Browsing by Department "Centro Científico Tecnológico de Valparaíso CCTVAL USM"

It is well known that beef produces volatile molecules. In this work, the detection of volatiles released by post-mortem bovine fast-twitch muscles (Musculus longissimus dorsi and Musculus cutaneus trunci) was done using GC/MS–SPME (gas chromatography/mass spectrum–solid-phase microextraction). The releases of volatile molecules were modeled against three factors (rigor-mortis, animal age and oxidative capacity) using a chemometrics approach (experimental design and partial least squares regression). The GC/MS–SPME technique produced more than 30 reproducible chromatographic peaks, but only 13 were associated significantly with two factors (rigor-mortis and animal age). The volatile profile was composed mainly of alcohols, aldehydes and alkanes. The factor “animal age” was the main variable related to the release of volatile molecules. The results strongly suggest that the release of volatile molecules change according to post-mortem metabolism and the animal age.

For functions f whose Taylor coefficients at the origin form a Hausdorff moment sequence we study the behaviour of w(y) := |f(γ + iy)| for y > 0 (γ ≤ 1 fixed)

This lecture presents a short review of the main features of diffractive processes and QCD inspired models. It includes the following topics: (1) Quantum mechanics of diffraction: general properties; (2) Color dipole description of diffraction; (3) Color transparency; (4) Soft diffraction in hard reactions: DIS, Drell-Yan, Higgs production; (5) Why Pomerons interact weakly; (6) Small gluonic spots in the proton; (7) Diffraction near the unitarity bound: the Goulianos-Schlein "puzzle"; (8) Diffraction on nuclei: diffractive Color Glass; (9) CGC and gluon shadowing.

An IEEE 802.11 analytical perfonnance evaluation model for ad-hoc WLAN's comprising tenninals with different traffk source characteristics is presen ted. Although some publications address this issue, most of them propose to modify the original standard by some means that will affect the probability of transmission of a device when the network reaches congestion. The approach of this publication is to be able to establish a set of equations such that an intelligent choice of configuration parameters of standard horne devices may improve the perfonnance of the wireless network. Actually, two models are presented and compared, a simple one based on stationary behavior ofthe network assuming collisions have a negligible effect on network perfonnance, and a second model based on a stationary stochastic model of a network, where devices have a packet ready for transmission at all times.

The nth cyclic function is defined by jn (z)=C . n=0 znn (nn)! (z ¥ C, 2 [ n ¥ N). We prove that if k is an integer with 1 [ k [ n−1, then R (n − k)! j(k) n (x) xn−k S a < jn (x) < R (n − k)! j(k) n (x) xn−k S b holds for all positive real numbers x with the best possible constants a=1 and b=R2n − k n S .

We propose a solution for the long standing puzzle of a too steeply falling fragmentation function for a quark fragmenting into a pion, calculated by Berger [E.L. Berger, Phys. Lett. B 89 (1980) 241] in the Born approximation. Contrary to the simple anticipation that gluon resummation worsens the problem, we find good agreement with data. Higher quark Fock states slow down the quark, an effect which we call jet lag. It can be also expressed in terms of vacuum energy loss. As a result, the space–time development of the jet shrinks and the z-dependence becomes flatter than in the Born approximation. The space–time pattern is also of great importance for in-medium hadronization.

Abstract.D. Brannan's conjecture says that for 0 <α,β≤1, |x|=1, and n∈N one has |A2n−1(α,β,x)|≤|A2n−1(α,β,1)|, where We prove this for the case α=β, and also prove a differentiated version of the Brannan conjecture. This has applications to estimates for Gegenbauer polynomials and also to coefficient estimates for univalent functions in the unit disk that are ‘starlike with respect to a boundary point’. The latter application has previously been conjectured by H. Silverman and E. Silvia. The proofs make use of various properties of the Gauss hypergeometric function.

An analytic function f (z) in the unit disc D is called stable if sn(f,·)/f ≺ 1/f holds for all for n ∈ N0. Here sn stands for the nth partial sum of the Taylor expansion about the origin of f , and ≺ denotes the subordination of analytic functions in D. We prove that (1 − z)λ, λ ∈ [−1, 1], are stable. The stability of √(1 + z)/(1 − z) turns out to be equivalent to a famous result of Vietoris on non-negative trigonometric sums. We discuss some generalizations of these results, and related conjectures, always with an eye on applications to positivity results for trigonometric and other polynomials