bluuebunny/crossref_metadata_2025 huggingface dataset:
A cluster of many small holes with negative imaginary surface impedances may generate a negative refraction index
Authors: Alsaedi Ahmed , Ahmad Bashir , Challa Durga Prasad , Kirane Mokhtar , Sini Mourad
Published: December 2015

We deal with the scattering of an acoustic medium modeled by an index of refraction n varying in a bounded region Ω of
and equal to unity outside Ω. This region is perforated with an extremely large number of small holes Dm's of maximum radius a, a << 1, modeled by surface impedance functions. Precisely, we are in the regime described by the number of holes of the order M:=O(aβ − 2), the minimum distance between the holes is d ∼ at, and the surface impedance functions of the form λm∼λm,0a−β with β > 0 and λm,0 being constants and eventually complex numbers. Under some natural conditions on the parameters β,t, and λm,0, we characterize the equivalent medium generating approximately the same scattered waves as the original perforated acoustic medium. We give an explicit error estimate between the scattered waves generated by the perforated medium and the equivalent one, respectively, as a→0. As applications of these results, we discuss the following findings:

If we choose negative‐valued imaginary surface impedance functions, attached to each surface of the holes, then the equivalent medium behaves as a passive acoustic medium only if it is an acoustic metamaterial with index of refraction $\tilde {n}(x)=‐n(x),\; x \in \upOmega $ñ(x)=−n(x),x∈Ω and $\tilde {n}(x)=1,\; x \in \mathbb {R}^{3}\setminus {\overline {\upOmega }}$ñ(x)=1,x∈R3∖Ω¯. This means that with this process, we can switch the sign of the index of the refraction from positive to negative values.

We can choose the surface impedance functions attached to each surface of the holes so that the equivalent index of refraction $\tilde {n}$ñ is $\tilde {n}(x)=1,\; x \in \mathbb {R}^{3}$ñ(x)=1,x∈R3. This means that the region Ω modeled by the original index of refraction n is approximately cloaked.

Copyright © 2015 John Wiley & Sons, Ltd.
Advanced processing and simulation of MRS data using the FID appliance (FID‐A)—An open source, MATLAB‐based toolkit
Authors: Simpson Robin , Devenyi Gabriel A. , Jezzard Peter , Hennessy T. Jay , Near Jamie
Published: December 2015

Purpose

To introduce a new toolkit for simulation and processing of magnetic resonance spectroscopy (MRS) data, and to demonstrate some of its novel features.

Methods

The FID appliance (FID‐A) is an open‐source, MATLAB‐based software toolkit for simulation and processing of MRS data. The software is designed specifically for processing data with multiple dimensions (eg, multiple radiofrequency channels, averages, spectral editing dimensions). It is equipped with functions for importing data in the formats of most major MRI vendors (eg, Siemens, Philips, GE, Agilent) and for exporting data into the formats of several common processing software packages (eg, LCModel, jMRUI, Tarquin). This paper introduces the FID‐A software toolkit and uses examples to demonstrate its novel features, namely 1) the use of a spectral registration algorithm to carry out useful processing routines automatically, 2) automatic detection and removal of motion‐corrupted scans, and 3) the ability to perform several major aspects of the MRS computational workflow from a single piece of software. This latter feature is illustrated through both high‐level processing of in vivo GABA‐edited MEGA‐PRESS MRS data, as well as detailed quantum mechanical simulations to generate an accurate LCModel basis set for analysis of the same data.

Results

All of the described processing steps resulted in a marked improvement in spectral quality compared with unprocessed data. Fitting of MEGA‐PRESS data using a customized basis set resulted in improved fitting accuracy compared with a generic MEGA‐PRESS basis set.

Conclusions

The FID‐A software toolkit enables high‐level processing of MRS data and accurate simulation of in vivo MRS experiments. Magn Reson Med 77:23–33, 2017. © 2015 Wiley Periodicals, Inc.
High‐order compact finite difference and laplace transform method for the solution of time‐fractional heat equations with dirchlet and neumann boundary conditions
Authors: Jacobs Byron A.
Published: December 2015

The work presents a novel coupling of the Laplace Transform and the compact fourth‐order finite‐difference discretization scheme for the efficient and accurate solution of linear time‐fractional nonhomogeneous diffusion equations subject to both Dirichlet and Neumann boundary conditions. A translational transformation of the dependent variable ensures the Caputo derivative is aligned with the Riemann‐Louiville fractional derivative. The resulting scheme is computationally efficient and shown to be uniquely solvable in all cases, accurate and convergent to in the spatial domain. The convergence rates in the temporal domain are contour dependent but exhibit geometric convergence. © 2015 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 32: 1184–1199, 2016
Data assimilation by delay‐coordinate nudging
Authors: Pazó D. , Carrassi A. , López J. M.
Published: December 2015

A new nudging method for data assimilation, delay‐coordinate nudging, is presented. Delay‐coordinate nudging makes explicit use of present and past observations in the formulation of the forcing driving the model evolution at each time step. Numerical experiments with a low‐order chaotic system show that the new method systematically outperforms standard nudging in different model and observational scenarios, also when using an unoptimized formulation of the delay‐nudging coefficients. A connection between the optimal delay and the dominant Lyapunov exponent of the dynamics is found based on heuristic arguments and is confirmed by the numerical results, providing a guideline for the practical implementation of the algorithm. Delay‐coordinate nudging preserves the easiness of implementation, the intuitive functioning and the reduced computational cost of the standard nudging, making it a potential alternative especially in the field of seasonal‐to‐decadal predictions with large Earth system models that limit the use of more sophisticated data assimilation procedures.
Students' regulation of their emotions in a science classroom
Authors: Tomas Louisa , Rigano Donna , Ritchie Stephen M.
Published: December 2015

Research aimed at understanding the role of the affective domain in student learning in classrooms has undergone a recent resurgence due to the need to understand students' affective response to science instruction. In a case study of a year 8 science class in North Queensland, students worked in small groups to write, film, edit, and produce short videos about the socio‐scientific issue of coal seam gas mining as part of a unit on energy. Student emotions over the course of the unit of work were recorded using emotion diaries (a self‐report measure), video recordings of lessons, and end‐of‐project interviews. We identify trends in student emotions and analyze their relation to classroom activities using two constructs for interpreting the affective dimension of student learning: emotional energy and emotion regulation. By analyzing a salient classroom event, we report students' regulation of negative emotions like frustration and anger as they worked together to complete the video project successfully. Furthermore, we propose that emotions, particularly positive emotions, elicited by the video task and not the socio‐scientific issue dominated students' experiences and perceptions of the unit. This raises questions about how students' positive emotions might be regulated effectively so that they remain focused on the intended learning. © 2015 Wiley Periodicals, Inc. J Res Sci Teach 53: 234–260, 2016.
Observation Versus Embolization in Patients with Blunt Splenic Injury After Trauma: A Propensity Score Analysis
Authors: Olthof Dominique C. , Joosse Pieter , Bossuyt Patrick M.M. , de Rooij Philippe P. , Leenen Loek P. H. , Wendt Klaus W. , Bloemers Frank W. , Goslings J. Carel
Published: December 2015

Background

Non‐operative management (NOM) is the standard of care in hemodynamically stable patients with blunt splenic injury after trauma. Splenic artery embolization (SAE) is reported to increase observation success rate. Studies demonstrating improved splenic salvage rates with SAE primarily compared SAE with historical controls. The aim of this study was to investigate whether SAE improves success rate compared to observation alone in contemporaneous patients with blunt splenic injury.

Methods

We included adult patients with blunt splenic injury admitted to five Level 1 Trauma Centers between January 2009 and December 2012 and selected for NOM. Successful treatment was defined as splenic salvage and no splenic re‐intervention. We calculated propensity scores, expressing the probability of undergoing SAE, using multivariable logistic regression and created five strata based on the quintiles of the propensity score distribution. A weighted relative risk (RR) was calculated across strata to express the chances of success with SAE.

Results

Two hundred and six patients were included in the study. Treatment was successful in 180 patients: 134/146 (92 %) patients treated with observation and 48/57 (84 %) patients treated with SAE. The weighted RR for success with SAE was 1.17 (0.94–1.45); for complications, the weighted RR was 0.71 (0.41–1.22). The mean number of transfused blood products was 4.4 (SD 9.9) in the observation group versus 9.1 (SD 17.2) in the SAE group.

Conclusions

After correction for confounders with propensity score stratification technique, there was no significant difference between embolization and observation alone with regard to successful treatment in patients with blunt splenic injury after trauma.
Does habitat use and ecological niche shift over the lifespan of wild species? Patterns of the bearded vulture population in the Western Alps
Authors: Milanesi P. , Giraudo L. , Morand A. , Viterbi R. , Bogliani G.
Published: December 2015

We analysed bearded vulture (Gypaetus barbatus) occurrences collected through long‐term monitoring (from 1993 to 2010) in the Western Alps (1) to test whether ecological niches shift due to individual development and (2) to verify whether these patterns could reflect their spatial distribution. Thus, we compared the distribution patterns of three age classes (‘young’, ‘sub‐adults’ and ‘adults’) through the K‐select analysis. We then computed ten species distribution models (SDMs) and their average prediction to test for differences in age class distribution. The K‐select analysis showed highly significant differences in the ecological niche among all the age classes and we also found highly significant differences in all the SDMs among the three age classes considered. Our results quantitatively showed that target species exhibits age specific shifts in the ecological niche and changes in the spatial distribution of individuals. Our methods are potentially widely applicable for testing differences among age classes of other species and thus, defining the best conservation actions (such as re‐introduction) by taking into account different requirements in different stages of the individuals’ life.
Isoprenoid Alcohols are Susceptible to Oxidation with Singlet Oxygen and Hydroxyl Radicals
Authors: Komaszylo née Siedlecka Joanna , Kania Magdalena , Masnyk Marek , Cmoch Piotr , Lozinska Iwona , Czarnocki Zbigniew , Skorupinska‐Tudek Karolina , Danikiewicz Witold , Swiezewska Ewa
Published: December 2015

Isoprenoids, as common constituents of all living cells, are exposed to oxidative agents—reactive oxygen species, for example, singlet oxygen or hydroxyl radicals. Despite this fact, products of oxidation of polyisoprenoids have never been characterized. In this study, chemical oxidation of isoprenoid alcohols (Prenol‐2 and ‐10) was performed using singlet oxygen (generated in the presence of hydrogen peroxide/molybdate or upon photochemical reaction in the presence of porphyrin), oxygen (formed upon hydrogen peroxide dismutation) or hydroxyl radical (generated by the hydrogen peroxide/sonication, UV/titanium dioxide or UV/hydrogen peroxide) systems. The structure of the obtained products, hydroxy‐, peroxy‐ and heterocyclic derivatives, was studied with the aid of mass spectrometry (MS) and nuclear magnetic resonance (NMR) methods. Furthermore, mass spectrometry with electrospray ionization appeared to be a useful analytical tool to detect the products of oxidation of isoprenoids (ESI–MS analysis), as well as to establish their structure on the basis of the fragmentation spectra of selected ions (ESI–MS/MS analysis). Taken together, susceptibility of polyisoprenoid alcohols to various oxidizing agents was shown for the first time.
Characteristics of Specialty Natural Micronutrients in Certain Oilseeds and Oils: Plastochromanol‐8, Resveratrol, 5‐Hydroxytryptamine Phenylpropanoid Amides, Lanosterol, Ergosterol and Cyclolinopeptides
Authors: Jin Jun , Sheraliev Gayrat , Xie Dan , Zhang Wei , Jin Qingzhe , Wang Xingguo
Published: December 2015

The current concern for health has raised the importance of natural micronutrients in edible oils and fats. Different from common micronutrients, e.g., tocopherols, tocotrienols, stigmasterol and sitosterol, new and emerging specialty micronutrients, such as plastochromanol‐8, resveratrol, phenylpropanoid amides of 5‐hydroxytryptamine, lanosterol, ergosterol and cyclolinopeptides, are becoming increasingly popular among health‐conscious people. The first three are phenolic compounds, the forth and fifth sterols, and sixth a peptide. These micronutrients are usually present in certain oils or oilseed‐related byproducts, including rapeseed, peanut, flaxseed, tea seed, and camellia oils, and safflower seed cakes, all of which are the highly valuable products of the lipid industry in China nowadays. The first object of this review is to discuss the characteristics of the micronutrients, mainly including their varieties, structures, and sources. Second, the antioxidant activities and indicative functions for oil quality were also analyzed in detail. Third, refining techniques, breeding programs and extraction methods are suggested. Suitable modification treatments of certain micronutrients are also advocated to make them easy to incorporate in other foods.
Enzymatic Synthesis of Tyrosol‐Based Phenolipids: Characterization and Effect of Alkyl Chain Unsaturation on the Antioxidant Activities in Bulk Oil and Oil‐in‐Water Emulsion
Authors: Pande Garima , Akoh Casimir C.
Published: December 2015

Oxidative stability of lipids is one of the most important parameters affecting their quality. Lipase‐catalyzed lipophilic tyrosyl esters with an equivalent carbon alkyl chain but different degrees of unsaturation (C18:0 to C18:4n3) were prepared, characterized, and used as antioxidants. Free fatty acids and fatty acid ethyl esters (substrate molar ratio tyrosol: acyl donor, 1:10) were used as acyl donors and immobilized lipase from Candida antarctica was the biocatalyst (10 %). The phenolipids were isolated and characterized using ESI–MS, 1H‐NMR, and 13C‐NMR. Peroxide value (PV) and para‐anisidine value (p‐AV) were measured to evaluate their antioxidant activities in bulk oil structured lipid (SL) and in an oil‐in‐water emulsion (SL‐based infant formula). No significant difference was found in yield and reaction time between the two types of acyl donors. However, as the unsaturation of the fatty acids increased the reaction time also increased. In SL, tyrosyl esters exhibited lower antioxidant activity than tyrosol whereas the addition of an alkyl chain enhanced the antioxidant efficiency of tyrosol in infant formula. Tyrosyl oleate was the most efficient antioxidant in the emulsion system followed by tyrosyl stearate and tyrosyl linoleate. These results suggest that the synthesized phenolipids may be used as potential antioxidants in lipid‐based products.
Responsibilizing individuals, regulating health: debating public spots, risk, and neoliberal governmentality in contemporary Turkey
Authors: Aykan Bahar , Güvenç-Salgırlı Sanem
Published: December 2015

Currently, a mass media campaign is underway in Turkey using a new communication means called the “public spot” (kamu spotu). This article concentrates on the public spots produced by Turkey’s Ministry of Health, and more specifically on those that advocate quitting smoking and preventing obesity. Drawing on interviews with Ministry of Health personnel and analyzing the content of these spots, we suggest that they operate as risk caveats. They caution individuals against smoking and obesity’s potential harms and guide her/him towards self-health governance by encouraging the maintenance of a particular lifestyle that embraces a balanced diet, regular activity, and no smoking. As such, we read these spots as a technique of neoliberal governmentality. This technique works primarily by responsibilizing individuals as health entrepreneurs investing in risk free lifestyles; that is, by conceptualizing health as a matter of self-conduct where personal responsibilities are emphasized.
Prospective, Head-to-Head Study of Three Computerized Neurocognitive Assessment Tools (CNTs): Reliability and Validity for the Assessment of Sport-Related Concussion
Authors: Nelson Lindsay D. , LaRoche Ashley A. , Pfaller Adam Y. , Lerner E. Brooke , Hammeke Thomas A. , Randolph Christopher , Barr William B. , Guskiewicz Kevin , McCrea Michael A.
Published: December 2015

Limited data exist comparing the performance of computerized neurocognitive tests (CNTs) for assessing sport-related concussion. We evaluated the reliability and validity of three CNTs—ANAM, Axon Sports/Cogstate Sport, and ImPACT—in a common sample. High school and collegiate athletes completed two CNTs each at baseline. Concussed (n=165) and matched non-injured control (n=166) subjects repeated testing within 24 hr and at 8, 15, and 45 days post-injury. Roughly a quarter of each CNT’s indices had stability coefficients (M=198 day interval) over .70. Group differences in performance were mostly moderate to large at 24 hr and small by day 8. The sensitivity of reliable change indices (RCIs) was best at 24 hr (67.8%, 60.3%, and 47.6% with one or more significant RCIs for ImPACT, Axon, and ANAM, respectively) but diminished to near the false positive rates thereafter. Across time, the CNTs’ sensitivities were highest in those athletes who became asymptomatic within 1 day before neurocognitive testing but was similar to the tests’ false positive rates when including athletes who became asymptomatic several days earlier. Test–retest reliability was similar among these three CNTs and below optimal standards for clinical use on many subtests. Analyses of group effect sizes, discrimination, and sensitivity and specificity suggested that the CNTs may add incrementally (beyond symptom scores) to the identification of clinical impairment within 24 hr of injury or within a short time period after symptom resolution but do not add significant value over symptom assessment later. The rapid clinical recovery course from concussion and modest stability probably jointly contribute to limited signal detection capabilities of neurocognitive tests outside a brief post-injury window. (JINS, 2016,22, 24–37)
Menu labelling is effective in reducing energy ordered and consumed: a systematic review and meta-analysis of recent studies
Authors: Littlewood Jodie Anne , Lourenço Sofia , Iversen Cecilie Lauberg , Hansen Gitte Laub
Published: December 2015

Objective

Menu labelling is a practical tool to inform consumers of the energy content of menu items and help consumers make informed decisions in the eating-out environment, and the volume of studies published recently regarding its effects is expanding, both quantitatively and geographically. The aim of the present review and meta-analysis is to consider the most recent evidence which assesses the effect of menu labelling regarding changes in energy consumed, ordered or selected in both real-world and experimental settings.

Design

The review included fifteen peer-reviewed, full-text articles published between 2012 and 2014. Pertinent methodological information was extracted from each of the included studies and a quality assessment scheme was applied to classify the studies, after which systematic across-study comparisons were conducted. A meta-analysis was conducted including twelve of the fifteen studies, and stratified according to type of research setting and outcome: energy consumed, ordered or selected.

Results

The rating yielded studies categorized by study quality: good (n 3), fair (n 9) and weak (n 3). Overall nine studies showed statistically significant reductions in energy consumed, ordered or selected. Three articles reported no effect of menu labelling. The meta-analysis showed statistically significant effects of menu labelling: overall energy consumed was reduced by a mean of 419·5 kJ (100·2 kcal) and energy ordered in real-world settings decreased by a mean of 325·7 kJ (77·8 kcal).

Conclusions

The review supports that menu labelling can effectively reduce energy ordered and consumed in the away-from-home food environment.
Preaching to, or Beyond, the Choir
Authors: Kutlaca Maja , Van Zomeren Martijn , Epstude Kai
Published: December 2015

Abstract. Although values motivate participation in collective action, little is known about whether their communication by a social movement motivates identification with it. In the context of student protests against budget cuts, we tested whether and how fitting a value (right to free education) to two relevant group identities (i.e., student vs. national identity) influenced politicized identification among individuals in ideologically different student subgroups (N = 168). Specifically, for students who shared the movement’s ideological background, we found that communicating values increased the predictive power of affective predictors of politicized identification over instrumental ones. However, for students who did not share the movement’s ideological background, fitting values to student (but not national) identity decreased politicized identification. These findings imply that value-identity fit must be taken into account if one wants to motivate a broad audience of potential followers with diverse ideological backgrounds for collective action.
Highly efficient siRNA delivery from core–shell mesoporous silica nanoparticles with multifunctional polymer caps
Authors: Möller Karin , Müller Katharina , Engelke Hanna , Bräuchle Christoph , Wagner Ernst , Bein Thomas
Published: December 2015

Intracellular siRNA delivery agents are constructed from medium-pore core–shell mesoporous silica nanoparticles capped with multifunctional block copolymers.
Highly selective luminescent nanostructures for mitochondrial imaging and targeting
Authors: Fanizza E. , Iacobazzi R. M. , Laquintana V. , Valente G. , Caliandro G. , Striccoli M. , Agostiano A. , Cutrignelli A. , Lopedota A. , Curri M. L. , Franco M. , Depalo N. , Denora N.
Published: December 2015

A multifunctional hybrid nanostructure based on luminescent QDs and a suitably designed TSPO ligand was used as a bioimaging agent for selective mitochondrial targeting.
Catalytic asymmetric hetero-Diels–Alder reactions of enones with isatins to access functionalized spirooxindole tetrahydropyrans: scope, derivatization, and discovery of bioactives
Authors: Cui Hai-Lei , Chouthaiwale Pandurang V. , Yin Feng , Tanaka Fujie
Published: December 2015

Concise hetero-Diels–Alder reactions were developed to provide various functionalized spirooxindole tetrahydropyrans useful for the discovery of bioactive molecules.
Fluorescent PET probes based on perylene-3,4,9,10-tetracarboxylic tetraesters
Authors: Dubey Rajeev K. , Knorr Gergely , Westerveld Nick , Jager Wolter F.
Published: December 2015

We demonstrate that perylene tetraester-based fluorescent PET probes with aniline receptors attached at the bay-positions are superior pH-sensitive “light-up” probes, with high fluorescence quantum yields ΦF and huge fluorescent enhancements.
Sr3Ce(PO4)3:Eu2+: a broadband yellow-emitting phosphor for near ultraviolet-pumped white light-emitting devices
Authors: Dai Pengpeng , Lee Szu-Ping , Chan Ting-Shan , Huang Chien-Hao , Chiang Yun-Wei , Chen Teng-Ming
Published: December 2015

White lighting-emitting diodes (WLEDs) using binary complementary color phosphors for n-UVLED chips are highly expected to realize a lighting source with high color rendering index and high luminous efficiency.
Flexible and transparent optically anisotropic films based on oriented assembly of nanofibers
Authors: Ma Zhijun , Hu Zhongliang , Zhang Hang , Peng Mingying , He Xin , Li Yang , Yang Zhongmin , Qiu Jianrong
Published: December 2015

Flexible and optically anisotropic film with high transparency and optical transmission contrast in the visible and near infrared region was prepared based on aligned assembly of electrospun PVA nanofibers and simple post soaking and drying. The strategy for preparation of optically anisotropic film proposed here is simple and scalable, and has the potential to replace the conventional approaches in many applications.
Design and optimization of a harmonic probe with step cross section in multifrequency atomic force microscopy
Authors: Cai Jiandong , Wang Michael Yu , Zhang Li
Published: December 2015

In multifrequency atomic force microscopy (AFM), probe’s characteristic of assigning resonance frequencies to integer harmonics results in a remarkable improvement of detection sensitivity at specific harmonic components. The selection criterion of harmonic order is based on its amplitude’s sensitivity on material properties, e.g., elasticity. Previous studies on designing harmonic probe are unable to provide a large design capability along with maintaining the structural integrity. Herein, we propose a harmonic probe with step cross section, in which it has variable width in top and bottom steps, while the middle step in cross section is kept constant. Higher order resonance frequencies are tailored to be integer times of fundamental resonance frequency. The probe design is implemented within a structural optimization framework. The optimally designed probe is micromachined using focused ion beam milling technique, and then measured with an AFM. The measurement results agree well with our resonance frequency assignment requirement.
A new parameter-free soft-core potential for silica and its application to simulation of silica anomalies
Authors: Izvekov Sergei , Rice Betsy M.
Published: December 2015

A core-softening of the effective interaction between oxygen atoms in water and silica systems and its role in developing anomalous thermodynamic, transport, and structural properties have been extensively debated. For silica, the progress with addressing these issues has been hampered by a lack of effective interaction models with explicit core-softening. In this work, we present an extension of a two-body soft-core interatomic force field for silica recently reported by us [S. Izvekov and B. M. Rice, J. Chem. Phys. 136(13), 134508 (2012)] to include three-body forces. Similar to two-body interaction terms, the three-body terms are derived using parameter-free force-matching of the interactions from ab initio MD simulations of liquid silica. The derived shape of the O–Si–O three-body potential term affirms the existence of repulsion softening between oxygen atoms at short separations. The new model shows a good performance in simulating liquid, amorphous, and crystalline silica. By comparing the soft-core model and a similar model with the soft-core suppressed, we demonstrate that the topology reorganization within the local tetrahedral network and the O–O core-softening are two competitive mechanisms responsible for anomalous thermodynamic and kinetic behaviors observed in liquid and amorphous silica. The studied anomalies include the temperature of density maximum locus and anomalous diffusivity in liquid silica, and irreversible densification of amorphous silica. We show that the O–O core-softened interaction enhances the observed anomalies primarily through two mechanisms: facilitating the defect driven structural rearrangements of the silica tetrahedral network and modifying the tetrahedral ordering induced interactions toward multiple characteristic scales, the feature which underlies the thermodynamic anomalies.
Kohn–Sham exchange-correlation potentials from second-order reduced density matrices
Authors: Cuevas-Saavedra Rogelio , Ayers Paul W. , Staroverov Viktor N.
Published: December 2015

We describe a practical algorithm for constructing the Kohn–Sham exchange-correlation potential corresponding to a given second-order reduced density matrix. Unlike conventional Kohn–Sham inversion methods in which such potentials are extracted from ground-state electron densities, the proposed technique delivers unambiguous results in finite basis sets. The approach can also be used to separate approximately the exchange and correlation potentials for a many-electron system for which the reduced density matrix is known. The algorithm is implemented for configuration-interaction wave functions and its performance is illustrated with numerical examples.
Interference between Coulombic and CT-mediated couplings in molecular aggregates: H- to J-aggregate transformation in perylene-based π-stacks
Authors: Hestand Nicholas J. , Spano Frank C.
Published: December 2015

The spectroscopic differences between J and H-aggregates are traditionally attributed to the spatial dependence of the Coulombic coupling, as originally proposed by Kasha. However, in tightly packed molecular aggregates wave functions on neighboring molecules overlap, leading to an additional charge transfer (CT) mediated exciton coupling with a vastly different spatial dependence. The latter is governed by the nodal patterns of the molecular LUMOs and HOMOs from which the electron (te) and hole (th) transfer integrals derive. The sign of the CT-mediated coupling depends on the sign of the product teth and is therefore highly sensitive to small (sub-Angstrom) transverse displacements or slips. Given that Coulombic and CT-mediated couplings exist simultaneously in tightly packed molecular systems, the interference between the two must be considered when defining J and H-aggregates. Generally, such π-stacked aggregates do not abide by the traditional classification scheme of Kasha: for example, even when the Coulomb coupling is strong the presence of a similarly strong but destructively interfering CT-mediated coupling results in “null-aggregates” which spectroscopically resemble uncoupled molecules. Based on a Frenkel/CT Holstein Hamiltonian that takes into account both sources of electronic coupling as well as intramolecular vibrations, vibronic spectral signatures are developed for integrated Frenkel/CT systems in both the perturbative and resonance regimes. In the perturbative regime, the sign of the lowest exciton band curvature, which rigorously defines J and H-aggregation, is directly tracked by the ratio of the first two vibronic peak intensities. Even in the resonance regime, the vibronic ratio remains a useful tool to evaluate the J or H nature of the system. The theory developed is applied to the reversible H to J-aggregate transformations recently observed in several perylene bisimide systems.
Vibrational renormalisation of the electronic band gap in hexagonal and cubic ice
Authors: Engel Edgar A. , Monserrat Bartomeu , Needs Richard J.
Published: December 2015

Electron-phonon coupling in hexagonal and cubic water ice is studied using first-principles quantum mechanical methods. We consider 29 distinct hexagonal and cubic ice proton-orderings with up to 192 molecules in the simulation cell to account for proton-disorder. We find quantum zero-point vibrational corrections to the minimum electronic band gaps ranging from −1.5 to −1.7 eV, which leads to improved agreement between calculated and experimental band gaps. Anharmonic nuclear vibrations play a negligible role in determining the gaps. Deuterated ice has a smaller band-gap correction at zero-temperature of −1.2 to −1.4 eV. Vibrations reduce the differences between the electronic band gaps of different proton-orderings from around 0.17 eV to less than 0.05 eV, so that the electronic band gaps of hexagonal and cubic ice are almost independent of the proton-ordering when quantum nuclear vibrations are taken into account. The comparatively small reduction in the band gap over the temperature range 0 − 240 K of around 0.1 eV does not depend on the proton ordering, or whether the ice is protiated or deuterated, or hexagonal, or cubic. We explain this in terms of the atomistic origin of the strong electron-phonon coupling in ice.
Sea-state modification and heaving float interaction factors from physical modelling of arrays of wave energy converters
Authors: Stratigaki V. , Troch P. , Stallard T. , Forehand D. , Folley M. , Kofoed J. P. , Benoit M. , Babarit A. , Vantorre M. , Kirkegaard J.
Published: December 2015

Wave energy converters (WECs) extract energy from ocean waves and have the potential to produce a significant amount of electricity from a renewable resource. However, large “WEC farms” or “WEC arrays” (composed of a large number of individual WECs) are expected to exhibit “WEC array effects”. These effects represent the impact of the WECs on the wave climate at an installation site, as well as on the overall power absorption of the WEC array. Tests have been performed in the Shallow Water Wave Basin of DHI (Denmark) to study such “WEC array effects”. Large arrays of up to 25 heaving point absorber type WECs have been tested for a range of geometric layout configurations and wave conditions. Each WEC consists of a buoy with a diameter of 0.315 m. Power take-off was modeled by realizing friction based energy dissipation through damping of the WECs' motion. The produced database is presented: WEC response, wave induced forces on the WECs, and wave field modifications have been measured. A first understanding of WEC array effects is obtained. This unique experimental set-up of up to 25 individual WEC units in an array layout, placed in a large wave tank, is at present the largest set-up of its kind studying the important WEC array effects. The data obtained from these experimental tests will be very useful for validation and extension of numerical models. This model validation will enable optimization of the geometrical layout of WEC arrays for realistic wave farm applications and reduction of the cost of energy from wave energy systems.
Effect of samarium doping on the physical properties of chemically sprayed titanium dioxide thin films
Authors: Naffouti Wafa , Ben Nasr Tarek , Battaglini Nicolas , Ammar Souad , Turki-Kamoun Najoua
Published: December 2015

Titanium dioxide (TiO2) thin films were doped with samarium ion at different concentration ratios (y = ([Sm3+]/[Ti4+]) in the range of 0–1 at. % by a step of 0.25 at. %) and deposited on glass substrates, using a spray pyrolysis technique. Samples were characterized using X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and photoluminescence spectroscopy, with a special emphasis on the evolution of their physic-chemical properties as a function of their Sm doping ratio. Typically, a decrease in the crystalline quality of the anatase phase is observed when the nominal Sm content increases from 0.25 to 1 at. %. A change of photoluminescence behavior of the titania films is also evidenced when the Sm content increases. Wemple-Di Domenico single oscillator model was applied in order to study the dispersion parameters as a function of Sm doping ratio.
Dynamic control of polarization-inverted modes in three-dimensionally trapped multiple nanogaps
Authors: Tamura Mamoru , Iida Takuya
Published: December 2015

We propose a guiding principle for the dynamic control of polarization-inverted modes in multiple nanogaps for unconventional optical transitions of molecules at arbitrary three-dimensional spatial positions. Based on our developed self-consistent theory for the optical assembly of nanoparticles (NPs), we clarified that spherical silver NPs can be optically trapped and aligned in the light-propagating direction via longitudinally polarized light; they form a rod-like nano-composite with multiple nanogaps. During trapping, there is a possibility that an additional irradiation of linearly polarized far-field light may excite the bonding and anti-bonding dark plasmon modes with low radiative decay rate of several meV via cancellation of inverted polarization. Our finding reveals that not only the steep change in the enhanced intensity of light field but also the phase inversion of light field between the dynamically formed nanogaps will pave the way to the highly sensitive sensors for molecules, the unconventional chemical reactions, and so on.
Research on calorimeter for high-power microwave measurements
Authors: Ye Hu , Ning Hui , Yang Wensen , Tian Yanmin , Xiong Zhengfeng , Yang Meng , Yan Feng , Cui Xinhong
Published: December 2015

Based on measurement of the volume increment of polar liquid that is a result of heating by absorbed microwave energy, two types of calorimeters with coaxial capacitive probes for measurement of high-power microwave energy are designed in this paper. The first is an “inline” calorimeter, which is placed as an absorbing load at the end of the output waveguide, and the second is an “offline” calorimeter that is placed 20 cm away from the radiation horn of the high-power microwave generator. Ethanol and high density polyethylene are used as the absorbing and housing materials, respectively. Results from both simulations and a “cold test” on a 9.3 GHz klystron show that the “inline” calorimeter has a measurement range of more than 100 J and an energy absorption coefficient of 93%, while the experimental results on a 9.3 GHz relativistic backward-wave oscillator show that the device’s power capacity is approximately 0.9 GW. The same experiments were also carried out for the “offline” calorimeter, and the results indicate that it can be used to eliminate the effects of the shock of the solenoid on the measurement curves and that the device has a higher power capacity of 2.5 GW. The results of the numerical simulations, the “cold tests,” and the experiments show good agreement.
CECO wave energy converter: Experimental proof of concept
Authors: Rosa-Santos Paulo , Taveira-Pinto Francisco , Teixeira Luís , Ribeiro José
Published: December 2015

This paper presents the experimental proof of concept of CECO, an innovative wave energy converter designed to convert simultaneously the kinetic and the potential energy of ocean waves into electrical energy, based on the oblique motion of two floating modules. First, the main characteristics of CECO and its work principle are briefly presented. Then, the behavior of the device is analyzed for different wave conditions and modes of operation (power take-off damping levels and device inclinations), based on results obtained with a physical model built on a geometric scale of 1/20. CECO performance strongly depends on the incident wave characteristics, the device inclination angle, and the damping introduced by the power-take-off. Relative capture widths of up to 14% were reached in this initial study, confirming that CECO is a valid technology to extract energy from waves. The application of wavelets showed that CECO response occurs mainly in the frequency of incident waves during the entire test duration.
Reconstructing the micrometeorological dynamics of the southern Amazonian transitional forest
Authors: de Paulo Sergio Roberto , de Paulo Iramaia Jorge Cabral , De Decker Yannick
Published: December 2015

In this work, we reconstruct and analyze the micrometeorological dynamics of the transitional forest located south of the Amazon basin. For this, we use time series of micrometeorological variables collected over five years in the transitional forest of Mato Grosso (Brazil). We employ local feature analysis, a recently proposed extension of principal component analysis, to extract the most relevant physical variables from this set. We show in this way that temperature records contain most of the dynamical information in all seasons. Based on this result, the dimensionality of the space spanned by the system's dynamics and the properties of the so defined attractors are obtained. In the dry season, the system presents a robust oscillatory character described by a well-defined limit cycle. In the wet season, the dynamics becomes more irregular but can still be seen as a periodic behavior affected by external noise. These results can help to develop accurate models for the meteorology of the Amazonian transitional forest and can thus lead to a better understanding of this important ecosystem.
Redox levels in aqueous solution: Effect of van der Waals interactions and hybrid functionals
Authors: Ambrosio Francesco , Miceli Giacomo , Pasquarello Alfredo
Published: December 2015

We investigate redox levels in aqueous solution using a combination of ab initio molecular dynamics (MD) simulations and thermodynamic integration methods. The molecular dynamics are performed with both the semilocal Perdew-Burke-Ernzerhof functional and a nonlocal functional (rVV10) accounting for van der Waals (vdW) interactions. The band edges are determined through three different schemes, namely, from the energy of the highest occupied and of the lowest unoccupied Kohn-Sham states, from total-energy differences, and from a linear extrapolation of the density of states. It is shown that the latter does not depend on the system size while the former two are subject to significant finite-size effects. For the redox levels, we provide a formulation in analogy to the definition of charge transition levels for defects in crystalline materials. We consider the H+/H2 level defining the standard hydrogen electrode, the OH−/OH∗ level corresponding to the oxidation of the hydroxyl ion, and the H2O/OH∗ level for the dehydrogenation of water. In spite of the large structural modifications induced in liquid water, vdW interactions do not lead to any significant structural effect on the calculated band gap and band edges. The effect on the redox levels is also small since the solvation properties of ionic species are little affected by vdW interactions. Since the electronic properties are not significantly affected by the underlying structural properties, it is justified to perform hybrid functional calculations on the configurations of our MD simulations. The redox levels calculated as a function of the fraction α of Fock exchange are found to remain constant, reproducing a general behavior previously observed for charge transition levels of defects. Comparison with experimental values shows very good agreement. At variance, the band edges and the band gap evolve linearly with α. For α ≃ 0.40, we achieve a band gap, band-edge positions, and redox levels in overall good agreement with experiment.
High performance InAs quantum dot lasers on silicon substrates by low temperature Pd-GaAs wafer bonding
Authors: Wang Zihao , Yao Ruizhe , Preble Stefan F. , Lee Chi-Sen , Lester Luke F. , Guo Wei
Published: December 2015

InAs quantum dot (QD) laser heterostructures have been grown by molecular beam epitaxy system on GaAs substrates, and then transferred to silicon substrates by a low temperature (250 °C) Pd-mediated wafer bonding process. A low interfacial resistivity of only 0.2 Ω cm2 formed during the bonding process is characterized by the current-voltage measurements. The InAs QD lasers on Si exhibit comparable characteristics to state-of-the-art QD lasers on silicon substrates, where the threshold current density Jth and differential quantum efficiency ηd of 240 A/cm2 and 23.9%, respectively, at room temperature are obtained with laser bars of cavity length and waveguide ridge of 1.5 mm and 5 μm, respectively. The InAs QD lasers also show operation up to 100 °C with a threshold current density Jth and differential quantum efficiency ηd of 950 A/cm2 and 9.3%, respectively. The temperature coefficient T0 of 69 K from 60 to 100 °C is characterized from the temperature dependent Jth measurements.
Tuning a microcavity-coupled terahertz laser
Authors: Castellano Fabrizio , Bianchi Vezio , Li Lianhe , Zhu Jingxuan , Tredicucci Alessandro , Linfield Edmund H. , Giles Davies A. , Vitiello Miriam S.
Published: December 2015

Tunable oscillators are a key component of almost all electronic and photonic systems. Yet, a technology capable of operating in the terahertz (THz)-frequency range and fully suitable for widescale implementation is still lacking. This issue is significantly limiting potential THz applications in gas sensing, high-resolution spectroscopy, hyper-spectral imaging, and optical communications. The THz quantum cascade laser is arguably the most promising solution in terms of output power and spectral purity. In order to achieve reliable, repeatable, and broad tunability, here we exploit the strong coupling between two different cavity mode concepts: a distributed feedback one-dimensional photonic resonator (providing gain) and a mechanically actuated wavelength-size microcavity (providing tuning). The result is a continuously tunable, single-mode emitter covering a 162 GHz spectral range, centered on 3.2 THz. Our source has a few tens of MHz resolution, extremely high differential efficiency, and unprecedented compact and simple design architecture. By unveiling the large potential that lies in this technique, our results provide a robust platform for radically different THz systems exploiting broadly tunable semiconductor lasers.
Towards higher stability of resonant absorption measurements in pulsed plasmas
Authors: Britun Nikolay , Michiels Matthieu , Snyders Rony
Published: December 2015

Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called “dynamic source triggering,” between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source.
Pressure-induced localisation of the hydrogen-bond network in KOH-VI
Authors: Hermann Andreas , Guthrie Malcolm , Nelmes Richard J. , Loveday John S.
Published: December 2015

Using a combination of ab initio crystal structure prediction and neutron diffraction techniques, we have solved the full structure of KOH-VI at 7 GPa. Rather than being orthorhombic and proton-ordered as had previously be proposed, we find that this high-pressure phase of potassium hydroxide is tetragonal (space group I4/mmm) and proton disordered. It has an unusual hydrogen bond topology, where the hydroxyl groups form isolated hydrogen-bonded square planar (OH)4 units. This structure is stable above 6.5 GPa and, despite being macroscopically proton-disordered, local ice rules enforce microscopic order of the hydrogen bonds. We suggest the use of this novel type of structure to study concerted proton tunneling in the solid state, while the topology of the hydrogen bond network could conceivably be exploited in data storage applications based solely on the manipulations of hydrogen bonds. The unusual localisation of the hydrogen bond network under applied pressure is found to be favored by a more compact packing of the constituents in a distorted cesium chloride structure.