1,001 research outputs found
PAIRWISE VELOCITIES OF GALAXIES IN THE CFA AND SSRS2 REDSHIFT SURVEYS
(compressed version) We combine the CfA Redshift Survey (CfA2) and the
Southern Sky Redshift Survey (SSRS2) to estimate the pairwise velocity
dispersion of galaxies \sig12 on a scale of \sim 1 \hmpc. Both surveys are
complete to an apparent magnitude limit . Our sample includes 12,812
galaxies distributed in a volume 1.8 \times 10^6 \hmpc3. We conclude: 1) The
pairwise velocity dispersion of galaxies in the combined CfA2+SSRS2 redshift
survey is \sig12=540 \kms \pm 180 \kms. Both the estimate and the variance of
\sig12 significantly exceed the canonical values \sig12=340 \pm40 measured
by Davis \& Peebles (1983) using CfA1. 2) We derive the uncertainty in \sig12
from the variation among subsamples with volumes on the order of \hmpc3. This variation is nearly an order of magnitude larger than the
formal error, 36 \kms, derived using least-squares fits to the CfA2+SSRS2
correlation function. This variation among samples is consistent with the
conclusions of Mo \etal (1993) for a number of smaller surveys and with the
analysis of CfA1 by Zurek \etal (1994). 3) When we remove Abell clusters with
from our sample, the pairwise velocity dispersion of the remaining
galaxies drops to 295 \pm 99 \kms. Thus the dominant source of variance in
\sig12 is the shot noise contributed by dense virialized systems. 4) The
distribution of pairwise velocities is consistent with an isotropic exponential
with velocity dispersion independent of scale.Comment: 61 pages uuencoded, compressed postscript in 5 pieces. Also available
in one piece at http://www.dao.nrc.ca/DAO/SCIENCE/science.htm
Adenovirus-mediated gene transfer to liver grafts: An improved method to maximize infectivity
Background. Adenoviral gene therapy in liver transplantation has many potential applications, but current vector delivery methods to grafts lack efficiency and require high titers. In this study, we attempted to improve gene delivery efficacy using three different delivery methods to liver grafts with adenoviral vector encoding the LacZ marker gene (AdLacZ). Methods. AdLacZ was delivered to cold preserved rat liver grafts by: (1) continuous perfusion via the portal vein (portal perfusion), (2) continuous perfusion via both the portal vein and hepatic artery (dual perfusion), and (3) trapping viral perfusate in the liver vasculature by clamping outflow (clamp technique). Results. Using 1x109 plaque-forming units of Ad-LacZ (multiplicity of infection of 0.4), transduction rate in 3-hr preserved liver grafts, determined by 5-bromo-4-chromo-3-indolyl-β-D-galactopyranoside staining and β-galactosidase assay 48 hr after transplantation, was best with clamp technique (21.5±2.7% 5-bromo-4-chromo-3-indolyl-β-D- galactopyranoside-positive cells and 81.1±3.6 U/g β-galactosidase), followed by dual perfusion (18.5±1.8%, 66.6±19.4 U/g) and portal perfusion (8.8±2.5%, 19.7±15.4 U/g). Further studies using clamp technique demonstrated a near-maximal gene transfer rate of 30% at multiplicity of infection of 0.4 with prolonged cold ischemia to 18 hr. Transgene expression was stable for 2 weeks and slowly declined to 7.8±12.1% at day 28. Lack of inflammatory response was confirmed by histopathological examination and liver enzymes. Transduction was selectively induced in hepatocytes with nearly no extrahepatic transgene expression in the lung and spleen. Conclusions. The clamp technique provides a highly efficient viral gene delivery method to cold preserved liver grafts. This method offers maximal infectivity of adenoviral vector with minimal technical manipulation
The Power Spectrum of Galaxies in the Nearby Universe
We compute the power spectrum of galaxy density fluctuations in a recently
completed redshift survey of optically-selected galaxies in the southern
hemisphere (SSRS2). The amplitude and shape of the SSRS2 power spectrum are
consistent with results of the Center for Astrophysics redshift survey of the
northern hemisphere (CfA2), including the abrupt change of slope on a scale of
30-50Mpc/h; these results are reproducible for independent volumes of space and
variations are consistent with the errors estimated from mock surveys. Taken
together, the SSRS2 and CfA2 form a complete sample of 14,383 galaxies which
covers one-third of the sky. The power spectrum of this larger sample continues
to rise on scales up to ~ 200Mpc/h, with weak evidence for flattening on the
largest scales. The SSRS2+CfA2 power spectrum and the power spectrum
constraints implied by COBE are well-matched by an Omega*h ~ 0.2,
Omega+lambda_0=1 CDM model with minimal biasing of optically-selected galaxies.Comment: Accepted for publication in The Astrophysical Journal Letters, Sept.
23, 1994. 10 pages uuencoded compressed postscript, including two figures.
JHU-9410200
Hepatic resection for metastatic colorectal adenocarcinoma: A proposal of a prognostic scoring system
Background: Hepatic resection for metastatic colorectal cancer provides excellent longterm results in a substantial proportion of patients. Although various prognostic risk factors have been identified, there has been no dependable staging or prognostic scoring system for metastatic hepatic tumors. Study Design: Various clinical and pathologic risk factors were examined in 305 consecutive patients who underwent primary hepatic resections for metastatic colorectal cancer. Survival rates were estimated by the Cox proportional hazards model using the equation: S(t) = [S(o)(t)](exp(R - R(o))), where S(o)(t) is the survival rate of patients with none of the identified risk factors and R(o) = 0. Results: Preliminary multivariate analysis revealed that independently significant negative prognosticators were: (1) positive surgical margins, (2) extrahepatic tumor involvement including the lymph node(s), (3) tumor number of three or more, (4) bilobar tumors, and (5) time from treatment of the primary tumor to hepatic recurrence of 30 months or less. Because the survival rates of the 62 patients with positive margins or extrahepatic tumor were uniformly very poor, multivariate analysis was repeated in the remaining 243 patients who did not have these lethal risk factors. The reanalysis revealed that independently significant poor prognosticators were: (1) tumor number of three or more, (2) tumor size greater than 8 cm, (3) time to hepatic recurrence of 30 months or less, and (4) bilobar tumors. Risk scores (R) for tumor recurrence of the culled cohort (n = 243) were calculated by summation of coefficients from the multivariate analysis and were divided into five groups: grade 1, no risk factors (R = 0); grade 2, one risk factor (R = 0.3 to 0.7); grade 3, two risk factors (R = 0.7 to 1.1); grade 4, three risk factors (R = 1.2 to 1.6); and grade 5, four risk factors (R > 1.6). Grade 6 consisted of the 62 culled patients with positive margins or extrahepatic tumor. Kaplan-Meier and Cox proportional hazards estimated 5-year survival rates of grade 1 to 6 patients were 48.3% and 48.3%, 36.6% and 33.7%, 19.9% and 17.9%, 11.9% and 6.4%, 0% and 1.1%, and 0% and 0%, respectively (p < 0.0001). Conclusions: The proposed risk-score grading predicted the survival differences extremely well. Estimated survival as determined by the Cox proportional hazards model was similar to that determined by the Kaplan-Meier method. Verification and further improvements of the proposed system are awaited by other centers or international collaborative studies
Alunos surdos dos anos iniciais do ensino fundamental e a construção do número
Este artigo analisa resultados de uma pesquisa de Mestrado sobre o ensino de conceitos numéricos iniciais com alunos surdos nos dois primeiros anos do Ensino Fundamental, em uma unidade especializada na educação de surdos. Por meio de uma abordagem qualitativa, constituíram-se reflexões sobre a importância do ensino ser pautado na língua de sinais e nas características pertinentes ao aluno surdo. O software Jclic configurou-se em uma ferramenta de auxílio à elaboração e aplicação de atividades, contribuindo para a aquisição dos conceitos numéricos e proporcionando opções de ludicidade e recursos para uma abordagem bilíngue, o que envolveu de maneira significativa os alunos na realização das tarefas
Compact Group Selection From Redshift Surveys
For the first time, we construct a catalog of compact groups selected from a
complete, magnitude-limited redshift survey. We select groups with
members based on projected separation and association in redshift space alone.
We evaluate the characteristics of the Redshift Survey Compact Groups (RSCG's).
Their physical properties (membership frequency, velocity dispersion, density)
are similar to those of the Hickson [ApJ, 255, 382 (1982)] Compact Groups.
Hickson's isolation criterion is a strong function of the physical and angular
group radii and is a poor predictor of the group environment. In fact, most
RSCG's are embedded in dense environments. The luminosity function for RSCG's
is mildly inconsistent with the survey luminosity function --- the
characteristic luminosity is brighter and the faint end shallower for the RSCG
galaxies. We construct a model of the selection function of compact groups.
Using this selection function, we estimate the abundance of RSCG's; for groups
with members the abundance is . For
all RSCG's () the abundance is .Comment: 41 pages, LaTeX, including 20 figures and 9 tables. Accepted for
publication in The Astronomical Journal. Figures 3 and 4 available at
ftp://cfa0.harvard.edu/outgoing/barto
Non-Gaussian velocity distributions - The effect on virial mass estimates of galaxy groups
We present a study of 9 galaxy groups with evidence for non-Gaussianity in
their velocity distributions out to 4R200. This sample is taken from 57 groups
selected from the 2PIGG catalog of galaxy groups. Statistical analysis
indicates that non-Gaussian groups have masses significantly higher than
Gaussian groups. We also have found that all non-Gaussian systems seem to be
composed of multiple velocity modes. Besides, our results indicate that
multimodal groups should be considered as a set of individual units with their
own properties. In particular, we have found that the mass distribution of such
units are similar to that of Gaussian groups. Our results reinforce the idea of
non-Gaussian systems as complex structures in the phase space, likely
corresponding to secondary infall aggregations at a stage before virialization.
The understanding of these objects is relevant for cosmological studies using
groups and clusters through the mass function evolution.Comment: 5 pages, 4 figures and 2 tables. Accepted for publication in the
MNRA
Cenário do uso educacional de redes sociais na região metropolitana de Porto Alegre/RS
sociedade, contudo, essa realidade não se reflete totalmente em sala de aula. Este artigo apresenta reflexões sobre um cenário do uso educacional de redes sociais na região metropolitana de Porto Alegre/RS, baseado em pesquisa realizada com 1.027 alunos e65 professores, através de questionários e entrevistas semiestruturadas. Para a análise dos dados coletados, utilizou-se o paradigma qualiquantitativo de investigação,apresentando reflexões sobre o perfil dos alunos, professores e diretores de escolas em relação ao uso de redes sociais na educação, aspectos positivos e principais entravespara o uso educacional das redes sociais
High Abilities or Giftedness in Integrated High-School Education: Perceptions of Mathematics Teachers
Background: The identification of the first ability or gifted students at the Federal Institute Sul-Rio-Grandense (IFSul), Campus Sapucaia do Sul, raised the need to analyse the mathematics teachers’ perceptions of the subject in the institute, intending to professionalise the attention offered to these students. Objectives: This article sought to present and reflect on how seven mathematics teachers of the integrated high school understand high abilities or giftedness. Design: Qualitative approach, participant observation, and interpretive and descriptive data analysis. Setting and participants: This study is part of a doctoral research involving seven mathematics teachers who work in regular classes at a Federal Institute in the metropolitan region of Porto Alegre. Data collection and analysis: The data were collected through a semi-structured interview, and their analysis was inspired by the descriptive-interpretive analysis. Results: Although lacking theoretical depth, mathematics teachers’ perceptions of the concept and characteristics of high abilities or giftedness are close to the theories presented and the current legislation. Conclusions: It is necessary to professionalise the processes of identification and assistance to high-ability/gifted students on campus, which is foreseen in a research project through continuing education
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