280 research outputs found

    On compact holomorphically pseudosymmetric K\"ahlerian manifolds

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    For compact K\"ahlerian manifolds, the holomorphic pseudosymmetry reduces to the local symmetry if additionally the scalar curvature is constant and the structure function is non-negative. Similarly, the holomorphic Ricci-pseudosymmetry reduces to the Ricci-symmetry under these additional assumptions. We construct examples of non-compact essentially holomorphically pseudosymmetric K\"ahlerian manifolds. These examples show that the compactness assumption cannot be omitted in the above stated theorem. Recently, the first examples of compact, simply connected essentially holomorphically pseudosymmetric K\"ahlerian manifolds are discovered by W. Jelonek. In his examples, the structure functions change their signs on the manifold

    Natural Diagonal Riemannian Almost Product and Para-Hermitian Cotangent Bundles

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    We obtain the natural diagonal almost product and locally product structures on the total space of the cotangent bundle of a Riemannian manifold. We find the Riemannian almost product (locally product) and the (almost) para-Hermitian cotangent bundles of natural diagonal lift type. We prove the characterization theorem for the natural diagonal (almost) para-K\"ahlerian structures on the total spaces of the cotangent bundle.Comment: 10 pages, will appear in Czechoslovak Mathematical Journa

    Riemannian submersions from almost contact metric manifolds

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    In this paper we obtain the structure equation of a contact-complex Riemannian submersion and give some applications of this equation in the study of almost cosymplectic manifolds with Kaehler fibres.Comment: Abh. Math. Semin. Univ. Hamb., to appea

    The association between imbalances in vaginal microflora and duration of pregnancy as well as selected maternal and neonatal parameters

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    Objectives: Abnormal vaginal flora (AVF) is a result of excessive growth of some aerobic bacteria and fungi in relation to the scarce presence of Lactobacillus spp. It has been suggested that AVF is responsible for preterm birth and such neonatal conditions as infections or sepsis.The aim of the study was to assess the influence of excessive vaginal colonization with aerobic bacteria and fungi on the selected postnatal parameters of newborns, duration of pregnancy and length of hospitalisation of neonates.Material and methods: Retrospective data of all 1057 patients who delivered between 01.2019 and 06.2019 in the Department of Perinatology of Medical University of Lodz was analyzed. Eight hundred nine patients were included in this retrospective study. The study group consisted of 396 patients with abundant growth of aerobic bacteria and fungi obtained between 26 and 42 weeks of gestation, while 413 patients with physiologic vaginal biocenosis constituted the control group. Two hundred forty-eight patients (23.46%) were excluded from the study due to incomplete data.Results: Patients with abnormal vaginal flora (AVF) gave birth prematurely (9.09%) more often than patients with balanced microflora (5.31%), p = 0.038. Newborns of mothers with AVF obtained an Apgar score under four more frequently (1.21% vs 0%; p = 0.024). Eutrophic neonates were born less frequently in the study group (82.08% vs 88.65%; p = 0.025). Hospitalisation period was longer for children of mothers with AVF (mean of 6.30 ± 9.87 days) than those of mothers from the control group (mean of 5.06 ± 5.30), p = 0.025. Newborns of mothers with AVF developed perinatal infections more often (23.97% vs 15.94%; p = 0.004). Four infants died in the study group whereas no deaths were recorded in the control group (p = 0.045). The most prevalent pathogens were: Streptococcus agalactiae (GBS) 57.32%, Candida spp. 39.64%, Klebsiella spp. 9.85%, Staphylococcus aureus 7.32%. Signs of infection were more frequently recorded in newborns of mothers infected with Klebsiella spp. (35.90% vs 19.16%; p = 0.011). Premature birth was more prevalent in GBS carriers (11.81% vs 6.28%; p = 0.022).Conclusions: Abundant growth of aerobic bacteria in the 3rd trimester of gestation contributes to preterm birth, causes the development of infection signs in newborns, increases their mortality rate and prolongs hospitalisation period

    A comparative study of different model families for the constitutive simulation of viscous clays

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    The simulation of the viscous behavior of some clays is of high importance in many geotechnical problems. The literature offers a vast amount of constitutive models able to simulate the rate dependence observed on these materials. Although most of thesemodels are calibrated to very similar experimental observations and share similar definitions ofmaterial parameters, some discrepancies of their response have been detected, which are related to their mathematical formulations. In this work, the causes of these discrepancies are carefully studied. To that end, four different model families are analyzed, namely, nonstationary flow surface (NSFS) models, viscoplasticity with overstress function (OVP), viscoplasticity with Norton\u27s power law (NVP), and visco-hypoplasticity (VHP). For the sake of a fair comparison, single constitutive models using the same set of material parameters, and following other requirements, are developed for each model family. Numerical implementations of the four resulting models are performed. Their response at different tests are carefully analyzed through simulation examples and direct examination of their constitutive equations. The set includes some basic tests at isotropic stress states and others as responses envelopes, undrained creep rupture, and an oedometer test with loading, unloading-reloading, creep, and relaxation. The article is concluded with some remarks about the observed discrepancies of these model families

    Renal Sodium Gradient Orchestrates a Dynamic Antibacterial Defense Zone.

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    Lower urinary tract infections are among the most common human bacterial infections, but extension to the kidneys is rare. This has been attributed to mechanical forces, such as urine flow, that prevent the ascent of bladder microbes. Here, we show that the regional hypersalinity, required for the kidney's urine-concentrating function, instructs epithelial cells to produce chemokines that localize monocyte-derived mononuclear phagocytes (MNPs) to the medulla. This hypersaline environment also increases the intrinsic bactericidal and neutrophil chemotactic activities of MNPs to generate a zone of defense. Because MNP positioning and function are dynamically regulated by the renal salt gradient, we find that patients with urinary concentrating defects are susceptible to kidney infection. Our work reveals a critical accessory role for the homeostatic function of a vital organ in optimizing tissue defense

    A conceptual framework for the adoption of big data analytics by e-commerce startups: a case-based approach

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    E-commerce start-ups have ventured into emerging economies and are growing at a significantly faster pace. Big data has acted like a catalyst in their growth story. Big data analytics (BDA) has attracted e-commerce firms to invest in the tools and gain cutting edge over their competitors. The process of adoption of these BDA tools by e-commerce start-ups has been an area of interest as successful adoption would lead to better results. The present study aims to develop an interpretive structural model (ISM) which would act as a framework for efficient implementation of BDA. The study uses hybrid multi criteria decision making processes to develop the framework and test the same using a real-life case study. Systematic review of literature and discussion with experts resulted in exploring 11 enablers of adoption of BDA tools. Primary data collection was done from industry experts to develop an ISM framework and fuzzy MICMAC analysis is used to categorize the enablers of the adoption process. The framework is then tested by using a case study. Thematic clustering is performed to develop a simple ISM framework followed by fuzzy analytical network process (ANP) to discuss the association and ranking of enablers. The results indicate that access to relevant data forms the base of the framework and would act as the strongest enabler in the adoption process while the company rates technical skillset of employees as the most important enabler. It was also found that there is a positive correlation between the ranking of enablers emerging out of ISM and ANP. The framework helps in simplifying the strategies any e-commerce company would follow to adopt BDA in future. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature
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