Search results for "lost"

Phylogeny and classification of poison frogs (Amphibia: dendrobatidae), based on mitochondrial 16S and 12S ribosomal RNA gene sequences.

2000

An analysis of partial sequences of the 16S ribosomal rRNA gene (582 bp) of 20 poison frog species (Dendrobatidae) confirmed their phylogenetic relationships to bufonid and leptodactylid frogs. Representatives of the ranoid families and subfamilies Raninae, Mantellinae, Petropedetinae, Cacosterninae, Arthroleptidae, Astylosternidae, and Microhylidae did not cluster as sister group of the Dendrobatidae. Similar results were obtained in an analysis using a partial sequence of the 12S gene (350 bp) in a reduced set of taxa and in a combined analysis. Within the Dendrobatidae, our data supported monophyly of the genus Phyllobates but indicated paraphyly of Epipedobates and Colostethus. Minyobat…

CHANGES OF ELECTRONIC NOISE INDUCED BY OSCILLATING FIELDS IN BULK GaAs SEMICONDUCTORS

2008

A Monte Carlo study of hot-electron intrinsic noise in a n-type GaAs bulk driven by one or two mixed cyclostationary electric fields is presented. The noise properties are investigated by computing the spectral density of velocity fluctuations. An analysis of the noise features as a function of the amplitudes and frequencies of two applied fields is presented. Numerical results show that it is possible to reduce the intrinsic noise. The best conditions to realize this effect are discussed.

Monte Carlo analysis of electronic noise in semiconductors under sub‐terahertz cyclostationary mixed fields

2006

This paper reports the results of Monte Carlo simulations of electronic noise in a GaAs bulk driven by two mixed high-frequency large-amplitude periodic electric fields. Under these conditions, the system response shows some peculiarities in the noise performance, such as a resonant-like enhancement of the spectra near the two frequencies of the applied fields. The relations among the frequency response and the velocity fluctuations as a function of intensities and frequencies of the sub-terahertz mixed excitation fields have been investigated. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Frequency influence on the hot-electron noise reduction in GaAs operating under periodic signals

2008

A Monte Carlo study of the role of the frequency on the hot-electron intrinsic noise reduction in an n-type GaAs bulk driven by two mixed cyclostationary electric fields is presented. Previous numerical results showed the possibility to reduce the diffusion noise under specific wave-mixing conditions. In this work the variations of the noise properties are investigated by computing and integrating the spectral density of the velocity fluctuations. We found that the effect of reduction of the noise level due to the addition of a second field at twice frequency is almost independent of the frequency.

The Internal Dynamics of Fibrinogen and Its Implications for Coagulation and Adsorption

2015

Fibrinogen is a serum multi-chain protein which, when activated, aggregates to form fibrin, one of the main components of a blood clot. Fibrinolysis controls blood clot dissolution through the action of the enzyme plasmin, which cleaves fibrin at specific locations. Although the main biochemical factors involved in fibrin formation and lysis have been identified, a clear mechanistic picture of how these processes take place is not available yet. This picture would be instrumental, for example, for the design of improved thrombolytic or anti-haemorrhagic strategies, as well as, materials with improved biocompatibility. Here, we present extensive molecular dynamics simulations of fibrinogen w…

A new automated plunger for cryopreparation of proteins in defined - even oxygen free - atmospheres

2009

We study the structure and function of hemocyanins. They are giant extracellular oxygen carriers in the hemolymph of many molluscs and arthropods. Since some of these blue, copper-containing proteins show the highest cooperativity in nature (h = 10), one of our goals is to understand the chemomechanical interaction between the different substructures during allosteric oxygen binding.

Clostridium perfringens (Holland) as an indicator of human effluent in the sediment of Lake Tuomiojärvi, central Finland

1983

The horizontal and vertical distribution of the gram-positive, non-motile, spore-forming and rod-shaped bacterium Clostridium perfringens Holland was studied. The aim of the study was to estimate the quantity of C. perfringens at different depths of the sediment and evaluate the effect of human effluent which the lake received between 1940 and 1956. C. perfringens lives in the colon of man. Because it is spore forming and cannot multiply under a temperature of 20 °C and, according to the studies of Seppanen et al. (1979) it can be at least 300 years old, it may be a suitable paleolimnological indicator of pollution by human effluent.

PIH47 Measuring the Burden of Disease and Injury in Spain Using Disability-Adjusted Life Years: A Population-Based Study

2011

Empirical and theoretical study of atelostomate (Echinoidea, Echinodermata) plate architecture: using graph analysis to reveal structural constraints.

2015

AbstractDescribing patterns of connectivity among organs is essential for identifying anatomical homologies among taxa. It is also critical for revealing morphogenetic processes and the associated constraints that control the morphological diversification of clades. This is particularly relevant for studies of organisms with skeletons made of discrete elements such as arthropods, vertebrates, and echinoderms. Nonetheless, relatively few studies devoted to morphological disparity have considered connectivity patterns as a level of morphological organization or developed comparative frameworks with proper tools. Here, we analyze connectivity patterns among apical plates in Atelostomata, the m…

The human milk microbiome changes over lactation and is shaped by maternal weight and mode of delivery

2012

Background Breast milk is recognized as the most important postpartum element in metabolic and immunologic programming of health of neonates. The factors influencing the milk microbiome and the potential impact of microbes on infant health have not yet been uncovered. Objective Our objective was to identify pre- and postnatal factors that can potentially influence the bacterial communities inhabiting human milk. Design We characterized the milk microbial community at 3 different time points by pyrosequencing and quantitative polymerase chain reaction in mothers (n = 18) who varied in BMI, weight gain, and mode of delivery. Results We found that the human milk microbiome changes over lactati…