Absorption and percolation in the production of J/psi in heavy ion collisions

We present a simple model with string absorption and percolation to describe the J/psi suppression in heavy ion collisions. The NA50 data are fairly well explained by the model.Comment: 6 pages, 3 postscript figures include

Superconducting charge qubits from a microscopic many-body perspective

The quantised Josephson junction equation that underpins the behaviour of charge qubits and other tunnel devices is usually derived through cannonical quantisation of the classical macroscopic Josephson relations. However, this approach may neglect effects due to the fact that the charge qubit consists of a superconducting island of finite size connected to a large superconductor. We show that the well known quantised Josephson equation can be derived directly and simply from a microscopic many-body Hamiltonian. By choosing the appropriate strong coupling limit we produce a highly simplified Hamiltonian that nevertheless allows us to go beyond the mean field limit and predict further finite-size terms in addition to the basic equation.Comment: Accepted for J Phys Condensed Matte

Produção e composição química de aveia não irrigada em quatro épocas de corte.

A aveia preta e os cultivadores UPF2, UPF3 e UPF7 de aveia amarela foram avaliados durante o período de inverno, sem irrigação em Jaboticabal-SP. As plantas foram colhidas aos 51, 64, 77 e 90 dias após a semeadura. A produção de MS variou de 931,6 a 2378,3 kg/ha para aveia preta, de 903,4 a 3135,2 kg/ha para a cv. UPF2 de 439,7 a 3920,9 kg/ha para a cv. UPF3 e de 1003,7 a 4351.1 kg/ha para a cv. UPF7. Dos 51 aos 90 dias após a semeadura os teores de PB na folha decresceram, de 18,0% para 10,2%, e os de FDN aumentaram de 41,6% para 47,9%.Resumo expandid

New microbial surface-active compounds: the ultimate alternative to chemical surfactants?

Surface active compounds (SACs) produced by microorganisms are attracting a pronounced interest due to their potential advantages over synthetic counterparts, and to the fact that they could replace some of the synthetics in many environmental and industrial applications. Bioemulsifier production by a Paenibacillus strain isolated from crude oil was studied. The bioemulsifier was produced using sucrose with and without adding hydrocarbons (paraffin or crude oil) under aerobic and anaerobic conditions at 40ºC. It formed stable emulsions with several hydrocarbons, exhibiting similar or better emulsifying activity when compared with chemical SACs, and its emulsifying ability was not affected by exposure to high salinities (up to 300 g/l), high temperatures (100-121ºC) or a wide range of pH values (2-13). In addition, it presented low toxicity and high biodegradability when compared with chemical surfactants, implying a greater environmental compatibility. A preliminary chemical characterization by Fourier Transform Infrared Spectroscopy (FT-IR), proton and carbon nuclear magnetic resonance (1H NMR and 13C CP-MAS NMR) and size exclusion chromatography indicated that the bioemulsifier is a low molecular weight oligosaccharide-lipid complex. To the best of our knowledge, bioemulsifier production by a Paenibacillus strain has not been previously reported. This is also the first description of a low molecular weight bioemulsifier. The features of this novel bioemulsifier make it an interesting biotechnological product for many environmental and industrial applications.Financial support from the projects BIOCLEAN-Desenvolvimento de produtos contendo surfactantes microbianos para limpeza e desinfeção de superfícies industriais e domésticas. QREN-n.º 2013/030215, and NCMICROBIOS -Desenvolvimento de bioprocessos usando microrganismos não convencionais para a produção de biosurfactantes - Convénio FCT-CNPq Nº 17/2013 – Ref.: Projecto nº 6818

Development of low-cost culture media for effective biosurfactant production

In this work, biosurfactant production by Pseudomonas aeruginosa and Bacillus subtillis strains was optimized using low-cost substrates. The highest biosurfactant production (3.2 g/L) by the P. aeruginosa strain was obtained using a culture medium containing corn steep liquor (CSL) (10% (v/v)) and molasses (10% (w/v)), whereas the best biosurfactant production by the B. subtillis isolate (1.3 g/L) was obtained using a culture medium consisting of 10% (v/v) of CSL. Subsequently, for the B. subtillis strain, the effect of different metals (iron, manganese and magnesium) on biosurfactant production was evaluated. When the culture medium CSL 10% was supplemented with the optimum concentration of those metals simultaneously, the biosurfactant production was increased up to 4.8 g/L. The biosurfactant produced by the P. aeruginosa strain was characterized as a mixture of eight different rhamnolipid congeners, being the most abundant the mono-rhamnolipid Rha-C10-C10, and the biosurfactant produced by the B. subtillis isolate consisted of a mixture of C13-, C14- and C15-surfactin. Both biosurfactants exhibited a good performance in oil recovery assays when compared with chemical surfactants, suggesting their potential use as an alternative to traditional chemical surfactants in enhanced oil recovery or bioremediation

Improved biosurfactant production by a Pseudomonas aeruginosa strain using agro-industrial wastes

Microbial surfactants are amphipathic molecules produced by a variety of microorganisms that exhibit pronounced surface and emulsifying activities. Biosurfactants can replace synthetic surfactants in environmental and industrial applications, such as bioremediation and microbial enhanced oil recovery. Furthermore, some biosurfactants have been reported as suitable alternatives to synthetic medicines and antimicrobial agents and may be used as effective therapeutic agents, due to their antibacterial, antifungal, antiviral and anti-adhesive activities. The main advantages of biosurfactants when compared with synthetic surfactants include their diversity, specificity, environmentally friendly nature, non-toxicity and high biodegradability, effectiveness at extreme temperatures or pH values, as well as their suitability for scale-up production. Many of the potential applications that have been considered for biosurfactants depend on whether they can be produced economically at large-scale. Several efforts have been conducted to reduce production costs, including the use of agro-industrial wastes as substrates, optimization of medium and culture conditions and efficient recovery processes. In this work, biosurfactant production by a Pseudomonas aeruginosa strain isolated from a crude oil sample was optimized using agro-industrial wastes. A culture medium containing corn step liquor (10% v/v) and molasses (10% w/v) led to the production of 5 g biosurfactant/l, which is about ten times the amount of biosurfactant produced when using LB medium. The crude biosurfactant reduced the surface tension of water to 31 mN/m and exhibited high emulsifying activity (60%), with a critical micelle concentration of 200 mg/l. Moreover, it showed antimicrobial activity against a broad range of Gram-positive and Gram-negative bacteria, as well as a high efficiency in removing oil from contaminated sand, when compared with chemical surfactants. The results obtained suggest the possibility of using this biosurfactant as an alternative to traditional chemical surfactants

Solid Freeform Fabrication of Functional Silicon Nitride Ceramics by Laminated Object Manufacturing 1

The processing of silicon nitride (Si3N4) structural ceramics by Laminated Object Manufacturing (LOM) using ceramic tape preforms was investigated. The key processing stages involved green shape formation (which used the LOM process), followed by the burnout of all organics, and final densification by pressureless sintering. Two material systems were considered. These were a) monolithic Si3N4 and b) a preceramic polymer infiltrated Si3N4. The raw materials for the process were tape preforms of Si3N4, which were fabricated by standard tape casting techniques. Mechanical property data obtained for the LOM processed Si3N4 showed high strength and fracture toughness values. The room temperature and high temperature (1260 o C) flexural strengths were in the range of 700-900 MPa and 360-400 MPa, respectively. The fracture toughness averaged from 5.5-7.5 MPa.m1/2. These strength and fracture toughness values are comparable to those reported for conventionally prepared Si3N4 ceramics. Thus, this research demonstrated that the LOM technique is a viable method for preparing functional Si3N4 ceramics with good physical and mechanical properties.Mechanical Engineerin

q-Deformed Kink Solutions

The q-deformed kink of the $\lambda\phi^4-$model is obtained via the normalisable ground state eigenfunction of a fluctuation operator associated with the q-deformed hyperbolic functions. From such a bosonic zero-mode the q-deformed potential in 1+1 dimensions is found, and we show that the q-deformed kink solution is a kink displaced away from the origin.Comment: REvtex, 11 pages, 2 figures. Preprint CBPF-NF-005/03, site at http://www.cbpf.br. Revised version to appear in International Journal of Modern Physics