38 research outputs found
Tests of the Las Campanas Distant Cluster Survey from Confirmation Observations for the ESO Distant Cluster Survey
The ESO Distant Cluster Survey (EDisCS) is a photometric and spectroscopic
study of the galaxy cluster population at two epochs, z~0.5 and z~0.8, drawn
from the Las Campanas Distant Cluster Survey (LCDCS). We report results from
the initial candidate confirmation stage of the program and use these results
to probe the properties of the LCDCS. Of the 30 candidates targeted, we find
statistically significant overdensities of red galaxies near 28. Of the ten
additional candidates serendipitously observed within the fields of the
targeted 30, we detect red galaxy overdensities near six. We test the
robustness of the published LCDCS estimated redshifts to misidentification of
the brighest cluster galaxy (BCG) in the survey data, and measure the spatial
alignment of the published cluster coordinates, the peak red galaxy
overdensity, and the brightest cluster galaxy. We conclude that for LCDCS
clusters out to z~0.8, 1) the LCDCS coordinates agree with the centroid of the
red galaxy overdensity to within 25'' (~150 h^{-1} kpc) for 34 out of 37
candidates with 3\sigma galaxy overdensities, 2) BCGs are typically coincident
with the centroid of the red galaxy population to within a projected separation
of 200 h^{-1} kpc (32 out of 34 confirmed candidates), 3) the red galaxy
population is strongly concentrated, and 4) the misidentification of the BCG in
the LCDCS causes a redshift error >0.1 in 15-20% of the LCDCS candidates. These
findings together help explain the success of the surface brightness
fluctuations detection method.Comment: 10 pages, 9 figures, accepted for publication in the November 10
issue of Ap
Hyperspectral microarray scanning: impact on the accuracy and reliability of gene expression data
BACKGROUND: Commercial microarray scanners and software cannot distinguish between spectrally overlapping emission sources, and hence cannot accurately identify or correct for emissions not originating from the labeled cDNA. We employed our hyperspectral microarray scanner coupled with multivariate data analysis algorithms that independently identify and quantitate emissions from all sources to investigate three artifacts that reduce the accuracy and reliability of microarray data: skew toward the green channel, dye separation, and variable background emissions. RESULTS: Here we demonstrate that several common microarray artifacts resulted from the presence of emission sources other than the labeled cDNA that can dramatically alter the accuracy and reliability of the array data. The microarrays utilized in this study were representative of a wide cross-section of the microarrays currently employed in genomic research. These findings reinforce the need for careful attention to detail to recognize and subsequently eliminate or quantify the presence of extraneous emissions in microarray images. CONCLUSION: Hyperspectral scanning together with multivariate analysis offers a unique and detailed understanding of the sources of microarray emissions after hybridization. This opportunity to simultaneously identify and quantitate contaminant and background emissions in microarrays markedly improves the reliability and accuracy of the data and permits a level of quality control of microarray emissions previously unachievable. Using these tools, we can not only quantify the extent and contribution of extraneous emission sources to the signal, but also determine the consequences of failing to account for them and gain the insight necessary to adjust preparation protocols to prevent such problems from occurring
Isolation of quiescent and nonquiescent cells from yeast stationary-phase cultures
Quiescence is the most common and, arguably, most poorly understood cell cycle state. This is in part because pure populations of quiescent cells are typically difficult to isolate. We report the isolation and characterization of quiescent and nonquiescent cells from stationary-phase (SP) yeast cultures by density-gradient centrifugation. Quiescent cells are dense, unbudded daughter cells formed after glucose exhaustion. They synchronously reenter the mitotic cell cycle, suggesting that they are in a G0 state. Nonquiescent cells are less dense, heterogeneous, and composed of replicatively older, asynchronous cells that rapidly lose the ability to reproduce. Microscopic and flow cytometric analysis revealed that nonquiescent cells accumulate more reactive oxygen species than quiescent cells, and over 21 d, about half exhibit signs of apoptosis and necrosis. The ability to isolate both quiescent and nonquiescent yeast cells from SP cultures provides a novel, tractable experimental system for studies of quiescence, chronological and replicative aging, apoptosis, and the cell cycle
The Las Campanas Distant Cluster Survey - The Catalog
We present an optically-selected catalog of 1073 galaxy cluster and group
candidates at 0.3<z<1. These candidates are drawn from the Las Campanas Distant
Clusters Survey (LCDCS), a drift-scan imaging survey of a 130 square degree
strip of the southern sky. To construct this catalog we utilize a novel
detection process in which clusters are detected as positive surface brightness
fluctuations in the background sky. This approach permits us to find clusters
with significantly shallower data than other matched-filter methods that are
based upon number counts of resolved galaxies. Selection criteria for the
survey are fully automated so that this sample constitutes a well-defined,
homogeneous sample that can be used to address issues of cluster evolution and
cosmology. Estimated redshifts are derived for the entire sample, and an
observed correlation between surface brightness and velocity dispersion (sigma)
is used to estimate the limiting velocity dispersion of the survey as a
function of redshift. We find a net surface density of 15.5 candidates per
square degree at z_{est}>0.3, with a false-detection rate of 30%. At z=0.3 we
probe down to the level of poor groups while by z=0.8 we detect only the most
massive systems (sigma>1000 km/s). We also present a supplemental catalog of
112 candidates that fail one or more of the automated selection criteria, but
appear from visual inspection to be bona fide clusters.Comment: 44 pages including 22 figures. Accepted to ApJS. Minor change in
section
3D Brownian Diffusion of Submicron-Sized Particle Clusters
We report on the translation and rotation of particle clusters made through
the combination of spherical building blocks. These clusters present ideal
model systems to study the motion of objects with complex shape. Because they
could be separated into fractions of well-defined configurations on a
sufficient scale and their overall dimensions were below 300 nm, the
translational and rotational diffusion coefficients of particle duplets,
triplets and tetrahedrons could be determined by a combination of polarized
dynamic light scattering (DLS) and depolarized dynamic light scattering (DDLS).
The use of colloidal clusters for DDLS experiments overcomes the limitation of
earlier experiments on the diffusion of complex objects near surfaces because
the true 3D diffusion can be studied. When the exact geometry of the complex
assemblies is known, different hydrodynamic models for calculating the
diffusion coefficient for objects with complex shapes could be applied. Because
hydrodynamic friction must be restricted to the cluster surface the so-called
shell model, in which the surface is represented as a shell of small friction
elements, was most suitable to describe the dynamics. A quantitative comparison
of the predictions from theoretical modeling with the results obtained by DDLS
showed an excellent agreement between experiment and theory
Characteristics and outcomes of over 300,000 patients with COVID-19 and history of cancer in the United States and Spain
Background: We described the demographics, cancer subtypes, comorbidities, and outcomes of patients with a history of cancer and coronavirus disease 2019 (COVID-19). Second, we compared patients hospitalized with COVID-19 to patients diagnosed with COVID-19 and patients hospitalized with influenza. Methods: We conducted a cohort study using eight routinely collected health care databases from Spain and the United States, standardized to the Observational Medical Outcome Partnership common data model. Three cohorts of patients with a history of cancer were included: (i) diagnosed with COVID-19, (ii) hospitalized with COVID-19, and (iii) hospitalized with influenza in 2017 to 2018. Patients were followed from index date to 30 days or death. We reported demographics, cancer subtypes, comorbidities, and 30-day outcomes. Results: We included 366,050 and 119,597 patients diagnosed and hospitalized with COVID-19, respectively. Prostate and breast cancers were the most frequent cancers (range: 5%–18% and 1%–14% in the diagnosed cohort, respectively). Hematologic malignancies were also frequent, with non-Hodgkin’s lymphoma being among the five most common cancer subtypes in the diagnosed cohort. Overall, patients were aged above 65 years and had multiple comorbidities. Occurrence of death ranged from 2% to 14% and from 6% to 26% in the diagnosed and hospitalized COVID-19 cohorts, respectively. Patients hospitalized with influenza (n ¼ 67,743) had a similar distribution of cancer subtypes, sex, age, and comorbidities but lower occurrence of adverse events. Conclusions: Patients with a history of cancer and COVID-19 had multiple comorbidities and a high occurrence of COVID-19-related events. Hematologic malignancies were frequent. Impact: This study provides epidemiologic characteristics that can inform clinical care and etiologic studies.</p
Circulating microRNAs in sera correlate with soluble biomarkers of immune activation but do not predict mortality in ART treated individuals with HIV-1 infection: A case control study
Introduction: The use of anti-retroviral therapy (ART) has dramatically reduced HIV-1 associated morbidity and mortality. However, HIV-1 infected individuals have increased rates of morbidity and mortality compared to the non-HIV-1 infected population and this appears to be related to end-organ diseases collectively referred to as Serious Non-AIDS Events (SNAEs). Circulating miRNAs are reported as promising biomarkers for a number of human disease conditions including those that constitute SNAEs. Our study sought to investigate the potential of selected miRNAs in predicting mortality in HIV-1 infected ART treated individuals. Materials and Methods: A set of miRNAs was chosen based on published associations with human disease conditions that constitute SNAEs. This case: control study compared 126 cases (individuals who died whilst on therapy), and 247 matched controls (individuals who remained alive). Cases and controls were ART treated participants of two pivotal HIV-1 trials. The relative abundance of each miRNA in serum was measured, by RTqPCR. Associations with mortality (all-cause, cardiovascular and malignancy) were assessed by logistic regression analysis. Correlations between miRNAs and CD4+ T cell count, hs-CRP, IL-6 and D-dimer were also assessed. Results: None of the selected miRNAs was associated with all-cause, cardiovascular or malignancy mortality. The levels of three miRNAs (miRs -21, -122 and -200a) correlated with IL-6 while miR-21 also correlated with D-dimer. Additionally, the abundance of miRs -31, -150 and -223, correlated with baseline CD4+ T cell count while the same three miRNAs plus miR- 145 correlated with nadir CD4+ T cell count. Discussion: No associations with mortality were found with any circulating miRNA studied. These results cast doubt onto the effectiveness of circulating miRNA as early predictors of mortality or the major underlying diseases that contribute to mortality in participants treated for HIV-1 infection
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High throughput instruments, methods, and informatics for systems biology.
High throughput instruments and analysis techniques are required in order to make good use of the genomic sequences that have recently become available for many species, including humans. These instruments and methods must work with tens of thousands of genes simultaneously, and must be able to identify the small subsets of those genes that are implicated in the observed phenotypes, or, for instance, in responses to therapies. Microarrays represent one such high throughput method, which continue to find increasingly broad application. This project has improved microarray technology in several important areas. First, we developed the hyperspectral scanner, which has discovered and diagnosed numerous flaws in techniques broadly employed by microarray researchers. Second, we used a series of statistically designed experiments to identify and correct errors in our microarray data to dramatically improve the accuracy, precision, and repeatability of the microarray gene expression data. Third, our research developed new informatics techniques to identify genes with significantly different expression levels. Finally, natural language processing techniques were applied to improve our ability to make use of online literature annotating the important genes. In combination, this research has improved the reliability and precision of laboratory methods and instruments, while also enabling substantially faster analysis and discovery
Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study
Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research