Non BPS topological defect associated with two coupled real field

We investigate a stability equation involving two-component eigenfunctions which is associated with a potential model in terms of two coupled real scalar fields, which presents non BPS topological defect.Comment: Revtex, 6 pages, no figures. This work was presented in the XXII Brazilian National Meeting on Particles and Fields (October/2001), to appear at http://www.sbf.if.usp.b

Optimization of fermentation conditions for the production of curcumin by engineered Escherichia coli

Curcumin is a plant secondary metabolite with outstanding therapeutic effects. Therefore, there is a great interest in developing new strategies to produce this high-value compound in a cheaper and environmentally friendly way. Curcumin heterologous production in E. coli using artificial biosynthetic pathways was previously demonstrated using synthetic biology approaches. However, the culturing conditions to produce this compound were not optimized and so far only a two-step fermentation involving the exchange of the culture medium allowed to obtain high concentrations of curcumin, which limits its production at an industrial scale. In this study, the culturing conditions to produce curcumin were evaluated and optimized. In addition, it was concluded that E. coli BL21 allows to produce higher concentrations compared to E. coli K-12 strains. Different IPTG concentrations, time of protein expression induction and substrate type and concentration were also evaluated. The highest curcumin production obtained was 959.3 µM (95.93% of percent yield), which was 3.1-fold higher than the highest concentration previously reported. This concentration was obtained using a two-stage fermentation with LB and M9. Moreover, TB demonstrated to be a very interesting alternative medium to produce curcumin since it also led to high concentrations (817.7 µM). The use of this single fermentation medium represents an advantage at industrial scale and although the final production is lower than the one obtained with the LB-M9 combination, it leads to a significantly higher curcumin production in the first 24 h of fermentation. This study allowed obtaining the highest concentrations of curcumin reported so far in a heterologous organism and is of interest for all of those working with the heterologous production of curcuminoids, other complex polyphenolic compounds or plant secondary metabolites.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of the UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01- 0145-FEDER-006684) and under the scope of the Project MultiBiorefinery-Multi-purpose strategies for broadband agro-forest and fisheries by-products valorization: a step forward for a truly integrated biorefinery (POCI-01-0145-FEDER-016403). The authors also acknowledge financial support from BioTecNorte operation (NORTE-01-0145-FEDER-000004), funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte and the post-doctoral grant (UMINHO/BPD/37/2015) to J.L.R. funded by FCT.info:eu-repo/semantics/publishedVersio

A Representation of the Virasoro Algebra via Wigner-Heisenberg Algebraic Technique to Bosonic Systems

Using the Wigner-Heisenberg algebra for bosonic systems in connection with oscillators we find a new representation for the Virasoro algebra.Comment: Revised version. Revtex, 7 pages, no figures. This work was presented in the XXII Brazilian National Meeting on Particles and Fields (October/2001), to appear in Braz. J. of Phys., 33, 1 (2003

New strategies for the production of biosurfactants towards biomedical applications

Microbial adhesion to biomaterial surfaces and subsequent biofilm formation has been observed on nearly all medical devices with severe economic and medical consequences. The significant resistance of biofilms to conventional antibiotic therapies has encouraged the development of new biomaterials and coatings. Biosurfactants represent an interesting approach as they can be used to modify the surface properties conferring it an anti-adhesive and antimicrobial activity, leading to new and effective means of combating colonization by pathogenic microorganisms without the use of synthetic drugs and chemicals. These microbial compounds constitute a diverse group of surface-active molecules occurring in a variety of chemical structures. Biosurfactants from lactic acid bacteria have been used as a strategy to avoid microbial colonization of silicone rubber voice prostheses. Also, they were found to be active against several bacteria and filamentous fungi responsible for diseases and infections in the urinary, vaginal and gastrointestinal tracts, and in the skin. Nevertheless, it is important to stress that the insufficient data on their toxicity for humans, as well as their high costs of large-scale production, have been restraining their commercialization and use in most medical applications. Many biotechnological strategies have been pursued to reduce the biosurfactants production costs including the use of agro-industrial wastes as substrates, optimization of medium and culture conditions, and efficient recovery processes. However, the improvements obtained from these strategies are marginal and to successfully compete with synthetic surfactants, novel microorganisms must be designed. The use of hyper-producer strains allows increasing the production yields and consequently reducing costs. These strains can be screened from the natural environment, or engineered using synthetic biology approaches. Hence, data on the genes involved on the production of biosurfactants is critical for designing organisms with improved features. Once the genes have been indentified and isolated, they can be expressed in other microorganisms, or they can be modified or placed under regulation of strong promoters to increase their expression and so enhance production. This knowledge will also allow the production of novel biosurfactants with specific new properties for different industrial applications. Further advances in genetic engineering of the known biosurfactant molecules could yield potent biosurfactants with altered antimicrobial profiles and decreased toxicity against mammalian cells

Inhibition of bacterial adhesion on medical devices

Microbial infections resulting from bacterial adhesion to biomaterial surfaces have been observed on almost all medical devices. Biofilm infections pose a number of clinical challenges due to their resistance to immune defence mechanisms and antimicrobials, and, regardless of the sophistication of the implant, all medical devices are susceptible to microbial colonisation and infection. Research efforts are currently directed towards eliminating or reducing infection of medical devices. Strategies to prevent biofilm formation include physiochemical modification of the biomaterial surface to create anti-adhesive surfaces, incorporation of antimicrobial agents into medical device polymers, mechanical design alternatives, and release of antibiotics. Nevertheless, the success of these alternatives has been modest, mainly due to the various environments into which devices are placed and the diversity of ways in which organisms can colonise surfaces. Biosurfactants have been reported as a promising strategy as they effectively inhibit bacterial adhesion and retard biofilm formation, and are thus potentially useful as a new generation of anti-adhesive and antimicrobial coatings for medical device

On disturbances caused by pressure taps in highly elastic flows

The objective of this work is to characterise the onset of laterally asymmetric flow of viscoelastic solutions around a confined microfluidic cylinder, which was encountered in a recent study [Rodrigues et al., $\textit{J. Non-Newton. Fluid Mech.}$ $\textbf{289}$, 104406 (2020)]. To this end, two non-Newtonian fluids were employed in the same micro-geometry. Two microchannels were studied, both with a cylinder of diameter 75 $\mathrm{\mu}$m, aspect ratio (channel height over width) of 0.37 and blockage ratio (cylinder diameter over channel width) of 0.28, differing only on the width of the pressure taps, located 500 $\mathrm{\mu}$m up- and downstream from the respective cylinder face, on opposing walls. The working fluids consist of two poly(ethylene oxide) (PEO) solutions: a weakly shear-thinning elastic fluid and an elastic shear-thinning fluid. Micro-Particle Image Velocimetry ($\mathrm{\mu}$PIV) and streak imaging techniques were used to evaluate the flow over a Weissenberg number range: $100\leq Wi\leq500$, while maintaining a low Reynolds number, $Re<1$. The elastic shear-thinning solution showed laterally asymmetric flow past the cylinder with both pressure tap designs, while with the weakly shear-thinning solution asymmetric flow was only observed with the wider pressure tap intake. In both cases, the fluids preferentially chose the cylinder/wall gap opposing the upstream pressure tap, which was found to influence the flow greatly, seemingly associated with time-dependent flow and possibly the lateral flow asymmetry itself. This work brings to light the necessary compromise between optimal pressure tap design for quality pressure measurements and minimal flow interference, due to the increased susceptibility of elastic microfluidic flows to flow perturbations