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Search Results: 1 - 10 of 320190 matches for " Katherine J. Martin "
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Growing the gas-giant planets by the gradual accumulation of pebbles
Harold F. Levison,Katherine A. Kretke,Martin J. Duncan
Physics , 2015, DOI: 10.1038/nature14675
Abstract: It is widely held that the first step in forming the gas giant planets, such as Jupiter and Saturn, is to form solid `cores' of roughly 10 M$_\oplus$. Getting the cores to form before the solar nebula dissipates ($\sim\!1-10\,$Myr) has been a major challenge for planet formation models. Recently models have emerged in which `pebbles' (centimeter- to meter-size objects) are first concentrated by aerodynamic drag and then gravitationally collapse to form 100 --- 1000 km objects. These `planetesimals' can then efficiently accrete leftover pebbles and directly form the cores of giant planets. This model known as `pebble accretion', theoretically, can produce 10 M$_\oplus$ cores in only a few thousand years. Unfortunately, full simulations of this process show that, rather than creating a few 10 M$_\oplus$ cores, it produces a population of hundreds of Earth-mass objects that are inconsistent with the structure of the Solar System. Here we report that this difficulty can be overcome if pebbles form slowly enough to allow the planetesimals to gravitationally interact with one another. In this situation the largest planetesimals have time to scatter their smaller siblings out of the disk of pebbles, thereby stifling their growth. Our models show that, for a large, and physically reasonable region of parameter space, this typically leads to the formation of one to four gas giants between 5 and 15 AU in agreement with the observed structure of the Solar System.
Prognostic Breast Cancer Signature Identified from 3D Culture Model Accurately Predicts Clinical Outcome across Independent Datasets
Katherine J. Martin, Denis R. Patrick, Mina J. Bissell, Marcia V. Fournier
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0002994
Abstract: Background One of the major tenets in breast cancer research is that early detection is vital for patient survival by increasing treatment options. To that end, we have previously used a novel unsupervised approach to identify a set of genes whose expression predicts prognosis of breast cancer patients. The predictive genes were selected in a well-defined three dimensional (3D) cell culture model of non-malignant human mammary epithelial cell morphogenesis as down-regulated during breast epithelial cell acinar formation and cell cycle arrest. Here we examine the ability of this gene signature (3D-signature) to predict prognosis in three independent breast cancer microarray datasets having 295, 286, and 118 samples, respectively. Methods and Findings Our results show that the 3D-signature accurately predicts prognosis in three unrelated patient datasets. At 10 years, the probability of positive outcome was 52, 51, and 47 percent in the group with a poor-prognosis signature and 91, 75, and 71 percent in the group with a good-prognosis signature for the three datasets, respectively (Kaplan-Meier survival analysis, p<0.05). Hazard ratios for poor outcome were 5.5 (95% CI 3.0 to 12.2, p<0.0001), 2.4 (95% CI 1.6 to 3.6, p<0.0001) and 1.9 (95% CI 1.1 to 3.2, p = 0.016) and remained significant for the two larger datasets when corrected for estrogen receptor (ER) status. Hence the 3D-signature accurately predicts breast cancer outcome in both ER-positive and ER-negative tumors, though individual genes differed in their prognostic ability in the two subtypes. Genes that were prognostic in ER+ patients are AURKA, CEP55, RRM2, EPHA2, FGFBP1, and VRK1, while genes prognostic in ER? patients include ACTB, FOXM1 and SERPINE2 (Kaplan-Meier p<0.05). Multivariable Cox regression analysis in the largest dataset showed that the 3D-signature was a strong independent factor in predicting breast cancer outcome. Conclusions The 3D-signature accurately predicts breast cancer outcome across multiple datasets and holds prognostic value for both ER-positive and ER-negative breast cancer. The signature was selected using a novel biological approach and hence holds promise to represent the key biological processes of breast cancer.
The Course of Well-Being in Romantic Relationships: Predicting Positive Affect in Dating Participants  [PDF]
Katherine J. Bao
Psychology (PSYCH) , 2012, DOI: 10.4236/psych.2012.312A161
Abstract:

People use different methods to make themselves happier, but their attempts at lasting happiness are often thwarted by the hedonic adaptation process. We examined changes in well-being over 8 weeks in participants who were involved in romantic relationships and those who were not. On average, both groups declined in well-being over time, but the relationship group experienced more positive emotions overall. High positive affect was predicted by higher aspirations, higher passionate love, and being in a same-ethnicity relationship. None of the variables we measured significantly predicted changes in positive affect over time, which may be due to the short duration of the study.

Skyrmions and Semilocal Strings in Cosmology
Katherine Benson,Martin Bucher
Physics , 1993, DOI: 10.1016/0550-3213(93)90172-L
Abstract: It has been pointed out that cosmic string solutions can exist in gauge field theories with broken symmetry even when $\pi _1(G/H)$ is trivial. The stability of such semilocal defects is not guaranteed by topology and depends on dynamical considerations. In the literature it has been tacitly assumed that if stable, such strings would form in the Early Universe in a manner analogous to the formation of a network of more robust topologically-stable strings. In this paper we find that except for unnaturally small values of the correlation length, a network of semilocal strings does not form. Instead, delocalized skyrmionic string configurations, which expand with the Hubble flow, dominate.
Survey of stress ulcer prophylaxis
Brian L Erstad, Jeffrey F Barletta, Judith Jacobi, Aaron D Killian, Katherine M Kramer, Steven J Martin
Critical Care , 1999, DOI: 10.1186/cc368
Abstract: Three hundred sixty-eight surveys were sent to all members of theSection of Pharmacy and Pharmacology of the Society of Critical Care Medicine.One hundred fifty-three (42%) surveys were returned. Representatives from 86%of institutions stated that medications for stress ulcer prophylaxis are usedin a majority (>90%) of patients admitted to the intensive care unit (ICU).Twenty-two per cent of institutions have recommendations for both ICU andnon-ICU settings. Fifty-eight per cent of institutions stated that there wasone preferred medication for stress ulcer prophylaxis, and in 77% of thesehistamine-2-antagonists were the most popular.There are wide variations in prescribing practices for stressulcer prophylaxis. Institutions should consult published literature and usepre-existing guidelines as templates for developing their own guidelines.Stress-induced gastroduodenal erosions are a frequent occurrence in critically ill patients, but it is the incidence of clinically important complications resulting from these erosions that is important in deciding which patients should receive prophylaxis. Clinically important complications include bleeding that requires transfusion, bleeding associated with hemodynamic instability, and gastrointestinal perforations. Failure to document these complications in published studies limits the conclusions that can be drawn from much of the available literature. There have been inconsistent results in those studies that did record clinically important bleeding, depending on severity of illness or injury, and concomitant or underlying disease states.Because the results of clinical investigations have led to different recommendations concerning stress ulcer prophylaxis, Cook et al [1] performed a meta-analysis of randomized trials to resolve the controversies associated with previous research in this area. They concluded that there was no clear agent of choice for prophylaxis based on efficacy considerations (ie ability to prevent clinicall
Epimorphin Alters the Inhibitory Effects of SOX9 on Mmp13 in Activated Hepatic Stellate Cells
James Pritchett, Varinder S. Athwal, Emma Harvey, Katherine Martin, Jessica Llewellyn, Philip Ireland, Alexander Nicolaides, Martin J. Humphries, Nicoletta Bobola, Neil A. Hanley, Karen Piper Hanley
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0100091
Abstract: Background and Aims Liver fibrosis is a major cause of morbidity and mortality. It is characterised by excessive extracellular matrix (ECM) deposition from activated hepatic stellate cells (HSCs). Although potentially reversible, treatment remains limited. Understanding how ECM influences the pathogenesis of the disease may provide insight into novel therapeutic targets for the disease. The extracellular protein Epimorphin (EPIM) has been implicated in tissue repair mechanisms in several tissues, partially, through its ability to manipulate proteases. In this study, we have identified that EPIM modulates the ECM environment produced by activated hepatic stellate cells (HSCs), in part, through down-regulation of pro-fibrotic Sex-determining region Y-box 9 (SOX9). Methods Influence of EPIM on ECM was investigated in cultured primary rat HSCs. Activated HSCs were treated with recombinant EPIM or SOX9 siRNA. Core fibrotic factors were evaluated by immunoblotting, qPCR and chromatin immunoprecipitation (ChIP). Results During HSC activation EPIM became significantly decreased in contrast to pro-fibrotic markers SOX9, Collagen type 1 (COL1), and α- Smooth muscle actin (α-SMA). Treatment of activated HSCs with recombinant EPIM caused a reduction in α-SMA, SOX9, COL1 and Osteopontin (OPN), while increasing expression of the collagenase matrix metalloproteinase 13 (MMP13). Sox9 abrogation in activated HSCs increased EPIM and MMP13 expression. Conclusion These data provide evidence for EPIM and SOX9 functioning by mutual negative feedback to regulate attributes of the quiescent or activated state of HSCs. Further understanding of EPIM's role may lead to opportunities to modulate SOX9 as a therapeutic avenue for liver fibrosis.
Risk factors for poor virological outcome at 12 months in a workplace-based antiretroviral therapy programme in South Africa: A cohort study
Katherine L Fielding, Salome Charalambous, Amy L Stenson, Lindiwe F Pemba, Des J Martin, Robin Wood, Gavin J Churchyard, Alison D Grant
BMC Infectious Diseases , 2008, DOI: 10.1186/1471-2334-8-93
Abstract: Among ART-na?ve individuals in a workplace ART programme in South Africa we determined virological outcomes at 12 months, and risk factors for suboptimal virological outcome, defined as plasma HIV-1 viral load >= 400 copies/ml.Among 1760 individuals starting ART before July 2004, 1172 were in follow-up at 12 months of whom 953 (81%) had a viral load measurement (median age 41 yrs, 96% male, median baseline CD4 count 156 × 106/l). 71% (681/953) had viral load < 400 copies/ml at 12 months. In a multivariable analysis, independent predictors of suboptimal virological outcome at 12 months were <1 log decrease in viral load at six weeks (odds ratio [OR] 4.71, 95% confidence interval [CI] 2.56–8.68), viral load at baseline (OR 3.63 [95% CI 1.88–7.00] and OR 3.54 [95% CI 1.79–7.00] for 10,001–100,000 and >100,000 compared to <= 10,000 copies/ml, respectively), adherence at six weeks (OR 3.50 [95% CI 1.92–6.35]), WHO stage (OR 2.08 [95% CI 1.28–3.34] and OR 2.03 [95% CI 1.14–3.62] for stage 3 and 4 compared to stage 1–2, respectively) and site of ART delivery. Site of delivery remained an independent risk factor even after adjustment for individual level factors. At 6 weeks, of 719 patients with self-reported adherence and viral load, 72 (10%) reported 100% adherence but had <1 log decrease in viral load; conversely, 60 (8%) reported <100% adherence but had >= 1 log decrease in viral load.Virological response at six weeks after ART start was the strongest predictor of suboptimal virological outcome at 12 months, and may identify individuals who need interventions such as additional adherence support. Self reported adherence was less strongly associated but identified different patients compared with viral load at 6 weeks. Site of delivery had an important influence on virological outcomes; factors at the health system level which influence outcome need further investigation to guide development of effective ART programmes.An unprecedented effort by global organisations, gov
Viewing Learning Through a New Lens: The Quantum Perspective of Learing  [PDF]
Katherine J. Janzen, Beth Perry, Margaret Edwards
Creative Education (CE) , 2012, DOI: 10.4236/ce.2012.36106
Abstract: We are living in a quantum world where virtuality allows us to transcend time and space. Boundaries, which were considered to be predetermined, are no longer absolute. This has important implications for the field of education as educators advance e-learning. However, education theory has been outpaced by practice. In this paper the authors propose a new learning perspective— the quantum perspective of learning which moves beyond current popular educational theories of constructivism (Siemens, 2005) and connectivism (Vygotsky, 1978). The five assumptions of the quantum perspective of learning are explored. Specifically, learning is multi-dimensional, occurs in various planes simultaneously, consists of potentialities which exist infinitely, is holistic/holographic in nature and is patterned within holographic realities, and learning environments are living systems. Implications that arise from this perspective are discussed.
From Genes to Milk: Genomic Organization and Epigenetic Regulation of the Mammary Transcriptome
Danielle G. Lemay, Katherine S. Pollard, William F. Martin, Courtneay Freeman Zadrowski, Joseph Hernandez, Ian Korf, J. Bruce German, Monique Rijnkels
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0075030
Abstract: Even in genomes lacking operons, a gene's position in the genome influences its potential for expression. The mechanisms by which adjacent genes are co-expressed are still not completely understood. Using lactation and the mammary gland as a model system, we explore the hypothesis that chromatin state contributes to the co-regulation of gene neighborhoods. The mammary gland represents a unique evolutionary model, due to its recent appearance, in the context of vertebrate genomes. An understanding of how the mammary gland is regulated to produce milk is also of biomedical and agricultural importance for human lactation and dairying. Here, we integrate epigenomic and transcriptomic data to develop a comprehensive regulatory model. Neighborhoods of mammary-expressed genes were determined using expression data derived from pregnant and lactating mice and a neighborhood scoring tool, G-NEST. Regions of open and closed chromatin were identified by ChIP-Seq of histone modifications H3K36me3, H3K4me2, and H3K27me3 in the mouse mammary gland and liver tissue during lactation. We found that neighborhoods of genes in regions of uniquely active chromatin in the lactating mammary gland, compared with liver tissue, were extremely rare. Rather, genes in most neighborhoods were suppressed during lactation as reflected in their expression levels and their location in regions of silenced chromatin. Chromatin silencing was largely shared between the liver and mammary gland during lactation, and what distinguished the mammary gland was mainly a small tissue-specific repertoire of isolated, expressed genes. These findings suggest that an advantage of the neighborhood organization is in the collective repression of groups of genes via a shared mechanism of chromatin repression. Genes essential to the mammary gland's uniqueness are isolated from neighbors, and likely have less tolerance for variation in expression, properties they share with genes responsible for an organism's survival.
Detection of a High Brightness Temperature Radio Core in the AGN-Driven Molecular Outflow Candidate NGC 1266
Kristina Nyland,Katherine Alatalo,J. M. Wrobel,Lisa M. Young,Raffaella Morganti,Timothy A. Davis,P. T. de Zeeuw,Susana Deustua,Martin Bureau
Physics , 2013, DOI: 10.1088/0004-637X/779/2/173
Abstract: We present new high spatial resolution Karl G. Jansky Very Large Array (VLA) HI absorption and Very Long Baseline Array (VLBA) continuum observations of the Active Galactic Nucleus (AGN)-driven molecular outflow candidate NGC 1266. Although other well-known systems with molecular outflows may be driven by star formation in a central molecular disk, the molecular mass outflow rate reported in Alatalo et al. (2011) in NGC 1266 of 13 M$_{\odot}$ year$^{-1}$ exceeds star formation rate estimates from a variety of tracers. This suggests that an additional energy source, such as an AGN, may play a significant role in powering the outflow. Our high spatial resolution HI absorption data reveal compact absorption against the radio continuum core co-located with the putative AGN, and the presence of a blueshifted spectral component re-affirms that gas is indeed flowing out of the system. Our VLBA observations at 1.65 GHz reveal one continuum source within the densest portion of the molecular gas, with a diameter d < 8 mas (1.2 pc), a radio power $P_{\mathrm{rad}}$ = 1.48 $\times$ 10$^{20}$ W Hz$^{-1}$, and a brightness temperature $T_{\mathrm{b}}$ > 1.5 x 10$^7$ K that is most consistent with an AGN origin. The radio continuum energetics implied by the compact VLBA source, as well as archival VLA continuum observations at lower spatial resolution, further support the possibility that the AGN in NGC 1266 could be driving the molecular outflow. These findings suggest that even low-level AGNs may be able to launch massive outflows in their host galaxies.
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