1,399 research outputs found
Tracking the phase-transition energy in disassembly of hot nuclei
In efforts to determine phase transitions in the disintegration of highly
excited heavy nuclei, a popular practice is to parametrise the yields of
isotopes as a function of temperature in the form
, where 's are the measured yields
and and are fitted to the yields. Here would be
interpreted as the phase transition temperature. For finite systems such as
those obtained in nuclear collisions, this parametrisation is only approximate
and hence allows for extraction of in more than one way. In this work we
look in detail at how values of differ, depending on methods of
extraction. It should be mentioned that for finite systems, this approximate
parametrisation works not only at the critical point, but also for first order
phase transitions (at least in some models). Thus the approximate fit is no
guarantee that one is seeing a critical phenomenon. A different but more
conventional search for the nuclear phase transition would look for a maximum
in the specific heat as a function of temperature . In this case is
interpreted as the phase transition temperature. Ideally and would
coincide. We invesigate this possibility, both in theory and from the ISiS
data, performing both canonical () and microcanonical ()
calculations. Although more than one value of can be extracted from the
approximate parmetrisation, the work here points to the best value from among
the choices. Several interesting results, seen in theoretical calculations, are
borne out in experiment.Comment: Revtex, 10 pages including 8 figures and 2 table
Genotyping of Bulgarian Vitis vinifera L. cultivars by microsatellite analysis
A characterization of the Bulgarian grapevine genepool (Vitis vinifera L. cultivars) was initiated through microsatellite analysis. Seventy four wine and table grapevine varieties from the National List of Cultivars, were analyzed at 9 microsatellite loci: VVS2, ssrVvUCH11, ssrVvUCH 29, ssrVrZAG21, ssrVrZAG47, ssrVrZAG62, ssrVrZAG64, ssrVrZAG79 and ssrVrZAG83. The high genetic diversity (78 %) allowed accurate identification and discrimination of the cultivars. The low PI value (1.201 x 10-8) reflects the high discriminative power of the chosen set of markers for the investigated population. Based on the microsatellite allele data, two pairs of old native varieties, Misket Cherven and Misket Vrachanski; Tamyanka and Tamyanka tvarda, were considered distinct cultivars. The synonymy ofTamyanka, Italian Moscato Bianco and Greek Moschato Kerkyras andPamid and Greek Pamidi was verified, while the putative synonymy of Mavrud and Greek Mavroudi Arachovis was rejected.Further utilization of microsatellite profiling in the management of the Bulgarian grapevine genepool is discussed.
Characteristics of Injuries in the Logging Industry of Louisiana, USA: 1986 to 1998
Characterizing injuries and their trends will allow safety managers to concentrate their resources on the areas of safety that will be most effective in the workplace. Injuries reported to the Louisiana Office of Workers' Compensation Administration for 1986 to 1998 were characterized according to the part of the body affected, the nature of the injury, the source of the injury, and the type of accident for the timber harvesting industry. Many of the injuries in the logging sector were sprains / strains to the knees. Injuries resulting from falling onto structures and surfaces were common and rising. Although the number of accidents in each category is generally decreasing, some trends should be of concern. There was no significant linear trend in overall accident rates since 1991. While the proportion of cuts and lacerations declined, the proportion of fractures increased. This coincided with a time period when logging operations in Louisiana experienced rapid mechanization and insurance companies started enforcing the use of personal protective equipment. The proportion of transportation accidents rose more than any other category. Some suggestions on focusing and improving current safety programs are given. The need for continued and improved training of managers and employees seems to be most critical
Methodology for Jointly Assessing Myocardial Infarct Extent and Regional Contraction in 3-D CMRI
Automated extraction of quantitative parameters from Cardiac Magnetic
Resonance Images (CMRI) is crucial for the management of patients with
myocardial infarct. This work proposes a post-processing procedure to jointly
analyze Cine and Delayed-Enhanced (DE) acquisitions in order to provide an
automatic quantification of myocardial contraction and enhancement parameters
and a study of their relationship. For that purpose, the following processes
are performed: 1) DE/Cine temporal synchronization and 3D scan alignment, 2) 3D
DE/Cine rigid registration in a region about the heart, 3) segmentation of the
myocardium on Cine MRI and superimposition of the epicardial and endocardial
contours on the DE images, 4) quantification of the Myocardial Infarct Extent
(MIE), 5) study of the regional contractile function using a new index, the
Amplitude to Time Ratio (ATR). The whole procedure was applied to 10 patients
with clinically proven myocardial infarction. The comparison between the MIE
and the visually assessed regional function scores demonstrated that the MIE is
highly related to the severity of the wall motion abnormality. In addition, it
was shown that the newly developed regional myocardial contraction parameter
(ATR) decreases significantly in delayed enhanced regions. This largely
automated approach enables a combined study of regional MIE and left
ventricular function
On the reliability of negative heat capacity measurements
A global protocol for the thermostatistical analysis of hot nuclear sources
is discussed. Within our method of minimization of variances we show that the
abnormal kinetic energy fluctuation signal recently reported in different
experimental data (M.D'Agostino et al.-Phys. Lett. B 473 (2000) 219, N. Le
Neindre et al.- contr. to the XXXVIII Bormio Winter Meeting on Nucl. Phys.
(2001) 404) is a genuine signal of a first order phase transition in a finite
system.Comment: 15 Postscript figures, submitted to NUCL. Phys. A on 24-apr-200
Assembly and Interrogation of Alzheimer’s Disease Genetic Networks Reveal Novel Regulators of Progression
Alzheimer’s disease (AD) is a complex multifactorial disorder with poorly characterized pathogenesis. Our understanding of this disease would thus benefit from an approach that addresses this complexity by elucidating the regulatory networks that are dysregulated in the neural compartment of AD patients, across distinct brain regions. Here, we use a Systems Biology (SB) approach, which has been highly successful in the dissection of cancer related phenotypes, to reverse engineer the transcriptional regulation layer of human neuronal cells and interrogate it to infer candidate Master Regulators (MRs) responsible for disease progression. Analysis of gene expression profiles from laser-captured neurons from AD and controls subjects, using the Algorithm for the Reconstruction of Accurate Cellular Networks (ARACNe), yielded an interactome consisting of 488,353 transcription-factor/ target interactions. Interrogation of this interactome, using the Master Regulator INference algorithm (MARINa), identified an unbiased set of candidate MRs causally responsible for regulating the transcriptional signature of AD progression. Experimental assays in autopsyderived human brain tissue showed that three of the top candidate MRs (YY1, p300 and ZMYM3) are indeed biochemically and histopathologically dysregulated in AD brains compared to controls. Our results additionally implicate p53 and loss of acetylation homeostasis in the neurodegenerative process. This study suggests that an integrative, SB approach can be applied to AD and other neurodegenerative diseases, and provide significant novel insight on the disease progression
A Quasi-Classical Model of Intermediate Velocity Particle Production in Asymmetric Heavy Ion Reactions
The particle emission at intermediate velocities in mass asymmetric reactions
is studied within the framework of classical molecular dynamics. Two reactions
in the Fermi energy domain were modelized, Ni+C and Ni+Au at 34.5
MeV/nucleon. The availability of microscopic correlations at all times allowed
a detailed study of the fragment formation process. Special attention was paid
to the physical origin of fragments and emission timescales, which allowed us
to disentangle the different processes involved in the mid-rapidity particle
production. Consequently, a clear distinction between a prompt pre- equilibrium
emission and a delayed aligned asymmetric breakup of the heavier partner of the
reaction was achieved.Comment: 8 pages, 7 figures. Final version: figures were redesigned, and a new
section discussing the role of Coulomb in IMF production was include
Prospects for the discovery of the next new element: Influence of projectiles with Z > 20
The possibility of forming new superheavy elements with projectiles having Z
> 20 is discussed. Current research has focused on the fusion of 48Ca with
actinides targets, but these reactions cannot be used for new element
discoveries in the future due to a lack of available target material. The
influence on reaction cross sections of projectiles with Z > 20 have been
studied in so-called analog reactions, which utilize lanthanide targets
carefully chosen to create compound nuclei with energetics similar to those
found in superheavy element production. The reactions 48Ca, 45Sc, 50Ti, 54Cr +
159Tb, 162Dy have been studied at the Cyclotron Institute at Texas A&M
University using the Momentum Achromat Recoil Spectrometer. The results of
these experimental studies are discussed in terms of the influence of
collective enhancements to level density for compound nuclei near closed
shells, and the implications for the production of superheavy elements. We have
observed no evidence to contradict theoretical predictions that the maximum
cross section for the 249Cf(50Ti, 4n)295120 and 248Cm(54Cr, 4n)298120 reactions
should be in the range of 10-100 fb.Comment: An invited talk given by Charles M. Folden III at the 11th
International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio,
Texas, USA, May 27-June 1, 2012. Also contains information presented by
Dmitriy A. Mayorov and Tyler A. Werke in separate contributions to the
conference. This contribution will appear in the NN2012 Proceedings in
Journal of Physics: Conference Series (JPCS
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