3,118 research outputs found
Characteristics of colliding sea breeze gravity current fronts : a laboratory study
Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Quarterly Journal of the Royal Meteorological Society 143 (2017): 1434–1441, doi:10.1002/qj.3015.Sea and land breeze circulations driven by surface temperature differences between
land and sea often evolve into gravity currents with sharp fronts. Along narrow
peninsulas, islands and enclosed seas, sea/land breeze fronts from opposing shorelines
may converge and collide and may initiate deep convection and heavy precipitation.
Here we investigate the collision of two sea breeze gravity current fronts in an
analogue laboratory setting. We examine these collisions by means of ‘lock-exchange’
experiments in a rectangular channel. The effects of differences in gravity current
density and height are studied. Upon collision, a sharp front separating the two currents
develops. For symmetric collisions (the same current densities and heights) this front is
vertical and stationary. For asymmetric collisions (density differences, similar heights)
the front is tilted, changes shape in time and propagates in the same direction as the
heavier current before the collision. Both symmetric and asymmetric collisions lead to
upward displacement of fluid from the gravity currents and mixing along the plane
of contact. The amount of mixing along the collision front decreases with asymmetry.
Height differences impact post-collision horizontal propagation: there is significant
propagation in the same direction as the higher current before collision, independent
of density differences. Collisions of two gravity current fronts force sustained ascending
motions which increase the potential for deep convection. From our experiments we
conclude that this potential is larger in stationary collision fronts from symmetric
sea breeze collisions than in propagating collision fronts from asymmetric sea breeze
collisions.National Science Foundation Grant Number: OCE-0824636;
Office of Naval Research Grant Number: N00014-09-1-0844;
National Aeronautics and Space Administration Grant Number: NASA NNX14A078
Alternative model of the Antonov problem
Astrophysical systems will never be in a real Thermodynamic equilibrium: they
undergo an evaporation process due to the fact that the gravity is not able to
confine the particles. Ordinarily, this difficulty is overcome by enclosing the
system in a rigid container which avoids the evaporation. We proposed an
energetic prescription which is able to confine the particles, leading in this
way to an alternative version of the Antonov isothermal model which unifies the
well-known isothermal and polytropic profiles. Besides of the main features of
the isothermal sphere model: the existence of the gravitational collapse and
the energetic region with a negative specific heat, this alternative model has
the advantage that the system size naturally appears as a consequence of the
particles evaporation.Comment: RevTex4, 9 pages, 10 figures, Version Submitted to PR
Galois theory and commutators
We prove that the relative commutator with respect to a subvariety of a
variety of Omega-groups introduced by the first author can be described in
terms of categorical Galois theory. This extends the known correspondence
between the Froehlich-Lue and the Janelidze-Kelly notions of central extension.
As an example outside the context of Omega-groups we study the reflection of
the category of loops to the category of groups where we obtain an
interpretation of the associator as a relative commutator.Comment: 14 page
One-year efficacy and safety of routine prasugrel in patients with acute coronary syndromes treated with percutaneous coronary intervention
Objective: To investigate 1‑year outcomes with routine prasugrel treatment after acute coronary syndrome (ACS) in a large-scale registry. Methods: The Rijnmond Collective Cardiology Research registry is a prospective, observational study that enrolled 4,258 consecutive ACS patients treated with percutaneous coronary intervention (PCI) with 1‑year follow-up. Patients received prasugrel as first-choice antiplatelet agent, except for increased bleeding risk patients in which clopidogrel was recommended. Events were validated by an independent clinical endpoint committee. Results: A total number of 2,677 patients received prasugrel at discharge after the index event. Eighty-one percent of the target population was on prasugrel treatment at hospital discharge. At 1 year, the primary endpoint, a composite of all-cause mortality and myocardial infarction, occurred in 2.4% of patients receiving prasugrel. All-cause mortality occurred in 1.0%, myocardial infarction in 1.5%, target-vessel revascularisation in 3.1%, stent thrombosis in 0.6%, and stroke in 0.5% of the patients treated with prasugrel. Thrombolysis in Myocardial Infarction defined major bleeding episodes not related to coronary artery bypass grafting were observed in 1.4% of patients receiving prasugrel. Conclusions: In routine practice, a tailored approach of prasugrel prescription in ACS patients undergoing PCI, resulted in low ischaemic and low bleeding rates up to 1 year post PCI
The Effect of Starburst Metallicity on Bright X-Ray Binary Formation Pathways
We investigate the characteristics of young ( 1e36
erg/s) High-Mass X-ray Binaries (HMXBs) and find the population to be strongly
metallicity-dependent. We separate the model populations among two distinct
formation pathways: (1) systems undergoing active Roche Lobe Overflow (RLO),
and (2) wind accretion systems with donors in the (super)giant (SG) stage,
which we find to dominate the HMXB population. We find metallicity to primarily
affect the number of systems which move through each formation pathway, rather
than the observable parameters of systems which move through each individual
pathway. We discuss the most important model parameters affecting the HMXB
population at both low and high metallicities. Using these results, we show
that (1) the population of ultra-luminous X-Ray sources can be consistently
described by very bright HMXBs which undergo stable Roche Lobe overflow with
mild super-Eddington accretion and (2) the HMXB population of the bright
starburst galaxy NGC~1569 is likely dominated by one extremely metal-poor
starburst cluster.Comment: 12 pages, 10 figures, Accepted by Ap
Current discharge management of acute coronary syndromes: Data from the Rijnmond Collective Cardiology Research (CCR) study
Background Medical discharge management of acute coronary syndromes (ACS) remains suboptimal outside randomised trials and constitutes an essential quality benchmark for ACS. We sought to evaluate the rates of key guideline-recommended pharmacological agents after ACS and characteristics associated with optimal treatment at discharge. Methods The Rijnmond Collective Cardiology Research (CCR) registry is an ongoing prospective, observational study in the Netherlands that aims to enrol 4000 patients with ACS. We examined discharge and 1-month follow-up medication use among the first 1000 patients enrolled in the CCR registry. Logistic regression was performed to identify patient and hospital characteristics associated with collective guidelinerecommended pharmacotherapy at hospital discharge. Results At discharge, 94%of patients received aspirin, 100% thienopyridines, 80 % angiotensin-converting enzyme inhibitors/angiotensin-II receptor blockers, 87 % β-blockers, 96 % statins, and 65 % the combination of all 5 agents. STsegment elevation myocardial infarction, hypertension, hypercholesterolaemia, and enrolment in an interventional centre were positive independent predictors of 5-drug combination therapy at discharge. Negative independent predictors were unstable angina and advanced age. Conclusion Current data from the CCR registry reflect a high quality of care for ACS discharge management in the Rotterdam-Rijnmond region. However, potential still remains for further optimisation
Feasibility, endocrine and anti-tumour effects of a triple endocrine therapy with tamoxifen, a somatostatin analogue and an antiprolactin in post-menopausal metastatic breast cancer: a randomized study with long-term follow-up.
Suppression of the secretion of prolactin, growth hormone and insulin-like growth factor 1 (IGF-1) might be important in the growth regulation and treatment of breast cancer. Because oestrogens may counteract the anti-tumour effects of such treatment, the combination of an anti-oestrogen (tamoxifen), a somatostatin analogue (octreotide) and a potent anti-prolactin (CV 205-502) might be attractive. In this respect, we performed a first exploratory long-term study on the feasibility of combined treatment and possible clear differences in endocrine and anti-tumour effects during such combined treatment vs standard treatment with tamoxifen alone. Twenty-two post-menopausal patients with metastatic breast cancer (ER and/or PR positive or unknown) were randomized to receive either 40 mg of tamoxifen per day or the combination of 40 mg of tamoxifen plus 75 microg of CV 205-502 orally plus 3 x 0.2 mg of octreotide s.c. as first-line endocrine therapy. An objective response was found in 36% of the patients treated with tamoxifen alone and in 55% of the patients treated with combination therapy. Median time to progression was 33 weeks for patients treated with tamoxifen and 84 weeks for patients treated with combination therapy, but the numbers are too small for hard conclusions. There was no difference in overall post-relapse survival between the two treatment arms. With respect to the endocrine parameters, there was a significant decrease of plasma IGF-1 levels in both treatment arms, whereas during combined treatment plasma growth hormone tended to decrease and plasma prolactin levels were strongly suppressed; in some patients insulin and transforming growth factor alpha (TGF-alpha) decreased during the triple therapy. Although there was no significant difference in mean decrease of plasma IGF-1 levels between the two treatment arms, combined treatment resulted in a more uniform suppression of IGF-1. Therefore, the addition of a somatostatin analogue and an anti-prolactin may potentially enhance the efficacy of anti-oestrogens in the treatment of breast cancer owing to favourable endocrine and possible direct anti-tumour effects. Large phase III trials using depot formulations (to increase the feasibility) of somatostatin analogues are warranted to demonstrate the potential extra beneficial anti-tumour effects of such combination therapy
Current discharge management of acute coronary syndromes: data from the Rijnmond Collective Cardiology Research (CCR) study
BACKGROUND: Medical discharge management of acute coronary syndromes (ACS) remains suboptimal outside randomised trials and constitutes an essential quality benchmark for ACS. We sought to evaluate the rates of key guideline-recommended pharmacological agents after ACS and characteristics associated with optimal treatment at discharge. METHODS: The Rijnmond Collective Cardiology Research (CCR) registry is an ongoing prospective, observational study in the Netherlands that aims to enrol 4000 patients with ACS. We examined discharge and 1-month follow-up medication use among the first 1000 patients enrolled in the CCR registry. Logistic regression was performed to identify patient and hospital characteristics associated with collective guideline-recommended pharmacotherapy at hospital discharge. RESULTS: At discharge, 94 % of patients received aspirin, 100 % thienopyridines, 80 % angiotensin-converting enzyme inhibitors/angiotensin-II receptor blockers, 87 % β-blockers, 96 % statins, and 65 % the combination of all 5 agents. ST-segment elevation myocardial infarction, hypertension, hypercholesterolaemia, and enrolment in an interventional centre were positive independent predictors of 5-drug combination therapy at discharge. Negative independent predictors were unstable angina and advanced age. CONCLUSION: Current data from the CCR registry reflect a high quality of care for ACS discharge management in the Rotterdam-Rijnmond region. However, potential still remains for further optimisation
Prediction of torsional failure in 22 cadaver femora with and without simulated subtrochanteric metastatic defects: a CT scan-based finite element analysis
BACKGROUND: In metastatic bone disease, prophylactic fixation of impending long bone fracture is preferred over surgical treatment of a manifest fracture. There are no reliable guidelines for prediction of pathological fracture risk, however. We aimed to determine whether finite element (FE) models constructed from quantitative CT scans could be used for predicting pathological fracture load and location in a cadaver model of metastatic bone disease. MATERIAL AND METHODS: Subject-specific FE models were constructed from quantitative CT scans of 11 pairs of human femora. To simulate a metastatic defect, a transcortical hole was made in the subtrochanteric region in one femur of each pair. All femora were experimentally loaded in torsion until fracture. FE simulations of the experimental set-up were performed and torsional stiffness and strain energy density (SED) distribution were determined. RESULTS: In 15 of the 22 cases, locations of maximal SED fitted with the actual fracture locations. The calculated torsional stiffness of the entire femur combined with a criterion based on the local SED distribution in the FE model predicted 82% of the variance of the experimental torsional failure load. INTERPRETATION: In the future, CT scan-based FE analysis may provide a useful tool for identification of impending pathological fractures requiring prophylactic stabilization
A computed tomography based study on rotational alignment accuracy of the femoral component in total knee arthroplasty using computer-assisted orthopaedic surgery
Rotation of the femoral component in total knee arthroplasty (TKA) is of high importance in respect of the balancing of the knee and the patellofemoral joint. Though it is shown that computer assisted surgery (CAOS) improves the anteroposterior (AP) alignment in TKA, it is still unknown whether navigation helps in finding the accurate rotation or even improving rotation. Therefore the aim of our study was to evaluate the postoperative femoral component rotation on computed tomography (CT) with the intraoperative data of the navigation system. In 20 navigated TKAs the difference between the intraoperative stored rotation data of the femoral component and the postoperative rotation on CT was measured using the condylar twist angle (CTA). This is the angle between the epicondylar axis and the posterior condylar axis. Statistical analysis consisted of the intraclass correlation coefficient (ICC) and Bland-Altman plot. The mean intraoperative rotation CTA based on CAOS was 3.5° (range 2.4–8.6°). The postoperative CT scan showed a mean CTA of 4.0° (1.7–7.2). The ICC between the two observers was 0.81, and within observers this was 0.84 and 0.82, respectively. However, the ICC of the CAOS CTA versus the postoperative CT CTA was only 0.38. Though CAOS is being used for optimising the position of a TKA, this study shows that the (virtual) individual rotational position of the femoral component using a CAOS system is significantly different from the position on a postoperative CT scan
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