2,102 research outputs found
The rate of CD4 decline as a determinant of progression to AIDS independent of the most recent CD4 count
The data of two cohort studies of HIV-infected individuals were used to examine whether the rate of CD4 decline is a determinant of HIV progression, independent of the most recent CD4 count. Time from seroconversion to clinical AIDS was the main outcome measure. Rates of CD4 decline were estimated using the ordinary least squares regression method. AIDS incidences were compared in individuals who had previously experienced either a steeper or a less steep rate of CD4 decline. Cox proportional hazards model including a time-dependent covariate for the rate of CD4 decline was performed. The rate of prior CD4 decline was significantly associated with the risk of developing AIDS independently from the most recent CD4 count, with a 2 % increase in hazard of AIDS (P < 0.01) for a difference of 10 cells/mm(3) in the estimated yearly drop in CD4 count. This finding gives scientific credit to the belief that individuals with a prior steeper CD4 decline consistently have a higher subsequent risk of developing AIDS than those with a less steep prior decline
Raman polarization analysis of highly crystalline polyethylene fiber
The complex orientation dependence in space of Raman active vibrations in the orthorhombic structure of polyethylene (PE) is discussed in terms of Raman tensor elements as intrinsic physical parameters of the lattice. Building upon the symmetry assignment of these vibrational modes, we systematically studied, from both theoretical and experimental viewpoints, the changes of polarized intensity for the A(g) and the B-2g + B-3g vibrational modes with respect to PE molecular orientation. After explicitly expanding the Raman selection rules associated with the Ag and the B-2g + B-3g modes, introducing them into general expressions of the orientation distribution function, and validating them by means of a least-square fitting procedure on experimental data, we compare here two mesostructural models for a highly crystallized and self-aligned PE fiber structure. Stereological arguments are shown concerning the arrangement of orthorhombic fibrils in such a sample that unfold the correct values of five independent Raman tensor elements for orthorhombic PE. Copyright (C) 2010 John Wiley & Sons, Ltd
Diseño de un instrumento portátil para aplicaciones ambientales por mediciones amperométricas sobre material biológico
El instrumento portátil optimizado para las medidas de amperometria, en el monitoreo de materiales bioactivos ha sido diseñado, fabricado y probado. Expresamente ha sido diseñado, para funcionar con una amplia gama de bio-muestras foto-activas. La cámara de medición del instrumento; destaca dos tipos de fuentes ópticas para detectar la actividad fotosintética de plantas (p. ej. spinacia oleracea) y microorganismos (p. ej. algas y cyanobacteria). En la cámara son inseridos los electrodos serigrafiados para medir la corriente fotogenerada, ademas cuenta con un sistema de flujo para el transporte del electrólito. La transferencia fotosintética de electrones, es activada por dos LEDs (470nm y 660nm de emisión), para permitir varias longitudes de onda de excitación para utilizarlos con diversos materiales biológicos. El objetivo de la aplicacion, es en campos como agroalimentario, farmacéutico y biomédico. Este Artículo describe algunas de las posibles aplicaciones ambientales ABSTRACT A portable instrument performing amperometric measurements for monitoring bioactive materials has been designed, manufactured and tested. It has been specifically designed to operate with a wide range of photoactive biosamples. The sensing chamber in the instrument features two different optical sources to detect the photosynthetical activity of plants (i.e. spinacia oleracea) and microorganisms (i.e. algae and cyanobacteria). The chamber is provided with screen-printed electrodes to measure the photogenerated current and with a fluidic system for the electrolyte transport. Photosynthetic electron transfer is activated by two LEDs (470nm and 660nm emission) in order to enable various excitation wavelengths and match several different biological materials. Target applications belong to the agro-food, pharmaceutical and biomedical fields. This paper describes some possible environmental application
Revisiting Kepler-444. II. Rotational, orbital and high-energy fluxes evolution of the system
Context. Kepler-444 is one of the oldest planetary systems known thus far.
Its peculiar configuration consisting of five sub-Earth-sized planets orbiting
the companion to a binary stellar system makes its early history puzzling.
Moreover, observations of HI-Ly- variations raise many questions
about the potential presence of escaping atmospheres today. Aims. We aim to
study the orbital evolution of Kepler-444-d and Kepler-444-e and the impact of
atmospheric evaporation on Kepler-444-e. Methods. Rotating stellar models of
Kepler-444-A were computed with the Geneva stellar evolution code and coupled
to an orbital evolution code, accounting for the effects of dynamical,
equilibrium tides and atmospheric evaporation. The impacts of multiple stellar
rotational histories and extreme ultraviolet (XUV) luminosity evolutionary
tracks are explored. Results. Using detailed rotating stellar models able to
reproduce the rotation rate of Kepler-444-A, we find that its observed rotation
rate is perfectly in line with what is expected for this old K0-type star,
indicating that there is no reason for it to be exceptionally active as would
be required to explain the observed HI-Ly- variations from a
stellar origin. We show that given the low planetary mass ( 0.03 M) and relatively large orbital distance ( 0.06 AU) of
Kepler-444-d and e, dynamical tides negligibly affect their orbits, regardless
of the stellar rotational history considered. We point out instead how
remarkable the impact is of the stellar rotational history on the estimation of
the lifetime mass loss for Kepler-444-e. We show that, even in the case of an
extremely slow rotating star, it seems unlikely that such a planet could retain
a fraction of the initial water-ice content if we assume that it formed with a
Ganymede-like composition
Regeneration of plants from embryogenic callus-derived protoplasts of Garganega and Sangiovese grapevine (Vitis vinifera L.) cultivars
Protoplasts are useful research tools for basic and applied plant science, but the regeneration of whole plants from protoplasts is challenging in most of agronomically important crops, including grapevine (Vitis vinifera L.). Here we describe an efficient protocol for the induction of embryogenic callus, the isolation of protoplasts, and the regeneration of whole grapevine plants in two Italian grapevine cultivars. Embryogenic callus was induced successfully from stamens collected from immature flowers. Isolated protoplasts were tested to confirm their viability and then cultivated using the disc-culture method, at a density of 1\u2009
7\u2009105 protoplasts/mL in solid Nitsch\u2019s medium supplemented with 2 mg/L 1-naphthaleneacetic acid and 0.5 mg/L 6-benzylaminopurine. After 3\u20134 months, the protoplasts of both cultivars regenerated with similar efficiency into cotyledonal-stage somatic embryos. The somatic embryos were transferred to solid Nitsch\u2019s medium supplemented with 30 g/L sucrose and 2 g/L gellan gum, and were maintained in the dark for 4 weeks. This step was necessary for the embryo to complete germination, allowing subsequent shoot elongation in response to light on a medium with 4 \ub5M 6-benzylaminopurine. Then root elongation occurred after transferring on a medium with 0.5 \ub5M 1-naphthaleneacetic. After\u2009~\u20096 months from the isolation of protoplasts, normal plants were regenerated, which were moved to the greenhouse. The protoplasts could also be transfected using the polyethylene glycol method, as confirmed using a plasmid carrying the yellow florescent protein marker gene. The new method is therefore compatible with biotechnological applications such as gene transfer and genome editing
Particle Flow with a Hybrid Segmented Crystal and Fiber Dual-Readout Calorimeter
In the reconstruction of physics events at future ee colliders the
calorimeter design has a crucial role in the overall detector performance. The
reconstruction of events with many jets in their final state sets stringent
requirements on the jet energy and angular resolutions. The energy resolution
for jets with energy of about 45 GeV is required to be at the 4-5\% level to
enable an efficient separation of the W and Z boson invariant masses. We
demonstrate in this paper how such a performance can be achieved by exploiting
a particle flow algorithm tailored for a hybrid dual-readout calorimeter made
of segmented crystals and fibers. The excellent energy resolution and linearity
of such calorimeter for both photons and neutral hadrons ( and
, respectively), inherent to the homogeneous crystals and
dual-readout technological choices, provides a powerful handle for the
development of a new approach for particle identification and jet
reconstruction. While the dual-readout particle flow algorithm (DR-PFA)
presented in this paper is at its early stage of development, it already
demonstrates the potential of a hybrid dual-readout calorimeter for jet
reconstruction by improving the jet energy resolution with respect to a
calorimeter-only reconstruction from 6.0\% to about 4.5\% for 45 GeV jets
Constraints on planetary tidal dissipation from a detailed study of Kepler 91b
Context. With the detection of thousands of exoplanets, characterising their
dynamical evolution in detail represents a key step in the understanding of
their formation. Studying the dissipation of tides occurring both in the host
star and in the planets is of great relevance in order to investigate the
distribution of the angular momentum occurring among the objects populating the
system and to studying the evolution of the orbital parameters. From a
theoretical point of view, the dissipation of tides throughout a body may be
studied by relying on the so-called phase or time-lag equilibrium tides model
in which the reduced tidal quality factor Q'p, or equivalently the product
between the love number and the time lag (k2DeltaT), describe how efficiently
tides are dissipated within the perturbed body. Constraining these factors by
looking at the current configuration of the exoplanetary system is extremely
challenging, and simulations accounting for the evolution of the system as a
whole might help to shed some light on the mechanisms governing this process.
Aims. We aim to constrain the tidal dissipation factors of hot-Jupiter-like
planets by studying the orbital evolution of Kepler-91b. Methods. We firstly
carried out a detailed asteroseismc characterisation of Kepler-91 and computed
a dedicated stellar model using both classical and astereoseismic constraints.
We then coupled the evolution of the star to the one of the planets by means of
our orbital evolution code and studied the evolution of the system by
accounting for tides dissipated both in the planet and in the host star.
Results. We found that the maximum value for k2DeltaT (or equivalently the
minimum value for Q'p) determining the efficiency of equilibrium tides
dissipation occurring within Kepler-91b is 0.4 pm 0.25 s (4.5+5.8 * 10^5).Comment: accepted for publication in Astronomy & Astrophysic
Raman tensor analysis of hexagonal polyoxymethylene and its application to study the molecular arrangement in highly crystalline electrospun nanofibers
The orientation dependence in space of Raman-active vibrations in the hexagonal structure of polyoxymethylene (POM) is discussed in terms of Raman tensor elements as intrinsic physical parameters of the lattice. The variation of polarized intensity for the A1 and the E1 vibrational modes with respect to the POM molecular orientation is systematically studied, from both theoretical and experimental viewpoints, according to the symmetry assignments of each vibrational mode. A set of working equations including the Raman selection rules associated with the A1 and the E1 modes and the orientation distribution function are explicitly formulated and validated by means of a least-square fitting procedure on experimental data. In addition, an approach based on the introduction of orientation distribution functions is applied to quantitatively assess and compare on a statistical base the molecular orientation of two different types of electrospun POM nanofibers. Copyright (c) 2012 John Wiley & Sons, Ltd
New method to measure thermal shock resistance in ceramics using a piezo-spectroscopic technique
A new method for assessing the critical temperature in thermally shocked ceramics is proposed. It is based on the measurement of stress relaxation of residual stresses as a consequence of thermal shock. The change in the stress-field is determined by piezo-spectroscopic technique. The technique is described and the results analyzed. The values obtained are compared with those obtained by the conventional method based on strength degradation measured on test pieces quenched at different temperatures. The agreement among the data is very good
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