621 research outputs found
Defect-unbinding transitions and inherent structures in two dimensions
We present a large-scale (36000-particle) computational study of the
"inherent structures" (IS) associated with equilibrium, two-dimensional,
one-component Lennard-Jones systems. Our results provide strong support both
for the inherent-structures theory of classical fluids, and for the KTHNY
theory of two-stage melting in two dimensions. This support comes from the
observation of three qualitatively distinct "phases" of inherent structures: a
crystal, a "hexatic glass", and a "liquid glass". We also directly observe, in
the IS, analogs of the two defect-unbinding transitions (respectively, of
dislocations, and disclinations) believed to mediate the two equilibrium phase
transitions. Each transition shows up in the inherent structures---although the
free disclinations in the "liquid glass" are embedded in a percolating network
of grain boundaries. The bond-orientational correlation functions of the
inherent structures show the same progressive loss of order as do the three
equilibrium phases: long-range to quasi-long-range to short-range.Comment: RevTeX, 8 pages, 15 figure
Recommended from our members
The experiences of Asian American females seeking vice president and president positions in community colleges : A view of the barriers and facilitators
This qualitative narrative inquiry study explored the experiences and perspectives of five Asian American females who have sought presidencies and/or vice presidencies in community colleges. All five of the participants are currently either a president or vice president in community colleges. This study found nine themes that capture the barriers and facilitators that these Asian American females encountered along their career path. The themes were mother as role model, biculturalism and bicultural efficacy, unplanned pathways and not self-identifying, earned leadership positions, strong work ethic, stereotyping and assumptions, Asian physicality and invisibility, fracturing the glass ceiling, and positive attitude and strength. Future implications for research and practice is also discussed
Binuclear Manganese(III) Complexes as Electron Donors in D1/D2/Cytochrome b559 Preparations Isolated from Spinach Photosystem II Membrane Fragments
The capability of different manganese complexes to act as PS II electron donors in D1/D2/ cytochrome b 559 complexes has been analyzed by measuring actinic light-induced absorption changes at 680 nm (650 nm) and 340 nm, reflecting the photoaccumulation of Pheophytin- (Pheo-) and the reduction of NADP+ respectively. The data obtained reveal: a) the donor capacity of synthetic binuclear Mn(III)2 complexes containing aromatic ligands significantly exceeds that for MnCl2 in both cases, i.e. Pheo- photoaccumulation and NADP+ reduction; b) manganese complexes can serve as suitable electron donors for light-induced NADP+ reduction catalyzed by D1/D2/cytochrome b559 complexes and ferredoxin plus ferredoxin- NADP+ reductase under anaerobic conditions and c) the specific turnover rate of the system leading to NADP+ reduction is extremely small. The implications of these findings are briefly discussed
Tissue factor as the main activator of the coagulation system during cardiopulmonary bypass
AbstractObjective: This study investigates the influence of foreign material and blood aspirated from nonvascular structures on activation of coagulation, hemolysis, and blood loss. Methods: The series comprises 3 randomized groups (groups C, S, and S+P) of 10 patients undergoing routine coronary artery bypass grafting with cardiopulmonary bypass. In group C, the control group, all aspirated blood was returned into the circulation. In group S suction blood was discarded, whereas group S+P was identical to group S, with surfaces coated with phosphorylcholine. Plasma concentrations of β-thromboglobulin, thrombin generation, haptoglobin, and free hemoglobin, as well as blood loss, were measured. Results: A steady increase in free plasma hemoglobin, as well as an increased generation of thrombin, was noticed in group C. Moreover, a close correlation (r = 0.916) between the generation of thrombin and its inhibition (thrombin-antithrombin complexes) was observed. Platelets were clearly activated in group C and, to a lesser extent, in group S. In contrast, platelet activation in group S+P was negligible, resulting in a 30% decrease in blood loss (P = .05). Conclusions: Aspirated blood contaminated by tissue contact is the most important activator of the coagulation system and the principal cause of hemolysis during cardiopulmonary bypass. Contact with a foreign surface is not a main variable in the procoagulant effect of bypass. Mimicking the outer cell membrane structure resulted in decreased platelet activation and decreased blood loss.J Thorac Cardiovasc Surg 2002;123:951-
RXTE Absolute Timing Results for the Pulsars B1821-24 and B1509-58
Observations with the Rossi X-ray Timing Explorer and the Jodrell Bank,
Parkes, and Green Bank telescopes have enabled us to determine the time delay
between radio and X-ray pulses in the two isolated pulsars B1821-24 and
B1509-58. For the former we find that the narrow X-ray and radio pulse
components are close to being coincident in time, with the radio peak leading
by 0.02 period (60 +/- 20 microsec), while the wide X-ray pulse component lags
the last of the two wider radio components by about 0.08 period. For the latter
pulsar we find, using the standard value for the dispersion measure, that the
X-ray pulse lags the radio by about 0.27 period, with no evidence for any
energy-dependence in the range 2-100 keV. However, uncertainties in the history
of the dispersion measure for this pulsar make a comparison with previous
results difficult. It is clear that there are no perceptable variations in
either the lag or the dispersion measure at time scales of a year or less.Comment: 20 pages including 6 figures, accepted by Astrophysical Journa
Cama de frango como substrato para a produção de biogás apĂłs diferentes perĂodos de estocagem.
RESUMO: Na avicultura a cama de frango Ă© produzida sazonalmente, em função do modo de produção. Para obter energia do biogás por meio da biodigestĂŁo da cama de frango, de forma contĂnua, o armazenamento do resĂduo pode ser uma solução. Ensaios de Potencial BioquĂmico de Metano (BMP) foram utilizados neste trabalho para estimar a capacidade de produção de biogás e metano da cama de frango removida apĂłs o sexto lote de reutilização e a diferentes tempos de armazenamento apĂłs a coleta, assim, verificar a viabilidade de utilização da cama de frango como um substrato em unidade produtora de biogás. A produção de biogás e metano, nas amostras em diferentes perĂodos de armazenamento, foi comparada: antes de armazenar 245 LN biogas.kgSV adic-1 e 159 LN CH4.kgSV adic-11, seis meses com 252 LN biogas.kgSV adic-1 e 160 LN CH4.kgSV adic-1 e um ano 209 LN biogas.kgSV adic-1 e 117 LNCH4.kgSV adic-1, demonstrando que o perĂodo de armazenamento Ă© caracterizado por uma relativa perda do conteĂşdo de matĂ©ria orgânica apĂłs um ano, contudo, nĂŁo há diferença significativa entre a produção de biogás e metano apĂłs seis meses armazenada e antes de armazenar. Verificou-se a viabilidade da estocagem de cama de frango do sexto lote de reutilização, no perĂodo de seis meses, sem perda significativa de matĂ©ria orgânica para a conversĂŁo em biogás e metano. ABSTRACT: In poultry litter is produced seasonally due to production mode. To get energy from biogas through the bio digestion of poultry litter, continuously, the storage of the residue can be a solution. Biochemical Methane Potential (BMP) assays were used in this study to estimate the production of biogas and methane poultry litter removed after the sixth lot of reuse and in different storage times after collect, so check the feasibility of use poultry litter as a feedstock in biogas producer unit. The production of biogas and methane in the samples in different periods of storage was compared: before storage 245 LN biogas.kgVS add-1 E 159 LN C H4 kg SV add-1, six months with 252 LN biogas.kgVS add-1 e 160 LN C H4 kg SV add-1 and a year 209 LN biogas.kgVS add-1 and one year 117 LN C H4 kg SV add-1, demonstrating that the storage period is characterized by a relative loss of content of organic matter after a year, however there's no significant difference between the production of biogas and methane in six months storaged and before storage . It was verified the viability of storage of poultry litter of the sixth lot of reuse, in the six-month period, without significant loss of organic matter for conversion to biogas and methane
Non-syndromic Sensorineural Prelingual Deafness: The Importance of Genetic Counseling in Demystifying Parents’ Beliefs About the Cause of Their Children’s Deafness
Recent advances in molecular genetics have allowed the determination of the genetic cause of some childhood non-syndromic deafness. In Portugal only a small proportion of families are referred to a clinical genetics service in order to clarify the etiology of the deafness and to provide genetic counseling. Consequently, there are no published studies of the prior beliefs of parents about the causes of hereditary deafness of their children and their genetic knowledge after receipt of genetic counseling. In order to evaluate the impact of genetic counseling, 44 parents of 24 children with the diagnosis of non-syndromic sensorineural prelingual deafness due to mutations in the GJB2 (connexin 26), completed surveys before and after genetic counseling. Before counseling 13.6 % of the parents knew the cause of deafness; at a post-counseling setting this percentage was significantly higher, with 84.1 % of the parents accurately identifying the etiology. No significant differences were found between the answers of mothers and fathers either before or after genetic counseling. Parents' level of education was a significant factor in pre-test knowledge. After genetic counseling 95.5 % of the parents stated that the consultation had met their expectations, 70.5 % remembered correctly the inheritance pattern, and 93.2 % correctly recalled the chance of risk of deafness. These results underline the importance of genetic counseling in demystifying parents' beliefs about the etiology of their children's deafness
Association of Atopobium vaginae, a recently described metronidazole resistant anaerobe, with bacterial vaginosis
BACKGROUND: Bacterial vaginosis (BV) is a polymicrobial syndrome characterized by a change in vaginal flora away from predominantly Lactobacillus species. The cause of BV is unknown, but the condition has been implicated in diverse medical outcomes. The bacterium Atopobium vaginae has been recognized only recently. It is not readily identified by commercial diagnostic kits. Its clinical significance is unknown but it has recently been isolated from a tuboovarian abcess. METHODS: Nucleotide sequencing of PCR amplified 16S rRNA gene segments, that were separated into bands within lanes on polyacrylamide gels by denaturing gradient gel electrophoresis (DGGE), was used to examine bacterial vaginal flora in 46 patients clinically described as having normal (Lactobacillus spp. predominant; Nugent score ≤ 3) and abnormal flora (Nugent score ≥ 4). These women ranged in age from 14 to 48 and 82% were African American. RESULTS: The DGGE banding patterns of normal and BV-positive patients were recognizably distinct. Those of normal patients contained 1 to 4 bands that were focused in the centre region of the gel lane, while those of BV positive patients contained bands that were not all focused in the center region of the gel lane. More detailed analysis of patterns revealed that bands identified as Atopobium vaginae were present in a majority (12/22) of BV positive patients, while corresponding bands were rare (2/24) in normal patients. (P < 0.001) Two A. vaginae isolates were cultivated from two patients whose DGGE analyses indicated the presence of this organism. Two A. vaginae 16S rRNA gene sequences were identified among the clinical isolates. The same two sequences were obtained from DGGE bands of the corresponding vaginal flora. The sequences differed by one nucleotide over the short (~300 bp) segment used for DGGE analysis and migrated to slightly different points in denaturing gradient gels. Both isolates were strict anaerobes and highly metronidazole resistant. CONCLUSION: The results suggest that A. vaginae may be an important component of the complex bacterial ecology that constitutes abnormal vaginal flora. This organism could play a role in treatment failure if further studies confirm it is consistently metronidozole resistant
- …