34 research outputs found
Supermassive black holes do not correlate with dark matter halos of galaxies
Supermassive black holes have been detected in all galaxies that contain
bulge components when the galaxies observed were close enough so that the
searches were feasible. Together with the observation that bigger black holes
live in bigger bulges, this has led to the belief that black hole growth and
bulge formation regulate each other. That is, black holes and bulges
"coevolve". Therefore, reports of a similar correlation between black holes and
the dark matter halos in which visible galaxies are embedded have profound
implications. Dark matter is likely to be nonbaryonic, so these reports suggest
that unknown, exotic physics controls black hole growth. Here we show - based
in part on recent measurements of bulgeless galaxies - that there is almost no
correlation between dark matter and parameters that measure black holes unless
the galaxy also contains a bulge. We conclude that black holes do not correlate
directly with dark matter. They do not correlate with galaxy disks, either.
Therefore black holes coevolve only with bulges. This simplifies the puzzle of
their coevolution by focusing attention on purely baryonic processes in the
galaxy mergers that make bulges.Comment: 12 pages, 9 Postscript figures, 1 table; published in Nature (20
January 2011
Characterizing the non-linear growth of large-scale structure in the Universe
The local Universe displays a rich hierarchical pattern of galaxy clusters
and superclusters. The early Universe, however, was almost smooth, with only
slight 'ripples' seen in the cosmic microwave background radiation. Models of
the evolution of structure link these observations through the effect of
gravity, because the small initially overdense fluctuations attract additional
mass as the Universe expands. During the early stages, the ripples evolve
independently, like linear waves on the surface of deep water. As the
structures grow in mass, they interact with other in non-linear ways, more like
waves breaking in shallow water. We have recently shown how cosmic structure
can be characterized by phase correlations associated with these non-linear
interactions, but hitherto there was no way to use that information to reach
quantitative insights into the growth of structures. Here we report a method of
revealing phase information, and quantify how this relates to the formation of
a filaments, sheets and clusters of galaxies by non-linear collapse. We use a
new statistic based on information entropy to separate linear from non-linear
effects and thereby are able to disentangle those aspects of galaxy clustering
that arise from initial conditions (the ripples) from the subsequent dynamical
evolution.Comment: Accepted for publication in Nature. For high-resolution Figure 3,
please see http://www.nottingham.ac.uk/~ppzpc/phases/n0colorphase.html, For
the animations and the idea of this paper please see
http://www.nottingham.ac.uk/~ppzpc/phases/index.htm
Role of Combination Antiplatelet and Anticoagulation Therapy in Diabetes Mellitus and Cardiovascular Disease: Insights From the COMPASS Trial
BACKGROUND: Patients with established coronary artery disease or peripheral artery disease often have diabetes mellitus. These patients are at high risk of future vascular events.METHODS: In a prespecified analysis of the COMPASS trial (Cardiovascular Outcomes for People Using Anticoagulation Strategies), we compared the effects of rivaroxaban (2.5 mg twice daily) plus aspirin (100 mg daily) versus placebo plus aspirin in patients with diabetes mellitus versus without diabetes mellitus in preventing major vascular events. The primary efficacy end point was the composite of cardiovascular death, myocardial infarction, or stroke. Secondary end points included all-cause mortality and all major vascular events (cardiovascular death, myocardial infarction, stroke, or major adverse limb events, including amputation). The primary safety end point was a modification of the International Society on Thrombosis and Haemostasis criteria for major bleeding.RESULTS: There were 10 341 patients with diabetes mellitus and 17 054 without diabetes mellitus in the overall trial. A consistent and similar relative risk reduction was seen for benefit of rivaroxaban plus aspirin (n=9152) versus placebo plus aspirin (n=9126) in patients both with (n=6922) and without (n=11 356) diabetes mellitus for the primary efficacy end point (hazard ratio, 0.74, P=0.002; and hazard ratio, 0.77,P=0.005, respectively, Pinteraction=0.77) and all-cause mortality (hazard ratio, 0.81, P=0.05; and hazard ratio, 0.84,P=0.09, respectively; Pinteraction=0.82). However, although the absolute risk reductions appeared numerically larger in patients with versus without diabetes mellitus, both subgroups derived similar benefit (2.3% versus 1.4% for the primary efficacy end point at 3 years, Gail-Simon qualitative PinteractionPinteraction=0.02; 2.7% versus 1.7% for major vascular events, PinteractionPinteraction=0.001).CONCLUSIONS: In stable atherosclerosis, the combination of aspirin plus rivaroxaban 2.5 mg twice daily provided a similar relative degree of benefit on coronary, cerebrovascular, and peripheral end points in patients with and without diabetes mellitus. Given their higher baseline risk, the absolute benefits appeared larger in those with diabetes mellitus, including a 3-fold greater reduction in all-cause mortality. Registration: Unique identifier: NCT01776424.</div
Transcriptome profiling of Pinus radiata juvenile wood with contrasting stiffness identifies putative candidate genes involved in microfibril orientation and cell wall mechanics
<p>Abstract</p> <p>Background</p> <p>The mechanical properties of wood are largely determined by the orientation of cellulose microfibrils in secondary cell walls. Several genes and their allelic variants have previously been found to affect microfibril angle (MFA) and wood stiffness; however, the molecular mechanisms controlling microfibril orientation and mechanical strength are largely uncharacterised. In the present study, cDNA microarrays were used to compare gene expression in developing xylem with contrasting stiffness and MFA in juvenile <it>Pinus radiata </it>trees in order to gain further insights into the molecular mechanisms underlying microfibril orientation and cell wall mechanics.</p> <p>Results</p> <p>Juvenile radiata pine trees with higher stiffness (HS) had lower MFA in the earlywood and latewood of each ring compared to low stiffness (LS) trees. Approximately 3.4 to 14.5% out of 3, 320 xylem unigenes on cDNA microarrays were differentially regulated in juvenile wood with contrasting stiffness and MFA. Greater variation in MFA and stiffness was observed in earlywood compared to latewood, suggesting earlywood contributes most to differences in stiffness; however, 3-4 times more genes were differentially regulated in latewood than in earlywood. A total of 108 xylem unigenes were differentially regulated in juvenile wood with HS and LS in at least two seasons, including 43 unigenes with unknown functions. Many genes involved in cytoskeleton development and secondary wall formation (cellulose and lignin biosynthesis) were preferentially transcribed in wood with HS and low MFA. In contrast, several genes involved in cell division and primary wall synthesis were more abundantly transcribed in LS wood with high MFA.</p> <p>Conclusions</p> <p>Microarray expression profiles in <it>Pinus radiata </it>juvenile wood with contrasting stiffness has shed more light on the transcriptional control of microfibril orientation and the mechanical properties of wood. The identified candidate genes provide an invaluable resource for further gene function and association genetics studies aimed at deepening our understanding of cell wall biomechanics with a view to improving the mechanical properties of wood.</p
On the Origin of S0 Galaxies
I will review the basic properties of S0 galaxies in the local Universe in
relation to both elliptical and spiral galaxies, their neighbours on the Hubble
sequence, and also in relation to dwarf spheroidal (dSph) galaxies. This will
include colours, luminosities, spectral features, information about the age and
metallicity composition of their stellar populations and globular clusters,
about their ISM content, as well as kinematic signatures and their implications
for central black hole masses and past interaction events, and the number
ratios of S0s to other galaxy types in relation to environmental galaxy
density. I will point out some caveats as to their morphological discrimination
against other classes of galaxies, discuss the role of dust and the wavelength
dependence of bulge/disk light ratios. These effects are of importance for
investigations into the redshift evolution of S0 galaxies -- both as individual
objects and as a population. The various formation and transformation scenarios
for S0 and dSph galaxies will be presented and confronted with the available
observations.Comment: Invited Review, 18 pages, ``BARS 2004'' Conference, South Africa,
June 2004, eds.: K. C. Freeman, D. L. Block, I. Puerari, R. Groess, Kluwer,
in pres
Rationale, Design and Baseline Characteristics of Participants in the Cardiovascular Outcomes for People Using Anticoagulation Strategies (COMPASS) Trial
BACKGROUND: Long-term aspirin prevents vascular events but is only modestly effective. Rivaroxaban alone or in combination with aspirin might be more effective than aspirin alone for vascular prevention in patients with stable coronary artery disease (CAD) or peripheral artery disease (PAD). Rivaroxaban as well as aspirin increase upper gastrointestinal (GI) bleeding and this might be prevented by proton pump inhibitor therapy. METHODS: Cardiovascular Outcomes for People Using Anticoagulation Strategies (COMPASS) is a double-blind superiority trial comparing rivaroxaban 2.5 mg twice daily combined with aspirin 100 mg once daily or rivaroxaban 5 mg twice daily vs aspirin 100 mg once daily for prevention of myocardial infarction, stroke, or cardiovascular death in patients with stable CAD or PAD. Patients not taking a proton pump inhibitor were also randomized, using a partial factorial design, to pantoprazole 40 mg once daily or placebo. The trial was designed to have at least 90% power to detect a 20% reduction in each of the rivaroxaban treatment arms compared with aspirin and to detect a 50% reduction in upper GI complications with pantoprazole compared with placebo. RESULTS: Between February 2013 and May 2016, we recruited 27,395 participants from 602 centres in 33 countries; 17,598 participants were included in the pantoprazole vs placebo comparison. At baseline, the mean age was 68.2 years, 22.0% were female, 90.6% had CAD, and 27.3% had PAD. CONCLUSIONS: COMPASS will provide information on the efficacy and safety of rivaroxaban, alone or in combination with aspirin, in the long-term management of patients with stable CAD or PAD, and on the efficacy and safety of pantoprazole in preventing upper GI complications in patients receiving antithrombotic therapy