bluuebunny/crossref_metadata_2025 huggingface dataset:
Targeting tumour-initiating cells to improve the cure rates for triple-negative breast cancer
Authors: Stratford Anna L. , Reipas Kristen , Maxwell Christopher , Dunn Sandra E.
Published: July 2010

Tumour recurrence is one of the biggest challenges in breast cancer management because it affects 25–30% of women with breast cancer and the tumours are often incurable. Women with triple-negative breast cancer (TNBC – lacking expression of the oestrogen receptor, progesterone receptor and the receptor HER2/ERBB2) have the highest rates of early recurrence relative to other breast cancer subtypes. Early recurrence might be due to tumour-initiating cells (TICs), which are resistant to conventional therapies, can remain dormant and can subsequently give rise to secondary tumours. In breast cancer, TICs are identified by the cell-surface markers CD44+/CD24−/EpCAM+and/or possess ALDH1 enzyme activity. This subpopulation has the ability to self-renew, grow as mammospheres and initiate tumour formation. Fuelling the problem of relapse is the fact that chemotherapy and radiation can induce or select for TICs; this was reported in preclinical models and more recently in women being treated for breast cancer. Thus, new therapeutic agents for TNBC are presently being sought to overcome this problem. Here we review the roles of receptor tyrosine kinases, signalling intermediates and transcription factors in sustaining the TIC subpopulation. Particular emphasis is placed on targeting these molecules in order to eliminate and/or prevent the induction of TICs and ultimately reduce the frequency of TNBC recurrence.
HF radar observations of the F region ionospheric plasma response to Storm Sudden Commencements
Authors: Kane T. A. , Makarevich R. A.
Published: July 2010

Performance of the Super Dual Auroral Radar Network (SuperDARN) HF radars during geomagnetic storms is investigated by analyzing the data collected during storm events over a 5‐year period. Changes in the occurrence of F region HF backscatter observed by the 6 most equatorward radars are analyzed statistically using a superposed epoch analysis method with respect to a Storm Sudden Commencement (SSC). Regular diurnal variations of the echo occurrence during geomagnetically quiet days are produced and the amount of detected backscatter during storms is adjusted using quiet time curves. All radars considered in this study show a significant decrease in the number of detected echoes approximately 24 hours following SSC. Unexpected significant changes in occurrence levels are also present within a few hours of SSC, with most radars observing an increase in the amount of backscatter detected. The typical time evolution of F region echo occurrence is highly reminiscent of that of the electron density reported previously. Also considered is the ionospheric convection response to SSC observed by the zonally looking SuperDARN Unwin radar in New Zealand. It is shown that the initial response to SSC is instantaneous within uncertainty and appears to be independent of the magnetic latitude and local time. The observed convection response timing and morphology are discussed in the context of possible ionospheric propagation mechanisms.
Substorm triggering by new plasma intrusion: THEMIS all‐sky imager observations
Authors: Nishimura Y. , Lyons L. , Zou S. , Angelopoulos V. , Mende S.
Published: July 2010

A critical, long‐standing problem in substorm research is identification of the sequence of events leading to substorm auroral onset. Based on event and statistical analysis of THEMIS all‐sky imager data, we show that there is a distinct and repeatable sequence of events leading to onset, the sequence having similarities to and important differences from previous ideas. The sequence is initiated by a poleward boundary intensification (PBI) and followed by a north‐south (N‐S) arc moving equatorward toward the onset latitude. Because of the linkage of fast magnetotail flows to PBIs and to N‐S auroras, the results indicate that onset is preceded by enhanced earthward plasma flows associated with enhanced reconnection near the pre‐existing open‐closed field line boundary. The flows carry new plasma from the open field line region to the plasma sheet. The auroral observations indicate that Earthward‐transport of the new plasma leads to a near‐Earth instability and auroral breakup ∼5.5 min after PBI formation. Our observations also indicate the importance of region 2 magnetosphere‐ionosphere electrodynamic coupling, which may play an important role in the motion of pre‐onset auroral forms and determining the local times of onsets. Furthermore, we find motion of the pre‐onset auroral forms around the Harang reversal and along the growth phase arc, reflecting a well‐developed region 2 current system within the duskside convection cell, and also a high probability of diffuse‐appearing aurora occurrence near the onset latitude, indicating high plasma pressure along these inner plasma sheet field lines, which would drive large region 2 currents.
Quasi‐stationary temperature structure in the upper troposphere over the tropical Indian Ocean inferred from radio occultation data
Authors: Nishi Noriyuki , Nishimoto Eriko , Hayashi Hiroo , Shiotani Masato , Takashima Hisahiro , Tsuda Toshitaka
Published: July 2010

Vertical fine structure of tropical temperature profiles in the upper troposphere was analyzed with data obtained by the global positioning system radio‐occultation limb‐sounding technique of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), which has very high vertical resolution and global coverage. Inversion layers in the upper troposphere were detected using a 1 year record taken during 2007. They are observed most frequently during the boreal summer over the Indian Ocean. The region has the characteristics of a shallow quasi‐stationary stable layer that is inclined from a horizontal surface; it is higher in the east and to the north of the equator. We also conducted statistical analysis with objective reanalysis data made by the European Center for Medium‐Range Weather Forecasts (ERA‐40, 1979–2001) and confirmed the presence of a warm anomaly that has a structure consistent with the stable layer detected by COSMIC analysis. We analyzed the three‐dimensional structure and relationship among the temperature, geopotential height, and wind field to discuss possible mechanisms for producing these quasi‐stationary structures from the viewpoints of response to the stationary heating of the Asian summer monsoon and equatorial trapped stationary Kelvin waves.
Global‐through‐urban nested three‐dimensional simulation of air pollution with a 13,600‐reaction photochemical mechanism
Authors: Jacobson Mark Z. , Ginnebaugh Diana L.
Published: July 2010

To date, gas photochemistry has not been simulated beyond a few hundred reactions in a three‐dimensional (3‐D) atmospheric model. Here, we treat 4675 gases and 13,626 tropospheric and stratospheric reactions in the 3‐D GATOR‐GCMOM climate‐pollution model and compare results with data and with results from a condensed 152‐gas/297‐reaction mechanism when the model was nested at increasing resolution from the globe to California to Los Angeles. Gases included C1‐C12 organic degradation products and H‐, O‐, N‐, Cl−, Br‐, Fl‐, and S‐containing inorganics. Organic reactions were from the Master Chemical Mechanism. Photolysis coefficients for 2644 photoprocesses and heating rates for 1909 photolyzing gases were solved with an online radiative code in each grid cell using quantum yield/cross section data over 86 UV/visible wavelengths. Spatial/temporal emissions of > 110 gases were derived from the 2005 U.S. National Emission Inventory. The condensed mechanism was a modified Carbon‐Bond IV (MCBIV). Three‐day simulation results indicate that the more‐explicit mechanism reduced the O3 gross error against data versus the MCBIV error against data by only ∼2 percentage points (from 28.3% to 26.5%) and NO2 and HCHO by ∼6 percentage points in Los Angeles. While more‐explicit photochemistry improved results, the condensed mechanism was not the main source of ozone error. The more explicit mechanism, which treated absorptive heating by more photolyzing gases, also resulted in a different magnitude of feedbacks to meteorological variables and back to gases themselves than did the less‐explicit mechanism. The computer time for all processes in GATOR‐GCMOM with the more explicit mechanism (solved with SMVGEAR II in all domains) was only ∼3.7 times that with the MCBIV despite the factors of 31 and 46 increases in numbers of species and reactions, respectively.
Ground‐penetrating radar observations of enhanced biological activity in a sandbox reactor
Authors: Schillig P. C. , Tsoflias G. P. , Roberts J. A. , Patterson E. M. , Devlin J. F.
Published: July 2010

In this study, we evaluate the use of ground‐penetrating radar (GPR) to investigate the effects of bacterial activity in water saturated sand. A 90‐day laboratory‐scale controlled experiment was conducted in a flow‐through polycarbonate sandbox using groundwater from the Kansas River alluvial aquifer as inoculum. After 40 days of collecting baseline data, bacterial growth was stimulated in the sandbox by the addition of a carbon and nutrient solution on a weekly basis. Radar signal travel time and attenuation were shown to increase downgradient of the nutrient release wells relative to upgradient locations. After 60 days, the frequency of nutrient injections was increased to twice per week, after which gaseous bubbles were visually observed downgradient of the nutrient release wells. Visual observation of active gas production correlated spatially and temporally with a rapid decrease in radar signal travel time, confirming that GPR can monitor the generation of biogenic gases in this system. Analysis of the sediments indicated microbial lipid biomass increased by approximately one order of magnitude and there were no changes in the inorganic carbon content of bulk sediment mineralogy. These findings suggest that the increase in biomass and gas production may be responsible for the observed changes in radar signal travel time reported in this study. Therefore, this study provides evidence that GPR can be used to monitor biological activity in water saturated sand.
Identification of Pacific Ocean sea surface temperature influences of Upper Colorado River Basin snowpack
Authors: Aziz Oubeidillah A. , Tootle Glenn A. , Gray Stephen T. , Piechota Thomas C.
Published: July 2010

Given the importance of Upper Colorado River Basin (UCRB) snowpack as the primary driver of streamflow (water supply) for the southwestern United States, the identification of Pacific Ocean climatic drivers (e.g., sea surface temperature (SST) variability) may prove valuable in long‐lead‐time forecasting of snowpack in this critical region. Previous research efforts have identified El Niño–Southern Oscillation (ENSO) and Pacific Decadel Oscillation (PDO) as the main drivers for western U.S. snowpack, but these drivers have limited influence on regional (Utah and Colorado) UCRB snowpack. The current research applies for the first time the Singular Value Decomposition (SVD) statistical method to Pacific Ocean SSTs and continental U.S. snowpack to identify the primary Pacific Ocean climatic driver of UCRB snowpack. The use of SSTs eliminates any “bias” as to specific climate signals. The second mode of SVD identified a UCRB snowpack region (Colorado and Utah) and a corresponding Pacific Ocean SST region. A “non‐ENSO/non‐PDO” Pacific Ocean SST region between 34°N–24°S and 150°E–160°W was identified as being the primary driver of UCRB snowpack. To confirm the UCRB snowpack results, data from 13 unimpaired (or naturalized) streamflow gages in Colorado and Utah were used to evaluate and support the snowpack findings. Finally, a new and beneficial data set (western U.S. 1 March, 1 April, and 1 May snow water equivalent) was developed, which may be used in future research efforts.
A linear model for the coupled surface‐subsurface flow in a meandering stream
Authors: Boano Fulvio , Camporeale Carlo , Revelli Roberto
Published: July 2010

The interest about the exchange of water between streams and aquifers has been increasing among the hydrologic community because of the implications of the exchange of heat, solutes, and colloids for the water quality of aquatic environments. Unfortunately, our understanding of the relevance of the exchange processes is limited by the great number of coupled hydrological and geomorphological factors that interact to generate the complex spatial patterns of exchange. In this context, the present work presents a mathematical model for the surface‐subsurface exchange through the streambed of a meandering stream. The model is based on the linearization of the equations that govern the hydrodynamics and the morphodynamics of the system, and it provides a first‐order analytical solution of the coupled flow field of both the surface and the subsurface flows. The results show that stream curvature determines a characteristic spatial pattern of hyporheic exchange, with water upwelling and downwelling concentrated near the stream banks. The exchange can drive surface water deep into the sediments, thus keeping deep alluvium regions connected with the stream. The relationships between hyporheic exchange flux and the geometrical and hydrodynamical properties of the stream‐aquifer system are also investigated.
Simplified simulation of steady state bioreactive transport with kinetic solute uptake by the biomass
Authors: Cirpka Olaf A.
Published: July 2010

Biodegradation of continuously emitted compounds that need a dissolved reaction partner, which is not jointly introduced with the contaminant into the subsurface, is mainly controlled by transverse dispersive mixing. Previous analytical approaches of evaluating mixing‐controlled bioreactive transport in steady state have been based on the assumption that the bulk aqueous‐phase concentration of the reactants is directly available to the specific biomass catalyzing the reaction. These models predict a very narrow stripe of active biomass with high specific biomass concentration. Experimental studies have indicated that such behavior may be unrealistic, particularly for anaerobic biodegradation. I extend the previous analysis to include kinetic solute uptake by the biomass, expressed as a first‐order mass‐transfer process coupled to dual Monod kinetics in the bio‐available domain. The approach is based on the evaluation of conservative components undergoing advective‐dispersive transport, the solution of a quadratic speciation problem within the immobile bio domain, and iterative simulation of linear transport of a single reactive constituent in steady state. Convergence is typically achieved within less than ten iterations. The comparison with simulations assuming instantaneous solute uptake by the biomass indicate that mass‐transfer kinetics may explain larger overlap of reactive constituents and a wider spatial distribution of specific biomass observed in experiments. Depending on the rate coefficient of mass transfer, the overall transformation of the contaminant may be significantly reduced or only slightly shifted to a region farther downstream.
Identification and characterization of PRG-1 as a neuronal calmodulin-binding protein
Authors: Tokumitsu Hiroshi , Hatano Naoya , Tsuchiya Mitsumasa , Yurimoto Saki , Fujimoto Tomohito , Ohara Naoki , Kobayashi Ryoji , Sakagami Hiroyuki
Published: July 2010

Intracellular Ca2+-dependent cellular responses are often mediated by the ubiquitous protein CaM (calmodulin), which, upon binding Ca2+, can interact with and alter the function of numerous proteins. In the present study, using a newly developed functional proteomic screen of rat brain extracts, we identified PRG-1 (plasticity-related gene-1) as a novel CaM target. A CaM-overlay and an immunoprecipitation assay revealed that PRG-1 is capable of binding the Ca2+/CaM complex in vitro and in transfected cells. Surface plasmon resonance and zero-length cross-linking showed that the C-terminal putative cytoplasmic domain (residues 466–766) of PRG-1 binds equimolar amounts of CaM in a Ca2+-dependent manner, with a relatively high affinity (a Kd value for Ca2+/CaM of 8 nM). Various PRG-1 mutants indicated that the Ca2+/CaM-binding region of PRG-1 is located between residues Ser554 and Gln588, and that Trp559 and Ile578 potentially anchor PRG-1 to CaM. This is supported by pronounced changes in the fluorescence emission spectrum of Trp559 in the PRG-1 peptide (residues 554–588) upon binding to Ca2+/CaM, showing the stoichiometrical binding of the PRG-1 peptide with Ca2+/CaM. Immunoblot analyses revealed that the PRG-1 protein is abundant in brain, but is weakly expressed in the testes. Immunohistochemical analysis revealed that PRG-1 is highly expressed in forebrain structures and in the cerebellar cortex. Furthermore, PRG-1 localizes at the postsynaptic compartment of excitatory synapses and dendritic shafts of hippocampal neurons, but is not present in presynaptic nerve terminals. The combined observations suggest that PRG-1 may be involved in postsynaptic functions regulated by intracellular Ca2+-signalling.
Biogeography and conservation of the genus Ficus (Moraceae) in Mexico
Authors: Serrato Alejandra , Ibarra‐Manríquez Guillermo , Oyama Ken
Published: July 2010

Aim  The main objective of this study is to document the biogeographical patterns, endemism and degree of conservation of the species of Ficus (Moraceae) in Mexico. There are over 750 species of the genus Ficus distributed worldwide, and Mexico practically represents its northernmost limit in the American continent. Detailed studies at regional scales may help to understand the biogeography of large genera such as Ficus.

Location  Mexico.

Methods  The biogeographical patterns of Mexican Ficus were obtained from information of fig specimens available in two of the main herbaria of Mexico (2140 vouchers), collecting figs throughout this country, and revising the specialized literature. The presence of each species of Ficus was recorded for every one of Mexico's states and several tropical countries of America. Besides, the Mexican territory was divided into cells of 1° × 1° and the presence or absence of all species of the genus was recorded. Rarity of species was classified based on the width of geographic distribution, habitat specificity and population size.

Results  A total of 21 species of Ficus occur in Mexico, including six species (28.6%) that are endemic to this country. Five species are included in subgenus Pharmacosycea and 16 species are documented under subgenus Urostigma. Affinities of Ficus flora with other tropical countries in America generally decreased as geographical distances from Mexico increased. Mexican states and cells with highest values of Ficus species richness (both total and endemic species) were located. Ten species, including three endemics, presented a wide distribution. Five species, including two endemics, possess the three attributes of rarity (narrow geographical distribution, high habitat specificity and scarce local populations). Three species of Ficus, including the endemic and very rare Ficuslapathifolia (Liebm.) Miq., are not recorded in any protected area existing in Mexico.

Main conclusions  Most of the Mexican Ficus show a great morphological variation and occupy different habitats along their geographic distribution. The biogeographical patterns described here establish a fundamental scenario for ongoing studies on Ficus–pollinator interactions. However, many local populations are considered to be at risk, as there have been significant reductions in the number and size of local populations. Further studies are needed to understand the process of colonization, maintenance and persistence of fig–pollinator mutualism in species with different patterns of geographic distribution. Mexican Ficus require special policies for conservation due to their complex degree of rarity, particularly their geographic distribution in different types of vegetation, ranging from dry scrublands to tropical rain forests.
Ferromagnetic resonance studies of exchange coupled ultrathin Py/Cr/Py trilayers
Authors: Topkaya R. , Erkovan M. , Öztürk A. , Öztürk O. , Aktaş B. , Özdemir M.
Published: July 2010

Magnetic properties of ultrathin Py/Cr/Py trilayers have been investigated as a function of Cr spacer layer thickness by using ferromagnetic resonance (FMR) and vibrating sample magnetometer (VSM) techniques. The Cr spacer layer thickness was increased from 4 to 40 Å with 1 Å steps to determine the dependence of interlayer exchange coupling between ferromagnetic layers on the spacer layer thickness. Two strong and well resolved peaks were observed which correspond to a strong (acoustic) and weak (optic) modes of magnetization precession in the effective dc field due to the exciting external microwave field as the external dc field orientation comes close to the film normal. The separation of the two modes in the field axis depends on the thickness of Cr spacer layer. An interchange in the relative positions of the acoustic and optic modes has been observed for a particular thickness of Cr spacer layer as well. A computer program for magnetically exchange coupled N magnetic layers was written to simulate the experimental FMR spectra and to obtain the magnetic parameters of ultrathin Py/Cr/Py trilayers. FMR data have been analyzed from every aspect by using this program and interlayer exchange coupling constant was calculated for the prepared structures. It was found that the relative position of the peaks depends on the nature (sign) of the interlayer exchange coupling between ferromagnetic layers through Cr spacer layer. In Py/Cr/Py trilayers, strength of the interlayer exchange coupling constant oscillates and changes its sign with Cr spacer layer thickness with a period of about 11 Å.
Transport properties and microstructures of polycrystalline In2O3–ZnO thin films
Authors: Makise K. , Mitsuishi K. , Kokubo N. , Yamaguchi T. , Shinozaki B. , Yano K. , Inoue K. , Nakamura H.
Published: July 2010

We prepared polycrystalline In2O3–ZnO films by post annealing the amorphous films (1.0 wt % ZnO) at 200 °C with various annealing times ta 0≤ta≤20 h. We have measured the electric resistivity and Hall mobility and also observed film structures by not only the x-ray diffraction but also scanning transmission electron microscopy (STEM) with electron energy-loss spectroscopy (EELS). We have found the following: (1) Hall mobility takes the maximum with respect to the carrier density and the annealed films clearly show the superconductivity of which transition temperature increases with increase in ta. (2) The data on EELS spectra mapping of indium plasmon indicate that droplets of the pure indium phase exist on grain boundaries and near the interface between the film and the glass substrate. However, it seems that these droplets do not form an electrical conducting path but contribute to the scattering centers for carrier electrons, from the dispersed distribution of these droplets in STEM-EELS spectra mapping and the relationship between the electron mean free path and the grain size.
A three-beam path photonic crystal fiber modal interferometer and its sensing applications
Authors: Zhang Shu-yi , Zhong Qi , Qian Xiao-shi , Lin Xiao-wen , Xu Fei , Hu Wei , Lu Yan-qing
Published: July 2010

Photonic crystal fiber (PCF) modal interferometer is studied for sensing applications. There is a trade-off between high sensitivity and wide sensing range due to the intrinsic two-beam interference. We propose and experimentally demonstrate a three-beam path reflective interferometer by exciting mode conversion at the end surface of a dual-mode PCF. Approximately 5% mode conversion is taken place at the PCF end surface according to our model. In comparison with the normal dual-mode interference in a PCF, the mode conversion induced three-beam interference generates sharper spectrum and expanded sensing range. Gas sensing experiment is implemented with a sensitivity of 3019 nm/RIU. The advantage of expanded sensing range is also experimentally demonstrated.
Strain relaxation effect on electronic properties of compressively strained InGaAs/InP vertically stacked multiple quantum wires
Authors: Park Seoung-Hwan , Shim Jong-In , Yi Sam Nyung
Published: July 2010

Electronic properties of compressively strained InGaAs/InP vertically stacked multiple quantum wires were investigated using an six-band strain-dependent k⋅p Hamiltonian. The strain tensor ϵyy (ϵxx) is found to relax from its initial strain. The amount of relaxation is dependent on the number of wire layers in the vertical stack and increases with the number of wire layers. The interband transition energy also decreases with the number of wire layers. This is mainly attributed to the decrease in the conduction band energy because subband energies in the valence band are nearly independent of the strain. The matrix element is shown to slightly decrease with increasing number of the wire layer in the vertical stack.
Thermodynamics and kinetics of the copper vacancy in CuInSe2, CuGaSe2, CuInS2, and CuGaS2 from screened-exchange hybrid density functional theory
Authors: Pohl Johan , Albe Karsten
Published: July 2010

Formation enthalpies and migration barriers of the copper vacancy in CuInSe2, CuGaSe22, CuInS2, and CuGaS2 are calculated by means of density functional theory with a screened-exchange hybrid functional of the Heyd–Scuseria–Ernzerhof type. The band gaps of all chalcopyrite phases are very well described by the hybrid functional using a single value for the Hartree–Fock screening parameter. The defect formation enthalpies of the copper vacancy in CuInS2 and CuGaS2 are around 0.8 eV higher than in CuInSe2 and CuGaSe2. This results in the absence of Fermi-level pinning for CuInS2 and explains a reduced tendency of CuInS2 and CuGaS2 to form ordered defect compounds. The calculated migration barrier of the copper vacancy in CuInSe2 is 1.26 eV and of comparable magnitude for CuGaSe2, CuInS2, and CuGaS2. From this data we estimate a diffusion coefficient for CuInSe2 and show that it is in agreement with measurements of diffusion in stoichiometric single crystalline samples when direct experimental methods are used.
Neuron adhesion and strengthening
Authors: Rocha Aracely , Jian Kuihuan , Ko Gladys , Liang Hong
Published: July 2010

Understanding the neuron/material adhesion is important for neuron stimulation and growth. The current challenges remain in the lack of precision of measuring techniques and understanding the behavior of neuron. Here, we report a fluid shear method to investigate adhesion at the neuron/poly-D-lysine interface. In this study, the adhesion of 12-day-old chick embryo-retina neurons cultured on poly-D-lysine coated glass coverslips was measured via parallel disk rotational flow. The shear stress experienced by the cells increases with the disk radius. There is a critical point along the radius (Rc) where the stress experienced by the neurons equals their adhesion. The measured Rc can be used to calculate the neuron adhesion. Our results demonstrate that neurons adhered to the poly-D-lysine had a strain hardening effect. The adhesive shear stress of the neuron-material increased with applied shear (τa). When the τa reached or exceeded the value of 40 dyn/cm2, the adhesion remained constant at approximately 30 dyn/cm2. The present work allowed us not only to quantify the adhesive strength and force but also to evaluate the value of strain hardening at the neuron/poly-D-lysine interface.
Demonstration of a Meissner-effect transition edge sensor
Authors: Woods S. I. , Carr S. M. , Jung T. M. , Carter A. C. , Datla R. U.
Published: July 2010

We have built and tested a transition edge sensor which monitors temperature change by measuring magnetic flux expulsion from a superconducting element. Flux change is sensed by a dc superconducting quantum interference device coupled to the element using a flux transformer in a gradiometer arrangement. The operating temperature of the sensor can be varied by application of moderate magnetic fields to the superconducting core, using an integrated solenoid. With a Sn core at 3.58 K, the thermometer has demonstrated a noise level of 2.25 nK/Hz1/2. We estimate that such a sensor will allow femtowatt sensitivity of an absolute cryogenic radiometer presently under development.
Edge versus interior in the chemical bonding and magnetism of zigzag edged triangular graphene molecules
Authors: Philpott Michael R. , Vukovic Sinisa , Kawazoe Yoshiyuki , Lester William A.
Published: July 2010

Ab initio density functional theory calculations show that the CC bond lengths fall into three distinct groups: core, apex, and edge, irrespective of whether the molecular center is a single atom or a C6-ring. The core, with a geometry that approximates infinite graphene, extends to the penultimate triangular row of carbon atoms, except in the vicinity of an apex. Impressed on the core bonds starting at the center is a small increasing length oscillation. The perimeter CC bonds joined at the apex are the shortest in the molecule. The edge carbon atoms are separated from interior atoms by the longest bonds in the molecule. The spin density localized primarily on edge (not apex) carbons with attached hydrogen (A-sublattice) is likely the highest attainable in any graphene molecule. The CC bonds in the high spin section of the edges are uniform in length and longer than perimeter CC bonds in the zigzag edged linear acenes, hexangulenes, annulenes, and benzene. This is attributed to the large number of edge localized nonbonding molecular orbitals (NBMOs) that sequestered π-charge making it unavailable for bonding.
Efficient electron spin injection in MnAs-based spin-light-emitting-diodes up to room temperature
Authors: Fraser E. D. , Hegde S. , Schweidenback L. , Russ A. H. , Petrou A. , Luo H. , Kioseoglou G.
Published: July 2010

Studies of ferromagnetic MnAs in recent years have revealed a wide range of properties desirable for spintronic applications. Previously studied MnAs spin-light-emitting-diodes exhibited a low value of spin injection into the device active region. In this work, we have investigated injection of spin polarized electrons from MnAs into AlGaAs(n)/GaAs(i)/AlGaAs(p) n-i-p structures. The band-edge electroluminescence emitted from these devices has a saturation circular polarization of 26% at 7 K and B=2 T. Using optical pumping measurements the corresponding electron spin polarization was determined to be 52%. Emission persists up to room temperature, with a saturation circular polarization of 6% at B=2 T.
Bragg grating writing in acoustically excited optical fiber
Authors: Oliveira Roberson A. , Cook Kevin , Canning John , Pohl Alexandre A. P.
Published: July 2010

The inscription of Bragg gratings in optical fiber under acoustic excitation is proposed and demonstrated. A permanent change in the refractive index as the period of the grating is modulated with periodic acoustic excitation during UV grating writing leads to sampling of the structure and the production of spectral combs. A physical contribution to index change through stress profiling reveals a complicated picture of UV-induced index change, well beyond simple localized defect and structural changes. The method offers the potential for tuning and tailoring conventional uniform gratings during the writing process using adjustable acoustic wave functions, an approach to control the writing process.
Memory bistable mechanisms of organic memory devices
Authors: Lee Ching-Ting , Yu Li-Zhen , Chen Hung-Chun
Published: July 2010

To investigate the memory bistable mechanisms of organic memory devices, the structure of [top Au anode/9,10-di(2-naphthyl)anthracene (ADN) active layer/bottom Au cathode] was deposited using a thermal deposition system. The Au atoms migrated into the ADN active layer was observed from the secondary ion mass spectrometry. The density of 9.6×1016 cm−3 and energy level of 0.553 eV of the induced trapping centers caused by the migrated Au atoms in the ADN active layer were calculated. The induced trapping centers did not influence the carrier injection barrier height between Au and ADN active layer. Therefore, the memory bistable behaviors of the organic memory devices were attributed to the induced trapping centers. The energy diagram was established to verify the mechanisms.
Differential conductance as a promising approach for rapid DNA sequencing with nanopore-embedded electrodes
Authors: He Yuhui , Shao Lubing , Scheicher Ralph H. , Grigoriev Anton , Ahuja Rajeev , Long Shibing , Ji Zhuoyu , Yu Zhaoan , Liu Ming
Published: July 2010

We propose an approach for nanopore-based DNA sequencing using characteristic transverse differential conductance. Molecular dynamics and electron transport simulations show that the transverse differential conductance during the translocation of DNA through the nanopore is distinguishable enough for the detection of the base sequence and can withstand electrical noise caused by DNA structure fluctuation. Our findings demonstrate several advantages of the transverse conductance approach, which may lead to important applications in rapid genome sequencing.
Co doping enhanced giant magnetocaloric effect in Mn1−xCoxAs films epitaxied on GaAs (001)
Authors: Xu P. F. , Nie S. H. , Meng K. K. , Wang S. L. , Chen L. , Zhao J. H.
Published: July 2010

A giant magnetocaloric effect was found in series of Mn1−xCoxAs films epitaxied on GaAs (001). The maximum magnetic entropy change caused by a magnetic field of 4 T is as large as 25 J/kg K around room temperature, which is about twice the value of pure MnAs film. The observed small thermal hysteresis is more suitable for practical application. Growing of layered Mn1−xCoxAs films with Co concentration changing gradually may draw layered active magnetic regenerator refrigerators closer to practical application. Our experimental result may provide the possibility for the combination of magnetocaloric effect and microelectronic circuitry.
Type I PIPK-α regulates directed cell migration by modulating Rac1 plasma membrane targeting and activation
Authors: Chao Wei-Ting , Daquinag Alexes C. , Ashcroft Felicity , Kunz Jeannette
Published: July 2010

Phosphatidylinositol-4,5-bisphosphate (PI4,5P2) is a critical regulator of cell migration, but the roles of the type I phosphatidylinositol-4-phosphate 5-kinases (PIPKIs), which synthesize PI4,5P2, have yet to be fully defined in this process. In this study, we report that one kinase, PIPKI-α, is a novel upstream regulator of Rac1 that links activated integrins to the regulation of cell migration. We show that PIPKI-α controls integrin-induced translocation of Rac1 to the plasma membrane and thereby regulates Rac1 activation. Strikingly, this function is not shared with other PIPKI isoforms, is independent of catalytic activity, and requires physical interaction of PIPKI-α with the Rac1 polybasic domain. Consistent with its role in Rac1 activation, depletion of PIPKI-α causes pronounced defects in membrane ruffling, actin organization, and focal adhesion formation, and ultimately affects the directional persistence of migration. Thus, our study defines the role of PIPKI-α in cell migration and describes a new mechanism for the spatial regulation of Rac1 activity that is critical for cell migration.
Model representation of the nonlinear step response in cardiac muscle
Authors: Ford Steven J. , Chandra Murali , Mamidi Ranganath , Dong Wenji , Campbell Kenneth B.
Published: July 2010

Motivated by the need for an analytical tool that can be used routinely to analyze data collected from isolated, detergent-skinned cardiac muscle fibers, we developed a mathematical model for representing the force response to step changes in muscle length (i.e., quick stretch and release). Our proposed model is reasonably simple, consisting of only five parameters representing: (1) the rate constant by which length change–induced distortion of elastic elements is dissipated; (2) the stiffness of the muscle fiber; (3) the amplitude of length-mediated recruitment of stiffness elements; (4) the rate constant by which this length-mediated recruitment takes place; and (5) the magnitude of the nonlinear interaction term by which distortion of elastic elements affects the number of recruited stiffness elements. Fitting this model to a family of force recordings representing responses to eight amplitudes of step length change (±2.0% baseline muscle length in 0.5% increments) enabled four things: (1) reproduction of all the identifiable features seen in a family of force responses to both positive and negative length changes; (2) close fitting of all records from the whole family of these responses with very little residual error; (3) estimation of all five model parameters with a great degree of certainty; and (4) importantly, ready discrimination between cardiac muscle fibers with different contractile regulatory proteins but showing only subtly different contractile function. We recommend this mathematical model as an analytic tool for routine use in studies of cardiac muscle fiber contractile function. Such model-based analysis gives novel insight to the contractile behavior of cardiac muscle fibers, and it is useful for characterizing the mechanistic effects that alterations of cardiac contractile proteins have on cardiac contractile function.
Reconstructing riverine mesohabitat unit composition using fish community data and an autecology matrix
Authors: Suen J. P. , Su W. C.
Published: July 2010

This research proposes a simplified method for estimating the mesohabitat composition that would favour members of a given set of aquatic species. The simulated composition of four types of mesohabitat units (deep pool, shallow pool, deep riffle and shallow riffle) could guide the design of in‐stream structures in creating pool‐riffle systems with ecological reference. Fish community data and an autecology matrix are used to support the development of a stream mesohabitat simulation based on regression models for reaches in mid to upper‐order streams. The fish community‐mesohabitat model results constitute a reference condition that can be used to guide stream restoration and ecological engineering decisions aimed at maintaining the natural ecological integrity and diversity of rivers.
Daclizumab induction therapy in liver transplant recipients with renal insufficiency
Authors: Asrani S. K. , Kim W. R. , Pedersen R. A. , Charlton M. R. , Kremers W. K. , Therneau T. M. , Rosen C. B. , Dean P. G.
Published: July 2010

Background  The role of interleukin 2 (IL‐2) receptor antibodies to avoid the nephrotoxic effects of calcineurin inhibitors in the early post‐liver transplant (LT) period is not well defined.

Aim  To examine the use of daclizumab induction in LT recipients with renal insufficiency.

Methods  Between 2002 and 2005, 62 patients (median pre‐LT creatinine 2.4 mg/dL, IQR 1.9–3.7) received daclizumab induction with tacrolimus being administered when serum creatinine was <2.0 mg/dL. A concurrent comparison group (n = 221, 2002–2005) received tacrolimus‐based immunosuppression without daclizumab (median pre‐LT creatinine 1.1 mg/dL, IQR 0.9–1.4). A second historical comparison group (n = 103, 1995–2005) not receiving daclizumab was matched to the daclizumab patients by pre‐LT serum creatinine (2.2 mg/dL, IQR 1.8–3.1). All patients received mycophenolate mofetil and steroids.

Results  Serum creatinine improved in the daclizumab group (−1.0 mg/dL, IQR −2.2 to −0.4) and worsened in the concurrent comparison group (+0.2 mg/dL, IQR 0–0.5) from pre‐LT to 4 months. However, there was no difference when daclizumab group was compared with the historical comparison group matched on pre‐LT creatinine (median change: −0.8 mg/dL vs. −0.7 mg/dL). Daclizumab induction was not associated with improvement in renal function at 4 months (P = 0.34) after adjusting for pre‐LT creatinine, age, gender, hepatitis C status and simultaneous liver kidney transplantation.

Conclusion  The incremental benefit offered by induction therapy with IL‐2 receptor antibodies to preserve renal function is questionable.
Pre‐oxygenation in healthy volunteers: a comparison of the supine and 45° seated positions*
Authors: Smith S. J. , Harten J. M. , Jack E. , Carter R. , Kinsella J.
Published: July 2010

Pre‐oxygenation in the seated (sitting) position has been associated with better oxygenation. This randomised, cross over study compared oxygenation in the supine position with that in the 45° seated position in 40 young, healthy volunteers. Oxygen was administered through a circle system and tight fitting facemask. Transcutaneous Po2 levels were recorded at 10‐s intervals from two measurement points during 4 min of oxygenation in the two positions. The mean (SD) values of 12 measurements taken between the third and fourth minute were recorded. There was no difference in the increase in tissue oxygenation when comparing the supine and seated positions (32.7 (7.3) vs 32.6 (6.7) kPa, respectively). We conclude that there is no evidence that pre‐oxygenation in the 45° seated position improves tissue oxygenation in young healthy volunteers compared with the supine position.
(R)‐ and (S)‐methadone and buprenorphine concentration ratios in maternal and umbilical cord plasma following chronic maintenance dosing in pregnancy
Authors: Gordon Andrea L. , Lopatko Olga V. , Somogyi Andrew A. , Foster David J. R. , White Jason M.
Published: July 2010

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Both methadone and buprenorphine cross the placenta during pregnancy which can result in neonatal abstinence syndrome (NAS). Reduced NAS in buprenorphine‐exposed infants may be as a result of relatively less buprenorphine reaching the foetal circulation compared with methadone.

WHAT THIS STUDY ADDS

Under chronic dosing conditions in humans, the transfer of methadone and buprenorphine appears greater than previously found in human placental tissue in vitro models. Infants born to buprenorphine maintained women may be exposed to relatively less of the maternal dose compared with infants born to women maintained on methadone during pregnancy. There is stereoselectivity in the transfer of the individual enantiomers of methadone across the placenta to the foetal circulation.

AIMS

The aim of this study was to compare the transfer of buprenorphine and methadone between maternal and cord blood in women under chronic dosing conditions and to determine if differences exist in the transfer of the two methadone enantiomers.

METHODS

Maternal and cord blood samples were collected at delivery from women maintained on methadone (35, 25–140 mg day−1) (median; range) or buprenorphine (6.00, 2–20 mg day−1) during pregnancy. Plasma concentration ratios are presented as an indicator of foetal exposure relative to the mother.

RESULTS

Methadone was quantified in all samples, with cord : maternal plasma methadone concentration ratios (n= 15 mother‐infant pairs) being significantly higher (P < 0.0001; mean difference (MD) 0.07; 95% confidence interval (CI) 0.048, 0.092) for the active (R)‐methadone enantiomer (0.41; 0.19, 0.56) (median; range) compared with (S)‐methadone (0.36; 0.15, 0.53). (R)‐ : (S)‐methadone concentration ratios were also significantly higher (P < 0.0001; MD 0.24 95% CI 0.300, 0.180) for cord (1.40; 0.95, 1.67) compared with maternal plasma (1.16; 0.81, 1.38). Half the infant buprenorphine samples were below the assay lower limit of quantification (LLOQ) (0.125 ng ml−1). The latter was four‐fold lower than the LLOQ for methadone (0.50 ng ml−1). The cord : maternal plasma buprenorphine concentration ratio (n= 9 mother‐infant pairs) was 0.35; 0.14, 0.47 and for norbuprenorphine 0.49; 0.24, 0.91.

CONCLUSIONS

The transfer of the individual methadone enantiomers to the foetal circulation is stereoselective. Infants born to buprenorphine maintained women are not exposed to a greater proportion of the maternal dose compared with methadone and may be exposed to relatively less of the maternal dose compared with infants born to women maintained on methadone during pregnancy.
Increased Haemopoietic Cell Survival in Vitro Induced by a Human Marrow Fibroblast Factor
Authors: Blackburn Mary J. , Goldman John M.
Published: July 2010

Summary. Human marrow fibroblasts were grown in vitro and examined for effects on human and mouse haemopoietic cells. When human marrow cells were incubated with fibroblasts or with fibroblast‐conditioned medium for 1 week and then assayed for committed granulocyte/monocyte (CFU‐c) and erythroid (BFU‐e) progenitor cells, the numbers of CFU‐c and BFU‐e were considerably increased compared with controls. In contrast, human marrow‐fibroblast‐conditioned medium, when added directly to CFU‐c or BFU‐e assay cultures, had no effect on colony formation by these progenitor cells. As these results suggest that the fibroblast‐derived factor may be acting on a relatively primitive progenitor cell, possibly a pluripotent haemopoietic stem cell, the effect of this factor on mouse pluripotent haemopoietic stem cells (CFU‐s) was examined. Human marrow‐fibroblast‐conditioned medium considerably enhanced CFU‐s survival after a 24 h incubation and increased the proportion of CFU‐s in cell‐cycle. The increase in CFU‐s survival depended on the concentration of the fibroblast‐conditioned medium but not on the age of the fibroblast culture. The evidence suggests therefore that human marrow fibroblasts produce a factor that acts on a human myeloid progenitor cell more primitive than BFU‐e and CFU‐c, possibly the pluripotent haemopoietic stem cell.
Spectrin‐haemoglobin crosslinkages associated with in vitro oxidant hypersensitivity in pathologic and artificially dehydrated red cells
Authors: Sauberman N. , Fortier N. L. , Joshi W. , Piotrowski J. , Snyder L. M.
Published: July 2010

Summary. Protein crosslinkages are apparent at 215000–250000 daltons in electrophoregrams of membranes from hydrogen peroxide treated erythrocytes (British Journal of Haematology, 48,435, 1981). Hydrogen peroxide is also capable of inducing crosslinkages of identical molecular weights in stage I and II (red) ghosts and in a mixture of purified spectrin and haemoglobin, but not in white ghosts or in either spectrin or haemoglobin alone. Autoradiographic studies using 14C‐methae‐moglobin and 32P‐spectrin confirm the involvement of spectrin and haemoglobin in this reaction. The alpha chains of both proteins are more reactive than the corresponding beta chains: 3 times more reactive in the case of spectrin and 10 times more reactive in haemoglobin. The reaction is almost totally inhibited by NaCN and partially inhibited by N‐ethylmaleimide. Direct addition of malondialdehyde to a spectrin‐haemoglobin mixture does not result in protein crosslinkage. Metabolic depletion (40 h), in vivo ageing and sucrose dehydration of fresh, normal cells enhance the reaction considerably, whereas in vitro rehydration of xerocytes normalizes their H2O2 sensitivity.
Change of pyruvate kinase isozymes from M2‐ to L‐type during development of the red cell
Authors: Takegawa S. , Fujii H. , Miwa S.
Published: July 2010

Summary. The relationship between erythroid cell maturation and the change of pyruvate kinase (PK) isozymes was studied using fluorescent antibody techniques. The fluorescence of M2‐type PK was strongest in the proerythroblast stage, and then steeply declined with red cell maturation so that only weak fluorescence was seen in orthochromatic erythroblasts. On the other hand, the fluorescence of L‐type PK was seen throughout the maturation of the erythroblasts, with stronger fluorescence in the basophilic or polychromatic erythroblasts than in proerythroblasts.