Dynamics of a driven probe molecule in a liquid monolayer

We study dynamics of a probe molecule, driven by an external constant force in a liquid monolayer on top of solid surface. In terms of a microscopic, mean-field-type approach, we calculate the terminal velocity of the probe molecule. This allows us to establish the analog of the Stokes formula, in which the friction coefficient is interpreted in terms of the microscopic parameters characterizing the system. We also determine the distribution of the monolayer particles as seen from the stationary moving probe molecule and estimate the self-diffusion coefficient for diffusion in a liquid monolayer.Comment: Latex, 7 pages, 1 figur

A proposal for beam-column interaction formulae

Peer reviewe

Molecular Weight Dependence of Spreading Rates of Ultrathin Polymeric Films

We study experimentally the molecular weight $M$ dependence of spreading rates of molecularly thin precursor films, growing at the bottom of droplets of polymer liquids. In accord with previous observations, we find that the radial extension R(t) of the film grows with time as R(t) = (D_{exp} t)^{1/2}. Our data substantiate the M-dependence of D_{exp}; we show that it follows D_{exp} \sim M^{-\gamma}, where the exponent \gamma is dependent on the chemical composition of the solid surface, determining its frictional properties with respect to the molecular transport. In the specific case of hydrophilic substrates, the frictional properties can be modified by the change of the relative humidity (RH). We find that \gamma \approx 1 at low RH and tends to zero when RH gets progressively increased. We propose simple theoretical arguments which explain the observed behavior in the limits of low and high RH.Comment: 4 pages, 2 figures, to appear in PR

Multiple Description Coding for Voice over IP using Sinusoidal Speech Coding

ABSTRACT CELP coders, such as G.729, are often used in VoIP systems as they offer good speech quality in the absence of packet losses. However, their reliance on long-term prediction causes propagation of errors across speech frames, and therefore makes CELP coders more sensitive to packet losses. Sinusoidal coders on the other hand do not rely on long-term prediction, and may be a good alternative for VoIP due to their higher resilience to packet losses. In this paper a comparison is made between CELP and sinusoidal coders in a VoIP application. A packetisation scheme based on Multiple Description Coding (MDC) applied to the sinusoidal coder is presented. The results show that under typical VoIP operating conditions, the sinusoidal coder based systems can outperform CELP based systems at equal bit rate, especially for high packet loss rates

Experimental X-ray characterization of Gekko-XII laser propagation through very low-density aerogels (2–5 mg/cc) creating multi-keV photons from a titanium solid foil

Describes measurements of laser propagations through low density aerogels

Vitamin D5 in Arabidopsis thaliana

Abstract Vitamin D3 is a secosterol hormone critical for bone growth and calcium homeostasis, produced in vertebrate skin by photolytic conversion of the cholesterol biosynthetic intermediate provitamin D3. Insufficient levels of vitamin D3 especially in the case of low solar UV-B irradiation is often compensated by an intake of a dietary source of vitamin D3 of animal origin. Small amounts of vitamin D3 were described in a few plant species and considered as a peculiar feature of their phytochemical diversity. In this report we show the presence of vitamin D5 in the model plant Arabidopsis thaliana. This plant secosterol is a UV-B mediated derivative of provitamin D5, the precursor of sitosterol. The present work will allow a further survey of vitamin D distribution in plant species

Autofluorescence endoscopic spectro-imaging and 2D-cartography for in situ localisation and diagnosis of cancerous lesions

Early diagnosis is the most efficient way to struggle against cancer. Among all the existing techniques, optical methods (photodiagnosis from NUV to NIR) show important characteristics required by the physicians : high sensitivity, non-ionising radiations and non-traumatic measurements. They are particularly well suited to the detection of cancers in hollow organs, that are usually superficial and hardly visible with classical endoscopy. This paper describes a methodological approach based on the use of tissue autofluorescence, applicable in clinical endoscopy, and leading to the definition of diagnosis indicators from the spectral parameters. Following a state-of-the-art on autofluorescence spectroscopic (LIFS) and endoscopic imaging methods, we present the efficiency of fibered LIFS in terms of sensitivity and specificity for the diagnosis of esophagus cancerous lesions (clinical study over 25 patients). We then present the technological characteristics of an autofluorescence endoscopic imaging prototype developed in our labs as well as its calibration. A second part is devoted to endoscopic image registration and mosaicing and to optics aberration correction in perspective of the automatic construction of a panoramic image (cartography) of the organ’s explored areas. Finally, exploiting the fluorescence data provided by the imager, the feasibility of the superimposition of spatial and spectral information is validated with a phantom.Le diagnostic précoce est le moyen le plus efficace de lutte contre le cancer. Parmi toutes les techniques possibles, les méthodes optiques (photodiagnostic du proche UV au proche IR) présentent des caractéristiques importantes recherchées par les médecins : grande sensibilité, radiations non ionisantes et mesures atraumatiques. Elles sont particulièrement bien adaptées à la détection des cancers des organes creux, par nature superficiels et difficilement décelables en endoscopie classique. Cet article décrit une approche méthodologique fondée sur l’exploitation de l’autofluorescence tissulaire, applicable en endoscopie clinique, et conduisant à l’élaboration d’indicateurs diagnostiques issus des paramètres spectraux. Après un état de l’art sur les méthodes spectroscopiques (LIFS) et d’imagerie endoscopique d’autofluorescence, nous montrons l’efficacité de la LIFS fibrée en terme de sensibilité et de spécificité pour le diagnostic de lésions cancéreuses de l’oesophage (étude clinique sur 25 patients). Nous présentons ensuite les caractéristiques technologiques et le calibrage du prototype d’imageur endoscopique d’autofluorescence développé. Une seconde partie traite du pré-traitement, du recalage et du mosaïquage des images endoscopiques appliqués à la construction automatique d’une image panoramique (cartographie) à partir de séquences vidéos des zones explorées de l’organe. Finalement, en exploitant les informations de fluorescence fournies par l’imageur, la faisabilité d’une superposition des informations spatiale et spectrale est validée sur fantôme

The effects of transurethral resection and cystoprostatectomy on dissemination of epithelial cells in the circulation of patients with bladder cancer

This study was undertaken to evaluate the risk of haematogenous dissemination of epithelial cells induced by endoscopic resection and/or cystoprostatectomy for transitional cell carcinoma of the bladder. Thirty-three patients were studied. Thirty-one had different stages and grades of bladder cancer and two patients had benign bladder conditions. Twenty-five cancer patients required transurethral resection of their bladder tumour. Of those, 20 had superficial disease (pTaG1–G2: n = 19; pT1G2: n = 1) and five had muscle invasive tumours (pT2G3: n = 2; pT3aG3: n = 1; pT4G3: n = 2). Five patients underwent radical cystoprostatectomy for muscle invasive cancers (pT2G3: n = 3; pT3bG3: n = 1; pT4G3: n = 1) and one man received chemotherapy for metastatic disease. Venous blood (10 ml) was obtained from the antecubital fossa in each patient, before and 1–2 h after completion of surgery, and prior to treatment in the metastatic patient. An indirect immunocytochemical technique was used to detect circulating epithelial cells after centrifugation on Ficoll gradient and fixation of mononuclear cells on slides, using a monoclonal antibody directed against three cytokeratins: CK8, CK18 and CK19. Circulating epithelial cells were detected only in the patient with metastatic disease. None of the other patients had evidence of epithelial circulating cells before or after surgery. The results suggest that irrespective of disease stage and grade, neither endoscopic nor open bladder surgery leads to detectable dissemination of urothelial cells in the peripheral circulation. These procedures are therefore unlikely to increase the risk of progression and metastasis in transitional cell carcinoma of the bladder. © 1999 Cancer Research Campaig