268 research outputs found
Casimir forces in binary liquid mixtures
If two ore more bodies are immersed in a critical fluid critical fluctuations
of the order parameter generate long ranged forces between these bodies. Due to
the underlying mechanism these forces are close analogues of the well known
Casimir forces in electromagnetism. For the special case of a binary liquid
mixture near its critical demixing transition confined to a simple parallel
plate geometry it is shown that the corresponding critical Casimir forces can
be of the same order of magnitude as the dispersion (van der Waals) forces
between the plates. In wetting experiments or by direct measurements with an
atomic force microscope the resulting modification of the usual dispersion
forces in the critical regime should therefore be easily detectable. Analytical
estimates for the Casimir amplitudes Delta in d=4-epsilon are compared with
corresponding Monte-Carlo results in d=3 and their quantitative effect on the
thickness of critical wetting layers and on force measurements is discussed.Comment: 34 pages LaTeX with revtex and epsf style, to appear in Phys. Rev.
AGN Feedback Driven Molecular Outflow in NGC 1266
NGC 1266 is a nearby field galaxy observed as part of the ATLAS3D survey
(Cappellari et al. 2011). NGC 1266 has been shown to host a compact (< 200 pc)
molecular disk and a mass-loaded molecular outflow driven by the AGN (Alatalo
et al. 2011). Very Long Basline Array (VLBA) observations at 1.65 GHz revealed
a compact (diameter < 1.2 pc), high bright- ness temperature continuum source
most consistent with a low-level AGN origin. The VLBA continuum source is
positioned at the center of the molecular disk and may be responsible for the
expulsion of molecular gas in NGC 1266. Thus, the candidate AGN-driven
molecular outflow in NGC 1266 supports the picture in which AGNs do play a
significant role in the quenching of star formation and ultimately the
evolution of the red sequence of galaxies.Comment: 2 pages, Proceedings from IAU Symposium 290: Feeding compact objects,
Accretion on all scale
Quenching of Star Formation in Molecular Outflow Host NGC 1266
We detail the rich molecular story of NGC 1266, its serendipitous discovery
within the ATLAS3D survey (Cappellari et al. 2011) and how it plays host to an
AGN-driven molecular outflow, potentially quenching all of its star formation
(SF) within the next 100 Myr. While major mergers appear to play a role in
instigating outflows in other systems, deep imaging of NGC 1266 as well as
stellar kinematic observations from SAURON, have failed to provide evidence
that NGC 1266 has recently been involved in a major interaction. The molecular
gas and the instantaneous SF tracers indicate that the current sites of star
formation are located in a hypercompact disk within 200 pc of the nucleus (Fig.
1; SF rate ~ 2 Msuns/yr). On the other hand, tracers of recent star formation,
such as the H{\beta} absorption map from SAURON and stellar population analysis
show that the young stars are distributed throughout a larger area of the
galaxy than current star formation. As the AGN at the center of NGC 1266
continues to drive cold gas out of the galaxy, we expect star formation rates
to decline as the star formation is ultimately quenched. Thus, NGC 1266 is in
the midst of a key portion of its evolution and continued studies of this
unique galaxy may help improve our understanding of how galaxies transition
from the blue to the red sequence (Alatalo et al. 2011).Comment: 1 page, Proceedings IAU symposium No. 292: Molecular gas, dust and
star formation in galaxies, ed. by Tony Wong and Juergen Ot
A stacked search for intermediate-mass black holes in 337 extragalactic star clusters
Forbes et al. recently used the Hubble Space Telescope to localize hundreds
of candidate star clusters in NGC 1023, an early-type galaxy at a distance of
11.1 Mpc. Old stars dominate the light of 92% of the clusters and
intermediate-age stars dominate the light of the remaining 8%. Theory predicts
that clusters with such ages can host intermediate-mass black holes (IMBHs)
with masses M_BH \lesssim 10^5 M_sun. To investigate this prediction, we used
264 s of 5.5 GHz data from the Karl G. Jansky Very Large Array (VLA) to search
for the radiative signatures of IMBH accretion from 337 candidate clusters in
an image spanning 492 arcsec (26 kpc) with a resolution of 0.40 arcsec (22 pc).
None of the individual clusters are detected, nor are weighted-mean image
stacks of the 311 old clusters, the 26 intermediate-age clusters, and the 20
clusters with stellar masses M_star \gtrsim 7.5 x 10^5 M_sun. The clusters thus
lack radio analogs of HLX-1, a strong IMBH candidate in a cluster in the
early-type galaxy ESO 243-49. This suggests that HLX-1 is accreting gas related
to its cluster's light-dominating young stars. Alternatively, the HLX-1
phenomenon could be so rare that no radio analog is expected in NGC 1023. Also,
using a formalism heretofore applied to star clusters in the Milky Way, the
radio-luminosity upper limit for the massive-cluster stack corresponds to a
mean 3 IMBH mass of M_BH(massive) < 2.3 x 10^5 M_sun, suggesting mean
black-hole mass fractions of M_BH(massive)/M_star < 0.05-0.29.Comment: 19 pages; 6 figures; accepted by A
Torsional stability of interference screws derived from bovine bone - a biomechanical study
Introduction: It has been proposed that individual genetic variation contributes to the course of severe infections and sepsis. Recent studies of single nucleotide polymorphisms (SNPs) within the endotoxin receptor and its signaling system showed an association with the risk of disease development. This study aims to examine the response associated with genetic variations of TLR4, the receptor for bacterial LPS, and a central intracellular signal transducer (TIRAP/Mal) on cytokine release and for susceptibility and course of severe hospital acquired infections in distinct patient populations. Methods: Three intensive care units in tertiary care university hospitals in Greece and Germany participated. 375 and 415 postoperative patients and 159 patients with ventilator associated pneumonia (VAP) were included. TLR4 and TIRAP/Mal polymorphisms in 375 general surgical patients were associated with risk of infection, clinical course and outcome. In two prospective studies, 415 patients following cardiac surgery and 159 patients with newly diagnosed VAP predominantly caused by Gram-negative bacteria were studied for cytokine levels in-vivo and after ex-vivo monocyte stimulation and clinical course. Results: Patients simultaneously carrying polymorphisms in TIRAP/Mal and TLR4 and patients homozygous for the TIRAP/Mal SNP had a significantly higher risk of severe infections after surgery (odds ratio (OR) 5.5; confidence interval (CI): 1.34 - 22.64; P = 0.02 and OR: 7.3; CI: 1.89 - 28.50; P < 0.01 respectively). Additionally we found significantly lower circulating cytokine levels in double-mutant individuals with ventilator associated pneumonia and reduced cytokine production in an ex-vivo monocyte stimulation assay, but this difference was not apparent in TIRAP/Mal-homozygous patients. In cardiac surgery patients without infection, the cytokine release profiles were not changed when comparing different genotypes. Conclusions: Carriers of mutations in sequential components of the TLR signaling system may have an increased risk for severe infections. Patients with this genotype showed a decrease in cytokine release when infected which was not apparent in patients with sterile inflammation following cardiac surgery
Mercury exposure, malaria, and serum antinuclear/antinucleolar antibodies in amazon populations in Brazil: a cross-sectional study
BACKGROUND: Mercury is an immunotoxic metal that induces autoimmune disease in rodents. Highly susceptible mouse strains such as SJL/N, A.SW, B10.S (H-2(s)) develop multiple autoimmune manifestations after exposure to inorganic mercury, including lymphoproliferation, elevated levels of autoantibodies, overproduction of IgG and IgE, and circulating immune complexes in kidney and vasculature. A few studies have examined relationships between mercury exposures and adverse immunological reactions in humans, but there is little evidence of mercury-associated autoimmunity in humans. METHODS: To test the immunotoxic effects of mercury in humans, we studied communities in Amazonian Brazil with well-characterized exposures to mercury. Information was collected on diet, mercury exposures, demographic data, and medical history. Antinuclear and antinucleolar autoantibodies (ANA and ANoA) were measured by indirect immunofluorescence. Anti-fibrillarin autoantibodies (AFA) were measured by immunoblotting. RESULTS: In a gold mining site, there was a high prevalence of ANA and ANoA: 40.8% with detectable ANoA at ≥1:10 serum dilution, and 54.1% with detectable ANA (of which 15% had also detectable ANoA). In a riverine town, where the population is exposed to methylmercury by fish consumption, both prevalence and levels of autoantibodies were lower: 18% with detectable ANoA and 10.7% with detectable ANA. In a reference site with lower mercury exposures, both prevalence and levels of autoantibodies were much lower: only 2.0% detectable ANoA, and only 7.1% with detectable ANA. In the gold mining population, we also examined serum for AFA in those subjects with detectable ANoA (≥1:10). There was no evidence for mercury induction of this autoantibody. CONCLUSIONS: This is the first study to report immunologic changes, indicative of autoimmune dysfunction in persons exposed to mercury, which may also reflect interactions with infectious disease and other factors
ALMA constraints on star-forming gas in a prototypical z=1.5 clumpy galaxy: the dearth of CO(5-4) emission from UV-bright clumps
We present deep ALMA CO(5-4) observations of a main sequence, clumpy galaxy at z = 1.5 in the HUDF. Thanks to the ∼0.500 resolution of the ALMA data, we can link stellar population properties to the CO(5-4) emission on scales of a few kpc. We detect strong CO(5-4) emission from the nuclear region of the galaxy, consistent with the observed LIR–L 0 CO(5−4) correlation and indicating on-going nuclear star formation. The CO(5-4) gas component appears more concentrated than other star formation tracers or the dust distribution in this galaxy. We discuss possible implications of this difference in terms of star formation efficiency and mass build-up at the galaxy centre. Conversely, we do not detect any CO(5-4) emission from the UV-bright clumps. This might imply that clumps have a high star formation efficiency (although they do not display unusually high specific star formation rates) and are not entirely gas dominated, with gas fractions no larger than that of their host galaxy (∼50%). Stellar feedback and disk instability torques funnelling gas towards the galaxy centre could contribute to the relatively low gas content. Alternatively, clumps could fall in a more standard star formation efficiency regime if their actual star-formation rates are lower than generally assumed. We find that clump star-formation rates derived with several different, plausible methods can vary by up to an order of magnitude. The lowest estimates would be compatible with a CO(5-4) non-detection even for main-sequence like values of star formation efficiency and gas content
The Evolution of Management Models: A Neo-Schumpeterian Theory
In the last century and a half, U.S. industry has seen the emergence of several different management models. We propose a theory of this evolution based on three nested and interacting processes. First, we identify several successive waves of technological revolution, each of which prompted a corresponding wave of change in the dominant organizational paradigm. Second, nested within these waves, each of these organizational paradigms emerged through two successive cycles—a primary cycle that generated a new management model making the prior organizational paradigm obsolete, and a secondary cycle that generated another model that mitigated the dysfunctions of the primary cycle’s model. Third, nested within each cycle is a problem-solving process in which each model’s development passed through four main phases: (1) identification of a widespread organizational and management problem, (2) creation of innovative managerial concepts that offer various solutions to this problem, (3) emergence and theorization of a new model from among these concepts, and (4) dissemination and diffusion of this model. By linking new models’ emergence to specific technological revolutions, we can explain changes in their contents. By integrating a dialectical account of the paired cycles with an account of the waves of paradigm change, we can see how apparently competing models are better understood as complementary pairs in a common paradigm. And by unpacking each model’s phases of development, we can identify the roles played by various actors and management concepts in driving change in the models’ contents and see the agency behind these structural changes
- …