184 research outputs found
The Two-Dimensional Stringy Black-Hole: A New Approach and a Pathology
The string propagation in the two-dimensional stringy black-hole is
investigated from a new approach. We completely solve the classical and quantum
string dynamics in the lorentzian and euclidean regimes. In the lorentzian case
all the physics reduces to a massless scalar particle described by a
Klein-Gordon type equation with a singular effective potential. The scattering
matrix is found and it reproduces the results obtained by coset CFT techniques.
It factorizes into two pieces : an elastic coulombian amplitude and an
absorption part. In both parts, an infinite sequence of imaginary poles in the
energy appear. The generic features of string propagation in curved
D-dimensional backgrounds (string stretching, fall into spacetime
singularities) are analyzed in the present case. A new physical phenomenon
specific to the present black-hole is found : the quantum renormalization of
the speed of light. We find c_{quantum} = \sqrt{{k\o{k-2}}}~c_{classical},
where is the integer in front of the WZW action. This feature is, however,
a pathology. Only for the pathology disappears (although the
conformal anomaly is present). We analyze all the classical euclidean string
solutions and exactly compute the quantum partition function. No critical
Hagedorn temperature appears here.Comment: 32 pages, uses phyzz
Semiclassical (QFT) and Quantum (String) Rotating Black Holes and their Evaporation: New Results
Combination of both quantum field theory (QFT) and string theory in curved
backgrounds in a consistent framework, the string analogue model, allows us to
provide a full picture of the Kerr-Newman black hole and its evaporation going
beyond the current picture. We compute the quantum emission cross section of
strings by a Kerr-Newmann black hole (KNbh). It shows the black hole emission
at the Hawking temperature T_{sem} in the early evaporation and the new string
emission featuring a Hagedorn transition into a string state of temperature T_
s at the last stages. New bounds on the angular momentum J and charge Q emerge
in the quantum string regime. The last state of evaporation of a semiclassical
KNbh is a string state of temperature T_s, mass M_s, J = 0 = Q, decaying as a
quantum string into all kinds of particles.(There is naturally, no loss of
information, (no paradox at all)). We compute the microscopic string entropy
S_s(m, j) of mass m and spin mode j. (Besides the usual transition at T_s), we
find for high j, (extremal string states) a new phase transition at a
temperature T_{sj} higher than T_s. We find a new formula for the Kerr black
hole entropy S_{sem}, as a function of the usual Bekenstein-Hawking entropy .
For high angular momentum, (extremal J = GM^2/c), a gravitational phase
transition operates and the whole entropy S_{sem} is drastically different from
the Bekenstein-Hawking entropy. This new extremal black hole transition occurs
at a temperature T_{sem J} higher than the Hawking temperature T_{sem}.Comment: New articl
Sostenibilidad y arquitectura tradicional: El caso de Moratalla (Murcia, España)
This paper attempts to demonstrate the relationship between sustainability and vernacular
architecture, being focused on a specific research carried out in the old part of Moratalla, a
town in Murcia (Spain).This study has been possible thanks to the collection of 265 field
records with in situ data so that quality and quantity can be measured. All these are
distinctive parameters of vernacular architecture of the centre in the Middle Ages, what
teaches us an important lesson of how traditional construction is environmentally friendly and
sustainable, thus leading to more practical bioclimatic architecture. The current study relies
on an agreement between the Catholic University of Murcia (UCAM) and the town council of
the aforementioned town (Moratalla), what gives an idea of its importance. Some
recommendations have been included at the end of the paper to be taken into account by
municipal legislation so that our building heritage can be preserved and maintained.``El Patrimonio Tradicional o Vernáculo construido es la expresión fundamental de la
identidad de una comunidad, de sus relaciones con el territorio y al mismo tiempo, la
expresión de la diversidad cultural del mundo (ICOMOS 1999)´´.
Este trabajo trata de evidenciar la relación existente entre la Arquitectura Vernácula y los
parámetros de sostenibilidad presentes en ella. Se ha elaborado un estudio de caso en el
casco antiguo del municipio de Moratalla en la provincia de Murcia (España), con la
realización de 265 fichas con datos de campo tomados in situ en las que se trata de extraer
con datos cualitativos y cuantitativos la medida de parámetros como: orientación de las
calles, orientación de fachadas principales, presencia de huecos de reducida dimensión,
relación entre partes opacas y huecos en fachadas, presencia de calles estrechas que
propician la sombra, presencia de protecciones solares en huecos, fachadas en colores
claros, disposición adaptada a la topografía, muros de gran inercia térmica, enfriamiento
evaporativo mediante agua y/o vegetación, presencia de patio interior, construcción
mediante materiales locales y sostenibilidad espacial.
Todos ellos son parámetros propios de la Arquitectura Vernácula de este centro preindustrial
de origen medieval que nos dan una importante lección de cómo las construcción tradicional
consideraba estos parámetros ambientales y sostenibles que hoy se busca con la
arquitectura bioclimática.
Este trabajo se ampara en un convenio de colaboración entre el ayuntamiento de la
localidad y la UCAM Universidad Católica San Antonio de Murcia y debe ser referente para
el análisis previo a cualquier intervención en este casco viejo.
Las conclusiones incluyen una serie de recomendaciones a seguir por la legislación
municipal con la intención de conocer, preservar y mantener nuestro patrimonio construido
Semiclassical and Quantum Black Holes and their Evaporation, de Sitter and Anti-de Sitter Regimes, Gravitational and String Phase Transitions
An effective string theory in physically relevant cosmological and black hole
space times is reviewed. Explicit computations of the quantum string entropy,
partition function and quantum string emission by black holes (Schwarzschild,
rotating, charged, asymptotically flat, de Sitter dS and AdS space times) in
the framework of effective string theory in curved backgrounds provide an
amount of new quantum gravity results as: (i) gravitational phase transitions
appear with a distinctive universal feature: a square root branch point
singularity in any space time dimensions. This is of the type of the de Vega -
Sanchez transition for the thermal self-gravitating gas of point particles.
(ii) There are no phase transitions in AdS alone. (iii) For background,
upper bounds of the Hubble constant H are found, dictated by the quantum string
phase transition.(iv) The Hawking temperature and the Hagedorn temperature are
the same concept but in different (semiclassical and quantum) gravity regimes
respectively. (v) The last stage of black hole evaporation is a microscopic
string state with a finite string critical temperature which decays as usual
quantum strings do in non-thermal pure quantum radiation (no information
loss).(vi) New lower string bounds are given for the Kerr-Newman black hole
angular momentum and charge, which are entirely different from the upper
classical bounds. (vii) Semiclassical gravity states undergo a phase transition
into quantum string states of the same system, these states are duals of each
other in the precise sense of the usual classical-quantum (wave-particle)
duality, which is universal irrespective of any symmetry or isommetry of the
space-time and of the number or the kind of space-time dimensions.Comment: review paper, no figures. to appear in Int Jour Mod Phys
Carbon dioxide enrichment: a technique to mitigate the negative effects of salinity on the productivity of high value tomatoes
The present study was conducted to determine the mitigating influence of greenhouse CO2 enrichment on the negative effects of salinity in Mediterranean conditions. Hybrid Raf (cv. Delizia) tomato plants were exposed to two salinity levels of the nutrient solution (5 and 7 dS/m) obtained by adding NaCl, and two CO2 concentrations (350 and 800 μmol/mol) in which CO2 enrichment was applied during the daytime according to a strategy linked to ventilation. Increasing water salinity negatively affected the leaf area index (LAI), the specific leaf area (SLA), the water use efficiency (WUE), the radiation use efficiency (RUE) and dry weight (DW) accumulation resulting in lower marketable yield. The high salinity treatment (7 dS/m) increased fruit firmness (N), total soluble solids content (SSC) and titratable acidity (TA), whereas pH was reduced in the three ripening stages: mature green/breaker (G), turning (T), and pink/light red (P). Also, the increase in electrical conductivity of the nutrient solution led to a general change in intensity of the sensory characteristics of tomato fruits. On the other hand, CO2 enrichment did not affect LAI although SLA was reduced. RUE and DW accumulation were increased resulting in higher marketable yield, through positive effects on fruit number and their average weight. WUE was enhanced by CO2 supply mainly through increased growth and yield. Physical-chemical quality parameters such as fruit firmness, TA and pH were not affected by CO2 enrichment whereas SSC was enhanced. Greenhouse CO2 enrichment did mitigate the negative effect of saline conditions on productivity without compromising organoleptic and sensory fruit quality
CLASSICAL SPLITTING OF FUNDAMENTAL STRINGS
We find exact solutions of the string equations of motion and constraints
describing the {\em classical}\ splitting of a string into two. We show that
for the same Cauchy data, the strings that split have {\bf smaller} action than
the string without splitting. This phenomenon is already present in flat
space-time. The mass, energy and momentum carried out by the strings are
computed. We show that the splitting solution describes a natural decay process
of one string of mass into two strings with a smaller total mass and some
kinetic energy. The standard non-splitting solution is contained as a
particular case. We also describe the splitting of a closed string in the
background of a singular gravitational plane wave, and show how the presence of
the strong gravitational field increases (and amplifies by an overall factor)
the negative difference between the action of the splitting and non-splitting
solutions.Comment: 27 pages, revtex
Estudio en estructuras de hormigón armado Velocidad de ultrasonidos y resistencia a compresión
So far, much of the research conducted to estimate the compressive strength of reinforced concrete elements of our structures have been made based on checkups witness many samples drawn from these elements.
By this investigation 185 real cases of reinforced concrete structural elements are studied by a structural check based on the correlation of results between the ultrasonic velocity (V) and compressive strength (R). The study was developed taking into account the location of the building relative to the shoreline and the age of the structure. Subsequently, a statistical analysis to the data obtained is performed. This work has achieved a scientific method of analysis of the two test methods and necessary for a full structural check, correlation between them and most innovativeprocess, making mathematical formulas and graphs mapping tools which demonstrate the effectiveness of the procedure, which is proposed as a contribution to policy.Hasta ahora, gran parte de las investigaciones llevadas a cabo para la estimación de las resistencias a compresión de los elementos de hormigón armado de nuestras estructuras, se han realizado en base a chequeos con gran número de probetas testigo, extraídas de esos elementos.Mediante la presente investigación se estudian 185 casos reales de elementos estructurales de hormigón armado, mediante un chequeo estructural basado en la correlación de resultados entre la Velocidad de Ultrasonidos (V) y la Resistencia a Compresión (R). El estudio se desarrolla teniendo en cuenta localización de la construcción respecto a la costa marina y la edad de la propia estructura. Posteriormente se realiza un análisis estadístico con los datos obtenidos con este trabajo se ha conseguido un claro procedimiento científico de análisis de los dos métodos de ensayo y de las herramientas necesarias para realizar un completo chequeo estructural, correlación entre ellos y lo más novedoso del proceso, la confección de fórmulas matemáticas y las gráficas de correlación, que ponen de manifiesto la efectividad del procedimiento, que se propone como aportación para normativa. 
Predicting the onset and persistence of episodes of depression in primary health care. The predictD-Spain study: Methodology
Background:
The effects of putative risk factors on the onset and/or persistence of depression remain unclear. We aim to develop comprehensive models to predict the onset and persistence of episodes of depression in primary care. Here we explain the general methodology of the predictD-Spain study and evaluate the reliability of the questionnaires used.
Methods:
This is a prospective cohort study. A systematic random sample of general practice attendees aged 18 to 75 has been recruited in seven Spanish provinces. Depression is being measured with the CIDI at baseline, and at 6, 12, 24 and 36 months. A set of individual, environmental, genetic, professional and organizational risk factors are to be assessed at each follow-up point. In a separate reliability study, a proportional random sample of 401 participants completed the test-retest (251 researcher-administered and 150 self-administered) between October 2005 and February 2006. We have also checked 118,398 items for data entry from a random sample of 480 patients stratified by province.
Results:
All items and questionnaires had good test-retest reliability for both methods of administration, except for the use of recreational drugs over the previous six months. Cronbach's alphas were good and their factorial analyses coherent for the three scales evaluated (social support from family and friends, dissatisfaction with paid work, and dissatisfaction with unpaid work). There were 191 (0.16%) data entry errors.
Conclusion:
The items and questionnaires were reliable and data quality control was excellent. When we eventually obtain our risk index for the onset and persistence of depression, we will be able to determine the individual risk of each patient evaluated in primary health car
Strings Propagating in the 2+1 Dimensional Black Hole Anti de Sitter Spacetime
We study the string propagation in the 2+1 black hole anti de Sitter
background (2+1 BH-ADS). We find the first and second order fluctuations around
the string center of mass and obtain the expression for the string mass. The
string motion is stable, all fluctuations oscillate with real frequencies and
are bounded, even at We compare with the string motion in the ordinary
black hole anti de Sitter spacetime, and in the black string background, where
string instabilities develop and the fluctuations blow up at We find the
exact general solution for the circular string motion in all these backgrounds,
it is given closely and completely in terms of elliptic functions. For the
non-rotating black hole backgrounds the circular strings have a maximal bounded
size they contract and collapse into No indefinitely growing
strings, neither multi-string solutions are present in these backgrounds. In
rotating spacetimes, both the 2+1 BH-ADS and the ordinary Kerr-ADS, the
presence of angular momentum prevents the string from collapsing into
The circular string motion is also completely solved in the black hole de
Sitter spacetime and in the black string background (dual of the 2+1 BH-ADS
spacetime), in which expanding unbounded strings and multi-string solutions
appear.Comment: Latex, 54 pages + 2 tables and 4 figures (not included). PARIS-DEMIRM
94/01
Towns with extremely low mortality due to ischemic heart disease in Spain
BACKGROUND: The cause of coronary disease inframortality in Spain is unknown. The aim of this study is to identify Spanish towns with very low ischemic heart disease mortality, describe their health and social characteristics, and analyze the relationship with a series of contextual factors. METHODS: We obtained the number of deaths registered for each of 8,122 Spanish towns in the periods 1989-1998 and 1999-2003. Expected deaths, standardized mortality ratio (SMR), smoothed Relative Risk (RR), and Posterior Probability (PP) of RR > 1 were calculated using Bayesian hierarchical models. Inframortality was defined as any town that displayed an RR below the 10th percentile, an SMR of under 1 for both sexes, and a PP of RR > 1 less than or equal to 0.002 for male and 0.005 for female mortality, during the two periods covered. All the remaining towns, except for those with high mortality classified as "tourist towns", were selected as controls. The association among socioeconomic, health, dietary, lifestyle and vascular risk factors was analyzed using sequential mixed logistic regression models, with province as the random-effects variable. RESULTS: We identified 32 towns in which ischemic heart disease mortality was half the national rate and four times lower than the European Union rate, situated in lightly populated provinces spread across the northern half of Spain, and revealed a surprising pattern of geographic aggegation for 23 of the 32 towns. Variables related with inframortality were: a less aged population (OR 0.93, 95% CI 0.89-0.99); a contextual dietary pattern marked by a high fish content (OR 2.13, 95% CI 1.38-3.28) and wine consumption (OR 1.50, 95% CI 1.08-2.07); and a low prevalence of obesity (OR 0.47, 95% CI 0.22-1.01); and, in the case of towns of over 1000 inhabitants, a higher physician-population ratio (OR 3.80, 95% CI 1.17-12.3). CONCLUSIONS: Results indicate that dietary and health care factors have an influence on inframortality. The geographical aggregation suggests that other factors with a spatial pattern, e.g., genetic or environmental might also be implicated. These results will have to be confirmed by studies in situ, with objective measurements at an individual level.This study was funded by research study grant no. PI06/0656 from Spain's Health Research Fund (Fondo de Investigación Sanitaria).S
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