bluuebunny/crossref_metadata_2025 huggingface dataset:
Cortical excitability is abnormal in patients with the “fixed dystonia” syndrome
Authors: Avanzino Laura , Martino Davide , van de Warrenburg Bart P. C. , Schneider Susanne A. , Abbruzzese Giovanni , Defazio Giovanni , Schrag Anette , Bhatia Kailash P. , Rothwell John C.
Published: January 2008

A form of fixed dystonia (FD) without evidence of basal ganglia lesions or neurodegeneration has been recently characterized (Schrag et al., Brain 2004;127:2360‐2372), which may overlap the clinical spectrum of either complex regional pain syndrome or psychogenic dystonia. Transcranial magnetic stimulation studies in typically mobile dystonia revealed abnormal motor cortical excitability and sensori‐motor integration. We compared 12 patients with limb FD to 10 patients with primary adult‐onset typically mobile dystonia and 11 age‐matched healthy volunteers. Measurements at the first digital interosseus representation area on both hemispheres included: short intracortical inhibition (SICI), contralateral silent period (cSP), and short and long afferent inhibition (SAI and LAI). Repeated measure ANOVA and post‐hoc t‐tests were used for statistical analysis. SICI was significantly reduced in both hemispheres of patients with “typical” and FD, compared to healthy subjects. For both hemispheres, cSP duration was shorter in both fixed and “typical” dystonia patients. SAI and LAI did not significantly differ between the three groups. The abnormal cortical excitability observed in FD might represent an underlying trait predisposing to different clinical forms of dystonia. © 2007 Movement Disorder Society
Patient and caregiver quality of life in Huntington's disease
Authors: Ready Rebecca E. , Mathews Melissa , Leserman Anne , Paulsen Jane S.
Published: January 2008

Little is known about subjective perceptions of quality of life (QOL) in Huntington's disease (HD). The current study determined correlates of patient and caregiver QOL and assessed change over time. Participants were 22 patient‐caregiver dyads, who rated QOL at baseline and 6 months later. Overall, patients' functional and cognitive impairment were significantly correlated with patient and caregiver QOL. Neuropsychiatric symptoms had differential impact on patient and caregiver QOL. Furthermore, when patients recalled their QOL about a previous time, their recall may have been negatively biased. Clinical implications of results are discussed. Future work is needed because subjective QOL is an important outcome measure in therapeutic trials. © 2008 Movement Disorder Society
Analyzing and modeling the inhibitory effect of phosphatidic acid on the GTP‐γ‐S binding activity of Goα
Authors: Qu Liang , Wan Jia , Cao Yu , Zhang Yinghao , Chen Runsheng , Huang Youguo
Published: January 2008

G proteins are the molecular switches of G‐protein‐coupled signal transmembrane transduction, which plays a pivotal role in diverse cellular processes. The guanine nucleotide binding states of Gα‐subunits are considered key factors for their functions. We report here that phosphatidic acid (PA) inhibits the [35S]‐GTPγS binding activity of Goα. To elucidate this inhibitory effect, biochemical analyses are carried out and a structure‐based model is proposed. The experimental results show that PA particularly inhibits the activity of the Goα in a dose‐dependent manner, whereas other lipids tested do not. Further analysis on the effects of PA analogs demonstrate that a phosphate head group together with at least one fatty acid chain is necessary for the inhibition. Using a lipid–protein binding assay, it is shown that Goα specifically and directly interacts with PA. In addition to these experimental studies, a 3D structure of Goα is constructed, based on sequence homology greater than 70% to E. coli Giα1. Molecular docking is performed with PA and PA analogs, and the results are compared and analyzed. Collectively, the results of this investigation provide direct experimental evidence for an inhibitory effect of PA on GTP binding activity of Goα, and also suggest a structural model for the inhibitory mechanism. The lipid–protein model suggests that PA may occupy the channel for exchanging guanine nucleotides, thus leading to the inhibition. These findings reveal a potential new drug target for the diseases caused by genetic G‐protein abnormalities. Proteins 2008. © 2008 Wiley‐Liss, Inc.
The 1.38 Å crystal structure of DmsD protein from Salmonella typhimurium, a proofreading chaperone on the Tat pathway
Authors: Qiu Yang , Zhang Rongguang , Binkowski T. Andrew , Tereshko Valentina , Joachimiak Andrzej , Kossiakoff Anthony
Published: January 2008

The DmsD protein is necessary for the biogenesis of dimethyl sulphoxide (DMSO) reductase in many prokaryotes. It performs a critical chaperone function initiated through its binding to the twin‐arginine signal peptide of DmsA, the catalytic subunit of DMSO reductase. Upon binding to DmsD, DmsA is translocated to the periplasm via the so‐called twin‐arginine translocation (Tat) pathway. Here we report the 1.38 Å crystal structure of the protein DmsD from Salmonella typhimurium and compare it with a close functional homolog, TorD. DmsD has an all‐α fold structure with a notable helical extension located at its N‐terminus with two solvent exposed hydrophobic residues. A major difference between DmsD and TorD is that TorD structure is a domain‐swapped dimer, while DmsD exists as a monomer. Nevertheless, these two proteins have a number of common features suggesting they function by using similar mechanisms. A possible signal peptide‐binding site is proposed based on structural similarities. Computational analysis was used to identify a potential GTP binding pocket on similar surfaces of DmsD and TorD structures. Proteins 2008; 71:525–533. Published 2007 Wiley‐Liss, Inc.
The conformational plasticity of calmodulin upon calcium complexation gives a model of its interaction with the oedema factor of Bacillus anthracis
Authors: Laine Elodie , Yoneda Julliane D. , Blondel Arnaud , Malliavin Thérèse E.
Published: January 2008

We analyzed the conformational plasticity of calmodulin (CaM) when it is bound to the oedema factor (EF) of Bacillus anthracis and its response to calcium complexation with molecular dynamics (MD) simulations. The EF‐CaM complex was simulated during 15 ns for three different levels of calcium bound to CaM. They were respectively no calcium ion (EF–(Apo‐CaM)), two calcium ions bound to the C‐terminal domain of CaM (EF–(2Ca‐CaM)), and four calcium ions bound to CaM (EF–(4Ca‐CaM)). Calculations were performed using AMBER package. The analysis of the MD simulations illustrates how CaM forces EF in an open conformation to form the adenylyl cyclase enzymatic site, especially with the two calcium form of CaM, best suited to fit the open conformation of EF. By contrast, CaM encounters bending and unwinding of its flexible interlinker in EF–(Apo‐CaM) and EF–(4Ca‐CaM). Calcium binding to one domain of CaM affects the other one, showing a transmission of information along the protein structure. The analysis of the CaM domains conformation along the simulations brings an atomistic and dynamic explanation for the instability of these complexes. Indeed the EF‐hand helices of the N‐terminal domain tend to open upon calcium binding (EF–(4Ca‐CaM)), although the domain is locked by EF. By contrast, the C‐terminal domain is strongly locked in the open conformation by EF, and the removal of calcium induces a collapse of EF catalytic site (EF–(Apo‐CaM)). Proteins 2008. © 2008 Wiley‐Liss, Inc.
pH sensitivity of type III secretion system tip proteins
Authors: Markham Aaron P. , Birket Susan E. , Picking William D. , Picking Wendy L. , Middaugh C. Russell
Published: January 2008

Many pathogenic gram‐negative bacteria employ type III secretion systems to transport proteins into the host cell membrane and cytoplasm to subvert normal cellular functions. The type III secretion apparatus consists of a basal body spanning the inner and outer bacterial membranes and a needle which extends away from the bacterium. Recent work has found that a special class of proteins localizes to the tip of the needle to control secretion of effector proteins. Five of these tip proteins are IpaD (Shigella flexneri), BipD (Burkholderia pseudomallei), SipD (Salmonella spp.), LcrV (Yersinia spp.), and PcrV (Pseudomonas aeruginosa). In this study, the conformational stability of these proteins was characterized as a function of pH and temperature. Understanding the stability of the proteins in different pH environments is particularly important since they are expected to encounter different pH environments in their passage through the gastrointestinal tract and are exposed to low pH microenvironments near the surface of target cell membranes. Secondary and tertiary structural changes were monitored using the spectroscopic techniques of far‐UV circular dichroism, Trp fluorescence, ANS fluorescence, and ultraviolet absorption spectroscopy. Optical density and right angle scattering measurements were also used to evaluate protein association/dissociation. Empirical phase diagrams were then applied to mathematically combine data from the various spectroscopic techniques to provide a global picture of the proteins' structural behavior in solution. The responses of the proteins to changes in temperature and pH conditions reveal two distinct subfamilies in terms of stability. The first is that of IpaD, BipD, and SipD whose corresponding phase diagrams show conformational differences at pH 5–6. The conserved pH dependence in this subfamily suggests possible common mechanistic function. In the second subfamily (LcrV and PcrV), conformational stability is directly related to pH, also indicating mechanistic similarities. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Comparison of the efficiency of evolutionary change‐based and side chain orientation‐based fold recognition potentials
Authors: Vishnepolsky Boris , Managadze Grigol , Pirtskhalava Malak
Published: January 2008

The present article describes residue level knowledge based potential SORDIS. SORDIS incorporates the information on side‐chain orientation in relation to hydrophobic core centres, distance of residue from the globule centre and secondary structure. SORDIS has been tested and compared with widespread evolutionary change‐based substitution matrices (BLOSUM, PAM, GONNET, Johnson‐Overington, BLAJ, HSDM, and STROMA) in fold recognition experiments within the zone of weak sequence similarity (<16%). The obtained results show that the lower is the amino acid similarity between homologous pairs the higher is the performance of SORDIS in comparison with the potentials, based on the information about the evolutionary changes. Therefore, we propose that the employment of SORDIS in fold recognition can be useful. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Complications Associated With Embolization in the Treatment of Blunt Splenic Injury
Authors: Wu Shih‐Chi , Chen Ray‐Jade , Yang Albert D. , Tung Cheng‐Cheng , Lee Kun‐Hua
Published: January 2008

Background

Nonoperative management (NOM) of blunt splenic injuries is widely accepted, and the use of splenic artery embolization (SAE) has become a valuable adjunct to NOM. We retrospectively review and discuss the complications derived from SAE.

Materials and methods

The medical records of 152 consecutive patients with blunt splenic trauma admitted to our trauma center during a 33‐month period were retrospectively reviewed. The patients were managed according to an established algorithm. The record review focused on the method of patient management (operative versus nonoperative) and use of SAE. The complications encountered following SAE are discussed in detail.

Results

Altogether, 73 patients underwent emergency surgery (58 splenectomies, 15 splenorrhaphies), and 79 patients had NOM. Of the 79 patients with NOM, 58 were successfully treated; 2 patients required splenectomy after 24 hours. The remaining 21 patients had SAE, including 18 distal and 3 proximal embolizations. Major complications occurred in 28.5% of the SAE‐treated patients and included total splenic infarction, splenic atrophy, and postprocedure bleeding. Minor complications occurred in 61.9% of the patients and included fever, pleural effusion, and partial splenic infarction.

Conclusion

SAE is considered a valuable adjunct to NOM in the treatment of blunt splenic injuries; however, risks of major and minor complications do exist, and SAE should be offered with caution and followed up appropriately.
Some Biochemical Properties of Lipase from Bay Laurel (Laurus nobilis L.) Seeds
Authors: Isbilir Sebnem Selen , Ozcan Hakki M. , Yagar Hulya
Published: January 2008

Lipase was isolated from bay laurel (Laurus nobilis L.) seeds, some biochemical properties were determined. The bay laurel oil was used as the substrate in all experiments. The pH optimum was found to be 8.0 in the presence of this substrate. The temperature optimum was 50 °C. The specific activity of the lipase was found to be 296 U mg protein−1 in optimal conditions. The enzyme activity is quite stable in the range of pH 7.0–10. The enzyme was stable for 1 h at its optimum temperature, and retained about 68% of activity at 60 °C during this time. Km and Vmax values were determined as 0.975 g and 1.298 U mg protein−1, respectively. Also, storage stability and metal effect on lipolytic activity were investigated. Enzyme activity was maintained for 9, 12, and 42 days at room temperature, 4 and −20 °C, respectively. Ca2+, Co2+, Cu2+, Fe2+, and Mg2+ lightly enhanced bay laurel lipase activity.
Sigma factor SigC is required for heat acclimation of the cyanobacterium Synechocystis sp. strain PCC 6803
Authors: Tuominen Ilona , Pollari Maija , von Wobeser Eneas Aguirre , Tyystjärvi Esa , Ibelings Bas W. , Matthijs Hans C.P. , Tyystjärvi Taina
Published: January 2008

The role of the primary‐like sigma factor SigC was studied in Synechocystis. Under high temperature stress (48 °C) the ΔsigC inactivation strain showed a lower survival rate than the control strain. The ΔsigC strain grew poorly at 43 °C in liquid cultures under normal air. However, change to 3% CO2 enhanced growth of ΔsigC at 43 °C. Differences in expression of many genes related to the carbon concentrating mechanisms between the control and the ΔsigC strain were recorded with a genome‐wide DNA microarray. We suggest that low solubility of CO2 at high temperature is one of the factors contributing to the poor thermotolerance of the ΔsigC strain.
Nodulation dynamics and nodule activity in leguminous tree species of a Mexican tropical dry forest
Authors: González-Ruiz Teresa , Jaramillo Víctor J. , Cabriales Juan José Peña , Flores Arturo
Published: January 2008

Biological N fixation by symbiotic micro-organisms plays a key role in making atmospheric N largely available to other organisms and nodule formation by rhizobia in roots of many legume species represents a very important pathway (Postgate 1998). Estimates of the contribution of symbiotic fixation to total N content in soils range from 44 to 200 Tg y−1(Bøckman 1997).
Sample size and appropriate design of fruit and seed traps in tropical forests
Authors: Stevenson Pablo R. , Vargas Ivonne N.
Published: January 2008

Studies of seed dispersal and fruit production often use fruit traps. Different trap designs may give dissimilar estimates; however, prior to this study there has been no tropical forest field comparison of trap designs. Likewise, there are no recommendations about the number of traps required to assess ecological parameters, such as fruit production, mass and number of seeds dispersed, and number of plant species producing fruits. We compared the effectiveness of five trap designs in terms of fruit/seed bouncing out of traps, wind effects, area effects and seed removal by predators. These studies took place in Colombia in two tropical rain forests and in laboratory conditions. We found that 300 traps (0.085 m2 each) were not enough to obtain stable estimates in two out of four parameters (number of species and dispersed seeds). All estimates were highly variable when using fewer than 100 traps. All trap designs evaluated (mesh on PVC frame, hanging mesh, basin and funnel traps) prevent seed removal by predators, in sharp contrast with removal from the ground. Mesh traps were less affected by bouncing effects than plastic traps, and this factor was a large source of bias among estimates from different traps. Since up to 68% of dry mass may bounce out, it is important to consider adequate trap designs and to be careful when comparing studies using different methodologies. Small traps received fewer seeds per area, however area affects were not evident when bouncing effects were controlled for. We recommend the use of mesh traps on PVC frames, although hanging mesh traps are a good option in tropical forests without strong winds.
Temporal and spatial variability in seedling dynamics: a cross-site comparison in four lowland tropical forests
Authors: Metz Margaret R. , Comita Liza S. , Chen Yu-Yun , Norden Natalia , Condit Richard , Hubbell Stephen P. , Sun I-Fang , Noor Nur Supardi bin Md. , Wright S. Joseph
Published: January 2008

Spatial and temporal variation in seedling dynamics was assessed using records of community-wide seedling demography collected with identical monitoring methods at four tropical lowland forests in Panama, Malaysia, Ecuador and French Guiana for periods of between 3 and 10 y. At each site, the fates of between 8617 and 391 777 seedlings were followed through annual censuses of the 370–1008 1-m2seedling plots. Within-site spatial and inter-annual variation in density, recruitment, growth and mortality was compared with among-site variability using Bayesian hierarchical modelling to determine the generality of each site's patterns and potential for meaningful comparisons among sites. The Malaysian forest, which experiences community-wide masting, was the most variable in both seedling density and recruitment. However, density varied year-to-year at all sites (CVamong years at site= 8–43%), driven largely by high variability in recruitment rates (CV = 40–117%). At all sites, recruitment was more variable than mortality (CV = 5–64%) or growth (CV = 12–51%). Increases in mortality rates lagged 1 y behind large recruitment events. Within-site spatial variation and inter-annual differences were greater than differences among site averages in all rates, emphasizing the value of long-term comparative studies when generalizing how spatial and temporal variation drive patterns of recruitment in tropical forests.
Reliability and validity of the Computerized Comprehension Task (CCT): data from American English and Mexican Spanish infants
Authors: FRIEND MARGARET , KEPLINGER MELANIE
Published: January 2008

Early language comprehension may be one of the most important predictors of developmental risk. The need for performance-based assessment is predicated on limitations identified in the exclusive use of parent report and on the need for a performance measure with which to assess the convergent validity of parent report of comprehension. Child performance data require the development of procedures to facilitate infant attention and compliance. Forty infants (20 at 1 ; 4 and 20 at 1 ; 8) acquiring English completed a standard picture book task and the same task was administered on a touch-sensitive screen. The computerized task significantly improved task attention, compliance and performance. Reliability was high, indicating that infants were not responding randomly. Convergent validity with parent report and 4-month stability was substantial. Preliminary data extending this approach to Mexican-Spanish are presented. Results are discussed in terms of the promise of this technique for clinical and research settings and the potential influences of cultural factors on performance.
Conveying information about adjective meanings in spoken discourse
Authors: CORRIGAN ROBERTA
Published: January 2008

This study examined information about adjective meanings available in adults' spoken discourse in the original 27 CHILDES corpora of typically developing English-speaking children. In order to increase the probability that adjectives would be novel to children to whom they were addressed, onlyrareadjectives were examined (those that occurred ⩽5 times in the corpus,N=878). Contexts surrounding adjectives (±3 utterances on either side of the target) were scored for linguistic clues to meaning, including related language, compare/contrast and evaluative information. Linguistic contexts contained more information in adult–child conversations than in adult–adult conversations. There were differences among information categories. For example, explicit definitions were relatively rare compared to other types of information and were far less frequent than reported in structured laboratory situations. Findings highlight the importance of looking at adult input in situations where teaching word meaning is not an explicit goal.
Absolute asymmetric synthesis from an isotropic racemic mixture of chiral molecules with the help of their laser orientation-dependent selection
Authors: Zhdanov Dmitry V. , Zadkov Victor N.
Published: January 2008

We analyzed the absolute asymmetric synthesis (AAS) of enantiomers from an isotropic racemic mixture of chiral molecules, which employs the laser electrodipole interaction, and revealed a set of basic symmetry-based conditions on the parameters of field-molecule interaction. Using these conditions, we developed a novel scenario of the AAS (through selective photodestruction of the enantiomers of a given type) based on the joint action of the strong multicomponent femtosecond and picosecond laser pulses. Key mechanism of this scenario is the partly modified scheme of laser orientation-dependent selection of molecules proposed by us earlier [D. V. Zhdanov et al., JETP 130, 387 (2006)]. Calculations made on example of chiral molecule SiHNaClF show rather high efficiency and stability of the proposed AAS scenario with respect to the parameters of the incident laser pulses and even feasibility of its realization at room temperature.
Phase separation kinetics of polyelectrolyte solutions
Authors: Kanai Sonoko , Muthukumar M.
Published: January 2008

The kinetics of phase separation of aqueous solutions of sodium-poly(styrene sulfonate) (NaPSS) containing barium chloride (BaCl2) is studied by static and dynamic light scattering. We report a novel mechanism of phase separation, where an enrichment of polymer aggregates of well-defined size occurs in the very early stage of nucleation, which is then followed by a growth process in the formation of the new phase. In the latter stage, the polymer aggregates formed in the early stage act as the templating nuclei. Even in the homogeneous phase at higher temperatures above the upper critical phase boundary, polymer aggregates are present in agreement with previously reported results. Upon rapidly cooling the system below the phase boundary, the number concentration of the aggregates increases first by maintaining their size to be relatively monodisperse, before the growth process takes over at later times. The size and fractal dimension of aggregates in the homogeneous phase and the early nucleation stage of phase separation and the dependence of nucleation time and growth rate on quench depth and salt concentration are determined. The hydrodynamic radius (RH) of the unaggregated chains is of the order of 1–10nm depending on the molecular weight of NaPSS, while RH of aggregates is of the order of 100nm independent of the molecular weight of NaPSS. Unaggregated chains follow good solution behavior with a fractal dimension of 5∕3 while the fractal dimension of aggregates is larger than 3.5 suggesting the branched nature of aggregates. Nucleation time is sensitive to quench depth and salt concentration. Increasing a quench depth or increasing BaCl2 concentration shortens the nucleation time. After the nucleation time, during the growth period, the size of aggregates grows linearly with time, with growth rate being higher for deeper quench depths and higher BaCl2 concentrations. The mechanism of phase separation of aqueous solutions of NaPSS and BaCl2 is seen to proceed by utilizing the already-existing aggregates to nucleate the new phase, in marked contrast to hitherto known results on phase separation in uncharged polymer systems.
Water trimer torsional spectrum from accurate ab initio and semiempirical potentials
Authors: van der Avoird Ad , Szalewicz Krzysztof
Published: January 2008

The torsional levels of (H2O)3 and (D2O)3 were calculated in a restricted dimensionality (three-dimensional) model with several recently proposed water potentials. Comparison with the experimental data provides a critical test, not only of the pair interactions that have already been probed on the water dimer spectra, but also of the nonadditive three-body contributions to the potential. The purely ab initio CC-pol and HBB potentials that were previously shown to yield very accurate water dimer levels, also reproduce the trimer levels well when supplemented with an appropriate three-body interaction potential. The TTM2.1 potential gives considerably less good agreement with experiment. Also the semiempirical VRT(ASP-W)III potential, fitted to the water dimer vibration-rotation-tunneling levels, gives substantial disagreement with the measured water trimer levels, which shows that the latter probe the potential for geometries other than those probed by the dimer spectrum. Although the three-body nonadditive interactions significantly increase the stability of the water trimer, their effect on the torsional energy barriers and vibration-tunneling frequencies is less significant.
Hybridab initioKohn-Sham density functional theory/frozen-density orbital-free density functional theory simulation method suitable for biological systems
Authors: Hodak Miroslav , Lu Wenchang , Bernholc J.
Published: January 2008

A hybrid computational method intended for simulations of biomolecules in solution is described. The ab initio Kohn-Sham (KS) density functional theory (DFT) method is used to describe the chemically active part of the system and its first solvation shells, while a frozen-density orbital-free (FDOF) DFT method is used to treat the rest of the solvent. The molecules in the FDOF method have fixed internal structures and frozen electron densities. The hybrid method provides a seamless description of the boundary between the subsystems and allows for the flow of molecules across the boundary. Tests on a liquid water system show that the total energy is conserved well during molecular dynamics and that the effect of the solvent environment on the KS subsystem is well described. An initial application to copper ion binding to the prion protein is also presented.
Improved powder filters for qubit measurements
Authors: Lukashenko A. , Ustinov A. V.
Published: January 2008

We designed and fabricated miniature low-pass metal powder filters suitable for noise-sensitive measurements at cryogenic temperatures. In comparison with previous powder filters, our filters have a much better frequency response and significantly smaller dimensions (0.7cm3 including the plugs) and can also be used as hermetic feedthroughs at low temperatures. Their transmission characteristics are smooth, contain no ripples, and have a steep decay above the cutoff frequency. At 4.2K the cutoff frequency of a single filter is fc=1MHz and the roll-off is −50dB per decade. All of the fabricated filters have identical frequency responses at 4.2K and their characteristics are reliably reproducible.
Characteristics of the low electron density surface layer on BaTiO3 thin films
Authors: Li X. L. , Lu H. B. , Li Ming , Mai Zhenhong , Kim Hyunjung , Jia Q. J.
Published: January 2008

The surfaces of epitaxial BaTiO3 films on SrTiO3 substrates were investigated by x-ray reflectivity (XRR) and angle-resolved x-ray photoelectron spectroscopy (ARXPS). It was shown by XRR analysis that there exists a low electron density surface layer (about 87%–93% of the electron density of the underneath BaTiO3 layer) of 15Å on top of the film. Moreover, ARXPS results revealed a surface core-level shift of Ba in layer of about 11Å, a value which is in agreement with the thickness obtained by XRR, indicating that the surface core-level shift of Ba stems from the low electron density surface layer.
Combinatorial study of zinc tin oxide thin-film transistors
Authors: McDowell M. G. , Sanderson R. J. , Hill I. G.
Published: January 2008

Groups of thin-film transistors using a zinc tin oxide semiconductor layer have been fabricated via a combinatorial rf sputtering technique. The ZnO:SnO2 ratio of the film varies as a function of position on the sample, from pure ZnO to SnO2, allowing for a study of zinc tin oxide transistor performance as a function of channel stoichiometry. The devices were found to have mobilities ranging from 2to12cm2∕Vs, with two peaks in mobility in devices at ZnO fractions of 0.80±0.03 and 0.25±0.05, and on/off ratios as high as 107. Transistors composed predominantly of SnO2 were found to exhibit light sensitivity which affected both the on/off ratios and threshold voltages of these devices.
Erasing characteristics of Cu2O metal-insulator-metal resistive switching memory
Authors: Chen A. , Haddad S. , Wu Y. C. , Fang T. N. , Kaza S. , Lan Z.
Published: January 2008

The erasing characteristics of Cu2O metal-insulator-metal resistive switching memory were measured on a 64Kb memory test array. The erasing yield reaches the maximum at an optimal erasing voltage. Effective erasing requires a threshold current compliance that is higher for shorter pulse width. The erasing current and erasing power both depend strongly on the on-state before erasing, while the erasing voltage is essentially unaffected. Erasing appears to be a power-driven process, which may be related to the thermal effect of power dissipation. The experimental data and analysis suggest that erasing can be explained by field-assisted thermal emission of trapped charges.
Influence of polymer coating on the low-temperature photoluminescence properties of ZnO nanowires
Authors: Richters Jan-Peter , Voss Tobias , Wischmeier Lars , Rückmann Ilja , Gutowski Jürgen
Published: January 2008

We report on low temperature photoluminescence studies of ZnO nanowires embedded in different polymers. Comparing the spectra of as-grown and embedded ZnO nanowires, we find a decrease of the deep-level emission and an increase of the near band-edge emission after the embedding process. The near band-edge emission of the embedded ZnO nanowires is dominated by a surface exciton band. The observed effects are independent of the selected polymer. The decrease of the deep-level emission scales with the balling abilities of the different polymers. We propose a model to explain the spectral changes.
Magnetic and structural properties of MnAs thin films on GaAs(111)B: Influence of the growth temperature
Authors: Garcia V. , Bibes M. , Vodungbo B. , Eddrief M. , Demaille D. , Marangolo M.
Published: January 2008

The magnetic and structural properties of MnAs thin films grown on GaAs(111)B at different temperatures (160–280°C) are investigated. A narrow optimum growth temperature window (200–240°C) is found where the Curie temperature and the room temperature magnetization are maximized. High-resolution x-ray diffraction experiments are performed on the samples showing that the films are epitaxial for a minimum growth temperature of 200°C. The room temperature fraction of the hexagonal phase is strongly dependent on the growth temperature in agreement with the magnetic properties.
Real-time observation of the dry oxidation of the Si(100) surface with ambient pressure x-ray photoelectron spectroscopy
Authors: Enta Yoshiharu , Mun Bongjin S. , Rossi Massimiliano , Ross Philip N. , Hussain Zahid , Fadley Charles S. , Lee Ki-Suk , Kim Sang-Koog
Published: January 2008

We have applied ambient-pressure x-ray photoelectron spectroscopy with Si 2p chemical shifts to study the real-time dry oxidation of Si(100), using pressures in the range of 0.01–1Torr and temperatures of 300–530°C, and examining the oxide thickness range from 0to∼25Å. The oxidation rate is initially very high (with rates of up to ∼225Å∕h) and then, after a certain initial thickness of the oxide in the range of 6–22Å is formed, decreases to a slow state (with rates of ∼1.5–4.0Å∕h). Neither the rapid nor the slow regime is explained by the standard Deal-Grove model for Si oxidation.
The physics of phages
Authors: Gelbart William M. , Knobler Charles M.
Published: January 2008

Experiments can measure, and theory explain, the energetics behind packaging a virus with DNA and the DNA’s injection into a cell.
Transporting water to the tops of trees
Authors: Holbrook N. Michele , Zwieniecki Maciej A.
Published: January 2008

The system of conduits found in a tree is far larger and more complex than any human-constructed microfluidic system.
SOCS1 is an inducible host factor during HIV-1 infection and regulates the intracellular trafficking and stability of HIV-1 Gag
Authors: Ryo Akihide , Tsurutani Naomi , Ohba Kenji , Kimura Ryuichiro , Komano Jun , Nishi Mayuko , Soeda Hiromi , Hattori Shinichiro , Perrem Kilian , Yamamoto Mikio , Chiba Joe , Mimaya Jun-ichi , Yoshimura Kazuhisa , Matsushita Shuzo , Honda Mitsuo , Yoshimura Akihiko , Sawasaki Tatsuya , Aoki Ichiro , Morikawa Yuko , Yamamoto Naoki
Published: January 2008

Human immunodeficiency virus type 1 (HIV-1) utilizes the macromolecular machinery of the infected host cell to produce progeny virus. The discovery of cellular factors that participate in HIV-1 replication pathways has provided further insight into the molecular basis of virus–host cell interactions. Here, we report that the suppressor of cytokine signaling 1 (SOCS1) is an inducible host factor during HIV-1 infection and regulates the late stages of the HIV-1 replication pathway. SOCS1 can directly bind to the matrix and nucleocapsid regions of the HIV-1 p55 Gag polyprotein and enhance its stability and trafficking, resulting in the efficient production of HIV-1 particles via an IFN signaling-independent mechanism. The depletion of SOCS1 by siRNA reduces both the targeted trafficking and assembly of HIV-1 Gag, resulting in its accumulation as perinuclear solid aggregates that are eventually subjected to lysosomal degradation. These results together indicate that SOCS1 is a crucial host factor that regulates the intracellular dynamism of HIV-1 Gag and could therefore be a potential new therapeutic target for AIDS and its related disorders.
Stress blunts serotonin- and hypocretin-evoked EPSCs in prefrontal cortex: Role of corticosterone-mediated apical dendritic atrophy
Authors: Liu Rong-Jian , Aghajanian George K.
Published: January 2008

Morphological studies show that repeated restraint stress leads to selective atrophy in the apical dendritic field of pyramidal cells in the medial prefrontal cortex (mPFC). However, the functional consequence of this selectivity remains unclear. The apical dendrite of layer V pyramidal neurons in the mPFC is a selective locus for the generation of increased excitatory postsynaptic currents (EPSCs) by serotonin (5-HT) and hypocretin (orexin). On that basis, we hypothesized that apical dendritic atrophy might result in a blunting of 5-HT- and hypocretin-induced excitatory responses. Using a combination of whole-cell recording and two-photon imaging in rat mPFC slices, we were able to correlate electrophysiological and morphological changes in the same layer V pyramidal neurons. Repeated mild restraint stress produced a decrement in both 5-HT- and hypocretin-induced EPSCs, an effect that was correlated with a decrease in apical tuft dendritic branch length and spine density in the distal tuft branches. Chronic treatment with the stress hormone corticosterone, while reducing 5-HT responses and generally mimicking the morphological effects of stress, failed to produce a significant decrease in hypocretin-induced EPSCs. Accentuating this difference, pretreatment of stressed animals with the glucocorticoid receptor antagonist RU486 blocked reductions in 5-HT-induced EPSCs but not hypocretin-induced EPSCs. We conclude: (
i
) stress-induced apical dendritic atrophy results in diminished responses to apically targeted excitatory inputs and (
ii
) corticosterone plays a greater role in stress-induced reductions in EPSCs evoked by 5-HT as compared with hypocretin, possibly reflecting the different pathways activated by the two transmitters.
Ca
2+
channel-independent requirement for MAGUK family
CACNB4
genes in initiation of zebrafish epiboly
Authors: Ebert A. M. , McAnelly C. A. , Srinivasan A. , Linker J. L. , Horne W. A. , Garrity D. M.
Published: January 2008

CACNB genes encode membrane-associated guanylate kinase (MAGUK) proteins once thought to function exclusively as auxiliary β subunits in assembly and gating of voltage-gated Ca
2+
channels. Here, we report that zygotic deficiency of zebrafish β4 protein blocks initiation of epiboly, the first morphogenetic movement of teleost embryos. Reduced β4 function in the yolk syncytial layer (YSL) leads to abnormal division and dispersal of yolk syncytial nuclei, blastoderm retraction, and death, effects highly similar to microtubule disruption by nocodazole. Epiboly is restored by coinjection of human β4 cRNA or, surprisingly, by mutant cRNA encoding β4 subunits incapable of binding to Ca
2+
channel α1 subunits. This study defines a YSL-driven zygotic mechanism essential for epiboly initiation and reveals a Ca
2+
channel-independent β4 protein function potentially involving the cytoskeleton.
The age of the Earth and the oldest rocks
Authors: MOORBATH STEPHEN
Published: January 2008

The ages of rocks and minerals can be determined by measuring the accumulation of the products of radioactive decay within them. The results provide a time–scale for the Earth and for the major geological events which have shaped the Earth's continental crust since it first started to separate from the mantle at least 3700 million years ago. The Earth itself is about 4600 million years old.
The Himalayas
Authors: WINDLEY BRIAN F.
Published: January 2008

After splitting from Gondwanaland, India drifted northwards to collide with the Asian landmass about 40 million years ago. The intervening Tethys ocean was closed by northwards subduction beneath southern Tibet, and the collision created the Himalayan orogenic belt. Continuing northward movement of India at a rate of about 5 cm per year over the last 40 million years has caused it to indent Asia, and the resultant massive shortening is expressed by thrusting of the northern margin of India, by faulting and earthquakes in the Himalayas and China, by rifting and faulting in Tibet, and by the uplift of the Himalayas which is still continuing at rates of up to several millimetres per year.
Venus and the VRM mission
Authors: FRANCIS PETER
Published: January 2008

The most profound advances in the Earth sciences during the next decade will not be made on Earth. This paradoxical situation has come about because, while it is becoming more and more difficult to find new approaches to investigating the planet we are so familiar with, by the end of the decade we will have had the opportunity to study a second planet that is remarkably similar to the Earth, but one that has evolved quite differently: Venus. Such study may help us to learn why the Earth evolved in the way that it did, with the unique combination of surface conditions that allow life to be sustained.
Antarctic geology and mineral resources
Authors: SPLETTSTOESSER JOHN F.
Published: January 2008

The geology of Antarctica is similar in many respects to that of the other southern continents that once formed the larger continent of Gondwana. Because of this former union with other land masses, mineral resources in Antarctica are probable, but none of any significance have been found, perhaps because of the widespread cover (97%) of ice over the continent. Offshore oil and gas are presently unknown, but would seem to hold the best prospect for any development in the near future, but perhaps not until questions of sovereignty and ownership of potential resources are resolved.
Urban geology: Glasgow's hidden industrial heritage
Authors: BROWNE MICHAEL A. E. , McMILLAN ANDREW A. , FORSYTH IAN H.
Published: January 2008

The growth of Glasgow from a small town into a heavily industrialised conurbation depended greatly on its local geological riches. Extensive mining and quarrying of a range of minerals took place from the 18th century onwards. The early underground stoop and room (pillar and stall) workings, and the backfilled quarries, together with variably consolidated natural superficial deposits, have bequeathed to the city a heritage of unwanted engineering problems which cannot easily be quantified. Recent work by the British Geological Survey (BGS) illustrates the scale of both geological and man‐made problems.
KRISP 85 — An international seismic investigation of the Kenya Rift
Authors: KHAN AFTAB , MAGUIRE PETER , HENRY BILL , HIGHAM MARTIN
Published: January 2008

British, German, American and Kenyan seismologists undertook a preliminary crustal seismic programme in the Kenya Rift in the summer of 1985. Thirteen explosions, totalling 7 tonnes, were fired in lakes and boreholes, and were recorded by 42 three‐component stations. Preliminary results show that the deep structure along the axis of the Rift is more complex than previous models have suggested.
Faulting
Authors: Hancock Paul
Published: January 2008

In this, the first article of a new series on recent developments in specialist fields, Paul Hancock outlines some new ideas about faulting that have excited general interest and which are important for understanding how sedimentary basins are created, filled and destroyed.
The origins and growth of Recent reefs
Authors: BRAITHWAITE C.J.R.
Published: January 2008

Research on present‐day reefs has sought to analyse the nature, rates of production and patterns of distribution of carbonate sediments. It attempts to relate structures and sequences of growth to ecology, hydrological conditions and histoties of accumulation. Shallow boreholes show that living reefs are characteristically young and suggest that the models of growth we apply to ancient reefs are in need of radical revision.
Patterns in the crust: a key to ore discovery
Authors: SELBY JONATHAN
Published: January 2008

Modern exploration geologists are confronted by a mass of information on the characteristics and localization of mineral deposits. Even so, the search for new economic deposits can be expensive and unrewarding. A theory developed by Tim O'Driscoll, consultant to the Australian mining giant Western Mining Corporation, attempts to explain the distribution of mineral deposits in terms of major crustal lineaments. The theory poses questions regarding the evolution of the Earth and planets, and creates problems for current plate tectonic theory.
Radio geology
Authors: GRAYSON ANNA
Published: January 2008

BBC Education has produced a series of six radio programmes on geology, to be broadcast in March 1988 on Radio 4 VHF. The programmes are supported by 117 slides (two of which are used ‐ in black‐and‐white form‐to illustrate this article) and three computer programs.
Our boot‐shaped ancestors in Wales
Authors: JEFFERIES R. P. S.
Published: January 2008

The marine Palaeozoic fossils called calcichordates, although traditionally regarded as echinoderms, were in fact chordates. They were ancestral to living chordates in general and to vertebrates in particular. The most primitive calcichordates were boot‐shaped. Recent discoveries of calcichordates in the Cambrian and Ordovician of Wales suggest they are commoner than has generally been thought. Geologists should look out for them.
The stones of Roman York
Authors: BUCKLAND P. C.
Published: January 2008

Economic geology is normally regarded as a modern discipline, yet examination of the use of stone in the Roman fortress and city of Eburacum, now known as York, suggests that the Romans had more than a casual knowledge of the sources and properties of stone. Millstone Grit was preferred for load‐bearing situations, whilst the Lower Magnesian Limestone provided the bulk of basic building stone. Other stones indicate the far‐flung trading connections of the Empire, ranging north to the frontier zone of Hadrian's Wall and south‐eastwards to another distant frontier, that of Egypt.
Volcano monitoring by satellite
Authors: ROTHERY DAVID A.
Published: January 2008

‘St Pierre, in the morning throbbing with life, thronged with people, is no more. Its ruins stretch before us, wrapped in their shroud of smoke and ashes, gloomy and silent, a city of the dead’. Thus was St Pierre described by the Vicar‐General of Martinique in the aftermath of the 8 May 1902 eruption of Mt Pelée. Had the warning signs been understood and heeded, 29 000 deaths might have been avoided. Observations recorded by remote sensing satellites now offer additional means of early warning of volcanic hazards and a new way to measure the energy budgets of volcanoes.
Cretaceous‐Tertiary crossroads of migration in the Sahel
Authors: MOODY RICHARD , SUTCLIFFE PETER
Published: January 2008

A series of expeditions undertaken over the last three years by a team of geologists from Kingston Polytechnic and the British Museum (Natural History) has increased our understanding of the Cretaceous and Tertiary palaeogeography of Central West Africa. The latest expedition discovered a dinosaur graveyard of Lower Cretaceous (Wealden) age. Studies of these and other fossils within the sedimentary rocks of the Iullemmeden Basin in Niger and Mali have shed new light on the Trans‐Saharan Seaway migration route during the Cretaceous and Tertiary periods.
Polar fossil forests
Authors: FRANCIS JANE E.
Published: January 2008

In the Arctic and Antarctic there are spectacular fossil forests. They are true ‘polar forests’ because not only are they found as fossils in high latitudes today‐they actually grew in the polar regions. They provide important evidence that the climate of the Earth was once much warmer, and that the trees must have been adapted to the strange polar light‐regime of winter darkness and continuous summer sunlight.
Auriferous sediments of the Yilgarn Block, Western Australia
Authors: TOMICH S. A.
Published: January 2008

Gold‐bearing sediments of mixed sedimentary‐igneous composition, and associated largely with various basic volcanic rocks (greenstones), abound in the Archaean of the Yilgarn Block. In the Coolgardie district, where perhaps they are best developed, many important gold mines and several series of minor gold deposits occur in a few such horizons. Practically identical occurrences, even when highly metamorphosed, are also found elsewhere in greenstone belts‐e.g. in the Southern Cross‐Westonia‐Yellowdine metamorphic zone.
The end for the Frodingham Ironstone?
Authors: KNELL SIMON
Published: January 2008

In 1988 the last Frodingham Ironstone was extracted for steelmaking. Is Britain's last‐but‐one Jurassic ironstone field destined to disappear as almost all the others have before it, or can some part of it be preserved for geologists?
Olympic Dam: a giant Australian ore deposit
Authors: SELBY JONATHAN
Published: January 2008

Events leading to the discovery of one of the world's largest accumulations of metals show that original thinking coupled with geological persistence can pay big dividends for mineral explorers. Ideas on the origin and method of emplacement of this orebody have changed since exploration began in the 1970s, but available ore resources are sufficient to support a major mining operation well into the next century.