bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron impact scattering by SF6 molecule over an extensive energy range
Authors: Goswami Biplab , Antony Bobby
Published: June 2014

Theoretical elastic and inelastic cross sections for e-SF6 scattering over 0.1–5000 eV energies are reported employing R-matrix and SCOP formalisms.
Amorphous nickel–boron and nickel–manganese–boron alloy as electrochemical pseudocapacitor materials
Authors: Zhang Wei , Tan Yueyue , Gao Yilong , Wu Jianxiang , Tang Bohejin , Zhao Jiachang
Published: June 2014

The nanoparticles of amorphous Ni–B and Ni–Mn–B alloys are synthesized and investigated as electrochemical pseudocapacitor materials for potential energy storage applications.
Facile quantitative comparison of specific activities of fusion-tagged enzyme/mutants in cell lysates via prediction of their maximum adsorption by anti-tag antibody immobilized in microplate wells
Authors: Li Y. L. , Yang X. L. , He C. X. , Hu X. L. , Pu J. , Liu L. , Long G. B. , Liao F.
Published: June 2014

Maximum activities of 6His-tagged enzyme/mutants from lysates adsorbed on immobilized anti-tag antibody were predicted as specific activities for comparison.
Polyaniline-wrapped 1D CoMoO4·0.75H2O nanorods as electrode materials for supercapacitor energy storage applications
Authors: Mandal Manas , Ghosh Debasis , Giri Soumen , Shakir Imran , Das Chapal Kumar
Published: June 2014

In this study, a simple and cost effective hydrothermal process followed by in situ oxidative polymerization has been carried out for the synthesis of CoMoO4·0.75H2O/PANI composite.
Electrospun hybrid fibers with substantial filler contents formed through kinetically arrested phase separation in liquid jet
Authors: Fan Jizhou , Liu Jianzhao , Bauer Adam J. P. , Uthaisar Chananate , Zeng Tingying , Wang Chao , Zhang Mingqiang , Fahs Gregory , Esker Alan , Moore Robert B. , Gao Feng , Li Bingbing
Published: June 2014

This study reports polyhedral oligomeric silsesquioxane (POSS)-based hybrid fibers of architectural hierarchy and compositional heterogeneity.
Vapour-based processing of hole-conductor-free CH3NH3PbI3 perovskite/C60 fullerene planar solar cells
Authors: Hu Hao , Wang Dong , Zhou Yuanyuan , Zhang Jiliang , Lv Siliu , Pang Shuping , Chen Xiao , Liu Zhihong , Padture Nitin P. , Cui Guanglei
Published: June 2014

High quality CH3NH3PbI3 perovskite films deposited using a new sequential vapour deposition method enables the all-vapour fabrication of efficient, hole-conductor-free CH3NH3PbI3 perovskite/C60 fullerene solar cells.
Experimental and theoretical studies on the mechanism for chemical oxidation of multiwalled carbon nanotubes
Authors: Maciejewska B. M. , Jasiurkowska-Delaporte M. , Vasylenko A. I. , Kozioł K. K. , Jurga S.
Published: June 2014

In this study, the oxidation of multiwalled carbon nanotubes (MWCNTs) sonicated and/or refluxed in acids (H2SO4/HNO3) was investigated using a combination of high-resolution transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, andab initiocomputational methods.
Fluorescent calix[4]arene chemosensor for acidic and basic amino acids in pure aqueous media
Authors: Xu Yao-Wei , Tan Li-Lin , Liu Jun-Min , Xiao Li-Min , Li Shao-Yong , Su Cheng-Yong
Published: June 2014

A fluorescent calix[4]arene chemosensor 2 displays high sensitivity toward acidic and basic amino acids in aqueous media through multiple H-bond interactions.
Variations of interlayer spacing in carbon nanotubes
Authors: Kharissova Oxana V. , Kharisov Boris I.
Published: June 2014

The analysis of previous classic and recent reports on the interlayer distances in MWCNTs is described in this review.
Efficiently suppressed thermal conductivity in ZnO thin films via periodic introduction of organic layers
Authors: Tynell Tommi , Giri Ashutosh , Gaskins John , Hopkins Patrick E. , Mele Paolo , Miyazaki Koji , Karppinen Maarit
Published: June 2014

A significant reduction in thermal conductivity is demonstrated upon incorporation of single layers of hydroquinone within ZnO or (Zn0.98Al0.02)O thin films to form hybrid inorganic–organic superlattice structures.
Dual-core@shell-structured Fe3O4–NaYF4@TiO2nanocomposites as a magnetic targeting drug carrier for bioimaging and combined chemo-sonodynamic therapy
Authors: Shen Song , Guo Xiaomeng , Wu Lin , Wang Meng , Wang Xinshi , Kong Fenfen , Shen Haijun , Xie Meng , Ge Yanru , Jin Yi
Published: June 2014

Dual-core@shell-structured Fe3O4–NaYF4@TiO2nanocomposites as a magnetic targeting drug carrier for bioimaging and combined chemo-sonodynamic therapy.
The neurotoxicity of 5-S-cysteinyldopamine is mediated by the early activation of ERK1/2 followed by the subsequent activation of ASK1/JNK1/2 pro-apoptotic signalling
Authors: Vauzour David , Pinto John T. , Cooper Arthur J. L. , Spencer Jeremy P. E.
Published: June 2014

Parkinson's disease is characterized by the progressive and selective loss of dopaminergic neurons in the substantia nigra. It has been postulated that endogenously formed CysDA (5-S-cysteinyldopamine) and its metabolites may be, in part, responsible for this selective neuronal loss, although the mechanisms by which they contribute to such neurotoxicity are not understood. Exposure of neurons in culture to CysDA caused cell injury, apparent 12–48 h post-exposure. A portion of the neuronal death induced by CysDA was preceded by a rapid uptake and intracellular oxidation of CysDA, leading to an acute and transient activation of ERK2 (extracellular-signal-regulated kinase 2) and caspase 8. The oxidation of CysDA also induced the activation of apoptosis signal-regulating kinase 1 via its de-phosphorylation at Ser967, the phosphorylation of JNK (c-Jun N-terminal kinase) and c-Jun (Ser73) as well as the activation of p38, caspase 3, caspase 8, caspase 7 and caspase 9. Concurrently, the inhibition of complex I by the dihydrobenzothiazine DHBT-1 [7-(2-aminoethyl)-3,4-dihydro-5-hydroxy-2H-1,4-benzothiazine-3-carboxylic acid], formed from the intracellular oxidation of CysDA, induces complex I inhibition and the subsequent release of cytochrome c which further potentiates pro-apoptotic mechanisms. Our data suggest a novel comprehensive mechanism for CysDA that may hold relevance for the selective neuronal loss observed in Parkinson's disease.
The inverse agonist propranolol confers no corticosteroid-sparing activity in mild-to-moderate persistent asthma
Authors: Anderson William J. , Short Philip M. , Williamson Peter A. , Manoharan Arvind , Lipworth Brian J.
Published: June 2014

The murine asthma model shows that switching off airway β2 receptors with an inverse agonist may confer anti-inflammatory effects as well as corticosteroid-sparing activity. We have assessed for any corticosteroid-sparing effects of propranolol, an inverse agonist, added to low-dose inhaled corticosteroid (ICS) compared with higher dose ICS. A randomized double-blind placebo-controlled cross-over trial in mild-to-moderate persistent asthmatic patients was performed. After a run-in (2 weeks) on hydrofluoroalkane-beclometasone dipropionate (HFA-BDP) at 100 μg/day (HFA-BDP100), patients received randomized treatments (4 weeks) with propranolol at 80 mg/day plus HFA-BDP at 100 μg/day compared with placebo plus HFA-BDP at 400 μg/day (HFA-BDP400). Propranolol was up-titrated to 80 mg/day over the initial 2 weeks. Tiotropium was co-administered until 5 days before each histamine challenge (the primary outcome). Sixteen patients completed the study [mean age, 38 years; forced expiratory volume in 1 s (FEV1), 86.4%; histamine provocative concentration causing a 20% fall in FEV1 (PC20), 1.39 mg/ml; ICS dose, 406 μg/day]. Histamine PC20 was unchanged by adding propranolol to HFA-BDP100 compared with baseline (HFA-BDP100) {0.17 doubling dilution (dd) difference [95% confidence interval (CI): −0.58 to 0.92]}, but there was a significant improvement with HFA-BDP400 compared with both baseline [1.05 dd (95% CI: 0.43–1.66); P=0.02], and propranolol+HFA-BDP100 [0.88 dd (95% CI: 0.45–1.30); P=0.006]. Significant improvements were also observed with HFA-BDP400 for exhaled nitric oxide, blood eosinophils, serum eosinophilic cationic protein and asthma quality-of-life questionnaire symptoms compared with propranolol+HFA-BDP100. Salbutamol recovery post-challenge was partially blunted by propranolol (median prolongation 5 min; P=0.002). Domiciliary evening FEV1 also fell with propranolol+HFA-BDP100 [mean reduction from baseline 0.22 litres (95% CI: 0.10–0.34); P=0.012], whereas Asthma Control Questionnaire remained unchanged. In conclusion, the inverse agonist propranolol produced no improvements when given with low-dose ICS, whereas further significant improvements in airway hyper-responsiveness and inflammation were demonstrated with higher dose ICS. Thus, propranolol does not confer corticosteroid-sparing activity in persistent asthma.
Neurobiology of Nondeclarative Memory: A Selected Review on Motor
Authors: Cavaco Sara
Published: June 2014

There is extensive evidence and it is widely recognized that motor skill learning is spared in patients with dense amnesia. However, the neural substrates of motor skill learning are a continuing topic of research and a current matter of debate. This review focuses on the differential contribution of the striatum and the cerebellum to learning skills that require either motor sequence or motor adaptation. A brief overview of the current knowledge helps understand why certain patient populations, such as patients with Parkinson's disease and patients with cerebellar ataxia, experience difficulty with motor skill acquisition.
Link layer protocol analysis of future 10 Gb/s infrared links
Authors: Yiannopoulos Konstantinos , Boucouvalas Anthony C.
Published: June 2014

In this study the authors discuss the performance of the link layer protocol of future 10 Gb/s short‐range infrared links. The authors utilise analytical and simulation results to calculate the protocol efficiency both in a half‐duplex mode of operation, which is currently standardised and a full‐duplex mode that is considered for the future standard. The results show that the half‐duplex protocol will require a significant extension on the window size, and optionally the frame size, in order to provide maximum efficiency for all possible physical layer arrangements. The full‐duplex protocol, on the other hand, requires limited window and frame sizes and therefore has the potential to provide a significant gain in link layer metrics, such as latency and buffering.
Stochastic multi‐objective tie‐line power flow and frequency control in market clearing of multi‐area electricity markets considering power system security
Authors: Rabbanifar Payam , Jadid Shahram
Published: June 2014

This study formulates a security‐constrained multi‐objective framework with unit commitment in multi‐area electricity markets for day‐ahead joint market‐clearing. The dynamic and inertial characteristics of the power system are derived and incorporated into the market‐clearing procedure in order to preserve power system security from the frequency viewpoint. In addition, two novel objective functions (tie‐flow deviation index and Rocof index) besides the frequency‐dependent social welfare and frequency excursion index have been defined to control the static frequency, rate of change of frequency (Rocof) and also the tie‐line power flows, following the occurrence of a contingency. Comprehensive analysis tools for multi‐area power systems and also pre‐ and post‐contingency intervals are presented to verify the characteristics of the proposed model. The developed multi‐objective programming is analysed through two case studies, a three‐area system scheduled over 1 h and the IEEE two‐area reliability test system over 24 h. It has been shown that the scheduling of energy and reserve services can be performed more effectively if the system frequency is considered in the market‐clearing process. The proposed model can reconcile the need for reasonable total generation cost with concern for the independent system operator's responsibilities about the pre‐ and post‐contingency tie‐line power flow control and system security.
Distributed electrical network modelling approach for spatially resolved characterisation of photovoltaic modules
Authors: Wu Xiaofeng , Bliss Martin , Sinha Archana , Betts Tom , Gupta Rajesh , Gottschalg Ralph
Published: June 2014

Distributed electrical modelling and simulation plays an important role in investigating local operating points and the overall power generation of photovoltaic (PV) modules. A PV module is a three‐dimensional device in which inhomogeneities can cause a non‐uniform performance and hence, electrical mismatches which consequently reduce the overall power generation. Distributed modelling and simulation can be used to identify local electrical properties and their impacts on the power output. In this study, a flexible, distributed electrical network modelling approach is presented. The proposed approach introduces a hierarchical architecture built up from the diode model‐based sub‐cell level to the module level. A PV‐oriented nodal analysis solver is developed to enable the spatially resolved quantitative analysis of electrical operating points by given local properties including irradiance, temperature, series resistance, shunt resistance and ideality factor. The approach has been verified by PSpice software. The case studies have shown that this modelling and simulation tool can be used to analyse spatially resolved characterisation results and to predict global and distributed operating points under different conditions.
The Ir-n-GaAs Schottky barrier contacts made by electrochemical deposition
Authors: Bozhkov V. G. , Shmargunov A. V. , Bekezina T. P. , Torkhov N. A. , Novikov V. A.
Published: June 2014

The Ir-n-GaAs contacts obtained by electrochemical deposition from a specially developed electrolyte are studied. The method of deposition is characterized by a high current efficiency and a wide range of permissible mode settings. This method allows one to made contacts of high perfection. For all contacts with the diameters from 500 to 5 μm, the values of the ideality factor (n) and the measured barrier height (φbm) are, as a rule, within the intervals 1.05–1.08 and 0.83–0.89 V, respectively. For small contacts, the breakdown voltage is close to the theoretical value. The dependencies of the parameters n and φbm on the bias voltage and contact diameter as well as the inverse relationship between n and φbm are explained by the nonlinear bias dependence of the effective barrier height φb(V) within the framework of the intimate contact model with an unified system of subsurface states distributed over energy and coordinate. Other features in the behavior of the characteristics of contacts are explained by the peculiarities of their structure and geometry. The possibility of using alternative models to explain the results is discussed.
Stabilization of a lean premixed flame using non-thermal plasma
Authors: Fukuda Daisuke , Shinjo Ryosuke , Okamoto Toshiya , Gotoda Hiroshi
Published: June 2014

This study experimentally investigates the effect of non-thermal plasma (NTP) on the stabilization of a lean premixed methane/air flame. The equivalence ratio of the methane/air mixture for the lean blowout limit (ϕCH4≈0.81) decreases to 0.79 when the fuel is strongly exposed to NTP. Both the flame temperature and the luminescence intensity of C2, CH, and OH radicals increase with increasing applied voltage, resulting in an increase in flame intensity. This allows the lean blowout limit of the methane/air mixture to be extended.
Marangoni induced force on a drop in a Hele Shaw cell
Authors: Gallaire François , Meliga Philippe , Laure Patrice , Baroud Charles N.
Published: June 2014

We analyse the force balance on a cylindrical drop in a Hele-Shaw cell, subjected to a Marangoni flow caused by a surface tension gradient. Depth-averaged Stokes equations, called Brinkman equations, are introduced and a general closed form solution is obtained. The validity of the averaging procedure is ascertained by considering a linear surface tension gradient acting on a cylindrical flattened drop. The Marangoni-driven flow field and resulting force predicted by the Brinkman model are seen to match well a full three-dimensional direct numerical simulation. A closed form expression of the force acting on the drop is obtained, calculated from contributions due to the normal viscous stress, tangential viscous stress, and pressure fields, integrated on the drop perimeter. This expression is used to predict the force balance when a stationary droplet is submitted to both a carrier flow and a Marangoni flow. We show that previous results in the literature had underestimated by a factor two the Marangoni-induced force.
Analysis of non-destructive current simulators of flux compression generators
Authors: O’Connor K. A. , Curry R. D.
Published: June 2014

Development and evaluation of power conditioning systems and high power microwave components often used with flux compression generators (FCGs) requires repeated testing and characterization. In an effort to minimize the cost and time required for testing with explosive generators, non-destructive simulators of an FCG's output current have been developed. Flux compression generators and simulators of FCGs are unique pulsed power sources in that the current waveform exhibits a quasi-exponential increasing rate at which the current rises. Accurately reproducing the quasi-exponential current waveform of a FCG can be important in designing electroexplosive opening switches and other power conditioning components that are dependent on the integral of current action and the rate of energy dissipation. Three versions of FCG simulators have been developed that include an inductive network with decreasing impedance in time. A primary difference between these simulators is the voltage source driving them. It is shown that a capacitor-inductor-capacitor network driving a constant or decreasing inductive load can produce the desired high-order derivatives of the load current to replicate a quasi-exponential waveform. The operation of the FCG simulators is reviewed and described mathematically for the first time to aid in the design of new simulators. Experimental and calculated results of two recent simulators are reported with recommendations for future designs.
Cholesky-decomposed density MP2 with density fitting: Accurate MP2 and double-hybrid DFT energies for large systems
Authors: Maurer Simon A. , Clin Lucien , Ochsenfeld Christian
Published: June 2014

Our recently developed QQR-type integral screening is introduced in our Cholesky-decomposed pseudo-densities Møller-Plesset perturbation theory of second order (CDD-MP2) method. We use the resolution-of-the-identity (RI) approximation in combination with efficient integral transformations employing sparse matrix multiplications. The RI-CDD-MP2 method shows an asymptotic cubic scaling behavior with system size and a small prefactor that results in an early crossover to conventional methods for both small and large basis sets. We also explore the use of local fitting approximations which allow to further reduce the scaling behavior for very large systems. The reliability of our method is demonstrated on test sets for interaction and reaction energies of medium sized systems and on a diverse selection from our own benchmark set for total energies of larger systems. Timings on DNA systems show that fast calculations for systems with more than 500 atoms are feasible using a single processor core. Parallelization extends the range of accessible system sizes on one computing node with multiple cores to more than 1000 atoms in a double-zeta basis and more than 500 atoms in a triple-zeta basis.
Endohedral confinement of a DNA dodecamer onto pristine carbon nanotubes and the stability of the canonical B form
Authors: Cruz Fernando J. A. L. , de Pablo Juan J. , Mota José P. B.
Published: June 2014

Although carbon nanotubes are potential candidates for DNA encapsulation and subsequent delivery of biological payloads to living cells, the thermodynamical spontaneity of DNA encapsulation under physiological conditions is still a matter of debate. Using enhanced sampling techniques, we show for the first time that, given a sufficiently large carbon nanotube, the confinement of a double-stranded DNA segment, 5′-D(*CP*GP*CP*GP*AP*AP*TP*TP*CP*GP*CP*G)-3′, is thermodynamically favourable under physiological environments (134 mM, 310 K, 1 bar), leading to DNA-nanotube hybrids with lower free energy than the unconfined biomolecule. A diameter threshold of 3 nm is established below which encapsulation is inhibited. The confined DNA segment maintains its translational mobility and exhibits the main geometrical features of the canonical B form. To accommodate itself within the nanopore, the DNA's end-to-end length increases from 3.85 nm up to approximately 4.1 nm, due to a ∼0.3 nm elastic expansion of the strand termini. The canonical Watson-Crick H-bond network is essentially conserved throughout encapsulation, showing that the contact between the DNA segment and the hydrophobic carbon walls results in minor rearrangements of the nucleotides H-bonding. The results obtained here are paramount to the usage of carbon nanotubes as encapsulation media for next generation drug delivery technologies.
The structure of D2O-nonane nanodroplets
Authors: Pathak Harshad , Obeidat Abdalla , Wilemski Gerald , Wyslouzil Barbara
Published: June 2014

We study the internal structure of nanometer-sized D2O-nonane aerosol droplets formed in supersonic nozzle expansions using a variety of experimental techniques including small angle X-ray scattering (SAXS). By fitting the SAXS spectra to a wide range of droplet structure models, we find that the experimental results are inconsistent with mixed droplets that form aqueous core–organic shell structures, but are quite consistent with spherically asymmetric lens-on-sphere structures. The structure that agrees best with the SAXS data and Fourier transform infra-red spectroscopy measurements is that of a nonane lens on a sphere of D2O with a contact angle in the range of 40°–120°.
Analytical solution of the Poisson-Nernst-Planck equations for an electrochemical system close to electroneutrality
Authors: Pabst M.
Published: June 2014

Single charge densities and the potential are used to describe models of electrochemical systems. These quantities can be calculated by solving a system of time dependent nonlinear coupled partial differential equations, the Poisson-Nernst-Planck equations. Assuming small deviations from the electroneutral equilibrium, the linearized and decoupled equations are solved for a radial symmetric geometry, which represents the interface between a cell and a sensor device. The densities and the potential are expressed by Fourier-Bessels series. The system considered has a ratio between the Debye-length and its geometric dimension on the order of 10−4 so the Fourier-Bessel series can be approximated by elementary functions. The time development of the system is characterized by two time constants, τc and τg. The constant τc describes the approach to the stationary state of the total charge and the potential. τc is several orders of magnitude smaller than the geometry-dependent constant τg, which is on the order of 10 ms characterizing the transition to the stationary state of the single ion densities.
Quasichemical analysis of the cluster-pair approximation for the thermodynamics of proton hydration
Authors: Pollard Travis , Beck Thomas L.
Published: June 2014

A theoretical analysis of the cluster-pair approximation (CPA) is presented based on the quasichemical theory of solutions. The sought single-ion hydration free energy of the proton includes an interfacial potential contribution by definition. It is shown, however, that the CPA involves an extra-thermodynamic assumption that does not guarantee uniform convergence to a bulk free energy value with increasing cluster size. A numerical test of the CPA is performed using the classical polarizable AMOEBA force field and supporting quantum chemical calculations. The enthalpy and free energy differences are computed for the kosmotropic Na+/F− ion pair in water clusters of size n = 5, 25, 105. Additional calculations are performed for the chaotropic Rb+/I− ion pair. A small shift in the proton hydration free energy and a larger shift in the hydration enthalpy, relative to the CPA values, are predicted based on the n = 105 simulations. The shifts arise from a combination of sequential hydration and interfacial potential effects. The AMOEBA and quantum chemical results suggest an electrochemical surface potential of water in the range −0.4 to −0.5 V. The physical content of single-ion free energies and implications for ion-water force field development are also discussed.
Photochemistry of glycolaldehyde in cryogenic matrices
Authors: Chin W. , Chevalier M. , Thon R. , Pollet R. , Ceponkus J. , Crépin C.
Published: June 2014

The photochemistry of glycolaldehyde (GA) upon irradiation at 266 nm is investigated in argon, nitrogen, neon, and para-hydrogen matrices by IR spectroscopy. Isomerization and fragmentation processes are found to compete. The hydrogen-bonded Cis-Cis form of GA is transformed mainly to the open Trans-Trans conformer and to CO and CH3OH fragments and their mixed complexes. Different photo-induced behaviours appear depending on the matrix. In nitrogen, small amounts of Trans-Gauche and Trans-Trans conformers are detected after deposition and grow together upon irradiation. The Trans-Gauche conformer is characterized for the first time. In para-hydrogen due to a weaker cage effect additional H2CO and HCO fragments are seen. Calculations of the potential energy surfaces of S0, S1, and T1 states – to analyse the torsional deformations which are involved in the isomerization process – and a kinetic analysis are presented to investigate the different relaxation pathways of GA. Fragmentation of GA under UV irradiation through the CO+CH3OH molecular channel is a minor process, as in the gas phase.
Certification and the potential energy landscape
Authors: Mehta Dhagash , Hauenstein Jonathan D. , Wales David J.
Published: June 2014

Typically, there is no guarantee that a numerical approximation obtained using standard nonlinear equation solvers is indeed an actual solution, meaning that it lies in the quadratic convergence basin. Instead, it may lie only in the linear convergence basin, or even in a chaotic region, and hence not converge to the corresponding stationary point when further optimization is attempted. In some cases, these non-solutions could be misleading. Proving that a numerical approximation will quadratically converge to a stationary point is termed certification. In this report, we provide details of how Smale's α-theory can be used to certify numerically obtained stationary points of a potential energy landscape, providing a mathematical proof that the numerical approximation does indeed correspond to an actual stationary point, independent of the precision employed.
Thermodynamic based resource classification of renewable geothermal energy in Nigeria
Authors: Amoo Olaleye M. A.
Published: June 2014

Geothermal resources are a source of renewable alternative energy, providing heat from below the Earth's surface. This is often regarded as “energy under our feet,” and has the potential to contribute significantly towards energy diversification and energy security. Geothermal heat has two primary applications: heating/cooling and electricity generation. As an oil-producing country with geopressured zones, Nigeria has considerable geothermal resource potential, with the capacity to reduce the overt dependence on fossil fuels. Categorizing and classifying her resource potential is of utmost importance. Temperature and enthalpy are two parameters that have been used previously to classify geothermal resources, but are inadequate for the purpose of estimating geothermal system potential. Two fluids (e.g., saturated water or saturated steam) can have the same temperature in different phases, with resulting differences in their ability to do work. The concept of exergy, based on the second law of thermodynamics, describes the maximum amount of useful work that can be extracted from a system and is widely used in the field for resource accounting. In this study, potential geothermal sites in Nigeria are classified based on their Specific Exergy Index. Data used were collated from published literature, although due to lack of a consistently developed and maintained database on geothermal resources in Nigeria, not all known areas may have been characterized here. Data obtained from the fields/sites (oil wells, natural gas, and geothermal) were classified using the exergy method. The results indicate that Nigeria's geothermal sites/fields are low exergy resources with the capacity to contribute to the nation's total energy use. Furthermore, the absence of a consistent geothermal database and coherent geothermal energy policies indicates that research and policy measures are needed to aid all stakeholders in developing the nation's geothermal resources.
Studies on the coupling transformer to improve the performance of microwave ion source
Authors: Misra Anuraag , Pandit V. S.
Published: June 2014

A 2.45 GHz microwave ion source has been developed and installed at the Variable Energy Cyclotron Centre to produce high intensity proton beam. It is operational and has already produced more than 12 mA of proton beam with just 350 W of microwave power. In order to optimize the coupling of microwave power to the plasma, a maximally flat matching transformer has been used. In this paper, we first describe an analytical method to design the matching transformer and then present the results of rigorous simulation performed using ANSYS HFSS code to understand the effect of different parameters on the transformed impedance and reflection and transmission coefficients. Based on the simulation results, we have chosen two different coupling transformers which are double ridged waveguides with ridge widths of 24 mm and 48 mm. We have fabricated these transformers and performed experiments to study the influence of these transformers on the coupling of microwave to plasma and extracted beam current from the ion source.
X-ray scattering in the vorticity direction and rheometry from confined fluids
Authors: Pfleiderer Patrick , Baik Seung Jae , Zhang Zhenkun , Vleminckx Giovanni , Lettinga Minne Paul , Grelet Eric , Vermant Jan , Clasen Christian
Published: June 2014

An X-ray flexure-based microgap rheometer (X-FMR) has been designed for combining rheology and in situ small-angle X-ray scattering from the vorticity plane. The gap distance can be varied continuously from 500 μm down to several μm, which provides the unique possibility to generate a strong confinement for many complex fluids. A singular advantage of this setup is the possibility to directly probe the vorticity direction of the flow field with a microfocus X-ray beam and to probe the structural response of the fluid to combined shear and confinement in the vorticity plane. The sliding-plate setup operates over a wide range of shear rates of $\dot \gamma$γ̇ = 10−3–103 s−1 and strains in the range of 10−4–102. The flexure-based bearing maintains the plate parallelism within 10−5 rad. The X-FMR requires very small sample volumes on the order of 10 μl. The applicability of the device is demonstrated here with limited examples of a nematic suspension of fd virus (rods), and a crystalline suspension containing sterically stabilized polystyrene-butylacrylate latex particles.
Lateral scaling of Pb(Mg1/3Nb2/3)O3-PbTiO3 thin films for piezoelectric logic applications
Authors: Keech Ryan , Shetty Smitha , Kuroda Marcelo A. , Hu Liu Xiao , Martyna Glenn J. , Newns Dennis M. , Trolier-McKinstry Susan
Published: June 2014

The dielectric and piezoelectric behavior of 70Pb(Mg1/3Nb2/3)O3-30PbTiO3 (70PMN-30PT) thin films was studied as a function of lateral scaling. Dense PMN-PT films 300–360 nm in thickness were prepared by chemical solution deposition using a 2-methoxyethanol solvent. These phase pure and strongly {001} oriented films exhibited dielectric constants exceeding 1400 and loss tangents of approximately 0.01. The films showed slim hysteresis loops with remanent polarizations of about 8 μC/cm2 and breakdown fields over 1500 kV/cm. Fully clamped films exhibited large signal strains of 1%, with a d33,f coefficient of 90 pm/V. PMN-PT films were patterned down to 200 nm in spatial scale with nearly vertical sidewalls via reactive ion etching. Upon lateral scaling, which produced partially declamped films, there was an increase in both small and large signal dielectric properties, including a doubling of the relative permittivity in structures with width-to-thickness aspect ratios of 0.7. In addition, declamping resulted in a counterclockwise rotation of the hysteresis loops, increasing the remanent polarization to 13.5 μC/cm2. Rayleigh analysis, Preisach modeling, and the relative permittivity as a function of temperature were also measured and further indicated changes in the domain wall mobility and intrinsic response of the laterally scaled PMN-PT.
Polymorphism and thermodynamic ground state of silver fulminate studied from van der Waals density functional calculations
Authors: Yedukondalu N. , Vaitheeswaran G.
Published: June 2014

Silver fulminate (AgCNO) is a primary explosive, which exists in two polymorphic phases, namely, orthorhombic (Cmcm) and trigonal (R\documentclass[12pt]{minimal}\begin{document}$\bar{3}$\end{document}3¯) forms at ambient conditions. In the present study, we have investigated the effect of pressure and temperature on relative phase stability of the polymorphs using planewave pseudopotential approaches based on Density Functional Theory (DFT). van der Waals interactions play a significant role in predicting the phase stability and they can be effectively captured by semi-empirical dispersion correction methods in contrast to standard DFT functionals. Based on our total energy calculations using DFT-D2 method, the Cmcm structure is found to be the preferred thermodynamic equilibrium phase under studied pressure and temperature range. Hitherto Cmcm and R\documentclass[12pt]{minimal}\begin{document}$\bar{3}$\end{document}3¯ phases denoted as α- and β-forms of AgCNO, respectively. Also a pressure induced polymorphic phase transition is seen using DFT functionals and the same was not observed with DFT-D2 method. The equation of state and compressibility of both polymorphic phases were investigated. Electronic structure and optical properties were calculated using full potential linearized augmented plane wave method within the Tran-Blaha modified Becke-Johnson potential. The calculated electronic structure shows that α, β phases are indirect bandgap insulators with a bandgap values of 3.51 and 4.43 eV, respectively. The nature of chemical bonding is analyzed through the charge density plots and partial density of states. Optical anisotropy, electric-dipole transitions, and photo sensitivity to light of the polymorphs are analyzed from the calculated optical spectra. Overall, the present study provides an early indication to experimentalists to avoid the formation of unstable β-form of AgCNO.
Assessment of amide I spectroscopic maps for a gas-phase peptide using IR-UV double-resonance spectroscopy and density functional theory calculations
Authors: Carr J. K. , Zabuga A. V. , Roy S. , Rizzo T. R. , Skinner J. L.
Published: June 2014

The spectroscopy of amide I vibrations has become a powerful tool for exploring protein structure and dynamics. To help with spectral interpretation, it is often useful to perform molecular dynamics (MD) simulations. To connect spectroscopic experiments to simulations in an efficient manner, several researchers have proposed “maps,” which relate observables in classical MD simulations to quantum spectroscopic variables. It can be difficult to discern whether errors in the theoretical results (compared to experiment) arise from inaccuracies in the MD trajectories or in the maps themselves. In this work, we evaluate spectroscopic maps independently from MD simulations by comparing experimental and theoretical spectra for a single conformation of the α-helical model peptide Ac-Phe-(Ala)5-Lys-H+ in the gas phase. Conformation-specific experimental spectra are obtained for the unlabeled peptide and for several singly and doubly 13C-labeled variants using infrared-ultraviolet double-resonance spectroscopy, and these spectra are found to be well-modeled by density functional theory (DFT) calculations at the B3LYP/6-31G** level. We then compare DFT results for the deuterated and 13C18O-labeled peptide with those from spectroscopic maps developed and used previously by the Skinner group. We find that the maps are typically accurate to within a few cm−1 for both frequencies and couplings, having larger errors only for the frequencies of terminal amides.
Distribution of diffusion constants and Stokes-Einstein violation in supercooled liquids
Authors: Sengupta Shiladitya , Karmakar Smarajit
Published: June 2014

It is widely believed that the breakdown of the Stokes-Einstein (SE) relation between the translational diffusivity and the shear viscosity in supercooled liquids is due to the development of dynamic heterogeneity, i.e., the presence of both slow and fast moving particles in the system. In this study we directly calculate the distribution of the diffusivity for a model system for different temperatures in the supercooled regime. We find that with decreasing temperature, the distribution evolves from Gaussian to bimodal indicating that on the time scale of the typical relaxation time, mobile (fluid like) and less mobile (solid like) particles in the system can be unambiguously identified. We also show that less mobile particles obey the Stokes-Einstein relation even in the supercooled regime and it is the mobile particles which show strong violation of the Stokes-Einstein relation in agreement with the previous studies on different model glass forming systems. Motivated by some of the recent studies where an ideal glass transition is proposed by randomly pinning some fraction of particles, we then studied the SE breakdown as a function of random pinning concentration in our model system. We showed that degree of SE breakdown increases quite dramatically with increasing pinning concentration, thereby providing a new way to unravel the puzzles of SE violation in supercooled liquids in greater details.
Lateral migration and focusing of microspheres in a microchannel flow of viscoelastic fluids
Authors: Seo Kyung Won , Kang Yang Jun , Lee Sang Joon
Published: June 2014

The lateral migration of microspheres across streamlines induced by elasticity and inertia in a square microchannel flow of viscoelastic fluids is investigated using a holographic microscopy technique. We experimentally demonstrate the exact particle positions driven by the elasticity of fluid in the channel cross-section. The effects of the blockage ratio, flow rate, and shear-thinning property of the viscoelastic fluids on particle migration are evaluated. In particular, the focusing patterns of microspheres in three-dimensional volume are analyzed under different conditions, namely, dominant inertia, dominant elasticity, and the combined effects of inertia and elasticity.
Electrostatics of liquid interfaces
Authors: Matyushov Dmitry V.
Published: June 2014

The standard Maxwell formulation of the problem of polarized dielectrics suffers from a number of difficulties, both conceptual and practical. These difficulties are particularly significant for liquid interfaces. For these systems, the ability of interfacial multipoles to change their orientations leads to the interfacial polarization localized within a thin microscopic layer. A formalism to capture this physical reality is proposed and is based on the surface charge as the source of microscopic electric fields in dielectrics. The surface charge density incorporates the local structure of the interface into electrostatic calculations. The corresponding surface susceptibility and interface dielectric constant provide local closures to the electrostatic boundary value problem. A robust approach to calculate the surface susceptibility from numerical simulations is formulated. The susceptibility can alternatively be extracted from a number of solution experiments, in particular those sensitive to the overall dipole moment of a closed dielectric surface. The theory is applied to the solvent-induced spectral shift and high-frequency dielectric response of solutions.
Carbon epoxy composites thermal conductivity at 77 K and 300 K
Authors: Battaglia J.-L. , Saboul M. , Pailhes J. , Saci A. , Kusiak A. , Fudym O.
Published: June 2014

The in-plane and in-depth thermal conductivities of epoxy-carbon fiber composites have been measured at 77 K and 300 K. The experimental technique rests on the hot disk method. The two thermal conductivities as well as the thermal contact resistance between the probe and the composite materials are estimated from measurement data and an analytical heat transfer model within the experimental configuration. The results obtained at 77 K explained well the ignition test results performed on the composites at 77 K with regards to liquid oxygen storage.
Performance of a size-selected nanocluster deposition facility and in situ characterization of grown films by x-ray photoelectron spectroscopy
Authors: Mondal Shyamal , Bhattacharyya S. R.
Published: June 2014

We report here on a newly installed gas aggregation type nanocluster deposition unit based on magnetron sputtering ion source with mass selection of the clusters by quadrupole mass filter. The system is ultra high vacuum compatible and is equipped with an in situ X-ray Photoelectron Spectroscopy facility, giving compositional information of the films formed by nanoclusters deposition on a substrate. Detailed descriptions and working of the components of the system are presented. For the characterization of the nanocluster source and associated mass filter for size selected clusters, the dependence of output performance as a function of aggregation length, sputter gas flow and magnetron power of the cluster source have been studied. Copper nanoclusters deposited on Silicon (100) surface and on transmission electron microscope grids are, respectively, studied with scanning electron microscopy and transmission electron microscopy for the morphology.
Communication: Remarkable electrophilicity of the oxalic acid monomer: An anion photoelectron spectroscopy and theoretical study
Authors: Buonaugurio Angela , Graham Jacob , Buytendyk Allyson , Bowen Kit H. , Ryder Matthew R. , Keolopile Zibo G. , Haranczyk Maciej , Gutowski Maciej
Published: June 2014

Our experimental and computational results demonstrate an unusual electrophilicity of oxalic acid, the simplest dicarboxylic acid. The monomer is characterized by an adiabatic electron affinity and electron vertical detachment energy of 0.72 and 1.08 eV (±0.05 eV), respectively. The electrophilicity results primarily from the bonding carbon-carbon interaction in the singly occupied molecular orbital of the anion, but it is further enhanced by intramolecular hydrogen bonds. The well-resolved structure in the photoelectron spectrum is reproduced theoretically, based on Franck-Condon factors for the vibronic anion → neutral transitions.
Diffraction-assisted micropatterning of silicon surfaces by ns-laser irradiation
Authors: Haro-Poniatowski E. , Acosta-Zepeda C. , Mecalco G. , Hernández-Pozos J. L. , Batina N. , Morales-Reyes I. , Bonse J.
Published: June 2014

Single-pulse (532 nm, 8 ns) micropatterning of silicon with nanometric surface modulation is demonstrated by irradiating through a diffracting pinhole. The irradiation results obtained at fluences above the melting threshold are characterized by scanning electron and scanning force microscopy and reveal a good agreement with Fresnel diffraction theory. The physical mechanism is identified and discussed on basis of both thermocapillary and chemicapillary induced material transport during the molten state of the surface.
The ion-ion hybrid Alfvén resonator in a fusion environment
Authors: Farmer W. A. , Morales G. J.
Published: June 2014

An investigation is made of a shear Alfvén wave resonator for burning plasma conditions expected in the ITER device. For small perpendicular scale-lengths the shear mode, which propagates predominantly along the magnetic field direction, experiences a parallel reflection where the wave frequency matches the local ion-ion hybrid frequency. In a tokamak device operating with a deuterium–tritium fuel, this effect can form a natural resonator because of the variation in local field strength along a field line. The relevant kinetic dispersion relation is examined to determine the relative importance of Landau and cyclotron damping over the possible resonator parameter space. A WKB model based on the kinetic dispersion relation is used to determine the eigenfrequencies and the quality factors of modes trapped in the resonator. The lowest frequency found has a value slightly larger than the ion-ion hybrid frequency at the outboard side of a given flux surface. The possibility that the resonator modes can be driven unstable by energetic alpha particles is considered. It is found that within a bandwidth of roughly 600 kHz above the ion-ion hybrid frequency on the outboard side of the flux surface, the shear modes can experience significant spatial amplification. An assessment is made of the form of an approximate global eigenmode that possesses the features of a resonator. It is identified that magnetic field shear combined with large ion temperature can cause coupling to an ion-Bernstein wave, which can limit the instability.
Effect of energy and momentum conservation on fluid resonances for resonant magnetic perturbations in a tokamak
Authors: Leitner Peter , Heyn Martin F. , Ivanov Ivan B. , Kasilov Sergei V. , Kernbichler Winfried
Published: June 2014

In this paper, the impact of momentum and energy conservation of the collision operator in the kinetic description for Resonant Magnetic Perturbations (RMPs) in a tokamak is studied. The particle conserving differential collision operator of Ornstein-Uhlenbeck type is supplemented with integral parts such that energy and momentum are conserved. The application to RMP penetration in a tokamak shows that energy conservation in the electron collision operator is important for the quantitative description of plasma shielding effects at the resonant surface. On the other hand, momentum conservation in the ion collision operator does not significantly change the results.
Scattering-based solar light collector
Authors: Wen J. , Berg M. J. , Steed M.
Published: June 2014

This work presents laboratory measurements to test the new concept that elastic scattering from micrometer and larger particles can be used to collect sunlight for use in photovoltaic power production. The collector design consists of a layer of particles dispersed across a mirrored glass plate. Photovoltaic cells line the edges of the plate, which receive light that is coupled into the plate via scattering from the particles and partially confined thereafter by total internal reflection. All materials used to construct the collector are low-cost and typically available off-the-shelf. The net electrical power produced is compared to a single, bare cell that is directly illuminated by the same light source. This comparison shows a promising trend in terms of the overall collector size that may eventually yield a solar collector producing more power than that produced by the same amount of cell material under direct illumination.