A simple method for the quantitative analysis of tyrosol by hplc in liquid Czapek Cultures from endophytic fungi

Tyrosol is a possible quorum sensing molecule in endophytic fungi. High-performance liquid chromatography (HPLC) coupled with diode array detector (DAD) was used for the analysis of tyrosol in liquid Czapek fungal cultures. The optimized conditions were gradient mobile phase, in linear mode, consisting initially of acetonitrile/water (1:9 v/v) and increasing up to acetonitrile (100%) in 30 minutes at a flow rate of 1 mL min-1. The column used was a ZORBAX® ODS (250 × 4.6 mm, 5 μm) at 25 ºC. Liquid-liquid extraction of 0.5 mL medium (pH 7.0) with ethyl acetate and injection of 20 μL after solvent evaporation under air flow gave good results. Some validation parameters obtained were: linearity 0.0125-5.0 μg mL-1 medium (r = 0.9967), quantification limit of 0.0125 μg mL-1 medium, %CV (precision) and %E (accuracy) bellow 15% and recovery around 80%. Therefore, the developed method presented satisfactory validation parameters and it was efficient for the analysis of tyrosol in Czapek medium.O tirosol é provavelmente uma molécula sinalizadora em fungos endofíticos. A análise do tirosol em cultura líquida Czapek de fungo endofítico foi realizada através de cromatografia líquida de alta eficiência acoplada a detector por arranjo de diodos. As análises foram obtidas em sistema de fase móvel utilizando gradiente, modo linear, iniciando em acetonitrila/água (1:9 v/v) e terminando em acetonitrila 100% em 30 minutos com vazão de 1 mL min-1. Coluna analítica ZORBAX® ODS (250 × 4,6 mm, 5 μm) à 25 ºC foi utilizada. Extração líquido-líquido de 0,5 mL do meio (pH 7,0) com acetato de etila e injeção de 20 μL após concentração do solvente sob ar comprimido originou bons resultados. Os parâmetros validados foram: linearidade 0,0125-5,0 μg mL-1 (r = 0,9967), limite de quantificação 0,0125 μg mL-1 obtidos pela média das análises; %CV (precisão) e %E (exatidão) com valores abaixo de 15% e recuperação de cerca de 80%. Além disso, o método desenvolvido apresentou valores de validação satisfatórios demonstrando eficiência na análise do tirosol em meio líquido Czapek.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FAPES

Fast Two-Robot Disk Evacuation with Wireless Communication

In the fast evacuation problem, we study the path planning problem for two robots who want to minimize the worst-case evacuation time on the unit disk. The robots are initially placed at the center of the disk. In order to evacuate, they need to reach an unknown point, the exit, on the boundary of the disk. Once one of the robots finds the exit, it will instantaneously notify the other agent, who will make a beeline to it. The problem has been studied for robots with the same speed~\cite{s1}. We study a more general case where one robot has speed $1$ and the other has speed $s \geq 1$. We provide optimal evacuation strategies in the case that $s \geq c_{2.75} \approx 2.75$ by showing matching upper and lower bounds on the worst-case evacuation time. For $1\leq s < c_{2.75}$, we show (non-matching) upper and lower bounds on the evacuation time with a ratio less than $1.22$. Moreover, we demonstrate that a generalization of the two-robot search strategy from~\cite{s1} is outperformed by our proposed strategies for any $s \geq c_{1.71} \approx 1.71$.Comment: 18 pages, 10 figure

Quantum properties of dichroic silicon vacancies in silicon carbide

The controlled generation and manipulation of atom-like defects in solids has a wide range of applications in quantum technology. Although various defect centres have displayed promise as either quantum sensors, single photon emitters or light-matter interfaces, the search for an ideal defect with multi-functional ability remains open. In this spirit, we investigate here the optical and spin properties of the V1 defect centre, one of the silicon vacancy defects in the 4H polytype of silicon carbide (SiC). The V1 centre in 4H-SiC features two well-distinguishable sharp optical transitions and a unique S=3/2 electronic spin, which holds promise to implement a robust spin-photon interface. Here, we investigate the V1 defect at low temperatures using optical excitation and magnetic resonance techniques. The measurements, which are performed on ensemble, as well as on single centres, prove that this centre combines coherent optical emission, with up to 40% of the radiation emitted into the zero-phonon line (ZPL), a strong optical spin signal and long spin coherence time. These results single out the V1 defect in SiC as a promising system for spin-based quantum technologies

Extração de DNA genômico de Brachiaria e Panicum maximum.

bitstream/CNPGC/10572/1/COT79.pd

Pushing Taxonomy to Extiction?

Can we describe all species on Earth before they disappear? We argue that this is possible only by endowing taxonomy with professional manpower and appropriate material resources as required by big science. Contrary to Costello et al.’s (CMS) (1) statements, taxonomy is not an easy discipline accessible to all through a smartphone. It requires exhaustive training and long familiarity with field, specimens and literature (2). CMS’s argument is framed in terms of species numbers, but different, non-overlapping species concepts apply to bacteria, brambles and birds (3,4,5): “the species” as common unit of biodiversity does not exist (6). Even ignoring this conceptual and semantic issue, CMS’s estimates of undescribed biodiversity and extinction rates are based on insufficient evidence and poorly supported models. Biodiversity hotspots steadily emerge in geographic areas where diversity was long assumed to be largely described (7,8). The number of species, whatever species are, cannot be easily estimated because of the historical, rather than deterministic or teleological, nature of biological evolution (9,10). Extinction rates are highly context-sensitive (11), lineage- and region-dependant, thus generally difficult to ascertain (12) without thorough analyses of data such as IUCN’s estimates of threats and extinctions (13). However, evidence being mainly restricted to vertebrates, the extinction risks in most other groups remain terra incognita. Furthermore, recent surveys (14,15) do not support CMS’s optimistic predictions regarding extinction rates. CMS’s agenda emphasizes technology, voluntary work and recognition of subjective “morphospecies” (16). However, improvement of data storage and retrieval cannot substitute for the production of sound data. Serious taxonomists cannot describe two new species per week, as suggested by CMS’s calculations. Describing new species, even with the help of molecular data and especially in best-investigated groups, is increasingly demanding, following the “law of diminishing returns” (17). More than anything else, taxonomy requires professional manpower, unrestricted fieldwork and permanent collections

Cytotoxic T cells and mycobacteria

How the immune system kills Mycobacterium tuberculosis is still a puzzle. the classical picture of killing due to phagocytosis by activated macrophages may be only partly correct. Based on recent evidence, we express here the view that cytotoxic T lymphocytes also make an important contribution and suggest that DNA vaccines might be a good way to enhance this. (C) 2001 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.Univ São Paulo, Sch Med Ribeirao Preto, Dept Biochem & Immunol, BR-14049900 Ribeirao Preto, SP, BrazilUniv São Paulo, Sch Pharmaceut Sci Ribeirao Preto, Dept Clin Anal Bromatol & Toxicol, BR-14049 Ribeirao Preto, SP, BrazilUniversidade Federal de São Paulo, Dept Microbiol & Immunol, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Microbiol & Immunol, São Paulo, BrazilWeb of Scienc