1,651 research outputs found

    Influence of freezing temperatures prior to freeze‐drying on viability of yeasts and lactic acid bacteria isolated from wine

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    Aims: To determine the effect of three different freezing temperatures on post-freeze-drying survival rates of wine yeasts and lactic acid bacteria (LAB). To know if a similar freeze-drying protocol can be used for both micro- organisms. Methods and Results: Cells from liquid culture media were recovered and concentrated in appropriate lyoprotectants. Aliquots of each strain were frozen at 20, 80 and 196°C before vacuum drying. Viable cell counts were done before freezing and after freeze-drying. Survival rates were calculated. Freezing temperatures differently affected yeast and bacteria survival. The highest survival rates were obtained at 20 and 80°C for yeasts, but at 196° C for LAB. Major differences in survival rates were recorded among freeze-dried yeasts, but were less drastic for LAB. Yeasts Pichia membranifaciens, Starmerella bacillaris and Metschnikowia pulcherrima, and LAB Lactobacillus paracasei, Pediococcus parvulus and Lactobacillus mali, were the most tolerant species to freeze-drying, regardless of freezing temperature. Conclusions: Yeast and LAB survival rates differed for each tested freezing temperature. For yeasts, 20°C ensured the highest post-freeze-drying viability and 196°C for LAB. Significance and Impact of the Study: Freezing temperature to freeze-dry cells is a crucial factor for ensuring good wine yeast and LAB survival. These results are important for appropriately preserving micro-organisms and for improving starter production processes

    Absence of molecular evidence of Leptospira spp. in urine samples collected from rodents captured in Yucatán, México

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    Leptospira spp. is a spirochete bacteria, causal agent of leptospirosis, zoonotic disease endemic in México that represents a serious public health and veterinary problem. Rodents are recognised as the most important reservoirs of this bacteria, which is transmitted mainly through direct or indirect contact with the Leptospira spp. excreted in the urine of infected individuals. Theaim of this study was to evaluate the circulation of Leptospira spp. in urine samples of wild and synanthropic rodents from Yucatán, México. Eighty-four rodents were captured in the community of Cenotillo, Yucatán. Twenty-six urine samples were collected from the bladder and were used in the total DNA extraction. The identification of Leptospira spp. was intended through the polymerase chain reaction test in its endpoint variant. No evidence of Leptospira spp. was found in the urine samples. It is necessary to use other tissues for the identification of Leptospira spp., before concluding that the rodents used in the present study are not reservoirs of this bacteri

    Nonadiabatic charged spherical gravitational collapse

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    We present a complete set of the equations and matching conditions required for the description of physically meaningful charged, dissipative, spherically symmetric gravitational collapse with shear. Dissipation is described with both free-streaming and diffusion approximations. The effects of viscosity are also taken into account. The roles of different terms in the dynamical equation are analyzed in detail. The dynamical equation is coupled to a causal transport equation in the context of Israel-Stewart theory. The decrease of the inertial mass density of the fluid, by a factor which depends on its internal thermodynamic state, is reobtained, with the viscosity terms included. In accordance with the equivalence principle, the same decrease factor is obtained for the gravitational force term. The effect of the electric charge on the relation between the Weyl tensor and the inhomogeneity of energy density is discussed.Comment: 23 pages, Latex. To appear in Phys. Rev. D. Some references correcte

    Genomic adaptations to aquatic and aerial life in mayflies and the origin of insect wings

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    The evolution of winged insects revolutionized terrestrial ecosystems and led to the largest animal radiation on Earth. However, we still have an incomplete picture of the genomic changes that underlay this diversification. Mayflies, as one of the sister groups of all other winged insects, are key to understanding this radiation. Here, we describe the genome of the mayfly Cloeon dipterum and its gene expression throughout its aquatic and aerial life cycle and specific organs. We discover an expansion of odorant-binding-protein genes, some expressed specifically in breathing gills of aquatic nymphs, suggesting a novel sensory role for this organ. In contrast, flying adults use an enlarged opsin set in a sexually dimorphic manner, with some expressed only in males. Finally, we identify a set of wing-associated genes deeply conserved in the pterygote insects and find transcriptomic similarities between gills and wings, suggesting a common genetic program. Globally, this comprehensive genomic and transcriptomic study uncovers the genetic basis of key evolutionary adaptations in mayflies and winged insects

    Advances in prevention and therapy of neonatal dairy calf diarrhoea : a systematical review with emphasis on colostrum management and fluid therapy

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    Neonatal calf diarrhoea remains the most common cause of morbidity and mortality in preweaned dairy calves worldwide. This complex disease can be triggered by both infectious and non-infectious causes. The four most important enteropathogens leading to neonatal dairy calf diarrhoea are Escherichia coli, rota-and coronavirus, and Cryptosporidium parvum. Besides treating diarrhoeic neonatal dairy calves, the veterinarian is the most obvious person to advise the dairy farmer on prevention and treatment of this disease. This review deals with prevention and treatment of neonatal dairy calf diarrhoea focusing on the importance of a good colostrum management and a correct fluid therapy

    Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

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    The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum
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