10,104 research outputs found
Electronic setup for fluorescence emission measurements and long-time constant-temperature maintenance of Single-Walled Carbon Nano-Tubes in water solutions
In our previous research we have observed that the fluorescence emission from water solutions of Single-Walled Carbon Nano-Tubes (SWCNT), excited by a laser with a wavelength of 830nm, diminishes with the time. We have already proved that such a fading is a function of the storage time and the storage temperature. In order to study the emission of the SWCNT as a function of these two parameters we have designed and realized a special measurement compartment with a cuvette holder where the SWCNT solutions can be measured and stored at a fixed constant temperature for periods of time as long as several weeks. To maintain the measurement setup under a constant temperature we have designed special experimental setup based on two Peltier cells with electronic temperature control
Landscapes and Fragilities
The concept of fragility provides a possibility to rank different supercooled
liquids on the basis of the temperature dependence of dynamic and/or
thermodynamic quantities. We recall here the definitions of kinetic and
thermodynamic fragility proposed in the last years and discuss their
interrelations. At the same time we analyze some recently introduced models for
the statistical properties of the potential energy landscape. Building on the
Adam-Gibbs relation, which connects structural relaxation times to
configurational entropy, we analyze the relation between statistical properties
of the landscape and fragility. We call attention to the fact that the
knowledge of number, energy depth and shape of the basins of the potential
energy landscape may not be sufficient for predicting fragility. Finally, we
discuss two different possibilities for generating strong behavior.Comment: 17 pages, 10 figures; accepted version, minor correction
Skewness as measure of the invariance of instantaneous renormalized drop diameter distributions – Part 1: Convective vs. stratiform precipitation
Abstract. We investigate the variability of the shape of the renormalized drop diameter instantaneous distribution using of the third order central moment: the skewness. Disdrometer data, collected at Darwin Australia, are considered either as whole or as divided in convective and stratiform precipitation intervals. We show that in all cases the distribution of the skewness is strongly peaked around 0.64. This allows to identify a most common distribution of renormalized drop diameters and two main variations, one with larger and one with smaller skewness. The distributions shapes are independent from the stratiform vs. convective classification
Skewness as measure of the invariance of instantaneous renormalized drop diameter distributions – Part 2: Orographic precipitation
Abstract. Here we use the skewness parameter, and the procedure developed in the companion paper (Ignaccolo and De Michele, 2012), to investigate the variability of instantaneous renormalized spectra of rain drop diameter in presence of orographic precipitation. Disdrometer data, available at Bodega Bay and Cazadero, California, are analyzed either as a whole, or as divided (using the bright band echo) in precipitation intervals weakly and strongly influenced by orography, and compared to results obtained at Darwin, Australia. We find that also at Bodega Bay and Cazadero exists a most common distribution of the skewness values of instantaneous spectra of drop diameter, but peaked at values greater than 0.64, found at Darwin. No appreciable differences are found in the skewness distributions of precipitation weakly and strongly influenced by orography. However the renormalized drop diameter spectra of precipitation with strong orographic component have fatter right tail than precipitation with a weaker orographic component. The differences between orographic and non-orographic precipitation are investigated within the parametric space represented by number of drops, mean value and standard deviation of drop diameter. A filter is developed which is able to identify 1 min time intervals during which precipitation is mostly of orographic origin
Viscoelasticity and Stokes-Einstein relation in repulsive and attractive colloidal glasses
We report a numerical investigation of the visco-elastic behavior in models
for steric repulsive and short-range attractive colloidal suspensions, along
different paths in the attraction-strength vs packing fraction plane. More
specifically, we study the behavior of the viscosity (and its frequency
dependence) on approaching the repulsive glass, the attractive glass and in the
re-entrant region where viscosity shows a non monotonic behavior on increasing
attraction strength. On approaching the glass lines, the increase of the
viscosity is consistent with a power-law divergence with the same exponent and
critical packing fraction previously obtained for the divergence of the density
fluctuations. Based on mode-coupling calculations, we associate the increase of
the viscosity with specific contributions from different length scales. We also
show that the results are independent on the microscopic dynamics by comparing
newtonian and brownian simulations for the same model. Finally we evaluate the
Stokes-Einstein relation approaching both glass transitions, finding a clear
breakdown which is particularly strong for the case of the attractive glass.Comment: 12 pages; sent to J. Chem. Phy
Capgras-like syndrome in a patient with an acute urinary tract infection.
Delusional misidentification syndromes are a group of delusional phenomena in which patients misidentify familiar persons, objects, or themselves, believing that they have been replaced or transformed. In 25%-40% of cases, misidentification syndromes have been reported in association with organic illness. We report an acute episode of Capgras-like delusion lasting 8 days, focused on the idea that people were robots with human bodies, in association with an acute urinary infection. To our knowledge, this is the first case report associating urinary tract infection with Capgras-like syndrome. Awareness of the prevalence of delusional misidentification syndromes associated with acute medical illness should promote diligence on the part of clinicians in recognizing this disorder
Impact of URI Canonicalization on Memento Count
Quantifying the captures of a URI over time is useful for researchers to
identify the extent to which a Web page has been archived. Memento TimeMaps
provide a format to list mementos (URI-Ms) for captures along with brief
metadata, like Memento-Datetime, for each URI-M. However, when some URI-Ms are
dereferenced, they simply provide a redirect to a different URI-M (instead of a
unique representation at the datetime), often also present in the TimeMap. This
infers that confidently obtaining an accurate count quantifying the number of
non-forwarding captures for a URI-R is not possible using a TimeMap alone and
that the magnitude of a TimeMap is not equivalent to the number of
representations it identifies. In this work we discuss this particular
phenomena in depth. We also perform a breakdown of the dynamics of counting
mementos for a particular URI-R (google.com) and quantify the prevalence of the
various canonicalization patterns that exacerbate attempts at counting using
only a TimeMap. For google.com we found that 84.9% of the URI-Ms result in an
HTTP redirect when dereferenced. We expand on and apply this metric to TimeMaps
for seven other URI-Rs of large Web sites and thirteen academic institutions.
Using a ratio metric DI for the number of URI-Ms without redirects to those
requiring a redirect when dereferenced, five of the eight large web sites' and
two of the thirteen academic institutions' TimeMaps had a ratio of ratio less
than one, indicating that more than half of the URI-Ms in these TimeMaps result
in redirects when dereferenced.Comment: 43 pages, 8 figure
Dynamics of uniaxial hard ellipsoids
We study the dynamics of monodisperse hard ellipsoids via a new event-driven
molecular dynamics algorithm as a function of volume fraction and aspect
ratio . We evaluate the translational and the rotational
diffusion coefficient and the associated isodiffusivity lines in the
plane. We observe a decoupling of the translational and rotational
dynamics which generates an almost perpendicular crossing of the
and isodiffusivity lines. While the self intermediate scattering
function exhibits stretched relaxation, i.e. glassy dynamics, only for large
and , the second order orientational correlator
shows stretching only for large and small values. We discuss these
findings in the context of a possible pre-nematic order driven glass
transition.Comment: accepted by Phys. Rev. Let
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