2,182 research outputs found
Functional infrared imaging of paroxysmal ischemic events in patients with Raynaud's phenomenon.
The use of thermal infrared (IR) imaging together with the study of the thermal recovery from a controlled cold challenge has been proposed in the diagnosis and follow-up of therapeutic response of Raynaud's Phenomenon (RP) and Systemic Sclerosis (SSc). The controlled cold challenge test usually performed during IR investigations may induce a RP in patients with the latter condition. In our Institution we routinely perform capillaroscopy and thermal IR to follow-up SSc patients. In this paper, we describe the thermal recovery patterns shown by two SSc patients (a 40 year-old male with diffuse variant of SSc and a 71 year-old female with a limited variant of SSc) who presented ischemic and paroxysmal RP attack while recovering from the routine controlled cold challenge test. During RP attack, the cutaneous temperature of some fingers continued to decrease for some minutes even after the cessation of the cold stress. To the best of our knowledge, to date, no literature report has documented the thermal behaviour of SSc patients' fingers which occasionally present ischemic and paroxysmal response. Triggering of ischemic RP attack appears to not rely only on morphological and structural finger impairment, but also upon other aspects, like the emotional attitude of the subject and the possible discomfort experienced with the proceeding of the functional cold stress test
Switching from an EFV-Based STR to a RPV-Based STR is Effective, Safe and Improves HIV Patients Health Status
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Bond of FRP bars in air-entrained concrete : experimental and statistical study
The combined use of Fibre Reinforced Polymer (FRP) and Air-Entrained Concrete (AEC) can be an alternative to traditional steel-reinforced concrete as this system is less affected by the corrosion of the reinforcement and by the freeze-thaw cycles induced concrete degradation. However, the viability of this system hinges on the bond performance of the reinforcing bars. A total of 236 pull-out specimens were prepared and tested to study the effect of air-entraining admixtures (AEA) on the bond behaviour of FRP bars to concrete with varying compressive strengths. Failure modes and bond stress-slip curves were reported and discussed. The bond energy, calculated as the area under the bond stress-slip diagram, was also analyzed. The experimental peak bond stresses (bond strength) were compared to the theoretical ones characterized by the formula proposed for steel bars by the Model Code 2010. In addition, the statistical significance of the effect of AEA on bond characteristics was determined, yielding a reduction factor to account for the effect of AEA on bond strength. The test results show that the bond strength of FRP bars in AEC was statistically significantly lower than in normal concrete. However, the decrease is sufficiently small that could be accounted for, during the design stage, by merely increasing the reinforcement development length
Thermodynamics and Kinetic Theory of Relativistic Gases in 2-D Cosmological Models
A kinetic theory of relativistic gases in a two-dimensional space is
developed in order to obtain the equilibrium distribution function and the
expressions for the fields of energy per particle, pressure, entropy per
particle and heat capacities in equilibrium. Furthermore, by using the method
of Chapman and Enskog for a kinetic model of the Boltzmann equation the
non-equilibrium energy-momentum tensor and the entropy production rate are
determined for a universe described by a two-dimensional Robertson-Walker
metric. The solutions of the gravitational field equations that consider the
non-equilibrium energy-momentum tensor - associated with the coefficient of
bulk viscosity - show that opposed to the four-dimensional case, the cosmic
scale factor attains a maximum value at a finite time decreasing to a "big
crunch" and that there exists a solution of the gravitational field equations
corresponding to a "false vacuum". The evolution of the fields of pressure,
energy density and entropy production rate with the time is also discussed.Comment: 23 pages, accepted in PR
Irreversible Processes in Inflationary Cosmological Models
By using the thermodynamic theory of irreversible processes and Einstein
general relativity, a cosmological model is proposed where the early universe
is considered as a mixture of a scalar field with a matter field. The scalar
field refers to the inflaton while the matter field to the classical particles.
The irreversibility is related to a particle production process at the expense
of the gravitational energy and of the inflaton energy. The particle production
process is represented by a non-equilibrium pressure in the energy-momentum
tensor. The non-equilibrium pressure is proportional to the Hubble parameter
and its proportionality factor is identified with the coefficient of bulk
viscosity. The dynamic equations of the inflaton and the Einstein field
equations determine the time evolution of the cosmic scale factor, the Hubble
parameter, the acceleration and of the energy densities of the inflaton and
matter. Among other results it is shown that in some regimes the acceleration
is positive which simulates an inflation. Moreover, the acceleration decreases
and tends to zero in the instant of time where the energy density of matter
attains its maximum value.Comment: 13 pages, 2 figures, to appear in PR
Effect of temperature on the bond behaviour of GFRP bars in concrete
Glass Fibre Reinforced Polymer (GFRP) bars have been employed as internal reinforcement for concrete members when corrosion of the commonly used steel bars is expected to be an issue. While a good bond is anticipated between GFRP bars and concrete at ambient temperature, the bond performance at high temperature is expected to be reduced due to the physical and mechanical changes that the matrix undergoes at temperatures approaching the glass transition temperature (Tg). Up to date this phenomenon has only been marginally investigated and most of the available bond tests are performed at ambient temperatures after cooling of the heated specimens.
This paper presents the results of an experimental investigation on the bond behaviour of GFRP bars in concrete and exposed to temperature levels ranging from ∼20 °C to 300 °C. The test specimens, consisting of an indented GFRP bar embedded in a cylindrical concrete block, were heated in an electric furnace. The pull-out tests were carried out within the furnace only after the temperature level, measured with thermocouples at the interface of GFRP and concrete, stabilized to the desired value.
The paper discusses the effect of temperature on bond behaviour in terms of bond strength, bond stress-slip relationships and failure modes. A contactless technique measuring the free-end slip during pull-out tests at high temperatures was developed and its effectiveness demonstrated. Finally, the experimental results were used to calibrate the parameters of the two most widely used analytical models: mBPE and CMR
A Wave-function for Stringy Universes
We define a wave-function for string theory cosmological backgrounds. We give
a prescription for computing its norm following an earlier analysis within
general relativity. Under Euclidean continuation, the cosmologies we discuss in
this paper are described in terms of compact parafermionic worldsheet systems.
To define the wave-function we provide a T-fold description of the
parafermionic conformal field theory, and of the corresponding string
cosmology. In specific examples, we compute the norm of the wave-function and
comment on its behavior as a function of moduli.Comment: 30 pages, 3 figures, v3: references adde
Dominant next-to-leading order QCD corrections to Higgs plus three jet production in vector-boson fusion
We present the calculation of the dominant next to leading order QCD
corrections to Higgs boson production in association with three jets via vector
boson fusion in the form of a NLO parton-level Monte Carlo program. QCD
corrections to integrated cross sections are modest, while the shapes of some
kinematical distributions change appreciably at NLO. Scale uncertainties are
shown to be reduced at NLO for the total cross section and for distributions.
We consider a central jet veto at the LHC and analyze the veto probability for
typical vector boson fusion cuts. Scale uncertainties of the veto probability
are sufficiently small at NLO for precise Higgs coupling measurements at the
LHC.Comment: 40 pages, 17 figures, 2 tables, published versio
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