bluuebunny/crossref_metadata_2025 huggingface dataset:
Melatonin receptors in human uveal melanocytes and melanoma cells
Authors: Roberts Joan E. , F. Wiechmann Allan , Hu Dan‐Ning
Published: June 2010

Previous work has demonstrated that melatonin inhibits growth of cultured human uveal melanoma cells. The goal of this study was to determine the expression of mRNA encoding the melatonin receptor subtypes and the effect of specific melatonin receptor agonists on cell growth of uveal melanoma cells and melanocytes. RNA expression of the human melatonin Mel1a and Mel1b receptor subtypes was
determined by reverse transcription‐polymerase chain reaction (RT‐PCR)
amplification of RNA isolated from two melanoma cell lines and from one
cell line of normal melanocytes. PCR‐amplified cDNA encoding the
Mel1b melatonin receptor subtype, but not the Mel1a
subtype, was detected in reverse‐transcribed RNA obtained from both
normal uveal melanocytes and melanoma cell lines. Uveal melanoma cells
and melanocytes were cultured for 24 hr, then melatonin or one of its
membrane receptor agonists, 6‐chloromelatonin (Mel1a–1b)
or S‐20098 (Mel1b) or its putative nuclear agonist, CGP‐52608
(Mel2), was added to the medium. After 5 days, the cells were
detached, counted, and compared to untreated controls. Melatonin and its
membrane receptor agonists (Mel1a–1b and Mel1b
), but not its putative nuclear receptor agonist (Mel2),
inhibited the growth of uveal melanoma cells, but not normal melanocytes,
at very low concentrations. In uveal melanoma cells, the expression of
RNA encoding the Mel1b receptor suggests that the growth
inhibiting effect of melatonin on uveal melanoma cells is related to
activation of the melatonin Mel1b membrane receptor. Furthermore, the expression of RNA encoding melatonin receptors in normal uveal melanocytes suggests that melatonin may play a role in the function of these cells.
Immunohistochemical study of the glutamate transporter proteins GLT‐1 and GLAST in rat and gerbil pineal gland
Authors: Redecker P , Pabst H
Published: June 2010

Several investigations performed during this decade have led to the hypothesis that small secretory vesicles of pinealocytes (generally referred to as synaptic‐like microvesicles, SLMVs) are components of a system for intercellular paracrine communication between pineal cells, which shares many features with the process of synaptic neurotransmission. According to a recent study, one parallel that can be drawn to synaptic signal transduction seems to be the presence of pineal re‐uptake systems for messenger molecules released from SLMVs, i.e. for neuroactive amino acids such as l‐glutamate. In order to further characterize these uptake mechanisms, we have carried out an immunhistochemical study to explore the presence and cellular localization of the glutamate transporters GLT‐1 and GLAST in rat and gerbil pineal glands. GLT‐1 and GLAST were always detected in a subpopulation of pineal parenchymal cells in both species. Using immunostaining of serial semithin sections with antibodies against marker proteins of pineal cell types, GLT‐1‐ and GLAST‐positive cells were identified as interstitial glial cells. In addition, some pinealocytes also displayed immunoreactivity for GLT‐1. In contrast to current thinking, our findings show that GLT‐1 is not the only glutamate transporter subtype expressed in the pineal gland. Moreover, our observations point to a significant participation of interstitial cells in the process of pineal glutamatergic communication, reminiscent of the role of glial cells during glutamatergic neurotransmission in the central nervous system.
Mechanistic and comparative studies of melatonin and classic antioxidants in terms of their interactions with the ABTS cation radical
Authors: Tan Dun‐xian , Hardeland Rüdiger , Manchester Lucien C. , Poeggeler Burkhard , Lopez‐Burillo Silvia , Mayo Juan C. , Sainz Rosa M. , Reiter Russel J.
Published: June 2010

Abstract: Melatonin and classic antioxidants possess the capacity to scavenge ABTSḃ+ with IC50s of 4, 11, 15.5, 15.5, 17 and 21 μm for melatonin, glutathione, vitamin C, trolox, NADH and NADPH, respectively. In terms of scavenging ABTSḃ+, melatonin exhibits a different profile than that of the classic antioxidants. Classic antioxidants scavenge one or less ABTSḃ+, while each melatonin molecule can scavenge more than one ABTSḃ+, probably with a maximum of four. Classic antioxidants do not synergize when combined in terms of scavenging ABTSḃ+. However, a synergistic action is observed when melatonin is combined with any of the classic antioxidants. Cyclic voltammetry indicates that melatonin donates an electron at the potential of 715 mV. The scavenging mechanism of melatonin on ABTSḃ+ may involve multiple‐electron donations via intermediates through a stepwise process. Intermediates including the melatoninyl cation radical, the melatoninyl neutral radical and cyclic 3‐hydroxymelatonin (cyclic 3‐OHM) and N1‐acetyl‐N2‐formyl‐5‐methoxykynuramine (AFMK) seem to participate in these reactions. More interestingly, the pH of the solution dramatically modifies the ABTSḃ+ scavenging capacity of melatonin while pH changes have no measurable influence on the scavenging activity of classic antioxidants. An acidic pH markedly reduces the ABTSḃ+ scavenging capacity of melatonin while an increased pH promotes the interaction of melatonin and ABTSḃ+. The major melatonin metabolites that develop when melatonin interacts with ABTSḃ+ are cyclic 3‐OHM and AFMK. Cyclic 3‐OHM is the intermediate between melatonin and AFMK, and cyclic 3‐OHM also has the ability to scavenge ABTSḃ+. Melatonin and the metabolites which are generated via the interaction of melatonin with ABTSḃ+, i.e. the melatoninyl cation radical, melatoninyl neutral radical and cyclic 3‐OHM, all scavenge ABTSḃ+. This unique cascade action of melatonin, in terms of scavenging, increases its efficiency to neutralized ABTSḃ+; this contrasts with the effects of the classic antioxidants.
Melatonin biological activity and binding sites in human melanoma cells
Authors: de Souza Andrea Vieira , Visconti Maria Aparecida , de Lauro Castrucci Ana Maria
Published: June 2010

Abstract:  The effects of melatonin, N‐acetylserotonin and serotonin on the growth and tyrosinase activity of SK‐Mel 23 and SK‐Mel 28 human melanoma cell lines were investigated. Binding assays were also performed to establish the nature of the binding site. SK‐Mel 28 cells were responsive to melatonin and its precursors, exhibiting a decrease in growth and an increase in tyrosinase activity after a 72 hr treatment. N‐acetylserotonin was as potent as melatonin, the minimal effective concentration (MEC, which is defined as the smallest concentration that elicits a measurable biological response, significantly different from control) being 10−8 m. Serotonin was the least potent (MEC  = 10−6 m). Both melatonin antagonists, prazosin and luzindole, exhibited no effect per se and reversed both responses to melatonin. SK‐Mel 23 cells, however, showed no significant responses to the indoleamines. Competition binding assays in SK‐Mel 28 cells demonstrated the presence of binding sites to 2‐[125 I]‐iodomelatonin, which was displaced by the unlabelled hormone, by both antagonists, and by N‐acetylserotonin. The curve adjustment of the displacement values with melatonin suggests the existence of two binding sites, with the following Ki values: 1.0 × 10−10 m and 6.5 × 10−6 m. Ki values for acetylserotonin, prazosin and luzindole were, respectively, 3.8 × 10−8 m, 1.2 × 10−8 m, and 8.3 × 10−6 m. Surprisingly, in SK‐Mel 23 cells, melatonin and luzindole were able to compete with the radioligand, with Ki values of 3.1 × 10−8 and 2.4 × 10−8 m, respectively. Our data suggest that SK‐Mel 28 cells probably possess high affinity binding sites to melatonin and, in addition, MT3 low affinity binding sites, because N‐acetylserotonin was as effective as the native hormone, and prazosin effectively blocked the actions of melatonin. Both sites are functional as demonstrated by the blockade promoted by both luzindole and prazosin on the proliferative and melanogenic responses. Although growth and tyrosinase activity of SK‐Mel 23 cells were not affected by melatonin or its precursors, this cell line possesses high affinity binding sites, which may be non‐functional, or trigger responses other than the ones herein investigated.
Altered neutrophil apoptosis activity is reversed by melatonin in liver ischemia‐reperfusion
Authors: Chen Jih‐Chang , Ng Chip‐Jin , Chiu Te‐Fa , Chen Han‐Ming
Published: June 2010

Delayed neutrophil apoptosis has been implicated as the mechanism of the systemic inflammatory response. Herein, we examined the effect of melatonin on the neutrophil apoptosis in ischemia and reperfusion of the human liver. We studied seven patients receiving elective hepatectomy for liver tumor and ten patients receiving laparoscopic cholecystectomy for gallstones. Ten milli liters of blood was drawn isolation and incubation of the human neutrophils. Neutrophil apoptosis activity and CD18 expression and respiratory burst activity were assessed flow cytometrically. Another group of neutrophils included those from the patients receiving hepatectomy and isolated and incubated with melatonin. Neutrophil apoptosis is delayed from patients after hepatectomy or laparoscopic cholecystectomy when compared with that of the preoperative state. The decrease in the apoptosis activity is more severe in patients receiving hepatectomy as compared with those receiving laparoscopic cholecystectomy. Neutrophils from patients receiving hepatectomy or laparoscopic cholecystectomy are functionally activated. Melatonin can reverse the delayed process and enhance the apoptosis activity in neutrophils from patients receiving hepatectomy. This study demonstrates that melatonin enhances neutrophil apoptosis in patients receiving hepatectomy involving ischemia and reperfusion of the human liver.
Neuroglobin Protects Neurons against Oxidative Stress in Global Ischemia
Authors: Li Richard Changxun , Guo Shang Zhi , Lee Seung Kwan , Gozal David
Published: June 2010

Neuroglobin (Ngb) is a recently discovered globin that affords protection against hypoxic/ischemic-induced cell injury in brain. Hypoxic/ischemic injury is associated with accumulation of reactive oxygen species (ROS) and/or reactive nitrogen species (RNS). In previous studies, we found that Ngb has antioxidative properties, and protects PC-12 cells against hypoxia- and β-amyloid-induced cell death. To further delineate the potential role of Ngb in protection against cerebral ischemia–reperfusion injury in vivo, we developed a transgenic mouse line that overexpresses Ngb. Hippocampal ischemia–reperfusion injury was induced by a 10-minute bilateral occlusion of the common carotid arteries, and the animal brains were assessed 3 days later. CA1 neural injury was determined by cresyl violet staining. Lipid peroxidation was assessed using a malonyldialdehyde assay kit, whereas ROS/RNS accumulation was determined by Het staining in the CA1 hippocampal region. Hippocampal Ngb mRNA and protein expressions were assessed by reverse transcriptase-PCR and western blotting, respectively. Neuroglobin was successfully overexpressed in the hippocampus of Ngb transgenic mice. After ischemia–reperfusion, CA1 ROS/RNS production and lipid peroxidation were markedly decreased in Ngb transgenic mice compared with wild-type mice. Furthermore, CA1 neuronal injury was also markedly reduced. Thus, Ngb may confer protection against ischemia–reperfusion injury in the brain through its intrinsic antioxidant properties.
Statistics in Experimental Cerebrovascular Research: Comparison of More than Two Groups with a Continuous Outcome Variable
Authors: Schlattmann Peter , Dirnagl Ulrich
Published: June 2010

A common setting in experimental cerebrovascular research is the comparison of more than two experimental groups. Often, continuous measures such as infarct volume, cerebral blood flow, or vessel diameter are the primary variables of interest. This article presents the principles of the statistical analysis of comparing more than two groups using analysis of variance (ANOVA). We will also explain post hoc comparisons, which are required to show which groups significantly differ once ANOVA has rejected the null hypothesis. Although statistical packages perform ANOVA and post hoc contrast at a key stroke, in this study, we use examples from experimental stroke research to reveal the simple math behind the calculations and the basic principles. This will enable the reader to understand and correctly interpret the readout of statistical packages and to help prevent common errors in the comparison of multiple means.
Dynamic CRM occupancy reflects a temporal map of developmental progression
Authors: Wilczyński Bartek , Furlong Eileen E M
Published: June 2010

Development is driven by tightly coordinated spatio‐temporal patterns of gene expression, which are initiated through the action of transcription factors (TFs) binding to cis‐regulatory modules (CRMs). Although many studies have investigated how spatial patterns arise, precise temporal control of gene expression is less well understood. Here, we show that dynamic changes in the timing of CRM occupancy is a prevalent feature common to all TFs examined in a developmental ChIP time course to date. CRMs exhibit complex binding patterns that cannot be explained by the sequence motifs or expression of the TFs themselves. The temporal changes in TF binding are highly correlated with dynamic patterns of target gene expression, which in turn reflect transitions in cellular function during different stages of development. Thus, it is not only the timing of a TF's expression, but also its temporal occupancy in refined time windows, which determines temporal gene expression. Systematic measurement of dynamic CRM occupancy may therefore serve as a powerful method to decode dynamic changes in gene expression driving developmental progression.
Dissecting spatio‐temporal protein networks driving human heart development and related disorders
Authors: Lage Kasper , Møllgård Kjeld , Greenway Steven , Wakimoto Hiroko , Gorham Joshua M , Workman Christopher T , Bendsen Eske , Hansen Niclas T , Rigina Olga , Roque Francisco S , Wiese Cornelia , Christoffels Vincent M , Roberts Amy E , Smoot Leslie B , Pu William T , Donahoe Patricia K , Tommerup Niels , Brunak Søren , Seidman Christine E , Seidman Jonathan G , Larsen Lars A
Published: June 2010

Aberrant organ development is associated with a wide spectrum of disorders, from schizophrenia to congenital heart disease, but systems‐level insight into the underlying processes is very limited. Using heart morphogenesis as general model for dissecting the functional architecture of organ development, we combined detailed phenotype information from deleterious mutations in 255 genes with high‐confidence experimental interactome data, and coupled the results to thorough experimental validation. Hereby, we made the first systematic analysis of spatio‐temporal protein networks driving many stages of a developing organ identifying several novel signaling modules. Our results show that organ development relies on surprisingly few, extensively recycled, protein modules that integrate into complex higher‐order networks. This design allows the formation of a complicated organ using simple building blocks, and suggests how mutations in the same genes can lead to diverse phenotypes. We observe a striking temporal correlation between organ complexity and the number of discrete functional modules coordinating morphogenesis. Our analysis elucidates the organization and composition of spatio‐temporal protein networks that drive the formation of organs, which in the future may lay the foundation of novel approaches in treatments, diagnostics, and regenerative medicine.
Violations of robustness trade‐offs
Authors: Kitano Hiroaki
Published: June 2010

Biological robustness is a principle that may shed light on system‐level characteristics of biological systems. One intriguing aspect of the concept of biological robustness is the possible existence of intrinsic trade‐offs among robustness, fragility, performance, and so on. At the same time, whether such trade‐offs hold regardless of the situation or hold only under specific conditions warrants careful investigation. In this paper, we reassess this concept and argue that biological robustness may hold only when a system is sufficiently optimized and that it may not be conserved when there is room for optimization in its design. Several testable predictions and implications for cell culture experiments are presented.
Superolateral Dislocation of the Mandibular Condyle: Report of a Case with Review of Literature and a Proposed Modification in the Classification
Authors: Tauro David , Lakshmi Subha , Mishra Madan
Published: June 2010

Anteromedial fracture dislocation of the mandibular condyle is common but a superolateral dislocation of an intact condyle is quite rare. Only ∼19 cases of such dislocation have been reported in the world English literature. This type of dislocation is often misdiagnosed or completely overlooked and hence inadequately addressed. A case of superolateral dislocation of the condyle associated with a symphyseal fracture is presented. We discuss the dynamics, diagnostic features and clinical management of such dislocations with the review of literature and propose a modification in the existing classification.
Homogeneous water nucleation in a laminar flow diffusion chamber
Authors: Manka Alexandra A. , Brus David , Hyvärinen Antti-Pekka , Lihavainen Heikki , Wölk Judith , Strey Reinhard
Published: June 2010

Homogeneous nucleation rates of water at temperatures between 240 and 270 K were measured in a laminar flow diffusion chamber at ambient pressure and helium as carrier gas. Being in the range of 102–106 cm−3 s−1, the experimental results extend the nucleation rate data from literature consistently and fill a pre-existing gap. Using the macroscopic vapor pressure, density, and surface tension for water we calculate the nucleation rates predicted by classic nucleation theory (CNT) and by the empirical correction function of CNT by Wölk and Strey [J. Phys. Chem. B 105, 11683 (2001)]. As in the case of other systems (e.g., alcohols), CNT predicts a stronger temperature dependence than experimentally observed, whereas the agreement with the empirical correction function is good for all data sets. Furthermore, the isothermal nucleation rate curves allow us to determine the experimental critical cluster sizes by use of the nucleation theorem. A comparison with the critical cluster sizes calculated by use of the Gibbs–Thomson equation is remarkably good for small cluster sizes, for bigger ones the Gibbs–Thomson equation overestimates the cluster sizes.
Variations in μτ measurements in cadmium zinc telluride
Authors: Jones K. A. , Datta A. , Lynn K. G. , Franks L. A.
Published: June 2010

A number of commonly employed experimental methods used to determine the μτ product in the semiconductor CdZnTe were investigated. The objective was to determine possible differences in results inherent in the techniques. A pixelated and two planar devices were studied using various distinct methods together with different excitation sources and amplifier shaping times. Variations in the results up to a factor of 5 were found. Variations due to shaping times, particle type, and energy were evident.
A comprehensive analysis of the contributions to the nonlinear optical properties of thin Ag films
Authors: Owens Daniel T. , Fuentes-Hernandez Canek , Hales Joel M. , Perry Joseph W. , Kippelen Bernard
Published: June 2010

The nonlinear optical properties of 20 nm thick Ag films are investigated by time-resolved white- light continuum pump-probe experiments in both transmission and reflection mode. The dynamics of changes in permittivity Δε are measured at wavelengths between 500 to 700 nm. The data is fitted to a modified Drude model in the frequency domain and to a two-temperature model in the time domain. Changes in the individual Drude parameters are calculated as a function of time. A single, coherent model is proposed based on these fittings that describes the dynamics of the nonlinear optical properties of Ag, which could be used to model the nonlinear responses of multilayer structures containing thin films of Ag. The physical origins of the observed responses are discussed.
Hysteresis and phase transitions for one-dimensional and three-dimensional models in shape memory alloys
Authors: Berti V. , Fabrizio M. , Grandi D.
Published: June 2010

By means of the Ginzburg–Landau theory of phase transitions, we study a nonisothermal model to characterize the austenite-martensite transition in shape memory alloys. In the first part of this paper, the one-dimensional model proposed by Berti et al. [“Phase transitions in shape memory alloys: A non-isothermal Ginzburg-Landau model,” Physica D 239, 95 (2010)] is modified by varying the expression of the free energy. In this way, the description of the phenomenon of hysteresis, typical of these materials, is improved and the related stress-strain curves are recovered. Then, a generalization of this model to the three-dimensional case is proposed and its consistency with the principles of thermodynamics is proven. Unlike other three-dimensional models, the transition is characterized by a scalar valued order parameter φ and the Ginzburg–Landau equation, ruling the evolution of φ, allows us to prove a maximum principle, ensuring the boundedness of φ itself.
Electrohydrodynamic instabilities at interfaces subjected to alternating electric field
Authors: Gambhire P. , Thaokar R. M.
Published: June 2010

Instabilities at the interface of two immiscible fluids, either perfect or leaky dielectrics, subjected to alternating electric fields, is studied using a linear stability analysis in the limit of the electrode spacing being large compared to the wavelength of the perturbation. The Floquet analysis of the stability of this system indicates a significant effect of the frequency on the value of smax, the growth rate of the fastest growing instabilities and ETaylor, the minimum field required to excite an instability. It is seen that alternating fields act to damp the system instabilities compared to the direct current (dc) case. Moreover, the growth rate of the instabilities can be tuned from that of leaky dielectric fluids subjected to dc fields, in the low frequency limit, to that of perfect dielectrics in the high frequency limit. It is also observed that for a leaky dielectric-leaky dielectric interface, the alternating current (ac) fields can induce instabilities in a system which is stable at zero frequency, by increasing the frequency of the applied voltage.
Polarization enhancement in compositionally graded vanadium doped bismuth titanate thin films
Authors: Chakraborty Pradip , Krupanidhi S. B.
Published: June 2010

Compositionally up and downgraded Bi4−x/3Ti3−xVxO12 (x=0.0,0.012,0.03,0.06) thin films were grown on Pt coated silicon substrates by pulsed laser deposition technique. Downgraded fabrication showed improved ferroelectric polarization in comparison to upgraded fabrication. Films deposited at 650 and 700 °C showed very large remnant polarization (2Pr) value of 82 μC cm−2, which is comparatively large among all bismuth based thin films reported so far. A mechanism based on vanadium enrich seeded layer formation in the downgraded structure is proposed for the improvement. Moreover, frequency independent behavior (100Hz–5kHz) of the graded films ensures its potential application for various microelectronic devices.
High brightness from unstable resonator mid-IR semiconductor lasers
Authors: Ongstad A. P. , Dente G. C. , Tilton M. L. , Chavez J. R. , Kaspi R. , Gianardi D. M.
Published: June 2010

We compare the performance of several optically pumped unstable resonator semiconductor lasers with cavity lengths of 4, 5, and 6 mm and operating in the mid-IR at 4.7 μm. The unstable resonator lasers (URLs) were fabricated by polishing a diverging cylindrical mirror on one of the facets. In general, the URL beam quality (BQ) was 1–2 times diffraction limited when operated at pump powers below 30 W (URL power ≤6 W) As the pump power is increased, the BQ is observed to degrade; at 60 W the URL’s were ∼3.5 times diffraction limited (URL power ≈11 W). The highest brightness URL, a 4-mm long device, was compared with an equivalent 4-mm long Fabry–Perot (FP) laser operated at different cavity widths. The performance of the broad area URL (500 μm width), as assessed by power-in-the-bucket measurements, was superior to both wide stripe (500 μm) and narrow pump stripe (100 μm) FP lasers.
Synthesis of L1-FePt perpendicular films with controllable coercivity and intergranular exchange coupling by interfacial microstructure control
Authors: Feng Chun , Zhang En , Yang Meiyin , Li Ning , Li Baohe , Jiang Yong , Yu Guanghua
Published: June 2010

A series of FePtBi/Au multilayers were fabricated by magnetron sputtering. The interfacial microstructure control of Bi and Au atoms and its effect on comprehensive properties of L10-FePt perpendicular films were carefully studied. Results show that: perpendicular magnetic anisotropy of the L10-FePt film can be remarkably enhanced with the epitaxial inducement of Au atoms. On the other hand, intergranular exchange coupling (IEC) of the film is greatly decreased due to the isolation of FePt particles by nonmagnetic Au particles. Moreover, the controllable coercivity of the film can be realized by adjusting ordering degree of the film through diffusion of Bi atoms. Thus, an L10-FePt perpendicular film with controllable coercivity and no IEC is realized with the interfacial microstructure control of surfactant Bi and Au atoms.
Transport properties of finite-β microturbulence
Authors: Pueschel M. J. , Jenko F.
Published: June 2010

Via nonlinear gyrokinetic simulations, microturbulent transport is investigated for electromagnetic trapped electron mode (TEM) and ion temperature gradient (ITG) tokamak core turbulence with β up to and beyond the kinetic ballooning mode threshold. Deviations from linear expectations are explained by zonal flow activity in the TEM case. For the ITG scenario, β-induced changes are observed in the nonlinear critical gradient upshift—from a certain β, a strong increase is observed in the Dimits shift. Additionally, a Rechester–Rosenbluth-type model for magnetic transport is applied, and the amplitudes of magnetic field fluctuations are quantified for different types of turbulence.
Enhanced sampling and applications in protein folding in explicit solvent
Authors: Zhang Cheng , Ma Jianpeng
Published: June 2010

We report a single-copy tempering method for simulating large complex systems. In a generalized ensemble, the method uses runtime estimate of the thermal average energy computed from a novel integral identity to guide a continuous temperature-space random walk. We first validated the method in a two-dimensional Ising model and a Lennard-Jones liquid system. It was then applied to folding of three small proteins, trpzip2, trp-cage, and villin headpiece in explicit solvent. Within 0.5∼1 microsecond, all three systems were reversibly folded into atomic accuracy: the alpha carbon root mean square deviations of the best folded conformations from the native states were 0.2, 0.4, and 0.4 Å, for trpzip2, trp-cage, and villin headpiece, respectively.
Dust acoustic dressed soliton with dust charge fluctuations
Authors: Asgari H. , Muniandy S. V. , Wong C. S.
Published: June 2010

Modeling of dust acoustic solitons observed in dusty plasma experiment [Bandyopadhyay et al., Phys. Rev. Lett. 101, 065006 (2008)] using the Korteweg–de Vries (KdV) equation showed significant discrepancies in the regime of large amplitudes (or high soliton speed). In this paper, higher order perturbation corrections to the standard KdV soliton are proposed and the resulting dressed soliton is shown to describe the experimental data better, in particular, at high soliton speed. The effects of dust charge fluctuations on the dust acoustic dressed soliton in a dusty plasma system are also investigated. The KdV equation and a linear inhomogeneous equation, governing the evolution of first and second order potentials, respectively, are derived for the system by using reductive perturbation technique. Renormalization procedure is used to obtain nonsecular solutions of these coupled equations. The characteristics of dust acoustic dressed solitons with and without dust charge fluctuations are discussed.
Stray magnetic field compensation with a scalar atomic magnetometer
Authors: Belfi J. , Bevilacqua G. , Biancalana V. , Cecchi R. , Dancheva Y. , Moi L.
Published: June 2010

We describe a system for the compensation of time-dependent stray magnetic fields using a dual channel scalar magnetometer based on nonlinear Faraday rotation in synchronously optically pumped Cs vapor. We detail the active control strategy, with an emphasis on the electronic circuitry, based on a simple phase-locked-loop integrated circuit. The performance and limits of the system developed are tested and discussed. The system was applied to significantly improve the detection of free induction decay signals from protons of remotely magnetized water precessing in an ultralow magnetic field.
Escape of a driven particle from a metastable state: A semiclassical approach
Authors: Ghosh Pradipta , Shit Anindita , Chattopadhyay Sudip , Chaudhuri Jyotipratim Ray
Published: June 2010

In this article we explore the dynamics of escape of a particle in the semiclassical regime by driving the particle externally. We demonstrate that under suitable approximations the semiclassical escape rate essentially assumes the structure of classical Kramers rate. Both internal (due to thermal bath) as well as external noises (due to driving) are being considered. The noises are stationary, Gaussian, and are characterized by arbitrary decaying memory kernel. Finally, we subject our formulation to rigorous numerical test under variedly changing conditions of the parameters.
Inhomogeneity of epidemic spreading
Authors: Liu Zhenzhen , Wang Xingyuan , Wang Mogei
Published: June 2010

In this study, we use the characteristic infected cluster size to investigate the inhomogeneity of the epidemic spreading in static and dynamic complex networks. The simulation results show that the epidemic spreads inhomogeneously in both cases. Also, the inhomogeneity of the epidemic spreading becomes smaller with increasing speed of moving individuals and almost disappears when the speed is high enough.
Microstructure and initial growth characteristics of nanocrystalline silicon films fabricated by very high frequency plasma enhanced chemical vapor deposition with highly H2 dilution of SiH4
Authors: Wang Xiang , Huang Rui , Song Jie , Guo Yanqing , Ding Honglin
Published: June 2010

Nanocrystalline silicon (nc-Si:H) film deposited on silicon oxide in a very high frequency plasma enhanced chemical vapor deposition with highly H2 dilution of SiH4 has been investigated by Raman spectroscopy and high resolution transmission electron microscopy. It is found that at early growth stage the initial amorphous incubation layer in nc-Si:H growth on silicon oxide can be almost eliminated and crystallites with diameter of about 6 to 10 nm are directly formed on the silicon oxide. Nearly parallel columnar structures with complex microstructure are found from cross-sectional transmission electron microscopy images of the film. It is considered that highly H2 dilution and higher excitation frequency are the main reason for eliminating the initial amorphous incubation layer in nc-Si:H growth on silicon oxide.
Structural phase transitions in AgTa0.5Nb0.5O3 thin films
Authors: Han Y. , Reaney I. M. , Johnson-Wilke R. L. , Telli M. B. , Tinberg D. S. , Levin I. , Fong D. D. , Fister T. T. , Streiffer S. K. , Trolier-McKinstry S.
Published: June 2010

Octahedral tilt transitions in epitaxial AgTa0.5Nb0.5O3 (ATN) films grown on (001)p (where p=pseudocubic) oriented SrRuO3/LaAlO3 and LaAlO3 substrates were characterized by electron diffraction and high resolution x-ray diffraction. It was found that the ATN films exhibited octahedral rotations characteristic of the Pbcm space group, similar to those seen in bulk materials; however, the temperature of the M3↔M2 phase transition has been suppressed by ∼250 K due to the fact that the correlation length for rotations about cp was significantly reduced. The average off-center B-cation displacements, which signify the degree of long-range order for these local cation positions, were negligibly small compared to bulk materials, as inferred from the near-zero intensity of the 1/4(00l)p-type reflections. On cooling, pronounced ordering of B-cation displacements occurred at ≈60 K which is significantly lower compared to bulk (≈310 K). The onset of this ordering coincides with a broad maximum in relative permittivity as a function of temperature. It is believed that point and planar defects in thin ATN films disrupt the complex sequence of in-phase and antiphase rotations around cp thereby reducing the effective strength of interactions between the tilting and cation displacements.
Magnetic properties and spin state transition of La0.7Ca0.3(Co1−yGay)O3
Authors: Wu Zhi-min , Kong Chun-yang , Wang Xin-qiang , Wang Fang-wei
Published: June 2010

Magnetic properties and spin state transfer in Ga doping perovskite cobaltites La0.7Ca0.3(Co1−yGay)O3 (y=0, 0.1, 0.2, 0.3, and 0.4) are carefully investigated in this work. On Ga doping, the Curie temperature sharply decreases and the magnetization is greatly reduced, indicating Ga doping breaks the ferromagnetic interaction in the system. For y≥0.2, the ferromagnetic and antiferromagnetic transitions have been observed in thermal magnetization measurement whereas the dominated antiferromagnetic interaction is confirmed by the negative Curie–Weiss temperatures. Evaluation of the effective moment of Co ions seems to imply that Ga doping stablizes Co-ion high spin state.
Impact of biomass burning on soil organic carbon and the release of carbon dioxide into the atmosphere in the coastal savanna ecosystem of Ghana
Authors: Parker Bismark Quarku , Osei Benjamin A. , Armah Frederick Ato , Yawson David Oscar
Published: June 2010

The impact of escalating human activities on greenhouse gas emission, global warming, and changes in global climate patterns is almost certainly the most discussed issue in the first decade of the 21st century. Two-thirds of Africa’s energy consumption consists of various forms of highly inefficient traditional biomass. In rural areas, low energy consumption is both a cause and consequence of poor development and also of the degradation of the natural environment. The burning of biomass or vegetation as a conventional land preparation method has a net negative impact on the soil organic carbon as well as on the environment through the oxidation of carbon into carbon dioxide, an anthropogenic greenhouse gas. This paper reports the findings of an experiment to investigate the impact of the heat due to burning on soil organic carbon at soil depths of 0–5 and 5–10 cm. It was observed that 21% decline in soil organic carbon resulted in the release of 1446 CO2 kg ha−1 into the atmosphere. This underscores the fact that burning of biomass as a land preparation method may not be sustainable when viewed against the backdrop that the African continent encompasses the most vulnerable regions and populations for current climate variability. This study is significant in that it is the first to shed light on the effects of burning on soil carbon in the coastal savanna ecosystem of Ghana and would potentially provide the impetus for further research.
Active microrheology of a colloidal suspension in the direct collision limit
Authors: Sriram Indira , Meyer Alexander , Furst Eric M.
Published: June 2010

The single-point active nonlinear microrheology of a colloidal suspension is measured using laser tweezers in the limit that the diameter of the probe particle approaches the diameter of the bath suspension particles. The microviscosity thins as the probe velocity (and corresponding microrheological Péclet number) increases. This thinning behavior correlates with the development of a nonequilibrium suspension microstructure surrounding the probe particle, in which a boundary layer forms on the upstream face of the probe and a wake depleted of bath particles trails the probe. The magnitude of the microviscosities and the thinning behavior are in good agreement with Brownian dynamics simulations reported by Carpen and Brady [J. Rheol. 49, 1483 (2005)]. The microviscosity increment collapses onto a single curve for all volume fractions when scaled by the contact distribution of bath particles around the probe. Scaling the microviscosity increment yields values lower than the dilute theory; furthermore, it plateaus at significantly higher Péclet numbers. The latter effect is corrected by rescaling the Péclet number with the suspension collective diffusion coefficient in place of the bath particle self-diffusivity. The magnitude of the microviscosity increment suggests the theory overestimates the frequency of bath-probe collisions. The presence and role of hydrodynamic interactions and the effect of the soft repulsive potential are discussed.
Enhancement of light extraction from GaN-based green light-emitting diodes using selective area photonic crystal
Authors: Kim Ja-Yeon , Kwon Min-Ki , Park Seong-Ju , Kim Sang Hoon , Lee Ki-Dong
Published: June 2010

We report the development of a GaN-based green light-emitting diode (LED) with a selective area photonic crystal (SPC) structure, which was formed outside the p-bonding electrode on p-GaN. As a result, the optical output power of LEDs with SPC was enhanced by 78% compared to that without PC. In addition, the forward voltage, series resistance, and leakage current of LEDs with SPC were remarkably improved. These results show that the light extraction efficiency of green LEDs can be greatly increased using the SPC structure, with no degradation of electrical properties.
Rigorous extraction tunability of Si-integrated Ba0.3Sr0.7TiO3 thin film up to 60 GHz
Authors: Ponchel Freddy , Legier Jean-Fançois , Soyer Caroline , Rémiens Denis , Midy Jean , Lasri Tuami , Guéguan Guillaume
Published: June 2010

400-nm-thick Ba0.3Sr0.7TiO3 thin films are deposited on high resistivity silicon by in situ radio frequency magnetron sputtering. Coplanar waveguides with 1 μm slot width are designed, with accurate knowledge frequency losses behavior, to determine ferroelectric thin-films properties up to 60 GHz. Permittivity, loss tangent, and tunability are extracted through measurements and home made finite element analysis. Tunability of 33% and 29%, with 30 V maximum applied voltage (electric field of 300 kV/cm), are measured at 5 GHz and 60 GHz, respectively, while the dielectric losses evolve from 0.5% to 5%. A brief highlight is proposed about tunable silicon integrated quarter wavelength transformer potentialities for impedance matching.
Magnetic susceptibility measurements as a probe of spin transfer driven magnetization dynamics
Authors: Lin Weiwei , Cucchiara J. , Berthelot C. , Hauet T. , Henry Y. , Katine J. A. , Fullerton Eric E. , Mangin S.
Published: June 2010

An experimental technique has been developed to characterize spin-transfer driven magnetization dynamics. It was tested on a nanopillar spin valve with perpendicular anisotropy by measuring the nanopillar voltage under ac injected current (dV/dI), and ac magnetic field (dV/dH). Both the amplitude and the sign of the signals are different which reveals the different influences of the current and the field on the magnetization dynamics. Comparison between experiments and macrospin simulation shows that dV/dH measurements reveal the presence of a “canted state” demonstrating that dV/dH and dV/dI measurements are complementary techniques to probe magnetic states and their dynamics.
Low power operation of ferroelectric liquid crystal system dispersed with zinc oxide nanoparticles
Authors: Joshi T. , Kumar A. , Prakash J. , Biradar A. M.
Published: June 2010

We present the results based on electro-optical properties of zinc oxide nanoparticles (ZnO-NPs) doped ferroelectric liquid crystal (FLC). It is observed that ZnO-NPs-FLC system has low operating voltage and improved optical contrast. The lowering in operating voltage and improvement in optical contrast has been attributed to larger dipole moment of ZnO-NPs that enhances the anchoring of FLC molecules around ZnO-NPs. The effect of ZnO-NPs on the material parameters of FLC has also been observed. These studies will certainly provide a tool to understand the interaction of ZnO-NPs with FLC molecules that can be utilized to fabricate low threshold electro-optic devices.
Ultrathin, transparent, and flexible graphene films for supercapacitor application
Authors: Yu Aiping , Roes Isaac , Davies Aaron , Chen Zhongwei
Published: June 2010

This study reports the preparation of ultrathin, transparent graphene films for use in supercapacitor applications. The surface morphology of the films was investigated by scanning electron microscopy and transmission electron microscopy, revealing a very homogeneous surface with intimate contact between graphene sheets. Electrochemical characterization demonstrated nearly ideal electrical double layer capacitive behavior. The capacitance obtained from charge-discharge analysis is 135 F/g for a film of approximately 25 nm which has a transmittance of 70% at 550 nm and a high power density of 7200 W/kg in 2 M KCl electrolyte.
Interplay of amorphous silicon disorder and hydrogen content with interface defects in amorphous/crystalline silicon heterojunctions
Authors: Schulze T. F. , Beushausen H. N. , Leendertz C. , Dobrich A. , Rech B. , Korte L.
Published: June 2010

We analyze the dependence of the interface defect density Dit in amorphous/crystalline silicon (a-Si:H/c-Si) heterojunctions on the microscopic properties of ultrathin (10 nm) undoped a-Si:H passivation layers. It is shown that the hydrogen bonding and network disorder, probed by infrared- and photoelectron spectroscopy, govern the initial Dit and its behavior upon a short thermal treatment at 200 °C. While the initial Dit is determined by the local and nonequilibrated interface structure, the annealed Dit is defined by the bulk a-Si:H network strain. Thus it appears that the equilibrated a-Si:H/c-Si interface does not possess unique electronic properties but is governed by the a-Si:H bulk defects.
Limiting and overlimiting conductance in field-effect gated nanopores
Authors: Liu Yang , Huber David E. , Dutton Robert W.
Published: June 2010

Numerical modeling of the coupled ionic and fluidic transport in field-effect gated nanopores reveals highly nonlinear current-voltage characteristics, including cross-over, rectification, and particularly limiting and overlimiting conductance. The limiting and overlimiting characteristics are shown to be greatly enhanced by the inherently coupled fluid flow and correlate with electrokinetic phenomena such as concentration polarization and vortex formation. The underlying reason for the observed nonlinear characteristics is explained by considering the symmetry properties of the electrical biasing.
Enhanced dielectric constant and fatigue-resistance of PbZr0.4Ti0.6O3 capacitor with magnetic intermetallic FePt top electrode
Authors: Liu B. T. , Zhao J. W. , Li X. H. , Zhou Y. , Bian F. , Wang X. Y. , Zhao Q. X. , Wang Y. L. , Guo Q. L. , Wang L. X. , Zhang X. Y.
Published: June 2010

Both FePt/PbZr0.4Ti0.6O3(PZT)/Pt and Pt/PZT/Pt ferroelectric capacitors have been fabricated on Si substrates. It is found that up to 109 switching cycles, the FePt/PZT/Pt capacitor, measured at 50 kHz, with polarization decreased by 57%, is superior to the Pt/PZT/Pt capacitor by 82%, indicating that an intermetallic FePt top electrode can also improve the fatigue-resistance of a PZT capacitor. Maximum dielectric constants are 980 and 770 for PZT capacitors with FePt and Pt, respectively. This is attributed to the interface effect between PZT film and the top electrode since the interfacial capacitance of FePt/PZT is 3.5 times as large as that of Pt/PZT interface.
Nonvolatile triode switch using electrochemical reaction in copper sulfide
Authors: Sakamoto Toshitsugu , Iguchi Noriyuki , Aono Masakazu
Published: June 2010

The nonvolatile switch with its compact size enhances the functionality and the performance of large-scale integrated circuits. We have demonstrated a nonvolatile resistive switch with a triode of source, drain, and gate electrodes. A conduction path forms or dissolves in a solid-state ionic conductor via an electrochemical reaction, which results in turning the switch on or off. The reaction is controlled by a biasing voltage of the gate, which is separated from the conduction path by the ionic conductor. Then, the current required to turn the switch on or off is small (<2 μA). Each conductance state is nonvolatile and the ON/OFF current ratio is more than 104. We also confirm a metal precipitate between two electrodes by using element analysis.
Continued population recovery by Australian fur seals
Authors: Kirkwood Roger , Pemberton David , Gales Rosemary , Hoskins Andrew J. , Mitchell Tony , Shaughnessy Peter D. , Arnould John P. Y.
Published: June 2010

Australian fur seals (Arctocephalus pusillus doriferus) are conspicuous, top-level predators in coastal waters of south-eastern Australia that were over-harvested during the 1800s and have had a delayed recovery. A previous species-wide estimate of live pups in 2002 recorded a near-doubling of annual pup production and a 5% annual growth rate since the 1980s. To determine if pup production increased after 2002, we estimated live pup numbers in 2007. Pups were recorded at 20 locations: 10 previously known colonies, three newly recognised colonies and seven haul-out sites where pups are occasionally born. Two colonies adjacent to the Victorian coast accounted for 51% of live pups estimated: Seal Rocks (5660 pups, 25.9%) and Lady Julia Percy Island (5574 pups, 25.5%). Although some colonies were up and some were down in pup numbers, the 2007 total of 21 882 ± 187 (s.e.) live pups did not differ significantly from a recalculated estimate of 21 545 ± 184 in 2002, suggesting little change to overall population size. However, the colonisation of three new sites between 2002 and 2007 indicates population recovery has continued.
Isolated short CTG/CAG DNA slip-outs are repaired efficiently by hMutSβ, but clustered slip-outs are poorly repaired
Authors: Panigrahi Gagan B. , Slean Meghan M. , Simard Jodie P. , Gileadi Opher , Pearson Christopher E.
Published: June 2010

Expansions of CTG/CAG trinucleotide repeats, thought to involve slipped DNAs at the repeats, cause numerous diseases including myotonic dystrophy and Huntington's disease. By unknown mechanisms, further repeat expansions in transgenic mice carrying expanded CTG/CAG tracts require the mismatch repair (MMR) proteins MSH2 and MSH3, forming the MutSβ complex. Using an in vitro repair assay, we investigated the effect of slip-out size, with lengths of 1, 3, or 20 excess CTG repeats, as well as the effect of the number of slip-outs per molecule, on the requirement for human MMR. Long slip-outs escaped repair, whereas short slip-outs were repaired efficiently, much greater than a G-T mismatch, but required hMutSβ. Higher or lower levels of hMutSβ or its complete absence were detrimental to proper repair of short slip-outs. Surprisingly, clusters of as many as 62 short slip-outs (one to three repeat units each) along a single DNA molecule with (CTG)50•(CAG)50 repeats were refractory to repair, and repair efficiency was reduced further without MMR. Consistent with the MutSβ requirement for instability, hMutSβ is required to process isolated short slip-outs; however, multiple adjacent short slip-outs block each other's repair, possibly acting as roadblocks to progression of repair and allowing error-prone repair. Results suggest that expansions can arise by escaped repair of long slip-outs, tandem short slip-outs, or isolated short slip-outs; the latter two types are sensitive to hMutSβ. Poor repair of clustered DNA lesions has previously been associated only with ionizing radiation damage. Our results extend this interference in repair to neurodegenerative disease-causing mutations in which clustered slip-outs escape proper repair and lead to expansions.