902 research outputs found
On the growth of ammonium nitrate(III) crystals
The growth rate of NH4NO3 phase III crystals is measured and interpreted using two models. The first is a standard crystal growth model based on a spiral growth mechanism, the second outlines the concept of kinetical roughening. As the crystal becomes rough a critical supersaturation can be determined and from this the step free energy. The step free energy versus temperature turns out to be well represented by a Kosterlitz¿Thouless type model. Further a phenomenological treatment of some peculiar growth observations is given
Parallel Shooting Sequential Quadratic Programming for Nonlinear MPC Problems
In this paper, we propose a parallel shooting algorithm for solving nonlinear
model predictive control problems using sequential quadratic programming. This
algorithm is built on a two-phase approach where we first test and assess
sequential convergence over many initial trajectories in parallel. However, if
none converge, the algorithm starts varying the Newton step size in parallel
instead. Through this parallel shooting approach, it is expected that the
number of iterations to converge to an optimal solution can be decreased.
Furthermore, the algorithm can be further expanded and accelerated by
implementing it on GPUs. We illustrate the effectiveness of the proposed
Parallel Shooting Sequential Quadratic Programming (PS-SQP) method in some
benchmark examples for nonlinear model predictive control. The developed PS-SQP
parallel solver converges faster on average and especially when significant
nonlinear behaviour is excited in the NMPC horizon.Comment: 7 pages, 6 figures, submitted and accepted for the 7th IEEE
Conference on Control Technology and Applications (CCTA) 202
Strain engineering in Ge/GeSn core/shell nanowires
Strain engineering in Sn-rich group IV semiconductors is a key enabling
factor to exploit the direct band gap at mid-infrared wavelengths. Here, we
investigate the effect of strain on the growth of GeSn alloys in a Ge/GeSn
core/shell nanowire geometry. Incorporation of Sn content in the 10-20 at.%
range is achieved with Ge core diameters ranging from 50nm to 100nm. While the
smaller cores lead to the formation of a regular and homogeneous GeSn shell,
larger cores lead to the formation of multi-faceted sidewalls and broadened
segregation domains, inducing the nucleation of defects. This behavior is
rationalized in terms of the different residual strain, as obtained by
realistic finite element method simulations. The extended analysis of the
strain relaxation as a function of core and shell sizes, in comparison with the
conventional planar geometry, provides a deeper understanding of the role of
strain in the epitaxy of metastable GeSn semiconductors
A2626 and Friends:Large- And Small-scale Structure
New MMT/Hectospec spectroscopy centered on the galaxy cluster A2626 and
covering a area out to more than
doubles the number of galaxy redshifts in this region. The spectra confirm four
clusters previously identified photometrically. A2625, which was previously
thought to be a close neighbor of A2626, is in fact much more distant. The new
data show six substructures associated with A2626 and five more associated with
A2637. There is also a highly collimated collection of galaxies and galaxy
groups between A2626 and A2637 having at least three and probably four
substructures. At larger scales, the A2626--A2637 complex is not connected to
the Pegasus--Perseus filament.Comment: 18 pages, 13 figures, accepted for publication in the Astronomical
Journa
Equilibrium morphology of incommensurately modulated crystals: a superspace description
Hypoxia-Inducible Factor-1 as a Therapeutic Target in Endometrial Cancer Management
In the Western world, endometrial cancer (EC) is the most common malignant tumor of the female genital tract. Solid tumors like EC outgrow their vasculature resulting in hypoxia. Tumor hypoxia is important because it renders an aggressive phenotype and leads to radio- and chemo-therapy resistance. Hypoxia-inducible factor-1α (HIF-1α) plays an essential role in the adaptive cellular response to hypoxia and is associated with poor clinical outcome in EC. Therefore, HIF-1 could be an attractive therapeutic target. Selective HIF-1 inhibitors have not been identified. A number of nonselective inhibitors which target signaling pathways upstream or downstream HIF-1 are known to decrease HIF-1α protein levels. In clinical trials for the treatment of advanced and/or recurrent EC are the topoisomerase I inhibitor Topotecan, mTOR-inhibitor Rapamycin, and angiogenesis inhibitor Bevacizumab. Preliminary data shows encouraging results for these agents. Further work is needed to identify selective HIF-1 inhibitors and to translate these into clinical trials
Neutral hydrogen in the nearby galaxies Dwingeloo 1 and Dwingeloo 2
We present observations made with the Westerbork Synthesis Radio Telescope of HI emission from Dwingeloo 1, a nearby barred spiral discovered during the Dwingeloo Obscured Galaxies Survey for galaxies hidden in the Zone of Avoidance, and of Dwingeloo 2, a small galaxy discovered in the beam of these WSRT observations. The WSRT data reveal the position of the dynamical center of Dw1, its systemic LSR velocity, its total (projected) width in velocity, its inclination on the sky, and its integrated HI flux, as well as details of the velocity field and gas distribution. Dw1 is the nearest grand-design barred spiral system, and is probably amongst the ten largest galaxies closer than about 5 Mpc. We report here also the discovery of Dwingeloo 2, a small galaxy located within the WSRT primary beam as pointed to Dw1. In view of its angular and kinematic proximity to Dw1, Dw2 may well be a companion to the larger system. The two galaxies are probably both members of the group containing Maffei 1 & 2 and IC342 and may influence the peculiar motions within that group and the morphology of its individual members
Exploring Neutral Hydrogen and Galaxy Evolution with the SKA
One of the key science drivers for the development of the SKA is to observe
the neutral hydrogen, HI, in galaxies as a means to probe galaxy evolution
across a range of environments over cosmic time. Over the past decade, much
progress has been made in theoretical simulations and observations of HI in
galaxies. However, recent HI surveys on both single dish radio telescopes and
interferometers, while providing detailed information on global HI properties,
the dark matter distribution in galaxies, as well as insight into the
relationship between star formation and the interstellar medium, have been
limited to the local universe. Ongoing and upcoming HI surveys on SKA
pathfinder instruments will extend these measurements beyond the local universe
to intermediate redshifts with long observing programmes. We present here an
overview of the HI science which will be possible with the increased
capabilities of the SKA and which will build upon the expected increase in
knowledge of HI in and around galaxies obtained with the SKA pathfinder
surveys. With the SKA1 the greatest improvement over our current measurements
is the capability to image galaxies at reasonable linear resolution and good
column density sensitivity to much higher redshifts (0.2 < z < 1.7). So one
will not only be able to increase the number of detections to study the
evolution of the HI mass function, but also have the sensitivity and resolution
to study inflows and outflows to and from galaxies and the kinematics of the
gas within and around galaxies as a function of environment and cosmic time out
to previously unexplored depths. The increased sensitivity of SKA2 will allow
us to image Milky Way-size galaxies out to redshifts of z=1 and will provide
the data required for a comprehensive picture of the HI content of galaxies
back to z~2 when the cosmic star formation rate density was at its peak.Comment: 25 pages, 5 figures, 3 tables. Contribution to the conference
'Advancing Astrophysics with the Square Kilometre Array', June 8-13, 2014,
Giardini Naxos, Ital
Mesh-related complications and recurrence after ventral mesh rectopexy with synthetic versus biologic mesh:a systematic review and meta-analysis
BACKGROUND: Ventral mesh rectopexy (VMR) is a widely accepted surgical treatment for rectal prolapse. Both synthetic and biologic mesh are used. No consensus exists on the preferred type of mesh material. The aim of this systematic review and meta-analysis was to establish an overview of the current literature on mesh-related complications and recurrence after VMR with synthetic or biologic mesh to aid evidence-based decision making in preferred mesh material. METHODS: A systematic search of the electronic databases of PubMed, Embase and Cochrane was performed (from inception until September 2020). Studies evaluating patients who underwent VMR with synthetic or biologic mesh were eligible. The MINORS score was used for quality assessment. RESULTS: Thirty-two studies were eligible after qualitative assessment. Eleven studies reported on mesh-related complications including 4001 patients treated with synthetic mesh and 762 treated with biologic mesh. The incidence of mesh-related complications ranged between 0 and 2.4% after synthetic versus 0–0.7% after biologic VMR. Synthetic mesh studies showed a pooled incidence of mesh-related complications of 1.0% (95% CI 0.5–1.7). Data of biologic mesh studies could not be pooled. Twenty-nine studies reported on the risk of recurrence in 2371 synthetic mesh patients and 602 biologic mesh patients. The risk of recurrence varied between 1.1 and 18.8% for synthetic VMR versus 0–15.4% for biologic VMR. Cumulative incidence of recurrence was found to be 6.1% (95% CI 4.3–8.1) and 5.8% (95% CI 2.9–9.6), respectively. The clinical and statistical heterogeneity was high. CONCLUSIONS: No definitive conclusions on preferred mesh type can be made due to the quality of the included studies with high heterogeneity amongst them
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