bluuebunny/crossref_metadata_2025 huggingface dataset:
Spread of
Escherichia coli
Strains with High-Level Cefotaxime and Ceftazidime Resistance between the Community, Long-Term Care Facilities, and Hospital Institutions
Authors: Oteo Jesús , Navarro Carmen , Cercenado Emilia , Delgado-Iribarren Alberto , Wilhelmi Isabel , Orden Beatriz , García Carmen , Miguelañez Silvia , Pérez-Vázquez María , García-Cobos Silvia , Aracil Belén , Bautista Verónica , Campos José
Published: July 2006

A total of 151
Escherichia coli
strains resistant to cefotaxime and ceftazidime were isolated during a prospective surveillance study. These strains were characterized by clinical, microbiological, and molecular analyses and were distributed into four clusters of 103, 11, 6, and 5 isolates, along with 25 unrelated strains. The principal cluster was isolated from urine, wound, blood, and other samples in three hospitals, eight nursing homes, and a community healthcare center. This cluster was associated with both nosocomial (65%) and community-acquired (35%) infections. Most strains were resistant to ciprofloxacin, gentamicin, tobramycin, cefepime, amoxicillin-clavulanic acid, and trimethoprim-sulfamethoxazole but were susceptible to imipenem. All isolates from the four clusters expressed the extended-spectrum β-lactamase (ESBL) CTX-M-15. This enzyme was also present in 8 (30.8%) of the 26 unrelated isolates. The other ESBLs, CTX-M-14 and CTX-M-32, were detected in five and seven cases, respectively, but they were detected in individual
E. coli
isolates only. In three clusters,
bla
CTX-M-15
alleles were linked to an IS
Ecp1
-like element, while in eight strains of cluster II an IS
26
element preceded the
bla
CTX-M-15
allele. An additional pool of resistance genes included
tetA
,
drfA14
or
dfrA17
,
sul1
or
sul2
,
aac(6′)Ib
, and
aac(3)IIb
. All except one of the 27 isolates tested for genetic virulence markers harbored the same three virulence genes:
iutA
and
fyuA
(siderophores), and
traT
(serum survival factor). Epidemic or occasional isolates of cefotaxime- and ceftazidime-resistant
E. coli
can spread between distinct health facilities including hospitals, community health centers, and long-term care centers.
Comparison of
Acinetobacter baumannii
Isolates from the United Kingdom and the United States That Were Associated with Repatriated Casualties of the Iraq Conflict
Authors: Turton Jane F. , Kaufmann Mary E. , Gill Martin J. , Pike Rachel , Scott Paul T. , Fishbain Joel , Craft David , Deye Gregory , Riddell Scott , Lindler Luther E. , Pitt Tyrone L.
Published: July 2006

Acinetobacter
isolates associated with casualties from the Iraq conflict from the United States were compared with those from the United Kingdom by pulsed-field gel electrophoresis and integron analysis. Representatives of the main outbreak strain associated with casualties from both countries were indistinguishable in DNA profile. Two further outbreak strains were common to both sets of isolates.
Selection of a Surrogate Agent (Vancomycin or Teicoplanin) for Initial Susceptibility Testing of Dalbavancin: Results from an International Antimicrobial Surveillance Program
Authors: Jones Ronald N. , Sader Helio S. , Fritsche Thomas R. , Hogan Patricia A. , Sheehan Daniel J.
Published: July 2006

The immediate lack of market-dominating commercial products (Vitek or MicroScan) for susceptibility testing of the new glycolipopeptide, dalbavancin, requires a surrogate marker agent to assist microbiologists in the correct categorization of potentially indicated species (staphylococci and streptococci). Error-rate analyses for 16,749 isolates using vancomycin or teicoplanin results to categorize dalbavancin susceptibilities demonstrated that both glycopeptide agents were highly predictive of dalbavancin-susceptible results (nearly 100%) with only a rare minor error. Vancomycin test results most reliably predict dalbavancin susceptibility until validated commercial reagents become available for direct testing in clinical practice.
Rapid Identification and Differentiation of Clinical Isolates of Enteropathogenic
Escherichia coli
(EPEC), Atypical EPEC, and Shiga Toxin-Producing
Escherichia coli
by a One-Step Multiplex PCR Method
Authors: Müller Daniel , Hagedorn Peter , Brast Sabine , Heusipp Gerhard , Bielaszewska Martina , Friedrich Alexander W. , Karch Helge , Schmidt M. Alexander
Published: July 2006

Enteropathogenic
Escherichia coli
(EPEC), atypical enteropathogenic
E. coli
, and Shiga toxin-producing
E. coli
differ in their virulence factor profiles, clinical manifestations, and prognosis, and they require different therapeutic measures. We developed and evaluated a robust multiplex PCR to identify these pathogroups based on sequences complementary to
escV
,
bfpB
,
stx
1
, and
stx
2
.
Comparative Study of the Epidemiology of Rotavirus in Children from a Community-Based Birth Cohort and a Hospital in South India
Authors: Banerjee Indrani , Ramani Sasirekha , Primrose Beryl , Moses Prabhakar , Iturriza-Gomara Miren , Gray James J. , Jaffar Shabbar , Monica Bindhu , Muliyil Jaya Prakash , Brown David W. , Estes Mary K. , Kang Gagandeep
Published: July 2006

Rotavirus gastroenteritis is the major cause of severe dehydrating diarrhea in children worldwide. This study compares rotavirus diarrhea in 351 children in a community-based cohort and 343 children admitted to a hospital during the same period. Clinical information and fecal specimens were obtained during diarrheal episodes. Fecal samples were screened for VP6 antigen, and the positive samples were G and P typed by reverse transcription-PCR. Rotavirus was detected in 82/1,152 (7.1%) episodes of diarrhea in the community and 94/343 (27.4%) cases in the hospital. The median age of affected children (7.5 versus 10.5 months) and the mean severity of symptoms (Vesikari score, 7.6 ± 3.4 versus 11 ± 2.5) were lower in the community. A larger proportion of children in the community were breast-fed than were children admitted to the hospital (73% versus 34.8%). In the community, the genotypes identified in symptomatic patients, in order of frequency, were G1 (36.5%), G10 (17.1%), G2 (15.9%), and G9 (7.3%) and mixed infections (7.3%). The most common G-P combinations were G1P[8], G2P[4], G1P[4], and G10P[11]. The distribution of G types from hospitalized children was G1 (46.8%), G9 (19.1%), G2 (8.5%), G10 (1.1%), and 4.3% mixed infections. The most common G-P combinations were G1P[8] and G9P[8]. This study documents significant genetic heterogeneity of rotaviruses in the community and the hospital. G10P[11] strains resembling a vaccine candidate strain caused disease in the community, indicating the need for careful epidemiological studies as well as safety studies for the vaccine candidates.
Identification and Characterization of Bacterial Pathogens Causing Bloodstream Infections by DNA Microarray
Authors: Cleven Berit E. E. , Palka-Santini Maria , Gielen Jörg , Meembor Salima , Krönke Martin , Krut Oleg
Published: July 2006

Bloodstream infections are potentially life-threatening and require rapid identification and antibiotic susceptibility testing of the causative pathogen in order to facilitate specific antimicrobial therapy. We developed a prototype DNA microarray for the identification and characterization of three important bacteremia-causing species:Staphylococcus aureus,Escherichia coli, andPseudomonas aeruginosa. The array consisted of 120 species-specific gene probes 200 to 800 bp in length that were amplified from recombinant plasmids. These probes represented genes encoding housekeeping proteins, virulence factors, and antibiotic resistance determinants. Evaluation with 42 clinical isolates, 3 reference strains, and 13 positive blood cultures revealed that the DNA microarray was highly specific in identifyingS. aureus,E. coli, andP. aeruginosastrains and in discriminating them from closely related gram-positive and gram-negative bacterial strains also known to be etiological agents of bacteremia. We found a nearly perfect correlation between phenotypic antibiotic resistance determined by conventional susceptibility testing and genotypic antibiotic resistance by hybridization to theS. aureusresistance gene probesmecA(oxacillin-methicillin resistance),aacA-aphD(gentamicin resistance),ermA(erythromycin resistance), andblaZ(penicillin resistance) and theE. coliresistance gene probesblaTEM-106(penicillin resistance) andaacC2(aminoglycoside resistance). Furthermore, antibiotic resistance and virulence gene probes permitted genotypic discrimination within a species. This novel DNA microarray demonstrates the feasibility of simultaneously identifying and characterizing bacteria in blood cultures without prior amplification of target DNA or preidentification of the pathogen.
Streptococcus pseudoporcinus
sp. nov., a Novel Species Isolated from the Genitourinary Tract of Women
Authors: Bekal Sadjia , Gaudreau Christiane , Laurence Robert A. , Simoneau Esther , Raynal Lélia
Published: July 2006

Streptococcus
strains from animal and human sources identified biochemically as
Streptococcus porcinus
were investigated by 16S rRNA gene sequencing. The nine human strains isolated between 1997 and 2005 formed a single cluster with more than 2.1% dissimilarity with
S. porcinus
strains from animal sources. A novel species,
Streptococcus pseudoporcinus
sp. nov., is proposed.
Risk factors for injuries in elite female soccer players
Authors: Faude O , Junge A , Kindermann W , Dvorak J
Published: July 2006

Objective:To describe risk factors for injuries in elite female soccer.

Methods:A total of 143 female soccer players from the German national league participated in the study. Baseline information on player characteristics—for example, anthropometric measurements and playing position—and medical history were recorded at the start of the study. During one outdoor season, injuries and training and match exposure times were prospectively documented for each player.

Results:The risk of a new anterior cruciate ligament (ACL) rupture was significantly increased in players with a previous rupture (odds ratio (OR)  =  5.24, p  =  0.01). This was not the case for ankle sprain (OR  =  1.39) or knee sprain (OR  =  1.50). In addition, no significantly increased risk of new sprains or ACL ruptures was found when the injured leg was the unit of analysis. Injury incidence was considerably higher in defenders (9.4 injuries per 1000 hours exposure) and strikers (8.4/1000 hours) than goalkeepers (4.8/1000 hours) and midfielders (4.6/1000 hours). Ten per cent of all players (n  =  14) sustained more than three injuries. Most of these were defenders (n  =  8) or strikers (n  =  4). Significantly more injuries occurred to the dominant leg (105v71, p  =  0.01); this was particularly true for contact injuries (52v29, p  =  0.01).

Conclusions:Injury risk should be assessed on an individual basis. Therefore it seems appropriate to individualise preventive training programmes, as is recommended for other training content. Evaluating the existing rules of soccer and their appropriate application may also help to decrease injury risk, particularly in contact situations.
The influence of bovine colostrum supplementation on exercise performance in highly trained cyclists
Authors: Shing C M , Jenkins D G , Stevenson L , Coombes J S
Published: July 2006

Purpose:The aim of this experiment was to investigate the influence of low dose bovine colostrum supplementation on exercise performance in cyclists over a 10 week period that included 5 days of high intensity training (HIT).

Methods:Over 7 days of preliminary testing, 29 highly trained male road cyclists completed a VO2maxtest (in which their ventilatory threshold was estimated), a time to fatigue test at 110% of ventilatory threshold, and a 40 km time trial (TT40). Cyclists were then assigned to either a supplement (n = 14, 10 g/day bovine colostrum protein concentrate (CPC)) or a placebo group (n = 15, 10 g/day whey protein) and resumed their normal training. Following 5 weeks of supplementation, the cyclists returned to the laboratory to complete a second series of performance testing (week 7). They then underwent five consecutive days of HIT (week 8) followed by a further series of performance tests (week 9).

Results:The influence of bovine CPC on TT40performance during normal training was unclear (week 7: 1±3.1%, week 9: 0.1±2.1%; mean±90% confidence limits). However, at the end of the HIT period, bovine CPC supplementation, compared to the placebo, elicited a 1.9±2.2% improvement from baseline in TT40performance and a 2.3±6.0% increase in time trial intensity (% VO2max), and maintained TT40heart rate (2.5±3.7%). In addition, bovine CPC supplementation prevented a decrease in ventilatory threshold following the HIT period (4.6±4.6%).

Conclusion:Low dose bovine CPC supplementation elicited improvements in TT40performance during an HIT period and maintained ventilatory threshold following five consecutive days of HIT.
NUMERICAL STUDIES OF BAND GAP RENORMALIZATION IN V-GROOVED NANO-WIRES
Authors: NOZARI K. , MADADI M. , NARIMANI N.
Published: July 2006

By considering a suitable confinement potential, we calculate the exchange-correlation induced band gap renormalization (BGR) in a V-grooved quantum wire as a function of the electron-hole plasma density and quantum wire width. The leading-order GW dynamical screening approximation is used in the calculation by treating the electron-electron Coulomb interaction and electron-optical phonon interaction. A numerical scheme has been proposed, and the screened Coulomb potential, density of states (profile of charge distribution) and the value of the renormalized gap energy are calculated. We will show that the carrier concentration, the screened confinement potential and the relative band gap renormalization are functions of the ratio of the well width in the x and y directions.
SPIN PRECESSION IN THE DVALI–GABADADZE–PORRATI BRANEWORLD SCENARIO
Authors: IORIO LORENZO
Published: July 2006

In this letter, we work out the secular precession of the spin of a gyroscope in geodesic motion around a central mass in the framework of the Dvali–Gabadadze–Porrati multidimensional gravity model. Such an effect, which depends on the mass of the central body and on the orbit radius of the gyroscope, contrary to the precessions of the orbital elements of the orbit of a test body, is far too small to be detected.
CAN SOLAR SYSTEM OBSERVATIONS TELL US SOMETHING ABOUT THE COSMOLOGICAL CONSTANT?
Authors: IORIO LORENZO
Published: July 2006

In this note, we show that the latest determinations of the residual perihelion advances [Formula: see text] of the inner planets of the Solar System, obtained by accounting for almost all known Newtonian and post-Newtonian orbital effects, yield only very broad constraints on the cosmological constant Λ. Indeed, from, e.g., [Formula: see text] arcseconds per century for Mercury, one gets -2 × 10-34 km -2 < Λ < 4 × 10-35 km -2. The currently accepted value for Λ, obtained from many independent cosmological and large-scale measurements, amounts to almost 10-46 km -2.
DERIVATION OF THE SOURCE-FREE MAXWELL AND GRAVITATIONAL RADIATION EQUATIONS BY GROUP THEORETICAL METHODS
Authors: RAMOS JAIRZINHO , GILMORE ROBERT
Published: July 2006

We derive source-free Maxwell-like equations in flat space–time for any helicity j by comparing the transformation properties of the 2(2j+1) states that carry the manifestly covariant representations of the inhomogeneous Lorentz group with the transformation properties of the two helicity j states that carry the irreducible representations of this group. The set of constraints so derived involves a pair of curl equations and a pair of divergence equations. These reduce to the free-field Maxwell equations for j = 1 and the analogous equations coupling the gravito-electric and the gravito-magnetic fields for j = 2.
GRAVITATIONAL ENERGY–MOMENTUM DENSITY IN BIANCHI TYPE II SPACE–TIMES
Authors: AYDOGDU OKTAY
Published: July 2006

In this paper, using Einstein, Landau and Lifshitz's energy–momentum complexes both in general relativity and teleparallel gravity, we calculate the total energy distribution (due to matter and fields, including gravitation) associated with locally rotationally symmetric (LRS) Bianchi type II cosmological models. We show that energy densities in these different gravitation theories are the same, so they agree with each other. We obtain the result that the total energy is zero. This result agrees with previous works of Cooperstock and Israelit, Rosen, Johri et al., Banerjee and Sen, Vargas, Aydogdu and Saltı. Moreover, our result supports the viewpoints of Albrow and Tryon.
PIONEER ANOMALY? GRAVITATIONAL PULL DUE TO THE KUIPER BELT
Authors: DE DIEGO JOSÉ A. , NÚÑEZ DARÍO , ZAVALA JESÚS
Published: July 2006

In this work, we study the gravitational influence of the material extending from Uranus orbit to the Kuiper belt and beyond on objects moving within these regions. We conclude that a density distribution given by [Formula: see text] generates a constant acceleration towards the Sun on those objects, which, with the proper amount of mass, accounts for the blue shift detected on the Pioneers space crafts. We also discuss the effect of this gravitational pull on Neptune, and comment on the possible origin of such a matter distribution.
BIANCHI TYPE-V AND VI0 UNIVERSES WITH DILATON AND MAGNETIC FIELDS
Authors: SINGH T. , CHAUBEY R.
Published: July 2006

The Einstein–Maxwell-dilaton field equations are considered for four-dimensional Bianchi type-V and VI0 models. The general solutions are obtained and their properties are discussed.
UPPER LIMITS ON DENSITY OF DARK MATTER IN SOLAR SYSTEM
Authors: KHRIPLOVICH I. B. , PITJEVA E. V.
Published: July 2006

The analysis of the observational data for the secular perihelion precession of Mercury, Earth, and Mars, based on the EPM2004 ephemerides, results in new upper limits on density of dark matter in the solar system.
Pulse Compression by Quasi-Steady Propagation along Switch Lines
Authors: Narahara Koichi , Otsuji Taiichi , Sano Eiichi
Published: July 2006

The characterization of wave propagation on a switch line, which means a transmission line periodically loaded with electronic switches such as diodes, is discussed for the generation of ultrashort electrical pulses. Once the input pulse crosses the threshold voltage of loaded shunt switches, the exponential wave is developed at the voltage range where the switch is on, and the ordinary sinusoidal wave is coupled to it at the voltage range where the switch is off. The wave number of this exponential wave has to be much larger than those of the waves forming the input pulse, so we expect a significant compression of the input pulse after its propagation along a switch line.
Relationship between Acid Generator Concentration and Acid Yield in Chemically Amplified Electron Beam Resist
Authors: Shigaki Takumi , Okamoto Kazumasa , Kozawa Takahiro , Yamamoto Hiroki , Tagawa Seiichi , Kai Toshiyuki , Shimokawa Tsutomu
Published: July 2006

Acids generated upon exposure play the most important role in the pattern formation of current standard resists, called chemically amplified resists. It is well known that acid yield depends on the acid generator concentration. However, the precise relationship between acid yield and acid generator concentration has not been investigated thus far. Understanding the details in acid generation is important for the development of resist materials and the process simulation. In this work, the dependence of acid yield on the acid generator concentration was studied using poly(4-hydroxystyrene) (PHS) and poly(methyl methacrylate) (PMMA) as a matrix. Both results showed a nonlinear dependence. With increase in acid generator concentration, acid yield showed a saturation tendency. The dependence differed between PHS and PMMA. This reflects the fact that protons of acids originate from the radical cation of polymers generated by ionization.
Effect of Dispersant on Preparation of Colloidal Magnetite Nanocrystals
Authors: Shauo Chang-Neng , Chao Chuen-Guang
Published: July 2006

Nanometer scale magnetite particles were prepared in a very low concentration dispersing system with a dispersant. The average size of the particles prepared under optimum conditions was determined by transmission electron microscopy to be approximately 1.8 nm. The magnetic properties were investigated using a superconducting quantum interference device (SQUID) magnetometer. The dried samples exhibited approximately superparamagnetic behavior. Rhelogical property measurement shows that the colloidal magnetite both with and without polyurethane reveals shear thinning. The surface morphology of the films of the magnetite nanoparticles on the glass, as shown by atomic force microscopy (AFM) images, produces well-formed surface structures that are evenly spaced by the magnetite nanoparticles. It also shows that this is an effective method of surface modification for nanometer scale magnetite.
Analysis of the Differential Phase Detection Signal in Multi-level Run-Length Limited Read-Only Disk Driver
Authors: Shen Quanhong , Pei Jing , Xu Haizheng , Wang Lin , Xu Duanyi
Published: July 2006

Multilevel run-length-limited (ML-RLL) recording technology could be employed to increase the capacity of the read-only disc without changing optical and mechanical units. In this paper, the tracking error signal (TES) of differential phase detection (DPD) for ML-RLL digital versatile disk (DVD) read-only disk driver is analyzed in both theoretical and experimental way, the uniformity and symmetry of which are worse than that of the DVD read-only disk driver. The variation of peak to peak (PP) value distribution of the DPD signal in open loop of ML-RLL DVD read-only disk driver is about 2.6 times of that of the conventional DVD driver while the asymmetry is about 4 times. It is predicted that some improvements of the tracking servo system are needed in ML-RLL system.
Optimum Arrangement of High-Order Series-Coupled Microring Resonator for Crosstalk Reduction
Authors: Goebuchi Yuta , Kato Tomoyuki , Kokubun Yasuo
Published: July 2006

Series-coupling of microring resonators with different ring radii is effective for expanding the free spectral range (FSR) to greater than 20 nm owing to the Vernier effect. In this study, we analyzed the dependence of the filter response of quadruple-series-coupled microrings with two different ring radii on the arrangement of ring radii. As a result, it was found that an asymmetric arrangement can reduce crosstalk compared with symmetric and antisymmetric arrangements, and the physical reason for the optimum arrangement was clarified. In addition, the dependence of adjacent channel crosstalk on the FSR expansion factor was analyzed.
DC-Free Four-Ary (2,8) Run-Length Limited Code for Multi-level Recording Channels
Authors: Hu Heng , Pei Jing , Xiong Jianping , Ni Yi , Pan Longfa , Hu Hua
Published: July 2006

A new high efficient DC-free (2,8) run-length limited (RLL) code for four-level optical recording channels is proposed. The proposed code can be represented by a finite state diagram (FSM) with three states and implemented easily. The code rate and density ratio of the code are 5/6 bits/symbols and 2.50 bits/minimum-recorded-mark, respectively. On the basis of the experimental results, the performances of the code are evaluated by using partial-response maximum-likelihood (PRML) technology, which is suitable for detecting multi-level RLL signals. By using four-ary (2,8)RLL modulation and PRML technology, one can increase the recording density 66.7% relative to conventional binary RLL modulation currently used in digital versatile disc (DVD), meanwhile the bit error rate (BER) still be acceptable.
Vertical Birefringence Characterization for Optical Polymer Films
Authors: Wu Pingfan , Sinha Moitreyee , Buckley Donald J.
Published: July 2006

This paper introduces a technique for precisely measuring the vertical birefringence of an optical polymer film. Analytical equations are derived to relate the phase retardation to the optical film birefringence. In the measurement, we first measure the in-plane birefringence of the film and locate the principal axes of refractive index ellipsoid. The film is then rotated with its normal at an angle to the incident light wave vector. The vertical birefringence is calculated from the retardations measured at several angles. Using the procedure, the vertical birefringence can be measured to a precision of 0.2 ×10-3.
Highly Selective Si3N4/SiOC Etching Using Dual Frequency Superimposed RF Capacitively Coupled Plasma
Authors: Takase Akihiro , Nishiwaki Junya , Yamamoto Katsumi , Kojima Akihiro , Sakai Itsuko , Hayashi Hisataka , Ohiwa Tokuhisa
Published: July 2006

Highly selective etching of Si3N4 to SiOC film has been studied, using dual frequency superimposed (DFS) rf capacitively coupled plasma, which controlled the self-bias voltage (-V
dc) independently of electron density (N
e). The SiOC etch rate was effectively suppressed by fluorocarbon polymer deposition, which was controlled by the additive H2 gas flow rate ratio and carbon-to-silicon ratio of the SiOC film, without reduction in Si3N4 etching rate. Infinitely highly selective etching could be realized with a H2 gas flow rate ratio of above 50%. Stringent V
dc control was required for line-and-space pattern etching in order to suppress the erosion of the SiOC pattern edge, even when a highly selective etching condition was used. The V
dc range that was available for selective etching of Si3N4 to SiOC was as small as 150 V, which was approximately 50 V lower than that for selective etching of SiOC to Si3N. However, a much lower -V
dc, such as 100 V, caused excess deposition and taper etching. It was also found that lower N
e, which was controlled by a 100 MHz rf power, was required to suppress the excess deposition.
In Situ Synthesis of Nanosized ZnO Particle/Organic Hybrids
Authors: Yogo Toshinobu , Nakafuku Tomoko , Kachi Masahiro , Sakamoto Wataru , Hirano Shin-ichi
Published: July 2006

A nanocrystalline ZnO particle/organic hybrid was synthesized in situ from zinc acrylate (ZA) using hydrazine derivatives. Nanosized ZnO particles were formed in the organic matrix by hydrolysis and polymerization of ZA at 65 °C. Methylhydrazine was the most suitable reagent for the synthesis of nanosized ZnO particles in the organic matrix. The crystallinity of ZnO particles depended upon the amount of water and the reaction time and increased with increasing reaction time as well as with the amount of water. Highly transparent ZnO particle/organic film was prepared from the hybrid solid between silica plates by pressing at 50 °C. UV–visible spectra showed an absorption edge corresponding to the size of the ZnO particles. The band gap energy of the hybrid was dependent upon the particle size, which reflected the synthesis conditions. ZnO particles in the hybrid exhibited stabilized particle size and absorption edge through chemical bonds to the polymer matrix at ambient temperature.
Density Control of Carbon Nanotubes through the Thickness of Fe/Al Multilayer Catalyst
Authors: Komukai Takuji , Aoki Katsunori , Furuta Hiroshi , Furuta Mamoru , Oura Kenjiro , Hirao Takashi
Published: July 2006

The density control of vertically aligned carbon nanotubes (CNTs) has been studied using a thermal chemical vapor deposition (CVD) method in correlation with the thicknesses of the Fe/Al multilayer catalyst on a Si substrate. The density of CNTs could be controlled through the thicknesses of both the Al layer and Fe catalyst layer. The low density of the Fe catalyst grains formed by thermal treatment, caused the formation of CNTs with random orientations, and resulted in a decrease in the CNT height. The optimum film thickness of the Fe/Al multilayer catalyst for obtaining long CNTs (220 µm) was determined for the case of a substrate temperature of 700 °C.
Characterization of Membrane Electrode Assembly for Fuel Cells Prepared by Electrostatic Spray Deposition
Authors: Umeda Minoru , Kawaguchi Syunsuke , Uchida Isamu
Published: July 2006

A novel electrocatalyst painting technique for realizing an extremely high yield of deposition in a limited surface area of a polymer electrolyte membrane has been developed by electrostatic spray deposition (ESD). First, a dispersion containing Pt/C powder and Nafion solution was sprayed by ESD. As a result, the dispersion was deposited on the entire surface area of a Nafion membrane placed on an Au counterelectrode, but not on the insulating poly(ethylene terephthalete) membrane. Second, for the highest-quality Pt/C catalyst layer, the solid content of the dispersion and the ejection rate were set to 3–4 wt % and 10–20 mm3·min-1, respectively. The catalyst layer thus prepared demonstrated a fine, smooth structure. Third, in the case in which the sizes of the Nafion membrane and Au electrode were the same, the deposition occurred only on the Nafion/Au layered structure. This enabled an extremely high yield of deposition. The ESD of the Pt/C dispersion was conducted on a dry Nafion membrane with a water droplet on the surface. Consequently, an electrocatalyst layer was successfully formed only at the wetted point of the Nafion membrane. This technique enables the painting of the electrocatalyst layer over a limited area without the use of any surface masks. Finally, the membrane electrode assembly prepared by ESD was installed in a fuel cell and demonstrated as high a performance as that prepared by air-spraying. The cross-sectional morphology of the catalyst layer explained the coupling strength in the peel-off test well, as well as the dependence of current–voltage characteristics on catalyst layer thickness.
How Does Voltage Open an Ion Channel?
Authors: Tombola Francesco , Pathak Medha M. , Isacoff Ehud Y.
Published: July 2006

Neurons transmit information through electrical signals generated by voltage-gated ion channels. These channels consist of a large superfamily of proteins that form channels selective for potassium, sodium, or calcium ions. In this review we focus on the molecular mechanisms by which these channels convert changes in membrane voltage into the opening and closing of “gates” that turn ion conductance on and off. An explosion of new studies in the last year, including the first X-ray crystal structure of a mammalian voltage-gated potassium channel, has led to radically different interpretations of the structure and molecular motion of the voltage sensor. The interpretations are as distinct as the techniques employed for the studies: crystallography, fluorescence, accessibility analysis, and electrophysiology. We discuss the likely causes of the discrepant results in an attempt to identify the missing information that will help resolve the controversy and reveal the mechanism by which a voltage sensor controls the channel's gates.
Of Extracellular Matrix, Scaffolds, and Signaling: Tissue Architecture Regulates Development, Homeostasis, and Cancer
Authors: Nelson Celeste M. , Bissell Mina J.
Published: July 2006

The microenvironment influences gene expression so that the behavior of a cell is largely determined by its interactions with the extracellular matrix, neighboring cells, and soluble local and systemic cues. We describe the essential roles of context and organ structure in directing mammary gland development and differentiated function and in determining the response to oncogenic insults, including mutations. We expand on the concept of “dynamic reciprocity” to present an integrated view of development, cancer, and aging and posit that genes are like the keys on a piano: Although they are essential, it is the context that makes the music.
Telomeres: Cancer to Human Aging
Authors: Stewart Sheila A , Weinberg Robert A.
Published: July 2006

The cell phenotypes of senescence and crisis operate to circumscribe the proliferative potential of mammalian cells, suggesting that both are capable of operating in vivo to suppress the formation of tumors. The key regulators of these phenotypes are the telomeres, which are located at the ends of chromosomes and operate to protect the chromosomes from end-to-end fusions. Telomere erosion below a certain length can trigger crisis. The relationship between senescence and telomere function is more complex, however: Cell-physiological stresses as well as dysfunction of the complex molecular structures at the ends of telomeric DNA can trigger senescence. Cells can escape senescence by inactivating the Rb and p53 tumor suppressor proteins and can surmount crisis by activating a telomere maintenance mechanism. The resulting cell immortalization is an essential component of the tumorigenic phenotype of human cancer cells. Here we discuss how telomeres are monitored and maintained and how loss of a functional telomere influences biological functions as diverse as aging and carcinogenesis.
Energy-Technology Innovation
Authors: Gallagher Kelly Sims , Holdren John P. , Sagar Ambuj D.
Published: July 2006

▪ Abstract  Energy-technology innovation (ETI) is the set of processes leading to new or improved energy technologies that can augment energy resources; enhance the quality of energy services; and reduce the economic, environmental, or political costs associated with energy supply and use. Advances achieved through ETI have made large contributions to the improvement of the human condition over the past 100 years. Still more will be required of ETI during the decades ahead if civilization is to succeed in meeting what we believe are the three greatest energy challenges still before it: reducing dependence on oil, drastically upgrading the energy services provided to the world's poor, and providing the energy required to increase and sustain prosperity everywhere without wrecking the global climate with the emissions from fossil-fuel burning. This will require significant enhancements to ETI through deeper analysis of ETI processes, greater investments in ETI, improved innovation policies, and better coordination and partnerships across sectors and countries.
Earth's Cryosphere: Current State and Recent Changes
Authors: Parkinson Claire L.
Published: July 2006

▪ Abstract  Earth continues to have a third of the ice that it had at the peak of the last ice age, although that ice continues to decrease, as it has, overall, for the past 18,000 years. Over the last 100 years, the retreat signal has been especially strong in ice shelves of the Arctic and along the Antarctic Peninsula, with a more mixed signal elsewhere. For instance, since the early 1990s, the massive Greenland and Antarctic ice sheets have thinned along the coasts but thickened in the interior, and since the late 1970s, sea ice has decreased in the Arctic but increased (slightly) in the Antarctic. Major difficulties in the interpretations of the climate record come from the high interannual variability of most cryosphere components and the lack of consistent long-term global data records; the latter problem is now being slowly remedied, in part, through satellite technology.
Predicting the Effects of Amino Acid Substitutions on Protein Function
Authors: Ng Pauline C. , Henikoff Steven
Published: July 2006

Nonsynonymous single nucleotide polymorphisms (nsSNPs) are coding variants that introduce amino acid changes in their corresponding proteins. Because nsSNPs can affect protein function, they are believed to have the largest impact on human health compared with SNPs in other regions of the genome. Therefore, it is important to distinguish those nsSNPs that affect protein function from those that are functionally neutral. Here we provide an overview of amino acid substitution (AAS) prediction methods, which use sequence and/or structure to predict the effect of an AAS on protein function. Most methods predict approximately 25–30% of human nsSNPs to negatively affect protein function, and such nsSNPs tend to be rare in the population. We discuss the utility of AAS prediction methods for Mendelian and complex diseases as well as their broader applications for understanding protein function.
The Evolutionary Dynamics of Human Endogenous Retroviral Families
Authors: Bannert Norbert , Kurth Reinhard
Published: July 2006

The capacity to integrate into the chromosomal DNA of germ-line cells has endowed retroviruses with the potential to be vertically transmitted from generation to generation and eventually become fixed in the genomes of the entire population. This has been independently accomplished by several ancient retroviruses that invaded the genomes of our early and more recent primate and hominoid ancestors. Some of the inherited elements then proliferated in the genome, resulting in a number of lineages with complex phylogenetic patterns. Although the vast majority of chromosomally integrated retroelements have suffered inactivating mutations and deletions, a significant impact on various aspects of human biology has been recently revealed and evidence for the present activity of at least one human endogenous retrovirus family continues to accumulate.
Protein Misfolding and Human Disease
Authors: Gregersen Niels , Bross Peter , Vang Søren , Christensen Jane H.
Published: July 2006

Protein misfolding is a common event in living cells. In young and healthy cells, the misfolded protein load is disposed of by protein quality control (PQC) systems. In aging cells and in cells from certain individuals with genetic diseases, the load may overwhelm the PQC capacity, resulting in accumulation of misfolded proteins. Dependent on the properties of the protein and the efficiency of the PQC systems, the accumulated protein may be degraded or assembled into toxic oligomers and aggregates. To illustrate this concept, we discuss a number of very different protein misfolding diseases including phenylketonuria, Parkinson's disease, α-1-antitrypsin deficiency, familial neurohypophyseal diabetes insipidus, and short-chain acyl-CoA dehydrogenase deficiency. Despite the differences, an emerging paradigm suggests that the cellular effects of protein misfolding provide a common framework that may contribute to the elucidation of the cell pathology and guide intervention and treatment strategies of many genetic and age-dependent diseases.
A 60-Year Tale of Spots, Maps, and Genes
Authors: McKusick Victor A.
Published: July 2006

This is an account of almost 60 years' experience in the clinical delineation of genetic disorders, mapping genes on chromosomes, and cataloging human disease–related genes and genetic disorders. The origins of medical genetics as a clinical specialty, of the Human Genome Project, of genomics (including the term), and of HUGO are recounted.
Preimplantation Genetic Diagnosis: An Overview of Socio-Ethical and Legal Considerations
Authors: Knoppers Bartha M. , Bordet Sylvie , Isasi Rosario M.
Published: July 2006

Preimplantation genetic diagnosis (PGD) permits the selection of embryos of a particular genotype prior to implantation. As a reproductive technology involving embryo selection, PGD has become associated with considerable controversy. This review examines some of the ethical, legal, and social issues raised by PGD. Relevant ethical considerations include the status of the embryo and the interests and duties of the parents. On a social policy level, considerations of access as well as the impact of this technology on families, women, and physician's duties also warrant consideration. An analysis of these issues in the context of using PGD for selecting embryos unaffected by a serious disorder and for sex selection is presented. We also present a brief survey of PGD-related regulatory schemes in several countries, including the United Kingdom and the United States.
Of Flies and Man:Drosophilaas a Model for Human Complex Traits
Authors: Mackay Trudy F. C. , Anholt Robert R. H.
Published: July 2006

Understanding the genetic and environmental factors affecting human complex genetic traits and diseases is a major challenge because of many interacting genes with individually small effects, whose expression is sensitive to the environment. Dissection of complex traits using the powerful genetic approaches available with Drosophila melanogaster has provided important lessons that should be considered when studying human complex traits. In Drosophila, large numbers of pleiotropic genes affect complex traits; quantitative trait locus alleles often have sex-, environment-, and genetic background-specific effects, and variants associated with different phenotypic are in noncoding as well as coding regions of candidate genes. Such insights, in conjunction with the strong evolutionary conservation of key genes and pathways between flies and humans, make Drosophila an excellent model system for elucidating the genetic mechanisms that affect clinically relevant human complex traits, such as alcohol dependence, sleep, and neurodegenerative diseases.
Resources for Genetic Variation Studies
Authors: Serre David , Hudson Thomas J.
Published: July 2006

The rapid growth of genome-wide diversity databases, as well as ongoing large-scale resequencing projects targeting genes and other functional components of our genome, provide valuable resources of natural variation at the DNA sequence level. In this review, we briefly summarize the wealth of data on DNA polymorphisms in humans, the distribution of this diversity in the genome as well as among individuals, and the consequence of recombination on its organization. These data provide a set of powerful tools that can be used to better understand inherited phenotypic variation in humans. We discuss the implications for the design of studies investigating correlations between genotypes and phenotypes, both at the fundamental level of genome function and regulation, and for the mapping of disease genes.
Origin of Mutations Under Selection: The Adaptive Mutation Controversy
Authors: Roth John R. , Kugelberg Elisabeth , Reams Andrew B. , Kofoid Eric , Andersson Dan I.
Published: July 2006

Growth under selection causes new genotypes to predominate in a population. It is difficult to determine whether selection stimulates formation of new mutations or merely allows faster growth of mutants that arise independent of selection. In the practice of microbial genetics, selection is used to detect and enumerate pre-existing mutants; stringent conditions prevent growth of the parent and allow only the pre-existing mutants to grow. Used in this way, selection detects rare mutations that cause large, easily observable phenotypic changes. In natural populations, selection is imposed on growing cells and can detect the more common mutations that cause small growth improvements. As slighly improved clones expand, they can acquire additional mutational improvements. Selected sequential clonal expansions have huge power to produce new genotypes and have been suggested to underlie tumor progression. We suggest that the adaptive mutation controversy has persisted because the distinction between these two uses of selection has not been appreciated.
Biochemical Aspects of Coronavirus Replication and Virus-Host Interaction
Authors: Enjuanes Luis , Almazán Fernando , Sola Isabel , Zuñiga Sonia
Published: July 2006

Infection by different coronaviruses (CoVs) causes alterations in the transcriptional and translational patterns, cell cycle, cytoskeleton, and apoptosis pathways of the host cells. In addition, CoV infection may cause inflammation, alter immune and stress responses, and modify the coagulation pathways. The balance between the up- and downregulated genes could explain the pathogenesis caused by these viruses. We review specific aspects of CoV-host interactions. CoV genome replication takes place in the cytoplasm in a membrane-protected microenvironment and may control the cell machinery by locating some of their proteins in the host cell nucleus. CoVs initiate translation by cap-dependent and cap-independent mechanisms. CoV transcription involves a discontinuous RNA synthesis (template switching) during the extension of a negative copy of the subgenomic mRNAs. The requirement for base-pairing during transcription has been formally demonstrated in arteriviruses and CoVs. CoV N proteins have RNA chaperone activity that may help initiate template switching. Both viral and cellular proteins are required for replication and transcription, and the role of selected proteins is addressed.
Structure and Function of RNA Replication
Authors: Ortín Juan , Parra Francisco
Published: July 2006

Contrary to their host cells, many viruses contain RNA as genetic material and hence encode an RNA-dependent RNA polymerase to replicate their genomes. This review discusses the present status of our knowledge on the structure of these enzymes and the mechanisms of RNA replication. The simplest viruses encode only the catalytic subunit of the replication complex, but other viruses also contribute a variable number of ancillary factors. These and other factors provided by the host cell play roles in the specificity and affinity of template recognition and the assembly of the replication complex. Usually, these host factors are involved in protein synthesis or RNA modification in the host cell, but they play roles in remodeling RNA-RNA, RNA-protein, and protein-protein interactions during virus RNA replication. Furthermore, viruses take advantage of and modify previous cell structural elements, frequently membrane vesicles, for the formation of RNA replication complexes.
The Structural and Functional Role of RNA in Icosahedral Virus Assembly
Authors: Schneemann Anette
Published: July 2006

Despite tremendous advances in high-resolution structure determination of virus particles, the organization of encapsidated genomes and their role during assembly are poorly understood. This article summarizes recent insights from structural, biochemical, and genetic analyses of icosahedral viruses that contain single-stranded, positive-sense RNA genomes. X-ray crystallography of several viruses in this category has provided tantalizing glimpses of portions of the packaged nucleic acid, contributing crucial information on how the genome might be folded within the virion. This information combined with theoretical considerations and data from molecular approaches suggests mechanisms by which coat proteins interact with genomic RNA to shape it into a conformation that is compatible with the geometry of the virion. It appears that RNA, in addition to its function as a repository for genetic information, plays an important structural role during assembly and can on occasion override the ability of the coat protein to form a particle with defined icosahedral symmetry.
Impaired intestinal NHE3 activity in the PDK1 hypomorphic mouse
Authors: Sandu Ciprian , Artunc Ferruh , Palmada Monica , Rexhepaj Rexhep , Grahammer Florian , Hussain Azeemudeen , Yun Chris , Alessi Dario R. , Lang Florian
Published: July 2006

In vitro experiments have demonstrated the stimulating effect of serum- and glucocorticoid-inducible kinase (SGK)1 on the activity of the Na+/H+exchanger (NHE3). SGK1 requires activation by phosphoinositide-dependent kinase (PDK)1, which may thus similarly play a role in the regulation of NHE3-dependent epithelial electrolyte transport. The present study was performed to explore the role of PDK1 in the regulation of NHE3 activity. Because mice completely lacking functional PDK1 are not viable, hypomorphic mice expressing ∼20% of PDK1 ( pdk1hm) were compared with their wild-type littermates ( pdk1wt). NHE3 activity in the intestine and PDK1-overexpressing HEK-293 cells was estimated by utilizing 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein fluorescence for the determination of intracellular pH. NHE activity was reflected by the Na+-dependent pH recovery from an ammonium prepulse (ΔpHNHE). The pH changes after an ammonium pulse allowed the calculation of cellular buffer capacity, which was not significantly different between pdk1hmand pdk1wtmice. ΔpHNHEwas in pdk1hmmice, only 30 ± 6% of the value obtained in pdk1wtmice. Conversely, ΔpHNHEwas 32 ± 7% larger in PDK1-overexpressing HEK-293 cells than in HEK-293 cells expressing the empty vector. The difference between pdk1hmand pdk1wtmice and between PDK1-overexpressing and empty vector-transfected HEK cells, respectively, was completely abolished in the presence of the NHE3 inhibitor S3226 (10 μM). In conclusion, defective PDK1 expression leads to significant impairment of NHE3 activity in the intestine, pointing to a role of PDK1-dependent signaling in the regulation of NHE-mediated electrolyte transport.