364 research outputs found
Optimal Layout for a Component Grid
Several puzzle games include a specific type of optimization problem: given components that produce and consume different resources and a grid of squares, find the optimal way to place the components to maximize output. I developed a method to evaluate potential solutions quickly and automated the solving of the problem using a genetic algorithm
Erythropoietin response in critically ill mechanically ventilated patients: a prospective observational study
INTRODUCTION: Anemia is a common problem in critically ill patients. The etiology of anemia of critical illness is often determined to be multifactorial in the clinical setting, but the pathophysiology remains to be elucidated. Erythropoietin (EPO) is an endogenous glycoprotein hormone that serves as the primary stimulus for erythropoiesis. Recent evidence has demonstrated a blunted EPO response as a factor contributing to anemia of critical illness in specific subsets of patients. Critically ill patients requiring mechanical ventilation who exhibit anemia have not been the subject of previous studies. Our goal was to evaluate the erythropoietic response to anemia in the critically ill mechanically ventilated patient. METHODS: A prospective observational study was undertaken in the medical intensive care unit of a tertiary care, military hospital. Twenty patients admitted to the medical intensive care unit requiring mechanical ventilation for at least 72 hours were enrolled as study patients. EPO levels and complete blood count were measured 72 hours after admission and initiation of mechanical ventilation. Admission clinical and demographic data were recorded, and patients were followed for the duration of mechanical ventilation. Twenty patients diagnosed with iron deficiency anemia in the outpatient setting were enrolled as a control population. Control patients had baseline complete blood count and iron panel recorded by primary care physicians. EPO levels were measured at the time of enrollment in conjunction with complete blood count. RESULTS: The mean EPO level for the control population was 60.9 mU/ml. The mean EPO level in the mechanically ventilated patient group was 28.7 mU/ml, which was significantly less than in the control group (P = 0.035). The mean hemoglobin value was not significantly different between groups (10.6 g/dl in mechanically ventilated patients versus 10.2 g/dl in control patients; P > 0.05). CONCLUSION: Mechanically ventilated patients demonstrate a blunted EPO response to anemia. Further study of therapies directed at treating anemia of critical illness and evaluating its potential impact on mechanical ventilation outcomes and mortality is warranted
High Mass Star Formation. II. The Mass Function of Submillimeter Clumps in M17
We have mapped an approximately 5.5 by 5.5 pc portion of the M17 massive
star-forming region in both 850 and 450 micron dust continuum emission using
the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk
Maxwell Telescope (JCMT). The maps reveal more than 100 dusty clumps with
deconvolved linear sizes of 0.05--0.2 pc and masses of 0.8--120 solar masses,
most of which are not associated with known mid-infrared point sources. Fitting
the clump mass function with a double power law gives a mean power law exponent
of alpha_high = -2.4 +/- 0.3 for the high-mass power law, consistent with the
exponent of the Salpeter stellar mass function. We show that a lognormal clump
mass distribution with a peak at about 4 solar masses produces as good a fit to
the clump mass function as does a double power law. This 4 solar mass peak mass
is well above the peak masses of both the stellar initial mass function and the
mass function of clumps in low-mass star-forming regions. Despite the
difference in intrinsic mass scale, the shape of the M17 clump mass function
appears to be consistent with the shape of the core mass function in low-mass
star-forming regions. Thus, we suggest that the clump mass function in
high-mass star-forming regions may be a scaled-up version of that in low-mass
regions, instead of its extension to higher masses.Comment: 33 pages, 6 figures, 3 tables. Accepted for publication in the
Astrophysical Journa
The Spectral Energy Distribution of Self-gravitating Interstellar Clouds I. Spheres
We derive the spectral energy distribution (SED) of dusty, isothermal, self
gravitating, stable and spherical clouds externally heated by the ambient
interstellar radiation field. For a given radiation field and dust properties,
the radiative transfer problem is determined by the pressure of the surrounding
medium and the cloud mass expressed as a fraction of the maximum stable cloud
mass above which the clouds become gravitational unstable.
To solve the radiative transfer problem a ray-tracing code is used to
accurately derive the light distribution inside the cloud. This code considers
both non isotropic scattering on dust grains and multiple scattering events.
The dust properties inside the clouds are assumed to be the same as in the
diffuse interstellar medium in our galaxy. We analyse the effect of the
pressure, the critical mass fraction, and the ISRF on the SED and present
brightness profiles in the visible, the IR/FIR and the submm/mm regime with the
focus on the scattered emission and the thermal emission from PAH-molecules and
dust grains.Comment: accepted for publication in ApJS, May 2008, v176n1 issu
S and P-wave heavy-light mesons in lattice NRQCD
The mass spectrum of S and P-wave mesons containing a single heavy quark is
computed in the quenched approximation, using NRQCD up to third order in the
inverse heavy quark mass expansion. Previous results found third order
contributions which are as large in magnitude as the total second order
contribution for the charmed S-wave spin splitting. The present work considers
variations such as anisotropic lattices, Landau link tadpole improvement, and a
highly-improved light quark action, and finds that the second order correction
to the charmed S-wave spin splitting is about 20% of the leading order
contribution, while the third order correction is about 20%(10%) for
D^*-D(D_s^*-D_s). Nonleading corrections are very small for the bottom meson
spectrum, and are statistically insignificant for the P-wave charmed masses.
The relative orderings among P-wave charmed and bottom mesons, and the sizes of
the mass splittings, are discussed in light of experimental data and existing
calculations.Comment: 21 pages including 6 figures, changed method of fitting correlators,
this version to be published in Phys Rev
Hypoxia-induced downregulation of microRNA-186-5p in endothelial cells promotes non-small cell lung cancer angiogenesis by upregulating protein kinase C alpha
The tumor microenvironment stimulates the angiogenic activity of endothelial cells (ECs) to facilitate tumor vascularization,
growth, and metastasis. The involvement of microRNA-186-5p
(miR-186) in regulating the aberrant activity of tumor-associated ECs has so far not been clarified. In the present study,
we demonstrated that miR-186 is significantly downregulated
in ECs microdissected from human non-small cell lung cancer
(NSCLC) tissues compared with matched non-malignant lung
tissues. In vitro analyses of primary human dermal microvascular ECs (HDMECs) exposed to different stimuli indicated
that this miR-186 downregulation is triggered by hypoxia
via activation of hypoxia-inducible factor 1 alpha (HIF1a).
Transfection of HDMECs with miR-186 mimic (miR-186m)
significantly inhibited their proliferation, migration, tube
formation, and spheroid sprouting. In contrast, miR-186
inhibitor (miR-186i) exerted pro-angiogenic effects. In vivo,
endothelial miR-186 overexpression inhibited the vascularization of Matrigel plugs and the initial growth of tumors
composed of NSCLC cells (NCI-H460) and HDMECs. Mechanistic analyses revealed that the gene encoding for protein
kinase C alpha (PKCa) is a bona fide target of miR-186. Activation of this kinase significantly reversed the miR-186mrepressed angiogenic activity of HDMECs. These findings
indicate that downregulation of miR-186 in ECs mediates hypoxia-stimulated NSCLC angiogenesis by upregulating PKCa
Suppression of endothelial miR-22 mediates non-small cell lung cancer cell-induced angiogenesis
MicroRNAs (miRNAs) expressed in endothelial cells (ECs) are
powerful regulators of angiogenesis, which is essential for
tumor growth and metastasis. Here, we demonstrated that
miR-22 is preferentially and highly expressed in ECs, while
its endothelial level is significantly downregulated in human
non-small cell lung cancer (NSCLC) tissues when compared
to matched nontumor lung tissues. This reduction of endothelial miR-22 is possibly induced by NSCLC cell-secreted interleukin-1b and subsequently activated transcription factor
nuclear factor-kB. Endothelial miR-22 functions as a potent
angiogenesis inhibitor that inhibits all of the key angiogenic
activities of ECs and consequently NSCLC growth through
directly targeting sirtuin 1 and fibroblast growth factor receptor 1 in ECs, leading to inactivation of AKT/mammalian target
of rapamycin signaling. These findings provide insight into the
molecular mechanisms of NSCLC angiogenesis and indicate
that endothelial miR-22 represents a potential target for the
future antiangiogenic treatment of NSCLC
High Mass Star Formation I: The Mass Distribution of Submillimeter Clumps in NGC 7538
We present submillimeter continuum maps at 450 and 850 microns of a 12 x 8
arcminute region of the NGC 7538 high-mass star-forming region, made using the
Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell
Telescope. We used an automated clump-finding algorithm to identify 67 clumps
in the 450 micron image and 77 in the 850 micron image. Contrary to previous
studies, we find a positive correlation between high spectral index, alpha, and
high submillimeter flux, with the difference being accounted for by different
treatments of the error beam. We interpret the higher spectral index at
submillimeter peaks as a reflection of elevated dust temperature, particularly
when there is an embedded infrared source, though it may also reflect changing
dust properties. The clump mass-radius relationship is well-fit by a power law
of the form M \propto R^(-x) with x = 1.5-2.1, consistent with theories of
turbulently-supported clumps. According to our most reliable analysis, the
high-mass end (approx. 100-2700 M_sun) of the submillimeter clump mass function
in NGC 7538 follows a Salpeter-like power law with index 2.0 +/- 0.3. This
result agrees well with similar studies of lower-mass regions rho Oph and Orion
B. We interpret the apparent invariance of the shape of the clump mass function
over a broad range of parent cloud masses as evidence for the self-similarity
of the physical processes which determine it. This result is consistent with
models which suggest that turbulent fragmentation, acting at early times, is
sufficient to set the clump mass function.Comment: 37 pages, 7 figures, accepted for publication in Ap
Microstructural characterization of natural fractures and faults in the Opalinus Clay: insights from a deep drilling campaign across central northern Switzerland
Abstract The Middle-Jurassic Opalinus Clay is the foreseen host rock for radioactive waste disposal in central northern Switzerland. An extensive drilling campaign aiming to characterize the argillaceous formation resulted in a comprehensive drill core data set. The rheologically weak Opalinus Clay is only mildly deformed compared to the over- and underlying rock units but shows a variety of natural fractures. While these structures are hydraulically indistinguishable from macroscopically non-deformed Opalinus Clay today, their analysis allows for a better understanding of the deformation behaviour in the geological past. Here, we present an overview of the different fracture and fault types recorded in the Opalinus Clay and a detailed microstructural characterization of veins—natural dilational fractures healed by secondary calcite and celestite mineralizations. Macroscopic drill core analysis revealed five different natural fracture types that encompass tension gashes of various orientations with respect to bedding and small-scale faults with displacements typically not exceeding the drill core diameter. The occurrence of different fault types generally fits well with the local tectonic setting of the different drilling sites and with respect to the neighbouring regional fault zones. The microstructural investigations of the various vein types revealed their often polyphase character. Fibrous bedding-parallel veins of presumable early age were found to be overprinted by secondary slickenfibres. The polyphase nature of fibrous bedding parallel veins and slickenfibres is supported by differing elemental compositions, pointing towards repeated fracturing and mineralization events. Direct dating of vein calcites with U–Pb was unsuccessful. Nevertheless, age constraints can be inferred from structural orientations and fault slip kinematics. Accordingly, some of the veins already formed during sediment compaction in Mesozoic times, others possibly relate to Early Cenozoic foreland uplift. The youngest veins are most likely related to Late Cenozoic regional tectonic events, such as the Jura fold-and-thrust belt to the south and the Hegau-Lake Constance Graben to the northeast of the study area. During these latest tectonic events, previously formed veins acted as rheologically stiff discontinuities in the otherwise comparably weak Opalinus Clay along which deformation of the rock formation was re-localized
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