Statistical Interpretation of Joint Multiplicity Distributions of Neutrons and Charged Particles

Experimental joint multiplicity distributions of neutrons and charged particles emitted in complex nuclear reactions provide an important test of theoretical models. The method is applied to test three different theoretical models of nuclear multi-fragmentation, two of which fail the test. The measurement of neutrons is decisive in distinguishing between the Berlin and Copenhagen models of nuclear multi-fragmentation and challenges the interpretation of pseudo- Arrhenius plots. Statistical-model evaporation calculations with GEMINI give a good reproduction first and second moments of the experimental multiplicity correlations.Comment: 12 pages, 3 figures Added GEMINI calculations of multiplicity correlations Added brief discussion of how neutron emission is treated in MMM

Heating of nuclei with energetic anti-protons

International audienceHigh-energy γ rays associated with the decay of the giant dipole resonance have been measured for two fusion reactions leading to the 140Sm compound nucleus at an excitation energy of 71 MeV. The observed yield increases with the asymmetry in the ratios of the number of neutrons to protons in the entrance channel. This is interpreted as resulting from giant dipole phonons excited at the moment of collision in an N/Z asymmetric reaction

A Novel Porcine In Vitro Model of the Blood-Cerebrospinal Fluid Barrier with Strong Barrier Function

Epithelial cells of the plexus choroideus form the structural basis of the blood-cerebrospinal fluid barrier (BCSFB). In vitro models of the BCSFB presenting characteristics of a functional barrier are of significant scientific interest as tools for examination of BCSFB function. Due to a lack of suitable cell lines as in vitro models, primary porcine plexus epithelial cells were subjected to a series of selective cultivation steps until a stable continuous subcultivatable epithelial cell line (PCP-R) was established. PCP-R cells grow in a regular polygonal pattern with a doubling time of 28–36 h. At a cell number of 1.5×105 in a 24-well plate confluence is reached in 56–72 h. Cells are cytokeratin positive and chromosomal analysis revealed 56 chromosomes at peak (84th subculture). Employing reverse transcription PCR mRNA expression of several transporters and components of cell junctions could be detected. The latter includes tight junction components like Claudin-1 and -3, ZO-1, and Occludin, and the adherens junction protein E-cadherin. Cellular localization studies of ZO-1, Occludin and Claudin-1 by immunofluorescence and morphological analysis by electron microscopy demonstrated formation of a dense tight junction structure. Importantly, when grown on cell culture inserts PCP-R developed typical characteristics of a functional BCSFB including high transepithelial electrical resistance above 600 Ω×cm2 as well as low permeability for macromolecules. In summary, our data suggest the PCP-R cell line as a suitable in vitro model of the porcine BCSFB

Hypervariable intronic region in NCX1 is enriched in short insertion-deletion polymorphisms and showed association with cardiovascular traits

<p>Abstract</p> <p>Background</p> <p>Conserved non-coding regions (CNR) have been shown to harbor gene expression regulatory elements. Genetic variations in these regions may potentially contribute to complex disease susceptibility.</p> <p>Methods</p> <p>We targeted CNRs of cardiovascular disease (CVD) candidate gene, <it>Na(+)-Ca(2+) exchanger (NCX1) </it>with polymorphism screening among CVD patients (n = 46) using DHPLC technology. The flanking region (348 bp) of the 14 bp indel in intron 2 was further genotyped by DGGE assay in two Eastern-European CVD samples: essential hypertension (HYPEST; 470 cases, 652 controls) and coronary artery disease, CAD (CADCZ; 257 cases, controls 413). Genotype-phenotype associations were tested by regression analysis implemented in PLINK. Alignments of primate sequences were performed by ClustalW2.</p> <p>Results</p> <p>Nine of the identified <it>NCX1 </it>variants were either singletons or targeted by commercial platforms. The 14 bp intronic indel (rs11274804) was represented with substantial frequency in HYPEST (6.82%) and CADCZ (14.58%). Genotyping in Eastern-Europeans (n = 1792) revealed hypervariable nature of this locus, represented by seven alternative alleles. The alignments of human-chimpanzee-macaque sequences showed that the major human variant (allele frequency 90.45%) was actually a human-specific deletion compared to other primates. In humans, this deletion was surrounded by other short (5-43 bp) deletion variants and a duplication (40 bp) polymorphism possessing overlapping breakpoints. This indicates a potential indel hotspot, triggered by the initial deletion in human lineage. An association was detected between the carrier status of 14 bp indel ancestral allele and CAD (<it>P </it>= 0.0016, OR = 2.02; Bonferroni significance level alpha = 0.0045), but not with hypertension. The risk for the CAD development was even higher among the patients additionally diagnosed with metabolic syndrome (<it>P </it>= 0.0014, OR = 2.34). Consistent with the effect on metabolic processes, suggestive evidence for the association with heart rate, serum triglyceride and LDL levels was detected (<it>P </it>= 0.04).</p> <p>Conclusions</p> <p>Compared to SNPs targeted by large number of locus-specific and genome-wide assays, considerably less attention has been paid to short indel variants in the human genome. The data of genome dynamics, mutation rate and population genetics of short indels, as well as their impact on gene expressional profile and human disease susceptibility is limited. The characterization of <it>NCX1 </it>intronic hypervariable non-coding region enriched in human-specific indel variants contributes to this gap of knowledge.</p

Source size scaling of fragment production in projectile breakup

Fragment production has been studied as a function of the source mass and excitation energy in peripheral collisions of $^{35}$Cl+$^{197}$Au at 43 MeV/nucleon and $^{70}$Ge+$^{nat}$Ti at 35 MeV/nucleon. The results are compared to the Au+Au data at 600 MeV/nucleon obtained by the ALADIN collaboration. A mass scaling, by $A_{source} \sim$ 35 to 190, strongly correlated to excitation energy per nucleon, is presented, suggesting a thermal fragment production mechanism. Comparisons to a standard sequential decay model and the lattice-gas model are made. Fragment emission from a hot, rotating source is unable to reproduce the experimental source size scaling.Comment: 13 pages LaTeX file, including 3 postscript figures (in .tar.gz fornmat), accepted in Phys. Rev. C . Also available at http://thomson.phy.ulaval.ca/ions_lourds/gil-en.htm

Polar Invasion and Translocation of Neisseria meningitidis and Streptococcus suis in a Novel Human Model of the Blood-Cerebrospinal Fluid Barrier

Acute bacterial meningitis is a life-threatening disease in humans. Discussed as entry sites for pathogens into the brain are the blood-brain and the blood-cerebrospinal fluid barrier (BCSFB). Although human brain microvascular endothelial cells (HBMEC) constitute a well established human in vitro model for the blood-brain barrier, until now no reliable human system presenting the BCSFB has been developed. Here, we describe for the first time a functional human BCSFB model based on human choroid plexus papilloma cells (HIBCPP), which display typical hallmarks of a BCSFB as the expression of junctional proteins and formation of tight junctions, a high electrical resistance and minimal levels of macromolecular flux when grown on transwell filters. Importantly, when challenged with the zoonotic pathogen Streptococcus suis or the human pathogenic bacterium Neisseria meningitidis the HIBCPP show polar bacterial invasion only from the physiologically relevant basolateral side. Meningococcal invasion is attenuated by the presence of a capsule and translocated N. meningitidis form microcolonies on the apical side of HIBCPP opposite of sites of entry. As a functionally relevant human model of the BCSFB the HIBCPP offer a wide range of options for analysis of disease-related mechanisms at the choroid plexus epithelium, especially involving human pathogens

Central Collisions of Au on Au at 150, 250 and 400 A MeV

Collisions of Au on Au at incident energies of 150, 250 and 400 A MeV were studied with the FOPI-facility at GSI Darmstadt. Nuclear charge (Z < 16) and velocity of the products were detected with full azimuthal acceptance at laboratory angles of 1-30 degrees. Isotope separated light charged particles were measured with movable multiple telescopes in an angular range of 6-90 degrees. Central collisions representing about 1 % of the reaction cross section were selected by requiring high total transverse energy, but vanishing sideflow. The velocity space distributions and yields of the emitted fragments are reported. The data are analysed in terms of a thermal model including radial flow. A comparison with predictions of the Quantum Molecular Model is presented.Comment: LateX text 62 pages, plus six Postscript files with a total of 34 figures, accepted by Nucl.Phys.