bluuebunny/crossref_metadata_2025 huggingface dataset:
Cerebrovascular reactivity to hypercapnia is unimpaired in breath‐hold divers
Authors: Ivancev Vladimir , Palada Ivan , Valic Zoran , Obad Ante , Bakovic Darija , Dietz Niki M. , Joyner Michael J. , Dujic Zeljko
Published: April 2007

Hypercapnic cerebrovascular reactivity is decreased in obstructive sleep apnoea and congestive heart disease perhaps as a result of repeated apnoeas. To test the hypothesis that repeated apnoeas blunt cerebrovascular reactivity to hypercapnia, we studied breath hold divers and determined cerebrovascular reactivity by measuring changes in middle cerebral artery velocity (MCAV, cm s−1) per mmHg change in end‐tidal partial pressure of CO2 () in response to two hyperoxic hypercapnia rebreathing manoeuvres (modified Read protocol) in elite breath‐hold divers (BHD, n= 7) and non‐divers (ND, n= 7). In addition, ventilation and central (beat‐to‐beat stroke volume measurement with Modelflow technique) haemodynamics were determined. Ventilatory responses to hypercapnia were blunted in BHD versus ND largely due to lower breathing frequency. Cerebrovascular reactivity did not differ between groups (3.7 ± 1.4 versus 3.4 ± 1.3% mmHg−1 in BHD and ND, respectively; P= 0.90) and the same was found for cerebral vascular resistance and MCAV recovery to baseline after termination of the CO2 challenge. Cardiovascular parameters were not changed significantly during rebreathing in either group, except for a small increase in mean arterial pressure for both groups. Our findings indicate that the regulation of the cerebral circulation in response to hypercapnia is intact in elite breath‐hold divers, potentially as a protective mechanism against the chronic intermittent cerebral hypoxia and/or hypercapnia that occurs during breath‐hold diving. These data also suggest that factors other than repeated apnoeas contribute to the blunting of cerebrovascular reactivity in conditions like sleep apnoea.
AMPA receptors associated with zebrafish Mauthner cells switch subunits during development
Authors: Patten Shunmoogum Aroonassala , Ali Declan W.
Published: April 2007

Glutamate AMPA receptors (AMPARs) are major excitatory receptors in the vertebrate CNS. In many biological systems there is a developmental speeding in AMPAR kinetics, which occurs either because of a switch in AMPAR subunits or a change in synaptic morphology. We studied the development of AMPAR‐mediated miniature excitatory postsynaptic currents (AMPAR‐mEPSCs) in zebrafish Mauthner cells (M‐cells) to determine the reasons underlying the speeding of AMPA mEPSCs in this preparation. We recorded AMPAR‐mEPSCs in zebrafish ranging in age from 33 h postfertilization (hpf) to 72 hpf. We found that the glutamate waveform in the synaptic cleft did not change during development, suggesting that synaptic morphology played little role in shaping the mEPSC. The current–voltage (I–V) relationship was linear at 33 hpf and outwardly rectified in older animals, while AMPAR decay kinetics were slower at positive potentials, compared with negative potentials. The relative change in τ with depolarization was found to be greater at 48 hpf than at 33 hpf. AMPARs in 33 hpf fish had a conductance of ∼9 pS, and in older fish ∼15 pS. Finally, the desensitization blocker, cyclothiazide, increased τ by ∼4‐fold in 48 hpf preparations, but only 1.5‐fold in 33 hpf fish. These results are consistent with the hypothesis that the major mechanism underlying the developmental speeding in AMPAR kinetics in zebrafish CNS is a switch in receptor subunits. To our knowledge this is the first study to suggest that AMPARs change subunits during development in fish.
Regulation of KCNQ channels by manipulation of phosphoinositides
Authors: Suh Byung‐Chang , Hille Bertil
Published: April 2007

Activation of phospholipase C (PLC) through G‐protein‐coupled receptors produces a large number of second messengers and regulates many physiological processes. Many membrane proteins including ion channels require the phosphoinositide phosphatidylinositol 4,5‐bisphosphate (PIP2) to function. Activation of PLC can shut down their activity if it depletes the PIP2 pool strongly. Such a mechanism accounts for the muscarinic suppression of current in KCNQ channels. We describe a variety of methods used to show that these channels require PIP2 and that current in the channels is suppressed when receptor‐activated PLC depletes PIP2. The methods include observing translocation of lipid‐sensitive protein domains, overexpression of enzymes of phosphoinositide metabolism, engineering these enzymes to move to the plasma membrane in response to a chemical signal, and direct chemical analysis of phospholipids. These approaches are general and can be used to test for PIP2 requirements of other membrane proteins.
On the CMP Material Removal at the Molecular Scale
Authors: Chang L.
Published: April 2007

Understanding of the mechanisms of material removal is of fundamental importance in chemical-mechanical planarization of semiconductor wafers. A plausible mechanism at work is that the material is removed at the molecular scale by debonding the chemistry-weakened molecules at the wafer surface. A sequence of order-of-magnitude calculations is carried out to substantiate this mechanism of chemical-mechanical polishing (CMP) materials removal. The analysis may lend further credence to the mechanism in addition to its underlying theoretical foundation.
Thermal model of miniaturized Schottky emitter for parallel electron beam lithography
Authors: Dokania A. K. , Velthuis J. F. M. , Zhang Yanxia , Kruit Pieter
Published: April 2007

For parallel electron beam lithography, an array of miniaturized Schottky emitters is proposed. The design of this miniaturized Schottky emitter unit is analyzed thermally to determine optimum power and filament dimensions. A numerical thermal analysis in steady state condition has been done and the temperature of the tip has been determined for different currents and heating filament dimensions. The model has been verified with some available experimental data. The optimized solution from the model will be used for fabrication of an array of miniaturized Schottky emitters.
Behaviors of single nitrogen molecule on pentagon at carbon nanotube tip observed by field emission microscopy
Authors: Waki Shunsaku , Hata Koichi , Sato Hideki , Saito Yahachi
Published: April 2007

Field emission microscopy (FEM) observations of behaviors of a single nitrogen molecule on a pentagon at the tip of a multiwall carbon nanotube and an attempt to control a desorption of the nitrogen molecule by pulse laser irradiation were carried out. The adsorbed gas molecule was recognized as a bright spot in a FEM image. In an adsorption of nitrogen, two types of bright spot were observed. They reflected two types of adsorption state that a molecular axis of the nitrogen was parallel or perpendicular to substrate pentagon. At energy density of under 35mJ∕cm2, the pulse laser irradiation was a responsive method to promote a desorption of physisorbed molecule without any damage to substrate pentagon.
CdTe x-ray sensing driven by electron beam from field emitters
Authors: Neo Yoichiro , Ikeda Yoshiaki , Sakata Takuya , Morii Hisashi , Shiozawa Kazufumi , Aoki Toru , Mimura Hidenori
Published: April 2007

The authors have demonstrated a novel CdTe x-ray sensing device that consists of a CdTe pn diode and a graphite nanoneedle field emitter. The CdTe diode was fabricated using an excimer laser doping method. The signal current was successfully read out by an electron beam from the field emitter and was found to be proportional to the x-ray intensity. The operation principle of the device is expounded in this article.
Work function of low index crystal facet of tungsten evaluated by the Seppen-Katamuki analysis
Authors: Gotoh Y. , Mukai K. , Kawamura Y. , Tsuji H. , Ishikawa J.
Published: April 2007

Work function of low index crystal facet of tungsten was evaluated by measuring field emission characteristics using a probe hole system. Unlike the conventional method, the authors derived the work function through the analysis of the relationship between the slope and intercept of the Fowler-Nordheim plot, which we call the Seppen-Katamuki analysis. Measurements were done in a vacuum vessel which was evacuated down to approximately 10−7Pa. The etched tungsten emitter was heated to have hemispherical apex with the radius of 110 or 220nm. The field emission was caused by an applied voltage between the emitter and a fluorescent screen. The screen has a small aperture with a diameter of 2mm as a probe hole. Behind the screen, the authors placed a transparent collector. The authors measured the field emission characteristics originating from (011), (111), (121), and (112) facets through the probe hole, for six times for each facet. The obtained characteristics were examined in a two-dimensional diagram of which abscissa and ordinate are the intercept and slope of the Fowler-Nordheim plot. The measured characteristics for each facet distributed along a straight line in the chart, and from the slope of the line, the authors derived the relative work function value. The obtained values agreed well with the values shown in the literature.
Low temperature growth of carbon nanotubes by alcohol catalytic chemical vapor deposition for field emitter applications
Authors: Sato Hideki , Hata Koichi , Hiasa Ken , Saito Yahachi
Published: April 2007

Growth of carbon nanotubes (CNTs) by an alcoholic catalytic chemical vapor deposition (ACCVD) technique has attracted much attention due to its simplicity in apparatus and its ability to grow high quality CNTs. Recently, the authors have found that the ACCVD method is also available for growth of CNTs at low temperature less than 500°C, which is required for a fabrication process of field emission displays (FEDs) using CNTs as electron sources. Here the authors report results of studies that were carried out to clarify the temperature dependence of CNT growth by ACCVD technique using a Co∕Al bilayer catalyst film. The result showed that growth of CNTs at low temperature less than 450°C is possible. It was also found that formation of a Mo buffer layer between Si substrate and the catalyst film enhances CNT growth at the low growth temperature. These results imply that ACCVD technique is suitable for CNT growth method for FED fabrication process.
Electron emission from low surface barrier cathodes
Authors: Semet V. , Adessi Ch. , Capron T. , Thien Binh Vu
Published: April 2007

A systematic study was done in order to relate the J-F characteristic variation with three emission mechanisms: tunneling, thermionic, and ballistic. All three are now effective during the field emission from cathodes with work function Φ less than 2eV. The current density is computed using the transmission probability for an electron to cross the barrier between the electron sea of the cathode and the vacuum. The corresponding Schrödinger equation is solved by means of the self-consistent Lippmann-Schwinger equation, with values of the effective potential corrected with the image potential between the cathode and the anode and resolved by spatial discretization. This method allows computing the exact current within a zero emitted current approximation. It fills the gap leave by the former analytical resolution by Murphy and Good [Phys. Rev. 102, 1464 (1956)]. The ln(J∕F2) vs (1∕F) plot shows three zones for the current variation. The first zone, corresponding to low applied electric fields, shows a nonlinear variation of the field emission current. It is followed by a second zone having a linear variation with a slope proportional to Φ3∕2. The third zone, concerning high field values, indicated saturation behavior specific to a field induced ballistic emission.
Field emission properties of plasma treated multiwalled carbon nanotube cathode layers
Authors: Nam J. W. , Alegaonkar P. S. , Park J. H. , Yoo J. B. , Choe D. H. , Kim J. M. , Kim W. S.
Published: April 2007

Improved field emission stability and lifetime have been observed for multiwalled carbon nanotube (MWCNT)-paste cathode layers, after plasma conditioning. Initially, MWCNT paste was synthesized and screen printed on an indium tin oxide coated glass substrate to obtain the cathode layers. These cathode layers were exposed to the Xe∕Ne plasma for a period of ∼1 or ∼3min under different biasing conditions (∼250 and ∼300V). The scanning electron microscopy micrographs, recorded for the untreated (virgin) and plasma treated cathode layers, showed significant variations in their morphology. The field emission analysis showed that the onset macroscopic field was increased from its virgin value of ∼4.65to∼9.05±0.05V∕μm for the plasma treated samples, with a subsequent decrease in the mean field-enhancement factor γav from 1251±13 to 779±43, computed from the Fowler-Nordheim plot. The variations in the current density was measured as a function of time, under low (∼10−6Torr) as well as high (∼10−8Torr) vacuum conditions, and corresponding degradation rates were computed. The degradation rate was found to be reduced by a factor of ∼103 under high vacuum conditions. The lifetime study revealed that the half-lifetime of the plasma treated samples was increased from its virgin value of ∼15to∼400h, at ∼10−6Torr. In another study, the estimated half-lifetime of the plasma treated cathode layers was found to be more than ∼20000h under high vacuum conditions (∼10−8Torr). The details of the analysis are presented.
KrF laser surface treatment of carbon nanotube cathodes with and without reactive ion etching
Authors: Ohsumi K. , Honda T. , Kim W. S. , Oh C. B. , Murakami K. , Abo S. , Wakaya F. , Takai M. , Nakata S. , Hosono A. , Okuda S.
Published: April 2007

Electron emission characteristics of carbon nanotube cathodes with and without reactive ion etching (RIE) followed by KrF laser irradiation were investigated. The emission characteristics of samples without RIE process, such as emission current density, turn-on field, and emission pattern, strongly depend on the laser power density, which is caused by a photon process at low laser power densities of 2–4MW∕cm2 and a thermal ablation at high power densities of 10–14MW∕cm2. The emission characteristics of samples with RIE, however, show little change when the laser power density is varied. Surface morphologies of CNT cathodes with RIE process show little change by laser treatment compared to the case of CNT cathodes without RIE process.
Inspection of all beams in multielectron beam system
Authors: Tanimoto Sayaka , Sugaya Masakazu , Furukawa Akihiro , Sohda Yasunari , Hosoda Masaki , Someda Yasuhiro , Muraki Masato , Tamamori Kenji , Hirose Futoshi , Nagae Kenichi , Kato Kazuhiko
Published: April 2007

A testing apparatus for inspecting the beams formed by a multisource module (MSM) was built for the feasibility study of a beam splitting array (BSA), a multielectron beam system the authors are developing. In this BSA, the MSM plays the following three key roles: splitting the beam from a single cathode into 32×32 beams, converging the 32×32 beams, and blanking them individually. Accordingly, the inspection of all beams formed by the MSM is essential for the feasibility study of the system. The testing apparatus was therefore designed for measuring all the beams formed by the MSM without demagnifying them. To maintain the accuracy during the inspection of all 32×32 beams, the measurement process was automated. This testing apparatus was used to measure the diameters and misalignments of all beams formed by a prototype MSM. As a result, the mean values of the transverse and the longitudinal diameters were found to be 0.88 and 0.92μm, respectively. A single stigmator can cancel the difference between these two mean values. The standard deviations of the transverse and the longitudinal misalignments were found to be 0.77 and 0.55μm, respectively. This result demonstrates that all beams will reach the substrate without being interrupted by the blanking aperture array. Furthermore, the distribution of misalignments demonstrated that the misalignments are mainly caused by astigmatic aberration occurring in the illumination optics and that they can be decreased by a stigmator. These results will be used as basic data for designing the optical and data-handling systems of the BSA.
Integration of electrodes in Si channels using low temperature polymethylmethacrylate bonding
Authors: Dukkipati V. R. , Pang S. W.
Published: April 2007

Low temperature Si to glass bonding using polymethylmethacrylate (PMMA) as an adhesive layer is developed to integrate electrodes with Si channels. The integrated microsystem contains channels dry etched in Si with widths ranging from 3to100μm and depths ranging from 100nmto30μm. The channels are bonded to a 100μm thick glass consisting of 600nm thick patterned PMMA and 20∕50nm thick Cr∕Au electrodes, with PMMA as an adhesive layer. The typical bond strength is 3MPa, obtained by bonding at 110°C with 600nm thick PMMA. Fluidic flow studies are carried out in channels that are 50 and 100μm wide with a depth of 100nm. De-ionized water flows through the sealed Si channels due to capillary pressure with an initial velocity of 0.65mm∕s for 50μm wide and 100nm deep channels. Electric fields are used to induce DNA motion with velocities from 2.4to14.5μm∕s in 100μm wide and 20μm deep channels. The forces generated by the fields and the fluid flow are also used to stretch the tethered DNA molecules up to 15μm long in the microchannels.
Simulation and characterization of a magnetic microdeflector for electron beam control in electron beam microcolumn system
Authors: Rong Rong , Kim Ho Seob , Park Seong Soon , Hwang Nam Woo , Kim Byung Jin , Ahn Chong H.
Published: April 2007

A magnetic microdeflector was developed for the electron beam microcolumn system to control the electron beam deflection/scanning. The magnetic microdeflector fabricated by the microelectromechanical system technology consists of four magnetic poles coupled with solenoid-type micromachined inductors with NiFe permalloy magnetic cores. The four magnetic poles are divided into two pairs which control the electron beam deflection/scanning in X and Y axes, respectively. Experimental results show that the electron beam deflection increases linearly to 210μm with a driving current of 50mA and an electrical power consumption of 3mW. The fabricated magnetic microdeflector has a good dynamic property, as shown by the rise time of 25ns with respect to a 50mA step signal. The developed magnetic deflector demonstrates excellent performance in controlling the electron beam deflection/scanning for the electron beam microcolumn system.
Nanolithographic patterning of transparent, conductive single-walled carbon nanotube films by inductively coupled plasma reactive ion etching
Authors: Behnam Ashkan , Choi Yongho , Noriega Leila , Wu Zhuangchun , Kravchenko Ivan , Rinzler Andrew G. , Ural Ant
Published: April 2007

The authors report successful patterning of transparent, conductive single-walled carbon nanotube films down to 100nm lateral dimensions by photolithography or e-beam lithography and subsequent O2 plasma etching using an inductively coupled plasma reactive ion etching (ICP-RIE) system. They systematically study the effect of ICP-RIE etch parameters, such as substrate bias power, chamber pressure, and substrate cooling, on the nanotube film etch rate and etch selectivity. They also characterize the effect of the linewidth etched on the nanotube film etch rate for widths ranging from 50μm down to 100nm. Furthermore, by fabricating standard four point probe structures using the patterning capability developed, the authors investigate the effect of different resist processes on the resistivity of patterned single-walled carbon nanotube films and the effect of ICP reactive ion etching on the resistivity of partially etched nanotube films. In addition, they demonstrate that using an ICP-RIE system provides significant advantages, such as faster etch rates and better etch selectivity, over conventional parallel plate RIE plasma systems, making it possible to pattern lateral features as small as 100nm in nanotube films. The simple and efficient “top-down” patterning capability developed in this article could open up many opportunities for integrating single-walled nanotube films into a wide range of electronic and optoelectronic devices.
Development of a high-resolution active-matrix electron emitter array for application to high-sensitivity image sensing
Authors: Negishi Nobuyasu , Matsuba Youhei , Tanaka Ryota , Nakada Tomonari , Sakemura Kazuto , Okuda Yoshiyuki , Watanabe Atsushi , Yoshikawa Takamasa , Ogasawara Kiyohide , Nanba Masakazu , Okazaki Saburo , Tanioka Kenkichi , Egami Norifumi , Koshida Nobuyoshi
Published: April 2007

An image sensor consisting of an active-matrix high-efficiency electron emission device (HEED) array and a high-gain avalanche rushing amorphous photoconductor (HARP) has been fabricated. Based on the demonstration that a prototyped 256×192pixel image sensor can pick up a high definition image with an ultrahigh sensitivity under poor light condition, the authors have been developing a 640×480pixel active-matrix HEED toward a practical use. The emission current density has been enhanced more than twice compared to that of previous one and has increased up to 1A∕cm2. The active-matrix HEED array combined with HARP is available for application to practical image sensing with an ultrahigh sensitivity and high definition.
Application of ZnO nanopins as field emitters in a field-emission-display device
Authors: Wei Lei , Zhang Xiaobing , Zuoya Zhu
Published: April 2007

From recent research work, it has been found that the ZnO nanostructures have good field-emission performance. This article compares the emission characteristics of ZnO nanopins (such as I-V curve, thermal stability, and aging process) with those of carbon nanotubes. From this comparison, it can be seen that the emission characteristic of ZnO nanopins is close to that of carbon nanotubes. However, the emission performance of ZnO nanopins is much better than that of carbon nanotubes after baking at high temperature. Apart from this, the emission uniformity of ZnO cathode is quite good without an activation process. Therefore, ZnO nanopins can be used as field emitters in a field-emission-display device.
Detailed analysis of the influence of an inductively coupled plasma reactive-ion etching process on the hole depth and shape of photonic crystals in InP∕InGaAsP
Authors: Strasser P. , Wüest R. , Robin F. , Erni D. , Jäckel H.
Published: April 2007

The authors report on the fabrication of photonic crystals in the InP∕InGaAsP∕InP material system for applications at telecommunication wavelengths. To achieve low optical loss, the photonic crystal holes must demonstrate smooth sidewalls and should be simultaneously deep and cylindrical. The authors present the etching process of these structures based on a Cl2∕Ar∕N2 chemistry with an inductively coupled plasma reactive-ion etching system. A systematic analysis is provided on the dependency of the hole sidewall roughness, depth, and shape on the process parameters such as etching power, pressure, and chemical composition of the plasma. They found that a low plasma excitation power and a low physical etching are beneficial for achieving deep holes, whereas for the nitrogen content in the plasma, a delicate balance needs to be found. Nitrogen has a negative impact on the hole shape and surface roughness but is capable of preventing underetching below the mask by passivation of the sidewalls. With the authors’ process more than 4μm deep holes with low conicity have been demonstrated.
High fidelity fabrication of microlens arrays by nanoimprint using conformal mold duplication and low-pressure liquid material curing
Authors: Peng Can , Liang Xiaogan , Fu Zengli , Chou Stephen Y.
Published: April 2007

The authors present a novel hyperfidelity fabrication method for microlens arrays. The method consists of the steps of (a) fabrication of a sacrificial master mold of a microlens array in a soft polymer by photolithography and thermal reflow, (b) conformal duplication of a daughter mold of complementary patterns in a hard material by dispensing an UV-curable material liquid on top of the polymer mold, planarizing the liquid with a flat quartz substrate, and curing the material, and (c) fabrication of microlens array using the hard daughter mold and nanoimprinting with an UV-curable lens material. This method has several advantages over conventional fabrication methods of microlens arrays including hyperfidelity, low cost, and high throughput.
Surface micromachining of a thin film microresonator using dry decomposition of a polymer sacrificial layer
Authors: Patil S. B. , Chu V. , Conde J. P.
Published: April 2007

Fabrication of thin film silicon bridge microresonators on glass substrates using an unzipping sacrificial polymer has been demonstrated. Polynorbornene, which can be thermally decomposed at ∼425°C, has been used as the sacrificial layer, allowing a simple, fully dry sacrificial layer removal. The polynorbornene is spin coated onto the substrate and patterned by photolithography. A thin film silicon structural layer is deposited by rf plasma-enhanced chemical vapor deposition and patterned to form a microbridge. The microbridges are electrostatically actuated and the resulting deflection is measured optically. The fabricated microbridges show resonance frequencies of the order of ∼4.4MHz and quality factors ∼450.
Iterative threshold segmentation for PET target volume delineation
Authors: Drever Laura , Roa Wilson , McEwan Alexander , Robinson Don
Published: April 2007

The purpose of this work is to create a rigorous method of segmenting PET images using an automated iterative technique. To this end a phantom study employing spherical targets was used to determine local (slice specific) threshold levels which produce correct cross‐sections based on the contrast between target and background. Numerous target to background activity concentration ratios were investigated but found to have minimal effect in comparison to the influence of target size. Functions were fit to this data and used to construct an iterative threshold segmentation algorithm. In all cases this approach yielded convergence within ten iterations. Iterative threshold segmentation was applied using both an axial and tri‐axial approach to the spherical targets and also to two irregularly shaped volumes. Of these two approaches, the tri‐axial method proved less susceptible to image noise and better at dealing with partial volume effects at the interface between target and background. For comparative purposes, single thresholds of 28% and 40% were also applied to the spherical data sets. The tri‐axial iterative method was found capable of delineating cross sections with areas greater than to within the maximum resolution possible ( width). Cross sections of less than in area were resolved by the tri‐axial method to within widths of their true physical extent. Local contrast based iterative threshold segmentation shows promise as a method of rigorously delineating PET target volumes with good accuracy subject to the limitations imposed by the image resolution which currently characterizes this modality.
Manual planimetric measurement of carotid plaque volume using three‐dimensional ultrasound imaging
Authors: Landry Anthony , Ainsworth Craig , Blake Chris , Spence J. David , Fenster Aaron
Published: April 2007

We investigated the utility of three manual planimetric methods to quantify carotid plaque volume. A single observer measured 15 individual plaques from 15 three‐dimensional (3D) ultrasound (3D US) images of patients ten times each using three different planimetric approaches. Individual plaque volumes were measured (range: ) using a standard planimetric approach (M1) whereby a plaque end was identified and sequential contours were measured. The same plaques were measured using a second approach (M2), whereby plaque ends were first identified and the 3D US image of the plaque was then subdivided into equal intervals. A third method (M3) was used to measure total plaque burden (range: ) in a region relative to the carotid bifurcation. M1 systematically underestimated individual plaque volume compared to M2 (, , ) due to a difference in the mean plaque length measured. Coefficients of variance (CV) for M1 and M2 decrease with increasing plaque volume, with M2 results less than M1. Root mean square difference between experimental and theoretical CV for M2 was 3.2%. The standard deviation in the identification of the transverse location of the carotid bifurcation was . CVs for plaque burden measured using M3 ranged from 1.2% to 7.6% and were less than CVs determined for individual plaque volumes of the same volume. The utility of M3 was demonstrated by measuring carotid plaque burden and volume change over a period of in three patients. In conclusion, M2 was determined to be a more superior measurement technique than M1 to measure individual plaque volume. Furthermore, we demonstrated the utility of M3 to quantify regional plaque burden and to quantify change in plaque volume.
Positive Regulation of Itk PH Domain Function by Soluble IP
4
Authors: Huang Yina H. , Grasis Juris A. , Miller Andrew T. , Xu Ruo , Soonthornvacharin Stephen , Andreotti Amy H. , Tsoukas Constantine D. , Cooke Michael P. , Sauer Karsten
Published: April 2007

Pleckstrin homology (PH) domain–mediated protein recruitment to cellular membranes is of paramount importance for signal transduction. The recruitment of many PH domains is controlled through production and turnover of their membrane ligand, phosphatidylinositol 3,4,5-trisphosphate (PIP
3
). We show that phosphorylation of the second messenger inositol 1,4,5-trisphosphate (IP
3
) into inositol 1,3,4,5-tetrakisphosphate (IP
4
) establishes another mode of PH domain regulation through a soluble ligand. At physiological concentrations, IP
4
promoted PH domain binding to PIP
3
. In primary mouse CD4
+
CD8
+
thymocytes, this was required for full activation of the protein tyrosine kinase Itk after T cell receptor engagement. Our data suggest that IP
4
establishes a feedback loop of phospholipase C–γ1 activation through Itk that is essential for T cell development.
Model Projections of an Imminent Transition to a More Arid Climate in Southwestern North America
Authors: Seager Richard , Ting Mingfang , Held Isaac , Kushnir Yochanan , Lu Jian , Vecchi Gabriel , Huang Huei-Ping , Harnik Nili , Leetmaa Ants , Lau Ngar-Cheung , Li Cuihua , Velez Jennifer , Naik Naomi
Published: April 2007

How anthropogenic climate change will affect hydroclimate in the arid regions of southwestern North America has implications for the allocation of water resources and the course of regional development. Here we show that there is a broad consensus among climate models that this region will dry in the 21st century and that the transition to a more arid climate should already be under way. If these models are correct, the levels of aridity of the recent multiyear drought or the Dust Bowl and the 1950s droughts will become the new climatology of the American Southwest within a time frame of years to decades.
Methicillin-resistant Staphylococcus aureus infections among healthy full-term newborns
Authors: James L , Gorwitz R J , Jones R C , Watson J T , Hageman J C , Jernigan D B , Lord Y , Caballes N , Cortes C , Golash R G , Price J S , Gerber S I
Published: April 2007

Objective:

Methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged in the community, causing disease among healthy people lacking traditional risk factors for MRSA infection. This article describes an outbreak of MRSA among healthy full-term newborns.

Design:

Cases were identified and corresponding medical information collected. Telephone interviews were conducted with mothers of cases ands surveillance cultures from mothers and newborns were performed. MRSA isolates were genotyped.

Setting:

Hospital in Chicago, Illinois, USA.

Participants:

Newborns, their mothers and hospital healthcare workers.

Intervention:

Nursery infection control practices were enhanced. The MRSA-colonised healthcare workers received intranasal mupirocin.

Main outcome:

Within 4–23 days of birth, 11 newborns were identified with pustules, vesicles or blisters located on the head, groin, perineum, ears, legs, chin and trunk. All received antimicrobials and recovered without incident.

Results:

None of 432 peripartum women, one of 399 newborns, and two of 135 healthcare workers were nasal MRSA carriers. Available isolates from six patients, two healthcare workers, and one from an MRSA-colonised newborn were similar by pulsed-field gel electrophoresis. Other than contact with the hospital, no common exposures of MRSA transmission were identified.

Conclusions:

MRSA strains that initially emerged in the community are now causing disease in healthcare settings. Providers should be aware that MRSA can cause skin infections among healthy newborns. Adherence to standard infection control practices is important to prevent transmission of MRSA in nurseries.
Upregulation of neutrophil gelatinase-associated lipocalin in oesophageal squamous cell carcinoma: significant correlation with cell differentiation and tumour invasion
Authors: Zhang Haihua , Xu Liyan , Xiao Dawei , Xie Jianjun , Zeng Hongmei , Wang Zhaoyang , Zhang Xiaoling , Niu Yongdong , Shen Zhongying , Shen Jinghui , Wu Xuan , Li Enmin
Published: April 2007

Background:Neutrophil gelatinase-associated lipocalin (NGAL) is a member of the lipocalin family. Recently, an elevated NGAL expression was reported in several types of cancers. However, the characteristics of NGAL expression in oesophageal squamous cell carcinoma (ESCC) are still unknown.

Aim:To demonstrate the role of NGAL in ESCC.

Methods:NGAL expression in 81 paraffin sections, including ESCC, normal mucosa, simple hyperplasia and dysplasia, and in 73 fresh specimens of ESCC was analysed by immunohistochemistry, western blot and gelatin zymography.

Results:On immunohistochemical study, ESCC showed a diverse staining pattern for NGAL. However, only a weak positive signal was present within a restricted cytoplasmic area in the normal oesophageal epithelium. In dysplasia, altered NGAL expression could also be observed. On western blot study, NGAL expression level was found to be significantly higher in ESCC than in normal mucosa (p = 0.030), and to be positively correlated with cell differentiation. However, no significant association was observed between NGAL expression and cell proliferation. In addition, the enzymic activity of the NGAL/matrix metalloproteinase 9 complex was much higher in ESCC than in normal mucosa, and was significantly correlated with the depth of tumour invasion in zymography analysis (p = 0.006).

Conclusions:The findings suggest that NGAL is involved in the differentiation pathway and invasive progression of ESCC.
Transfusion in sub-Saharan Africa: does a Western model fit?
Authors: Field Stephen P , Allain Jean-Pierre
Published: April 2007

This review examines the current state of transfusion services in sub-Saharan Africa and presents the argument for and against the Western model of a centralised blood service with 100% voluntary non-remunerated blood donors as advocated by the World Health Organization. The current practice of family replacement donors in hospital-based blood service is the most economical option, but in the face of high child and maternal mortality rates the blood supply has proved to be insufficient. With estimates of 5–10% of HIV transmission in Africa being the result of contaminated blood transfusions, there is a need to improve testing for transfusion transmissible diseases and the selection of blood donors. Of major concern, with respect to testing, is the quality of kits being used and the continuity of supply. The need to produce components is discussed in the context of the transfusion needs in sub-Saharan Africa. The running costs of establishing and maintaining centralised blood services need careful consideration as such projects need to be sustainable in the future. It is concluded that both options are viable while centralised programmes are being developed, and a pragmatic approach should be taken to ensure that the patients’ needs are met and that resources are suitably utilised to ensure sustainability.
Altered gastric corpus expression of tissue inhibitors of metalloproteinases in human and murineHelicobacterinfection
Authors: Bodger K , Ahmed S , Pazmany L , Pritchard D M , Micheal A , Khan A L , Dimaline R , Dockray G J , Varro A
Published: April 2007

Background:

Matrix metalloproteinases (MMPs) have roles in inflammation and other processes relevant to the architectural disturbances seen in the gastric mucosa in response toHelicobacter pyloriinfection. Upregulation of MMPs has been reported inH pyloriinfection, but there are no detailed reports regarding altered production of their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs).

Aims:

To investigate changes in the abundance of TIMPs in human gastric corpus mucosa and murine stomach inHelicobacterinfection, and to study cellular sources in man.

Methods:

Gastric corpus biopsy samples were assessed for abundance of mRNA or protein for TIMP-1 to -4 by real-time quantitative PCR or western blotting, respectively. Antral and corpus biopsies were processed for histology,H pyloristatus and inflammatory scoring. Cellular sources of TIMP-1, -3 and -4 were examined by indirect immunohistochemistry. Circulating gastrin was measured by radioimmunoassay. Also, abundance of TIMP-1, -3 and -4 mRNA in the stomach ofHelicobacter felisinfected mice post-infection was compared with that of uninfected control animals.

Results:

Compared with uninfected patients, mRNA and protein for TIMP-1, -3 and -4 were significantly more abundant in the gastric corpus ofH pyloriinfected subjects. Gastric TIMP expression did not differ significantly between hyper- and normogastrinaemic subjects within theH pylorinegative and positive groups. There was no difference in mRNA abundance for MMP-3 or -8. Immunohistochemistry showed TIMP proteins localised to gastric epithelial, stromal cells and inflammatory cells. MurineH felisinfection was associated with upregulation of TIMP-1 and -3 mRNA.

Conclusions:

Helicobacterinfection is associated with upregulation of specific TIMPs (TIMP-1 and -3) in glandular epithelium and stroma. It is suggested that increased expression of specific protease inhibitors in the corpus mucosa may exert important effects on extracellular matrix remodelling and influence the outcome ofH pyloriinfection.
THE IMPACT OF THE 1997 HANDOVER ON THE EFFICIENCY OF THE HONG KONG STOCK MARKET
Authors: CHONG TERENCE TAI-LEUNG , LOK LILY
Published: April 2007

On the first of July 1997, the formerly British colony of Hong Kong was returned to China. This paper compares the profitability of various trading rules on the Hang Seng Index both before and after the handover. Our work extends that of Coutts and Cheung (2000), whose study focuses on pre-1997 Hong Kong, in terms of both the data collection period as well as the number of trading rules studied. The authors find that, among the trading rules examined herein, the Trade Range Breakout rule generates the highest returns. We also conclude that, in general, the handover of Hong Kong to China does not affect the efficiency of the Hong Kong stock market.
GROWTH OF ZnO NANOSTRUCTURES ON ZINC AND Pt SUBSTRATES
Authors: TABET N. , FAIZ M. , AL-OTEIBI A.
Published: April 2007

Nanocrystalline ZnO of various shapes was obtained without the use of catalysts by dry oxidation of metallic zinc. Oxidation treatments performed below the melting point of Zn (T m = 419°C) led to the formation of flakes-type structure. At 500°C, long nanofibers of circular and uniform cross section covering the surface of the oxidized samples were observed. At 600°C, large density of cone-shape needles covered the oxidized surface. High quality nanocrystals of hexagonal shape were obtained by vapor deposition on Pt substrate. XRD results showed that the lattice parameters of the needles are 1% smaller than those of microcrystalline ZnO .
AN INTERESTING RELATIONSHIP BETWEEN INTERELECTRONIC DISTANCE AND THE CORRESPONDING COULOMB INTEGRAL
Authors: HOLLETT JOSHUA W. , POIRIER RAYMOND A.
Published: April 2007

A simple expression for the distance between two electrons, (δr12)ab, has been defined from one-electron expectation values. This value is calculated for triplet and singlet systems of two electrons, and closed-shell molecules of up to 58 electrons. When (δr12)ab is compared to the corresponding coulomb integral, Jab, an interesting relationship is observed. The relationship is followed extremely closely by all pairs of electrons, except for some deviations involving delocalized core–core electron pairs.
MOLECULAR DYNAMICS STUDY OF Tin, Vn AND Crn CLUSTERS
Authors: BÖYÜKATA MUSTAFA
Published: April 2007

Using a Morse type pair potential, molecular-dynamics simulations have been performed to investigate the atomic geometries, growing patterns, structural stabilities, energetics and magic sizes of Ti n, V n and Cr n (n = 2-50) clusters. Following rearrangement collision of the atom–cluster system in fusion process, and absorbing their energies step by step down to 0 K, possible optimal equilibrium geometries of the clusters have been generated to tackle the structural determination problem. This approach serves an efficient alternative to the growing path identification and the optimization techniques. It has been found that titanium, vanadium and chromium clusters prefer to form three-dimensional compact structures in the determined configurations and the appearances of medium sizes are, in general, five-fold symmetry on the spherical clusters. Moreover, relevant relations between atomic arrangements in the clusters and the magic sizes have been observed.
Phosphorylation of human inhibitor-1 at Ser67 and/or Thr75 attenuates stimulatory effects of protein kinase A signaling in cardiac myocytes
Authors: Rodriguez Patricia , Mitton Bryan , Nicolaou Persoulla , Chen Guoli , Kranias Evangelia G.
Published: April 2007

The depressed function of failing hearts has been partially attributed to increased protein phosphatase-1 through its impaired regulation by inhibitor-1. Phosphorylation of inhibitor-1 at Thr35 by PKA results in potent inhibition of protein phosphatase-1 activity, while phosphorylation at Ser67 or Thr75 by PKC attenuates the inhibitory activity. To examine the functional role of dual-site (Ser67, Thr75) phosphorylation of inhibitor-1 by PKC, the constitutively phosphorylated Ser67 (S67D) and/or Thr75 (T75D) human inhibitor-1 forms were expressed in adult cardiomyocytes. Expression of either single or double phosphorylated inhibitor-1 was associated with similar decreases in cardiac contractility, indicating that maximal inhibition can be elicited by each of these sites alone and that their inhibitory effects are not additive. Notably, activation of the cAMP pathway could only partially reverse the depressed contractile parameters. Accordingly, protein phosphatase-1 activity remained elevated, phosphorylation of phospholamban at Ser16 was decreased, and the EC50 values of the sarcoplasmic reticulum calcium transport system were higher compared with controls. Thus phosphorylation of Ser67 and/or Thr75 in inhibitor-1 may mitigate the stimulatory effects of the cAMP pathway, resulting in compromised cardiac function.
Preserved reflex cutaneous vasodilation in cystic fibrosis does not include an enhanced nitric oxide-dependent mechanism
Authors: Wilkins Brad W. , Martin Elizabeth A. , Roberts Shelly K. , Joyner Michael J.
Published: April 2007

In humans, vasoactive intestinal peptide (VIP) may play a role in reflex cutaneous vasodilation during body heating. We tested the hypothesis that the nitric oxide (NO)-dependent contribution to active vasodilation is enhanced in the skin of subjects with cystic fibrosis (CF), compensating for sparse levels of VIP. In 2 parallel protocols, microdialysis fibers were placed in the skin of 11 subjects with CF and 12 controls. Lactated Ringer was perfused at one microdialysis site and NG-nitro-l-arginine methyl ester (2.7 mg/ml) was perfused at a second microdialysis site. Skin blood flow was monitored over each site with laser-Doppler flowmetry. In protocol 1, local skin temperature was increased 0.5°C every 5 s to 42°C, and then it maintained at 42°C for ∼45 min. In protocol 2, subjects wore a tube-lined suit perfused with water at 50°C, sufficient to increase oral temperature (Tor) 0.8°C. Cutaneous vascular conductance (CVC) was calculated (flux/mean arterial pressure) and scaled as percent maximal CVC (sodium nitroprusside; 8.3 mg/ml). Vasodilation to local heating was similar between groups. The change (Δ%CVCmax) in CVC with NO synthase inhibition on the peak (9 ± 3 vs. 12 ± 5%CVCmax; P = 0.6) and the plateau (45 ± 3 vs. 35 ± 5%CVCmax; P = 0.1) phase of the skin blood flow response to local heating was similar in CF subjects and controls, respectively. Reflex cutaneous vasodilation increased CVC in CF subjects (58 ± 4%CVCmax) and controls (53 ± 4%CVCmax; P = 0.37) and NO synthase inhibition attenuated CVC in subjects with CF (37 ± 6%CVCmax) and controls (35 ± 5%CVCmax; P = 0.8) to a similar degree. Thus the preservation of cutaneous active vasodilation in subjects with CF is not associated with an enhanced NO-dependent vasodilation.
Refinements in modeling the passive properties of laryngeal soft tissue
Authors: Hunter Eric J. , Titze Ingo R.
Published: April 2007

The nonlinear viscoelastic passive properties of three canine intrinsic laryngeal muscles, the lateral cricoarytenoid (LCA), the posterior cricoarytenoid (PCA), and the interarytenoid (IA), were fit to the parameters of a modified Kelvin model. These properties were compared with those of the thyroarytenoid (TA) and cricothyroid (CT) muscles, as well as previously unpublished viscoelastic characteristics of the human vocal ligament. Passive parameters of the modified Kelvin model were summarized for the vocal ligament, mucosa, and all five laryngeal muscles. Results suggest that the LCA, PCA, and IA muscles are functionally different from the TA and CT muscles in their load-bearing capacity. Furthermore, the LCA, PCA, and IA have a much larger stress-strain hysteresis effect than has been previously reported for the TA and CT or the vocal ligament. The variation in this effect suggests that the connective tissue within the TA and CT muscles is somehow similar to the vocal ligament but different from the LCA, PCA, or IA muscles. Further demonstrating the potential significance of grouping tissues in the laryngeal system by functional groups in the laryngeal system was the unique finding that, over their working elongation range, the LCA and PCA were nearly as exponentially stiff as the vocal ligament. This paper was written in conjunction with an online technical report ( http://www.ncvs.org/ncvs/library/tech ) in which comprehensive muscle data and sensitivity analysis, as well as downloadable data files and computer scripts, are made available.