132 research outputs found
Raman studies of suspensions and solutions of singlewall carbon nanotubes
Raman spectroscopy is used to probe the structure and electronic properties
of nanotubes dispersed in a liquid phase. We show that the radial breathing
modes are upshifted in suspensions due to the molecular pressure of the
solvent. On the other hand, we directly probe charge transfer in solutions of
nanotube polyelectrolytes and its reversibility after oxydation in air
Nanotube-based systems for broadband optical limiting: towards an operational system
Nanotube-based systems are good candidates for optical limiting against
broadband laser pulses. We explore new routes to improve their limiting
performances. We show that the diameter of the nanotubes is a key factor to
control the performances. On the other hand, we demonstrate that chemically
modified nanotubes can be mixed with organic chromophores, leading to high
performance composite limiting systems which are particularly efficient in the
nanosecond regime due to the cumulative effects of nonlinear scattering and
multiphoton absorption
Multi-spectroscopic investigation of the structure of single-wall carbon nanotubes
We present a multispectroscopic structural study of various nanotube samples
with different tube diameters. We determine for each sample the mean bundle and
tube diameter as well as the tube diameter distribution. The possibility to
work on SWNT of various structural characteristics opens new opportunities to
correlate the nanotube structure and their physical properties.Comment: Conf\'{e}rence : 8 au 15 mars 200
Broadband optical limiting optimisation by combination of carbon nanotubes and two-photon absorbing chromophores in liquids
International audienceWe report here on the optical limiting studies performed with nanosecond laser pulses on several families of multiphoton absorbers in chloroform, with carbon nanotubes suspended in solutions. Performances of these samples are compared with those of simple multiphoton absorber solutions and carbon nanotube suspensions, and the differences observed are interpreted in terms of cumulative NLO effects and adverse aggregation phenomenon
Small Angle Neutron Scattering of Aerogels: Simulations and Experiments
A numerical simulation of silica aerogels is performed using
diffusion-limited cluster-cluster aggregation of spheres inside a cubic box
(with periodic boundary conditions). The volume fraction is taken to be
sufficiently large to get a gel structure at the end of the process. In the
case of monodisperse spheres, the wavevector dependent scattered intensity
is calculated from the product of the form factor of a sphere by
the structure factor , which is related to the Fourier transform of
, where is the pair correlation function between sphere centers.
The structure factor exhibits large- damped oscillations
characteristics of the short range (intra-aggregate) correlations between
spheres. These oscillations influence the curve in the -region
between the fractal regime and the Porod regime and quantitative comparisons
are made with experiments on colloidal aerogels. Moreover, at small- values,
goes through a maximum characteristic of large range (inter-aggregate)
correlations. Quantitative fits of the maximum in the experimental
curves of base-catalyzed aerogel are presented. In the case of polydisperse
spheres, is calculated directly from a single aggregate simulation. It
is shown that increasing polydispersity shifts the location of the cross-over
between the fractal and Porod regimes towards low -value.Comment: RevTex, 9 pages + 11 postscript figures, compressed using "uufiles".
Proceeding of the 4th International Simposium on Aerogels (To appear in J. of
Non-Cryst. Solids
PLoS One
INTRODUCTION: The Temprano and START trials provided evidence to support early ART initiation recommendations. We projected long-term clinical and economic outcomes of immediate ART initiation in Cote d'Ivoire. METHODS: We used a mathematical model to compare three potential ART initiation criteria: 1) CD4 <350/muL (ART<350/muL); 2) CD4 <500/muL (ART<500/muL); and 3) ART at presentation (Immediate ART). Outcomes from the model included life expectancy, 10-year medical resource use, incremental cost-effectiveness ratios (ICERs) in 90/person-year). We assessed cost-effectiveness relative to Cote d'Ivoire's 2017 per capita annual gross domestic product (680/YLS compared to ART<350/muL, ranging from cost-saving to an ICER of 801.9M to $812.6M compared to ART<350/muL. CONCLUSIONS: In Cote d'Ivoire, immediate compared to later ART initiation will increase life expectancy, decrease HIV transmission, and be cost-effective over the long-term, with modest budget impact. Immediate ART initiation is an appropriate, high-value standard of care in Cote d'Ivoire and similar settings
Low CD4 count plus coma predicts cryptococcal meningitis in Tanzania
<p>Abstract</p> <p>Background</p> <p>Largely due to the lack of diagnostic reagents, the prevalence and clinical presentation of cryptococcal meningitis in Tanzania is poorly understood. This in turn is limiting the impact of increased fluconazole availability.</p> <p>Methods</p> <p>We evaluated a cohort of 149 consecutive HIV-infected adult inpatients presenting with headache or altered mental status for clinical features, CD4 count, cryptococcal infection, and outcome. Cryptococcal meningitis was diagnosed via India ink and latex agglutination assay of CSF (<it>n </it>= 24 and 40 positive, respectively). Associations between cryptococcal meningitis and clinical features were evaluated by t-test. The sensitivity, specificity, and positive likelihood ratio of such features were determined.</p> <p>Results</p> <p>Cryptococcal meningitis was associated with confusion, social withdrawal, seizures, fever, tachycardia, meningismus, oral candidiasis, and low Glasgow coma scales and CD4 count. CD4 count < 100/μl provided the highest sensitivity for the diagnosis (93%), coma (Glasgow coma scale ≤ 8) provided the highest specificity (84%), and the combination provided the highest positive likelihood ratio (3.8). All cryptococcal meningitis patients were initiated on 800 milligrams of fluconazole daily and 50% survived to discharge, however no clinical or laboratory findings correlated with prognosis.</p> <p>Conclusion</p> <p>Cryptococcal meningitis is common among Tanzanian HIV inpatients presenting with headache or altered mental status. Purely clinical features are insensitive for establishing the diagnosis or prognosis. We advocate expanding laboratory capacity for cryptococcal antigen testing to maximize survival.</p
Cost-Effectiveness of Preventing Loss to Follow-up in HIV Treatment Programs: A Côte d'Ivoire Appraisal
Based on data from West Africa, Elena Losina and colleagues predict that interventions to reduce dropout rates from HIV treatment programs (such as eliminating copayments) will be cost-effective
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