Structure and Magnetism of well-defined cobalt nanoparticles embedded in a niobium matrix

Our recent studies on Co-clusters embedded in various matrices reveal that the co-deposition technique (simultaneous deposition of two beams : one for the pre-formed clusters and one for the matrix atoms) is a powerful tool to prepare magnetic nanostructures with any couple of materials even though they are miscible. We study, both sharply related, structure and magnetism of the Co/Nb system. Because such a heterogeneous system needs to be described at different scales, we used microscopic and macroscopic techniques but also local selective absorption ones. We conclude that our clusters are 3 nm diameter f.c.c truncated octahedrons with a pure cobalt core and a solid solution between Co and Nb located at the interface which could be responsible for the magnetically inactive monolayers we found. The use of a very diluted Co/Nb film, further lithographed, would allow us to achieve a pattern of microsquid devices in view to study the magnetic dynamics of a single-Co cluster.Comment: 7 TeX pages, 9 Postscript figures, detailed heading adde

EXAFS characterization of oxaliplatin anticancer drug and its degradation in chloride media.

Oxaliplatin is a second-generation platinum-based anticancer drug. Its degradation is studied in solution, in the presence of chloride ions (in neutral or acidic media) in excess. In both cases the degradation product precipitates immediately. The EXAFS spectra of these products show that they are identical. EXAFS modeling and refinement of the first coordination sphere shows that two light atoms are replaced by two chloride ions. The complete refinement of the local structure is possible by studying the multiple-scattering signal. The results show that the main multiple-scattering contribution is due to the binding oxalato group and that the degradation product is [Cl(2)-(diaminocyclohexane)-Pt(II)]

Periodontal disease and some adverse perinatal outcomes in a cohort of low risk pregnant women

Objective: To evaluate the association of periodontal disease (PD) in pregnancy with some adverse perinatal outcomes. Method: This cohort study included 327 pregnant women divided in groups with or without PD. Indexes of plaque and gingival bleeding on probing, probing pocket depth, clinical attachment level and gingival recession were evaluated at one periodontal examination below 32 weeks of gestation. The rates of preterm birth (PTB), low birth weight (LBW), small for gestational age (SGA) neonates and prelabor rupture of membranes (PROM) were evaluated using Risk Ratios (95%CI) and Population Attributable Risk Fractions. Results: PD was associated with a higher risk of PTB (RRadj. 3.47 95% CI 1.62-7.43), LBW (RRadj. 2.93 95% CI 1.36-6.34) and PROM (RRadj. 2.48 95% CI 1.35-4.56), but not with SGA neonates (RR 2.38 95% CI 0.93 - 6.10). Conclusions: PD was a risk factor for PT, LBW and PROM among Brazilian low risk pregnant women

Preterm low birthweight and the role of oral bacteria

Preterm and low birthweight (PTLBW) continues to be a major cause of mortality and morbidity across the world. In recent years, maternal periodontal disease has been implicated as a risk factor for adverse pregnancy outcomes. There is conflicting evidence to support such an outcome as illustrated by descriptive, case control and randomised controlled trials involving pregnant women from across the world, using different measurement tools to determine the level of periodontal disease. Whilst considering the literature, there is evidence for both arguments, based on the effect of periodontal inflammatory by products. Bacteria associated with periodontal disease are not dissimilar to those known to be associated with genito-urinary bacterial infections and adverse pregnancy outcomes. Several groups have demonstrated the apparent translocation of Fusobacterium nucleatum, Prevotella nigrescens, Prevotella intermedia, Porphyromonus gingivalis, Treponema denticola to the foetal placental unit whereby a maternal or foetal response has been detected resulting in premature birth or low birthweight. The normal process of parturition involves a cascade of events including a build-up of inflammatory mediators as linked to inflammation, whereby the maternal environment becomes hostile and threatens the well-being of the infant, and the foetus expelled. The question remains therefore, is there a greater risk of delivering a PTLBW infant when the mother has detectable periodontal disease, or is the release of inflammatory mediators and their translocation via the haematogenous route sufficient to induce a poor pregnancy outcome? The data investigated would suggest that there is a positive outcome when certain oral gram-negative bacteria create a cumulative effect sufficient to trigger early delivery, which represents the final straw to result in preterm or low birthweight delivery. There is equally sufficient epidemiological evidence that does not support this outcome, but it is agreed that maintaining oral health during pregnancy is beneficial to the mother and her infant

Measurement of the polarization parameter in π−p\pi^{-}p backward elastic scattering at 6 GeV/c

The polarization parameter in pi /sup -/p elastic scattering has been measured in the backward angular region at an incident momentum of 6 GeV/c. The measurements cover the range of four momentum transfer u=0 to -1(GeV/c)/sup 2/, and were obtained with a high intensity pion beam, a butanol polarized proton target, and arrays of scintillation counter hodoscopes. The polarization is different from zero, in contradiction to the prediction of the naive one trajectory Regge- exchange model. It increases positively with the four-momentum transfer u, reaching a maximum of about 0.4 at u approximately=-0.3(Ge V/c)/sup 2/. It then decreases and becomes slightly negative beyond u approximately=-0.5(GeV/c)/sup 2/. A variety of baryon exchange models are briefly reviewed and none are found to be in complete agreement with all the experimental data

Epigenetic change in e-cardherin and COX-2 to predict chronic periodontitis

<p>Abstract</p> <p>Background</p> <p>DNA methylation of certain genes frequently occurs in neoplastic cells. Although the cause remains unknown, many genes have been identified with such atypical methylation in neoplastic cells. The hypermethylation of E-Cadherin and Cyclooxygenase 2 (COX-2) in chronic inflammation such as chronic periodontitis may demonstrate mild lesion/mutation epigenetic level. This study compares the hypermethylation status of E-Cadherin and COX-2 genes which are often found in breast cancer patients with that in chronic periodontitis.</p> <p>Methods</p> <p>Total DNA was extracted from the blood samples of 108 systemically healthy non-periodontitis subjects, and the gingival tissues and blood samples of 110 chronic periodontitis patient as well as neoplastic tissues of 106 breast cancer patients. Methylation-specific PCR for E-Cadherin and COX-2 was performed on these samples and the PCR products were analyzed on 2% agarose gel.</p> <p>Results</p> <p>Hypermethylation of E-Cadherin and COX-2 was observed in 38% and 35% of the breast cancer samples, respectively. In chronic periodontitis patients the detection rate was 25% and 19% respectively, and none was found in the systemically healthy non-periodontitis control subjects. The hypermethylation status was shown to be correlated among the three groups with statistical significance (p < 0.0001). The methylation of CpG islands in E-Cadherin and COX-2 genes in periodontitis patients occurs more frequently in periodontitis patients than in the control subjects, but occurs less frequently than in the breast cancer patients.</p> <p>Conclusions</p> <p>This set of data shows that the epigenetic change in E-Cadherin and Cyclooxygenase-2 is associated with chronic periodontitis. The epigenetic changes presented in chronic inflammation patients might demonstrate an irreversible destruction in the tissues or organs similar to the effects of cancer. Chronic periodontitis to some extent might be associated with DNA hypermethylation which is related to cancer risk factors.</p

Heavy Metal Tolerance in Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an aerobic, non-fermentative Gram-negative bacterium widespread in the environment. S. maltophilia Sm777 exhibits innate resistance to multiple antimicrobial agents. Furthermore, this bacterium tolerates high levels (0.1 to 50 mM) of various toxic metals, such as Cd, Pb, Co, Zn, Hg, Ag, selenite, tellurite and uranyl. S. maltophilia Sm777 was able to grow in the presence of 50 mM selenite and 25 mM tellurite and to reduce them to elemental selenium (Se0) and tellurium (Te0) respectively. Transmission electron microscopy and energy dispersive X-ray analysis showed cytoplasmic nanometer-sized electron-dense Se0 granules and Te0 crystals. Moreover, this bacterium can withstand up to 2 mM CdCl2 and accumulate this metal up to 4% of its biomass. The analysis of soluble thiols in response to ten different metals showed eightfold increase of the intracellular pool of cysteine only in response to cadmium. Measurements by Cd K-edge EXAFS spectroscopy indicated the formation of Cd-S clusters in strain Sm777. Cysteine is likely to be involved in Cd tolerance and in CdS-clusters formation. Our data suggest that besides high tolerance to antibiotics by efflux mechanisms, S. maltophilia Sm777 has developed at least two different mechanisms to overcome metal toxicity, reduction of oxyanions to non-toxic elemental ions and detoxification of Cd into CdS