On Useful Conformal Tranformations In General Relativity

Local conformal transformations are known as a useful tool in various applications of the gravitational theory, especially in cosmology. We describe some new aspects of these transformations, in particular using them for derivation of Einstein equations for the cosmological and Schwarzschild metrics. Furthermore, the conformal transformation is applied for the dimensional reduction of the Gauss-Bonnet topological invariant in $d=4$ to the spaces of lower dimensions.Comment: 17 pages, LaTeX. The paper is intended mainly for pedagogical purposes and represents a collection of exercises concerning local conformal transformations and dimensional reduction. To be published in "Gravitation and Cosmology

Effect of disorder on the vortex-lattice melting transition

We use a three dimensional stacked triangular network of Josephson junctions as a model for the study of vortex structure in the mixed state of high Tc superconductors. We show that the addition of disorder destroys the first order melting transition occurring for clean samples. The melting transition splits in two different (continuous) transitions, ocurring at temperatures Ti and Tp (>Ti). At Ti the perpendicular-to-field superconductivity is lost, and at Tp the parallel-to-field superconductivity is lost. These results agree well with recent experiments in YBaCuO.Comment: 4 pages + 2 figure

Equality of opportunity and educational achievement in Portugal

Portugal has one of the highest levels of income inequality in Europe, and low wages and unemployment are concentrated among low skill individuals. Education is an important determinant of inequality. However, there are large differences in the educational attainment of different individuals in the population, and the sources of these differences emerge early in the life-cycle when families play a central role in individual development. We estimate that most of the variance of school achievement at age 15 is explained by family characteristics. Observed school inputs explain very little of adolescent performance. Children from highly educated parents benefit of rich cultural environments in the home and become highly educated adults. Education policy needs to be innovative: (1) it needs to explicitly recognize the fundamental long run role of families on child development; (2) it needs to acknowledge the failure of traditional input based policies

Comparative susceptibility of southern and western corn rootworm adults and larvae to vATPase-A and Snf7 dsRNAs.

Corn rootworms (CRW) are the most important corn pests in the U.S. Corn Belt. Damage is caused by larval feeding on the plant roots. RNAi has been studied in CRW and has proven to be effective for the management of this insect with effects on both larval and adult stages. The objective of this study was to determine comparative susceptibility of adult and larva of Southern Corn Rootworm (SCR) and Western Corn Rootworm (WCR) to two different lethal RNAi target genes (vacuolar (v)-ATPase-A and Snf7). Adults and larvae were exposed to dsRNAs overlaid on artificial diet five times every other day. WCR larval susceptibility to vATPase-A was approximately 4-fold more tolerant than SCR, but were similar for Snf7 (2.6 ng/cm2 for both species). For adults, LC50s were generally higher for vATPase-A dsRNA relative to larvae with a 20-fold higher LC50 for WCR (SCR=33.3 ng/cm2; WCR=657.3 ng/cm2) relative to Snf7 dsRNAs (SCR=13.2 ng/cm2; WCR=60.2 ng/cm2). Gene silencing was also evaluated in adults and larvae exposed to the LC50 dsRNAs, and gene knockdown ranged from 48% up to 83% in adults fed for eight days in dsRNA, and from 55% to 89% in larvae fed for 24, 48 and 72 h, compared to control treatments. This is the first study to report LC50 values for dsRNA in WCR and SCR adults. The results indicate that both larvae and adults of both species were affected by vATPase-A and Snf7 dsRNAs suggesting that RNAi for the management of CRW should be considered for both stages

Helicity Modulus and Fluctuating Type II Superconductors: Elastic Approximation and Numerical Simulations

We develop the helicity modulus as a criterion for superconducting order in the mixed phase of a fluctuating type II superconductor. We show that there is a duality relation between this helicity modulus and the superfluid density of a system of analog 2D bosons. We show that the vortex line lattice exhibits a perfect Meissner effect with respect to a shearing perturbation of the applied magnetic field, and this becomes our creterion for "longitudinal superconductivity" parallel to the applied field. We present arguments based on the 2D boson analogy, as well as the results of numerical simulations, that suggest that longitudinal superconductivity can persist into the vortex line liquid state for systems of finite thickness, comparable to those commonly found in experiments.Comment: 63 pages, 22 postscript figure

Footprinting microbial metabolites in nature and medicine

The study of metabolic alterations in response to genetic and environmental perturbations has been a central topic in microbial metabolomics (Fiehn, 2002; Kol et al., 2010; Villas-Boas et al., 2008). Some of these alterations can be readily detected by changes in their surroundings, normally associated with metabolites that are released by cells as by-products of the metabolism or as extracellular signalling molecules to mediate cross-talk within microbial communities. The analysis of these metabolites, also known as metabolic footprinting, has been widely applied with different purposes: discriminating between metabolic phenotypes in order to classify and identify mutant strains (Villas-Boas et al., 2008); monitoring bioprocesses with the aim to detect specific metabolites that indicate alterations in the culture performance (Carneiro et al., 2011; Sue et al., 2011); and identifying quorum-sensing metabolites that indicate potential targets to annihilate pathogens (Birkenstock et al., 2012). These metabolic readouts have been also useful to give insights into intracellular metabolic activities and provide a straightforward way to analyse simultaneously multiple metabolic activities, since no extraction procedures are required to analyse the endometabolome (i.e., intracellular metabolites). Thus, through metabolic footprint analysis we can assess central metabolic activities that characterize the reproduction and survival of organisms. We have developed a methodology to evaluate the metabolic state of microbial cultures by analysing the footprints of two microbial systems: the bacterium Escherichia coli and the human pathogen Helicobacter pylori. Strategies for sampling and sample preparation were developed, as well as the analytical procedures based on gas chromatography with mass spectrometry (GC-MS). A wide variety of metabolites was detected, including fatty, amino and organic acids, which allowed us to address changes in most central metabolic pathways, such as the tricarboxylic acid cycle (TCA cycle), the biosynthesis of amino and fatty acids, as well as other energy generating metabolic reactions. The analysis of extracellular metabolites of E. coli cultures at different growth conditions were first performed to discriminate the physiological state of cultures and to evaluate the metabolic alterations produced at different growth conditions. According to our results in these experiments, metabolic footprints are good indicators of alterations in the intracellular metabolism. Next, the metabolic footprints of H. pylori cultures were investigated to get insights on the catabolism of this human pathogen. Overall, fifteen amino acids were detected in extracellular medium; six of them were confirmed as essentials for H. pylori growth, four amino acids were identified as non-essentials and can be used as carbon source, whilst five amino acids were identified as non-essentials and non-carbon source. In addition, some organic acids were also identified as carbon sources for H. pylori. This metabolic footprint analysis of H. pylori cultures allowed us to uncover key metabolic activities, mainly related with amino acids catabolism and to get insight on the metabolic behaviour of this organism. The characterization of catabolic pathways, as well as of possible metabolic constraints, is of major importance to understand the dynamic basis of the interactions host–microbe in the human gut, and in particular to discover potential ‘diagnostic’ biomarkers. It is well-known that pathogen's metabolism can influence the host health and may affect drug metabolism, toxicity and the efficacy of therapies (Holmes et al., 2011). However, little is known about their metabolic structure and behaviour. Our methodology allows uncovering part of the metabolic structure of H. pylori metabolism and undisclosed catabolic activities. Acknowledgments This work was partially supported by the MIT-Portugal Program in Bioengineering (MIT-Pt/BS-BB/0082/2008), the research project HeliSysBio-Molecular Systems Biology Helicobacter pylori (FCT PTDC/EBB-EBI/104235/2008) and a Post-doc grant from Portuguese FCT (Fundação para a Ciência e Tecnologia) (ref. SFRH/BPD/73951/2010). 1. Fiehn O. 2002. Metabolomics - the link between genotypes and phenotypes. Plant Molecular Biology 48: 155-71. 2. Kol S, Merlo ME, Scheltema RA, de VM, Vonk RJ, Kikkert NA, Dijkhuizen L, Breitling R, Takano E. 2010. Metabolomic characterization of the salt stress response in Streptomyces coelicolor. Applied and Environmental Microbiology 76: 2574-81. 3. Villas-Boas SG, Moon CD, Noel S, Hussein H, Kelly WJ, Cao M, Lane GA, Cookson AL, Attwood GT. 2008. Phenotypic characterization of transposon-inserted mutants of Clostridium proteoclasticum B316(T) using extracellular metabolomics. Journal of Biotechnology 134: 55-63. 4. Sue T, Obolonkin V, Griffiths H, Villas-Boas SG. 2011. An exometabolomics approach to monitoring microbial contamination in microalgal fermentation processes by using metabolic footprint analysis. Appl Environ Microbiol 77: 7605-10. 5. Carneiro S, Villas-Boas SG, Ferreira EC, Rocha I. 2011. Metabolic footprint analysis of recombinant Escherichia coli strains during fed-batch fermentations. Molecular Biosystems 7: 899-910. 6. Birkenstock T, Liebeke M, Winstel V, Krismer B, Gekeler C, Niemiec MJ, Bisswanger H, Lalk M, Peschel A. 2012. Exometabolome analysis identifies pyruvate dehydrogenase as a target for the antibiotic triphenylbismuthdichloride in multiresistant bacterial pathogens. J Biol Chem 287: 2887-95. 7. Holmes E, Li JV, Athanasiou T, Ashrafian H, Nicholson JK. 2011. Understanding the role of gut microbiome-host metabolic signal disruption in health and disease. Trends Microbiol 19: 349-59

Host status of different crops for Meloidogyne ethiopica control.

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Distinction between plant samples according to allele dosage by semiquantitative polymerase chain reaction.

The lack of informativity of samples from heterozygotic individuals is one of the hindrances in the mapping of quantitative trait loci of outbred populations, since it is not normally possible to identify the origin of each allele. One way to include these individuals in analyses would be to genotype their endosperm, considering that heterozygote (Aa) has AAa endosperm, when the female genitor donates the A or a allele, respectivelly. We used semiquantitative polymerase chain reaction to determine allele dosages in DNA mixtures, by simulating the observed conditions for endospermic tissue. Semiquantitative polymerase chain reaction on agarose gels, along with regression analysis, allowed differentiation of the samples according to the amount of DNA. This type of information will help decrease the number of non-informative individuals in quantitative trait locus mapping of outbred populations, thereby increasing mapping accuracy