421 research outputs found
Manifestation of pairing modes in nuclear collisions
We discuss the possible manifestation of pairing dynamics in nuclear
collisions beyond the standard quasi-static treatment of pairing correlations.
These involve solitonic excitations induced by pairing phase difference of
colliding nuclei and pairing dynamic enhancement in the di-nuclear system
formed by merging nuclei.Comment: 2 figures, 56th Zakopane Conference On Nuclear Physic
Exploring Zeptosecond Quantum Equilibration Dynamics: From Deep-Inelastic to Fusion-Fission Outcomes in Ni+Ni Reactions
Energy dissipative processes play a key role in how quantum many-body systems
dynamically evolve towards equilibrium. In closed quantum systems, such
processes are attributed to the transfer of energy from collective motion to
single-particle degrees of freedom; however, the quantum many-body dynamics of
this evolutionary process are poorly understood. To explore energy dissipative
phenomena and equilibration dynamics in one such system, an experimental
investigation of deep-inelastic and fusion-fission outcomes in the
Ni+Ni reaction has been carried out. Experimental outcomes have
been compared to theoretical predictions using Time Dependent Hartree Fock and
Time Dependent Random Phase Approximation approaches, which respectively
incorporate one-body energy dissipation and fluctuations. Excellent
quantitative agreement has been found between experiment and calculations,
indicating that microscopic models incorporating one-body dissipation and
fluctuations provide a potential tool for exploring dissipation in low-energy
heavy ion collisions.Comment: 11 pages, 9 figures, 1 table, including Supplemental Material -
Version accepted for publication in Physical Review Letter
Transport and Magnetic Studies on the Spin State Transition of Pr1-xCaxCoO3 up to High Pressure
Transport and magnetic measurements and structural and NMR studies have been
carried out on (Pr1-yR'y)1-xAxCoO3 {R'=(rare earth elements and Y); A=(Ca, Ba
and Sr)} at ambient pressure or under high pressure. The system exhibits a
phase transition from a nearly metallic to an insulating state with decreasing
temperature T, where the low spin (LS) state of Co3+ is suddenly stabilized.
For y=0, we have constructed a T-x phase diagram at various values of the
external pressure p. It shows that the (T, x) region of the low temperature
phase, which is confined to a very narrow region around x=0.5 at ambient
pressure, expands as p increases, suggesting that the transition is not due to
an order-disorder type one. For the occurrence of the transition, both the Pr
and Ca atoms seem to be necessary. The intimate relationship between the local
structure around the Co ions and the electronic (or spin) state of Co3+ ions is
discussed: For the smaller unit cell volume or the smaller volume of the CoO6
octahedra and for the larger tilting angle of the octahedra, the temperature of
the transition becomes higher. The role of the carriers introduced by the
doping of the A atoms, is also discussed. By analyzing the data of 59Co-NMR
spectra and magnetic susceptibilities of Pr1-xCaxCoO3 the energy separations
among the different spin states of Co3+ and Co4+ are roughly estimated.Comment: 15 pages, 15 figures, 2 tables, submitted to J. Phys. Soc. Jp
Association analysis of tissue inhibitor of metalloproteinase2 gene polymorphisms with COPD in Egyptians
AbstractProteinase/antiproteinase imbalance is recognized to play an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). A relative increase in the activities of matrix metalloproteinases might be caused by mutations of tissue inhibitor of metalloproteinase2 (TIMP2). Recently, two polymorphisms of the TIMP2 gene, +853 G/A and −418 G/C (+551 and −720 from the translation initiation site), have been shown to be associated with the development of COPD in the Japanese population. In this study, a case-control association analysis for these polymorphisms was conducted in the Egyptian population using 106 COPD patients and 72 healthy controls. The genotype frequency of +853 G/A was significantly different between the patient and the control groups (P=0.029), although no significant difference was detected in the allele frequency between the two groups. These results suggest that the +853 G/A polymorphism of the TIMP2 gene might be associated with COPD across ethnicities. In contrast, neither the distributions of genotype nor allele frequencies of –418 G/C were significantly different between the two groups, raising the possibility that a combination of different genetic factors contributes to the development of COPD in different ethnic groups
Cryo-EM structure of lysenin pore elucidates membrane insertion by an aerolysin family protein
Lysenin from the coelomic fluid of the earthworm Eisenia fetida belongs to the aerolysin family of small β-pore-forming toxins (β-PFTs), some members of which are pathogenic to humans and animals. Despite efforts, a high-resolution structure of a channel for this family of proteins has been elusive and therefore the mechanism of activation and membrane insertion remains unclear. Here we determine the pore structure of lysenin by single particle cryo-EM, to 3.1 Å resolution. The nonameric assembly reveals a long β-barrel channel spanning the length of the complex that, unexpectedly, includes the two pre-insertion strands flanking the hypothetical membrane-insertion loop. Examination of other members of the aerolysin family reveals high structural preservation in this region, indicating that the membrane-insertion pathway in this family is conserved. For some toxins, proteolytic activation and pro-peptide removal will facilitate unfolding of the pre-insertion strands, allowing them to form the β-barrel of the channel
In vivo and ex vivo percutaneous absorption of [14C]-bisphenol A in rats: a possible extrapolation to human absorption?
Bisphenol A (BPA) is a monomer used mainly in the synthesis of polycarbonates and epoxy resins. Percutaneous absorption is the second source of exposure, after inhalation, in the work environment. However, studies on this route of absorption are lacking or incomplete. In this study, percutaneous BPA absorption was measured in vivo and ex vivo in the rat, and ex vivo in humans. An approximately 12-fold difference in permeability between rat skin and human skin was found, with permeability being higher in the rat. In addition, inter- and intra-individual variability of up to tenfold was observed in humans. No accumulation of BPA in the skin was found during exposure. The skin clearance rate following exposure was estimated at 0.4 μg/cm²/h. Ex vivo and in vivo percutaneous absorption fluxes of BPA in the rat were in the same range (about 2.0 μg/cm²/h), suggesting that extrapolation to the in vivo situation in humans may be possible. The European tolerable daily intake (TDI) of BPA is 50 μg/kg body weight. However, many research projects have highlighted the significant effects of BPA in rodents at doses lower than 10 μg/kg/day. A 1-h occupational exposure over 2,000 cm² (forearms and hands) may lead to a BPA absorption of 4 μg/kg/day. This is 8% of the European TDI and is very close to the value at which effects have been observed in animals. This absorption must therefore be taken into account when evaluating risks of BPA exposure, at least until more relevant results on the toxicity of BPA in humans are available
SPring-8 BL36XU: Catalytic Reaction Dynamics for Fuel Cells
A tapered undulator beamline BL36XU was constructed at SPring-8 to conduct structural and electronic analysis of dynamic events on polymer electrolyte fuel cell (PEFC) cathode catalysts for the development of next-generation PEFCs. BL36XU provides various time and spatially resolved XAFS techniques in an energy range from 4.5 to 35 keV for investigating PEFCs under the operating conditions. In addition, we developed in-situ complementary measurement systems, such as in-situ time-resolved XAFS/XRD and ambient pressure HAXPES systems. This report describes the performance and present status of the BL36XU
Nasal Chemosensory-Stimulation Evoked Activity Patterns in the Rat Trigeminal Ganglion Visualized by In Vivo Voltage-Sensitive Dye Imaging
Mammalian nasal chemosensation is predominantly mediated by two independent neuronal pathways, the olfactory and the trigeminal system. Within the early olfactory system, spatiotemporal responses of the olfactory bulb to various odorants have been mapped in great detail. In contrast, far less is known about the representation of volatile chemical stimuli at an early stage in the trigeminal system, the trigeminal ganglion (TG), which contains neurons directly projecting to the nasal cavity. We have established an in vivo preparation that allows high-resolution imaging of neuronal population activity from a large region of the rat TG using voltage-sensitive dyes (VSDs). Application of different chemical stimuli to the nasal cavity elicited distinct, stimulus-category specific, spatiotemporal activation patterns that comprised activated as well as suppressed areas. Thus, our results provide the first direct insights into the spatial representation of nasal chemosensory information within the trigeminal ganglion imaged at high temporal resolution
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