1,806 research outputs found
Radiative feedback and cosmic molecular gas: the role of different radiative sources
We present results from multifrequency radiative hydrodynamical chemistry
simulations addressing primordial star formation and related stellar feedback
from various populations of stars, stellar energy distributions (SEDs) and
initial mass functions. Spectra for massive stars, intermediate-mass stars and
regular solar-like stars are adopted over a grid of 150 frequency bins and
consistently coupled with hydrodynamics, heavy-element pollution and
non-equilibrium species calculations. Powerful massive population III stars are
found to be able to largely ionize H and, subsequently, He and He, causing
an inversion of the equation of state and a boost of the Jeans masses in the
early intergalactic medium. Radiative effects on star formation rates are
between a factor of a few and 1 dex, depending on the SED. Radiative processes
are responsible for gas heating and photoevaporation, although emission from
soft SEDs has minor impacts. These findings have implications for cosmic gas
preheating, primordial direct-collapse black holes, the build-up of "cosmic
fossils" such as low-mass dwarf galaxies, the role of AGNi during reionization,
the early formation of extended disks and angular-momentum catastrophe.Comment: 19 pages on MNRA
Non-critical string pentagon equations and their solutions
We derive pentagon type relations for the 3-point boundary tachyon
correlation functions in the non-critical open string theory with generic
c_{matter} < 1 and study their solutions in the case of FZZ branes. A new
general formula for the Liouville 3-point factor is derived.Comment: 18 pages, harvmac; misprints corrected, section 3.2 extended, a new
general formula for the Liouville 3-point factor adde
Anomalous thickness dependence of the Hall effect in ultrathin Pb layers on Si(111)
The magnetoconductive properties of ultrathin Pb films deposited on Si(111)
are measured and compared with density-functional electronic band-structure
calculations on two-dimensional, free-standing, 1 to 8 monolayers thick Pb(111)
slabs. A description with free-standing slabs is possible because it turned out
that the Hall coefficient is independent of the substrate and of the
crystalline order in the film. We show that the oscillations in sign of the
Hall coefficient observed as a function of film thickness can be explained
directly from the thickness dependent variations of the electronic
bandstructure at the Fermi energy.Comment: 4 pages incl. 3 figures, RevTeX, to appear in Phys. Rev.
Sonochemical synthesis and stabilization of concentrated antimicrobial silver-chitosan nanoparticle dispersions
This work reports on a green synthetic route to produce concentrated aqueous dispersions of silver nanoparticles (AgNP)
employing high-intensity ultrasound (US) and chitosan (CS) as a non-toxic reducing agent for Ag1 salts and AgNP stabilizer. The sonication simultaneously boosted the synthesis and improved the stability of the AgNP, capping them with CS. Hybrid AgNP-CS antimicrobial dispersions, stable for at least 6 months, were synthesized in a simple single step process. The use of US allowed for applying relatively mild processing temperatures (608C) and reaction time between 30 min and 3 h to obtain concentrated disper- sions of AgNP that otherwise could not be obtained even after 72 h under mechanical stirring at the same reaction conditions. Upon sonication spherical AgNP-CS with a size between 60 and 100 nm were generated, in contrast to the average diameter of 200 nm of the particles obtained by stirring. The antibacterial efficiency of the AgNP-CS hybrids was evaluated against the medically relevant pathogens Staphylococcus aureus and Escherichia coli. The US-synthesized AgNP-CS showed more than 3-fold higher antibacterial activity compared to the particles obtained under stirring, due to their higher concentration and smaller size.Postprint (author's final draft
A Finite Liouville Dress for c
We review the derivation of a general formula for the Liouville dressing factor in the boundary 3-point tachyon correlator with c < 1 degenerate matter
The Boundary Conformal Field Theories of the 2D Ising critical points
We present a new method to identify the Boundary Conformal Field Theories
(BCFTs) describing the critical points of the Ising model on the strip. It
consists in measuring the low-lying excitation energies spectra of its quantum
spin chain for different boundary conditions and then to compare them with
those of the different boundary conformal field theories of the
minimal model.Comment: 7 pages, no figures. Talk given at the XXth International Conference
on Integrable Systems and Quantum Symmetries (ISQS-20). Prague, June 201
Use of Peptide Libraries for Identification and Optimization of Novel Antimicrobial Peptides.
The increasing rates of resistance among bacteria and to a lesser extent fungi have resulted in an urgent need to find new molecules that hold therapeutic promise against multidrug-resistant strains. Antimicrobial peptides have proven very effective against a variety of multidrug-resistant bacteria. Additionally, the low levels of resistance reported towards these molecules are an attractive feature for antimicrobial drug development. Here we summarise information on diverse peptide libraries used to discover or to optimize antimicrobial peptides. Chemical synthesized peptide libraries, for example split and mix method, tea bag method, multi-pin method and cellulose spot method are discussed. In addition biological peptide library screening methods are summarized, like phage display, bacterial display, mRNA-display and ribosomal display. A few examples are given for small peptide libraries, which almost exclusively follow a rational design of peptides of interest rather than a combinatorial approach
The boundary states and correlation functions of the tricritical Ising model from the Coulomb-gas formalism
We consider the minimal conformal model describing the tricritical Ising
model on the disk and on the upper half plane. Using the coulomb-gas formalism
we determine its consistents boundary states as well as its 1-point and 2-point
correlation functions.Comment: 20 pages, no figure. Version 2:A paragraph for the calculation of the
2-point correlators was added. Some typos and garammatical errors were
corrected.Version 3: Equations 24 are modified. Version 4 : new introduction
and minor correction
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