Charge exchange in relativistic heavy ion collisions

Elastic charge-exchange in relativistic heavy ion collisions is responsible for the non-disruptive change of the charge state of the nuclei. We show that it can be reliably calculated within the eikonal approximation for the reaction part. The formalism is applied to the charge-pickup cross sections of 158 GeV/nucleon Pb projectiles on several targets. The relative contributions of pion- and rho-exchange are determined, using a single-particle model for the internal structure of the nuclei. The calculated cross sections are non-negligible for heavy targets. It is shown that these cross sections can be useful to obtain information on the Gamow-Teller transition strengths of the nuclei.Comment: 12 pages, 4 postscript figure

Pair production with electron capture in peripheral collisions of relativistic heavy ions

The production of electron-positron pairs with the capture of the electron in an atomic orbital is investigated for the conditions of the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider LHC). Dirac wave functions for the leptons are used, taking corrections to orders of Z.alpha into account. The dependence on the transverse momentum transfer is studied and the accuracy of the equivalent photon approximation is discussed as a function of the nuclear charge.Comment: 4 postscript figure

Self-Consistent Separable Rpa Approach for Skyrme Forces: Axial Nuclei

The self-consistent separable RPA (random phase approximation) method is formulated for Skyrme forces with pairing. The method is based on a general self-consistent procedure for factorization of the two-body interaction. It is relevant for various density- and current-dependent functionals. The contributions of the time-even and time-odd Skyrme terms as well as of the Coulomb and pairing terms to the residual interaction are taken self-consistently into account. Most of the expression have a transparent analytical form, which makes the method convenient for the treatment and analysis. The separable character of the residual interaction allows to avoid diagonalization of high-rank RPA matrices and thus to minimize the calculation effort. The previous studies have demonstrated high numerical accuracy and efficiency of the method for spherical nuclei. In this contribution, the method is specified for axial nuclei. We provide systematic and detailed presentation of formalism and discuss different aspects of the model.Comment: 42 page

Transcriptome analysis of differentiating spermatogonia stimulated with kit ligand

Kit ligand (KL) is a survival factor and a mitogenic stimulus for differentiating spermatogonia. However, it is not known whether KL also plays a role in the differentiative events that lead to meiotic entry of these cells. We performed a wide genome analysis of difference in gene expression induced by treatment with KL of spermatogonia from 7-day-old mice, using gene chips spanning the whole mouse genome. The analysis revealed that the pattern of RNA expression induced by KL is compatible with the qualitative changes of the cell cycle that occur during the subsequent cell divisions in type A and B spermatogonia, i.e. the progressive lengthening of the S phase and the shortening of the G2/M transition. Moreover, KL up-regulates in differentiating spermatogonia the expression of early meiotic genes (for instance: Lhx8, Nek1, Rnf141, Xrcc3, Tpo1, Tbca, Xrcc2, Mesp1, Phf7, Rtel1), whereas it down-regulates typical spermatogonial markers (for instance: Pole, Ptgs2, Zfpm2, Egr2, Egr3, Gsk3b, Hnrpa1, Fst, Ptch2). Since KL modifies the expression of several genes known to be up-regulated or down-regulated in spermatogonia during the transition from the mitotic to the meiotic cell cycle, these results are consistent with a role of the KL/kit interaction in the induction of their meiotic differentiation

Three-dimensional superimposition for patients with facial palsy: an innovative method for assessing the success of facial reanimation procedures

Facial palsy is a severe condition that may be ameliorated by facial reanimation, but there is no consensus about how to judge its success. In this study we aimed to test a new method for assessing facial movements based on 3-dimensional analysis of the facial surfaces. Eleven patients aged between 42 and 77 years who had recently been affected by facial palsy (onset between 6 and 18 months) were treated by an operation based on triple innervation: the masseteric to temporofacial nerve branch, 30% of the hypoglossal fibres to the cervicofacial nerve branch, and the contralateral facial nerve through two cross-face sural nerve grafts. Each patient had five stereophotogrammetric scans: at rest, smiling on the healthy side (facial stimulus), biting (masseteric stimulus), moving the tongue (hypoglossal stimulus), and corner-of-the-mouth smile (Mona Lisa). Each scan was superimposed onto the facial model of the "rest" position, and the point-to-point root mean square (RMS) value was automatically calculated on both the paralysed and the healthy side, together with an index of asymmetry. One-way and two-way ANOVA tests, respectively, were applied to verify the significance of possible differences in the RMS and asymmetry index according to the type of stimulus (p = 0.0329) and side (p < 0.0001). RMS differed significantly according to side between the facial stimulus and the masseteric one on the paralysed side (p = 0.0316). Facial stimulus evoked the most asymmetrical movement, whereas the masseteric produced the most symmetrical expression. The method can be used for assessing facial movements after facial reanimation

SOHLH1 and SOHLH2 control Kit expression during postnatal male germ cell development

How Kit expression is regulated in the germline remains unknown. SOHLH1 and SOHLH2, two bHLH transcription factors specifically expressed in germ cells, are involved in spermatogonia and oocyte differentiation. In the male, deletion of each factor causes loss of Kit-expressing spermatogonia in the prepuberal testis. In the female, SOHLH1 and SOHLH2 ablations cause oocyte loss in the neonatal ovary. To investigate whether Kit expression is regulated by these two factors in male germ cells, we examined SOHLH1 and SOHLH2 expression during fetal and postnatal mouse development. We found a strong positive correlation between Kit and the two transcription factors only in postnatal spermatogonia. SOHLH2 was enriched in undifferentiated spermatogonia, whereas SOHLH1 expression was maximal at Kit-dependent stages. Expression of SOHLH1, but not SOHLH2, was increased in postnatal mitotic germ cells by treatment with all-trans retinoic acid. We found that E-box sequences within the Kit promoter and its first intron can be transactivated in transfection experiments overexpressing Sohlh1 or Sohlh2. Co-transfection of both factors showed a cooperative effect. EMSA experiments showed that SOHLH1 and SOHLH2 can independently and cooperatively bind an E-box-containing probe. In vivo co-immunoprecipitations indicated that the two proteins interact and overexpression of both factors increases endogenous Kit expression in embryonic stem cells. SOHLH1 was found by ChIP analysis to occupy an E-box-containing region within the Kit promoter in spermatogonia chromatin. Our results suggest that SOHLH1 and SOHLH2 directly stimulate Kit transcription in postnatal spermatogonia, thus activating the signaling involved in spermatogonia differentiation and spermatogenetic progression

Infrared electron modes in light deformed clusters

Infrared quadrupole modes (IRQM) of the valence electrons in light deformed sodium clusters are studied by means of the time-dependent local-density approximation (TDLDA). IRQM are classified by angular momentum components $\lambda\mu =$20, 21 and 22 whose $\mu$ branches are separated by cluster deformation. In light clusters with a low spectral density, IRQM are unambiguously related to specific electron-hole excitations, thus giving access to the single-electron spectrum near the Fermi surface (HOMO-LUMO region). Most of IRQM are determined by cluster deformation and so can serve as a sensitive probe of the deformation effects in the mean field. The IRQM branch $\lambda\mu =$21 is coupled with the magnetic scissors mode, which gives a chance to detect the latter. We discuss two-photon processes, Raman scattering (RS), stimulated emission pumping (SEP), and stimulated adiabatic Raman passage (STIRAP), as the relevant tools to observe IRQM. A new method to detect the IRQM population in clusters is proposed.Comment: 22 pages, 6 figure

Analysis of the gene expression profile of mouse male meiotic germ cells

Wide genome analysis of difference in gene expression between spermatogonial populations from 7-day-old mice and pachytene spermatocytes from 18-day-old mice was performed using Affymetrix gene chips representing approximately 12,500 mouse known genes or EST sequences, spanning approximately 1/3rd of the mouse genome. To delineate differences in the profile of gene expression between mitotic and meiotic stages of male germ cell differentiation, expressed genes were grouped in functional clusters. The analysis confirmed the previously described pre-meiotic or meiotic expression for several genes, in particular for those involved in the regulation of the mitotic and meiotic cell cycle, and for those whose transcripts are accumulated during the meiotic stages to be translated later in post-meiotic stages. Differential expression of several additional genes was discovered. In few cases (pro-apoptotic factors Bak, Bad and Bax), data were in conflict with the previously published stage-dependent expression of genes already known to be expressed in male germ cells. Northern blot analysis of selected genes confirmed the results obtained with the microarray chips. Six of these were novel genes specifically expressed in pachytene spermatocytes: a chromatin remodeling factor (chrac1/YCL1), a homeobox gene (hmx1), a novel G-coupled receptor for an unknown ligand (Gpr19), a glycoprotein of the intestinal epithelium (mucin 3), a novel RAS activator (Ranbp9), and the A630056B21Rik gene (predicted to encode a novel zinc finger protein). These studies will help to delineate the global patterns of gene expression characterizing male germ cell differentiation for a better understanding of regulation of spermatogenesis in mammals

SN 2002cv: A Heavily Obscured Type Ia Supernova

We present VRIJHK photometry, and optical and near-infrared spectroscopy, of the heavily extinguished Type Ia supernova (SN) 2002cv, located in NGC 3190, which is also the parent galaxy of the Type Ia SN 2002bo. SN 2002cv, not visible in the blue, has a total visual extinction of 8.74 +- 0.21 mag. In spite of this we were able to obtain the light curves between -10 and +207 days from the maximum in the I band, and also to follow the spectral evolution, deriving its key parameters. We found the peak I-band brightness to be Imax = 16.57 +- 0.10 mag, the maximum absolute I magnitude to be MmaxI = -18.79 +- 0.20, and the parameter dm15(B) specifying the width of the B-band light curve to be 1.46 +- 0.17 mag. The latter was derived using the relations between this parameter and dm40(I) and the time interval dtmax(I) between the two maxima in the I-band light curve. As has been found for previously observed, highly extinguished SNe Ia, a small value of 1.59 +- 0.07 was obtained here for the ratio Rv of the total-to-selective extinction ratio for SN 2002cv, which implies a small mean size for the grains along the line of sight toward us. Since it was found for SN 2002bo a canonical value of 3.1, here we present a clear evidence of different dust properties inside NGC 3190.Comment: 18 pages, 18 figures. Accepted for publication in MNRAS. Added co-author