638 research outputs found
Superconductivity in an Einstein Solid AxV2Al20 (A = Al and Ga)
A cage compound AxV2Al20 (Al10V), that was called an Einstein solid by Caplin
and coworkers 40 years ago, is revisited to investigate the low-energy, local
vibrations of the A atoms and their influence on the electronic and
superconducting properties of the compound. Polycrystalline samples with A =
Al, Ga, Y, and La are studied through resistivity and heat capacity
measurements. Weak-coupling BCS superconductivity is observed below Tc = 1.49,
1.66, and 0.69 K for Ax = Al0.3, Ga0.2, and Y, respectively, but not above 0.4
K for Ax = La. Low-energy modes are detected only for A = Al and Ga, which are
approximately described by the Einstein model with Einstein temperatures of 24
and 8 K, respectively. A weak but significant coupling between the low-energy
modes, which are almost identical to those called rattling in recent study, and
conduction electrons manifests itself as anomalous enhancement in resistivity
at around low temperatures corresponding to the Einstein temperatures.Comment: 12 pages, 5 figures, to be published in J. Phys. Soc. Jp
Anisotropy of the space orientation of radio sources. I: The catalog
A catalog of the extended extragalactic radio sources consisting of 10461
objects is compiled based on the list of radio sources of the FIRST survey. A
total of 1801 objects are identified with galaxies and quasars of the SDSS
survey and the Veron-Veron catalog. The distribution of the position angles of
the axes of radio sources from the catalog is determined, and the probability
that this distribution is equiprobable is shown to be less then 10^(-7). This
result implies that at Z equal to or smaller then 0.5, spatial orientation of
the axes of radio sources is anisotropic at a statistically significant level.Comment: 8 pages, 7 figure
Stellar turbulence and mode physics
An overview of selected topical problems on modelling oscillation properties
in solar-like stars is presented. High-quality oscillation data from both
space-borne intensity observations and ground-based spectroscopic measurements
provide first tests of the still-ill-understood, superficial layers in distant
stars. Emphasis will be given to modelling the pulsation dynamics of the
stellar surface layers, the stochastic excitation processes and the associated
dynamics of the turbulent fluxes of heat and momentum.Comment: Proc. HELAS Workshop on 'Synergies between solar and stellar
modelling', eds M. Marconi, D. Cardini, M. P. Di Mauro, Astrophys. Space
Sci., in the pres
Circular Polarization Induced by Scintillation in a Magnetized Medium
A new theory is presented for the development of circular polarization as
radio waves propagate through the turbulent, birefringent interstellar medium.
The fourth order moments of the wavefield are calculated and it is shown that
unpolarized incident radiation develops a nonzero variance in circular
polarization. A magnetized turbulent medium causes the Stokes parameters to
scintillate in a non-identical manner. A specific model for this effect is
developed for the case of density fluctuations in a uniform magnetic field.Comment: 16 pages, 1 figure, Phys. Rev. E, accepte
Entre défiance et amitié... Des relations politiques, diplomatiques et militaires tourmentées entre le roi de France et le prince-évêque de Liège au bas Moyen Âge (XIIIe-XVe siècles)
audience: researcher, professional, studen
On handling urban informality in southern Africa
In this article I reconsider the handling of urban informality by urban planning and management systems in southern Africa. I argue that authorities have a fetish about formality and that this is fuelled by an obsession with urban modernity. I stress that the desired city, largely inspired by Western notions of modernity, has not been and cannot be realized. Using illustrative cases of top–down interventions, I highlight and interrogate three strategies that authorities have deployed to handle informality in an effort to create or defend the modern city. I suggest that the fetish is built upon a desire for an urban modernity based on a concept of formal order that the authorities believe cannot coexist with the “disorder” and spatial “unruliness” of informality. I question the authorities' conviction that informality is an abomination that needs to be “converted”, dislocated or annihilated. I conclude that the very configuration of urban governance and socio-economic systems in the region, like the rest of sub-Saharan Africa, renders informality inevitable and its eradication impossible
African ancestry of New World, Bemisia tabaci-whitefly species
Bemisia tabaci whitefly species are some of the world’s most devastating agricultural pests and plant-virus disease vectors. Elucidation of the phylogenetic relationships in the group is the basis for understanding their evolution, biogeography, gene-functions and development of novel control technologies. We report here the discovery of five new Sub-Saharan Africa (SSA) B. tabaci putative species, using the partial mitochondrial cytochrome oxidase 1 gene: SSA9, SSA10, SSA11, SSA12 and SSA13. Two of them, SSA10 and SSA11 clustered with the New World species and shared 84.8‒86.5% sequence identities. SSA10 and SSA11 provide new evidence for a close evolutionary link between the Old and New World species. Re-analysis of the evolutionary history of B. tabaci species group indicates that the new African species (SSA10 and SSA11) diverged from the New World clade c. 25 million years ago. The new putative species enable us to: (i) re-evaluate current models of B. tabaci evolution, (ii) recognise increased diversity within this cryptic species group and (iii) re-estimate divergence dates in evolutionary time
Responsiveness to exercise training in juvenile dermatomyositis: a twin case study
<p>Abstract</p> <p>Background</p> <p>Patients with juvenile dermatomyositis (JDM) often present strong exercise intolerance and muscle weakness. However, the role of exercise training in this disease has not been investigated.</p> <p>Purpose</p> <p>this longitudinal case study reports on the effects of exercise training on a 7-year-old patient with JDM and on her unaffected monozygotic twin sister, who served as a control.</p> <p>Methods</p> <p>Both the patient who was diagnosed with JDM as well as her healthy twin underwent a 16-week exercise training program comprising aerobic and strengthening exercises. We assessed one repetition-maximum (1-RM) leg-press and bench-press strength, balance, mobility and muscle function, blood markers of inflammation and muscle enzymes, aerobic conditioning, and disease activity scores. As a result, the healthy child had an overall greater absolute strength, muscle function and aerobic conditioning compared to her JDM twin pair at baseline and after the trial. However, the twins presented comparable relative improvements in 1-RM bench press, 1-RM leg press, VO<sub>2peak</sub>, and time-to-exhaustion. The healthy child had greater relative increments in low-back strength and handgrip, whereas the child with JDM presented a higher relative increase in ventilatory anaerobic threshold parameters and functional tests. Quality of life, inflammation, muscle damage and disease activity scores remained unchanged.</p> <p>Results and Conclusion</p> <p>this was the first report to describe the training response of a patient with non-active JDM following an exercise training regimen. The child with JDM exhibited improved strength, muscle function and aerobic conditioning without presenting an exacerbation of the disease.</p
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