14,281 research outputs found
Cosmological scaling solutions of minimally coupled scalar fields in three dimensions
We examine Friedmann-Robertson-Walker models in three spacetime dimensions.
The matter content of the models is composed of a perfect fluid, with a
-law equation of state, and a homogeneous scalar field minimally
coupled to gravity with a self-interacting potential whose energy density
red-shifts as , where a denotes the scale factor. Cosmological
solutions are presented for different range of values of and .
The potential required to agree with the above red-shift for the scalar field
energy density is also calculated.Comment: LaTeX2e, 11 pages, 4 figures. To be published in Classical and
Quantum Gravit
Energy Performance Certification of Faculty Buildings in Spain: The gap between estimated and real energy consumption
A systematic method has been established to perform and analyse in detail the Energy Performance Certification of 21 Faculty Buildings located at the University of Zaragoza (Spain), according to the transposition of Directive 2010/31/EU. First of all, the problem background and a review of the state-of-the-art of the energy certification in buildings is outlined, regarding both the actual state of the Government regulations and the studies undertaken in several countries to assess the energy performance of different types of buildings, residential and non-residential. A summary of the causes found in other studies for the discrepancies between the estimated (by simulation) and actual energy consumption is shown which is afterwards tested and compared with the results found in the present study. Thereafter, the method followed to undertake the buildings’ Energy Performance Certification is explained, and the main results found together with the discussion are detailed, comparing actual vs. estimated energy consumption in the different case studies and proposing reasons for these deviations. The energy consumption breakdown by uses for several buildings is also analysed, and potential improvements for the simulation software are assessed
Neutron scattering study of magnetic phase separation in nanocrystalline LaCaMnO
We demonstrate that magnetic phase separation and competing spin order in the
colossal magnetoresistive (CMR) manganites can be directly explored via tuning
strain in bulk samples of nanocrystalline LaCaMnO. Our results
show that strain can be reversibly frozen into the lattice in order to
stabilize coexisting antiferromagnetic domains within the nominally
ferromagnetic metallic state of LaCaMnO. The measurement of
tunable phase separation via magnetic neutron powder diffraction presents a
direct route of exploring the correlated spin properties of phase separated
charge/magnetic order in highly strained CMR materials and opens a potential
avenue for realizing intergrain spin tunnel junction networks with enhanced CMR
behavior in a chemically homogeneous material.Comment: 6 pages, 4 figures. New figure and text added to manuscrip
Magnetic order and the electronic ground state in the pyrochlore iridate Nd2Ir2O7
We report a combined muon spin relaxation/rotation, bulk magnetization,
neutron scattering, and transport study of the electronic properties of the
pyrochlore iridate Nd2Ir2O7. We observe the onset of strongly hysteretic
behavior in the temperature dependent magnetization below 120 K, and an abrupt
increase in the temperature dependent resistivity below 8 K. Zero field muon
spin relaxation measurements show that the hysteretic magnetization is driven
by a transition to a magnetically disordered state, and that below 8 K a
complex magnetically ordered ground state sets in, as evidenced by the onset of
heavily damped spontaneous muon precession. Our measurements point toward the
absence of a true metal-to-insulator phase transition in this material and
suggest that Nd2Ir2O7 lies either within or on the metallic side of the
boundary of the Dirac semimetal regime within its topological phase diagram.Comment: 21 pages, 7 figure
Pattern formation on the surface of cationic-anionic cylindrical aggregates
Charged pattern formation on the surfaces of self--assembled cylindrical
micelles formed from oppositely charged heterogeneous molecules such as
cationic and anionic peptide amphiphiles is investigated. The net
incompatibility among different components results in the formation of
segregated domains, whose growth is inhibited by electrostatics. The transition
to striped phases proceeds through an intermediate structure governed by
fluctuations, followed by states with various lamellar orientations, which
depend on cylinder radius and . We analyze the specific heat,
susceptibility , domain size and morphology as a
function of and .Comment: Sent to PRL 11Jan05 Transferred from PRL to PRE 10Jun0
Psychometric Evaluation of the Yale-Brown Obsessive-Compulsive Scale Modified for Body Dysmorphic Disorder for Adolescents (BDD-YBOCS-A)
The Yale-Brown Obsessive-Compulsive Scale Modified for Body Dysmorphic Disorder for Adolescents (BDD-YBOCS-A) is a clinician-rated measure of BDD symptom severity in youth. Despite widespread use in both research and clinical practice, its psychometric properties have not been formally evaluated. The current study examined the factor structure, reliability, validity, and sensitivity to change of the BDD-YBOCS-A in 251 youths with BDD attending two specialist clinics. A principal component analysis identified two factors, explaining 56% of the variance. The scale showed good internal consistency (Cronbach’s alpha = 0.87) and adequate convergent and divergent validity. In a subgroup of participants receiving BDD treatment (n = 175), BDD-YBOCS-A scores significantly decreased over time, demonstrating sensitivity to change. BDD-YBOCS-A change scores over treatment were highly correlated with severity changes measured by the Clinical Global Impression – Severity scale (r =.84). The study provides empirical support for the use of the BDD-YBOCS-A in children and adolescents with BDD
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