bluuebunny/crossref_metadata_2025 huggingface dataset:
Inversion of tracer test data using tomographic constraints
Authors: Linde Niklas , Finsterle Stefan , Hubbard Susan
Published: April 2006

We have developed a methodology for inverting tracer test data using zonation information obtained from two‐dimensional radar tomograms to improve the (typically overly smooth) hydraulic conductivity fields obtained from conventional inversion of tracer test data. The method simultaneously yields two‐dimensional estimates of hydraulic conductivity as well as petrophysical relationships that relate hydraulic conductivity to radar velocity; these relationships can be assumed to be stationary throughout the area of investigation or to vary as a function of zonation. Using a synthetic three‐dimensional hydraulic conductivity field, we apply the developed inversion methodology and explore the impact of the strength and stationarity of the petrophysical relationship as well as the impact of errors that are often associated with radar data acquisition (such as unknown borehole deviation). We find that adding radar tomographic data to tracer test data improves hydrogeological site characterization, even in the presence of minor radar data errors. The results are contingent on the assumption that a relationship between radar velocity and hydraulic conductivity exists. Therefore the applicability of the proposed method may be limited to field sites where this condition is partially or fully satisfied.
Variations in the 3He/4He ratios of hot springs on Shikoku Island, southwest Japan
Authors: Umeda Koji , Kanazawa Sunao , Kakuta Chifumi , Asamori Koichi , Oikawa Teruki
Published: April 2006

New helium isotopic data from hot springs on Shikoku Island were obtained from a larger number of sampling points than previous studies in order to elucidate the geographical distribution of 3He/4He ratios in the fore‐arc regions of southwest Japan. Systematic, regional variations in 3He/4He ratios were observed on both Shikoku Island and the Kii Peninsula. The hot springs on Shikoku Island have 3He/4He ratios between 0.21 RA and 2.5 RA. On the other hand, the majority of hot springs in the Kii Peninsula have significantly higher 3He/4He ratios than those on Shikoku Island. It has been suggested that the anomalously high 3He/4He ratios in the fore‐arc region of southwest Japan are related to the migration of MORB‐type helium with aqueous fluids generated by dehydration of the subducting Philippine Sea plate and mixing with terrestrial waters (e.g., Matsumoto et al., 2003). According to recent seismological observations of crustal microearthquakes and their focal mechanisms, the geotectonic environment beneath Shikoku Island is subject to a stress field with no normal faulting and with extremely low crustal seismicity. This argues against migration of aqueous fluids from the subcrustal lithosphere, resulting in a relatively small influence of mantle‐derived helium at the surface. As a consequence, the regional variation in 3He/4He ratios of hot springs on Shikoku Island is interpreted as a three‐component mixture of mantle‐derived helium associated with magmatism of middle Miocene of age (<3.4 RA), crustal, radiogenic helium and atmospheric helium.
Propagation of dikes at Vesuvio (Italy) and the effect of Mt. Somma
Authors: Acocella V. , Porreca M. , Neri M. , Massimi E. , Mattei M.
Published: April 2006

Dikes provide crucial information on how magma propagates within volcanoes. Somma‐Vesuvio (Italy) consists of the active Vesuvio cone, partly bordered by the older Mt. Somma edifice. Historical chronicles on the fissure eruptions in 1694–1944 are matched with an analytical solution to define the propagation path of the related dikes and to study any control of the Mt. Somma relief. The fissures always consisted of the downslope migration of vents from an open summit conduit, indicating lateral propagation as the predominant mechanism for shallow dike emplacement. No fissure emplaced beyond Mt. Somma, suggesting that its buttressing hinders the propagation of the radial dikes. An analytical solution is defined to describe the mechanism of formation of the laterally propagating dikes and to evaluate the effect of topography. The application to Somma‐Vesuvio suggests that, under ordinary excess magmatic pressures, the dikes should not propagate laterally at depths >240–480 m below the surface, as the increased lithostatic pressure requires magmatic pressures higher than average. This implies that, when the conduit is open, the lateral emplacement of dikes is expectable on the S, W and E slopes. The lack of fissures N of Mt. Somma is explained by its buttressing, which hinders dike propagation.
Mapping of drift surfaces in toroidal systems with chaotic magnetic fields
Authors: Abdullaev S. S. , Wingen A. , Spatschek K. H.
Published: April 2006

Drift orbits of test particles are studied using a recently proposed Hamiltonian theory of guiding-center motion in toroidal systems. A symplectic mapping procedure in symmetric form is developed which allows a fast and accurate characterization of the Poincaré plots in poloidal cross sections. It is shown that the stochastic magnetic field acts differently on the onset of chaotic motion for co- and counterpassing particles, respectively. Resonant drift surfaces are shifted inward for the co-passing particles, and are shifted outward for the counterpassing particles, when compared with resonant magnetic surfaces. The overall result is an inward (outward) shift of chaotic zones of co-passing (counterpassing) particles with respect to the magnetic ergodic zone. The influence of a stationary radial electric field is discussed. It shifts the orbits farther inward for the co-passing particles and outward for the counterpassing particles, respectively. The shifts increase with the energies of the particles. A rotation of the magnetic field perturbations and its effect on drift motion is also investigated. Estimates for the local diffusion rates are presented. For applications, parameters of the dynamic ergodic divertor of the Torus Experiment for Technology-Oriented Research are used [Fusion Eng. Design 37, 337 (1997)].
Excluded volume in the generic van der Waals equation of state and the self-diffusion coefficient of the Lennard-Jones fluid
Authors: Laghaei Rozita , Eskandari Nasrabad Afshin , Eu Byung Chan
Published: April 2006

In the previous papers applying the generic van der Waals equation of state the mean excluded volume was defined with the contact diameter of particles at which the potential energy is equal to zero—the size parameter in the case of the Lennard-Jones potential. This parameter appears as the upper limit of the integral for the generic van der Waals parameter B (mean excluded volume divided by the density) in the generic van der Waals equation of state. Since the choice is not unique, in this paper we reexamine the manner of defining the upper limit and propose another choice for the upper limit. We also propose an interpretation of the free volume overlap factor α appearing in the free volume theory of diffusion and a method of estimating it in terms of the intermolecular potential energy only. It is shown that with the so-estimated free volume overlap factor and the new choice of the upper limit of the integral for B the self-diffusion coefficient in the modified free volume theory of diffusion not only acquires a better accuracy than before, but also becomes calculable in terms of only the intermolecular interaction potential without an adjustable parameter. We also assess some of effective diameters of molecules proposed in the literature for their ability to predict the self-diffusion coefficient within the framework of the modified free volume theory of diffusion.
Self-injection and acceleration of electrons during ionization of gas atoms by a short laser pulse
Authors: Singh K. P.
Published: April 2006

Using a relativistic three-dimensional single-particle code, acceleration of electrons created during the ionization of nitrogen and oxygen gas atoms by a laser pulse has been studied. Barrier suppression ionization model has been used to calculate ionization time of the bound electrons. The energy gained by the electrons peaks for an optimum value of laser spot size. The electrons created near the tail do not gain sufficient energy for a long duration laser pulse. The electrons created at the tail of pulse escape before fully interacting with the trailing part of the pulse for a short duration laser pulse, which causes electrons to retain sufficient energy. If a suitable frequency chirp is introduced then energy of the electrons created at the tail of the pulse further increases.
Finite-size effects in the microscopic structure of a hard-sphere fluid in a narrow cylindrical pore
Authors: Román F. L. , White J. A. , González A. , Velasco S.
Published: April 2006

We examine the microscopic structure of a hard-sphere fluid confined to a small cylindrical pore by means of Monte Carlo simulation. In order to analyze finite-size effects, the simulations are carried out in the framework of different statistical mechanics ensembles. We find that the size effects are specially relevant in the canonical ensemble where noticeable differences are found with the results in the grand canonical ensemble (GCE) and the isothermal isobaric ensemble (IIE) which, in most situations, remain very close to the infinite system results. A customary series expansion in terms of fluctuations of either the number of particles (GCE) or the inverse volume (IIE) allows us to connect with the results of the canonical ensemble.
Toroidally localized soft x-ray expulsion at the termination of the improved confinement regime in the TPE-RX reversed-field pinch experiment
Authors: Frassinetti L. , Yagi Y. , Koguchi H. , Shimada T. , Hirano Y. , Sakakita H.
Published: April 2006

The pulsed poloidal current drive technique reduces the magnetic chaos that characterizes reversed-field pinch configurations and produces a regime with an improved confinement. In this paper, we describe that, in TPE-RX [Y. Yagi et al., Fusion Eng. Des. 45, 409 (1999)], the termination phase of this regime is due to the increase of the slinky structure that creates a stochastic region and produces the expulsion of energy in a localized toroidal position. Before the plasma reaches the improved confinement regime, the slinky distorts the chain of m=0 islands on the reversal surface. During this regime, the magnetic activity and the phase locking decrease, the distortion in the island chain disappears, and the confinement increases. At the termination of this regime the magnetic activity markedly increases, as well as the phase locking, recreating the distortion in the m=0 magnetic island chain. As a consequence, at the position of the distortion the plasma region inside the reversal surface is characterized by a rapid energy loss, and outside the reversal surface a toroidally localized energy expulsion is induced.
Damping of magnetohydrodynamic disturbances in multi-ion-species plasmas
Authors: Toida Mieko , Yoshiya Takashi , Ohsawa Yukiharu
Published: April 2006

The evolution of macroscopic magnetohydrodynamic disturbances across a magnetic field is studied, with particular attention to the effect of multiple ion species. Analyses are carried out on disturbances where the initial magnetic profiles are sinusoidal. Both the theory and electromagnetic simulations show that, in a single-ion-species plasma, the disturbance is undamped, with its energy oscillating between the magnetic field and ion velocity. In a multi-ion-species plasma, however, it is initially damped, owing to the phase mixing of the magnetosonic mode and the modes having ion-ion hybrid cutoff frequencies. Furthermore, it is found from long-time simulations that the amplitude of the disturbance continues to decrease in a multi-ion-species plasma. This is due to nonlinear mode couplings. The magnetic energy is irreversibly transferred to the ions.
Hot surface ionic line emission and cold K-inner shell emission from petawatt-laser-irradiated Cu foil targets
Authors: Theobald W. , Akli K. , Clarke R. , Delettrez J. A. , Freeman R. R. , Glenzer S. , Green J. , Gregori G. , Heathcote R. , Izumi N. , King J. A. , Koch J. A. , Kuba J. , Lancaster K. , MacKinnon A. J. , Key M. , Mileham C. , Myatt J. , Neely D. , Norreys P. A. , Park H.-S. , Pasley J. , Patel P. , Regan S. P. , Sawada H. , Shepherd R. , Snavely R. , Stephens R. B. , Stoeckl C. , Storm M. , Zhang B. , Sangster T. C.
Published: April 2006

A hot, 2to3keV electron temperature surface plasma was observed in the interaction of a 0.7ps petawatt laser beam with solid copper-foil targets at intensities >1020W∕cm2. Copper K-shell spectra were measured in the range of 8to9keV using a single-photon-counting x-ray charged-coupled-device camera. In addition to Kα and Kβ inner-shell lines, the emission contained the Cu Heα and Lyα lines, allowing the temperature to be inferred. These lines have not been observed previously with ultrafast laser pulses. For intensities less than 3×1018W∕cm2, only the Kα and Kβ inner-shell emissions are detected. Measurements of the absolute Kα yield as a function of the laser intensity are in general agreement with a model that includes refluxing and confinement of the suprathermal electrons in the target volume.
On the self-heating phenomenon in nonmodal shear flow
Authors: Li J. W. , Chen Y. , Li Z. Y.
Published: April 2006

In this article, the nonmodal self-heating phenomenon of linear shear flow [A. D. Rogava, Astrophys. Space Sci. 293, 189 (2004)] is investigated with an initially excited Alfvénic perturbation focusing on the factors determining the efficiency of the heating process. It is found that to get an efficient self-heating process, the initial Alfvén wave must be at least partially transformed into the fast mode. This is because only the fast mode, among the three types of magnetohydrodynamic modes, can get amplified significantly by the shear flow. This requires the initial wave number along the shear to be positive so that the Spatial Fourier Harmonics can pass through the degeneration region, and also puts constraints on the plasma parameter β [β=CS2∕VA2, where CS (VA) is the sound (Alfvénic) velocity]. It is shown that the self-heating function, which represents the total energy dissipated at a certain time, decreases monotonically with increasing β. In addition, to get efficient heating the viscous coefficient should be in an appropriate range. A smaller viscosity results in an insufficient thermalization of the perturbation energy, while a larger one corresponds to a suppressed nonmodal amplification.
Defect characterization of Si-doped GaN films by a scanning near-field optical microscope-induced photoluminescence
Authors: Yoshikawa M. , Sugie R. , Murakami M. , Matsunobe T. , Matsuda K. , Ishida H.
Published: April 2006

We developed a tapping-mode-scanning near-field optical microscope to measure near-field photoluminescence (SNOM-PL) with nanometer spatial resolution using an ultraviolet laser, and we measured the defect distribution of a Si-doped GaN film. The obtained result was compared with one measured by high spatial resolution cathodoluminescence (CL) spectroscopy. Some dark spots with an average period of 100–300nm were observed in the image of the peak intensity of near-field PL at about 362nm, measured with a pyramidical cantilever, and in a plan-view CL image at the same wavelength. The near-field PL image agreed well with the plan-view CL image. The threading dislocations in GaN films were found to act as nonradiative recombination centers not only for band-edge emission but also for yellow luminescence around 580nm. Furthermore, it was found that free carrier concentration decreased near the threading dislocations. The SNOM-PL we developed has at least a spatial resolution of about 100nm. The SNOM-PL could potentially be applied to the estimation at a nanometer scale of defects in semiconductor films without requiring a vacuum environment.
Nonlinearly driven second harmonics of Alfvén cascades
Authors: Smith H. , Breizman B. N. , Lisak M. , Anderson D.
Published: April 2006

In recent experiments on Alcator C-Mod [J. A. Snipes et al., Phys. Plasmas 12, 056102 (2005)], measurements of density fluctuations with phase contrast imaging through the plasma core show a second harmonic of the basic Alfvén cascade (AC) signal. The present paper presents a theory that describes the second-harmonic perturbation as a nonlinear sideband produced by the AC eigenmode via quadratic terms in the magnetohydrodynamic equations. It is shown that in a low-pressure plasma the nonlinear coupling to compressional Alfvén and acoustic perturbations can be neglected when calculating the second-harmonic density. The derived expressions for this density perturbation can potentially be used together with experimental measurements to determine the AC amplitude inside the plasma, rather than just at the edge as with magnetic probes.
Zonal flows generated by small-scale drift-Alfvén modes
Authors: Mikhailovskii A. B. , Smolyakov A. I. , Kovalishen E. A. , Shirokov M. S. , Tsypin V. S. , Botov P. V. , Galvão R. M. O.
Published: April 2006

The generation of zonal flows by small-scale drift-Alfvén (SSDA) modes is investigated. It is shown that these zonal flows can be generated by a monochromatic wave packet of SSDA modes propagating in the ion diamagnetic drift direction. The corresponding zonal-flow instability resembles a hydrodynamic one. Its growth rate depends on the spectrum purity of the wave packet; it decreases for relatively weak spectrum broadening and the instability turns into a resonant one, and eventually is suppressed, as the broadening increases. A general conclusion of this work is that the SSDA modes are less effective for driving zonal flows than standard drift modes.
Measurements of energy and angular distribution of hot electrons and protons emitted from a p- and s-polarized intense femtosecond laser pulse driven thin foil target
Authors: Li Z. , Daido H. , Fukumi A. , Sagisaka A. , Ogura K. , Nishiuchi M. , Orimo S. , Hayashi Y. , Mori M. , Kado M. , Bulanov S. V. , Esirkepov T. Zh. , Oishi Y. , Nayuki T. , Fujii T. , Nemoto K. , Nakamura S. , Noda A.
Published: April 2006

The energy spectra and angular distributions of hot electrons as well as protons emitted from a 3-μm-thick tantalum foil irradiated by a 70-fs laser pulse with an intensity of ∼1018W∕cm2 are measured. Three hot electron flows are found, in the rear target normal, specular, and target surface directions. The angular distribution of hot electrons is found to depend on the polarization of the incident light. The measured energy spectrum of hot electrons in the rear target normal direction can explain the generated proton beam.
Methicillin-ResistantStaphylococcus AureusCarriage Among Patients After Hospital Discharge
Authors: Vriens Menno R. , Blok Hetty E. M. , Gigengack-Baars Ada C. M. , Mascini Ellen M. , Werken Chris van der , Verhoef Jan , Troelstra Annet
Published: April 2006

Background and Objective:

At the University Medical Center Utrecht (UMCU), follow-up implies an inventory of risk factors and screening for MRSA colonization among all MRSA-positive patients for at least 6 months. If risk factors or positive cultures persist or re-emerge, longer follow-up is indicated and isolation at readmission. This study investigated how long MRSA-positive patients remained colonized after hospital discharge and which risk factors were important. Furthermore, the results of eradication therapy were evaluated.

Design:

All patients who were positive for MRSA at the UMCU between January 1991 and January 2001 were analyzed regarding carriage state, presence of risk factors for prolonged carriage ofStaphylococcus aureus, and eradication treatment.

Results:

A total of 135 patients were included in the study. The median follow-up time was 1.2 years. Eighteen percent of the patients were dismissed from follow-up 1 year after discharge. Only 5 patients were dismissed after 6 months. Among patients with no risk factors, eradication treatment was effective for 95% within 1 year. Among patients with persistent risk factors, treatment was effective for 89% within 2 years.

Conclusions:

Based on these findings, eradication therapy should be prescribed for all MRSA carriers, independent of the presence of risk factors. MRSA-positive patients should be evaluated for 6 months for the presence of risk factors and MRSA carriage. Screening for risk factors is important because intermittent MRSA carriage was found in a significant number of our patients. Patients with negative MRSA cultures and without risk factors for 12 months can be safely dismissed from follow-up. (Infect Control Hosp Epidemiol 2005;26:629-633)
Reduction in Nosocomial Transmission of Drug-Resistant Bacteria After Introduction of an Alcohol-Based Handrub
Authors: Gordin Fred M. , Schultz Maureen E. , Huber Ruth A , Gill Janet A.
Published: April 2006

Objective:

To assess quantitatively the clinical impact of using an alcohol-based handrub (ABHR) in the hospital environment, measuring impact as the incidence of new, nosocomial isolates of drug-resistant organisms.

Design:

An observational survey from 1998 to 2003 comparing the first 3 years of no ABHR use with the 3 years following, when an ABHR was provided for hand hygiene.

Setting:

An inner-city, tertiary-care medical center.

Intervention:

At baseline, an antimicrobial soap with 0.3% triclosan was provided for staff hand hygiene. The intervention was placement in all inpatient and all outpatient clinic rooms of wall-mounted dispensers of an ABHR with 62.5% ethyl alcohol. Data were collected on change in the incidence of three drug-resistant bacteria.

Results:

During the 6 years of the survey, all new, nosocomially acquired isolates of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), and Clostridium difficile-associated diarrhea were recorded. On comparison of the first 3 years with the final 3 years, there was a 21% decrease in new, nosocomially acquired MRSA (90 to 71 isolates per year; P = .01) and a 41% decrease in VRE (41 to 24 isolates per year; P < .001). The incidence of new isolates of C. difficile was essentially unchanged.

Conclusion:

In the 3 years following implementation of an ABHR, this hospital experienced the value of reductions in the incidence of nosocomially acquired drug-resistant bacteria. These reductions provide clinical validation of the recent CDC recommendation that ABHRs be the primary choice for hand decontamination. (Infect Control Hosp Epidemiol 2005;26:650-653)
Risk Factors for Nosocomial Infective Endocarditis in Patients with Methicillin-ResistantStaphylococcus AureusBacteremia
Authors: Hsu Ron-Bin
Published: April 2006

Background and Objective:

Nosocomial infections caused by methicillin-resistantStaphylococcus aureus(MRSA) are increasing. Only a few studies of MRSA infective endocarditis have been conducted, and none have reported its risk factors. We sought to determine the host-related risk factors for infective endocarditis in patients with nosocomial MRSA bacteremia.

Setting:

A 2,000-bed, university-affiliated, tertiary-care hospital.

Patients:

Thirty-one patients with nosocomial MRSA infective endocarditis between October 1996 and May 2003.

Design:

A retrospective chart review was conducted. Data were compared with those from a control group of patients with nosocomial MRSA bacteremia. Logistic regression was used to identify independent risk factors for nosocomial infective endocarditis.

Results:

Compared with patients who had nosocomial MRSA bacteremia and no infective endocarditis, patients who had infective endocarditis had a higher incidence of chronic liver disease and a lower incidence of immunodeficiency. The risk of developing infective endocarditis was approximately 10% for patients with nosocomial MRSA bacteremia.

Conclusion:

Patients with MRSA bacteremia and underlying chronic liver disease were prone to infective endocarditis. (Infect Control Hosp Epidemiol 2005;26:654-657)
Mupirocin for Controlling Methicillin-ResistantStaphylococcus Aureus: Lessons From a Decade of Use at a University Hospital
Authors: Vivoni Adriana M. , Santos Kátia R. N. , de-Oliveira Márcia P. , Giambiagi-deMarval Marcia , Ferreira Adriana L. P. , Riley Lee W. , Moreira Beatriz M.
Published: April 2006

Background:

From 1990 to 1995 at Hospital Universitario dementino Fraga Filho, patients colonized or infected with methicillin-resistantStaphylococcus aureus(MRSA) were treated with mupirocin to eliminate MRSA carriage. In 1995, 65% of MRSA patients at this hospital had mupirocin-resistant isolates. Starting in 1996, mupirocin use was restricted to patients colonized, but not infected, with MRSA.

Objectives:

To describe the use of mupirocin for controlling MRSA over a decade and to analyze the molecular epidemiology of mupirocin-resistant MRSA infections at this hospital.

Setting:

A 490-bed, tertiary-care university hospital.

Methods:

The incidence densities of patients with MRSA and acquisition of mupirocin by the hospital were calculated for the period 1992–2001.S. aureusisolates from 1999–2000 were analyzed by pulsed-field gel electrophoresis. Mupirocin-resistant MRSA isolates from 1994–1995 and 1999–2000 were analyzed forileS-2gene background polymorphisms.

Results:

The incidence density of MRSA patients increased slightly over time, whereas the purchase of mupirocin decreased dramatically. Mupirocin-resistant MRSA infections decreased from 65% in 1994–1995 to 15% in 1999–2000. The MRSA Brazilian clone, detected in 1992, was still highly prevalent. The sameileS-2 encoding plasmid found in 1994–1995 persisted in three identical MRSA isolates from 1999–2000 belonging to the Brazilian clone.

Conclusions:

After mupirocin use decreased, theileS-2 encoding plasmid persisted in only a few Brazilian clone isolates. Our data on mupirocin-resistant MRSA incidence and mupirocin use strongly suggested that restricted use was related to decreased rates of mupirocin resistance at our hospital. (Infect Control Hosp Epidemiol 2005;26:662-667)
Risk Factors for Acquisition of Clostridium difficile–Associated Diarrhea among Outpatients at a Cancer Hospital
Authors: Palmore Tara N. , Sohn SeJean , Malak Sharp F. , Eagan Janet , Sepkowitz Kent A
Published: April 2006

Background:

Clostridium difficile-associated diarrhea (CDAD) is an important infection in hospital settings. Its impact on outpatient care has not been well defined.

Objective:

To examine risk factors of ambulatory cancer patients with CDAD.

Design:

Case-control study.

Setting:

Memorial Sloan-Kettering Cancer Center, a tertiary-care hospital.

Methods:

Cases of CDAD among oncology outpatients from January 1999 through December 2000 were identified via positive C. difficile toxin assay results on stool specimens sent from clinics or the emergency department. A 1:3 matched case-control study examined exposures associated with CDAD.

Results:

Forty-eight episodes of CDAD were identified in cancer outpatients. The mean age was 51 years; 44% were female. Forty-one (85%) had received antibiotics within 60 days of diagnosis, completing courses a median of 16.5 days prior to diagnosis. Case-patients received longer courses of first-generation cephalosporins (4.8 vs 3.2 days; P = .03) and fluoroquinolones (23.6 vs 8 days; P < .01) than did control-patients. Those receiving clindamycin were 3.9-fold more likely to develop CDAD (P < .01). For each additional day of clindamycin or third-generation cephalosporin exposure, patients were 1.29- and 1.26-fold more likely to develop CDAD (P < .01 and .04, respectively). The 38 CDAD patients hospitalized during the risk period (79.2%) spent more time as inpatients than did control-patients (19.3 vs 9.7 days; P <. 001).

Conclusions:

Antibiotic use, especially with cephalosporins and clindamycin, and prolonged hospitalization contributed to the development of CDAD. Outpatient CDAD appears to be most strongly related to inpatient exposures; reasons for the delayed development of symptoms are unknown.
Nonuniform Risk of Bloodstream Infection with Increasing Central Venous Catheter-Days
Authors: McLaws Mary-Louise , Berry Geoffrey
Published: April 2006

Objective:

To determine whether the conventional rate for central venous catheter (CVC)-associated bloodstream infection (BSI) accurately reflects risk for patients exposed for a variety of in situ periods.

Patients and Methods:

Intensive care unit patients (n = 1,375) were monitored for 7,467 CVC-days. They were monitored until catheter removal, until diagnosis of CVC-associated BSI, or for 24 hours after discharge.

Results:

The BSI rate was 3.7 per 1,000 CVC-days. Ninety-three percent of these patients had CVCs in situ for 1-15 days. These patients were exposed to 59.7% of all CVC-days; the remaining 7% were exposed to 40.3% of all CVC-days. BSI rates stratified by exposure periods of 1-5 and 6-15 days were 2.1 and 4.5 per 1,000 CVC-days, respectively. The rates for 16-30 and 31-320 days were 10.2 and 2.1 per 1,000 CVC-days, respectively. The probability of BSI with a CVC in situ was 6 in 100 by day 15, 14 in 100 by day 25, 21 in 100 by day 30, and 53 in 100 by day 320.

Conclusion:

The conventional aggregated rate better reflects the risk for the majority of patients rather than for patients exposed to the majority of CVC-days. It does not reflect the true probability of risk for all exposures, especially beyond 30 days. CVCs in situ from 1 to 15 days had less risk of BSI than CVCs in situ more than 15 days, which may explain why scheduled CVC replacement at days 5 to 7 has not been found beneficial.
Surveillance of Nosocomial Infections in a Neurologic Intensive Care Unit
Authors: Zolldann Dirk , Spitzer Christoph , Häfner Helga , Waitschies Birgit , Klein Wolfgang , Sohr Dorit , Block Frank , Lütticken Rudolf , Lemmen Sebastian W.
Published: April 2006

Objective:

To assess data on the epidemiology of nosocomial infection (N1) among neurologic intensive care patients.

Design:

Prospective periodic surveillance study.

Setting:

An 8-bed neurologic intensive care unit (ICU).

Patients:

All those admitted for more than 24 hours during five 3-month periods between January 1999 and March 2003.

Methods:

Standardized surveillance within the German infection surveillance system.

Results:

Three hundred thirty-eight patients with a total of 2,867 patient-days and a mean length of stay of 8.5 days were enrolled during the 15-month study period. A total of 71 NIs were identified among 52 patients. Urinary tract infections (UTIs) were the most frequent N1 (36.6%), followed by pneumonia (29.6%) and bloodstream infections (BSIs) (15.5%). The overall incidence and incidence density of NIs were 21.0 per 100 patients and 24.8 per 1,000 patient-days, respectively. Incidence densities were 9.8 UTIs per 1,000 urinary catheter-days (CI95, 6.4-14.4), 5.6 BSIs per 1,000 central venous catheter-days (CI95, 2.8-10.0), and 12.8 cases of pneumonia per 1,000 ventilation-days (CI95, 8.0-19.7). Device-associated UTI and pneumonia rates were in the upper range of national and international reference data for medical ICUs, despite the intensive infection control and prevention program in operation in the hospital.

Conclusion:

Neurologic intensive care patients have relatively high rates of device-associated nosocomial pneumonia and UTI. For a valid comparison of surveillance data and implementation of targeted prevention strategies, we would strongly recommend provision of national benchmarks for the neurologic ICU setting.
THE HOCHSCHILD COHOMOLOGY RING MODULO NILPOTENCE OF A MONOMIAL ALGEBRA
Authors: GREEN EDWARD L. , SNASHALL NICOLE , SOLBERG ØYVIND
Published: April 2006

For a finite dimensional monomial algebra Λ over a field K we show that the Hochschild cohomology ring of Λ modulo the ideal generated by homogeneous nilpotent elements is a commutative finitely generated K-algebra of Krull dimension at most one. This was conjectured to be true for any finite dimensional algebra over a field in [13].
UNITARY UNITS IN GROUP ALGEBRAS AND FIBONACCI SEQUENCES
Authors: VIEIRA ANA C. , DA SILVA VIVIANE RIBEIRO T.
Published: April 2006

Let * denote the canonical involution of the group algebra KG induced by the map x ↦ x-1 for x ∈ G. In case K is a real extension of ℚ, we consider Cayley unitary elements built out of skew elements k = α(x - x-1) in KG such that 1 + k is invertible in KG, for α ∈ K and x ∈ G. The constructions involve an interesting sequence in the coefficients of (1 + k)-1 which is the Fibonacci sequence when α = 1.
REFLECTION OF SOME QUASI-LOCAL DOMAINS
Authors: AYACHE AHMED , DOBBS DAVID E. , ECHI OTHMAN
Published: April 2006

If (R, M) and (S, N) are quasi-local domains and f : R → S is a ring homomorphism, then f is said to be a strong local homomorphism if f(M) = N. Let PVD be the category whose objects are the pseudo-valuation domains that are not fields and whose morphisms are the strong local homomorphisms; let VD be the full subcategory of PVD whose objects are all the valuation domains that are not fields. Then VD is shown to be a reflective subcategory of PVD. This result is extended by obtaining a reflective conclusion for a category whose class of objects properly contains all pseudo-valuation domains.
Characterization of a Novel Human Tumor Antigen Interleukin-13 Receptor α2 Chain
Authors: Kawakami Koji , Terabe Masaki , Kawakami Mariko , Berzofsky Jay A. , Puri Raj K.
Published: April 2006

The interleukin (IL)-13 receptor α2 (IL-13Rα2) chain is a primary binding and internalization subunit for a Th2-derived immune regulatory cytokine, IL-13. Although extremely high levels of IL-13Rα2 chain are expressed on a variety of human tumor cells and specimens, its precise role in tumor immunology has not been defined. To investigate the role of IL-13Rα2 in tumor immunity, we used D5 melanoma cells stably transfected with the human IL-13Rα2 gene (D5α2) to assess the effect of an IL-13Rα2 DNA vaccine in immunocompetent animals. Prophylactic immunization of mice with the IL-13Rα2 DNA vaccine resulted in protection against D5α2 tumor development. In vivo depletion experiments in C57BL/6 and RAG-2 knockout mice indicated that both T and B cells, but not natural killer cells, were required for the tumor protection. In addition, antibody induced by the IL-13Rα2 DNA vaccine showed a modest but significant inhibitory effect on D5α2 cells in vitro, suggesting that the antibody is biologically functional. The IL-13Rα2 DNA vaccine also exhibited antitumor activity against established D5α2 tumors in mice. Histologic analysis of regressing tumors identified infiltration of CD4+ and CD8+ T cells and the expression of CXCL9 chemokine in tumors. Taken together, our results identify the human IL-13Rα2 chain as a novel tumor rejection antigen. (Cancer Res 2006; 66(8): 4434-42)
Radiation-Induced Caspase-8 Mediates p53-Independent Apoptosis in Glioma Cells
Authors: Afshar Golnar , Jelluma Nannette , Yang Xiaodong , Basila Daniel , Arvold Nils D. , Karlsson Amelia , Yount Garret L. , Dansen Tobias B. , Koller Erich , Haas-Kogan Daphne A.
Published: April 2006

Malignant gliomas are almost uniformly fatal and display exquisite radiation resistance. Glioma cells lacking wild-type (WT) p53 function are more susceptible to radiation-induced apoptosis than their isogenic counterparts expressing WT p53. We explored the mechanisms of such apoptosis and found that, in the absence of WT p53, radiation increases caspase-8 expression and activity. Inhibition of caspase-8 expression using caspase-8 antisense or small interfering RNA (siRNA) oligonucleotides partially blocks radiation-induced apoptosis. In contrast, inhibition of the mitochondrial death pathway by expression of Bcl-2 has no effect on radiation-induced caspase-8 activity or apoptosis. Our data indicate that, in contrast to commonly accepted models of p53-dependent radiation-induced apoptosis, in our cell system, radiation relies on caspase-8 activity to help mediate p53-independent cell death. In a system of inducible E2F1 activity, E2F1 activated caspase-8 and, accordingly, decreased cellular viability, effects that were abolished by caspase-8 siRNA. In this model, in the absence of WT p53, p21Cip1 is not induced, and E2F1 activity is sustained and allows transcription and activation of caspase-8. This model may explain why p53 mutations in adult gliomas paradoxically correlate with improved survival and enhanced response to radiation. (Cancer Res 2006; 66(8): 4223-32)
Discovery and Evaluation of Dual CDK1 and CDK2 Inhibitors
Authors: Payton Marc , Chung Grace , Yakowec Peter , Wong Andrew , Powers Dave , Xiong Ling , Zhang Nancy , Leal Juan , Bush Tammy L. , Santora Vincent , Askew Ben , Tasker Andrew , Radinsky Robert , Kendall Richard , Coats Steve
Published: April 2006

In eukaryotic cells, cyclin-dependent kinase (CDK) complexes regulate the temporal progression of cells through the cell cycle. Deregulation in the cell cycle is an essential component in the evolution of cancer. Here, we validate CDK1 and CDK2 as potential therapeutic targets using novel selective small-molecule inhibitors of cyclin B1/CDK1 and cyclin E2/CDK2 enzyme complexes (CDKi). Flow cytometry–based methods were developed to assess intracellular retinoblastoma (Rb) phosphorylation to show inhibition of the CDK pathway. Tumor cells treated with CDK inhibitors showed an overall decrease in cell proliferation, accumulation of cells in G1 and G2, and apoptosis in a cell line–specific manner. Although CDK inhibitors activate p53, the inhibitors were equipotent in arresting the cell cycle in isogenic breast and colon tumor cells lacking p53, suggesting the response is independent of p53. In vivo, the CDK inhibitors prevented the growth of colon and prostate tumors, blocked proliferation of tumor cells, and inhibited Rb phosphorylation. The discovery and evaluation of novel potent and selective CDK1 and CDK2 inhibitors will help delineate the role that CDK complexes play in regulating tumorigenesis. (Cancer Res 2006; 66(8): 4299-308)
Soluble Human LAG-3 Molecule Amplifies theIn vitroGeneration of Type 1 Tumor-Specific Immunity
Authors: Casati Chiara , Camisaschi Chiara , Rini Francesca , Arienti Flavio , Rivoltini Licia , Triebel Frédéric , Parmiani Giorgio , Castelli Chiara
Published: April 2006

The adjuvant activities of the human lymphocyte activation gene-3 (LAG-3) molecule have been evaluated in a human setting by investigating the ability of a soluble recombinant human LAG-3 protein (hLAG-3Ig) to enhance the in vitro induction of viral- and tumor-specific CTLs. We found that soluble human LAG-3 significantly sustained the generation and expansion of influenza matrix protein Melan-A/MART-1 and survivin-specific CD8+ T lymphocytes in peripheral blood mononuclear cells (PBMC) of both cancer patients and healthy donors, showing its ability to boost CD8+ T-cell memory response or to prime naive T cells in vitro. The peptide-specific T cells generated in the presence of hLAG-3Ig were endowed with cytotoxic activity and enhanced release of type 1 cytotoxic T (Tc1) cytokines and were able to recognize tumor cells expressing their nominal antigen. Phenotype and cytokine/chemokines produced by antigen-presenting cells (APC) of PBMCs exposed in vitro for 2 days to peptide and hLAG-3Ig indicate that the LAG-3–mediated adjuvant effect may depend on a direct activation of circulating APCs. Our data revealed the activity of hLAG-3Ig in inducing tumor-associated, antigen-specific CD8+ T-cell responses in a human setting and strongly support the conclusion that this recombinant protein is a potential candidate adjuvant for cancer vaccines. (Cancer Res 2006; 66(8): 4450-60)
Multiple Adaptive Mechanisms to Chronic Liver Disease Revealed at Early Stages of Liver Carcinogenesis in the Mdr2-Knockout Mice
Authors: Katzenellenbogen Mark , Pappo Orit , Barash Hila , Klopstock Naama , Mizrahi Lina , Olam Devorah , Jacob-Hirsch Jasmine , Amariglio Ninette , Rechavi Gidi , Mitchell Leslie Ann , Kohen Ron , Domany Eytan , Galun Eithan , Goldenberg Daniel
Published: April 2006

Molecular events preceding the development of hepatocellular carcinoma were studied in the Mdr2-knockout (Mdr2-KO) mice. These mice lack the liver-specific P-glycoprotein responsible for phosphatidylcholine transport across the canalicular membrane. Portal inflammation ensues at an early age followed by hepatocellular carcinoma development after the age of 1 year. Liver tissue samples of Mdr2-KO mice in the early and late precancerous stages of liver disease were subjected to histologic, biochemical, and gene expression profiling analysis. In an early stage, multiple protective mechanisms were found, including induction of many anti-inflammatory and antioxidant genes and increase of total antioxidant capacity of liver tissue. Despite stimulation of hepatocyte DNA replication, their mitotic activity was blocked at this stage. In the late stage of the disease, although the total antioxidant capacity of liver tissue of Mdr2-KO mice was normal, and inflammation was less prominent, many protective genes remained overexpressed. Increased mitotic activity of hepatocytes resulted in multiple dysplastic nodules, some of them being steatotic. Expression of many genes regulating lipid and phospholipid metabolism was distorted, including up-regulation of choline kinase A, a known oncogene. Many other oncogenes, including cyclin D1, Jun, and some Ras homologues, were up-regulated in Mdr2-KO mice at both stages of liver disease. However, we found no increase of Ras activation. Our data suggest that some of the adaptive mechanisms induced in the early stages of hepatic disease, which protect the liver from injury, could have an effect in hepatocarcinogenesis at later stages of the disease in this hepatocellular carcinoma model. (Cancer Res 2006; 66(8): 4001-10)
Altered Expression of c-IAP1, Survivin, and Smac Contributes to Chemotherapy Resistance in Thyroid Cancer Cells
Authors: Tirrò Elena , Consoli Maria Letizia , Massimino Michele , Manzella Livia , Frasca Francesco , Sciacca Laura , Vicari Luisa , Stassi Giorgio , Messina Luigi , Messina Angelo , Vigneri Paolo
Published: April 2006

Resistance to chemotherapy predicts an unfavorable outcome for patients with radioiodine-insensitive thyroid cancer. To investigate the mechanisms underlying this resistance, we evaluated the expression of four different inhibitor of apoptosis proteins, and their antagonist, Smac, in thyroid cancer cells that survived 48 hours of exposure to cisplatin, doxorubicin, or taxol. We found high levels of c-IAP1 after cisplatin treatment and increased expression of survivin following exposure to doxorubicin. Cells that endured treatment with taxol showed reduced expression of Smac and released minimal amounts of this protein from the mitochondria. Down-regulation of c-IAP1 and survivin increased the cytotoxicity of cisplatin and doxorubicin, whereas overexpression of Smac improved the efficacy of taxol. Finally, thyroid cancer cells permanently resistant to doxorubicin or cisplatin showed increased expression of c-IAP1 and survivin, respectively. However, silencing of these proteins by RNA interference restored sensitivity to doxorubicin and cisplatin. Thus, in thyroid cancer cells, early resistance to chemotherapeutic agents requires high levels of c-IAP1 and survivin and low levels of Smac. Furthermore, increased expression of c-IAP1 and survivin contributes to the acquisition of permanent resistance to cytotoxic compounds. (Cancer Res 2006; 66(8): 4263-72)
Colony-Stimulating Factor-1 Antibody Reverses Chemoresistance in Human MCF-7 Breast Cancer Xenografts
Authors: Paulus Patrick , Stanley E. Richard , Schäfer Romana , Abraham Dietmar , Aharinejad Seyedhossein
Published: April 2006

Overexpression of colony-stimulating factor-1 (CSF-1) and its receptor in breast cancer is correlated with poor prognosis. Based on the hypothesis that blockade of CSF-1 would be beneficial in breast cancer treatment, we developed a murinized, polyethylene glycol–linked antigen-binding fragment (Fab) against mouse (host) CSF-1 (anti-CSF-1 Fab). Mice bearing human, chemoresistant MCF-7 breast cancer xenografts were treated with combination chemotherapy (CMF: cyclophosphamide, methotrexate, 5-fluorouracil; cycled twice i.p.), anti-CSF-1 Fab (i.p., cycled every 3 days for 14 days), combined CMF and anti-CSF-1 Fab, or with Ringer's solution as a control. Anti-CSF-1 Fab alone suppressed tissue CSF-1 and retarded tumor growth by 40%. Importantly, in combination with CMF, anti-CSF-1 Fab reversed chemoresistance of MCF-7 xenografts, suppressing tumor development by 56%, down-regulating expression of the chemoresistance genes breast cancer–related protein, multidrug resistance gene 1, and glucosylceramide synthase, and prolonging survival significantly. Combined treatment also reduced angiogenesis and macrophage recruitment and down-regulated tumor matrix metalloproteinase-2 (MMP-2) and MMP-12 expression. These studies support the paradigm of CSF-1 blockade in the treatment of solid tumors and show that anti-CSF-1 antibodies are potential therapeutic agents for the treatment of mammary cancer. (Cancer Res 2006; 66(8): 4349-56)
Inhibition of Cyclooxygenase-2 Disrupts Tumor Vascular Mural Cell Recruitment and Survival Signaling
Authors: Lee Alice , Frischer Jason , Serur Anna , Huang Jianzhong , Bae Jae-O , Kornfield Zev Noah , Eljuga Lucy , Shawber Carrie J. , Feirt Nikki , Mansukhani Mahesh , Stempak Diana , Baruchel Sylvain , Bender Julia Glade , Kandel Jessica J. , Yamashiro Darrell J.
Published: April 2006

Much evidence supports an important role for the inducible enzyme cyclooxygenase-2 (COX-2) in tumor angiogenesis. Previous studies have focused on the role of COX-2 in stimulating endothelial proliferation, with blockade of this enzyme impairing endothelial homeostasis. However, recent data suggest that COX-2 also regulates molecules implicated in endothelial trafficking with pericytes/vascular mural cells (VMC), an interaction crucial to vessel stability. We investigated the role of COX-2 in vascular assembly by testing the effect of the specific COX-2 inhibitor SC-236 in an orthotopic xenograft model of human Wilms' tumor. Tumor growth was significantly suppressed by SC-236 (78% at day 28, 55% at day 35). Perfusion studies and immunostaining showed a marked decrease in vasculature, particularly in small vessels. Specifically, SC-236 inhibited participation of VMC in xenograft vessels. SC-236–treated tumors developed segmentally dilated, architecturally erratic tumor vessels with decreased nascent pericytes and scant mature VMC. Although vascular endothelial growth factor expression was unchanged, expression of the chemokine receptor CXCR4 was decreased in tumor vessels, consistent with defective homing of vascular progenitor cells. Vascular expression of phosphorylated platelet-derived growth factor receptor-β was also diminished, indicating impaired VMC-endothelial trafficking. Consistent with the key role of this interaction in vessel homeostasis, vascular cells in SC-236–treated tumors displayed markedly diminished phosphorylated Akt, indicating disrupted survival signaling. These results show that SC-236 causes defective vascular assembly by attenuating incorporation of VMC into tumor vessels, impairing endothelial survival, and raise the possibility that blockade of COX-2 may provide therapeutic synergies with antiangiogenic molecules that more selectively target endothelial cells. (Cancer Res 2006; 66(8): 4378-84)