8,544 research outputs found
Ricci Collineations of the Bianchi Types I and III, and Kantowski-Sachs Spacetimes
Ricci collineations of the Bianchi types I and III, and Kantowski-Sachs
space- times are classified according to their Ricci collineation vector (RCV)
field of the form (i)-(iv) one component of is nonzero, (v)-(x)
two components of are nonzero, and (xi)-(xiv) three components of
are nonzero. Their relation with isometries of the space-times is
established. In case (v), when , some metrics are found under
the time transformation, in which some of these metrics are known, and the
other ones new. Finally, the family of contracted Ricci collineations (CRC) are
presented.Comment: 21 Pages, LaTeX, no figures, accepted for publication in the
International Journal of Modern Physics
PAC-MAN endocarditis: Atypical vegetation on the mitral valve
Abstract Not Availabl
Top quark FCNC couplings at future circular hadron electron colliders
A study of single top quark production via flavor changing neutral current
interactions at vertices is performed at future circular hadron
electron collider. The signal cross sections for the processes and in the collision of electron
beam with energy 60 GeV and proton beam with energy 50 TeV are
calculated. In the analysis, the invariant mass distributions of three jets
reconstructing top quark mass, requiring one b-tagged jet and other two jets
reconstructing the mass are used to count signal and background events
after all selection cuts. The upper limits on the anomalous flavor changing
neutral current couplings are found to be 0.01 at
future circular hadron electron collider for fb with the
fast simulation of detector effects. Signal significance depending on the
couplings is analyzed and an enhanced sensitivity is found to the
branching ratio BR() at the future circular hadron electron
collider when compared to the current experimental results.Comment: 11 pages, 4 Figures, 4 Tables, to appear in Phys. Rev.
Cosmological test of the Yilmaz theory of gravity
We test the Yilmaz theory of gravitation by working out the corresponding
Friedmann-type equations generated by assuming the Friedmann-Robertson-Walker
cosmological metrics. In the case that space is flat the theory is consistent
only with either a completely empty universe or a negative energy vacuum that
decays to produce a constant density of matter. In both cases the total energy
remains zero at all times, and in the latter case the acceleration of the
expansion is always negative. To obtain a more flexible and potentially more
realistic cosmology, the equation of state relating the pressure and energy
density of the matter creation process must be different from the vacuum, as
for example is the case in the steady-state models of Gold, Bondi, Hoyle and
others. The theory does not support the cosmological principle for curved space
K =/= 0 cosmological metrics
An Expandable Machine Learning-Optimization Framework to Sequential Decision-Making
We present an integrated prediction-optimization (PredOpt) framework to
efficiently solve sequential decision-making problems by predicting the values
of binary decision variables in an optimal solution. We address the key issues
of sequential dependence, infeasibility, and generalization in machine learning
(ML) to make predictions for optimal solutions to combinatorial problems. The
sequential nature of the combinatorial optimization problems considered is
captured with recurrent neural networks and a sliding-attention window. We
integrate an attention-based encoder-decoder neural network architecture with
an infeasibility-elimination and generalization framework to learn high-quality
feasible solutions to time-dependent optimization problems. In this framework,
the required level of predictions is optimized to eliminate the infeasibility
of the ML predictions. These predictions are then fixed in mixed-integer
programming (MIP) problems to solve them quickly with the aid of a commercial
solver. We demonstrate our approach to tackling the two well-known dynamic
NP-Hard optimization problems: multi-item capacitated lot-sizing (MCLSP) and
multi-dimensional knapsack (MSMK). Our results show that models trained on
shorter and smaller-dimensional instances can be successfully used to predict
longer and larger-dimensional problems. The solution time can be reduced by
three orders of magnitude with an average optimality gap below 0.1%. We compare
PredOpt with various specially designed heuristics and show that our framework
outperforms them. PredOpt can be advantageous for solving dynamic MIP problems
that need to be solved instantly and repetitively
Concentration and localization of zinc during seed development and germination in wheat
In a field experiment, the effect of foliar Zn applications on the concentration of Zn in seeds of a bread wheat cultivar (Triticum aestivum L. cv. Balatilla) was studied during different stages of seed development. In addition, a staining method using dithizone (DTZ: diphenyl thiocarbazone) was applied to (1) study the localization of Zn in seeds, (2) follow the remobilization of Zn during germination, and (3) develop a rapid visual Zn screening method for seed and flour samples. In all seed development stages, foliar Zn treatments were effective in increasing seed Zn concentration. The highest Zn concentration in the seeds was found in the first stage of seed development (around the early milk stage); after this, seed Zn concentration gradually decreased until maturity. When reacting with Zn, DTZ forms a redcolored complex. The DTZ staining of seed samples revealed that Zn is predominantly located in the embryo and aleurone parts of the seeds. After 36 h of germination, the coleoptile and roots that emerged from seeds showed very intensive red color formation and had Zn concentrations up to 200 mg kg1, indicating a substantial remobilization of Zn from seed pools into the developing roots (radicle) and coleoptile. The DTZ staining method seems to be useful in ranking flour samples for their Zn concentrations. There was a close relationship between the seed Zn concentrations and spectral absorbance of the methanol extracts of the flour samples stained with DTZ. The results suggest that (1) accumulation of Zn in seeds is particularly high during early seed development, (2) Zn is concentrated in the embryo and aleurone parts, and (3) the DTZ staining method can be used as a rapid, semiquantitative method to estimate Zn concentrations of flour and seed samples and to screen genotypes for their Zn concentrations in seeds
Studies of ecomorphological variations of the European hare (Lepus europaeus) in Turkey
Hares (Lepus spp.) are widely distributed across the globe and are adapted to diverse climatic conditions. In order to study the ecomorphological variations of hares from Turkey, the body and cranial measurements and body weight, as well as coat color types, of 138 hares collected from all over Turkey between 2006 and 2012, were examined. Statistically significant differences between regional samples (p <0.05, ANOVA) only in terms of body weight and hindfoot length were found; however, there were a good number of external phenotypes, particularly in terms of coat color variants of the hare specimens. Furthermore, populations had similar variations in terms of morphometric measurement, body weight and coat coloration between different geographical regions. Turkish hares did not exhibit clinal variations from south to north in body and cranial measurements depending on the mean annual temperatures and precipitation. Therefore, it was assumed that all of these variations might be a polymorphism related to the local adaptations and high level of admixture of gene pools in Anatolia
Case report: A Stauffer’s syndrome variant associated with renal cell carcinoma and thrombocytopenia
Stauffer’s syndrome is a rare paraneoplastic manifestation of renal cell carcinoma which is characterized by elevated alkaline phosphatase, erythrocyte sedimentation rate, -2-globulin, -glutamyl transferase, thrombocytosis, prolongation of prothrombin time and hepatosplenomegaly, in the absence of hepatic metastasis and jaundice. In this case report, we report a patient who was admitted with fever, fatigue, abdominal pain, weight loss and pruritus in whom renal cell carcinoma was incidentally found in the right kidney during an initial workup.KEYWORDS: Cholestasis; Paraneoplastic syndrome; RCC; Stauffer’s syndrome; Thrombocytopeni
Internal relaxation time in immersed particulate materials
We study the dynamics of the solid to liquid transition for a model material
made of elastic particles immersed in a viscous fluid. The interaction between
particle surfaces includes their viscous lubrication, a sharp repulsion when
they get closer than a tuned steric length and their elastic deflection induced
by those two forces. We use Soft Dynamics to simulate the dynamics of this
material when it experiences a step increase in the shear stress and a constant
normal stress. We observe a long creep phase before a substantial flow
eventually establishes. We find that the typical creep time relies on an
internal relaxation process, namely the separation of two particles driven by
the applied stress and resisted by the viscous friction. This mechanism should
be relevant for granular pastes, living cells, emulsions and wet foams
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