842 research outputs found
Structural and Electronic Properties of Small Neutral (MgO)n Clusters
Ab initio Perturbed Ion (PI) calculations are reported for neutral
stoichiometric (MgO)n clusters (n<14). An extensive number of isomer structures
was identified and studied. For the isomers of (MgO)n (n<8) clusters, a full
geometrical relaxation was considered. Correlation corrections were included
for all cluster sizes using the Coulomb-Hartree-Fock (CHF) model proposed by
Clementi. The results obtained compare favorably to the experimental data and
other previous theoretical studies. Inclusion of correlaiotn is crucial in
order to achieve a good description of these systems. We find an important
number of new isomers which allows us to interpret the experimental magic
numbers without the assumption of structures based on (MgO)3 subunits. Finally,
as an electronic property, the variations in the cluster ionization potential
with the cluster size were studied and related to the structural isomer
properties.Comment: 24 pages, LaTeX, 7 figures in GIF format. Accepted for publication in
Phys. Rev.
Calculation of The Band Gap Energy and Study of Cross Luminescence in Alkaline-Earth Dihalide Crystals
The band gap energy as well as the possibility of cross luminescence
processes in alkaline-earth dihalide crystals have been calculated using the ab
initio Perturbed-Ion (PI) model. The gap is calculated in several ways: as a
difference between one-electron energy eigenvalues and as a difference between
total energies of appropriate electronic states of the crystal, both at the HF
level and with inclusion of Coulomb correlation effects. In order to study the
possibility of ocurrence of cross luminescence in these materials, the energy
difference between the valence band and the upmost core band for some
representative crystals has been calculated. Both calculated band gap energies
and cross luminescence predictions compare very well with the available
experimental results.Comment: LaTeX file containing 8 pages plus 1 postscript figure. Final version
accepted for publication in The Journal of the Physical Society of Japan. It
contains a more complete list of references, as well as a more detailed
comparison with previous theoretical investigations on the subjec
A Human Monoclonal Antibody with Neutralizing Activity against Highly Divergent Influenza Subtypes
The interest in broad-range anti-influenza A monoclonal antibodies (mAbs) has recently been strengthened by theidentification of anti-hemagglutinin (HA) mAbs endowed with heterosubtypic neutralizing activity to be used in the designof ‘‘universal’’ prophylactic or therapeutic tools. However, the majority of the single mAbs described to date do not bindand neutralize viral isolates belonging to highly divergent subtypes clustering into the two different HA-based influenzaphylogenetic groups: the group 1 including, among others, subtypes H1, H2, H5 and H9 and the group 2 including, amongothers, H3 subtype. Here, we describe a human mAb, named PN-SIA28, capable of binding and neutralizing all testedisolates belonging to phylogenetic group 1, including H1N1, H2N2, H5N1 and H9N2 subtypes and several isolates belongingto group 2, including H3N2 isolates from the first period of the 1968 pandemic. Therefore, PN-SIA28 is capable ofneutralizing isolates belonging to subtypes responsible of all the reported pandemics, as well as other subtypes withpandemic potential. The region recognized by PN-SIA28 has been identified on the stem region of HA and includes residueshighly conserved among the different influenza subtypes. A deep characterization of PN-SIA28 features may represent auseful help in the improvement of available anti-influenza therapeutic strategies and can provide new tools for thedevelopment of universal vaccinal strategies
Entropy and equilibrium state of free market models
Many recent models of trade dynamics use the simple idea of wealth exchanges
among economic agents in order to obtain a stable or equilibrium distribution
of wealth among the agents. In particular, a plain analogy compares the wealth
in a society with the energy in a physical system, and the trade between agents
to the energy exchange between molecules during collisions. In physical
systems, the energy exchange among molecules leads to a state of equipartition
of the energy and to an equilibrium situation where the entropy is a maximum.
On the other hand, in the majority of exchange models, the system converges to
a very unequal condensed state, where one or a few agents concentrate all the
wealth of the society while the wide majority of agents shares zero or almost
zero fraction of the wealth. So, in those economic systems a minimum entropy
state is attained. We propose here an analytical model where we investigate the
effects of a particular class of economic exchanges that minimize the entropy.
By solving the model we discuss the conditions that can drive the system to a
state of minimum entropy, as well as the mechanisms to recover a kind of
equipartition of wealth
The SHOX gene and the short stature. Roundtable on diagnosis and treatment of short stature due to SHOX haploinsufficiency: How genetics, radiology and anthropometry can help the pediatrician in the diagnostic process padova (April 20th, 2011)
The growth of the human body depends from a complex interaction between nutritional, environmental and hormonal factors and by a large number of different genes. One of these genes, short stature homeobox (SHOX), is believed to play a major role in growth. SHOX haploinsufficiency is associated with a wide spectrum of conditions, all characterized growth failure such as Leri-Weill dyschondrosteosis , Turner syndrome, short stature with subtle auxological and radiological findings and the so called “idiopathic short stature” (short stature with no specific findings other than growth failure). The document was prepared by a multidisciplinary team (paediatric endocrinologists, paediatrician, radiologist, geneticist and epidemiologist) to focus on the investigation of children with suspected SHOX- deficiency (SHOX-D) for an early identification and a correct diagnostic work - up of this genetic disorder. On the basis of a number of screening studies, SHOX-D appears to be a relatively frequent cause of short stature. The following recommendations were suggested by our multidisciplinary team: (i) a careful family history, measurements of body proportions and detection of any dysmorphic features are important for the suspect of a genetic disorder ,(ii)the presence of any combination of the following physical findings, such as reduced arm span/ height ratio, increased sitting height/height ratio, above average BMI, Madelung deformity, cubitus valgus, short or bowed forearm, dislocation of the ulna at the elbow, or the appearance of muscular hypertrophy, should prompt the clinician to obtain a molecular analysis of the SHOX region, (iii) it is of practical importance to recognise early or mild signs of Madelung deformity on hand and wrist radiographs, (iv) growth hormone ,after stimulation test, is usually normal . However, treatment with rhGH may improve final adult height; the efficacy of treatment is similar to that observed in those treated for Turner syndrome
Subjectivities in transition: gender and sexual identities in cases of sex change and hermaphroditism in Spain, c. 1500-1800
Electron exchange model potential: Application to positronium-helium scattering
The formulation of a suitable nonlocal model potential for electron exchange
is presented, checked with electron-hydrogen and electron-helium scattering,
and applied to the study of elastic and inelastic scattering and ionization of
ortho positronium (Ps) by helium. The elastic scattering and the
excitations of Ps are investigated using a three-Ps-state close-coupling
approximation. The higher () excitations and ionization of Ps atom are
treated in the framework of Born approximation with present exchange.
Calculations are reported of phase shifts, and elastic, Ps-excitation, and
total cross sections. The present target elastic total cross section agrees
well with experimental results at thermal to medium energies.Comment: 16 latex pages, 7 postscript figure
Relativistic kinetics and power-law tailed distributions
The present paper is devoted to the relativistic statistical theory,
introduced in Phys. Rev. E {\bf 66} (2002) 056125 and Phys. Rev. E {\bf 72}
(2005) 036108, predicting the particle distribution function with , and . This, experimentally observed,
relativistic distribution, at low energies behaves as the exponential,
Maxwell-Boltzmann classical distribution, while at high energies presents power
law tails. Here, we obtain the evolution equation, conducting asymptotically to
the above distribution, by using a new deductive procedure, starting from the
relativistic BBGKY hierarchy and by employing the relativistic molecular chaos
hypothesis.Comment: 5 two-column page
Escape from the vicinity of fractal basin boundaries of a star cluster
The dissolution process of star clusters is rather intricate for theory. We
investigate it in the context of chaotic dynamics. We use the simple Plummer
model for the gravitational field of a star cluster and treat the tidal field
of the Galaxy within the tidal approximation. That is, a linear approximation
of tidal forces from the Galaxy based on epicyclic theory in a rotating
reference frame. The Poincar\'e surfaces of section reveal the effect of a
Coriolis asymmetry. The system is non-hyperbolic which has important
consequences for the dynamics. We calculated the basins of escape with respect
to the Lagrangian points and . The longest escape times have been
measured for initial conditions in the vicinity of the fractal basin
boundaries. Furthermore, we computed the chaotic saddle for the system and its
stable and unstable manifolds. The chaotic saddle is a fractal structure in
phase space which has the form of a Cantor set and introduces chaos into the
system.Comment: Accepted by MNRAS, Figures have lower qualit
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