bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics and origin of quasi‐biweekly oscillation over the western North Pacific during boreal summer
Authors: Chen Guanghua , Sui Chung‐Hsiung
Published: July 2010

This study investigates the structure, energetic, and origin of quasi‐biweekly oscillation (QBWO) over the western North Pacific (WNP), using NCEP reanalyses for the years 2000–2007. In the context of vorticity there appears to be a significant QBWO mode over the WNP during the summer. QBWO emerges from the equatorial region and propagates northwestward. Its horizontal structure exhibits a slight southwest‐northeast tilt but mainly longitudinal elongation. In the vertical the QBWO has a northwest tilt with height that gives rise to a structure of the first baroclinic mode. The centers of vorticity and vertical motion near the equator show a phase lag of about one‐quarter wavelength, consistent with the characteristics of equatorial waves, whereas the cyclonic circulation is tightly coupled with anomalous convection as the wave moves away from the equator. Energetic analysis of the QBWO reveals that diabatic heating in the tropics and baroclinic processes in the subtropics play important roles in the generation of eddy available potential energy (EAPE). In turn, the conversion from EAPE to eddy kinetic energy (EKE) and the barotropic conversion are major sources for EKE to compensate the loss by EKE redistribution and dissipation. Tracing the QBWO to equatorial disturbances, our results show some features of equatorially trapped n = 1 Rossby mode, such as phase speed and group velocity. This mode is generally characterized by a zonal planetary wave number of about 6 and nearly symmetric circulation about the equator. A typical case from 2002 is chosen to illustrate that the origin of the QBWO is closely associated with the theoretical equatorial Rossby wave.
Inverted fluvial features in the Aeolis/Zephyria Plana region, Mars: Formation mechanism and initial paleodischarge estimates
Authors: Burr Devon M. , Williams Rebecca M. E. , Wendell Kimberly D. , Chojnacki Matthew , Emery Joshua P.
Published: July 2010

A subset of the sinuous ridges (SRs) in the Aeolis/Zephyria Plana (AZP) region of Mars has been previously hypothesized to be inverted fluvial features, although the precise induration and erosion mechanisms were not specified. Morphological observations and thermal inertia data presented here support this hypothesis. A variety of mechanisms can cause inversion, and identification of the specific events that lead to fluvial SR formation can provide insights into the sedimentological, geochemical, and climatic processes of the region. Reconnaissance of two terrestrial lava‐capped ridges suggests some criteria that may be used to identify inverted fluvial features formed by lava infill on Mars, but these criteria are not satisfied by the majority of the AZP fluvial SRs. Armoring also appears inconsistent with terrestrial analogs. Layering and surface textures of fluvial SRs indicate that the most likely induration mechanism was geochemical cementation of fluvial sediments, and that the primary erosional mechanism that exposed the fluvial SRs was aeolian abrasion. This analysis of formation mechanism provides a foundation for estimating paleodischarge using an empirical form‐discharge approach, to which we have applied scaling, for Martian gravity. For those fluvial SRs meeting a set of criteria for accurate paleodischarge estimates, paleodischarge values generally range between 101and 103m3s−1. The largest of these initial estimates are comparable to paleodischarge estimates for some late‐stage Noachian fluvial channels on Mars, and provide a constraint on the atmospheric conditions at this equatorial location during the late Hesperian to early Amazonian time frame.
Surface ice motion deviating toward the margins during speed‐up events at Gornergletscher, Switzerland
Authors: Sugiyama S. , Bauder A. , Riesen P. , Funk M.
Published: July 2010

High frequency ice flow measurements during speed‐up events in Gornergletscher, Switzerland, revealed intriguing ice motion which has never been reported in detail before. During the summer 2005, more than a 100% flow speed increase was observed three times at four GPS stations installed across Gornergletscher. The speed‐ups were accompanied by a decimeter scale surface uplift. Two of the events were triggered by intensive surface melt and rainfall, while the third one was due to the outburst of Gornersee, a glacier‐dammed lake located 2 km upglacier. An interesting observation was ice motion deviating toward the side margins during the events. As the glacier accelerated, a transverse (cross glacier) velocity component was generated, turning the flow direction away from the central flow line toward the margins. When the glacier decelerated, the transverse velocity component reversed so that the ice flowed back to the azimuth of the initial flow direction. In the most significant case, the trajectory of the survey stake deviated from the original track by 0.2 m in the transverse direction. We hypothesize that the observed lateral ice motion was caused by locally elevated subglacial water pressure. When the ice sole decoupled from the bed at a part of the glacier, a point source of vertical displacement was transmitted to the surface through viscous ice. This caused the transverse as well as vertical surface motion, as observed in ground motion during magma intrusion. The hypothesis was tested with a two‐dimensional ice flow model applied to the transverse glacier cross section. The model confirmed that the surface ice would move toward the margins as observed in Gornergletscher, if subglacial water pressure exceeded the ice overburden pressure over a limited part of the bed.
Topographic complexity and roughness of a tropical benthic seascape
Authors: Zawada David G. , Piniak Gregory A. , Hearn Clifford J.
Published: July 2010

Topographic complexity is a fundamental structural property of benthic marine ecosystems that exists across all scales and affects a multitude of processes. Coral reefs are a prime example, for which this complexity has been found to impact water flow, species diversity, nutrient uptake, and wave‐energy dissipation, among other properties. Despite its importance, only limited assessments are available regarding the distribution or range of topographic complexity within or between benthic communities. Here, we show substantial variability in topographic complexity over the entire inner‐shelf seascape of a tropical island. Roughness, estimated in terms of fractal dimension, served as a proxy for topographic complexity, and was computed for linear transects (DT), as well as the benthic surface (DS). Spatial variability in both DT and DS was correlated with the known distribution of benthic cover types in the seascape. Transect roughness values ranged from 1.0 to 1.7, with features along the shelf edge being markedly anisotropic with an along‐shore bias, whereas regions with high scleractinian coral cover were nearly isotropic and exhibited minimal directional bias. Surface‐roughness values ranged from 2.0 in predominantly hardbottom areas with low coral cover to 2.5 in areas with high coral cover. Quantifying roughness across the substrates and biological communities for an entire seascape provides a synoptic view of its spatial variability at scales appropriate for numerous research efforts, including ecosystem studies, parameterizing hydrodynamic models, and designing monitoring programs.
The rainfall‐no rainfall transition in a coupled land‐convective atmosphere system
Authors: Konings Alexandra G. , Katul Gabriel G. , Porporato Amilcare
Published: July 2010

A one‐dimensional representation of the atmospheric boundary layer (ABL) depth is coupled to a soil moisture bucket model to dynamically explore the relative roles of surface and free atmospheric conditions on convective precipitation occurrence and resulting soil moisture states. This occurrence is taken to depend on the crossing of the ABL height and the lifting condensation level in the presence of pure convective instability. If rainfall occurs (unrealistically) whenever these conditions are met, and free atmospheric conditions are constant, the resulting system state evolves towards a limit cycle with precipitation every day or every few days, or to a completely dry state. The free atmospheric humidity profile has a larger effect on determining the stationary soil moisture state than the temperature profile. The effect of dry air entrainment on surface energy partitioning decreases soil moisture sensitivity to free atmospheric conditions.
Cassini observations of a Kelvin‐Helmholtz vortex in Saturn's outer magnetosphere
Authors: Masters A. , Achilleos N. , Kivelson M. G. , Sergis N. , Dougherty M. K. , Thomsen M. F. , Arridge C. S. , Krimigis S. M. , McAndrews H. J. , Kanani S. J. , Krupp N. , Coates A. J.
Published: July 2010

We present Cassini observations of a plasma vortex in Saturn's dayside outer magnetosphere. The vortex encounter took place on 13 December 2004 as Cassini was travelling toward the planet. The spacecraft crossed the magnetopause 3 times, before being immersed in the low‐latitude boundary layer. During the transition between the boundary layer and the magnetosphere proper, the spacecraft observed deflected boundary layer plasma, a twisted magnetic field topology, and high‐energy (>20 keV) directional electron fluxes. These observations are consistent with an encounter with a vortex on the inner edge of the boundary layer, an interface that is expected to be susceptible to the growth of the Kelvin‐Helmholtz (K‐H) instability due to its low magnetic shear. The size of the vortex is determined to be at least 0.55 RS, and a simple model of the current system resulting from the formation of the vortex is proposed. The possible acceleration mechanisms responsible for the high‐energy electrons are discussed. The identification of the structure provides compelling evidence of the operation of the nonlinear K‐H instability at Saturn's morning magnetospheric boundaries and has implications for our understanding of the transfer of energy and momentum between the solar wind and Saturn's magnetosphere.
Mutation of megalin leads to urinary loss of selenoprotein P and selenium deficiency in serum, liver, kidneys and brain
Authors: Chiu-Ugalde Jazmin , Theilig Franziska , Behrends Thomas , Drebes Julia , Sieland Carolin , Subbarayal Prema , Köhrle Josef , Hammes Annette , Schomburg Lutz , Schweizer Ulrich
Published: July 2010

Distribution of selenium (Se) within the mammalian body is mediated by SePP (selenoprotein P), an Se-rich glycoprotein secreted by hepatocytes. Genetic and biochemical evidence indicate that the endocytic receptors ApoER2 (apolipoprotein E receptor 2) and megalin mediate tissue-specific SePP uptake. In the present study megalin-mutant mice were fed on diets containing adequate (0.15 p.p.m.) or low (0.08 p.p.m.) Se content and were analysed for tissue and plasma Se levels, cellular GPx (glutathione peroxidase) activities and protein expression patterns. Megalin-mutant mice displayed increased urinary Se loss, which correlated with SePP excretion in their urine. Accordingly, serum Se and SePP levels were significantly reduced in megalin-mutant mice, reaching marginal levels on the low-Se diet. Moreover, kidney Se content and expression of renal selenoproteins were accordingly reduced, as was SePP internalization along the proximal tubule epithelium. Although GPx4 expression was not altered in testis, Se and GPx activity in liver and brain were significantly reduced. When fed on a low-Se diet, megalin-mutant mice developed impaired movement co-ordination, but no astrogliosis. These findings suggest that megalin prevents urinary SePP loss and participates in brain Se/SePP uptake.
Cancer cell sensitivity to arginine deprivation in vitro is not determined by endogenous levels of arginine metabolic enzymes
Authors: Bobak Yaroslav P. , Vynnytska Bozhena O. , Kurlishchuk Yuliya V. , Sibirny Andriy A. , Stasyk Oleh V.
Published: July 2010

Single amino acid Arg (arginine) deprivation is currently considered as a therapeutic approach to treat certain types of tumours; the molecular mechanisms that underlie tumour cell sensitivity or resistance to Arg restriction are still little understood. Here, we address the question of whether endogenous levels of key Arg metabolic enzymes [catabolic: arginases, ARG1 (arginase type 1) and ARG2 (arginase type 2), and anabolic: OTC (ornithine transcarbamylase) and ASS (argininosuccinate synthetase)] affect cellular responses to arginine deprivation in vitro. Human epithelial cancer cells of different organs of origin exhibiting variable sensitivity to Arg deprivation provided the experimental models. Neither the basal expression status of the analysed enzymes, nor their changes upon arginine withdrawal correlated with cancer cell sensitivity to arginine deprivation. However, the ability to utilize exogenous Arg precursors (ornithine and citrulline) for growth in Arg‐deficient medium strongly correlated with expression of the corresponding enzymes, OTC and ASS. We also observed that OTC expression was below the level of detection in all the types of tumour cells analysed, suggesting that in vitro, at least for them, Arg is an essential amino acid.
Investigating Energy Issues in Dominica's Accommodations
Authors: Nelson Velvet
Published: July 2010

In light of global climate change, issues of energy consumption in the international tourism industry have been receiving increased attention. Although the transport sector of the industry is the largest consumer of energy, the accommodation sector has been identified as an area in which improvements in the type and quantity of energy used could be made. This article presents the results of a first-stage research project which sought to investigate the issues associated with energy consumption and the strategies utilized in the accommodation sector on the Caribbean island of Dominica primarily through in-depth interviews with operators. The findings of the project indicate that, while operators are interested in, and motivated by, environmental sustainability and maintaining the island's reputation as a green destination, this does not always translate into action for a number of reasons, the most significant of which is the cost of energy.
Re-Branding Alternative Tourism in the Caribbean: The Case for ‘Slow Tourism’
Authors: Conway Dennis , Timms Benjamin F.
Published: July 2010

Slow tourism represents a progressive genre of alternative tourism for remote locales in the Caribbean beyond mass-tourism complexes. We propose this new form of slow tourism as a viable promotional identity for alternative tourist offerings, which are in need of re-branding, through the decentralized medium of information technologies. A further contribution to this new construct's identity is our recognition of the potential for the Caribbean diaspora to participate as stakeholders in slow tourism ventures in under-developed spaces of the Caribbean that lack the requisite resources and bundle of social and economic advantages that mass- tourism relies upon. Thus, the unevenness of tourism-driven development in the Caribbean can be countered progressively, and more inclusively, than in times past. In addition to developing the theoretical construct of slow tourism, we offer several prototype examples to demonstrate quality offerings already in praxis.
Pulsed thermoelectricity
Authors: Apostol M. , Nedelcu M.
Published: July 2010

A special mechanism of thermoelectric transport is described, consisting of pulses of charge carriers which “fly” periodically through the external circuit from the hot end of the sample to the cold end, with a determined duration of the “on” and “off” times of the electric contacts, while maintaining continuously the thermal contacts. It is shown that such a “resonant” ideal thermogenerator may work cyclically, with the same efficiency quotient as the ideal efficiency quotient of the thermoelectric devices operated in the usual stationary transport regime but the electric flow and power are increased, as a consequence of the concentration of the charge carriers on pulses of small spatial extent. The process is reversible, in the sense that it can be operated either as a thermoelectric generator or as an electrothermal cooler.
Gate-field dependent photosensitivity of soluble 1,2,4,5-tetra(5′-hexyl-[2,2′]terthiophenyl-5-vinyl)-benzene based organic thin film transistors
Authors: Cho Mi Yeon , Kim Kihyun , Kim Su Jin , Jo Seong Gi , Kim Kyung Hwan , Jung Ki Hwa , Choi Dong Hoon , Kim Sangsig , Joo Jinsoo
Published: July 2010

The photoresponsive current-voltage characteristics of organic thin film transistors (OTFTs) have been studied as a function of gate-bias. For the active layer of the OTFTs, soluble 1,2,4,5-tetra(5′-hexyl-[2,2′]terthiophenyl-5-vinyl)-benzene materials have been used, and the thickness of the active layers varied. The photosensitivity of the OTFTs was controlled through both gate-bias (Vg) and incident light power. With increasing incident light power, the photosensitivity decreased during the source-drain current actively varied with Vg [i.e., at on-state with accumulated hole channel (Vg<Vonset)], while it increased for Vg≥Vonset (at off-state without accumulated hole channel). These variations are caused by two kinds of photocurrent mechanisms: one based on the photovoltaic effect for Vg<Vonset and another based on the photoconductive effect for Vg≥Vonset. The maximum photosensitivity of OTFTs was found to be approximately 40 times higher in the on-state than in the off-state due to the contribution of photovoltaic effect in the on-state.
Direct and indirect band gap room temperature electroluminescence of Ge diodes
Authors: de Kersauson M. , Jakomin R. , El Kurdi M. , Beaudoin G. , Zerounian N. , Aniel F. , Sauvage S. , Sagnes I. , Boucaud P.
Published: July 2010

Germanium is a promising material for electrically pumped light emitters integrated on silicon. In this work, we have investigated the room temperature electroluminescence of pure germanium diodes grown by metal organic chemical vapor deposition. The dependence of the optical response of the p-n diodes is studied as a function of the injected current. Both direct and indirect band gap recombinations are observed at room temperature around 1.6 and 1.8 μm. The amplitude of the direct band gap recombination is equivalent to the one of the indirect band gap.
Experimental aspects of multiharmonic-order coherent diffractive imaging
Authors: Teichmann Sven , Chen Bo , Dilanian Ruben A. , Hannaford Peter , Van Dao Lap
Published: July 2010

We describe some experimental aspects required for the implementation of a few-order high-harmonic source for coherent diffractive imaging in the extreme-ultraviolet region. Polychromatic high-angle diffractive images have been successfully processed for both periodic and aperiodic inorganic samples using a modified Gerchberg–Saxton algorithm and maximum-entropy-method refinement and reconstructions yielding a resolution of 100 nm can now be achieved at harmonic wavelengths around 32 nm.
Percolation and polaritonic effects in periodic planar nanostructures evolving from holes to islands
Authors: Peng Y. , Paudel T. , Chen W.-C. , Padilla W. J. , Ren Z. F. , Kempa K.
Published: July 2010

We study interaction of the electromagnetic radiation with a series of thin film periodic nanostructures evolving from holes to islands. We show, through model calculations, simulations, and experiments, that the responses of these structures evolve accordingly, with two topologically distinct spectral types for holes and islands. We find also, that the response at the transitional pattern is singular. We show that the corresponding effective dielectric function follows the critical behavior predicted by the percolation theory and thus the hole-to-island structural evolution in this series is a topological analog of the percolation problem, with the percolation threshold at the transitional pattern.
Fundamentals and applications of the photocatalytic treatment for the removal of industrial organic pollutants and effects of operational parameters: A review
Authors: Thakur Rajendra Singh , Chaudhary Rubina , Singh Chandan
Published: July 2010

Photocatalysis process, as an environmental application, is a relatively novel subject with tremendous potential in the near future. A number of studies determine the economic viability of applying various ultraviolet advanced oxidation processes for the purpose of degradation and destroying of various pollutant solutions. The present paper reviews the treatment of hazardous wastewater bearing organic compounds and the effects of various parameters such as pH, initial concentration, mass of catalyst, wavelength, light intensity, electron acceptor, temperature, etc., with the treatment cost for different reactor type. This study investigates the effect of various types of waste-water treatment parameters and the treatment cost for various designs of photocatalytic reactors, using both solar and artificial light, have been proposed for their different types of pollutants.
Resistance switching in polycrystalline BiFeO3 thin films
Authors: Yin Kuibo , Li Mi , Liu Yiwei , He Congli , Zhuge Fei , Chen Bin , Lu Wei , Pan Xiaoqing , Li Run-Wei
Published: July 2010

We report resistance switching effects in polycrystalline pure BiFeO3 films prepared by a sol-gel method. By current-voltage and conductive atomic force microscope (c-AFM) measurements, resistance switching effects are observed in BiFeO3 films annealed at and above 650 °C. A fresh sample can be transformed into a low-resistive state by applying a high positive voltage without forming process and then be switched to a high-resistive state by applying a negative voltage. Both c-AFM and retention results suggest that the redistribution of oxygen vacancies in grain boundaries could play a key role on the resistance switching in the polycrystalline pure BiFeO3 films.
Design of acoustic devices with isotropic material via conformal transformation
Authors: Ren Chunyu , Xiang Zhihai , Cen Zhangzhi
Published: July 2010

The known realization of transformation acoustic devices requires exotic material parameters and has been hampered by limited available materials. By merging the conformal mapping and the embedded coordinate transformation method, we demonstrate that transformation-based acoustic devices can be made from isotropic materials, which greatly facilitates their implementation. The acoustic directional antenna based on such approach is presented and validated by full-wave simulations using the finite element method.
Use of complex configuration interaction calculations and the stationary principle for the description of metastable electronic states of HCl−
Authors: Honigmann Michael , Liebermann Heinz-Peter , Buenker Robert J.
Published: July 2010

The complex multireference single- and double-excitation configuration interaction method has been employed to compute potential curves for the anion of the hydrogen chloride molecule. First, conventional CI calculations with real basis functions have been carried out to determine the potential curves of both HCl and its anion over a large range of internuclear distance. It is shown that adding basis functions with very small exponents leads to sharply avoided crossings for the HCl− potentials that greatly complicate the search for resonance states thought to be responsible for features observed in electron collision experiments. By limiting the number of such diffuse-type functions it is possible to describe resonance states at a highly correlated level and still account for their interaction with the continuum in which they are embedded. In the present study of the HCl− anion the complex basis function technique of Moiseyev–Corcoran and McCurdy–Resigno is employed to calculate the energy positions and line-widths of the resonance states. Two states of Σ2+ symmetry are calculated which have potentials that have significantly different shapes than that of the neutral ground state and thus contribute to the cross section for vibrational excitation of the neutral HCl molecule induced by low-energy electron collisions. The lower of these (1 Σ2+) correlates smoothly with the bound anionic ground state at large internuclear distances and is seen to be responsible for the sharp peaks observed in the low-energy region of the spectrum. The upper state (3 Σ2+) has a much larger bond length and is assigned to the broad bands observed with a maximum in the 2.5–3.0 eV range. The present calculations thus stand in contradiction to earlier claims that the above peaks are caused by so-called virtual states without a definite autoionization lifetime.
Sum-frequency generation in doubly resonant GaP photonic crystal nanocavities
Authors: Rivoire Kelley , Lin Ziliang , Hatami Fariba , Vučković Jelena
Published: July 2010

We demonstrate and characterize continuous wave χ(2) sum-frequency generation in gallium phosphide photonic crystal nanocavities. We use two confined modes of the nanocavity in the wavelength range 1500–1600 nm to enhance conversion efficiency. Our results show that these nanocavities can serve as integrated light sources across a range of wavelengths, and are promising for on-chip upconversion of weak intensity telecommunication wavelengths signals to visible wavelengths.
Gapless insulator and a band gap scaling law in semihydrogenated graphene
Authors: Wright A. R. , O’Brien T. E. , Beaven D. , Zhang C.
Published: July 2010

We demonstrate two unusual electronic properties of semihydrogenated graphene with variable sized A- or B-hydrogenated domains within the tight-binding formalism as follows: (i) a universal band gap scaling law which states that the band gap depends linearly upon the ratio of the number of A- to B-hydrogenated atoms, NA/NB, reaching zero gap at NA=NB, but independent of the domain size, and (ii) an insulating state with zero band gap at NA=NB, a rare phenomenon in nature. We confirm this gapless insulator state by the zero optical conductance at low frequencies.
DNA damage signaling in response to double-strand breaks during mitosis
Authors: Giunta Simona , Belotserkovskaya Rimma , Jackson Stephen P.
Published: July 2010

The signaling cascade initiated in response to DNA double-strand breaks (DSBs) has been extensively investigated in interphase cells. Here, we show that mitotic cells treated with DSB-inducing agents activate a “primary” DNA damage response (DDR) comprised of early signaling events, including activation of the protein kinases ataxia telangiectasia mutated (ATM) and DNA-dependent protein kinase (DNA-PK), histone H2AX phosphorylation together with recruitment of mediator of DNA damage checkpoint 1 (MDC1), and the Mre11–Rad50–Nbs1 (MRN) complex to damage sites. However, mitotic cells display no detectable recruitment of the E3 ubiquitin ligases RNF8 and RNF168, or accumulation of 53BP1 and BRCA1, at DSB sites. Accordingly, we found that DNA-damage signaling is attenuated in mitotic cells, with full DDR activation only ensuing when a DSB-containing mitotic cell enters G1. Finally, we present data suggesting that induction of a primary DDR in mitosis is important because transient inactivation of ATM and DNA-PK renders mitotic cells hypersensitive to DSB-inducing agents.
Actin-based motility drives baculovirus transit to the nucleus and cell surface
Authors: Ohkawa Taro , Volkman Loy E. , Welch Matthew D.
Published: July 2010

Most viruses move intracellularly to and from their sites of replication using microtubule-based mechanisms. In this study, we show that nucleocapsids of the baculovirus Autographa californica multiple nucleopolyhedrovirus undergo intracellular motility driven by actin polymerization. Motility requires the viral P78/83 capsid protein and the host Arp2/3 complex. Surprisingly, the virus directs two sequential and coordinated phases of actin-based motility. Immediately after cell entry, motility enables exploration of the cytoplasm and collision with the nuclear periphery, speeding nuclear entry and the initiation of viral gene expression. Nuclear entry itself requires transit through nuclear pore complexes. Later, after the onset of early gene expression, motility is required for accumulation of a subpopulation of nucleocapsids in the tips of actin-rich surface spikes. Temporal coordination of actin-based nuclear and surface translocation likely enables rapid transmission to neighboring cells during infection in insects and represents a distinctive evolutionary strategy for overcoming host defenses.
Oscillations in Cdc14 release and sequestration reveal a circuit underlying mitotic exit
Authors: Manzoni Romilde , Montani Francesca , Visintin Clara , Caudron Fabrice , Ciliberto Andrea , Visintin Rosella
Published: July 2010

In budding yeast, the phosphatase Cdc14 orchestrates progress through anaphase and mitotic exit, thereby resetting the cell cycle for a new round of cell division. Two consecutive pathways, Cdc fourteen early anaphase release (FEAR) and mitotic exit network (MEN), contribute to the progressive activation of Cdc14 by regulating its release from the nucleolus, where it is kept inactive by Cfi1. In this study, we show that Cdc14 activation requires the polo-like kinase Cdc5 together with either Clb–cyclin-dependent kinase (Cdk) or the MEN kinase Dbf2. Once active, Cdc14 triggers a negative feedback loop that, in the presence of stable levels of mitotic cyclins, generates periodic cycles of Cdc14 release and sequestration. Similar phenotypes have been described for yeast bud formation and centrosome duplication. A common theme emerges where events that must happen only once per cycle, although intrinsically capable of oscillations, are limited to one occurrence by the cyclin–Cdk cell cycle engine.
Ion permeation and block of the gating pore in the voltage sensor of NaV1.4 channels with hypokalemic periodic paralysis mutations
Authors: Sokolov Stanislav , Scheuer Todd , Catterall William A.
Published: July 2010

Hypokalemic periodic paralysis and normokalemic periodic paralysis are caused by mutations of the gating charge–carrying arginine residues in skeletal muscle NaV1.4 channels, which induce gating pore current through the mutant voltage sensor domains. Inward sodium currents through the gating pore of mutant R666G are only ∼1% of central pore current, but substitution of guanidine for sodium in the extracellular solution increases their size by 13- ± 2-fold. Ethylguanidine is permeant through the R666G gating pore at physiological membrane potentials but blocks the gating pore at hyperpolarized potentials. Guanidine is also highly permeant through the proton-selective gating pore formed by the mutant R666H. Gating pore current conducted by the R666G mutant is blocked by divalent cations such as Ba2+ and Zn2+ in a voltage-dependent manner. The affinity for voltage-dependent block of gating pore current by Ba2+ and Zn2+ is increased at more negative holding potentials. The apparent dissociation constant (Kd) values for Zn2+ block for test pulses to −160 mV are 650 ± 150 µM, 360 ± 70 µM, and 95.6 ± 11 µM at holding potentials of 0 mV, −80 mV, and −120 mV, respectively. Gating pore current is blocked by trivalent cations, but in a nearly voltage-independent manner, with an apparent Kd for Gd3+ of 238 ± 14 µM at −80 mV. To test whether these periodic paralyses might be treated by blocking gating pore current, we screened several aromatic and aliphatic guanidine derivatives and found that 1-(2,4-xylyl)guanidinium can block gating pore current in the millimolar concentration range without affecting normal NaV1.4 channel function. Together, our results demonstrate unique permeability of guanidine through NaV1.4 gating pores, define voltage-dependent and voltage-independent block by divalent and trivalent cations, respectively, and provide initial support for the concept that guanidine-based gating pore blockers could be therapeutically useful.
Evaluation of a Large-Scale Quantitative Respirator-Fit Testing Program for Healthcare Workers: Survey Results
Authors: Wilkinson Irene J. , Pisaniello Dino , Ahmad Junaid , Edwards Suzanne
Published: July 2010

Objective.

To present the evaluation of a large-scale quantitative respirator-fit testing program.

Design.

Concurrent questionnaire survey of fit testers and test subjects.

Setting.

Ambulatory care, home nursing care, and acute care hospitals across South Australia.

Methods.

Quantitative facial-fit testing was performed with TSI PortaCount instruments for healthcare workers (HCWs) who wore 5 different models of a disposable P2 (N95-equivalent) respirator. The questionnaire included questions about the HCWs age, sex, race, occupational category, main area of work, smoking status, facial characteristics, prior training and experience in use of respiratory masks, and number of attempts to obtain a respirator fit.

Results.

A total of 6,160 HCWs were successfully fitted during the period from January through July 2007. Of the 4,472 HCWs who responded to the questionnaire and were successfully fitted, 3,707 (82.9%) were successfully fitted with the first tested respirator, 551 (12.3%) required testing with a second model, and 214 (4.8%) required 3 or more tests. We noted an increased pass rate on the first attempt over time. Asians (excluding those from South and Central Asia) had the highest failure rate (16.3% [45 of 276 Asian HCWs were unsuccessfully fitted]), and whites had the lowest (9.8% [426 of 4,338 white HCWs]). Race was highly correlated with facial shape. Among occupational groups, doctors had the highest failure rate (13.4% [81 of 604 doctors]), but they also had the highest proportion of Asians. Prior education and/or training in respirator use were not associated with a higher pass rate.

Conclusions.

Certain facial characteristics were associated with higher or lower pass rates with regard to fit testing, and fit testers were able to select a suitable respirator on the basis of a visual assessment in the majority of cases. For the fit tester, training and experience were important factors; however, for the HCW being fitted, prior experience in respirator use was not an important factor.
Use of Gloves and Reduction of Risk of Injury Caused by Needles or Sharp Medical Devices in Healthcare Workers: Results from a Case-Crossover Study
Authors: Kinlin Laura M. , Mittleman Murray A. , Harris Anthony D. , Rubin Michael A. , Fisman David N.
Published: July 2010

Objective.

Standard precautions are advocated for reducing the number of injuries caused by needles and sharp medical devices (“sharps injuries”), but the effectiveness of gloves in preventing such injuries has not been established. We evaluated factors associated with gloving practices and identified associations between gloving practices and sharps-injury risk.

Design.

Usual-frequency case-crossover study.

Setting.

Thirteen medical centers in the United States and Canada.

Participants.

Six hundred thirty-six healthcare workers who presented to employee health clinics after sharps injury.

Methods.

Structured telephone questionnaires were administered to assess usual behaviors and circumstances at the time of injury.

Results.

Of 636 injured healthcare workers, 195 were scrubbed in an operating room or procedure suite when injured, and 441 were injured elsewhere. Nonscrubbed individuals were more commonly gloved when treating patients who were perceived to have a high risk of human immunodeficiency virus, hepatitis B virus, or hepatitis C virus infection than when treating other patients (adjusted odds ratio [aOR], 2.53 [95% confidence interval {CI}, 1.30-4.91]). Nurses (aOR, 0.11 [95% CI, 0.04-0.32]) and other employees (aOR, 0.24 [95% CI, 0.07-0.77]) were less commonly gloved at injury than were physicians and physician trainees. Gloves reduced injury risk in case-crossover analyses (incidence rate ratio [IRR], 0.33 [95% CI, 0.22-0.50]). In scrubbed individuals, involvement in an orthopedic procedure was associated with double gloving at injury (aOR, 13.7 [95% CI, 4.55-41.3]); this gloving practice was associated with decreased injury risk (IRR, 0.20 [95% CI, 0.10-0.42]).

Conclusions.

Although the use of gloves reduces the risk of sharps injuries in health care, use among healthcare workers is inconsistent and may be influenced by risk perception and healthcare culture. Glove use should be emphasized as a key element of multimodal sharps-injury reduction programs.
Form factor of anN-layered helical tape and its application to nanotube formation of hexa-peri-hexabenzocoronene-based molecules
Authors: Teixeira Cilâine V. , Amenitsch Heinz , Fukushima Takanori , Hill Jonathan P. , Jin Wusong , Aida Takuso , Hotokka Matti , Lindén Mika
Published: July 2010

Self-assembled helical supramolecular structures are widely found in nature and have also been observed in several systems based on synthetic amphiphiles. Such structures often exhibit interesting properties that can be utilized in different nanotechnological applications. Based on previous work concerning the form factor of helical filaments with a finite cross section, the present work gives the helical form factor generalized for a tape containingNlayers. The presented form factor is applied to the characterization of an intermediate structure obtained during the formation of self-assembled graphitic nanotubes. The structure was modeled as a centrosymmetric bilayer containing five layers including a structure factor. These results have been compared with that obtained using a model based on polydisperse cylinders, and it is shown that the full description with helical model and structure factor is the superior one.
Prediction of hexagonal lattice parameters of various apatites by artificial neural networks
Authors: Kockan Umit , Evis Zafer
Published: July 2010

In this study, the hexagonal lattice parameters of apatite compounds,M10(TO4)6X2, whereMis Na+, Ca2+, Ba2+, Cd2+, Pb2+, Sr2+, Mn2+, Zn2+, Eu2+, Nd3+, La3+or Y3+,Tis As+5, Cr+5, P5+, V5+or Si+4, andXis F−, Cl−, OH−or Br−, were predicted from their ionic radii by artificial neural networks. A multilayer perceptron network was used for training and the best results were obtained with a Bayesian regularization method. Four neurons were used in the hidden layer, utilizing a tangent sigmoid activation function, while one neuron was used in the output layer with a pure linear function. The results of the training showed that the correlation coefficients for the hexagonal lattice parameters were 0.991 for the training data set, which is very close to unity, demonstrating that the learning process was successful. In addition, the average errors of the predicted lattice parameters were less than 1% for the data set prepared with single ions at theM,TandXsites, as well as for apatites with coupled substitutions involving up to three different ions at each site. Simple mathematical formulae were derived for the prediction of lattice parameters using average ionic radii as independent variables.
Temperature-induced structure and microstructure evolution of nanostructured Ni0.9Zn0.1O
Authors: Kremenović Aleksandar , Antić Bratislav , Vučinić-Vasić Milica , Colomban Philippe , Jovalekić Čedomir , Bibić Nataša , Kahlenberg Volker , Leoni Matteo
Published: July 2010

The crystal structure and microstructure of as-prepared and annealed Ni0.9Zn0.1O were refined at room temperature in both theFm{\overline 3}mandR{\overline 3}mspace groups. It is shown that below the Néel point (458 K), where magnetic ordering triggers the presence of a trigonal strain, the common usage of a higher-symmetry non-admissible space group for crystal structure and microstructure analysisviathe Rietveld method may result in both an incorrect structure description and incorrect microstructure parameters (size and strain). More realistic microstructure data can be obtained by whole powder pattern modelling of the powder diffraction data. Increasing the annealing temperature causes a reduction of the trigonal distortion as well as an increase in domain size. Simultaneously, the Raman spectra become less resolved, a clear indication of domain growth and structural evolution of the structure towards cubic symmetry (R{\overline 3}m→Fm{\overline 3}m).
Continuous flow supercritical water synthesis and crystallographic characterization of anisotropic boehmite nanoparticles
Authors: Lock Nina , Hald Peter , Christensen Mogens , Birkedal Henrik , Iversen Bo Brummerstedt
Published: July 2010

Crystalline boehmite nanoparticles have been prepared in a few minutes from thermal decomposition of aluminium nitrate in near- and supercritical water. Highly anisotropic nanoparticles are formed under continuous flow conditions using T-piece mixing and a large size tube diameter. The shapes and sizes of the synthesized nanocrystals were determined from peak shape analysis of powder X-ray diffraction data. The crystallite morphology is pressure dependent, and the size increases with temperature for constant reaction time and pressure. The modelled crystallite sizes and anisotropic shapes are in good agreement with transmission electron microscopy studies. At lower synthesis pressures the boehmite crystallite morphology is a mixture of platelets and bar-shaped crystals. The bar-shaped crystals align into polycrystalline fibre-like long thin needles, which again align sidewise in bundles. At higher pressures, only the polycrystalline fibres are formed. Full conversion of dried boehmite to γ-Al2O3is observed after short-term heating to 773 K with an overall conservation of the morphology.
FitGISAXS: software package for modelling and analysis of GISAXS data using IGOR Pro
Authors: Babonneau David
Published: July 2010

A software package for performing modelling and analysis of GISAXS (grazing-incidence small-angle X-ray scattering) data within the distorted-wave Born approximation has been developed using the IGOR Pro scripting language (http://www.wavemetrics.com). The tool suite uses a slab-model approach with the Abélès matrix method to calculate X-ray reflectivity curves, electric field intensity distributions and GISAXS intensities from supported or buried scatterers arranged in two or three dimensions in a stratified medium. Models are included to calculate the scattered intensity for monodisperse, polydisperse and interacting particles with various size distributions, form factors and structure factors. The source code for the entire package is freely available, allowing anyone to develop additional tools.
Absorption correction for cylindrical and annular specimens and their containers or supports
Authors: Bowden Mark , Ryan Martin
Published: July 2010

The absorption correction for cylindrical specimens, typically capillary or annular, is affected by absorption in both the specimen and the supporting material. These corrections are calculated here using numerical integration of the lengths through the different regions of the specimen that the beam traverses. Suitable formulae have been derived and built in to a computer program for calculating the absorption correction for a range of cylindrical geometries. The influence of absorption in the support is most significant for annular specimens on a highly absorbing core, and for capillary specimens of highly absorbing compounds. The error arising from neglecting absorption in the specimen and additionally in the capillary is demonstrated in Rietveld refinements of LaB6. Interpolation of correction factors between values calculated at discrete θ intervals, and θ offsets arising from absorption, are also discussed.
publCIF: software for editing, validating and formatting crystallographic information files
Authors: Westrip Simon P.
Published: July 2010

publCIFis an application designed for creating, editing and validating crystallographic information files (CIFs) that are used in journal publication. It validates syntax and dictionary-defined data attributes through internal routines, and also provides a web interface to thecheckCIFservice of the International Union of Crystallography (IUCr), which provides a full crystallographic analysis of the structural data. The graphical interface allows users to edit the CIF either in its `raw' ASCII form (using a text editor with context-sensitive data validation and input facilities) or as a formatted representation of a structure report (using a word-processing environment), as well asviaa number of convenience tools (e.g.spreadsheet representations of looped data). Beyond file and data validation,publCIFprovides access to resources to facilitate preparation of a structure report (e.g.databases of author details, experimental data, standard referencesetc., either distributed with the program or collected during its use), along with tools for reference parsing, spell checking, structure visualization and image management.publCIFwas commissioned by the IUCr, both as free software for authors and as a tool for in-house journal production; the tool for authors is described here. Binary distributions for Linux, MacOS and Windows operating systems are available.
Experimental determination of resolution function parameters from small-angle neutron scattering data of a colloidal SiO2dispersion
Authors: Vad T. , Sager W. F. C. , Zhang J. , Buitenhuis J. , Radulescu A.
Published: July 2010

A dilute dispersion of charge-stabilized, monodisperse silica nanoparticles has been used to determine the instrumental resolution function parameters of a conventional small-angle neutron scattering instrument in pinhole geometry over the entire accessible range of momentum transferq. Independent determination of the structure parameters of the colloidal silica dispersion by small-angle X-ray scattering enables refinement of both theq-independent geometric and theq-dependent (wavelength spread or polychromaticity of the neutron beam) contributions to the resolution function. The procedure described is appropriate if no further instrumental characterization is available. It is demonstrated that the sample used for refining the resolution function parameters has to exhibit sharp structural scattering features such as Bragg reflections, form factor maxima and minima, or an inter-particle correlation peak for each instrumental configuration at which the measurements have been performed to cover aqrange of two orders of magnitude (0.03 <q< 3.2 nm−1).
A refinement strategy for Monte Carlo modelling of diffuse scattering from molecular crystal systems
Authors: Chan E. J. , Welberry T. R. , Goossens D. J. , Heerdegen A. P.
Published: July 2010

A new strategy for modelling diffuse scattering from molecular crystals using Monte Carlo simulation is described. The use of harmonic (Hooke's law) springs to representeffectiveintermolecular interactions is preserved, in order to minimize computer requirements, but use is now made of a simple empirical formula to specify spring constants and provide an objective means for limiting the number of springs needed to be used. The method has been tested on diffuse scattering data obtained for form I of paracetamol.