bluuebunny/crossref_metadata_2025 huggingface dataset:
A study on the reliability of indium solder die bonding of high power semiconductor lasers
Authors: Liu Xingsheng , Davis Ronald W. , Hughes Lawrence C. , Rasmussen Michael H. , Bhat Rajaram , Zah Chung-En , Stradling Jim
Published: July 2006

High power semiconductor lasers have found increased applications. Indium solder is one of the most widely used solders in high power laser die bonding. Indium solder has some advantages in laser die bonding. It also has some concerns, however, especially in terms of reliability. In this paper, the reliability of indium solder die bonding of high power broad area semiconductor lasers was studied. It was found that indium solder bonded lasers have much shorter lifetime than AuSn solder bonded devices. Catastrophic degradation was observed in indium solder bonded lasers. Nondestructive optical and acoustic microscopy was conducted during the lifetime testing to monitor the failure process and destructive failure analysis was performed after the lasers failed. It was found that the sudden failure was caused by electromigration of indium solder at the high testing current of up to 7A. It was shown that voids were created and gradually enlarged by indium solder electromigration, which caused local heating near the facets of the laser. The local heating induced catastrophic optical mirror damage (COMD) of the lasers. It was discussed that current crowding, localized high temperature, and large temperature gradient contributed to the fast indium solder electromigration. It was observed that some bright pattern structures appeared on the front facet of the indium solder bonded lasers after the devices failed and the bright patterns grew and spread upon further testing. Failure analysis showed that the bright pattern structure apparent on the front facet was due to crystallization of the TiOx material of the front facet coating as a result of overheating during lifetime testing. It was concluded that indium solder is not suitable for high power laser applications due to electromigration at high current densities and high temperatures.
Mechanism of poly(methyl methacrylate) film formation by pulsed laser deposition
Authors: Süske Erik , Scharf Thorsten , Krebs Hans-Ulrich , Junkers Tanja , Buback Michael
Published: July 2006

The formation of poly(methyl methacrylate) films during pulsed laser deposition was studied by deposition at different substrate temperatures and by using targets with defined molecular mass and tacticity. At room temperature, the films (deposited from high-molecular weight polymer targets) mainly consist of macromolecules with average molecular masses of about 8000g∕mol. Up to substrate temperatures of 100°C, this average mass remains constant, suggesting the transport of larger polymeric fragments from the target to the substrate surface. This hypothesis is also confirmed by experiments using target material of lower molecular weight and of defined tacticity. At temperatures above 100°C and thus at conditions of enhanced mobility, the substrate molecular weight increases with temperature. The experiments indicate that the films are formed by deposition and reaction of macromolecular species. Radical polymerization of monomers described in the literature as a dominating film formation process plays no significant role.
The influence of oxygen content on the α to ω phase transformation and shock hardening of titanium
Authors: Cerreta E. , Gray G. T. , Lawson A. C. , Mason T. A. , Morris C. E.
Published: July 2006

In this study the influence of alloy chemistry on the propensity of omega phase formation in two titanium alloys during shock loading is examined. The effect of peak shock stress on the phase stability and substructural evolution of high purity and A-70 (3700ppm oxygen) titanium was probed utilizing velocity interferometer system for any reflector and post shock substructural analysis. While in the high purity titanium the alpha to omega phase transformation was found to occur at 10.4GPa, no transformation was observed in the A-70 material for stresses up to 35GPa. Transmission electron microscopy analysis and neutron diffraction of shock-recovered samples confirmed these results and probed the details of twin and dislocation structures. Debye temperature data are also presented and the Debye-Waller temperatures for the alpha and omega phases in the high purity titanium are calculated. Finally, the compressive, quasistatic reload behaviors of both high purity and A-70 titanium are compared to the as-annealed counterparts at comparable strains and discussed in terms of the phase transformation and the shock-induced defect generation.
Segregation trends of the metal alloys Mo–Re and Mo–Pt on HfO2: A first-principles study
Authors: Knizhnik A. A. , Gavrikov A. V. , Safonov A. A. , Iskandarova I. M. , Bagatur’yants A. A. , Potapkin B. V. , Fonseca L. R. C. , Stoker M. W.
Published: July 2006

Using first-principles calculations, we compared the segregation trends at the surface of metal alloys with those at an interface with HfO2. The choice of this oxide was motivated by its significance as a potential replacement for SiO2 in advanced transistors. We considered Mo–Re and Mo–Pt alloys as typical examples of disordered and ordered alloys, respectively. The segregation to the surface/interface was analyzed in terms of metal and oxygen adsorption energies. It is shown that chemical bonding at the metal/oxide interface strongly influences segregation both in Mo–Re and Mo–Pt alloys. In particular, bonding with oxygen atoms at the oxide/Mo–Re alloy interface depletes the Re content of the interfacial layer. In the case of Mo–Pt on HfO2 an oxygen-rich interface promotes the formation of one monolayer (but not two monolayers) of Mo separating PtMox from HfO2, while a stoichiometric interface favors an abrupt PtMox∕HfO2 interface. This study also shows that the presence of Mo in the alloy stabilizes Pt which can potentially decrease the tendency of Pt to diffuse into the oxide matrix. The individual constituents of these intermetallic compounds exhibit high vacuum work functions, and therefore these alloys are also likely to have sufficiently high work functions to be considered as promising candidates for p-type gate electrodes in future generations of transistors.
In situ determination of nitrogen content in InGaAsN quantum wells
Authors: Reentilä O. , Mattila M. , Knuuttila L. , Hakkarainen T. , Sopanen M. , Lipsanen H.
Published: July 2006

The growth of InGaAsN∕GaAs multiple quantum well structures by metal-organic vapor phase epitaxy is monitored by in situ reflectometry. The nitrogen incorporation is found to depend superlinearly on the precursor flow and a threshold value for the flow is observed. By in situ measurements of the InGaAsN quantum well samples with a fixed indium content, the change in the reflectance during the quantum well growth is found to be linearly dependent on the quantum well nitrogen content. A model to determine the nitrogen content already during the growth is developed. Moreover, the field of application of in situ reflectance monitoring is extended from thick layers to thin layers, including quantum wells.
Thermal variation of current perpendicular-to-plane giant magnetoresistance in laminated and nonlaminated spin valves
Authors: Delille F. , Manchon A. , Strelkov N. , Dieny B. , Li M. , Liu Y. , Wang P. , Favre-Nicolin E.
Published: July 2006

The current perpendicular-to-plane (CPP) giant magnetoresistance (GMR) was investigated as a function of temperature in 500nm diameter spin-valve pillars of the form PtMn 7nm∕AP2∕Ru0.8nm∕AP1∕Cu3.2nm∕F. AP2∕Ru∕AP1 represents a synthetic ferrimagnetic pinned layer and F is either a simple Co50Fe50 5nm free layer or a laminated (Co50Fe501nm∕Cu0.3nm)4∕Co50Fe501nm free layer. The purpose of the lamination is to increase the CPP resistance by taking advantage of the large CoFe∕Cu interfacial resistance. As expected, we observed that the CPP resistance and absolute magnetoresistance (AΔR) are increased in the laminated structure. However, the CPP magnetoresistance ratio (ΔR∕R) does not increase as much as expected if considering the increase in the relative resistance weight of the active part of the spin valve due to lamination. To understand this observation, the semiclassical theory of CPP GMR including bulk and interfacial spin relaxation effects was used to quantitatively interpret the data between 2 and 300K. The quantitative analysis indicates that a quite significant spin-memory loss takes place at CoFe∕Cu interfaces which reduces the expected GMR of the laminated multilayer. The spin-memory loss at Co50Fe50∕Cu interfaces is found to be 52% at 4K and 56% at 300K, to be compared with 25% at 300K for Cu∕Co interfaces [Eid et al., J. Appl. Phys. 93, 3445 (2003) and Bozec et al., J. Appl. Phys. 87, 4334 (2000)].
Lattice thermal conductivity in a silicon nanowire with square cross section
Authors: Lü Xiang , Chu Junhao
Published: July 2006

We present a theoretical model of lattice thermal conductivity in a silicon nanowire with square cross section. This model takes into account the modifications of the acoustic phonon dispersion and boundary scattering on the side walls. A good approximation of exact lattice thermal conductivity is obtained by the yielded precise phonon dispersion relations under the xyz algorithm of Nishiguchi et al. [J. Phys.: Condens. Matter 9, 5751 (1997)] and the inclusion of three scattering events on the side walls from the phonon Boltzmann transport equation. Comparison is also made with the thermal conductivity of a cylindrical nanowire.
Laser mode conversion into a surface plasma wave in a metal coated optical fiber
Authors: Liu C. S. , Kumar Gagan , Tripathi V. K.
Published: July 2006

An optical fiber, coated with thin metal film, supports two distinct kinds of waves, viz., body waves that propagate through the fiber as transverse magnetic (TM) and transverse electric modes, and surface plasma waves that propagate on metal free space interface. When the metal has a ripple of suitable wave number q, a body wave of frequency ω and propagation constant kz induces a current at ω,kz+q in the ripple region that resonantly derives a surface plasma wave. When the metal surface has metallic particles attached to it and molecules are adsorbed on them, the surface plasma wave undergoes surface enhanced Raman scattering with them. The scattered signals propagate backward as a TM body wave and can be detected.
Fabrication of quasi-one-dimensional oxide nanoconstriction array via nanosphere lithography: A simple approach to nanopatterns of multicomponent oxides
Authors: Liu H. J. , Sow C. H. , Ong C. K.
Published: July 2006

A simple but effective approach is demonstrated for the fabrication of an array of La0.67Sr0.33MnO3−δ nanoconstriction via nanosphere lithography. Such nanoconstrictions can be treated as quasi-one-dimensional conductors. A monolayer of hexagonally arranged SiO2 microspheres, whose dimension was reduced by reactive ion etching, is employed as a mask for pulsed laser deposition. Nanoconstriction array of around 100nm could be obtained. Conventional photolithography and the lift-off technique were employed to shape the nanoconstriction array into the bridge geometry for transport property measurements. The results showed that the nanoconstriction array exhibited nonlinear transport properties different from those exhibited by continuous film. This approach opens the possibility of fabricating and studying nanopatterned multicomponent oxides which include magnetoresistive manganites, superconducting cuprates, and other perovskite oxides.
Effect of substrate surface on the structure and electronic properties of cubic boron nitride films
Authors: Zhou X. T. , Sham T. K. , Chan C. Y. , Zhang W. J. , Bello I. , Lee S. T. , Hofsäss H.
Published: July 2006

Cubic boron nitride (c-BN) films were prepared by mass-selected ion beam deposition (MSIBD) technique. The effects of substrate surface roughness were investigated by boron and nitrogen k-edge x-ray absorption near-edge structure, x-ray diffraction, and atomic force microscopy. All the films are a mixture of nanocrystalline sp3-bonded c-BN and sp2-bonded BN phases. The substrate with a rough surface causes a decrease of the c-BN phase content of the film on it. A significant large lattice contraction of the c-BN crystallites in the films, relative to the bulk, is observed. It is also found that the electronic structure of the nanocrystalline c-BN films by MSIBD technique is somewhat different from that of microcrystalline c-BN∕h-BN references. We attribute the effect of the nature of the substrate on the morphology and structure of the c-BN films to the orientation of sp2-bonded graphitic BN basal plane on the top surface of the films during their growth, and the lattice contraction and energy band structure modification of c-BN films to the large compressive stress, respectively.
Si nanocrystal based memories: Effect of the nanocrystal density
Authors: Lu T. Z. , Alexe M. , Scholz R. , Talalaev V. , Zhang R. J. , Zacharias M.
Published: July 2006

Si nanocrystals designed for memory applications were prepared in a layered arrangement by using a SiOx∕SiO2 multilayer structure with a variation of the stoichiometry parameter x from 0.9 to 1.63. The stoichiometry of the SiOx layers is controlled by adjusting the oxygen pressure during the growth which influences the resulting area density of the Si nanocrystals after high temperature annealing from around (2.8–0.93)×1012∕cm2. The tuning of the Si nanocrystal area density in the layers is demonstrated by transmission electron microscopy as well as by comparison of capacitance-voltage and photoluminescence measurements. The influence of the nanocrystal density on the charge behavior is demonstrated and discussed. Our method realizes a simple way to control the area density by maintaining equally sized nanocrystals, that gives unique possibilities to study the influence of the nanocrystal density on the electrical properties.
Effects of thermal treatment on the formation of the columnar structures in ZnO thin films grown on p-Si (100) substrates
Authors: Shin J. W. , Lee J. Y. , No Y. S. , Kim T. W. , Choi W. K.
Published: July 2006

X-ray diffraction patterns showed that crystallinity of the annealed ZnO films was improved by thermal annealing. Transmission electron microscopy images showed that columnar structures were preferentially formed in ZnO thin films due to thermal annealing, and electron energy loss spectroscopy images showed that annealing caused O2 atoms to diffuse out from the upper region in the ZnO thin film. The effects of thermal treatment on the formation of the columnar structures in ZnO thin films grown on Si (100) substrates are described on the basis of the experimental results.
Long-time dynamics of variable coefficient modified Korteweg-de Vries solitary waves
Authors: Dejak S. I. , Jonsson B. L. G.
Published: July 2006

We study the long-time behavior of solutions to the Korteweg-de Vries-type equation ∂tu=−∂x(∂x2u+f(u)−b(t,x)u), with initial conditions close to a stable, b=0 solitary wave. The coefficient b is a bounded and slowly varying function, and f is a nonlinearity. For a restricted class of nonlinearities, we prove that for long time intervals, such solutions have the form of the solitary wave, whose center and scale evolve according to a certain dynamical law involving the function b(t,x), plus an H1(R)-small fluctuation. The result is stronger than those previously obtained for general nonlinearities f.
Oxidation treatment of carbon nanotubes: An essential process in nanocomposite with RuO2 for supercapacitor electrode materials
Authors: Kim Yong-Tae , Mitani Tadaoki
Published: July 2006

In the nanocomposite of multiwalled carbon nanotubes (MWNTs) and RuO2 for supercapacitor electrode materials, upon immersion of the purified MWNT into a RuCl3 solution, Ru metal having no contribution to pseudocapacitance was unexpectedly formed on the MWNT surface by spontaneous reduction, because of the higher Fermi level of MWNT than the absolute energy level of Ru∕RuCl3 pair. In contrast, no such phenomenon was observed for oxidized MWNT, because of lowered Fermi level and the surface carboxyl groups as protector against charge transfer. The oxidation treatment of MWNT is therefore not optional but rather is an essential process in nanocomposite.
Thermal contributions to the bending of bimaterial cantilever sensors
Authors: Zhao Jun , Berger Rüdiger , Gutmann Jochen S.
Published: July 2006

The thickness dependent contribution of thermal expansion and surface potential to the thermal response behavior of polymer coated micromechanical cantilevers is investigated. Polystyrene films in a thickness range of 2–150nm are used as coatings on silicon micromechanical cantilever arrays. Depending on coating thickness, either thermal expansion or interfacial tension dominates the response. For thick films we obtain a thermal expansion coefficient of 2.3×10−5±1.0×10−5°C−1 for the polystyrene coating. Using this value a temperature coefficient of interfacial tension of −50×10−5±14×10−5Jm−2°C−1 is determined for the silicon oxide/polystyrene interface. This establishes a method to measure the temperature coefficient of interfacial tension at solid/solid interfaces.
Investigations of InAs surface dots on InP
Authors: Ellström C. , Trägårdh J. , Samuelson L. , Seifert W. , Pistol M.-E. , Lemeshko S. , Pryor C.
Published: July 2006

We have fabricated InAs dots on the surface of InP, determined their structure, and measured the optical transition energy. This energy was found to be in excellent agreement with theoretical calculations, where no free parameters have been used. The calculations were performed using eight-band k∙p theory in the envelope function approximation. We conclude that this theory is adequate to describe quantum dots also when one of the confining materials is vacuum.
Investigation of the initial stage of GaN epitaxial growth on 6H-SiC (0001) at room temperature
Authors: Kim M. H. , Oshima M. , Kinoshita H. , Shirakura Y. , Miyamura K. , Ohta J. , Kobayashi A. , Fujioka H.
Published: July 2006

We have investigated the initial stage of GaN epitaxial growth on 6H-SiC (0001) at low substrate temperatures by pulsed laser deposition (PLD). We found that GaN grows epitaxially even at room temperature (RT) on atomically flat 6H-SiC (0001) surfaces, which can be explained by the enhanced surface migration of film precursors due to the use of PLD and atomically flat substrates. In situ reflection high-energy election diffraction observations have revealed that GaN films grown at above 300°C proceed in a three-dimensional mode, while those at RT proceed in a layer-by-layer growth mode with atomically flat terraces and steps. The step height turned out to be 1.5nm, which is the same height as the steps on the SiC substrates. This result indicates that the step height on the SiC surface is retained as the GaN grows.
Carryover Bias in Visual Assessment
Authors: Ferris Steven J , Kempton Rob A , Deary Ian J , Austin Elizabeth J , Shorter Margaret V
Published: July 2006

Carryover of stimuli in sequential judgments was studied for a visual assessment task involving estimation of the percentage cover of black circles on a white image. Seven image types with different levels of cover density were arranged in a sequentially balanced design in which each image type was preceded the same number of times by all image types. In the absence of carryover, when images were preceded by images with the same cover density, the response scores were well fitted by a power function of percentage cover with a mean exponent of 0.73 over subjects. Carryover took the form of an assimilation, so that the cover estimate for a target image was generally higher when preceded by an image with higher cover, and lower when preceded by an image with lower cover. However, the magnitude of the carryover effect showed little evidence of increasing with difference in cover between successive images. Nonparametric and parametric methods for testing for carryover are presented. The need for development of psychological models to explain the proposed statistical models is discussed.
The cannabinoid WIN 55,212-2 inhibits transient receptor potential vanilloid 1 (TRPV1) and evokes peripheral antihyperalgesia via calcineurin
Authors: Patwardhan Amol M. , Jeske Nathaniel A. , Price Theodore J. , Gamper Nikita , Akopian Armen N. , Hargreaves Kenneth M.
Published: July 2006

Cannabinoids can evoke antihyperalgesia and antinociception at a peripheral site of action. However, the signaling pathways mediating these effects are not clearly understood. We tested the hypothesis that certain cannabinoids directly inhibit peripheral capsaicin-sensitive nociceptive neurons by dephosphorylating and desensitizing transient receptor potential vanilloid 1 (TRPV1) via a calcium calcineurin-dependent mechanism. Application of the cannabinoid WIN 55,212-2 (WIN) to cultured trigeminal (TG) neurons or isolated skin biopsies rapidly and significantly inhibited capsaicin-activated inward currents and neuropeptide exocytosis by a mechanism requiring the presence of extracellular calcium. The inhibitory effect did not involve activation of G protein-coupled cannabinoid receptors, because neither pertussis toxin nor GDPβS treatments altered the WIN effect. However, application of WIN-activated calcineurin, as measured by nuclear translocation of the nuclear factor of activated T cells (NFAT)c4 transcription factor, dephosphorylated TRPV1. The WIN-induced desensitization of TRPV1 was mediated by calcineurin, because the application of structurally distinct calcineurin antagonists (calcineurin autoinhibitory peptide and cyclosporine/cyclophilin complex) abolished WIN-induced inhibition of capsaicin-evoked inward currents and neuropeptide exocytosis. This mechanism also contributed to peripheral antinociceptive/antihyperalgesic effects of WIN because pretreatment with the calcineurin antagonist calcineurin autoinhibitory peptide (CAIP) significantly reduced peripherally mediated WIN effects in two behavioral models. Collectively, these data demonstrate that cannabinoids such as WIN directly inhibit TRPV1 functional activities via a calcineurin pathway that represents a mechanism of cannabinoid actions at peripheral sites.
Family predictors of parent participation in an adolescent drug abuse prevention program
Authors: DÍAZ SUSANA AL‐HALABI , SECADES‐VILLA ROBERTO , PÉREZ JOSÉ MANUEL ERRASTI , FERNÁNDEZ‐HERMIDA JOSÉ RAMÓN , GARCÍA‐RODRÍGUEZ OLAYA , CRESPO JOSÉ LUIS CARBALLO
Published: July 2006

Low participation rates constitute a serious problem faced by family drug abuse prevention programs. In this study we analyse the factors related to participation in a Life Skills Training program implemented in three schools in Spain. Participants in the study were 485 pupils aged 12–14 years and their respective parents. The variables that predicted participation in the program were: number of children and educational level of parents, children's drug use, family conflict, parental rearing style, relationships between parents and children and family communication. The results from Spain are similar to those found in international studies, and indicate that the families most at risk of drug use are those least likely to participate in prevention programs. There is a need for strategies to increase participation in prevention programs of the families most at risk.
Illicit drug use and responses in six Pacific Island countries
Authors: DEVANEY MADONNA L. , REID GARY , BALDWIN SIMON , CROFTS NICK , POWER ROBERT
Published: July 2006

We report here on the illicit drug situation in six Pacific nations: Fiji, Papua New Guinea, Samoa, Solomon Islands, Tonga and Vanuatu. The report is based on the ‘Situational analysis of illicit drug issues and responses in Asia and the Pacific’, commissioned by the Australian National Council on Drugs Asia Pacific Drug Issues Committee. The situational analysis was a comprehensive desk‐based review; data sources included published and unpublished literature and information from key informants. A range of psychoactive substances have been used traditionally across the Pacific region. Cannabis is the by far the most common and widespread illicit drug used in the six Pacific Islands reviewed. Drugs such as heroin, methamphetamines and cocaine are not used commonly due to their high cost compared to the average income. Currently, there is no overall regional or country‐based illicit drug policy for the Pacific and few treatment programs; limited data exist to aid in understanding illicit drug use and the harms associated with its use in the Pacific. This review highlights the urgent need for strategic alcohol and drug research in the Pacific as a foundation for the development of policy.
A NOTE ON ADDED INFORMATION IN THE RAS PROCEDURE: REEXAMINATION OF SOME EVIDENCE
Authors: De Mesnard Louis , Miller Ronald E.
Published: July 2006

ABSTRACT An example in Miernyk (1977) presented a rather counterintuitive result, namely, that introducing accurate exogenous information into an RAS matrix estimating procedure could lead to an estimate that was worse than one generated by RAS using no exogenous information at all. This became an oft‐cited black mark against RAS. Miller and Blair (1985) included a different (and small) illustration of the same possibility. It was recently pointed out by one of us that the Miller–Blair numerical results are wrong. For that reason, we decided to reexamine all the empirical evidence we could find on the subject. While figures in both Miernyk and Miller–Blair appear to be wrong, more recent published examples seem to have it right. In short, it is possible to identify examples in which additional (correct) information leads to poorer RAS estimates, at least under several fairly common metrics for comparing “closeness” of matrices. However, the overwhelming majority of the evidence is to the contrary. As a general rule, introduction of accurate exogenous information into RAS improves the resulting estimates, and counterexamples should probably not be taken too seriously.
Arginine-Dependent Acid Resistance in
Salmonella enterica
Serovar Typhimurium
Authors: Kieboom Jasper , Abee Tjakko
Published: July 2006

Salmonella enterica
serovar Typhimurium does not survive a pH 2.5 acid challenge under conditions similar to those used for
Escherichia coli
(J. W. Foster, Nat. Rev. Microbiol. 2:898-907, 2004). Here, we provide evidence that
S. enterica
serovar Typhimurium can display arginine-dependent acid resistance (AR) provided the cells are grown under anoxic conditions and not under the microaerobic conditions used for assessment of AR in
E. coli
. The role of the arginine decarboxylase pathway in
Salmonella
AR was shown by the loss of AR in mutants lacking
adiA
, which encodes arginine decarboxylase;
adiC
, which encodes the arginine-agmatine antiporter; or
adiY
, which encodes an AraC-like regulator. Transcription of
adiA
and
adiC
was found to be dependent on AdiY, anaerobiosis, and acidic pH.
Multilocus Sequence Typing as an Approach for Population Analysis of
Medicago
-Nodulating Rhizobia
Authors: van Berkum Peter , Elia Patrick , Eardly Bertrand D.
Published: July 2006

Multilocus sequence typing (MLST), a sequence-based method to characterize bacterial genomes, was used to examine the genetic structure in a large collection of
Medicago
-nodulating rhizobial strains. This is the first study where MLST has been applied in conjunction with eBURST analysis to determine the population genetic structure of nonpathogenic bacteria recovered from the soil environment. Sequence variation was determined in 10 chromosomal loci of 231 strains that predominantly originated from southwest Asia. Genetic diversity for each locus ranged from 0.351 to 0.819, and the strains examined were allocated to 91 different allelic profiles or sequence types (STs). The genus
Medicago
is nodulated by at least two groups of rhizobia with divergent chromosomes that have been classified as
Sinorhizobium meliloti
and
Sinorhizobium medicae
. Evidence was obtained that the degree of genetic exchange among the chromosomes across these groups is limited. The symbiosis with
Medicago polymorpha
of nine strains placed in one of these groups, previously identified as
S. medicae
, ranged from ineffective to fully effective, indicating that there was no strong relationship between symbiotic phenotype and chromosomal genotype.
Straight-Chain Fatty Acids Are Dispensable in the Myxobacterium
Myxococcus xanthus
for Vegetative Growth and Fruiting Body Formation
Authors: Bode Helge B. , Ring Michael W. , Kaiser Dale , David Anna C. , Kroppenstedt Reiner M. , Schwär Gertrud
Published: July 2006

Inactivation of the MXAN_0853 gene blocked the production in
Myxococcus xanthus
of straight-chain fatty acids which otherwise represent 30% of total fatty acids. Despite this drastic change in the fatty acid profile, no change in phenotype could be observed, which contrasts with previous interpretations of the role of straight-chain fatty acids in the organism's development.
Enhanced Biofilm Formation and Loss of Capsule Synthesis: Deletion of a Putative Glycosyltransferase inPorphyromonas gingivalis
Authors: Davey Mary E. , Duncan Margaret J.
Published: July 2006

Periodontitis is a biofilm-mediated disease.Porphyromonas gingivalisis an obligate anaerobe consistently associated with severe manifestations of this disease. As an opportunistic pathogen, the ability to proliferate within and disseminate from subgingival biofilm (plaque) is central to its virulence. Here, we report the isolation of aP. gingivalistransposon insertion mutant altered in biofilm development and the reconstruction and characterization of this mutation in three different wild-type strains. The mutation responsible for the altered biofilm phenotype was in a gene with high sequence similarity (∼61%) to a glycosyltransferase gene. The gene is located in a region of the chromosome that includes up to 16 genes predicted to be involved in the synthesis and transport of capsular polysaccharide. The phenotype of the reconstructed mutation in all three wild-type backgrounds is that of enhanced biofilm formation. In addition, in strain W83, a strain that is encapsulated, the glycosyltransferase mutation resulted in a loss of capsule. Further experiments showed that the W83 mutant strain was more hydrophobic and exhibited increased autoaggregation. Our results indicate that we have identified a gene involved in capsular-polysaccharide synthesis inP. gingivalisand that the production of capsule prevented attachment and the initiation of in vitro biofilm formation on polystyrene microtiter plates.
Hepatic glucose production is more sensitive to insulin-mediated inhibition than hepatic VLDL-triglyceride production
Authors: den Boer Marion A. M. , Voshol Peter J. , Kuipers Folkert , Romijn Johannes A. , Havekes Louis M.
Published: July 2006

Insulin is an important inhibitor of both hepatic glucose output and hepatic VLDL-triglyceride (VLDL-TG) production. We investigated whether both processes are equally sensitive to insulin-mediated inhibition. To test this, we used euglycemic clamp studies with four increasing plasma concentrations of insulin in wild-type C57Bl/6 mice. By extrapolation, we estimated that half-maximal inhibition of hepatic glucose output and hepatic VLDL-TG production by insulin were obtained at plasma insulin levels of ∼3.6 and ∼6.8 ng/ml, respectively. In the same experiments, we measured that half-maximal decrease of plasma free fatty acid levels and half-maximal stimulation of peripheral glucose uptake were reached at plasma insulin levels of ∼3.0 and ∼6.0 ng/ml, respectively. We conclude that, compared with insulin sensitivity of hepatic glucose output, peripheral glucose uptake and hepatic VLDL-TG production are less sensitive to insulin.
High urea and creatinine concentrations and urea transporter B in mammalian urinary tract tissues
Authors: Spector David A. , Yang Qing , Wade James B.
Published: July 2006

Although the mammalian urinary tract is generally held to be solely a transit and storage vehicle for urine made by the kidney, in vivo data suggest reabsorption of urea and other urine constituents across urinary tract epithelia. To determine whether urinary tract tissue concentrations are increased as a result of such reabsorption, we measured urea nitrogen and creatinine concentrations and determined whether urea transporter B (UT-B) was present in bladder, ureter, and other tissues from dogs and rats. Mean urea nitrogen and creatinine concentrations in dogs and rats were three- to sevenfold higher in urinary tract tissues than in serum and were comparable to those in renal cortex. In water-restricted or water-loaded rats, urea nitrogen concentrations in bladder tissues fell inversely with the state of hydration, were proportional to urine urea nitrogen concentrations, and were greater than the corresponding serum urea nitrogen concentration in every animal. Immunoblots of rat and dog urinary tract tissues demonstrated the presence of UT-B in homogenates of bladder and ureter, and immunocytochemical analysis localized UT-B to epithelial cell membranes. These findings are consistent with the notion that urea and creatinine are continuously reabsorbed from the urine across the urothelium, urea in part via UT-B, and that urine is thus altered in its passage through the urinary tract. Urea reabsorption across urinary tract epithelia may be important during conditions requiring nitrogen conservation and may contribute to pathophysiological states characterized by high blood urea nitrogen, such as prerenal azotemia and obstructive uropathy.
ADAMTS-13 regulates platelet adhesion under flow
Authors: Budde Ulrich , Angerhaus Dorothea , Lubetsky Aharon , Savion Naphtali , Seligsohn Uri , Varon David , Shenkman Boris
Published: July 2006

ADAMTS-13 cleaves large and ultra-large vonWillebrand factor multimers normally secreted by endothelial cells. Severe deficiency of this enzyme leads to thrombotic thrombocytopenic purpura (TTP). We applied the Impact-R system [Cone and plate(let) Analyzer, CPA] to determine optimal conditions for ADAMTS-13 function, to assess it’s activity in TTP patients and to distinguish inheritedTTP (inTTP) from acquiredTTP (acTTP). The role of ADAMTS-13 in platelet adhesion under different conditions was investigated applying recombinant forms of VWF and ADAMTS-13. rVWF was first treated by rADAMTS-13 either in solution or when immobilized on the surface of the well, under static or flow conditions, in the presence or absence of BaCl2. The resulting cleavedVWF fragments were then immobilized and served to assess type 3 von Willebrand disease whole blood platelet adhesion under flow. Maximal effect of the rADAMTS-13 (decrease of platelet adhesion in the absence compared to the presence of BaCl2), was observed when the rVWF was pre-immobilized and the cleavage step took place under flow (85%). Mixing plasma ofTTP patients with normal blood (1:3) yielded a 1.6 to 2-fold increase of platelet adhesion under flow compared to mixing normal plasma with normal blood, at shear rate range of 1,800–2,500s−1. Maximal increase of platelet adhesion was observed under 2,050s−1. Under these conditions, the extent of adhesion was similarly higher in patients with inTTP and acTTP versus control [surface coverage (SC) 14.5 ± 2.8% and 14.6 ± 2.5% vs. 7.4 ± 1.7%, respectively]. ADAMTS-13 activity measured by collagen-binding test was similarly low (4.2 ± 3.8% and 3.5 ± 2.4% vs. 72.2 ± 8.0%, respectively). An inverse correlation between SC and ADAMTS-13 activity was observed in a patient with inTTP assayed eight times during plasma infusion treatment. Addition of BaCl2 to the mixture of TTP plasma and normal whole blood yieldeda decrease in platelet adhesion in inTTP (by 51%) but not in acTTP. The lack of reduction of platelet adhesion in acTTP could presumably be due to the presence of ADAMTS-13 inhibitor in these patients. These results suggest that VWF immobilization and high shear flow yielded optimal conditions for ADAMTS-13 activity, and that introduction of BaCl2 in the Impact-R (CPA) test may be useful for differentiation between inherited and acquired TTP.
Formation of tissue factor-factor VIIa-factor Xa complex prevents apoptosis in human breast cancer cells
Authors: Jiang Xiaofeng , Guo Yan , Bromberg Michael
Published: July 2006

Summary Tissue factor (TF) is a transmembrane glycoprotein that initiates blood coagulation when complexed with factorVIIa (FVIIa).TF is constitutively expressed ina variety of tumor cells and has been shown to playa role in cellular signaling and tumor progression. In this study, we investigated the effect of TF-FVIIa mediated signaling on apoptosis in human breast cancer cells. Apoptosis was induced by prolonged serum starvation and studied using the Adr-MCF-7 cell line, which has high endogenous TF expression. Treatment of the cells with the combination of FVIIa (10 nM) and FX (150 nM), reduced apoptosis by nearly 50% compared with untreated, control cells using an ELISA that detects histone-DNA fragments. In contrast, FVIIa (10 nM) alone did not significantly prevent apoptosis. Pretreatment of the Adr-MCF-7 cells with hirudin, a specific thrombin inhibitor, did not inhibit the anti-apoptotic effect of the combination of FVIIa and FX, whereas this effect could be abrogated by inhibition of phosphorylation of either p44/42 mitogen-activated protein kinase (MAPK) or protein kinaseB (PKB/Akt). In addition, treatment of theAdr-MCF-7 cells with the combination of FVIIa and FX led to a 30-50% increase in the level of the anti-apoptotic protein, survivin, compared with untreated cells usingWestern blot analysis. These results indicate that formation of TF-FVIIa-FXa complex prevents apoptosis in breast cancer cells by a thrombin-independent pathway. Moreover, the anti-apoptotic effect of this signaling pathway involves phosphorylation of both p44/42 MAPK and PKB/Akt and might be mediated in part by an increase in cell survivin levels.
Prevention effect of orally active heparin derivative on deep vein thrombosis
Authors: Kim Sang , Lee Dong , Kim Choong , Moon Hyun , Byun Youngro
Published: July 2006

The use of heparin as the most potent anticoagulant for the prevention of deep vein thrombosis and pulmonary embolism is nevertheless limited, because it is available to patients only by parenteral administration. Toward overcoming this limitation in the use of heparin, we have previously developed an orally active heparin-deoxycholic acid conjugate (LMWH-DOCA) in 10% DMSO formulation. The present study evaluates the anti-thrombogenic effect of this orally active LMWH-DOCA using a venous thrombosis animal model with Sprague-Dawley rats. When 5 mg/kg of LMWH-DOCA was orally administered in rats, the maximum anti-FXa activity in plasma was 0. 35 ± 0. 02, and anti-FXa activity in plasma was maintained above 0. 1 IU/ml [the minimum effective anti-FXa activity for the prevention of deep venous thrombosis (DVT) and pulmonary embolism (PE)] for five hours. LMWH-DOCA (5 mg/kg, 430 IU/kg) that was orally administered reduced the thrombus formation by 56. 3 ± 19. 8%;on the other hand, subcutaneously administered enoxaparin (100 IU/kg) reduced the thrombus formation by 36. 4 ± 14. 5%. Also, LMWH-DOCA was effectively neutralized by protamine that was used as an antidote. Therefore, orally active LMWH-DOCA could be proposed as a new drug that is effective for the longterm prevention of DVT and PE.
Leukemic lymphoblasts, a novel expression site of coagulation factor XIII subunit A
Authors: Veszprémi Anikó , Katona Éva , Kiss Csongor , Vereb György , Muszbek László , Kiss Flóra , Hevessy Zsuzsanna , Kappelmayer János
Published: July 2006

Blood coagulation factor XIII (FXIII) is a protransglutaminase circulating asa tetramer formed by two types of subunits (A2B2). The intracellular dimeric form of FXIII (A2) is present in platelets, megakaryocytes, monocytes and macrophages and has been detected in mono-and megakaryocytic leukemias. The aim of our study was to investigate FXIII-A expression in newly diagnosed B cell acute lymphoblastic leukemia (ALL) samples. We examined 47 de novo ALL cases of B cell origin by triple color labeling with flow cytometry. FXIII-A was detected by a FITC conjugated monoclonal antibody combined with CD34 and CD45 staining. In selected cases FXIII-A was investigated on slides prepared from blasts and visualized with a fluorescent microscope. In addition, blasts were studied by Western blot analysis and FXIII-A was measured by a highly sensitive ELISA method. By flow cytometry 19 samples of the 47 cases were found to be FXIII-A positive. Antigen concentration was 3.11± 1.19 fg/blast, while normal lymphoid precursors and mature lymphocytes from B-CLL did not contain FXIII-A. In the lysate of lymphoblasts that were positive by flow cytometry, a single band (82 kDa) corresponding to FXIII-A was detected on Western blots. Confocal laser scanning microscopic examination revealed the presence of FXIII-A in the cytoplasm of these lymphoblasts. This novel expression site of FXIII-A in leukemic lymphoblasts can be utilized as a diagnostic tool and may also gain functional significance in B-lineage ALL.
Drug Utilization Pattern in the Intensive Care Unit of a Tertiary Care Hospital
Authors: Biswal S. , Mishra P. , Malhotra S. , Puri G. D. , Pandhi P.
Published: July 2006

The authors studied the factors affecting drug use pattern, cost of therapy, and the association between the pattern of drug use and survival as well as the duration of stay in a prospective, observational study in an intensive care unit between February and May 2005. Data were collected regarding drugs used, severity of the disease, and their outcome. The mean ± SD of the Acute Physiology and Chronic Health Evaluation (APACHE III) and Glasgow Coma Scale (GCS) scores of 84 patients were 52.2 ± 19.4 and 7.5 ± 2.4, respectively. Although the mean number of drugs at the time of admission to the intensive care unit was 5.3, it increased to 12.9 on the first day and 22.2 during the entire stay. More than 50% of the average expenditure on drugs and nutrition was accounted by antibiotics. Requirement of insulin or inotropes signified an adverse outcome on mortality (odds ratios of 3.43 and 8.44, respectively). In conclusion, there is a tremendous impact of antibiotic use on the cost of therapy in the intensive care unit. The requirement of certain drugs such as insulin and inotropes is of prognostic significance.
Lipid raft adhesion receptors and Syk regulate selectin-dependent rolling under flow conditions
Authors: Abbal Claire , Lambelet Martine , Bertaggia Debora , Gerbex Carole , Martinez Manuel , Arcaro Alexandre , Schapira Marc , Spertini Olivier
Published: July 2006

Selectins and their ligand P-selectin glycoprotein ligand-1 (PSGL-1) mediate leukocyte rolling along inflamed vessels. Cell rolling is modulated by selectin interactions with their ligands and by topographic requirements including L-selectin and PSGL-1 clustering on tips of leukocyte microvilli. Lipid rafts are cell membrane microdomains reported to function as signaling platforms. Here, we show that disruption of leukocyte lipid rafts with cholesterol chelating agents depleted raft-associated PSGL-1 and L-selectin and strongly reduced L-, P-, and E-selectin–dependent rolling. Cholesterol repletion reversed inhibition of cell rolling. Importantly, leukocyte rolling on P-selectin induced the recruitment of spleen tyrosine kinase (Syk), a tyrosine kinase associated to lipid raft PSGL-1. Furthermore, inhibition of Syk activity or expression, with pharmacologic inhibitors or by RNA interference, strongly reduced leukocyte rolling on P-selectin, but not on E-selectin or PSGL-1. These observations identify novel regulatory mechanisms of leukocyte rolling on selectins with a strong dependency on lipid raft integrity and Syk activity.
Alexithymia and Neuroendocrine‐ Immune Response in Patients with Autoimmune Diseases
Authors: BRUNI R. , SERINO F.M. , GALLUZZO S. , COPPOLINO G. , CACCIAPAGLIA F. , VADACCA M. , NILO S. , TERMINIO N. , AFELTRA A.
Published: July 2006

Abstract:  Alexithymia is conceptualized as a disorder of emotion regulation mechanisms, which involves a dissociation of emotional and physic responses to life events and bodily sensations. Our results might suggest a possible relationship between the alexithymic construct and TNF levels in RA patients. These preliminary findings corroborate the integrated bidirectional interactions between neuropsychological mechanisms and the neuroendocrine‐immune system in patients affected by autoimmune diseases and contribute to finding a common biological pathway linking alexithymia and autoimmune‐inflammatory diseases.
Estrogens in Pregnancy and Systemic Lupus Erythematosus
Authors: DORIA ANDREA , IACCARINO LUCA , SARZI‐PUTTINI PIERCARLO , GHIRARDELLO ANNA , ZAMPIERI SANDRA , ARIENTI SILVIA , CUTOLO MAURIZIO , TODESCO SILVANO
Published: July 2006

Abstract:  Successful pregnancy depends on an adaptation of the maternal immune system that becomes tolerant to fetal antigens of paternal origin. The altered immune regulation induced by pregnancy occurs predominantly at the maternal–fetal interface, but it has also been observed in the maternal circulation. Th1/Th2 shift is one of the most important immunologic changes during gestation. It is due to the progressive increase of estrogens, which reach peak level in the third trimester of pregnancy. At these high levels, estrogens suppress the Th1‐mediated responses and stimulate Th2‐mediated immunologic responses. For this reason Th1‐mediated diseases, such as rheumatoid arthritis, tend to improve, while Th2‐mediated diseases, such as systemic lupus erythematosus (SLE) tend to worsen during pregnancy. However, in some recent studies SLE flare‐ups were less frequently observed in the third trimester of gestation in comparison to the second trimester and postpartum period. These data are apparently in contrast to the Th2 immune‐response polarization expected during pregnancy due to the progressive increase of estrogens. Some further data suggest that in SLE patients estradiol serum levels are surprisingly lower than expected during the third trimester of pregnancy, probably due to a placental compromise. This occurrence could lead to a lower‐than‐expected increase of IL‐6, accounting for the low humoral immune response and the low disease activity observed in the third trimester of pregnancy in such patients.