Showing papers by "University of Bordeaux published in 2004"

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Analytic Number Theory

Abstract: Introduction Arithmetic functions Elementary theory of prime numbers Characters Summation formulas Classical analytic theory of $L$-functions Elementary sieve methods Bilinear forms and the large sieve Exponential sums The Dirichlet polynomials Zero-density estimates Sums over finite fields Character sums Sums over primes Holomorphic modular forms Spectral theory of automorphic forms Sums of Kloosterman sums Primes in arithmetic progressions The least prime in an arithmetic progression The Goldbach problem The circle method Equidistribution Imaginary quadratic fields Effective bounds for the class number The critical zeros of the Riemann zeta function The spacing of zeros of the Riemann zeta-function Central values of $L$-functions Bibliography Index.

Magnetic nanoparticle design for medical diagnosis and therapy

Abstract: Magnetic nanoparticles have attracted attention because of their current and potential usefulness as contrast agents for magnetic resonance imaging (MRI) or colloidal mediators for cancer magnetic hyperthermia. This review examines these in vivo applications through an understanding of the involved problems and the current and future possibilities for resolving them. A special emphasis is made on magnetic nanoparticle requirements from a physical viewpoint (e.g. relaxivity for MRI and specific absorption rate for hyperthermia), the factors affecting their biodistribution (e.g. size, surface hydrophobic/hydrophilic balance, etc.) and the solutions envisaged for enhancing their half-life in the blood compartment and targeting tumour cells.

IntAct: an open source molecular interaction database

Abstract: IntAct provides an open source database and toolkit for the storage, presentation and analysis of protein interactions. The web interface provides both textual and graphical representations of protein interactions, and allows exploring interaction networks in the context of the GO annotations of the interacting proteins. A web service allows direct computational access to retrieve interaction networks in XML format. IntAct currently contains approximately 2200 binary and complex interactions imported from the literature and curated in collaboration with the Swiss-Prot team, making intensive use of controlled vocabularies to ensure data consistency. All IntAct software, data and controlled vocabularies are available at http://www.ebi.ac.uk/intact.

Technique and Results of Linear Ablation at the Mitral Isthmus

Abstract: Background— This prospective clinical study evaluates the feasibility and efficacy of combined linear mitral isthmus ablation and pulmonary vein (PV) isolation in patients with paroxysmal atrial fibrillation (AF). Methods and Results— One hundred consecutive patients (13 women; age 55±10 years) with drug-refractory, symptomatic paroxysmal AF underwent PV isolation and linear ablation of the cavotricuspid isthmus and the mitral isthmus (lateral mitral annulus to the left inferior PV). They were compared with 100 consecutive patients (14 women; age, 52±10 years) undergoing PV isolation and cavotricuspid ablation without mitral isthmus ablation. Bidirectional mitral isthmus block was confirmed by demonstrating (1) a parallel corridor of double potentials during coronary sinus (CS) pacing, (2) an activation detour by pacing either side of the line, and (3) differential pacing techniques. Isolation of all PVs and cavotricuspid isthmus ablation were performed successfully in all. Mitral isthmus block was achiev...

Sites of Neocortical Reorganization Critical for Remote Spatial Memory

Abstract: The hippocampus is crucial for spatial memory formation, yet it does not store long-lasting memories By combining functional brain imaging and region-specific neuronal inactivation in mice, we identified prefrontal and anterior cingulate cortex as critical for storage and retrieval of remote spatial memories Imaging of activity-dependent genes also revealed an involvement of parietal and retrosplenial cortices during consolidation of remote memory Long-term memory storage within some of these neocortical regions was accompanied by structural changes including synaptogenesis and laminar reorganization, concomitant with a functional disengagement of the hippocampus and posterior cingulate cortices Thus, consolidation of spatial memory requires a time-dependent hippocampal-cortical dialogue, ultimately enabling widespread cortical networks to mediate effortful recall and use of cortically stored remote memories independently

Molecular‐Scale Logic Gates

Abstract: Currently available approaches to molecular-scale logic gates are summarized and compared. These include: chemically-controlled fluorescent and transmittance-based switches concerned with small molecules, DNA oligonucleotides with fluorescence readout, oligonucleotide reactions with DNA-based catalysts, chemically-gated photochromics, reversibly denaturable proteins, molecular machines with optical and electronic signals, two-photon fluorophores and multichromophoric transient optical switches. The photochemical principles of electron and energy transfer are involved in several of these approaches. More complex molecular logic systems with reconfigurability and superposability provide contrasts with current semiconductor electronics. Integration of simple logic functions to produce more complex ones is also discussed in terms of recent developments.

Differential activity-dependent regulation of the lateral mobilities of AMPA and NMDA receptors.

Abstract: The basis for differences in activity-dependent trafficking of AMPA receptors (AMPARs) and NMDA receptors (NMDARs) remains unclear. Using single-molecule tracking, we found different lateral mobilities for AMPARs and NMDARs: changes in neuronal activity modified AMPAR but not NMDAR mobility, whereas protein kinase C activation modified both. Differences in mobility were mainly detected for extrasynaptic AMPARs, suggesting that receptor diffusion between synaptic and extrasynaptic domains is involved in plasticity processes.

Vigorous exchange between the Indian and Atlantic oceans at the end of the past five glacial periods

Abstract: The magnitude of heat and salt transfer between the Indian and Atlantic oceans through 'Agulhas leakage' is considered important for balancing the global thermohaline circulation. Increases or reductions of this leakage lead to strengthening or weakening of the Atlantic meridional overturning and associated variation of North Atlantic Deep Water formation. Here we show that modern Agulhas waters, which migrate into the south Atlantic Ocean in the form of an Agulhas ring, contain a characteristic assemblage of planktic foraminifera. We use this assemblage as a modern analogue to investigate the Agulhas leakage history over the past 550,000 years from a sediment record in the Cape basin. Our reconstruction indicates that Indian-Atlantic water exchange was highly variable: enhanced during present and past interglacials and largely reduced during glacial intervals. Coherent variability of Agulhas leakage with northern summer insolation suggests a teleconnection to the monsoon system. The onset of increased Agulhas leakage during late glacial conditions took place when glacial ice volume was maximal, suggesting a crucial role for Agulhas leakage in glacial terminations, timing of interhemispheric climate change and the resulting resumption of the Atlantic meridional overturning circulation.

Boltzmann Samplers for the Random Generation of Combinatorial Structures

Abstract: This article proposes a surprisingly simple framework for the random generation of combinatorial configurations based on what we call Boltzmann models. The idea is to perform random generation of possibly complex structured objects by placing an appropriate measure spread over the whole of a combinatorial class – an object receives a probability essentially proportional to an exponential of its size. As demonstrated here, the resulting algorithms based on real-arithmetic operations often operate in linear time. They can be implemented easily, be analysed mathematically with great precision, and, when suitably tuned, tend to be very efficient in practice.

Tulip — A Huge Graph Visualization Framework

Abstract: The research by the information visualization community (“Info Viz”) shows clearly that using a visual representation of data-sets enables faster analysis by the end users. Several scientific reasons explain these results. First of all, the visual perception system is the most powerful of all the human perception systems. In the human brain, 70% of the receptors and 40% of the cortex are used for the vision process [27,34]. Furthermore, human beings are better at “recognition” tasks than at “memorization” tasks [10]. This implies that textual representations are less efficient than visual metaphors when one wants to analyze huge data-sets. This comes from the fact that reading is both a memorization task and a recognition task.

Photothermal Heterodyne Imaging of Individual Nonfluorescent Nanoclusters and Nanocrystals

Abstract: We introduce a new, highly sensitive, and simple heterodyne optical method for imaging individual nonfluorescent nanoclusters and nanocrystals. A 2 order of magnitude improvement of the signal is achieved compared to previous methods. This allows for the unprecedented detection of individual small absorptive objects such as metallic clusters (of 67 atoms) or nonluminescent semiconductor nanocrystals. The measured signals are in agreement with a calculation based on the scattering field theory from a photothermal-induced modulated index of refraction profile around the nanoparticle.

Mechanical and Barrier Properties of Biodegradable Films Made from Chitosan and Poly (Lactic Acid) Blends

Abstract: Biodegradable film blends of chitosan with poly(lactic acid) (PLA) were prepared by solution mixing and film casting. The main goal of these blends is to improve the water vapor barrier of chitosan by blending it with a hydrophobic biodegradable polymer from renewable resources. Mechanical properties of obtained films were assessed by tensile test. Thermal properties, water barrier properties, and water sensitivity were studied by differential scanning calorimeter analysis, water vapor permeability measurements, and surface-angle contact tests, respectively. The incorporation of PLA to chitosan improved the water barrier properties and decreased the water sensitivity of chitosan film. However, the tensile strength and elastic modulus of chitosan decreased with the addition of PLA. Mechanical and thermal properties revealed that chitosan and PLA blends are incompatible, consistent with the results of Fourier transform infrared (FTIR) analysis that showed the absence of specific interaction between chitosan and PLA.

Direct measurement of the single-metal-cluster optical absorption.

Abstract: The absorption of a single isolated metal cluster is directly measured using a novel far-field optical technique based on modulation of its position. Single gold nanoparticles with average diameters down to 5 nm, dispersed on a transparent substrate, are optically detected and their absolute absorption cross section determined.

Validation of Horne and Ostberg Morningness-Eveningness Questionnaire in a Middle-Aged Population of French Workers

Abstract: As suggested by the authors, the Horne and Ostberg morning/evening questionnaire (MEQ) has never been adapted to evaluate a nonstudent population. The purpose of this study was to validate this MEQ in a sample of middle-aged workers by modifying only the cutoffs. It was administered in 566 non-shift-workers aged 51.2 to 3.2 years who presented no sleep disorders. According to the Horne and Ostberg classification, the sample consisted of 62.1% morning type, 36.6% neither type, and 2.2% evening type. Multiple correspondence analysis, which determines the principal components, was performed on all MEQ items. Then an ascending hierarchical classification was applied to determine 3 clusters from these principal components. On the basis of these 3 clusters, new cutoffs were determined: evening types were considered as scoring under 53 and morning types above 64, thus giving 28.1% morning type, 51.7% neither type, and 20.2% evening type. As an external validation, eveningness was associated with later bedtime an...

Gas transfer velocities of CO2 in three European estuaries (Randers Fjord, Scheldt, and Thames)

Abstract: We measured the flux of CO 2 across the air‐water interface using the floating chamber method in three European estuaries with contrasting physical characteristics (Randers Fjord, Scheldt, and Thames). We computed the gas transfer velocity of CO2 (k) from the CO2 flux and concomitant measurements of the air‐water gradient of the partial pressure of CO2 (pCO2). There was a significant linear relationship between k and wind speed for each of the three estuaries. The differences of the y-intercept and the slope between the three sites are related to differences in the contribution of tidal currents to water turbulence at the interface and fetch limitation. The contribution to k from turbulence generated by tidal currents is negligible in microtidal estuaries such as Randers Fjord but is substantial, at low to moderate wind speeds, in macrotidal estuaries such as the Scheldt and the Thames. Our results clearly show that in estuaries a simple parameterization of k as a function of wind speed is site specific and strongly suggest that the y-intercept of the linear relationship is mostly influenced by the contribution of tidal currents, whereas the slope is influenced by fetch limitation. This implies that substantial errors in flux computations are incurred if generic relationships of the gas transfer velocity as a function of wind speed are employed in estuarine environments for the purpose of biogas air‐water flux budgets and ecosystem metabolic studies. Based on organic carbon flux budgets, the overall picture of the net ecosystem metabolism in the coastal ocean is that temperate open continental shelves (bordered by a continental margin) are net autotrophic (net exporters of carbon and thus potential sinks for atmospheric CO2) while near-shore

Pooled analysis of alcohol dehydrogenase genotypes and head and neck cancer: A HuGE review

Abstract: Possession of the fast metabolizing alleles for alcohol dehydrogenase (ADH), ADH1B*2 and ADH1C*1, and the null allele for aldehyde dehydrogenase (ALDH), ALDH2*2, results in increased acetylaldehyde levels and is hypothesized to increase the risk of head and neck cancer. To examine this association, the authors undertook a Human Genome Epidemiology review on these three genes and a pooled analysis of published studies on ADH1C. The majority of Asians had the fast ADH1B*2 and ADH1C*1 alleles, while the majority of Caucasians had the slow ADH1B*1/1 and ADH1C*1/2 genotypes. The ALDH2*2 null allele was frequently observed among Asians, though it was rarely observed in other populations. In a pooled analysis of data from seven case-control studies with a total of 1,325 cases and 1,760 controls, an increased risk of head and neck cancer was not observed for the ADH1C*1/2 genotype (odds ratio = 1.00, 95% confidence interval: 0.81, 1.23) or the ADH1C*1/1 genotype (odds ratio = 1.14, 95% confidence interval: 0.92, 1.41). Increased relative risks of head and neck cancer were reported for the ADH1B*1/1 and ALDH2*1/2 genotypes in several studies. Recommendations for future studies include larger sample sizes and incorporation of relevant ADH and ALDH genes simultaneously, as well as other genes. These considerations suggest the potential for the organization of a consortium of investigators conducting studies in this field.

Baseline mood and psychosocial characteristics of patients developing depressive symptoms during interleukin-2 and/or interferon-alpha cancer therapy.

Abstract: It has been suggested that patients with subclinical mood symptoms prior to initiating cytokine treatment (as revealed by elevated baseline scores on depression rating scales) are more likely to become clinically depressed during the course of cytokine therapy. The present study was designed to identify which specific preexisting symptoms predict development of depressive symptomatology during treatment with the cytokines, interleukin-2 (IL-2) and/or interferon-alpha (IFN-alpha), in patients with cancer. Thirty-two patients with renal cell carcinoma or malignant melanoma eligible to receive treatment with IL-2 and/or IFN-alpha were enrolled in the study. At baseline and after one month of cytokine therapy (endpoint), depressive symptoms were assessed using the clinician-administered Montgomery-Asberg depression rating scale (MADRS). Illness-related coping strategies, social support, somatic complaints, quality of sleep and demographic factors were also assessed as relevant baseline predictive factors. MADRS scores significantly increased during cytokine therapy. Patients with moderate to marked depressive symptomatology at study endpoint exhibited higher baseline scores in dimensions of the MADRS scale assessing emotional (especially reported sadness), cognitive (especially pessimistic thoughts) and neurovegetative (sleep disturbances) symptoms compared to patients who remained free of depressive symptoms during cytokine therapy. Interestingly, only emotional symptoms and sleep disturbance at baseline, along with low social support, predicted severity of depressive symptoms at the end of the first month of therapy. By documenting specific behavioral vulnerability factors for cytokine-induced depressive symptoms, these findings may help identify patients at risk for mood disturbances during cytokine treatment and help target specific patient populations and specific symptoms for preventative strategies.