bluuebunny/crossref_metadata_2025 huggingface dataset:
Motor cortex activity predicts response alternation during sensorimotor decisions
Authors: Pape Anna-Antonia , Siegel Markus
Published: October 2016

Our actions are constantly guided by decisions based on sensory information. The motor cortex is traditionally viewed as the final output stage in this process, merely executing motor responses based on these decisions. However, it is not clear if, beyond this role, the motor cortex itself impacts response selection. Here, we report activity fluctuations over motor cortex measured using MEG, which are unrelated to choice content and predict responses to a visuomotor task seconds before decisions are made. These fluctuations are strongly influenced by the previous trial's response and predict a tendency to switch between response alternatives for consecutive decisions. This alternation behaviour depends on the size of neural signals still present from the previous response. Our results uncover a response-alternation bias in sensorimotor decision making. Furthermore, they suggest that motor cortex is more than an output stage and instead shapes response selection during sensorimotor decision making.
The smallest chimera state for coupled pendula
Authors: Wojewoda Jerzy , Czolczynski Krzysztof , Maistrenko Yuri , Kapitaniak Tomasz
Published: October 2016

Chimera states in the systems of coupled identical oscillators are spatiotemporal patterns in which different groups of oscillators can exhibit coexisting synchronous and incoherent behaviors despite homogeneous coupling. Although these states are typically observed in large ensembles of oscillators, recently it has been suggested that chimera states may occur in the systems with small numbers of oscillators. Here, considering three coupled pendula showing chaotic behavior, we find the pattern of the smallest chimera state, which is characterized by the coexistence of two synchronized and one incoherent oscillator. We show that this chimera state can be observed in simple experiments with mechanical oscillators, which are controlled by elementary dynamical equations derived from Newton’s laws. Our finding suggests that chimera states are observable in small networks relevant to various real-world systems.
Increasing the Efficiency of CRISPR/Cas9-mediated Precise Genome Editing of HSV-1 Virus in Human Cells
Authors: Lin Chaolong , Li Huanhuan , Hao Mengru , Xiong Dan , Luo Yong , Huang Chenghao , Yuan Quan , Zhang Jun , Xia Ningshao
Published: October 2016

Genetically modified HSV-1 viruses serve as promising vectors for tumour therapy and vaccine development. The CRISPR/Cas9 system is one of the most powerful tools for precise gene editing of the genomes of organisms. However, whether the CRISPR/Cas9 system can precisely and efficiently make gene replacements in the genome of HSV-1 remains essentially unknown. Here, we reported CRISPR/Cas9-mediated editing of the HSV-1 genome in human cells, including the knockout and replacement of large genes. In established cells stably expressing CRISPR/Cas9, gRNA in coordination with Cas9 could direct a precise cleavage within a pre-defined target region and foreign genes were successfully used to replace the target gene seamlessly by HDR-mediated gene replacement. Introducing the NHEJ inhibitor SCR7 to the CRISPR/Cas9 system greatly facilitated HDR-mediated gene replacement in the HSV-1 genome. We provided the first genetic evidence that two copies of the ICP0 gene in different locations on the same HSV-1 genome could be simultaneously modified with high efficiency and with no off-target modifications. We also developed a revolutionized isolation platform for desired recombinant viruses using single-cell sorting. Together, our work provides a significantly improved method for targeted editing of DNA viruses, which will facilitate the development of anti-cancer oncolytic viruses and vaccines.
The transcription factor Ets21C drives tumor growth by cooperating with AP-1
Authors: Toggweiler Janine , Willecke Maria , Basler Konrad
Published: October 2016

Tumorigenesis is driven by genetic alterations that perturb the signaling networks regulating proliferation or cell death. In order to block tumor growth, one has to precisely know how these signaling pathways function and interplay. Here, we identified the transcription factor Ets21C as a pivotal regulator of tumor growth and propose a new model of how Ets21C could affect this process. We demonstrate that a depletion of Ets21C strongly suppressed tumor growth while ectopic expression of Ets21C further increased tumor size. We confirm that Ets21C expression is regulated by the JNK pathway and show that Ets21C acts via a positive feed-forward mechanism to induce a specific set of target genes that is critical for tumor growth. These genes are known downstream targets of the JNK pathway and we demonstrate that their expression not only depends on the transcription factor AP-1, but also on Ets21C suggesting a cooperative transcriptional activation mechanism. Taken together we show that Ets21C is a crucial player in regulating the transcriptional program of the JNK pathway and enhances our understanding of the mechanisms that govern neoplastic growth.
Accurate modeling of high-repetition rate ultrashort pulse amplification in optical fibers
Authors: Lindberg Robert , Zeil Peter , Malmström Mikael , Laurell Fredrik , Pasiskevicius Valdas
Published: October 2016

A numerical model for amplification of ultrashort pulses with high repetition rates in fiber amplifiers is presented. The pulse propagation is modeled by jointly solving the steady-state rate equations and the generalized nonlinear Schrödinger equation, which allows accurate treatment of nonlinear and dispersive effects whilst considering arbitrary spatial and spectral gain dependencies. Comparison of data acquired by using the developed model and experimental results prove to be in good agreement.
Allosteric regulation in NMDA receptors revealed by the genetically encoded photo-cross-linkers
Authors: Tian Meilin , Ye Shixin
Published: October 2016

Allostery is essential to neuronal receptor function, but its transient nature poses a challenge for characterization. The N-terminal domains (NTDs) distinct from ligand binding domains are a major locus for allosteric regulation of NMDA receptors (NMDARs), where different modulatory binding sites have been observed. The inhibitor ifenprodil, and related phenylethanoamine compounds specifically targeting GluN1/GluN2B NMDARs have neuroprotective activity. However, whether they use differential structural pathways than the endogenous inhibitor Zn2+ for regulation is unknown. We applied genetically encoded unnatural amino acids (Uaas) and monitored the functional changes in living cells with photo-cross-linkers specifically incorporated at the ifenprodil binding interface between GluN1 and GluN2B subunits. We report constraining the NTD domain movement, by a light induced crosslinking bond that introduces minimal perturbation to the ligand binding, specifically impedes the transduction of ifenprodil but not Zn2+ inhibition. Subtle distance changes reveal interfacial flexibility and NTD rearrangements in the presence of modulators. Our results present a much richer dynamic picture of allostery than conventional approaches targeting the same interface, and highlight key residues that determine functional and subtype specificity of NMDARs. The light-sensitive mutant neuronal receptors provide complementary tools to the photo-switchable ligands for opto-neuropharmacology.
Understanding the multiferroicity in TmMn2O5 by a magnetically induced ferrielectric model
Authors: Yang L. , Li X. , Liu M. F. , Li P. L. , Yan Z. B. , Zeng M. , Qin M. H. , Gao X. S. , Liu J.-M.
Published: October 2016

The magnetically induced electric polarization behaviors in multiferroic TmMn2O5 in response to varying temperature and magnetic field are carefully investigated by means of a series of characterizations including the high precision pyroelectric current technique. Here polycrystalline rather than single crystal samples are used for avoiding the strong electrically self-polarized effect in single crystals, and various parallel experiments on excluding the thermally excited current contributions are performed. The temperature-dependent electric polarization flop as a major character is identified for different measuring paths. The magneto-current measurements indicate that the electric polarization in the low temperature magnetic phase region has different origin from that in the high temperature magnetic phase. It is suggested that the electric polarization does have multiple components which align along different orientations, including the Mn3+-Mn4+-Mn3+ exchange striction induced polarization PMM, the Tm3+-Mn4+-Tm3+ exchange striction induced polarization PTM, and the low temperature polarization PLT probably associated with the Tm3+ commensurate phase. The observed electric polarization flop can be reasonably explained by the ferrielectric model proposed earlier for DyMn2O5, where PMM and PTM are the two antiparallel components both along the b-axis and PLT may align along the a-axis. Finally, several issues on the unusual temperature dependence of ferroelectric polarizations are discussed.
Non-equilibrium quantum phase transition via entanglement decoherence dynamics
Authors: Lin Yu-Chen , Yang Pei-Yun , Zhang Wei-Min
Published: October 2016

We investigate the decoherence dynamics of continuous variable entanglement as the system-environment coupling strength varies from the weak-coupling to the strong-coupling regimes. Due to the existence of localized modes in the strong-coupling regime, the system cannot approach equilibrium with its environment, which induces a nonequilibrium quantum phase transition. We analytically solve the entanglement decoherence dynamics for an arbitrary spectral density. The nonequilibrium quantum phase transition is demonstrated as the system-environment coupling strength varies for all the Ohmic-type spectral densities. The 3-D entanglement quantum phase diagram is obtained.
Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites
Authors: Rahneshin Vahid , Khosravi Farhad , Ziolkowska Dominika A. , Jasinski Jacek B. , Panchapakesan Balaji
Published: October 2016

The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors.
Intra-islet lesions and lobular variations in β-cell mass expansion in ob/ob mice revealed by 3D imaging of intact pancreas
Authors: Parween Saba , Kostromina Elena , Nord Christoffer , Eriksson Maria , Lindström Per , Ahlgren Ulf
Published: October 2016

The leptin deficient ob/ob mouse is a widely used model for studies on initial aspects of metabolic disturbances leading to type 2 diabetes, including insulin resistance and obesity. Although it is generally accepted that ob/ob mice display a dramatic increase in β-cell mass to compensate for increased insulin demand, the spatial and quantitative dynamics of β-cell mass distribution in this model has not been assessed by modern optical 3D imaging techniques. We applied optical projection tomography and ultramicroscopy imaging to extract information about individual islet β-cell volumes throughout the volume of ob/ob pancreas between 4 and 52 weeks of age. Our data show that cystic lesions constitute a significant volume of the hyperplastic ob/ob islets. We propose that these lesions are formed by a mechanism involving extravasation of red blood cells/plasma due to increased islet vessel blood flow and vessel instability. Further, our data indicate that the primary lobular compartments of the ob/ob pancreas have different potentials for expanding their β-cell population. Unawareness of the characteristics of β-cell expansion in ob/ob mice presented in this report may significantly influence ex vivo and in vivo assessments of this model in studies of β-cell adaptation and function.
Cell surface GRP78 as a biomarker and target for suppressing glioma cells
Authors: Kang Bo Ram , Yang Seung-Hoon , Chung Bo-Ryehn , Kim Woong , Kim YoungSoo
Published: October 2016

High-grade glioma is a highly malignant and metastatic brain cancer, resistant to many existing anticancer treatments. In such glioma cancer cells, the glucose-regulated protein 78 kDa (GRP78) is particularly highly up-regulated. Former studies have thus targeted mutation-free GRP78 not only to detect glioma cancer cells specifically but also to enhance cytotoxic effect. We focus on cell surface-expressed GRP78 as a target for suppressing high-grade glioma cell lines. Glioblastoma multiforme (GBM) cell line, highly malignant glioma cells, was first injected into 5-week-old athymic mice to confirm and compare GRP78 expression in vivo in xenografted and normal brain tissue. Immunofluorescence and immunoblotting were utilized to detect surface-localized GRP78 in diverse high-grade glioma cell lines. By treating glioma cell lines with the polyclonal N-20 antibody against surface-localized GRP78, we subsequently studied the significance of surface GRP78 to the survival and growth of the glioma cell lines. We found that inhibiting the function of surface GRP78 suppressed cancer cell survival and growth proving that the surface-expressed GRP78 is a vital receptor involved in the proliferation of high-grade glioma. Our findings provide opportunities to target surface GRP78 as a biomarker for high-grade glioma and to develop effective cell-specific anticancer therapy.
Behaviors of Microcystis aeruginosa cells during floc storage in drinking water treatment process
Authors: Xu Hangzhou , Pei Haiyan , Xiao Hongdi , Jin Yan , Li Xiuqing , Hu Wenrong , Ma Chunxia , Sun Jiongming , Li Hongmin
Published: October 2016

This is the first study to systematically investigate the different behaviors of Microcystis aeruginosa in the sludges formed by AlCl3, FeCl3, and polymeric aluminium ferric chloride (PAFC) coagulants during storage. Results show that the viability of Microcystis aeruginosa in PAFC sludge was stronger than that of cells in either AlCl3 or FeCl3 sludge after the same storage time, while the cells’ viability in the latter two systems stayed at almost the same level. In AlCl3 and FeCl3 sludges high concentrations of Al and Fe were toxic to Microcystis aeruginosa, whereas in PAFC sludge low levels of Al showed little toxic effect on Microcystis aeruginosa growth and moderate amounts of Fe were beneficial to growth. The lysis of Microcystis aeruginosa in AlCl3 sludge was more serious than that in PAFC sludge, for the same storage time. Although the cell viability in FeCl3 sludge was low (similar to AlCl3 sludge), the Microcystis aeruginosa cells remained basically intact after 10 d storage (similar to PAFC sludge). The maintenance of cellular integrity in FeCl3 sludge might be due to the large floc size and high density, which had a protective effect for Microcystis aeruginosa.
Tooth enamel oxygen “isoscapes” show a high degree of human mobility in prehistoric Britain
Authors: Pellegrini Maura , Pouncett John , Jay Mandy , Pearson Mike Parker , Richards Michael P.
Published: October 2016

A geostatistical model to predict human skeletal oxygen isotope values (δ18Op) in Britain is presented here based on a new dataset of Chalcolithic and Early Bronze Age human teeth. The spatial statistics which underpin this model allow the identification of individuals interpreted as ‘non-local’ to the areas where they were buried (spatial outliers). A marked variation in δ18Op is observed in several areas, including the Stonehenge region, the Peak District, and the Yorkshire Wolds, suggesting a high degree of human mobility. These areas, rich in funerary and ceremonial monuments, may have formed focal points for people, some of whom would have travelled long distances, ultimately being buried there. The dataset and model represent a baseline for future archaeological studies, avoiding the complex conversions from skeletal to water δ18O values–a process known to be problematic.
Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification
Authors: Liao Quanwen , Zeng Lingping , Liu Zhichun , Liu Wei
Published: October 2016

Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents.
Identifying molecular signatures of hypoxia adaptation from sex chromosomes: A case for Tibetan Mastiff based on analyses of X chromosome
Authors: Wu Hong , Liu Yan-Hu , Wang Guo-Dong , Yang Chun-Tao , Otecko Newton O. , Liu Fei , Wu Shi-Fang , Wang Lu , Yu Li , Zhang Ya-Ping
Published: October 2016

Genome-wide studies on high-altitude adaptation have received increased attention as a classical case of organismal evolution under extreme environment. However, the current genetic understanding of high-altitude adaptation emanated mainly from autosomal analyses. Only a few earlier genomic studies paid attention to the allosome. In this study, we performed an intensive scan of the X chromosome of public genomic data generated from Tibetan Mastiff (TM) and five other dog populations for indications of high-altitude adaptation. We identified five genes showing signatures of selection on the X chromosome. Notable among these genes was angiomotin (AMOT), which is related to the process of angiogenesis. We sampled additional 11 dog populations (175 individuals in total) at continuous altitudes in China from 300 to 4,000 meters to validate and test the association between the haplotype frequency of AMOT gene and altitude adaptation. The results suggest that AMOT gene may be a notable candidate gene for the adaptation of TM to high-altitude hypoxic conditions. Our study shows that X chromosome deserves consideration in future studies of adaptive evolution.
Tribological Properties of Water-lubricated Rubber Materials after Modification by MoS2 Nanoparticles
Authors: Dong Conglin , Yuan Chengqing , Wang Lei , Liu Wei , Bai Xiuqin , Yan Xinping
Published: October 2016

Frictional vibration and noise caused by water-lubricated rubber stern tube bearings, which are generated under extreme conditions, severely threaten underwater vehicles’ survivability and concealment performance. This study investigates the effect of flaky and spherical MoS2nanoparticles on tribological properties and damping capacity of water-lubricated rubber materials, with the aim of decreasing frictional noise. A CBZ-1 tribo-tester was used to conduct the sliding tests between rubber ring-discs and ZCuSn10Zn2ring-discs with water lubrication. These materials’ typical mechanical properties were analysed and compared. Coefficients of friction (COFs), wear rates, and surface morphologies were evaluated. Frictional noise and critical velocities of generating friction vibration were examined to corroborate above analysis. Results showed that spherical MoS2nanoparticles enhanced rubber material’s mechanical and tribological properties and, in turn, reduced the friction noise and critical velocity. Flaky MoS2nanoparticles reduced COF but did not enhance their mechanical properties, i.e., the damping capacity, wear resistance property; thus, these nanoparticles did not reduce the critical velocity obviously, even though increased the frictional noise at high load. The knowledge gained in the present work will be useful for optimizing friction pairs under extreme conditions to decrease frictional noise of water-lubricated rubber stern tube bearings.
PB1 as a potential target for increasing the breadth of T-cell mediated immunity to Influenza A
Authors: Uddbäck Ida E. M. , Steffensen Maria A. , Pedersen Sara R. , Nazerai Loulieta , Thomsen Allan R. , Christensen Jan P.
Published: October 2016

Recently, we showed that combined intranasal and subcutaneous immunization with a non-replicating adenoviral vector expressing NP of influenza A, strain PR8, induced long-standing protection against a range of influenza A viruses. However, H-2b mice challenged with an influenza A strain mutated in the dominant NP366 epitope were not efficiently protected. To address this problem, we envision the use of a cocktail of adenovectors targeting different internal proteins of influenza A virus. Consequently, we investigated the possibility of using PB1 as a target for an adenovector-based vaccine against influenza A. Our results showed that PB1 is not as immunogenic as the NP protein. However, by tethering PB1 to the murine invariant chain we were able to circumvent this problem and raise quite high numbers of PB1-specific CD8+ T cells in the circulation. Nevertheless, mice immunized against PB1 were not as efficiently protected against influenza A challenge as similarly NP-vaccinated animals. The reason for this is not a difference in the quality of the primed cells, nor in functional avidity. However, under similar conditions of immunization fewer PB1-specific cells were recruited to the airways, and surface expression of the dominant PB1 peptide, PB1703, was less stable than in the case of NP366.
Thermal and Thermoelectric Transport in Highly Resistive Single Sb2Se3 Nanowires and Nanowire Bundles
Authors: Ko Ting-Yu , Shellaiah Muthaiah , Sun Kien Wen
Published: October 2016

In this study, we measured the thermal conductivity and Seebeck coefficient of single Sb2Se3 nanowires and nanowire bundles with a high resistivity (σ ~ 4.37 × 10−4 S/m). Microdevices consisting of two adjacent suspended silicon nitride membranes were fabricated to measure the thermal transport properties of the nanowires in vacuum. Single Sb2Se3 nanowires with different diameters and nanowire bundles were carefully placed on the device to bridge the two membranes. The relationship of temperature difference on each heating/sensing suspension membranes with joule heating was accurately determined. A single Sb2Se3 nanowire with a diameter of ~ 680 nm was found to have a thermal conductivity (kNW) of 0.037 ± 0.002 W/m·K. The thermal conductivity of the nanowires is more than an order of magnitude lower than that of bulk materials (k ~ 0.36–1.9 W/m·K) and highly conductive (σ ~ 3 × 104 S/m) Sb2Se3 single nanowires (k ~ 1 W/m·K). The measured Seebeck coefficient with a positive value of ~ 661 μV/K is comparable to that of highly conductive Sb2Se3 single nanowires (~ 750 μV/K). The thermal transport between wires with different diameters and nanowire bundles was compared and discussed.
Visible light-mediated decarboxylative amination of indoline-2-carboxylic acids catalyzed by Rose Bengal
Authors: Zhang Meng-Jie , Schroeder Griffin M. , He Yan-Hong , Guan Zhi
Published: October 2016

A visible-light-induced decarboxylative amination of N-protected indoline-2-carboxylic acids and azodicarboxylate esters catalyzed by Rose Bengal has been developed.
Self-expansion, self-exfoliation and self-dispersion: insights into colloidal formation of atomically thin two-dimensional MoO2.5(OH)0.5
Authors: Wang Hai , Su Yan
Published: October 2016

Schematic of the formation mechanism of highly self-dispersible colloidal solutions of monolayered MoO2.5(OH)0.5 nanosheets by self-expansion and self-exfoliation process.
Synthetic investigation on chirally pure Mannich derivatives of pseudophenylpropanolamine and their anticancer properties against HepG-2 cells with inhibition of JAK2/STAT3
Authors: Balachandran C. , Rao K. Chennakesava , Arun Y. , Emi N. , Yamamoto N. , Inaguma Y. , Okamoto A. , Easwaramoorthi K. , Perumal P. T.
Published: October 2016

In vitro and in vivo anticancer activity of compound 3a was proved as a novel blocker of JAK2/STAT3 signaling pathway and exerts both anti-proliferative and apoptotic activities in HepG-2 cells with xenograft mice model.
Robust bioinspired graphene-based nanocomposites via synergistic toughening of zinc ions and covalent bonding
Authors: Gong Shanshan , Jiang Lei , Cheng Qunfeng
Published: October 2016

Inspired by the hierarchical layered structure and interfacial interactions of nacre, robust graphene-based nanocomposites were demonstratedviasynergistic interfacial interactions.
Triazatruxene-based materials for organic electronics and optoelectronics
Authors: Li Xiang-Chun , Wang Chun-Yu , Lai Wen-Yong , Huang Wei
Published: October 2016

This review summarizes investigations into triazatruxene-based materials from synthesis and self-assembly to functional properties for organic electronics and optoelectronics.
Are dangling bond centers important interface traps in 4H-SiC metal oxide semiconductor field effect transistors?
Authors: Anders M. A. , Lenahan P. M. , Lelis A. J.
Published: October 2016

Silicon carbide (SiC) based metal-oxide-semiconductor field-effect transistors (MOSFETs) have great promise in high power and high temperature applications. Unfortunately, effective channel mobilities remain disappointingly low, typically about 30 cm2/Vs. A major contributor to the disappointing effective channel mobilities is the presence of substantial densities of interface traps at the SiC/SiO2 interface. Many investigators have invoked silicon or carbon dangling bonds to be the dominating source of these interface defects, but very little, if any, direct experimental evidence exists to support this assumption in the SiC/SiO2 system. Cantin et al. [Phys. Rev. Lett. 92, 1 (2004)] have used conventional electron paramagnetic resonance measurements on porous oxidized SiC structures to measure the g tensor for the SiC/SiO2 interface carbon dangling bond. These results provide a particularly straightforward means to search for the presence of carbon dangling bonds in fully processed SiC MOSFETs using electrically detected magnetic resonance. Additionally, simple theory provides guidance to search for silicon dangling bond defects. In this study, we utilize K band electrically detected magnetic resonance via spin dependent charge pumping measurements in which almost all of the SiC band gap at the SiC/SiO2 interface is accessed. Although quite high signal to noise measurements are achieved, we are unable to detect any trace of the carbon dangling bond spectra. However, in very poor quality p-channel devices, we observe a spectrum which could be consistent with silicon dangling bonds. Other defect centers are clearly present and we conclude that these other centers dominate the interface trap density of states.
Two-dimensional fluid dynamics in a sharply bent channel: Laminar flow, separation bubble, and vortex dynamics
Authors: Matsumoto Daichi , Fukudome Koji , Wada Hirofumi
Published: October 2016

Understanding the hydrodynamic properties of fluid flow in a curving pipe and channel is important for controlling the flow behavior in technologies and biomechanics. The nature of the resulting flow in a bent pipe is extremely complicated because of the presence of a cross-stream secondary flow. In an attempt to disentangle this complexity, we investigate the fluid dynamics in a bent channel via the direct numerical simulation of the Navier-Stokes equation in two spatial dimensions. We exploit the absence of secondary flow from our model and systematically investigate the flow structure along the channel as a function of both the bend angle and Reynolds number of the laminar-to-turbulent regime. We numerically suggest a scaling relation between the shape of the separation bubble and the flow conductance, and construct an integrated phase diagram.
Reducing current noise in cryogenic experiments by vacuum-insulated cables
Authors: Mykkänen E. , Lehtinen J. S. , Kemppinen A. , Krause C. , Drung D. , Nissilä J. , Manninen A. J.
Published: October 2016

We measure the current noise of several cryogenic cables in a pulse tube based dilution refrigerator at frequencies between about 1 mHz and 50 kHz. We show that vibration-induced noise can be efficiently suppressed by using vacuum-insulated cables between room temperature and the 2nd pulse tube stage. A noise peak below 4 fA at the 1.4 Hz operation frequency of the pulse tube and a white noise density of 0.44 fA/Hz in the millihertz range are obtained.
Driving frequency optimization of a piezoelectric transducer and the power supply development
Authors: Dong Xiaoxiao , Yuan Tao , Hu Minqiang , Shekhani Husain , Maida Yuichi , Tou Tonshaku , Uchino Kenji
Published: October 2016

Piezoelectric transducers are commonly operated at their resonance frequency. However, from a power dissipation standpoint, this is not the ideal driving frequency. In this paper, an optimized driving frequency in between the resonance and antiresonance frequencies is proposed for the piezo-transducer. First, the optimum driving frequency is characterized using a constant vibration velocity measurement method. The actual input power reveals the lowest power dissipation frequency between the resonance and the antiresonance frequencies, where the transducer behaves inductive. The electrical parameters of the transducer are then determined by an equivalent circuit formulation, which is useful for the electrical circuit analysis of the driver design. A Class E resonant inverter is used to design a capacitive output impedance driver at the optimized frequency by utilizing a series capacitor. Compared with the traditional resonance drive, driving at the optimized frequency reduces the required power by approximately half according to the measurements performed.
Orbital stability of spatially synchronized solitary waves of an m-coupled nonlinear Schrödinger system
Authors: Liu Chuangye , Nguyen Nghiem V. , Wang Zhi-Qiang
Published: October 2016

In this paper, we investigate the orbital stability of solitary-wave solutions for an m-coupled nonlinear Schrödinger system i∂∂tuj+∂2∂x2uj+∑i=1mbijui2uj=0,j=1,…,m, where m ≥ 2, uj are complex-valued functions of (x, t) ∈ ℝ2, bjj ∈ ℝ, j = 1, 2, …, m, and bij, i ≠ j are positive coupling constants satisfying bij = bji. It will be shown that spatially synchronized solitary-wave solutions of the m-coupled nonlinear Schrödinger system exist and are orbitally stable. Here, by synchronized solutions we mean solutions in which the components are proportional to one another. Our results completely settle the question on the existence and stability of synchronized solitary waves for the m-coupled system while only partial results were known in the literature for the cases of m ≥ 3 heretofore. Furthermore, the conditions imposed on the symmetric matrix B = (bij) satisfied here are both sufficient and necessary for the m-coupled nonlinear Schrödinger system to admit synchronized ground-state solutions.
Simulation of stimuli-triggered release of molecular species from halloysite nanotubes
Authors: Elumalai Divya Narayan , Tully Joshua , Lvov Yuri , Derosa Pedro A.
Published: October 2016

A Monte Carlo model is used to study the effect of environmental variables (pH and temperature) on the transport and release of dexamethasone molecules from Halloysite Nanotubes (HNTs) in a dielectric fluid medium. The model used for this study was introduced elsewhere and it is based on basic physics interactions without experimental parameters for these interactions. An intermediate phase between the burst and saturation phase is found and explained. Molecules experience a 1-D diffusion process that is different from the diffusion in the burst phase or the surface diffusion experienced by molecules attached to the wall. It is predicted that this phase exists when the molecule-wall interaction is attractive but not always noticeable in the release profile. In this work, it is shown that an agreement with the experiment better than previously reported is obtained when simulated delivery curves are produced by the weighted average of the release profiles from a collection of HNTs with diameters and lengths distributed according to the experimental sample, highlighting the relevance of HNTs' morphology in the release. HNTs are suitable for environment-triggered release and thus the effect of temperature, molecule zeta potential, and pH is studied. It is observed that for temperatures that significantly differ from room temperature (by 100's of degrees), the release profile changes significantly, increasing the delivery speed at high temperature and reducing that speed at low temperature. Finally, it is observed that as the pH becomes more acidic, both the molecule and inner wall surface become more positive (or less negative) with both eventually becoming positive leading to a repulsive interaction; thus, molecules are pushed out by electrostatic repulsion. On the contrary, as the pH becomes more basic, positive molecules become more positive while the wall becomes less negative, but even at pH 12, the wall remains negative and the interaction is attractive. Changes in pH between different regions may act as a trigger for delivery or as a control in the delivery rate.
Zeta functions of the Dirac operator on quantum graphs
Authors: Harrison J. M. , Weyand T. , Kirsten K.
Published: October 2016

We construct spectral zeta functions for the Dirac operator on metric graphs. We start with the case of a rose graph, a graph with a single vertex where every edge is a loop. The technique is then developed to cover any finite graph with general energy independent matching conditions at the vertices. The regularized spectral determinant of the Dirac operator is also obtained as the derivative of the zeta function at a special value. In each case the zeta function is formulated using a contour integral method, which extends results obtained for Laplace and Schrödinger operators on graphs.
Partial classification of modules for the algebra of skew-derivations over the d-dimensional torus
Authors: Xu Chengkang
Published: October 2016

For the algebra of skew-derivations over a torus, we classify the irreducible weight modules with some restrictions.
On the infinitely many nonperturbative solutions in a transmission eigenvalue problem for Maxwell’s equations with cubic nonlinearity
Authors: Smirnov Yu. G. , Valovik D. V.
Published: October 2016

The paper focuses on a transmission eigenvalue problem for Maxwell’s equations with cubic nonlinearity that describes the propagation of transverse magnetic waves along the boundaries of a dielectric layer filled with nonlinear (Kerr) medium. Using an original approach, it is proved that even for small values of the nonlinearity coefficient, the nonlinear problem has infinitely many nonperturbative solutions (eigenvalues and eigenwaves), whereas the corresponding linear problem always has a finite number of solutions. This fact implies the theoretical existence of a novel type of eigenwaves that do not reduce to the linear ones in the limit in which the nonlinear coefficient reduces to zero. Asymptotic distribution of the eigenvalues is found, periodicity of the eigenfunctions is proved, the exact formula for the period is found, and the zeros of the eigenfunctions are determined.
Lattice model of spatial correlations in catalysis
Authors: Loring Roger F.
Published: October 2016

Optically detected single-turnover measurements of biological and inorganic catalysts provide a detailed picture of structural and dynamical influences on catalytic activity. Measurement at the single-molecule level of catalysis of a fluorogenic reaction (or its reverse) yields a stochastic fluorescence trajectory reflecting the statistics of individual reaction and product dissociation events. Analysis of time correlations displayed by this trajectory reveals reaction details inaccessible in a bulk measurement of averaged dynamics. Superresolution optical detection techniques can provide a spatial resolution over which correlations could be observed in space as well as time. A model is constructed here for spatial correlations in catalytic activity produced by an entity transported among multiple active sites. An approximation strategy based on perturbation theory in the coupling between transport and reaction dynamics is applied to calculate the mean dwell time of a reactant on an active site and the correlation between dwell times of reactants at different locations.
A molecular dynamics study of the role of molecular water on the structure and mechanics of amorphous geopolymer binders
Authors: Sadat Mohammad Rafat , Bringuier Stefan , Asaduzzaman Abu , Muralidharan Krishna , Zhang Lianyang
Published: October 2016

In this paper, molecular dynamics simulations are used to study the effect of molecular water and composition (Si/Al ratio) on the structure and mechanical properties of fully polymerized amorphous sodium aluminosilicate geopolymer binders. The X-ray pair distribution function for the simulated geopolymer binder phase showed good agreement with the experimentally determined structure in terms of bond lengths of the various atomic pairs. The elastic constants and ultimate tensile strength of the geopolymer binders were calculated as a function of water content and Si/Al ratio; while increasing the Si/Al ratio from one to three led to an increase in the respective values of the elastic stiffness and tensile strength, for a given Si/Al ratio, increasing the water content decreased the stiffness and strength of the binder phase. An atomic-scale analysis showed a direct correlation between water content and diffusion of alkali ions, resulting in the weakening of the AlO4 tetrahedral structure due to the migration of charge balancing alkali ions away from the tetrahedra, ultimately leading to failure. In the presence of water molecules, the diffusion behavior of alkali cations was found to be particularly anomalous, showing dynamic heterogeneity. This paper, for the first time, proves the efficacy of atomistic simulations for understanding the effect of water in geopolymer binders and can thus serve as a useful design tool for optimizing composition of geopolymers with improved mechanical properties.
Probing dissociative electron attachment through heavy-Rydberg ion-pair production in Rydberg atom collisions
Authors: Buathong S. , Kelley M. , Dunning F. B.
Published: October 2016

Electron transfer in collisions between low-n, n = 12, Rydberg atoms and targets that attach low-energy electrons can lead to the formation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair that orbit each other at large separations. Measurements of the velocity and angular distribution of ion-pair states produced in collisions with 1,1,1-C2Cl3F3, CBrCl3, BrCN, and Fe(CO)5 are used to show that electron transfer reactions furnish a new technique with which to examine the lifetime and decay energetics of the excited intermediates formed during dissociative electron capture. The results are analyzed with the aid of Monte Carlo simulations based on the free electron model of Rydberg atom collisions. The data further highlight the capabilities of Rydberg atoms as a microscale laboratory in which to probe the dynamics of electron attachment reactions.
Curvature and geodesic instabilities in a geometrical approach to the planar three-body problem
Authors: Krishnaswami Govind S. , Senapati Himalaya
Published: October 2016

The Maupertuis principle allows us to regard classical trajectories as reparametrized geodesics of the Jacobi-Maupertuis (JM) metric on configuration space. We study this geodesic reformulation of the planar three-body problem with both Newtonian and attractive inverse-square potentials. The associated JM metrics possess translation and rotation isometries in addition to scaling isometries for the inverse-square potential with zero energy E. The geodesic flow on the full configuration space ℂ3 (with collision points excluded) leads to corresponding flows on its Riemannian quotients: the center of mass configuration space ℂ2 and shape space ℝ3 (as well as 𝕊3 and the shape sphere 𝕊2 for the inverse-square potential when E = 0). The corresponding Riemannian submersions are described explicitly in “Hopf” coordinates which are particularly adapted to the isometries. For equal masses subject to inverse-square potentials, Montgomery shows that the zero-energy “pair of pants” JM metric on the shape sphere is geodesically complete and has negative gaussian curvature except at Lagrange points. We extend this to a proof of boundedness and strict negativity of scalar curvatures everywhere on ℂ2, ℝ3, and 𝕊3 with collision points removed. Sectional curvatures are also found to be largely negative, indicating widespread geodesic instabilities. We obtain asymptotic metrics near collisions, show that scalar curvatures have finite limits, and observe that the geodesic reformulation “regularizes” pairwise and triple collisions on ℂ2 and its quotients for arbitrary masses and allowed energies. For the Newtonian potential with equal masses and zero energy, we find that the scalar curvature on ℂ2 is strictly negative though it could have either sign on ℝ3. However, unlike for the inverse-square potential, geodesics can encounter curvature singularities at collisions in finite geodesic time.
Modeling and numerical analysis of a magneto-inertial fusion concept with the target created through FRC merging
Authors: Li Chenguang , Yang Xianjun
Published: October 2016

The Magnetized Plasma Fusion Reactor concept is proposed as a magneto-inertial fusion approach based on the target plasma created through the collision merging of two oppositely translating field reversed configuration plasmas, which is then compressed by the imploding liner driven by the pulsed-power driver. The target creation process is described by a two-dimensional magnetohydrodynamics model, resulting in the typical target parameters. The implosion process and the fusion reaction are modeled by a simple zero-dimensional model, taking into account the alpha particle heating and the bremsstrahlung radiation loss. The compression on the target can be 2D cylindrical or 2.4D with the additive axial contraction taken into account. The dynamics of the liner compression and fusion burning are simulated and the optimum fusion gain and the associated target parameters are predicted. The scientific breakeven could be achieved at the optimized conditions.
Formation of huge in-plane anisotropy of intrinsic stress by off-axis growth of diamond
Authors: Gallheber B.-C. , Fischer M. , Klein O. , Schreck M.
Published: October 2016

The present study shows that the heteroepitaxial growth of diamond by chemical vapour deposition (CVD) on Ir/YSZ/Si(111) substrates with off-axis angles of few degrees can generate intrinsic stress with huge anisotropy of several GPa in the diamond films. For all investigated off-axis directions and angles, a plane stress state with a perpendicular component σ33 ∼ 0 GPa is derived by X-ray diffraction. The size and direction of the associated in-plane stress tensor components exhibit a unique dependency on the off-axis tilt direction. They can combine the simultaneous presence of tensile and compressive stress within a layer. Stress anisotropy increases with the off-axis angle. For diamond with off-axis tilt towards [110] and [112], the principal axes of the tensor are parallel and perpendicular, respectively, to the projection of the off-axis direction into the film plane, whereas for [11¯0] they are rotated by an angle of ∼30°. For a consistent explanation of this complex behaviour, it is suggested that the measured stress is generated by the combined action of growth parameter controlled effective climb of dislocations and off-axis growth induced dislocation tilting. It is supposed that the described mechanism is not only valid for diamond CVD but also contributes to anisotropic stress formation in other semiconductor materials grown on vicinal surfaces.
A low-cost, do-it-yourself data-logging system to record animal activity in laboratory and small-enclosure experiments
Authors: Story P. G. , Walker B.
Published: October 2016

With the increasing cost of prepackaged research equipment and restrictions on research budgets, there is a growing need for inexpensive solutions for data collection in laboratory and small enclosures across a range of research topics investigating responses of animals to experimental parameters. We present here a low-cost, modular passive infrared sensor and data-logging system for use in experiments evaluating animal activity and behaviour, easily assembled in a laboratory setting. This system comprises accessible kit-based components purchased from popular electronics suppliers. We present the hardware configuration, software coding, build of materials, circuit diagram and a sample dataset demonstrating that the system collects reliable data that is easily downloaded either through any terminal program, directly from the unit or via an SD card. It is hoped that this ‘freeware’ approach to activity-monitoring equipment will enable laboratory and enclosure-based research to be undertaken more cost-effectively.