7,789 research outputs found
Black hole solutions in f(R) gravity coupled with non-linear Yang-Mills field
It is shown that in the static, spherically symmetric spacetime the problem
of metric f(R) gravity coupled with non-linear Yang-Mills (YM) field
constructed from the Wu-Yang ansatz as source, can be solved in all dimensions.
By non-linearity it is meant that the YM Lagrangian depends arbitrarily on its
invariant. A particular form is considered to be in the power-law form with
limit of the standard YM theory. The formalism admits black hole solutions with
single or double horizons in which f(R) can be obtained, in general
numerically. In 6-dimensional case we obtain an exact solution given by
f(R)=\surdR gravity that couples with the YM field in a consistent manner.Comment: 12 pages, 8 figures, revised version with major changes including
expanded references. Dedicated to the memory of Yavuz Nutku (1943-2010
Molecular mechanism of regulation of OGG1: tuberin deficiency results in cytoplasmic redistribution of transcriptional factor NF-YA
The tuberous sclerosis complex (TSC) is caused by defects in one of two tumor suppressor genes, TSC-1 or TSC-2. TSC-2 gene encodes tuberin, a protein involved in the pathogenesis of kidney tumors, both angiomyolipomas and renal cell carcinomas. On the other hand, mice-deficient in the DNA repair enzyme OGG1 spontaneously develop adenoma and carcinoma. Downregulation of tuberin results in a marked decrease of OGG1 and accumulation of oxidative DNA damage, (8-oxodG) in cultured cells. In addition, tuberin haploinsufficiency is associated with the loss of OGG1 and accumulation of 8-oxodG in rat kidney tumor. Deficiency in tuberin results in decreased OGG1 and NF-YA protein expression and increased 8-oxodG in kidney tumor from TSC patients. In the current study, molecular mechanisms by which tuberin regulates OGG1 were explored. The deficiency of tuberin was associated with a significant decrease in NF-YA and loss of OGG1 in kidney tumors of Eker rat. Downregulation of tuberin by siRNA resulted in a marked decrease in NF-YA and OGG1 protein expression in human renal epithelial cells. Localization of NF-YA in wild type and tuberin-deficient cells was examined by western blot and immunostaining assays. In wild type cells, NF-YA was detected in the nucleus while in tuberin deficient cells in the cyotoplasm. Introducing adenovirus-expressing tuberin (Ad-TSC2) into tuberin-deficient cells restored the nuclear localization of NF-YA. These data define a novel mechanism of regulation of OGG1 through tuberin. This mechanism may be important in the pathogenesis of kidney tumors in patients with TSC disease
Effect of debris size on the tribological performance of thermally sprayed coatings
This research aims to assess the effect of the debris particle size on the tribological performance
and lubrication regime parameters of a Ni-based alloy coating. This is a key industrial problem,
and its resolution can contribute to better machine endurance and proper maintenance.
The debris particles are simulated by hard Al2O3 particles of size ranging from nanometers to 45
μm and dispersed in an oil lubricant. The coating studied is NiCrBSi deposited by flame spraying
technique followed by the Surface Flame Melting (SFM) process. The counterpart disk sample
was fabricated from quenched and tempered F-5220 steel (in line with A681(O1) ASTM). This
pair was tested under linear sliding contact.
Our results show that the addition of alumina particles contributes to a significant increase in
wear, particularly for the largest particles (micrometric size). In the case of micrometric particles,
it is possible to observe the formation of higher surface roughness, numerous microgrooves, and
plastic flow of NiCrBSi coating perpendicular to the sliding direction, resulting in higher loss of
volume.
It was found that the actual surface roughness (obtained as a function of the debris particle size)
allows better identification and prediction of the lubrication regime for wear processes instead of
the traditional approach that uses the initial surface roughness as a parameter
Bispectrum as Baryon Acoustic Oscillation Interferometer
The galaxy bispectrum, measuring excess clustering of galaxy triplets, offers
a probe of dark energy via baryon acoustic oscillations (BAOs). However up to
now it has been severely underused due to the combinatorically explosive number
of triangles. Here we exploit interference in the bispectrum to identify
triangles that amplify BAOs. This approach reduces the computational cost of
estimating covariance matrices, offers an improvement in BAO constraints
equivalent to lengthening BOSS by 30%, and simplifies adding bispectrum BAO
information to future large-scale redshift survey analyses.Comment: 6 pages, 3 figures; revised to match published versio
Resource targets for advanced underground coal extraction systems
Resource targets appropriate for federal sponsorship of research and development of advanced underground coal mining systems are identified. A comprehensive examination of conventional and unconventional coals with particular attention to exceptionally thin and thick seams, steeply dipping beds, and multiple seam geometry was made. The results indicate that the resource of primary importance is flat lying bituminous coal of moderate thickness, under moderate cover, and located within the lower 48 states. Resources of secondary importance are the flat lying multiple seams and thin seams (especially those in Appalachia). Steeply dipping coals, abandoned pillars, and exceptionally thick western coals may be important in some regions of subregions, but the limited tonnage available places them in a position of tertiary importance
Anisotropic low-temperature piezoresistance in (311)A GaAs two-dimensional holes
We report low-temperature resistance measurements in a modulation-doped,
(311)A GaAs two-dimensional hole system as a function of applied in-plane
strain. The data reveal a strong but anisotropic piezoresistance whose
magnitude depends on the density as well as the direction along which the
resistance is measured. At a density of cm and for a
strain of about applied along [01], e.g., the
resistance measured along this direction changes by nearly a factor of two
while the resistance change in the [33] direction is less than 10% and
has the opposite sign. Our accurate energy band calculations indicate a
pronounced and anisotropic deformation of the heavy-hole dispersion with
strain, qualitatively consistent with the experimental data. The extremely
anisotropic magnitude of the piezoresistance, however, lacks a quantitative
explanation.Comment: 4 pages. Submitted to Applied Physics Letter
Intervensi Psikologis Pada Pendidikan Anak Dengan Keterlambatan Bicara
As the ability to ride a bike, speech is a child's ability to learn. The more frequent practice, these abilities will be more perfect. Many factors affect the process of learning or practice speaking. Among others is the maturity or physical and mental readiness, a good model to be emulated, the motivation they need, the opportunities provided by the environment, and the existence guidance of significant others. Then, how to help children who have spent time to learn speech and due to several factors as mentioned above, have experienced delays in speech?. Excavation data about the causes of overdue talking to children, followed by the deepening problems in a mature, will find the steps that can be taken to help overdue talking children in speech
Colourings of cubic graphs inducing isomorphic monochromatic subgraphs
A -bisection of a bridgeless cubic graph is a -colouring of its
vertex set such that the colour classes have the same cardinality and all
connected components in the two subgraphs induced by the colour classes
(monochromatic components in what follows) have order at most . Ban and
Linial conjectured that every bridgeless cubic graph admits a -bisection
except for the Petersen graph. A similar problem for the edge set of cubic
graphs has been studied: Wormald conjectured that every cubic graph with
has a -edge colouring such that the two
monochromatic subgraphs are isomorphic linear forests (i.e. a forest whose
components are paths). Finally, Ando conjectured that every cubic graph admits
a bisection such that the two induced monochromatic subgraphs are isomorphic.
In this paper, we give a detailed insight into the conjectures of Ban-Linial
and Wormald and provide evidence of a strong relation of both of them with
Ando's conjecture. Furthermore, we also give computational and theoretical
evidence in their support. As a result, we pose some open problems stronger
than the above mentioned conjectures. Moreover, we prove Ban-Linial's
conjecture for cubic cycle permutation graphs.
As a by-product of studying -edge colourings of cubic graphs having linear
forests as monochromatic components, we also give a negative answer to a
problem posed by Jackson and Wormald about certain decompositions of cubic
graphs into linear forests.Comment: 33 pages; submitted for publicatio
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