bluuebunny/crossref_metadata_2025 huggingface dataset:
A novel harvesting method for cultured cells using iron‐cross‐linked alginate films as culture substrates
Authors: Machida‐Sano Ikuko , Matsuda Yasushi , Namiki Hideo
Published: November 2009

The present study was conducted to assess the efficiency of a novel cell‐harvesting method involving dissolution of the culture substrate composed of Fe‐alginate (ferric‐ion‐cross‐linked alginate). Cell harvesting is an essential step for recovery of cultured adherent cells, but conventional methods such as trypsinization or scraping cause considerable damage to the cells. We therefore devised an original method for harvesting cultured cells using Fe‐alginate films as a culture substrate and then retrieving the cells by disintegration of the alginate gel. Fe‐alginate was easily dissolved under physiological conditions by exchange of cross‐linked ions using chelating agents such as citrate. The effects of this cell‐harvesting method were investigated in comparison with trypsinization and scraping. Cells harvested by dissolution of the Fe‐alginate substrate showed high viability and metabolic activity, high recovery rate on subculture, a low degree of membrane damage with superior expression of cell adhesion molecules (β1 integrin and N‐cadherin), high resistance to oxidative stress, and high viability, metabolic activity and recovery rate after cryopreservation, in contrast with the cells harvested by trypsinization or scraping from tissue‐culture polystyrene substrates. These results suggest that our new system involving dissolution of Fe‐alginate culture substrate is effective for cell harvesting and may be advantageous for biomedical applications.
Activation of autophagy through modulation of 5′-AMP-activated protein kinase protects pancreatic β-cells from high glucose
Authors: Han Diana , Yang Byungho , Olson L. Karl , Greenstein Alexander , Baek Seung-Hoon , Claycombe Kate J. , Goudreau John L. , Yu Seong-Woon , Kim Eun-Kyoung
Published: November 2009

Chronic hyperglycaemia is detrimental to pancreatic β-cells by causing impaired insulin secretion and diminished β-cell function through glucotoxicity. Understanding the mechanisms underlying β-cell survival is crucial for the prevention of β-cell failure associated with glucotoxicity. Autophagy is a dynamic lysosomal degradation process that protects organisms against metabolic stress. To date, little is known about the physiological function of autophagy in the pathogenesis of diabetes. In the present study, we explored the roles of autophagy in the survival of pancreatic β-cells exposed to high glucose using pharmacological and genetic manipulation of autophagy. We demonstrated that chronic high glucose increases autophagy in rat INS-1 (832/13) cells and pancreatic islets, and that this increase is enhanced by inhibition of 5′-AMP-activated protein kinase. Our results also indicate that stimulation of autophagy rescues pancreatic β-cells from high-glucose-induced cell death and inhibition of autophagy augments caspase-3 activation, suggesting that autophagy plays a protective role in the survival of pancreatic β-cells. Greater knowledge of the molecular mechanisms linking autophagy and β-cell survival may unveil novel therapeutic targets needed to preserve β-cell function.
Biomembrane liquid–liquid phase separation and detergent resistance: a relationship strengthened
Authors: Holowka David
Published: November 2009

Since evidence first appeared for ‘detergent-resistant membranes’ in the early to mid-1990s, cell biologists from a wide spectrum of biological sciences have been intrigued by the functional relevance of this indication of membrane heterogeneity, commonly referred to as ‘lipid rafts’. Model membrane studies revealed that these lipid rafts are related to the more ordered liquid phase that forms in a ternary mixture of cholesterol with a phospholipid containing saturated acyl chains and one with unsaturated acyl chains. Giant plasma membrane vesicles that pinch off from cells undergo similar liquid–liquid phase separation as ternary model membranes, and have provided an experimental bridge between these and intact cells. The study by Levental et al. in this issue of the Biochemical Journal provides new insights into the relationship between liquid–liquid phase separation in these plasma membrane vesicles and detergent-resistance of cellular lipid rafts.
Celecoxib-loaded liposomes: effect of cholesterol on encapsulation and in vitro release characteristics
Authors: Deniz Asli , Sade Asli , Severcan Feride , Keskin Dilek , Tezcaner Aysen , Banerjee Sreeparna
Published: November 2009

CLX (celecoxib) is a highly hydrophobic non-steroidal anti-inflammatory drug with high plasma protein binding. We describe here the encapsulation of CLX in MLVs (multilamellar vesicles) composed of DSPC (1,2-distearoyl-sn-glycero-3-phosphocholine) and variable amounts of cholesterol. The effects of cholesterol content on liposome size, percentage drug loading and in vitro drug release profiles were investigated. Differential scanning calorimetry and FTIR (Fourier-transform infrared) spectroscopy were used to determine molecular interactions between CLX, cholesterol and DSPC. The phase transition temperature (Tm) of vesicles was reduced in a synergistic manner in the presence of both CLX and cholesterol. Encapsulation efficiency, loading and release of CLX decreased with increasing cholesterol content. FTIR results indicated that this decrease was due to a competition between CLX and cholesterol for the co-operativity region of the phospholipids. In the presence of cholesterol, CLX was pushed further into the hydrophobic core of the bilayer. However, MLVs prepared with DSPC only (without cholesterol) exhibited the lowest ability for drug retention after 72 h. Our results indicated that CLX, without the requirement of modifications to enhance solubilization, can be encapsulated and released from liposomal formulations. This method of drug delivery may be used to circumvent the low bioavailability and systemic side effects of oral CLX formulations.
Characterization of a novel murine preadipocyte line, AP‐18, isolated from subcutaneous tissue: Analysis of adipocyte‐related gene expressions
Authors: Chen Chen , Takahashi Kazuma , Yoshida Ayumi , Takizawa Yumiko , Lee Yan , Nakui Masaki , Doi Hideyuki , Takebayashi Yuji , Fukumoto Manabu , Yamada Testuya , Katagiri Hideki , Oka Yoshitomo , Satoh Jo
Published: November 2009

Adipocyte lines are a useful tool for adipocyte research. Recently, a new preadipocyte line designated AP‐18 was established from subcutaneous tissue of the C3H/He mouse. In this study, we further characterized AP‐18 cells. Adipocyte differentiation was assessed by accumulation of fat droplets stained by Oil Red O. The expression of the preadipocyte‐ or adipocyte‐specific genes and adipocytokine genes was analysed qualitatively by RT‐PCR and quantitatively by real‐time PCR in comparison with the LM cell, a murine fibroblast line, and the 3T3‐L1 cell, respectively. AP‐18 cells were fibroblastoid in maintenance culture. After the confluence, fat droplets were accumulated in 50–60% of the cells cultured in the medium alone and in 70–90% of the cells cultured with insulin within 2 to 3 weeks. The fat accumulation was not promoted by the addition of dexamethazone, IBMX (3‐isobutyl‐1‐methylxanthine) or troglitazone in combination with insulin, which were obligatory for differentiation of the 3T3‐L1 cell, a murine preadipocyte line. Throughout the differentiation, AP‐18 cells expressed Pref‐1, LPL, C/EBPβ, C/EBPδ, RXRα, C/EBPα, PPARγ, RXRγ, aP2, GLUT4, SCD1, UCP2, UCP3, TNFα, resistin, leptin, adiponectin and PAI‐1 genes, but not the UCP1 gene, indicating that the cell is derived from WAT (white adipose tissue). The time course of these gene expressions was similar to that of 3T3‐L1 cells, although the expressions were slower and lower in AP‐18 cells. These data indicate that AP‐18 cells are preadipocytes originated from WAT and differentiate into adipocytes under more physiological conditions than 3T3‐L1 cells. AP‐18 may be useful in adipocyte research.
Hypoxia and non-alcoholic fatty liver disease
Authors: Byrne Christopher D.
Published: November 2009

NAFLD (non-alcoholic fatty liver disease) represents a spectrum of fatty liver diseases associated with an increased risk of Type 2 diabetes and cardiovascular disease. The spectrum of fatty liver diseases comprises simple steatosis, steatosis with inflammation [i.e. NASH (non-alcoholic steatohepatitis)], fatty liver disease with inflammation and fibrosis (severe NASH) and cirrhosis. The molecular mechanisms contributing to NASH are the subject of considerable investigation, as a better understanding of the pathogenesis of NASH will lead to novel therapies for a condition that hitherto remains difficult to treat. In the present issue of Clinical Science, Piguet and co-workers have investigated the effects of hypoxia in the PTEN (phosphatase and tensin homologue deleted on chromosome 10)-deficient mouse, a mouse model that develops NAFLD. The authors show that a short period (7 days) of exposure to hypoxia aggravates the NAFLD phenotype, causing changes in the liver that are in keeping with NASH with increased lipogenesis and inflammation.
Influence of combined external stress and electric field on electric properties of 0.5% Fe-doped lead zirconate titanate ceramics
Authors: Suchanicz J. , Kim-Ngan N.-T. H. , Konieczny K. , Jankowska-Sumara I. , Sitko D. , Goc-Jaglo D. , Balogh A. G.
Published: November 2009

Influence of uniaxial pressure (0–1000 bars) applied parallel to or perpendicularly to the ac or dc electric field (in one-dimensional or two-dimensional manner) on dielectric and ferroelectric properties of hard lead zirconate titanate (PZT) ceramics were investigated. The experimental results revealed that applying uniaxial pressure leads to a reduction in the peak intensity of the electric permittivity (ε), of the frequency dispersion as well as of the dielectric hysteresis. Moreover, with increasing pressure the peak intensity of ε becomes diffused and shifts to a higher temperature. It was also found that simultaneous application of uniaxial pressure and electric field (perpendicular to each other) in the poling process improves the ferroelectric properties. This indeed indicates new possibility for poling materials with a high coercive field and/or high electric conductivity. The effects of uniaxial load are weaker than that obtained for soft PZT ceramics. It was concluded that applying uniaxial pressure induces similar effects as increasing the Ti ion concentration in PZT system. The obtained results were interpreted through Cochran soft mode and domain switching processes under applying of pressure.
Modification of a commercial cavity ring-down spectroscopy NO2 detector for enhanced sensitivity
Authors: Castellanos Patricia , Luke Winston T. , Kelley Paul , Stehr Jeffrey W. , Ehrman Sheryl H. , Dickerson Russell R.
Published: November 2009

Nitrogen dioxide (NO2) plays a central role in atmospheric chemistry, air pollution, and biogeochemical cycles. Many analytical techniques have been developed to detect NO2, but only chemiluminescence-based instruments are commonly, commercially available. There remains a need for a fast, light, and simple method to directly measure NO2. In this work we describe the modification and characterization of a small, commercially available cavity ring-down spectroscopy (CRDS) NO2 detector suitable for surface and aircraft monitoring. A metal oxide scrubber was added to remove NO2, and provide a chemical zero, improving the detection limit (3σ of the background noise) from several parts per billion by volume (ppbv) to 0.06 ppbv, integrated over 60 s. Known interferences by water and particles were removed using Nafion tubing and a 1 μm Teflon® filter, respectively. A 95% response time of 18±1 s was observed for a step change in concentration. The CRDS detector was run in parallel to an ozone chemiluminescence device with photolytic conversion of NO2 to NO. The two instruments measured ambient air in suburban Maryland. A least-squares fit to the comparison data resulted a slope of 0.960±0.002 and R of 0.995, showing agreement within experimental uncertainty.
Single-crystal elastic properties of (Y,Yb)3Al5O12
Authors: Marquardt Hauke , Speziale Sergio , Jahn Sandro , Ganschow Steffen , Schilling Frank R.
Published: November 2009

Brillouin scattering experiments were performed on single crystals in the solid solution series Y3Al5O12–Yb3Al5O12 (with XYb=0,0.39,0.81,1). Elastic stiffness tensor, bulk modulus K, Young’s modulus, and shear modulus were determined, which were previously only known for the yttrium end member. In our experiments, K increased by ∼4% from Y3Al5O12 to Yb3Al5O12, whereas shear modulus and Young’s modulus were insensitive to compositional change. To complement our experimental results, we performed ab initio density functional theory (DFT) simulations for Y3Al5O12 and classical interatomic potential calculations for Yb3Al5O12. While the experimental results are in good agreement with our DFT calculations, the results from classical potential calculations differ significantly from experiments.
Realization of reliable and flexible logic gates using noisy nonlinear circuits
Authors: Murali K. , Rajamohamed I. , Sinha Sudeshna , Ditto William L. , Bulsara Adi R.
Published: November 2009

It was shown recently [Murali et al., Phys. Rev. Lett. 102, 104101 (2009)] that when one presents two square waves as input to a two-state system, the response of the system can produce a logical output (NOR/OR) with a probability controlled by the interplay between the system noise and the nonlinearity (that characterizes the bistable dynamics). One can switch or “morph” the output into another logic operation (NAND/AND) whose probability displays analogous behavior; the switching is accomplished via a controlled symmetry-breaking dc input. Thus, the interplay of nonlinearity and noise yields flexible and reliable logic behavior, and the natural outcome is, effectively, a logic gate. This “logical stochastic resonance” is demonstrated here via a circuit implementation using a linear resistor, a linear capacitor and four CMOS-transistors with a battery to produce a cubiclike nonlinearity. This circuit is simple, robust, and capable of operating in very high frequency regimes; further, its ease of implementation with integrated circuits and nanoelectronic devices should prove very useful in the context of reliable logic gate implementation in the presence of circuit noise.
Soft x-ray virtual diagnostics for tokamak simulations
Authors: Kim J. S. , Zhao L. , Bogatu I. N. , In Y. , Turnbull A. , Osborne T. , Maraschek M. , Comer K.
Published: November 2009

The numerical toolset, FAR-TECH Virtual Diagnostic Utility, for generating virtual experimental data based on theoretical models and comparing it with experimental data, has been developed for soft x-ray diagnostics on DIII-D. The virtual (or synthetic) soft x-ray signals for a sample DIII-D discharge are compared with the experimental data. The plasma density and temperature radial profiles needed in the soft x-ray signal modeling are obtained from experimental data, i.e., from Thomson scattering and electron cyclotron emission. The virtual soft x-ray diagnostics for the equilibriums have a good agreement with the experimental data. The virtual diagnostics based on an ideal linear instability also agree reasonably well with the experimental data. The agreements are good enough to justify the methodology presented here for utilizing virtual diagnostics for routine comparison of experimental data. The agreements also motivate further detailed simulations with improved physical models such as the nonideal magnetohydrodynamics contributions (resistivity, viscosity, nonaxisymmetric error fields, etc.) and other nonlinear effects, which can be tested by virtual diagnostics with various stability modeling.
Formation of atomic gold chain on hydrogen terminated Si(001):3×1 surface: A density functional study
Authors: Konar Shyamal , Gupta Bikash C. , Sen Prasenjit
Published: November 2009

Electronic structure calculations are carried out for investigating the formation of a stable atomic gold wire on the hydrogen terminated Si(001):3×1 [H–Si(001):3×1] surface. The H–Si(001):3×1 surface is patterned in various ways by removing desired hydrogen atoms from the surface. Gold atoms are adsorbed on the patterned H–Si(001):3×1 surface at various submonolayer coverage. However, zigzag continuous Au chains are found to be favorable on patterned H–Si(001):3×1 surfaces at a 4/9 monolayer (ML) coverage. The stabilities of continuous atomic gold chains on the patterned H–Si(001):3×1 surfaces are compared. In addition, the Au chains on the patterned H–Si(001):3×1 surfaces are compared with the existing results of the favorable Au chain structures on patterned H–Si(001):1×1 surfaces [Konar et al., Phys. Rev. B 77, 245411 (2008)], and it is found that a continuous Au chain on the H–Si(001):3×1 surface is energetically more favorable. Our calculations also reveal that beyond the 4/9 ML coverage, the additional Au atoms take part in the formation of Au clusters on the surface. However, beyond the 4/9 ML coverage, the gold structures on the surface are found to be less favorable compared to the chain structures at the 4/9 ML coverage. The continuous atomic gold chains supported by a substrate may be used as atomic scale devices, and therefore, experiments may be designed in this direction to produce a continuous atomic Au chain on the patterned H–Si(001):3×1 surface.
Prediction of surface passivation doping of silicon nanowires with phosphorus
Authors: Yang X. B. , Guo C. S. , Zhang R. Q.
Published: November 2009

We report a prediction of enhanced surface passivation doping effect in silicon nanowires (SiNWs) by phosphorus adsorption based on first-principles calculations. Recent theoretical and experimental studies all showed that hydrogen-passivated SiNWs present typical p-type characteristic due to charge transfer between the surface passivant and the SiNW core. Here, we show that a phosphorus-passivated SiNW with a moderate diameter facilitates improved hole generation in the core and efficient separation of electron and hole, which may provide a practical avenue for fabricating low cost solar cells with high efficiency.
Compact vibration isolation and suspension for Australian International Gravitational Observatory: Performance in a 72 m Fabry Perot cavity
Authors: Barriga P. , Dumas J. C. , Woolley A. A. , Zhao C. , Blair D. G.
Published: November 2009

This paper describes the first demonstration of vibration isolation and suspension systems, which have been developed with view to application in the proposed Australian International Gravitational Observatory. In order to achieve optimal performance at low frequencies new components and techniques have been combined to create a compact advanced vibration isolator structure. The design includes two stages of horizontal preisolation and one stage of vertical preisolation with resonant frequencies ∼100 mHz. The nested structure facilitates a compact design and enables horizontal preisolation stages to be configured to create a superspring configuration, where active feedback can enable performance close to the limit set by seismic tilt coupling. The preisolation stages are combined with multistage three–dimensional (3D) pendulums. Two isolators suspending mirror test masses have been developed to form a 72 m optical cavity with finesse ∼700 in order to test their performance. The suitability of the isolators for use in suspended optical cavities is demonstrated through their ease of locking, long term stability, and low residual motion. An accompanying paper presents the local control system and shows how simple upgrades can substantially improve residual motion performance.
Compact vibration isolation and suspension for Australian International Gravitational Observatory: Local control system
Authors: Dumas Jean-Charles , Barriga Pablo , Zhao Chunnong , Ju Li , Blair David G.
Published: November 2009

High performance vibration isolators are required for ground based gravitational wave detectors. To attain very high performance at low frequencies we have developed multistage isolators for the proposed Australian International Gravitational Observatory detector in Australia. New concepts in vibration isolation including self-damping, Euler springs, LaCoste springs, Roberts linkages, and double preisolation require novel sensors and actuators. Double preisolation enables internal feedback to be used to suppress low frequency seismic noise. Multidegree of freedom control systems are required to attain high performance. Here we describe the control components and control systems used to control all degrees of freedom. Feedback forces are injected at the preisolation stages and at the penultimate suspension stage. There is no direct actuation on test masses. A digital local control system hosted on a digital signal processor maintains alignment and position, corrects drifts, and damps the low frequency linear and torsional modes without exciting the very high Q-factor test mass suspension. The control system maintains an optical cavity locked to a laser with a high duty cycle even in the absence of an autoalignment system. An accompanying paper presents the mechanics of the system, and the optical cavity used to determine isolation performance. A feedback method is presented, which is expected to improve the residual motion at 1 Hz by more than one order of magnitude.
Calculation of the magnetic energy barrier in nanostructured cells of synthetic ferrimagnets
Authors: Han C. W. , Han J. K. , Lim S. H.
Published: November 2009

A method is proposed to calculate the magnetic energy barrier of nanostructured cells of synthetic ferrimagnets. An important feature of the method is the use of an equation for the total energy that contains the magnetostatic fields at the saddle point as parameters of the energy equation. With no suitable methods of accessing the magnetic configuration at the unstable saddle point, it is difficult to obtain the saddle point magnetostatic fields. This difficulty is overcome with the use of equations that link the magnetostatic fields at the saddle point and critical fields, which are readily obtained by micromagnetic simulation. The present method is essentially based on the micromagnetic simulation, and, therefore, it should provide accurate results for the magnetic energy barrier. A contour diagram showing the thermal stability parameter is constructed as a function of the cell geometry and the thickness asymmetry, and the result should be of great value in designing magnetic cells for high density magnetic random access memory.
Stress-induced phenomena in nanosized copper interconnect structures studied by x-ray and electron microscopy
Authors: Zschech Ehrenfried , Huebner Rene , Chumakov Dmytro , Aubel Oliver , Friedrich Daniel , Guttmann Peter , Heim Stefan , Schneider Gerd
Published: November 2009

We present the first dynamic study of damage mechanisms in nanosized on-chip Cu interconnects caused by stress-induced voiding in advanced integrated circuits. Synchrotron-based transmission x-ray microscopy is applied to visualize the void evolution and conical dark-field analysis in the transmission electron microscopy to characterize the Cu microstructure. Our x-ray microscopy measurements showed, in contradiction to electromigration studies, no void movement over large dimensions during the stress-induced void evolution. We observed in via/line Cu interconnect structures that voids are formed directly beneath the via, i.e., in the Cu wide line at the edge of the via bottom. It is concluded that voids are originally formed at the site where eventually the catastrophic failure occurs. During stress migration tests, Cu atoms migrate from regions of low stress to regions of high tensile stress, and simultaneously, vacancies migrate along the stress gradient (within a limited range of some microns) in the opposite direction to the location where small vias connect wide Cu lines. The stress distribution and the driving forces for atomic transport depend strongly on the particular geometry of the tested structure but also on interface bonding and metal microstructure. Vacancies form agglomerates and subsequently voids that grow further. The void growth rate depends on the Cu thin film material and its microstructure, particularly the grain size and the grain orientations. The Cu microstructure in the surroundings of the formed void shows that Cu grains are predominantly (111) oriented relatively to the wafer surface. Interfaces and grain boundaries, and particularly their orientation, determine the void evolution dynamics.
Simultaneous measurement of temperature and thermal stress in AlGaN/GaN high electron mobility transistors using Raman scattering spectroscopy
Authors: Batten T. , Pomeroy J. W. , Uren M. J. , Martin T. , Kuball M.
Published: November 2009

Raman spectroscopy, utilizing both the GaN E2 and A1(LO) phonon modes, has been used to simultaneously probe temperature and thermal stress in operating AlGaN/GaN high electron mobility transistors (HEMTs). Temperature and thermal stress profiles across the active region of an AlGaN/GaN HEMT were determined. The results were found to be in good agreement with thermal and thermomechanical simulations. The maximum temperature rise and thermal stress measured in the GaN layer are located close to the drain edge of the gate contact, reaching 240 °C and −0.37 GPa, respectively, for a power dissipation of 25 W/mm (40 V).
Scaling the dynamics of orientationally disordered mixed crystals
Authors: Romanini M. , Martinez-Garcia J. C. , Tamarit J. Ll. , Rzoska S. J. , Barrio M. , Pardo L. C. , Drozd-Rzoska A.
Published: November 2009

The evolution of the primary relaxation time of orientationally disordered (OD) mixed crystals [(CH3)2C(CH2OH)2]1−X[(CH3)C(CH2OH)3]X, with 0<X≤0.5, on approaching the glass temperature (Tg) is discussed. The application of the distortion-sensitive, derivative-based procedure revealed a limited adequacy of the Vogel–Fulcher–Tammann parametrization and a superiority of the critical-like description τ∝(T−TC)−ϕ′, ϕ′=9–11.5, and TC∼Tg−10 K. Basing on these results as well as that of Drozd-Rzoska et al. [J. Chem. Phys. 129, 184509 (2008)] the question arises whether such behavior may be suggested as the optimal universal pattern for dynamics in vitrifying OD crystals (plastic crystals). The obtained behavior is in fair agreement with the dynamic scaling model (DSM) [R. H. Colby, Phys. Rev. E 61, 1783 (2000)], originally proposed for vitrifying molecular liquids and polymers. The application of DSM made it possible to estimate the size of the cooperatively rearranging regions (“heterogeneities”) in OD phases near Tg.
Reactivity of aluminum cluster anions with ammonia: Selective etching of Al11− and Al12−
Authors: Grubisic Andrej , Li Xiang , Gantefoer Gerd , Bowen Kit H. , Schnöckel Hansgeorg , Tenorio Francisco J. , Martinez Ana
Published: November 2009

Reactivity of aluminum cluster anions toward ammonia was studied via mass spectrometry. Highly selective etching of Al11− and Al12− was observed at low concentrations of ammonia. However, at sufficiently high concentrations of ammonia, all other sizes of aluminum cluster anions, except for Al13−, were also observed to deplete. The disappearance of Al11− and Al12− was accompanied by concurrent production of Al11NH3− and Al12NH3− species, respectively. Theoretical simulations of the photoelectron spectrum of Al11NH3− showed conclusively that its ammonia moiety is chemisorbed without dissociation, although in the case of Al12NH3−, dissociation of the ammonia moiety could not be excluded. Moreover, since differences in calculated Aln−+NH3 (n=9–12) reaction energies were not able to explain the observed selective etching of Al11− and Al12−, we concluded that thermodynamics plays only a minor role in determining the observed reactivity pattern, and that kinetics is the more influential factor. In particular, the conversion from the physisorbed Aln−(NH3) to chemisorbed AlnNH3− species is proposed as the likely rate-limiting step.
Self-assembled multilayers and enhanced superconductivity in (YBa2Cu3O7−x)0.5:(BaZrO3)0.5 nanocomposite films
Authors: Yang H. , Wang H. , Maiorov B. , Lee J. , Talbayev D. , Hinton M. J. , Feldmann D. M. , MacManus-Driscoll J. L. , Taylor A. J. , Civale L. , Lemberger T. R. , Jia Q. X.
Published: November 2009

Nanocomposite (YBa2Cu3O7−x)0.5:(BaZrO3)0.5 thin films were fabricated on (001) oriented SrTiO3 substrates by pulsed laser deposition using a single uniformly mixed target. Both x-ray diffraction and transmission electron microscopy revealed remarkable, spontaneous formation of YBa2Cu3O7−x (YBCO) and BaZrO3 (BZO) multilayers. The high integrity and continuity of the multilayer made it possible to achieve a critical temperature of 88 K, given that the BaZrO3 fraction in the films is 50 mol %. The unique self-assembled microstructure led to a surprising field dependent critical current density along the ab plane.
ZnO
/
TiO
2
nanonetwork as efficient photoanode in excitonic solar cells
Authors: Vomiero A. , Concina I. , Natile M. M. , Comini E. , Faglia G. , Ferroni M. , Kholmanov I. , Sberveglieri G.
Published: November 2009

An innovative nanonetwork composed of TiO2 nanoparticles and single-crystalline ZnO nanowires is demonstrated as efficient photoanode in excitonic solar cells. Such architecture benefits of the capability of high sensitizer loading offered by the nanoparticles and of the direct conduction path for electrons guaranteed by the nanowires. The combination of these features leads to improved light absorption, electron photogeneration, and charge collection. The nanonetwork was implemented in a dye-sensitized solar-cell architecture demonstrating threefold enhancement of the efficiency with respect to a nanowire photoanode of the same thickness. Cell efficiency of 1.6% was obtained in 1.5 μm thick nanonetwork.
Intermolecular proton-transfer in acetic acid clusters induced by vacuum-ultraviolet photoionization
Authors: Ohta Keisuke , Matsuda Yoshiyuki , Mikami Naohiko , Fujii Asuka
Published: November 2009

Infrared (IR) spectroscopy based on vacuum-ultraviolet one-photon ionization detection was carried out to investigate geometric structures of neutral and cationic clusters of acetic acid: (CH3COOH)2, CH3COOH–CH3OH, and CH3COOH–H2O. All the neutral clusters have cyclic-type intermolecular structures, in which acetic acid and solvent molecules act as both hydrogen donors and acceptors, and two hydrogen-bonds are formed. On the other hand, (CH3COOH)2+ and (CH3COOH–CH3OH)+ form proton-transferred structures, where the acetic acid moiety donates the proton to the counter molecule. (CH3COOH–H2O)+ has a non-proton-transferred structure, where CH3COOH+ and H2O are hydrogen-bonded. The origin of these structural differences among the cluster cations is discussed with the relative sizes of the proton affinities of the cluster components and the potential energy curves along the proton-transfer coordinate.
Electrostatic correlations at the Stern layer: Physics or chemistry?
Authors: Travesset A. , Vangaveti S.
Published: November 2009

We introduce a minimal free energy describing the interaction of charged groups and counterions including both classical electrostatic and specific interactions. The predictions of the model are compared against the standard model for describing ions next to charged interfaces, consisting of Poisson–Boltzmann theory with additional constants describing ion binding, which are specific to the counterion and the interfacial charge (“chemical binding”). It is shown that the “chemical” model can be appropriately described by an underlying “physical” model over several decades in concentration, but the extracted binding constants are not uniquely defined, as they differ depending on the particular observable quantity being studied. It is also shown that electrostatic correlations for divalent (or higher valence) ions enhance the surface charge by increasing deprotonation, an effect not properly accounted within chemical models. The charged phospholipid phosphatidylserine is analyzed as a concrete example with good agreement with experimental results. We conclude with a detailed discussion on the limitations of chemical or physical models for describing the rich phenomenology of charged interfaces in aqueous media and its relevance to different systems with a particular emphasis on phospholipids.
Metastable helium density probe for remote plasmas
Authors: Miura Naoto , Hopwood Jeffrey
Published: November 2009

Helium metastable atom density was spatially determined by a modified electrostatic probe in a remote plasma. The probe structure was similar to that of a guard ring probe. Opposite polarity voltages were applied to the inner probe and the guard ring to shield both electrons and ions from the vicinity of the inner probe. Therefore, the inner probe current is due to secondary electrons generated by the de-exciting helium metastable atom flux. The photoelectron current was removed by shielding and orienting the probe 90° to the direction of the plasma-generated photon flux. Helium metastable atom density on the order of 107 cm−3 was measured. Limitations on the use of this technique are revealed by comparisons with simulated metastable distributions.
Electrically detected magnetic resonance using radio-frequency reflectometry
Authors: Huebl H. , Starrett R. P. , McCamey D. R. , Ferguson A. J. , Willems van Beveren L. H.
Published: November 2009

The authors demonstrate readout of electrically detected magnetic resonance at radio frequencies by means of a LCR tank circuit. Applied to a silicon field-effect transistor at millikelvin temperatures, this method shows a 25-fold increased signal-to-noise ratio of the conduction band electron spin resonance and a higher operational bandwidth of >300 kHz compared to the kilohertz bandwidth of conventional readout techniques. This increase in temporal resolution provides a method for future direct observations of spin dynamics in the electrical device characteristics.
Isotope effects in liquid water by infrared spectroscopy. III. H2O and D2O spectra from 6000tocm−1
Authors: Max Jean-Joseph , Chapados Camille
Published: November 2009

The infrared spectra (IR) of pure liquid light (H2O) and heavy (D2O) water were obtained with attenuated total reflection (ATR) and transmission measurements in the mid-IR and far-IR. With these and with other values obtained from the literature, the real (n) and imaginary parts (k) of the refractive index were meticulously derived in the complete IR region from 6000to0cm−1. The reliability of the results resides in the critical comparison of our experimental data with that obtained from other laboratories and between calculated and experimental spectra, obtained by ATR and transmission techniques. The new optical properties (n and k) can now be used as standards for liquid H2O and D2O. To these we have added the water (H and D) absorption coefficients (K) that are derived from the k values. These can be used as references for spectra obtained by transmission with an absorbance intensity scale because they are almost the same.
Inertial oscillations in a confined monopolar vortex subjected to background rotation
Authors: Duran-Matute M. , Kamp L. P. J. , Trieling R. R. , van Heijst G. J. F.
Published: November 2009

We study the axisymmetric inertial oscillations in a confined monopolar vortex under the influence of background rotation. By first focusing on the inviscid linear dynamics, and later studying the effects of viscosity and of a no-slip bottom, we characterize the effects of rotation and confinement. It was found that background rotation allows for oscillations outside the vortex core even with frequencies larger than 2Ω, with Ω the background rotation rate. However, confinement is necessary for the system to sustain oscillations with frequencies smaller than 2Ω. Through the analytical solution for a small perturbation of a Rankine vortex, we obtain five regimes where the oscillations are qualitatively different, depending on their frequency. Numerical results for the linear inviscid waves sustained by a Lamb–Oseen vortex show a similar behavior. The effects of viscosity are twofold: the oscillations are damped and the vortex sustaining the oscillations is modified. When a no-slip bottom is considered, a boundary layer drives a secondary motion superimposed on the inertial oscillations. In this case, the vortex is quickly damped, but the oscillations persist due to the background rotation.
Nematic and smectic ordering in a system of two-dimensional hard zigzag particles
Authors: Varga Szabolcs , Gurin Péter , Armas-Pérez Julio C. , Quintana-H Jacqueline
Published: November 2009

The orientational and positional ordering of the two-dimensional system of hard zigzag particles has been investigated by means of Onsager theory. Analytical results are obtained for the transition densities of the isotropic-nematic and the nematic-smectic phase transitions. It is shown that the stability of the nematic and smectic phases is very sensitive to the molecular shape. In the hard needle limit, only the isotropic-nematic phase transition takes place, while increasing the tail length and the bent angle between the central core and the tails destabilizes the nematic phase. On the other hand the stability of the smectic phase is due to the increasing excluded area cost with bent angle and the tail length. The zigzag particles pack in a layered structure such that they are tilted and form semi-ideal gas in the layers to push the high cost excluded area regions into the interstitial regions. The predictions of Onsager theory are in good agreement with MC simulation data.
Symmetry breaking of the density distribution of a quantum fluid in a nanoslit
Authors: Berim Gersh O. , Ruckenstein Eli
Published: November 2009

The phenomenon of symmetry breaking (SB) of the fluid density distribution in a slit between parallel identical solid walls examined previously for a classical fluid (argon) [G. O. Berim and E. Ruckenstein, J. Chem. Phys. 126, 124503 (2007)] is examined for a quantum fluid (H4e) on the basis of a nonlocal density functional theory. The Lennard-Jones potential was employed for the fluid-fluid and fluid-solid interactions. Regarding the latter interaction potential, it was supposed that each wall generates a hard core repulsion at some distance hr from the wall. In addition, the Chizmeshya–Cole–Zaremba (CCZ) potential was considered for the fluid-solid interactions. SB was found at all considered temperatures (0 K≤T≤3.0 K) in ranges of average densities of the fluid which decreased, as for classical fluids, with increasing temperature. It was concluded that the existence of SB does not depend on the value of the parameter hr, whereas, for classical fluids, SB did not occur when hr became smaller than a critical value, hr,c. For the CCZ potential, the asymmetric (symmetry breaking) density profile can be metastable, whereas for the Lennard-Jones potential when an asymmetric density profile occurred it was always stable (had a smaller free energy than the symmetric profile). No effect of the H4e transition from nonsuperfluid to superfluid state was detected.
Local chemical states and thermal stabilities of nitrogen dopants in ZnO film studied by temperature-dependent x-ray photoelectron spectroscopy
Authors: Li X. H. , Xu H. Y. , Zhang X. T. , Liu Y. C. , Sun J. W. , Lu Y. M.
Published: November 2009

Local chemical states and thermal stabilities of N dopants in ZnO:N film are investigated by temperature-dependent x-ray photoelectron spectroscopy. Different types of N local states are detected, including N2 molecules occupying O sites [(N2)O], –NO species, substitutional N atoms in O- and N-rich local environments (α- and β-NO). Compared to the β-NO, the α-NO shows a better thermal stability up to 723 K. However, the transformation from α-NO acceptor to undesirable (N2)O donor occurs above 743 K. The variation of N local states also affects Zn and O binding energies. Photoluminescence studies indicate the shallow acceptor nature of α-NO.
Effect of anisotropic charge transport on device characteristics of polymer solar cells
Authors: Shah Manas , Pryamitsyn Victor , Ganesan Venkat
Published: November 2009

We present a model for photovoltaic device characteristics based on drift-diffusion ideas which allows for prescription of arbitrary morphologies of donor and acceptor phases while simultaneously incorporating the role of anisotropic charge transport of holes and excitons. We use such a model to address the interplay between anisotropic charge transport and the orientational and/or crystalline ordering of donor molecules. We presents results illustrating the influence of the degree of orientational ordering, the impact of ordering parallel and perpendicular to the electrodes and the role of device thickness.
Photon statistics in enhanced fluorescence from a single CdSe/ZnS quantum dot in the vicinity of silver nanoparticles
Authors: Masuo Sadahiro , Naiki Hiroyuki , Machida Shinjiro , Itaya Akira
Published: November 2009

Single-photon emission behavior in the enhanced fluorescence from single colloidal quantum dots (QDs) near silver nanoparticles (AgNPs) was investigated using a single molecule fluorescence spectroscopy technique. It was found that the degree of fluorescence enhancement from single QDs with AgNPs increased with decrease in the lifetime and the probability of single-photon emission, that is, highly enhanced fluorescence with a shortened lifetime exhibited a low probability of single-photon emission. The present results yield new insights into fundamentals of QD-metal nanostructure interactions, and are also important to understand the mechanism of the fluorescence enhancement by localized surface plasmon of metal nanostructures.
Anisotropic electron spin relaxation in bulk GaN
Authors: Buß J. H. , Rudolph J. , Natali F. , Semond F. , Hägele D.
Published: November 2009

Electron spin dynamics in n-type c-oriented wurtzite GaN epilayers is studied by time-resolved Kerr-rotation measurements at T=80 K. The electron spin lifetime shows a sudden increase if an external magnetic field is applied in the sample plane. This enhancement is explained by anisotropic Dyakonov–Perel spin relaxation in bulk GaN as a direct consequence of the anisotropy of spin-orbit coupling in semiconductors with wurtzite structure.
Synchronization in coupled time-delayed systems with parameter mismatch and noise perturbation
Authors: Sun Yongzheng , Ruan Jiong
Published: November 2009

In this paper, a design of coupling and effective sufficient condition for stable complete synchronization and antisynchronization of a class of coupled time-delayed systems with parameter mismatch and noise perturbation are established. Based on the LaSalle-type invariance principle for stochastic differential equations, sufficient conditions guaranteeing complete synchronization and antisynchronization with constant time delay are developed. Also delay-dependent sufficient conditions for the case of time-varying delay are derived by using the Lyapunov approach for stochastic differential equations. Numerical examples fully support the analytical results.
High-resolution cavity ringdown spectroscopy of the jet-cooled ethyl peroxy radical C2H5O2
Authors: Just Gabriel M. P. , Rupper Patrick , Miller Terry A. , Meerts W. Leo
Published: November 2009

We have recorded high resolution, partially rotationally resolved, jet-cooled cavity ringdown spectra of the origin band of the Ã−X̃ electronic transition of both the G and T conformers of the perproteo and perdeutero isotopologues of the ethyl peroxy radical, C2H5O2. This transition, located in the near infrared, was studied using a narrow band laser source (≲250 MHz) and a supersonic slit-jet expansion coupled with an electric discharge allowing us to obtain rotational temperatures of about 15 K. All four spectra have been successfully simulated using an evolutionary algorithm approach with a Hamiltonian including rotational and spin-rotational terms. Excellent agreement with the experimental spectra was obtained by fitting seven molecular parameters in each ground and the first excited electronic states as well as the band origin of the electronic transition. This analysis unambiguously confirms the assignment of the lower frequency origin band to the G conformer and the higher frequency one to the T conformer.
Surface plasmon excitation of amplified spontaneous emission from laser dye molecules embedded in polymer matrix
Authors: Popov O. , Lirtsman V. , Davidov D.
Published: November 2009

We report on amplified spontaneous emission (ASE) from a polymer waveguide film containing laser dye molecules (active layer) excited by surface plasmon. The polymer waveguide is deposited on an intermediate polymer layer on top of a metal film on a prism, forming a planar Kretschmann–Raether configuration. The ASE was observed in both a surface plasmon mode and a waveguide mode. In both cases, the photoluminescence was enhanced by a factor of 4 with respect to that which was observed from the same active layer deposited on a bare glass substrate. We show that efficient excitation can be achieved only when the active layer is placed on top of an intermediate polymer layer. The intermediate layer prevents back coupling of light into the prism and possible quenching.
Effects of Li doping on the performance and environmental stability of solution processed ZnO thin film transistors
Authors: Nayak Pradipta K. , Jang Jongsu , Lee Changhee , Hong Yongtaek
Published: November 2009

We report the effects of lithium (Li) doping on the performance and environmental stability of solution processed zinc oxide (ZnO) thin film transistors (TFTs). It was found that appropriate amount of Li doping significantly reduced the background conductivity of ZnO films and also improved the orientation of ZnO crystallites along the c-axis. A highest field-effect mobility of 3.07 cm2/V s was found for the 5 at. % Li-doped ZnO TFTs. However, 15 and 25 at. % Li-doped ZnO TFTs showed good environmental stability of Ion/Ioff ratio with reasonable field-effect mobility.
Improving optical performance of inverted organic solar cells by microcavity effect
Authors: Long Yongbing
Published: November 2009

Optical simulations have been performed to investigate the performance of inverted organic solar cells with metal-mirror microcavity structure formed by central active layer sandwiched between semitransparent silver (Ag) cathode and thick Ag anode. Compared to nearly optimized noncavity devices with indium tin oxide cathode, the total absorbed photons (TAPs) in a 70 nm-thick active layer for cavity devices can be improved by 16.3% due to microcavity effect. Furthermore, an improvement of over 10% in TAPs can be obtained when thin Ag layer is optimized to be 10–16 nm thick, indicating thin Ag layer is a good choice as transparent electrode material.
Noncontact and noninvasive study of plant leaves using air-coupled ultrasounds
Authors: Gómez Álvarez-Arenas T. E. , Sancho-Knapik D. , Peguero-Pina J. J. , Gil-Pelegrín E.
Published: November 2009

Plant leaves are studied by the analysis of the magnitude and phase spectra of their thickness mechanical resonances. These resonances appear at ultrasonic frequencies and have been excited and sensed using air-coupled ultrasounds. In spite of the complex leaf microstructure, the effective medium approach can be applied to solve the inverse problem, at least in the vicinity of the first thickness resonance. Results suggest that these resonances are sensitive to leaf microstructure, composition water content and water status in the leaf.