National University of La Plata

About: National University of La Plata is a education organization based out in La Plata, Argentina. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 12993 authors who have published 30013 publications receiving 495118 citations. The organization is also known as: UNLP & Universidad Nacional de La Plata.

Posterior Cramer-Rao bounds for discrete-time nonlinear filtering

Abstract: A mean-square error lower bound for the discrete-time nonlinear filtering problem is derived based on the van Trees (1968) (posterior) version of the Cramer-Rao inequality. This lower bound is applicable to multidimensional nonlinear, possibly non-Gaussian, dynamical systems and is more general than the previous bounds in the literature. The case of singular conditional distribution of the one-step-ahead state vector given the present state is considered. The bound is evaluated for three important examples: the recursive estimation of slowly varying parameters of an autoregressive process, tracking a slowly varying frequency of a single cisoid in noise, and tracking parameters of a sinusoidal frequency with sinusoidal phase modulation.

The role of constraints within generalized nonextensive statistics

Abstract: The Gibbs–Jaynes path for introducing statistical mechanics is based on the adoption of a specific entropic form S and of physically appropriate constraints. For instance, for the usual canonical ensemble, one adopts (i) S 1 =−k∑ i p i ln p i , (ii) ∑ipi=1, and (iii) ∑ i p i e i =U 1 ({ei}≡ eigenvalues of the Hamiltonian; U1≡ internal energy). Equilibrium consists in optimizing S1 with regard to {pi} in the presence of constraints (ii) and (iii). Within the recently introduced nonextensive statistics, (i) is generalized into Sq=k[1−∑ipiq]/[q−1] (q→1 reproduces S1), (ii) is maintained, and (iii) is generalized in a manner which might involve piq. In the present effort, we analyze the consequences of some special choices for (iii), and their formal and practical implications for the various physical systems that have been studied in the literature. To illustrate some mathematically relevant points, we calculate the specific heat respectively associated with a nondegenerate two-level system as well as with the classical and quantum harmonic oscillators.

Self-assembled monolayers of thiols and dithiols on gold: new challenges for a well-known system

Abstract: Self-assembled monolayers (SAMs) of alkanethiols and dialkanethiols on gold are key elements for building many systems and devices with applications in the wide field of nanotechnology. Despite the progress made in the knowledge of these fascinating two-dimensional molecular systems, there are still several “hot topics” that deserve special attention in order to understand and to control their physical and chemistry properties at the molecular level. This critical review focuses on some of these topics, including the nature of the molecule–gold interface, whose chemistry and structure remain elusive, the self-assembly process on planar and irregular surfaces, and on nanometre-sized objects, and the chemical reactivity and thermal stability of these systems in ambient and aqueous solutions, an issue which seriously limits their technological applications (375 references).

The Simons Genome Diversity Project: 300 genomes from 142 diverse populations

Abstract: Here we report the Simons Genome Diversity Project data set: high quality genomes from 300 individuals from 142 diverse populations. These genomes include at least 5.8 million base pairs that are not present in the human reference genome. Our analysis reveals key features of the landscape of human genome variation, including that the rate of accumulation of mutations has accelerated by about 5% in non-Africans compared to Africans since divergence. We show that the ancestors of some pairs of present-day human populations were substantially separated by 100,000 years ago, well before the archaeologically attested onset of behavioural modernity. We also demonstrate that indigenous Australians, New Guineans and Andamanese do not derive substantial ancestry from an early dispersal of modern humans; instead, their modern human ancestry is consistent with coming from the same source as that of other non-Africans.

Techniques in insect nematology

Abstract: Publisher Summary This chapter focuses on the techniques used for identifying, isolating, propagating, assaying, and preserving nematodes that are parasitic in or pathogenic to insects. Nematodes are nonsegmented animals with excretory, nervous, digestive, reproductive, and muscular systems but lacking circulatory and respiratory systems. The stage of entomogenous and entomopathogenic nematodes that is infective varies depending on the group. A good stereomicroscope is essential for nematode identification and should have a range of magnification between 10 and 100X, a fairly fiat field, and good resolution. The gonads and other structures of fixed nematodes may be obscured by the granular appearance of the intestine. Specimens can be cleared by processing to lactophenol or glycerin. The cephalic structures and the number of longitudinal chords are diagnostic characters for genetic or specific determination of certain groups of nematodes. Extraction methods for insect nematodes are derived from techniques developed with plant-parasitic nematodes. It is found that the most common methods are the Baermann funnel, sieving, elutriation, and centrifugal flotation.