889 research outputs found
Criticality of an isotropic-to-smectic transition induced by anisotropic quenched disorder
We report combined optical birefringence and neutron scattering measurements
on the liquid crystal 12CB nanoconfined in mesoporous silicon layers. This
liquid crystal exhibits strong nematic-smectic coupling responsible for a
discontinuous isotropic-to-smectic phase transition in the bulk state. Confined
in porous silicon, 12CB is subjected to strong anisotropic quenched disorder: a
short-ranged smectic state evolves out of a paranematic phase. This
transformation appears continuous, losing its bulk first order character. This
contrasts with previously reported observations on liquid crystals under
isotropic quenched disorder. In the low temperature phase, both orientational
and translational order parameters obey the same power-law
Monatomic Excitation Temperature in Theoretical Study of Discharge with Liquid Non-Metallic (Tap Water) Electrodes in Air at Atmospheric Pressure
The discharge with liquid non-metallic electrodes under study is out of thermal equilibrium. From probe and micro-wave absorption measurements the electronic concentration has been evaluated. The spectral intensities of N2 and Oxygen triplet have been measured locally. In this work, we propose to compare the results of calculation with the experimental results for two hypotheses on the monatomic excitation temperature. The first is when we assume the monatomic excitation temperature close to heavy particle translational temperature and the second is when we assume the monatomic excitation temperature close to the electronic translational temperature
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
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
Dual tumor suppressing and promoting function of Notch1 signaling in human prostate cancer.
Adenocarcinomas of the prostate arise as multifocal heterogeneous lesions as the likely result of genetic and epigenetic alterations and deranged cell-cell communication. Notch signaling is an important form of intercellular communication with a role in growth/differentiation control and tumorigenesis. Contrasting reports exist in the literature on the role of this pathway in prostate cancer (PCa) development. We show here that i) compared to normal prostate tissue, Notch1 expression is significantly reduced in a substantial fraction of human PCas while it is unaffected or even increased in others; ii) acute Notch activation both inhibits and induces process networks associated with prostatic neoplasms; iii) down-modulation of Notch1 expression and activity in immortalized normal prostate epithelial cells increases their proliferation potential, while increased Notch1 activity in PCa cells suppresses growth and tumorigenicity through a Smad3-dependent mechanism involving p21WAF1/CIP1; iv) prostate cancer cells resistant to Notch growth inhibitory effects retain Notch1-induced upregulation of pro-oncogenic genes, like EPAS1 and CXCL6, also overexpressed in human PCas with high Notch1 levels. Taken together, these results reconcile conflicting data on the role of Notch1 in prostate cancer
drainage hyperlent
Dans ce travail, le processus de drainage hyper lent est étudié d'une part à travers une approche théorique issue de la théorie de la percolation, et d'autre part par l'intermédiaire de simulations sur réseau de pores. En utilisant des réseaux modèles, une étude sera présentée montrant comment les courbes de rétention capillaire et de perméabilité relative au gaz doivent être spécifiées dans la gamme des très fortes saturations en eau de façon à obtenir une prédiction optimale à l'aide du modèle diphasique classique
High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanopores
International audienceWe report a high-resolution dielectric study on a pyrene-based discotic liquid crystal (DLC) in the bulk state and confined in parallel tubular nanopores of monolithic silica and alumina membranes. The positive dielectric anisotropy of the DLC molecule at low frequencies (in the quasistatic case) allows us to explore the thermotropic collective orientational order. A face-on arrangement of the molecular discs on the pore walls and a corresponding radial arrangement of the molecules is found. In contrast to the bulk, the isotropic-to-columnar transition of the confined DLC is continuous, shifts with decreasing pore diameter to lower temperatures, and exhibits a pronounced hysteresis between cooling and heating. These findings corroborate conclusions from previous neutron and x-ray-scattering experiments as well as optical birefringence measurements. Our study also indicates that the relative simple dielectric technique presented here is a quite efficient method in order to study the thermotropic orientational order of DLC-based nanocomposites
IMF isotopic properties in semi-peripheral collisions at Fermi energies
We study the neutron and proton dynamical behavior along the fragmentation
path in semi-peripheral collisions: 58Fe+58Fe (charge asymmetric, N/Z = 1.23)
and 58Ni+58Ni (charge symmetric, N/Z = 1.07), at 47 AMeV. We observe that
isospin dynamics processes take place also in the charge-symmetric system
58Ni+58Ni, that may produce more asymmetric fragments. A neutron enrichment of
the neck fragments is observed, resulting from the interplay between
pre-equilibrium emission and the phenomenon of "isospin-migration". Both
effects depend on the EoS (Equation of State) symmetry term. This point is
illustrated by comparing the results obtained with two different choices of the
symmetry energy density dependence.
New correlation observables are suggested, to study the reaction mechanism
and the isospin dynamics.Comment: 5 pages, 8 figures, Revtex4 Latex Styl
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