7,612 research outputs found
Spin dependent Momentum Distributions in Deformed Nuclei
We study the properties of the spin dependent one body density in momentum
space for odd--A polarized deformed nuclei within the mean field approximation.
We derive analytic expressions connecting intrinsic and laboratory momentum
distributions. The latter are related to observable transition densities in
{\bf p}--space that can be probed in one nucleon knock--out reactions from
polarized targets. It is shown that most of the information contained in the
intrinsic spin dependent momentum distribution is lost when the nucleus is not
polarized. Results are presented and discussed for two prolate nuclei,
Ne and Mg, and for one oblate nucleus, Ar. The effects of
deformation are highlighted by comparison to the case of odd--A nuclei in the
spherical model.Comment: Latex 2.09. 25 pages and 6 figures (available from
[email protected]), to appear in Ann. of Phy
AB responses: from bare nucleons to complex nuclei
We study the occurrence of factorization in polarized and unpolarized
observables in coincidence quasi-elastic electron scattering. Starting with the
relativistic distorted wave impulse approximation, we reformulate the effective
momentum approximation and show that the latter leads to observables which
factorize under some specific conditions. Within this framework, the role
played by final state interactions and, in particular, by the spin-orbit term
is explored. Connection with the nonrelativistic formalism is studied in depth.
Numerical results are presented to illustrate the analytical derivations and to
quantify the differences between factorized and unfactorized approaches.Comment: 26 pages, 5 figures. Improved and extended version. To be published
in Phys. Rev.
Hints on the quadrupole deformation of the (1232)
The E2/M1 ratio (EMR) of the (1232) is extracted from the world data
in pion photoproduction by means of an Effective Lagrangian Approach (ELA).This
quantity has been derived within a crossing symmetric, gauge invariant, and
chiral symmetric Lagrangian model which also contains a consistent modern
treatment of the (1232) resonance. The \textit{bare} s-channel
(1232) contribution is well isolated and Final State Interactions (FSI)
are effectively taken into account fulfilling Watson's theorem. The obtained
EMR value, EMR%, is in good agreement with the latest lattice
QCD calculations [Phys. Rev. Lett. 94, 021601 (2005)] and disagrees with
results of current quark model calculations.Comment: Enlarged conclusions and explanations on the E2/M1 ratio. Figure 3
improved. References updated. 5 pages. 3 figures. 2 tables. Accepted for
publication in Physical Review
Blood–brain barrier and foetal-onset hydrocephalus, with a view on potential novel treatments beyond managing CSF flow
[EN] Despite decades of research, no compelling non-surgical therapies have been developed for foetal hydrocephalus. So
far, most efforts have pointed to repairing disturbances in the cerebrospinal fluid (CSF) flow and to avoid further brain
damage. There are no reports trying to prevent or diminish abnormalities in brain development which are inseparably
associated with hydrocephalus. A key problem in the treatment of hydrocephalus is the blood–brain barrier
that restricts the access to the brain for therapeutic compounds or systemically grafted cells. Recent investigations
have started to open an avenue for the development of a cell therapy for foetal-onset hydrocephalus. Potential cells
to be used for brain grafting include: (1) pluripotential neural stem cells; (2) mesenchymal stem cells; (3) geneticallyengineered
stem cells; (4) choroid plexus cells and (5) subcommissural organ cells. Expected outcomes are a proper
microenvironment for the embryonic neurogenic niche and, consequent normal brain development
S-Locus genotyping in Japanese plum by high throughput sequencing using a synthetic S-loci reference sequence
Self-incompatibility in Prunus species is governed by a single locus consisting of two highly multi-allelic and tightly linked genes, one coding for an F-box protein—i.e., SFB in Prunus- controlling the pollen specificity and one coding for an S-RNase gene controlling the pistil specificity. Genotyping the allelic combination in a fruit tree species is an essential procedure both for cross-based breeding and for establishing pollination requirements. Gel-based PCR techniques using primer pairs designed from conserved regions and spanning polymorphic intronic regions are traditionally used for this task. However, with the great advance of massive sequencing techniques and the lowering of sequencing costs, new genotyping-by-sequencing procedures are emerging. The alignment of resequenced individuals to reference genomes, commonly used for polymorphism detection, yields little or no coverage in the S-locus region due to high polymorphism between different alleles within the same species, and cannot be used for this purpose. Using the available sequences of Japanese plum S-loci concatenated in a rosary-like structure as synthetic reference sequence, we describe a procedure to accurately genotype resequenced individuals that allowed the analysis of the S-genotype in 88 Japanese plum cultivars, 74 of them are reported for the first time. In addition to unraveling two new S-alleles from published reference genomes, we identified at least two S-alleles in 74 cultivars. According to their S-allele composition, they were assigned to 22 incompatibility groups, including nine new incompatibility groups reported here for the first time (XXVII-XXXV)
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