance enterography was performed. Fourty-three patients (25.6 %) underwent endoscopic treatments, mainly: argon plasma coagulation in angioectasias (53.4 %) and polypectomy (34.9 %). The most common diagnoses made with SBE were findings consistent with inflammatory small bowel disease (21.8 %) and vascular lesions (14.2 %). The diagnostic yield of SBE was of 69 %, confirming the suspicion of small bowel disease. The degree of concordance between CE and SBE for positive findings was substantial, κ-coefficient = 0.635 (P < 0.001). However, the degree of concordance between imaging examinations (CT or MR) and SBE was only moderate, κ-coefficient = 0.410 (P < 0.001). SBE had an immediate effect in 20 % of patients, changing diagnostic approaches, medical and surgical treatments.

Conclusions Our study supports the idea that for suspected small bowel disease, CE and SBE have an overall good degree of concordance for all the diagnostics included.
Clinical outcomes of EUS-guided drainage of debris-containing pancreatic pseudocysts: a large multicenter study
Authors: Yang Dennis , Amin Sunil , Gonzalez Susana , Mullady Daniel , Edmundowicz Steven , DeWitt John , Khashab Mouen , Wang Andrew , Nagula Satish , Buscaglia Jonathan , Bucobo Juan , Wagh Mihir , Draganov Peter , Stevens Tyler , Vargo John , Khara Harshit , Diehl David , Keswani Rajesh , Komanduri Srinadh , Yachimski Patrick , Prabhu Anoop , Kwon Richard , Watson Rabindra , Goodman Adam , Benias Petros , Carr-Locke David , DiMaio Christopher
Published: February 2017

Background and study aims Data on clinical outcomes of endoscopic drainage of debris-free pseudocysts (PDF) versus pseudocysts containing solid debris (PSD) are very limited. The aims of this study were to compare treatment outcomes between patients with PDF vs. PSD undergoing endoscopic ultrasound (EUS)-guided drainage via transmural stents.

Patients and methods Retrospective review of 142 consecutive patients with pseudocysts who underwent EUS-guided transmural drainage (TM) from 2008 to 2014 at 15 academic centers in the United States. Main outcome measures included TM technical success, treatment outcomes (symptomatic and radiologic resolution), need for endoscopic re-intervention at follow-up, and adverse events (AEs).

Results TM was performed in 90 patients with PDF and 52 with PSD. Technical success: PDF 87 (96.7 %) vs. PSD 51 (98.1 %). There was no difference in the rates for endoscopic re-intervention (5.5 % in PDF vs. 11.5 % in PSD; P = 0.33) or AEs (12.2 % in PDF vs. 19.2 % in PSD; P = 0.33). Median long-term follow-up after stent removal was 297 days (interquartile range [IQR]: 59 – 424 days) for PDF and 326 days (IQR: 180 – 448 days) for PSD (P = 0.88). There was a higher rate of short-term radiologic resolution of PDF (45; 66.2 %) vs. PSD (21; 51.2 %) (OR = 0.30; 95 % CI: 0.13 – 0.72; P = 0.009). There was no difference in long-term symptomatic resolution (PDF: 70.4 % vs. PSD: 66.7 %; P = 0.72) or radiologic resolution (PDF: 68.9 % vs. PSD: 78.6 %; P = 0.72)

Conclusions There was no difference in need for endoscopic re-intervention, AEs or long-term treatment outcomes in patients with PDF vs. PSD undergoing EUS-guided drainage with transmural stents. Based on these results, the presence of solid debris in pancreatic fluid collections does not appear to be associated with a poorer outcome.
A few thoughts on proper orthogonal decomposition in turbulence
Authors: Podvin Bérengère , Fraigneau Yann
Published: February 2017

Proper orthogonal decomposition was originally introduced in turbulence to identify large-scale patterns in turbulent flows. Over the years, several extensions have been formulated in order to strengthen its model-predictive abilities, with limited success in the case of fully developed turbulence. We argue that physics-based insight obtained from the proper orthogonal decomposition structures and other turbulence analysis techniques could lead to significant developments in that respect. Numerical results from channel flow simulations are used to illustrate our conjectures.
Insights into the growth rate of spatially evolving plane turbulent free-shear layers from 2D vortex-gas simulations
Authors: Suryanarayanan Saikishan , Narasimha Roddam
Published: February 2017

Although the free-shear or mixing layer has been a subject of extensive research over nearly a century, there are certain fundamental issues that remain controversial. These include the influence of initial and downstream conditions on the flow, the effect of velocity ratio across the layer, and the nature of any possible coupling between small scale dynamics and the large scale evolution of layer thickness. In the spirit of the temporal vortex-gas simulations of Suryanarayanan et al. [“Free turbulent shear layer in a point vortex gas as a problem in nonequilibrium statistical mechanics,” Phys. Rev. E 89, 013009 (2014)], we revisit the simple 2D inviscid vortex-gas model with extensive computations and detailed analysis, in order to gain insights into some of the above issues. Simulations of the spatially evolving vortex-gas shear layer are carried out at different velocity ratios using a computational model based on the work of Basu et al. [“Vortex sheet simulation of a plane canonical mixing layer,” Comput. Fluids 21, 1–30 (1992) and “Modelling plane mixing layers using vortex points and sheets,” Appl. Math. Modell. 19, 66–75 (1995)], but with a crucial improvement that ensures conservation of global circulation. The simulations show that the conditions imposed at the origin of the free shear layer and at the exit to the computational domain can affect flow evolution in their respective downstream and upstream neighbourhoods, the latter being particularly strong in the single stream limit. In between these neighbourhoods at the ends is a regime of universal self-preserving growth rate given by a universal function of velocity ratio. The computed growth rates are generally located within the scatter of experimental data on plane mixing layers and closely agree with recent high Reynolds number experiments and 3D large eddy simulation studies. These findings support the view that observed free-shear layer growth can be largely explained by the 2D vortex dynamics of the quasi-2D large-scale structures known to be a characteristic of plane mixing layers.
Application of POD on time-resolved schlieren in supersonic multi-stream rectangular jets
Authors: Berry M. G. , Magstadt A. S. , Glauser M. N.
Published: February 2017

In this paper, we present an experimental investigation of a supersonic rectangular nozzle with aft deck used for three-stream engines. The jet utilizes a single expansion ramp nozzle (SERN) configuration along with multiple streams, operating at a bulk flow Mj,1 = 1.6 and bypass stream Mj,3 = 1.0. This idealized representation consists of two canonical flows: a supersonic convergent-divergent (CD) jet and a sonic wall jet. Time-resolved schlieren experiments were performed up to 100 kHz. Proper orthogonal decomposition (POD), as suggested by Lumley for structure identification in turbulent flows, is applied to the schlieren images and the spatial eigenfunctions and time-dependent coefficients are related to the flow structures. This research seeks to lay a foundation for fundamental testing of multi-stream SERNs and the identification of the flow physics that dominate these modern military nozzles.
Influence of the fluid structure on the binding potential: Comparing liquid drop profiles from density functional theory with results from mesoscopic theory
Authors: Hughes Adam P. , Thiele Uwe , Archer Andrew J.
Published: February 2017

For a film of liquid on a solid surface, the binding potential g(h) gives the free energy as a function of the film thickness h and also the closely related (structural) disjoining pressure Π=−∂g/∂h. The wetting behaviour of the liquid is encoded in the binding potential and the equilibrium film thickness corresponds to the value at the minimum of g(h). Here, the method we developed in the work of Hughes et al. [J. Chem. Phys. 142, 074702 (2015)], and applied with a simple discrete lattice-gas model, is used with continuum density functional theory (DFT) to calculate the binding potential for a Lennard-Jones fluid and other simple liquids. The DFT used is based on fundamental measure theory and so incorporates the influence of the layered packing of molecules at the surface and the corresponding oscillatory density profile. The binding potential is frequently input in mesoscale models from which liquid drop shapes and even dynamics can be calculated. Here we show that the equilibrium droplet profiles calculated using the mesoscale theory are in good agreement with the profiles calculated directly from the microscopic DFT. For liquids composed of particles where the range of the attraction is much less than the diameter of the particles, we find that at low temperatures g(h) decays in an oscillatory fashion with increasing h, leading to highly structured terraced liquid droplets.
New insights into mechanistic photoisomerization of ethylene-bridged azobenzene from ab initio multiple spawning simulation
Authors: Liu Lihong , Wang Yating , Fang Qiu
Published: February 2017

Ethylene-bridged azobenzene (br-AB) has aroused broad interests due to its unique photoswitching properties. Numerous dynamical simulations have been performed for the br-AB photoisomerization, which focused mainly on the conformational effect and the funnel role of minimum-energy conical intersection (MECI) on the mechanism. In the present work, we use the “full quantum” ab initio multiple spawning method to simulate the br-AB photoisomerization, which provides new insights into the mechanism. Upon irradiation of br-AB to the first excited singlet state (S1), most of the excess energies are trapped in the azo-moiety. Since the intramolecular vibrational energy redistribution is slower than the S1 relaxation processes, the nonadiabatic transition from S1 to the ground state (S0) occurs in the vicinity of high-energy crossing seam and even the largest probabilities of the S1 → S0 transition are not distributed in the MECI regions. Once decaying to the S0 state through the high-energy region, the subsequent isomerization and re-formation of the initial isomer are ultrafast processes in the S0 state. It is the nonergodic behavior of the S1 and S0 dynamics that is mainly responsible for the unique photoswitching properties of the ethylene-bridged azobenzene, which will be discussed in detail.
NMR shieldings from density functional perturbation theory: GIPAW versus all-electron calculations
Authors: de Wijs G. A. , Laskowski R. , Blaha P. , Havenith R. W. A. , Kresse G. , Marsman M.
Published: February 2017

We present a benchmark of the density functional linear response calculation of NMR shieldings within the gauge-including projector-augmented-wave method against all-electron augmented-plane-wave+local-orbital and uncontracted Gaussian basis set results for NMR shieldings in molecular and solid state systems. In general, excellent agreement between the aforementioned methods is obtained. Scalar relativistic effects are shown to be quite large for nuclei in molecules in the deshielded limit. The small component makes up a substantial part of the relativistic corrections.
On the numbers of images of two stochastic gravitational lensing models
Authors: Wei Ang
Published: February 2017

We study two gravitational lensing models with Gaussian randomness: the continuous mass fluctuation model and the floating black hole model. The lens equations of these models are related to certain random harmonic functions. Using Rice’s formula and Gaussian techniques, we obtain the expected numbers of zeros of these functions, which indicate the amounts of images in the corresponding lens systems.
2D lattice model of a lipid bilayer: Microscopic derivation and thermodynamic exploration
Authors: Hakobyan Davit , Heuer Andreas
Published: February 2017

Based on all-atom Molecular Dynamics (MD) simulations of a lipid bilayer we present a systematic mapping on a 2D lattice model. Keeping the lipid type and the chain order parameter as key variables we derive a free energy functional, containing the enthalpic interaction of adjacent lipids as well as the tail entropy. The functional form of both functions is explicitly determined for saturated and polyunsaturated lipids. By studying the lattice model via Monte Carlo simulations it is possible to reproduce the temperature dependence of the distribution of order parameters of the pure lipids, including the prediction of the gel transition. Furthermore, application to a mixture of saturated and polyunsaturated lipids yields the correct phase separation behavior at lower temperatures with a simulation time reduced by approximately 7 orders of magnitude as compared to the corresponding MD simulations. Even the time-dependence of the de-mixing is reproduced on a semi-quantitative level. Due to the generality of the approach we envisage a large number of further applications, ranging from modeling larger sets of lipids, sterols, and solvent proteins to predicting nucleation barriers for the melting of lipids. Particularly, from the properties of the 2D lattice model one can directly read off the enthalpy and entropy change of the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine gel-to-liquid transition in excellent agreement with experimental and MD results.
Molecular dynamics study of nanoscale organization and hydrogen bonding in binary mixtures of butylammonium nitrate ionic liquid and primary alcohols
Authors: Shrivastav Gourav , Gupta Aditya , Rastogi Aman , Dhabal Debdas , Kashyap Hemant K.
Published: February 2017

Molecular dynamics simulations are utilized here to explore the nanoscale morphology and the nature of hydrogen bonding in the equimolar mixtures of butylammonium nitrate protic ionic liquid with ethanol, propanol, and butanol. The X-ray scattering experimental study of Greaves et al. [Phys. Chem. Chem. Phys. 13, 13 501 (2011)] has evidenced that alkylammonium nitrate plus alcohol mixtures possess nanoscale structural order which becomes more pronounced as the chain length of the alcohol increases. Our analysis carried out using simulated total and partial X-ray scattering structure functions quantifies the basis of these observations. The partial structure functions highlight the off-phase density correlations of alcohol with both cation and anion in the low-q region. We demonstrate that the chain lengthening of alcohols offers significant variation in the structuring of the polar and apolar moieties in the mixtures. The inspection based on radial distribution functions manifests the non-linear hydrogen bonds of cations with nitrate anions as well as alcohol molecules. The alcohol’s hydroxyl group prefers to form linear hydrogen bonds with anions and with other alcohol molecules. Incremented chain length of alcohol improves the extent of hydrogen bonding but does not alter their geometry. Spatial distribution functions delineate similar preferences. It shows stronger directional preferences of the hydroxyl group of alcohols than cation in the vicinity of an anion. Enhanced pair correlations associated with the terminal methyl carbons suggest aggregation of butanol chains in apolar domains. Triplet correlation functions (TCFs) are also used to evaluate the orientational preferences of the present polar moieties in the mixtures. Information based on TCFs for distribution of polar head group of cations and anions unveils the dominance of equilateral configurations over the less frequent isosceles configurations in all the three mixtures.
Structure-property relationships in cubic cuprous iodide: A novel view on stability, chemical bonding, and electronic properties
Authors: Pishtshev A. , Karazhanov S. Zh.
Published: February 2017

Based on the combination of density functional theory and theory-group methods, we performed systematic modeling of γ-CuI structural design at the atomistic level. Being started from the metallic copper lattice, we treated a crystal assembly as a stepwise iodination process characterized in terms of a sequence of intermediate lattice geometries. These geometries were selected and validated via screening of possible structural transformations. The genesis of chemical bonding was studied for three structural transformations by analyzing the relevant changes in the topology of valence electron densities. We determined structural trends driven by metal-ligand coupling. This allowed us to suggest the improved scenario of chemical bonding in γ-CuI. In particular, the unconventional effect of spatial separation of metallic and covalent interactions was found to be very important with respect to the preferred arrangements of valence electrons in the iodination process. We rigorously showed that useful electronic and optical properties of γ-CuI originate from the combination of two separated bonding patterns—strong covalency established in I–Cu tetrahedral connections and noncovalent interactions of copper cores is caused by the 3d10 closed-shell electron configurations. The other finding of ours is that the self-consistency of the GW calculations is crucial for correctly determining the dynamic electronic correlations in γ-CuI. Detail reinvestigation of the quasi-particle energy structure by means of the self-consistent GW approach allowed us to explain how p-type electrical conductivity can be engineered in the material.
Macroscopic dielectric function within time-dependent density functional theory—Real time evolution versus the Casida approach
Authors: Sander Tobias , Kresse Georg
Published: February 2017

Linear optical properties can be calculated by solving the time-dependent density functional theory equations. Linearization of the equation of motion around the ground state orbitals results in the so-called Casida equation, which is formally very similar to the Bethe-Salpeter equation. Alternatively one can determine the spectral functions by applying an infinitely short electric field in time and then following the evolution of the electron orbitals and the evolution of the dipole moments. The long wavelength response function is then given by the Fourier transformation of the evolution of the dipole moments in time. In this work, we compare the results and performance of these two approaches for the projector augmented wave method. To allow for large time steps and still rely on a simple difference scheme to solve the differential equation, we correct for the errors in the frequency domain, using a simple analytic equation. In general, we find that both approaches yield virtually indistinguishable results. For standard density functionals, the time evolution approach is, with respect to the computational performance, clearly superior compared to the solution of the Casida equation. However, for functionals including nonlocal exchange, the direct solution of the Casida equation is usually much more efficient, even though it scales less beneficial with the system size. We relate this to the large computational prefactors in evaluating the nonlocal exchange, which renders the time evolution algorithm fairly inefficient.
Rotational excitation of the interstellar NH2 radical by H2
Authors: Bouhafs Nezha , Lique François , Faure Alexandre , Bacmann Aurore , Li Jun , Guo Hua
Published: February 2017

We present quantum close-coupling calculations for the rotational excitation of the interstellar amidogen radical NH2 due to collisions with H2 molecules. The calculations are based on a recent, high-accuracy full-dimensional NH4 potential energy surface adapted for rigid-rotor scattering calculations. The collisional cross section calculations are performed for all transitions among the first 15 energy levels of both ortho- and para-NH2 and for total energies up to 1500 cm−1. Both para- and ortho-H2 colliding partners are considered. The cross sections for collision with para- and ortho-H2 are found to differ significantly, the magnitude of the ortho-H2 ones being dominant. No strong propensity rules are observed but transitions with Δkc=0 are slightly favored.
Electron transport through a spin crossover junction. Perspectives from a wavefunction-based approach
Authors: Vela Sergi , Verot Martin , Fromager Emmanuel , Robert Vincent
Published: February 2017

The present paper reports the application of a computational framework, based on the quantum master equation, the Fermi’s golden Rule, and conventional wavefunction-based methods, to describe electron transport through a spin crossover molecular junction (Fe(bapbpy) (NCS)2, 1, bapbpy = N-(6-(6-(Pyridin-2-ylamino)pyridin-2-yl)pyridin-2-yl)-pyridin-2-amine). This scheme is an alternative to the standard approaches based on the relative position and nature of the frontier orbitals, as it evaluates the junction’s Green’s function by means of accurate state energies and wavefunctions. In the present work, those elements are calculated for the relevant states of the high- and low-spin species of 1, and they are used to evaluate the output conductance within a given range of bias- and gate-voltages. The contribution of the ground and low-lying excited states to the current is analyzed, and inspected in terms of their 2S + 1 Ms-states. In doing so, it is shown the relevance of treating not only the ground state in its maximum-Ms projection, as usually done in most computational-chemistry packages, but the whole spectrum of low-energy states of the molecule. Such improved representation of the junction has a notable impact on the total conductivity and, more importantly, it restores the equivalence between alpha and beta transport, which means that no spin polarization is observed in the absence of Zeeman splitting. Finally, this work inspects the strong- and weak-points of the suggested theoretical framework to understand electron transport through molecular switchable materials, identifies a pathway for future improvement, and offers a new insight into concepts that play a key role in spintronics.
In situ correction of the spherical aberration in a double-toroidal electron analyzer
Authors: Liu Xiao-Jing , Nicolas Christophe , Miron Catalin
Published: February 2017

In an energy-dispersive electron spectrometer, the electrons with the same kinetic energy but different polar angles fly along different paths and impinge upon the detector at different locations. This behavior materializes the spherical aberration of the electron optics, which deteriorates the focussing quality on the detector, and thus the energy resolution of the instrument. Here, we demonstrate that, in general, the electron time of flight changes monotonically as a function of the polar angle. Combining the impact position on the detector and the time of flight of electrons, the spherical aberration can be corrected and the energy resolution can be significantly improved, 1.5× in the case of our double toroidal analyser. This correction method has a general applicability and can be of interest to experimentalists willing to push further the performances of their electron spectrometers when the time of flight is available.
Angles-centroids fitting calibration and the centroid algorithm applied to reverse Hartmann test
Authors: Zhao Zhu , Hui Mei , Xia Zhengzheng , Dong Liquan , Liu Ming , Liu Xiaohua , Kong Lingqin , Zhao Yuejin
Published: February 2017

In this paper, we develop an angles-centroids fitting (ACF) system and the centroid algorithm to calibrate the reverse Hartmann test (RHT) with sufficient precision. The essence of ACF calibration is to establish the relationship between ray angles and detector coordinates. Centroids computation is used to find correspondences between the rays of datum marks and detector pixels. Here, the point spread function of RHT is classified as circle of confusion (CoC), and the fitting of a CoC spot with 2D Gaussian profile to identify the centroid forms the basis of the centroid algorithm. Theoretical and experimental results of centroids computation demonstrate that the Gaussian fitting method has a less centroid shift or the shift grows at a slower pace when the quality of the image is reduced. In ACF tests, the optical instrumental alignments reach an overall accuracy of 0.1 pixel with the application of laser spot centroids tracking program. Locating the crystal at different positions, the feasibility and accuracy of ACF calibration are further validated to 10−6–10−4 rad root-mean-square error of the calibrations differences.
Free energy functionals for polarization fluctuations: Pekar factor revisited
Authors: Dinpajooh Mohammadhasan , Newton Marshall D. , Matyushov Dmitry V.
Published: February 2017

The separation of slow nuclear and fast electronic polarization in problems related to electron mobility in polarizable media was considered by Pekar 70 years ago. Within dielectric continuum models, this separation leads to the Pekar factor in the free energy of solvation by the nuclear degrees of freedom. The main qualitative prediction of Pekar’s perspective is a significant, by about a factor of two, drop of the nuclear solvation free energy compared to the total (electronic plus nuclear) free energy of solvation. The Pekar factor enters the solvent reorganization energy of electron transfer reactions and is a significant mechanistic parameter accounting for the solvent effect on electron transfer. Here, we study the separation of the fast and slow polarization modes in polar molecular liquids (polarizable dipolar liquids and polarizable water force fields) without relying on the continuum approximation. We derive the nonlocal free energy functional and use atomistic numerical simulations to obtain nonlocal, reciprocal space electronic and nuclear susceptibilities. A consistent transition to the continuum limit is introduced by extrapolating the results of finite-size numerical simulation to zero wavevector. The continuum nuclear susceptibility extracted from the simulations is numerically close to the Pekar factor. However, we derive a new functionality involving the static and high-frequency dielectric constants. The main distinction of our approach from the traditional theories is found in the solvation free energy due to the nuclear polarization: the anticipated significant drop of its magnitude with increasing liquid polarizability does not occur. The reorganization energy of electron transfer is either nearly constant with increasing the solvent polarizability and the corresponding high-frequency dielectric constant (polarizable dipolar liquids) or actually noticeably increases (polarizable force fields of water).
A comparative first-principles study of the structural and electronic properties of the liquid Li–Si and Li–Ge alloys
Authors: Chiang Han-Hsin , Kuo Chin-Lung
Published: February 2017

We have performed a comparative first-principles study on the structural and electronic properties of the liquid Li1-xSix and Li1-xGex alloys over a range of composition from x = 0.09 to 0.50. Our calculations showed that Si and Ge atoms can exhibit very distinct local bonding characteristics as they were alloyed with the Li atoms in the liquid state, where Si atoms tended to form a variety of covalent bonding configurations while Ge atoms predominantly appeared as the isolated anions in the liquid alloys. These differences in bonding characteristics were reflected in their electronic density of states, in which the liquid Li1-xGex alloys have a lower degree of s-p hybridization with narrower distributions of the 3s and 3p states than the liquid Li1-xSix alloys. Our calculations also showed that the optical conductivities of these two liquid alloys can undergo a transition from the Drude-like metallic nature to the semiconductor-like character as the Si/Ge content increases from 0.09 to 0.22. However, as the Si/Ge content further increases to 0.50, the liquid Li1-xGex alloys may transit to exhibit the Drude-like metallic nature, while the liquid Li1-xSix alloys can still hold the semiconductor-like character. Moreover, our calculations revealed that the dc conductivities of these liquid alloys are predominantly determined by the number of total electronic states at the Fermi level. As the liquid Li1-xSix alloys are within the composition range between 0.20 and 0.50, the increment of the states at the Fermi level with increasing the Si content is nearly identical to the amount of the Li states decreased, leading to an almost unchanged number of total electronic states at the Fermi level. However, since Ge atoms do not favor forming covalent bonding in the liquid alloys to keep the Fermi level at a minimum of the density of states, the liquid Li1-xGex alloys would have more electronic states at the Fermi level and thereby higher dc conductivities than the liquid Li1-xSix alloys within the same composition range.
Ultrafast internal conversion dynamics of highly excited pyrrole studied with VUV/UV pump probe spectroscopy
Authors: Horton Spencer L. , Liu Yusong , Chakraborty Pratip , Matsika Spiridoula , Weinacht Thomas
Published: February 2017

We study the relaxation dynamics of pyrrole after excitation with an 8 eV pump pulse to a state just 0.2 eV below the ionization potential using vacuum ultraviolet/ultraviolet pump probe spectroscopy. Our measurements in conjunction with electronic structure calculations indicate that pyrrole undergoes rapid internal conversion to the ground state in less than 300 fs. We find that internal conversion to the ground state dominates over dissociation.
Discriminating single-molecule sensing by crown-ether-based molecular junctions
Authors: Ismael Ali K. , Al-Jobory Alaa , Grace Iain , Lambert Colin J.
Published: February 2017

Crown-ether molecules are well known to selectively bind alkali atoms, so by incorporating these within wires, any change in electrical conductance of the wire upon binding leads to discriminating sensing. Using a density functional theory-based approach to quantum transport, we investigate the potential sensing capabilities of single-molecule junctions formed from crown ethers attached to anthraquinone units, which are in turn attached to gold electrodes via alkyl chains. We calculate the change in electrical conductance for binding of three different alkali ions (lithium, sodium, and potassium). Depending on the nature of the ionic analyte, the conductance is enhanced by different amounts. This change in electrical conductance is due to charge transfer from the ion to molecular wire causing the molecular resonances to shift closer to the electrode Fermi energy.
Theoretical study of enhancing the piezoelectric nanogenerator’s output power by optimizing the external force’s shape
Authors: Xu Qi , Qin Yong
Published: February 2017

The average power is one of the key parameters of piezoelectric nanogenerators (PENGs). In this paper, we demonstrate that the PENG’s output can be gigantically improved by choosing driving force with an appropriate shape. When the load resistance is 100 MΩ and the driven forces have a magnitude of 19.6 nN, frequency of 10 Hz, the average power of PENG driven by square shaped force is six orders of magnitude higher than that driven by triangular shaped and sinusoidal shaped forces. These results are of importance for optimizing the average power of the PENGs in practical applications.
Plasmon-coupled resonance energy transfer: A real-time electrodynamics approach
Authors: Ding Wendu , Hsu Liang-Yan , Schatz George C.
Published: February 2017

This paper presents a new real-time electrodynamics approach for determining the rate of resonance energy transfer (RET) between two molecules in the presence of plasmonic or other nanostructures (inhomogeneous absorbing and dispersive media). In this approach to plasmon-coupled resonance energy transfer (PC-RET), we develop a classical electrodynamics expression for the energy transfer matrix element which is evaluated using the finite-difference time-domain (FDTD) method to solve Maxwell’s equations for the electric field generated by the molecular donor and evaluated at the position of the molecular acceptor. We demonstrate that this approach yields RET rates in homogeneous media that are in precise agreement with analytical theory based on quantum electrodynamics (QED). In the presence of gold nanoparticles, our theory shows that the long-range decay of the RET rates can be significantly modified by plasmon excitation, with rates increased by as much as a factor of 106 leading to energy transfer rates over hundreds of nm that are comparable to that over tens of nm in the absence of the nanoparticles. These promising results suggest important future applications of the PC-RET in areas involving light harvesting or sensing, where energy transfer processes involving inhomogeneous absorbing and dispersive media are commonplace.