bluuebunny/crossref_metadata_2025 huggingface dataset:
Dihedral angle principal component analysis of molecular dynamics simulations
Authors: Altis Alexandros , Nguyen Phuong H. , Hegger Rainer , Stock Gerhard
Published: July 2007

It has recently been suggested by Mu et al. [Proteins 58, 45 (2005)] to use backbone dihedral angles instead of Cartesian coordinates in a principal component analysis of molecular dynamics simulations. Dihedral angles may be advantageous because internal coordinates naturally provide a correct separation of internal and overall motion, which was found to be essential for the construction and interpretation of the free energy landscape of a biomolecule undergoing large structural rearrangements. To account for the circular statistics of angular variables, a transformation from the space of dihedral angles {φn} to the metric coordinate space {xn=cosφn,yn=sinφn} was employed. To study the validity and the applicability of the approach, in this work the theoretical foundations underlying the dihedral angle principal component analysis (dPCA) are discussed. It is shown that the dPCA amounts to a one-to-one representation of the original angle distribution and that its principal components can readily be characterized by the corresponding conformational changes of the peptide. Furthermore, a complex version of the dPCA is introduced, in which N angular variables naturally lead to N eigenvalues and eigenvectors. Applying the methodology to the construction of the free energy landscape of decaalanine from a 300ns molecular dynamics simulation, a critical comparison of the various methods is given.
Significance of cross correlations in the stress relaxation of polymer melts
Authors: Ramírez Jorge , Sukumaran Sathish K. , Likhtman Alexei E.
Published: July 2007

According to linear response theory, all relaxation functions in the linear regime can be obtained using time correlation functions calculated under equilibrium. In this paper, we demonstrate that the cross correlations make a significant contribution to the partial stress relaxation functions in polymer melts. We present two illustrations in the context of polymer rheology using (1) Brownian dynamics simulations of a single chain model for entangled polymers, the slip-spring model, and (2) molecular dynamics simulations of a multichain model. Using the single chain model, we analyze the contribution of the confining potential to the stress relaxation and the plateau modulus. Although the idea is illustrated with a particular model, it applies to any single chain model that uses a potential to confine the motion of the chains. This leads us to question some of the assumptions behind the tube theory, especially the meaning of the entanglement molecular weight obtained from the plateau modulus. To shed some light on this issue, we study the contribution of the nonbonded excluded-volume interactions to the stress relaxation using the multichain model. The proportionality of the bonded/nonbonded contributions to the total stress relaxation (after a density dependent “colloidal” relaxation time) provides some insight into the success of the tube theory in spite of using questionable assumptions. The proportionality indicates that the shape of the relaxation spectrum can indeed be reproduced using the tube theory and the problem is reduced to that of finding the correct prefactor.
Infrared spectra of ClCN+, ClNC+, and BrCN+ trapped in solid neon
Authors: Jacox Marilyn E. , Thompson Warren E.
Published: July 2007

When a mixture of ClCN or BrCN with a large excess of neon is codeposited at 4.3K with a beam of neon atoms that have been excited in a microwave discharge, the infrared spectrum of the resulting solid includes prominent absorptions of the uncharged isocyanide, ClNC or BrNC, and of the corresponding cation, ClCN+ or BrCN+. The NC-stretching fundamentals of the isocyanides trapped in solid neon lie close to the positions for their previously reported argon-matrix counterparts. The CN-stretching absorptions of ClCN+ and BrCN+ and the CCl-stretching absorption of ClCN+ appear very close to the gas-phase band centers. Absorptions of two overtones and one combination band of ClCN+ are identified. Reversible photoisomerization of ClCN+ to ClNC+ occurs. The two stretching vibrational fundamentals and several infrared and near infrared absorptions associated with electronic transitions of ClNC+ are observed. Minor infrared peaks are attributed to the vibrational fundamental absorptions of the CX and CX+ species (X=Cl,Br).
Relationship between refractive index and density of synthetic silica glasses
Authors: Kitamura N. , Fukumi K. , Nishii J. , Ohno N.
Published: July 2007

The effect of impurity and density on refractive index was studied for silica glasses synthesized with direct, sol-gel, and vapor phase axial deposition (VAD) processes. Linear relationships between the refractive index and density n=Cρ+D were found in a wide wavelength region from ultraviolet to infrared. The correlation coefficient C decreased from 0.081±0.007cm3∕g at 1.707μm to 0.061±0.008cm3∕g at 0.238μm. The relationship was different from those of the VAD or direct glasses formed by high-pressure densification, that is, the coefficient increased from 0.200±0.011cm3∕g at 1.707μm to 0.229±0.012cm3∕g at 0.238μm for VAD glass. Chlorine and hydroxyl impurities affected the refractive index; however, these impurities did not cause the linear relationship. After adjusting the index according to the chlorine related effect and the effect of the sample density, the difference between the sample’s refractive indices Δ(n2−1) showed a similar dispersion relation irrespective of the synthetic process. An analysis using a two-term harmonic oscillator model suggested that the origin of the refractive index dispersion is the oxygen 2p-silicon 3s interband transition, as is the dispersion relation of silica glass. The difference in the refractive indices in these synthetic silica glasses is deduced to be due to a stoichiometric excess or deficiency of oxygen atoms of forms ≡Si–OHHO–Si≡, ≡Si–Si≡, ≡Si––SI, etc., and the density arising from these forms in these synthetic processes.
Surface layer in relaxor ferroelectric PZN-4.5%PT single crystals
Authors: Chang W. S. , Shanthi M. , Rajan K. K. , Lim L. C. , Wang F. T. , Tseng C. T. , Tu C. S. , Yang Ping , Moser H. O.
Published: July 2007

The origin of the extremely broad peak at the lower 2θ side of the main (002) rhombohedral x-ray peak in an unpoled (001)-cut Pb(Zn1/3Nb2/3)0.955Ti0.045O3 (PZN-4.5%PT) single crystal has been examined. This peak, located at about 2θ∼43°–44°, was absent on fractured surfaces of the crystal but reappeared when the fractured surfaces were polished mechanically. High-resolution synchrotron x-ray mesh scans revealed that the as-polished surface was covered with a “deformed layer” of heavily stressed rhombohedral phase of monoclinic symmetry having its c axis lying perpendicular to the surface. This deformed phase can be structurally likened to one full of “incipient monoclinic nuclei/phases,” which are microscopic in size and subject to intense compression in the plane of the surface. With a given polishing direction, this surface layer showed parallel domain patterns when viewed under the polarized light microscope. This surface layer could be largely eliminated by appropriate poling at 0.7–1.5 kV/mm at room temperature but became resistant to poling after annealing.
Molecular properties and potential energy surfaces of the cyanides of the groups 1 and 11 metal atoms
Authors: Lee Dong-ki , Lim Ivan S. , Lee Yoon Sup , Hagebaum-Reignier Denis , Jeung Gwang-Hi
Published: July 2007

Ab initio calculations on the metal (groups 1 and 11) cyanide complexes show two stable configurations for the ground state geometry, a linear cyanide (MCN) and a triangular (MNC) form with an obtuse M–N–C angle. Lithium complex may exist in a linear isocyanide (MNC) form, but it cannot be differentiated from the triangular configuration because of the flatness of the potential energy surface connecting the two isomers. The metal atom and cyano radical are bonded through a strongly ionic configuration (M+CN−) in both geometrical forms. The MNC triangular form is a very floppy structure having one low frequency for the bending mode, whereas the MCN linear form is more rigid. The CN complexes of the alkali atoms have a triangular geometry as the lowest energy conformer, while the noble metal atoms prefer the linear cyanide one. The relative stability of the two isomers, dipole moments, and effective charges are reported in this paper. The essential aspects of the potential energy surfaces for the ground and the first excited states exhibiting a closely avoided crossing are also explained.
Prepulse effect on laser-induced water-window radiation from a liquid nitrogen jet
Authors: Son J. , Cho M. , Kim D. , Ahn B. , Kim J.
Published: July 2007

The authors show the prepulse effect on the conversion efficiency of a visible laser into water-window (λ=2.3–4.4nm) x ray from a liquid nitrogen jet. It is observed that a prepulse of only 2mJ enhances the conversion efficiency by 10–15 times for the main pulse of 15–60mJ at a delay of 3–6ns. The photon flux is ∼1.2×1012photons∕pulsesr at a delay of 4ns for a main pulse of 60mJ with a prepulse of 4–8mJ. It is noticed that the conversion efficiency increases with the delay up to 3ns and is then saturated.
Optical emission of directly contacted copper/sapphire interface under shock compression of megabar
Authors: Hao G. Y. , Liu F. S. , Zhang D. Y. , Zhang M. J.
Published: July 2007

The shock-induced optical emission histories from copper/sapphire interface were measured under two different contact conditions, which simulated the typical situations of pyrometry experiments. Results showed that the “peak” feature of the radiation, previously interpreted as the appearance of so-called high-temperature layer, was nearly diminished by finely polishing and uniformly prepressing technique, and that it is possible to directly measure the equilibrium temperature of bulk metal/window interface. Study also demonstrated that the saturated value of the apparent temperature in nonideal contact situation is related to the color temperature of the shock-induced “bright spot” in sapphire window under megabar pressures.
Magnetically controlled gravity for protein crystal growth
Authors: Heijna M. C. R. , Poodt P. W. G. , Tsukamoto K. , de Grip W. J. , Christianen P. C. M. , Maan J. C. , Hendrix J. L. A. , van Enckevort W. J. P. , Vlieg E.
Published: July 2007

The occurrence of convective flows during crystal growth is believed to adversely affect crystal quality. Space-based crystal growth is therefore actively pursued, particularly for protein crystals, because buoyancy-driven convection is suppressed in microgravity. Here the authors demonstrate that magnetic fields can be used to tune the effective gravity from 1to−0.15g during the growth of diamagnetic lysozyme crystals and that convection can be damped, stopped, and even reversed. The growth velocity is strongly reduced in simulated microgravity. This method provides a versatile and accessible way to realize an earth-based tunable gravity environment for crystal growth in which protein crystal quality may be optimized.
Effective tuning of exciton polarization splitting in coupled quantum dots
Authors: Zhu Jia-Lin , Xu Dong
Published: July 2007

The polarization splitting of the exciton ground state in two laterally coupled quantum dots under an in-plane electric field is investigated, and its effective tuning is designed. It is found that there are significant Stark effect and anticrossing in energy levels. Due to the coupling between inter- and intradot states, the absolute value of polarization splitting is significantly reduced, and it could be tuned to zero by the electric field for proper interdot separations. The scheme of the authors is interesting for the research on the quantum dot–based entangled-photon source.
Low-frequency eigenvibrations of hollow carbon microspheres
Authors: Li Y. , Lim H. S. , Ng S. C. , Kuok M. H. , Su F. , Zhao X. S.
Published: July 2007

Monodisperse hollow carbon microspheres have been fabricated using silica spheres as templates via a three-step chemical vapor deposition method. The vibrational eigenmodes of these hollow carbon microspheres have been measured by Brillouin light scattering. The frequencies of the eigenvibrations of a free surface hollow carbon sphere are also calculated within the framework of the elasticity theory. A comparison of the theoretical and measured frequencies shows that the observed Brillouin peaks are due to the spheroidal modes of the hollow spheres.
The European Union & the Commodity Debate: From Trade to Aid
Authors: Orbie Jan
Published: July 2007

This article departs from the renewed interest in commodity market regulation and assesses the position of the European Union (EU) on supply-management in tropical commodities. After sketching the resurgence of the commodity debate on the international trade front, the second section recapitulates the thesis that Europe's trade relations shifted from innovative and interventionist arrangements in the 1970s, to a neo-liberal outlook by the end of the 1990s. Based on this historical account, we examine whether the EU's role has changed during the commodity debate since 2003-2004. The analysis makes clear that, although EU policy-makers and institutions have addressed the issue, supply-management schemes are not considered. Without challenging the mainstream approach to commodity trade, Europe's initiatives with regard to 1) export stabilisation, 2) commodity protocols and 3) market access rather show an evolution ‘from trade to aid’. The article concludes with a number of explanations for this recent shift.
‘Like Worms in the Entrails of a Natural Man’: A Conceptual Analysis of Warlords
Authors: Vinci Anthony
Published: July 2007

Warlords are increasingly significant actors in domestic and international politics. Yet, our understanding of them is often one-sided – based on either the ‘greed’ or ‘grievance’ approach. This paper seeks to mend this deficiency through a detailed and holistic conceptual analysis of warlords, which integrates political, economic, military, and social aspects of warlord organisations. It begins with an overview of past efforts to define and analyse warlords and then explores the features of warlord organisation. Borrowing from theoretical accounts of states by authors such as Weber and Schmitt, the paper examines the relationship between the warlord and his fighters, the warlord organisation as a political community, the nature of warlord governance and command, as well as motivational and logistical factors in perpetuating the warlord organisation.
Rebuilding the Future or Revisiting the Past? Post-apartheid Afrikaner Politics
Authors: Davies Rebecca
Published: July 2007

Orthodox analyses have presented a bleak future for the Afrikaner community in contemporary South Africa, subjugated under the stewardship of a state entirely dominated by an African National Congress (ANC) government that is broadly aligned against Afrikaner interests. This paper seeks to clarify the changes and tensions apparent within a very heterodox Afrikaner community, as well as the mutually empowering linkages between the globalised political economy and various domestic social forces, by presenting a political economy of post-apartheid Afrikaner identifications and diversity. What this focus does is to emphasise the global political economy and closely associated ideology of globalisation as a major catalyst for change in these identifications. It will highlight how Afrikaner identity politics are situated within broader hegemony-seeking processes, both globally and within South Africa. And it will demonstrate that contemporary struggles around Afrikaner identifications are responses to a global neo-liberal hegemonic project that also determines, in large measure, the political and economic agenda pursued by the ANC-led government in South Africa. This paper forms part of a larger project to provide a richer, more critical framework of analysis for understanding identity politics under conditions of increasing globalisation.
Disinfection of a Probe Used in Ultrasound-Guided Prostate Biopsy
Authors: Rutala William A. , Gergen Maria F. , Weber David J.
Published: July 2007

Background.

Transrectal ultrasound (TRUS)-guided prostate biopsies are among the most common outpatient diagnostic procedures in urology clinics and carry the risk of introducing pathogens that may lead to infection.

Objective.

To investigate the effectiveness of procedures for disinfecting a probe used in ultrasound-guided prostate biopsy.

Method.

The effectiveness of disinfection was determined by inoculating 107 colony forming units (cfu) of Pseudomonas aeruginosa at the following 3 sites on the probe: the interior lumen of the biopsy needle guide, the outside surface of the biopsy needle guide, and the interior lumen of the ultrasound probe where the needle guide passes through the transducer. Each site was investigated separately. After inoculation, the probe was immersed in 2% glutaraldehyde for 20 minutes and then assessed for the level of microbial contamination.

Results.

The results demonstrated that disinfection (ie, a reduction in bacterial load of greater than 7 log10 cfu) could be achieved if the needle guide was removed from the probe. However, if the needle guide was left in the probe channel during immersion in 2% glutaraldehyde, disinfection was not achieved (ie, the reduction was approximately 1 log10 cfu).

Conclusions.

Recommendations for probe disinfection are provided and include disassembling the device and immersing the probe and the needle guide separately in a high-level disinfectant.
Efficacy of 2 Alcohol-Based Gels and 1 Alcohol-Based Rinse for Surgical Hand Disinfection
Authors: Barbut Frédéric , Djamdjian Laura , Neyme Denis , Passot Christophe , Petit Jean-Claude
Published: July 2007

We assessed the efficacy of 2 alcohol-based gels and 1 alcohol-based rinse for surgical hand disinfection, using European standard EN 12791. Volunteers performed surgical hand disinfection with a reference product and each of the 3 study products, with 1-week intervals between disinfection episodes. The immediate and sustained antimicrobial activities of each study product were not significantly less than those of the reference product. The study products passed the efficacy requirements of the EN 12791 standard, and they are considered suitable for surgical hand disinfection.
Prevalence of Nasal Colonization Among Patients With Community-Associated Methicillin-ResistantStaphylococcus aureusInfection and Their Household Contacts
Authors: Zafar Uzma , Johnson Leonard B. , Hanna Michel , Riederer Kathleen , Sharma Mamta , Fakih Mohamad G. , Thirumoorthi Muthayipalayam C. , Farjo Rand , Khatib Riad
Published: July 2007

Objective.

To evaluate the prevalence of colonization among patients with community-associated methicillin-resistantStaphylococcus aureus(CA-MRSA) infection and their household contacts.

Design.

Prospective, observational laboratory study of nasal colonization among patients and their household members from September 15, 2004, to February 20, 2006.

Setting.

A 600-bed, urban, academic medical center.

Patients.

Fifty-one patients who presented with CA-MRSA infections and 49 household members had cultures of nasal swab specimens performed.

Results.

Skin and soft-tissue infections were seen in 50 patients (98%) and 2 household members. Twenty-one (41%) of 51 patients and 10 (20%) of 49 household members were colonized with MRSA. An additional 5 patients (10%) and 12 household members (24%) were colonized with methicillin-susceptibleStaphylococcus aureus.Most MRSA isolates (95%; infective and colonizing) carried the staphylococcal cassette chromosomemectype IV complex, and 67% represented a single clone, identical to USA 300. Of the colonized household members, 5 had isolates related to the patients' infective isolate.

Conclusions.

The frequency of CA-MRSA colonization among household members of patients with CA-MRSA infections is higher than rates reported among the general population. Among colonized household members, only half of the MRSA strains were related to the patients' infective isolate. Within the same household, multiple strains of CA-MRSA may be present.
A Population-Based Investigation of Invasive Vancomycin-ResistantEnterococcusInfection in Metropolitan Atlanta, Georgia, and Predictors of Mortality
Authors: Camins Bernard C. , Farley Monica M. , Jernigan John J. , Ray Susan M. , Steinberg James P. , Blumberg Henry M.
Published: July 2007

Background.

Vancomycin-resistantEnterococcusorganisms (VRE) have emerged as common nosocomial pathogens, but few population-based data are available on the impact of invasive VRE infections.

Methods.

We assessed the incidence of invasive VRE infections and predictors of mortality among patients identified during prospective, population-based surveillance performed in the metropolitan statistical area (MSA) of Atlanta, Georgia.

Results.

From July 1997 through June 2000, a total of 192 patients who resided in the Atlanta MSA developed an invasive VRE infection, for a rate of 1.57 cases per 100,000 person-years. The incidence of invasive VRE disease significantly increased from 0.91 cases per 100,000 person-years during the first year of the study to 1.73 cases per 100,000 person-years during the third year of the study (P<.001). Rates of invasive VRE infection were significantly higher among African American patients than white patients (2.59 vs 0.70 cases per 100,000 person-years;P< .001). Blood was the most common sterile site from which VRE was recovered (161 [83%] of 193 isolates), followed by deep surgical sites (17 [9%]), peritoneal fluid (10 [5%]), pleural fluid (3 [2%]), and cerebrospinal fluid (1 [0.5%]). In multivariate analysis, a Charlson comorbidity index of 5 or greater, previous receipt of antibiotic therapy, having 2 or more sets of blood cultures positive for VRE, and receipt of central parenteral nutrition were independent predictors of mortality, whereas receipt of an antibiotic with in vitro activity against the VRE isolate was associated with a decreased risk of mortality. Molecular typing revealed 38 different pulsed-field gel electrophoresis patterns, but the 2 most common pulsed-field gel electrophoresis types were found at 3 Emory University-affiliated hospitals.

Conclusions.

The incidence of invasive VRE infection significantly increased in the Atlanta MSA during the 3-year study period, with significant racial disparities detected. Receipt of an antimicrobial agent with in vitro activity against VRE was associated with a lower mortality rate. Molecular typing results demonstrated polyclonal emergence of VRE in Atlanta.
Risk Factors forBurkholderia cepaciaComplex Bacteremia Among Intensive Care Unit Patients Without Cystic Fibrosis: A Case-Control Study
Authors: Bressler Adam M. , Kaye Keith S. , LiPuma John J. , Alexander Barbara D. , Moore Christopher M. , Reller L. Barth , Woods Christopher W.
Published: July 2007

Background.

TheBurkholderia cepaciacomplex is associated with colonization or disease in patients with cystic fibrosis (CF). For patients without CF, this complex is poorly understood apart from its presence in occasional point source outbreaks.

Objective.

To investigate risk factors forB. cepaciabacteremia in hospitalized, intensive care unit patients without CF.

Methods.

We identified patients with 1 or more blood cultures positive forB. cepaciabetween May 1, 1996, and March 31, 2002, excluding those with CF. Control patients were matched to case patients by ward, duration of hospitalization, and onset date of bacteremia. Matched analyses were used to identify risk factors forB. cepaciabacteremia.

Results.

We enrolled 40 patients withB. cepaciabacteremia into the study. No environmental or other point source forB. cepaciacomplex was identified, although horizontal spread was suspected. Implementation of contact precautions was effective in decreasing the incidence ofB. cepaciabacteremia. We selected 119 matched controls. Age, sex, and race were similar between cases and controls. In multivariable analysis, renal failure that required dialysis, recent abdominal surgery, 2 or more bronchoscopic procedures before detection ofB. cepaciabacteremia, tracheostomy, and presence of a central line before detection ofB. cepaciabacteremia were independently associated with development ofB. cepaciabacteremia, whereas presence of a percutaneous feeding tube was associated with a lower risk of disease.

Conclusions.

B. cepaciacomplex is an important emerging group of nosocomial pathogens in patients with and patients without CF. Nosocomial spread is likely facilitated by cross-transmission, frequent pulmonary procedures, and central venous access. Infection control measures appear useful for limiting the spread of virulent, transmissible clones ofB. cepaciacomplex.
Onset of Symptoms and Time to Diagnosis of Clostridium difficile–Associated Disease Following Discharge From an Acute Care Hospital
Authors: Chang Heidi T. , Krezolek Dorota , Johnson Stuart , Parada Jorge P. , Evans Charlesnika T. , Gerding Dale N.
Published: July 2007

Objective.

To identify patients with a diagnosis of Clostridium difficile–associated disease (CDAD) in the ambulatory care setting and determine the relationship of symptom onset and diagnosis to prior hospitalization and exposure to antimicrobials.

Design.

Single-center, retrospective study.

Methods.

Medical records were reviewed for outpatients and hospitalized patients with a stool assay positive for C. difficile toxin A from January 1998 through March 2005. Patients with recurrent CDAD or residing in an extended-care facility were excluded. CDAD in patients who had been hospitalized in the 100 days prior to diagnosis was considered potentially hospital-associated.

Results.

Of the 84 patients who met the inclusion criteria, 75 (89%) received a diagnosis 1-60 days after hospital discharge (median, 12 days), and 71 (85%) received a diagnosis within 30 days after discharge. Of the 69 patients whose records contained information regarding time of symptom onset, 62 (90%) developed diarrhea within 30 days of a previous hospital discharge, including 7 patients with symptom onset prior to discharge and 9 with onset on the day of discharge. The median time from symptom onset to diagnosis was 6 days. Of 84 patients, 77 (92%) had received antimicrobials during a prior hospitalization, but 55 (65%) received antimicrobials both as inpatients and as outpatients.

Conclusion.

If all cases of CDAD diagnosed within 100 days of hospital discharge were assumed to be hospital-associated, 71 (85%) of 84 patients with CDAD were identified within 30 days, and 75 (89%) of 84 were identified by day 60. Continued outpatient antimicrobial exposure confounds determination of whether late-onset cases are community- or hospital-associated.
Appropriateness of Antibiotic Prophylaxis for Major Surgery in Korea
Authors: Choi Won Suk , Song Joon Young , Hwang Jung Hae , Kim Nam Soon , Cheong Hee Jin
Published: July 2007

Objective.

To determine the appropriateness of antibiotic prophylaxis regimens for major surgery in Korea.

Design.

Retrospective study using a written survey for each patient who underwent arthroplasty, colon surgery, or hysterectomy.

Setting.

Six tertiary hospitals in Seoul and Gyeonggi Province.

Patients.

From each hospital, a maximum of 150 patients who underwent each type of surgery were randomly chosen for the study.

Results.

Of 2,644 eligible patients, 1,914 patients were included in the analysis; 677 of these patients underwent arthroplasty, 578 underwent colon surgery, and 659 underwent hysterectomy. Nineteen patients were excluded from the analyses of the class and number of antibiotics used for prophylaxis because they underwent multiple surgeries at different sites. For each of the 1,895 remaining patients, antibiotic prophylaxis involved a mean ( ± SD) of 2.8 ± 0.9 classes of antibiotics. The most commonly prescribed agents were cephalosporins (prescribed for 1,875 [98.9%] of the patients) and aminoglycosides (1,404 [74.1%]). A total of 1,574 (83.1%) of patients received at least 2 classes of antibiotics simultaneously. Only 15 (0.8%) of 1,895 patients received antibiotic prophylaxis in accordance with published guidelines. Of 506 patients for whom the initial dose of antibiotics was evaluated, 374 (73.9%) received an appropriate initial dose. Of the 1,676 patients whose medical records included information about antibiotic administration relative to the time of surgery, only 188 (11.2%) received antibiotic prophylaxis an hour or less before the surgical incision was made. Of the 1,748 patients whose medical records included information about duration of surgery, antibiotic prophylaxis was discontinued 24 hours or less after surgery for only 3 (0.2%) of the patients.

Conclusion.

Most patients who had major surgery in Korea received inappropriate antibiotic prophylaxis. Measures to improve the appropriateness of antibiotic prophylaxis are urgently required.
Emergence and Control of Fluoroquinolone-Resistant, Toxin A–Negative, Toxin B–PositiveClostridium difficile
Authors: Drudy Denise , Harnedy Norma , Fanning Séamus , Hannan Margaret , Kyne Lorraine
Published: July 2007

Background.

Clostridium difficileis a major cause of infectious diarrhea in hospitalized patients. Between August 2003 and January 2004, we experienced an increase in the incidence ofC. difficile–associated disease. We describe the investigation into and management of the outbreak in this article.

Methods.

A total of 73 consecutive patients with nosocomialC. difficile–associated diarrhea were identified.C. difficileisolates were characterized using toxin-specific enzyme immunoassays, a tissue-culture fibroblast cytotoxicity assay, polymerase chain reaction (PCR), and antimicrobial susceptibility tests. Rates of recurrence and ofC. difficilecolitis were recorded. Changes in antibiotic use and infection control policies were documented.

Results.

The incidence ofC. difficile–associated diarrhea peaked at 21 cases per 1,000 patient admissions. Of theC. difficileisolates recovered, 85 (95%) were identical toxin A–negative and toxin B-positive strains, corresponding to toxinotype VIII and PCR ribotype 017. All clonal isolates were resistant to multiple antibiotics, including ofloxacin, ciprofloxacin, levofloxacin, moxifloxacin, and gatifloxacin (minimum inhibitory concentrations [MICs] of greater than 32μg/mL) and erythromycin, clarithromycin, and clindamycin (MICs of greater than 256μg/mL). RecurrentC. difficile–associated disease occurred in 26 (36%) of the patients. At least 10 (14%) of the patients developedC. difficilecolitis. Additional infection control measures introduced included the use of ward memos, a hand-hygiene awareness campaign, increased environmental cleaning, attention to prescribing practices for antibiotics, increased awareness of diarrheal illness, and early isolation of affected patients. Total use of fluoroquinolones did not change throughout the study period. Despite persistence of this toxin-variant strain, the incidence ofC. difficile–associated disease in our institution decreased to fewer than 5 cases per 1,000 admissions.

Conclusions.

We report on the emergence of a fluoroquinolone- and clindamycin-resistant, toxin A–negative, and toxin B–positive strain ofC. difficileassociated with an outbreak ofC. difficile–associated disease in our institution during a 6-month period. We found that careful attention to improvement of infection control interventions was the most important means of controlling this nosocomial pathogen.
Ralstonia pickettiiBacteremia Associated With Pediatric Extracorporeal Membrane Oxygenation Therapy in a Canadian Hospital
Authors: Forgie Sarah , Kirkland Terri , Rennie Robert , Chui Linda , Taylor Geoff
Published: July 2007

We describe 2 pediatric patients withRalstonia pickettiibacteremia associated with extracorporeal membrane oxygenation (ECMO) therapy. Investigation revealed a common environmental source—the ECMO temperature-control units. We created guidelines for disinfecting these units that do not void the manufacturer's warranty and have prevented additional cases of bacteremia due to this organism.
Inhibiting Endoplasmic Reticulum (ER)-associated Degradation of Misfolded Yor1p Does Not Permit ER Export Despite the Presence of a Diacidic Sorting Signal
Authors: Pagant Silvere , Kung Leslie , Dorrington Mariana , Lee Marcus C.S. , Miller Elizabeth A.
Published: July 2007

Capture of newly synthesized proteins into endoplasmic reticulum (ER)-derived coat protomer type II (COPII) vesicles represents a critical juncture in the quality control of protein biogenesis within the secretory pathway. The yeast ATP-binding cassette transporter Yor1p is a pleiotropic drug pump that shows homology to the human cystic fibrosis transmembrane conductance regulator (CFTR). Deletion of a phenylalanine residue in Yor1p, equivalent to the major disease-causing mutation in CFTR, causes ER retention and degradation via ER-associated degradation. We have examined the relationship between protein folding, ERAD and forward transport during Yor1p biogenesis. Uptake of Yor1p into COPII vesicles is mediated by an N-terminal diacidic signal that likely interacts with the “B-site” cargo-recognition domain on the COPII subunit, Sec24p. Yor1p-ΔF is subjected to complex ER quality control involving multiple cytoplasmic chaperones and degradative pathways. Stabilization of Yor1p-ΔF by inhibiting its degradation does not permit access of Yor1p-ΔF to COPII vesicles. We propose that the ER quality control checkpoint engages misfolded Yor1p even after it has been stabilized by inhibition of the degradative pathway.
The long‐range transport of birch (Betula) pollen from Poland and Germany causes significant pre‐season concentrations in Denmark
Authors: Skjøth C. A. , Sommer J. , Stach A. , Smith M. , Brandt J.
Published: July 2007

Background
Birch pollen is highly allergic and has the potential for episodically long‐range transport. Such episodes will in general occur out of the main pollen season. During this time, allergy patients are unprotected and high pollen concentrations will therefore have a full allergenic impact.

Objective
To show that Denmark obtains significant quantities of birch pollen from Poland or Germany before the local trees start to flower.

Methods
Simultaneous observations of pollen concentrations and phenology in the potential source area in Poland as well as in Denmark were performed in 2006. The Danish pollen records from 2000 to 2006 were analysed for possible long‐range transport episodes and analysed with trajectories in combination with a birch tree source map.

Results
In 2006, high pollen concentrations were observed in Denmark with bi‐hourly concentrations above 500 grains/m3 before the local trees began to flower. Poland was identified as a source region. The analysis of the historical pollen record from Copenhagen shows significant pre‐seasonal pollen episodes almost every year from 2000 to 2006. In all episodes, trajectory analysis identified Germany or Poland as source regions.

Conclusion
Denmark obtains significant pre‐seasonal quantities of birch pollen from either Poland or Germany almost every year. Forecasting of birch pollen quantities relevant to allergy patients must therefore, take into account long‐range transport. This cannot be based on measured concentrations in Denmark. The most effective way to improve the current Danish pollen forecasts is to extend the current forecasts with atmospheric transport models that take into account pollen emission and transport from countries such as Germany and Poland. Unless long‐range transport is taken into account, pre‐seasonal pollen episodes will have a full allergic impact, as the allergy patients in general will be unprotected during that time.
Clinical features and genetic analysis of four Brazilian kindreds with resistance to thyroid hormone
Authors: Magalhães Patricia Künzle Ribeiro , Rodrigues Dare Gustavo Leopoldo , Rodrigues dos Santos Sandra , Nogueira Celia Regina , De Castro Margaret , Zanini Maciel Lea Maria
Published: July 2007

Objective  Resistance to thyroid hormone (RTH) is a dominantly inherited syndrome of reduced tissue responsiveness to thyroid hormone usually due to mutations located in the ligand‐binding domain and adjacent hinge region of the thyroid hormone receptor β (TRβ). In the present report we describe the clinical and laboratory characteristics and the genetic analysis of patients with this rare disorder from a Brazilian population.

Patients  Four unrelated Brazilian families with diagnosis of RTH were studied. Age at diagnosis varied from 14 months to 29 years.

Results  All affected individuals were clinically euthyroid, except for one patient who presented immediately after birth with hyperthyroidism. All individuals had tachycardia and goitre, elevated concentrations of free thyroid hormones and reduced sensitivity to thyroid hormone. Direct sequencing analysis of the TRβ gene revealed four previously reported mutations: c.949G→A, c.1313G→A, c.1357C→A and c.1358dupC in families A, B, C and D, respectively.

Conclusion  The present report shows that the frequent mutations described in the thyroid hormone receptor worldwide are also present in the Brazilian population, which is characterized by a variable ethnic background.
Economic burden of a gluten‐free diet
Authors: Lee A. R. , Ng D. L. , Zivin J. , Green P. H. R.
Published: July 2007

Background  Coeliac disease is a common, autoimmune disorder, for which the only treatment is lifelong adherence to a gluten‐free diet. This study evaluates the economic burden of adhering to a gluten‐free diet.

Methods  A market basket of products identified by name brand, weight or package size for both regular wheat‐based products and gluten‐free counterparts was developed. The differences in price between purchase venues, both type of store (general grocery store, an upscale grocery store and a health food store and four internet‐based grocery sites) and region was also analysed.

Results  Availability of gluten‐free products varied between the different venues, regular grocery stores carried 36%, while upscale markets carried 41%, and health food stores 94%, compared with 100% availability on the internet. Overall, every gluten‐free product was more expensive than their wheat‐based counterpart (P ≤ 0.05). Bread and pasta was twice as expensive as their wheat‐based counterparts. Cost was affected more by shopping venue than geographic location.

Conclusions  This study demonstrated that gluten‐free foods have poor availability and are more expensive than their gluten‐containing counterparts. The impact of these findings on dietary compliance and the quality of life needs to be addressed.
Genetic intratumour heterogeneity in high‐grade brain tumours is associated with telomere‐dependent mitotic instability
Authors: Glanz C. , Rebetz J. , Stewénius Y. , Persson A. , Englund E. , Mandahl N. , Mertens F. , Salford L. G. , Widegren B. , Fan X. , Gisselsson D.
Published: July 2007

Glioblastoma multiforme (GBM) and other high‐grade brain tumours are typically characterized by complex chromosome abnormalities and extensive intratumour cytogenetic heterogeneity. The mechanisms behind this diversity have been little explored. In this study, we analysed the pattern of chromosome segregation at mitosis in 20 brain tumours. We found an abnormal segregation of chromatids at mitosis through anaphase bridging (10–25% of anaphase cells) in all 10 GBMs. Anaphase bridging was also found in two medulloblastomas (7–15%), one anaplastic astrocytoma (17%) and one oligodendroglioma (6%). These tumours showed a relatively high degree of cytogenetic complexity and heterogeneity. In contrast, cell division abnormalities were not found in low‐grade brain tumours with less complex karyotypes, including two pilocytic astrocytomas and two ependymomas. Further analysis of two GBMs by fluorescence in situ hybridization with telomeric repeat probes revealed excessive shortening of TTAGGG repeats, indicating dysfunctional protection of chromosome ends. In xenografts established from these GBMs, there was a gradual reduction in cytogenetic heterogeneity through successive passages as the proportion of abnormally short telomeres was reduced and the frequency of anaphase bridges decreased from >25% to 0. However, bridging could be reintroduced in late‐passage xenograft cells by pharmacological induction of telomere shortening, using a small‐molecule telomerase inhibitor. Telomere‐dependent abnormal segregation of chromosomes at mitosis is thus a common phenomenon in high‐grade brain tumours and may be one important factor behind cytogenetic intratumour diversity in GBM.
Fitting photosynthetic carbon dioxide response curves for C3 leaves
Authors: SHARKEY THOMAS D. , BERNACCHI CARL J. , FARQUHAR GRAHAM D. , SINGSAAS ERIC L.
Published: July 2007

Photosynthetic responses to carbon dioxide concentration can provide data on a number of important parameters related to leaf physiology. Methods for fitting a model to such data are briefly described. The method will fit the following parameters: Vcmax, J, TPU, Rd and gm[maximum carboxylation rate allowed by ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco), rate of photosynthetic electron transport (based on NADPH requirement), triose phosphate use, day respiration and mesophyll conductance, respectively]. The method requires at least five data pairs of net CO2 assimilation (A) and [CO2] in the intercellular airspaces of the leaf (Ci) and requires users to indicate the presumed limiting factor. The output is (1) calculated CO2 partial pressure at the sites of carboxylation, Cc, (2) values for the five parameters at the measurement temperature and (3) values adjusted to 25 °C to facilitate comparisons. Fitting this model is a way of exploring leaf level photosynthesis. However, interpreting leaf level photosynthesis in terms of underlying biochemistry and biophysics is subject to assumptions that hold to a greater or lesser degree, a major assumption being that all parts of the leaf are behaving in the same way at each instant.
Beetle evolution in the Asian highlands: insight from a phylogeny of the scarabaeid subgenus Serica (Coleoptera, Scarabaeidae)
Authors: AHRENS DIRK
Published: July 2007

Abstract The phylogeny of the species of the scarabaeid subgenus Serica (genus Serica MacLeay, 1819) was inferred from a parsimony analysis and the use of 117 morphological characters of adults. Successive weighting was employed to further evaluate the phylogenetic relationships, and the geographical changes in the distribution in certain lineages were explored. Four major lineages may be recognized from the strict consensus tree within the ingroup: (1) Calloserica; (2) Gastroserica +Neoserica; (3) Lasioserica; and (4) Serica including the representatives of Taiwanoserica. Pachyserica proved to be monophyletic only after successive weighting based on the retention index. The taxa of Taiwanoserica are nested within the species of Serica. Consequently, Taiwanoserica (stat.n.) is ranked as a subgenus of Serica. The clade Serica (subgenus Serica) comprised the majority of the species included in this study. Serica (sensu stricto) species of the Himalayas are a polyphyletic group. Several major younger clades of Serica (sensu stricto) are not restricted to just one geographical region, but cover widely distant ranges (such as the Himalaya and eastern Tibet). Dispersal is hypothesized multiple times from the Himalaya to eastern Tibet/Indochina and vice versa, and also between the Japanese islands and eastern Tibet. Several hypotheses are discussed for an important role of the entire Himalaya–south‐eastern Tibet orogenic system for the evolution of the subgenus Serica. More recently, the progressive uplift of the Tibetan Plateau provided an efficient barrier to the westward dispersal of eastern Palaearctic species.
Systematics and biogeography of Polietina Schnabl & Dziedzicki (Diptera, Muscidae): Neotropical area relationships and Amazonia as a composite area
Authors: NIHEI SILVIO SHIGUEO , DE CARVALHO CLAUDIO JOSÉ BARROS
Published: July 2007

Abstract The genus Polietina Schnabl & Dziedzicki, 1911 (Diptera, Muscidae) groups 15 species distributed throughout the Neotropical region. Here, generic and specific diagnoses and a species identification key are provided, with cladistic and biogeographical analyses performed and results discussed. In the cladistic analysis, the application of equal, successive and implied character weighting schemes resulted in the single cladogram ((P. flavidicincta (P. rubella (P. concinna (P. orbitalis, P. wulpi)))) (P. steini ((P. flavithorax, P. major) (P. nigra, P. prima) (P. bicolor, P. minor, P. univittata)))). In the biogeographical analysis, the Brooks parsimony analysis was performed by experimenting several combinations of areas of endemism proposed previously in the literature, and one area cladogram ((Caribbean, north‐west Amazonia) (south‐east Amazonia (Chacoan, Paraná))) favours a previously proposed hypothesis of a composite history for Amazonia.
Assessment of live kidney donors by magnetic resonance angiography: reliability and impact on outcomes
Authors: Monroy‐Cuadros Mauricio , McLaughlin Kevin , Salazar Anastasio , Yilmaz Serdar
Published: July 2007

Abstract: Background:  Kidney allograft retrieval from live donors requires accurate determination of kidney anatomy prior to surgery, particularly the arterial supply. Traditionally, conventional angiography has been used to obtain this information. Magnetic resonance angiography (MRA) offers a non‐invasive, cost‐effective alternative, but has been considered to be less accurate. Despite this criticism, many centers have moved to MRA screening of potential kidney donors. The objective of this study is to evaluate our experience of the reliability of MRA in determining the arterial anatomy of living kidney donors as compared to the intra‐operative findings.

Methods:  We performed a retrospective review of gadolinium‐enhanced, ultra‐fast, three‐dimensional, spoiled gradient‐echo MRA in live kidney donors in the Southern Alberta Transplant Program and compared these results with the intra‐operative findings during nephrectomy, as the gold standard.

Results:  Of the 66 patients, an accessory renal artery was found intra‐operatively in eight cases; two of which were erroneously diagnosed as normal by MRA. The negative predictive value for MRA was 0.97, false‐negative rate was 0.25, and sensitivity was 0.75. No patient experienced side‐effects from the MRA procedure. No donor needed conversion to open nephrectomy because of an undetected accessory renal artery. One allograft with an accessory renal artery developed thrombosis of the lower pole of the kidney despite arterial reconstruction. Kidney function in the recipient of this allograft was excellent and there was no urinary leak.

Conclusion:  In our hands, MRA determined the vascular anatomy of potential kidney donors with an acceptable negative predictive value of 97%.