bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of catalysis by haloalkane dehalogenases in aqueous solutions of deep eutectic and organic solvents
Authors: Stepankova Veronika , Vanacek Pavel , Damborsky Jiri , Chaloupkova Radka
Published: February 2014

Excellent compatibility of ethaline with dehalogenase DhaA was demonstrated by retention of its activity at high ethaline concentration (≥75% v/v).
Dynamic trapping and two-dimensional transport of swimming microorganisms using a rotating magnetic microrobot
Authors: Ye Zhou , Sitti Metin
Published: February 2014

Non-contact, selective and dynamic trapping and transportation of motile microorganisms using locally induced flows with minimal damage.
Dual-mode hydrodynamic railing and arraying of microparticles for multi-stage signal detection in continuous flow biochemical microprocessors
Authors: Sochol Ryan D. , Corbett Daniel , Hesse Sarah , Krieger William E. R. , Wolf Ki Tae , Kim Minkyu , Iwai Kosuke , Li Song , Lee Luke P. , Lin Liwei
Published: February 2014

We present a continuous flow microfluidic “rail-trap-and-rail” reactor for passively: (i) executing multi-stage particulate-based mixing processes, and (ii) arraying select particles at each reaction stage.
A novel synthetic approach to the bicyclo[5.3.1]undecan-11-one framework of vinigrol
Authors: Wang Xian-Lei , Lu Yun-Yu , Wang Jie , Wang Xuan , Yao He-Quan , Lin Guo-Qiang , Sun Bing-Feng
Published: February 2014

A unique approach to the [5.3.1] bicyclic core of vinigrol is described featuring highly stereoselective C–C bond forming reactions through exploring the inherent conformational bias of the cyclooctane-ring system.
Ultra-fast photonic curing of electrically conductive adhesives fabricated from vinyl ester resin and silver micro-flakes for printed electronics
Authors: Cui Hui-Wang , Jiu Jin-Ting , Nagao Shijo , Sugahara Tohru , Suganuma Katsuaki , Uchida Hiroshi , Schroder Kurt A.
Published: February 2014

Electrically conductive vinyl ester resin–silver micro-flake adhesives, combined with intense pulsed light, present ultra-fast photonic curing within a second.
Sensitive and regenerable organochalcogen probes for the colorimetric detection of thiols
Authors: Balkrishna Shah Jaimin , Hodage Ananda S. , Kumar Shailesh , Panini Piyush , Kumar Sangit
Published: February 2014

Isothiazolone and isoselenazolone based colorimetric probes for the detection of thiols have been reported. A regenerable probe for the detection of organothiols is developed from isoselenazolone. Both of these probes possess higher selectivity for aromatic thiols, cysteine and glutathione.
Solvothermal synthesis of FeCo nanoparticles for magneto-controllable biocatalysis
Authors: Hou Jianxuan , Kuang Yun , Shen Huaqing , Cao Hui , Luo Liang , Liu Junfeng , Wan Pengbo , Chen Biqiang , Sun Xiaoming , Tan Tianwei
Published: February 2014

FeCo nanoparticles were synthesized by a solvothermal method, and could work as a fuel-free magneto-controllable carrier to load biocatalytically-active cargo for magneto-controllable and recyclable biocatalysis.
Nitrogen-doped open pore channeled graphene facilitating electrochemical performance of TiO2 nanoparticles as an anode material for sodium ion batteries
Authors: Cha Hyun Ae , Jeong Hyung Mo , Kang Jeung Ku
Published: February 2014

We report electrochemical performance of a TiO2 combined with a nitrogen-doped open channeled graphene anode composite for sodium ion batteries.
Chitinase-3-like protein 1 protects skeletal muscle from TNFα-induced inflammation and insulin resistance
Authors: Görgens Sven W. , Eckardt Kristin , Elsen Manuela , Tennagels Norbert , Eckel Jürgen
Published: February 2014

CHI3L1 (chitinase-3-like protein 1) is a glycoprotein consisting of 383 amino acids with a molecular mass of 40 kDa, and its serum level is elevated in inflammatory diseases. Although CHI3L1 is described as a biomarker of inflammation, the function of this protein is not completely understood. In the present study, we examined the regulation of CHI3L1 in primary human skeletal muscle cells. Moreover, we analysed potential autocrine effects of CHI3L1. We show that myotubes express CHI3L1 in a differentiation-dependent manner. Furthermore, pro-inflammatory cytokines up-regulate CHI3L1 expression (6-fold) and release (3-fold). Importantly, CHI3L1 treatment blocked TNFα (tumour necrosis factor α)-induced inflammation by inhibiting NF-κB (nuclear factor κB) activation in skeletal muscle cells. We show that this effect is mediated via PAR2 (protease-activated receptor 2). In addition, CHI3L1 treatment diminished the TNFα-induced expression and secretion of IL (interleukin)-8, MCP1 (monocyte chemoattractant protein 1) and IL-6. In addition, impaired insulin action at the level of Akt and GSK3α/β (glycogen synthase kinase 3α/β) phosphoryl-ation and insulin-stimulated glucose uptake was normalized by CHI3L1. In conclusion, the novel myokine CHI3L1, which is induced by pro-inflammatory cytokines, can counteract TNFα-mediated inflammation and insulin resistance in human skeletal muscle cells, potentially involving an auto- and/or para-crine mechanism.
Suppression of adipogenesis by valproic acid through repression of USF1-activated fatty acid synthesis in adipocytes
Authors: Yuyama Miki , Fujimori Ko
Published: February 2014

VPA (valproic acid), a short-chain fatty acid that is a HDAC (histone deacetylase) inhibitor, is known to suppress adipogenesis. In the present study, we identified the molecular mechanism of VPA-mediated suppression of adipogenesis in adipocytes. VPA suppressed the accumulation of intracellular triacylglycerol. The expression levels of PPARγ (peroxisome-proliferator-activated receptor γ) and C/EBPα (CCAAT/enhancer-binding protein α), which are key regulators of adipogenesis, as well as the expression of SCD (stearoyl-CoA desaturase), were decreased by the treatment with VPA. Moreover, glycerol release was decreased in the VPA-treated cells, even though the transcription levels of ATGL (adipose triacylglycerol lipase), HSL (hormone-sensitive lipase) and MGL (monoacylglycerol lipase), all of which are involved in lipolysis, were elevated by the treatment with VPA. It is noteworthy that the expression level of FAS (fatty acid synthase) was significantly suppressed when the cells were cultured in medium containing VPA. Furthermore, VPA-mediated suppression of the accumulation of the intracellular triacylglycerols was prevented by the treatment with palmitic acid, a major product of FAS. The results of promoter-luciferase and chromatin immunoprecipitation assays demonstrated that USF1(upstream stimulating factor 1) bound to the E-box of the promoter region of the FAS gene. In addition, the expression of USF1 was decreased by the treatment with VPA. siRNA-mediated knockdown of the expression of the USF1 gene repressed adipogenesis along with the decreased expression of the FAS gene. The overexpression of USF1 enhanced both adipogenesis and the expression of FAS in VPA-treated cells. These results indicate that VPA suppressed adipogenesis through the down-regulation of USF1-activated fatty acid synthesis in adipocytes.
High‐resolution three‐dimensional laser radar with static unitary detector
Authors: Mheen Bongki , Shim Jea‐Sik , Oh Myoung Sook , Song Jungho , Song Minhyup , Choi Gyu Dong , Seo Hongsoek , Kwon Yong‐Hwan
Published: February 2014

A new simple method to obtain real‐time high‐resolution three‐dimensional (3D) images based on a static unitary detector (STUD) is reported. The STUD consists of a common bias network, a partitioned photodetector, a preamplifier array and a combiner, which makes it possible to easily increase the effective photo‐detection area for a wider 3D image acquisition without affecting the ability to detect short laser pulses for high‐resolution 3D images. From an implemented experimental prototype based on a STUD, the intensity and 3D images with a very high resolution (320 pixels × 240 pixels) were obtained. The achieved range resolution and the spatial resolution of remote 3D objects at 50 m were measured to be <0.3 and 1.1 cm, respectively.
Robust audio fingerprinting based on GammaChirp frequency cepstral coefficients and chroma
Authors: Chen N. , Xiao H.D. , Zhu J.
Published: February 2014

A novel auditory feature that combines an auditory model and music theory is proposed for audio fingerprinting. First, the input audio is filtered by a GammaChirp (GC) filterbank to model the cochlear frequency selectivity. Then, the output of the filterbank is down‐sampled and decorrelated by a discrete cosine transform to obtain the GammaChirp frequency cepstral coefficients (GCFCCs). Next, some lowest order GCFCCs are projected onto the chroma to characterise both melodic and harmonic information of the input. Finally, non‐negative matrix factorisation is applied to the chroma matrix to reduce its dimension while maintaining its discriminative power. The experimental results illustrate that the proposed scheme achieves a stabler identification rate and lower computational complexity than the schemes based on the Mel‐frequency cepstral coefficients.
Monolithically integrated dual‐lock‐in optical sensor
Authors: Davidovic M. , Seiter J. , Hofbauer M. , Gaberl W. , Zimmermann H.
Published: February 2014

A single‐pixel sensor consisting of a dual‐lock‐in amplifier with an innovative dual‐cathode photodetector is presented. The sensor is fabricated in 0.35 µm CMOS and is designed to be integrated in a multipixel array working with a frequency shifted feedback (FSF) laser. The realised single‐pixel structure occupies an area of 120 × 100 µm² at a 58% fill factor. This pixel ensures frequency detection of the optical signal independently of its phase and power. The bandwidth of the interleaved pin photodiodes is larger than 100 MHz even for 850 nm. The sensor shows a dynamic range of ∼24 dB at a modulation frequency of 10 MHz. Signals up to 35 MHz can be detected.
Versatility provided by electrostatic torsional microstructure as consequence of its complex dynamics
Authors: Scerri J. , Grech I. , Gatt E. , Casha O.
Published: February 2014

The results presented show that a simple microstructure involving a plate supported by two tethers can exhibit varied dynamics due to its nonlinearities. The plate vibrates such that the tethers experience a torsional twisting and it is designed within the constraints imposed by the MetalMUMPs process. Each region of operation has different applications and one can traverse through these regions by adjusting the sensing and actuation voltages. As one would expect, the nonlinearities dominate at higher voltages, with the first signs of chaotic trajectories appearing at 75 V. Parameters of the nonlinear model are first determined from finite‐element analysis responses, and results from subsequent numerical simulations for each region are presented.
SP‐SIFT: enhancing SIFT discrimination via super‐pixel‐based foreground–background segregation
Authors: Navarro F. , Escudero‐Viñolo M. , Bescós J.
Published: February 2014

Existing point‐of‐interest (POI) descriptions are biased by the information surrounding the point. Whereas in self‐contained images this information is useful for enhancing the repeatability of the description, its use is inadequate for the description of objects that might be surrounded by variable backgrounds. To tackle these situations, a new POI descriptor – super‐pixel‐based isolation of the scale invariant feature transform (SP‐SIFT) – is proposed. The classical SIFT descriptor is modified by isolating the information of the flat areas that compose it. It is proposed to include superpixel information in the description stage of the SIFT. The obtained results suggest that a so‐built descriptor increases the repeatability of SIFT points in these scenarios while keeping its robustness to global transformations of the image: blurring, changes in viewpoint, scale and lighting. The method is presented here as an extension of the SIFT. However, the idea behind it may be easily exported to most of the existing POI‐descriptors in the state‐of‐the‐art.
Metastability occurrence based physical unclonable functions for FPGAs
Authors: Wieczorek P.Z. , Golofit K.
Published: February 2014

A novel concept of a physical obfuscation of cryptographic keys is introduced which basically utilises identification of the metastable behaviour of field programmable gate array (FPGA) flip‐flops, i.e. the time variability of the metastability's appearance. Clock and data intervals leading to metastability (δ) are measured with the use of programmable delay lines available in digital clock managers (DCMs). The DCM acts as a variable clock phase regulator, whereas another circuit detects metastable events. The parts of binary words representing δ become segments of a physical unclonable function key. Preliminary results show significant differences in interval δ values when a slight change in circuit implementation occurs (in placement, node connections, surrounding sub‐circuits etc.). Similar FPGA devices manufactured in the same process having an identical structure also behave significantly differently due to the intrinsic inter‐class randomness.
MPGraph: multi‐view penalised graph clustering for predicting drug–target interactions
Authors: Li Limin
Published: February 2014

Identifying drug–target interactions has been a key step for drug repositioning, drug discovery and drug design. Since it is expensive to determine the interactions experimentally, computational methods are needed for predicting interactions. In this work, the authors first propose a single‐view penalised graph (SPGraph) clustering approach to integrate drug structure and protein sequence data in a structural view. The SPGraph model does clustering on drugs and targets simultaneously such that the known drug–target interactions are best preserved in the clustering results. They then apply the SPGraph to a chemical view with drug response data and gene expression data in NCI‐60 cell lines. They further generalise the SPGraph to a multi‐view penalised graph (MPGraph) version, which can integrate the structural view and chemical view of the data. In the authors' experiments, they compare their approach with some comparison partners, and the results show that the SPGraph could improve the prediction accuracy in a small scale, and the MPGraph can achieve around 10% improvements for the prediction accuracy. They finally give some new targets for 22 Food and Drug Administration approved drugs for drug repositioning, and some can be supported by other references.
The micro-structure and composition evolution of Ti-Sb-Te alloy during reversible phase transition in phase change memory
Authors: Zhu Min , Wu Liangcai , Rao Feng , Song Zhitang , Xia Mengjia , Ji Xinglong , Lv Shilong , Feng Songling
Published: February 2014

We contrastively investigate the micro-structure and composition evolution of Ti0.53Sb2Te2.6 (TST) alloy in phase change memory cells respectively undergoing three repeated and 105 endurance operations. For the cell experiencing three repeated operations, the active phase change region is not formed while many small crystal grains are found in TST/W interfaces, and the composition of TST in phase change region is almost unchanged. However, for another cell going through endurance operation, the active region is clearly observed in TST layer with abnormally large residual grains, which are found in Ti-rich and Sb, Te-deficient composition.
Smooth cubic commensurate oxides on gallium nitride
Authors: Paisley Elizabeth A. , Gaddy Benjamin E. , LeBeau James M. , Shelton Christopher T. , Biegalski Michael D. , Christen Hans M. , Losego Mark D. , Mita Seiji , Collazo Ramón , Sitar Zlatko , Irving Douglas L. , Maria Jon-Paul
Published: February 2014

Smooth, commensurate alloys of ⟨111⟩-oriented Mg0.52Ca0.48O (MCO) thin films are demonstrated on Ga-polar, c+ [0001]-oriented GaN by surfactant-assisted molecular beam epitaxy and pulsed laser deposition. These are unique examples of coherent cubic oxide|nitride interfaces with structural and morphological perfection. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100× reduction in leakage current density for the surfactant-assisted samples. HAADF-STEM images of the MCO|GaN interface show commensurate alignment of atomic planes with minimal defects due to lattice mismatch. STEM and DFT calculations show that GaN c/2 steps create incoherent boundaries in MCO over layers which manifest as two in-plane rotations and determine consequently the density of structural defects in otherwise coherent MCO. This new understanding of interfacial steps between HCP and FCC crystals identifies the steps needed to create globally defect-free heterostructures.
Photo response of silver-TiO2 film
Authors: Viernes M. A. J. , Mahinay C. L. S. , Villamayor M. M. S. , Ramos H. J.
Published: February 2014

Silver and TiO2 films were deposited on glass substrates via the plasma sputter type negative ion source and a compact planar magnetron, respectively. A silver target was biased and is sputtered by argon plasma for 30 min. TiO2 was deposited by sputtering a titanium disk and introducing oxygen in a 1:13 ratio with argon plasma for 2 h. The resulting composite films (silver on TiO2 and TiO2 on silver) were analyzed by its transmissivity in the UV-VIS region showing increased optical absorbance. The synthesized films were used in the photocatalytic degradation of methylene blue showing an increase in photocatalytic degradation when only TiO2 is used. The introduction of silver with TiO2 inhibited the effective photocatalytic degradation of methylene blue.
A novel tape spring hinge mechanism for quasi-static deployment of a satellite deployable using shape memory alloy
Authors: Jeong Ju Won , Yoo Young Ik , Shin Dong Kil , Lim Jae Hyuk , Kim Kyung Won , Lee Jung Ju
Published: February 2014

A tape spring hinge (TSH) is a typical flexible deployment device for a satellite and becomes frequently used due to its simplicity, lightweight, low cost, and high deployment reliability. However, the performance of a TSH is quite limited due to trade-offs among deployed stiffness, deployment torque, and latch-up shock despite its many advantages. In this study, a novel conceptual design that circumvents the trade-offs among functional requirements (FRs) is proposed. The trade-offs are obviated by a newly proposed shape memory alloy damper that converts the deployment behavior of a conventional TSH from unstable dynamic to stable quasi-static. This makes it possible to maximize the deployment stiffness and deployment torque of a conventional TSH, which are larger-the-better FR, without any increase in the latch-up shock. Therefore, in view of conceptual design, it is possible to design a highly improved TSH that has much higher deployed stiffness and deployment torque compared to a conventional TSH while minimizing latch-up shock and deployment unstableness. Detailed design was performed through response surface method and finite element analysis. Finally, a prototype was manufactured and tested in order to verify its performance (four point, deployment torque, and latch-up shock tests). The test results confirm the feasibility of the proposed TSH mechanism.
Adjustable low frequency and broadband metamaterial absorber based on magnetic rubber plate and cross resonator
Authors: Cheng Yongzhi , Nie Yan , Wang Xian , Gong Rongzhou
Published: February 2014

In this paper, the magnetic rubber plate absorber (MRPA) and metamaterial absorber (MA) based on MRP substrate were proposed and studied numerically and experimentally. Based on the characteristic of L-C resonances, experimental results show that the MA composed of cross resonator (CR) embedded single layer MRP could be adjustable easily by changing the wire length and width of CR structure and MRP thickness. Finally, experimental results show that the MA composed of CR-embedded two layers MRP with the total thickness of 2.42 mm exhibit a −10 dB absorption bandwidth from 1.65 GHz to 3.7 GHz, which is 1.86 times wider than the same thickness MRPA.
Kinetically constrained ring-polymer molecular dynamics for non-adiabatic chemical reactions
Authors: Menzeleev Artur R. , Bell Franziska , Miller Thomas F.
Published: February 2014

We extend ring-polymer molecular dynamics (RPMD) to allow for the direct simulation of general, electronically non-adiabatic chemical processes. The kinetically constrained (KC) RPMD method uses the imaginary-time path-integral representation in the set of nuclear coordinates and electronic states to provide continuous equations of motion that describe the quantized, electronically non-adiabatic dynamics of the system. KC-RPMD preserves the favorable properties of the usual RPMD formulation in the position representation, including rigorous detailed balance, time-reversal symmetry, and invariance of reaction rate calculations to the choice of dividing surface. However, the new method overcomes significant shortcomings of position-representation RPMD by enabling the description of non-adiabatic transitions between states associated with general, many-electron wavefunctions and by accurately describing deep-tunneling processes across asymmetric barriers. We demonstrate that KC-RPMD yields excellent numerical results for a range of model systems, including a simple avoided-crossing reaction and condensed-phase electron-transfer reactions across multiple regimes for the electronic coupling and thermodynamic driving force.
Phase diagram of a square-well model in two dimensions
Authors: Armas-Pérez Julio C. , Quintana-H Jacqueline , Chapela Gustavo A. , Velasco Enrique , Navascués Guillermo
Published: February 2014

The phase behavior of a two-dimensional square-well model of width 1.5σ, with emphasis on the low-temperature and/or high-density region, is studied using Monte Carlo simulation in the canonical and isothermal-isobaric ensembles, and discontinuous molecular-dynamics simulation in the canonical ensemble. Several properties, such as equations of state, Binder cumulant, order parameters, and correlation functions, were computed. Numerical evidence for vapor, liquid, hexatic, and triangular solid is given, and, in addition, a non-compact solid with square-lattice symmetry is obtained. The global phase diagram is traced out in detail (or sketched approximately whenever only inaccurate information could be obtained). The solid region of the phase diagram is explained using a simple mean-field model.
High-resolution spectroscopy and quantum-defect model for the gerade triplet np and nf Rydberg states of He2
Authors: Sprecher D. , Liu J. , Krähenmann T. , Schäfer M. , Merkt F.
Published: February 2014

Photoionization spectra and Rydberg-state-resolved threshold-ionization spectra of the gerade triplet np Rydberg states of 4He2 located in the vicinity of the \documentclass[12pt]{minimal}\begin{document}$X^+ \, ^2\Sigma _u^+ \, (v^+=0)$\end{document}X+Σu+2(v+=0) ionization threshold were recorded from the \documentclass[12pt]{minimal}\begin{document}$2s\sigma \, a \, ^3\Sigma _u^+$\end{document}2sσaΣu+3 metastable state. An accuracy of 0.01 cm−1 was achieved for the experimental term values of the observed Rydberg states. The data were combined with spectroscopic data on low-lying triplet np and nf Rydberg states from the literature to derive energy- and internuclear-distance-dependent eigenquantum-defect parameters of multichannel quantum-defect theory (MQDT). The MQDT calculations reproduce the experimental data within their experimental uncertainties and enabled the derivation of potential-energy curves for the lowest triplet p Rydberg states (n = 2–5) of He2. The eigenquantum-defect parameters describing the p -f interaction were found to be larger than 0.002 at the energies corresponding to the high-n Rydberg states, so that the p -f interaction plays an important role in the autoionization dynamics of np Rydberg states with v+ = 0. By extrapolating the experimental term values of triplet np Rydberg states of 4He2 in the range of principal quantum number n between 87 and 110, the positions of the (v+ = 0, N+ = 3) and (v+ = 0, N+ = 5) levels of the ground state of 4\documentclass[12pt]{minimal}\begin{document}${\rm He}_2^+$\end{document} He 2+ were determined to lie 70.937(3) cm−1 and 198.369(6) cm−1, respectively, above the (v+ = 0, N+ = 1) ground rotational level.
Time-dependent pseudo Jahn-Teller effect: Phonon-mediated long-time nonadiabatic relaxation
Authors: Vaikjärv Taavi , Hizhnyakov Vladimir
Published: February 2014

Our system under theoretical consideration is an impurity center in a solid. We are considering the time evolution of the center in a quasi-degenerate electronic state. Strict quantum mechanical treatment of non-adiabadicity of the state is used. The phonon continuum is taken into account in addition to the vibration responsible for the main vibronic interaction. To describe the dynamics of the excited state a master equation has been used. The theoretical considerations are illustrated by the calculations of the long-time evolution of vibrations of the center, influenced by the emission of phonons to the bulk.
A novel low-jitter plasma-jet triggered gas switch operated at a low working coefficient
Authors: Tie Weihao , Liu Shanhong , Liu Xuandong , Zhang Qiaogen , Pang Lei , Liu Longchen
Published: February 2014

In this paper, we described the fabrication and testing of a novel plasma-jet triggered gas switch (PJTGS) operated at extremely low working coefficients with excellent triggered jitters. While the structure of the PJTGS is similar to that of a traditional three-electrode field-distortion gas switch, to improve its triggered performance we used a conical micro-plasma-gun with a needle-to-plate spark gap embedded in the trigger electrode. Applying a nanosecond pulse to the trigger electrode caused a spark discharge in the micro-plasma-gun. The electric field drove the discharge plasma to spray into the spark gap of the gas switch, causing fast breakdown. We tested the PJTGS with charging voltages of ±25 kV and a trigger voltage of +80 kV (5 ns rise time and 80 ns full width at half maximum) in two working modes. The PJTGS operated in Mode II had a lower triggered jitter and could be operated over a wider range of working coefficients than in Mode I under the same conditions. At working coefficients higher than 70%, we obtained sub-ns triggered jitters (<0.89 ns) from the PJTGS, at working coefficients lower than 50%, we obtained triggered jitters of 1.6–3.5 ns without no-fires or pre-fires. Even at a working coefficient of 27.4%, the PJTGS could still be triggered reliably with a delay time of 96.1 ns and a triggered jitter of 3.5 ns, respectively.
Magnetic force micropiston: An integrated force/microfluidic device for the application of compressive forces in a confined environment
Authors: Fisher J. K. , Kleckner N.
Published: February 2014

Cellular biology takes place inside confining spaces. For example, bacteria grow in crevices, red blood cells squeeze through capillaries, and chromosomes replicate inside the nucleus. Frequently, the extent of this confinement varies. Bacteria grow longer and divide, red blood cells move through smaller and smaller passages as they travel to capillary beds, and replication doubles the amount of DNA inside the nucleus. This increase in confinement, either due to a decrease in the available space or an increase in the amount of material contained in a constant volume, has the potential to squeeze and stress objects in ways that may lead to changes in morphology, dynamics, and ultimately biological function. Here, we describe a device developed to probe the interplay between confinement and the mechanical properties of cells and cellular structures, and forces that arise due to changes in a structure's state. In this system, the manipulation of a magnetic bead exerts a compressive force upon a target contained in the confining space of a microfluidic channel. This magnetic force microfluidic piston is constructed in such a way that we can measure (a) target compliance and changes in compliance as induced by changes in buffer, extract, or biochemical composition, (b) target expansion force generated by changes in the same parameters, and (c) the effects of compression stress on a target's structure and function. Beyond these issues, our system has general applicability to a variety of questions requiring the combination of mechanical forces, confinement, and optical imaging.
Tetrazole acetic acid: Tautomers, conformers, and isomerization
Authors: Araujo-Andrade C. , Reva I. , Fausto R.
Published: February 2014

Monomers of (tetrazol-5-yl)-acetic acid (TAA) were obtained by sublimation of the crystalline compound and the resulting vapors were isolated in cryogenic nitrogen matrices at 13 K. The conformational and tautomeric composition of TAA in the matrix was characterized by infrared spectroscopy and vibrational calculations carried out at the B3LYP/6-311++G(d,p) level. TAA may adopt two tautomeric modifications, 1H- and 2H-, depending on the position of the annular hydrogen atom. Two-dimensional potential energy surfaces (PESs) of TAA were theoretically calculated at the MP2/6-311++G(d,p) level, for each tautomer. Four and six symmetry-unique minima were located on these PESs, for 1H- and 2H-TAA, respectively. The energetics of the detected minima was subsequently refined by calculations at the QCISD level. Two 1H- and three 2H-conformers fall within the 0–8 kJ mol−1 energy range and should be appreciably populated at the sublimation temperature (∼330 K). Observation of only one conformer for each tautomer (1ccc and 2pcc) is explained in terms of calculated barriers to conformational rearrangements. All conformers with the cis O=COH moiety are separated by low barriers (less than 10 kJ mol−1) and collapse to the most stable 1ccc (1H-) and 2pcc (2H-) forms during deposition of the matrix. On the trans O=COH surfaces, the relative energies are very high (between 12 and 27 kJ mol−1). The trans forms are not thermally populated at the sublimation conditions and were not detected in matrices. One high-energy form in each tautomer, 1cct (1H-) and 2pct (2H-), was found to differ from the most stable form only by rotation of the OH group and separated from other forms by high barriers. This opened a perspective for their stabilization in a matrix. 1cct and 2pct were generated in the matrices selectively by means of narrow-band near-infrared (NIR) irradiations of the samples at 6920 and 6937 cm−1, where the first OH stretching overtone vibrations of 1ccc and 2pcc occur. The reverse transformations could be induced by irradiations at 7010 and 7030 cm−1, transforming 1cct and 2pct back to 1ccc and 2pcc, also selectively. Besides the NIR-induced transformations, the photogenerated 1cct and 2pct forms also decay in N2 matrices back to 1ccc and 2pcc spontaneously, with characteristic decay times of hours (1H) and tens of minutes (2H). The decay mechanism is rationalized in terms of the proton tunneling. In crystals, TAA exists exclusively as 1H-tautomer. By contrast, the tautomeric composition of the matrix-isolated monomers was found to consist of both 1H- and 2H-tautomers, in comparable amounts. A mechanistic discussion of the tautomerization process occurring during sublimation, accounting also for the observed minor decomposition of TAA leading to CO2 and 5-methyl-tetrazole, is proposed.
Large bandwidth op-amp based white noise current source
Authors: Giusi Gino , Scandurra Graziella , Ciofi Carmine
Published: February 2014

Electrical noise sources are basic building blocks in many measurement and instrumentation applications and in communication systems. In this paper, we propose a quite simple topology for the realization of a programmable, wide bandwidth, white noise current source that requires only two resistors and one operational amplifier. We validate the proposed approach by means of SPICE simulations and demonstrate, by means of proper measurements, the capability of generating a flat current noise spectrum in a frequency range up to four decades from a few Hz up to 100 kHz.
Diffraction-induced subradiant transverse-magnetic lattice plasmon modes in metal nanoparticle arrays
Authors: Nikitin Andrey G.
Published: February 2014

This Letter reports theoretical and experimental study of transverse-magnetic-like lattice plasmon modes originating from diffraction in periodic two dimensional arrays of metal nanoparticles. These modes lead to the transmission and reflection spectra exhibiting narrow linewidth Fano-like resonances which can appear as maxima, minima, or can have asymmetric peak-and-dip profile. The dependencies of the position and lineshape of the resonance on the lattice periodicity and angle of incidence are investigated. Numerical simulations of electric field distributions for different excitation conditions of lattice plasmon modes are also performed.
Epitaxial growth of VO2 by periodic annealing
Authors: Tashman J. W. , Lee J. H. , Paik H. , Moyer J. A. , Misra R. , Mundy J. A. , Spila T. , Merz T. A. , Schubert J. , Muller D. A. , Schiffer P. , Schlom D. G.
Published: February 2014

We report the growth of ultrathin VO2 films on rutile TiO2 (001) substrates via reactive molecular-beam epitaxy. The films were formed by the cyclical deposition of amorphous vanadium and its subsequent oxidation and transformation to VO2 via solid-phase epitaxy. Significant metal-insulator transitions were observed in films as thin as 2.3 nm, where a resistance change ΔR/R of 25 was measured. Low angle annular dark field scanning transmission electron microscopy was used in conjunction with electron energy loss spectroscopy to study the film/substrate interface and revealed the vanadium to be tetravalent and the titanium interdiffusion to be limited to 1.6 nm.
Effects of sub-Tg annealing on Cu64.5Zr35.5 glasses: A molecular dynamics study
Authors: Zhang Feng , Mendelev M. I. , Zhang Yue , Wang Cai-Zhuang , Kramer M. J. , Ho Kai-Ming
Published: February 2014

Creating metallic glasses by cooling liquid melts in molecular dynamics simulations faces a well-known challenge that the cooling rate is too fast compared with experiments. Taking the prototypical Cu64.5Zr35.5 glasses as an example, we propose an efficient cooling strategy in which most of the computer time is spent on a prolonged isothermal process slightly below the glass-transition temperature, Tg. The glassy sample prepared in this way demonstrates significant energetic stability, slow dynamics, and well-developed short-range icosahedral order. By conventional uniform cooling, similar properties can only be obtained using a cooling rate more than 15 times slower.
Design of single-mode waveguides for enhanced light-sound interaction in honeycomb-lattice silicon slabs
Authors: Escalante Jose M. , Martínez Alejandro , Laude Vincent
Published: February 2014

We present the design of two waveguides (ladder and slot-ladder waveguides) implemented in a silicon honeycomb photonic-phononic crystal slab, which can support slow electromagnetic and elastic guided modes simultaneously. Interestingly, the photonic bandgap extends along the first Brillouin zone; so with an appropriate design, we can suppress propagation losses that arise coupling to radiative modes. From the phononic point of view, we explain the slow elastic wave effect by considering the waveguide as a chain of coupled acoustic resonators (coupled resonant acoustic waveguide), which provides the mechanism for slow elastic wave propagation. The ladder waveguide moreover supports guided phononic modes outside the phononic bandgap, similar to photonic slab modes, resulting in highly confined phononic modes propagating with low losses. Such waveguides could find important applications to the observation of optomechanical and electrostriction effects, as well as to enhanced stimulated Brillouin scattering and other opto-acoustical effects in nanoscale silicon structures. We also suggest that they can be the basis for a “perfect” photonic-phononic cavity in which damping by coupling to the surroundings is completely forbidden.
Magnetization dynamics of cobalt grown on graphene
Authors: Berger A. J. , Amamou W. , White S. P. , Adur R. , Pu Y. , Kawakami R. K. , Hammel P. C.
Published: February 2014

Ferromagnetic resonance (FMR) spin pumping is a rapidly growing field which has demonstrated promising results in a variety of material systems. This technique utilizes the resonant precession of magnetization in a ferromagnet to inject spin into an adjacent non-magnetic material. Spin pumping into graphene is attractive on account of its exceptional spin transport properties. This article reports on FMR characterization of cobalt grown on chemical vapor deposition graphene and examines the validity of linewidth broadening as an indicator of spin pumping. In comparison to cobalt samples without graphene, direct contact cobalt-on-graphene exhibits increased FMR linewidth—an often used signature of spin pumping. Similar results are obtained in Co/MgO/graphene structures, where a 1 nm MgO layer acts as a tunnel barrier. However, magnetometry, magnetic force microscopy, and Kerr microscopy measurements demonstrate increased magnetic disorder in cobalt grown on graphene, perhaps due to changes in the growth process and an increase in defects. This magnetic disorder may account for the observed linewidth enhancement due to effects such as two-magnon scattering or mosaicity. As such, it is not possible to conclude successful spin injection into graphene from FMR linewidth measurements alone.
Chirality dependent elastic properties of single-walled boron nitride nanotubes under uniaxial and torsional loading
Authors: Anoop Krishnan N. M. , Ghosh Debraj
Published: February 2014

The elastic behavior of single-walled boron nitride nanotubes is studied under axial and torsional loading. Molecular dynamics simulation is carried out with a tersoff potential for modeling the interatomic interactions. Different chiral configurations with similar diameter are considered to study the effect of chirality on the elastic and shear moduli. Furthermore, the effects of tube length on elastic modulus are also studied by considering different aspects ratios. It is observed that both elastic and shear moduli depend upon the chirality of a nanotube. For aspect ratios less than 15, the elastic modulus reduces monotonically with an increase in the chiral angle. For chiral nanotubes, the torsional response shows a dependence on the direction of loading. The difference between the shear moduli against and along the chiral twist directions is maximum for chiral angle of 15°, and zero for zigzag (0°) and armchair (30°) configurations.
The origin of white luminescence from silicon oxycarbide thin films
Authors: Nikas V. , Gallis S. , Huang M. , Kaloyeros A. E. , Nguyen A. P. D. , Stesmans A. , Afanas'ev V. V.
Published: February 2014

Silicon oxycarbide (SiCxOy) is a promising material for achieving strong room-temperature white luminescence. The present work investigated the mechanisms for light emission in the visible/ultraviolet range (1.5–4.0 eV) from chemical vapor deposited amorphous SiCxOythin films, using a combination of optical characterizations and electron paramagnetic resonance(EPR) measurements. Photoluminescence(PL) and EPR studies of samples, with and without post-deposition passivation in an oxygen and forming gas (H2 5 at. % and N2 95 at. %) ambient, ruled out typical structural defects in oxides, e.g., Si-related neutral oxygen vacancies or non-bridging oxygen hole centers, as the dominant mechanism for white luminescence from SiCxOy. The observed intense white luminescence (red, green, and blue emission) is believed to arise from the generation of photo-carriers by optical absorption through C-Si-O related electronic transitions,and the recombination of such carriers between bands and/or at band tail states. This assertion is based on the realization that the PL intensity dramatically increased at an excitation energy coinciding with the E04 band gaps of the material, as well as by the observed correlation between the Si-O-C bond density and the PLintensity. An additional mechanism for the existence of a blue component of the white emission is also discussed.
The relationship between ultrasonic backscatter and trabecular anisotropic microstructure in cancellous bone
Authors: Liu Chengcheng , Ta Dean , Fujita Fuminori , Hachiken Takuma , Matsukawa Mami , Mizuno Katsunori , Wang Weiqi
Published: February 2014

To investigate the relationship between ultrasonic backscatter and trabecular microstructure, ultrasonic backscatter measurements were performed on cylindrical bovine cancellous bone samples in vitro. The backscatter signals from different specimen angles were obtained by rotating the specimen at various central frequencies. The backscatter signal varied a lot as the specimen angle changed. The main trabecular alignment (MTA) orientation was estimated by the maximum of signal energy and integrated reflection coefficient, or the minor axis of fitted ellipse for apparent integrated backscatter and the backscattered spectrum centroid frequency versus specimen angle. The degree of anisotropy (DA) was estimated by the eccentricity of the fitted ellipse with highly significant correlations. The MTA orientation and DA value estimation method proposed in this study is useful for ultrasonic cancellous bone assessment.
Direct hexagonal transition of amorphous (Ge2Sb2Te5)0.9Se0.1 thin films
Authors: Vinod E. M. , Ramesh K. , Ganesan R. , Sangunni K. S.
Published: February 2014

Ge2Sb2Te5 (GST) is well known for its phase change properties and applications in memory and data storage. Efforts are being made to improve its thermal stability and transition between amorphous and crystalline phases. Various elements are doped to GST to improve these properties. In this work, Se has been doped to GST to study its effect on phase change properties. Amorphous GST film crystallized in to rock salt (NaCl) type structure at 150 °C and then transformed to hexagonal structure at 250 °C. Interestingly, Se doped GST ((GST)0.9Se0.1) film crystallized directly into hexagonal phase and the intermediate phase of NaCl is not observed. The crystallization temperature (Tc) of (GST)0.9Se0.1 is around 200 °C, which is 50 °C higher than the Tc of GST. For (GST)0.9Se0.1, the threshold switching occurs at about 4.5 V which is higher than GST (3 V). Band gap (Eopt) values of as deposited films are calculated from Tauc plot which are 0.63 eV for GST and 0.66 eV for (GST)0.9Se0.1. The Eopt decreases for the films annealed at higher temperatures. The increased Tc, Eopt, the contrast in resistance and the direct transition to hexagonal phase may improve the data readability and thermal stability in the Se doped GST film.
Microscopic modulation of mechanical properties in transparent insect wings
Authors: Arora Ashima , Kumar Pramod , Bhagavathi Jithin , Singh Kamal P. , Sheet Goutam
Published: February 2014

We report on the measurement of local friction and adhesion of transparent insect wings using an atomic force microscope cantilever down to nanometre length scales. We observe that the wing-surface is decorated with 10 μm long and 2 μm wide islands that have higher topographic height. The friction on the islands is two orders of magnitude higher than the back-ground while the adhesion on the islands is smaller. Furthermore, the high islands are decorated with ordered nano-wire-like structures while the background is full of randomly distributed granular nano-particles. Coherent optical diffraction through the wings produce a stable diffraction pattern revealing a quasi-periodic organization of the high islands over the entire wing. This suggests a long-range order in the modulation of friction and adhesion which is directly correlated with the topography. The measurements unravel novel functional design of complex wing surface and could find application in miniature biomimetic devices.
Asymmetric actuating structure generates negligible influence on the supporting base for high performance scanning probe microscopies
Authors: Yi Yan Gang , Bin Liu Yong , Hua Feng Zhi
Published: February 2014

An asymmetric actuating structure generating negligible influence on the supporting base for high performance scanning probe microscopies is proposed in this paper. The actuator structure consists of two piezostacks, one is used for actuating while the other is for counterbalancing. In contrast with balanced structure, the two piezostacks are installed at the same side of the supporting base. The effectiveness of the structure is proved by some experiments with the actuators fixed to the free end of a cantilever. Experimental results show that almost all of the vibration modes of the cantilever are suppressed effectively at a wide frequency range of 90 Hz–10 kHz.
Nanoscale nuclei in phase change materials: Origin of different crystallization mechanisms of Ge2Sb2Te5 and AgInSbTe
Authors: Lee Bong-Sub , Shelby Robert M. , Raoux Simone , Retter Charles T. , Burr Geoffrey W. , Bogle Stephanie N. , Darmawikarta Kristof , Bishop Stephen G. , Abelson John R.
Published: February 2014

Phase change memory devices are based on the rapid and reversible amorphous-to-crystalline transformations of phase change materials, such as Ge2Sb2Te5 and AgInSbTe. Since the maximum switching speed of these devices is typically limited by crystallization speed, understanding the crystallization process is of crucial importance. While Ge2Sb2Te5 and AgInSbTe show very different crystallization mechanisms from their melt-quenched states, the nanostructural origin of this difference has not been clearly demonstrated. Here, we show that an amorphous state includes different sizes and number of nanoscale nuclei, after thermal treatment such as melt-quenching or furnace annealing is performed. We employ fluctuation transmission electron microscopy to detect nanoscale nuclei embedded in amorphous materials, and use a pump-probe laser technique and atomic force microscopy to study the kinetics of nucleation and growth. We confirm that melt-quenched amorphous Ge2Sb2Te5 includes considerably larger and more quenched-in nuclei than its as-deposited state, while melt-quenched AgInSbTe does not, and explain this contrast by the different ratio between quenching time and nucleation time in these materials. In addition to providing insights to the crystallization process in these technologically important devices, this study presents experimental illustrations of temperature-dependence of nucleation rate and growth speed, which was predicted by theory of phase transformation but rarely demonstrated.
Properties of ferroelectric/ferromagnetic thin film heterostructures
Authors: Chen Daming , Harward Ian , Linderman Katie , Economou Evangelos , Nie Yan , Celinski Zbigniew
Published: February 2014

Ferroelectric/ferromagnetic thin film heterostructures, SrBi2Ta2O9/BaFe12O19 (SBT/BaM), were grown on platinum-coated Si substrates using metal-organic decomposition. X-ray diffraction patterns confirmed that the heterostructures contain only SBT and BaM phases. The microwave properties of these heterostructures were studied using a broadband ferromagnetic resonance (FMR) spectrometer from 35 to 60 GHz, which allowed us to determine gyromagnetic ratio and effective anisotropy field. The FMR linewidth is as low as140 Oe at 58 GHz. In addition, measurements of the effective permittivity of the heterostructures were carried out as a function of bias electric field. All heterostructures exhibit hysteretic behavior of the effective permittivity. These properties indicate that such heterostructures have potential for application in dual electric and magnetic field tunable resonators, filters, and phase shifters.