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Comportamento de sistemas pós-filtros adsorvedores na remoção de compostos orgânicos precursores e subprodutos da desinfecção.; Behavior of post-filter adsorbers in the removal of organic precursors and disinfection byproducts.

Pereira, Claudia Mota Santos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 14/08/2009 PT
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27.76%
O presente trabalho teve como objetivo avaliar a eficiência de pós-filtros adsorvedores constituídos de Carvão Ativado Granular (CAG) na remoção de compostos orgânicos precursores e na formação de subprodutos da desinfecção, em particular dos trialometanos (THM) na Estação de Tratamento de Água Alto da Boa Vista (ETA ABV), abastecida por reservatórios de água bruta com elevado grau de eutrofização. Os ensaios foram conduzidos em ETA Piloto composta por tanque de reservação de água filtrada, ozonizador, tanque de reservação de água ozonizada e 4 pós-filtros adsorvedores, sendo duas unidades dotadas de CAG de origem mineral e duas unidades dotadas de CAG de origem vegetal. Os filtros foram operados em paralelo, sendo que duas colunas foram alimentadas com água filtrada da ETA ABV (Filtro F3 CAG de origem mineral e Filtro F4 CAG de origem vegetal) e as outras duas alimentadas com água filtrada e ozonizada (Filtro F1 CAG de origem mineral e Filtro F2 CAG de origem vegetal). A avaliação da remoção de compostos orgânicos precursores e formação de subprodutos da desinfecção foi feita através de análises de carbono orgânico total (COT), UV-254 nm e formação de THM. A análise dos resultados gerados de julho de 2007 a dezembro de 2008 permitiu concluir que 93% do THM é formado nas primeiras 24 horas de contato da amostra com o cloro...

Controle de compostos orgânicos precursores e subprodutos da desinfecção em mananciais eutrofizados mediante combinação de interozonização e sistemas pós-filtros adsorvedores.; Organic precursor and disinfection by-product control in eutrofic water supplies by means of inter-ozonization and post-filter GAC adsorbers.

Mendes, Ricardo Lazzari
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/05/2010 PT
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27.51%
O objetivo deste trabalho foi avaliar o desempenho da combinação dos processos de interozonização e sistemas pós-filtros adsorvedores na remoção de compostos orgânicos precursores e na formação de subprodutos da desinfecção, em particular os trialometanos (THM). Os ensaios foram desenvolvidos com a água filtrada proveniente da estação de tratamento de água do Alto da Boa Vista, localizada no município de São Paulo, tipo convencional, com água bruta oriunda de reservatório com elevado estado de eutrofização. O aparato experimental é constituído de um sistema de ozonização com quatro colunas em série e tempo de detenção hidráulica total de 16 minutos; e, por um sistema de quatro pós-filtros adsorvedores com diferentes tipos de carvão ativado granular, filtros F1 e F3 dotados de carvão mineral (CAG1, betuminoso) e filtros F2 e F4 compostos por carvão vegetal (CAG2, casca de coco) sendo todos operados em paralelo com valores de Tempo de Contato de Leito Vazio (TCLV) entre 15 e 20 minutos. Duas colunas receberam como afluente água filtrada pré-ozonizada (F1 e F2) e as demais colunas apenas água filtrada (F3 e F4). Os resultados indicaram que a ozonização não alterou de forma significativa os parâmetros utilizados para avaliação dos precursores...

Biosorption of Cr(VI) by an E. coli biofilm supported on GAC

Quintelas, C.; Fernandes, Bruno Daniel; Castro, J.; Tavares, M. T.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em 09/07/2006 ENG
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The increasing concern with environmental pollution significantly motivates the investigation and development of safe remediation technologies. The retention of contaminants by a biofilm supported on granular activated carbon is one of the promising technologies. This study aims the investigation and development of an innovative process for the removal of chromium (VI) from wastewater. The effect of the initial concentration of metal was tested, the polysaccharide and polymeric net of the E.Coli biofilm were quantified and the application of this system to a real effluent was made. The industrial effluent was provided by tannery factories. The support used for the biofilm formation was granular activated carbon (GAC) from MERCK with an average particle size of 2.5 mm, characterised by N2 adsorption (77K) with an ASAP Micromeritics 2001 which indicated a Langmuir area of 1270 m2g-1 and an average pore diameter of 2 nm. The use of activated carbon as a support is justified by the fact that this material is a versatile adsorbent due to its high surface area, porous structure, high adsorption capacity and surface chemical nature. The role of the biofilm was evaluated considering that microorganisms are quite adequate for heavy metals biosorption due to their ability to sorb metal ions...

A organização topográfica do GAC face aos novos equipamentos topográficos da Artilharia de Campanha Portuguesa

Godinho, Carlos
Fonte: Academia Militar. Direção de Ensino Publicador: Academia Militar. Direção de Ensino
Tipo: Outros
Publicado em 01/07/2008 POR
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27.43%
No âmbito do Estágio de Natureza Profissional do Tirocínio para Oficial Aluno da Arma de Artilharia (TPO), nomeadamente na componente do Trabalho de Investigação Aplicada, escolheu-se como tema de investigação a rganização topográfica do Grupo de Artilharia de Campanha (GAC) face aos novos equipamentos topográficos da Artilharia de Campanha (AC). Tendo em conta a permanente evolução tecnológica e o reequipamento do Exército Português como uma etapa de um ciclo contínuo que visa o acompanhamento dessas transformações e a adaptação às necessidades de um moderno campo de batalha, surge o interesse em saber como está a sua vertente topográfica. È desta forma que abordamos e pretendemos dar a conhecer os novos equipamentos topográficos adquiridos pelo Exército Português. De igual modo, foi nosso objectivo perceber até que ponto houve ou deverá haver alterações na organização topográfica e na execução dos trabalhos topográficos de um GAC. Julgámos ainda ser possível indicar, com base nos relatos dos militares que desempenharam ou exercem funções que implicam o relacionamento directo com os equipamentos, situações úteis para complementar a doutrina topográfica existente na AC. Os resultados obtidos demonstram que a aquisição e a utilização destes equipamentos topográficos são enormemente proveitosas para a nossa AC e para as outras Unidades que dos seus trabalhos necessitem. O desempenho da missão topográfica passou a ser mais rápido e oportuno...

Redes Internas do GAC. Alterações decorrentes da implementação do SACC

Janeiro, Hugo
Fonte: Academia Militar. Direção de Ensino Publicador: Academia Militar. Direção de Ensino
Tipo: Outros
Publicado em 01/09/2013 POR
Relevância na Pesquisa
27.78%
O presente trabalho tem como objetivo analisar as Redes Internas do Grupo de Artilharia de Campanha (GAC), da Brigada de Reação Rápida (BrigRR), e a implementação do Sistema Automático de Comando e Controlo (SACC) nesta unidade. No Exército Português, e para fazer face ao ambiente operacional contemporâneo, foi adquirido o SACC para a Artilharia, pelo que se tornou necessário efetuar uma investigação no sentido de verificar se são necessárias alterações e quais as que devem ser feitas ao nível das Redes Internas do GAC/BrigRR, decorrentes da implementação do SACC. Para a elaboração deste trabalho, começamos por caracterizar o ambiente operacional contemporâneo e as consequentes novas exigências para a Artilharia de Campanha (AC). De seguida, realizou-se o estudo das capacidades e necessidades para a implementação do SACC e seus subsistemas, e explanamos as várias fases da implementação do SACC no GAC/BrigRR, desde a sua aquisição até aos dias de hoje. Realizou-se também o estudo, ao nível das Redes Internas de um GAC, primeiramente da doutrina portuguesa e da doutrina americana, que decidimos expor como referência. Numa segunda fase...

Disruption of the Borrelia burgdorferi gac Gene, Encoding the Naturally Synthesized GyrA C-Terminal Domain

Knight, Scott W.; Kimmel, Betsy J.; Eggers, Christian H.; Samuels, D. Scott
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2000 EN
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27.15%
The C-terminal domain of the A subunit of DNA gyrase, which we term Gac, is naturally synthesized in Borrelia burgdorferi as an abundant DNA-binding protein. Full-length GyrA, which includes the C-terminal domain, is also synthesized by the spirochete and functions as a subunit of DNA gyrase. We have disrupted synthesis of Gac as an independent protein and demonstrated that it is not essential for growth in a coumarin-resistant background. We detected no alterations in DNA maintenance, condensation, or topology in B. burgdorferi lacking this small DNA-binding protein.

The purine-rich trinucleotide repeat sequences d(CAG)15 and d(GAC)15 form hairpins.

Yu, A; Dill, J; Mitas, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 25/10/1995 EN
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27.51%
The structures of single-stranded (ss) oligonucleotides containing (CAG)15 [ss(CAG)15] or (GAC)15 [ss(GAC)15] were examined. At 10 degrees C, the electrophoretic mobilites of the two DNAs were similar to ss(CTG)15, a DNA that forms a hairpin containing base paired and/or stacked thymines. At 37 degrees C in 50 mM NaCl, single-strand-specific P1 nuclease cleaved the G33-G36 phosphodiesters of ss(GAC)15, and the G32-A34, G35-C36 phosphodiesters of ss(CAG)15 (where the loop apex of both DNAs = A34). Electrophoretic mobility melting profiles indicated that the melting temperature (Tm) of ss(CAG)15 in low (approximately 1 mM Na+) ionic strength was 38 degrees C. In contrast, the Tm of ss(GAC)15 was 49 degrees C, a value similar to the Tm of ss(CTG)15. These results provide evidence that ss(GAC)15 and ss(CAG)15 form similar, but distinguishable hairpin structures.

Transcription influences the types of deletion and expansion products in an orientation-dependent manner from GAC•GTC repeats

Mochmann, Liliana H.; Wells, Robert D.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.69%
The genetic instability of (GAC•GTC)n (where n = 6–74) was investigated in an Escherichia coli-based plasmid system. Prior work implicated the instability of a (GAC•GTC)5 tract in the cartilage oligomeric matrix protein (COMP) gene to the 4, 6 or 7mers in the etiology of pseudoachondroplasia and multiple epiphyseal dysplasia. The effects of triplet repeat length and orientation were studied after multiple replication cycles in vivo. A transcribed plasmid containing (GAC•GTC)49 repeats led to large deletions (>3 repeats) after propagation in E.coli; however, if transcription was silenced by the LacIQ repressor, small expansions and deletions (<3 repeats) predominated the mutation spectra. In contrast, propagation of similar length but opposing orientation (GTC•GAC)53 containing plasmid led to small instabilities that were unaffected by the repression of transcription. Thus, by inhibiting transcription, the genetic instability of (GAC•GTC)49 repeats did not significantly differ from the opposing orientation, (GTC•GAC)53. We postulate that small instabilities of GAC•GTC repeats are achieved through replicative slippage, whereas large deletion events are found when GAC•GTC repeats are transcribed. Herein, we report the first genetic study on GAC•GTC repeat instability describing two types of mutational patterns that can be partitioned by transcription modulation. Along with prior biophysical data...

Spontaneous Gac Mutants of Pseudomonas Biological Control Strains: Cheaters or Mutualists? ▿

Driscoll, William W.; Pepper, John W.; Pierson, Leland S.; Pierson, Elizabeth A.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /10/2011 EN
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Bacteria rely on a range of extracellular metabolites to suppress competitors, gain access to resources, and exploit plant or animal hosts. The GacS/GacA two-component regulatory system positively controls the expression of many of these beneficial external products in pseudomonad bacteria. Natural populations often contain variants with defective Gac systems that do not produce most external products. These mutants benefit from a decreased metabolic load but do not appear to displace the wild type in nature. How could natural selection maintain the wild type in the presence of a mutant with enhanced growth? One hypothesis is that Gac mutants are “cheaters” that do not contribute to the public good, favored within groups but selected against between groups, as groups containing more mutants lose access to ecologically important external products. An alternative hypothesis is that Gac mutants have a mutualistic interaction with the wild type, so that each variant benefits by the presence of the other. In the biocontrol bacterium Pseudomonas chlororaphis strain 30-84, Gac mutants do not produce phenazines, which suppress competitor growth and are critical for biofilm formation. Here, we test the predictions of these alternative hypotheses by quantifying interactions between the wild type and the phenazine- and biofilm-deficient Gac mutant within growing biofilms. We find evidence that the wild type and Gac mutants interact mutualistically in the biofilm context...

The Gac-Rsm and SadB Signal Transduction Pathways Converge on AlgU to Downregulate Motility in Pseudomonas fluorescens

Martínez-Granero, Francisco; Navazo, Ana; Barahona, Emma; Redondo-Nieto, Miguel; Rivilla, Rafael; Martín, Marta
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 20/02/2012 EN
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27.15%
Flagella mediated motility in Pseudomonas fluorescens F113 is tightly regulated. We have previously shown that motility is repressed by the GacA/GacS system and by SadB through downregulation of the fleQ gene, encoding the master regulator of the synthesis of flagellar components, including the flagellin FliC. Here we show that both regulatory pathways converge in the regulation of transcription and possibly translation of the algU gene, which encodes a sigma factor. AlgU is required for multiple functions, including the expression of the amrZ gene which encodes a transcriptional repressor of fleQ. Gac regulation of algU occurs during exponential growth and is exerted through the RNA binding proteins RsmA and RsmE but not RsmI. RNA immunoprecipitation assays have shown that the RsmA protein binds to a polycistronic mRNA encoding algU, mucA, mucB and mucD, resulting in lower levels of algU. We propose a model for repression of the synthesis of the flagellar apparatus linking extracellular and intracellular signalling with the levels of AlgU and a new physiological role for the Gac system in the downregulation of flagella biosynthesis during exponential growth.

Roles of the Gac-Rsm pathway in the regulation of phenazine biosynthesis in Pseudomonas chlororaphis 30-84

Wang, Dongping; Lee, Sung-Hee; Seeve, Candace; Yu, Jun Myoung; Pierson, Leland S; Pierson, Elizabeth A
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
EN
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27.58%
The GacS/GacA two-component regulatory system activates the production of secondary metabolites including phenazines crucial for biological control activity in Pseudomonas chlororaphis 30-84. To better understand the role of the Gac system on phenazine regulation, transcriptomic analyses were conducted by comparing the wild-type strain to a gacA mutant. RNA-seq analysis identified 771 genes under GacA control, including many novel genes. Consistent with previous findings, phenazine biosynthetic genes were significantly downregulated in a gacA mutant. The transcript abundances of phenazine regulatory genes such as phzI, phzR, iopA, iopB, rpoS, and pip also were reduced. Moreover, the transcript abundance of three noncoding RNAs (ncRNAs) including rsmX, rsmY, and rsmZ was significantly decreased by gacA mutation consistent with the presence of consensus GacA-binding sites associated with their promoters. Our results also demonstrated that constitutive expression of rsmZ from a non-gac regulated promoter resulted in complete restoration of N-acyl-homoserine lactone (AHL) and phenazine production as well as the expression of other gac-dependent secondary metabolites in gac mutants. The role of RsmA and RsmE in phenazine production also was investigated. Overexpression of rsmE...

The Diguanylate Cyclase SadC Is a Central Player in Gac/Rsm-Mediated Biofilm Formation in Pseudomonas aeruginosa

Moscoso, Joana A.; Jaeger, Tina; Valentini, Martina; Hui, Kailyn; Jenal, Urs; Filloux, Alain
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2014 EN
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27.32%
Pseudomonas aeruginosa is a Gram-negative opportunistic human pathogen and a threat for immunocompromised and cystic fibrosis patients. It is responsible for acute and chronic infections and can switch between these lifestyles upon taking an informed decision involving complex regulatory networks. The RetS/LadS/Gac/Rsm network and the cyclic-di-GMP (c-di-GMP) signaling pathways are both central to this phenomenon redirecting the P. aeruginosa population toward a biofilm mode of growth, which is associated with chronic infections. While these two pathways were traditionally studied independently from each other, we recently showed that cellular levels of c-di-GMP are increased in the hyperbiofilm retS mutant. Here, we have formally established the link between the two networks by showing that the SadC diguanylate cyclase is central to the Gac/Rsm-associated phenotypes, notably, biofilm formation. Importantly, SadC is involved in the signaling that converges onto the RsmA translational repressor either via RetS/LadS or via HptB/HsbR. Although the level of expression of the sadC gene does not seem to be impacted by the regulatory cascade, the production of the SadC protein is tightly repressed by RsmA. This adds to the growing complexity of the signaling network associated with c-di-GMP in P. aeruginosa. While this organism possesses more than 40 c-di-GMP-related enzymes...

Discriminating and assessing adsorption and biodegradation removal mechanisms during granular activated carbon filtration of microcystin toxins

Wang, H.; Ho, L.; Lewis, D.; Brookes, J.; Newcombe, G.
Fonte: Pergamon-Elsevier Science Ltd Publicador: Pergamon-Elsevier Science Ltd
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
27.66%
Microcystins are cyanobacterial toxins that are problematic for water authorities due to their resistance to conventional water treatment. Granular activated carbon (GAC) filtration has been shown to be effective in removing microcystin from water using both adsorption and biodegradation removal mechanisms; however, little is known regarding which removal mechanism predominates and to what extent. In this study, microcystin removal due to adsorption and biodegradation in GAC filtration were discriminated and assessed by commissioning three parallel laboratory columns, including a sterile GAC column, a conventional GAC column and a sand column. The results demonstrate that biodegradation is an efficient removal mechanism once it commences and that the rate of biodegradation was dependent upon temperature and initial bacterial concentration. Adsorption of microcystins was prevalent during the initial stages of the GAC columns and was modelled using the homogeneous surface diffusion model (HSDM). The HSDM provided evidence that an active biofilm present on the surface of the conventional GAC hindered adsorption of microcystin compared with the sterile GAC with no active biofilm. Up to 70% removal of microcystin-LR was still observed after 6 months of operation of the sterile GAC column...

Separated adsorption and bacterial degradation of microcystins in GAC filtration

Wang, H.; Lewis, D.; Newcombe, G.; Brookes, J.; Ho, L.
Fonte: Inderscience Publishers Publicador: Inderscience Publishers
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
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27.32%
For removal of microcystins from drinking water, Granular Activated Carbon (GAC) filtration has shown to be promising as it is not only an efficient adsorbent, but also can support biodegradation of microcystins, extending the lifetime of this application. In this study, a sterile and non-sterile GAC column, in addition to a sand column, was studied to distinguish the adsorption and biodegradation removal mechanisms. Effective microcystin adsorption was considerably short in a virgin GAC bed, ∼10-15 days. Biodegradation was shown to be the primary removal mechanism after its commencement (∼1 month), with complete reduction until the study's completion (∼11 months).; Haixiang Wang, David Lewis, Gayle Newcombe, Justin Brookes and Lionel Ho; Copyright © 2009 Inderscience Enterprises Limited. All rights reserved.

Dealing with GAC Issues in Project Lending : The Special Case of Fragile and Conflict-Affected States

World Bank
Fonte: Washington, DC Publicador: Washington, DC
Tipo: Economic & Sector Work :: Knowledge Economy Study; Economic & Sector Work
ENGLISH; EN_US
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The principal objective of the Bank's governance work should be to help develop capable and accountable states to deliver services to the poor, promote private-sector-led growth, and tackle corruption effectively. The agenda for action has been defined, new tools and approaches have been developed, and governance and anticorruption (GAC) issues and concerns are increasingly being mainstreamed in the Bank's operational work at the country, sector, and project levels. With the introduction of the operational risk assessment framework (ORAF), the Bank has undertaken a major effort to improve how it manages GAC risks in the development projects and programs it supports. This note provides principles-based advice and guidance to task teams working at the sector and project levels on fragile and conflict-affected states (FCS) countries in Africa. It aims to provide a common conceptual framework for understanding the challenges and opportunities they face in project design, implementation, and supervision; highlight key lessons learned and good practice examples from others working in this area; and suggest some topics where further work is needed to understand and mitigate key operational risks. A communications strategy that frames GAC issues in a constructive way...

Impact of UV–H2O2 Advanced Oxidation and Aging Processes on GAC Capacity for the Removal of Cyanobacterial Taste and Odor Compounds

Zamyadi, Arash; Sawade, Emma; Ho, Lionel; Newcombe, Gayle; Hofmann, Ron
Fonte: Libertas Academica Publicador: Libertas Academica
Tipo: Artigo de Revista Científica
Publicado em 01/10/2015 EN
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27.43%
Cyanobacteria and their taste and odor (T&O) compounds are a growing concern in water sources globally. Geosmin and 2-methylisoborneol (MIB) are the most commonly detected T&O compounds associated with cyanobacterial presence in drinking water sources. The use of ultraviolet and hydrogen peroxide (H2O2) as an advanced oxidation treatment for T&O control is an emerging technology. However, residual H2O2 (>80% of the initial dose) has to be removed from water prior final disinfection. Recently, granular activated carbon (GAC) is used to remove H2O2 residual. The objective of this study is to assess the impact of H2O2 quenching and aging processes on GAC capacity for the removal of geosmin and MIB. Pilot columns with different types of GAC and presence/absence of H2O2 have been used for this study. H2O2 removal for the operational period of 6 months has no significant impact on GAC capacity to remove the geosmin and MIB from water.

LAMOST Spectroscopic Survey of the Galactic Anti-centre (LSS-GAC): target selection and the first release of value-added catalogues

Yuan, Haibo; Liu, Xiaowei; Huo, Zhiying; Xiang, Maosheng; Huang, Yang; Chen, Bingqiu; Zhang, Huihua; Sun, Ningchen; Wang, Chun; Zhang, Huawei; Zhao, Yongheng; Luo, Ali; Shi, Jianrong; Li, Guoping; Yuan, Hailong; Dong, Yiqiao; Li, Guangwei; Hou, Yonghui; Z
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/12/2014
Relevância na Pesquisa
27.43%
As a major component of the LAMOST Galactic surveys, the LAMOST Spectroscopic Survey of the Galactic Anti-centre (LSS-GAC) aims to survey a significant volume of the Galactic thin/thick discs and halo for a contiguous sky area of over 3,400 deg$^2$ centred on the Galactic anti-centre ($|b| \leq 30^{\circ}$, $150 \leq l \leq 210^{\circ}$), and obtain $\lambda\lambda$3700 -- 9000 low resolution ($R \sim 1,800$) spectra for a statistically complete sample of $\sim 3$\,M stars of all colours down to a limiting magnitued of $r$ $\sim$ 17.8\,mag (to 18.5\,mag for limited fields). Together with Gaia, the LSS-GAC will yield a unique dataset to advance our understanding of the structure and assemblage history of the Galaxy, in particular its disk(s). In addition to the main survey, the LSS-GAC will also target hundreds of thousands objects in the vicinity fields of M\,31 and M\,33 and survey a significant fraction (over a million) of randomly selected very bright stars (VB; $r \le 14$ mag) in the northern hemisphere. During the Pilot and the first year Regular Surveys of LAMOST, a total of 1,042,586 [750,867] spectra of a signal to noise ratio S/N(7450\AA) $\ge$ 10 [S/N(4650\AA) $\ge$ 10] have been collected. In this paper, we present a detailed description of the target selection algorithm...

Determination of the Local Standard of Rest using the LSS-GAC DR1

Huang, Yang; Liu, Xiaowei; Yuan, Haibo; Xiang, Maosheng; Huo, Zhiying; Chen, Bingqiu; Zhang, Yong; Hou, Yonghui
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/01/2015
Relevância na Pesquisa
27.32%
We re-estimate the peculiar velocity of the Sun with respect to the local standard of rest using a sample of local stars within 600 pc of the Sun, selected from the LAMOST Spectroscopic Survey of the Galactic Anti-centre (LSS-GAC). The sample consists of 94332 FGK main-sequence stars with well-determined radial velocities and atmospheric parameters. To derive the LSR, two independent analyses are applied to the data. Firstly, we determine the solar motion by comparing the observed velocity distribution to that generated with the analytic formulism of Schonrich & Binney that has been demonstrated to show excellent agreement with rigorous torus-based dynamics modelling by Binney & McMillan. Secondly, we propose that cold populations of thin disc stars, selected by applying an orbital eccentricity cut, can be directly used to determine the LSR without the need of asymmetric drift corrections. Both approaches yield consistent results of solar motion in the direction of Galactic rotation, V_sun, that are much higher than the standard value adopted hitherto, derived from Stromgren's equation. The newly deduced values of V_sun are 1-2 km/s smaller than the more recent estimates derived from the Geneva-Copenhagen Survey sample of stars in the solar neighbourhood (within 100 pc). We attribute the small difference to the presence of several well-known moving groups in the GCS sample that...

DA white dwarfs from the LSS-GAC survey DR1: the preliminary luminosity and mass functions and formation rate

Rebassa-Mansergas, A.; Liu, X. -W.; Cojocaru, R.; Yuan, H. -B.; Torres, S.; Garcia-Berro, E.; Xiang, M. -X.; Huang, Y.; Koester, D.; Hou, Y.; Li, G.; Zhang, Y.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/03/2015
Relevância na Pesquisa
27.43%
Modern large-scale surveys have allowed the identification of large numbers of white dwarfs. However, these surveys are subject to complicated target selection algorithms, which make it almost impossible to quantify to what extent the observational biases affect the observed populations. The LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) Spectroscopic Survey of the Galactic anti-center (LSS-GAC) follows a well-defined set of criteria for selecting targets for observations. This advantage over previous surveys has been fully exploited here to identify a small yet well-characterised magnitude-limited sample of hydrogen-rich (DA) white dwarfs. We derive preliminary LSS-GAC DA white dwarf luminosity and mass functions. The space density and average formation rate of DA white dwarfs we derive are 0.83+/-0.16 x 10^{-3} pc^{-3} and 5.42 +/- 0.08 x 10^{-13} pc^{-3} yr^{-1}, respectively. Additionally, using an existing Monte Carlo population synthesis code we simulate the population of single DA white dwarfs in the Galactic anti-center, under various assumptions. The synthetic populations are passed through the LSS-GAC selection criteria, taking into account all possible observational biases. This allows us to perform a meaningful comparison of the observed and simulated distributions. We find that the LSS-GAC set of criteria is highly efficient in selecting white dwarfs for spectroscopic observations (80-85 per cent) and that...

Patrones fenológicos de la Provincia de Mendoza, Argentina, mediante serie temporal de imágenes NOAA-AVHRR NDVI GAC

González Loyarte,M. M; Menenti,M.; Roig,F. A.
Fonte: Boletín de la Sociedad Argentina de Botánica Publicador: Boletín de la Sociedad Argentina de Botánica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2010 ES
Relevância na Pesquisa
37.15%
Se describe la dinámica temporal de la vegetación de Mendoza mediante análisis de la fenología foliar regional con una serie de 108 imágenes mensuales de índice de vegetación NOAA-AVHRR NDVI GAC. La serie se descompone aplicando la Transformada Rápida de Fourier en parámetros dinámicos: NDVI medio, amplitudes (máxima variabilidad del NDVI) y fases (tiempo entre inicio del ciclo y máximo NDVI) para diferentes períodos. Con los parámetros con mayor información (variablilidad inter e intraanual) se hace una clasificación y se obtiene un mapa de 18 áreas de comportamiento fenológico. Éste se vincula con los ecosistemas y con las unidades de vegetación. Se modela el patrón fenológico (curva NDVI mensual) para 17 unidades de vegetación. El mapa aporta elementos dinámicos al estudio regional de la vegetación generando una zonificación nueva explicada por variables que determinan la actividad vegetativa. El patrón fenológico describe el funcionamiento de la vegetación y permite comprender sus variaciones geográficas. El conjunto de la vegetación de Mendoza responde a un ciclo anual con matices localizados de ligera bimodalidad. Los patrones de bajo contraste invierno-verano corresponden a condiciones climáticas xéricas expresando su máximo vegetativo al final del verano; la disponibilidad hídrica incrementa este contraste acortando el tiempo de máxima expresión vegetativa.