bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding viscous magnetization of multidomain magnetite
Authors: Williams Wyn , Muxworthy Adrian R.
Published: February 2006

Viscous magnetization (VM) and viscous remanent magnetization (VRM) have been measured, as a function of temperature, between room temperature and the Curie temperature using a suite of well‐characterized synthetic and natural multidomain (MD) magnetite samples. Particular attention was given to possible diffusion aftereffects such as dislocation creep (stress relaxation) and disaccommodation (vacancy and ionic reordering) and their contribution to viscous behavior in what has been commonly thought of as a purely thermal fluctuation process. Dislocation creep was examined by measuring viscosity before and after annealing. Annealing was found to reduce the non‐log(t) behavior, where t is time. Non‐log(t) behavior has been associated with diffusion aftereffects, suggesting that these are a major contributor to viscosity and (de)magnetization processes in MD samples. The positive curvature of the non‐log(t) acquisition processes indicates that dislocation creep dominates over disaccommodation. This does not imply that VM and VRM are due solely to dislocation creep, but rather that VRM and VM reflect a number of unrelated temperature‐dependent processes, primarily thermal fluctuations and dislocation creep. This is the first time that dislocation creep has been directly identified as contributing to viscosity at temperature. These findings will have particular implications for paleointensity determinations, as on heating a sample, its dislocation structure may relax, giving rise to demagnetizations not associated with thermal fluctuations. This will lead to incorrect intensity estimates. If no heating is performed on a geological specimen, then it is very likely that laboratory timescale stress relaxation processes will have already occurred in situ.
Laurentide Ice Sheet meltwater and abrupt climate change during the last glaciation
Authors: Hill Heather W. , Flower Benjamin P. , Quinn Terrence M. , Hollander David J. , Guilderson Thomas P.
Published: February 2006

A leading hypothesis to explain abrupt climate change during the last glacial cycle calls on fluctuations in the margin of the North American Laurentide Ice Sheet (LIS), which may have routed fresh water between the Gulf of Mexico (GOM) and the North Atlantic, affecting North Atlantic Deep Water variability and regional climate. Paired measurements of δ18O and Mg/Ca of foraminiferal calcite from GOM sediments reveal five episodes of LIS meltwater input from 28 to 45 thousand years ago (ka) that do not match the millennial‐scale Dansgaard‐Oeschger warmings recorded in Greenland ice. We suggest that summer melting of the LIS may occur during Antarctic warming and likely contributed to sea level variability during marine isotope stage 3.
An assessment of the tracer‐based approach to quantifying groundwater contributions to streamflow
Authors: Jones J. P. , Sudicky E. A. , Brookfield A. E. , Park Y.‐J.
Published: February 2006

The use of conservative geochemical and isotopic tracers along with mass balance equations to determine the pre‐event groundwater contributions to streamflow during a rainfall event is widely used for hydrograph separation; however, aspects related to the influence of surface and subsurface mixing processes on the estimates of the pre‐event contribution remain poorly understood. Moreover, the lack of a precise definition of “pre‐event” versus “event” contributions on the one hand and “old” versus “new” water components on the other hand has seemingly led to confusion within the hydrologic community about the role of Darcian‐based groundwater flow during a storm event. In this work, a fully integrated surface and subsurface flow and solute transport model is used to analyze flow system dynamics during a storm event, concomitantly with advective‐dispersive tracer transport, and to investigate the role of hydrodynamic mixing processes on the estimates of the pre‐event component. A number of numerical experiments are presented, including an analysis of a controlled rainfall‐runoff experiment, that compare the computed Darcian‐based groundwater fluxes contributing to streamflow during a rainfall event with estimates of these contributions based on a tracer‐based separation. It is shown that hydrodynamic mixing processes can dramatically influence estimates of the pre‐event water contribution estimated by a tracer‐based separation. Specifically, it is demonstrated that the actual amount of bulk flowing groundwater contributing to streamflow may be much smaller than the quantity indirectly estimated from a separation based on tracer mass balances, even if the mixing processes are weak.
Infrared absorption spectra of matrix-isolated cis, cis-HOONO and its ab initio CCSD(T) anharmonic vibrational bands
Authors: Zhang Xu , Nimlos Mark R. , Ellison G. Barney , Varner Mychel E. , Stanton John F.
Published: February 2006

The infrared absorption spectra of matrix-isolated cis, cis-peroxynitrous acid (HOONO and DOONO) in argon have been observed. Six of the nine fundamental vibrational modes for cis, cis-HOONO have been assigned definitively, and one tentatively. Coupled-cluster, ab initio anharmonic force field calculations were used to help guide some of the assignments. The experimental matrix frequencies (cm−1) for cis, cis-HOONO are (a′modes)ν1=3303±1,ν2=1600.6±0.6,ν3=1392±1,ν4=922.8±0.5,ν5=789.7±0.4,ν6=617±1; and (a″mode)ν8=462±1. The fundamentals for the deuterated isotopomer, cis, cis-DOONO, are (a′modes)ν1=2447.2±0.6,ν2=1595.7±0.7,ν3=1089.1±0.4,ν4=888.1±0.4,ν5=786.6±0.5,ν6=613.9±0.9; and (a″mode)ν8=456.5±0.5.
The structural properties of a two-Yukawa fluid: Simulation and analytical results
Authors: Broccio Matteo , Costa Dino , Liu Yun , Chen Sow-Hsin
Published: February 2006

Standard Monte Carlo simulations are carried out to assess the accuracy of theoretical predictions for the structural properties of a model fluid interacting through a hard-core two-Yukawa potential composed of a short-range attractive well next to a hard repulsive core, followed by a smooth, long-range repulsive tail. Theoretical calculations are performed in the framework provided by the Ornstein-Zernike equation, solved either analytically with the mean spherical approximation (MSA) or iteratively with the hypernetted-chain (HNC) closure. Our analysis shows that both theories are generally accurate in a thermodynamic region corresponding to a dense vapor phase around the critical point. For a suitable choice of potential parameters, namely, when the attractive well is deep and/or large enough, the static structure factor displays a secondary low-Q peak. In this case HNC predictions closely follow the simulation results, whereas MSA results progressively worsen the more pronounced this low-Q peak is. We discuss the appearance of such a peak, also experimentally observed in colloidal suspensions and protein solutions, in terms of the formation of equilibrium clusters in the homogeneous fluid.
Infrared laser spectroscopy of CH3⋯HF in helium nanodroplets: The exit-channel complex of the F+CH4 reaction
Authors: Merritt J. M. , Rudić S. , Miller R. E.
Published: February 2006

High-resolution infrared laser spectroscopy is used to study the CH3⋯HF and CD3⋯HF radical complexes, corresponding to the exit-channel complex in the F+CH4→HF+CH3 reaction. The complexes are formed in helium nanodroplets by sequential pickup of a methyl radical and a HF molecule. The rotationally resolved spectra presented here correspond to the fundamental v=1←0 H–F vibrational band, the analysis of which reveals a complex with C3v symmetry. The vibrational band origin for the CH3⋯HF complex (3797.00cm−1) is significantly redshifted from that of the HF monomer (3959.19cm−1), consistent with the hydrogen-bonded structure predicted by theory [E. Ya. Misochko et al., J. Am. Chem. Soc. 117, 11997 (1995)] and suggested by previous matrix isolation experiments [M. E. Jacox, Chem. Phys. 42, 133 (1979)]. The permanent electric dipole moment of this complex is experimentally determined by Stark spectroscopy to be 2.4±0.3D. The wide amplitude zero-point bending motion of this complex is revealed by the vibrational dependence of the A rotational constant. A sixfold reduction in the line broadening associated with the H–F vibrational mode is observed in going from CH3⋯HF to CD3⋯HF. The results suggest that fast relaxation in the former case results from near-resonant intermolecular vibration-vibration (V-V) energy transfer. Ab initio calculations are also reported (at the MP2 level) for the various stationary points on the F+CH4 surface, including geometry optimizations and vibrational frequency calculations for CH3⋯HF.
Time-resolved small-angle neutron scattering during heat-induced fibril formation from bovine β-lactoglobulin
Authors: Arnaudov Luben N. , de Vries Renko , Cohen Stuart Martien A.
Published: February 2006

We study in situ the kinetics of heat-induced fibrilar aggregation of bovine β-lactoglobulin at pH 2.0 and 80°C for the first time by time-resolved small-angle neutron scattering. A simple model for the scattering from a mixture of monodisperse charged spheres (monomeric β-lactoglobulin) interacting via a screened electrostatic repulsion and noninteracting long cylinders (protein fibrils) is used to describe the data. The experimental data are fitted to the model and the concentration of the monomeric protein and the protein incorporated in fibrils are obtained as adjustable parameters. Thus, a simple physical model allows the determination of realistic kinetic parameters during fibrilar protein aggregation. This result constitutes an important step in understanding the process of irreversible fibrilar aggregation of proteins.
Fluid simulations of toroidal ion temperature gradient turbulence
Authors: Sandberg I. , Isliker H. , Pavlenko V. P. , Hizanidis K. , Vlahos L.
Published: February 2006

The evolution of the toroidal ion temperature gradient mode instability is numerically studied by using the equations based on the standard reactive fluid model. The long-term dynamics of the instability are investigated using random-phase, small-amplitude fluctuations for initial conditions. The main events during the evolution of the instability that lead to the formation of large-scale coherent structures are described and the role of the dominant nonlinearities is clarified. The polarization drift nonlinearity leads to the inverse energy cascade while the convective ion heat nonlinearity is responsible for the saturation of the instability. Finally, the sensitivity of the saturated state to the initial plasma conditions is examined.
A credible model describing radiation-driven implosion in cylindrical hohlraums
Authors: Chang Tieqiang , Sheng Jiatian , Miao Wenyong , Li Yunsheng , Jiang Shaoen , Pei Wenbing , Chen Jiabin , Gao Yaoming , Yang Jiamin , Feng Tinggui , Zheng Zhijian , Zhang Lifa , Ding Yongkun , Li Jinghong , Li Meng
Published: February 2006

A one-dimensional model describing the radiation-driven implosion in cylindrical hohlraums is proposed in this article. For the model, the radiation flux boundary condition is composed of both the equilibrium and the nonequilibrium parts by means of the experimentally measured radiation temperature and the nonequilibrium x-ray spectra emitted from laser spots. The correctness of the model is guaranteed by a criterion, the capsule-absorbed radiation energy inferred from the hohlraum radiation theory, which is independent of any implosion simulation [Chang et al., Phys. Plasmas 11, 4286 (2004)]. In this article the model is applied to the implosion experiments performed at the Shenguang II laser facility [Zunqi et al., Chin. J. Lasers, B10, 6 (2001)], and the neutron yields are consistent with the experimental data if the hydrodynamic instability is appropriately considered.
Improvement of two-step K+–Na+ and Ag+–Na+ ion-exchanged glass waveguides by surface removal
Authors: Zou Jizuo , Chen Ray T.
Published: February 2006

We introduce a simple approach to improve the properties of waveguides fabricated by two-step K+–Na+ and Ag+–Na+ ion exchange in BK7 glass. By etching a 0.25-μm-thick layer off the waveguide surface, the propagation losses and polarization dependent losses caused by silver colloids formed during the ion exchange process can be significantly reduced. In addition, this method can improve the uniformity of the waveguides with varying waveguide patterns. After 24 h of annealing at 300 °C, the propagation losses of the etched waveguides have a value of 0.25–0.35dB∕cm, which is about 0.1dB∕cm lower than the waveguides without etch. The etch has little impact on the waveguide mode profiles.
Photodissociation dynamics of pyrimidine
Authors: Lin Ming-Fu , Dyakov Yuri A. , Tseng Chien-Ming , Mebel Alexander M. , Lin Sheng Hsien , Lee Yuan T. , Ni Chi-Kung
Published: February 2006

Photodissociation of pyrimidine at 193 and 248nm was investigated separately using vacuum ultraviolet photoionization at 118.4 and 88.6nm and multimass ion imaging techniques. Six dissociation channels were observed at 193nm, including C4N2H4→C4N2H3+H and five ring opening dissociation channels, C4N2H4→C3NH3+HCN, C4N2H4→2C2NH2, C4N2H4→CH3N+C3NH, C4N2H4→C4NH2+NH2, and C4N2H4→CH2N+C3NH2. Only the first four channels were observed at 248nm. Photofragment translational energy distributions and dissociation rates indicate that dissociation occurs in the ground electronic state after internal conversion at both wavelengths. The dissociation rates were found to be >5×107 and 1×106s−1 at 193 and 248nm, respectively. Comparison with the potential energies from ab initio calculations have been made.
Acceptor influence on hole mobility in fullerene blends with alternating copolymers of fluorene
Authors: Andersson L. Mattias , Inganäs Olle
Published: February 2006

Hole mobility in polyfluorene/fullerene blends has been studied with field effect transistors. Two different C60 derivatives and one C70 derivative have been investigated together with two different polyfluorenes. Mobility is presented as a function of acceptor loading at ratios suitable for photovoltaics and varies between 10−3 and 10−5cm2V−1s−1 depending on the polymer/acceptor combination. The hole mobility is increased in blends with the commonly used acceptor [6-6]-phenyl-C61-butyric acid methylester (PCBM). With related C60 and C70 derivatives the hole mobility is decreased under the same circumstances.
Evolutionary dynamics of social dilemmas in structured heterogeneous populations
Authors: Santos F. C. , Pacheco J. M. , Lenaerts Tom
Published: February 2006

Real populations have been shown to be heterogeneous, in which some individuals have many more contacts than others. This fact contrasts with the traditional homogeneous setting used in studies of evolutionary game dynamics. We incorporate heterogeneity in the population by studying games on graphs, in which the variability in connectivity ranges from single-scale graphs, for which heterogeneity is small and associated degree distributions exhibit a Gaussian tale, to scale-free graphs, for which heterogeneity is large with degree distributions exhibiting a power-law behavior. We study the evolution of cooperation, modeled in terms of the most popular dilemmas of cooperation. We show that, for all dilemmas, increasing heterogeneity favors the emergence of cooperation, such that long-term cooperative behavior easily resists short-term noncooperative behavior. Moreover, we show how cooperation depends on the intricate ties between individuals in scale-free populations.
Disc1
is mutated in the 129S6/SvEv strain and modulates working memory in mice
Authors: Koike Hiroko , Arguello P. Alexander , Kvajo Mirna , Karayiorgou Maria , Gogos Joseph A.
Published: February 2006

Disrupted-In-Schizophrenia (
DISC1
) is a leading candidate schizophrenia susceptibility gene. Here, we describe a deletion variant in
mDisc1
specific to the 129S6/SvEv strain that introduces a termination codon at exon 7, abolishes production of the full-length protein, and impairs working memory performance when transferred to the C57BL/6J genetic background. Our findings provide insights into how
DISC1
variation contributes to schizophrenia susceptibility in humans and the behavioral divergence between 129S6/SvEv and C57BL/6J mouse strains and have implications for modeling psychiatric diseases in mice.
The molecular architecture of the metalloprotease FtsH
Authors: Bieniossek Christoph , Schalch Thomas , Bumann Mario , Meister Markus , Meier Reto , Baumann Ulrich
Published: February 2006

The ATP-dependent integral membrane protease FtsH is universally conserved in bacteria. Orthologs exist in chloroplasts and mitochondria, where in humans the loss of a close FtsH-homolog causes a form of spastic paraplegia. FtsH plays a crucial role in quality control by degrading unneeded or damaged membrane proteins, but it also targets soluble signaling factors like σ
32
and λ-CII. We report here the crystal structure of a soluble FtsH construct that is functional in caseinolytic and ATPase assays. The molecular architecture of this hexameric molecule consists of two rings where the protease domains possess an all-helical fold and form a flat hexagon that is covered by a toroid built by the AAA domains. The active site of the protease classifies FtsH as an Asp-zincin, contrary to a previous report. The different symmetries of protease and AAA rings suggest a possible translocation mechanism of the target polypeptide chain into the interior of the molecule where the proteolytic sites are located.
Studies of the Toxicological Potential of Tripeptides (L-Valyl-L-prolyl-L-proline and L-lsoleucyl-L-prolyl-L-proline): IV. Assessment of the Repeated-Dose Toxicological Potential of Synthesized L-Valyl-L-prolyl-L-proline in Male and Female Rats and Dogs
Authors: Nakamura Yasunori , Bando Izuki , Mennear John H. , Bernard Bruce K.
Published: February 2006

The objective of these repeated-dose, 8-week studies was to assess the toxicological potential of a synthetic tripeptide, L-valyl-L-prolyl-L-proline (VPP), when administered to Charles River rats and Beagle dogs. Groups of 20 male and 20 female rats were fed powdered diets containing sufficient VPP to afford daily doses of 0, 2, 8, or 16 mg/kg body weight (BW)/day. Groups of five male and five female dogs were administered 0, 2, 8, or 16 mg/kg BW/day in hard gelatin capsules. Antemortem evaluative parameters for both species included grossly observable clinical signs, body weight and food consumption, clinical pathology (hematology, clinical chemistry, urinalysis), and ophthalmological examinations. Dogs also received electrocardiographic examinations. Postmortem evaluations in both species included complete necropsy, determination of major organ weights, and histopathological examination of specimens from approximately 50 organs and tissues. All rats and dogs survived to the scheduled termination of the studies and neither species exhibited evidence of VPP effects on appetite or body weight gain/maintenance. Ophthalmic examinations revealed occasional lens clouding in rats, but this occurred in all groups and was not attributable to VPP. Some clinical pathology parameters in both species were occasionally altered, but there was no evidence that this was dose-related. Electrocardiographic examinations in dogs revealed no VPP-associated changes. Mid- and high-dose male rats (but not females) had slightly reduced mean pituitary and kidney weight parameters, whereas mid- and high-dose females had slightly increased mean uterus:body weight ratios. There were no microscopic correlates for these minor changes. Ten percent to 20 % of all female rats (but not males) exhibited corticomedullary mineralization of the kidney and gliosis of the optic nerve, and 10% to 20% of males (but not females) had thymic hemorrhage. Postmortem evaluations of dogs revealed no VPP-related effects on organ weights or either macro- or microscopic appearances of organs. The results of these studies provided no evidence of either local or systemic toxicity. Similarly, there was no evidence of neurotoxicity that might have been detected by the appearance of physical or behavioral changes during gross observations of animals. Although these results do not identify target organs for VPP toxicity, the no-observable-effect level and maximally tolerated dose are both greater than 16 mg/kg/day when administered to male and female rats and dogs for 8 consecutive weeks. Based upon food enhancement levels of VPP currently being evaluated, the resultant margin of safety (160) is substantial.
Studies of the Toxicological Potential of Tripeptides (L-Valyl-L-prolyl-L-proline and L-lsoleucyl-L-prolyl-L-proline): V. A 13-Week Toxicity Study of Tripeptides-Containing Casein Hydrolysate in Male and Female Rats
Authors: Mizuno Seiichi , Mennear John H. , Matsuura Keiichi , Bernard Bruce K.
Published: February 2006

The objective of this multiple-dose toxicity study was to assess the toxicological potential of two tripeptides, L-valyl-L-prolyl-L-proline (VPP) and L-isoleucyl-L-prolyl-L-proline (IPP), when administered once daily for 91 consecutive days to rats. The test article, powdered casein hydrolysate (CH) known to contain 0.6% VPP plus IPP, was prepared using Aspergillus oryzae protease. Prior to administration to the rats by oral gavage, the test article was suspended in sterile water. Groups of 12 male and 12 female Charles River rats were administered once daily doses of 0, 40, 200, or 1000 mg of CH (0, 0.2,1.2, or 6 mg VPP plus IPP/kg body weight [BW]). Antemortem evaluative parameters included gross observations of behavior and clinical signs; food consumption and body weight gains; ophthalmologic examinations; clinical pathology (hematology, clinical chemistry); and urinalysis. Postmortem parameters included determination of absolute and relative (to fasting body weight) organ weights and histopathological evaluation of approximately 50 organs and tissues from each animal. All rats survived until the scheduled termination of the study and no treatment-related clinical signs were observed. Food consumption was unaffected by administration of CH. All animals gained weight and there were no statistical differences between groups with respect to weight gains. There were no meaningful changes in hematological or coagulation parameters. Mid- and high-dose males (but not females) had slightly (<2%) increased mean serum chloride concentrations, but because the difference was so small and it was observed in only one sex, the authors considered its association with CH administration to be doubtful. Urinalysis revealed the occasional presence of crystals, leukocytes, and epithelial cells in animals from all experimental groups. Similarly, ophthalmic changes (lenticular clouding) were observed in both control and dosed animals. Mean relative (to body weight) kidney weight was decreased by 8 % in low-dose males and mean relative uterus weight was elevated 46 % in low-dose females. Absolute organ weights were not affected. Only naturally occurring microscopic changes were observed in all groups and none could be attributed to CH administration. It was concluded that, under the conditions of these experiments, the maximally tolerated dose (MTD) and the no-observable-effect level (NOEL) for powdered CH administered once daily for 13 weeks was greater than 1000 mg/kg BW/day or greater than 6 mg of VPP plus IPP/kg BW/day. There was no evidence of target organ toxicity associated with administration of the tripeptides. This corresponds to an margin of safety (MOS) of 60 based upon current thinking regarding incorporation in food.
Studies of the Toxicological Potential of Tripeptides (L-Valyl-L-prolyl-L-proline and L-lsoleucyl-L-prolyl-L-proline): VI. Effects of Lactobacillus helveticus-fermented Milk Powder on Fertility and Reproductive Performance of Rats
Authors: Kurosaki Takahiro , Maeno Masafumi , Mennear John H. , Bernard Bruce K.
Published: February 2006

The objective of these studies was to assess the effects of the tripeptides, L-valyl-L-prolyl-L-proline (VPP) and L-isoleucyl-L-prolyl-L-proline (IPP), on reproductive capabilities of male and female rats. The specific goals of the experiments were (1) to determine the effects of orally administered tripeptides on (a) fertility and reproductive behavior in both sexes of rats, (b) embryo-fetal development in pregnant rats, and (c) pre- and postnatal development of rats exposed to tripeptides in utero and during lactation; and (2) to estimate the no-observable-adverse-effect doses of tripeptides in maternal and fetal rats. During the conduct of these classical segment I, II, and III studies, the test material was powdered Lactobacillus helveticus-fermented milk (FM), which contains the tripeptides, VPP and IPP. FM (0, 500, 1000 or 2000 mg/kg body weight [BW]/day—equivalent to 0, 0.8, 1.6, or 3.3 mg/kg BW/day of VPP plus IPP) was administered to males by oral gavage from 4 weeks prior to mating until sacrifice, and to females from 2 weeks prior to mating through day 20 of lactation. Evaluative parameters included monitoring grossly observable clinical signs; food consumption and body weight gains; mating behavior and fertility indices of both sexes; implantation and maintenance of embryos; sex ratio of live pups ; fetal viability; incidences of external, visceral or skeletal variations; growth and behavioral development; as well as reproductive capabilities of Fi offspring exposed to FM during gestation and lactation. All animals were subjected to macroscopic examination at termination of their segment of the studies. Clinical signs, body weights, and food consumption were unaffected by administration of FM. During segment I, the test agent had no effect on estrus cycle, mating behavior, fertility index, or reproductive competence of either males or females. The results of segment II experiments revealed no effects of FM on postimplantation survival-loss, sex ratio or birth weights of live fetuses, and there was no evidence of treatment-associated developmental or teratological effects. During segment III, FM was without effect on pup viability, behavioral and sexual maturation, and reproductive capability of the F1 generation. Under the conditions of these experiments, the no-observable-adverse-effect level (NOAEL) of FM on reproductive performance in male and female rats is greater than 2000 mg/kg BW/day, the equivalent of 3.3 mg/kg BW/day of VPP plus IPP.
Studies of the Toxicological Potential of Tripeptides (L-Valyl-L-prolyl-L-proline and L-lsoleucyl-L-prolyl-L-proline): VII. Micronucleus Test of Tripeptides-Containing Casein Hydrolysate and Lactobacillus helveticus-fermented Milk Powders in Rats and Mice
Authors: Matsuura Keiichi , Mennear John H. , Maeno Masafumi , Bernard Bruce K.
Published: February 2006

The objective of these in vivo experiments was to assess the mutagenic potential of tripeptides as reflected by the ability of the test compound to induce the formation of micronuclei in mouse polychromatic erythrocytes. The test agents used in these experiments were (1) powdered Aspergillus oryzae protease casein hydrolysate (CH) and (2) powdered Lactobacillus helveticus-fermented milk (FM). Both test agents contain two tripeptides, L-valyl-L-prolyl-L-proline (VPP) and L-isoleucyl-L-prolyl-L-proline (IPP). Male Sprague-Dawley rats (five per group) were administered doses of 0, 500, 1000, or 2000 mg (0, 3, 6, or 12 mg VPP plus IPP)/kg body weight (BW)/day CH by oral gavage for 2 days. Male CD-I mice (six per group) received a single oral gavage dose of 0, 500, 1000, or 2000 mg (0, 0.8, 1.6 or 3.3 mg VPP plus IPP)/kg BW of FM. Positive-control agents were cyclophosphamide (10 mg/kg, intraperitoneal [i.p.]) in rats and mitocycin C (2 mg/kg, i.p.) in mice. Twenty-four hours after the second dose of CH, or the dose of cyclophosphamide to rats, or FM or mitocycin C to mice, bone marrow cells were fixed and examined for the presence of polychromatic erythrocytes (PCEs) and the presence or absence of mi-cronucleated PCEs (MNPCEs). Administration of CH to rats and FM to mice produced neither changes in body weights nor signs of systemic toxicity. Similarly, neither CH nor FM caused statistically significant variations in the incidences of either PCEs or MNPCEs. Both positive-control agents caused unequivocal increases in the incidence of MNPCEs and cyclophosphamide significantly reduced the percent of rat erythrocytes appearing as PCEs. The results of these micronucleus assays conducted with either powdered CH or FM in rats and mice, respectively, show that neither form of the tripeptides possesses the potential to induce micronuclei formation in these rodent species.
Studies of the Toxicological Potential of Tripeptides (L-Valyl-L-prolyl-L-proline and L-lsoleucyl-L-prolyl-L-proline): IX. Evaluation of the Mutagenic Potential of Synthesized L-Valyl-L-prolyl-L-proline in the Salmonella-Escherichia coli/Microsome, Incorporation Assay
Authors: Bernard Bruce K. , Nakamura Yasunori , Aihara Kotaro , Mennear John H.
Published: February 2006

The objective of this study was to assess the mutagenic potential of a synthesized tripeptide, L-valyl-L-prolyl-L-proline (VPP), to induce mutational changes in Salmonella typhimurium LT2 strains TA1535, TA1537, TA98, and TA100, and Escherichia coli strain WP2uvrA in the classical Ames test protocol. Bacteria were exposed to plate concentrations of VPP of 0,156.2, 312.5, 625, 1250, 2500, and 5,000 /ig/plate in distilled water, in the presence and absence of Aroclor 1254-induced rat liver homogenate preparation (S9). Positive-control agents included sodium azide (TA100 and TA1535); 2-aminoanthracene (TA98, TA100, TA1535, TA1537, and WP2uvrA); 9-aminoacridine (TA1537); 2-nitrofluorene (TA98); and N-ethyl-N-nitro-N-nitrosoguanidine (WP2uvrA) in DMSO. Incubations were conducted at 37° C for about 48 h then revertant colonies were counted. All positive-control agents were consistently and unequivocally positive, but there was no evidence that VPP induced increases in the incidences of revertant colonies in any bacterial strain with and without metabolic activation. These findings were replicated in a second, confirmatory test performed with and without S9. The results of the experiments revealed no treatment-associated changes in the incidence of revertant colonies in any bacterial strain tested. These results support a conclusion that, under the experimental conditions described, there is no evidence that VPP possesses mutagenic potential.
Community, Belonging and Intimate Ethnicity
Authors: Fortier Anne-Marie
Published: February 2006

This paper analyses the role of the Centro Scalabrini in London in defining a sense of belonging and identification for Italians in Britain. The essay broadens the conventional focus on how community organizations contribute to constructing an ‘imagined community’ for minority or migrant populations by suggesting that organizations are used as cultural objects and collective props for enacting and experiencing collective affective belonging abroad. The paper examines the processes through which community spaces themselves are constructed as scenes of ethnicity, for example, in the visual and narrative accounts of events found in the community press. However, rather than arguing that ethnic organizations simply reproduce an identity and culture, it is argued that the community centre offers intimations of ethnicity, as well as ‘intimate ethnicity’, for those who use it and move through it. As a locale in which Italians and other migrants can find themselves again (ritrovarsi), what the centre offers is not the continuity or reproduction of the old world; it is the production of a portable Italianness through traces that are filled with sensuality, with the bodily experience of contact.
Seeing Ethnic Succession in Little Italy: Change despite Resistance
Authors: Krase Jerome
Published: February 2006

This illustrated paper is the latest in a long series based on visual sociological research which I have conducted about how the meanings of neighbourhood spaces are changed by the agency of even the least of their inhabitants. Specifically, it attempts to demonstrate how the Italian-American character, or version of Italianness (Italianità), of four of New York City's most well-known Little Italies (Mulberry Street and East Harlem in Manhattan, Bensonhurst, Brooklyn, Belmont, Bronx) has been affected by the invasions of new and different ethnic groups. The spatial and semiotic logic of diasporic/transnational processes that have taken place over the course of a century is presented here in the form of scholarly and journalistic reportage, as well as photographic images. All these sources document and illustrate contrasting and changing demography, but here special attention is paid to commercial vernacular landscapes which play a major role in defining the ethnic (in this case Italian) quality of city neighbourhoods. It is also suggested that this Visual Sociological approach might have value if applied in parallel studies of how immigrants are changing the meanings of urban spaces in contemporary Italy.
Two Bases of the Compatibility Effect in the Implicit Association Test (IAT)
Authors: Kinoshita Sachiko , Peek-O'leary Marie
Published: February 2006

Four experiments are reported, investigating the mechanisms underlying the compatibility effect in the Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998). All experiments involved two IATs: flower IAT, in which the target categories were flowers and insects, and number IAT, involving even and odd numbers as target categories. In Experiment 1, using the standard IAT procedure, the two IATs produced equal IAT effects, despite large differences in rated valence contrast between flowers and insects and between even and odd numbers. Experiment 2 used a procedure developed by Klauer and Mierke (2005) and produced results consistent with the view that valence plays a role in the flower IAT but not in the number IAT. Experiments 3 and 4 used manipulations similar to those developed by Rothermund and Wentura (2004) and showed that these manipulations affected the flower IAT and number IAT differently. The results provide converging evidence that the two types of IAT effects—one based on valence and one based on familiarity—are empirically dissociable.
EPS Mid-Career Award 2005: Developmental Cognitive Genetics: How Psychology can Inform Genetics and Vice Versa
Authors: Bishop Dorothy V. M.
Published: February 2006

Developmental neuropsychology is concerned with uncovering the underlying basis of developmental disorders such as specific language impairment (SLI), developmental dyslexia, and autistic disorder. Twin and family studies indicate that genetic influences play an important part in the aetiology of all of these disorders, yet progress in identifying genes has been slow. One way forward is to cut loose from conventional clinical criteria for diagnosing disorders and to focus instead on measures of underlying cognitive mechanisms. Psychology can inform genetics by clarifying what the key dimensions are for heritable phenotypes. However, it is not a one-way street. By using genetically informative designs, one can gain insights about causal relationships between different cognitive deficits. For instance, it has been suggested that low-level auditory deficits cause phonological problems in SLI. However, a twin study showed that, although both types of deficit occur in SLI, they have quite different origins, with environmental factors more important for auditory deficit, and genes more important for deficient phonological short-term memory. Another study found that morphosyntactic deficits in SLI are also highly heritable, but have different genetic origins from impairments of phonological short-term memory. A genetic perspective shows that a search for the underlying cause of developmental disorders may be misguided, because they are complex and heterogeneous and are associated with multiple risk factors that only cause serious disability when they occur in combination.
Nosocomial Transmission of Mycobacterium tuberculosis From an Extrapulmonary Site
Authors: D'Agata Erika M.C. , Wise Sharon , Stewart Amelia , Lefkowitz Lewis B.
Published: February 2006

Objective:

To assess the extent of nosocomial transmission and risk factors associated with tuberculin skin test (TST) conversions among healthcare workers (HCWs) exposed to a patient with genitourinary Mycobacterium tuberculosis.

Design:

Retrospective cohort study of exposed HCWs.

Setting:

A 275-bed community hospital in Middle Tennessee.

Participants:

A total of 128 exposed HCWs and the index patient, who required drainage of a prostatic abscess and bilateral orchiectomy and expired after a 27-day hospitalization. Disseminated tuberculosis was diagnosed at autopsy.

Methods:

Contact tracing was performed on exposed HCWs. Logistic regression was used to identify independent risk factors associated with TST conversion.

Results:

A total of 128 HCWs were exposed to the index patient. There was no evidence of active pulmonary tuberculosis throughout the patient's hospitalization; TST conversions occurred only among HCWs who were exposed to the patient during or after his surgical procedures. A total of 12 (13%) of 95 exposed HCWs who were previously nonreactive had newly positive TST: 6 of 28 nurses, 3 of 3 autopsy personnel, 2 of 17 respiratory therapists, and 1 of 12 surgical staff. By logistic regression, irrigation or packing of the surgical site was the only independent risk factor associated with TST conversion among nurses (odds ratio, 9; 95% confidence interval, 1.2-67; P=.03).

Conclusion:

Manipulation of infected tissues of the genitourinary tract can result in nosocomial transmission of tuberculosis.
An Evaluation of Hospital Special-Ventilation-Room Pressures
Authors: Rice Nancy , Streifel Andrew , Vesley Donald
Published: February 2006

Objective:

To quantitate the magnitude and consistency of positive (airflow out) and negative (airflow in) hospital special-ventilation-room (SVR) airflow.

Design:

A room-pressure evaluation was conducted during two seasons on a total of 18 rooms: standard rooms, airborne infection isolation rooms, and protective environment rooms. The pressures were measured using a digital pressure gaugepiezoresistive pressure sensor that measured pressure differentials. With doors closed, the rooms were measured a minimum of 30 times each for a cooling season and a heating season.

Results:

The standard rooms showed the least amount of variability in pressure differential, with an average of −0.2 Pa (median, −0.2 Pa), and an interquartile range (IQR) of 0.4 Pa. Airborne infection isolation rooms showed more variability in pressure, with an average of −0.3 Pa (median, −0.2 Pa) and an IQR of 0.5 Pa. Protective environment rooms had the greatest fluctuation in pressure, with an average of 8.3 Pa (median, 7.7 Pa) and an IQR of 8.8 Pa. Dramatic pressure changes were observed during this evaluation, which may have been influenced by room architectural differences (sealed vs unsealed); heating, ventilation, and air-conditioning zone interactions; and stack effect.

Conclusion:

The pressure variations noted in this study, which potentially affect containment or exclusion of contaminants, support the need for standardization of pressure requirements for SVRs. To maintain consistent pressure levels, creating an airtight seal and continuous pressure monitoring may be necessary.
Epidemiology of Surgical-Site Infections Diagnosed After Hospital Discharge A Prospective Cohort Study
Authors: Delgado-Rodríguez Miguel , Gómez-Ortega Antonio , Sillero-Arenas Maria , Llorca Javier
Published: February 2006

Objective:

To study postoperative infections in hospital and after discharge, and to identify the risk factors for such infections.

Design:

Prospective cohort study, with telephone follow-up for 1 month after hospital discharge.

Setting:

The general surgery service of a tertiary hospital in Spain.

Main Outcome Measure:

In-hospital and postdischarge surgical-site infection (SSI), always confirmed by a physician.

Results:

Of the 1,506 patients initially enrolled, 29 died during hospital stay, and 33 were lost to postdischarge follow-up. An SSI was identified prior to discharge in 123 patients and after discharge in 103. For several variables (age, serum albumin, glycemia, lengths of preoperative and postoperative hospital stay, etc), there were no differences between patients with postdischarge SSI and noninfected patients; however, there were differences detected between patients with postdischarge SSI and in-hospital SSI, as well as between patients with in-hospital SSI and noninfected patients. The analysis of risk factors showed that most predictors for in-hospital SSI did not behave in the same manner for postdischarge SSI. Stepwise logistic regression only identified chemoprophylaxis, age (advanced age was a preventive factor), and body mass index as independent risk factors for postdischarge SSI. Differences in risk factors between in-hospital and postdischarge SSIs remained even after controlling for time from operation to diagnosis.

Conclusions:

Most predictors of in-hospital SSI were not predictors of postdischarge SSI.
Converting Incidence and Prevalence Data of Nosocomial Infections Results From Eight Hospitals
Authors: Gastmeier Petra , Bräuer Helga , Sohr Dorit , Geffers Christine , Forster Dietmar H. , Daschner Franz , Rüden Henning
Published: February 2006

Objective:

To investigate the use of the formula of Rhame and Sudderth for the interconversion of prevalence and incidence data on the frequency of nosocomial infections.

Design:

Comparison of observed and calculated incidence data and prevalence data.

Setting:

One 8-week incidence investigation in the surgical and intensive care units of eight medium-sized hospitals; three separate point-prevalence studies in the same units.

Results:

The overall prevalence observed after the three prevalence studies in 2,169 patients was 6.8% (95% confidence interval [CI95], 5.7-8.0). In 2,882 discharged patients observed during the incidence study, the mean hospitalization was 9.8 days; patients with one or more nosocomial infection had a mean hospitalization time of 22.3 days and a mean interval of 8.2 days from admission to the first day of infection. Based on these data, the overall calculated incidence was 4.7%, whereas the observed incidence was 4.3% (CI95, 3.6-5.2). Vice versa, an overall prevalence of 6.2% was found when calculated from the observed incidence data.

The incidence data calculated from prevalence data also were within the confidence interval of the incidences observed for urinary tract infections and surgical-site infections. (However, it was not possible to convert the data for two of the eight hospitals.)

Conclusion:

The approximate mathematical relationship between the prevalence and incidence data of nosocomial infection is confirmed by this study. However, although it is theoretically possible, we would not recommend the conversion of prevalence into incidence data or vice versa.
An Outbreak of Imipenem-ResistantAcinetobacter baumanniiin Critically Ill Surgical Patients
Authors: Fierobe Lisiane , Lucet Jean-Christophe , Decré Dominique , Muller-Serieys Claudette , Deleuze Arnaud , Joly-Guillou Marie-Laure , Mantz Jean , Desmonts Jean-Marie
Published: February 2006

Objective:

To describe an outbreak of imipenem-resistantAcinetobacter baumannii(IR-Ab) and the measures for its control, and to investigate risk factors for IR-Ab acquisition.

Design:

An observational and a case-control study.

Setting:

A surgical intensive care unit (ICU) in a university tertiary care hospital.

Methods:

After admission to the ICU of an IR-Ab-positive patient, patients were prospectively screened for IR-Ab carriage upon admission and then once a week. Environmental cleaning and barrier safety measures were used for IR-Ab carriers. A case-control study was performed to identify factors associated with IR-Ab acquisition. Cases were patients who acquired IR-Ab. Controls were patients who were hospitalized in the ICU at the same time as cases and were exposed to IR-Ab for a similar duration as cases. The following variables were investigated as potential risk factors: baseline characteristics, scores for severity of illness and therapeutic intervention, presence and duration of invasive procedures, and antimicrobial administration.

Results:

Beginning in May 1996, the outbreak involved 17 patients over 9 months, of whom 12 acquired IR-Ab (cases), 4 had IR-Ab isolates on admission to the ICU, and 1 could not be classified. Genotypic analysis identified two different IR-Ab isolates, responsible for three clusters. Ten of the 12 nosocomial cases developed infection. Control measures included reinforcement of barrier safety measures, limitation of the number of admissions, and thorough environmental cleaning. No new case was identified after January 1997. Eleven of the 12 cases could be compared to 19 controls. After adjustment for severity of illness, a high individual therapeutic intervention score appeared to be a risk factor for IR-Ab acquisition.

Conclusion:

The outbreak ended after strict application of control measures. Our results suggest that high work load contributes to IR-Ab acquisition.
A Nosocomial Outbreak of MultiresistantAcinetobacter baumanniiOriginating From an Intensive Care Unit
Authors: Ling Moi Lin , Ang Angela , Wee Molly , Wang Grace Chee Yang
Published: February 2006

An outbreak of a multiresistantAcinetobacter baumanniiin February through September 1996 affected 103 patients in a regional hospital in Singapore. We describe the effectiveness of closure of the outbreak area and the importance of good teamwork in the management of the outbreak.
An In-Use Evaluation of an Alcohol-Based Pre-Surgical Hand Disinfectant
Authors: Bryce Elizabeth A. , Spence Darlene , Roberts Frederick J.
Published: February 2006

Objective:

To determine whether alcohol hand disinfection is an effective alternative to traditional agents for the pre-surgical scrub.

Design:

A prospective clinical trial of a 70% isopropanol pre-surgical hand disinfectant.

Setting:

The operating room suites at two hospital sites in British Columbia.

Methods:

Cases were selected to evaluate both short and longer procedures. The hand disinfectant was compared to agents in current use as surgical scrubs (4% chlorhexidine and 7.5% povidone-iodine). Surgical technique and glove use were not modified. Pre- and postoperative fingertip impression and “glove-juice” cultures were used to determine microbial burden, and hands were evaluated for skin integrity.

Results:

There was no statistical difference between the microbial hand counts following use of the alcohol-based product or the current agents, for cases less than 2 hours' duration. Comparison of longer surgical cases revealed significantly better pre- and postoperative culture results with the alcohol hand rinse, but analysis of matched pairs showed no significant difference in microbial counts. The alcohol hand rinse was equivalent to the operative scrub in terms of skin integrity and user acceptability.

Conclusion:

An alcohol hand rinse was equivalently effective in reducing microbial hand counts as the traditional pre-surgical scrub, both immediately after hand disinfection and at the end of the surgical procedure.
Hospital Management of Tuberculosis in a Region With a Low Incidence of Tuberculosis and a High Prevalence of Nontuberculous Mycobacteria
Authors: Alexander Barbara D. , Stout Jason E. , Reller L. Barth , Hamilton Carol Dukes
Published: February 2006

We prospectively assessed the management of patients with suspected tuberculosis (TB) in an area with a high prevalence of nontuberculous mycobacteria (NTM) and a low incidence of TB. Clinicians' assessments were sensitive for TB but had poor predictive value. The acid-fast smear was a weak predictor of TB, owing to a high rate of isolation of NTM.