bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphorylation of τ Protein by Casein Kinase‐1 Converts It to an Abnormal Alzheimer‐Like State
Authors: Singh Toolsee J. , Grundke‐Iqbal Inge , Iqbal Khalid
Published: July 2010

Abstract: The microtubule‐associated protein τ is abnormally hyperphosphorylated in Alzheimer's disease. Both proline‐dependent protein kinases (PDPKs) and non‐PDPKs are involved in this hyperphosphorylation of τ. Several PDPKs can phosphorylate τ in vitro and induce Alzheimer‐like epitopes to many phosphorylation‐dependent antibodies. A similar induction has not been reported with non‐PDPKs. In this study we have evaluated six non‐PDPKs [cyclic AMP‐dependent (A‐kinase), calcium/phospholipid‐dependent (C‐kinase), casein kinase‐1 (CK‐1), casein kinase‐2 (CK‐2), calcium/calmodulin‐dependent protein kinase II, and calcium/calmodulin‐dependent protein kinase from rat cerebellum] for their abilities to induce Alzheimer‐like epitopes on τ. Such epitopes were induced by A‐kinase, C‐kinase, CK‐1, and CK‐2, but the degree of induction achieved by CK‐1 was much greater than with the other kinases. These results suggest that CK‐1 may play an important role in the conversion of τ from the normal to the abnormal phosphorylation state in Alzheimer's disease.
Characterization of Wild‐Type and Amyotrophic Lateral Sclerosis‐Related Mutant Cu,Zn‐Superoxide Dismutases Overproduced in Baculovirus‐Infected Insect Cells
Authors: Fujii Junichi , Myint Theingi , Seo Han Geuk , Kayanoki Yoshiro , Ikeda Yoshitaka , Taniguchi Naoyuki
Published: July 2010

Abstract: We describe the use of a baculovirus expression system to overproduce human Cu,Zn‐superoxide dismutase (SOD). Spodoptera frugiperda (Sf21) insect cells infected with a baculovirus carrying the Cu,Zn‐SOD cDNA synthesized a large amount of Cu,Zn‐SOD apoprotein in the conventional medium. The SOD activity of the apoprotein, which was initially very low, increased in a dose‐dependent manner when Cu2+ and Zn2+ were added to the medium. Cells grown in media supplemented with Cu2+ alone exhibited nearly maximal SOD activity. SOD activity reached 40% of the maximal level within 2 h after addition of Cu2+ to postinfected cells cultivated for 3 days in the conventional medium, and the activity gradually increased thereafter. The protein produced by the infected cells was purified by a simple procedure involving two chromatographic steps, DE52 ion exchange and ACA54 gel filtration. Identification of the recombinant Cu,Zn‐SOD with the human erythrocyte enzyme was confirmed by immunochemical reactivity to anti‐human Cu,Zn‐SOD antibody and by partial amino acid sequencing of peptides from purified protein (50 amino acid residues in total). We constructed three mutant enzymes, which have been found in familial amyotrophic lateral sclerosis and are overproduced in Sf21 cells, and purified them. Mutant enzymes Gly41Asp, His43Arg, and Gly85Arg exhibited 47, 66, and 99% of wild‐type SOD activity, respectively. The availability of this protein will facilitate investigation of the relationship between the structure and function of the mutant enzymes found in familial amyotrophic lateral sclerosis.
Regulation of Phenylethanolamine N‐Methyltransferase Gene Expression by Imidazoline Receptors in Adrenal Chromaffin Cells
Authors: Evinger Marian J. , Ernsberger Paul , Regunathan Soundararajan , Reis Donald J.
Published: July 2010

Abstract: As adrenal medullary chromaffin cells express imidazoline binding sites in the absence of α2‐adrenergic receptors, these cells provide an ideal system in which to determine whether imidazolines can influence catecholamine gene expression through nonadrenergic receptors. This study evaluates the ability of clonidine and related drugs to regulate expression of the gene for the epinephrine‐synthesizing enzyme phenylethanolamine N‐methyltransferase (PNMT) in the rat adrenal gland and in bovine adrenal chromaffin cell cultures. In vivo, PNMT and tyrosine hydroxylase (TH) mRNA levels increase in rat adrenal medulla after a single injection of clonidine. Clonidine also dose‐dependently stimulates PNMT mRNA expression in vitro in primary cultures of bovine chromaffin cells, with a threshold dose of 0.1 μM. Other putative imidazoline receptor agonists, including cimetidine, rilmenidine, and imidazole‐4‐acetic acid, likewise enhance PNMT mRNA production showing relative potencies that correlate with their binding affinities at chromaffin cell I1‐imidazoline binding sites. The effects of clonidine on PNMT mRNA appear to be distinct from and additive with those exerted by nicotine. Moreover, neither nicotinic antagonists nor calcium channel blockers, which attenuate nicotine's influence on PNMT mRNA production, diminish clonidine's effects on PNMT mRNA. Although 100 μM clonidine diminishes nicotine‐stimulated release of epinephrine and norepinephrine in chromaffin cells, this effect appears unrelated to stimulation of imidazoline receptor subtypes. This is the first report to link imidazoline receptors to neurotransmitter gene expression.
Time‐Resolved Signaling Pathways of Nerve Growth Factor Diverge Downstream of the p140trk Receptor Activation Between Chick Sympathetic and Dorsal Root Ganglion Sensory Neurons
Authors: Klinz Franz‐Josef , Heumann Rolf
Published: July 2010

Abstract: We have recently shown that the small GTP binding protein p21 ras is essential for nerve growth factor (NGF)‐mediated survival of peripheral embryonic chick dorsal root ganglia (DRG) sensory but not sympathetic neurons. To investigate at which level of the signaling cascade the pathways diverge, we have studied the time‐resolved pattern of NGF‐stimulated tyrosine phosphorylation of proteins within 4 h after addition of the neurotrophin. In both chick sympathetic neurons [embryonic day (E) 12] and DRG sensory neurons (E9) NGF induces within 1 min the autophosphorylation of the receptor tyrosine kinase p140trk. However, the pattern of substrate protein tyrosine phosphorylation downstream of p140trk is distinctly different in both neuronal subtypes. In sympathetic neurons, we observe within 1 min the tyrosine phosphorylation of a new substrate protein, p105, reaching maximal levels at 3 min. Tyrosine phosphorylation of p105 remains elevated for up to 4 h. Subsequent to p105, NGF induces the tyrosine phosphorylation of p42, a protein belonging to the family of mitogen‐activated protein (MAP) kinases. This stimulation is transient, reaching maximal levels at 10 min and returning to very low levels already after 2 h. In DRG sensory neurons, tyrosine phosphorylation of p105 is weak and very short lived, disappearing already after treatment with NGF for 10 min. In contrast, activation of MAP kinase p42 in DRG sensory neurons is more stable than in sympathetic neurons. All NGF‐stimulated tyrosine phosphorylation events were inhibited by preincubation of neurons with the tropomyosin‐related kinase (trk) inhibitor K252a. We suggest the working hypothesis that persistent tyrosine phosphorylation of p105 may play a role in the p21ras‐independent NGF survival pathway of chick sympathetic neurons.
Melatonin Biosynthesis in Cultured Chick Retinal Photoreceptor Cells: Calcium and Cyclic AMP Protect Serotonin N‐Acetyltransferase from Inactivation in Cycloheximide‐Treated Cells
Authors: Alonso‐Gómez Angel L. , Iuvone P. Michael
Published: July 2010

Abstract: The aim of the present study was to examine the roles of membrane depolarization, calcium influx, and cyclic AMP synthesis in regulating the stability and inactivation of serotonin N‐acetyltransferase activity (NAT) in cultured chick photoreceptor cells. NAT activity was induced by pretreating cells for 6 h with 1 µM forskolin. Cycloheximide was subsequently added, and the rate of loss of enzyme activity (inactivation) was determined. After induction, in the presence of cycloheximide, NAT activity declined with a half‐life of ∼30 min. The rate of inactivation was greatly reduced when depolarizing concentrations of K+, forskolin, 8‐bromoadenosine 3′,5′‐cyclic monophosphate, or 3‐isobutyl‐1‐methylxanthine were added together with cycloheximide. The apparent increase in NAT stability caused by K+ was abolished by addition of EGTA or nifedipine and potentiated by Bay K 8644, indicating the involvement of Ca2+ influx through dihydropyridine‐sensitive channels. MDL‐12330A, an inhibitor of K+‐stimulated cyclic AMP formation, blocked the effect of depolarizing concentrations of K+. This result suggests that the effect of Ca2+ influx on the stability of NAT is at least partially mediated by increased levels of cyclic AMP. Thus, depolarization‐evoked Ca2+ influx and cyclic AMP formation have two roles in the regulation of NAT activity in chick photoreceptor cells. First, they stimulate the de novo synthesis of NAT or a regulatory protein required for NAT activity. Second, they increase the half‐life of the enzyme, presumably by regulating the turnover of existing enzyme molecules.
Glutamate Receptor‐Mediated Calcium Surges in Neurons Derived from P19 Cells
Authors: Morley Paul , MacPherson Paul , Whitfield James F. , Harris Eric W. , McBurney Michael W.
Published: July 2010

Abstract: Retinoic acid‐treated murine P19 embryonal carcinoma cells differentiate into cells with neuronal morphology that display typical neuronal markers. In this study, the presence of glutamate receptors linked to Ca2+‐signaling mechanisms on these neurons was demonstrated by testing the effects of glutamate agonists and antagonists on the intracellular calcium ion concentration ([Ca2+]i). Glutamate (1 mM) induced either sustained or transient increases in [Ca2+]i. The sustained glutamate‐induced increase in [Ca2+]i was mimicked by NMDA (40 µM). The NMDA‐triggered [Ca2+]i response was abolished by incubating the cells in Ca2+‐free medium or by pretreating them with Mg2+ (2 mM) or MK‐801 (0.1 µM). These responses were unaffected by the non‐NMDA antagonist CNQX (10 µM), but they required glycine (3–30 µM). Kainate (40 µM) and AMPA (40 µM) did not affect [Ca2+]i. Without external Ca2+, glutamate triggered transient, sometimes oscillating, increases in [Ca2+]i. These responses were mimicked by the metabotropic agonist trans‐(1S,3R)‐1‐amino‐1,3‐cyclopentanedicarboxylic acid (300 µM). These results suggest that neurons derived from P19 embryonal carcinoma cells have NMDA and metabotropic, but not AMPA/kainate receptors, which are linked to Ca2+‐signaling mechanisms. These cells could provide a consistent and reproducible model with which to study neuronal differentiation, neurotoxicity, and glutamate receptor‐signaling mechanisms.
Multiple Levels for Regulation of TrkA in PC12 Cells by Nerve Growth Factor
Authors: Zhou Jie , Valletta Janice S. , Grimes Mark L. , Mobley William C.
Published: July 2010

Abstract: TrkA is a receptor tyrosine kinase for nerve growth factor (NGF). Recent studies indicate that NGF regulates not only activation of trkA kinase but also expression of the trkA gene. To further define NGF actions on trkA, we examined binding and signaling through trkA after both short and long intervals of NGF treatment. Induction of tyrosine phosphorylation on gp140trkA was rapidly followed by down‐regulation of cell surface and total cellular gp140trkA. At later intervals, increased expression of trkA was evident in increased mRNA and protein levels. At 7 days, there was increased binding to gp140trkA and increased signaling through this receptor. NGF appears to regulate trkA at several levels. In neurons persistently exposed to NGF, maintenance of NGF signaling may require increased trkA gene expression.
Age‐Dependent Neurotoxicity of Striatal Lesions Produced by Aminooxyacetic Acid: Quantitative In Vitro 1H NMR Spectroscopic Studies
Authors: Chang Chen , Jang Taichang
Published: July 2010

Abstract: Aminooxyacetic acid, a potent inhibitor of the mitochondrial malate‐aspartate shunt, was used to assess the role of mitochondrial energy metabolism in damaged brain of rats of different age groups. Three age groups—juvenile (<1 month), young adult (3–4 months), and adult (7 months)—were subjected to examine the age‐related aminooxyacetic acid effect. We measured the absolute concentrations of metabolites in perchloric acid extracts of rat striatum after intraperitoneal administration of aminooxyacetic acid using 1H NMR spectroscopy. Among aminooxyacetic acid‐treated groups, a twofold increase of GABA concentration was observed in juveniles and young adults, and a threefold elevation of GABA level was observed in adults, whereas there were no significant differences of alanine and glutamate levels in all three aminooxyacetic acid‐treated groups as compared with the age‐matched controls. Statistically significant decreases of N‐acetylaspartate, glutamine, and creatine levels were detected in treated adults. A statistically significant elevation of lactate concentration was found in the adult treated group. These data have demonstrated that the impairment of energy metabolism in rat striatum induced by aminooxyacetic acid can be revealed by quantitative in vitro 1H NMR spectroscopy and that aminooxyacetic acid produces age‐dependent striatal abnormalities.
Two-dimensional symmetric and antisymmetric generalizations of sine functions
Authors: Hrivnák Jiří , Motlochová Lenka , Patera Jiří
Published: July 2010

The properties of two-dimensional generalizations of sine functions that are symmetric or antisymmetric with respect to permutations of their two variables are described. It is shown that the functions are orthogonal when integrated over a finite region F of the real Euclidean space, and that they are discretely orthogonal when summed up over a lattice of any density in F. The decomposability of the products of functions into their sums is shown by explicitly decomposing products of all types. The formalism is set up for Fourier-like expansions of the digital data over two-dimensional lattices in F. Analogs of the common cosine transforms of types I–IV are described. Continuous interpolation of the digital data is studied.
Spectral resolution of the Liouvillian of the Lindblad master equation for a harmonic oscillator
Authors: Honda Daigo , Nakazato Hiromichi , Yoshida Motoyuki
Published: July 2010

A Lindblad master equation for a harmonic oscillator, which describes the dynamics of an open system, is formally solved. The solution yields the spectral resolution of the Liouvillian, that is, all eigenvalues and eigenprojections are obtained. This spectral resolution is discussed in depth in the context of the biorthogonal system and the rigged Hilbert space, and the contribution of each eigenprojection to expectation values of physical quantities is revealed. We also construct the ladder operators of the Liouvillian, which clarify the structure of the spectral resolution.
On the atomic structure of Zr–Ni and Zr–Ni–Al metallic glasses
Authors: Georgarakis K. , Yavari A. R. , Aljerf M. , Louzguine-Luzgin D. V. , Stoica M. , Vaughan G. , Inoue A.
Published: July 2010

Using real space pair distribution functions derived from high precision x-ray diffraction data, the local atomic structure of Zr–Ni and Zr–Ni–Al metallic glasses was investigated. Unlike Zr–Cu metallic glasses, the structure of Zr–Ni metallic glasses cannot be approached with an ideal solution model, due to strong attractive interactions between Zr and Ni atoms, which promote chemical short range order. Addition of Al can be beneficial for the glass forming ability of Zr–Ni metallic glasses. The atomic size of Al, being intermediate to those of Zr and Ni and the strongly attractive interactions between Zr–Al and Zr–Ni atoms can lead to highly negative volumes of mixing ΔVmix, and to denser atomic structures, reduced atomic mobility in the liquid and easier suppression of crystallization in the undercooled liquid state
Ge-stabilized tetragonal ZrO2 as gate dielectric for Ge metal-oxide-semiconductor capacitors fabricated on Si substrate
Authors: Wu Yung-Hsien , Wu Min-Lin , Wu Jia-Rong , Chen Lun-Lun
Published: July 2010

A Ge-stabilized tetragonal ZrO2 (t-ZrO2) film formed by incorporating Ge atoms thermally driven from an underlying Ge layer into a ZrO2 film was investigated as the gate dielectric for Ge metal-oxide-semiconductor (MOS) capacitors fabricated on a Si substrate. A sole t-ZrO2 film on Ge is not eligible for the gate dielectric because of the poor interface quality. By using a thermally-grown ultrathin GeO2 film as an interfacial layer, the t-ZrO2/GeO2/Ge stack shows improved interface characteristics and a permittivity (κ) value of 36.6 for the t-ZrO2. In addition, the stack also demonstrates good leakage current since the amorphous GeO2 layer terminates grain boundary channels in the crystalline ZrO2. Further leakage current suppression can be achieved by a H2 annealing of the t-ZrO2/GeO2/Ge stack since the defects at grain boundaries can be effectively passivated, which makes a leakage current of 1.08×10−6 A/cm2 at VFB−1 V for effective oxide thickness of 1.66 nm and paves an alternative avenue to develop a high-performance crystalline gate dielectric for Ge MOS devices.
Chemical structure of vanadium-based contact formation on n-AlN
Authors: Pookpanratana S. , France R. , Blum M. , Bell A. , Bär M. , Weinhardt L. , Zhang Y. , Hofmann T. , Fuchs O. , Yang W. , Denlinger J. D. , Mulcahy S. , Moustakas T. D. , Heske C.
Published: July 2010

We have investigated the chemical interaction between a Au/V/Al/V layer structure and n-type AlN epilayers using soft x-ray photoemission, x-ray emission spectroscopy, and atomic force microscopy. To understand the complex processes involved in this multicomponent system, we have studied the interface before and after a rapid thermal annealing step. We find the formation of a number of chemical phases at the interface, including VN, metallic vanadium, aluminum oxide, and metallic gold. An interaction mechanism for metal contact formation on the entire n-(Al,Ga)N system is proposed.
Thermodynamic model for the dewetting instability in ultrathin films
Authors: Shirato N. , Krishna H. , Kalyanaraman R.
Published: July 2010

The spontaneous pattern formation via the classical spinodal dewetting instability in ultrathin films is a nonlinear process. However, the physical manifestation of the instability in terms of characteristic length and time scales can be described by a linearized form of the initial conditions of the film’s dynamics. Alternately, the thermodynamic (TH) approach based on equating the rate of free energy decrease to the rate of frictional loss via viscous dissipation [de Gennes, C. R. Acad. Paris 298, 111 (1984)] can give similar information. Here we have evaluated dewetting in the presence of film-thickness- (h) dependent thermocapillary forces. Such a situation can be found during pulsed laser melting of ultrathin metal films where nanoscale effects lead to a local h-dependent temperature. The TH approach provides an analytical description of this thermocapillary dewetting. The results of this approach agree with those from linear theory and experimental observations provided the minimum dissipation is equated to the rate of free energy decrease. The flow boundary condition that produces this minimum dissipation is when the film-substrate tangential stress is zero. The physical implication of this finding is that the spontaneous dewetting instability follows the path of minimum rate of energy loss.
Modulation mechanism of infrared photoreflectance in narrow-gap HgCdTe epilayers: A pump power dependent study
Authors: Shao Jun , Chen Lu , Zha F.-X. , Lu Wei , Lü Xiang , Guo Shaoling , He Li , Chu Junhao
Published: July 2010

Modulation of built-in surface electric field was well established as a mechanism of photoreflectance (PR) processes in bulklike semiconductors, though pump light induced excess carrier concentration was once suggested theoretically as another possibility. In this work, pump power dependent infrared PR measurements were carried out on two arsenic-doped narrow-gap HgCdTe epilayer samples in a wide power range from about 1 mW to up to 480 mW. The relation between the integral intensity I of main PR features and pump power P can be described with I∝Pk, and the k is sensitive to temperature and pump power. While it takes a value of about 0.5 at 11 K or under considerably high pumping power at 77 and 150 K, it is close to 1.0 in a low pump power range at 77 and 150 K. The modulation mechanism is indicated as a combination of the modulation of built-in surface electric field and the pumping induced excess carrier concentration near the band edge. The modulation of built-in surface electric field takes place when the Debye screening length is larger than the pump light penetration depth, otherwise the pumping induced excess carrier concentration also comes into force. High pump power significantly enhances the signal and improves the signal-to-noise ratio of PR spectrum especially when the pumping induced excess carrier concentration plays a dominant role and can, therefore, serve as a primary choice for performing infrared PR measurements on narrow-gap HgCdTe epilayers efficiently.
Integration of plasma-assisted surface chemical modification, soft lithography, and protein surface activation for single-cell patterning
Authors: Cheng Q. , Komvopoulos K.
Published: July 2010

Surface patterning for single-cell culture was accomplished by combining plasma-assisted surface chemical modification, soft lithography, and protein-induced surface activation. Hydrophilic patterns were produced on Parylene C films deposited on glass substrates by oxygen plasma treatment through the windows of polydimethylsiloxane shadow masks. After incubation first with Pluronic F108 solution and then serum medium overnight, surface seeding with mesenchymal stem cells in serum medium resulted in single-cell patterning. The present method provides a means of surface patterning with direct implications in single-cell culture.
Deconvolution of charged particle spectra from neutron depth profiling using Simplex method
Authors: Hnatowicz V. , Vacík J. , Fink D.
Published: July 2010

Neutron depth profiling (NDP), based on neutron induced nuclear reactions, is a well known, nondestructive technique for the determination of the concentration depth profiles of some isotopes in the surface layers of solids. The profile determination consists of deconvolution of a relevant part of the energy spectra of the charged reaction products. Several solutions have been suggested for this problem. In this work, an alternative computer code (LIBOR), which makes use of the Simplex minimization technique for the deconvolution of the NDP spectra, is described and its performance is documented on several examples.
A model for column angle evolution during oblique angle deposition
Authors: Tanto B. , Ten Eyck G. , Lu T.-M.
Published: July 2010

We present a semiempirical model based on the shadowing effect to describe quantitatively the aggregation of columnar structure during physical vapor condensation onto a surface with an array of line seeds and a flat surface. Specifically, we predict the relationship between the column angle and the incident flux angle and how this relationship changes with processing conditions and materials. The model uses one input parameter, the fan angle generated at normal incident flux. The model describes well our experimental data on the Ge column angle evolution as a function of a wide range of incident flux angles.
A new magnetron based gas aggregation source of metal nanoclusters coupled to a double time-of-flight mass spectrometer system
Authors: Momin Tahzeeb , Bhowmick Ashok
Published: July 2010

A new magnetron based gas-aggregation source for continuous production of metal nanoclusters has been built and coupled to a double time-of-flight mass spectrometer system. The capability of the source to produce neutral, positive, and negative nanoclusters within one production cycle, particularly under the same optimized experimental conditions, has been tested. The source performs steadily for continuous long operations and has high beam intensity that would be preferable for size selective measurements in gas phase on individual nanoclusters. This paper describes on the instrumentation of the integrated complete experimental setup for gas-phase measurement on nanoclusters including the source. It reports on the production of copper nanoclusters using the source. Mass abundances of neutral and charged clusters have been investigated and the results are discussed with respect to reported results using various other types of sources. The experimental isotopic distributions of C63u versus C65u within individual cluster mass peaks have been derived and compared to corresponding theoretical profiles.
Nanoheteroepitaxy of gallium arsenide on strain-compliant silicon–germanium nanowires
Authors: Chin Hock-Chun , Gong Xiao , Ng Tien Khee , Loke Wan Khai , Wong Choun Pei , Shen Zexiang , Wicaksono Satrio , Yoon Soon Fatt , Yeo Yee-Chia
Published: July 2010

Heterogeneous integration of high-quality GaAs on Si-based substrates using a selective migration-enhanced epitaxy (MEE) of GaAs on strain-compliant SiGe nanowires was demonstrated for the first time. The physics of compliance in nanoscale heterostructures was captured and studied using finite-element simulation. It is shown that nanostructures can provide additional substrate compliance for strain relief and therefore contribute to the formation of defect-free GaAs on SiGe. Extensive characterization using scanning electron microscopy and cross-sectional transmission electron microscopy was performed to illustrate the successful growth of GaAs on SiGe nanowire. Raman and Auger electron spectroscopy measurements further confirmed the quality of the GaAs grown and the high growth selectivity of the MEE process.
Multiple ferromagnetic secondary phases in Fe implanted yttria stabilized zirconia
Authors: Shalimov A. , Zhou Shengqiang , Roshchupkina O. , Jeutter N. , Baehtz C. , Talut G. , Reuther H. , Potzger K.
Published: July 2010

The formation of secondary phases inside yttria stabilized zirconia (YSZ) crystals implanted with Fe ions was investigated by means of synchrotron radiation x-ray diffraction, conversion electron Mössbauer spectroscopy, and x-ray diffraction reciprocal space mapping. Fe ions have been implanted into single crystals of YSZ(001) at elevated temperatures. As the implanted ion fluence is increased an increase in α-Fe cluster formation was observed, along with the appearance of γ-Fe and secondary phases of Fe oxide(s). The clusters are proposed to consist of a metallic core and an oxide shell. Ferromagnetic hyperfine splitting was detected by Mössbauer spectroscopy and was mainly attributed to the presence of Fe3+ and α-Fe.
Multitone harmonic-balance simulations of an x-ray transition-edge sensor characterized at BESSY II
Authors: Rostem K. , Goldie D. J. , Withington S. , Hoevers H. F. C. , Gottardi L. , van der Kuur J.
Published: July 2010

We present multitone harmonic-balance (MTHB) simulations of a Ti–Au x-ray transition-edge sensor (TES) microcalorimeter in a 5×5 pixel spectrometer array. The dynamic response of the TES microcalorimeter under simulation has been extremely well characterized at the BESSY II Synchrotron Radiation Facility in Berlin. We compare our simulated results directly with these measurements, and show that the MTHB algorithm is able to simulate to great accuracy the dynamic behavior of the TES, even when saturated by 6 keV photons. In this paper, we provide a detailed account of the MTHB simulations, and discuss the impact of this work on future missions such as the International X-ray Observatory.
Scaling and universality of ac conductivity and dielectric response in disordered materials under pressure
Authors: Sakellis I. , Papathanassiou A. N. , Grammatikakis J.
Published: July 2010

Scaling of physical quantities describing the ac response is a common feature of disordered matter, while in some cases, empirical functions have been proposed. The exact forms of analytic functions that scale complex conductivity and permittivity are derived in this work by exploring the effect of pressure at various temperatures on the ac conductivity of polypyrrole. The scaling behavior is visualized within the frame of percolation and self-similarity.
Modeling of tunnel junctions for high efficiency solar cells
Authors: Hauser John R. , Carlin Zach , Bedair S. M.
Published: July 2010

Ultrahigh efficiency, in the range of 40%, can be achieved in multijunction solar cells operating at high solar concentrations, larger than 100 suns. Critical to this approach are high band gap tunnel junctions that serve as electrically low loss interconnections between the cells. The purpose of this work is to theoretically model such wide band gap tunnel junctions and to explore the advantages of a staggered band line up for improving the peak tunnel current. Theoretical results are calculated for heterojunction diodes made of n+-InGaP/p+-AlGaAs over a range of doping levels. The results illustrate the advantage of a conduction band discontinuity in achieving low interconnect resistance for multijunction solar cells.
Miniband formation in InGaAs quantum dot superlattice
Authors: Sugaya Takeyoshi , Amano Takeru , Mori Masahiko , Niki Shigeru
Published: July 2010

We report the formation of a miniband in a quantum dot (QD) superlattice with 20-stack InGaAs QD layers, which we confirmed by the excitation power dependence in photoluminescence (PL) measurements. The PL peak of a QD superlattice shifts to a shorter wavelength as the excitation power is increased. The blueshifted energy of the PL peak is 8 meV for a QD superlattice with an interdot spacing of 3.5 nm, whereas the blueshift is not observed for a multistacked QD structure with an interdot spacing of 15 nm. The blueshifted energy becomes larger as the interdot spacing is reduced.
Position and mass determination of multiple particles using cantilever based mass sensors
Authors: Dohn Søren , Schmid Silvan , Amiot Fabien , Boisen Anja
Published: July 2010

Resonant microcantilevers are highly sensitive to added masses and have the potential to be used as mass-spectrometers. However, making the detection of individual added masses quantitative requires the position determination for each added mass. We derive expressions relating the position and mass of several added particles to the resonant frequencies of a cantilever, and an identification procedure valid for particles with different masses is proposed. The identification procedure is tested by calculating positions and mass of multiple microparticles with similar mass positioned on individual microcantilevers. Excellent agreement is observed between calculated and measured positions and calculated and theoretical masses.
Type II heterostructures formed by zinc-blende inclusions in InP and GaAs wurtzite nanowires
Authors: Jancu J.-M. , Gauthron K. , Largeau L. , Patriarche G. , Harmand J.-C. , Voisin P.
Published: July 2010

Crystal phase heterostructures, consisting of homogeneous composition zinc-blende inclusions in wurtzite InP and GaAs nanowires are investigated theoretically in the frame of the extended-basis tight-binding approach. Increased band gap for the wurtzite phase and staggered type II band alignment are predicted for both materials. Comparison of theoretical results with microphotoluminescence measurements on single InP nanowires yields fair semiquantitative agreement.
Responding to Diversity: Workforce Intermediation in a Transitioning Regional Economy
Authors: Lowe Nichola J
Published: July 2010

In this paper I examine workforce intermediation as a tool for regional economic transition. While most studies of workforce intermediation in the United States focus on targeted programs that work with less-advantaged socioeconomic groups, I examine strategies adopted by state-funded community colleges that have a more encompassing or universalistic mandate. Through a case study of North Carolina's BioWork initiative I examine college-level strategies for assisting two distinct groups of job seekers in biopharmaceuticals—those with less education and traditional manufacturing backgrounds and those with college degrees and considerable technology experience. In documenting these strategies I suggest lessons for other regions seeking to influence local labor-market conditions and, in turn, balance the employment needs of diverse socioeconomic groups.
Succession of microbial consortia in the developing infant gut microbiome
Authors: Koenig Jeremy E. , Spor Aymé , Scalfone Nicholas , Fricker Ashwana D. , Stombaugh Jesse , Knight Rob , Angenent Largus T. , Ley Ruth E.
Published: July 2010

The colonization process of the infant gut microbiome has been called chaotic, but this view could reflect insufficient documentation of the factors affecting the microbiome. We performed a 2.5-y case study of the assembly of the human infant gut microbiome, to relate life events to microbiome composition and function. Sixty fecal samples were collected from a healthy infant along with a diary of diet and health status. Analysis of >300,000 16S rRNA genes indicated that the phylogenetic diversity of the microbiome increased gradually over time and that changes in community composition conformed to a smooth temporal gradient. In contrast, major taxonomic groups showed abrupt shifts in abundance corresponding to changes in diet or health. Community assembly was nonrandom: we observed discrete steps of bacterial succession punctuated by life events. Furthermore, analysis of ≈500,000 DNA metagenomic reads from 12 fecal samples revealed that the earliest microbiome was enriched in genes facilitating lactate utilization, and that functional genes involved in plant polysaccharide metabolism were present before the introduction of solid food, priming the infant gut for an adult diet. However, ingestion of table foods caused a sustained increase in the abundance of Bacteroidetes, elevated fecal short chain fatty acid levels, enrichment of genes associated with carbohydrate utilization, vitamin biosynthesis, and xenobiotic degradation, and a more stable community composition, all of which are characteristic of the adult microbiome. This study revealed that seemingly chaotic shifts in the microbiome are associated with life events; however, additional experiments ought to be conducted to assess how different infants respond to similar life events.
T-cell regulation by
casitas B-lineage lymphoma
(
Cblb
) is a critical failsafe against autoimmune disease due to
autoimmune regulator
(
Aire
) deficiency
Authors: Teh Charis E. , Daley Stephen R. , Enders Anselm , Goodnow Christopher C.
Published: July 2010

Autoimmune polyendocrinopathy syndrome type 1 (APS1) results from homozygous
Aire
mutations that cripple thymic deletion of organ-specific T cells. The clinical course in man and mouse is characterized by high variability both in the latent period before onset of autoimmune disease and in the specific organs affected, but the reasons for this are unknown. Here we test the hypothesis that the latent period reflects the failsafe action of discrete postthymic mechanisms for imposing self-tolerance in peripheral T cells.
Aire
-deficient mice were crossed with mice of a uniform major histocompatibility complex (MHC) haplotype and genetic background carrying specific genetic defects in one of four distinct peripheral tolerance mechanisms: activation-induced cell death (
Fasl
gld/gld
), anergy and requirement for CD28 costimulation (
Cblb
−/−
), inhibition of ICOS and T
FH
cells (
Rc3h1
san/san
), or decreased numbers of Foxp3
+
T regulatory cells (
Card11
unm/unm
).
Cblb
-deficiency was unique among these four in precipitating rapid clinical autoimmune disease when combined with
Aire
-deficiency, resulting in autoimmune exocrine pancreatitis with median age of survival of only 25 d. Massive lymphocytic infiltration selectively destroyed most of the exocrine acinar cells of the pancreas and submandibular salivary gland, and CD4
+
and CD8
+
subsets were necessary and sufficient to transfer the disease. Intrinsic regulation of peripheral T cells by CBL-B thus serves a uniquely critical role as a failsafe against clinical onset of autoimmune disease in AIRE deficiency, and multiple peripheral tolerance mechanisms may need to fail before onset of clinical autoimmunity to many organs.
International–local remuneration differences across six countries: Do they undermine poverty reduction work?
Authors: Carr Stuart C. , McWha Ishbel , MacLachlan Malcolm , Furnham Adrian
Published: July 2010

Despite the rhetoric of a single global economy, professionals in poorer countries continue to be remunerated differently depending on whether they are compensated at a local vs. international rate. Project ADDUP (Are Development Discrepancies Undermining Performance?) surveyed 1290 expatriate and local professionals (response rate = 47%) from aid, education, government, and business sectors in (1) Island Nations (Papua New Guinea, Solomon Islands), (2) landlocked economies (Malaŵi, Uganda), and (3) emerging economies (India, China). Difference in pay was estimated using purchasing power parity, from the World Bank's World Development Indicators 2007. Psychological measures included self‐reported pay and benefits (remuneration), self‐attributed ability, remuneration comparison, sense of justice in remuneration, remuneration‐related motivation, thoughts of turnover and thoughts about international mobility. We included control measures of candour, culture shock, cultural values (horizontal/vertical individualism/collectivism), personality (from the “big five”), job satisfaction and work engagement. Controlling for these and country (small effects) and organization effects (medium), (a) pay ratios between international and local workers exceeded what were perceived to be acceptable pay thresholds among respondents remunerated locally; who also reported a combination of a sense of relative (b) injustice and demotivation; which (c) together with job satisfaction/work engagement predicted turnover and international mobility. These findings question the wisdom of dual salary systems in general, expose and challenge a major contradiction between contemporary development policy and practice, and have a range of practical, organizational, and theoretical implications for poverty reduction work.
Liberal nationalism, nationalist liberalization, and democracy: the cases of post-Soviet Estonia and Ukraine
Authors: Surzhko-Harned Lena
Published: July 2010

The bulk of scholarly literature views nationalism as harmful to democratic transition. Yet Juan Linz and Alfred Stepan indirectly suggest that nationalism may benefit democratization. This study shows that under the right conditions nationalism can benefit democratic transition. Building on the typology of Linz and Stepan and the liberal nationalism tradition of Yael Tamir and David Miller, this study examines the transitions in Estonia and Ukraine. It introduces an important layer, the multinational federal state, into the typologies developed by Linz and Stepan to show that nationalism can prove a useful political tool of mobilization in a multiethnic setting.
Romania is a family and it needs a strict father: conceptual metaphors at work in radical right populist discourses
Authors: Norocel Ov Cristian
Published: July 2010

Investigating Romanian radical right populism, I evidence the gendered nature of conceptual metaphors and provide insights on the specific masculinities that they underpin in such political discourses. With the 2004 presidential elections as a backdrop, the analysis focuses on how the radical right populist candidates articulated in their discourses the conceptual metaphor of the “strict father.” At first, the theoretical standpoints on conceptual metaphors are corroborated with the conceptualization of populist charismatic leadership. Subsequently, a gendered perspective is added to the populist conceptualizations. The leaders’ self-representation as messianic fathers of the national family is evidenced by investigating their discursive appeals to protect, discipline and punish the people. Furthermore, I elaborate how conceptual metaphors may be employed to consolidate a position of uncontested leadership and moral superiority of the radical right populist leaders.
Prince Adam Czartoryski as a liminal figure in the development of modern nationalism in Eastern Europe at the turn of the eighteenth and nineteenth centuries
Authors: Brykczynski Paul
Published: July 2010

In Polish history, Prince Adam Czartoryski is almost universally regarded as one of the most important Polish statesmen and patriots of the first half of the nineteenth century. In Russian history, on the other hand, he is remembered chiefly as the Foreign Minister of the Russian Empire, and a close personal friend of Tsar Alexander I. How did Czartoryski reconcile his commitment to the Polish nation with his service to the Russian Empire (a state which occupied most of Poland)? This paper will attempt to place Prince Adam's friendship with Alexander, and his service to Imperial Russia, in the broader context of national identity formation in early nineteenth-century eastern Europe. It will be argued that the idea of finding a workable relationship between Poland and Russia, even within the framework of a single state for a “Slavic nation,” was an important and forgotten feature of Polish political thought at the turn of the eighteenth and nineteenth centuries. By answering the question of precisely how Czartoryski was able to negotiate between the identities of a “Polish patriot” and “Russian statesman,” the paper will shed light on the broader development of national identity in early nineteenth-century Poland and Russia.
Stalin: authoritarian populist or great Russian chauvinist?
Authors: Marples David R.
Published: July 2010

David Brandenberger argues that contemporary Russian identity was mainly a result of a “historical accident.” He maintains that this national identity was a product of the twentieth century rather than the nineteenth, which is more commonly cited, and that in terms of the state formulating a conception of what it meant to be Russian, the first decade of the Soviet period achieved little. However, by the late 1920s Soviet ideologists began to seek something more appealing than the mundane party slogans and eventually added non-proletarian, historical Russian heroes to the Soviet pantheon, particularly after the purges when the latter group was sorely depleted. This campaign was largely successful in inducing an understanding of national identity from a non-proletarian past as is evident today. He perceives this process as the formation of a Soviet populism, designed to mobilize society “on the mass level” and compares Stalin's USSR with Latin American dictatorships in this regard. Stalin, he argues, “was an authoritarian populist rather than a nationalist.” By 1953, Russians had a much better idea about their identity than in the period before 1937.
Features of ion and electron fishbone instabilities on HL-2A*
Authors: Chen W. , Ding X.T. , Liu Yi. , Yang Q.W. , Ji X.Q. , Isobe M. , Yuan G.L. , Zhang Y.P. , Zhou Y. , Song X.Y. , Dong Y.B. , Li W. , Zhou J. , Lei G.J. , Cao J.Y. , Deng W. , Song X.M. , Duan X.R.
Published: July 2010

The features of ion and electron fishbone instabilities have been investigated during neutral beam injection (NBI) and electron cyclotron resonance heating (ECRH) on HL-2A. Some new phenomena, such as frequency jumps and V-font-style sweeping, have been presented in the paper. Three kinds of i-fishbones, including hybrid sawtooth–fishbone (sawbone), run-on fishbone and classical fishbone, have been identified during NBI. During high power (P
ECRH > 0.7 MW) ECRH, the experimental results indicate that the e-fishbone frequencies are higher than those during low power ECRH, and are provided with up- and down-chirping behaviours, and sometimes also with V-font-style sweeping. The periodic mode frequency jumps have also been detected by a soft x-ray array. It is possible to correlate these phenomena with the redistribution of energetic electrons.
Effects of energetic-ion-driven instabilities on plasma heating, transport and rotation in toroidal systems
Authors: Kolesnichenko Ya.I. , Yakovenko Yu.V. , Lutsenko V.V. , White R.B. , Weller A.
Published: July 2010

A theory is developed from which it follows that energetic-ion-driven instabilities can, first, channel the energy of the energetic ions outside the region where these ions are located and, second, considerably affect the electron heat flux across the magnetic field. A new mechanism of frequency chirping is revealed, namely it is shown that instabilities caused by the energetic ions can influence the plasma rotation, in which case the development of instabilities results in a variation of the Doppler shift in time. It is concluded that a key factor responsible for the mentioned phenomena is the local imbalance of the wave emission by energetic ions and the wave absorption by electrons along the radius. On the basis of the developed theory, experiments on the stellarator Wendelstein 7-AS and the spherical torus NSTX, where the effects of Alfvénic activity on the plasma temperature were observed, are considered.
Mode coupling in Alfvén instabilities
Authors: Yakovenko Yu.V. , Kolesnichenko Ya.I. , Lutsenko V.V. , White R.B. , Werner A.
Published: July 2010

It is shown numerically that even a weak deviation from the axial symmetry of the magnetic configuration in tokamaks can drastically change the spatial structure of toroidicity-induced Alfvén eigenmodes (TAEs), turning them into modes characterized by strong dependence of the amplitude on the toroidal coordinate. The reason for this lies in the fact that the TAEs are close to degeneracy: TAEs with different toroidal mode numbers (n) may have almost the same frequency. A condition necessary for a certain steady-state non-axisymmetric harmonic of the magnetic field to couple TAEs and ellipticity-induced Alfvén eigenmodes (EAEs) with different n (the ‘selection rule’) is obtained. In particular, a coupling harmonic of significant amplitude can be found more easily in a stellarator with large rotational transform and a small number of field periods. In tokamaks, any magnetic island satisfies the selection rule and can thus couple TAEs. This may explain why multiple modes with different n often appear and disappear simultaneously in TAE bursts. This may also explain an observation of a TAE with the amplitude varying in phase with a quasi-steady-state magnetic perturbation in the spherical torus NSTX.
Nonlinear magnetohydrodynamic effects on Alfvén eigenmode evolution and zonal flow generation
Authors: Todo Y. , Berk H.L. , Breizman B.N.
Published: July 2010

Nonlinear magnetohydrodynamic (MHD) effects on Alfvén eigenmode evolution were investigated via hybrid simulations of an MHD fluid interacting with energetic particles. The investigation focused on the evolution of an n = 4 toroidal Alfvén eigenmode (TAE) which is destabilized by energetic particles in a tokamak. In addition to fully nonlinear code, a linear-MHD code was used for comparison. The only nonlinearity in that linear code is from the energetic-particle dynamics. No significant difference was found in the results of the two codes for low saturation levels, δB/B ∼ 10−3. In contrast, when the TAE saturation level predicted by the linear code is δB/B ∼ 10−2, the saturation amplitude in the fully nonlinear simulation was reduced by a factor of 2 due to the generation of zonal (n = 0) and higher-n (n ⩾ 8) modes. This reduction is attributed to the increased dissipation arising from the nonlinearly generated modes. The fully nonlinear simulations also show that geodesic acoustic mode is excited by the MHD nonlinearity after the TAE mode saturation.