bluuebunny/crossref_metadata_2025 huggingface dataset:
Familial urticaria pigmentosa associated with thrombocytosis as the initial symptom of systemic mastocytosis and Down's syndrome
Authors: Jappe U , Aumann V , Mittler U , Gollnick H
Published: October 2003

Most cases of urticaria pigmentosa are confined to the skin, but visceral involvement and/or haematological abnormalities have been observed. It is still a matter of debate whether all forms of mastocytosis are true neoplasias or reactive hyperplasias. Familial inheritance of urticaria pigmentosa is rare. We report on a fraternal set with urticaria pigmentosa as part of a systemic mastocytosis. The first patient additionally revealed persistent thrombocytosis and splenomegaly. His brother developed urticaria pigmentosa, intermittent diarrhoea, hepatomegaly and asthma bronchiale associated with trisomy 21 (Down's syndrome). The association of mastocytosis with thrombocytosis has seldom been described. In our patient it preceded the development of systemic mastocytosis. The association with Down's syndrome has not been reported until now.
Invasive Pneumococcal Disease in Older Adults Residing in Long‐Term Care Facilities and in the Community
Authors: Kupronis Benjamin A. , Richards Chesley L. , Whitney Cynthia G. ,   the Active Bacterial Core Surveillance Team
Published: October 2003

Objectives: To examine the epidemiology of invasive pneumococcal disease in older adults hospitalized for invasive pneumococcal disease who are living in the community and in long‐term care facilities (LTCFs) in the United States.

Design: Analysis of 2,402 cases of invasive pneumococcal disease requiring hospitalization in 2000 and 2001 that the Centers for Disease Control and Prevention's Active Bacterial Core Surveillance collected in nine states.

Setting: Hospital.

Participants: Hospitalized LTCF residents and community‐living older adults in the United States.

Measurements:

Age‐ and residence‐specific pneumococcal disease incidence rates per 100,000 persons, case‐fatality rates, and trends in antimicrobial resistance.

Results: Nationally, the rate of invasive pneumococcal disease in LTCF residents was 194.2 cases per 100,000 persons aged 65 and older and 44.6 for community‐living older adults (relative risk=4.4, 95% confidence interval (CI)=4.2–4.5). Compared with community‐living older adults, case‐fatality rates were 1.9 times higher (30.8% vs 16.0%, 95% CI=1.5–2.5). Pneumococcal strains from LTCF residents were significantly more likely to be nonsusceptible to levofloxacin than strains from community‐ living older adults (5.7% vs 0.4%, P<.001).

Conclusion: Older adults living in LTCFs are at a higher risk for invasive pneumococcal disease and death than are community‐living older adults. Additionally, fluoroquinolone resistance is significantly higher in older adults living in LTCFs and may provide clues to emerging antimicrobial resistance in the general population.
Benzodiazepine Use and Physical Performance in Community‐Dwelling Older Women
Authors: Gray Shelly L. , Penninx Brenda W. J. H. , Blough David K. , Artz Margaret B. , Guralnik Jack M. , Wallace Robert B. , Buchner Dave M. , LaCroix Andrea Z.
Published: October 2003

Objectives: To determine whether benzodiazepine use in older women increased the risk of decline in physical function.

Design: A four‐year prospective cohort study.

Setting: The communities of Iowa and Washington counties, Iowa.

Participants: Eight hundred eighty‐five women aged 70 and older who had completed physical performance tests in 1988 and 1992.

Measurements: Benzodiazepine use was determined during in‐home interviews and classified by dose, duration, indication for use, and half‐life. Physical performance tests included an assessment of standing balance, walking speed (8‐foot distance), and repeated chair raises.

Results: Ninety (10.2%) reported benzodiazepine use at baseline. After adjustment for baseline physical performance score and potential confounders, benzodiazepine use was associated with a greater decline in physical performance over 4 years than nonuse (β=–1.16; standard error (SE)=0.25; P<.001). The use of higher‐than‐recommended dose was related to decline (β=–2.26; SE=0.47; P<.001), and use of lower doses was not (β=–0.53; SE=0.46; P=.246). Long‐term use (≥3 years) was related to decline (β=–1.65; SE=0.34; P<.001), whereas recent and past use were not. Similar results were obtained when restricting the sample to those without disability at baseline.

Conclusion: This study provides evidence that older women who used benzodiazepines were at risk for decline in physical performance. Subgroup analyses indicated that risk was greater with use of higher‐than‐recommended doses or for long duration (≥3 years). These findings highlight the importance of using benzodiazepines at the lowest effective dose for a limited duration in older women.
Ertapenem Therapy for Community‐Acquired Pneumonia in the Elderly
Authors: Woods Gail L. , Isaacs Robin D. , McCarroll Kathleen A. , Friedland Ian R.
Published: October 2003

Objectives: To compare the efficacy and safety of ertapenem, 1 g once a day, with ceftriaxone, 1 g once a day, for treatment of the subgroup of patients aged 65 and older with community‐acquired pneumonia (CAP) requiring parenteral therapy.

Design: Combined data from patients aged 65 and older in two randomized, double‐blind clinical trials.

Setting: Eighty international centers.

Participants: Eight hundred fifty‐seven treated patients, of whom 351 were aged 65 and older.

Interventions: Intravenous or intramuscular ertapenem or ceftriaxone with the option to switch to oral amoxicillin‐clavulanate after at least 3 days of parenteral therapy.

Measurements: Clinical efficacy was assessed at completion of parenteral therapy and 7 to 14 days after all therapy had been completed (test of cure (TOC) assessment). Bacterial eradication was assessed at the TOC visit. Safety was assessed daily during study therapy and for 14 days thereafter.

Results: One hundred forty‐eight clinically evaluable patients aged 65 and older were treated with ertapenem and 125 with ceftriaxone. Pathogens were identified in 157 (57.5%) patients (the most common being Streptococcus pneumoniae), most of which were penicillin‐susceptible. Clinical cure rates were 95.9% for patients in the ertapenem group and 92.7% for patients in the ceftriaxone group at completion of parenteral therapy and 93.9% and 90.4%, respectively, at the TOC assessment. Overall bacterial eradication rates were 92.8% (77 of 83) for patients treated with ertapenem and 93.2% (69 of 74) for those treated with ceftriaxone. The most common drug‐related adverse experiences in both treatment groups were diarrhea and mild to moderate elevation of serum aminotransferase levels.

Conclusion: Ertapenem 1 g once a day was highly effective for treatment of elderly patients with CAP requiring parenteral therapy and was as effective as ceftriaxone. Ertapenem was generally well tolerated, with an overall safety profile similar to ceftriaxone.
Does Delirium Increase Hospital Stay?
Authors: McCusker Jane , Cole Martin G. , Dendukuri Nandini , Belzile Eric
Published: October 2003

Objectives: To determine the effects of prevalent and incident delirium on length of hospital stay.

Design: Prospective cohort study, comparing (1) length of stay after admission in cases of prevalent delirium versus controls without prevalent delirium with (2) length of stay after diagnosis in cases of incident delirium versus controls matched by day of diagnosis.

Setting: The medical services of a primary, acute care hospital.

Participants: Medical admissions of patients aged 65 and older from the emergency department with delirium diagnosed during the first week in hospital. Patients admitted to intensive care or oncology and those with a primary diagnosis of stroke were excluded. A sample of those without delirium was also enrolled.

Measurements: Delirium was diagnosed using the Confusion Assessment Method. Data on length of stay and diagnosis‐related groups (DRGs) were abstracted from administrative data. Measures of covariates included the Informant Questionnaire on Cognitive Decline in the Elderly, the Delirium Index, the instrumental activities of daily living questionnaire from the Older American Resources and Services project, the Charlson Comorbidity Index, the Clinical Severity Scale, and the Acute Physiology Score.

Results: The study sample comprised 359 patients: 204 with prevalent delirium, 37 with incident delirium, and 118 without delirium. After controlling for covariates, prevalent delirium was not associated with a significantly longer hospital stay, but incident delirium was associated with an excess stay after diagnosis of 7.78 days (95% confidence interval=3.07, 12.48). Similar results were obtained using log‐transformed or DRG‐adjusted estimates of length of stay.

Conclusion: In older medical inpatients, incident but not prevalent delirium is an important predictor of longer hospital stay. Interventions to prevent incident delirium may reduce length of stay.
End‐of‐Life Care in Assisted Living and Related Residential Care Settings: Comparison with Nursing Homes
Authors: Sloane Philip D. , Zimmerman Sheryl , Hanson Laura , Mitchell C. Madeline , Riedel‐Leo Charlene , Custis‐Buie Verita
Published: October 2003

Objectives: To define the current state of end‐of‐life care in residential care/assisted living (RC/AL) facilities and nursing homes (NHs) and to compare these two types of care settings.

Design: Interviews of staff and family informants about deaths that occurred during a longitudinal study.

Setting: Fifty‐five RC/AL facilities and 26 NHs in Florida, Maryland, New Jersey, and North Carolina.

Participants: Two hundred twenty‐four staff and family informants that best knew the 73 RC/AL residents and 72 NH residents who died in or within 3 days after discharge from a study facility.

Measurements: Telephone interviews conducted with the facility staff member who knew the decedent best and the family member who was most involved in care during the last month of life of the decedent. Data were collected on circumstances of death, perceptions of dying process, cause of death, care during the last month of life, mood, discomfort, and family satisfaction.

Results: Most decedents died in the facility where they had resided, and more than half of the subjects were alone when they died. Greater proportions of staff and family in the NHs knew that the resident's death was only days or weeks away. Both RC/AL and NH residents experienced few highly negative moods, and even on their most uncom‐fortable day, the overall discomfort was low for residents in both facility types. Summary ratings of family satisfaction were significantly higher for the RC/AL (32.1) than the NH (41.2) group (P=.016).

Conclusion: These data suggest that end‐of‐life care in RC/AL settings appears similar in process and outcomes to that provided in NHs. Thus, aging and dying‐in‐place can effectively occur in RC/AL.
Measuring Life‐Space Mobility in Community‐Dwelling Older Adults
Authors: Baker Patricia S. , Bodner Eric V. , Allman Richard M.
Published: October 2003

Objectives: To evaluate the validity and reliability of a standardized approach for assessing life‐space mobility (the University of Alabama at Birmingham Study of Aging Life‐Space Assessment (LSA)) and its ability to detect changes in life‐space over time in community‐dwelling older adults.

Design: Prospective, observational cohort study.

Setting: Five counties (three rural and two urban) in central Alabama.

Participants: Community‐dwelling Medicare beneficiaries (N=306; 46% male, 43% African American) who completed in‐home baseline interviews and 2‐week and 6‐month telephone follow‐up interviews.

Measurements: The LSA assessed the range, independence, and frequency of movement over the 4 weeks preceding assessments. Correlations between the baseline LSA and measures of physical and mental health (physical performance, activities of daily living, instrumental activities of daily living, a global measure of health (the short form‐12 question survey), the Geriatric Depression Scale, and comorbidities) established validity. Follow‐up LSA scores established short‐term test‐retest reliability and the ability of the LSA to detect change.

Results: For all LSA scoring methods, baseline and 2‐week follow‐up LSA correlations were greater than 0.86 (95% confidence interval=0.82–0.97). Highest correlations with measures of physical performance and function were noted for the LSA scoring method considering all attributes of mobility. The LSA showed both increases and decreases at 6 months.

Discussion: Life‐space correlated with observed physical performance and self‐reported function. It was stable over a 2‐week period yet showed changes at 6 months.
Residual cell content in plasma produced by three centrifugal apheresis procedures
Authors: Burnouf Thierry , Kappelsberger Claudia , Frank Kerstin , Burkhardt Thomas
Published: October 2003

BACKGROUND:  Understanding the impact of collection procedures on the residual amount of blood cells in plasma for transfusion and for fractionation is of current interest. This prospective work evaluated plasma donations collected on an apheresis machine (PCS 2, Haemonetics) with three different automatic centrifugal apheresis procedures, currently largely used in the US (Revision G) and in Europe (Revision F), and included a new procedure that uses a high‐separation core (HSC) that is designed with a second separation chamber to further separate cells from plasma.

STUDY DESIGN AND METHODS:  A total of 90 collection procedures have been performed from a population of 37 donors, under comprehensively standardized conditions. There were 30 well‐matched donors in each group. Plasma aliquots were taken from the plasma units within 30 minutes of the end of the collection procedures and immediately assessed for WBCs, RBCs, PLTs, and supernatant Hb.

RESULTS:  In Revision F and Revision G plasma donations, the mean numbers of WBCs were 83.1 × 104 and 311 × 104 per L; PLTs, 5.01 × 109 and 20 × 109 per L; and RBCs, 58 × 109 and 43 × 109 per L, respectively. Significantly lower values were found with the HSC procedure (mean WBC, RBC, and PLT counts, 3.01 × 104/L [p < 0.05], 9 × 106/L [p < 0.001], and 3.5 × 109/L [p < 0.001], respectively). The amount of free Hb was similar in all three procedures.

CONCLUSION:  Significant differences in numbers of cells in plasma were found depending on the centrifugal procedures used and the design of the separation bowl. The lowest level of cell contamination was found with the new HSC bowl, which without a filtration step, yielded plasma that met the standard for WBC‐reduced plasma. Plasma collectors can select the most appropriate method of plasma collection based on donor criteria, use of plasma (transfusion, viral inactivation, or fractionation), and local or international regulations, when in place.
Antibodies to high‐frequency antigens may decrease the quality of transfusion support: an observational study
Authors: Seltsam Axel , Wagner Franz F. , Salama Abdulgabar , Flegel Willy A.
Published: October 2003

BACKGROUND:  There is only little information on the transfusion support of patients with antibodies to high‐frequency RBC antigens.

STUDY DESIGN AND METHODS:  In cooperation with reference laboratories and transfusion services in Austria, Germany, and Switzerland, the transfusion support provided to hospitalized patients identified as having such antibodies was reviewed during a 20‐month period.

RESULTS:  A total of 52 patients with antibodies to high‐frequency antigens were treated in hospitals. Twenty‐two of them received 104 units of antigen‐negative RBCs. In 23 cases, a deviation from the standard transfusion policy (e.g., transfusion of antigen‐incompatible units) occurred. The use of frozen or fresh units varied amongst the different countries but did not affect the rate of deviation from protocol. About 20 percent of all units were supplied internationally. Four antibody specificities, anti‐Kpb, anti‐Vel, anti‐Lub, and anti‐Yta, were identified in two‐thirds of the patients.

CONCLUSION:  This survey indicated that transfusion support was unsatisfactory in about one‐third of the hospitalized patients with antibodies to high‐frequency antigens. Maintaining a rapidly accessible stock of just four types of rare blood units would ensure adequate transfusion support for most of these patients.
Increased transmigration of G–CSF‐mobilized peripheral blood CD34+ cells after overnight storage at 37°C
Authors: Greco Nicholas J. , Lee Wendy R. , Moroff Gary
Published: October 2003

BACKGROUND:  G–CSF‐mobilized PBPCs are utilized in allogeneic and autologous PBPC transplants. Homing, adhesion, and transmigration of hematopoietic CD34+ cells are required for successful engraftment. Hematopoietic CD34+ cells undergo directional migration toward the CXCR4 receptor ligand stromal‐derived factor‐1 (SDF‐1). Limited data are available on the effects of liquid storage and cryopreservation on PBPC CD34+ cells.

STUDY DESIGN AND METHODS:  Magnetic‐assisted cell sorting (MACS)‐selected CD34+ cells were assayed for retention of in vitro transmigration and phenotypic changes of unit‐matched liquid‐stored and cryopreserved PBPC samples from healthy donors. Studies evaluated whether transmigration of CD34+ cells in Iscove's modified Dulbecco's medium plus 1 percent HSA alone or in medium supplemented with SCF or allogeneic plasma was affected by overnight incubation at 37°C, relative to nonincubated conditions.

RESULTS:  Transmigration was maintained during liquid storage at 1 to 6°C during a 2‐day period and in unit‐matched cryopreserved‐thawed samples that had been initially liquid stored. Overnight incubation at 37°C of MACS‐selected unit‐matched liquid‐stored or cryopreserved‐thawed CD34+ cells resulted in substantially increased transmigration, in particular with noncoated filters chemoattracted with the chemokine SDF‐1.

CONCLUSION:  CD34+ cell transmigration was comparable between liquid‐stored and cryopreserved samples, and both demonstrated similar increases after overnight incubation at 37°C.
Laser evaporation and the production of pentacene films
Authors: Blanchet Graciela B. , Fincher C. R. , Malajovich I.
Published: October 2003

The formation of high-quality thin films of pentacene is important in electronic applications. We show here that laser ablation, a technique widely used to deposit a variety of inorganic materials, can also be employed for forming thin oligomeric films. Pentacene films produced by the evaporation of a solid target with a pulsed ultraviolet laser are comparable to those produced via thermal evaporation. The composition of the ablation plume suggests that deposition proceeds by way of a laser-induced evaporation followed by condensation on a nearby surface. Laser deposited films are single-phase material with interlamella spacing characteristic of thin-film structures. The optical properties, field effect mobilities, and surface morphology of laser deposited pentacene films as compared to those produced via thermal evaporation are discussed.
Impurity transport measurements in beam heated low-confinement mode discharges in the National Spherical Torus Experiment
Authors: Stutman D. , Finkenthal M. , Bell R. E. , Kaye S. M. , LeBlanc B. P. , Menard J. E. , Synakowski E. J. , Darrow D. S. , Soukhanovskii V. , Bourdelle C. ,   The NSTX Team
Published: October 2003

Impurity injection experiments were performed in the National Spherical Torus Experiment [NSTX, M. Ono et al., Nucl. Fusion 40, 557 (2000)] for a first assessment of low-Z impurity transport in a low field, low-aspect ratio device. Short neon puffs were injected in beam heated, co-rotating L-mode (low confinement) discharges and the radial penetration of the successive neon charge states has been monitored with arrays of filtered ultrasoft x-ray diodes. Time-dependent modeling of the neon emissivity in several spectral bands indicates a core diffusion coefficient in the neoclassical range (<1 m2/s) in these strongly rotating plasmas, consistent with the low thermal ion transport inferred from the power balance analysis. By contrast, due to the large Larmor radii in NSTX turbulent diffusion would reach tens of m2/s if tokamak-like instability growth rates were assumed. The much lower experimental diffusivity then suggests that turbulent ion transport must be largely suppressed in the NSTX core. It is not yet clear in what measure this is due to the large E×B flow shear characteristic of beam heated NSTX discharges, or to the long wavelength instability growth rates being intrinsically low in the NSTX core, as recently predicted.
Recent advances on electromigration in very-large-scale-integration of interconnects
Authors: Tu K. N.
Published: October 2003

Today, the price of building a factory to produce submicron size electronic devices on 300 mm Si wafers is over billions of dollars. In processing a 300 mm Si wafer, over half of the production cost comes from fabricating the very-large-scale-integration of the interconnect metallization. The most serious and persistent reliability problem in interconnect metallization is electromigration. In the past 40 years, the microelectronic industry has used Al as the on-chip conductor. Due to miniaturization, however, a better conductor is needed in terms of resistance–capacitance delay, electromigration resistance, and cost of production. The industry has turned to Cu as the on-chip conductor, so the question of electromigration in Cu metallization must be examined. On the basis of what we have learned from the use of Al in devices, we review here what is current with respect to electromigration in Cu. In addition, the system of interconnects on an advanced device includes flip chip solder joints, which now tend to become weak links in the system due to, surprisingly, electromigration. In this review, we compare the electromigration in Al, Cu, and solder on the basis of the ratio of their melting point to the device operating temperature of 100 °C. Accordingly, grain boundary diffusion, surface diffusion, and lattice diffusion dominate, respectively, the electromigration in Al, Cu, and solder. In turn, the effects of microstructure, solute, and stress on electromigration in Al, Cu, and solder are different. The stress induced by electromigration in Cu/low-k interconnects will be a very serious issue since the low-k dielectric (with a value of k around 2) tends to be weak mechanically. In a multilevel interconnect, a electromigration force due to current crowding, acting normal to current flow, has been proposed to explain why many electromigration induced damages occur away from the high current density region. In mean-time-to-failure analysis, the time taken to nucleate a void is found to be much longer than the growth of the void in Al and solder interconnects. This is not the case for Cu interconnects for the nucleation of a void on a surface. On accelerated tests of electromigration in Cu interconnects, the results gathered above 300 °C will be misleading since the mass transport will have a large contribution of grain boundary diffusion, which is irrelevant to electromigration failure in real devices induced by surface diffusion.
Drift ballooning instabilities in tokamak edge plasmas
Authors: Hastie R. J. , Ramos J. J. , Porcelli F.
Published: October 2003

The linear stability of high-toroidal-number drift-ballooning modes in tokamaks is investigated with a model that includes resistive and viscous dissipation, and assumes the mode frequency to be comparable to both the sound and diamagnetic frequencies. The coupled effect of ion drift waves and electron drift-acoustic waves is shown to be important, resulting in destabilization over an intermediate range of toroidal mode numbers. The plasma parameters where the assumed orderings hold would be applicable to the edge conditions in present day tokamaks, so these instabilities might be related to the observed quasicoherent edge-localized fluctuations.
Ring-shaped exact Hopf solitons
Authors: Adam C. , Sánchez-Guillén J.
Published: October 2003

The existence of ring-like structures in exact Hopfion solutions is shown.
The carbon pentamer dication C52+: Toward thermochemical stability
Authors: Hogreve H. , Jalbout A. F.
Published: October 2003

Various computational ab-initio methods are employed to study the doubly-charged carbon system C52+. For its electronic ground state, equilibrium geometries are identified, and their stability against dissociation investigated. Multireference configuration-interaction results indicate a weakly bound but thermochemically stable dication.
Charge transport in micas: The kinetics of FeII/III electron transfer in the octahedral sheet
Authors: Rosso Kevin M. , Ilton Eugene S.
Published: October 2003

The two principal FeII/III electron exchange reactions underlying charge transport in the octahedral sheet of ideal end-member annite were modeled using a combination of ab initio calculations and Marcus electron transfer theory. A small polaron model was applied which yielded electron hopping activation energies that agree well with the limited available experimental data. A small ab initio cluster model successfully reproduced several important structural, energetic, and magnetic characteristics of the M1 and M2 Fe sites in the annite octahedral sheet. The cluster enabled calculation of the internal reorganization energy and electronic coupling matrix elements for the M2–M2 and M1–M2 electron transfer reactions. The M2–M2 electron transfer is symmetric with a predicted forward/reverse electron hopping rate of 106 s−1. The M1–M2 electron transfers are asymmetric due to the higher ionization potential by 0.46 eV of FeII in the M1 site. The electronic coupling matrix elements for these reactions are predicted to be small and of similar magnitude, suggesting the possibility that the coupling is essentially direction independent amongst hopping directions in the octahedral sheet. M1 Fe sites are predicted to be efficient electron traps and charge transport should occur by nearest-neighbor electron hops along the M2 Fe sublattice.
Response to “Comment on ‘Measurement of the ion drag force on falling dust particles and its relation to the void formation in complex (dusty) plasmas’ ” [Phys. Plasmas 10, 4579 (2003)]
Authors: Zafiu C. , Melzer A. , Piel A.
Published: October 2003

In this Response, it is shown that the use of the electron Debye length in the determination of the ion drag force is well justified. The claim of an incorrect analysis of our results is strongly refuted. The applicability of various ion drag models and the role of the shielding length of dust grains is discussed.
Tiling spaces are inverse limits
Authors: Sadun Lorenzo
Published: October 2003

Let M be an arbitrary Riemannian homogeneous space, and let Ω be a space of tilings of M, with finite local complexity (relative to some symmetry group Γ) and closed in the natural topology. Then Ω is the inverse limit of a sequence of compact finite-dimensional branched manifolds. The branched manifolds are (finite) unions of cells, constructed from the tiles themselves and the group Γ. This result extends previous results of Anderson and Putnam, of Ormes, Radin, and Sadun, of Bellissard, Benedetti, and Gambaudo, and of Gähler. In particular, the construction in this paper is a natural generalization of Gähler’s.
Preconditioned iterative minimization for linear-scaling electronic structure calculations
Authors: Mostofi Arash A. , Haynes Peter D. , Skylaris Chris-Kriton , Payne Mike C.
Published: October 2003

Linear-scaling electronic structure methods are essential for calculations on large systems. Some of these approaches use a systematic basis set, the completeness of which may be tuned with an adjustable parameter similar to the energy cut-off of plane-wave techniques. The search for the electronic ground state in such methods suffers from an ill-conditioning which is related to the kinetic contribution to the total energy and which results in unacceptably slow convergence. We present a general preconditioning scheme to overcome this ill-conditioning and implement it within our own first-principles linear-scaling density functional theory method. The scheme may be applied in either real space or reciprocal space with equal success. The rate of convergence is improved by an order of magnitude and is found to be almost independent of the size of the basis.
Exploring repulsive interactions in a model helical peptide: A parallel tempering Monte Carlo study
Authors: Ocasio Mayra , Maury-Evertsz Johnny R. , Pastrana-Rı́os Belinda , López Gustavo E.
Published: October 2003

By implementing the parallel-tempering algorithm to the canonical ensemble, the conformational changes of an isolated Ac–W(RAAAR)5A–NH2 model peptide were determined. The interparticle interactions were modeled using a minimalist potential, i.e., a beadlike model that uses harmonic oscillators to describe covalent interactions and modified Lennard-Jones potentials to model nonbonding interactions. In particular, the interactions between arginines are modeled by repulsive interactions, causing a stabilization of the alpha-helix structure at low temperatures. The conformational changes were identified by anomalies in the constant volume heat capacity as a function of temperature. Namely, the temperature at which the constant volume heat capacity reached a maximum in the transition region was associated with the temperature at which a conformational change occurred. The transitions were also characterized by computing the radius of gyration of the peptide and the most probable isomeric structure obtained at a given temperature. Three changes were observed at low temperatures and one at high temperature. The low temperature transitions were analogous to the peptide folding, whereas the high temperature transition was related to the peptide unfolding. The results obtained were compared with experimental data generated from isotope edited Fourier transform infrared spectroscopy and two-dimensional correlation analysis for a similar peptide containing salt bridge interactions.
Sterilization using a microwave-induced argon plasma system at atmospheric pressure
Authors: Park Bong Joo , Lee D. H. , Park J.-C. , Lee I.-S. , Lee K.-Y. , Hyun S. O. , Chun M.-S. , Chung K.-H.
Published: October 2003

The use of microwave plasma for sterilization is relatively new. The advantages of this method are the relatively low temperature, time-savings and its nontoxic nature, in contrast to traditional methods such as heat and gas treatment, and radiation. This study investigated the sterilization effects of microwave-induced argon plasma at atmospheric pressure on materials contaminated with various microorganisms, such as bacteria and fungi. A low-cost and reliable 2.45 GHz, waveguide-based applicator was designed to generate microwave plasma at atmospheric pressure. This system consisted of a 1 kW magnetron power supply, a WR-284 copper waveguide, an applicator including a tuning section, and a nozzle section. Six bacterial and fungal strains were used for the sterilization test. The results showed that regardless of the strain, all the bacteria used in this study were fully sterilized within 20 seconds and all the fungi were sterilized within 1 second. These results show that this sterilization method is easy to use, requires significantly less time than the other traditional methods and established plasma sterilization methods, and it is nontoxic. It can be used in the field of sterilization in medical and dental clinics as well as in laboratory settings.
Fast numerical calculation for crack modeling in eddy current testing of ferromagnetic materials
Authors: Huang Haoyu , Takagi Toshiyuki , Uchimoto Tetsuya
Published: October 2003

Eddy current testing (ECT) is a nondestructive testing method for metal materials. Numerical methods are applied to predict the ECT signals, to aid in the design of ECT probes, and to reconstruct crack shapes from their ECT signals. For the testing of nonferromagnetic materials, the high accuracy of some numerical simulation techniques has been demonstrated and several fast computational methods have been presented. However, the numerical calculation of electromagnetic fields in ferromagnetic materials remains a difficult and time-consuming task. Representing cracks in ferromagnetic materials with secondary electric and magnetic sources leads to a fast method for predicting ECT signals as presented in this article. The method developed here, that can be used to treat ferromagnetics, is an extension of the precomputed database approach based on the magnetic vector potential method. With the aid of precomputed databases, ECT signals of different cracks can be computed from changes in the secondary sources in a small region, without considering the geometries of the whole conductor. This results in fewer degrees of freedom than those of typical finite element approaches, and the method provides a forward simulator that is about 80 times faster than the conventional one without loss of accuracy, even in the case of ferromagnetic materials.
Threshold ion-pair production spectroscopy of HCl/DCl: Born–Oppenheimer breakdown in HCl and HCl+ and dynamics of photoion-pair formation
Authors: Hu Q. J. , Melville T. C. , Hepburn J. W.
Published: October 2003

Threshold ion-pair production spectroscopy (TIPPS) has been applied to two isotopomers, HCl and DCl. From the high-resolution TIPP spectra the ion-pair thresholds of the two molecules have been precisely measured. Combined with the known ionization energy of H(D) and the electron affinity of Cl, the difference between their bond dissociation energies is calculated, and therefore an experimental determination of the effect of Born–Oppenheimer breakdown on the dissociation limit of the ground state potential curve has been obtained. The difference in De for the two isotopomers was found to be: De(H–Cl)−De(D–Cl)=3.2±1.0 cm−1. The bond energy for HCl was in agreement with our previous determination, D0(H–Cl)=35748.2±0.8 cm−1. These results are compared to a recent study of Born–Oppenheimer breakdown in HCl by Coxon and Hajigeorgiou, where high resolution spectroscopic data was used to fit Born–Oppenheimer breakdown correction terms for the intramolecular potential function. The present study also measured the high resolution spectra for photoion-pair production for HCl and DCl in the threshold region for ion-pair production (∼86 nm). Although there is qualitative agreement between the current results and previous experimental and theoretical work, there are some important differences. The possible mechanism for ion-pair formation in HCl and DCl is discussed in light of these high resolution results.
Bounds on dissipation in magnetohydrodynamic Couette and Hartmann shear flows
Authors: Alexakis A. , Pétrélis F. , Morrison P. J. , Doering Charles R.
Published: October 2003

Shear flow with an applied cross-stream magnetic field is studied using dissipative incompressible magnetohydrodynamics. The study incorporates exact solutions, the energy stability method, and exact bounds on the total energy dissipation rate. Two physical configurations are examined: magnetic Couette flow and Hartmann flow, the latter being Poiseuille flow with the existence of a perpendicular magnetic field. Explicit expressions are derived for energy stability regions in the parameter space and these expressions are compared with numerically obtained results. For large enough Reynolds numbers the energy dissipation rate is shown to be bounded by a function of the magnetic Prandtl number. The bounds obtained on the dissipation rate are compared with experimental results.
Influence of vibrational anharmonicity and vacancies on the thermodynamic properties of rare gas crystals
Authors: Karasevskii A. I. , Holzapfel W. B.
Published: October 2003

A statistical method is used to calculate thermodynamic properties of Ar, Kr and Xe (isobaric and isochoric heat capacity, bulk modulus, thermal expansion coefficient, interatomic distances, Grüneisen parameter), and good agreement with experimental values is observed. It is shown that at high temperature, slightly above the melting point of the rare gas crystals, an instability of the crystalline state occurs. As the temperature approaches this instability, the isobaric heat capacity and the thermal expansion coefficient show strong increases similar to the experimentally observed anomalies.
Barrier softening near the onset of nonactivated transport in supercooled liquids: Implications for establishing detailed connection between thermodynamic and kinetic anomalies in supercooled liquids
Authors: Lubchenko Vassiliy , Wolynes Peter G.
Published: October 2003

According to the random first-order transition (RFOT) theory of glasses, the barriers for activated dynamics in supercooled liquids vanish as the temperature of a viscous liquid approaches the dynamical transition temperature from below. This occurs due to a decrease of the surface tension between local metastable molecular arrangements much like at a spinodal. The dynamical transition thus represents a crossover from the low T activated behavior to a collisional transport regime at high T. This barrier softening explains the deviation of the relaxation times, as a function of temperature, from the simple log τ ∝1/sc dependence at the high viscosity to a mode–mode coupling dominated result at lower viscosity. By calculating the barrier softening effects, the RFOT theory provides a unified microscopic way to interpret structural relaxation data for many distinct classes of structural glass formers over the measured temperature range. The theory also provides an unambiguous procedure to determine the size of dynamically cooperative regions in the presence of barrier renormalization effects using the experimental temperature dependence of the relaxation times and the configurational entropy data. We use the RFOT theory framework to discuss data for tri-naphthyl benzene, salol, propanol, and silica as representative systems.
A study on diffusion of H atoms in solid parahydrogen
Authors: Fushitani M. , Momose T.
Published: October 2003

Diffusion of hydrogen atoms in solid parahydrogen was investigated using high-resolution infrared spectroscopy. Hydrogen atoms were produced as by-products of a photoinduced reaction of nitric oxides embedded in solid parahydrogen. The diffusion of the hydrogen atoms is mainly terminated by the reaction H+NO→HNO. The diffusion rate determined from the increase of the intensity of rotation–vibration transitions of HNO molecules was found to be two orders of magnitude larger than that determined by the self-recombination reaction of H+H→H2 in pure parahydrogen crystals.
Tunneling dynamics in cryocrystals: localization and delocalization
Authors: Storchak V. G.
Published: October 2003

The phenomenon of quantum diffusion of muonium in cryocrystals with rotational degrees of freedom is discussed. The quantum tunneling dynamics and electron transport are considered with the effects of disorder taken into account.
Exciton relaxation in KBr and CaF2 at low temperature: molecular dynamics study
Authors: Song K. S.
Published: October 2003

The results of a molecular-dynamics simulation of exciton relaxation in several ionic crystals at low temperature are reported. Both the lowest energy spin triplet and some of the low lying hole excited states are allowed to relax for the purpose of studying the radiation defect formation channels. The previously used semi-classical program has been modified to implement the solution of Newton’s equations with a 0.48 fs time step. The relaxation of an exciton localized on a single site (as Br0+e or F0+e, respectively) is studied at 10 K in KBr and in CaF2. In KBr the triplet self-trapped exciton leads to separated Frenkel pair in about 1–2 ps, followed by slow oscillation of the hole center along the (110) axis. The defect pair created is separated by about 10 Å (third-nearest neighbor). In CaF2, the relaxation reaches the geometry of the nearest Frenkel pair, with the hole center oriented along a (111) axis in about 0.3 ps at 10 K. However, at 80 K the system can undergo further relaxation into slightly more distant defect pairs. When the hole is excited to higher levels, the molecular bond of the hole center undergoes violent oscillations. In KBr, the hole center is found to form in the second-nearest-neighbor position within about 0.5 ps. The species formed are, however, different from the well-known primary radiation defects. A similar process is also observed in CaF2.
Crystalline and amorphous polymeric solid nitrogen
Authors: Yakub L. N.
Published: October 2003

The structure and thermodynamic functions of solid high-density nonmolecular nitrogen in the crystalline and amorphous phases are studied by a Monte Carlo simulation technique on the basis of the potential model proposed earlier for the cubic gauche polymeric crystal. The solid amorphous state was created by fast melting followed by instantaneous quenching of the crystalline structure. The computed atom–atom distribution functions in such solids are characteristic for amorphous structure. The simulation also reveals negativity of the thermal expansion coefficient of the amorphous solid at high density and low temperatures, as was previously found to be the case in the cubic gauche nonmolecular nitrogen crystal. Analysis of the force model shows specific anharmonicity characteristics of the crystalline vibrations responsible for this effect.
The contribution of tunneling to the diffusion of protons and deuterons in rare gas solids
Authors: Beyer M. K. , Bondybey V. E. , Savchenko E. V.
Published: October 2003

The stability and diffusion of protons and deuterons in rare gas matrices are reexamined. These are known to be stabilized in rare gas matrices in the form of linear, centrosymmetric Rg2H+ cations. The elementary step in their diffusion, displacement from one Rg–Rg bond to a neighboring one, can be modeled as an isomerization of the triangular Rg3H+ cation. Using an analytic approximation for the thermally averaged transmission coefficients for tunneling through and reflection by a truncated parabolic potential barrier [R. T. Skodje and D. G. Truhlar, J. Phys. Chem. 85, 624 (1981)], we calculate the rate constants for this elementary diffusion step. The calculated rate constants are consistent with all experimental observations and confirm that tunneling makes the dominant contribution to the diffusion of protons and deuterons in rare gas solids. Deuteration reduces the tunneling rates by 5 to 8 orders of magnitude, which agrees with the observation that D+ in rare gas solids is signficantly more stable than H+.
Molecular probing of low-temperature incommensurate phases
Authors: Kikas J. , Suisalu A. , Laisaar A. , Kuznetsov An.
Published: October 2003

Two-dimensional (2D) excitation–emission spectra of biphenyl doped with free-base chlorin are measured at 5 K under various pressures up to 350 MPa. Besides the features related to zero-phonon lines and their phonon sidebands, a broad spectral band amounting to 80% of the total intensity at 5 K is revealed in the 2D spectra. The inhomogeneous distribution function obtained shows drastic changes with increasing pressure—the triplet structure observable at normal pressure in the incommensurate phase ICIII of biphenyl converges to a singlet in the high-pressure commensurate phase CI. These observations are assumed to reflect a relaxation specific to incommensurate phases after optical excitation of the probe molecules and their interaction with the incommensurate modulation wave.
Molecular structures of thymidine isomers isolated in low-temperature inert matrices
Authors: Ivanov A. Yu. , Sheina G. G. , Krasnokutski S. A.
Published: October 2003

The Fourier transform infrared spectra of 2′-deoxyribonucleoside–thymidine (dT) in low-temperature Ar matrices are obtained in the range 4000–1300 cm−1. It is determined that anti-conformers of thymidine are dominant. The ribose rings of the main anti-conformers dT_a0, dT_a1 are in the C2′-endo conformation, but the ribose rings of minor anti-conformers dT_a2, dT_a3 have the C3′-endo conformation, stabilized by intramolecular hydrogen bonds O3′H…O5′ and O5′H…O3′, respectively. The main syn-conformer dT_s2 is stabilized by the intramolecular hydrogen bond O5′H…O2 and has C2′-endo conformation of the ribose ring.
Molecular dynamics study of the weakly solvent dependent relaxation dynamics following chlorine dioxide photoexcitation
Authors: Brooksby Craig , Prezhdo Oleg V. , Reid Philip J.
Published: October 2003

The solvation dynamics following photoexcitation of chlorine dioxide (OClO) in different solvents are investigated by classical molecular dynamics. Following previous work on the aqueous response to OClO photoexcitation [J. Chem. Phys. 118, 4563 (2003)], the present study considers the response of chloroform and cyclohexane; these three liquids present unique solvent environments that differ significantly in both polarity and structure. The study is designed to ascertain the origin of the solvent-invariant homogeneous linewidth associated with OClO photoexcitation and to confirm, at the molecular level, whether the relaxation dynamics are similar across dissimilar solvents due to chance or a common relaxation origin. The results obtained here are used to predict the time scale of solvent-induced optical dephasing, and excellent agreement with experiment is observed for all solvents. Analysis demonstrates that the solvation dynamics of OClO are dominated by short-ranged mechanical solute–solvent interactions regardless of the identity and electrostatic properties of the solvent. Low-frequency translational motions dominate the coupling spectrum, and virtually no contribution to energy gap relaxation is achieved through intramolecular solvent motions. The invariant homogeneous linewidth is attributed to the similarity in the primary response of all solvents to OClO photoexcitation.
Reorientation and vibrational energy relaxation of pseudohalide ions confined in reverse micelle water pools
Authors: Zhong Q. , Baronavski A. P. , Owrutsky J. C.
Published: October 2003

Reorientation and vibrational energy relaxation times have been measured by ultrafast transient polarization IR spectroscopy for the antisymmetric stretching band in the 2000–2200 cm−1 region of pseudohalide ions, N3−, NCO−, and NCS−, confined in nanosize water pools of reverse micelles (RMs). The RMs are composed of nonionic nonylphenyl poly-oxyethylene surfactant in cyclohexane. Vibrational energy relaxation times (T1) of the NCO− and NCS− ions are about three times longer in small RMs compared to bulk water, similar to our earlier results on the N3− ion [J. Chem. Phys. 118, 7074 (2003)]. The longer T1 times are attributed to the reduced interaction between the ions and water molecules due to confinement effects and hydration of the surfactant headgroups by water molecules. Reorientation times (TR) of the N3− and NCS− ions are found to be more than one order of magnitude longer in small RMs than in bulk H2O. The observed longer TR times support the notion that water molecules inside RMs have very restricted mobility. As the water pool becomes larger with increasing water content, the interior water is less affected by the interface and bulk water properties reappear, leading to shorter T1 and TR times.