bluuebunny/crossref_metadata_2025 huggingface dataset:
Three-dimensional instabilities and transient growth of a counter-rotating vortex pair
Authors: Donnadieu Claire , Ortiz Sabine , Chomaz Jean-Marc , Billant Paul
Published: September 2009

This paper investigates the three-dimensional instabilities and the transient growth of perturbations on a counter-rotating vortex pair. The two dimensional base flow is obtained by a direct numerical simulation initialized by two Lamb–Oseen vortices that quickly adjust to a flow with elliptic vortices. In the present study, the Reynolds number, ReΓ=Γ/ν, with Γ the circulation of one vortex and ν the kinematic viscosity, is taken large enough for the quasi steady assumption to be valid. Both the direct linearized Navier–Stokes equation and its adjoint are solved numerically and used to investigate transient and long time dynamics. The transient dynamics is led by different regions of the flow, depending on the optimal time considered. At very short times compared to the advection time of the dipole, the dynamics is concentrated on the points of maximal strain of the base flow, located at the periphery of the vortex core. At intermediate times, depending on the symmetry of the perturbation, one of the hyperbolic stagnation points provides the optimal amplification by stretching of the perturbation vorticity as in the classical hyperbolic instability. The growth of both short time and intermediate time transient perturbations are non- or weakly dependent of the axial wavenumber whereas the long time behavior strongly selects narrow bands of wavenumbers. We show that, for all unstable spanwise wavenumbers, the transient dynamics last until the nondimensional time t=2, during which the dipole has traveled twice the separation distance between vortices b. During that time, all the wavenumbers exhibit a transient growth of energy by a factor of 50, for the Reynolds number ReΓ=2000. For time larger than t=2, energy starts growing at a rate given by the standard temporal stability theory. For all wavenumbers and two Reynolds numbers, ReΓ=2000 and ReΓ=105, different instability branches have been computed using a high resolution Krylov method. At large Reynolds number, the computed Crow and elliptic instability branches are in excellent agreement with the inviscid theory [S. C. Crow, AIAA J. 8, 2172 (1970); S. Le Dizes and F. Laporte, J. Fluid Mech. 471, 120 (2002)] and numerical analysis [D. Sipp and L. Jacquin, Phys. Fluids 15, 1861 (2003)]. A novel oscillatory elliptic instability involving Kelvin waves with azimuthal wavenumbers m=0 and |m|=2, that was missed in previous numerical analysis [D. Sipp and L. Jacquin, Phys. Fluids 15, 1861 (2003)] is found. For the stationary elliptic instability, we show that viscous effect may be estimated using the large Reynolds number direct and adjoint eigenmodes. This asymptotically exact estimate of the viscous damping of elliptic instability mode agrees with our direct numerical computation of instability branches at moderate Reynolds number and demonstrates that formula proposed by Le Dizes and Laporte [J. Fluid Mech. 471, 120 (2002)] strongly over estimated the viscous correction.
Vacuum-compatible pulse selector for free-electron laser
Authors: Kudo Togo , Hirono Toko , Nagasono Mitsuru , Yabashi Makina
Published: September 2009

We developed a vacuum-compatible pulse selector for a free-electron laser. A rotating cylinder with eight apertures in a vacuum is driven by a closed-loop stepping motor system through a magnetically coupled rotary feedthrough. A field programmable gate array is used to synchronize the cylinder rotation with a trigger signal of the accelerator at a maximum repetition rate of 60 Hz. We achieved to select specific pulses from a continuous pulse train of the SPring-8 Compact SASE Source.
Born–Oppenheimer quantum dynamics of the C(D1)+H2 reaction on the CH2 ã A11 and b̃ B11 surfaces
Authors: Defazio Paolo , Petrongolo Carlo , Bussery-Honvault Béatrice , Honvault Pascal
Published: September 2009

We present the Born–Oppenheimer coupled-channel dynamics of the reaction C12(D1)+H12(X Σ1g+)→CH(X Π2)+H(S2), considering the uncoupled CH2 states ã A11 and b̃ B11, the permutation-inversion symmetry, and Coriolis interactions. Using accurate MRCI potential energy surfaces (PESs), we obtain initial-state-resolved reaction probabilities, cross sections, and rate constants through the time-dependent, real wavepacket (WP) and flux methods, taking into account the proton-spin statistics for both electronic species. Comparing results on both PESs, we point out the role of the b̃ B11 upper state on the initial-state-resolved dynamics and on the thermal kinetic rate. WP probabilities at J=0 and cross sections at Ecol=0.080 eV agree quite well with quantum-mechanical time-independent findings. Probabilities and WP snapshots show the different reaction mechanisms on the PESs, i.e., an ã A11 indirect perpendicular insertion and a b̃ B11 direct sideways collision, associated with many and few sharp resonances, respectively. All cross sections are very large at low Ecol, decrease at high energies, and that of the lowest reactant state presents some weak resonances. As the temperature increases from 100 to 400 K, the ã A11 rate constant increases slightly from 1.37×10−10 to 1.43×10−10 cm3 s−1, whereas the b̃ B11 one decreases from 1.30×10−10 to 0.98×10−10 cm3 s−1. In this temperature range, the b̃ B11 contribution to the total rate constant thus decreases from 49% to 41%. At 300 K, the WP and experimental rates are equal to (2.45±0.08)×10−10 and (2.0±0.6)×10−10 cm3 s−1, respectively.
Guided growth of in-plane silicon nanowires
Authors: Yu Linwei , Oudwan Maher , Moustapha Oumkelthoum , Fortuna Franck , Roca i Cabarrocas Pere
Published: September 2009

We report on a guided growth of silicon nanowires (SiNWs) based on an in-plane solid-liquid-solid mechanism, which provides a general strategy to deploy SiNWs precisely into desired circuits. During a reacting-gas-free annealing process, the SiNWs are activated to grow and be guided into predefined patterns by effective controlling the movement of the catalyst drops. We demonstrate three different approaches to achieve a guided growth of SiNWs, which are as follows: (1) by an a-Si:H channel, (2) by a step edge, and (3) by an a-Si:H edge. These results provide a design principle for future SiNWs-based nanodevices.
Fabrication of single electron transistors using transfer-printed aligned single walled carbon nanotubes arrays
Authors: Tabata Hiroshi , Shimizu Maki , Ishibashi Koji
Published: September 2009

A technique has been developed to transfer the aligned single-walled carbon nanotubes (SWCNTs) grown on a single-crystal quarz substrate to a SiO2/Si substrate. Aligned single electron transistors (SETs) have been fabricated with the transferred SWCNTs, and the low-temperature transport measurements have been carried out at 1.5 K. Several SETs fabricated in this approach exhibited regular Coulomb oscillations and closed Coulomb diamonds, which indicate the single quantum dot behavior. This suggests that the mechanical transfer technique does not produce serious damage to the SETs and would be useful for future integrated SET devices and circuits.
Orientational bonding model for temperature dependent micellization and solubility of diblock surfactants
Authors: Davis Jonathan R. , Panagiotopoulos Athanassios Z.
Published: September 2009

A lattice model for diblock surfactants that incorporates orientational bonding has been developed for studying self-assembly in dilute solutions. Using grand canonical Monte Carlo simulations with histogram reweighting and mixed field finite size scaling, we examine the effect of amphiphile architecture on phase transitions and distinguish between first order transitions that create a disordered liquid phase and higher order transitions that indicate the formation of finite sized aggregates. As the solution temperature increases, we find that the critical micelle concentration for the orientational bonding model surfactants reaches a minimum value at a temperature that can be controlled by varying the number of bonding orientations between the solvophobic surfactant monomers and the implicit solvent. This trend is qualitatively similar to experimental data for ionic and nonionic surfactants in aqueous solutions. A comparable dependence on temperature is observed in the limit of amphiphile solubility for phase separating systems. None of the model surfactants considered here undergo both a first and a higher order transition over the range of densities and temperatures examined.
Förster transfer outside the weak-excitation limit
Authors: Camley Brian A. , Brown Frank L. H. , Lipman Everett A.
Published: September 2009

The efficiency of resonance energy transfer can be used to determine nanometer-scale separations between dye molecules in a donor-acceptor pair. We argue that the standard method for making this determination in single-pair experiments is valid only when excitation by the applied field is much slower than the other photophysical processes in the system. We derive a simple relation between measured transfer efficiency and interdye distance that is valid regardless of excitation rate for a broad class of currently accepted models for dye photophysics. Significant deviations from weak-field results are predicted for typical experimental conditions.
An ab initio study of the (H2O)20H+ and (H2O)21H+ water clusters
Authors: Kuś Tomasz , Lotrich Victor F. , Perera Ajith , Bartlett Rodney J.
Published: September 2009

The study of the minimum Born–Oppenheimer structures of the protonated water clusters, (H2O)nH+, is performed for n=20 and 21. The structures belonging to four basic morphologies are optimized at the Hartree–Fock, second-order many-body perturbation theory and coupled cluster level, with the 6–31G, 6-31G∗, and 6-311G∗∗ basis sets, using the parallel ACES III program. The lowest energy structure for each n is found to be the cagelike form filled with H2O, with the proton located on the surface. The cage is the distorted dodecahedron for the 21-mer case, and partially rearranged dodecahedral structure for the 20-mer. The results confirm that the lowest energy structure of the magic number n=21 clusters corresponds to a more stable form than that of the 20-mer clusters.
Coexistence of shrubs and grass in a semi-arid landscape: a case study of mulga (Acacia aneura, Mimosaceae) shrublands embedded in fire-prone spinifex (Triodia pungens, Poaceae) hummock grasslands
Authors: Nicholas Anstee M. M. , Franklin Donald C. , Bowman David M. J. S.
Published: September 2009

The persistence of relatively fire-sensitive mulga (Acacia aneura F.Muell. ex Benth., Mimosaceae) shrublands within a landscape matrix of highly flammable spinifex (Triodia spp. R.Br., Poaceae) hummock grassland is a central question in the ecology of semiarid Australia. It is also a special case of questions about the coexistence of grasses and woody plants that have general application in semiarid rangelands and tropical savannas. With the use of field surveys and a 24-year fire history, we examined their coexistence on a sandplain in the Tanami Desert, Northern Territory, Australia. Mulga and spinifex each formed discrete monodominant stands with generally abrupt boundaries that did not correspond to obvious edaphic or topographic discontinuities. Spinifex hummock grasslands burnt almost three times as often as mulga shrublands and tended to occur on lighter soils with less biological crusting and more physical soil crusting. A combination of fire and soil variables described the environmental partitioning better than did either alone. Biological crusting increased with time since fire in both vegetation types. The demographic structure of mulga stands reflected their fire history, the more frequently burnt stands comprising almost entirely small plants. One fifth of mulga plants <0.5 m tall were resprouts. Our data provide support for the hypothesis that abrupt boundaries between mulga shrublands and spinifex hummock grasslands can be generated across diffuse environmental gradients by fire–soil–vegetation feedback loops. The oft-severe demographic impact of fire on mulga that is burnt raises questions about the appropriateness of frequent intense fires in this landscape.
Physiological responses in Macadamia integrifolia on exposure to manganese treatment
Authors: Fernando D. R. , Baker A. J. M. , Woodrow I. E.
Published: September 2009

Macadamia integrifolia Maiden & Betche (Proteaceae) from eastern Australia is farmed for its edible nuts and is capable of accumulating high foliar concentrations of manganese (Mn). It was investigated here in a pot trial, where a range of physiological responses to Mn treatment were measured. Although Mn uptake was initially slow, final foliar concentrations increased linearly with treatment levels. The highest observed mean foliar concentration of Mn was 7900 μg g–1 dry weight (dwt). No negative effect of Mn accumulation on plant growth was apparent, even at the highest treatment concentration. Two groups of plants, each exposed to either full sunlight or part shade were identically treated with Mn. At the highest treatment concentration of Mn, the mean foliar concentrations of Mn of the former group were found to be significantly higher than those of the latter. Because M. integrifolia is cyanogenic, leaf cyanogenic glycosides were quantified to test for a relationship between the known chemical defence strategy of cyanogenesis and a proposed one of Mn accumulation. However, further studies are required to clarify this. Quantitative organic acid analyses showed that oxalate ion may bind excess Mn in M. integrifolia leaves. That Mn is not accumulated in M. integrifolia fruit could render the species potentially useful for remediating Mn-affected soils long-term, while serving as a food crop.
Labour scarcity restricts the potential scale of grazed perennial plants in the Western Australian wheatbelt
Authors: Doole Graeme J. , Bathgate Andrew D. , Robertson Michael J.
Published: September 2009

Rural populations in Australia are in decline and rural farm businesses now endure chronic labour shortages. Livestock enterprises traditionally require more labour than their cropping counterparts and this threatens future increases in their intensity and scale. The influence that labour scarcity has on the profitability of mixed-farming systems in the Central Wheatbelt of Western Australia is investigated in this study. When labour supply is assumed to be non-limiting, perennial plants are profitable where their out-of-season production sustains a sizeable breeding flock in a prime-lamb enterprise. However, when labour supply is limited and labour demand is defined as a function of enterprise mix, cropping activity increases and livestock production decreases. In addition, the proportion of the farm planted with perennial pasture declines. This has implications for natural resource management, with perennial pasture helping to prevent soil erosion, decrease waterlogging, and reduce recharge to saline watertables. Efforts to improve the labour efficiency of livestock production are therefore highly pertinent if perennial pastures are to offset land degradation on a broader scale.
Chemical dynamics of triacetylene formation and implications to the synthesis of polyynes in Titan's atmosphere
Authors: Gu X. , Kim Y. S. , Kaiser R. I. , Mebel A. M. , Liang M. C. , Yung Y. L.
Published: September 2009

For the last four decades, the role of polyynes such as diacetylene (HCCCCH) and triacetylene (HCCCCCCH) in the chemical evolution of the atmosphere of Saturn's moon Titan has been a subject of vigorous research. These polyacetylenes are thought to serve as an UV radiation shield in planetary environments; thus, acting as prebiotic ozone, and are considered as important constituents of the visible haze layers on Titan. However, the underlying chemical processes that initiate the formation and control the growth of polyynes have been the least understood to date. Here, we present a combined experimental, theoretical, and modeling study on the synthesis of the polyyne triacetylene (HCCCCCCH) via the bimolecular gas phase reaction of the ethynyl radical (CCH) with diacetylene (HCCCCH). This elementary reaction is rapid, has no entrance barrier, and yields the triacetylene molecule via indirect scattering dynamics through complex formation in a single collision event. Photochemical models of Titan's atmosphere imply that triacetylene may serve as a building block to synthesize even more complex polyynes such as tetraacetylene (HCCCCCCCCH).
Crystal structure of the catalytic domain of the tumor-associated human carbonic anhydrase IX
Authors: Alterio Vincenzo , Hilvo Mika , Di Fiore Anna , Supuran Claudiu T. , Pan Peiwen , Parkkila Seppo , Scaloni Andrea , Pastorek Jaromir , Pastorekova Silvia , Pedone Carlo , Scozzafava Andrea , Monti Simona Maria , De Simone Giuseppina
Published: September 2009

Carbonic anhydrase (CA) IX is a plasma membrane-associated member of the α-CA enzyme family, which is involved in solid tumor acidification. It is a marker of tumor hypoxia and a prognostic factor in several human cancers. An aberrant increase in CA IX expression in chronic hypoxia and during development of various carcinomas contributes to tumorigenesis through at least two mechanisms: pH regulation and cell adhesion control. Here we report the X-ray structure of the catalytic domain of CA IX in complex with a classical, clinically used sulfonamide inhibitor, acetazolamide. The structure reveals a typical α-CA fold, which significantly differs from the other CA isozymes when the protein quaternary structure is considered. Thus, two catalytic domains of CA IX associate to form a dimer, which is stabilized by the formation of an intermolecular disulfide bond. The active site clefts and the PG domains are located on one face of the dimer, while the C-termini are located on the opposite face to facilitate protein anchoring to the cell membrane. A correlation between the three-dimensional structure and the physiological role of the enzyme is here suggested, based on the measurement of the pH profile of the catalytic activity for the physiological reaction, CO
2
hydration to bicarbonate and protons. On the basis of the structural differences observed between CA IX and the other membrane-associated α-CAs, further prospects for the rational drug design of isozyme-specific CA inhibitors are proposed, given that inhibition of this enzyme shows antitumor activity both in vitro and in vivo.
Reversal of long-term dendritic spine alterations in Alzheimer disease models
Authors: Smith Donna L. , Pozueta Julio , Gong Bing , Arancio Ottavio , Shelanski Michael
Published: September 2009

Synapse loss is strongly correlated with cognitive impairment in Alzheimer's disease (AD). We have previously reported the loss of dendritic spines and the presence of dystrophic neurites in both the hippocampi of transgenic mice overexpressing amyloid precursor protein (APP) and in the human brain affected with AD. In the studies reported here we have asked whether the acute alterations in dendritic spines induced by Aβ, as well as the chronic loss of spine density seen in hAPP transgenic mice, are reversible by treatments that restore the cAMP/PKA/CREB signaling pathway or proteasome function to control levels. The results show that both rolipram and TAT-HA-Uch-L1 restore spine density to near control conditions, even in elderly mice. The results suggest that changes in dendritic structure and function that occur after Aβ elevation are reversible even after long periods of time, and that one could envision therapeutic approaches to AD based on this restoration that could work independently of therapies aimed at lowering Aβ levels in the brain.
Interpreting Cantonese utterance-final particles in bilingual courtroom discourse
Authors: Leung Ester , Gibbons John
Published: September 2009

This paper examines an unusual feature of spoken Cantonese — the utterance-final particle — to see how it is deployed and rendered by interpreters in courtroom discourse. The data is based on five rape trials heard in the Hong Kong courtrooms. It is a known fact that different participants in the courtroom construct their version of the truth utilizing different linguistic devices. However, different language systems have different linguistic phenomenon which may be common in one language but non-existent in another. Utterance particle is one of those unique language devices in Cantonese which is not available in English. Court interpreters often find themselves facing the task of maintaining the coherence and modality of all the participants’ languages while interpreting for these different language systems.
Role of ERO1-α–mediated stimulation of inositol 1,4,5-triphosphate receptor activity in endoplasmic reticulum stress–induced apoptosis
Authors: Li Gang , Mongillo Marco , Chin King-Tung , Harding Heather , Ron David , Marks Andrew R. , Tabas Ira
Published: September 2009

Endoplasmic reticulum (ER) stress–induced apoptosis is involved in many diseases, but the mechanisms linking ER stress to apoptosis are incompletely understood. Based on roles for C/EPB homologous protein (CHOP) and ER calcium release in apoptosis, we hypothesized that apoptosis involves the activation of inositol 1,4,5-triphosphate (IP3) receptor (IP3R) via CHOP-induced ERO1-α (ER oxidase 1 α). In ER-stressed cells, ERO1-α is induced by CHOP, and small interfering RNA (siRNA) knockdown of ERO1-α suppresses apoptosis. IP3-induced calcium release (IICR) is increased during ER stress, and this response is blocked by siRNA-mediated silencing of ERO1-α or IP3R1 and by loss-of-function mutations in Ero1a or Chop. Reconstitution of ERO1-α in Chop−/− macrophages restores ER stress–induced IICR and apoptosis. In vivo, macrophages from wild-type mice but not Chop−/− mice have elevated IICR when the animals are challenged with the ER stressor tunicamycin. Macrophages from insulin-resistant ob/ob mice, another model of ER stress, also have elevated IICR. These data shed new light on how the CHOP pathway of apoptosis triggers calcium-dependent apoptosis through an ERO1-α–IP3R pathway.
Coassembly of Mgm1 isoforms requires cardiolipin and mediates mitochondrial inner membrane fusion
Authors: DeVay Rachel M. , Dominguez-Ramirez Lenin , Lackner Laura L. , Hoppins Suzanne , Stahlberg Henning , Nunnari Jodi
Published: September 2009

Two dynamin-related protein (DRP) families are essential for fusion of the outer and inner mitochondrial membranes, Fzo1 (yeast)/Mfn1/Mfn2 (mammals) and Mgm1 (yeast)/Opa1 (mammals), respectively. Fzo1/Mfns possess two medial transmembrane domains, which place their critical GTPase and coiled-coil domains in the cytosol. In contrast, Mgm1/Opa1 are present in cells as long (l) isoforms that are anchored via the N terminus to the inner membrane, and short (s) isoforms were predicted to be soluble in the intermembrane space. We addressed the roles of Mgm1 isoforms and how DRPs function in membrane fusion. Our analysis indicates that in the absence of a membrane, l- and s-Mgm1 both exist as inactive GTPase monomers, but that together in trans they form a functional dimer in a cardiolipin-dependent manner that is the building block for higher-order assemblies.
Distinct roles for E12 and E47 in B cell specification and the sequential rearrangement of immunoglobulin light chain loci
Authors: Beck Kristina , Peak Mandy M. , Ota Takayuki , Nemazee David , Murre Cornelis
Published: September 2009

The E2A gene products, E12 and E47, are critical regulators of B cell development. However, it remains elusive whether E12 and E47 have overlapping and/or distinct functions during B lymphopoiesis. We have generated mice deficient for either E12 or E47 and examined their roles in B cell maturation. We show that E47 is essential for developmental progression at the prepro–B cell stage, whereas E12 is dispensable for early B cell development, commitment, and maintenance. In contrast, both E12 and E47 play critical roles in pre–B and immature B cells to promote immunoglobulin λ (Igλ) germline transcription as well as Igλ VJ gene rearrangement. Furthermore, we show that E12 as well as E47 is required to promote receptor editing upon exposure to self-antigen. We demonstrate that increasing levels of E12 and E47 act to induce Igλ germline transcription, promote trimethylated lysine 4 on histone 3 (H3) as well as H3 acetylation across the Jλ region, and activate Igλ VJ gene rearrangement. We propose that in the pre–B and immature B cell compartments, gradients of E12 and E47 activities are established to mechanistically regulate the sequential rearrangement of the Ig light chain genes.
The Use of a Selective Staphylococcal Broth v Direct Plating for the Recovery of Staphylococcus aureus
Authors: Sautter R.L. , Brown W.J. , Mattman L.H.
Published: September 2009

Nine hundred seventy-two cultures taken from the external nares and the vaginal vestibules of 54 women for the isolation of Staphylococcus aureus were studied. The swabs were plated directly to a trypticase soy agar plate containing 5% sheep blood and were then placed into a selective staphylococcal broth. Both culture methods were compared for the ability to recover S aureus.

Twenty percent (26/131) and 66% (38/58) of the S aureus-positive cultures taken from the nares and vagina respectively were cultured from the selective broth only. We believe that a selective staphylococcal broth should be used in addition to routine culture techniques to isolate S aureus from infection control surveillance cultures.
The Multi-lumen Catheter: Proposed Guidelines for Its Use
Authors: Farber Bruce F.
Published: September 2009

Infusion therapy for the administration of blood products, fluids, and parenteral nutrition are essential parts of medical practice. The risks associated with such therapy are well documented but frequently unappreciated. Intravascular infusions are the single most common cause of nosocomial bacteremia.’ Many studies have focused on the epidemiology, microbiology, and pathophysiology of these infections.

In recent years, several companies have introduced a multi-lumen intravenous catheter that is placed through the subclavian or internal jugular vein. Unlike a multi-lumen pulmonary artery catheter, the multi-lumen intravenous catheter is designed solely for intravenous access. The first of these catheters was introduced in 1983, and it was soon followed by several others. These catheters have been designed to allow multiple infusions to be given simultaneously. In addition, one of the ports can be used for venous access. The advantages of these catheters are obvious. The clinician is given three ports for use instead of one. The catheter may be used to simplify infusion therapy. In some instances, cut-downs and other invasive procedures (Hickmans, Broviacs, Mediports) may be avoided. It is not surprising that the use of these catheters has grown. In many institutions, multi-lumen catheters account for a majority of all centrally placed catheters, and in some intensive care units, they are used almost exclusively. The enormous growth of the use of the multi-lumen catheter has occurred despite minimal data regarding risk, cost, and the proper procedures needed for its care.
Increased Incidence of Infections in Intravenous Drug Users
Authors: Horsburgh Charles R. , Anderson Judith R. , Boyko Edward J.
Published: September 2009

To ascertain the incidence of infections in intravenous users of illicit drugs, we performed a retrospective study of 270 intravenous drug users (IVDUs) and 562 controls who did not use drugs over a seven-year period from 1978-1985. IVDUs had an increased overall incidence of infections (P <0.00l) compared to controls, which was explained to a large degree by an increased incidence of hepatitis. Endocarditis and disseminated gonococcal infection were seen with increased frequency in IVDUs (P <0.05), but abscess and cellulitis were not. Neither acquired immunodeficiency syndrome (AIDS), tuberculosis, Pneumocystis pneumonia, nor disseminated viral or fungal infection were seen in IVDUs or controls. Heroin users, but not other IVDUs, had an increased incidence of infections not thought to be associated with needle use, suggesting impaired immunity. This study demonstrates that IVDUs have an increased incidence of infection compared to control subjects, but the kinds of infections have changed substantially over the past two decades. The presence of opportunistic pathogens in these patients should suggest concurrent infection with human immunodeficiency virus (HIV).
Pseudoepidemic of Urinary Tract Infections due to Trichosporon beigelii
Authors: Stone Judy , Manasse Robert
Published: September 2009

During the period April, 1985 to March, 1986, Trichosporon beigelii was isolated from the urine of 15 intensive care unit patients. All of these patients had Foley catheters in place at the time of T beigelii isolation. None of them had urinary tract infections on admission, and it was initially felt that this organism was a source of infection in these critically ill individuals. Subsequent investigation revealed this to be a pseudoepidemic secondary to contamination of the urinary catheter drainage system. Urine obtained by gravity drainage from the outlet port of urimeters yielded growth of T beigelii, whereas urines obtained concurrently from the proximal tubing sampling port were negative. T beigelii was isolated from the drainage port as well as from various items used in the collection and sampling of urine specimens. It is felt that these items were the source of perpetuation of this pseudoepidemic due to the repeated contamination and colonization of the distal portion of the urine catheter collection system. In-services to nursing and housekeeping personnel in the proper collection of urine specimens and cleaning of potentially contaminated items, the replacement of metal urine graduates with disposable plastic ones and increased monitoring of personnel's activities stopped the outbreak abruptly.
Infection Control Measures for Human Parvovirus Bl9 in the Hospital Setting
Authors: Naides Stanley J.
Published: September 2009

A human parvovirus was first discovered serendipitously in blood from asymptomatic donors in 1975' and designated B19 because of the location of the original positive serum in a test panel. Subsequently, the newly discovered virus was determined to be the etiologic agent of most cases of transient aplastic crisis in the setting of chronic hemolytic anemia and of the childhood exanthem erythema infectiosum, or fifth disease. While erythema infectiosum with its classic “slapped-cheek” rash is a childhood illness, “fifth disease” in the adult should not be overlooked. At least 40% of adults lack serological evidence of past human parvovirus B19 infection and are at risk. Adults tend to have a more subtle rash, often lacking the “slapped cheeks,” and tend to have a more severe constitutional, flu-like illness with prominent joint symptoms. While the arthralgia and arthritis of adult “fifth disease” are often self-limiting, they may become chronic and lead to an arthropathy that meets American College of Kheumatology criteria for a diagnosis of rheumatoid arthritis. The arthropathy has been reported to persist up to five years, the longest follow-up now available (A. Wolf; MD, personal communication, August 27, 1987).
Epidemiologic and Clinical Utility of Typing Systems for Differentiating Among Strains of Methicillin-Resistant Staphylococcus aureus
Authors: Mulligan Maury E. , Arbeit Robert D.
Published: September 2009

Typing systems for differentiating among strains of methicillin-resistant Staphylococcus aureus (MRSA) can be valuable tools for the epidemiologist and the clinician. Specific criteria for evaluating such systems are typeability, reproducibility, and discriminatory power. An ideal typing system also would be rapid, inexpensive, technically simple, and readily available. Systems based on the detection of phenotypic variations include antimicrobial susceptibility testing, bacteriophage typing, multilocus enzyme electrophoresis, and electrophoretic methods such as protein eletrophoresis and immunoblotting. Systems that directly detect genotypic variations include plasmid profile analysis, restriction enzyme analysis of plasmid DNA, restriction enzyme analysis of chromosomal DNA, Southern blot analysis of specific restriction fragment length polymorphisms, and pulse field gel electrophoresis. in general, the more widely available typing systems based on phenotypic assays and plasmid analysis have limitations in typeability and/or discriminatory power.The chromosomal DNA-based techniques, although promising, are unproven approaches still under active investigation.
Treatment of Infection and Colonization Caused by Methicillin-Resistant Staphylococcus aureus
Authors: Chambers Henry F.
Published: September 2009

The mechanism of methicillin resistance confers resistance to all available B-lactam antibiotics; consequently, B-lactam antibiotics have no role in therapy of methicillin-resistant Staphylococcus aureus (MRSA) infections. Vancomycin remains the drug of choice. Teicoplanin and daptomycin are two investigational antibiotics related to vancomycin in structure and in spectrum of activity. In clinical trials employing relatively low doses, neither was as effective as vancomycin. Trials at higher doses are on-going. Quinolones, ciprofloxacin in particular, have been used successfully to treat infections caused by MRSA; however, the usefulness of quinolones may be limited by the tendency of resistance to emerge during therapy. Quinolones probably should be used only in combination with another active agent, such as rifampin, when treating serious infections caused by MRSA. Other agents may be active in vitro against MRSA, but clinical data showing their effectiveness are lacking. Rifampin combination regimens appear most effectively to eradicate colonization with MRSA.
Nursing Home Outbreak of Influenza A (H3N2): Evaluation of Vaccine Efficacy and Influenza Case Definitions
Authors: Taylor Jean Lin , Dwyer Diane M. , Coffman Thelma , Groves Carmela , Patel Jagdish , Israel Ebenezer
Published: September 2009

Objectives:

Describe an outbreak of influenza A (H3N2); provide an analysis of vaccine efficacy; measure the sensitivity specificity, and positive predictive value of 3 clinical case definitions of influenza.

Setting:

A nursing home in Washington County, Maryland. The outbreak involved 52 residents (attack rate = 47.7%) and at least 10 of 140 employees (minimum attack rate = 7.1%).

Results:

Twenty-five residents exhibited a 4-fold or greater increase in titer to influenza A/Sichuan/2/87. Vaccine efficacy was measured at -7.1%, suggesting that the influenza vaccine in 1988/1989 did not offer optimal protection against influenza A infection for the institutionalized elderly.

Conclusions:

The outbreak was a clear indicator of the need for rapid diagnosis. With the use of rapid diagnostic tests, influenza A could have been detected in time to use amantadine.
A Second Look at the Cost of Mandatory Human Immunodeficiency Virus and Hepatitis B Virus Testing for Healthcare Workers Performing Invasive Procedures
Authors: Russo Gerard , La Croix Sumner J.
Published: September 2009

Recently in this journal, Dr. Julie Gerberding analyzed the financial cost to a hospital of testing healthcare workers for human immunodeficiency virus (HIV) and hepatitis B virus (HBV) and restricting the employment of healthcare workers infected with these viruses.’ Dr. Gerberding calculated that a 350-bed university-affiliated public teaching hospital in San Francisco, California, would incur an annual cost of $433,875 to test healthcare workers performing invasive procedures and a cost of $402,125 to replace and retrain HIV-infected healthcare workers. On the basis of these estimates, she concluded that “the total cost of implementing [such] a testing program...for all healthcare workers is staggering” and that other methods of reducing the risk of HIV transmission from healthcare workers to patients should be considered more carefully.
Introduction of a “Safety” Intravenous Catheter for Use in an Emergency Department: A Pediatric Hospital's Experience
Authors: Friedland Leonard R. , Brown Robert
Published: September 2009

Little concern was given to the frequency of needlestick injuries in the workplace before the acquired immunodeficiency syndrome (AIDS) epidemic, despite the risk of acquiring more than 20 different infectious diseases from blood or body fluid-contaminated needlestick injuries. Reports of occupational human immunodeficiency virus (HIV) transmission after accidental needlestick injuries' have not only heightened healthcare worker awareness of this occupational hazard, but also galvanized industry to create safety devices designed to reduce this risk.

We recently introduced a “safety” intravenous catheter for use in our emergency department at St. Christopher's Hospital for Children, Philadelphia, Pennsylvania. The catheter we chose is, to our knowledge, the only one readily available on the US market. This catheter is the Protectiv™ IV Catheter Safety System, marketed by Critikon, Inc., Tampa, Florida. The catheter's safety mechanism is an external plastic sheath that, as the user advances the catheter off the introducer needle, slides over the contaminated needle and locks it safely inside. The sheath acts as a needle cap, and the user's hands remain behind the introducer needle during all stages of operation. We prospectively evaluated our registered nurses’ acceptance and proficiency with this “safety” catheter.
Impact of Central Venous Catheter Removal on the Recurrence of Catheter-Related Coagulase-Negative Stahylococcal Bacteremia
Authors: Raad Issam , Davis Steve , Khan Asma , Tarrand Jeffrey , Elting Linda , Bodey Gerald P.
Published: September 2009

Objective:

To determine the impact of catheter management on the acute and long-term outcome of catheter-related coagulase-negative staphylococcal bacteremia.

Design:

Retrospective surveillance of catheter-related sepsis using quantitative blood and catheter cultures.

Setting:

University-affiliated tertiary cancer center.

Patients and Methods:

seventy patients with catheter-related coagulase-negative staphylococcal bacteremia were studied by retrospective chart review. The clinical characteristics of the patients and the management of the bacteremias were determined. The impact of immuno-suppressive risk factors, antibiotic therapy, and catheter management on the recurrence of the bacteremia was investigated.

Results:

Acute sepsis-related morbidity and mortality were not related to catheter management. However, during a 12-week followup period, the bacteremia recurred in 20% of the patients whose catheters remained in place, compared with only 3% of those whose catheters were removed (p<.05). By multivariate analysis, patients whose catheters remained in place were 2.9 times more likely to experience a recurrence than those whose catheters were removed (odds ratio = 2.9, 95% confidence interval = 1.2-8.8, p= .03). All other potential risk factors were equally distributed between patients, with and without a recurrence.

Conclusions:

Although patients with catheter-related coagulase-negative staphylococcal bacteremia could be treated successfully while the catheter remains in place with the majority remaining free of recurrence, catheter retention results in a significantly higher risk for the recurrence of the bacteremia.
Nosocomial Transmission of Salmonella Gastroenteritis to Laundry Workers in a Nursing Home
Authors: Standaert Steven M. , Hutcheson Robert H. , Schaffner William
Published: September 2009

Background:

Outbreaks of salmonella gastroenteritis in nursing homes are common. Person-to-person transmission to nursing home personnel occurs occasionally, but infection of laundry staff as a result of handling soiled linen rarely has been reported.

Objective:

To examine the nosocomial transmission of infection to laundry staff during an outbreak of salmonellosis in a nursing home.

Setting:

A 250-bed nursing home in a rural Tennessee county.

Methods:

Residents and staff of the nursing home were interviewed and cultures of stool samples examined for enteric pathogens.

Results:

Stool cultures from 32 residents and 8 employees were positive for Salmonella hadar. Infection among the residents was food-borne, but infection among employees likely represented secondary transmission, as none of the employees ate food prepared in the kitchen and their onset of symptoms occurred seven to 10 days after that of ill residents. Three laundry personnel who had no contact with residents were infected. Most of the ill residents (81%) were incontinent, which led to an increase in both the degree of fecal soiling and the amount of soiled linen received by the laundry during the outbreak. Laundry personnel regularly ate in the laundry room, did not wear protective clothing, and did not wear gloves consistently while handling soiled laundry,

Conclusions:

This investigation implicates linen soiled with feces as the source of nosocomial S hadar infection in laundry workers and underscores the importance of using appropriate precautions when handling linen.
Epidemiology of Staphylococcus Aureus Infections in Patients on Hemodialysis
Authors: Ena J. , Boelaert J.R. , Boyken L.D. , Van Landuyt H.W. , Godard C.A. , Herwaldt LA.
Published: September 2009

Objective:

To determine the epidemiology of Staphylococcus aureus infections in hemodialysis patients.

Method:

S aureus isolates from surveillance cultures and from sites of infection were evaluated by both bacteriophage typing and restriction endonuclease digestion of plasmid DNA.

Setting:

A hemodialysis unit in Brugge, Belgium.

Organisms:

S aureus isolates from 11 chronic hemodialysis patients who had participated in the placebo arm of a previously reported placebo-mupirocin comparative study.

Results:

Of 75 S aureus isolates evaluated, 63 were from cultures of nares and 12 from infections (three arteriovenous fistula infections, four wound infections, and five bacteremias). All isolates were typed by bacteriophages and 56 (75%) had plasmids. Three patients developed 12 infections. Eleven infections were caused by isolates previously identified in surveillance cultures. Only one infection was caused by a strain not identified previously in surveillance cultures.

Conclusion:

These results support the hypothesis that S aureus isolates causing infections in hemodialysis patients are of endogenous origin.
Predominance of Gram-Positive Microorganisms as a Cause of Septicemia in Patients with Hematological Malignancies
Authors: Rubio M. , Palau L. , Vivas J. Romero , del Potro E. , Diaz-Mediavilla J. , Alvarez A. , Martinez R. , Picazo J.J.
Published: September 2009

Objective:

To ascertain the etiology and outcome of episodes of bacteremia and fungemia over a three-year period (1990-1992) in patients with hematological malignancies.

Design:

Retrospective study.

Setting:

Hematology service of a 1,500-bed Spanish university hospital.

Results:

Of a total of 178 episodes of significant bacteremia or fungemia in 101 patients, 53% affected patients with acute leukemia. Grampositive microorganisms were found to be the cause in 70% of the monomicrobial episodes. The most frequently isolated microorganism was coag-ulase-negative Staphylococcus (35%), followed by Staphylococcus aureus (11%). Most bloodstream infections occurred during an episode of neutropenia (59%). A total of 34 patients died during hospitalization; in 14, infection was the cause of death.

Conclusions:

A marked increase in the incidence of bacteremias caused by grampositive microorganisms has been observed in our hospital over the last 10 years, especially in patients with hematological malignancies. The mortality due to bacteremia is similar to that found by other authors in series of bacteremia in hematological patients, and we have not found significant differences in the mortality due to bacteremia between neutropenic and non-neutropenic patients.
Methicillin-Resistant Staphylococcus aureus (MRSA): A Briefing for Acute Care Hospitals and Nursing Facilities
Authors: Boyce John M. , Jackson Marguerite M. , Pugliese Gina , Batt Murray D. , Fleming David , Garner Julia S. , Hartstein Alan I. , Kauffman Carol A. , Simmons Mildred , Weinstein Robert , Williams Carol O'Boyle ,   AHA Technical Panel on Infections Within Hospitals
Published: September 2009

The incidence of methicillin-resistant Staphylococcus aureus (MRSA) has increased in communities and in healthcare facilities in the United States since the mid-1970s. Although MRSA often is thought of as a nosocomial infection problem because it is encountered in facilities of all types and sizes, it also causes many community-acquired infections. Approaches to control of MRSA vary widely, and there is lack of agreement on the most appropriate measures to control MRSA in healthcare facilities. The wide variation in approaches is due, in part, to the lack of data establishing the efficacy of specific control measures. As a result, the approaches that have been advocated have resulted in confusing and often conflicting recommendations and control measures. In some settings, there also have been unreasonable barriers and administrative hurdles that delay or prevent the transfer of patients between acute care and nursing (extended care) facilities.
Variation in Medical Practice: Implications for the Hospital Epidemiologist
Authors: Kritchevsky Stephen B. , Simmons Bryan P.
Published: September 2009

Why do two physicians faced with similar patients make different decisions about the care their patients should receive? This area of health services research has been energized by recent concerns about rising healthcare costs. In 1982, Wennberg and Gittelsohn described the great variation in surgical procedure rates throughout the northeastern United States during the 1970s. Population rates of hysterectomy and prostatectomy varied fourfold between local service areas; tonsilectomy rates varied sixfold. Differences in patient populations could not explain the variation in rates. The authors concluded that a large portion of the variability was attributable to the personal preferences of the surgeons practicing in the various communities. Similar differences in procedure rates are easy to replicate and are evident at several levels of aggregation. On larger scales, regional and international differences can be documented easily. On a smaller scale, practice variation within individual hospitals is frequently evident.