2,324 research outputs found
Fission studies with 140 MeV -Particles
Binary fission induced by 140 MeV -particles has been measured for
Ag, La, Ho and Au targets. The measured
quantities are the total kinetic energies, fragment masses, and fission cross
sections. The results are compared with other data and systematics. A minimum
of the fission probability in the vicinity is observed.Comment: 4 figures, 2 table
Classification of life by the mechanism of genome size evolution
The classification of life should be based upon the fundamental mechanism in
the evolution of life. We found that the global relationships among species
should be circular phylogeny, which is quite different from the common sense
based upon phylogenetic trees. The genealogical circles can be observed clearly
according to the analysis of protein length distributions of contemporary
species. Thus, we suggest that domains can be defined by distinguished
phylogenetic circles, which are global and stable characteristics of living
systems. The mechanism in genome size evolution has been clarified; hence main
component questions on C-value enigma can be explained. According to the
correlations and quasi-periodicity of protein length distributions, we can also
classify life into three domains.Comment: 53 pages, 9 figures, 2 table
The Growth of Fetal Human Sensory Ganglion Neurons in Culture: A Scanning Electron Microscopic Study
Sensory neurons of 8-week human fetal dorsal root ganglia were dissociated into single cells by trypsinization and cultured on coverslips for 4 months, in either serum-containing or serum-free chemically defined media. At different times the cultures were fixed and prepared for scanning electron microscopy. Fetal sensory neurons in culture regenerated axons within 24 hours which were characterized by axonal growth cones at their tips and the neuronal perikarya assumed spherical or a bonnet-like morphology
Survival and Growth of Adult Human Oligodendrocytes in Culture: Scanning Electron Microscopy
The oligodendrocytes in culture serve as an important model for the study of demyelination diseases. We have previously originated a method of isolating human oligodendrocytes. In order to establish their three dimensional morphology, scanning electron microscopy of the cultured oligodendrocytes was performed.
The oligodendrocytes bulk isolated from adult human brain were maintained in culture for more than 2 months. At the various periods in culture, the cells were studied by scanning electron microscopy and immunofluorescence staining using marker antibodies for the identification of oligodendrocytes. The three dimensional organization and the surface morphology of the cultured oligodendrocytes were investigated. They displayed an extensive network of the cell processes and characteristic surface morphology
On the elliptical flow in asymmetric collisions and nuclear equation of state
We here present the results of elliptical flow for the collision of different
asymmetric nuclei (10Ne20 +13 Al27, 18Ar40 +21 Sc45, 30Zn64 +28 Ni58, 36Kr86
+41 Nb93) by using the Quantum Molecular Dynamics (QMD) model. General features
of elliptical flow are investigated with the help of theoretical simulations.
The simulations are performed at different beam energies between 40 and 105
MeV/nucleon. A significant change can be seen from in-plane to out-of-plane
elliptical flow of different fragments with incident energy. A comparison with
experimental data is also made. Further, we predict, for the first time that,
elliptical flow for different kind of fragments follow power law dependence ?
C(Atot)? for asymmetric systems
Freeze-out Configuration in Multifragmentation
The excitation energy and the nuclear density at the time of breakup are
extracted for the reaction at beam energies of 1 and 3.6
GeV/nucleon. These quantities are calculated from the average relative velocity
of intermediate mass fragments (IMF) at large correlation angles as a function
of the multiplicity of IMFs using a statistical model coupled with many-body
Coulomb trajectory calculations. The Coulomb component and
thermal component are found to depend oppositely on the
excitation energy, IMFs multiplicity, and freeze-out density. These
dependencies allow the determination of both the volume and the mean excitation
energy at the time of breakup. It is found that the volume remained constant as
the beam energy was increased, with a breakup density of about ,
but that the excitation energy increased to about 5.5 MeV/nucleon.Comment: 12 pages, 2 figures available upon resues
Fragment size correlations in finite systems - application to nuclear multifragmentation
We present a new method for the calculation of fragment size correlations in
a discrete finite system in which correlations explicitly due to the finite
extent of the system are suppressed. To this end, we introduce a combinatorial
model, which describes the fragmentation of a finite system as a sequence of
independent random emissions of fragments. The sequence is accepted when the
sum of the sizes is equal to the total size. The parameters of the model, which
may be used to calculate all partition probabilities, are the intrinsic
probabilities associated with the fragments. Any fragment size correlation
function can be built by calculating the ratio between the partition
probabilities in the data sample (resulting from an experiment or from a Monte
Carlo simulation) and the 'independent emission' model partition probabilities.
This technique is applied to charge correlations introduced by Moretto and
collaborators. It is shown that the percolation and the nuclear statistical
multifragmentaion model ({\sc smm}) are almost independent emission models
whereas the nuclear spinodal decomposition model ({\sc bob}) shows strong
correlations corresponding to the break-up of the hot dilute nucleus into
nearly equal size fragments
Liquid-Drop Model and Quantum Resistance Against Noncompact Nuclear Geometries
The importance of quantum effects for exotic nuclear shapes is demonstrated.
Based on the example of a sheet of nuclear matter of infinite lateral
dimensions but finite thickness, it is shown that the quantization of states in
momentum space, resulting from the confinement of the nucleonic motion in the
conjugate geometrical space, generates a strong resistance against such a
confinement and generates restoring forces driving the system towards compact
geometries. In the liquid-drop model, these quantum effects are implicitly
included in the surface energy term, via a choice of interaction parameters, an
approximation that has been found valid for compact shapes, but has not yet
been scrutinized for exotic shapes.Comment: 9 pages with 3 figure
Flux pile-up and plasma depletion at the high latitude dayside magnetopause during southward interplanetary magnetic field: a cluster event study
An event of strong flux pile-up and plasma depletion at the high latitude magnetopause tailward of the cusp has been analyzed based on observations by the suite of Cluster spacecraft. The multi-satellite analysis facilitates the separation of temporal and spatial features and provides a direct estimate for the strength of the plasma depletion layer for this event. A doubling of the magnetic field strength and a forty percent reduction of the density are found. Our analysis shows that roughly half of the total magnetic field increase occurs within 0.6 RE of the magnetopause and another quarter within a distance of 1.2 RE. In addition, the plasma depletion signatures exhibit temporal variations which we relate to magnetopause dynamics.<br><br> <b>Keywords.</b> Magnetospheric physics (Magnetopause, Cusp and boundary layers; Magnetosheath; Solar windmagnetosphere interactions
Absolute Fluorescence Spectrum and Yield Measurements for a wide range of experimental conditions
For the JEM-EUSO CollaborationThe fluorescence yield is a key ingredient in cosmic ray energy determination. It is sensitive to pressure, temperature and humidity. Up to now the fluorescence yield of the brightest line at 337 nm has been measured in an absolute way in one set of conditions, whereas fluorescence yields at the other wavelengths have been relatively measured for different conditions. Thus, absolute calibration for all the lines is unclear. We will do all measurements at once using the same apparatus: all the lines will be measured absolutely and not relatively for all conditions. For that we will use the 3-5 MeV electron beam of the PHIL accelerator (Photon Injector at LAL), shooting in a box filled with air at varying pressures, temperatures and humidity. Delta rays resulting from the beam collisions with Nitrogen are responsible for the light yield. The light detection probability should be independent of its emission point especially at the delta ray stopping point. The idea is to use an integrating sphere, encapsulated in a vessel where pressure, temperature and humidity can be varied. This sphere will have two ports for the beam (in and out), one more port dedicated to a NIST photodiode for calibration and another port feeding optical fibers going to: A) a grating spectrometer equipped with cooled CCD. B) a photomultiplier with BG3 filters to measure directly the integrated yield. Calibrations at the percent level, will give each line spectrum yields with a precision between 2 to 5%. A special issue will be to estimate the leakage due to "high energy" delta rays. Thus, we the air density will be increased, the beam energy will be lowered until the beam stops inside the sphere. Then, the energy loss will be precisely derived from the Bethe-Bloch formula. We will present the set-up
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