Noise and diffusion of particles obeying asymmetric exclusion processes

The relation between noise and Fick's diffusion coefficient in barrier limited transport associated with hopping or tunneling mechanisms of particles obeying the asymmetric simple exclusion processes (ASEP) is physically assessed by Monte Carlo simulations. For a closed ring consisting of a large number of barriers the diffusion coefficient is related explicitly to the current noise thus revealing the existence of a generalized Nyquist-Einstein relation. Both diffusion and noise are confirmed to decrease as the square root of the number of barriers as a consequence of the correlation induced by ASEP. By contrast, for an open linear chain of barriers the diffusion coefficient is found to be no longer related to current noise. Here diffusion depends on particle concentration but is independent of the number of barriers

A macroscopic model for pedestrian flows in panic situations

International audienceIn this paper we present the macroscopic model for pedestrian flows proposed by Colombo and Rosini [10] and show its main properties. In particular, this model is able to properly describe the movements of crowds, even after panic has arisen. Furthermore, it is able to reproduce the so called Braess' paradox for pedestrians. From the mathematical point of view, it provides one of the few examples of non classical shocks motivated by real problems, for which a global existence result is available. Finally, its assumptions were experimentally confirmed by an empirical study of a crowd crush on the Jamarat Bridge in Mina, Saudi Arabia, near Mecca, see [17]

Glyphosate resistance by engineering the flavoenzyme glycine oxidase.

Glycine oxidase from Bacillus subtilis is a homotetrameric flavoprotein of great potential biotechnological use because it catalyzes the oxidative deamination of various amines and D-isomer of amino acids to yield the corresponding \u3b1-keto acids, ammonia/amine, and hydrogen peroxide. Glyphosate (N-phosphonomethylglycine), a broad spectrum herbicide, is an interesting synthetic amino acid: this compound inhibits 5-enolpyruvylshikimate-3-phosphate synthase in the shikimate pathway, which is essential for the biosynthesis of aromatic amino acids in plants and certain bacteria. In recent years, transgenic crops resistant to glyphosate were mainly generated by overproducing the plant enzyme or by introducing a 5-enolpyruvylshikimate-3-phosphate synthase insensitive to this herbicide. In this work, we propose that the enzymatic oxidation of glyphosate could be an effective alternative to this important biotechnological process. To reach this goal, we used a rational design approach (together with site saturation mutagenesis) to generate a glycine oxidase variant more active on glyphosate than on the physiological substrate glycine. The glycine oxidase containing three point mutations (G51S/A54R/H244A) reaches an up to a 210-fold increase in catalytic efficiency and a 15,000-fold increase in the specificity constant (the kcat/Km ratio between glyphosate and glycine) as compared with wild-type glycine oxidase. The inspection of its three-dimensional structure shows that the \u3b12-\u3b13 loop (comprising residues 50-60 and containing two of the mutated residues) assumes a novel conformation and that the newly introduced residue Arg54 could be the key residue in stabilizing glyphosate binding and destabilizing glycine positioning in the binding site, thus increasing efficiency on the herbicide

Practical use of blactchford score

Aim: To retrospectively evaluate the use of proton pump inhibitor infusions. Methods: A retrospective chart review was conducted of all patients who received an 80 mg bolus of esomeprazole follow by an infusion at 8 mg/hr. An analysis was performed to determine if a Blatchford Score of \u3e 5 was a predictor of upper gastrointestinal ulcers. Results: 300 patients received high dose esomeprazole over a 15 month period. 32% had an ulcer identified on endoscopy. Gastritis and esophagitis were the second most common diagnosis accounting for 16% of patients. A Blatchford Score of \u3e5 as a predictor of upper gastrointestinal ulcers had a sensitivity of 86.5% with a specificity of 32%. Conclusion: Utilizing the Blatchford Score to predict patients that have an upper gastrointestinal ulcer does not appear to be effective in clinical practice