Coframe teleparallel models of gravity. Exact solutions

The superstring and superbrane theories which include gravity as a necessary and fundamental part renew an interest to alternative representations of general relativity as well as the alternative models of gravity. We study the coframe teleparallel theory of gravity with a most general quadratic Lagrangian. The coframe field on a differentiable manifold is a basic dynamical variable. A metric tensor as well as a metric compatible connection is generated by a coframe in a unique manner. The Lagrangian is a general linear combination of Weitzenb\"{o}ck's quadratic invariants with free dimensionless parameters \r_1,\r_2,\r_3. Every independent term of the Lagrangian is a global SO(1,3)-invariant 4-form. For a special choice of parameters which confirms with the local SO(1,3) invariance this theory gives an alternative description of Einsteinian gravity - teleparallel equivalent of GR. We prove that the sign of the scalar curvature of a metric generated by a static spherical-symmetric solution depends only on a relation between the free parameters. The scalar curvature vanishes only for a subclass of models with \r_1=0. This subclass includes the teleparallel equivalent of GR. We obtain the explicit form of all spherically symmetric static solutions of the ``diagonal'' type to the field equations for an arbitrary choice of free parameters. We prove that the unique asymptotic-flat solution with Newtonian limit is the Schwarzschild solution that holds for a subclass of teleparallel models with \r_1=0. Thus the Yang-Mills-type term of the general quadratic coframe Lagrangian should be rejected.Comment: 28 pages, Latex error is fixe

On a class of invariant coframe operators with application to gravity

Let a differential 4D-manifold with a smooth coframe field be given. Consider the operators on it that are linear in the second order derivatives or quadratic in the first order derivatives of the coframe, both with coefficients that depend on the coframe variables. The paper exhibits the class of operators that are invariant under a general change of coordinates, and, also, invariant under the global SO(1,3)-transformation of the coframe. A general class of field equations is constructed. We display two subclasses in it. The subclass of field equations that are derivable from action principles by free variations and the subclass of field equations for which spherical-symmetric solutions, Minkowskian at infinity exist. Then, for the spherical-symmetric solutions, the resulting metric is computed. Invoking the Geodesic Postulate, we find all the equations that are experimentally (by the 3 classical tests) indistinguishable from Einstein field equations. This family includes, of course, also Einstein equations. Moreover, it is shown, explicitly, how to exhibit it. The basic tool employed in the paper is an invariant formulation reminiscent of Cartan's structural equations. The article sheds light on the possibilities and limitations of the coframe gravity. It may also serve as a general procedure to derive covariant field equations

Efeito do resfriamento na ploidia de ovócitos bovinos maturados in vitro.

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Post-hatching development of bovine embryos in vitro: the effects of tunnel preparation and gender.

The objective of this study was to compare morphological characteristics, kinetics of development, and gene expression ofmale and female IVP embryos thatwere cultured until day (D)15 (fertilization = D0), using either phosphate-buffered saline (PBS) or Milli-Q water (MQW) to dilute the agarose gel used for tunnel construction. On D11, embryos (n = 286) were placed in agarose gel tunnels diluted in PBS and MQW. Embryos were evaluated for morphology, and embryo size was recorded on D11, D12.5, D14 and D15. Then, embryos were sexed and used for gene expression analyses (G6PD, GLUT1, GLUT3, PGK1, PLAC8, KRT8, HSF1 and IFNT). The percentage of elongated embryos at D15 was higher (p < 0.05) in the PBS (54%) than in theMQW(42%) gel. However, embryos produced inMQWwere bigger (p < 0.05) and had a lower expression of GLUT1 (p = 0.08) than those cultured in PBS. There was a higher proportion of male than female embryos at D15 in both treatments, MQW(65% vs. 35%; p < 0.05) and PBS (67% vs. 33%; p < 0.05); however, embryo size was not signi?cantly different between genders. Moreover, D15 female embryos had greater expression of G6PD (p = 0.05) and KRT8 (p = 0.03) than male embryos. In conclusion, the diluent used for tunnel construction affected embryo development in the post-hatching development (PHD) system, and the use ofMQWwas the most indicative measure for the evaluation of embryo quality. Male and female embryos cultured from D11 to D15, either in an MQW or PBS agarose gel, demonstrated similar development but different gene expression

Manifesto for a European research network into Problematic Usage of the Internet

Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.The Internet is now all-pervasive across much of the globe. While it has positive uses (e.g. prompt access to information, rapid news dissemination), many individuals develop Problematic Use of the Internet (PUI), an umbrella term incorporating a range of repetitive impairing behaviours. The Internet can act as a conduit for, and may contribute to, functionally impairing behaviours including excessive and compulsive video gaming, compulsive sexual behaviour, buying, gambling, streaming or social networks use. There is growing public and National health authority concern about the health and societal costs of PUI across the lifespan. Gaming Disorder is being considered for inclusion as a mental disorder in diagnostic classification systems, and was listed in the ICD-11 version released for consideration by Member States (http://www.who.int/classifications/icd/revision/timeline/en/). More research is needed into disorder definitions, validation of clinical tools, prevalence, clinical parameters, brain-based biology, socio-health-economic impact, and empirically validated intervention and policy approaches. Potential cultural differences in the magnitudes and natures of types and patterns of PUI need to be better understood, to inform optimal health policy and service development. To this end, the EU under Horizon 2020 has launched a new four-year European Cooperation in Science and Technology (COST) Action Programme (CA 16207), bringing together scientists and clinicians from across the fields of impulsive, compulsive, and addictive disorders, to advance networked interdisciplinary research into PUI across Europe and beyond, ultimately seeking to inform regulatory policies and clinical practice. This paper describes nine critical and achievable research priorities identified by the Network, needed in order to advance understanding of PUI, with a view towards identifying vulnerable individuals for early intervention. The network shall enable collaborative research networks, shared multinational databases, multicentre studies and joint publications.Peer reviewe

Quadro citológico vaginal, concentração plasmática de progesterona durante a gestação e medidas fetais em paca (Cuniculus paca Linnaeus, 1766).

Em 27 pacas (Cuniculus paca Linnaeus, 1766) objetivou-se descrever aos 30, 60 e 90 dias (D) de prenhez diagnosticada por ultrassonografia (US), os tipos celulares do epitélio vaginal em esfregaços vaginais, relatar as condições de abertura da vulva e as características do muco vaginal, determinar a concentração plasmática de progesterona (P4) por radioimunoensaio, e ainda, mensurar por ultrassonografia (US) o diâmetro biparietal (DBP) fetal aos 60 e 90 dias de prenhez. No D30, 40% das amostras exibiram células (com características estrogênicas) superficiais e presença de núcleos nus. Nos D60 e D90, células parabasais, intermediárias, superficiais e naviculares estavam presentes nas mesmas proporções, mas células endocervicais foram descritas em apenas 73,9% e 69% das amostras daqueles dias, respectivamente. No D30 a maior proporção de células naviculares e superficiais diferiu (p < 0,05) em relação aos outros tipos celulares presentes. O muco vaginal apresentou-se cristalino e fluido em 100% e em 70% das fêmeas nos D30 e D60, respectivamente. Observou-se o vestíbulo vaginal aberto em torno de 50% das fêmeas em todos os dias de exames. Valores mínimos detectáveis de P4 foram obtidos em 72% e em 83% das fêmeas, enquanto que as médias das medidas dos DBP foram 1,25 cm (± 0,16) e 2,34 cm (± 0,25) nos D60 e D90, respectivamente. O quadro citológico vaginal nos D30, D60 e D90 e o DBP fornecem elementos que contribuem para diagnóstico de gestação em pacas. A concentração de P4 demonstra a necessidade de maiores estudos da endocrinologia da gestação em pacas

Injeção intracitoplasmatica de células espermáticas e suas aplicações na reprodução dos bovinos.

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Axial-Vector Torsion and the Teleparallel Kerr Spacetime

In the context of the teleparallel equivalent of general relativity, we obtain the tetrad and the torsion fields of the stationary axisymmetric Kerr spacetime. It is shown that, in the slow rotation and weak field approximations, the axial-vector torsion plays the role of the gravitomagnetic component of the gravitational field, and is thus the responsible for the Lense-Thirring effect.Comment: 9 pages, no figures, to appear in Class. Quant. Gra

Rapidity gaps in perturbative QCD

We analyze diffractive deep inelastic scattering within perturbative QCD by studying lepton scattering on a heavy quark target. Simple explicit expressions are derived in impact parameter space for the photon wave function and the scattering cross sections corresponding to single and double Coulomb gluon exchange. At limited momentum transfers to the target, the results agree with the general features of the ``aligned jet model''. The color--singlet exchange cross section receives a leading twist contribution only from the aligned jet region, where the transverse size of the photon wave function remains finite in the Bjorken scaling limit. In contrast to inclusive DIS, in diffractive events there is no leading twist contribution to $\sigma_L/\sigma_T$ from the lowest order $(q\bar q)$ photon Fock state, and the cross section for heavy quarks is power suppressed in the quark mass. There are also important contributions with large momentum transfer to the target, which corresponds to events having high transverse momentum production in both the projectile and target rapidity regions, separated by a rapidity gap.Comment: 27 pages, LaTeX, 6 figures. Duplicate figure removed, paper unchange