313 research outputs found

    Synthesis and characterization of multiferroic BiMn7_7O12_{12}

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    We report on the high pressure synthesis of BiMn7_7O12_{12}, a manganite displaying a "quadruple perovskite" structure. Structural characterization of single crystal samples shows a distorted and asymmetrical coordination around the Bi atom, due to presence of the 6s26s^{2} lone pair, resulting in non-centrosymmetric space group Im, leading to a permanent electrical dipole moment and ferroelectric properties. On the other hand, magnetic characterization reveals antiferromagnetic transitions, in agreement with the isostructural compounds, thus evidencing two intrinsic properties that make BiMn7_7O12_{12} a promising multiferroic material.Comment: 4 pages, 3 figure

    The relation between the incidence of hypernatremia and mortality in patients with severe traumatic brain injury

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    INTRODUCTION: The study was aimed at verifying whether the occurrence of hypernatremia during the intensive care unit (ICU) stay increases the risk of death in patients with severe traumatic brain injury (TBI). We performed a retrospective study on a prospectively collected database including all patients consecutively admitted over a 3-year period with a diagnosis of TBI (post-resuscitation Glasgow Coma Score < or = 8) to a general/neurotrauma ICU of a university hospital, providing critical care services in a catchment area of about 1,200,000 inhabitants. METHODS: Demographic, clinical, and ICU laboratory data were prospectively collected; serum sodium was assessed an average of three times per day. Hypernatremia was defined as two daily values of serum sodium above 145 mmol/l. The major outcome was death in the ICU after 14 days. Cox proportional-hazards regression models were used, with time-dependent variates designed to reflect exposure over time during the ICU stay: hypernatremia, desmopressin acetate (DDAVP) administration as a surrogate marker for the presence of central diabetes insipidus, and urinary output. The same models were adjusted for potential confounding factors. RESULTS: We included in the study 130 TBI patients (mean age 52 years (standard deviation 23); males 74%; median Glasgow Coma Score 3 (range 3 to 8); mean Simplified Acute Physiology Score II 50 (standard deviation 15)); all were mechanically ventilated; 35 (26.9%) died within 14 days after ICU admission. Hypernatremia was detected in 51.5% of the patients and in 15.9% of the 1,103 patient-day ICU follow-up. In most instances hypernatremia was mild (mean 150 mmol/l, interquartile range 148 to 152). The occurrence of hypernatremia was highest (P = 0.003) in patients with suspected central diabetes insipidus (25/130, 19.2%), a condition that was associated with increased severity of brain injury and ICU mortality. After adjustment for the baseline risk, the incidence of hypernatremia over the course of the ICU stay was significantly related with increased mortality (hazard ratio 3.00 (95% confidence interval: 1.34 to 6.51; P = 0.003)). However, DDAVP use modified this relation (P = 0.06), hypernatremia providing no additional prognostic information in the instances of suspected central diabetes insipidus. CONCLUSIONS: Mild hypernatremia is associated with an increased risk of death in patients with severe TBI. In a proportion of the patients the association between hypernatremia and death is accounted for by the presence of central diabetes insipidus

    Internal-strain mediated coupling between polar Bi and magnetic Mn ions in the defect-free quadruple-perovskite BiMn3_3Mn4_4O12_{12}

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    By means of neutron powder diffraction, we investigated the effect of the polar Bi3+^{3+} ion on the magnetic ordering of the Mn3+^{3+} ions in BiMn3_3Mn4_4O12_{12}, the counterpart with \textit{quadruple} perovskite structure of the \textit{simple} perovskite BiMnO3_3. The data are consistent with a \textit{noncentrosymmetric} spacegroup ImIm which contrasts the \textit{centrosymmetric} one I2/mI2/m previously reported for the isovalent and isomorphic compound LaMn3_3Mn4_4O12_{12}, which gives evidence of a Bi3+^{3+}-induced polarization of the lattice. At low temperature, the two Mn3+^{3+} sublattices of the A′A' and BB sites order antiferromagnetically (AFM) in an independent manner at 25 and 55 K, similarly to the case of LaMn3_3Mn4_4O12_{12}. However, both magnetic structures of BiMn3_3Mn4_4O12_{12} radically differ from those of LaMn3_3Mn4_4O12_{12}. In BiMn3_3Mn4_4O12_{12} the moments MA′\textbf{M}_{A'} of the A′A' sites form an anti-body AFM structure, whilst the moments \textbf{M}B_{B} of the BB sites result from a large and \textit{uniform} modulation ±MB,b\pm \textbf{M}_{B,b} along the b-axis of the moments \textbf{M}B,ac_{B,ac} in the acac-plane. The modulation is strikingly correlated with the displacements of the Mn3+^{3+} ions induced by the Bi3+^{3+} ions. Our analysis unveils a strong magnetoelastic coupling between the internal strain created by the Bi3+^{3+} ions and the moment of the Mn3+^{3+} ions in the BB sites. This is ascribed to the high symmetry of the oxygen sites and to the absence of oxygen defects, two characteristics of quadruple perovskites not found in simple ones, which prevent the release of the Bi3+^{3+}-induced strain through distortions or disorder. This demonstrates the possibility of a large magnetoelectric coupling in proper ferroelectrics and suggests a novel concept of internal strain engineering for multiferroics design.Comment: 9 pages, 7 figures, 5 table

    Leptospira seroprevalence in colombian dairy herds

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    Leptospirosis in cattle has important economic effects on the infected farms. Moreover, livestock farming is considered a major occupational risk factor for the transmission of Leptospira infection to humans. A survey was performed to determine the overall and within-herd seroprevalence and mapping of different Leptospira serovars in dairy cattle from farms located in some municipalities of the Colombian department of Boyacá. Nine hundred and fifty-nine animals, from 20 unvaccinated and one vaccinated herd, were included in the study. Anti-Leptospira serum antibodies were detected by the microscopic agglutination test (MAT). Only one herd was seronegative. Overall seroprevalence to at least one serovar of Leptospira was 24.1% for unvaccinated animals and 62.3% for animals from the vaccinated herd. A very high within-herd seroprevalence (&gt;60%) was present in 20% of the unvaccinated herds. The presence in the vaccinated herd of 20/398 animals showing high titers, between 1000 and 4000, to at least one serovar of Leptospira suggest that some animals could have been infected. Moreover, due to the presence of seronegative animals, a failure of vaccination immunity or the presence of unvaccinated animals in the vaccinated herd cannot be excluded. In all farms, domestic animals other than cattle were present. Considering the farming practices occurring on dairy farms in the study area, higher hygienic standards and stricter biosecurity measures are suggested

    Hydrogeochemical processes controlling water and dissolved gas chemistry at the Accesa sinkhole (southern Tuscany, central Italy).

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    The 38.5 m deep Lake Accesa is a sinkhole located in southern Tuscany (Italy) that shows a peculiar water composition, being characterized by relatively high total dissolved solids (TDS) values (2 g L-1) and a Ca(Mg)-SO4 geochemical facies. The presence of significant amounts of extra-atmospheric gases (CO2 and CH4), which increase their concentrations with depth, is also recognized. These chemical features, mimicking those commonly shown by volcanic lakes fed by hydrothermal-magmatic reservoirs, are consistent with those of mineral springs emerging in the study area whose chemistry is produced by the interaction of meteoric-derived waters with Mesozoic carbonates and Triassic evaporites. Although the lake has a pronounced thermocline, water chemistry does not show significant changes along the vertical profile. Lake water balance calculations demonstrate that Lake Accesa has &gt;90% of its water supply from sublacustrine springs whose subterranean pathways are controlled by the local structural assessment that likely determined the sinking event, the resulting funnel-shape being then filled by the Accesa waters. Such a huge water inflow from the lake bottom (~9·106 m3 yr-1) feeds the lake effluent (Bruna River) and promotes the formation of water currents, which are able to prevent the establishment of a vertical density gradient. Consequently, a continuous mixing along the whole vertical water column is established. Changes of the drainage system by the deep-originated waters in the nearby former mining district have strongly affected the outflow rates of the local mineral springs; thus, future intervention associated with the ongoing remediation activities should carefully be evaluated to preserve the peculiar chemical features of Lake Accesa.</p

    Zinc, thymic endocrine activity and mitogen responsiveness (PHA) in piglets exposed to maternal aflatoxicosis B1 and G1

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    Growth retardation, thymic involution and impaired peripheral immune efficiency are constantevents in piglets exposed to maternal aflatoxicosis. Zinc may play a key role because of itsrequirement for good immune responses, including thymic endocrine activity. Zinc is required to.activate a thymic hormone, i.e. thymulin ZnFTS , which is responsible for cell-mediatedimmunity. Zinc deficiency and decreased thymic endocrine activity are present in piglets fed from.sows exposed to aflatoxins AF B and G as compared with healthy control piglets. In particular,11.active ZnFTS is decreased while concentrations of inactive thymulin FTS are high. The in vitroaddition of zinc up to the plasma samples induces a reduction of inactive thymulin. The.lymphocytes mitogen responsiveness PHA is decreased and a thymic cortical lymphocytedepletion is also present. These data suggest that the thymic defect, followed by impairedperipheral immune efficiency, may largely depend by the low peripheral zinc bioavailability tosaturate all thymulin molecules produced

    Survey on Carbapenem-Resistant Bacteria in Pigs at Slaughter and Comparison with Human Clinical Isolates in Italy

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    This study is focused on resistance to carbapenems and third-generation cephalosporins in Gram-negative microorganisms isolated from swine, whose transmission to humans via pork consumption cannot be excluded. In addition, the common carriage of carbapenem-resistant (CR) bacteria between humans and pigs was evaluated. Sampling involved 300 faecal samples collected from slaughtered pigs and 300 urine samples collected from 187 hospitalised patients in Parma Province (Italy). In swine, MIC testing confirmed resistance to meropenem for isolates of Pseudomonas aeruginosa and Pseudomonas oryzihabitans and resistance to cefotaxime and ceftazidime for Escherichia coli, Ewingella americana, Enterobacter agglomerans, and Citrobacter freundii. For Acinetobacter lwoffii, Aeromonas hydrofila, Burkolderia cepacia, Corynebacterium indologenes, Flavobacterium odoratum, and Stenotrophomonas maltophilia, no EUCAST MIC breakpoints were available. However, ESBL genes (blaCTXM-1, blaCTX-M-2, blaTEM-1, and blaSHV) and AmpC genes (blaCIT, blaACC, and blaEBC) were found in 38 and 16 isolates, respectively. P. aeruginosa was the only CR species shared by pigs (4/300 pigs; 1.3%) and patients (2/187; 1.1%). P. aeruginosa ST938 carrying blaPAO and blaOXA396 was detected in one pig as well as an 83-year-old patient. Although no direct epidemiological link was demonstrable, SNP calling and cgMLST showed a genetic relationship of the isolates (86 SNPs and 661 allele difference), thus suggesting possible circulation of CR bacteria between swine and humans
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