bluuebunny/crossref_metadata_2025 huggingface dataset:
Pre‐operative planning of multiple probes in three dimensions for liver cryosurgery: comparison of different optimization methods
Authors: Jaberzadeh Amir , Essert Caroline
Published: September 2015

Pre‐operative planning of percutaneous thermal ablations is a difficult but decisive task for a safe and successful intervention. The purpose of our research is to assist surgeons in preparing cryoablation with an automatic pre‐operative path planning algorithm able to propose a placement for multiple needles in three dimensions. The aim is to optimize the tumor coverage problem while taking into account a precise computation of the frozen area. Using an implementation of the precise estimation of the ice balls, this study focuses on the optimization in an acceptable time of multiple probes positions with 5 degrees of freedom, regarding the constraint of optimal volumetric coverage of the tumor by the combined necrosis. Pennes equation was used to solve the propagation of cold within the tissues, and included in an objective function of the optimization process. The propagation computation being time‐consuming, seven optimization algorithms from the literature were experimented under different conditions and compared, in order to reduce overall computation time while preserving precision. Moreover, several hybrid algorithms were tested to reduce required time for the computations. Some of these methods were found suitable for the conditions of our cryosurgery planning. We conclude that this combination of bioheat simulation and optimization can be appropriate for a use by practitioners in acceptable conditions of time and precision. Copyright © 2015 John Wiley & Sons, Ltd.
“I know exactly what I'm going into”: recommendations for pre‐nursing experience from an evaluation of a pre‐nursing scholarship in rural Scotland
Authors: Smith Annetta , Beattie Michelle , Kyle Richard G.
Published: September 2015

Aim

To develop a model of pre‐nursing experience from evaluation of a pre‐nursing scholarship for school pupils in Scotland.

Design

Action research study.

Methods

School pupils (n = 42) completed questionnaire surveys and participated in anecdote circles. Student nurses acting as pupil ‘buddies’ (n = 33) participated in focus groups. Descriptive quantitative data and thematic analyses of qualitative data were integrated across cohorts and campuses.

Results

Ten recommended components of a model of pre‐nursing experience were identified: educational experience of: (1) face‐to‐face on‐campus teaching; (2) hands‐on clinical skills sessions; and (3) andragogy, practice exposure to (4) nursing language; (5) nurses’ emotional labour; (6) patients’ stories; (7) pupils socializing with buddies; (8) buddies planning placement activities; and (9) supporting pupils during placements. Academic attainment was not a central component of the model due to pupils’ need to (10) prioritize examined work for further/higher education entry.
NMR analysis of the interaction of picornaviral proteinases Lb and 2A with their substrate eukaryotic initiation factor 4GII
Authors: Aumayr Martina , Fedosyuk Sofiya , Ruzicska Katharina , Sousa‐Blin Carla , Kontaxis Georg , Skern Tim
Published: September 2015

Messenger RNA is recruited to the eukaryotic ribosome by a complex including the eukaryotic initiation factor (eIF) 4E (the cap‐binding protein), the scaffold protein eIF4G and the RNA helicase eIF4A. To shut‐off host–cell protein synthesis, eIF4G is cleaved during picornaviral infection by a virally encoded proteinase; the structural basis of this reaction and its stimulation by eIF4E is unclear. We have structurally and biochemically investigated the interaction of purified foot‐and‐mouth disease virus (FMDV) leader proteinase (Lbpro), human rhinovirus 2 (HRV2) 2A proteinase (2Apro) and coxsackievirus B4 (CVB4) 2Apro with purified eIF4GII, eIF4E and the eIF4GII/eIF4E complex. Using nuclear magnetic resonance (NMR), we completed 13C/15N sequential backbone assignment of human eIF4GII residues 551–745 and examined their binding to murine eIF4E. eIF4GII551–745 is intrinsically unstructured and remains so when bound to eIF4E. NMR and biophysical techniques for determining stoichiometry and binding constants revealed that the papain‐like Lbpro only forms a stable complex with eIF4GII551–745 in the presence of eIF4E, with KD values in the low nanomolar range; Lbpro contacts both eIF4GII and eIF4E. Furthermore, the unrelated chymotrypsin‐like 2Apro from HRV2 and CVB4 also build a stable complex with eIF4GII/eIF4E, but with KD values in the low micromolar range. The HRV2 enzyme also forms a stable complex with eIF4E; however, none of the proteinases tested complex stably with eIF4GII alone. Thus, these three picornaviral proteinases have independently evolved to establish distinct triangular heterotrimeric protein complexes that may actively target ribosomes involved in mRNA recruitment to ensure efficient host cell shut‐off.
Characterization of the internal properties of InGaN/GaN core–shell LEDs
Authors: Ledig Johannes , Wang Xue , Fündling Sönke , Schuhmann Henning , Seibt Michael , Jahn Uwe , Wehmann Hergo‐Heinrich , Waag Andreas
Published: September 2015

In this paper, we present the structural, optical, and electrical characterization of InGaN/GaN core‐shell micro‐LED structures selectively grown by metal organic vapor phase epitaxy (MOVPE) in arranged arrays. In particular we analyze the core‐shell geometry of the pillars, consisting of a fivefold InGaN/GaN multiple quantum well and a p‐type layer on all sidewall and top facets. Additionally we analyze the optical properties of the structure and the active region with high spatial resolution by cathodoluminescence. Electron beam induced current measurements (EBIC) are performed using an SEM based manipulator setup, giving proof of the presence of a depletion region as well as the intended doping polarity of the n‐type core and a p‐type shell wrapped around the whole structure. Using a p–n–p configuration also current crowding is discussed by EBIC and electroluminescence is demonstrated by measuring emission patterns from single core–shell structures.

Color overlay of SE image (grey, FOV = 12.7 μm) and EBIC image (red) of a cleaved core–shell LED pillar contacted by two probe tips at a substrate tilt of 30°.
Photoluminescence of InGaN/GaN quantum wells grown on c‐plane substrates with locally variable miscut
Authors: Dróżdż Piotr A. , Korona Krzysztof P. , Sarzyński Marcin , Suski Tadeusz , Czernecki Robert , Wasik Dariusz
Published: September 2015

Growth of high‐quality nitride‐based structures requires use of miscut substrates, which means that the growth plane is tilted with respect to the c lattice plane (0001). In order to investigate the miscut influence on grown layers, patterned GaN substrates with separate regions tilted between 0.34° and 0.97° to the c‐plane were used to grow multiquantum well InGaN/GaN structures by metalorganic vapor phase epitaxy. The quantum wells had a nominal 6% indium content. Precise values of miscut in each region were determined by atomic‐force microscopy. Recombination dynamics in each region was studied using time‐resolved microphotoluminescence (PL) from 4 K to room temperature. It was found that the PL energy increases with miscut angle from 3.17 to 3.29 eV (at 4 K). The PL lifetime also correlated with the miscut angle, it decreased from 1.2 down to 0.8 ns (at 4 K). These results suggest that an increase of the angle causes a decrease of the indium content. Less indium naturally leads to a higher bandgap, and to reduction of electric field inside the quantum wells (QWs). Both effects lead to a PL energy increase. Moreover, the decrease of the electric field reduces the electron–hole separation that explains the shorter radiative recombination at 4 K at regions of high‐miscut angles. The shape of temperature dependence of PL decay times suggests that at low temperatures PL decay is determined by the localization of carriers, whereas in room temperature LO phonon‐assisted delocalization processes play a dominant role.
In vitro digestibility of kudzu starch by using α‐amylase and glucoamylase
Authors: Guo Li , Hu Jian , Zhou Xin , Li Xueling , Du Xianfeng
Published: September 2015

Kudzu starch is used as a nutritious food in East Asia, however, its impact on glycemic response is unclear. The objective was to investigate its susceptibility to digestive enzymes compared to other root starches. We investigated the enzyme kinetics and hydrolytic rate of porcine pancreatic α‐amylase, examined the in vitro starch digestibility using digestive enzymes, and measured rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) of kudzu starch. The results indicated that, compared to other root starches, the Km value of granular kudzu starch was the largest, but after gelatinization, the Km value significantly decreased. During the in vitro digestion, the crystallinity of granular kudzu starch increased from 34.8 to 38.4% and 43.6% after 20 and 120 min, respectively. The RDS, SDS, and RS of granular kudzu starch were 5.66, 25.88, and 68.46%, respectively. After gelatinization, RDS and SDS of kudzu starch increased to 48.79 and 39.83%, and the RS decreased to 11.38%. Thus, it is important to regulate gelatinization to keep the optimal RS and SDS levels of kudzu starch in order to maintain the balance in blood glucose levels. Incompletely gelatinized kudzu starch will be of interest from the viewpoint of developing slowly digestible starchy foods.
Dielectric properties of three liquid crystal polymers
Authors: Yang Peng , Ohki Yoshimichi
Published: September 2015

Dielectric properties of three kinds of liquid crystal polymers (LCPs) were investigated by measuring their thermal properties, thermally stimulated polarization and depolarization currents, and complex dielectric permittivity. To make clear the differences among the three LCP samples, complex electric modulus was introduced, which was found to be effective to suppress the effects of large conduction currents at high temperatures. Moreover, the slopes of the frequency dependence of ɛ[r' and ɛ]r'' are different below and above the phase transition temperature, indicating that the accumulation of charges occurs in front of the electrodes. The experimental results indicate that the phase transition has a significant influence on both the electrical conduction and dielectric relaxation for all LCPs. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
RBFNN‐based adaptive crowbar protection scheme designed for the doubly fed induction generator in large‐scale wind farms
Authors: Tong Ning , He Shan , Lin Xiangning , Zheng Peiwen , Li Zhengtian
Published: September 2015

The doubly fed induction generator (DFIG) and its relative technique, especially in the case where crowbar protection is provided for enhanced low‐voltage‐ride‐through (LVRT) performance, have been hot issues for a long time. In this paper, the wind farm LVRT standard and the dilemma that the conventional crowbar protection encounters are introduced in the first place. Then, the variation of the DFIG rotor faulted current is analyzed, with part of its duration being considered as a black box. Therefore, the radial basis function neural network (RBFNN) is utilized for the black box modeling. Based on above studies, an adaptive crowbar protection scheme is finally put forward and assessed. Emphasis is mainly placed on the black box modeling, error analysis, and the investigation of its impact on the wind farm LVRT capability. DIgSILENT‐based simulation results indicate that, with the novel scheme, it becomes possible for the crowbar to be adaptively switched out at a certain reasonable moment, so as to generate reactive power within the faulted duration. As a result, the steady‐state voltage of the point of common coupling (PCC) is enhanced and the safety of the rotor‐side convertor (RSC) can be ensured at the same time. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Cost allocation of spinning reserve based on risk contribution
Authors: Liu Yangyang , Jiang Chuanwen , Shen Jingshuang , Hu Jiakai
Published: September 2015

Current cost allocation methods require generating companies (GENCOs) to afford spinning reserve (SR) costs according to their energy production rather than the impact on grid stabilization. The differences in generator reliability and forecast accuracy of renewables cause difficulty in quantifying the contribution of individual factors on the SR requirements (SRRs). First, this paper employs a reliability‐constrained unit commitment (RCUC) model to determine the SRR and SR costs according to the grid reliability. Then, a cost allocation method is proposed to allocate these SR costs based on risk contribution theories. The risk contribution theories, marginal contribution, and stand‐alone contribution are employed to measure the effect of individual risk factors on grid safety. The cost allocation method is demonstrated and discussed in the IEEE‐RTS. The proposed risk contribution method can quantify the impacts of risk factors on grid safety and allocate SR costs into them according to their contributions. Additionally, this risk‐based cost allocation method can encourage GENCOs to enhance the reliability level of generators and continuously improve the forecast accuracy of renewables to lower SR costs. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Impact of a Standard Rodent Chow Diet on Tissue n‐6 Fatty Acids, Δ9‐Desaturation Index, and Plasmalogen Mass in Rats Fed for One Year
Authors: Pédrono F. , Boulier‐Monthéan N. , Catheline D. , Legrand P.
Published: September 2015

Although many studies focus on senescence mechanisms, few habitually consider age as a biological parameter. Considering the effect of interactions between food and age on metabolism, here we depict the lipid framework of 12 tissues isolated from Sprague–Dawley rats fed standard rodent chow over 1 year, an age below which animals are commonly studied. The aim is to define relevant markers of lipid metabolism influenced by age in performing a fatty acid (FA) and dimethylacetal profile from total lipids. First, our results confirm impregnation of adipose and muscular tissues with medium‐chain FA derived from maternal milk during early infancy. Secondly, when animals were switched to standard croquettes, tissues were remarkably enriched in n‐6 FA and especially 18:2n‐6. This impregnation over time was coupled with a decrease of the desaturation index and correlated with lower activities of hepatic Δ5‐ and Δ6‐desaturases. In parallel, we emphasize the singular status of testis, where 22:5n‐6, 24:4n‐6, and 24:5n‐6 were exceptionally accumulated with growth. Thirdly, 18:1n‐7, usually found as a discrete FA, greatly accrued over the course of time, mostly in liver and coupled with Δ9‐desaturase expression. Fourthly, skeletal muscle was characterized by a surprising enrichment of 22:6n‐3 in adults, which tended to decline in older rats. Finally, plasmalogen‐derived dimethylacetals were specifically abundant in brain, erythrocytes, lung, and heart. Most notably, a shift in the fatty aldehyde moiety was observed, especially in brain and erythrocytes, implying that red blood cell analysis could be a good indicator of brain plasmalogens.
Jackson Receives 2015 William Gilbert Award
Authors:   AGU
Published: September 2015

Michael Jackson will receive the 2015 William Gilbert Award at the 2015 American Geophysical Union Fall Meeting, to be held 14–18 December in San Francisco, Calif. The award recognizes outstanding and unselfish work in magnetism of Earth materials and of the Earth and planets.
Chang and Zhang Receive the 2015 Mineral and Rock Physics Graduate Research Award
Authors:   AGU
Published: September 2015

Yun-Yuan Chang and Dongzhou Zhang will receive the 2015 Mineral and Rock Physics Graduate Research Award, given annually to one or more promising young scientists for outstanding contributions achieved during their Ph.D. research. Recipients of this award are engaged in experimental and/or theoretical studies of Earth and planetary materials with the purpose of unraveling the physics and chemistry that govern their origin and physical properties.
Brantut Receives 2015 Mineral and Rock Physics Early Career Award
Authors:   AGU
Published: September 2015

Nicolas Brantut will receive the 2015 Mineral and Rock Physics Early Career Award at the 2015 American Geophysical Union Fall Meeting, to be held 14–18 December in San Francisco, Calif. The award is for promising young scientists in recognition of outstanding contributions achieved during their Ph.D. research.
What Formed These Curious Ripples on Mars?
Authors: Minnehan Catherine
Published: September 2015

Dunes, ridges, or something else? Scientists seek to understand the origins of transverse aeolian ridges.
The trimeric serine protease HtrA1 forms a cage-like inhibition complex with an anti-HtrA1 antibody
Authors: Ciferri Claudio , Lipari Michael T. , Liang Wei-Ching , Estevez Alberto , Hang Julie , Stawicki Scott , Wu Yan , Moran Paul , Elliott Mike , Eigenbrot Charles , Katschke Kenneth J. , van Lookeren Campagne Menno , Kirchhofer Daniel
Published: September 2015

High temperature requirement A1 (HtrA1) is a trypsin-fold serine protease implicated in the progression of age-related macular degeneration (AMD). Our interest in an antibody therapy to neutralize HtrA1 faces the complication that the target adopts a trimeric arrangement, with three active sites in close proximity. In the present study, we describe antibody 94, obtained from a human antibody phage display library, which forms a distinct macromolecular complex with HtrA1 and inhibits the enzymatic activity of recombinant and native HtrA1 forms. Using biochemical methods and negative-staining EM we were able to elucidate the molecular composition of the IgG94 and Fab94 complexes and the associated inhibition mechanism. The 246-kDa complex between the HtrA1 catalytic domain trimer (HtrA1_Cat) and Fab94 had a propeller-like organization with one Fab bound peripherally to each protomer. Low-resolution EM structures and epitope mapping indicated that the antibody binds to the surface-exposed loops B and C of the catalytic domain, suggesting an allosteric inhibition mechanism. The HtrA1_Cat–IgG94 complex (636 kDa) is a cage-like structure with three centrally located IgG94 molecules co-ordinating two HtrA1_Cat trimers and the six active sites pointing into the cavity of the cage. In both complexes, all antigen-recognition regions (paratopes) are found to bind one HtrA1 protomer and all protomers are bound by a paratope, consistent with the complete inhibition of enzyme activity. Therefore, in addition to its potential therapeutic usefulness, antibody 94 establishes a new paradigm of multimeric serine protease inhibition.
Compound semiconductor alloys: From atomic-scale structure to bandgap bowing
Authors: Schnohr C. S.
Published: September 2015

Compound semiconductor alloys such as InxGa1−xAs, GaAsxP1−x, or CuInxGa1−xSe2 are increasingly employed in numerous electronic, optoelectronic, and photonic devices due to the possibility of tuning their properties over a wide parameter range simply by adjusting the alloy composition. Interestingly, the material properties are also determined by the atomic-scale structure of the alloys on the subnanometer scale. These local atomic arrangements exhibit a striking deviation from the average crystallographic structure featuring different element-specific bond lengths, pronounced bond angle relaxation and severe atomic displacements. The latter, in particular, have a strong influence on the bandgap energy and give rise to a significant contribution to the experimentally observed bandgap bowing. This article therefore reviews experimental and theoretical studies of the atomic-scale structure of III-V and II-VI zincblende alloys and I-III-VI2 chalcopyrite alloys and explains the characteristic findings in terms of bond length and bond angle relaxation. Different approaches to describe and predict the bandgap bowing are presented and the correlation with local structural parameters is discussed in detail. The article further highlights both similarities and differences between the cubic zincblende alloys and the more complex chalcopyrite alloys and demonstrates that similar effects can also be expected for other tetrahedrally coordinated semiconductors of the adamantine structural family.
Direct evidence of an incommensurate phase in NaNbO3 and its implication in NaNbO3-based lead-free antiferroelectrics
Authors: Guo Hanzheng , Shimizu Hiroyuki , Randall Clive A.
Published: September 2015

Hot-stage in situ transmission electron microscopy was employed to investigate the temperature-induced complex sequence of phase transitions in NaNbO3 polycrystalline. In addition to the commonly recognized P (Pbma) → R (Pmnm) → S (Pnmm) phase transitions, incommensurate phases were observed to exist in P and R phase regions. The former (in the P → R transition region) is coincident with a diffused dielectric peak appearing at ∼170 °C, and the latter (in the R → S transition region) serves as an intermediate structure to bridge the two sub-phases in the R phase region. The incommensurate phase in the P phase region can be inferred from the polarization current density and differential dielectric permittivity anomalies, and it provides the bridge structure during the electric field-induced polarization reversal and antiferroelectric-to-ferroelectric transition in NaNbO3 solid solutions.
Exohedral M–C60 and M2–C60 (M = Pt, Pd) systems as tunable-gap building blocks for nanoarchitecture and nanocatalysis
Authors: Özdamar Burak , Boero Mauro , Massobrio Carlo , Felder-Flesch Delphine , Le Roux Sébastien
Published: September 2015

Transition metal–fullerenes complexes with metal atoms bound on the external surface of C60 are promising building blocks for next-generation fuel cells and catalysts. Yet, at variance with endohedral M@C60, they have received a limited attention. By resorting to first principles simulations, we elucidate structural and electronic properties for the Pd–C60, Pt–C60, PtPd–C60, Pd2–C60, and Pt2–C60 complexes. The most stable structures feature the metal atom located above a high electron density site, namely, the π bond between two adjacent hexagons (π-66 bond). When two metal atoms are added, the most stable configuration is those in which metal atoms still stand on π-66 bonds but tends to clusterize. The electronic structure, rationalized in terms of localized Wannier functions, provides a clear picture of the underlying interactions responsible for the stability or instability of the complexes, showing a strict relationship between structure and electronic gap.
Beam based alignment and its relevance in Indus-2
Authors: Jena Saroj Kumar , Husain Riyasat , Gandhi M. L. , Agrawal R. K. , Yadav S. , Ghodke A. D.
Published: September 2015

Initially in the Indus-2 storage ring, the closed orbit distortion (COD) could be best corrected to 1.3 mm rms in the horizontal and 0.43 mm rms in the vertical plane. The strength of the corrector magnets required high values for COD correction. This revealed that offsets in COD readout by the beam position monitors (BPMs) played a role in not achieving a rms COD lower than the above value. Thus, the offset between the electrical center of BPMs and the magnetic center of the nearest quadrupole magnet could be estimated using the beam based alignment (BBA) method. It prefers that the quadrupole magnet is able to be controlled individually and active shunt power supply (ASPS) system was designed for this purpose that works efficiently. This paper describes the methodology of BBA, topology of ASPS and its performance, and COD minimization using the measured BPM offsets. After BBA, the COD could be reduced to 0.45 mm rms and 0.2 mm rms in horizontal and vertical planes, respectively.
Construction by bosonization of a fermion-phonon model
Authors: Langmann Edwin , Moosavi Per
Published: September 2015

We discuss an extension of the (massless) Thirring model describing interacting fermions in one dimension which are coupled to phonons and where all interactions are local. This fermion-phonon model can be solved exactly by bosonization. We present a construction and solution of this model which is mathematically rigorous by treating it as a continuum limit of a Luttinger-phonon model. A self-contained account of the mathematical results underlying bosonization is included, together with complete proofs.
Polarization contributions to intermolecular interactions revisited with fragment electric-field response functions
Authors: Horn Paul R. , Head-Gordon Martin
Published: September 2015

The polarization energy in intermolecular interactions treated by self-consistent field electronic structure theory is often evaluated using a constraint that the atomic orbital (AO) to molecular orbital transformation is blocked by fragments. This approach is tied to AO basis sets, overestimates polarization energies in the overlapping regime, particularly in large AO basis sets, and lacks a useful complete basis set limit. These problems are addressed by the construction of polarization subspaces based on the responses of isolated fragments to weak electric fields. These subspaces are spanned by fragment electric-field response functions, which can capture effects up to the dipole (D), or quadrupole (DQ) level, or beyond. Schemes are presented for the creation of both non-orthogonal and orthogonal fragment subspaces, and the basis set convergence of the polarization energies computed using these spaces is assessed. Numerical calculations for the water dimer, water–Na+, water–Mg2+, water–F−, and water–Cl− show that the non-orthogonal DQ model is very satisfactory, with small differences relative to the orthogonalized model. Additionally, we prove a fundamental difference between the polarization degrees of freedom in the fragment-blocked approaches and in constrained density schemes. Only the former are capable of properly prohibiting charge delocalization during polarization.
Large eddy simulation of turbulent buoyant flow in a confined cavity with conjugate heat transfer
Authors: Cintolesi C. , Petronio A. , Armenio V.
Published: September 2015

Turbulent natural convection in enclosure is a paradigmatic case for wide class of processes of great interest for industrial and environmental problems. The solid-fluid thermal interaction, the anisotropy of the turbulence intensity in the flow field along with the transient nature of heat transfer processes, pose challenges regarding the numerical modeling. The case of a square cavity with differently heated vertical walls and two horizontal conductive plates is studied at Ra = 1.58 × 109. The study is carried out numerically, using large-eddy simulation together with a dynamic Lagrangian turbulence model and a conjugate heat transfer method to take into account heat transfer at the solid surfaces. First, validation is carried out against the literature experimental and numerical data. The results of validation tests evidence the limitations of using the adiabatic conditions as a model for reproducing an insulator. In fact, the adiabatic condition represents the asymptotic behavior which is often difficult to reach in real conditions. Successively, the model is used to investigate the effect on the flow field of different materials composing the horizontal walls. Initial conditions representative of physical experiment are used. In order to reduce the computational time required for a simulation with insulating materials at the walls, a four-step temperature advancement strategy is proposed, based on the artificial reduction-first and recover-later of the specific heat coefficient Cp of the materials at different stages of the simulation. The conductivity of the solid media is found to influence the flow configuration since heat transfer at the solid walls substantially modifies the turbulent field and makes the flow field less homogeneous along the horizontal direction.
A triple quantum dot based nano-electromechanical memory device
Authors: Pozner R. , Lifshitz E. , Peskin U.
Published: September 2015

Colloidal quantum dots (CQDs) are free-standing nano-structures with chemically tunable electronic properties. This tunability offers intriguing possibilities for nano-electromechanical devices. In this work, we consider a nano-electromechanical nonvolatile memory (NVM) device incorporating a triple quantum dot (TQD) cluster. The device operation is based on a bias induced motion of a floating quantum dot (FQD) located between two bound quantum dots (BQDs). The mechanical motion is used for switching between two stable states, “ON” and “OFF” states, where ligand-mediated effective interdot forces between the BQDs and the FQD serve to hold the FQD in each stable position under zero bias. Considering realistic microscopic parameters, our quantum-classical theoretical treatment of the TQD reveals the characteristics of the NVM.
Local structure of temperature and pH-sensitive colloidal microgels
Authors: Nigro Valentina , Angelini Roberta , Bertoldo Monica , Bruni Fabio , Castelvetro Valter , Ricci Maria Antonietta , Rogers Sarah , Ruzicka Barbara
Published: September 2015

The temperature dependence of the local intra-particle structure of colloidal microgel particles, composed of interpenetrated polymer networks, has been investigated by small-angle neutron scattering at different pH and concentrations, in the range (299÷315) K, where a volume phase transition from a swollen to a shrunken state takes place. Data are well described by a theoretical model that takes into account the presence of both interpenetrated polymer networks and cross-linkers. Two different behaviors are found across the volume phase transition. At neutral pH and T ≈ 307 K, a sharp change of the local structure from a water rich open inhomogeneous interpenetrated polymer network to a homogeneous porous solid-like structure after expelling water is observed. Differently, at acidic pH, the local structure changes almost continuously. These findings demonstrate that a fine control of the pH of the system allows to tune the sharpness of the volume-phase transition.
An ultra-high vacuum chamber for scattering experiments featuring in-vacuum continuous in-plane variation of the angle between entrance and exit vacuum ports
Authors: Englund Carl-Johan , Agåker Marcus , Fredriksson Pierre , Olsson Anders , Johansson Niklas , Rubensson Jan-Erik , Nordgren Joseph
Published: September 2015

A concept that enables in-vacuum continuous variation of the angle between two ports in one plane has been developed and implemented. The vacuum chamber allows for measuring scattering cross sections as a function of scattering angle and is intended for resonant inelastic X-ray scattering experiments. The angle between the ports can be varied in the range of 30°-150°, while the pressure change is less than 2 × 10−10 mbars.
Opto-electronic modeling of light emission from avalanche-mode silicon p+n junctions
Authors: Dutta Satadal , Hueting Raymond J. E. , Annema Anne-Johan , Qi Lin , Nanver Lis K. , Schmitz Jurriaan
Published: September 2015

This work presents the modeling of light emission from silicon based p+n junctions operating in avalanche breakdown. We revisit the photon emission process under the influence of relatively high electric fields in a reverse biased junction (>105 V/cm). The photon emission rate is described as a function of the electron temperature Te, which is computed from the spatial distribution of the electric field. The light emission spectra lie around the visible spectral range (λ∼ 300–850 nm), where the peak wavelength and the optical intensity are both doping level dependent. It is theoretically derived that a specific minimum geometrical width (∼170 nm) of the active region of avalanche is required, corresponding to a breakdown voltage of ∼5 V, below which the rate of photon emission in the desired spectrum drops. The derived model is validated using experimental data obtained from ultra-shallow p+n junctions with low absorption through a nm-thin p+ region and surface coverage of solely 3 nm of pure boron. We observe a peak in the emission spectra near 580 nm and 650 nm for diodes with breakdown voltages 7 V and 14 V, respectively, consistent with our model.
Simultaneous differential spinning disk fluorescence optical sectioning microscopy and nanomechanical mapping atomic force microscopy
Authors: Miranda Adelaide , Martins Marco , De Beule Pieter A. A.
Published: September 2015

Combined microscopy techniques offer the life science research community a powerful tool to investigate complex biological systems and their interactions. Here, we present a new combined microscopy platform based on fluorescence optical sectioning microscopy through aperture correlation microscopy with a Differential Spinning Disk (DSD) and nanomechanical mapping with an Atomic Force Microscope (AFM). The illumination scheme of the DSD microscope unit, contrary to standard single or multi-point confocal microscopes, provides a time-independent illumination of the AFM cantilever. This enables a distortion-free simultaneous operation of fluorescence optical sectioning microscopy and atomic force microscopy with standard probes. In this context, we discuss sample heating due to AFM cantilever illumination with fluorescence excitation light. Integration of a DSD fluorescence optical sectioning unit with an AFM platform requires mitigation of mechanical noise transfer of the spinning disk. We identify and present two solutions to almost annul this noise in the AFM measurement process. The new combined microscopy platform is applied to the characterization of a DOPC/DOPS (4:1) lipid structures labelled with a lipophilic cationic indocarbocyanine dye deposited on a mica substrate.
Possible atomic structures responsible for the sub-bandgap absorption of chalcogen-hyperdoped silicon
Authors: Wang Ke-Fan , Shao Hezhu , Liu Kong , Qu Shengchun , Wang Yuanxu , Wang Zhanguo
Published: September 2015

Single-crystal silicon was hyperdoped with sulfur, selenium, and tellurium using ion implantation and nanosecond laser melting. The hyperdoping of such chalcogen elements led to strong and wide sub-bandgap light absorption. Annealing the hyperdoped silicon, even at low temperatures (such as 200–400 °C), led to attenuation of the sub-bandgap absorption. To explain the attenuation process, we modeled it as chemical decomposition reaction from an optically absorbing structure to a non-absorbing structure. Attenuation of the experimental absorption coefficient was fit using the Arrhenius equation. From the fitted data, we extracted the reaction activation energies of S-, Se-, and T-hyperdoped silicon as 0.338 ± 0.029 eV, 0.471 ± 0.040 eV, and 0.357 ± 0.028 eV, respectively. We discuss these activation energies in terms of the bond energies of chalcogen–Si metastable bonds, and suggest that several high-energy interstitial sites, rather than substitutional sites, are candidates for the atomic structures that are responsible for the strong sub-bandgap absorption of chalcogen hyperdoped silicon.
Doping dependent blue shift and linewidth broadening of intersubband absorption in non-polar m-plane AlGaN/GaN multiple quantum wells
Authors: Kotani Teruhisa , Arita Munetaka , Arakawa Yasuhiko
Published: September 2015

Blue shift and broadening of the absorption spectra of mid-infrared intersubband transition in non-polar m-plane AlGaN/GaN 10 quantum wells were observed with increasing doping density. As the doping density was increased from 6.6 × 1011 to 6.0 × 1012 cm−2 per a quantum well, the intersubband absorption peak energy shifted from 274.0 meV to 302.9 meV, and the full width at half maximum increased from 56.4 meV to 112.4 meV. Theoretical calculations reveal that the blue shift is due to many body effects, and the intersubband linewidth in doped AlGaN/GaN QW is mainly determined by scattering due to interface roughness, LO phonons, and ionized impurities.
The benzene⋯naphthalene complex: A more challenging system than the benzene dimer for newly developed computational methods
Authors: Wang Weizhou , Sun Tao , Zhang Yu , Wang Yi-Bo
Published: September 2015

High-level coupled cluster singles, doubles, and perturbative triples [CCSD(T)] computations with up to the aug-cc-pVQZ basis set (1924 basis functions) and various extrapolations toward the complete basis set (CBS) limit are presented for the sandwich, T-shaped, and parallel-displaced benzene⋯naphthalene complex. Using the CCSD(T)/CBS interaction energies as a benchmark, the performance of some newly developed wave function and density functional theory methods has been evaluated. The best performing methods were found to be the dispersion-corrected PBE0 functional (PBE0-D3) and spin-component scaled zeroth-order symmetry-adapted perturbation theory (SCS-SAPT0). The success of SCS-SAPT0 is very encouraging because it provides one method for energy component analysis of π-stacked complexes with 200 atoms or more. Most newly developed methods do, however, overestimate the interaction energies. The results of energy component analysis show that interaction energies are overestimated mainly due to the overestimation of dispersion energy.
Non-gated laser-induced breakdown spectroscopy in bulk water by position-selective detection
Authors: Tian Ye , Xue Boyang , Song Jiaojian , Lu Yuan , Zheng Ronger
Published: September 2015

Temporal and spatial evolutions of the laser-induced plasma in bulk water are investigated using fast imaging and emission spectroscopic techniques. By tightly focusing a single-pulse nanosecond Nd: YAG laser beam into the bulk water, we generate a strongly expanded plasma with high reproducibility. Such a strong expanding plasma enables us to obtain well-resolved spectral lines by means of position-selective detection; hence, the time-gated detector becomes abdicable. The present results suggest not only a possible non-gated approach for underwater laser-induced breakdown spectroscopy but also give an insight into the plasma generation and expansion in bulk water.
Magnetooptical study of Zeeman effect in Mn modulation-doped InAs/InGaAs/InAlAs quantum well structures
Authors: Terent'ev Ya. V. , Danilov S. N. , Plank H. , Loher J. , Schuh D. , Bougeard D. , Weiss D. , Durnev M. V. , Tarasenko S. A. , Rozhansky I. V. , Ivanov S. V. , Yakovlev D. R. , Ganichev S. D.
Published: September 2015

We report on a magneto-photoluminescence (PL) study of Zeeman effect in Mn modulation-doped InAs/InGaAs/InAlAs quantum wells (QW). Two PL lines corresponding to the radiative recombination of photoelectrons with free and bound-on-Mn holes have been observed. In the presence of a magnetic field applied in the Faraday geometry, both lines split into two circularly polarized components. While temperature and magnetic field dependence of the splitting are well described by the Brillouin function, providing an evidence for exchange interaction with spin polarized manganese ions, the value of the splitting exceeds by two orders of magnitude the value of the giant Zeeman splitting estimated for the average Mn density in QW obtained by the secondary ion mass spectroscopy.
A compact, high-voltage pulsed charging system based on an air-core pulse transformer
Authors: Zhang Tianyang , Chen Dongqun , Liu Jinliang , Liu Chebo , Yin Yi
Published: September 2015

Charging systems of pulsed power generators on mobile platforms are expected to be compact and provide high pulsed power, high voltage output, and high repetition rate. In this paper, a high-voltage pulsed charging system with the aforementioned characteristics is introduced, which can be applied to charge a high-voltage load capacitor. The operating principle of the system and the technical details of the components in the system are described in this paper. The experimental results show that a 600 nF load capacitor can be charged to 60 kV at 10 Hz by the high-voltage pulsed charging system for a burst of 0.5 s. The weight and volume of the system are 60 kg and 600 × 500 × 380 mm3, respectively.
Compton polarimeter for 10–30 keV x rays
Authors: Weber S. , Beilmann C. , Shah C. , Tashenov S.
Published: September 2015

We present a simple and versatile polarimeter for x rays in the energy range of 10–30 keV. It uses Compton scattering in low-Z materials such as beryllium or boron carbide. The azimuthal distribution of the scattered x rays is sampled by an array of 12 silicon PIN diodes operated at room temperature. We evaluated the polarimetry performance using Monte-Carlo simulations and show experimental results.
Nonlinear bubble nucleation and growth following filament and white-light continuum generation induced by a single-shot femtosecond laser pulse into dielectrics based on consideration of the time scale
Authors: Mizushima Yuki , Saito Takayuki
Published: September 2015

Bubble nucleation and growth following plasma channeling (filament) and white-light continuum in liquid irradiated by a single-shot fs-pulse were experimentally investigated with close observation of the time scale. Making full use of a new confocal system and time-resolved visualization techniques, we obtained evidence suggestive of a major/minor role of the non-linear/thermal effects during the fs-pulse-induced bubble's fountainhead (10−13 s) and growth (10−7 s), which was never observed with the use of the ns-pulse (i.e., optic cavitation). In this context, the fs-pulse-induced bubble is not an ordinary optic cavitation but rather is nonlinear-optic cavitation. We present the intrinsic differences in the dominant-time domain of the fs-pulse and ns-pulse excitation, and intriguingly, a mere hundred femtoseconds' excitation predetermines the size of the bubble appearing several microseconds after irradiation. That is, the nucleation happens temporally beyond a six-order-of-magnitude difference.
Passive mode locking of a GaSb-based quantum well diode laser emitting at 2.1 μm
Authors: Merghem K. , Teissier R. , Aubin G. , Monakhov A. M. , Ramdane A. , Baranov A. N.
Published: September 2015

We demonstrate passive mode locking of a GaSb-based diode laser emitting at 2.1 μm. The active region of the studied device consists in two 10-nm-thick GaInSbAs/GaAlSbAs quantum wells. Passive mode locking has been achieved in a two-section laser with one of the sections used as a saturable absorber. A microwave signal at 20.6 GHz, measured in the electrical circuit of the absorber, corresponds to the fundamental photon round-trip frequency in the laser resonator. The linewidth of this signal as low as ∼10 kHz has been observed at certain operating conditions, indicating low phase noise mode-locked operation.
Collapse of the low temperature insulating state in Cr-doped V2O3 thin films
Authors: Homm P. , Dillemans L. , Menghini M. , Van Bilzen B. , Bakalov P. , Su C.-Y. , Lieten R. , Houssa M. , Nasr Esfahani D. , Covaci L. , Peeters F. M. , Seo J. W. , Locquet J.-P.
Published: September 2015

We have grown epitaxial Cr-doped V2O3 thin films with Cr concentrations between 0% and 20% on (0001)-Al2O3 by oxygen-assisted molecular beam epitaxy. For the highly doped samples (>3%), a regular and monotonous increase of the resistance with decreasing temperature is measured. Strikingly, in the low doping samples (between 1% and 3%), a collapse of the insulating state is observed with a reduction of the low temperature resistivity by up to 5 orders of magnitude. A vacuum annealing at high temperature of the films recovers the low temperature insulating state for doping levels below 3% and increases the room temperature resistivity towards the values of Cr-doped V2O3 single crystals. It is well-know that oxygen excess stabilizes a metallic state in V2O3 single crystals. Hence, we propose that Cr doping promotes oxygen excess in our films during deposition, leading to the collapse of the low temperature insulating state at low Cr concentrations. These results suggest that slightly Cr-doped V2O3 films can be interesting candidates for field effect devices.
Neutron intensity modulation and time-focusing with integrated Larmor and resonant frequency techniques
Authors: Zhao Jinkui , Hamilton William A. , Lee Sung-Woo , Robertson J. L. , Crow Lowell , Kang Yoon W.
Published: September 2015

The analysis of neutron diffraction experiments often assumes that neutrons are elastically scattered from the sample. However, there is growing evidence that a significant fraction of the detected neutrons is in fact inelastically scattered, especially from soft materials and aqueous samples. Ignoring these inelastic contributions gives rise to inaccurate experimental results. To date, there has been no simple method with broad applicability for inelastic signal separation in neutron diffraction experiments. Here, we present a simple and robust method that we believe could be suited for this purpose. We use two radio frequency resonant spin flippers integrated with a Larmor precession field to modulate the neutron intensity and to encode the inelastic scattering information into the neutron data. All three components contribute to the spin encoding. The Larmor field serves several additional purposes. Its usage facilitates neutron time-focusing, eliminates the need for stringent magnetic shielding, and allows for compact setups. The scheme is robust, simple, and flexible. We believe that, with further improvements, it has the potential of adding inelastic signal discrimination capabilities to many existing diffraction instruments in the future.
New insight into the helium-induced damage in MAX phase Ti3AlC2 by first-principles studies
Authors: Xu Yiguo , Bai Xiaojing , Zha Xianhu , Huang Qing , He Jian , Luo Kan , Zhou Yuhong , Germann Timothy C. , Francisco Joseph S. , Du Shiyu
Published: September 2015

In the present work, the behavior of He in the MAX phase Ti3AlC2 material is investigated using first-principle methods. It is found that, according to the predicted formation energies, a single He atom favors residing near the Al plane in Ti3AlC2. The results also show that Al vacancies are better able to trap He atoms than either Ti or C vacancies. The formation energies for the secondary vacancy defects near an Al vacancy or a C vacancy are strongly influenced by He impurity content. According to the present results, the existence of trapped He atoms in primary Al vacancy can promote secondary vacancy formation and the He bubble trapped by Al vacancies has a higher tendency to grow in the Al plane of Ti3AlC2. The diffusion of He in Ti3AlC2 is also investigated. The energy barriers are approximately 2.980 eV and 0.294 eV along the c-axis and in the ab plane, respectively, which means that He atoms exhibit faster migration parallel to the Al plane. Hence, the formation of platelet-like bubbles nucleated from the Al vacancies is favored both energetically and kinetically. Our calculations also show that the conventional spherical bubbles may be originated from He atoms trapped by C vacancies. Taken together, these results are able to explain the observed formation of bubbles in various shapes in recent experiments. This study is expected to provide new insight into the behaviors of MAX phases under irradiation from electronic structure level in order to improve the design of MAX phase based materials.