879 research outputs found
COLD WAVES IN THE ROMANIAN CARPATHIANS, AN INDICATOR OF NEGATIVE TEMPERATURE EXTREMES
Cold waves in the Romanian Carpathians, an indicator of negative temperature extremes. Cold waves are a representative indicator frequently used to analyze the incidence of cold extremes in a given area. This study was undertaken on these cold extremes in the Romanian Carpathians defined by the STARDEX project. Investigations had in view mountain weather stations located >1,000 m a.s.l. (15 sites) over the 1961-2003 period of available daily temperature records. Long-term records of daily minimum temperature (blended) were also studied from the available ECA&D data sets at Omu Peak station (1928-2011). Regional patterns of cold waves were expressed by comparing their frequency, duration and intensity at the weather stations located in the alpine, sub-alpine and forest vegetation belts. There is an evident inter-annual variability of cold wave duration, showing a significant increase particularly in some forest belt locations in the Southern Carpathians. However, the long-term variability trend (83 years) at Omu Peak alpine station showed quite an opposite trend, corresponding to the warming process in terms of minimum temperature values. Cold waves are usually associated to a high number of consecutive frosty nights and freeze days, but they have low effects on the characteristics of snow season
Artificial Intelligence Techniques Applied to Electromagnetic Interference Problems Between Power Lines and Metal Pipelines
European ecological regulations meant to protect nature and wild life along with construction cost reduction policies generated a set of government regulations that limit the access to new transmission and distribution corridors. As a result, gas, water or oil supply pipelines are forced to share the same distribution corridors with Electrical Power Lines (EPL), AC Railway Systems or Telecommunication Lines (figure 1)
A q-Deformed Schr\"odinger Equation
We found hermitian realizations of the position vector , the angular
momentum and the linear momentum , all behaving like
vectors under the algebra, generated by and . They are
used to introduce a -deformed Schr\" odinger equation. Its solutions for the
particular cases of the Coulomb and the harmonic oscillator potentials are
given and briefly discussed.Comment: 14 pages, latex, no figure
The decay constants of pseudoscalar mesons in a relativistic quark model
The decay constants of pseudoscalar mesons are calculated in a relativistic
quark model which assumes that mesons are made of a valence quark antiquark
pair and of an effective vacuum like component. The results are given in terms
of quark masses and of some free parameters entering the expression of the
internal wave functions of the mesons. By using the pion and kaon decay
constants to fix the parameters of the
model one gets for the light quark masses
and the heavy quark masses in the
range: . In the case of
light neutral mesons one obtains with the same set of parameters
. The
values are in agreement with the experimental data and other theoretical
results.Comment: 11 pages, LaTe
Inter-observer reliability of ultrasound detection of tendon abnormalities at the wrist and ankle in patients with rheumatoid arthritis
OBJECTIVE: To assess inter-observer reliability in US detection of tendon inflammatory and structural changes at wrists and ankles in RA patients.
METHODS: Fourteen consecutive RA patients underwent bilateral US assessment of the extensor carpi ulnaris (ECUT) and tibialis posterior tendons (TPTs) by two blinded rheumatologists, with different level of experience in musculoskeletal (MS) US. Grey scale and power Doppler (PD) US assessment was focused on detection of tenosynovitis, tenosynovial and intra-tendon PD signal and structural lesions (i.e. tendinosis, tendon erosion, partial or total rupture).
RESULTS: The frequency of US findings detected by Investigator 1 was 28.6% for inflammatory changes and 51.8% for structural damage changes while Investigator 2 detected 34 and 53.6% for the corresponding abnormalities. A high overall agreement (82.7%) was found for inflammatory pathology and 89.7% for structural lesions in all tendons. Mean kappa (Îș) values for all tendons and pathology was moderate (Îș = 0.42), with fair level of agreement for the wrist region (0.27-0.34) and moderate to good values for the ankle region (Îș = 0.47-0.62). Subclinical abnormalities were detected in 37.5% of the tendons by Investigator 1 and 28.6% of the tendons by Investigator 2.
CONCLUSIONS: MSUS showed high overall agreement and fair to moderate inter-observer Îș-values between investigators with different levels of experience in detection of tendon pathology at the wrist and ankle in RA patients. Further standardization of scanning method and pathology definitions may improve MSUS reproducibility
Strong Two--Body Decays of Light Mesons
In this paper, we present results on strong two-body decay widths of light
mesons calculated in a covariant quark model. The model is based on
the Bethe-Salpeter equation in its instantaneous approximation and has already
been used for computing the complete meson mass spectrum and many electroweak
decay observables. Our approach relies on the use of a phenomenological
confinement potential with an appropriate spinorial Dirac structure and 't
Hooft's instanton--induced interaction as a residual force for pseudoscalar and
scalar mesons. The transition matrix element for the decay of one initial meson
into two final mesons is evaluated in lowest order by considering conventional
decays via quark loops as well as Zweig rule violating instanton--induced
decays generated by the six--quark vertex of 't Hooft's interaction; the latter
mechanism only contributes if all mesons in the decay have zero total angular
momentum. We show that the interference of both decay mechanisms plays an
important role in the description of the partial widths of scalar and
pseudoscalar mesons.Comment: 35 pages, 7 figure
Local regularity for fractional heat equations
We prove the maximal local regularity of weak solutions to the parabolic
problem associated with the fractional Laplacian with homogeneous Dirichlet
boundary conditions on an arbitrary bounded open set
. Proofs combine classical abstract regularity
results for parabolic equations with some new local regularity results for the
associated elliptic problems.Comment: arXiv admin note: substantial text overlap with arXiv:1704.0756
Improvements to the Method of Dispersion Relations for B Nonleptonic Decays
We bring some clarifications and improvements to the method of dispersion
relations in the external masses variables, that we proposed recently for
investigating the final state interactions in the B nonleptonic decays. We
first present arguments for the existence of an additional term in the
dispersion representation, which arises from an equal-time commutator in the
LSZ formalism and can be approximated by the conventional factorized amplitude.
The reality properties of the spectral function and the Goldberger-Treiman
procedure to perform the hadronic unitarity sum are analyzed in more detail. We
also improve the treatment of the strong interaction part by including the
contributions of both t and u-channel trajectories in the Regge amplitudes.
Applications to the and decays are
presented.Comment: 16 pages, 4 new figures. modifications of the dispersion
representatio
A New Method for Finding Vacua in String Phenomenology
One of the central problems of string-phenomenology is to find stable vacua
in the four dimensional effective theories which result from compactification.
We present an algorithmic method to find all of the vacua of any given
string-phenomenological system in a huge class. In particular, this paper
reviews and then extends hep-th/0606122 to include various non-perturbative
effects. These include gaugino condensation and instantonic contributions to
the superpotential.Comment: 27 pages, 5 .eps figures. V2: Minor corrections, reference adde
Moduli Stabilisation in Heterotic Models with Standard Embedding
In this note we analyse the issue of moduli stabilisation in 4d models
obtained from heterotic string compactifications on manifolds with SU(3)
structure with standard embedding. In order to deal with tractable models we
first integrate out the massive fields. We argue that one can not only
integrate out the moduli fields, but along the way one has to truncate also the
corresponding matter fields. We show that the effective models obtained in this
way do not have satisfactory solutions. We also look for stabilised vacua which
take into account the presence of the matter fields. We argue that this also
fails due to a no-go theorem for Minkowski vacua in the moduli sector which we
prove in the end. The main ingredient for this no-go theorem is the constraint
on the fluxes which comes from the Bianchi identity.Comment: 20 pages, LaTeX; references adde
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