Finsler geometry on higher order tensor fields and applications to high angular resolution diffusion imaging.

We study 3D-multidirectional images, using Finsler geometry. The application considered here is in medical image analysis, specifically in High Angular Resolution Diffusion Imaging (HARDI) (Tuch et al. in Magn. Reson. Med. 48(6):1358–1372, 2004) of the brain. The goal is to reveal the architecture of the neural fibers in brain white matter. To the variety of existing techniques, we wish to add novel approaches that exploit differential geometry and tensor calculus. In Diffusion Tensor Imaging (DTI), the diffusion of water is modeled by a symmetric positive definite second order tensor, leading naturally to a Riemannian geometric framework. A limitation is that it is based on the assumption that there exists a single dominant direction of fibers restricting the thermal motion of water molecules. Using HARDI data and higher order tensor models, we can extract multiple relevant directions, and Finsler geometry provides the natural geometric generalization appropriate for multi-fiber analysis. In this paper we provide an exact criterion to determine whether a spherical function satisfies the strong convexity criterion essential for a Finsler norm. We also show a novel fiber tracking method in Finsler setting. Our model incorporates a scale parameter, which can be beneficial in view of the noisy nature of the data. We demonstrate our methods on analytic as well as simulated and real HARDI data

Morphological assessment of Niger Kuri cattle using multivariate methods

A total of 406 adult cows and 34 bulls belonging to the Niger Kuri cattle population were assessed for 16 body measurements and 11 qualitative traits to contribute to the characterization of this unique cattle breed. Body measurements included facial, horn, ear and rump lengths; facial, cranial, shoulder, pelvic and ischium widths; height at withers and at hips; muzzle circumference; heart girth; body and tail lengths; and thorax depth. Qualitative traits included cephalic profile, ear shape, muzzle pigmentation, eyelid pigmentation, hoof pigmentation, horn colour, dewlap size, backline profile, horn shape, spotting pattern, and coat colour pattern. Data were analysed jointly with 377 individuals from four other West African taurine cattle breeds (N’Dama, Lagunaire, Lobi and Somba) using multivariate statistical methods, including canonical and correspondence analyses. Among the breeds analysed, Kuri cattle had the highest mean values for all body measurements: height at withers and body length had mean values of 124.0 ± 0.4 and 146.8 ± 1.0 cm in Kuri cows, respectively, and 126.0 ± 2.2 and 155.7 ± 3.6 cm, respectively, in Kuri bulls. Canonical analysis allowed the construction of contour plots to illustrate the high differentiation between Kuri cattle and the other breeds, regardless of the sex of the individuals. Further, the Mahalanobis distance matrices showed that pairs involving Kuri cattle had the higher differentiation of these populations. Correspondence analysis carried out on these 11 qualitative traits allowed the researchers to ascertain a clear differentiation between the Kuri and the other taurine cattle breeds. The N’Dama, Lagunaire, Lobi, and Somba breeds did not show clear differentiation at qualitative-type trait level with 75% confidence regions computed for these four breeds being highly intermingled. In the current data, Kuri cattle had the highest frequency in qualitative features, such as concave cephalic profile, dropped ears, non-pigmented muzzle and grey-coloured horns, which are absent in West African taurine and zebu cattle breeds, according to the literature. The current evidence would suggest that unique Kuri cattle type features may result from breeding decisions rather than from zebu admixture. This work confirms that at type trait level Kuri cattle is a unique population within the West African taurine cattle group. The implementation of genetic analyses aiming at ascertaining the degree of uniqueness of the breed is advised.Keywords: Body measurements, Bos taurus, multivariate analyses, qualitative traits, West African cattl

THE INFLUENCE OF INDIUM DOPING ON STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES OF SnO2:IN THIN FILMS DEPOSITED BY SPRAY TECHNIQUE

In this present work, undoped and Indium doped tin dioxide were deposited on glass substrate by Ultrasonic spray method. We investigated the effect of deposition conditions to obtain In doped SnO2 thin films with various concentration (1 to 8 wt.%). XRD analysis confirmed that SnO2 thin films crystallize in the tetragonal structure of SnO2. The grain size average decreases with In content increase. We found that the maximum films transmittance varies from 65-93% in the visible range of the spectrum. The films optical gap varies between 3.48 and 3.80 eV. However, we have noticed that the sheet resistance increases up to 880*103 (Ω/sqr) with increasing the in doping concentration. Owing to their high optical gap and high sheet resistance; the prepared films can be employed in optoelectronic devices

Extended Birkhoff's Theorem in the f(T) Gravity

The f(T) theory, a generally modified teleparallel gravity, has been proposed as an alternative gravity model to account for the dark energy phenomena. Following our previous work [Xin-he Meng and Ying-bin Wang, EPJC(2011), arXiv:1107.0629v1], we prove that the Birkhoff's theorem holds in a more general context, specifically with the off diagonal tetrad case, in this communication letter. Then, we discuss respectively the results of the external vacuum and internal gravitational field in the f(T) gravity framework, as well as the extended meaning of this theorem. We also investigate the validity of the Birkhoff's theorem in the frame of f(T) gravity via conformal transformation by regarding the Brans-Dicke-like scalar as effective matter, and study the equivalence between both Einstein frame and Jordan frame.Comment: 7 pages, 1 figure, submitted to EPJ-C. arXiv admin note: substantial text overlap with arXiv:1107.062

Scalar models for the generalized Chaplygin gas and the structure formation constraints

The generalized Chaplygin gas model represents an attempt to unify dark matter and dark energy. It is characterized by a fluid with an equation of state $p = - A/\rho^\alpha$. It can be obtained from a generalization of the DBI action for a scalar, tachyonic field. At background level, this model gives very good results, but it suffers from many drawbacks at perturbative level. We show that, while for background analysis it is possible to consider any value for $\alpha$, the perturbative analysis must be restricted to positive values of $\alpha$. This restriction can be circumvented if the origin of the generalized Chaplygin gas is traced back to a self-interacting scalar field, instead of the DBI action. But, in doing so, the predictions coming from formation of large scale structures reduce the generalized Chaplygin gas model to a kind of quintessence model, and the unification scenario is lost, if the scalar field is the canonical one. However, if the unification condition is imposed from the beginning as a prior, the model may remain competitive. More interesting results, concerning the unification program, are obtained if a non-canonical self-interacting scalar field, inspired by Rastall's theory of gravity, is imposed. In this case, an agreement with the background tests is possible.Comment: Latex file, 25 pages, 33 figures in eps format. New section on scalar models. Accepted for publication in Gravitation&Cosmolog

Birkhoff's Theorem in f(T) Gravity up to the Perturbative Order

f(T) gravity, a generally modified teleparallel gravity, has become very popular in recent times as it is able to reproduce the unification of inflation and late-time acceleration without the need of a dark energy component or an inflation field. In this present work, we investigate specifically the range of validity of Birkhoff's theorem with the general tetrad field via perturbative approach. At zero order, Birkhoff's theorem is valid and the solution is the well known Schwarzschild-(A)dS metric. Then considering the special case of the diagonal tetrad field, we present a new spherically symmetric solution in the frame of f(T) gravity up to the perturbative order. The results with the diagonal tetrad field satisfy the physical equivalence between the Jordan and the so-called Einstein frames, which are realized via conformal transformation, at least up to the first perturbative order.Comment: 8 pages, no figure. Final version, accepted for publication in EPJ

Reconstruction of some cosmological models in f(R,T) gravity

In this paper, we reconstruct cosmological models in the framework of $f(R,T)$ gravity, where $R$ is the Ricci scalar and $T$ is the trace of the stress-energy tensor. We show that the dust fluid reproduces $\Lambda$CDM, phantom-non-phantom era and the phantom cosmology. Further, we reconstruct different cosmological models including, Chaplygin gas, scalar field with some specific forms of $f(R,T)$. Our numerical simulation for Hubble parameter shows good agreement with the BAO observational data for low redshifts $z<2$.Comment: 12 pages, 2 figure

Deep brain stimulation for refractory obsessive-compulsive disorder (OCD): emerging or established therapy?

A consensus has yet to emerge whether deep brain stimulation (DBS) for treatment-refractory obsessive-compulsive disorder (OCD) can be considered an established therapy. In 2014, the World Society for Stereotactic and Functional Neurosurgery (WSSFN) published consensus guidelines stating that a therapy becomes established when “at least two blinded randomized controlled clinical trials from two different groups of researchers are published, both reporting an acceptable risk-benefit ratio, at least comparable with other existing therapies. The clinical trials should be on the same brain area for the same psychiatric indication.” The authors have now compiled the available evidence to make a clear statement on whether DBS for OCD is established therapy. Two blinded randomized controlled trials have been published, one with level I evidence (Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score improved 37% during stimulation on), the other with level II evidence (25% improvement). A clinical cohort study (N = 70) showed 40% Y-BOCS score improvement during DBS, and a prospective international multi-center study 42% improvement (N = 30). The WSSFN states that electrical stimulation for otherwise treatment refractory OCD using a multipolar electrode implanted in the ventral anterior capsule region (including bed nucleus of stria terminalis and nucleus accumbens) remains investigational. It represents an emerging, but not yet established therapy. A multidisciplinary team involving psychiatrists and neurosurgeons is a prerequisite for such therapy, and the future of surgical treatment of psychiatric patients remains in the realm of the psychiatrist