On the MIMO Capacity with Multiple Linear Transmit Covariance Constraints

This paper presents an efficient approach to computing the capacity of multiple-input multiple-output (MIMO) channels under multiple linear transmit covariance constraints (LTCCs). LTCCs are general enough to include several special types of power constraints as special cases such as the sum power constraint (SPC), per-antenna power constraint (PAPC), or a combination thereof. Despite its importance and generality, most of the existing literature considers either SPC or PAPC independently. Efficient solutions to the computation of the MIMO capacity with a combination of SPC and PAPC have been recently reported, but were only dedicated to multipleinput single-output (MISO) systems. For the general case of LTCCs, we propose a low-complexity semi-closed-form approach tothecomputationoftheMIMOcapacity.Specifically,amodified minimax duality is first invoked to transform the considered problem in the broadcast channel into an equivalent minimax problem in the dual multiple access channel. Then alternating optimization and concave-convex procedure are utilized to derive water-filling-based algorithms to find a saddle point of the minimax problem. This is different from the state-of-the-art solutions to the considered problem, which are based on interiorpoint or subgradient methods. Analytical and numerical results are provided to demonstrate the effectiveness of the proposed low-complexity solution under various MIMO scenarios

A pilot study demonstrating the altered gut microbiota functionality in stable adults with Cystic Fibrosis

peer-reviewedCystic Fibrosis (CF) and its treatment result in an altered gut microbiota composition compared to non-CF controls. However, the impact of this on gut microbiota functionality has not been extensively characterised. Our aim was to conduct a proof-of-principle study to investigate if measurable changes in gut microbiota functionality occur in adult CF patients compared to controls. Metagenomic DNA was extracted from faecal samples from six CF patients and six non-CF controls and shotgun metagenomic sequencing was performed on the MiSeq platform. Metabolomic analysis using gas chromatography-mass spectrometry was conducted on faecal water. The gut microbiota of the CF group was significantly different compared to the non-CF controls, with significantly increased Firmicutes and decreased Bacteroidetes. Functionality was altered, with higher pathway abundances and gene families involved in lipid (e.g. PWY 6284 unsaturated fatty acid biosynthesis (p = 0.016)) and xenobiotic metabolism (e.g. PWY-5430 meta-cleavage pathway of aromatic compounds (p = 0.004)) in CF patients compared to the controls. Significant differences in metabolites occurred between the two groups. This proof-of-principle study demonstrates that measurable changes in gut microbiota functionality occur in CF patients compared to controls. Larger studies are thus needed to interrogate this further

RFA Guardian: Comprehensive Simulation of Radiofrequency Ablation Treatment of Liver Tumors

The RFA Guardian is a comprehensive application for high-performance patient-specific simulation of radiofrequency ablation of liver tumors. We address a wide range of usage scenarios. These include pre-interventional planning, sampling of the parameter space for uncertainty estimation, treatment evaluation and, in the worst case, failure analysis. The RFA Guardian is the first of its kind that exhibits sufficient performance for simulating treatment outcomes during the intervention. We achieve this by combining a large number of high-performance image processing, biomechanical simulation and visualization techniques into a generalized technical workflow. Further, we wrap the feature set into a single, integrated application, which exploits all available resources of standard consumer hardware, including massively parallel computing on graphics processing units. This allows us to predict or reproduce treatment outcomes on a single personal computer with high computational performance and high accuracy. The resulting low demand for infrastructure enables easy and cost-efficient integration into the clinical routine. We present a number of evaluation cases from the clinical practice where users performed the whole technical workflow from patient-specific modeling to final validation and highlight the opportunities arising from our fast, accurate prediction techniques

Realizing General Education: Reconsidering Conceptions and Renewing Practice

General Education is widely touted as an enduring distinctive of higher education in the United States (Association of American Colleges and Universities, [11]; Boyer, [37]; Gaston, [86]; Zakaria, [202]). The notion that undergraduate education demands wide‐ranging knowledge is a hallmark of U.S. college graduates that international educators emulate (Blumenstyk, [25]; Rhodes, [158]; Tsui, [181]). The veracity of this distinct educational vision is supported by the fact that approximately one third of the typically 120 credits required for the bachelor\u27s degree in the United States consist of general education courses (Lattuca & Stark, [120]). Realizing a general education has been understood to be central to achieving higher education\u27s larger purposes, making it a particularly salient concern

The Physics of the B Factories

This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C

Weighted Sum Rate Maximization for Zero-forcing Methods with General Linear Covariance Constraints

In this paper, an efficient approach for weighted sum rate maximization (WSRMax) for zero-forcing(ZF)methods with general linear transmit covariance constraints (LTCCs) is proposed. This problem has been extensively studied separately for some special cases such as for sum power or per-antenna power constraints (PAPC). Due to some practical and regulatory requirements, these power constraints alone are not in general sufficient, which motivates the consideration of general LTCCs. On the other hand, the zero-forcing (ZF) is a simple linear precoding technique to mitigate inter-user interference. The problem of WSRMax for ZF methods with LTCCs was studied previously using a gradient descent algorithm with barrier functions, but this method was also shown to converge slowly. To derive an efficient solution to this problem, we first reformulate it as an equivalent minimax problem using Lagrangian duality. The obtained result in fact resembles BC-MAC duality but is specialized for ZF methods. We then combine alternating optimization and concave-convex procedure to efficiently compute a saddle point of the minimax problem. The proposed method is numerically shown to converge very fast and its complexity scales linearly with the number of users

Modelling of radiative heat transfer of a square trihedral design radiator panel on the lunar surface

In this study, a radiative thermal model is developed which can be used to predict the heat transfer performance of radiator panels on the lunar surface. It includes the effects of all environmental sources of radiation experienced on the lunar surface, namely direct and indirect solar radiation, lunar albedo, and infra-red thermal heating from the lunar surface. Ray tracing is used to capture the direct solar irradiation and also to determine surface-to-surface view factors. The radiation network methodology is employed to determine the contribution from diffuse reflections. This model is applied to a retro-reflector-like trihedral design radiator panel. A trihedral is defined as a shape with three sides which meet at a common point. This form aims to minimise the negative effects of environmental radiation while maximising the heat transfer to deep space. For the geometry and conditions studied here, the radiator panel shows good potential as an effective lunar radiator when compared to a flat plate. A change in radiative dissipative performance is observed across the lunar day when the apex angle is varied, with smaller apex angles showing greater rates of heat transfer in the morning compared to larger angles which work best at noon. The orientation of the radiator on the lunar surface was also investigated. It was found that heat transfer rate was largely unaffected by the azimuth angle, however varying the inclination angle from horizontal to vertical causes a significant reduction due to increa sed view factors to the lunar surface. Further work is required to fully characterise this design, including increasing the number of trihedral elements and the inclusion of thermal conduction in the model