bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular structure and orientation of gel‐spun polyethylene fibers
Authors: Karacan Ismail
Published: April 2006

Characterization of molecular structure and orientation of six commercially available gel‐spun polyethylene fibers have been carried out using infra‐red and Raman spectroscopy, thermal and X‐ray diffraction analysis, together with optical microscopy techniques. Thermal and X‐ray diffraction analysis revealed the existence of highly oriented orthorhombic and monoclinic crystallites together with a highly oriented intermediate phase known as pseudohexagonal mesophase structure. The results suggest the existence of a three‐phase structure consisting, at room temperature, of orthorhombic and monoclinic polymorphic crystallites, oriented noncrystalline and un‐oriented noncrystalline (amorphous) phases, respectively. The crystallinity measurements have been carried out using density, thermal and X‐ray diffraction analysis together with infra‐red and Raman spectroscopy techniques whereas the molecular orientation measurements have been carried out using birefringence and polarized IR spectroscopy, respectively. The results obtained from density, thermal analysis, and Raman spectroscopy based on a simple two‐phase modeling approach lead to the overestimated amorphous fractions and appears to ignore the presence of an intermediate phase known as oriented noncrystalline structure. X‐ray analysis has also been used for the measurement of the apparent crystallite sizes. The birefringence values have been used to determine the overall orientation parameters whereas the dichroic measurements of IR bands have been used to determine the crystalline and oriented noncrystalline orientation parameters. The results show that the orthorhombic and monoclinic phases are more highly oriented than the oriented pseudohexagonally packed noncrystalline chains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1317–1333, 2006
Melt spinning and drawing process of PET side‐by‐side bicomponent fibers
Authors: Hwan Oh Tae
Published: April 2006

The change of crimp contraction and shrinkage in the melt spinning and drawing process of polyethylene terephthalate (PET) side‐by‐side bicomponent fibers was studied. Regular PET and modified PET were selected to make a latent crimp yarn. The modified PET was synthesized to increase thermal shrinkage. The crimp contraction is mainly dependent on drawing conditions such as draw ratio, heat‐set temperature, and drawing temperature. Difference in shrinkage between the PET and the modified PET causes the self‐crimping of bicomponent fibers. Although changing the heat‐set temperature and the drawing temperature can not affect dimensional change, the crimp contraction varies with those variables. As the heat‐set temperature and the drawing temperature decrease, the crimp contraction increases. Difference in elongation also affects the crimp contraction in the effect of draw ratio. When the modified PET with neopentyl group was used for highly shrinkable part, the crimp contraction is greater in comparison with modified PET with dimethyl isophthalate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1362–1367, 2006
Water‐soluble copolymers. II. Inverse emulsion terpolymerization of acrylamide, sodium acrylate, and acryloyloxyethyl trimethylammonium chloride
Authors: Peng Xiaohong , Peng Xiaochun
Published: April 2006

Inverse emulsion terpolymerization of acrylamide, sodium acrylate, and acryloyloxyethyl trimethylammonium chloride was investigated. Aqueous monomer solutions were emulsified in diesel oil with a blend of two surfactants (SPAN80 and TWEEN80) using 2,2′‐azobis(2‐amidinopropen)‐dihydrochloride as the initiator. The effects of temperature, initiator concentration, monomer concentration and composition, and emulsifier content on the polymerization conversion and the polymer intrinsic viscosity were examined. Polymer intrinsic viscosity increased with a decreasing concentration of initiator and an increasing concentration of monomer. The sizes of the latex particles of the terpolymer emulsions were observed with a scanning electron microscope, and the structure of the terpolymer was identified by FTIR spectroscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1381–1385, 2006
Non‐genomic immunosuppressive actions of progesterone inhibits PHA‐induced alkalinization and activation in T cells
Authors: Chien Eileen Jea , Chang Ching‐Pang , Lee Wen‐Feng , Su Tsung‐Hsien , Wu Chia‐Hsun
Published: April 2006

Progesterone is an endogenous immunomodulator, and can suppress T‐cell activation during pregnancy. When analyzed under a genome time scale, the classic steroid receptor pathway does not have any effect on ion fluxes. Therefore, the aim of this study was to investigate whether the non‐genomic effects on ion fluxes by progesterone could immunosuppress phytohemagglutinin (PHA)‐induced human peripheral T‐cell activation. The new findings indicated that, first, only progesterone stimulated both [Ca2+]i elevation and pHi decrease; in contrast, estradiol or testosterone stimulated [Ca2+]i elevation and hydrocortisone or dexamethasone stimulated pHi decrease. Secondly, the [Ca2+]i increase by progesterone was dependent on Ca2+ influx, and the acidification was blocked by Na+/H+ exchange (NHE) inhibitor, 3‐methylsulphonyl‐4‐piperidinobenzoyl, guanidine hydrochloride (HOE‐694) but not by 5‐(N,N‐dimethyl)‐amiloride (DMA). Thirdly, progesterone blocked phorbol 12‐myristate 13‐acetate (PMA) or PHA‐induced alkalinization, but PHA did not prevent progesterone‐induced acidification. Fourthly, progesterone did not induce T‐cell proliferation; however, co‐stimulation progesterone with PHA was able to suppress PHA‐induced IL‐2 or IL‐4 secretion and proliferation. When progesterone was applied 72 h after PHA stimulation, progesterone could suppress PHA‐induced T‐cell proliferation. Finally, immobilization of progesterone by conjugation to a large carrier molecule (BSA) also stimulated a rapid [Ca2+]i elevation, pHi decrease, and suppressed PHA‐induced proliferation. These results suggested that the non‐genomic effects of progesterone, especially acidification, are exerted via plasma membrane sites and suppress the genomic responses to PHA. Progesterone might act directly through membrane specific nonclassical steroid receptors to cause immunomodulation and suppression of T‐cell activation during pregnancy. J. Cell. Biochem. © 2006 Wiley‐Liss, Inc.
Molecular dynamics simulation and automated docking of the pro‐apoptotic bax protein and its complex with a peptide designed from the Bax‐binding domain of anti‐apoptotic Ku70
Authors: Mancinelli Fabrizio , Caraglia Michele , Budillon Alfredo , Abbruzzese Alberto , Bismuto Ettore
Published: April 2006

Bax, a multi‐domain protein belonging to the large family of Bcl‐2 proteins, has a pivotal role for the initiation of the cytochrome c‐mediated apoptosis, a vital physiologic process to eliminate damaged or unwanted cells. In response to specific stimuli Bax translocates from cytosol to mitochondria outer membrane where a process of oligomerization occurs with pore formation through which cytochrome c and other death molecules escape. The pro‐death action of Bax is regulated by the interaction with other pro‐survival proteins. However, the conformational changes and the structural details necessary for homo and hetero interaction with other regulating proteins are largely unknown. This article reports a combined investigation of molecular dynamics (MD) simulation and automated docking that evidence the molecular regions of Bax involved in the binding with anti‐apoptotic exapeptide (Bip) designed from Ku70, a subunit of the protein complex essential for non‐homologous DNA repair but that inhibits also the Bax translocation to mitochondria. Since Bip suppresses apoptosis induced by several anti‐cancer drugs, it appears relevant to achieve a better understanding of the structural and dynamical aspects that characterize the Bip–Bax complex in view of potential therapeutic implications. The present results show that the Bax region with the highest affinity for Bip is located in proximity of BH3 homology domain of Bax and also involves the α‐helices 1 and 8. Moreover, the comparison of essential motions of Bax at 300 and 400 K before and after the formation of the complex with Bip evidences how the binding with the exa‐peptide affects the collective motions of specific molecular districts of Bax considered to have functional relevance. J. Cell. Biochem. © 2006 Wiley‐Liss, Inc.
Role of metal‐responsive transcription factor‐1 (MTF‐1) in EGF‐dependent DNA synthesis in primary hepatocytes
Authors: Kimura Tomoki , Itoh Norio , Sone Tomomichi , Kondoh Masuo , Tanaka Keiichi , Isobe Masakazu
Published: April 2006

Metal‐responsive transcription factor‐1 (MTF‐1), which is involved in sensing heavy metal load, induces the transcription of several protective genes. The mouse Mtf‐1 gene is essential, and Mtf‐1−/− embryos die from liver degeneration. We showed that DNA synthesis induced in hepatocytes by epidermal growth factor (EGF) was delayed by inhibition of MTF‐1. To inhibit MTF‐1 activity, MTFΔC, a C‐terminal deletion mutant of MTF‐1, was expressed by infection with the virus Ad5MTFΔC. Lactate dehydrogenase (LDH) release and/or caspase‐3/7 activation was not observed under our experimental conditions. The inhibitory effect of MTFΔC on EGF‐dependent DNA synthesis in hepatocytes was not eliminated by zinc addition. EGF‐dependent extracellular signal‐related kinase (ERK) phosphorylation, an essential reaction for EGF‐dependent DNA synthesis, was decreased in MTF‐1‐inhibited hepatocytes. Moreover, decrease of ERK phosphorylation was observed by using siRNA in MTF‐1‐downregulated hepatocytes. These results indicate that MTF‐1 is particularly important for proper hepatocyte proliferation. This is the first report to suggest the function of MTF‐1 in the ERK pathway. J. Cell. Biochem. 99: 485–494, 2006. © 2006 Wiley‐Liss, Inc.
Anti‐apoptotic factor humanin is expressed in the testis and prevents cell‐death in leydig cells during the first wave of spermatogenesis
Authors: Colón Eugenia , Strand Mona‐Lisa , Carlsson‐Skwirut Christine , Wahlgren Aida , Svechnikov Konstantin V. , Cohen Pinchas , Söder Olle
Published: April 2006

Humanin (HN) is a 24 amino acids peptide with potent neuro‐survival properties that protects against damage associated with Alzheimer's disease. In the present report, we have demonstrated by immunohistochemical analysis and Western blotting the pattern of expression of rat humanin (HNr) in the testis of 10‐ to 60‐day‐old rats. The Leydig cells of 10‐ and 40‐ day‐old rats expressed this peptide at high levels; and in the testis of 60‐day‐old rats the expression of HNr expanded to include Leydig, endothelial, peritubular and germ cells. As monitored by Western blotting, HNr was released into the medium of cultures of Leydig cells isolated from 10‐, 40‐, and 60‐days‐old rats. HNr stimulated the incorporation of [3H]TdR into DNA of Leydig cells from 10‐days‐old rats, in a manner that indicated promotion of cell survival rather than an increase in the rate of cell multiplication. This peptide also enhanced steroidogenesis by cultured Leydig cells from 10‐ to 40‐day‐old rats both alone and synergistically with IGF‐I. The expression of HNr in cultured Leydig cells increased in response to GH and IGF‐I. In summary, we demonstrated here that HNr was expressed at all stages of maturation in the rat testis. This peptide promoted the survival of Leydig cells in culture and interacted with IGF‐I to stimulate DNA synthesis and steroidogenesis. We propose that HNr is a novel testicular anti‐apoptotic factor. J. Cell. Physiol. 208: 373–385, 2006. © 2006 Wiley‐Liss, Inc.
Ab initio insight on the interaction of ascorbate with Li+, Na+, K+, Be2+, Mg2+, and Ca2+metal cations
Authors: Allen Reeshemah N. , Shukla M. K. , Leszczynski Jerzy
Published: April 2006

The structures and interactions of different possible ascorbic acid anions (ascorbates) with Li+, Na+, K+, Be2+, Mg2+, and Ca2+metal cations were studied at the density functional theory level employing the B3LYP exchange correlation functional and the 6‐311++G(d,p) basis set. The interactions of the metal cations at the different basic sites of ascorbate were considered. The single‐point energy calculations were also performed at the MP2/6‐311++G(d,p) level. Tomasi's polarized continuum model (PCM) was used to evaluate the influence of aqueous solvent on the relative stability of different complexes. The interaction energies for the complexes were corrected for the basis set superposition error (BSSE) using the counterpoise method. The AIM theory was used to characterize the electron density distribution involved in the coordination of studied metal cations with ascorbate. In water, the most preferred position for the interaction of Li+, Na+, and K+cations is through bicoordination with the O2and O3sites of the AAOanion, while all divalent cations Be2+, Mg2+, and Ca2+prefer bicoordination with the O1and O2sites of AAOanion of ascorbic acid. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Fitting potential energy surface of reactive systems via genetic algorithm
Authors: Ferreira Da Cunha Wiliam , Roncaratti Luiz Fernando , Gargano Ricardo , E Silva Geraldo Magela
Published: April 2006

We present a new fitting of the Na+HF potential energy surface (PES) using a new optimization method based on genetic algorithm. Topology studies, such as isoenergetic contours and minimum energy path (MEP), show that the quality of this new PES is comparable to the best PES of literature. These facts suggest that this new approach can be used as a new tool to fit PES of reactive systems. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Re: Sources
Authors: Fern Annette
Published: April 2006

In July 2005, the Art Institute of Chicago announced plans for the demolition of the Kenneth Sawyer Goodman Memorial Theatre in order to make room for additional gallery and administrative spaces for the museum. The Goodman Theatre had been a museum department from its founding in 1925 to 2000, when the company became an independent producing organization and moved to a new facility in Chicago's theatre district. Since then, the building had been an unproductive appendage to the Art Institute, but numerous attempts to tear it down had been met with resistance by architectural preservationists who felt that the structure, by noted Chicago architect Howard Van Doren Shaw, was historically significant and warranted landmark status.
The Past as Present in the Drama of August Wilson
Authors: Shannon Sandra G.
Published: April 2006

Time, timing, and timelessness all converge in Harry J. Elam's The Past as Present in the Drama of August Wilson (2004), a major addition to Wilson studies at this profound juncture in the history of American theatre. First, Elam's study offers a sweeping retrospective of Wilson's blending of past and present time in his recently completed cycle of plays. Yet it is the timing of the book's release that affords it an added advantage. Though published in 2004, The Past as Present in the Drama of August Wilson can easily be regarded as a most fitting tribute to one of the great voices of the American stage. As the nation—indeed the world—mourns the sudden loss of August Wilson, current and future generations of scholars, students, educators, theatre practitioners, and lovers of theatre may find comfort in knowing that the foundation has already been laid for serious and sustained study of his phenomenal legacy and far-reaching influence. Elam's work adds a vital cornerstone to that foundation.
Konstantin Stanislavsky Michael Chekhov Vsevolod Meyerhold Jacques Lecoq
Authors: Daboo Jerri
Published: April 2006

The Routledge Performance Practitioners series, edited by Franc Chamberlain, is a new set of introductory guides to a range of key figures in the development of twentieth-century performance practice. Each book focuses on a single practitioner, examining his or her life, historical context, key writings, and productions, and a selection of practical exercises. These concise volumes are intended to offer students an initial introduction to the practitioner and to “provide an inspiring spring-board for future study, unpacking and explaining what can initially seem daunting” (Merlin, ii). The list of practitioners in the complete series include Stanislavsky, Brecht, Boal, Lecoq, Grotowski, Anna Halprin, and Ariane Mnouchkine, thus examining a range of performance styles and practices, creating a valuable overview of the development of performer training through the twentieth and into the twenty-first centuries. Such interest in the history of specific approaches to training performers has been addressed in other volumes, such as Twentieth-Century Actor Training, edited by Alison Hodge (New York: Routledge, 2000), and Acting (Re)considered: A Theoretical and Practical Guide, edited by Phillip Zarrilli (London: Routledge 2002). Both those collections contain in-depth chapters focusing on aspects of the selected practitioners' theoretical and practical approaches to the principles and concerns in their work. Where the books in the Routledge Performance Practitioners series differ is that they offer a more general overview of the practitioner in one volume, and in addition to the historical context, they provide a set of practical exercises that can be carried out by the student or teacher, as well as by the actor or director. The books are well presented, divided into clear sections, with relevant photographs and diagrams. There are also sidebars providing definitions and further information on key figures and terms mentioned in the main text. This review covers the first four books in the series, examining the work of Konstantin Stanislavsky, Michael Chekhov, Vsevolod Meyerhold, and Jacques Lecoq.
Ab initio study of the electronic structure of manganese carbide
Authors: Kalemos Apostolos , Dunning Thom H. , Mavridis Aristides
Published: April 2006

We report electronic structure calculations on 13 states of the experimentally unknown manganese carbide (MnC) using standard multireference configuration interaction (MRCI) methods coupled with high quality basis sets. For all states considered we have constructed full potential energy curves and calculated zero point energies. The X state, correlating to ground state atoms, is of Σ−4 symmetry featuring three bonds, with a recommended dissociation energy of D0=70.0kcal∕mol and re=1.640Å. The first and second excited states, which also correlate to ground state atoms, are of Σ−6 and Σ−8 symmetry, respectively, and lie 17.7 and 28.2kcal∕mol above the X state at the MRCI level of theory.
Relative stability of planar versus double-ring tubular isomers of neutral and anionic boron cluster B20 and B20−
Authors: An Wei , Bulusu Satya , Gao Yi , Zeng X. C.
Published: April 2006

High-level ab initio molecular-orbital methods have been employed to determine the relative stability among four neutral and anionic B20 isomers, particularly the double-ring tubular isomer versus three low-lying planar isomers. Calculations with the fourth-order Møller-Plessset perturbation theory [MP4(SDQ)] and Dunning’s correlation consistent polarized valence triple zeta basis set as well as with the coupled-cluster method including single, double, and noniteratively perturbative triple excitations and the 6-311G(d) basis set show that the double-ring tubular isomer is appreciably lower in energy than the three planar isomers and is thus likely the global minimum of neutral B20 cluster. In contrast, calculations with the MP4(SDQ) level of theory and 6-311+G(d) basis set show that the double-ring anion isomer is appreciably higher in energy than two of the three planar isomers. In addition, the temperature effects on the relative stability of both B20−10 and B20−11 anion isomers are examined using the density-functional theory. It is found that the three planar anion isomers become increasingly more stable than the double-ring isomer with increasing the temperature. These results are consistent with the previous conclusion based on a joint experimental/simulated anion photoelectron spectroscopy study [B. Kiran et al., Proc. Natl. Acad. Sci. U.S.A. 102, 961 (2005)], that is, the double-ring anion isomer is notably absent from the experimental spectra. The high stability of the double-ring neutral isomer of B20 can be attributed in part to the strong aromaticity as charaterized by its large negative nucleus-independent chemical shift. The high-level ab initio calculations suggest that the planar-to-tubular structural transition starts at B20 for neutral clusters but should occur beyond the size of B20− for the anion clusters.
Describing the component dynamics in miscible polymer blends: Towards a fully predictive model
Authors: Schwartz Gustavo A. , Cangialosi Daniele , Alegría Ángel , Colmenero Juan
Published: April 2006

We have recently proposed [D. Cangialosi et al., J. Chem. Phys. 123, 144908 (2005)] an extension of the Adam-Gibbs [J. Chem. Phys. 43, 139 (1965)] theory, combined with the concept of self-concentration, to describe the temperature dependence of the relaxation time for the component segmental dynamics in miscible polymer blends. Thus, we were able to obtain the dynamics of each component in the blend starting from the knowledge of the dynamic and thermodynamic data of the pure polymers, with a single fitting parameter (α) which had to be obtained from the fitting of the experimental data. In the present work we demonstrate that this model is also suitable to describe the polymer segmental dynamics in concentrated polymer solutions. From this result we have developed a new route for determining the value of the α parameter associated with any given polymer. Once this value is known for the two components of a possible polymer blend, our model for polymer blends dynamics becomes fully predictive.
Tri-Hamiltonian extensions of separable systems in the plane
Authors: Degiovanni Luca
Published: April 2006

A method to construct tri-Hamiltonian extensions of a separable system is presented. The procedure is tested for systems, with a Hamiltonian quadratic in the momenta, separable in classical sense in any of the four sets of orthogonal separable coordinates on the Euclidean plane. Some explicit examples are constructed. Finally a conjecture on possible generalizations to other classes of systems is discussed: in particular, the method can be adapted to the 11 orthogonal separable coordinate sets of the Euclidean three-space.
Collective electric field effects on the confinement of fast ions in tokamaks
Authors: McClements K. G. , Thyagaraja A.
Published: April 2006

The injection of neutral particle beams counter to the plasma current direction in the Mega-Ampère Spherical Tokamak (MAST) [A. Sykes, R. J. Akers, L. C. Appel et al., Nucl. Fusion, 41, 1423 (2001)] leads to substantial losses of energetic beam ions and also rapid toroidal rotation. The electrodynamic consequences of energetic ion loss on tokamak plasmas are explored in light of results from the MAST counterinjection experiments and test particle calculations of the current density due to escaping ions. Previous authors have noted that there are two possible consequences of such a current: either a compensating bulk plasma return current is set up, or the plasma behaves as an insulator, with the energetic ion current balanced by a displacement current rather than a conduction current. Radial electric fields and hence toroidal flows occur in both cases, but higher fields are predicted in the insulating case. Such fields are important because they can confine both fast ions and bulk plasma (via the suppression of turbulent transport). The return current scenario, which appears to be operative during counterinjection in MAST, is shown to be applicable if there is a sufficiently high level of momentum transport in the bulk ions; electrons cannot carry the return current, although they contribute to an ambipolar particle flux on the plasma confinement time scale. The insulating scenario may be applicable to high confinement regimes in burning tokamak plasmas.
Electron trajectories and gain for an electromagnetic wiggler with ion-channel guiding
Authors: Esmaeilzadeh Mahdi , Ghafouri Vahid , Taghavi Amin , Namvar Esmaeil
Published: April 2006

A theory is developed for a free-electron laser with electromagnetic wiggler and ion-channel guiding. The electron trajectories due to a large amplitude backward propagating electromagnetic wiggler and an ion-channel electrostatic field are obtained and the stability of orbits is discussed. Then the gain equation describing the interaction between an electron and the radiation field is derived in the low-gain-per-pass limit. The results of a numerical study of electron orbits and gain are presented and discussed. It is shown that the maximum gain obtained in an electromagnetic wiggler is about twice the maximum gain obtained in a magnetostatic wiggler.
Electronic structure and chemical environment of silicon nanoclusters embedded in a silicon dioxide matrix
Authors: Zimina Anna , Eisebitt Stefan , Eberhardt Wolfgang , Heitmann Johannes , Zacharias Margit
Published: April 2006

Using photon-in photon-out soft x-ray spectroscopy, the electronic structure of silicon nanoclusters embedded in an electrically insulating SiO2 host matrix is investigated as a function of nanocluster size. We find the nanoclusters to be of a core-shell structure with a crystalline Si core and a thin transition layer of a suboxide. Effects of electronic quantum confinement are detected in the Si cores. We find that the influence of confined excitonic states manifests itself predominantly in the unoccupied electronic states.
Ultrafast carrier dynamics in Au∕GaAs interfaces studied by terahertz emission spectroscopy
Authors: Shi Yulei , Yang Yuping , Xu Xinlong , Ma Shihua , Yan Wei , Wang Li
Published: April 2006

The measurements of optically generated terahertz emission from Au∕GaAs interfaces are investigated in detail. We observe that, under high laser power excitation, terahertz signals from bare GaAs wafers and Au∕GaAs samples exhibit an opposite polarity. The polarity-flip behaviors are also observed in temperature-dependent and femtosecond pump-generation studies of the Au∕GaAs interfaces.
Experimental realization of sonic demultiplexing devices based on inverse designed scattering acoustic elements
Authors: Håkansson Andreas , Sánchez-Dehesa José , Cervera Francisco
Published: April 2006

We present experiments demonstrating sonic demultiplex devices able to separate spatially several wavelengths. The devices are based on clusters of circular scatterers whose position and size are determined by using an inverse design approach. Two prototypes are built and characterized, a first that spatially separates two wavelengths (i.e., 20.0 and 22.7cm) and a second that separates three wavelengths: 20.0, 21.3, and 22.7cm. Both prototypes are typical examples of acoustic scattering elements, a name here introduced to define inverse designed devices that are characterized by their great adaptability in controlling the scattering image, including both the reflected and transmitted waves.
Use of Stochastic Epidemic Modeling to Quantify Transmission Rates of Colonization With Methicillin-Resistant Staphylococcus Aureus in an Intensive Care Unit
Authors: Forrester Marie , Pettitt Anthony N.
Published: April 2006

Objective:

To consider statistical methods for estimating transmission rates for colonization of patients with methicillin-resistant Staphylococcus aureus (MRSA) in an intensive care unit (ICU) from three different sources: background contamination, non-isolated patients, and isolated patients.

Methods:

We developed statistical methods that allowed for the analysis of interval-censored, routine surveillance data and extended the general epidemic model for the flow of patients through the ICU.

Results:

Within this ICU, the rate of transmission to susceptible patients from a background source of MRSA (0.0092 case per day; 95% confidence interval [CI95], 0.0062–0.0126) is approximately double the rate of transmission from a non-isolated patient (0.0052 case per day; CI95, 0.0013–0.0096) and six times the rate of transmission from an isolated patient (0.0015 case per day; CI95, 0.0001–0.0043). We used the methodology to investigate whether transmission rates vary with workload.

Conclusion:

Our methodology has general application to infection by and transmission of pathogens in a hospital setting and is appropriate for quantifying the effect of infection control interventions. (Infect Control Hosp Epidemiol 2005;26:598-606)
Modeling Transmission of Methicillin-ResistantStaphylococcus AureusAmong Patients Admitted to a Hospital
Authors: Raboud Janet , Saskin Refik , Simor Andrew , Loeb Mark , Green Karen , Low Don E. , McGeer Allison
Published: April 2006

Objective:

To determine the impact of the screening test, nursing workload, handwashing rates, and dependence of handwashing on risk level of patient visit on methicillin-resistantStaphylococcus aureus(MRSA) transmission among hospitalized patients.

Setting:

General medical ward.

Methods:

Monte Carlo simulation was used to model MRSA transmission (median rate per 1,000 patient-days). Visits by healthcare workers (HCWs) to patients were simulated, and MRSA was assumed to be transmitted among patients via HCWs.

Results:

The transmission rate was reduced from 0.89 to 0.56 by the combination of increasing the sensitivity of the screening test from 80% to 99% and being able to report results in 1 day instead of 4 days. Reducing the patient-to-nurse ratio from 4.3 in the day and 6.8 at night to 3.8 and 5.7, respectively, reduced the number of nosocomial infections from 0.89 to 0.85; reducing the ratio to 1 and 1, respectively, further reduced the number of nosocomial infections to 0.32. Increases in handwashing rates by 0%, 10%, and 20% for high-risk visits yielded reductions in nosocomial infections similar to those yielded by increases in handwashing rates for all visits (0.89, 0.36, and 0.24, respectively). Screening all patients for MRSA at admission reduced the transmission rate to 0.81 per 1,000 patient-days from 1.37 if no patients were screened.

Conclusion:

Within the ranges of parameters studied, the most effective strategies for reducing the rate of MRSA transmission were increasing the handwashing rates for visits involving contact with skin or bodily fluid and screening patients for MRSA at admission. (Infect Control Hosp Epidemiol 2005;26:607- 615)
Use of Strain Typing Data to Estimate Bacterial Transmission Rates in Healthcare Settings
Authors: Jackson Brian R. , Thomas Alun , Carroll Karen C. , Adler Frederick R. , Samore Matthew H.
Published: April 2006

Objective:

To create an affordable and accurate method for continuously monitoring bacterial transmission rates in healthcare settings.

Design:

We present a discrete simulation model that relies on the relationship between in-hospital transmission rates and strain diversity. We also present a proof of concept application of this model to a prospective molecular epidemiology data set to estimate transmission rates forPseudomonas aeruginosaandStaphylococcus aureus.

Setting:

Inpatient units of an academic referral center.

Patients:

All inpatients with nosocomial infections.

Intervention:

Mathematical model to estimate transmission rates.

Results:

Maximum likelihood estimates for transmission rates of these two species on different hospital units ranged from 0 to 0.36 transmission event per colonized patient per day.

Conclusions:

This approach is feasible, although estimates of transmission rates based solely on strain typed clinical cultures may be too imprecise for routine use in infection control. A modest level of surveillance sampling substantially improves the estimation accuracy. (Infect Control Hosp Epidemiol 2005;26:638-645)
Varying Rates of Clostridium Difficile-Associated Diarrhea at Prevention Epicenter Hospitals
Authors: Sohn SeJean , Climo Michael , Diekema Daniel , Fraser Victoria , Herwaldt Loreen , Marino Susan , Noskin Gary , Perl Trish , Song Xiaoyan , Tokars Jerome , Warren David , Wong Edward , Yokoe Deborah S. , Zembower Theresa , Sepkowitz Kent A. ,   Prevention Epicenter Hospitals
Published: April 2006

Background:

Clostridium difficile-associated diarrhea (CDAD) causes substantial healthcare-associated morbidity. Unlike other common healthcare-associated pathogens, little comparative information is available about CDAD rates in hospitalized patients.

Objectives:

To determine CDAD rates per 10,000 patient-days and per 1,000 hospital admissions at 7 geographically diverse tertiary-care centers from 2000 to 2003, and to survey participating centers on methods of CDAD surveillance and case definition.

Methods:

Each center provided specific information for the study period, including case numbers, patient-days, and hospital characteristics. Case definitions and laboratory diagnoses of healthcare-associated CDAD were determined by each institution. Within institutions, case definitions remained consistent during the study period.

Results:

Overall, mean annual case rates of CDAD were
12.1 per 10,000 patient-days (range, 3.1 to 25.1) and 7.4 per 1,000 hospital admissions (range, 3.1 to 13.1). No significant increases were observed in CDAD case rates during the 4-year interval, either at individual centers or in the Prevention Epicenter hospitals as a whole. Prevention Epicenter hospitals differed in their CDAD case definitions. Different case definitions used by the hospitals applied to a fixed data set resulted in a 30% difference in rates. No associations were identified between diagnostic test or case definition used and the relative rate of CDAD at a specific medical center.

Conclusions:

Rates of CDAD vary widely at tertiary-care centers across the United States. No significant increases in case rates were identified. The varying clinical and laboratory approaches to diagnosis complicated comparisons between hospitals. To facilitate benchmarking and comparisons between institutions, we recommend development of a more standardized case definition.
Clostridium difficile Among Hospitalized Patients Receiving Antibiotics A Case-Control Study
Authors: Modena Scott , Bearelly Dilip , Swartz Kenneth , Friedenberg Frank K.
Published: April 2006

Objectives:

Clostridium difficile is the most common cause of infectious nosocomial diarrhea and can be found in up to 30% of asymptomatic hospitalized patients. Our primary aim was to compare the clinical characteristics of hospitalized patients who received antibiotics and developed C. difficile-associated diarrhea (CDAD) with those of hospitalized patients who received antibiotics and did not develop the disease.

Design:

Case-control study comprising inpatients at a single institution.

Patients:

Case-patients were defined as patients who had diarrhea and tested positive for C. difficile. Control-patients (matched 4:1 to case-patients) were defined as patients who received antibiotics for at least 5 days and did not develop CDAD.

Results:

On univariate analysis, nine variables were associated with CDAD. Only three of the variables, need for intensive care, length of stay, and macrolide antibiotic use, were found to be significant (P < .05) on logistic regression analysis. The odds ratios for status as a CDAD case were 3.68 (CI95, 1.44 to 9.40) for stay in the intensive care unit and 1.03 (CI95, 1.02 to 1.05) for each day of hospital stay. Receipt of macrolide antibiotics reduced risk significantly; the odds ratio was 0.23 (CI95, 0.19 to 0.87).

Conclusions:

We identified need for intensive care and length of stay as important risk factors for the development of CDAD. We also identified macrolide antibiotic use as protective against its development. Patients receiving intensive care may represent a population to study for targeted prophylaxis.
Octenidine Hydrochloride for the Care of Central Venous Catheter Insertion Sites in Severely Immunocompromised Patients
Authors: Tietz Andreas , Frei Reno , Dangel Marc , Bolliger Dora , Passweg Jakob R. , Gratwohl Alois , Widmer Andreas F.
Published: April 2006

Objective:

To determine the efficacy and tolerability of octenidine hydrochloride, a non-alcoholic skin antiseptic, for the care of central venous catheter (CVC) insertion sites.

Design:

Prospective, observational study.

Setting:

Bone marrow transplantation unit of a university hospital.

Patients:

All consecutive patients with a nontunneled CVC were enrolled prospectively after informed consent.

Methods:

Octenidine hydrochloride (0.1%) was applied for disinfection at the CVC insertion site during dressing changes. The following cultures were performed weekly as well as at the occurrence of any systemic inflammatory response syndrome criteria: cultures of the skin surrounding the CVC entry site, cultures of the three-way hub connected to the CVC, blood cultures, and cultures of the CVC tip on removal. Enhanced microbiological methods (skin swabs of a 24-cm2 standardized area, roll plate, and sonication of catheter tips) were applied.

Results:

One hundred thirty-five CVCs were inserted in 62 patients during the study period and remained for a mean period of 19.1 days, corresponding to 2,462 catheter-days. Bacterial density at the insertion site declined substantially over time, and most cultures became negative 2 weeks after insertion. Only 6 patients had a documented catheter-related bloodstream infection. The incidence density was 2.39 catheter infections per 1,000 catheter-days. No side effects were noted with application of the antiseptic.

Conclusions:

Disinfection with a skin antiseptic that contains octenidine hydrochloride is highly active and well tolerated. It leads to a decrease in skin colonization over time and may be a new option for CVC care.
A Large Outbreak of Hepatitis B Virus Infections Associated With Frequent Injections at a Physician's Office
Authors: Samandari Taraz , Malakmadze Naile , Balter Sharon , Perz Joseph F. , Khristova Marina , Swetnam Leah , Bornschlegel Katherine , Phillips Michael S. , Poshni Iqbal A. , Nautiyal Preeti , Nainan Omana V. , Bell Beth P. , Williams Ian T.
Published: April 2006

Objectives:

To determine whether hepatitis B virus (HBV) transmission occurred among patients visiting a physician's office and to evaluate potential transmission mechanisms.

Design:

Serologic survey, retrospective cohort study, and observation of infection control practices.

Setting:

Private medical office.

Patients:

Those visiting the office between March 1 and December 26, 2001.

Results:

We identified 38 patients with acute HBV infection occurring between February 2000 and February 2002. The cohort study, limited to the 10 months before outbreak detection, included 91 patients with serologic test results and available charts representing 18 case-patients and 73 susceptible patients. Overall, 67 patients (74%) received at least one injection during the observation period. Case-patients received a median of 14 injections (range, 2-25) versus 2 injections (range, 0-17) for susceptible patients (P < .001). Acute infections occurred among 18 (27%) of 67 who received at least one injection versus none of 24 who received no injections (RR, 13.6; CI95, 2.4-undefined). Risk of infection increased 5.2-fold (CI95, 0.6-47.3) for those with 3 to 6 injections and 20.0-fold (CI95, 2.8-143.5) for those with more than 6 injections. Typically, injections consisted of doses of atropine, dexamethasone, vitamin B12, or a combination of these mixed in one syringe. HBV DNA genetic sequences of 24 patients with acute infection and 4 patients with chronic infection were identical in the 1,500-bp region examined. Medical staff were seronegative for HBV infection markers. The same surface was used for storing multidose vials, preparing injections, and dismantling used injection equipment.

Conclusion:

Administration of unnecessary injections combined with failure to separate clean from contaminated areas and follow safe injection practices likely resulted in patient-to-patient HBV transmission in a private physician's office.
Workers' Compensation Claims for Needlestick Injuries Among Healthcare Workers in Washington State, 1996-2000
Authors: Shah Syed M. , Bonauto David , Silverstein Barbara , Foley Michael
Published: April 2006

Objectives:

To characterize accepted workers' compensation claims for needlestick injuries filed by healthcare workers (HCWs) in non-hospital compared with hospital settings in Washington State.

Design:

Descriptive study of all accepted workers' compensation claims filed between 1996 and 2000 for needlestick injuries.

Participants:

All Washington State HCWs eligible to file a state fund workers' compensation claim and those who filed a workers' compensation claim for a needlestick injury.

Results:

There were 3,303 accepted state fund HCW needlestick injury claims. The incidence of needlestick injury claims per 10,000 full-time-equivalent HCWs in hospitals was 158.6; in dental offices, 104.7; in physicians' offices, 87.0; and in skilled nursing facilities, 80.8. The most common mechanisms of needlestick injury by work location were as follows: for hospitals, suturing and other surgical procedures (16.7%), administering an injection (12.7%), and drawing blood (10%); for dentists' offices, recapping (21.3%) and cleaning trays and instruments (18.2%); for physicians' offices, disposal (22.2%) and administering an injection (10.2%); and for skilled nursing facilities, disposal (23.7%) and administering an injection (14.9%). Nurses accounted for the largest (29%) proportion of HCWs involved, followed by dental assistants (17%) and laboratory technicians and phlebotomists (12%) in non-hospital settings. Rates of needlestick injury claims increased for non-hospital settings by 7.5% annually (95% confidence interval [CI95], 4.89% to 10.22%; P < .0001). Rates decreased for hospital settings by 5.8% annually, but the decline was not statistically significant (CI95, -12.50% to 1.34%; P < .1088). HCWs were exposed to hepatitis B, hepatitis C, and human immunodeficiency viruses in non-hospital settings.

Conclusion:

There was a difference in the incidence rate and mechanisms of needlestick injuries on review of workers' compensation claim records for HCWs in non-hospital and hospital settings.
Antiretroviral Drug Resistance Among Patients With Human Immunodeficiency Virus Who Act as Sources or Potential Sources in Occupational Accidents Involving Healthcare Workers
Authors: El-Far Fabiane , Medeiros Eduardo Alexandrino Servolo , Gasparoto Carlos Teodoro , Diaz Ricardo Sobhie
Published: April 2006

Objective:

To determine human immunodeficiency virus (HIV) type 1 genotypic antiretroviral drug resistance profiles of patients presenting a risk or potential risk for occupational exposure of healthcare workers.

Design:

Observational survey involving HIV-infected patients. Blood samples collected from source-patients and potential source-patients underwent HIV-1 genotypic antiretroviral resistance testing and determination of CD4 counts and viral load. Affected healthcare workers were monitored for 6 months after exposure.

Setting:

The survey was conducted in a tertiary-care hospital located in Sao Paulo, Brazil. Sao Paulo is considered the epicenter of the HIV-acquired immunodeficiency (AIDS) virus epidemic in Brazil.

Participants:

Source-patients, potential source-patients, and affected healthcare workers.

Results:

A total of 371 occupational exposures to biological materials were reported, 46 (12.3%) of which were from HIV-seropositive source-patients. Samples from 18 source-patients and 26 patients considered “potential sources for accidents” were analyzed. Of these 44 samples, 18 (41%) presented resistance-related mutations in reverse transcriptase, protease, or both. Of these 18 samples, 16 (89%) had resistance to drugs included in the prophylactic schedule recommended by the Brazilian Ministry of Health.

Conclusions:

Use of the Centers for Disease Control and Prevention-Brazilian post-exposure prophylaxis regimen will result in the administration of antiretroviral agents to which the source HIV-1 isolate will often be resistant. Therefore, it would be advisable to carefully investigate the history of use of antiretroviral agents by source-patients and adjust the prophylactic therapy based on those data and, subsequently, the results of resistance testing.
Control of leaf vascular patterning by polar auxin transport
Authors: Scarpella Enrico , Marcos Danielle , Friml Jiří , Berleth Thomas
Published: April 2006

The formation of the leaf vascular pattern has fascinated biologists for centuries. In the early leaf primordium, complex networks of procambial cells emerge from homogeneous subepidermal tissue. The molecular nature of the underlying positional information is unknown, but various lines of evidence implicate gradually restricted transport routes of the plant hormone auxin in defining sites of procambium formation. Here we show that a crucial member of the AtPIN family of auxin-efflux-associated proteins, AtPIN1, is expressed prior to pre-procambial and procambial cell fate markers in domains that become restricted toward sites of procambium formation. Subcellular AtPIN1 polarity indicates that auxin is directed to distinct “convergence points” in the epidermis, from where it defines the positions of major veins. Integrated polarities in all emerging veins indicate auxin drainage toward pre-existing veins, but veins display divergent polarities as they become connected at both ends. Auxin application and transport inhibition reveal that convergence point positioning and AtPIN1 expression domain dynamics are self-organizing, auxin-transport-dependent processes. We derive a model for self-regulated, reiterative patterning of all vein orders and postulate at its onset a common epidermal auxin-focusing mechanism for major-vein positioning and phyllotactic patterning.
A SIMPLE CONSTRUCTION OF A FAITHFUL, IRREDUCIBLE REPRESENTATION OF Sn
Authors: BERNHARDT CHRIS
Published: April 2006

A simple direct method of constructing a faithful, irreducible representation of Sn of degree n - 1 is given.
Placenta Growth Factor Overexpression Inhibits Tumor Growth, Angiogenesis, and Metastasis by Depleting Vascular Endothelial Growth Factor Homodimers in Orthotopic Mouse Models
Authors: Xu Lei , Cochran David M. , Tong Ricky T. , Winkler Frank , Kashiwagi Satoshi , Jain Rakesh K. , Fukumura Dai
Published: April 2006

The role of placenta growth factor (PlGF) in pathologic angiogenesis is controversial. The effects of PlGF on growth, angiogenesis, and metastasis from orthotopic tumors are not known. To this end, we stably transfected three human cancer cell lines (A549 lung, HCT116 colon, and U87-MG glioblastoma) with human plgf-2 full-length cDNA. Overexpression of PlGF did not affect tumor cell proliferation or migration in vitro. The growth of PlGF-overexpressing tumors grown orthotopically or ectopically was impaired in all three tumor models. This decrease in tumor growth correlated with a decrease in tumor angiogenesis. The PlGF-overexpressing tumors had decreased vessel density and increased vessel diameter, but vessel permeability was not different from the parental tumors. Tumors overexpressing PlGF exhibited higher levels of PlGF homodimers and PlGF/vascular endothelial growth factor (VEGF) heterodimers but decreased levels of VEGF homodimers. Our study shows that PlGF overexpression decreases VEGF homodimer formation and inhibits tumor progression. (Cancer Res 2006; 66(8): 3971-7)