12,502 research outputs found
Additional Light Waves in Hydrodynamics and Holography
We study the phenomenon of additional light waves (ALWs), observed in crystal
optics: two or more electromagnetic waves with the same polarization, but
different refractive index, propagate simultaneously in a isotropic medium. We
show that ALWs are common in relativistic hydrodynamics, and in particular in
strongly coupled systems that admit a dual gravitational description, where the
ALWs are dual to quasi normal modes in the AdS gravity. We study both the
transverse and the longitudinal light wave propagation. In the longitudinal
channel we find a transition between regimes with different number of excitonic
resonances which resembles the transition to standard optics observed in
crystals.Comment: 20 pages, 17 figure
On supersymmetry breaking and the Dijkgraaf-Vafa conjecture
We investigate the Dijkgraaf-Vafa proposal when supersymmetry is broken. We
consider U(N) SYM with chiral adjoint matter where the coupling constants in
the tree-level superpotential are promoted to chiral spurions. The holomorphic
part of the low-energy glueball superpotential can still be analyzed. We
compute the holomorphic supersymmetry breaking contributions using methods of
the geometry underlying the N=1 effective gauge theory viewed as a Whitham
system. We also study the change in the effective glueball superpotential using
perturbative supergraph techniques in the presence of spurions.Comment: 24 pages, LaTeX; minor changes, one reference added, version to
appear in JHE
Laser driven self-assembly of shape-controlled potassium nanoparticles in porous glass
We observe growth of shape-controlled potassium nanoparticles inside a random
network of glass nanopores, exposed to low-power laser radiation. Visible laser
light plays a dual role: it increases the desorption probability of potassium
atoms from the inner glass walls and induces the self-assembly of metastable
metallic nanoparticles along the nanopores. By probing the sample transparency
and the atomic light-induced desorption flux into the vapour phase, the
dynamics of both cluster formation/evaporation and atomic photo-desorption
processes are characterized. Results indicate that laser light not only
increases the number of nanoparticles embedded in the glass matrix but also
influences their structural properties. By properly choosing the laser
frequency and the illumination time, we demonstrate that it is possible to
tailor the nanoparticles'shape distribution. Furthermore, a deep connection
between the macroscopic behaviour of atomic desorption and light-assisted
cluster formation is observed. Our results suggest new perspectives for the
study of atom/surface interaction as well as an effective tool for the
light-controlled reversible growth of nanostructures.Comment: 14 pages,6 figures, http://iopscience.iop.org/1612-202X/11/8/085902
Culture of human cell lines by a pathogen-inactivated human platelet lysate
Alternatives to the use of fetal bovine serum (FBS) have been investigated to ensure xeno-free growth condition. In this study we evaluated the efficacy of human platelet lysate (PL) as a substitute of FBS for the in vitro culture of some human cell lines. PL was obtained by pools of pathogen inactivated human donor platelet (PLT) concentrates. Human leukemia cell lines (KG-1, K562, JURKAT, HL-60) and epithelial tumor cell lines (HeLa and MCF-7) were cultured with either FBS or PL. Changes in cell proliferation, viability, morphology, surface markers and cell cycle were evaluated for each cell line. Functional characteristics were analysed by drug sensitivity test and cytotoxicity assay. Our results demonstrated that PL can support growth and expansion of all cell lines, although the cells cultured in presence of PL experienced a less massive proliferation compared to those grown with FBS. We found a comparable percentage of viable specific marker-expressing cells in both conditions, confirming lineage fidelity in all cultures. Functionality assays showed that cells in both FBS- and PL-supported cultures maintained their normal responsiveness to adriamycin and NK cell-mediated lysis. Our findings indicate that PL is a feasible serum substitute for supporting growth and propagation of haematopoietic and epithelial cell lines with many advantages from a perspective of process standardization, ethicality and product safety
I terremoti e i maremoti dello Stretto di Messina dal mondo antico alla fine del XX secolo: descrizioni e parametri
Un excursus storico di oltre duemila anni sintetizza le conoscenze attestate
da fonti scritte. Antiche testimonianze, annotazioni in codici medievali,
ma anche dettagliate relazioni di epoca moderna e rilevazioni
contemporanee consentono di delineare un quadro il più possibile completo
della sismicità di quest’area, abitata fin dai tempi più remoti.
Emergono diversi terremoti minori, alcuni dei quali quasi dimenticati,
che tuttavia confermano un’immagine dell’attività sismica nell’area
dello Stretto caratterizzata da eventi frequenti, ma dominata da rari terremoti
catastrofici
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