856 research outputs found
CdTe Raman Line Shape in Resonance: a Space Correlation Zone Study
We show that the line shape of resonant Raman spectra of CdTe can be reproduced using the spatial correlation model (SCM). Our results show that the resonant Raman spectrum for a surface with a RMS of 430 nm is characterized by the presence of two intense sharp peaks located at frequencies corresponding to LO and 2LOmodes. The resonant Raman spectrum for a surface with a RMS of 6 nm on the other hand, can be reproduced using the contribution of high frequency phonons related with the acoustic transverse harmonics. These results suggest that under resonance conditions, such acoustic transverse modes define the line shape for a small size correlation region diameter. This study provides a new application of SCM to estimate the size grain of a surface where this information is not available
Glutathione-Induced Release of Zeatin From Functionalized Gold Nanovectors
The paper shows our preliminary results on the different spectroscopic behavior of three types of gold nanoparticles (obtained respectively by chemical synthesis, laser ablation in pure water and laser ablation in a citrate solution) modified with trans-zeatin, a plant growth regulator, in presence of glutathione. The reaction of ligand substitution of the adsorbed zeatin with glutathione is studied through surface enhanced Raman spectroscopy and is revealed to occur only when citrate-laser ablated gold nanoparticles are employed, making these particles potentially good candidates as vehicles of zeatin inside plant cells for future agricultural applications
Glutathione-Induced Release of Zeatin From Functionalized Gold Nanovectors
The paper shows our preliminary results on the different spectroscopic behavior of three types of gold nanoparticles (obtained respectively by chemical synthesis, laser ablation in pure water and laser ablation in a citrate solution) modified with trans-zeatin, a plant growth regulator, in presence of glutathione. The reaction of ligand substitution of the adsorbed zeatin with glutathione is studied through surface enhanced Raman spectroscopy and is revealed to occur only when citrate-laser ablated gold nanoparticles are employed, making these particles potentially good candidates as vehicles of zeatin inside plant cells for future agricultural applications
Analyticity and compactness of semigroups of composition operators
This paper provides a complete characterization of quasicontractive groups and analytic C0C0-semigroups on Hardy and Dirichlet space on the unit disc with a prescribed generator of the form Af=Gf′Af=Gf′. In the analytic case we also give a complete characterization of immediately compact semigroups. When the analyticity fails, we obtain sufficient conditions for compactness and membership in the trace class. Finally, we analyse the case where the unit disc is replaced by the right-half plane, where the results are drastically different
CdTe Raman Line Shape in Resonance: a Space Correlation Zone Study
We show that the line shape of resonant Raman spectra of CdTe can be reproduced using the spatial correlation model (SCM). Our results show that the resonant Raman spectrum for a surface with a RMS of 430 nm is characterized by the presence of two intense sharp peaks located at frequencies corresponding to LO and 2LOmodes. The resonant Raman spectrum for a surface with a RMS of 6 nm on the other hand, can be reproduced using the contribution of high frequency phonons related with the acoustic transverse harmonics. These results suggest that under resonance conditions, such acoustic transverse modes define the line shape for a small size correlation region diameter. This study provides a new application of SCM to estimate the size grain of a surface where this information is not available
Ultra Long Period Cepheids: a primary standard candle out to the Hubble flow
The cosmological distance ladder crucially depends on classical Cepheids
(with P=3-80 days), which are primary distance indicators up to 33 Mpc. Within
this volume, very few SNe Ia have been calibrated through classical Cepheids,
with uncertainty related to the non-linearity and the metallicity dependence of
their period-luminosity (PL) relation. Although a general consensus on these
effects is still not achieved, classical Cepheids remain the most used primary
distance indicators. A possible extension of these standard candles to further
distances would be important. In this context, a very promising new tool is
represented by the ultra-long period (ULP) Cepheids (P \geq 80 days), recently
identified in star-forming galaxies. Only a small number of ULP Cepheids have
been discovered so far. Here we present and analyse the properties of an
updated sample of 37 ULP Cepheids observed in galaxies within a very large
metallicity range of 12+log(O/H) from ~7.2 to 9.2 dex. We find that their
location in the colour(V-I)-magnitude diagram as well as their Wesenheit (V-I)
index-period (WP) relation suggests that they are the counterparts at high
luminosity of the shorter-period (P \leq 80 days) classical Cepheids. However,
a complete pulsation and evolutionary theoretical scenario is needed to
properly interpret the true nature of these objects. We do not confirm the
flattening in the studied WP relation suggested by Bird et al. (2009). Using
the whole sample, we find that ULP Cepheids lie around a relation similar to
that of the LMC, although with a large spread (~0.4 mag).Comment: 8 pages, 4 figures, accepted for publication in Astrophysics & Space
Scienc
Neural model of dopaminergic control of arm movements in Parkinson’s disease bradykinesia
Patients suffering from Parkinson’s disease display a number of
symptoms such a resting tremor, bradykinesia, etc. Bradykinesia is the hallmark
and most disabling symptom of Parkinson’s disease (PD). Herein, a basal
ganglia-cortico-spinal circuit for the control of voluntary arm movements in PD
bradykinesia is extended by incorporating DAergic innervation of cells in the
cortical and spinal components of the circuit. The resultant model simulates
successfully several of the main reported effects of DA depletion on neuronal,
electromyographic and movement parameters of PD bradykinesia
Resummations of free energy at high temperature
We discuss resummation strategies for free energy in quantum field theories
at nonzero temperatures T. We point out that resummations should be performed
for the short- and long-distance parts separately in order to avoid spurious
interference effects and double-counting. We then discuss and perform Pade
resummations of these two parts for QCD at high T. The resummed results are
almost invariant under variation of the renormalization and factorization
scales. We perform the analysis also in the case of the massless scalar
theory.Comment: 16 pages, revtex4, 15 eps-figures; minor typographic errors
corrected; the version as it appears in Phys.Rev.
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