14,063 research outputs found
Comment on current correlators in QCD at finite temperature
We address some criticisms by Eletsky and Ioffe on the extension of QCD sum
rules to finite temperature. We argue that this extension is possible, provided
the Operator Product Expansion and QCD-hadron duality remain valid at non-zero
temperature. We discuss evidence in support of this from QCD, and from the
exactly solvable two- dimensional sigma model O(N) in the large N limit, and
the Schwinger model.Comment: 10 pages, LATEX file, UCT-TP-208/94, April 199
Experimental evidence of delocalized states in random dimer superlattices
We study the electronic properties of GaAs-AlGaAs superlattices with
intentional correlated disorder by means of photoluminescence and vertical dc
resistance. The results are compared to those obtained in ordered and
uncorrelated disordered superlattices. We report the first experimental
evidence that spatial correlations inhibit localization of states in disordered
low-dimensional systems, as our previous theoretical calculations suggested, in
contrast to the earlier belief that all eigenstates are localized.Comment: 4 pages, 5 figures. Physical Review Letters (in press
L\u2019IPONATRIEMIA NELL\u2019ANZIANO: UNA PROBLEMATICA SEMPRE ATTUALE
Le alterazioni della concentrazione plasmatica del sodio rappresentano una delle disionie di pi\uf9 frequente riscontro nei pazienti ricoverati e che l\u2019incidenza e la prevalenza aumentano con l\u2019et\ue0. Molteplici fattori correlati all\u2019invecchiamento giocano un ruolo in tal senso; ad esempio, variazioni anatomiche e funzionali, modificazioni della composizione corporea, alterazioni dei meccanismi fisiologici che regolano il metabolismo e l\u2019omeostasi del sodio e dell\u2019acqua. L\u2019aumento dell\u2019incidenza di tali disturbi nella popolazione anziana rappresenta un chiaro esempio di come l\u2019invecchiamento \ue8 in grado di compromettere le capacit\ue0 di compenso, di adattamento e l\u2019omeostasi dell\u2019organismo.Alterations in the plasma concentration of sodium represent one of the most frequently ionic disorders in hospitalized patients. The incidence and prevalence of hyponatremia increase with age. Multiple factors related to aging play a role in this process: for example, anatomical and functional changes, body composition modifications, alterations of physiological mechanisms that regulate metabolism and homeostasis of sodium and water. The increased incidence of these disorders in the older population is a clear example of how aging can affect the ability of compensation, adaptation and homeostasis of the organism
LE IPERNATRIEMIE NELL\u2019ANZIANO
L\u2019pernatremia \ue8 caratterizzata da un deficit di acqua corporea totale rispetto al sodio ed \ue8 definita da una concentrazione plasmatica superiore a 145 mmol/L. L\u2019ipersodiemia nella popolazione geriatrica \ue8 un disturbo comune, associato ad una significativa morbilit\ue0 e mortalit\ue0. Le persone anziane sono predisposte a sviluppare ipernatriemia a causa di modificazioni fisiologiche legate all'et\ue0: ad esempio la diminuzione della sete, una ridotta capacit\ue0 di concentrazione delle urine e la diminuzione del contenuto di acqua corporea totale. I farmaci possono aumentare questa predisposizione. Nelle case di cura e di riposo, l\u2019ipernatremia e la disidratazione sono considerate prevenibili, per cui vengono ritenute indicatori di negligenza e di scarsa qualit\ue0 delle cure.Hypernatremia is characterized by a deficit of total body water relative to total body sodium and is defined by a sodium plasma concentration greater than 145 mmol/L. Hypernatremia in the geriatric population is a common disorder associated with significant morbidity and mortality. Older people are predisposed to developing hypernatremia because of age-related physiologic changes such as decreased thirst drive, impaired urinary concentrating ability, and reduced total body water. Medications may exacerbate this predisposition.
In nursing home residents, hypernatremia and dehydration are considered preventable; hence, they are indicators of neglect and substandard care
A Physical Model for SN 2001ay, a normal, bright, extremely slowly declining Type Ia supernova
We present a study of the peculiar Type Ia supernova 2001ay (SN 2001ay). The
defining features of its peculiarity are: high velocity, broad lines, and a
fast rising light curve, combined with the slowest known rate of decline. It is
one magnitude dimmer than would be predicted from its observed value of
Delta-m15, and shows broad spectral features. We base our analysis on detailed
calculations for the explosion, light curves, and spectra. We demonstrate that
consistency is key for both validating the models and probing the underlying
physics. We show that this SN can be understood within the physics underlying
the Delta-m15 relation, and in the framework of pulsating delayed detonation
models originating from a Chandrasekhar mass, white dwarf, but with a
progenitor core composed of 80% carbon. We suggest a possible scenario for
stellar evolution which leads to such a progenitor. We show that the unusual
light curve decline can be understood with the same physics as has been used to
understand the Delta-m15 relation for normal SNe Ia. The decline relation can
be explained by a combination of the temperature dependence of the opacity and
excess or deficit of the peak luminosity, alpha, measured relative to the
instantaneous rate of radiative decay energy generation. What differentiates SN
2001ay from normal SNe Ia is a higher explosion energy which leads to a shift
of the Ni56 distribution towards higher velocity and alpha < 1. This result is
responsible for the fast rise and slow decline. We define a class of SN
2001ay-like SNe Ia, which will show an anti-Phillips relation.Comment: 35 pages, 14 figures, ApJ, in pres
Cryoablation for Small Renal Masses
Advances in imaging techniques (CT and MRI) and widespread use of imaging especially ultrasound scanning have resulted in a dramatic increase in the detection of small renal masses. While open partial nephrectomy is still the reference standard for the management of these small renal masses, its associated morbidity has encouraged clinicians to exploit the advancements in minimally invasive ablative techniques. The last decade has seen the rapid development of laparoscopic partial nephrectomy and novel ablative techniques such as, radiofrequency ablation (RFA), high-intensity focused ultrasound (HIFU), and cryoablation (CA). In particular, CA for small renal masses has gained popularity as it combines nephron-sparing surgery with a minimally invasive approach. Studies with up to 5-year followup have shown an overall and cancer-specific 5-year survival of 82% and 100%, respectively. This manuscript will focus on the principles and clinical applications of cryoablation of small renal masses, with detailed review of relevant literature
Modelling transport and real-estate values interactions in urban systems
This article presents hedonic Multiple Linear Regression models (MLR), Spatial Auto-Regressive hedonic models (SAR), Spatial autoregressive hedonic in the Error term Models (SEM) and spatial Durbin hedonic Models (SDM) to estimate houses price variations in metropolitan areas as a result of changing environmental and accessibility conditions. The goodness of fit of the different models has been compared along with a series of hypotheses about the performance of the specifications considering spatial relationships between observations. The case study for such analysis was the urban area of Santander (Spain). It has been observed the models which considered spatial dependence between observations offered a greater degree of fit in a scenario showing strong spatial correlation in MLR residuals. The SEM model combined with a Queen-Contiguity matrix provided a good fit to the data and at the same time presented significant parameters with theoretically coherent signs. This model estimated increases of 1.8% for each additional transit line present in the areas of housing, as well as a reduction of 1.1% in their prices for each additional minute in travelling time to the Central Business District. Closeness to the train stations, however, implied reductions in house prices
Phenomenology of Decays
Using the QCD sum rules technique we study several aspects of the
phenomenology of the b-flavoured strange meson . In particular, we
evaluate the mass of the particle, the leptonic constant and the form factors
of the decays , , . We also calculate, in the factorization approximation, a number of
two-body non leptonic decays.Comment: 19 pages, 2 figures (not included) available upon request, LaTex,
BARI-TH/93-139, UTS-DFT-93-1
Conservation Laws in Smooth Particle Hydrodynamics: the DEVA Code
We describe DEVA, a multistep AP3M-like-SPH code particularly designed to
study galaxy formation and evolution in connection with the global cosmological
model. This code uses a formulation of SPH equations which ensures both energy
and entropy conservation by including the so-called \bn h terms. Particular
attention has also been paid to angular momentum conservation and to the
accuracy of our code. We find that, in order to avoid unphysical solutions, our
code requires that cooling processes must be implemented in a non-multistep
way.
We detail various cosmological simulations which have been performed to test
our code and also to study the influence of the \bn h terms. Our results
indicate that such correction terms have a non-negligible effect on some
cosmological simulations, especially on high density regions associated either
to shock fronts or central cores of collapsed objects. Moreover, they suggest
that codes paying a particular attention to the implementation of conservation
laws of physics at the scales of interest, can attain good accuracy levels in
conservation laws with limited computational resources.Comment: 36 pages, 10 figures. Accepted for publication in The Astrophysical
Journa
Review of the ELI-NP-GBS low level rf and synchronization systems
The Gamma Beam System (GBS) of ELI-NP is a linac based gamma-source in construction at Magurele (RO) by the European consortium EuroGammaS led by INFN. Photons with tunable energy and with intensity and brilliance well beyond the state of the art will be produced by Compton back-scattering between a high quality electron beam (up to 740 MeV) and a 515 nm intense laser pulse. Production of very intense photon flux with narrow bandwidth requires multi-bunch operation at 100 Hz repetition rate. A total of 13 klystrons, 3 S-band (2856 MHz) and 10 C-band (5712 MHz) will power a total of 14 Travelling Wave accelerating sections (2 S-band and 12 C-band) plus 3 S-band Standing Wave cavities (a 1.6 cell RF gun and 2 RF deflectors). Each klystron is individually driven by a temperature stabilized LLRF module, for a maximum flexibility in terms of accelerating gradient, arbitrary pulse shaping (e.g. to compensate beam loading effects in multi-bunch regime) and compensation of long-term thermal drifts. In this paper, the whole LLRF system architecture and bench test results, the RF reference generation and distribution together with an overview of the synchronization system will be described
- …