Changes in the cerebellar cytoarchitecture of hibernating hedgehog Erinaceus europaeus L. (Mammalia): an immunocytochemical approach

Hibernation is an amazing animal strategy to survive when the environmental temperature is very low and food resources are scarce. Successful hibernation requires a variety of complex biological adaptations, in which the brain plays a central regulatory role. Currently, little information is available regarding the morphology and functional activity of specific neurons within the cerebellar cytoarchitecture of hibernating animals. In the present study, we investigated the immunohistochemical expression of essential proteins in the cerebellum of a mammalian hibernator (i.e. hedgehog Erinaceus europaeus L.), focusing on (i) Purkinje neurons, the sole output cells of the cerebellar cortex; (ii) selected neurotransmitters involved in hibernation processes; (iii) intracellular calcium homeostasis, considering that calcium is also an important regulator of neurotransmission mechanisms; and (iv) cytoskeletal proteins, involved in maintenance of neuronal shape and axon calibre. Specifically, we studied in situ immunocytochemical changes during the torpor state of hibernation (November–March) versus the activity phase (April–September). We employed different selected markers, i.e. glutamic acid decarboxylase (GAD67) and postsynaptic glutamate ionotropic receptor GluR2-3, different calcium-binding proteins (i.e. calbindin, parvalbumin and calretinin) and cytoskeletal components (i.e. pNF-H and MAP2). In summary, our data in hibernating animals demonstrated: (i) downregulation of GAD67, indicating loss/changes of synaptic contacts on Purkinje somata and dendrites; (ii) GluR2-3 upregulation in Purkinje neurons, with a drastic decrease of calbindin expression; and (iii) decrease of normal mechanisms regulating intracellular calcium homeostasis. We also found a decrease/modification in the distribution of cytoskeletal proteins, particularly evident for pNF-H. Changes in the functional activity of Purkinje cells were accompanied by some morphological dendrite alterations, signs of degeneration in cell somata and flattened basket pinceaux at the Purkinje axon hillock. These findings confirm that hibernation makes heterothermic animals a valuable model to study physiological adaptations to adverse conditions, and also for understanding cellular and molecular mechanisms aimed at preserving mammalian organs from full degeneration and death

Self-energy Effects in the Superfluidity of Neutron Matter

The superfluidity of neutron matter in the channel $^1 S_0$ is studied by taking into account the effect of the ground-state correlations in the self-energy. To this purpose the gap equation has been solved within the generalized Gorkov approach. A sizeable suppression of the energy gap is driven by the quasi-particle strength around the Fermi surface.Comment: 8 pages and 3 figure

Effective interactions and shell model studies of heavy tin isotopes

We calculate the low-lying spectra of heavy tin isotopes from A=120 to A=130 using the 2s1d0g_{7/2}0h_{11/2} shell to define the model space. An effective interaction has been derived using 132Sn as closed core employing perturbative many-body techniques. We start from a nucleon-nucleon potential derived from modern meson exchange models. This potential is in turn renormalized for the given medium, 132Sn, yielding the nuclear reaction matrix, which is then used in perturbation theory to obtain the shell model effective interaction.Comment: 19 pages, Elsevier latex style espart.sty, submitted to Nuclear Physics

Cooper pair sizes in 11Li and in superfluid nuclei: a puzzle?

We point out a strong influence of the pairing force on the size of the two neutron Cooper pair in $^{11}$Li, and to a lesser extent also in $^6$He. It seems that these are quite unique situations, since Cooper pair sizes of stable superfluid nuclei are very little influenced by the intensity of pairing, as recently reported. We explore the difference between $^{11}$Li and heavier superfulid nuclei, and discuss reasons for the exceptional situation in $^{11}$Li.Comment: 9 pages. To be published in J. of Phys. G special issue on Open Problems in Nuclear Structure (OPeNST

Fragmentation in Peripheral Heavy-Ion Collisions: from Neck Emission to Spectator Decays

Invariant cross sections of intermediate mass fragments in peripheral collisions of Au on Au at incident energies between 40 and 150 AMeV have been measured with the 4-pi multi-detector INDRA. The maximum of the fragment production is located near mid-rapidity at the lower energies and moves gradually towards the projectile and target rapidities as the energy is increased. Schematic calculations within an extended Goldhaber model suggest that the observed cross-section distributions and their evolution with energy are predominantly the result of the clustering requirement for the emerging fragments and of their Coulomb repulsion from the projectile and target residues. The quantitative comparison with transverse energy spectra and fragment charge distributions emphasizes the role of hard scattered nucleons in the fragmentation process.Comment: 5 pages, 5 eps figures, RevTeX4, submitted to Phys. Lett.

Upper Bounds on the Neutrino-Nucleon Inelastic Cross Section

Extraterrestrial neutrinos can initiate deeply developing air showers, and those that traverse the atmosphere unscathed may produce cascades in the ice or water. Up to now, no such events have been observed. This can be translated into upper limits on the diffuse neutrino flux. On the other hand, the observation of cosmic rays with primary energies > 10^{10} GeV suggests that there is a guaranteed flux of cosmogenic neutrinos, arising from the decay of charged pions (and their muon daughters) produced in proton interactions with the cosmic microwave background. In this work, armed with these cosmogenic neutrinos and the increased exposure of neutrino telescopes we bring up-to-date model-independent upper bounds on the neutrino-nucleon inelastic cross section. Uncertainties in the cosmogenic neutrino flux are discussed and taken into account in our analysis. The prospects for improving these bounds with the Pierre Auger Observatory are also estimated. The unprecedented statistics to be collected by this experiment in 6 yr of operation will probe the neutrino-nucleon inelastic cross section at the level of Standard Model predictions.Comment: To be published in JCA

The Particle Physics Reach of High-Energy Neutrino Astronomy

We discuss the prospects for high-energy neutrino astronomy to study particle physics in the energy regime comparable to and beyond that obtainable at the current and planned colliders. We describe the various signatures of high-energy cosmic neutrinos expected in both neutrino telescopes and air shower experiments and discuss these measurements within the context of theoretical models with a quantum gravity or string scale near a TeV, supersymmetry and scenarios with interactions induced by electroweak instantons. We attempt to access the particle physics reach of these experiments.Comment: Mini-review article for New Journal of Physics, "Focus on Neutrinos" issue. 27 pages, 11 figure

Statistical signatures of critical behavior in small systems

The cluster distributions of different systems are examined to search for signatures of a continuous phase transition. In a system known to possess such a phase transition, both sensitive and insensitive signatures are present; while in systems known not to possess such a phase transition, only insensitive signatures are present. It is shown that nuclear multifragmentation results in cluster distributions belonging to the former category, suggesting that the fragments are the result of a continuous phase transition.Comment: 31 pages, two columns with 30 figure

The energy dependence of flow in Ni induced collisions from 400 to 1970A MeV

We study the energy dependence of collective (hydrodynamic-like) nuclear matter flow in 400-1970 A MeV Ni+Au and 1000-1970 A MeV Ni+Cu reactions. The flow increases with energy, reaches a maximum, and then gradually decreases at higher energies. A way of comparing the energy dependence of flow values for different projectile-target mass combinations is introduced, which demonstrates a common scaling behaviour among flow values from different systems.Comment: 12 pages, 3 figures. Submitted to Physical Review Letter