278 research outputs found
A Study of Particle Motion in the Presence of Clusters
The motivation for this study came from the task of analysing the kinetic
behavior of single molecules in a living cell based on Single Molecule
Localization Microscopy. Given measurements of both the motion of clusters and
molecules, the main task consists in detecting if a molecule belongs to a
cluster. While the exact size of the clusters is usually unknown, upper bounds
are available. In this study, we simulate the cluster movement by a Brownian
motion and those of the particles by a Gaussian mixture model with two modes
depending on the position of the particle within or outside a cluster. We
propose various variational models to detect if a particle lies within a
cluster based on the Wasserstein and maximum mean discrepancy distances between
measures. We compare the performance of the proposed models for simulated data
Glassy correlations and microstructures in randomly crosslinked homopolymer blends
We consider a microscopic model of a polymer blend that is prone to phase
separation. Permanent crosslinks are introduced between randomly chosen pairs
of monomers, drawn from the Deam-Edwards distribution. Thereby, not only
density but also concentration fluctuations of the melt are quenched-in in the
gel state, which emerges upon sufficient crosslinking. We derive a Landau
expansion in terms of the order parameters for gelation and phase separation,
and analyze it on the mean-field level, including Gaussian fluctuations. The
mixed gel is characterized by thermal as well as time-persistent (glassy)
concentration fluctuations. Whereas the former are independent of the
preparation state, the latter reflect the concentration fluctuations at the
instant of crosslinking, provided the mesh size is smaller than the correlation
length of phase separation. The mixed gel becomes unstable to microphase
separation upon lowering the temperature in the gel phase. Whereas the length
scale of microphase separation is given by the mesh size, at least close to the
transition, the emergent microstructure depends on the composition and
compressibility of the melt. Hexagonal structures, as well as lamellae or
random structures with a unique wavelength, can be energetically favorable.Comment: 19 pages, 10 figures. Submitted to the Journal of Chemical Physics
(http://jcp.aip.org
Generative Sliced MMD Flows with Riesz Kernels
Maximum mean discrepancy (MMD) flows suffer from high computational costs in
large scale computations. In this paper, we show that MMD flows with Riesz
kernels , have exceptional properties which
allow for their efficient computation. First, the MMD of Riesz kernels
coincides with the MMD of their sliced version. As a consequence, the
computation of gradients of MMDs can be performed in the one-dimensional
setting. Here, for , a simple sorting algorithm can be applied to reduce
the complexity from to for two empirical
measures with and support points. For the implementations we
approximate the gradient of the sliced MMD by using only a finite number of
slices. We show that the resulting error has complexity , where
is the data dimension. These results enable us to train generative models
by approximating MMD gradient flows by neural networks even for large scale
applications. We demonstrate the efficiency of our model by image generation on
MNIST, FashionMNIST and CIFAR10
Extra force in modified theories of gravity
The equation of motion for test particles in modified theories of
gravity is derived. By considering an explicit coupling between an arbitrary
function of the scalar curvature, , and the Lagrangian density of matter, it
is shown that an extra force arises. This extra force is orthogonal to the
four-velocity and the corresponding acceleration law is obtained in the weak
field limit. Connections with MOND and with the Pioneer anomaly are further
discussed.Comment: Revtex4 file, 5 pages. Version to appear in Physical Review
Die Europäische Agrarpolitik im Spannungsfeld von Osterweiterung und WTO-Verhandlungen
The paper presents a political economy analysis of the present and future CAP reform induced under different policy scenarios regarding future EU enlargement and future WTO agreements. Theoretically, the analysis is based on a political exchange model suggested by HENNING (2000). Main results are: (i) Both present and future CAP reforms are significantly biased by the political influence of farmers' lobby. (ii) In quantitative terms an EU enlargement would induce a much stronger shift in the future CAP when compared to increased WTO restrictions. (iii) The timing of the reform is important, given the fact that induced CAP reforms would be supported by a qualified majority within the EU-15, but within the EU-25 these reforms would be defeated by coalition of the new Eastern European member states using their common veto-power. (iv) The majority of political actors within the EU-15 including both politicians and interest groups evaluate induced CAP reforms negatively in comparison to the status quo, while from society’s perspective these imply a positive shift of total economic welfare within EU-15.political economy analysis, CAP, EU enlargement, WTO, Agricultural and Food Policy, International Relations/Trade, Political Economy,
Die Europäische Agrarpolitik im Spannungsfeld von Osterweiterung und WTO-Verhandlungen
Der Artikel umfasst eine quantitative polit-ökonomische Analyse aktueller und zukünftiger Reformen der Gemeinsamen Europäischen Agrarpolitik unter unterschiedlichen Szenarios einer zukünftigen EU-Osterweiterung und zukünftigen WTO-Verhandlungen. Theoretische Grundlage der Analysen ist ein politisches Tauschmodells von HENNING (2000). Zentrale Ergebnisse der quantitativen Analysen sind: (i) Es lässt sich ein signifikanter Einfluss der Agrarlobby auf die aktuelle und zukünftige Neuformulierung der Agrarpolitik in der EU-15 bzw. erweiterten EU-25 feststellen. (ii) Eine Osterweiterung hätte im Ve rgleich zu verschärften WTO-Restriktionen einen erheblich stärkeren Einfluss auf zukünftige Agrarreformen. Inhaltlich induziert eine Osterweiterung ein deutlich niedrigeres Agrarprotektionsniveau sowie eine geringere Förderung der Multifunktionalität der Landwirtschaft. (iii) Während innerhalb der EU-15 eine qualifizierte Mehrheit für eine entsprechende Agrarreform wäre, würde diese in einer erweiterten EU-25 am ?Veto? der osteuropäischen Mitglieder scheitern. Insofern ist das timing der Reform wichtig. (iv) Die Mehrheit der politischen Akteure in der EU-15 bewertet die außenpolitisch induzierten Reformen negativ, während diese aus gesamtgesellschaftlicher Perspektive der EU-15 positiv zu bewerten sind. -- The paper presents a quantitative politico-economic analysis of the present and future CAP-reform induced under different policy scenarios regarding a potential EU-enlargement and future WTO-agreements. Theoretically, the analysis is based on a political exchange model suggested by Henning (2000). Main results are: (i) Both present and future CAP-reforms are significantly biased by the political influence of farmer?s lobby. (ii) In quantitative terms an EU-enlargement would induce a much stronger shift in the future CAP when compared to increased WTO-restrictions. Generally, induced CAP-reforms imply a significant lower level of protection and a lower support of multifunctional services of the agricultural sector. (iii) The timing of the reform is important, given the fact that induced CAP-reforms would be supported by a qualified majority within the EU-15, but within the EU-25 these reforms would be defeated by coalition of the new Eastern European member states using their common veto-power. (iv) The majority of political actors within the EU-15 including both politicians and interest groups evaluate induced CAP-reforms negatively in comparison to the status quo, while from society?s perspective these imply a positive shift of total economic welfare within EU-15.
Retinometer predicts visual outcome in Descemet membrane endothelial keratoplasty.
PURPOSE
To analyze the preoperative predictive value of retinometer visual acuity (VA) in eyes following Descemet membrane endothelial keratoplasty (DMEK).
METHODS
Patients undergoing DMEK between August 2011 and July 2020 were included. Preoperative interference visual acuity was assessed using Heine Lambda 100 Retinometer. Depending on the presence or absence of concomitant ocular disease, the Retinometer was evaluated for its ability to preoperatively predict best-corrected visual acuity (BCVA) six months after surgery using correlation, simple and multiple linear regression, contingency analyses, and receiver operating characteristic (ROC) analysis. Preoperative corneal backscatter was correlated with Retinometer prediction accuracy.
RESULTS
A total of 198 eyes were included in the analysis. There was a significant correlation between Retinometer VA and postoperative BCVA (r = 0.647, P < 0.001). Regardless of the presence or absence of concomitant ocular disease and the surgery procedure (DMEK & triple DMEK), Retinometer VA was the most significant predictor of postoperative BCVA (P < 0.001). ROC analysis revealed reliable diagnostic performance of the Retinometer (AUC = 0.829, P < 0.001). A Retinometer VA ≥ 0.5 accurately predicted a postoperative BCVA ≥ 0.5 in 91% of cases. No association was found between corneal backscatter and prediction accuracy (P = 0.566).
CONCLUSIONS
Retinometer VA can be used for preoperative prediction of postoperative BCVA in DMEK and triple DMEK patients, independent of increased backscatter values and the presence or absence of concomitant ocular disease. By using this simple but effective tool, indication for DMEK can be facilitated and postoperative outcomes can be realistically predicted preoperatively
Piezoelectric titanium based microfluidic pump and valves for implantable medical applications
Medical devices often require precise movement of fluids. Automated implants with no need for manual handling improve patient care significantly. However, existing microfluidic devices do not fulfil the necessary specifications of size, safety, hermetic sealing, and artefact free medical imaging, as well as energy efficiency combined with adapted fluidic properties. In this work we designed, manufactured, and experimentally evaluated three piezoelectric microfluidic devices for implant automation: a diaphragm pump, a normally closed valve, and a normally open valve. All devices are made of titanium, minimizing the risk of artefacts in medical imaging. They have similar form factors and use the same actuation method. For the later, a specific mounting process of the piezo actuator enables outstanding fluidic performance during experimental evaluations. The titanium micropumps show a maximal flow of (14 ± 2.2) ml/min and pressure build-up of 75 kPa. The normally closed valve’s leakage rates are extremely low with less than 1 μL/min. Detailed investigations further include the actuator stroke, a lifetime study for normally open valves, and a numerical and experimental evaluation of the normally closed valve’s spring foil. The introduced titanium technology platform is ideally suited for system integration accounted for by the use of the same actuation principle and the similar form factor and a simple design. The development of small, smart, and energy efficient implants for improved treatment is possible based on the introduced platform
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