3,971 research outputs found
Uniqueness of the Fock quantization of fields with unitary dynamics in nonstationary spacetimes
The Fock quantization of fields propagating in cosmological spacetimes is not
uniquely determined because of several reasons. Apart from the ambiguity in the
choice of the quantum representation of the canonical commutation relations,
there also exists certain freedom in the choice of field: one can scale it
arbitrarily absorbing background functions, which are spatially homogeneous but
depend on time. Each nontrivial scaling turns out into a different dynamics
and, in general, into an inequivalent quantum field theory. In this work we
analyze this freedom at the quantum level for a scalar field in a
nonstationary, homogeneous spacetime whose spatial sections have
topology. A scaling of the configuration variable is introduced as part of a
linear, time dependent canonical transformation in phase space. In this
context, we prove in full detail a uniqueness result about the Fock
quantization requiring that the dynamics be unitary and the spatial symmetries
of the field equations have a natural unitary implementation. The main
conclusion is that, with those requirements, only one particular canonical
transformation is allowed, and thus only one choice of field-momentum pair (up
to irrelevant constant scalings). This complements another previous uniqueness
result for scalar fields with a time varying mass on , which selects a
specific equivalence class of Fock representations of the canonical commutation
relations under the conditions of a unitary evolution and the invariance of the
vacuum under the background symmetries. In total, the combination of these two
different statements of uniqueness picks up a unique Fock quantization for the
system. We also extend our proof of uniqueness to other compact topologies and
spacetime dimensions.Comment: 12 page
Chromosomal control of non-gliadin proteins from the 70% ethanol extract of wheat endosperm
The non-gliadin fraction of the 70% ethanol extracts of compensated nulli-tetrasomics and ditelosomics of Triticum aestivum cv. Chinese Spring has been analyzed by combined electrofocusing and electrophoresis. Seventeen of the 21 protein map components of the euploid have been ascribed to eight chromosomes: 4A, 3BS, 6BS, 7BS, 3D, 4D, 5D and 7DS.
The relationship of the different map components with other proteins previously associated with the same chromosomes is discusse
Unique Fock quantization of scalar cosmological perturbations
We investigate the ambiguities in the Fock quantization of the scalar
perturbations of a Friedmann-Lema\^{i}tre-Robertson-Walker model with a massive
scalar field as matter content. We consider the case of compact spatial
sections (thus avoiding infrared divergences), with the topology of a
three-sphere. After expanding the perturbations in series of eigenfunctions of
the Laplace-Beltrami operator, the Hamiltonian of the system is written up to
quadratic order in them. We fix the gauge of the local degrees of freedom in
two different ways, reaching in both cases the same qualitative results. A
canonical transformation, which includes the scaling of the matter field
perturbations by the scale factor of the geometry, is performed in order to
arrive at a convenient formulation of the system. We then study the
quantization of these perturbations in the classical background determined by
the homogeneous variables. Based on previous work, we introduce a Fock
representation for the perturbations in which: (a) the complex structure is
invariant under the isometries of the spatial sections and (b) the field
dynamics is implemented as a unitary operator. These two properties select not
only a unique unitary equivalence class of representations, but also a
preferred field description, picking up a canonical pair of field variables
among all those that can be obtained by means of a time-dependent scaling of
the matter field (completed into a linear canonical transformation). Finally,
we present an equivalent quantization constructed in terms of gauge-invariant
quantities. We prove that this quantization can be attained by a mode-by-mode
time-dependent linear canonical transformation which admits a unitary
implementation, so that it is also uniquely determined.Comment: 19 pages, minor impovementes included, typos correcte
Pattern of injuries in beach volleyball at the spanish national university championship
Este artículo pretende establecer y determinar las lesiones más
frecuentes en jugadores de vóley playa universitarios a través de una muestra
de 33 participantes en el Campeonato de España Universitario. Para estudiar las
lesiones, se realizó una entrevista personal mediante un cuestionario validado.
Los resultados mostraron que la región corporal con mayor incidencia lesiva fue
el tobillo (33,3%), seguido de los dedos de la mano (18,5%), las rodillas (13,0%),
los hombros (11,1%) y la espalda (5,6%). Además también se obtuvieron datos
sobre el momento de la lesión (competición o entrenamiento), su origen (impacto
o sobreuso) y característica de la lesión (nueva lesión o repetida). El tratamiento
de los datos para el establecimiento de las diferencias significativas se realizó a
través de la prueba estadística Chi-Cuadrado. Los resultados establecen un
patrón de lesiones diferente al que se produce en vóley playa profesional,
probablemente como consecuencia directa del nivel, horas de entrenamiento y exigencia del juegoThe aim of this paper is to study the most common injuries in university beach
volleyball players. The sample consisted in 33 athletes participating in the
University Spanish Championship. Injuries were assessed by means of
personal interviews and a validated questionnaire. Results show that the body
region with the highest incidence was the ankle (33%), followed by the fingers
(18.5%), knees (13.0%), shoulders (11.1%) and back (5.6%). Also, information
on the moment of injury (competition or training), origin (impact or overuse) and
characteristic of the injury (new or recurrent injury). Statistical processing of
data for establishing significant differences was performed using the Chi-square
test. Results showed a harmful effect, which differs from that of professional
volley players, probably as a result of the level, hours of training and
requirements of the gam
Indicators of nutritional status of turbot Scophthalmus maximus (L., 1758) larvae
Se han analizado diferentes indicadores del estado nutricional de larvas de rodaballo Scophthalmus maximus (L., 1758) alimentadas de hasta 53 días de edad y se han comparado con los de otras larvas sometidas a condiciones de inanición. Los indicadores estudiados fueron longitud, peso seco, condición relativa larvaria, diámetro del otolito, histología digestiva de las larvas, contenido en ácidos grasos, ácido ascórbico, RNA, DNA Y proteínas. Los procesos de inanición se llevaron a cabo a los 3, 9, 16, 23 Y 27 días de edad y los análisis de estas larvas fueron comparados con los de larvas alimentadas de las mismas edades. Durante las primeras 24 horas de inanición, las goticulas lipídicas en las células epiteliales desaparecen por completo del intestino. Después, la condición relativa disminuye aproximadamente el 5% por día y el diámetro relativo del otolito se incrementa en el 5% por día. Se producen también disminuciones en el peso seco, el contenido proteico, los niveles de ácidos grasos 18:1Ω-9, 20:5Ω-3 (EPA) y los de otros ácidos grasos altamente insaturados (Ω-3 HUFA), y en la relación RNA/DNA. Sin embargo, la mayoría de los indicadores investigados muestran una alta variación, incluso entre las distintas experiencias de cultivo realizadas, por lo que se concluye que las gotículas de lípidos en las células epiteliales del intestino, la condición relativa y el diámetro relativo del otolito son las únicas variables que pueden ser útiles para detectar un proceso de inanición en larvas de rodaballo.Nutritional status indicators of larvae of turbot Scophthalmus maximus (L., 1758) were investigated in feeding and starving turbot larvae from hatching up to an age of 53 days. The study included the whole-larvae parameters of length, dry weight and relative condition; the organ-related characteristics otolith diameter and intestinal histology; and the biochemical indicators fatty acids, ascorbic acid, RNA, DNA and total protein. Starvation was started at day 3, 9, 16, 23 and 27, and starved larvae were compared with feeding larvae from the same rearing group. After onset of starvation, lipid droplets in the intestinal epithelial cells disappeared within 24 h. Later; the influence of starvation also became apparent in most of the other indicators studied. Relative condition decreased by about 5%/day and relative otolith diameter increased by about 5%/day. A histologically observed total disappearance of chylomicrons and lipid droplets in the intestinal epithelial cells was in accordance with a drop in dry weight, protein content, and the fatty acids 18:1Ω-9, 20:5Ω-3 (EPA) and Ω-3 HUFA (Highly Unsaturated Fatty Acids), as well as the RNA/DNA ratio in starved larvae. However, most of the indicators studied showed such a high variation between individual rearing groups that only the parameters lipid droplets in intestinal epithelial cells, relative condition and relative otolith diameter seem useful for detecting starvation in turbot larvae.Instituto Español de Oceanografí
PRACTICAL DESIGN EXAMPLES FOR HUMAN HABITATS IN SPACE, OFF-GRID, AND IN LOW-IMPACT COMMUNITIES
All human habitat problems fall into three major categories- the environment, the habitat itself, and the occupants. By breaking these problems down into common themes and addressing them directly, we can build a common knowledge base for all three challenges faced by humanity. A crew living in space has the new problems of coping with radiation, microgravity, and vacuum. All the while, they are dealing the usual issues of eating, sleeping, and getting along with the rest of the occupants. By isolating the differences between space and earth habitats, we can create common architectural styles for each human habitat challenge where commonality is appropriate. We can then examine the differences, then isolate and modularize the secondary systems where possible. This simplifies experimentation and testing of the physical and psychological design of a structure on Earth prior to attempting use in space. It also allows spin-off architectures for extreme environments, off-grid settlements, research bases, and low impact communities on Earth. By isolating and testing each attribute of the system in parallel with control groups, we can scientifically refine the systems for human shelter regardless of environment. This paper will show numerous examples of architectures designed for space or space analog research bases. These designs can be both de-scoped to off-grid sustainable architecture, and scoped up for space habitat applications. Concepts such as internal greenhouses, enclosed permaculture, thermal protection, energy management, and radiation shielding are included for both minimal habitats and large bases. These systems can then be applied for disaster first responders, research bases in extreme environments, o-grid homes, and low-impact communities
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