854 resultados para Use and habitat selection
Resumo:
Accessibility is an essential concept widely used to evaluate the impact of transport and land-use strategies in urban planning and policy making. Accessibility is typically evaluated by using separately a transport model or a land-use model. This paper embeds two accessibility indicators (i.e., potential and adaptive accessibility) in a land use and transport interaction (LUTI) model in order to assess transport policies implementation. The first aim is to define the adaptive accessibility, considering the competition factor at territorial level (e.g. workplaces and workers). The second aim is to identify the optimal implementation scenario of policy measures using potential and adaptive accessibility indicators. The analysis of the results in terms of social welfare and accessibility changes closes the paper. Two transport policy measures are applied in Madrid region: a cordon toll and increase bus frequency. They have been simulated through the MARS model (Metropolitan Activity Relocation Simulator, i.e. LUTI model). An optimisation procedure is performed by MARS for maximizing the value of the objective function in order to find the optimal policy implementation (first best). Both policy measures are evaluated in terms of accessibility. Results show that the introduction of the accessibility indicators (potential and adaptive) influence the optimal value of the toll price and bus frequency level, generating different results in terms of social welfare. Mapping the difference between potential and adaptive accessibility indicator shows that the main changes occur in areas where there is a strong competition among different land-use opportunities.
Resumo:
With more than 10 fully sequenced, publicly available prokaryotic genomes, it is now becoming possible to gain useful insights into genome evolution. Before the genome era, many evolutionary processes were evaluated from limited data sets and evolutionary models were constructed on the basis of small amounts of evidence. In this paper, I show that genes on the Borrelia burgdorferi genome have two separate, distinct, and significantly different codon usages, depending on whether the gene is transcribed on the leading or lagging strand of replication. Asymmetrical replication is the major source of codon usage variation. Replicational selection is responsible for the higher number of genes on the leading strands, and transcriptional selection appears to be responsible for the enrichment of highly expressed genes on these strands. Replicational–transcriptional selection, therefore, has an influence on the codon usage of a gene. This is a new paradigm of codon selection in prokaryotes.
Novel human DNA alkyltransferases obtained by random substitution and genetic selection in bacteria.
Resumo:
DNA repair alkyltransferases protect organisms against the cytotoxic, mutagenic, and carcinogenic effects of alkylating agents by transferring alkyl adducts from DNA to an active cysteine on the protein, thereby restoring the native DNA structure. We used random sequence substitutions to gain structure-function information about the human O6-methylguanine-DNA methyltransferase (EC 2.1.1.63), as well as to create active mutants. Twelve codons surrounding but not including the active cysteine were replaced by a random nucleotide sequence, and the resulting random library was selected for the ability to provide alkyltransferase-deficient Escherichia coli with resistance to the methylating agent N-methyl-N'-nitro-N-nitrosoguanidine. Few amino acid changes were tolerated in this evolutionarily conserved region of the protein. One mutation, a valine to phenylalanine change at codon 139 (V139F), was found in 70% of the selected mutants; in fact, this mutant was selected much more frequently than the wild type. V139F provided alkyltransferase-deficient bacteria with greater protection than the wild-type protein against both the cytotoxic and mutagenic effects of N-methyl-N'-nitro-N-nitrosoguanidine, increasing the D37 over 4-fold and reducing the mutagenesis rate 2.7-5.5-fold. This mutant human alkyltransferase, or others similarly created and selected, could be used to protect bone marrow cells from the cytotoxic side effects of alkylation-based chemotherapeutic regimens.
Resumo:
To gain insight into the regulation of expression of peroxisome proliferator-activated receptor (PPAR) isoforms, we have determined the structural organization of the mouse PPAR gamma (mPPAR gamma) gene. This gene extends > 105 kb and gives rise to two mRNAs (mPPAR gamma 1 and mPPAR gamma 2) that differ at their 5' ends. The mPPAR gamma 2 cDNA encodes an additional 30 amino acids N-terminal to the first ATG codon of mPPAR gamma 1 and reveals a different 5' untranslated sequence. We show that mPPAR gamma 1 mRNA is encoded by eight exons, whereas the mPPAR gamma 2 mRNA is encoded by seven exons. Most of the 5' untranslated sequence of mPPAR gamma 1 mRNA is encoded by two exons, whereas the 5' untranslated sequence and the extra 30 N-terminal amino acids of mPPAR gamma 2 are encoded by one exon, which is located between the second and third exons coding for mPPAR gamma 1. The last six exons of mPPAR gamma gene code for identical sequences in mPPAR gamma 1 and mPPAR gamma 2 isoforms. The mPPAR gamma 1 and mPPAR gamma 2 isoforms are transcribed from different promoters. The mPPAR gamma gene has been mapped to chromosome 6 E3-F1 by in situ hybridization using a biotin-labeled probe. These results establish that at least one of the PPAR genes yields more than one protein product, similar to that encountered with retinoid X receptor and retinoic acid receptor genes. The existence of multiple PPAR isoforms transcribed from different promoters could increase the diversity of ligand and tissue-specific transcriptional responses.
Resumo:
Men who have sex with men (MSM) remain most at risk for developing HIV infection. The best prevention in this population is to identify risk factors associated with unprotected sex. Recent research suggests that sexual sensation seeking (SSS) and level of average drinking moderates the relationship between drinking alcohol in the context of sex and risky sexual behavior in a young MSM population (ages 16-20). Current study is an exploratory analysis using multilevel modeling to examine if these results are consistent across a MSM population with a wider range of ages who are also heavy drinkers. Participants (n = 181) included MSM (ages 18-75 years) from a longitudinal clinical research trial. Results indicate that MSM with higher SSS were more likely to have unprotected anal sex if they drank alcohol 3 hours prior to sex than those who did not, (OR = 1.07; 95% CI: 1.03 – 1.12). There was no significant interaction effect for average levels of drinking.
Resumo:
It is almost 20 years since a series of conferences known as CULT (Corpus Use and Learning to Translate) started. The first and second took place in Bertinoro, Italy, back in 1997 and 2000, respectively. The third was held in 2004 in Barcelona, and the fourth in 2015 in Alicante. Each was organized by a few enthusiastic lecturers and scholars who also happened to be corpus lovers. Guy Aston, Silvia Bernardini, Dominic Stewart and Federico Zanettin, from the Universitá di Bologna; Allison Beeby, Patricia Rodríguez-Inés and Pilar Sánchez-Gijón, from the Universitat Autònoma de Barcelona; and Daniel Gallego-Hernández, from the Universidad de Alicante, organized CULT conferences in the belief that spreading the word about the usefulness of corpora for teaching and professional translation purposes would have positive results.
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Headed on the first page with the words "Nomenclatura hebraica," this handwritten volume is a vocabulary with the Hebrew word in the left column, and the English translation on the right. While the book is arranged in sections by letter, individual entries do not appear in strict alphabetical order. The small vocabulary varies greatly and includes entries like enigma, excommunication, and martyr, as well as cucumber and maggot. There are translations of the astrological signs at the end of the volume. Poem written at the bottom of the last page in different hand: "Women when good the best of saints/ that bright seraphick lovely/ she, who nothing of an angel/ wants but truth & immortality./ Verse 2: Who silken limbs & charming/ face. Keeps nature warm."
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Background Research has raised significant concern regarding the affective consequences of synthetic drug use. However, little evidence from well-controlled longitudinal studies exists on these consequences. The aim of this study was to determine whether use of meth/amphetamine (speed) and 63,4- methylenedioxymethamphetamine (MDMA, ecstasy) is independently predictive of subsequent depressive symptoms in adolescents. Methods A sample of 3880 adolescents from secondary schools in disadvantaged areas of Quebec, Canada, were followed over time (2003e2008). Logistic regression was used to test the association between meth/ amphetamine and MDMA use in grade 10 (ages 15e16 years) and elevated depressive symptoms on an abridged Center for Epidemiologic Studies-Depression scale in grade 11, controlling for pre-existing individual and contextual characteristics. Results After adjustment, both MDMA use (OR 1.7, 95% CI 1.1 to 2.6) and meth/amphetamine use (OR 1.6, 95% CI 1.1 to 2.3) in grade 10 significantly increased the odds of elevated depressive symptoms in grade 11. These relationships did not vary by gender or pre-existing depressive symptoms. Increased risk was particularly observed in concurrent usage (OR 1.9, 95% CI 1.2 to 2.9). Conclusions Adolescent use of meth/amphetamine and MDMA (particularly concurrent use) is independently associated with subsequent depressive symptoms. Further enquiry must determine whether these associations reflect drug-induced neurotoxicity and whether adolescence is a period of increased vulnerability to the hazards of synthetic drug exposure.
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Background: Questions remain regarding the consequences of illicit drug use on adolescent adjustment and the nature of mechanisms that may explain these consequences. In this study, we examined whether early-onset illicit drug use predicts subsequent academic and psychosocial adjustment and whether associations are socially-mediated by decreased school engagement and increased peer deviancy. Method: 4885 adolescents were followed throughout secondary school. We used regressions to determine whether illicit drug use in grade 7 predicted academic achievement, school dropout, depressive symptoms, and conduct problems in grades 10–11, adjusting for potential confounders. We used path analysis to test whether significant associations were mediated by school engagement and peer deviancy in grade 8. Results: Illicit drug use predicted conduct problems and school dropout, but not academic achievement and depressive symptoms. The association between illicit drug use and conduct problems was fully mediated by increased peer deviancy. The association between illicit drug use and school dropout was partially mediated by increased peer deviancy, but remained mostly direct. No indirect association via decreased school engagement was found. Examination of reverse pathways revealed that conduct problems and academic achievement in grade 7 predicted drug use in grades 10–11. These associations were mediated by peer deviancy and school engagement (conduct problems only). Conclusion: Adolescent illicit drug use influences the risk of school dropout and conduct problems in part by contributing to deviant peer affiliation. Reciprocal social mediation characterizes the association between drug use and conduct problems. A reverse mechanism best explains the association with academic achievement.
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The Common European Asylum System (CEAS) is an EU policy area that is particularly evocative of the ‘politics of numbers’. The European Union has at its disposal a wide array of sources providing detailed information about the capacities and pressures of its member states’ asylum systems. This paper discusses the content of asylum data and the evolving interaction between its different sources, ranging from the United Nations High Commissioner for Refugees to the European Commission’s EUROSTAT and DG HOME, the European Asylum Support Office, FRONTEX, the European Migration Network (EMN) and national databases. However, the way in which such data are often misused, or even omitted, in political debate affects the soundness of policy decisions in the CEAS. Drawing on debates over the contested phenomenon of ‘asylum shopping’ and the exemption of victims of torture and unaccompanied minors from accelerated and border procedures in the recast asylum procedures Directive, this briefing paper argues that solid data-based evidence is often absent from political negotiations on CEAS measures affecting refugees and asylum-seekers.