341 research outputs found
Influence of damping on the excitation of the double giant resonance
We study the effect of the spreading widths on the excitation probabilities
of the double giant dipole resonance. We solve the coupled-channels equations
for the excitation of the giant dipole resonance and the double giant dipole
resonance. Taking Pb+Pb collisions as example, we study the resulting effect on
the excitation amplitudes, and cross sections as a function of the width of the
states and of the bombarding energy.Comment: 8 pages, 3 figures, corrected typo
Community-based benchmarking improves spike rate inference from two-photon calcium imaging data
In recent years, two-photon calcium imaging has become a standard tool to probe the function of neural circuits and to study computations in neuronal populations. However, the acquired signal is only an indirect measurement of neural activity due to the comparatively slow dynamics of fluorescent calcium indicators. Different algorithms for estimating spike rates from noisy calcium measurements have been proposed in the past, but it is an open question how far performance can be improved. Here, we report the results of the spikefinder challenge, launched to catalyze the development of new spike rate inference algorithms through crowd-sourcing. We present ten of the submitted algorithms which show improved performance compared to previously evaluated methods. Interestingly, the top-performing algorithms are based on a wide range of principles from deep neural networks to generative models, yet provide highly correlated estimates of the neural activity. The competition shows that benchmark challenges can drive algorithmic developments in neuroscience
A randomized phase II trial of tacrolimus, mycophenolate mofetil and sirolimus after non-myeloablative unrelated donor transplantation
The study is a randomized phase II trial investigating graft-versus-host disease prophylaxis after non-myeloablative (90 mg/m(2) fludarabine and 2 Gy total body irradiation) human leukocyte antigen matched unrelated donor transplantation. Patients were randomized as follows: arm 1 – tacrolimus 180 days and mycophenolate mofetil 95 days (n=69); arm 2 – tacrolimus 150 days and mycophenolate mofetil 180 days (n=71); arm 3 – tacrolimus 150 days, mycophenolate mofetil 180 days and sirolimus 80 days (n=68). All patients had sustained engraftment. Grade II-IV acute graft-versus-host disease rates in the 3 arms were 64%, 48% and 47% at Day 150, respectively (arm 3 vs. arm 1 (hazard ratio 0.62; P=0.04). Owing to the decreased incidence of acute graft-versus-host disease, systemic steroid use was lower at Day 150 in arm 3 (32% vs. 55% in arm 1 and 49% in arm 2; overall P=0.009 by hazard ratio analysis). The Day 150 incidence of cytomegalovirus reactivation was lower in arm 3 (arm 1, 54%; arm 2, 47%; arm 3, 22%; overall P=0.002 by hazard ratio analysis). Non-relapse mortality was comparable in the three arms at two years (arm 1, 26%; arm 2, 23%; arm 3, 18%). Toxicity rates and other outcome measures were similar between the three arms. The addition of sirolimus to tacrolimus and mycophenolate mofetil is safe and associated with lower incidence of acute graft-versus-host disease and cytomegalovirus reactivation. (clinicaltrials.gov identifier: 00105001)
Natural Image Coding in V1: How Much Use is Orientation Selectivity?
Orientation selectivity is the most striking feature of simple cell coding in
V1 which has been shown to emerge from the reduction of higher-order
correlations in natural images in a large variety of statistical image models.
The most parsimonious one among these models is linear Independent Component
Analysis (ICA), whereas second-order decorrelation transformations such as
Principal Component Analysis (PCA) do not yield oriented filters. Because of
this finding it has been suggested that the emergence of orientation
selectivity may be explained by higher-order redundancy reduction. In order to
assess the tenability of this hypothesis, it is an important empirical question
how much more redundancies can be removed with ICA in comparison to PCA, or
other second-order decorrelation methods. This question has not yet been
settled, as over the last ten years contradicting results have been reported
ranging from less than five to more than hundred percent extra gain for ICA.
Here, we aim at resolving this conflict by presenting a very careful and
comprehensive analysis using three evaluation criteria related to redundancy
reduction: In addition to the multi-information and the average log-loss we
compute, for the first time, complete rate-distortion curves for ICA in
comparison with PCA. Without exception, we find that the advantage of the ICA
filters is surprisingly small. Furthermore, we show that a simple spherically
symmetric distribution with only two parameters can fit the data even better
than the probabilistic model underlying ICA. Since spherically symmetric models
are agnostic with respect to the specific filter shapes, we conlude that
orientation selectivity is unlikely to play a critical role for redundancy
reduction
The High-Resolution Coronal Imager, Flight 2.1
The third flight of the High-Resolution Coronal Imager (Hi-C 2.1) occurred on May 29, 2018; the Sounding Rocket was launched from White Sands Missile Range in New Mexico. The instrument has been modified from its original configuration (Hi-C 1) to observe the solar corona in a passband that peaks near 172 Å, and uses a new, custom-built low-noise camera. The instrument targeted Active Region 12712, and captured 78 images at a cadence of 4.4 s (18:56:22 – 19:01:57 UT; 5 min and 35 s observing time). The image spatial resolution varies due to quasi-periodic motion blur from the rocket; sharp images contain resolved features of at least 0.47 arcsec. There are coordinated observations from multiple ground- and space-based telescopes providing an unprecedented opportunity to observe the mass and energy coupling between the chromosphere and the corona. Details of the instrument and the data set are presented in this paper
Are Metastases from Metastases Clinical Relevant? Computer Modelling of Cancer Spread in a Case of Hepatocellular Carcinoma
Background: Metastasis formation remains an enigmatic process and one of the main questions recently asked is whether metastases are able to generate further metastases. Different models have been proposed to answer this question; however, their clinical significance remains unclear. Therefore a computer model was developed that permits comparison of the different models quantitatively with clinical data and that additionally predicts the outcome of treatment interventions. Methods: The computer model is based on discrete events simulation approach. On the basis of a case from an untreated patient with hepatocellular carcinoma and its multiple metastases in the liver, it was evaluated whether metastases are able to metastasise and in particular if late disseminated tumour cells are still capable to form metastases. Additionally, the resection of the primary tumour was simulated. The simulation results were compared with clinical data. Results: The simulation results reveal that the number of metastases varies significantly between scenarios where metastases metastasise and scenarios where they do not. In contrast, the total tumour mass is nearly unaffected by the two different modes of metastasis formation. Furthermore, the results provide evidence that metastasis formation is an early event and that late disseminated tumour cells are still capable of forming metastases. Simulations also allow estimating how the resection of the primary tumour delays the patient’s death. Conclusion: The simulation results indicate that for this particular case of a hepatocellular carcinoma late metastases, i.e.
Kapitel 9. Synopsis – Synergien, Zielkonflikte und Umsetzungsbarrieren von Klimaanpassungs- und Klimaschutzmaßnahmen
Es existiert eine Fülle von potenziellen Maßnahmen der Klimawandelanpassung und Emissionsminderung im Bereich der Landnutzung. Allerdings stehen Klimawandelanpassung und Emissionsminderung nicht notwendigerweise in einem synergistischen Zusammenhang. Neben der Klimarelevanz sind auch andere Kriterien von Bedeutung, wenn die integrative Leistungsfähigkeit von Maßnahmen bewertet werden soll. Dazu gehören vor allem mögliche und erwartete Auswirkungen auf die Biodiversität und denWasserhaushalt. Dieses Kapitel fasst die Klimawandelanpassungs- und Emissionsminderungsmaßnahmen und ihre Auswirkungen tabellarisch zusammen. Dabei soll eine integrative, übersichtliche Bewertung der im Special Report behandelten Maßnahmen ermöglicht werden
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