2,795 research outputs found
The resistible effects of Coulomb interaction on nucleus-vapor phase coexistence
We explore the effects of Coulomb interaction upon the nuclear liquid vapor
phase transition. Because large nuclei (A>60) are metastable objects, phases,
phase coexistence, and phase transitions cannot be defined with any generality
and the analogy to liquid vapor is ill-posed for these heavy systems. However,
it is possible to account for the Coulomb interaction in the decay rates and
obtain the coexistence phase diagram for the corresponding uncharged system.Comment: 5 pages, 5 figure
Modeling a Slicer Mirror Using Zemax User-Defined Surface
A slicer mirror is a complex surface composed by many tilted and decentered
mirrors sub-surfaces. The major difficulty to model such a complex surface is
the large number of parameters used to define it. The Zemax's
multi-configuration mode is usually used to specify each parameters (tilts,
curvatures, decenters) for each mirror sub-surface which are then considered
independently. Otherwise making use of the User-Defined Surface (UDS-DLL) Zemax
capability, we are able to consider the set of sub-surfaces as a whole surface.
In this paper, we present such a UDS-DLL tool comparing its performance with
those of the classical multi-configuration mode. In particular, we explore the
use of UDS-DLL to investigate the cross-talk due to the diffraction on the
slicer array mirrors which has been a burden task when using
multi-configuration mode.Comment: Submitted to the proceedings of the Durham Integral Field
Spectroscopy Workshop July 4th-8th 200
Compound nuclear decay and the liquid to vapor phase transition: a physical picture
Analyses of multifragmentation in terms of the Fisher droplet model (FDM) and
the associated construction of a nuclear phase diagram bring forth the problem
of the actual existence of the nuclear vapor phase and the meaning of its
associated pressure. We present here a physical picture of fragment production
from excited nuclei that solves this problem and establishes the relationship
between the FDM and the standard compound nucleus decay rate for rare particles
emitted in first-chance decay. The compound thermal emission picture is
formally equivalent to a FDM-like equilibrium description and avoids the
problem of the vapor while also explaining the observation of Boltzmann-like
distribution of emission times. In this picture a simple Fermi gas thermometric
relation is naturally justified and verified in the fragment yields and time
scales. Low energy compound nucleus fragment yields scale according to the FDM
and lead to an estimate of the infinite symmetric nuclear matter critical
temperature between 18 and 27 MeV depending on the choice of the surface energy
coefficient of nuclear matter.Comment: Five page two column pages, four figures, submitted to Phys. Rev.
New Wrinkles on an Old Model: Correlation Between Liquid Drop Parameters and Curvature Term
The relationship between the volume and surface energy coefficients in the
liquid drop A^{-1/3} expansion of nuclear masses is discussed. The volume and
surface coefficients in the liquid drop expansion share the same physical
origin and their physical connection is used to extend the expansion with a
curvature term. A possible generalization of the Wigner term is also suggested.
This connection between coefficients is used to fit the experimental nuclear
masses. The excellent fit obtained with a smaller number of parameters
validates the assumed physical connection.Comment: 6 pages, 2 figure
Exploring supply chain finance along different supply chain stages: a case-based research in the agri-food industry
PurposeSince 2008's financial crisis, attention toward supply chain finance (SCF) has increased. However, most research investigates SCF considering single supply chain (SC) stages or buyer-supplier dyads and focuses on a single SCF solution. It is important to see how different solutions are adopted at different SC stages, by actors with different financing needs. This study aims to analyze SCF at different SC stages, to understand why different solutions are implemented at different SC stages and the contingency factors (regulation, SC stage, product category and size) influencing their adoption. Design/methodology/approachThe paper is based on multiple exploratory case studies in the Italian agri-food industry, considering firms distributed at different SC stages and adopting multiple SCF solutions. The paper exploits a contingent approach (Sousa and Voss, 2008) to analyze how contingent factors influence SCF adoption at different SC stages. FindingsFindings explain how and why different SC stages (producer, cooperative, processor and retailer) implement different SCF solutions (reverse factoring, dynamic discounting, inventory finance and Minibond), describing contingency variables' impact on their adoption. Originality/valueTo the best of the authors' knowledge, the research is original in its description of SCF at different SC stages, considering different SC actors' drivers and barriers, and questioning the importance of a coordinated approach in SCF adoption along an entire SC. Moreover, the paper adopts a contingent approach, contributing to SCF research, seldomly based on theoretical lenses
The reproductive system of Opisthogonimus philodryadum (West, 1896) (Digenea)
O sistema reprodutor do adulto de Opisthogonimus philodryadum(West, 1896) foi estudado anatomica e histologicamente ao microscópio. Esta análise mostra que o canal de Laurer, metratermo, cirro e duto ejaculatório possuem um epitélio aprofundado. 0 metratermo e a franja citoplasmática do cirro ou tectum tem uma camada esclerótica diferenciada, semelhante em aspecto e cor às dos espinhos do tegumento do animal
TSPAN5 IS A KEY PLAYER IN DENDRITIC SPINES FORMATION AND AMPA RECEPTORS RECYCLING
TSPAN5 is a brain enriched protein member of the tetraspanin superfamily, a group of
transmembrane proteins some of which have been shown to fundamentally regulate the
development of mammalian nervous system. This class of proteins presents the peculiar ability
to clusterize forming specialized membrane region called Tetraspanin Enriched Microdomains
(TEMs) where they can accumulate other proteins.
We found that in developing neurons TSPAN5 was mainly present at the surface membrane
while it was concentrated in an intracellular compartment in the postsynapse of mature
neurons. We hypothesized that these different localisations could be due to different functions.
To deepen the first function of the protein, we knocked down the expression of the protein and
found that this led to a dramatic reduction in the number of dendritic spines. We, thus,
hypothesized that TSPAN5, through the formation of TEMs, could be responsible of dendritic
spines formation. We observed in differential lysis of developing rat hippocampal neurons that
two proteins, fundamental for dendritic spines formation, Neuroligin-1 and GluA2 AMPA
receptor subunit, were associated with TSPAN5 TEMs. We found that the knockdown of
TSPAN5 led to increased mobility of Neuroligin-1 and GluA2 AMPA receptors suggesting the
loss of clusterization typical of the first moments of spines formation.
To understand the second function of TSPAN5 we identified AP-4 complex as an interactor of
the C-terminal intracellular tail of TSPAN5. This complex is known to act on AMPARs trafficking
through direct binding of Stargazin, an AMPARs auxiliary subunit.
We observed that the knockdown of TSPAN5, carried out after the majority of the
synaptogenesis was occurred, caused a strong decrease in surface and total level of GluA2.
Different evidences suggested an involvement of TSPAN5 in vesicular transport of GluA2 and
we demonstrated that TSPAN5 was necessary for the correct recycling of this receptor.
These results highlight multiple roles of TSPAN5 in the regulation of both synapse formation
and synaptic functioning in mammalian brain through two distinct mechanisms of action
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
Simulation of cellular irradiation with the CENBG microbeam line using GEANT4
Light-ion microbeams provide a unique opportunity to irradiate biological
samples at the cellular level and to investigate radiobiological effects at low
doses of high LET ionising radiation. Since 1998 a single-ion irradiation
facility has been developed on the focused horizontal microbeam line of the
CENBG 3.5 MV Van de Graaff accelerator. This setup delivers in air single
protons and alpha particles of a few MeV onto cultured cells, with a spatial
resolution of a few microns, allowing subcellular targeting. In this paper, we
present results from the use of the GEANT4 toolkit to simulate cellular
irradiation with the CENBG microbeam line, from the entrance to the microprobe
up to the cellular medium.Comment: 6 pages, 8 figures, presented at the 2003 IEEE-NSS conference,
Portland, OR, USA, October 20-24, 200
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