Message-Passing Monte Carlo: Generating low-discrepancy point sets via graph neural networks.

Discrepancy is a well-known measure for the irregularity of the distribution of a point set. Point sets with small discrepancy are called low discrepancy and are known to efficiently fill the space in a uniform manner. Low-discrepancy points play a central role in many problems in science and engineering, including numerical integration, computer vision, machine perception, computer graphics, machine learning, and simulation. In this work, we present a machine learning approach to generate a new class of low-discrepancy point sets named Message-Passing Monte Carlo (MPMC) points. Motivated by the geometric nature of generating low-discrepancy point sets, we leverage tools from Geometric Deep Learning and base our model on graph neural networks. We further provide an extension of our framework to higher dimensions, which flexibly allows the generation of custom-made points that emphasize the uniformity in specific dimensions that are primarily important for the particular problem at hand. Finally, we demonstrate that our proposed model achieves state-of-the-art performance superior to previous methods by a significant margin. In fact, MPMC points are empirically shown to be either optimal or near-optimal with respect to the discrepancy for low dimension and small number of points, i.e., for which the optimal discrepancy can be determined.

Sci-Sat AM(2): Brachy-04: Spectral and dosimetric study of the Xoft electronic brachytherapy system.

The Axxent developed by Xoft Inc. is a miniature x-ray tube capable of generating a 50 kVp x-ray spectrum with dose-rates suitable for HDR applications. Results of spectral measurements compared with Geant4 Monte Carlo simulations have been published. This study is a continuation of previous work with shifting emphasis towards dosimetric characterization of the miniature x-ray tube. Dose distributions using EBT Gafchromic films agree to within 10 % of Geant4 results. In addition, TG-43 parameters can be calculated. However, consideration should be given to the biological effectiveness of the spectrum at different depths. Spectral measurements show significant beam hardening with 1st HVL increasing from 0.55 to 1.20 mm Al after 11.50 mm of water filtration. This effect may be attributed to the significant loss of low energy characteristic photons. Furthermore, the degree of beam hardening is dependent of the material, with 1st HVLs of 1.20 and 1.03 mm Al after 11.50 mm of water and Lucite respectively. The biological effect is quantified by calculating the number of single and double strand breaks. The number of strand breaks for the 50 kVp x-ray spectrum is similar to that of I-125 radiation.

[Housing of dogs and cats in animal shelters]. / Haltung von Hunden und Katzen in Tierheimen.

The results of an examination of 10 animal shelters was, that anyone was unical. The everyday and fundamental problems in administration, housing animals and animal care were the same: Most of them employ laity, which do their job with a lot of commitment but without knowledge. Therefore they come into conflict with the demands of animal protection. Veterinary surgeons, responsible authorities and communities are strongly asked to take steps against the situation. The reason for the fact, that such steps are missed, is, that there is no guideline or recommendation available for these persons, which handles animal shelters relative to "animal justice" and the right housing of animals. The results of the survey helps to make a guideline for animal home owners and builders, veterinary surgeons, veterinary authorities and communities, which gives suggestions to build, equip and run animal shelters for cats and dogs responsible regarding the individual circumstances and in the best way for animals.

Signal processing methods for pulse oximetry.

Current signal processing technology has driven many advances in almost every aspect of life, including medical applications. It follows that applying signal processing techniques to pulse oximetry could also provide major improvements. This research was designed to identify and implement one or more techniques that could improve pulse oximetry oxygen saturation (SpO2) measurements. The hypothesis was that frequency domain analysis could more easily extract the cardiac rate and amplitude of interest from the time domain signal. The focus was on the digital signal processing algorithms that had potential to improve pulse oximetry readings, and then test those algorithms. This was accomplished using the Fast Fourier Transform (FFT) and the Discrete Cosine Transform (DCT). The results indicate that the FFT and DCT computation of oxygen saturation were as accurate without averaging, as weighted moving average (WMA) algorithms currently being used, and directly indicate when erroneous calculations occur.