Chemical disorder determines the deviation of the Slater-Pauling rule for Fe2MnSi-based Heusler alloys: evidences from neutron diffraction and density functional theory.

Fe2MnSi fails to follow the Slater-Pauling rule. This phenomenon is thought to originate from either: (i) an antiferromagnetic arrangement of Mn ions at low temperature and/or (ii) chemical disorder. An important insight on this issue could be achieved by considering Fe2MnSi1-x Ga x compounds, thoroughly studied here by means of magnetization, neutron diffraction and density functional calculations (DFT). Our results indicate that chemical disorder (and not the antiferromagnetic arrangement) is responsible for the deviation of the Slater-Pauling rule on Fe2MnSi-based Heusler alloys. Furthermore, evidences suggest that Ga substitution into Si site favors the Fe/Mn disorder, further enhancing the observed deviation.

Polarization selection rules for inter-Landau-level transitions in epitaxial graphene revealed by the infrared optical Hall effect.

We report on the polarization selection rules of inter-Landau-level transitions using reflection-type optical Hall effect measurements from 600 to 4000 cm(-1) on epitaxial graphene grown by thermal decomposition of silicon carbide. We observe symmetric and antisymmetric signatures in our data due to polarization preserving and polarization mixing inter-Landau-level transitions, respectively. From field-dependent measurements, we identify that transitions in coupled graphene monolayers are governed by polarization mixing selection rules, whereas transitions in decoupled graphene monolayers are governed by polarization preserving selection rules. The selection rules may find explanation by different coupling mechanisms of inter-Landau-level transitions with free charge carrier magneto-optic plasma oscillations.

Switching mechanisms in flexible solution-processed TiO2 memristors.

Memristors are emerging as unique electrical devices with potential applications in memory, reconfigurable logic and biologically inspired computing. Due to the novelty of these devices, the complete details of their switching mechanism is not yet well established. In this work, the switching mechanism of our solution-processed titanium dioxide-based memristor is investigated by studying how variations in the device area and film thickness affect electrical behavior and correlating these behavioral changes to proposed switching mechanisms. The conduction path of the switching is also investigated through electrical characterization of devices both before and after physically cutting the devices in half, as well as through infrared imaging of the devices during operation. The results suggest that the electrical behavior of these devices is dominated by a localized, charge-based phenomenon that exhibits a dependence on device area.

Postpartum depression: in relation to life events and patterns of coping.

The purpose of this study was to estimate the prevalence of postpartum depression (PPD) and its relationship with life events (LE) and patterns for coping. We performed a cross-sectional study of 113 women, on the 10(th) day of puerperium, at the Obstetric Clinic of the São Paulo University Medical School. The study was based on the following: Pitt (1967) and Stein (1980) Scales, Beck Depression Inventory (1961), Holmes and Rahe Schedule of Recent Events (1967), Folkman and Lazarus Ways of Coping (1985) and questionnaire of social-demographic and obstetric data. Logistic regression was performed to calculate prevalence of PPD and its association with several risk factors. The significance level was defined at 5%. The prevalence of PPD was 15.9% (IC 9.7% to 24.0%). According to the multivariate analyses, the variables of coping with distancing, number of children and ethnic origin were significant. There were no association between PPD and LE. The depressed puerperal women have a low educational level, greater number of children and resort to inadequate coping strategies, such as distancing. This pattern of coping might be an etiological factor of the PPD as well as a reaction to their difficult life environment.

Parto pré-termo: análise dos aspectos psicológicos / Pre-term birth: analisys of psychological aspects

Este estudo teve como objetivo analisar qualitativamente os fatores psicológicos associados ao parto pré-termo. Foram estudados vinte pacientes, assistidas no Departamento de Obstetrícia e Ginecologia da Santa Casa de Sao Paulo, no período de setembro de 1994 a junho de 1995, nas quais nao foi possível a identificaçao de fator causal de parto pré-termo. Como instrumento de pesquisa, foram utilizados um questionário e a prova gráfica do Desenho da Figura Humana de Karen Machover. Dificuldade em identificar-se com o papel de mae, adaptaçao emocional insuficiente à maternidade, dificuldade em lidar com situaçoes de estresse, as quais refletiram um aumento no nível de ansiedade, foram aspectos que apresentaram significativa associaçao nos casos estudados. A realizaçao sistemática de pré-natal e a falta de intercorrências clínicas foram elevadas, reafirmando que o cuidado pré-natal merece ser ampliado, isto é, prestar assistência nao só médico-obstétrica, mas também psicológica.

Leishmaniose visceral durante a gestaçäo: relato de caso / Visceral leishmaniasis in pregnancy: a case report

Leishmaniose é uma doença tropical causada por um protozoário e raramente é vista em associaçao com gravidez. Neste trabalho apresentaremos um caso de gravidez de 30 semanas em paciente com leishmaniose.

The photocatalytic production of organic-free water for molecular biological and pharmaceutical applications.

The inability of conventional water-purification systems to meet the ultra-high purity needs of molecular biology and biopharmaceuticals reliably was attributed to their almost exclusive utilization of phase-transfer technologies. Water quality may unpredictably degrade when confronted by microorganism blooms or altered feed water characteristics. Photocatalytic point-of-use water-purification systems fed by deionized water were demonstrated to meet the most stringent water-purity needs of the molecular biologist. The reliability of the photocatalytic water-purification technology was attributed to its ability to destroy organic contaminants rather than just effect their phase transfer. Photocatalytically produced water was shown to be free of detectable microorganisms, DNA, endotoxins and RNAses. It is suitable for immunological studies involving tissue and other cell cultures because of its lack of detectable endotoxins. Because DNA was also undetectable, it is suitable for DNA and endotoxin zero-standards as well as pharmaceutical formulation. The photocatalytic water is a reliable substitute for diethyl pyrocarbonate-treated water used in RNA work, compatible with PCR and sufficiently free from other contaminants to be useful for most biochemical and enzymatic assays.

[Bacteremia induced by labor. Is prophylaxis for infective endocarditis necessary?]. / Bacteremia induzida pelo trabalho de parto. Cabe a profilaxia da endocardite infecciosa?

PURPOSE: To characterize the occurrence of bacteremia during delivery and to verify the necessity of prophylaxis against infective endocarditis. METHODS: The authors collected hemoculture of 100 women, 15,30 and 45 minutes after delivery. The data were collected from May 1992 until May 1993. The positive hemocultures were followed by antibiogram. RESULTS: Seven hemocultures were positive: six for Staphylococcus, one for Candida sp, Penicilium sp, Clandosporum sp and Aspergillus sp that were found in association. Four patients had prematures amniorrhexis, longer than 6 hours before delivery (p < 0.05). Six patients had labor longer than 6 hours after admission (p < 0.05). The authors did not observe differences related to vaginal delivery with or without forceps or cesarean section. The samples were all sensible to cefalotin at the antibiogram. CONCLUSION: Labor and delivery is a high risk procedure for bacteremia and so for ineffective endocarditis in susceptible patients. The statistical analysis recognize as risk factors labor longer than 6 hours inside the hospital and premature amniorrhexis. We propose the use of intravenous cefalotin 1g 60 minutes before expulsion and repeated 6 and 12 hours later.

Synthesis of wild type and mutant human hemoglobins in Saccharomyces cerevisiae.

We have expressed human alpha and beta-globin cDNA clones from separate, synthetic galactose-regulated hybrid promoters contained on a single plasmid in Saccharomyces cerevisiae. Co-expression of the alpha and beta-globin chains in S. cerevisiae results in the assembly of these proteins into soluble tetrameric hemoglobin that accumulates to 3-5 percent of the total cell protein. Endogenously produced heme is incorporated into the tetramer and the protein produced is functionally and structurally indistinguishable from human Ao hemoglobin. This expression system has been used to produce both wild type hemoglobin and a low O2-affinity hemoglobin mutant that has oxygen binding and dissociation characteristics similar to human whole blood. The yeast expression system we describe may be suitable for the production of a recombinant hemoglobin based blood substitute as well as for detailed structure-activity studies of human hemoglobin.

Expression of fully functional tetrameric human hemoglobin in Escherichia coli.

Synthetic genes encoding the human alpha- and beta-globin polypeptides have been expressed from a single operon in Escherichia coli. The alpha- and beta-globin polypeptides associate into soluble tetramers, incorporate heme, and accumulate to greater than 5% of the total cellular protein. Purified recombinant hemoglobin has the correct stoichiometry of alpha- and beta-globin chains and contains a full complement of heme. Each globin chain also contains an additional methionine as an extension to the amino terminus. The recombinant hemoglobin has a C4 reversed-phase HPLC profile essentially identical to that of human hemoglobin A0 and comigrates with hemoglobin A0 on SDS/PAGE. The visible spectrum and oxygen affinity are similar to that of native human hemoglobin A0. The recombinant protein shows a reduction in Bohr and phosphate effects, which may be attributed to the presence of methionine at the amino termini of the alpha and beta chains. We have also expressed the alpha- and beta-globin genes separately and found that the expression of the alpha-globin gene alone results in a marked decrease in the accumulation of alpha-globin in the cell. Separate expression of the beta-globin gene results in high levels of insoluble beta-globin. These observations suggest that the presence of alpha- and beta-globin in the same cell stabilizes alpha-globin and aids the correct folding of beta-globin. This system provides a simple method for expressing large quantities of recombinant hemoglobin and allows facile manipulation of the genes encoding hemoglobin to produce functionally altered forms of this protein.

[The porcine valve prosthesis and pregnancy]. / Prótese valvar porcina e gravidez.

Anticoagulation is the chief problem during pregnancy of women with mechanical prosthetic valves. Many studies have investigated a nonthrombogenic valve. Since 1978 we have used a biological porcine prosthetic valves in 16 pregnancies, 11 patients with regular clinical electrocardiographic, echocardiographic and chest roentgenographic follow-up. The patients' ages were 19 to 32 years during pregnancy. Nine had mitral, one aortic and one mitro-aortic prosthesis. Two patients dropped out during the study so we completed it with 14 pregnancies. Six patients coursed with grade I heart failure (HYHA), five grade II and three grade IV. All of them were treated clinically. Four valves had dysfunction and calcification during pregnancy and two before pregnancy. The pregnancies resulted in three abortions, seven normal deliveries and four caesarean section with obstetric indication. Fetal distress was not observed during or after delivery. The physiopathology of valve dysfunction during pregnancy was discussed and it was concluded that the biologic porcine prosthetic valve allows hemodynamic stabilization. If dysfunction appears it may be clinically controlled without need of anticoagulation, risk of calcification nor dysfunction during pregnancy. The biologic valves are best indicated for women who wish to become pregnant after valve substitution.

Comparison of midforceps, low-forceps, and spontaneous vaginal deliveries.

A prospective, six-month study compared various maternal and neonatal parameters among spontaneous vaginal (n = 47), low-forceps (n = 21), and midforceps (n = 15) deliveries. All three groups had good neonatal and maternal outcomes. The only significant differences (P greater than .01) were the one-minute Apgar scores between the low-forceps and midforceps groups and parity between the spontaneous vaginal and low-forceps deliveries. The findings did not reveal poorer neonatal outcomes or excessive maternal morbidity, thus supporting the continued use of forceps in properly selected patients.

Molecular receptors and their potential for artificial transduction.

The thesis is presented that molecular receptor physical chemistry offers an interesting model for the design of biosensors with respect to chemical recognition and transduction. In order to appreciate the desirable features of this system and the inherent difficulties, the structures and binding state energetics of molecular receptors are considered via a direct comparison with enzyme chemistry. Detailed analyses of the candidate species nicotinic and beta-adrenergic receptors are provided to illustrate the complexity of molecular receptor binding properties. A revised ternary-complex model, which combines enzymatic and receptor energetics, is proposed to explain the free-energy changes which drive ligand-binding reactions of coupled systems. Throughout this discussion the relevance of the various arguments to applications in biosensor development is highlighted. Finally, a brief appraisal of attempts to produce devices ready for marriage to molecular receptor material is presented.

Affinity purification of the mammalian beta-2-adrenergic receptor.

The efficiency of covalently linking alprenolol to Sepharose via a 14-atom spacer prepared from 1,4-butanediol diglycidyl ether has been increased. This in turn has aided in increasing the specific yield of beta-2-adrenergic receptor by a factor of 3 over earlier results. Further development of extraction and solubilization protocols are also described. The adsorption of the affinity-purified receptor to stainless steel was measured, and is cited as a potential problem in further purification by high-pressure liquid chromatography.

Tear lysozyme and lactoferrin levels in giant papillary conjunctivitis and vernal conjunctivitis.

We measured tear lysozyme by a radial immunodiffusion assay in patients with contact lens induced giant papillary conjunctivitis (GPC) and in patients with vernal conjunctivitis (VC). The VC and GPC patients had normal levels of tear lysozyme when compared to control individuals who did not have eye disease and to normal individuals who wore contact lenses without difficulty. In contrast, the tear concentration of lactoferrin (another important tear protein produced by the lacrimal glands) was reduced both in VC and GPC patients. Normal levels of tear lysozyme in the presence of reduced tear concentrations of lactoferrin may be a unique pattern in these two ocular conditions. The reduced tear levels of lactoferrin are probably not related to lacrimal gland dysfunction but to other factor(s) important in the pathogenesis of these two ocular disorders.

Níveis plasmáticos de ferritina durante a gravidez / Plasma levels of ferritin during pregnancy

Säo estabelecidos os valores de ferritina plasmática na gravidez normal em nosso meio. Constatou-se nítida tendência à queda da ferritina plasmática a partir da 30ª semana. Sugere-se que a ferritina plasmática deva ser considerada como indicador dos depósitos orgânicos de ferro e valorizada para fins terapêuticos