bluuebunny/crossref_metadata_2025 huggingface dataset:
Synchrotron-Based Chemical Nano-Tomography of Microbial Cell-Mineral Aggregates in their Natural, Hydrated State
Authors: Schmid Gregor , Zeitvogel Fabian , Hao Likai , Ingino Pablo , Kuerner Wolfgang , Dynes James J. , Karunakaran Chithra , Wang Jian , Lu Yingshen , Ayers Travis , Schietinger Chuck , Hitchcock Adam P. , Obst Martin
Published: February 2014

Chemical nano-tomography of microbial cells in their natural, hydrated state provides direct evidence of metabolic and chemical processes. Cells of the nitrate-reducing Acidovorax sp. strain BoFeN1 were cultured in the presence of ferrous iron. Bacterial reduction of nitrate causes precipitation of Fe(III)-(oxyhydr)oxides in the periplasm and in direct vicinity of the cells. Nanoliter aliquots of cell-suspension were injected into custom-designed sample holders wherein polyimide membranes collapse around the cells by capillary forces. The immobilized, hydrated cells were analyzed by synchrotron-based scanning transmission X-ray microscopy in combination with angle-scan tomography. This approach provides three-dimensional (3D) maps of the chemical species in the sample by employing their intrinsic near-edge X-ray absorption properties. The cells were scanned through the focus of a monochromatic soft X-ray beam at different, chemically specific X-ray energies to acquire projection images of their corresponding X-ray absorbance. Based on these images, chemical composition maps were then calculated. Acquiring projections at different tilt angles allowed for 3D reconstruction of the chemical composition. Our approach allows for 3D chemical mapping of hydrated samples and thus provides direct evidence for the localization of metabolic and chemical processes in situ.
The Importance of Averaging to Interpret Electron Correlographs of Disordered Materials
Authors: Sun Tao , Treacy Michael M.J. , Li Tian , Zaluzec Nestor J. , Murray Gibson J.
Published: February 2014

The development of effective new tools for structural characterization of disordered materials and systems is becoming increasingly important as such tools provide the key to understanding, and ultimately controlling, their properties. The relatively novel technique of correlograph analysis (i.e., the approach of calculating angular autocorrelations within diffraction patterns) promises unique advantages for probing the local symmetries of disordered structures. Because correlograph analysis examines a component of the high-order four-body correlation function, it is more sensitive to medium-range ordering than conventional diffraction methods. As a follow-up of our previous publication, where we studied thin samples of sputtered amorphous silicon, we describe here the practical experimental method and common systematic errors of electron correlograph analysis. Using both experimental data and numerical simulations, we demonstrate that reliable structural information about the sample can only be extracted from the mean correlograph averaged over a sufficient number of individual results.
Multi-Scale Visualization of Dynamic Changes in Poplar Cell Walls During Alkali Pretreatment
Authors: Ji Zhe , Ma Jianfeng , Xu Feng
Published: February 2014

Alkali pretreatment is a promising pretreatment technology that can effectively deconstruct plant cell walls to enhance sugar release performance. In this study, multi-scale visualization of dynamic changes in poplar cell walls during sodium hydroxide pretreatment (2% w/v, 121°C) was carried out by light microscopy (LM), confocal Raman microscopy (CRM) and atomic force microscopy (AFM). LM observations indicated that swelling occurred primarily in the secondary wall (S) but alkali had little effect on the cell corner middle lamella (CCML). Correspondingly, there was a preferential delignification in the S at the beginning of pretreatment, while the level of delignification in CCML (~88%) was higher than that in the S (~83%) for the whole process revealed by Raman spectra. It also suggested that prolonging residence time to 180 min would not remove lignin completely but cause rapid loss of carbohydrates, which was further visualized by Raman spectroscopy images. Furthermore, AFM measurements illustrated that pretreatment with alkali exposed the embedded microfibrils from noncellulosic polymers clearly, enlarged the diameter of microfibrils, and decreased the surface porosity. These results suggested that there was a synergistic mechanism of lignocellulose deconstruction regarding cell wall swelling, main components dissolution, and microfibril morphological changes that occurred during alkali pretreatment.
Liquid Scanning Transmission Electron Microscopy: Imaging Protein Complexes in their Native Environment in Whole Eukaryotic Cells
Authors: Peckys Diana B. , de Jonge Niels
Published: February 2014

Scanning transmission electron microscopy (STEM) of specimens in liquid, so-called Liquid STEM, is capable of imaging the individual subunits of macromolecular complexes in whole eukaryotic cells in liquid. This paper discusses this new microscopy modality within the context of state-of-the-art microscopy of cells. The principle of operation and equations for the resolution are described. The obtained images are different from those acquired with standard transmission electron microscopy showing the cellular ultrastructure. Instead, contrast is obtained on specific labels. Images can be recorded in two ways, either via STEM at 200 keV electron beam energy using a microfluidic chamber enclosing the cells, or via environmental scanning electron microscopy at 30 keV of cells in a wet environment. The first series of experiments involved the epidermal growth factor receptor labeled with gold nanoparticles. The labels were imaged in whole fixed cells with nanometer resolution. Since the cells can be kept alive in the microfluidic chamber, it is also feasible to detect the labels in unfixed, live cells. The rapid sample preparation and imaging allows studies of multiple whole cells.
The Cyborg Astrobiologist: matching of prior textures by image compression for geological mapping and novelty detection
Authors: McGuire P.C. , Bonnici A. , Bruner K.R. , Gross C. , Ormö J. , Smosna R.A. , Walter S. , Wendt L.
Published: February 2014

We describe an image-comparison technique of Heidemann and Ritter (2008a, b), which uses image compression, and is capable of: (i) detecting novel textures in a series of images, as well as of: (ii) alerting the user to the similarity of a new image to a previously observed texture. This image-comparison technique has been implemented and tested using our Astrobiology Phone-cam system, which employs Bluetooth communication to send images to a local laptop server in the field for the image-compression analysis. We tested the system in a field site displaying a heterogeneous suite of sandstones, limestones, mudstones and coal beds. Some of the rocks are partly covered with lichen. The image-matching procedure of this system performed very well with data obtained through our field test, grouping all images of yellow lichens together and grouping all images of a coal bed together, and giving 91% accuracy for similarity detection. Such similarity detection could be employed to make maps of different geological units. The novelty-detection performance of our system was also rather good (64% accuracy). Such novelty detection may become valuable in searching for new geological units, which could be of astrobiological interest. The current system is not directly intended for mapping and novelty detection of a second field site based on image-compression analysis of an image database from a first field site, although our current system could be further developed towards this end. Furthermore, the image-comparison technique is an unsupervised technique that is not capable of directly classifying an image as containing a particular geological feature; labelling of such geological features is donepost factoby human geologists associated with this study, for the purpose of analysing the system's performance. By providing more advanced capabilities for similarity detection and novelty detection, this image-compression technique could be useful in giving more scientific autonomy to robotic planetary rovers, and in assisting human astronauts in their geological exploration and assessment.
Globalisation, Democratisation and the Institutional Transformation of Taiwan's Welfare Regime
Authors: Lue Jen-Der
Published: February 2014

In the context of the discussion about the governance capacity of small states in the world market raised by Katzenstein, the case of East Asian newly industrialised countries is an interesting one. This article takes the development of social policy in Taiwan as a case study through which to explore the role of social policy in the process of rapid industrialisation in small states. It is argued that in the initial phase of industrialisation the productive component of social policy was highlighted by the developmental state to serve the goal of economic development. Social policy functioned at this stage as an effective instrument to dampen the cost of labour and thus contributed to the low-cost strategy of developmental state. Since the 1980s, however, social policy has been profoundly transformed as a consequence of economic globalisation on the one hand and domestic democratisation on the other. It is argued that social policy making since the 1990s in Taiwan has shifted in emphasis from the productive to the consumptive component. Finally, it is suggested that three factors will be decisive in determining Taiwan's social policy in the future: limited governmental revenues, fiscal strain due the public debt problem and the steering capacity of minority governments.
Simulation of heterodyne RoF systems based on 2 DFB lasers: application to an optical phase-locked loop design
Authors: Kassa Wosen-Eshetu , Billabert Anne-Laure , Faci Salim , Algani Catherine
Published: February 2014

This paper presents a simulation approach of optical heterodyne systems by using the equivalent circuit representation of a distributed feedback laser (DFB) in the electrical domain. Since the electrical representation of the DFB laser is developed from the rate equations, its characteristics such as non-linearity, relative intensity noise (RIN), and phase noise can be predicted precisely for various biasing conditions. The model is integrated in a heterodyne radio over fiber (RoF) system where two DFB lasers are used to generate a millimeter-wave (mm-wave) signal. An optical phase-locked loop is also introduced to reduce the phase noise on the mm-wave signal. The optical phase noise contribution of individual lasers to the mm-wave signal is evaluated and compared with theoretical results. It is shown that the phase noise of the mm-wave is reduced considerably depending on the loop bandwidth and propagation delay. With the circuit simulation approach proposed, optical and mm-wave phase noises can be studied together with other circuit environments such as parasitic effects and driver circuits.
Tract-Specific Fractional Anisotropy Predicts Cognitive Outcome in a Community Sample of Middle-Aged Participants with White Matter Lesions
Authors: Soriano-Raya Juan José , Miralbell Júlia , López-Cancio Elena , Bargalló Núria , Arenillas Juan Francisco , Barrios Maite , Cáceres Cynthia , Toran Pere , Alzamora Maite , Dávalos Antoni , Mataró Maria
Published: February 2014

Cerebral white matter lesions (WMLs) have been consistently related to cognitive dysfunction but the role of white matter (WM) damage in cognitive impairment is not fully determined. Diffusion tensor imaging is a promising tool to explain impaired cognition related to WMLs. We investigated the separate association of high-grade periventricular hyperintensities (PVHs) and deep white matter hyperintensities (DWMHs) with fractional anisotropy (FA) in middle-aged individuals. We also assessed the predictive value to cognition of FA within specific WM tracts associated with high-grade WMLs. One hundred participants from the Barcelona-AsIA Neuropsychology Study were divided into groups based on low- and high-grade WMLs. Voxel-by-voxel FA were compared between groups, with separate analyses for high-grade PVHs and DWMHs. The mean FA within areas showing differences between groups was extracted in each tract for linear regression analyses. Participants with high-grade PVHs and participants with high-grade DWMHs showed lower FA in different areas of specific tracts. Areas showing decreased FA in high-grade DWMHs predicted lower cognition, whereas areas with decreased FA in high-grade PVHs did not. The predictive value to cognition of specific WM tracts supports the involvement of cortico-subcortical circuits in cognitive deficits only in DWMHs.
Changes in Human Brain Glutamate Concentration during Hypoglycemia: Insights into Cerebral Adaptations in Hypoglycemia-Associated Autonomic Failure in Type 1 Diabetes
Authors: Terpstra Melissa , Moheet Amir , Kumar Anjali , Eberly Lynn E , Seaquist Elizabeth , Öz Gülin
Published: February 2014

Hypoglycemia-associated autonomic failure (HAAF) is a condition in which patients with type 1 diabetes (T1D) who experience frequent hypoglycemia develop defective glucose counter-regulation and become unable to sense hypoglycemia. Brain glutamate may be involved in the mechanism of HAAF. The goal of this study was to follow the human brain glutamate concentration during experimentally induced hypoglycemia in subjects with and without HAAF. 1H magnetic resonance spectroscopy was used to track the occipital cortex glutamate concentration throughout a euglycemic clamp followed immediately by a hypoglycemic clamp. T1D patients with HAAF were studied in comparison to two control groups, i.e., T1D patients without HAAF and healthy controls ( n = 5 per group). Human brain glutamate concentration decreased ( P≥0.01) after the initiation of hypoglycemia in the two control groups, but a smaller trend toward a decrease in patients with HAAF did not reach significance ( P>0.05). These findings are consistent with a metabolic adaptation in HAAF to provide higher glucose and/or alternative fuel to the brain, eliminating the need to oxidize glutamate. In an exploratory analysis, we detected additional metabolite changes in response to hypoglycemia in the T1D patient without HAAF control group, namely, increased aspartate and decreased lactate.
Tissue Oxygen is Reduced in White Matter of Spontaneously Hypertensive-Stroke Prone Rats: A Longitudinal Study with Electron Paramagnetic Resonance
Authors: Weaver John , Jalal Fakhreya Y , Yang Yi , Thompson Jeffrey , Rosenberg Gary A , Liu Ke J
Published: February 2014

Small vessel disease is associated with white-matter (WM) magnetic resonance imaging (MRI) hyperintensities (WMHs) in patients with vascular cognitive impairment (VCI) and subsequent damage to the WM. Although WM is vulnerable to hypoxic-ischemic injury and O2 is critical in brain physiology, tissue O2 level in the WM has not been measured and explored in vivo. We hypothesized that spontaneously hypertensive stroke-prone rat (SHR/SP) fed a Japanese permissive diet (JPD) and subjected to unilateral carotid artery occlusion (UCAO), a model to study VCI, would lead to reduced tissue oxygen (pO2) in the deep WM. We tested this hypothesis by monitoring WM tissue pO2 using in vivo electron paramagnetic resonance (EPR) oximetry in SHR/SP rats over weeks before and after JPD/UCAO. The SHR/SP rats experienced an increase in WM pO2 from 9 to 12 weeks with a maximal 32% increase at week 12, followed by a dramatic decrease in WM pO2 to near hypoxic conditions during weeks 13 to 16 after JPD/UCAO. The decreased WM pO2 was accompanied with WM damage and hemorrhages surrounding microvessels. Our findings suggest that changes in WM pO2 may contribute to WM damage in SHR/SP rat model, and that EPR oximetry can monitor brain pO2 in the WM of small animals.
Intermittent Fasting Attenuates Increases in Neurogenesis after Ischemia and Reperfusion and Improves Recovery
Authors: Manzanero Silvia , Erion Joanna R , Santro Tomislav , Steyn Frederik J , Chen Chen , Arumugam Thiruma V , Stranahan Alexis M
Published: February 2014

Intermittent fasting (IF) is neuroprotective across a range of insults, but the question of whether extending the interval between meals alters neurogenesis after ischemia remains unexplored. We therefore measured cell proliferation, cell death, and neurogenesis after transient middle cerebral artery occlusion (MCAO) or sham surgery (SHAM) in mice fed ad libitum (AL) or maintained on IF for 3 months. IF was associated with twofold reductions in circulating levels of the adipocyte cytokine leptin in intact mice, but also prevented further reductions in leptin after MCAO. IF/MCAO mice also exhibit infarct volumes that were less than half those of AL/MCAO mice. We observed a 30% increase in basal cell proliferation in the hippocampus and subventricular zone (SVZ) in IF/SHAM, relative to AL/SHAM mice. However, cell proliferation after MCAO was limited in IF mice, which showed twofold increases in cell proliferation relative to IF/SHAM, whereas AL/MCAO mice exhibit fivefold increases relative to AL/SHAM. Attenuation of stroke-induced neurogenesis was correlated with reductions in cell death, with AL/MCAO mice exhibiting twice the number of dying cells relative to IF/MCAO mice. These observations indicate that IF protects against neurological damage in ischemic stroke, with circulating leptin as one possible mediator.
Evaluating Systems Pharmacology Models Is Different From Evaluating Standard Pharmacokinetic–Pharmacodynamic Models
Authors: Agoram B
Published: February 2014

Based on the author's recent experience, there appears to be some confusion regarding the steps required to qualify a systems pharmacology model as adequate for the intended purpose. This manuscript outlines the model evaluation approach used in the author's recent publication1 on the systems pharmacology of a 5‐lipoxygenase inhibitor and is an attempt to generate discussion on this topic within the pharmacometrics and systems pharmacology community.

CPT Pharmacometrics Syst. Pharmacol. (2014) 3, e101; doi:10.1038/psp.2013.77; published online 19 February 2014
When two symmetrically independent molecules must be different: “Crystallization-induced diastereomerization” of chiral pinanyl sulfone
Authors: Lodochnikova Olga A. , Startseva Valeriya A. , Nikitina Liliya E. , Bodrov Andrei V. , Klimovitskii Alexander E. , Klimovitskii Evgenii N. , Litvinov Igor A.
Published: February 2014

The stereochemical transformation accompanying crystallization of homochiral pinanyl sulfone has been studied.
Alkoxyallenes as building blocks for organic synthesis
Authors: Zimmer Reinhold , Reissig Hans-Ulrich
Published: February 2014

This Tutorial Review demonstrates the synthetic versatility of alkoxyallenes and the use of synthons derived from these C3 building blocks.
Developing Demonstration Test Catchments as a platform for transdisciplinary land management research in England and Wales
Authors: McGonigle D. F. , Burke S. P. , Collins A. L. , Gartner R. , Haft M. R. , Harris R. C. , Haygarth P. M. , Hedges M. C. , Hiscock K. M. , Lovett A. A.
Published: February 2014

This paper describes a research platform approach that has been developed in England to bring together researchers and stakeholders from a wide range of institutions to undertake multi-disciplinary, catchment-scale research on approaches to tackle agricultural water pollution.
Enhanced hydrogen desorption of an ammonia borane and lithium hydride system through synthesised intermediate compounds
Authors: Wang Yiwen , Guo Z. X.
Published: February 2014

Low energy mixing and higher LiH content effectively destabilize AB for enhanced hydrogen release at a desirable temperature.
Platinum@regular indium oxide nanooctahedra as difunctional counter electrodes for dye-sensitized solar cells
Authors: Zhang Bo , Li Yu Hang , Zhong Ju Hua , Yang Xiao Hua , Zhang Hai Min , Zhao Hui Jun , Yang Hua Gui
Published: February 2014

A difunctional counter electrode composed of platinum nanoparticles supported on regular In2O3nanooctahedra demonstrates good catalytic activity and excellent light scattering.
Oxygen-mediated enzymatic polymerization of thiol–ene hydrogels
Authors: Zavada S. R. , McHardy N. R. , Scott T. F.
Published: February 2014

Aqueous thiol–ene solutions formulated with enzymatic radical initiation systems polymerize to form hydrogels exclusively upon oxygen exposure.
Non-covalent functionalization of carbon nanotubes with boronic acids for the wiring of glycosylated redox enzymes in oxygen-reducing biocathodes
Authors: Reuillard Bertrand , Le Goff Alan , Holzinger Michael , Cosnier Serge
Published: February 2014

Easy covalent binding and efficient electrical wiring of enzymes onto carbon nanotube deposits by pyrene-boronic acid derivatives.
Chemical imaging of artificial fingerprints by desorption electro-flow focusing ionization mass spectrometry
Authors: Forbes Thomas P. , Sisco Edward
Published: February 2014

Artificial fingerprints, comprised of endogenous material and trace exogenous compounds, were imaged using desorption electro-flow focusing ionization mass spectrometry.
Synthesis of NaYF4:Yb–Tm thin film with strong NIR photon up-conversion photoluminescence using electro-deposition method
Authors: Jia Hong , Xu Cheng , Wang Juecheng , Chen Ping , Liu Xiaofeng , Qiu Jianrong
Published: February 2014

The NaYF4:20%Yb–2%Tm thin film prepared by electro-deposition shows strong UC photoluminescence.
Human serum albumin binding to silica nanoparticles – effect of protein fatty acid ligand
Authors: Ang Joo Chuan , Henderson Mark J. , Campbell Richard A. , Lin Jhih-Min , Yaron Peter N. , Nelson Andrew , Faunce Thomas , White John W.
Published: February 2014

Fat containing and defatted human serum albumin adsorption to silica nanoparticles have different structures and time dependence to form.
Advanced thermoelectrics governed by a single parabolic band: Mg2Si0.3Sn0.7, a canonical example
Authors: Liu Wei , Chi Hang , Sun Hui , Zhang Qiang , Yin Kang , Tang Xinfeng , Zhang Qingjie , Uher Ctirad
Published: February 2014

Enhanced thermoelectric performance of Bi-doped Mg2Si0.3Sn0.7 with conduction band convergence has been successfully interpreted using the single parabolic band (SPB) model. The improved understanding of scattering parameters is important and instructive for further optimization of n-type Mg2Si0.3Sn0.7.
Multicomponent reactions: advanced tools for sustainable organic synthesis
Authors: Cioc Răzvan C. , Ruijter Eelco , Orru Romano V. A.
Published: February 2014

This review discusses the utility of multicomponent reactions as green chemistry methods.
Insights on recyclable catalytic system composed of task-specific ionic liquids for the chemical fixation of carbon dioxide
Authors: Girard Anne-Lise , Simon Nathália , Zanatta Marcileia , Marmitt Sandro , Gonçalves Paulo , Dupont Jairton
Published: February 2014

Several imidazolium ionic liquids display high efficiency as catalysts for the sequential oxidation of alkene and carboxylation of epoxide.
Insitu grown graphitic carbon/Fe2O3/carbon nanofiber composites for high performance freestanding anodes in Li-ion batteries
Authors: Zhang Biao , Xu Zheng-Long , Kim Jang-Kyo
Published: February 2014

C/Fe2O3/CNF composites are produced through a one-pot electrospinning process. The onion-shaped graphene coating layer not only prevents the Fe2O3 particles from peeling off from the carbon nanofiber substrate, but also it buffers the volume change of Fe2O3 and improves the conductivity of the electrode.
Recent advances in 4(3H)-quinazolinone syntheses
Authors: He Lin , Li Haoquan , Chen Jianbin , Wu Xiao-Feng
Published: February 2014

The new routes and strategies for the synthesis of valuable 4(3H)-quinazolinones have been summarized.
Amine-functionalized metal-organic frameworks for the transesterification of triglycerides
Authors: Chen Jinzhu , Liu Ruliang , Gao Hui , Chen Limin , Ye Daiqi
Published: February 2014

Amine-functionalized metal–organic frameworks are used as a solid base for the transesterification of triglycerides with methanol.
Combination of geometric clustering and nonlocal means for SAR image despeckling
Authors: Feng Wensen , Lei Hong
Published: February 2014

Recently, nonlocal filtering methods for synthetic aperture radar (SAR) despeckling have attracted a lot of attention. In general, a suitable similarity measure well suited to SAR images is derived by incorporating the noise statistics. One important nonlocal framework is the probabilistic patch‐based (PPB) filter, which derives the similarity measure in a data‐driven way and provides promising results. A drawback of this filter is the suppression of thin and dark details since the PPB method takes into account the photometrically similar patches, yet it ignores the geometric structure of image patches. To overcome these disadvantages, a new patch‐based despeckling method is presented which exploits both geometrical and photometrical similarities. Numerical experiments suggest that the proposed method is on a par with or exceeds the state‐of‐the‐art PPB method, both visually and quantitatively.
Laboratory transferability of optimally shaped laser pulses for quantum control
Authors: Moore Tibbetts Katharine , Xing Xi , Rabitz Herschel
Published: February 2014

Optimal control experiments can readily identify effective shaped laser pulses, or “photonic reagents,” that achieve a wide variety of objectives. An important additional practical desire is for photonic reagent prescriptions to produce good, if not optimal, objective yields when transferred to a different system or laboratory. Building on general experience in chemistry, the hope is that transferred photonic reagent prescriptions may remain functional even though all features of a shaped pulse profile at the sample typically cannot be reproduced exactly. As a specific example, we assess the potential for transferring optimal photonic reagents for the objective of optimizing a ratio of photoproduct ions from a family of halomethanes through three related experiments. First, applying the same set of photonic reagents with systematically varying second- and third-order chirp on both laser systems generated similar shapes of the associated control landscape (i.e., relation between the objective yield and the variables describing the photonic reagents). Second, optimal photonic reagents obtained from the first laser system were found to still produce near optimal yields on the second laser system. Third, transferring a collection of photonic reagents optimized on the first laser system to the second laser system reproduced systematic trends in photoproduct yields upon interaction with the homologous chemical family. These three transfers of photonic reagents are demonstrated to be successful upon paying reasonable attention to overall laser system characteristics. The ability to transfer photonic reagents from one laser system to another is analogous to well-established utilitarian operating procedures with traditional chemical reagents. The practical implications of the present results for experimental quantum control are discussed.
Nanostructured VO2 film with high transparency and enhanced switching ratio in THz range
Authors: Shi Qiwu , Huang Wanxia , Lu Tiecheng , Zhang Yaxin , Yue Fang , Qiao Shen , Xiao Yang
Published: February 2014

We investigated the terahertz (THz) transmission characteristics of semiconductor VO2 film and its THz suppression behavior after the phase transition. The VO2 films were deposited by the sol-gel method, and an in situ growth with surface nanocrystallization occurring in the films with increasing thickness was presented. Morphology-induced percolation leads to high THz transparency in the semiconductor VO2 film, and the more compact nanostructure could account for the enhanced THz switching ratio in the metallic film. These results may offer insights into the artificial design of VO2 films for THz device applications.
Energy transfer between a nanosystem and its host fluid: A multiscale factorization approach
Authors: Sereda Yuriy V. , Espinosa-Duran John M. , Ortoleva Peter J.
Published: February 2014

Energy transfer between a macromolecule or supramolecular assembly and a host medium is considered from the perspective of Newton's equations and Lie-Trotter factorization. The development starts by demonstrating that the energy of the molecule evolves slowly relative to the time scale of atomic collisions-vibrations. The energy is envisioned to be a coarse-grained variable that coevolves with the rapidly fluctuating atomistic degrees of freedom. Lie-Trotter factorization is shown to be a natural framework for expressing this coevolution. A mathematical formalism and workflow for efficient multiscale simulation of energy transfer is presented. Lactoferrin and human papilloma virus capsid-like structure are used for validation.
Straight-line climbing flight aerodynamics of a fruit bat
Authors: Viswanath K. , Nagendra K. , Cotter J. , Frauenthal M. , Tafti D. K.
Published: February 2014

From flight data obtained on a fruit bat, Cynopterus brachyotis, a kinematic model for straight-line flapping motion is extracted and analyzed in a computational fluid dynamics (CFD) framework to gain insight into the complexity of bat flight. The intricate functional mechanics and architecture of the bat wings set it apart from other vertebrate flight. The extracted kinematic model is simulated for a range of Reynolds numbers, to observe the effect these phenomena have on the unsteady transient mechanisms of the flow produced by the flapping wings. The Strouhal number calculated from the data is high indicating that the oscillatory motion dominates the flow physics. From the obtained data, the bat exhibits fine control of its mechanics by actively varying wing camber, wing area, torsional rotation of the wing, forward and backward translational sweep of the wing, and wing conformation to dictate the fluid dynamics. As is common in flapping flight, the primary force generation is through the attached unsteady vortices on the wing surface. The bat through varying the wing camber and the wing area modulates this force output. The power requirement for the kinematics is analyzed and correlated with the aerodynamic performance.
Degenerate Ising model for atomistic simulation of crystal-melt interfaces
Authors: Schebarchov D. , Schulze T. P. , Hendy S. C.
Published: February 2014

One of the simplest microscopic models for a thermally driven first-order phase transition is an Ising-type lattice system with nearest-neighbour interactions, an external field, and a degeneracy parameter. The underlying lattice and the interaction coupling constant control the anisotropic energy of the phase boundary, the field strength represents the bulk latent heat, and the degeneracy quantifies the difference in communal entropy between the two phases. We simulate the (stochastic) evolution of this minimal model by applying rejection-free canonical and microcanonical Monte Carlo algorithms, and we obtain caloric curves and heat capacity plots for square (2D) and face-centred cubic (3D) lattices with periodic boundary conditions. Since the model admits precise adjustment of bulk latent heat and communal entropy, neither of which affect the interface properties, we are able to tune the crystal nucleation barriers at a fixed degree of undercooling and verify a dimension-dependent scaling expected from classical nucleation theory. We also analyse the equilibrium crystal-melt coexistence in the microcanonical ensemble, where we detect negative heat capacities and find that this phenomenon is more pronounced when the interface is the dominant contributor to the total entropy. The negative branch of the heat capacity appears smooth only when the equilibrium interface-area-to-volume ratio is not constant but varies smoothly with the excitation energy. Finally, we simulate microcanonical crystal nucleation and subsequent relaxation to an equilibrium Wulff shape, demonstrating the model's utility in tracking crystal-melt interfaces at the atomistic level.
Flow and heat transfer enhancement in condensing water drops in steam flows
Authors: Yang Zhen , Duan Yuan-Yuan , Zhu Zhao , Gong Wei , Ma Xiao-Chen , Chen Ying , Wu Di
Published: February 2014

Internal flow and heat transfer enhancement were experimentally and numerically investigated for 0.1- to 1-mm-sized water drops condensing in steam flows. The experimental data and computational fluid dynamics results are in agreement, showing that the external steam flow causes an internal flow in the drops via viscous shearing at the liquid-vapor interface. The velocity of the internal flow is only several percent of that of the external flow, but it enhances heat transfer by up to 117%. The effects of steam flow on heat transfer increase as the contact angle or the size of the drop increases.
Highly mobile segments in crystalline poly(ethylene oxide)8:NaPF6 electrolytes studied by solid-state NMR spectroscopy
Authors: Luo Huan , Liang Xinmiao , Wang Liying , Zheng Anmin , Liu Chaoyang , Feng Jiwen
Published: February 2014

Two types of high-crystallinity poly(ethylene oxide)/NaPF6 electrolytes with ethylene oxide (EO)/Na molar ratios of 8:1 and 6:1, termed as PEO8:NaPF6 and PEO6:NaPF6 with Mw = 6000 g mol−1 were prepared, and their ionic conductivity, structure, and segmental motions were investigated and compared. PEO8:NaPF6 polymer electrolyte exhibits the room-temperature ionic conductivity 7.7 × 10−7 S cm−1 which is about five times higher than the PEO6:NaPF6. By variable-temperature measurements of static powder spectra and 1H spin-lattice relaxation time in rotation frame (1H T1ρ), we demonstrate that crystalline segments are more highly mobile in the crystalline PEO8:NaPF6 with higher ionic conductivity than in the PEO6:NaPF6 with lower ionic conductivity. The large-angle reorientation motion of polymer segments in the PEO8:NaPF6 onsets at lower temperature (∼233 K) with a low activation energy 0.31 eV that is comparable with that of the pure PEO crystal. Whereas, the large-angle reorientation motion of polymer segments in the PEO6:NaPF6 starts around 313 K with a high activation energy of 0.91 eV. As a result of the temperature-enhanced large-angle reorientations, the 13C static powder lineshape changes markedly from a low-temperature wide pattern with apparent principal values of chemical shift δ33 < δ22 < δ11 to a high-temperature narrow pattern of uniaxial chemical shift anisotropy δ33 > δ22 (δ11). It is suggested that the segmental motion in crystalline PEO-salt complex promotes ionic conductivity.
Enhancement of surface phonon modes in the Raman spectrum of ZnSe nanoparticles on adsorption of 4-mercaptopyridine
Authors: Islam Syed K. , Lombardi John R.
Published: February 2014

By chemically etching a thin film of crystalline ZnSe with acid, we observe a strong Raman enhancement of the surface phonon modes of ZnSe on adsorption of a molecule (4-mercaptopyridine). The surface is composed of oblate hemi-ellipsoids, which has a large surface-to-bulk ratio. The assignment of the observed modes (at 248 and 492 cm−1) to a fundamental and first overtone of the surface optical mode is consistent with observations from high-resolution electron energy loss spectroscopy as well as calculations.
Melting temperatures of H2O up to 72 GPa measured in a diamond anvil cell using CO2 laser heating technique
Authors: Kimura T. , Kuwayama Y. , Yagi T.
Published: February 2014

The melting curve of H2O from 49 to 72 GPa was determined by using a laser-heated diamond anvil cell. Double-sided CO2 laser heating technique was employed in order to heat the sample directly. Discontinuous changes of the heating efficiency attributed to the H2O melting were observed between 49 and 72 GPa. The obtained melting temperatures at 49 and 72 GPa are 1200 and 1410 K, respectively. We found that the slope of the melting curve significantly decreases with increasing pressure, only 5 K/GPa at 72 GPa while 44 K/GPa at 49 GPa. Our results suggest that the melting curve does not intersect with the isentropes of Uranus and Neptune, and hence, H2O should remain in the liquid state even at the pressure and temperature conditions found deep within Uranus and Neptune.
Design of sub-1g microelectromechanical systems accelerometers
Authors: Yamane D. , Konishi T. , Matsushima T. , Machida K. , Toshiyoshi H. , Masu K.
Published: February 2014

This paper presents a design of microelectromechanical systems (MEMS) accelerometers for sensing sub-1g (g = 9.8 m/s2) acceleration. The accelerometer has a high-density proof mass to suppress the Brownian noise that dominates the output noise of the sensor. The low-temperature (<400 °C) process enables to integrate the accelerometer on the sensing complementary metal-oxide semiconductor circuit by electroplating of gold; a proof mass of 1020 μm × 1020 μm in area with the thickness of 12 μm has been found to suppress the measured noise floor to 0.78 μg/Hz at 300 K, which is nearly one order of magnitude smaller than those of the conventional MEMS accelerometers made of silicon.
Phase behavior and dynamics of a cholesteric liquid crystal
Authors: Roy D. , Fragiadakis D. , Roland C. M. , Dabrowski R. , Dziaduszek J. , Urban S.
Published: February 2014

The synthesis, equation of state, phase diagram, and dielectric relaxation properties are reported for a new liquid crystal, 4′-butyl-4-(2-methylbutoxy)azoxybenzene (4ABO5*), which exhibits a cholesteric phase at ambient temperature. The steepness of the intermolecular potential was characterized from the thermodynamic potential parameter, Γ = 4.3 ± 0.1 and the dynamic scaling exponent, γ = 3.5 ± 0.2. The difference between them is similar to that seen previously for nematic and smectic liquid crystals, with the near equivalence of Γ and γ consistent with the near constancy of the relaxation time of 4ABO5* at the cholesteric to isotropic phase transition (i.e., the clearing line). Thus, chirality does not cause deviations from the general relationship between thermodynamics and dynamics in the ordered phase of liquid crystals. The ionic conductivity of 4ABO5* shows strong coupling to the reorientational dynamics.
Thickness dependence of room temperature ferromagnetism observed in Fe-doped NiO thin films
Authors: Zhang Yu-Jun , Luo Yi-Dong , Lin Yuan-Hua , Nan Ce-Wen
Published: February 2014

We synthesized Fe-doped NiO thin films on SrTiO3(100) substrate with different thicknesses by a pulsed laser deposition method. An obvious room-temperature ferromagnetism can be observed in these films and the ferromagnetism is closely dependent on the film thickness. Our results indicate that the saturated magnetization can be greatly enhanced as the film thickness increases, which may be ascribed to the defects and strain induced by the substrate, resulting effective ferromagnetic exchange interaction of the NiO films.
Eckart frame vibration-rotation Hamiltonians: Contravariant metric tensor
Authors: Pesonen Janne
Published: February 2014

Eckart frame is a unique embedding in the theory of molecular vibrations and rotations. It is defined by the condition that the Coriolis coupling of the reference structure of the molecule is zero for every choice of the shape coordinates. It is far from trivial to set up Eckart kinetic energy operators (KEOs), when the shape of the molecule is described by curvilinear coordinates. In order to obtain the KEO, one needs to set up the corresponding contravariant metric tensor. Here, I derive explicitly the Eckart frame rotational measuring vectors. Their inner products with themselves give the rotational elements, and their inner products with the vibrational measuring vectors (which, in the absence of constraints, are the mass-weighted gradients of the shape coordinates) give the Coriolis elements of the contravariant metric tensor. The vibrational elements are given as the inner products of the vibrational measuring vectors with themselves, and these elements do not depend on the choice of the body-frame. The present approach has the advantage that it does not depend on any particular choice of the shape coordinates, but it can be used in conjunction with allshape coordinates. Furthermore, it does not involve evaluation of covariant metric tensors, chain rules of derivation, or numerical differentiation, and it can be easily modified if there are constraints on the shape of the molecule. Both the planar and non-planar reference structures are accounted for. The present method is particular suitable for numerical work. Its computational implementation is outlined in an example, where I discuss how to evaluate vibration-rotation energies and eigenfunctions of a general N-atomic molecule, the shape of which is described by a set of local polyspherical coordinates.
Direct current tunable noise suppressor using sub-micrometer patterned permalloy films
Authors: Farid Rahman B. M. , Divan Ralu , Zhang Hanqiao , Rosenmann Daniel , Peng Yujia , Wang Xuehe , Wang Guoan
Published: February 2014

A tunable noise suppressor at gigahertz frequency using sub-micrometer patterned Permalloy (Py) loaded coplanar waveguide transmission line is presented. The transmission line consists of 100 nm thick Py patterns on top of 0.9 μm thick gold lines. Measured results show that the stop band frequency of the noise suppressor is changed from 4.8 GHz to 6 GHz depending on the aspect ratios of Py patterns. Variation of the gap in between Py patterns changed the stop band frequency from 4 GHz to 6 GHz. Furthermore, a novel way of tuning the stop band frequency of the noise suppressor by using an external direct current is reported. By applying 150 mA direct current along the transmission line, the frequency is changed from 6 GHz to 4.3 GHz. The measured results of 1.5% pass band loss, 2° transmitted signal phase distortion, and 3 dB extra return loss of the designed noise suppressor are demonstrated. Noise suppression frequency and the magnitude of signal attenuation can be further improved by increasing the thickness of Py or using multi-layer Py.
Multilevel unipolar resistive memory switching in amorphous SmGdO3 thin film
Authors: Sharma Yogesh , Misra Pankaj , Pavunny Shojan P. , Katiyar Ram S.
Published: February 2014

Multilevel resistive switching was observed in random access memory device using amorphous SmGdO3 (SGO) ternary oxide thin films. Non-volatile and stable 4-level resistance states with sufficient margin of resistance ratios were observed by varying compliance current which was attributed to compliance current dependent variation in size of conducting filaments. As fabricated Pt/SGO/Pt devices exhibited excellent switching parameters such as stable resistance ratios of reset (ON) to set (OFF) states, non-overlapping switching voltages, excellent data retention, and endurance. Temperature dependent variation of resistances of ON and OFF states of the device was studied to elucidate current conduction and resistive switching mechanisms.
Temperature dependence of interlayer coupling between perpendicular magnetic [CoFeB/Pd] multilayers: Influence of interfacial CoFeB layer
Authors: Xiao Yili , Zhang Zongzhi , Ma Bin , Jin Q. Y. , Liu Yaowen
Published: February 2014

Temperature dependence of interlayer coupling field in the perpendicular antiferromagnetic structure of [Pd/CoFeB]2/Pd/CoFeB(tCFB)/Ru(tRu)/CoFeB(tCFB)/Pd/[CoFeB/Pd]2 is found to be sensitive to tCFB, showing various non-monotonic behaviors. The coupling strength increases with tCFB, reaching bulk-like value of up to 0.28 erg/cm2 at room temperature as tCFB is over 0.6 nm. We attribute the phenomena to interfacial effects, including lowered Curie temperature in ultrathin CoFeB layers and increased effective dead layer thickness. The coupling peak position of tRu also shifts with temperature and tCFB, corresponding to variations in dead layer thicknesses. These effects should be considered when designing practical devices employing perpendicular synthetic antiferromagnetic structures.
Plasmon-enhanced terahertz emission from a semiconductor/metal interface
Authors: Ramakrishnan Gopakumar , Kumar Nishant , Ramanandan Gopika K. P. , Adam Aurèle J. L. , Hendrikx Ruud W. A. , Planken Paul C. M.
Published: February 2014

Terahertz emission by ultrafast optical excitation of semiconductor/metal interfaces strongly depends on the strength of the depletion-field. Here, we report on the strong enhancement of the emission after optical excitation of surface plasmons at these interfaces. The enhancement is caused by the plasmonic localization of the pump light near the metal surface, where the depletion-field is the strongest. Compared to the case where no surface plasmons are excited, a terahertz field enhancement of more than an order of magnitude is obtained for a particular thickness of cuprous oxide layer on gold, where localized surface plasmons are excited at the interface.
A truly hyperbolic elastic metamaterial lens
Authors: Oh Joo Hwan , Min Seung Hong , Young Kim Yoon
Published: February 2014

Sub-wavelength imaging is possible if metamaterial lenses realizing hyperbolic or elliptic Equi-Frequency Contours (EFCs) are used. Theoretically, lenses exhibiting hyperbolic EFCs allow imaging with unlimited resolution, but only metamaterials of elliptic EFCs producing limited resolution have been so far realized in elastic field. Thus, an elastic metamaterial lens realizing truly hyperbolic EFCs can lead to superior-resolution ultrasonic imaging. This Letter presents the realization of an elastic lens exhibiting truly hyperbolic EFCs and its experimental verification.
Optimizing the internal electric field distribution of alternating current driven organic light-emitting devices for a reduced operating voltage
Authors: Fröbel Markus , Hofmann Simone , Leo Karl , Gather Malte C.
Published: February 2014

The influence of the thickness of the insulating layer and the intrinsic organic layer on the driving voltage of p-i-n based alternating current driven organic light-emitting devices (AC-OLEDs) is investigated. A three-capacitor model is employed to predict the basic behavior of the devices, and good agreement with the experimental values is found. The proposed charge regeneration mechanism based on Zener tunneling is studied in terms of field strength across the intrinsic organic layers. A remarkable consistency between the measured field strength at the onset point of light emission (3–3.1 MV/cm) and the theoretically predicted breakdown field strength of around 3 MV/cm is obtained. The latter value represents the field required for Zener tunneling in wide band gap organic materials according to Fowler-Nordheim theory. AC-OLEDs with optimized thickness of the insulating and intrinsic layers show a reduction in the driving voltage required to reach a luminance of 1000 cd/m2 of up to 23% (8.9 V) and a corresponding 20% increase in luminous efficacy.
Evidence of the metal-insulator transition in ultrathin unstrained V2O3 thin films
Authors: Dillemans L. , Smets T. , Lieten R. R. , Menghini M. , Su C.-Y. , Locquet J.-P.
Published: February 2014

We report the strain state and transport properties of V2O3 layers and V2O3/Cr2O3 bilayers deposited by molecular beam epitaxy on (0001)-Al2O3. By changing the layer on top of which V2O3 is grown, we change the lattice parameters of ultrathin V2O3 films significantly. We find that the metal-insulator transition is strongly attenuated in ultrathin V2O3 layers grown coherently on Al2O3. This is in contrast with ultrathin V2O3 layers grown on Cr2O3 buffer layers, where the metal-insulator transition is preserved. Our results provide evidence that the existence of the transition in ultrathin films is closely linked with the lattice deformation.