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Percentagem de plaquetas reticuladas : um parâmetro útil no diagnóstico da Púrpura Trombocitopénica Imune Primária

Pinheiro, Ana Cristina da Costa Abrantes
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Dissertação de Mestrado
POR
Relevância na Pesquisa
27.91%
A Púrpura Trombocitopénica Imune (PTI) é uma doença auto-imune que se caracteriza pela presença de auto-anticorpos contra as glicoproteínas plaquetares, que levam à destruição das plaquetas no sistema reticulo-endotelial. Para o diagnóstico diferencial entre trombocitopenias por hiperdestruição periférica, como a PTI, ou por hipoprodução medular (aplasia ou invasão medular por proliferação celular anormal) é necessário, frequentemente, fazer a observação morfológica da medula óssea. As plaquetas reticuladas (rP – reticulated platelet) são plaquetas recentemente libertadas da medula óssea, têm um maior volume, são mais densas e têm ácido ribonucleico (RNA – ribonucleic acid) residual. A percentagem de rP (%rP) é um novo parâmetro plaquetar do CELL-DYN® Sapphire que utiliza o marcador de fluorescência CD4K-530. Objectivo: O objectivo principal deste trabalho é determinar a fiabilidade da %rP na avaliação da actividade trombopoiética da medula óssea, com o intuito de vir a substituir o medulograma na abordagem diagnóstica da maioria dos casos de PTI primária. Material e métodos: Em 139 amostras de sangue periférico, colhidas em ácido etilenodiaminotetracético tripotássico (EDTA K3 – ethylenediaminetetraacetic acid tripotassic)...

Antisense inhibition of the PTI-1 oncogene reverses cancer phenotypes

Su, Zao-zhong; Goldstein, Neil I.; Fisher, Paul B.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 17/02/1998 EN
Relevância na Pesquisa
27.89%
The genetic alterations and molecular events mediating human prostate cancer development and progression remain to be defined. Rapid expression cloning and differential RNA display detect a putative oncogene, prostate tumor-inducing gene 1 (PTI-1), that is differentially expressed in human prostate (as well as breast, colon, and small cell lung) cancer cell lines, patient-derived prostate carcinomas, and blood from patients with metastatic prostate cancer. PTI-1 consists of a unique 5′ untranslated region (5′ UTR) with significant sequence homology to Mycoplasma hyopneumoniae 23S ribosomal RNA juxtaposed to a sequence that encodes a truncated and mutated human elongation factor 1α (Trun-EF). Stable expression of a nearly full-length 1.9-kb PTI-1 gene, but not the separate PTI-1 5′ UTR or Trun-EF region, in normal rat embryo fibroblast cells, CREF-Trans 6, induces an aggressive tumorigenic phenotype in athymic nude mice. Blocking PTI-1 expression with antisense PTI-1 results in reversion of transformed PTI-1-expressing cells to a more normal cellular morphology with suppression in both anchorage-independent growth and tumorigenic potential in athymic nude mice. These findings document that PTI-1 is indeed an oncogene, and directly blocking PTI-1 expression can nullify cancer phenotypes. In these contexts...

T-DNA of pTi-15955 from Agrobacterium tumefaciens is transcribed into a minimum of seven polyadenylated RNAs in a sunflower crown gall tumor.

Murai, N; Kemp, J D
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 11/03/1982 EN
Relevância na Pesquisa
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Northern blot hybridization analysis of polysomal polyadenylated RNA isolated from sunflower crown gall tumor PSCG-15955 demonstrated that a minimum of seven RNAs were transcribed from T-DNA of pTi-15955 from Agrobacterium tumefaciens. The sizes of the T-DNA transcripts were 1.8, 1.6, 1.5, 1.1, 1.0 kilo bases (kb) and two transcripts of 0.8 kb long. The relative abundance of these polyadenylated RNAs varied greatly, the 1.0 kb RNA being the most abundant and the 1.6 kb RNA being the least abundant. Assignment of map locations of the seven polyadenylated RNAs indicated that the conserved region of T-DNA which may play a central role in tumorigenesis contained four RNAs of 1.8, 1.1, 0.8(a) and a portion of 0.8(b) kb long.

Of PAMPs and Effectors: The Blurred PTI-ETI Dichotomy[OA]

Thomma, Bart P.H.J.; Nürnberger, Thorsten; Joosten, Matthieu H.A.J.
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.46%
Typically, pathogen-associated molecular patterns (PAMPs) are considered to be conserved throughout classes of microbes and to contribute to general microbial fitness, whereas effectors are species, race, or strain specific and contribute to pathogen virulence. Both types of molecule can trigger plant immunity, designated PAMP-triggered and effector-triggered immunity (PTI and ETI, respectively). However, not all microbial defense activators conform to the common distinction between PAMPs and effectors. For example, some effectors display wide distribution, while some PAMPs are rather narrowly conserved or contribute to pathogen virulence. As effectors may elicit defense responses and PAMPs may be required for virulence, single components cannot exclusively be referred to by one of the two terms. Therefore, we put forward that the distinction between PAMPs and effectors, between PAMP receptors and resistance proteins, and, therefore, also between PTI and ETI, cannot strictly be maintained. Rather, as illustrated by examples provided here, there is a continuum between PTI and ETI. We argue that plant resistance is determined by immune receptors that recognize appropriate ligands to activate defense, the amplitude of which is likely determined by the level required for effective immunity.

Assay for Pathogen-Associated Molecular Pattern (PAMP)-Triggered Immunity (PTI) in Plants

Chakravarthy, Suma; Velásquez, André C.; Martin, Gregory B.
Fonte: MyJove Corporation Publicador: MyJove Corporation
Tipo: Artigo de Revista Científica
Publicado em 09/09/2009 EN
Relevância na Pesquisa
27.29%
To perceive potential pathogens in their environment, plants use pattern recognition receptors (PRRs) present on their plasma membranes. PRRs recognize conserved microbial features called pathogen-associated molecular patterns (PAMPs) and this detection leads to PAMP-triggered immunity (PTI), which effectively prevents colonization of plant tissues by non-pathogens1,2. The most well studied system in PTI is the FLS2-dependent pathway3. FLS2 recognizes the PAMP flg22 that is a component of bacterial flagellin.

Assessing the Diverse Functions of BAK1 and Its Homologs in Arabidopsis, beyond BR Signaling and PTI Responses

Kim, Beg Hab; Kim, Sun Young; Nam, Kyoung Hee
Fonte: Korea Society for Molecular and Cellular Biology Publicador: Korea Society for Molecular and Cellular Biology
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27%
Plants possess a variety of extracellular leucine-rich repeats receptor-like kinases (LRR-RLKs) to coordinate developmental programs with responses to environmental changes. Out of sixteen families of LRR-RLKs in Arabidopsis, the LRR-RLKII family consists of fourteen individual members, including five Arabidopsis thaliana somatic embryogenesis receptor kinases (AtSERKs). BAK1/AtSERK3 was first identified as a dual co-receptor of BRI1 and FLS2, mediating BR signaling and pathogen-associated molecular pattern (PAMP) triggered immunity (PTI), respectively. Since its identification, many researchers have attempted to elucidate the phosphorylation mechanisms between receptor complexes and identify additional components that interact with receptor complexes to transduce the signaling downstream. Relatively detailed early events in complex formation, phosphorylation sites on the BRI1/BAK1 complex and BAK1-interacting proteins, such as BIK1 and PUB13, have been identified. Small receptor complexes consisting of BAK1 and BIR1 or BAK1 and AtSERK4 regulate cell death during steady state conditions. Moreover, the redundant and distinct functions of AtSERK proteins and other members of the LRR-RLKII family have been revealed. This review focuses on the integration of the information from the most recent studies concerning BAK1 and its homologs.

The novel GrCEP12 peptide from the plant-parasitic nematode Globodera rostochiensis suppresses flg22-mediated PTI

Chen, Shiyan; Chronis, Demosthenis; Wang, Xiaohong
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
Publicado em 01/09/2013 EN
Relevância na Pesquisa
27.67%
The potato cyst nematode Globodera rostochiensis is a biotrophic pathogen that secretes effector proteins into host root cells to promote successful plant parasitism. In addition to the role in generating within root tissue the feeding cells essential for nematode development,1 nematode secreted effectors are becoming recognized as suppressors of plant immunity.2-4 Recently we reported that the effector ubiquitin carboxyl extension protein (GrUBCEP12) from G. rostochiensis is processed into free ubiquitin and a 12-amino acid GrCEP12 peptide in planta. Transgenic potato lines overexpressing the derived GrCEP12 peptide showed increased susceptibility to G. rostochiensis and to an unrelated bacterial pathogen Streptomyces scabies, suggesting that GrCEP12 has a role in suppressing host basal defense or possibly pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) during the parasitic interaction.3 To determine if GrCEP12 functions as a PTI suppressor we evaluated whether GrCEP12 suppresses flg22-induced PTI responses in Nicotiana benthamiana. Interestingly, we found that transient expression of GrCEP12 in N. benthamiana leaves suppressed reactive oxygen species (ROS) production and the induction of two PTI marker genes triggered by the bacterial PAMP flg22...

Modulação da expressão dos genes EF1A e PTI-1 no câncer de próstata

Cordeiro, Elisângela Rosa
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
37.83%
A descoberta de marcadores moleculares que possam melhorar o diagnóstico clínico e as perspectivas de cura não só do câncer de próstata como de várias outras doenças tem se tornado o objetivo central da biologia molecular. Nosso trabalho teve por objetivo rever o papel do gene EF1A e do seu homólogo PTI-1 no câncer de próstata. Para tal, foram analisadas amostras de sangue periférico e tecido de peça cirúrgica provenientes de pacientes diagnosticados com hiperplasia prostática benigna (HPB) e câncer de próstata (CaP) e amostras de sangue de um grupo de homens jovens, considerados controle negativo (CN). Observamos que o gene EF1A tem níveis relativos de expressão maiores no grupo de pacientes do grupo Cap do que nos grupos de HPB e CN. Em sangue periférico, níveis relativos de expressão do EF1A maiores do 1,5, conferem uma razão de chances 10,56 vezes maior de o indivíduo apresentar CaP em relação aos com menores níveis de expressão. No tecido essa chance é de 4,6 vezes para níveis de expressão com média entre 1 e 1,5. A presença do transcrito do gene PTI-1, região 5’ UTR, faz com que os indivíduos tenham uma chance 1,94 vezes maior de desenvolver CaP. A associação do biomarcador DD3 ao gene PTI-1 faz com que a chance de desenvolver CaP seja de 3...

Guanine nucleotides regulate sphingosine kinase 1 activation by eukaryotic elongation factor 1A and provide a mechanism for eEF1A-associated oncogenesis

Leclercq, T.; Moretti, P.; Pitson, S.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
27.67%
Sphingosine kinase 1 (SK1) catalyses the formation of bioactive phospholipid sphingosine 1-phosphate (S1P). Elevated cellular SK1 activity and S1P levels enhance cell proliferation and survival, and are strongly implicated in tumourigenesis. Regulation of SK1 activity can occur through various mechanisms, including phosphorylation and protein–protein interactions. We have previously shown that eukaryotic elongation factor 1A (eEF1A) interacts with and directly activates SK1, but the mechanisms regulating this were undefined. Notably, eEF1A has GTPase activity and can exist in GTP- or GDP-bound forms, which are associated with distinct structural conformations of the protein. Here, we show that the guanine nucleotide-bound state of eEF1A regulates its ability to activate SK1, with eEF1A.GDP, but not eEF1A.GTP, enhancing SK1 activity in vitro. Furthermore, we show that enhancing cellular eEF1A.GDP levels through expression of a guanine nucleotide dissociation inhibitor of eEF1A, translationally controlled tumour protein (TCTP), increased SK1 activity in cells. We also examined a truncated isoform of eEF1A1, termed prostate tumour inducer-1 (PTI-1), which can induce neoplastic cell transformation through undefined mechanisms. PTI-1 lacks the G protein domain of eEF1A1 and is therefore unable to undergo the GTP-binding-induced conformational change. Notably...

Services and support for IU School of Medicine and Clinical Affairs Schools by the UITS/PTI Advanced Biomedical Information Technology Core and Research Technologies Division in FY 2013 - Extended Version

Stewart, Craig A.; Barnett, William K.; Link, Matt R.; Shankar, Ganesh; Miller, Therese; Michael, Scott; Henschel, Robert; Boyles, Mike J.; Wernert, Eric; Quick, Robert
Fonte: Indiana University: UITS/PTI ABITC and RT Division Publicador: Indiana University: UITS/PTI ABITC and RT Division
Tipo: Relatório
EN
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The report presents information on services delivered in FY 2013 by ABITC and RT to the IU School of Medicine and the other Clinical Affairs schools that include the Schools of Nursing, Dentistry, Health and Rehabilitation Sciences, and Optometry; the Fairbanks School of Public Health at IUPUI; the School of Public Health at IU Bloomington; and the School of Social Work.

Indiana University’s advanced cyberinfrastructure in service of IU strategic goals: Activities of the Research Technologies Division of UITS and National Center for Genome Analysis Support – two Pervasive Technology Institute cyberinfrastructure and service centers - during FY2014

Stewart, Craig A.; Barnett, William K.; Hancock, David Y.; Henschel, Robert; Link, Matthew R.; Miller, Therese; Wernert, Eric A.
Fonte: Indiana University Publicador: Indiana University
Tipo: Relatório
EN_US
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27%
This report presents information on the activities of the Research Technologies Division of UITS and the National Center for Genome Analysis Support, two cyberinfrastructure and service centers of the Pervasive Technology Institute. Research Technologies (RT) is a subunit of University Information Technology Services (UITS) and it operates and supports the largest computational, data, and visualization systems at IU. The National Center for Genome Analysis Support (NCGAS) is primarily federally funded, serving the national community of genome scientists. NCGAS leadership is drawn from the Office of the Vice President for Information Technology, UITS, the College, and the School of Informatics and Computing. This report focuses on contributions of RT and NCGAS to accomplishment of IU’s bicentennial goals, and is organized according to those goals. Together the activities of NCGAS and RT represent a large share of the activities of PTI in support of the IU community. PTI’s Research Centers (Data to Insight Center, Digital Science Center, and the Center for Applies Cybersecurity Research) also provide support to the IU community in various forms but the primary focus of these research centers is informatics, information technology...

Subcellular dynamics of the endogenous elicitor peptide AtPep1 and its receptors in Arabidopsis: implications for the plant immunity; Dinâmica subcelular do peptídeo endógeno AtPep1 e seus receptores em Arabidopsis: implicações na imunidade de plantas

Morea, Fausto Andres Ortiz
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 14/08/2015 EN
Relevância na Pesquisa
27.58%
This work investigated the subcellular dynamics of the plant elicitor peptide AtPep1 and its interplay with plant defense responses. First, an introduction of the plant innate immunity system is provided with emphasis on pattern trigger immunity (PTI), which is based on the recognition of "non-self" and "self" elicitor molecules by surface-localized patternrecognition receptors (PRRs). Then, the Arabidopsis endogenous peptides that act as selfelicitor molecules are presented, with details on AtPep1 and its PEPR receptors. Plant endomembrane trafficking is described, encompassing endocytic pathways, clathrin mediated endocytosis (CME) and receptor-mediated endocytosis (RME). In the next chapter, we explored strategies for the in vivo study of the subcellular behavior of AtPep1; to this end, we fused the precursor protein of AtPep1 (PROPEP1) to GFP and assessed its localization. We found that PROPEP1 was associated with the tonoplast and accumulated in the vacuole, suggesting that this organelle could work as the station where PROPEP1 is stored and later released, only in a danger situation, hence initiating AtPep1. Moreover, we generated AtPep1 versions labeled with fluorescent dyes and demonstrated that this peptide could be fluorescently tagged without loss of its biological activity. In chapter 3...

Information technology in support of research, scholarship, and creative activities: A strategic plan for Research Technologies – a division of UITS and a PTI Service and Cyberinfrastructure Center

Stewart, Craig A.; Link, Matthew R.; Wernert, Eric; Barnett, William K.; Miller, Therese M.
Fonte: Universidade de Indiana Publicador: Universidade de Indiana
Tipo: Relatório
EN_US
Relevância na Pesquisa
27.46%
Stewart, C.A., M.R. Link, E. Wernert, W.K. Barnett, T.M. Miller. 2012. Information technology in support of research, scholarship, and creative activities: A strategic plan for Research Technologies – a division of UITS and a PTI Service and Cyberinfrastructure Center. Indiana University, Bloomington, IN. PTI Technical Report PTI-TR12-007.; IU is currently executing its second information technology strategic plan – Empowering People: Indiana University's Strategic Plan for Information Technology 2009 (hereafter referred to as Empowering People). In this document, we set out long-term goals for the Research Technologies (RT) division of UITS, reaffirm specific goals set for RT for 2019, describe Actions within Empowering People for which RT is responsible, and describe the new internal structure of Research Technologies. The mission of the Research Technologies division of UITS is to develop, deliver, and support advanced technology solutions that improve productivity of and enable new possibilities in research, scholarly endeavors, and creative activity at Indiana University and beyond; and to complement this with education and technology translation activities to improve the quality of life of people in Indiana, the nation, and the world.

Avaliação da relação entre produção plaquetária e expressão de proteínas do sistema apoptótico plaquetário em diferentes graus de plaquetopenia da Trombocitopenia Imune (PTI); Assessment of ratio between platelet production and apoptosis in Immune Thrombocytopenia (ITP) at different degrees of thrombocytopenia

Barros, Francisco Erivaldo Vidal
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 27/01/2015 PT
Relevância na Pesquisa
27.79%
A Trombocitopenia imune (PTI) é uma doença imuno mediada adquirida de adultos e crianças caracterizada por plaquetopenia transitória ou persistente, onde o grau de plaquetopenia aumenta o risco de sangramento. Geralmente, os pacientes apresentam manifestações clínicas apenas em plaquetopenias abaixo de 50x103/mm3, e contagem de plaquetas entre 100 e 150 x103/mm3, se estável por mais de 6 meses, necessariamente não indica uma condição patológica. Tem sido sugerido diferentes processos fisiopatológicos relacionados às plaquetas de acordo com a intensidade da plaquetopenia, e que alterações na megacariocitopoiese e diminuição da sobrevida plaquetária são eventos determinantes na PTI. Contagem de plaquetas reticuladas em citometria de fluxo é um teste muito útil para avaliação da plaquetopenia, pois reflete a atividade megacariocitopoiética, destruição das plaquetas e a própria contagem de plaquetas. Tanto as plaquetas quanto os megacariócitos apresentam a via intrínseca da apoptose. A atividade dos principais mediadores da apoptose intrínseca, como Bax a Bak, é regulada por proteínas anti-apoptótica da família Bcl-2, tais como Bcl-xL. Um balanço entre Bcl-xL e Bax regula a sobrevivência plaquetária. Pacientes de PTI apresentam aumento da ativação plaquetária e da formação de micropartículas derivadas de plaquetas (MPP). Nosso objetivo foi avaliar a relação entre produção e apoptose plaquetária...

Nucleotide sequence of the tmr locus of Agrobacterium tumefaciens pTi T37 T-DNA.

Goldberg, S B; Flick, J S; Rogers, S G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 11/06/1984 EN
Relevância na Pesquisa
27.46%
The nucleotide sequence of the tmr locus from the nopaline-type pTi T37 plasmid of Agrobacterium tumefaciens was determined. Examination of this sequence allowed us to identify an open reading frame of 720 nucleotides capable of encoding a protein with a derived molecular weight of 27025 d. Comparison of the pTi T37 tmr sequence with the published sequence of the pTi Ach5 tmr locus shows over 88% homology in the 240 bases 5' to the translational initiation codon and over 91% homology in the coding sequences. The 3' nontranslated regions show less than 50% homology as expected for the 3' regions of divergent related genes. The possible significance of areas of conserved sequences, particularly in the 5' regulatory regions, is discussed.

Identification of the human prostatic carcinoma oncogene PTI-1 by rapid expression cloning and differential RNA display.

Shen, R; Su, Z Z; Olsson, C A; Fisher, P B
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 18/07/1995 EN
Relevância na Pesquisa
27.91%
Elucidating the relevant genomic changes mediating development and evolution of prostate cancer is paramount for effective diagnosis and therapy. A putative dominant-acting nude mouse prostatic carcinoma tumor-inducing gene, PTI-1, has been cloned that is expressed in patient-derived human prostatic carcinomas but not in benign prostatic hypertrophy or normal prostate tissue. PTI-1 was detected by cotransfecting human prostate carcinoma DNA into CREF-Trans 6 cells, inducing tumors in nude mice, and isolating genes displaying increased expression in tumor-derived cells by using differential RNA display (DD). Screening a human prostatic carcinoma (LNCaP) cDNA library with a 214-bp DNA fragment found by DD permitted the cloning of a full-length 2.0-kb PTI-1 cDNA. Sequence analysis indicates that PTI-1 is a gene containing a 630-bp 5' sequence and a 3' sequence homologous to a truncated and mutated form of human elongation factor 1 alpha. In vitro translation demonstrates that the PTI-1 cDNA encodes a predominant approximately 46-kDa protein. Probing Northern blots with a DNA fragment corresponding to the 5' region of PTI-1 identifies multiple PTI-1 transcripts in RNAs from human carcinoma cell lines derived from the prostate, lung, breast...

Generación de un Plan de Acción para el PTI Salmón Aysén de la XI Región para enfrentar la expansión de la industria

Collado González, Diego Andrés
Fonte: Universidad de Chile; Programa Cybertesis Publicador: Universidad de Chile; Programa Cybertesis
Tipo: Tesis
ES
Relevância na Pesquisa
27%

The PTI Carbon Star Angular Size Survey: Effective Temperatures and Non-Sphericity

van Belle, Gerard T.; Paladini, Claudia; Aringer, Bernhard; Hron, Josef; Ciardi, David R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/07/2013
Relevância na Pesquisa
27%
We report new interferometric angular diameter observations of 41 carbon stars observed with the Palomar Testbed Interferometer (PTI). Two of these stars are CH carbon stars and represent the first such measurements for this subtype. Of these, 39 have Yamashita (1972,1975) spectral classes and are of sufficiently high quality that we may determine the dependence of effective temperature on spectral type. We find that there is a tendency for the effective temperature to increase with increasing temperature index by ~120K per step, starting at T_EFF ~= 2500K for C3,y, although there is a large amount of scatter about this relationship. Overall, the median effective temperature for the carbon star sample is found to be 2800 +- 270K, and the median linear radius is 360 +- 100 R_SUN. We also find agreement on average within 15K with the T_EFF determinations of Bergeat (2001,2002a,b), and a refinement of carbon star angular size prediction based on V & K magnitudes is presented that is good to an rms of 12%. A subsample of our stars have sufficient {u,v} coverage to permit non-spherical modeling of their photospheres, and a general tendency for detection of statistically significant departures from sphericity with increasing signal-to-noise of the interferometric data is seen. The implications of most - and potentially all - carbon stars being non-spherical is considered in the context of surface inhomogeneities and a rotation-mass loss connection.; Comment: 59 pages...

The dynamic atmospheres of Mira stars: comparing the CODEX models to PTI time series of TU And

Hillen, M.; Verhoelst, T.; Degroote, P.; Acke, B.; van Winckel, H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/01/2012
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Our comprehension of stellar evolution on the AGB still faces many difficulties. To improve on this, a quantified understanding of large-amplitude pulsator atmospheres and interpretation in terms of their fundamental stellar parameters are essential. We wish to evaluate the effectiveness of the recently released CODEX dynamical model atmospheres in representing M-type Mira variables through a confrontation with the time-resolved spectro-photometric and interferometric PTI data set of TU And. We calibrated the interferometric K-band time series to high precision. This results in 50 nights of observations, covering 8 subsequent pulsation cycles. At each phase, the flux at 2.2$\mu$m is obtained, along with the spectral shape and visibility points in 5 channels across the K-band. We compared the data set to the relevant dynamical, self-excited CODEX models. Both spectrum and visibilities are consistently reproduced at visual minimum phases. Near maximum, our observations show that the current models predict a photosphere that is too compact and hot, and we find that the extended atmosphere lacks H2O opacity. Since coverage in model parameter space is currently poor, more models are needed to make firm conclusions on the cause of the discrepancies. We argue that for TU And...

The Palomar Testbed Interferometer Calibrator Catalog

van Belle, G. T.; van Belle, G.; Creech-Eakman, M. J.; Coyne, J.; Boden, A. F.; Akeson, R. L.; Ciardi, D. R.; Rykoski, K. M.; Thompson, R. R.; Lane, B. F.; Collaboration, for The PTI
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/11/2007
Relevância na Pesquisa
27.46%
The Palomar Testbed Interferometer (PTI) archive of observations between 1998 and 2005 is examined for objects appropriate for calibration of optical long-baseline interferometer observations - stars that are predictably point-like and single. Approximately 1,400 nights of data on 1,800 objects were examined for this investigation. We compare those observations to an intensively studied object that is a suitable calibrator, HD217014, and statistically compare each candidate calibrator to that object by computing both a Mahalanobis distance and a Principal Component Analysis. Our hypothesis is that the frequency distribution of visibility data associated with calibrator stars differs from non-calibrator stars such as binary stars. Spectroscopic binaries resolved by PTI, objects known to be unsuitable for calibrator use, are similarly tested to establish detection limits of this approach. From this investigation, we find more than 350 observed stars suitable for use as calibrators (with an additional $\approx 140$ being rejected), corresponding to $\gtrsim 95%$ sky coverage for PTI. This approach is noteworthy in that it rigorously establishes calibration sources through a traceable, empirical methodology, leveraging the predictions of spectral energy distribution modeling but also verifying it with the rich body of PTI's on-sky observations.; Comment: 100 pages...