bluuebunny/crossref_metadata_2025 huggingface dataset:
Costs and benefits of multidrug, multidose antiretroviral therapy for prevention of mother‐to‐child transmission of HIV in the Dominican Republic
Authors: Schmidt Nicole C. , Roman‐Pouriet José , Fernandez Aracelis D. , Beck‐Sagué Consuelo M. , Leonardo‐Guerrero José , Nicholas Stephen W.
Published: December 2011

Objective

To investigate whether costs of multidose antiretroviral regimens (MD‐ARVs), including highly active antiretroviral therapy (HAART), for prevention of mother‐to‐child transmission (PMTCT) of HIV might be offset by savings gained from treating fewer perinatally acquired infections.

Methods

Rates of MTCT reported in the Dominican Republic among mother‐infant pairs treated with single‐dose nevirapine (SD‐NVP; n = 39) and MD‐ARVs (n = 91) for PMTCT were compared. Annual births to women infected with HIV were estimated from seroprevalence studies. Antiretroviral costs for both PMTCT and for HAART during the first 2 years of life (in cases of perinatal infection) were based on 2008 low‐income country price estimates.

Results

Rates of MTCT were 3.3% and 15.4% for the MD‐ARV and SD‐NVP groups, respectively (P= 0.02). Assuming that 5775 of 231 000 annual births (2.5%) were to HIV‐positive women, it was estimated that 191 perinatally acquired infections would occur using MD‐ARVs and 889 using SD‐NVP. High costs of maternal MD‐ARVs (HAART, US$914,760 versus SD‐NVP, $1155) would be offset by lower 2‐year HAART costs ($250,344 versus $1,168,272 for infants in the SD‐NVP group) for the lower number of children with prenatally acquired infection (191 versus 889) associated with the use of MD‐ARVs for PMTCT (net national saving $3168).

Conclusion

Despite the high costs, use of MD‐ARVs, such as HAART, for PMTCT offer societal savings because fewer perinatally acquired infections are anticipated to require treatment.
A Cost‐Effectiveness Analysis of Screening Methods for Dysphagia After Stroke
Authors: Wilson Richard D. , Howe Evan C.
Published: December 2011

Objective

To provide a cost‐effectiveness analysis of dysphagia screening in the acute poststroke period with use of a videofluoroscopic swallowing study, a clinical bedside swallowing evaluation, or a combined approach.

Design

Decision‐analysis model.

Methods

A decision‐analysis model was used with information derived from multiple data sources, including meta‐analyses and other relevant clinical studies. Univariate and probabilistic sensitivity analyses were performed.

Main Outcome Measures

The analysis assessed direct medical costs of pneumonia. Strategies were compared on the basis of an incremental cost‐effectiveness analysis, with effectiveness measured in quality‐adjusted life‐years.

Results

The strategy of having each patient undergo a videofluoroscopic swallowing study for dysphagia was more effective and less costly than the strategies of clinical bedside swallowing evaluation alone or a combined approach. The model was most influenced by the reduction in the risk of pneumonia attributable to the treatment of mild/moderate and severe dysphagia, the effectiveness of treatment with clinical bedside swallowing evaluation, the baseline probability of pneumonia, and the cost of a videofluoroscopic swallowing study.

Conclusions

A videofluoroscopic swallowing study is cost‐effective and often saves costs compared with a clinical bedside swallowing evaluation alone or a combined approach. Research aimed at improving the understanding of the effectiveness of treatment for dysphagia in the prevention of aspiration pneumonia and resulting mortality would improve the model.
Glatiramer acetate elevates cell production in the mature retinal pigment epithelium
Authors: SHAHABI GOLNAZ , JEFFERY GLEN
Published: December 2011

The retinal-pigmented epithelium (RPE) is critical for visual function. Throughout life, central RPE cells are lost but replenished by peripheral cell production. Glatiramer acetate increases neuronal production in mature brains and is thought to erode age-related deposits in the human retina that are risk factors for macular degeneration. Here, we ask whether this agent also elevates RPE production in mature rat eyes. If so, it may be used to replenish these cells in damaged eyes. Glatiramer acetate was given systemically for 14 days combined with Bromodeoxyuridine (BrdU) to mark cell division. One eye was then processed for the cell cycle marker Ki67 and the other for BrdU. Glatiramer acetate significantly elevated the number of RPE cells in the cell cycle, with more labeled with Ki67. There were also significantly more BrdU-labeled cells over the 14 days, confirming that some cells divided. However, while Ki67 positive cell numbers increased by approximately 100% following examination at one time point, BrdU cell numbers increased by only 3% when averaged per day. Hence, glatiramer acetate induces cells to proliferate, but many may fail either to complete division or to survive. This may have long-term consequences for this tissue.
Residual abilities in age-related macular degeneration to process spatial frequencies during natural scene categorization
Authors: MUSEL BENOIT , HERA RUXANDRA , CHOKRON SYLVIE , ALLEYSSON DAVID , CHIQUET CHRISTOPHE , ROMANET JEAN-PAUL , GUYADER NATHALIE , PEYRIN CAROLE
Published: December 2011

Age-related macular degeneration (AMD) is characterized by a central vision loss. We explored the relationship between the retinal lesions in AMD patients and the processing of spatial frequencies in natural scene categorization. Since the lesion on the retina is central, we expected preservation of low spatial frequency (LSF) processing and the impairment of high spatial frequency (HSF) processing. We conducted two experiments that differed in the set of scene stimuli used and their exposure duration. Twelve AMD patients and 12 healthy age-matched participants in Experiment 1 and 10 different AMD patients and 10 healthy age-matched participants in Experiment 2 performed categorization tasks of natural scenes (Indoors vs. Outdoors) filtered in LSF and HSF. Experiment 1 revealed that AMD patients made more no-responses to categorize HSF than LSF scenes, irrespective of the scene category. In addition, AMD patients had longer reaction times to categorize HSF than LSF scenes only for indoors. Healthy participants’ performance was not differentially affected by spatial frequency content of the scenes. In Experiment 2, AMD patients demonstrated the same pattern of errors as in Experiment 1. Furthermore, AMD patients had longer reaction times to categorize HSF than LSF scenes, irrespective of the scene category. Again, spatial frequency processing was equivalent for healthy participants. The present findings point to a specific deficit in the processing of HSF information contained in photographs of natural scenes in AMD patients. The processing of LSF information is relatively preserved. Moreover, the fact that the deficit is more important when categorizing HSF indoors, may lead to new perspectives for rehabilitation procedures in AMD.
Origin of localized fast mantle flow velocity in numerical models of subduction
Authors: Billen Magali I. , Jadamec Margarete
Published: December 2011

The origin of localized fast mantle flow near subduction zones found in regional (Jadamec and Billen, 2010, 2012) and global (Stadler et al., 2010; Alisic et al., 2010) numerical models using non‐Newtonian rheology is explored using 3D models with simple geometry. Two suites of models, using both a free slab and a slab attached to a lithospheric layer, are presented to determine (1) the origin of high magnitudes of mantle flow (>50 cm/yr) and (2) focusing of flow within the mantle wedge, with mantle wedge velocities up to two times higher than slab sinking velocities. The rheology in the models is either Newtonian with a prescribed low viscosity wedge (LVW) or non‐Newtonian wherein low viscosity regions form in response to high stress surrounding the sinking slab. The results show that there are two aspects of the models that lead to localized fast velocities: reduction in the mantle viscosity surrounding the sinking slab leads to faster overall flow rates induced by the negative buoyancy of the sinking slab; and geometric effects that are caused by lateral variations in viscosity, including retrograde pivoting motion of the slab.
Understanding target‐like signals in coastal altimetry: Experimentation of a tomographic imaging technique
Authors: Scozzari A. , Gómez‐Enri J. , Vignudelli S. , Soldovieri F.
Published: December 2011

Usage and availability of Sea Surface Height (SSH) information from satellite radar altimeters undergo known limitations in the coastal zone, where such data are of great importance and usefulness. In fact, coastal regions are a crucial zone to be investigated and monitored, due to the high impact that sea level and circulation changes have on the environmental security and the related economic and societal issues. It is known that radar returns from the sea surface sometimes present target‐like echoes (“bright targets”), especially in correspondence of particular features of the coastal zone, thus entailing a potential interference with the measurement of SSH. Such spiky echoes generate hyperbolic patterns in the radargram domain, which the recent literature has tentatively explained as resulting from flat water areas in the proximity of the coastline, but the physical mechanism that underlies their occurrence still remains unclear. To probe further into this aspect, this work describes a novel application of a microwave tomographic reconstruction approach, applied to the Envisat RA‐2 signals, tested on selected passes over the Pianosa Island (a 10 km2 island in the NW Mediterranean). The aim of this study is the analytical identification of the signal contamination sources in terms of location and extension of their associated electromagnetic anomaly. The obtained results confirm the idea that the origin of such signatures is connected with particular conditions of the sea surface, which are easier to be found in the proximity of coastal closed areas such as gulfs, but presumably not limited to such circumstances.
The role of rheology and slab shape on rapid mantle flow: Three‐dimensional numerical models of the Alaska slab edge
Authors: Jadamec M. A. , Billen M. I.
Published: December 2011

Away from subduction zones, the surface motion of oceanic plates is well correlated with mantle flow direction, as inferred from seismic anisotropy. However, this correlation breaks down near subduction zones, where shear wave splitting studies suggest the mantle flow direction is spatially variable and commonly non‐parallel to plate motions. This implies local decoupling of mantle flow from surface plate motions, yet the magnitude of this decoupling is poorly constrained. We use 3D numerical models of the eastern Alaska subduction‐transform plate boundary system to further explore this decoupling, in terms of both direction and magnitude. Specifically, we investigate the role of the slab geometry and rheology on the mantle flow velocity at a slab edge. The subducting plate geometry is based on Wadati‐Benioff zone seismicity and tomography, and the 3D thermal structure for both the subducting and overriding plates, is constrained by geologic and geophysical observations. In models using the composite viscosity, a laterally variable mantle viscosity emerges as a consequence of the lateral variations in the mantle flow and strain rate. Spatially variable mantle velocity magnitudes are predicted, with localized fast velocities (greater than 80 cm/yr) close to the slab where the negative buoyancy of the slab drives the flow. The same models produce surface plate motions of less than 10 cm/yr, comparable to observed plate motions. These results show a power law rheology, i.e., one that includes the effects of the dislocation creep deformation mechanism, can explain both observations of seismic anisotropy and decoupling of mantle flow from surface motion.
Co-evolution with lytic phage selects for the mucoid phenotype of Pseudomonas fluorescens SBW25
Authors: Scanlan Pauline Deirdre , Buckling Angus
Published: December 2011

The effects of co-evolution with lytic phage on bacterial virulence-related traits are largely unknown. In this study we investigate the incidence of the mucoid phenotype of the bacterium Pseudomonas fluorescens SBW25 in response to co-evolution with the lytic phage phi2 (φ2). The mucoid phenotype of Pseudomonas spp. is due to overproduction of alginate and is a considerable virulence factor contributing to the intractability of infections most notably in cystic fibrosis (CF) lung, but also in pathogenic infections of plants. Our data show that this phenotype can evolve as an adaptive response to phage predation and is favoured under specific abiotic conditions, in particular a homogenous spatial structure and a high rate of nutrient replacement. The mucoid phenotype remains partially sensitive to phage infection, which facilitates ‘apparent competition’ with phage-sensitive competitors, partially offsetting the costs of alginate production. Although P. fluorescens SBW25 is not a pathogen, several key characteristics typical of Pseudomonas aeruginosa clinical isolates from CF lung were noted, including loss of motility on mucoid conversion and a high rate of spontaneous reversion to the wild-type phenotype. Although the genetic mechanisms of this phenotype remain unknown, they do not include mutations at many of the commonly reported loci implicated in mucoid conversion, including mucA and algU. These data not only further our understanding of the potential role phage have in the ecology and evolution of bacteria virulence in both natural and clinical settings, but also highlight the need to consider both biotic and abiotic variables if bacteriophages are to be used therapeutically.
Geographical and chronological origin and evolution of Hepatitis C Virus.
Authors: revikumar amjesh , S. Nair Achuthsankar , V.S. Sugunan
Published: December 2011

Hepatitis C Virus (HCV) infection is a major health problem that leads to cirrhosis and hepatocellular carcinoma. World over, more than 270-300 million people are estimated to be infected with the virus. HCV is a positive sense single stranded RNA virus and replicates within the cytoplasm of the hepatocyte using its own RNA dependent RNA polymerase (RdRp). RdRp does not have proof reading capacity, and hence generates mutants of the virus, resulting in a chronic infection, which ultimately ends in hepatocellular carcinoma. Such mutations have given rise to several genotypes, subtypes, strains and variants with significant difference in disease outcomes. The mutation rate varies among genotypes, subtypes, strains or even in different sites of the genome. Yet, the extent of heterogeneity is usually moderate, so that estimates of the time of divergence can be computed. The evolution of variants seems to be influenced by the genetic make-up and the immune response of the host and has geographical significance. Here we used phylogenetic analysis and Computational molecular dating techniques to conclude that the ancestral genotype is 7a and that it originated in Canada 363 years ago. Molecular dating was based on the fact that the rate of mutation across all evolutionary lineages is constant over time. Surprisingly, our analyses show that genotype 1d isolated from Canada5 is the most recent with an evolutionary date of just 33 years. It is evident that HCV is still an emerging virus and demographical parameters seem to have a very strong influence in its evolution. We believe that this emphasises the need for developing drugs that are customised to act against strains that evolve and become geographically endemic.
A snake of a different color: physiological color change in Arizona black rattlesnakes
Authors: Amarello Melissa , Smith Jeffrey
Published: December 2011

Coloration may serve a variety of behavioral (e.g., crypsis, communication) and physiological (e.g., thermoregulation, protection) functions for terrestrial ectotherms. However, optimal coloration for a given function may vary over environments (spatial or temporal) or conflict with other functions. Physiological color change (rapid change due to movement of pigment granules within chromatophores) may be an adaptation to resolve conflicting selective pressures on coloration. The proximate factors related to physiological color change are well known in many animals, but few studies have investigated the ecological or evolutionary implications of this behavior. Here, we present alternative hypotheses for physiological color change and discuss biotic and abiotic factors that may have led to the maintenance and/or loss of this behavior among populations of Arizona black rattlesnakes (Crotalus cerberus). We discuss what is known about this behavior and propose to investigate the function and evolution of coloration and color change in C. cerberus.
Transcriptional control of glyoxalase 1 by Nrf2 provides a stress-responsive defence against dicarbonyl glycation
Authors: Xue Mingzhan , Rabbani Naila , Momiji Hiroshi , Imbasi Precious , Anwar M. Maqsud , Kitteringham Neil , Park B. Kevin , Souma Tomokazu , Moriguchi Takashi , Yamamoto Masayuki , Thornalley Paul J.
Published: December 2011

Abnormal cellular accumulation of the dicarbonyl metabolite MG (methylglyoxal) occurs on exposure to high glucose concentrations, inflammation, cell aging and senescence. It is associated with increased MG-adduct content of protein and DNA linked to increased DNA strand breaks and mutagenesis, mitochondrial dysfunction and ROS (reactive oxygen species) formation and cell detachment from the extracellular matrix. MG-mediated damage is countered by glutathione-dependent metabolism by Glo1 (glyoxalase 1). It is not known, however, whether Glo1 has stress-responsive up-regulation to counter periods of high MG concentration or dicarbonyl stress. We identified a functional ARE (antioxidant-response element) in the 5′-untranslated region of exon 1 of the mammalian Glo1 gene. Transcription factor Nrf2 (nuclear factor-erythroid 2 p45 subunit-related factor 2) binds to this ARE, increasing basal and inducible expression of Glo1. Activators of Nrf2 induced increased Glo1 mRNA, protein and activity. Increased expression of Glo1 decreased cellular and extracellular concentrations of MG, MG-derived protein adducts, mutagenesis and cell detachment. Hepatic, brain, heart, kidney and lung Glo1 mRNA and protein were decreased in Nrf2−/− mice, and urinary excretion of MG protein and nucleotide adducts were increased approximately 2-fold. We conclude that dicarbonyl stress is countered by up-regulation of Glo1 in the Nrf2 stress-responsive system, protecting protein and DNA from increased damage and preserving cell function.
Bone Maturity and Thyroidal Status at Birth: Role of the Ultrasonographic Evaluation of the Distal Femoral Epiphysis
Authors: Savino A. , Carinci S. , Bucci I. , Sabatino G. , Chiarelli F. , Tumini S.
Published: December 2011

Purpose: Thyroidal hormones are important for bone development, and ultrasonographic (US) evaluation of the distal femoral epiphysis (DFE) has recently been suggested as a new method for the assessment of skeletal maturity in infants. A delayed bone maturation, expressed by a smaller or absent DFE nucleus (in terms of DFE surface area, sum of the epiphyseal diameters, or DFE height and acetabular size), has been largely demonstrated in diagnosed hypothyroid infants, while no data analyze the role and meaning of the DFE dimensions (in terms of volume) in newborn before knowledge of the congenital neonatal screening results. The aims of the present study were to ultrasonographically evaluate the volume of DFE in newborns, and to determine whether it has any predictive role for the thyroidal status at birth.

Materials and Methods: 238 newborns (M/F: 121 /117) were evaluated. The gestational age, body weight and length at birth were registered. Neonatal screening for congenital hypothyroidism (CH), based on TSH levels on blood spot, was performed in all on the 3 rd day of life. The DFE volume was ultrasonographically evaluated, taking into account the three diameters of the DFE nucleus, within 48 hours of birth.

Results: No newborn was found to have CH on neonatal screening. The DFE volume ranged between 0.00 cm and 0.61 cm (mean 0.14 ± 0.10 cm, median 0.13 cm). The DFE volume did not differ between males and females, while it was significantly greater in at term babies than in preterm babies. No differences in TSH values at screening were noted among the groups. The DFE volume was significantly related to gestational age, birth weight and length. A significant relationship was found between the DFE volume and TSH concentrations at screening.

Conclusion: US evaluation of DFE volume provides a simple method for assessing bone maturity at birth, which is related to gestational age, body weight and length at birth. Nonetheless, it has any predictive role for thyroidal status at birth, being not related to TSH levels on neonatal screening for CH.
Differentiation Between Phyllodes Tumor and Fibroadenoma Using Real-Time Elastography
Authors: Adamietz B. , Kahmann L. , Fasching P. , Schulz-Wendtland R. , Uder M. , Beckmann M. , Meier-Meitinger M.
Published: December 2011

Purpose: Phyllodes tumors (PT) are a rare entity accounting for less than 1 % of all breast lesions. They have a malignancy rate of 25 – 30 %. Differentiation from benign fibroadenomas is difficult using ultrasound, mammogram and MRI. The elastic characteristics of both tumors were examined using real-time elastography (RTE) to find specific patterns that make differentiation possible.

Materials and Methods: From February 2007 to May 2009, a total of 620 women were examined by RTE. Histological diagnosis was achieved using core needle biopsy. 123 of the lesions were fibroadenomas, 8 were phyllodes tumors. All patients underwent mammography and ultrasound followed by RTE. Sonography was performed by Acuson Antares, Premium Edition® (Siemens, Erlangen, Germany) with a 7 and 10 MHz transducer.

Results: All phyllodes tumors had a similar elastic pattern with an elastic center and inelastic outer limits, referred to as the “ring sign”. It was found in 5 % of all fibroadenomas.

Conclusion: RTE provides a specific elastic pattern, which is sufficient for differentiating between a fibroadenoma and a phyllodes tumor. Therefore, the detection of the most suspicious lesion in women with the coexistence of multiple fibroadenomas and phyllodes tumors seems easier.
Minimally Invasive versus Open Cervical Foraminotomy: A Systematic Review
Authors: Clark Jeffrey G. , Abdullah Kalil G. , Steinmetz Michael P. , Benzel Edward C. , Mroz Thomas E.
Published: December 2011

Posterior cervical laminoforaminotomy is an effective treatment for cervical radiculopathy due to disc herniations or spondylosis. Over the last decade, minimally invasive (i.e., percutaneous) procedures have become increasingly popular due to a smaller incision size and presumed benefits in postoperative outcomes. We performed a systematic review of the literature and identified studies of open or percutaneous laminoforaminotomy that reported one or more perioperative outcomes. Of 162 publications found by our initial screening, 19 were included in the final analysis. Summative results indicate that patients undergoing percutaneous cervical laminoforaminotomy have lower blood loss by 120.7 mL (open: 173.5 mL, percutaneous: 52.8 mL, n = 670), a shorter surgical time by 50.0 minutes (open: 108.3 minutes, percutaneous: 58.3 minutes, n = 882), less inpatient analgesic use by 25.1 Eq (open: 27.6 Eq, percutaneous: 2.5 Eq, n = 356), and a shorter hospital stay by 2.2 days (open: 3.2 days, percutaneous: 1.0 days, n = 1472), compared with patients undergoing open procedures. However, the heterogeneous nature of published data calls into question the reliability of these summative results. Further structured trials should be conducted to better characterize the risks and benefits of percutaneous laminoforaminotomy.
Primary Cerebellar Tuberculoma in Arnold-Chiari Malformation Mimicking Posterior Cranial Fossa Tumor: the First Report
Authors: Nabiuni Mohsen , Sarvarian Saeedeh
Published: December 2011

Chiari malformations are a congenital heterogeneous group of disorders characterized by anatomic anomalies of the cerebellum, brain stem, and craniocervical junction associated with downward displacement of the cerebellum, alone or with lower medulla, into the cervical spine canal. The patient was a 23-year-old woman, a known case of Arnold-Chiari malformation with peripheral neuropathy and muscular atrophy, who presented with headache, drowsiness, decreased vision, and severe gait dysfunction lasting for several years. Brain magnetic resonance imaging confirmed a hypointense signal mass in the left hemisphere of the cerebellum causing mass effects on the fourth ventricle, which shifted it, accompanied with dilation of third and lateral ventricles.
Hybrid density functional/molecular mechanics studies on activated adsorption of oxygen on zeolite supported gold monomer
Authors: Baishya Subhi , Deka Ramesh C.
Published: December 2011

Density functional theory calculations on oxygen adsorption over gas phase and faujasite supported Au monomer has been studied using hybrid quantum mechanics/molecular mechanics method, surface integrated molecular orbital molecular mechanics implemented in GAMESS package. Three different oxidation states of Au (0, +1, +3) and three different adsorption modes viz., top, bridge, and dissociative adsorption of oxygen have been considered in our calculations. Redshift in the νO–O value from that in gas phase O2 indicates activation of O2 upon adsorption over faujasite supported gold monomer. The activation of O2 is an important step in the catalytic oxidation of CO. The presence of adsorbed O2 increases the interaction of the Au monomer with the faujasite support. In faujasite supported cationic Au monomer, O2 preferably remains bridge bonded to Au rather than being dissociated.
Scaling percolation in thin porous layers
Authors: Médici E. F. , Allen J. S.
Published: December 2011

Percolation in porous media is a complex process that depends on the flow rate, material, and fluids properties as well as the boundary conditions. Traditional methods of characterizing percolation rely upon visual observation of a flow pattern or a pressure-saturation relation valid only in the limit of no flow. In this paper, the dynamics of fluid percolation in thin porous media is approached through a new scaling. This new scaling in conjunction with the capillary number and the viscosity ratio has resulted in a linear non-dimensional correlation of the percolation pressure and wetted area in time unique to each porous media. The effect of different percolation flow patterns on the dynamic pressure-saturation relation can be condensed into a linear correlation using this scaling. The general trend and implications of the scaling have been analyzed using an analytical model of a fluid percolating between two parallel plates and by experimental testing on thin porous media. Cathode porous transport layers (PTLs), also known as gas diffusion layers, of a proton exchange membrane (PEM) fuel cell having different morphological and wetting properties were tested under drainage conditions. Images of the fluid percolation evolution and the percolation pressure in the PTLs were simultaneously recorded. A unique linear correlation is obtained for each type of PTL samples using the new scaling. The correlation derived from this new scaling can be used to quantitatively characterize porous media with respect to percolation. While the characterization method discussed herein was developed for the study of porous materials used in PEM fuel cells, the method and scaling are applicable to any porous media.
Unambiguous optimization of effective potentials in finite basis sets
Authors: Jacob Christoph R.
Published: December 2011

The optimization of effective potentials is of interest in density-functional theory (DFT) in two closely related contexts. First, the evaluation of the functional derivative of orbital-dependent exchange-correlation functionals requires the application of optimized effective potential methods. Second, the optimization of the effective local potential that yields a given electron density is important both for the development of improved approximate functionals and for the practical application of embedding schemes based on DFT. However, in all cases this optimization turns into an ill-posed problem if a finite basis set is introduced for the Kohn–Sham orbitals. So far, this problem has not been solved satisfactorily. Here, a new approach to overcome the ill-posed nature of such finite-basis set methods is presented for the optimization of the effective local potential that yields a given electron density. This new scheme can be applied with orbital basis sets of reasonable size and makes it possible to vary the basis sets for the orbitals and for the potential independently, while providing an unambiguous potential that systematically approaches the numerical reference.
Iron and nitrogen self-diffusion in non-magnetic iron nitrides
Authors: Gupta Mukul , Tayal Akhil , Gupta Ajay , Gupta Rachana , Stahn J. , Horisberger M. , Wildes A.
Published: December 2011

The self-diffusion of iron and nitrogen is measured in nm range non-magnetic iron nitride thin films. Two non-magnetic iron nitrides, Fe2.23N and FeN, were studied using neutron reflectivity. Neutron reflectivity with a depth resolution in the sub-nm range has a different scattering cross section for isotopes, providing a unique opportunity to measure very small diffusivities. The isotope heterostructure in thin film multilayers [Fe-N/57Fe-N]10 and [Fe-N/Fe-15N]10 were prepared using magnetron sputtering. It was observed that nitrogen diffuses slower than iron although the atomic size of iron is larger than that of nitrogen. It was found that a significantly larger group of N atoms participates in the diffusion process than of Fe, making N diffusion slower than that of Fe.
Two-domain formation during the epitaxial growth of GaN (0001) on c-plane Al2O3 (0001) by high power impulse magnetron sputtering
Authors: Junaid M. , Lundin D. , Palisaitis J. , Hsiao C.-L. , Darakchieva V. , Jensen J. , Persson P. O. Å. , Sandström P. , Lai W.-J. , Chen L.-C. , Chen K.-H. , Helmersson U. , Hultman L. , Birch J.
Published: December 2011

We study the effect of high power pulses in reactive magnetron sputter epitaxy on the structural properties of GaN (0001) thin films grown directly on Al2O3 (0001) substrates. The epilayers are grown by sputtering from a liquid Ga target, using a high power impulse magnetron sputtering power supply in a mixed N2/Ar discharge. X-ray diffraction, micro-Raman, micro-photoluminescence, and transmission electron microscopy investigations show the formation of two distinct types of domains. One almost fully relaxed domain exhibits superior structural and optical properties as evidenced by rocking curves with a full width at half maximum of 885 arc sec and a low temperature band edge luminescence at 3.47 eV with the full width at half maximum of 10 meV. The other domain exhibits a 14 times higher isotropic strain component, which is due to the higher densities of the point and extended defects, resulting from the ion bombardment during growth. Voids form at the domain boundaries. Mechanisms for the formation of differently strained domains, along with voids during the epitaxial growth of GaN are discussed.
Structural and magnetic properties of self-doped perovskite manganites La0.8-xSr0.2MnO3−δ
Authors: Liu Shao-Peng , Xie Yan , Xie Juan , Tang Gui-De
Published: December 2011

Self-doped perovskite manganites with nominal composition La0.8−xSr0.2MnO3−δ (0 ≤ x ≤ 0.20) have been prepared by the sol-gel method. The highest heat treatment temperature used was 1073 K. The x-ray diffraction (XRD) patterns indicate that the samples had a single phase with the ABO3 perovskite structure when the doping content was x ≤ 0.10 and that when the doping content was x ≥ 0.15 the samples had two phases with the ABO3 perovskite structure being the dominant phase and Mn3O4 being the minor phase. On the basis of the thermal equilibrium theory of crystal defects, the contents of various ions were estimated for the perovskite phases in which there are Mn2+ ions and no vacancies at the A sites. The ion contents have been corrected by Rietveld fitting of the powder sample x-ray diffraction data. Magnetic measurements indicated that the evolution of the Curie temperature (TC) vs. the Mn4+ ion content ratio at the B sites of the ABO3 structure is in accord with experimental results for La1−xSrxMnO3 samples.
Modeling and quantitative nanocalorimetric analysis to assess interdiffusion in a Ni/Al bilayer
Authors: Vohra M. , Grapes M. , Swaminathan P. , Weihs T. P. , Knio O. M.
Published: December 2011

A computational model is developed to describe the evolution of the temperature field in a nanocalorimeter that comprises inert material layers on which a nanoscale Ni/Al bilayer has been deposited. The model incorporates a reduced continuum description of mixing and heat release in the Ni/Al bilayer, and of the energy equation in the inert layers. Due to the small thicknesses of individual layers that are several orders of magnitude smaller than the corresponding length, a simplified, transient, homogeneous representation of the temperature field can be adopted. The resulting lumped model is valid over short enough timescales, which are nonetheless sufficiently large to capture the formation reaction. By using experimental observations of the evolution of the temperature on the surface of the nanocalorimeter, the model is used to estimate the transient heat release rate. Assuming an Arrhenius model for the mixing between Ni and Al, the estimated heat release rate is used to determine the Arrhenius pre-exponent and activation energy of the atomic diffusivity. Computed results indicate that the present approach provides a promising means of characterizing atomic diffusion rates. Limitations arise, however, due to the low amplitudes of the heat release term at low temperature, and also due to phase-change effects, which make the heat release rate unobservable in the neighborhood of the melting temperature of individual constituents. For the present system, reliable estimates are extracted for temperatures ranging from about 600 K to the Al melting temperature.
Hydrodynamic cavitation in microsystems. I. Experiments with deionized water and nanofluids
Authors: Medrano M. , Zermatten P. J. , Pellone C. , Franc J. P. , Ayela F.
Published: December 2011

An experimental study of hydrodynamic cavitation downstream microdiaphragms and microventuris is presented. Deionized water and nanofluids have been characterized within silicon–Pyrex micromachined devices with hydraulic diameters ranging from 51 μm to 104 μm. The input pressure could reach up to 10 bars, and the flow rate was below 1 liter per hour. The output pressure of the devices was fixed at values ranging from 0.3 bar to 2 bars, so that it was possible to study the evolution of the cavitation number as a function of the Reynolds number in the orifice of the diaphragms or in the throat of the venturis. A delay on the onset of cavitation has been recorded for all the devices when they are fed with deionized water, because of the metastability of the liquid and because of the lack of roughness of the walls. For the first time, hydrodynamic cavitation of nanofluids (nanoparticles dispersed into the liquid) has been considered. The presence of nano-aggregates in the liquid does not exhibit any noticeable effect on the cavitation threshold through the venturis. However, such a presence has a strong influence on the cavitation onset in microdiaphragms: above a critical volume solid concentration of ≈10−5, the metastability is broken and the nanofluids behave as tap water filled up with large nuclei. These microdevices, where a low amount of fluid is required to reach cavitating flows, appear to be useful tools in order to study cavitating phenomena in localized area with specific fluids.
Asymmetry of red blood cell motions in a microchannel with a diverging and converging bifurcation
Authors: Leble Vladimir , Lima Rui , Dias Ricardo , Fernandes Carla , Ishikawa Takuji , Imai Yohsuke , Yamaguchi Takami
Published: December 2011

In microcirculation, red blood cells (RBCs) flowing through bifurcations may deform considerably due to combination of different phenomena that happen at the micro-scale level, such as: attraction effect, high shear, and extensional stress, all of which may influence the rheological properties and flow behavior of blood. Thus, it is important to investigate in detail the behavior of blood flow occurring at both bifurcations and confluences. In the present paper, by using a micro-PTV system, we investigated the variations of velocity profiles of two working fluids flowing through diverging and converging bifurcations, human red blood cells suspended in dextran 40 with about 14% of hematocrit level (14 Hct) and pure water seeded with fluorescent trace particles. All the measurements were performed in the center plane of rectangular microchannels using a constant flow rate of about 3.0 × 10−12 m3/s. Moreover, the experimental data was compared with numerical results obtained for Newtonian incompressible fluid. The behavior of RBCs was asymmetric at the divergent and convergent side of the geometry, whereas the velocities of tracer particles suspended in pure water were symmetric and well described by numerical simulation. The formation of a red cell-depleted zone immediately downstream of the apex of the converging bifurcation was observed and its effect on velocity profiles of RBCs flow has been investigated. Conversely, a cell-depleted region was not formed around the apex of the diverging bifurcation and as a result the adhesion of RBCs to the wall surface was enhanced in this region.
Evanescent waves and deaf bands in sonic crystals
Authors: Romero-García V. , Garcia-Raffi L. M. , Sánchez-Pérez J. V.
Published: December 2011

The properties of sonic crystals (SC) are theoretically investigated in this work by solving the inverse problem k(ω) using the extended plane wave expansion (EPWE). The solution of the resulting eigenvalue problem gives the complex band structure which takes into account both the propagating and the evanescent modes. In this work we show the complete mathematical formulation of the EPWE for SC and the supercell approximation for its use in both a complete SC and a SC with defects. As an example we show a novel interpretation of the deaf bands in a complete SC in good agreement with multiple scattering simulations.
‘You’re more likely to tell the GP if you’re asked’: women’s views of care from general practitioners in the first postpartum year
Authors: Hartley Stefanie , Sutherland Georgina , Brown Stephanie , Yelland Jane
Published: December 2011

New mothers and their infants are high frequency users of primary health care services in Australia providing opportunities for GPs to engage with women about common postnatal morbidities. This study aimed to explore women’s views of GP care in the first year following birth. We used semistructured interviews with a subsample of women who had participated in a population-based survey of women who gave birth in two Australian states (Victoria and South Australia) in 2007. Twenty-nine women were interviewed. Prominent themes that emerged were around issues of disclosure, including women’s views on ways practitioner interactions and systems of care facilitate or hinder disclosure and subsequent discussion of health problems. Women reflected on the role GPs played in their health and wellbeing after childbirth, the importance of enquiry, communication style and the way access to, and time in, consultations impact on disclosure, perceived support and discussions. To improve care for women after childbirth we need to know the contexts that facilitate disclosure. Findings from this qualitative study deliver an important message to clinicians: women value primary care, identify issues that facilitate and hinder disclosure and describe ‘good’ encounters as ones where they feel understood, supported and reassured.
Political model of social evolution
Authors: Acemoglu Daron , Egorov Georgy , Sonin Konstantin
Published: December 2011

Almost all democratic societies evolved socially and politically out of authoritarian and nondemocratic regimes. These changes not only altered the allocation of economic resources in society but also the structure of political power. In this paper, we develop a framework for studying the dynamics of political and social change. The society consists of agents that care about current and future social arrangements and economic allocations; allocation of political power determines who has the capacity to implement changes in economic allocations and future allocations of power. The set of available social rules and allocations at any point in time is stochastic. We show that political and social change may happen without any stochastic shocks or as a result of a shock destabilizing an otherwise stable social arrangement. Crucially, the process of social change is contingent (and history-dependent): the timing and sequence of stochastic events determine the long-run equilibrium social arrangements. For example, the extent of democratization may depend on how early uncertainty about the set of feasible reforms in the future is resolved.
Stabilizing brokerage
Authors: Stovel Katherine , Golub Benjamin , Milgrom Eva M. Meyersson
Published: December 2011

A variety of social and economic arrangements exist to facilitate the exchange of goods, services, and information over gaps in social structure. Each of these arrangements bears some relationship to the idea of brokerage, but this brokerage is rarely like the pure and formal economic intermediation seen in some modern markets. Indeed, for reasons illuminated by existing sociological and economic models, brokerage is a fragile relationship. In this paper, we review the causes of instability in brokerage and identify three social mechanisms that can stabilize fragile brokerage relationships: social isolation, broker capture, and organizational grafting. Each of these mechanisms rests on the emergence or existence of supporting institutions. We suggest that organizational grafting may be the most stable and effective resolution to the tensions inherent in brokerage, but it is also the most institutionally demanding.
Bayesian analysis of the astrobiological implications of life’s early emergence on Earth
Authors: Spiegel David S. , Turner Edwin L.
Published: December 2011

Life arose on Earth sometime in the first few hundred million years after the young planet had cooled to the point that it could support water-based organisms on its surface. The early emergence of life on Earth has been taken as evidence that the probability of abiogenesis is high, if starting from young Earth-like conditions. We revisit this argument quantitatively in a Bayesian statistical framework. By constructing a simple model of the probability of abiogenesis, we calculate a Bayesian estimate of its posterior probability, given the data that life emerged fairly early in Earth’s history and that, billions of years later, curious creatures noted this fact and considered its implications. We find that, given only this very limited empirical information, the choice of Bayesian prior for the abiogenesis probability parameter has a dominant influence on the computed posterior probability. Although terrestrial life's early emergence provides evidence that life might be abundant in the universe if early-Earth-like conditions are common, the evidence is inconclusive and indeed is consistent with an arbitrarily low intrinsic probability of abiogenesis for plausible uninformative priors. Finding a single case of life arising independently of our lineage (on Earth, elsewhere in the solar system, or on an extrasolar planet) would provide much stronger evidence that abiogenesis is not extremely rare in the universe.
Low temperature formation of naphthalene and its role in the synthesis of PAHs (Polycyclic Aromatic Hydrocarbons) in the interstellar medium
Authors: Parker Dorian S. N. , Zhang Fangtong , Kim Y. Seol , Kaiser Ralf I. , Landera Alexander , Kislov Vadim V. , Mebel Alexander M. , Tielens A. G. G. M.
Published: December 2011

Polycyclic aromatic hydrocarbons (PAHs) are regarded as key molecules in the astrochemical evolution of the interstellar medium, but the formation mechanism of even their simplest prototype—naphthalene (C
10
H
8
)—has remained an open question. Here, we show in a combined crossed beam and theoretical study that naphthalene can be formed in the gas phase via a barrierless and exoergic reaction between the phenyl radical (C
6
H
5
) and vinylacetylene (CH
2
 = CH-C ≡ CH) involving a van-der-Waals complex and submerged barrier in the entrance channel. Our finding challenges conventional wisdom that PAH-formation only occurs at high temperatures such as in combustion systems and implies that low temperature chemistry can initiate the synthesis of the very first PAH in the interstellar medium. In cold molecular clouds, barrierless phenyl-type radical reactions could propagate the vinylacetylene-mediated formation of PAHs leading to more complex structures like phenanthrene and anthracene at temperatures down to 10 K.
Functional Interactions between Starch Synthase III and Isoamylase-Type Starch-Debranching Enzyme in Maize Endosperm
Authors: Lin Qiaohui , Huang Binquan , Zhang Mingxu , Zhang Xiaoli , Rivenbark Joshua , Lappe Ryan L. , James Martha G. , Myers Alan M. , Hennen-Bierwagen Tracie A.
Published: December 2011

This study characterized genetic interactions between the maize (Zea mays) genes dull1 (du1), encoding starch synthase III (SSIII), and isa2, encoding a noncatalytic subunit of heteromeric isoamylase-type starch-debranching enzyme (ISA1/ISA2 heteromer). Mutants lacking ISA2 still possess the ISA1 homomeric enzyme. Eight du1- mutations were characterized, and structural changes in amylopectin resulting from each were measured. In every instance, the same complex pattern of alterations in discontinuous spans of chain lengths was observed, which cannot be explained solely by a discrete range of substrates preferred by SSIII. Homozygous double mutants were constructed containing the null mutation isa2-339 and either du1-Ref, encoding a truncated SSIII protein lacking the catalytic domain, or the null allele du1-R4059. In contrast to the single mutant parents, double mutant endosperms affected in both SSIII and ISA2 were starch deficient and accumulated phytoglycogen. This phenotype was previously observed only in maize sugary1 mutants impaired for the catalytic subunit ISA1. ISA1 homomeric enzyme complexes assembled in both double mutants and were enzymatically active in vitro. Thus, SSIII is required for normal starch crystallization and the prevention of phytoglycogen accumulation when the only isoamylase-type debranching activity present is ISA1 homomer, but not in the wild-type condition, when both ISA1 homomer and ISA1/ISA2 heteromer are present. Previous genetic and biochemical analyses showed that SSIII also is required for normal glucan accumulation when the only isoamylase-type debranching enzyme activity present is ISA1/ISA heteromer. These data indicate that isoamylase-type debranching enzyme and SSIII work in a coordinated fashion to repress phytoglycogen accumulation.