bluuebunny/crossref_metadata_2025 huggingface dataset:
Breakdown-induced light emission and poling dynamics of porous fluoropolymers
Authors: Zhukov S. , von Seggern H.
Published: April 2007

To date the charging mechanism of porous electret materials is not completely understood. The present study is focused on the investigation of light emission during corona poling of individual films of expanded polytetrafluoroethylene (ePTFE) with nominal porosity of 91% and of the same film sandwiched between two solid poly-fluroethylene propylene copolymer (FEP) films. One observes that as soon as the applied electric field exceeds a certain threshold value (Vth), the individual film and sandwiched structure start to emit light. For the sandwich structure the light intensity decays with time to zero, whereas for an individual ePTFE film a continuous light emission at V>Vth is observed. The emitted light is a result of electrical breakdown events in air developing in the pores of the media. For the sandwich sample the positive and negative charges generated during breakdown are trapped at opposite ePTFE/solid film interfaces, thus resulting in a macroscopic dipole formation (polarization). In the case of individual ePTFE films the continuous light emission indicates that these charges are not trapped permanently at the fibers in the open-pore media. The present results explain the drastic difference in piezoactivity between individual porous films and sandwiched structures.
Monoenergetic source of kilodalton ions from Taylor cones of ionic liquids
Authors: Larriba C. , Castro S. , Fernandez de la Mora J. , Lozano P.
Published: April 2007

The ionic liquid ion sources (ILISs) recently introduced by Lozano and Martinez Sanchez [J. Colloid Interface Sci. 282, 415 (2005)], based on electrochemically etched tungsten tips as emitters for Taylor cones of ionic liquids (ILs), have been tested with ionic liquids [A+B−] of increasing molecular weight and viscosity. These ILs have electrical conductivities well below 1S∕m and were previously thought to be unsuitable to operate in the purely ionic regime because their Taylor cones produce mostly charged drops from conventional capillary tube sources. Strikingly, all the ILs tried on ILIS form charged beams composed exclusively of small ions and cluster ions A+(AB)n or B−(AB)n, with abundances generally peaking at n=1. Particularly interesting are the positive and negative ion beams produced from the room temperature molten salts 1-methyl-3-pentylimidazolium tris(pentafluoroethyl) trifluorophosphate (C5MI–(C2F5)3PF3) and 1-ethyl-3-methylimidazolium bis(pentafluoroethyl) sulfonylimide (EMI–(C2F5SO3)2N). We extend to these heavier species the previous conclusions from Lozano and Martinez Sanchez on the narrow energy distributions of the ion beams. In combination with suitable ILs, this source yields nanoamphere currents of positive and negative monoenergetic molecular ions with masses exceeding 2000amu. Potential applications are in biological secondary ion mass spectrometry, chemically assisted high-resolution ion beam etching, and electrical propulsion. Advantages of the ILISs versus similar liquid metal ion sources include the possibility to form negative as well as positive ion beams and a much wider range of ion compositions and molecular masses.
Molecular dynamics study on ultrathin liquid water film sheared between platinum solid walls: Liquid structure and energy and momentum transfer
Authors: Torii Daichi , Ohara Taku
Published: April 2007

Molecular dynamics simulation has been performed on a liquid film that is sheared in between solid surfaces. As a shear is given to the liquid film, a Couette-like flow is generated in the liquid and energy conversion occurs from the macroscopic flow to the thermal energy, which is discharged back to the solid walls. In such a way, momentum and thermal energy fluxes are present simultaneously. And all these thermal and fluid phenomena take place in highly nonequilibrium state where thermal energy is not distributed equally to each degree of freedom of molecular motion in the vicinities of the solid-liquid interface. In the present paper, platinum and water are employed as solid and liquid, respectively. First, the structure and orientation of water molecules in the vicinities of the solid surfaces are analyzed and how these structure and orientation are influenced by the shear is considered. Based on this result, momentum and thermal energy transfer in the vicinities of and at the solid-liquid interfaces are investigated in detail. Results are compared with those of our previous study, in which monatomic and diatomic molecules are employed as liquid.
Photoluminescence dynamics in highly nonhomogeneously excited GaN
Authors: Kuokstis E. , Tamulaitis G. , Liu K. , Shur M. S. , Li J. W. , Yang J. W. , Asif Khan M.
Published: April 2007

The analysis of the room-temperature photoluminescence (PL) dynamics in GaN 4.5-μm-thick layers under different excitation intensities revealed nonexponentional PL decay with the fast and slow transients. The fast decay is clearly resolved under lower excitation (<100MW∕cm2) and high excitation (>100MW∕cm2). Theoretical modeling and comparison of the calculated results with the experimental data showed that the observed PL behavior is determined by the space nonhomogeneity of carriers generated by strongly absorbed 25ps duration laser pulse, the diffusion processes, as well as by the surface recombination. The latter mechanism plays an important role in the PL decay at lower excitation intensities, whereas the surface recombination saturates at high excitation levels. The radiative bimolecular recombination along with the stimulated emission predominates under these circumstances. The extracted carrier parameters are in good agreement with the values measured using other techniques.
Photodissociation yield spectroscopy of vinyl bromide cation generated by mass-analyzed threshold ionization: Vibrational spectroscopy and decay dynamics in the B̃ state
Authors: Lee Mina , Kim Myung Soo
Published: April 2007

A new technique [mass-analyzed threshold ionization (MATI)–photodissociation yield spectroscopy] to probe bound excited states of a cation was developed, which measures photodissociation yield of the cation generated by mass-analyzed threshold ionization. A vibrational spectrum of vinyl bromide cation in the B̃ state was obtained using this technique. Optical resolution in the low vibrational energy range of the spectrum was far better than in conventional MATI spectra. The origin of the B̃ state was found at 2.2578±0.0003eV above the first ionization onset. Almost complete vibrational assignment was possible for peaks appearing in the spectrum. Analysis of time-of-flight profiles of C2H3+ product ion obtained with different laser polarization angles suggested that photoexcited vinyl bromide cation remained in the B̃ state for several hundred picoseconds prior to internal conversion to the ground state and dissociation therein.
Vertical and lateral electrostatic forces in a tip-plane system studied with a Green function plus surface charge method
Authors: Konior J.
Published: April 2007

An effective method to calculate the electrostatic force between a microscopic tip and an infinite metallic plane is proposed and tested. The Green function method is used to integrate out exactly the potential distribution in the plane. The plane plus tip problem is thus reduced to a boundary value problem for the tip surface only, enabling solution by a standard numerical method. The main advantage of this approach is that systems with an arbitrary plane potential distribution may be solved with the same method and comparable numerical efficiency to problems with a constant plane potential. The method is used to calculate the electrostatic force on a tip due to a plane with a step potential and a local quadratic potential island. The calculated perpendicular force components agree with previously published theoretical results. In addition, lateral components of the tip-surface force are computed and shown to be comparable to the vertical component close to a potential step, in agreement with the published experimental data. This suggests the possibility of using lateral, as well as vertical force data in atomic force microscopy for the detection and imaging of potential steps.
High-density data acquisition system and signal preprocessor for interfacing with microelectromechanical system-based biosensor arrays
Authors: Rokkam M. , Chatni M. R. , ul Haque A. , De Carlo A. R. , Robinson B. F. , Irazoqui P. P. , Porterfield D. M.
Published: April 2007

Microelectromechanical system (MEMS) development has become an active area for research in over the last decade. This area has advanced rapidly in recent years due to the potential ability of MEMS devices to perform complex functions in a smaller area. There is also the prospect to develop devices that can (1) be easily manufactured, (2) offer low power consumption, and (3) reduce waste. Especially in the BioMEMS area these advantages are important in terms of applied devices for biosensing, clinical diagnostics, physiological sensing, flow cytometry, and other lab-on-a-chip applications. However, one major obstacle that has been overlooked is the interface of these microdevices with the macroworld. This is critical to enable applications and development of the technology, as currently testing and analysis of data from these devices is mostly limited to generic microprobe stations. New advancements in BioMEMS have to occur in concert with the development of data acquisition systems and signal preprocessors to fully appreciate and test these developing technologies. In this work, we present the development of a cost effective, high throughput data acquisition system (Bio-HD DAQ) and a signal preprocessor for a MEMS-based cell electrophysiology lab-on-a-Chip (CEL-C) device. The signal preprocessor consists of a printed circuit board mounted with the CEL-C device and a 64-channel filter/amplifier circuit array. The data acquisition system includes a high-density crosspoint switching matrix that connects the signal preprocessor to a 16-channel, 18bit, and 625kS∕s DAQ card. Multimodule custom software designed on LABVIEW 7.0 is used to control the DAQ system. While this version of the Bio-HD DAQ system and accompanying software are designed keeping in view the specific requirements of the CEL-C device, it is highly adaptable and, with minor modifications, can become a generic data acquisition system for MEMS development, testing, and application.
Electronic and structural properties of implanted xenon in amorphous silicon
Authors: Barbieri P. F. , Landers R. , Marques F. C.
Published: April 2007

The electronic and structural characteristics of xenon implanted in amorphous silicon are investigated. A different implantation approach, in which xenon atoms are implanted during the film deposition, was developed. Up to about 5at.% of xenon were implanted at energy as low as 100eV. X-ray absorption spectroscopy reveals that xenon atoms are dispersed in the amorphous Si network. The xenon 3d5∕2 binding energy, from x-ray photoelectron spectroscopy, as well as the initial state contribution and relaxation energy, from x-ray excited Auger electron spectroscopy, depend on the implantation energy and indicate that the xenon atoms are trapped in voids of different sizes.
Room temperature ferroelectric and ferromagnetic properties of multiferroics xLa0.7Sr0.3MnO3–(1−x)ErMnO3 (weight percent x=0.1, 0.2) composites
Authors: Dey P. , Nath T. K. , Nanda Goswami M. L. , Kundu T. K.
Published: April 2007

A different kind of multiferroics with composite character, xLa0.7Sr0.3MnO3 (LSMO)–(1−x)ErMnO3 (EMO) (x=0.1, 0.2), where EMO is the ferroelectric (FE) and LSMO is the ferromagnetic (FM) component, has been studied. Magnetization versus magnetic field measurements at 300K show prominent hysteresis loops, attesting room temperature FM behavior of these multiferroic composites. Dielectric constant (ε) as a function of temperature reveals that paraelectric-FE transition temperature TC* (525K) and maximum value of ε (318) remain almost unaffected for x=0.1 composite compared to pure EMO. Polarization versus electric field study at 300K give conclusive evidence of the presence of spontaneous polarization in this x=0.1 composite. For x=0.2 composite, decreasing TC* (430K) with increase in ε value (774) indicates diffusive FE character.
Fabrication of GeO2 layers using a divalent Ge precursor
Authors: Perego M. , Scarel G. , Fanciulli M. , Fedushkin I. L. , Skatova A. A.
Published: April 2007

Good quality and perfectly stoichiometric GeO2 layers are promising interlayers to be implemented in alternative devices based on high dielectric constant oxide/Ge(100). In this work, the authors report on the growth by atomic layer deposition of GeO2 films using a divalent Ge precursor combined with O3. The films are composed of smooth and perfectly stoichiometric GeO2. The contamination level is extremely low. The deposited GeO2 films have a band gap of 5.81±0.04eV. The conduction and valence band offsets at the GeO2∕Ge heterojunction are found to be 0.6±0.1 and 4.5±0.1eV, respectively.
Ordered silicon nanowire arrays via nanosphere lithography and metal-induced etching
Authors: Peng Kuiqing , Zhang Mingliang , Lu Aijiang , Wong Ning-Bew , Zhang Ruiqin , Lee Shuit-Tong
Published: April 2007

Two-dimensional silica colloidal crystal template is used to create metal nanohole arrays on a silicon surface, which enables the controlled fabrication of aligned silicon nanowire (SiNW) arrays via metal catalytic etching. By varying the size of silica colloidal crystals, aligned arrays of SiNWs with desirable diameter and density could be obtained. The formation of ordered SiNW arrays is due to selective and anisotropic etching of silicon induced by the silver pattern. The orientation of SiNW arrays is influenced by silver movement in silicon, and the wire axes are primarily along the ⟨100⟩ direction.
Kinetics of visible light photo-oxidation of Ge nanocrystals: Theory and in situ measurement
Authors: Sharp I. D. , Xu Q. , Yuan C. W. , Beeman J. W. , Ager J. W. , Chrzan D. C. , Haller E. E.
Published: April 2007

Photo-oxidation of Ge nanocrystals illuminated with visible laser light under ambient conditions was investigated. The photo-oxidation kinetics were monitored by in situ measurement of the crystalline Ge volume fraction by Raman spectroscopy. The effects of laser power and energy on the extent of oxidation were measured using both in situ and ex situ Raman scattering techniques. A mechanistic model in which the tunneling of photoexcited carriers to the oxide surface for electron activated molecular oxygen dissociation is proposed. This quantitative model describes all experimental photo-oxidation observations using physical parameters.
Localized etching of an insulator film coated on a copper wire using an atmospheric-pressure microplasma jet
Authors: Yoshiki Hiroyuki
Published: April 2007

Atmospheric-pressure microplasma jets (APμPJs) of Ar and Ar∕O2 gases were generated from the tip of a stainless steel surgical needle having outer and inner diameters of 0.4 and 0.2mm, respectively, with a rf excitation of 13.56MHz. The steel needle functions both as a powered electrode and a gas nozzle. The operating power is 1.2–6W and the corresponding peak-to-peak voltage Vp.p. is about 1.5kV. The APμPJ was applied to the localized etching of a polyamide-imide insulator film (thickness of 10μm) of a copper winding wire of 90μm diameter. The insulator film around the copper wire was completely removed by the irradiated plasma from a certain direction without fusing the wire. The removal time under the Ar APμPJ irradiation was only 3s at a rf power of 4W. Fluorescence microscopy and scanning electron microscope images reveal that good selectivity of the insulator film to the copper wire was achieved. In the case of Ar∕O2 APμPJ irradiation with an O2 concentration of 10% or more, the removed copper surface was converted to copper monoxide CuO.
Coulomb blockade in a self-assembled GaN quantum dot
Authors: Nakaoka T. , Kako S. , Arakawa Y. , Tarucha S.
Published: April 2007

The authors report on transport phenomena in single self-assembled GaN quantum dots using metallic leads with a nanoscale gap. The nitride device works as a single electron transistor. Measurement of the stability diagram at 12K shows Coulomb blockade regions with a single electron charging energy of about 10meV.
Anisotropy and strength of vortex pinning centers in YBa2Cu3O7−x coated conductors
Authors: Gutiérrez J. , Puig T. , Obradors X.
Published: April 2007

An experimental powerful methodology is proposed to evaluate and quantify the anisotropy and strength of the different pinning contributions of YBa2Cu3O7−x coated conductors by combining angular dependent in-field critical current measurements in the whole temperature range. A clear separation between isotropic and anisotropic pinning centers and a further classification into weak and strong pinning centers are performed. These analyses envision to establish a correlation between defect microstructure and critical currents which is essential for artificial engineering high-performance nanostructured coated conductors.
Well-ordered L1-FePt nanoparticles synthesized by improved SiO2-nanoreactor method
Authors: Tamada Yoshinori , Yamamoto Shinpei , Takano Mikio , Nasu Saburou , Ono Teruo
Published: April 2007

It was found that the well-ordered L10 structure is formed in the FePt nanoparticles synthesized by the improved “SiO2-nanoreactor” method, whereas the previously employed annealing condition has suffered from the presence of the unconverted fcc-FePt nanoparticles which are superparamagnetic at room temperature. The L10-FePt nanoparticles prepared by this method showed a smooth hysteresis loop with no kink, and the room temperature coercivity reaches an extremely large value of 28kOe, even though the particle size is 6.7nm in diameter. The Mössbauer hyperfine parameters of the nanoparticles are very close to those of the bulk L10-FePt alloy, indicating that they possess magnetic moments comparable to the bulk even at the particle surface.
Synthesis of gold regular octahedra with controlled size and plasmon resonance
Authors: Zhang Jianhui , Liu Huaiyong , Wang Zhenlin , Ming Naiben
Published: April 2007

Using polyvinyl pyrrolidone (PVP) as the structure-directing agent, the high shape-selective synthesis of the gold regular octahedra with purity up to 90% has been realized in the water/PVP/n-pentanol system created to realize the specific selective adsorption of PVP on Au which directs Au to grow in the form of regular octahedron. By modifying the water/PVP/n-pentanol interface via varying the amount of PVP and water and adding C6H5O7Na3∙2H2O, the edge length and plasmon resonance position of the Au regular octahedra can be tuned in the ranges of 33–120 and 538–683nm, respectively. The truncation of octahedron reduces the plasmon resonance in wavelength.
Formation process of high reflective Ni∕Ag∕Au Ohmic contact for GaN flip-chip light-emitting diodes
Authors: Chang Liann-Be , Shiue Ching-Chuan , Jeng Ming-Jer
Published: April 2007

The combinations of Ni, Ag, and Au which form both Ohmic and reflective multilayer contacts for flip-chip light-emitting diode applications are examined. A strong interdiffusion of Ohmic metals and GaN during the annealing process is found to result in poor reflectance (63% at the wavelength of 465nm). The authors propose a two step metallization method, the Ni∕Ag double layer is first deposited/annealed followed by the deposition of Au, to improve the correspondent reflectivity (as high as 92%). This method is different from the conventional one step Ni∕Ag∕Au formation method in which these three metals are deposited together and then annealed. The secondary ion mass spectrometry depth profiles indicate that a wide interdiffusion region existed only in the conventional one step formation samples; thus the low reflectivity of Ni∕Ag∕Au-annealed contacts can be attributed to the strong interdiffusion of Ohmic metal into GaN. Their proposed two step metallization method avoids the strong interdiffusion and improves the reflectivity effectively.
Cluster glass induced exchange biaslike effect in the perovskite cobaltites
Authors: Luo Wanju , Wang Fangwei
Published: April 2007

Exchange biaslike phenomenon is observed in the Ba doped perovskite polycrystalline LaCoO3. The magnetic hysteresis loop shifts in both horizontal and vertical directions at 5K when the samples are cooled down to 5K in a magnetic field. The nature of this magnetic anisotropy is ascribed to the freezing properties of the local anisotropy in the cluster glass system. The magnetic shifts in horizontal and vertical directions can be derived directly under the principle that the spins of a cluster are frozen in random orientations and aligned to the field direction upon zero field and field cooling, respectively.
Compact and inexpensive continuous-wave subterahertz imaging system with a fiber-coupled multimode laser diode
Authors: Shibuya Kyoji , Tani Masahiko , Hangyo Masanori , Morikawa Osamu , Kan Hirofumi
Published: April 2007

The authors demonstrate a continuous-wave subterahertz imaging system using a fiber-coupled multimode laser diode (MLD) and photoconductive antennas. The terahertz wave generation is based on photomixing between simultaneously oscillating longitudinal modes of the MLD. The system is compact and inexpensive since a fiber-coupled MLD is used as a light source. By using the nearly monochromatic property of the generated terahertz wave, both amplitude and phase information at a specific frequency are obtained by measuring the signal at appropriate two points on the delay line.
Carrier dynamics with blue emission in asymmetrically coupled GaN∕Al0.5Ga0.5N∕GaN multiquantum wells
Authors: Park Young S. , Im Hyunsik , Kang T. W.
Published: April 2007

Coupled multiquantum well structures consisting of GaN(10Å)∕Al0.5Ga0.5N(22Å)∕GaN(20Å) bounded by Al0.5Ga0.5N (100Å) barriers were characterized by photoluminescence measurements. The recombination dynamics of carriers localized in asymmetric double quantum wells were studied by analyzing temperature-dependent and time-resolved photoluminescence spectra. The authors observed carrier transfer between weakly and strongly localized states which resulted in a stronger blue emission with increasing temperature, and they analyzed its effects on the spectra in terms of the quantum confined screening effect. Time-resolved measurements yielded lifetimes of various transitions which had different origins ranging between ∼120 and ∼1300ns.
Terahertz luminescence in strained GaAsN:Be layers under strong electric fields
Authors: Shalygin V. A. , Vorobjev L. E. , Firsov D. A. , Panevin V. Yu. , Sofronov A. N. , Andrianov A. V. , Zakhar’in A. O. , Egorov A. Yu. , Gladyshev A. G. , Bondarenko O. V. , Ustinov V. M. , Zinov’ev N. N. , Kozlov D. V.
Published: April 2007

The authors report on the experimental studies of terahertz emission from strained GaAsN∕GaAs microstructures doped with beryllium at the conditions of electric breakdown of the shallow impurity. The terahertz emission spectrum demonstrates several distinctive signatures that are related to spontaneous optical transitions between resonant and localized states of the acceptor. The energy spectrum calculated for the Be acceptor in the GaAsN∕GaAs heterostructure fits reasonably well with the experimentally observed peaks.
Super-Poissonian noise in a quantum dot p-i-n junction
Authors: Chen Yueh-Nan
Published: April 2007

The shot-noise spectrum of a quantum dot p-type/intrinsic/n-type (p-i-n) junction is investigated theoretically. Without making the Markovian approximation, effect from the nonrelativistic cutoff frequency of the exciton decay may be revealed with the feature of super-Poissonian noise. To become practically observable in experiments, high quality quantum well or quantum dot arrays, which exhibit super-radiance, in a p-i-n junction is suggested to enhance the zero-frequency noise (Fano factor).
Plasmonic surface-wave splitter
Authors: Gan Qiaoqiang , Guo Baoshan , Song Guofeng , Chen Lianghui , Fu Zhan , Ding Yujie J. , Bartoli Filbert J.
Published: April 2007

The authors present an analysis of a plasmonic surface-wave splitter, simulated using a two-dimensional finite-difference time-domain technique. A single subwavelength slit is employed as a high-intensity nanoscale excitation source for plasmonic surface waves, resulting in a miniaturized light-surface plasmon coupler. With different surface structures located on the two sides of the slit, the device is able to confine and guide light waves of different wavelengths in opposite directions. Within the 15μm simulation region, it is found that the intensity of the guided light at the interface is roughly two to eight times the peak intensity of the incident light, and the propagation length can reach approximately 42 and 16μm and at the wavelengths of 0.63 and 1.33μm, respectively.
Response of mannitol-producing Arabidopsis thaliana to abiotic stress
Authors: Sickler Christine M. , Edwards Gerald E. , Kiirats Olavi , Gao Zhifang , Loescher Wayne
Published: April 2007

In celery, mannitol is a primary photosynthetic product that is associated with celery’s exceptional salt tolerance. Arabidopsis plants transformed with celery’s mannose-6-phosphate reductase (M6PR) gene produce mannitol and grow normally in the absence of stress. Daily analysis of the increase in growth (fresh and dry weight, leaf number, leaf area per plant and specific leaf weight) over a 12-day period showed less effect of salt (100 mm NaCl) on the M2 transformant than wild type (WT). Following a 12-day treatment of WT, M2 and M5 plants with 100 or 200 mm NaCl the total shoot fresh weight, leaf number, and leaf area were significantly greater in transformants than in WT plants. The efficiency of use of energy for photochemistry by PSII was measured daily under growth conditions. In WT plants treated with 100 mm NaCl, the PSII yield begin decreasing after 6 days with a 50% loss in yield after 12 days, indicating a severe loss in PSII efficiency; whereas, there was no effect on the transformants. Under atmospheric levels of CO2, growth with 200 mm NaCl caused an increase in the substomatal levels of CO2 in WT plants but not in transformants. It also caused a marked decrease in carboxylation efficiency under limiting levels of CO2 in WT compared with transformants. When stress was imposed and growth reduced by withholding water for 12 days, which resulted in a similar decrease in relative water content to salt-treated plants, there were no differences among the genotypes in PSII yields or growth. The results suggest mannitol, which is known to be a compatible solute and antioxidant, protects photosynthesis against salt-related damage to chloroplasts.
Research note:Autoradiography utilising labelled ascorbic acid reveals biochemical and morphological details in diverse calcium oxalate crystal-forming species
Authors: Kostman Todd A. , Tarlyn Nathan M. , Franceschi Vincent R.
Published: April 2007

Many plant species accumulate calcium oxalate crystals in specialised cells called crystal idioblasts. In one species of crystal-forming plants (Pistia stratiotes L.; forming raphide crystals), it has been shown that ascorbic acid is the primary precursor of oxalic acid. The question remains if this is true of other calcium oxalate crystal-forming plants. One way of answering the above question is by examining ascorbic acid as the oxalic acid precursor in diverse species with a variety of crystal types. In this study we tested ascorbic acid as the primary precursor of oxalic acid in four different species, each forming one of the four, thus far, unexamined crystal types: water hyacinth, styloid (and raphide); tomato, crystal sand; winged-bean, prismatic; water lily, astrosclereids with surface prismatic crystals. Pulse–chase feeding of 1-[14C]-ascorbic acid followed by resin embedding, microautoradiography and light microscopy were employed to examine incorporation of label into calcium oxalate crystals. For the species and crystal types studied, ascorbic acid is the primary precursor of oxalic acid and further, oxalic acid is added to crystals in patterns that correlate with the age and type of crystal involved.
Phase-separation in ion-containing mixtures in electric fields
Authors: Tsori Yoav , Leibler Ludwik
Published: April 2007

When a liquid mixture is subjected to external electric fields, ionic screening leads to field gradients. We point out that, if the mixture is initially in the homogeneous phase, this screening can bring about a robust phase-separation transition with two main features: (
i
) the phase separation is expected to occur in any electrode geometry, and (
ii
) the voltage required is typically of the order of 1 V and even less. We discuss several applications of the effect relevant to the field of microfluidics, focusing on the creation of a nanometer-scale lubrication layer in the phase separation process and the modification of the slip length.
Efficacy of a Silicone Urinary Catheter Impregnated with Chlorhexidine and Triclosan Against Colonization With Proteus mirabilis and Other Uropathogens
Authors: Gaonkar Trupti A. , Caraos Lauserpina , Modak Shanta
Published: April 2007

We sought to develop an infection-resistant urinary catheter. We evaluated 3 types of catheters for their efficacy against uropathogens in an in vitro model of the urinary tract. The catheter impregnated with Chlorhexidine and triclosan suppressed the growth of uropathogens, includingProteus mirabilis, for 20-30 days or longer.
Two Nosocomial Pertussis Outbreaks and Their Associated Costs—King County, Washington, 2004
Authors: Baggett Henry C. , Duchin Jeffrey S. , Shelton William , Zerr Danielle M. , Heath Joan , Ortega-Sanchez Ismael R. , Tiwari Tejpratap
Published: April 2007

Objective.

Pertussis outbreaks in healthcare settings result in resource-intensive control activities, but studies have rarely evaluated the associated costs. We describe and estimate costs associated with 2 nosocomial pertussis outbreaks in King County, Washington, during the period from July 25 to September 15, 2004. One outbreak occurred at a 500-bed tertiary care hospital (hospital A), and the other occurred at a 250-bed pediatric hospital (hospital B).

Methods.

We estimated the costs of each outbreak from the hospitals' perspective through standardized interviews with hospital staff and review of contact tracing logs. Direct costs included personnel time and laboratory and medication costs, whereas indirect costs were those resulting from hospital staff furloughs.

Results.

Hospital A incurred direct costs of $195,342 and indirect costs of $68,015; hospital B incurred direct costs of $71,130 and indirect costs of $50,000. Cost differences resulted primarily from higher personnel costs at hospital A ($134,536), compared with hospital B ($21,645). Total cost per pertussis case was $43,893 for hospital A (6 cases) and $30,282 for hospital B (4 cases). Total cost per person exposed to a pertussis patient were $357 for hospital A (738 exposures) and $164 for hospital B (737 exposures).

Conclusions.

Nosocomial pertussis outbreaks result in substantial costs to hospitals, even when the number of pertussis cases is low. The cost-effectiveness of strategies to prevent nosocomial pertussis outbreaks, including vaccination of healthcare workers, should be evaluated.
Quality of Hand Hygiene in a Pediatric Hospital in Rio de Janeiro, Brazil
Authors: Hofer C. B. , Abreu T. F. , Silva E. G. , Sepúlveda C. A. , Gibara F. A. , Lopes N. R. L. , Mota A. F. , Barreiro S. A. , Santos L. M. , Souza E. N. , Frota A. C. C.
Published: April 2007

We assessed the quality of hand hygiene among healthcare workers at a pediatrics hospital in Rio de Janeiro, Brazil. Hand hygiene was performed in 491 (34%) of 1,455 opportunities. Of these hand hygiene events, correct performance was observed in only 173 (35%). Multivariate analysis revealed that correct performance of hand hygiene was associated with the use of an alcohol-based product and a lack of jewelry (for all events) and employment in an infirmary with a comparatively higher ratio of nurses to patients (for events involving nurses).
Associations Between Surgical Site Infection Risk and Hospital Operation Volume and Surgeon Operation Volume Among Hospitals in the Dutch Nosocomial Infection Surveillance Network
Authors: Muilwijk Jan , Hof Susan van den , Wille Jan C.
Published: April 2007

Objective.

To examine the association between hospital operation volume and surgeon operation volume and the risk of surgical site infection (SSI).

Design.

Prospective, multicenter cohort study based on surveillance data.

Methods.

Data were obtained from the Dutch surveillance network for nosocomial infections (Preventie Ziekenhuisinfecties door Surveillance [PREZIES]) on 9 different types of orthopedic surgery, general surgery, and gynecology procedures performed during 1996-2003. Multilevel logistic regression analysis was performed to assess the independent effect of hospital volume and surgeon volume on SSI risk.

Results.

Hospital volume was not significantly associated with SSI risk for any of the selected procedures. Low surgeon volume was associated with an increased risk for an infection for 7 of 9 types of procedures, although this effect was statistically significant only for knee arthroplasty. For 4 procedures, the odds of exceeding the 75th percentile for duration of surgery were greater when the surgeon volume was low than when the surgeon volume was moderate or high.

Conclusions.

Patients operated on by surgeons with a low operation volume seem to have a higher risk of developing an SSI with some procedures, particularly knee arthroplasty. The higher SSI risk for surgeons with a low operation volume is possibly partly mediated by the longer duration of surgery, a well-known risk factor for development of SSI.
Policies for Endotracheal Suctioning of Patients Receiving Mechanical Ventilation: A Systematic Review of Randomized Controlled Trials
Authors: Niël-Weise B. S. , Snoeren R. L. M. M. , van den Broek P. J.
Published: April 2007

Objective.

The Dutch Working Party on Infection Prevention (Werkgroep Infectiepreventie [WIP]) aimed to determine whether certain policies on endotracheal suctioning are better than others in terms of prevention of ventilator-associated pneumonia (VAP) in patients receiving mechanical ventilation in the intensive care unit.

Methods.

Publications were retrieved by a systematic search of Medline and the Cochrane Library for literature published before February 2006. Additionally, the reference lists of all identified trials were examined. All randomized trials, quasi-randomized trials, and systematic reviews or meta-analyses of randomized or quasi-randomized trials that compared different policies on endotracheal suctioning for patients receiving mechanical ventilation in the intensive care unit were selected. Two reviewers independently assessed trial quality and extracted data. Disagreements were resolved by discussion with a third reviewer. Data from the original publications were used to calculate the relative risk of VAP. Data for VAP were combined in the analysis where appropriate, by use of a random-effects model.

Results.

Ten trials were included in the review. The quality of the trials and the way they were reported were generally unsatisfactory. Eight low-quality trials indicate that use of closed instead of open suction systems has no effect on the incidence of VAP. Two moderate-quality trials indicate that changing in-line suction catheters less frequently than every 24 hours does not increase the incidence of VAP.

Conclusion.

The WIP recommends that there be no preferential use of either open or closed endotracheal suction systems to reduce the rate of VAP, but it elucidates that the quality of the evidence is low. Considerations other than prevention of VAP should determine the choice of the suction system. When closed systems are used, the WIP recommends changing the in-line suction catheters every 48 hours. In case of mechanical failure or soiling of the suction system, they may be changed more frequently.
Immunity Against Infectious Diseases Predictive Value of Self-Reported History of Vaccination and Disease
Authors: Trevisan Andrea , Frasson Clara , Morandin Marta , Beggio Michela , Bruno Alberto , Davanzo Elisabetta , Marco Livio Di , Simioni Livio , Amato Guglielmo
Published: April 2007

Objective.

To determine whether self-reported history of disease and/or vaccination is predictive of immunity against hepatitis B, varicella, rubella, mumps, and measles.

Design.

The seroprevalence of viral antibodies and the predictive value of a self-report questionnaire were determined for 616 paramedical students who matriculated into Padua Medical School (Padua, Italy) during 2003-2005.

Results.

The majority of subjects (86.9%) remembered being vaccinated against hepatitis B but had no recollection of disease. Among vaccinees, 1.5% showed markers of previous infection, 6.7% tested negative for anti-hepatitis B virus surface antigen (anti-HBsAg) antibodies, and 91.8% tested positive for anti-HBsAg. Self-reported vaccination history had a positive predictive value of 93.2% for test results positive for immunity against hepatitis B. Immunity against varicella (93.7% of subjects) and rubella (95.5%) was high, compared with immunity against mumps (79.9%) and measles (83.1%). In addition, results of tests for detection of immunity against mumps and measles were equivocal for more than 7% of subjects, probably because their vaccination regimen was not completed. Self-reported histories of varicella disease and rubella disease and vaccination had high positive predictive values (greater than 98% each) for testing positive for antiviral antibodies, compared with self-reported histories of mumps disease and vaccination and measles disease and vaccination; however, high positive predictive values were observed for self-reported histories of mumps only (92.0%) and measles only (94.7%).

Conclusions.

The self-report questionnaire used in this study did not accurately predict immunity against 5 transmittable but vaccine-preventable diseases. A complete serological evaluation of healthcare workers, followed by vaccination of those with negative or equivocal results of serological tests, is an appropriate measure to decrease the risk of infection in this population.
Text and Identity
Authors: Lieu Judith
Published: April 2007

The literary productivity of early Christianity invites the model of textual communities. This productivity includes the appropriation of the Jewish Scriptures and other writings and the claim to their correct interpretation, as well as the creation of a range of new writings reflecting both continuities and discontinuities with contemporary conventions. The selection of particular texts as authoritative is part of a process of self-definition, which excludes other claimants. Approached independently of such processes allows the diversity of texts to challenge rigid categories of Christianity versus Judaism or of orthodoxy versus heresy.
Boundaries
Authors: Lieu Judith
Published: April 2007

Recent social-scientific study has explored the role of boundaries in the construction and maintenance of identity as points of transformation and negotiation as well as of exclusion. Applied to Judaism, her boundary-markers are shown to be more fluid and subject to selection and transformation than is often recognized. Patterns of continuity and of discontinuity with these produce different and even competing understandings of early Christianity. Different contexts and different genres also highlight different boundary lines, while in all cases there is evidence that socially these boundaries between groups were regularly crossed or negotiated.
Space and Place
Authors: Lieu Judith
Published: April 2007

Spatial origins and a place to inhabit are integral to perceptions of Roman identity. In Jewish thought, land, city, and temple play a focal role, while the experience of exile and diaspora demanded their reinterpretation. Besides redefining these concepts, early Christian writings had to negotiate, with a range of results, the tensions between the local and the universal, and between belonging to and choosing alienation from society.
The Christian Race
Authors: Lieu Judith
Published: April 2007

The use of and claims to labels such as Jews, Israelis, and Hebrew carry different resonances and potential in Jewish and Graeco-Roman sources, which are furthered in early Christian writings. The Jewish development of a language and of strategies of ethnic identity is adopted by some early Christian writings. In others, the emergence of a distinctive terminology, ‘Christian’ and ‘Christianity’, is focal, although others found this hazardous and avoided it. The use of labels both to separate and claim authenticity for oneself as well as to denigrate others is common throughout.
‘The Other’
Authors: Lieu Judith
Published: April 2007

Common to nearly all constructions of identity is that of ‘the [stereotyped] other’, the ‘not-us’, often defined negatively, in opposition to, and in order to sustain, a self-understanding. In Graeco-Roman thought, this is represented by the idea of ‘the barbarian’, and in Jewish thought by ‘the Gentiles’. In early Christian writings, we can explore the function and construction of ‘the Gentiles’, ‘the Greeks, and ‘the Jews’. In addition, the language of otherness is applied to an undifferentiated ‘world’ as well as to those who hold other views, the construction of heresy. Yet, as in modern debate, other models of a relationship with the Other than the hostile are possible and leave their traces.
Tissue Transglutaminase Antibodies Are a Useful Serological Marker for the Diagnosis of Celiac Disease in Patients With Down Syndrome
Authors: Shamaly Hussein , Hartman Corina , Pollack Shimon , Hujerat Mohammad , Katz Rina , Gideoni Osnat , Shamir Raanan
Published: April 2007

Background:

Celiac disease (CD) is overrepresented among patients with Down syndrome (DS), who frequently lack any typical symptoms. Therefore, screening for CD is recommended in this high‐risk group. The aim of the study was to determine the prevalence of CD in Arab children with DS and evaluate the contribution of immunoglobulin (Ig) A and IgG anti‐gliadin antibodies (AGA), IgA and IgG tissue transglutaminase (TTG) antibodies, and IgA anti‐endomysial antibodies (EMA) to screen for CD in children with DS.

Patients and Methods:

A total of 52 Arab patients with DS and 52 healthy Arab control subjects were studied for CD using various serological markers. Data on age, sex, weight, height, gastrointestinal symptoms, and endocrine abnormalities were recorded. Human leukocyte antigen (HLA) was studied in patients undergoing small intestinal biopsy.

Results:

Five patients with DS were IgA TTG–positive and only 1 patient with DS was IgG TTG–positive. EMA was negative in all patients with DS. TTG (IgA and IgG) and EMA were negative in all control children. IgA AGA was positive in 12 patients with DS and 3 control subjects (P = 0.02), whereas IgG AGA was positive in 41 patients with DS and 26 control subjects (P = 0.004). Only children testing positive for TTG underwent upper endoscopy with duodenal biopsy. Two children with DS were diagnosed with CD. Both patients were IgA TTG–positive. One was HLA DQ2–positive and another was negative for HLA DQ2 and DQ8.

Conclusions:

CD is prevalent (3.8%) in Arab patients with DS. Based on our cohort, IgA TTG is useful in diagnosing patients with CD and DS.
Association between fluconazole susceptibility and genetic relatedness among Candida tropicalis isolates in Taiwan
Authors: Wang Jang-Shiun , Li Shu-Ying , Yang Yun-Liang , Chou Hsiao-Hui , Lo Hsiu-Jung
Published: April 2007

Among the 162 Candida tropicalis isolates collected in the Taiwan Surveillance of Antimicrobial Resistance of Yeasts in 1999, 23 (14.2 %) had fluconazole MICs ≥64 mg l−1, and thus fulfilled the definition of resistance. Random amplified polymorphic DNA assay showed that all 23 fluconazole-resistance C. tropicalis isolates collected from different hospitals around Taiwan were closely related. Two distinct pulsotypes associated with fluconazole susceptibility were identified when these 23 resistant isolates, along with 13 susceptible ones, were analysed by PFGE.
A paradigm for the molecular identification of Mycobacterium species in a routine diagnostic laboratory
Authors: Williams K. J. , Ling C. L. , Jenkins C. , Gillespie S. H. , McHugh T. D.
Published: April 2007

The aim of this study was to improve the identification ofMycobacteriumspecies in the context of a UK teaching hospital. Real-time PCR assays were established to enable the rapid differentiation betweenMycobacterium tuberculosis(MTB) complex andMycobacteriumspecies other thantuberculosis(MOTT), followed by 16S rRNA gene sequencing for the speciation of MOTT. Real-time PCR assays gave comparable results to those from the reference laboratory. The implementation of these PCR assays using an improved bead extraction method has enhanced the mycobacterial diagnostic service at the Royal Free Hospital by providing a rapid means of differentiating between MTB complex and MOTT, and would be simple to implement in similar laboratories. Sequence analysis successfully identified a range ofMycobacteriumspp. representative of those encountered in the clinical setting of the authors, includingMycobacterium aviumcomplex,Mycobacterium fortuitumgroup,Mycobacterium chelonae–Mycobacterium abscessusgroup,Mycobacterium xenopiandMycobacterium gordonae. It provides a useful tool for the identification of MOTT when clinically indicated.
Effect of intensive handwashing in the prevention of diarrhoeal illness among patients with AIDS: a randomized controlled study
Authors: Huang David B. , Zhou Jing
Published: April 2007

Patients with AIDS frequently develop diarrhoeal illness. In this randomized, controlled study, 260 patients were screened for those who had not had diarrhoea in the preceding 3 months and who had received a stable highly active antiretroviral therapy regimen for at least 6 weeks prior to the study enrolment. A total of 148 patients met the inclusion criteria and were enrolled: 75 patients were randomly assigned to an intensive handwashing intervention (i.e. handwashing after defecation, after cleaning infants who had defecated, before preparing food, before eating, and before and after sex) and 73 patients were randomly assigned to the control group. Patients in both groups were called weekly by telephone to determine compliance with handwashing and to determine the number of diarrhoeal episodes for the preceding week. Patients were observed for 1 year. Patients assigned to the intensive handwashing intervention group washed their hands more frequently compared with the control group (seven vs four times a day, respectively; P <0.05) and developed fewer episodes of diarrhoeal illness (1.24±0.9 vs 2.92±0.6 new episodes of diarrhoea, respectively; P <0.001) during the 1 year observation. The most common pathogens identified in both groups in patients who developed diarrhoeal illness were Giardia lamblia, Cryptosporidium, Entamoeba histolytica and Shigella flexneri. These data suggest that intensive handwashing reduces diarrhoeal illness in patients with AIDS.