Discreteness effects on soliton dynamics: a simple experiment

We present a simple laboratory experiment to illustrate some aspects of the soliton theory in discrete lattices with a system that models the dynamics of dislocations in a crystal or the properties of adsorbed atomic layers. The apparatus not only shows the role of the Peierls-Nabarro potential but also illustrates the hierarchy of depinning transitions and the importance of the collective motion in mass transport.Comment: 9 pages, 4 Figures, to Appear in American Journal of Physic

Using infrared and raman microspectroscopies to compare ex vivo involved psoriatic skin with normal human skin

Psoriasis is a chronic dermatosis that affects around 3% of the world’s population. The etiology of this autoimmune pathology is not completely understood. The barrier function of psoriatic skin is known to be strongly altered, but the structural modifications at the origin of this dysfunction are not clear. To develop strategies to reduce symptoms of psoriasis or adequate substitutes for modeling, a deep understanding of the organization of psoriatic skin at a molecular level is required. Infrared and Raman microspectroscopies have been used to obtain direct molecular-level information on psoriatic and healthy human skin biopsies. From the intensities and positions of specific vibrational bands, the lipid and protein distribution and the lipid order have been mapped in the different layers of the skin. Results showed a similar distribution of lipids and collagen for normal and psoriatic human skin. However, psoriatic skin is characterized by heterogeneity in lipid/protein composition at the micrometer scale, a reduction in the definition of skin layer boundaries and a decrease in lipid chain order in the stratum corneum as compared to normal skin. A global decrease of the structural organization is exhibited in psoriatic skin that is compatible with an alteration of its barrier properties

Theory of molecular excitation and relaxation near a plasmonic device

International audienceThe new optical concepts currently developed in the research field of plasmonics can have significant practical applications for integrated optical device miniaturization as well as for molecular sensing applications. Particularly, these new devices can offer interesting opportunities for optical addressing of quantum systems. In this article, we develop a realistic model able to explore the various functionalities of a plasmon device connected to a single fluorescing molecule. We show that this theoretical method provides a useful framework to understand how quantum and plasmonic entities interact in a small area. Thus, the fluorescence signal evolution from excitation control to relaxation control depending on the incident light power is clearly observed

Transdermal diffusion, spatial distribution and physical state of a potential anticancer drug in mouse skin as studied by diffusion and spectroscopic techniques

Background:Understanding the efficiency of a transdermal medical drug requires the characterization of its diffusion process, including its diffusion rate, pathways and physical state. Objective:The aim of this work is to develop a strategy to achieve this goal. Methods:FTIR spectroscopic imaging in conjunction with a Franz cell and HPLC measurements were used to examine the transdermal penetration of deuterated tert-butyl phenylchloroethylurea (tBCEU), a molecule with a potential anticancer action. tBCEU has been solubilized in an expedient solvent mixture and its diffusion in hairless mouse skin has been studied. Results:The results indicate that tBCEU diffuses across the skin for more than 10 hours with a rate comparable to selegiline, an officially-approved transdermal drug. IR image analyses reveal that after 10 hours, tBCEU penetrates skin and that its spatial distribution does not correlate with neither the distribution of lipids nor proteins. tBCEU accumulates in cluster domains but overall low concentrations are found in skin. FTIR spectroscopic imaging additionally reveals that tBCEU is in a crystalline form. Conclusions:The results suggest that tBCEU is conveyed through the skin without preferential pathway. FTIR spectroscopic imaging and transdermal diffusion measurements appear as complementary techniques to investigate drug diffusion in skin

Chromosome looping in yeast: telomere pairing and coordinated movement reflect anchoring efficiency and territorial organization

Long-range chromosome organization is known to influence nuclear function. Budding yeast centromeres cluster near the spindle pole body, whereas telomeres are grouped in five to eight perinuclear foci. Using live microscopy, we examine the relative positions of right and left telomeres of several yeast chromosomes. Integrated lac and tet operator arrays are visualized by their respective repressor fused to CFP and YFP in interphase yeast cells. The two ends of chromosomes 3 and 6 interact significantly but transiently, forming whole chromosome loops. For chromosomes 5 and 14, end-to-end interaction is less frequent, yet telomeres are closer to each other than to the centromere, suggesting that yeast chromosomes fold in a Rabl-like conformation. Disruption of telomere anchoring by deletions of YKU70 or SIR4 significantly compromises contact between two linked telomeres. These mutations do not, however, eliminate coordinated movement of telomere (Tel) 6R and Tel6L, which we propose stems from the territorial organization of yeast chromosomes

Influence of hydrological conditions on the Escherichia coli population structure in the water of a creek on a rural watershed.

International audienceBACKGROUND: Escherichia coli is a commensal bacterium of the gastro-intestinal tract of human and vertebrate animals, although the aquatic environment could be a secondary habitat. The aim of this study was to investigate the effect of hydrological conditions on the structure of the E. coli population in the water of a creek on a small rural watershed in France composed of pasture and with human occupation. RESULTS: It became apparent, after studying the distribution in the four main E. coli phylo-groups (A, B1, B2, D), the presence of the hly (hemolysin) gene and the antibiotic resistance pattern, that the E. coli population structure was modified not only by the hydrological conditions (dry versus wet periods, rainfall events), but also by how the watershed was used (presence or absence of cattle). Isolates of the B1 phylo-group devoid of hly and sensitive to antibiotics were particularly abundant during the dry period. During the wet period and the rainfall events, contamination from human sources was predominantly characterized by strains of the A phylo-group, whereas contamination by cattle mainly involved B1 phylo-group strains resistant to antibiotics and exhibiting hly. As E. coli B1 was the main phylo-group isolated in water, the diversity of 112 E. coli B1 isolates was further investigated by studying uidA alleles (beta-D-glucuronidase), the presence of hly, the O-type, and antibiotic resistance. Among the forty epidemiolgical types (ETs) identified, five E. coli B1 ETs were more abundant in slightly contaminated water. CONCLUSIONS: The structure of an E. coli population in water is not stable, but depends on the hydrological conditions and on current use of the land on the watershed. In our study it was the ratio of A to B1 phylo-groups that changed. However, a set of B1 phylo-group isolates seems to be persistent in water, strengthening the hypothesis that they may correspond to specifically adapted strains

Strontium ranelate and alendronate have differing effects on distal tibia bone microstructure in women with osteoporosis

The structural basis of the antifracture efficacy of strontium ranelate and alendronate is incompletely understood. We compared the effects of strontium ranelate and alendronate on distal tibia microstructure over 2years using HR-pQCT. In this pre-planned, interim, intention-to-treat analysis at 12months, 88 osteoporotic postmenopausal women (mean age 63.7±7.4) were randomized to strontium ranelate 2g/day or alendronate 70mg/week in a double-placebo design. Primary endpoints were changes in microstructure. Secondary endpoints included lumbar and hip areal bone mineral density (aBMD), and bone turnover markers. This trial is registered with http://www.controlled-trials.com, number ISRCTN82719233. Baseline characteristics of the two groups were similar. Treatment with strontium ranelate was associated with increases in mean cortical thickness (CTh, 5.3%), cortical area (4.9%) and trabecular density (2.1%) (all P<0.001, except cortical area P=0.013). No significant changes were observed with alendronate. Between-group differences in favor of strontium ranelate were observed for CTh, cortical area, BV/TV and trabecular density (P=0.045, 0.041, 0.048 and 0.035, respectively). aBMD increased to a similar extent with strontium ranelate and alendronate at the spine (5.7% versus 5.1%, respectively) and total hip (3.3% versus 2.2%, respectively). No significant changes were observed in remodeling markers with strontium ranelate, while suppression was observed with alendronate. Within the methodological constraints of HR-pQCT through its possible sensitivity to X-ray attenuation of different minerals, strontium ranelate had greater effects than alendronate on distal tibia cortical thickness and trabecular volumetric densit

Short-Term cost impact of compliance with clinical practice guidelines for initial sarcoma treatment

Background: The impact of compliance to clinical practice guidelines (CPG) on outcomes and/or costs of care has not been completely clarified.Objective: To estimate relationships between medical expenditures and compliance to CPG for initial sarcoma treatment.Research design: Selected cohorts of patients diagnosed with sarcoma in 2005 and 2006, and treated at the University hospital and/or the cancer centre of the Rhône-Alpes region, France (n=90). Main outcome measurements were: patient characteristics, compliance with CPG, health outcomes, and costs. Data were mainly extracted from patient records. The logarithm of treatment costs was modelled using linear and Tobit regressions.Results: Rates of compliance with CPG were 86%, 66%, 88%, 89%, and 95% for initial diagnosis, primary surgical excision, wide surgical excision, chemotherapy, and radiotherapy, respectively. Total average costs reached €24,439, with €1,784, €11,225, €10,360, and €1,016 for diagnosis, surgery (primary and wide surgical excisions), chemotherapy, and radiotherapy, respectively. Compliance of diagnosis with CPG decreased the cost of diagnosis, whereas compliance of primary surgical excision increased the cost of chemotherapy. Compliance of chemotherapy with CPG decreased the cost of radiotherapy.Conclusion: Since chemotherapy is one of the major cost drivers, these results support that compliance with guidelines increases medical care expenditures in short term.Oncology; Sarcoma; Cost; Clinical guidelines; Efficacy; Medical Practices; Government Policy; Regulation; Public Health

Theory of molecular excitation and relaxation near a plasmonic device

The new optical concepts currently developed in the research field of plasmonics can have significant practical applications for integrated optical device miniaturization as well as for molecular sensing applications. Particularly, these new devices can offer interesting opportunities for optical addressing of quantum systems. In this article, we develop a realistic model able to explore the various functionalities of a plasmon device connected to a single fluorescing molecule. We show that this theoretical method provides a useful framework to understand how quantum and plasmonic entities interact in a small area. Thus, the fluorescence signal evolution from excitation control to relaxation control depending on the incident light power is clearly observed. (C) 2007 American Institute of Physics