Linear and Dirty-Paper Techniques for the Multiuser MIMO Downlink

Multi-input, multi-output (MIMO) communications systems have attracted considerable attention over the past decade, mostly for single-user, point-to-point scenarios. The multiple-user MIMO case has attracted less attention, and most of the research on this problem has focused on uplink communications. Only recently has the multi-user MIMO downlink been addressed, beginning with information-theoretic capacity results [1–5], and followed by prac-tical implementations, including those based on linear techniques [6, 7] and non-linear pre-coding [8–11]. In this chapter we review these techniques and discuss some important open problems

A High Throughput Configurable SDR Detector for Multi-user MIMO Wireless Systems

Spatial division multiplexing (SDM) in MIMO technology significantly increases the spectral efficiency, and hence capacity, of a wireless communication system: it is a core component of the next generation wireless systems, e.g. WiMAX, 3GPP LTE and other OFDM-based communication schemes. Moreover, spatial division multiple access (SDMA) is one of the widely used techniques for sharing the wireless medium between different mobile devices. Sphere detection is a prominent method of simplifying the detection complexity in both SDM and SDMA systems while maintaining BER performance comparable with the optimum maximum-likelihood (ML) detection. On the other hand, with different standards supporting different system parameters, it is crucial for both base station and handset devices to be configurable and seamlessly switch between different modes without the need for separate dedicated hardware units. This challenge emphasizes the need for SDR designs that target the handset devices. In this paper, we propose the architecture and FPGA realization of a configurable sort-free sphere detector, Flex-Sphere, that supports 4, 16, 64-QAM modulations as well as a combination of 2, 3 and 4 antenna/user configuration for handsets. The detector provides a data rate of up to 857.1 Mbps that fits well within the requirements of any of the next generation wireless standards. The algorithmic optimizations employed to produce an FPGA friendly realization are discussed.Xilinx Inc.National Science Foundatio

Reporting guidelines for surgical technique could be improved: a scoping review and a call for action.

To identify reporting guidelines related to surgical technique and propose recommendations for areas that require improvement. A protocol-guided scoping review was conducted. A literature search of MEDLINE, the EQUATOR Network Library, Google Scholar, and Networked Digital Library of Theses and Dissertations was conducted to identify surgical technique reporting guidelines published up to December 31, 2021. We finally included 55 surgical technique reporting guidelines, vascular surgery (n = 18, 32.7%) was the most common among the clinical specialties covered. The included guidelines generally showed a low degree of international and multidisciplinary cooperation. Few guidelines provided a detailed development process (n = 14, 25.5%), conducted a systematic literature review (n = 13, 23.6%), used the Delphi method (n = 4, 7.3%), or described post-publication strategy (n = 6, 10.9%). The vast majority guidelines focused on the reporting of intraoperative period (n = 50, 90.9%). However, of the guidelines requiring detailed descriptions of surgical technique methodology (n = 43, 78.2%), most failed to provide guidance on what constitutes an adequate description. Our study demonstrates significant deficiencies in the development methodology and practicality of reporting guidelines for surgical technique. A standardized reporting guideline that is developed rigorously and focuses on details of surgical technique may serve as a necessary impetus for change

Vitamin C and infectious diseases

Non peer reviewe

Microvascular density and hypoxia-inducible factor pathway in pancreatic endocrine tumours: negative correlation of microvascular density and VEGF expression with tumour progression

Tumour-associated angiogenesis is partly regulated by the hypoxia-inducible factor (HIF) pathway. Endocrine tumours are highly vascularised and the molecular mechanisms of their angiogenesis are not fully delineated. The aim of this study is to evaluate angiogenesis and expression of HIF-related molecules in a series of patients with pancreatic endocrine tumours (PETs). The expression of vascular endothelial growth factor (VEGF), HIF-1α, HIF-2α and carbonic anhydrase 9 (CA9) was examined by immunohistochemistry in 45 patients with PETs and compared to microvascular density (MVD), endothelial proliferation, tumour stage and survival. Microvascular density was very high in PETs and associated with a low endothelial index of proliferation. Microvascular density was significantly higher in benign PETs than in PETs of uncertain prognosis, well-differentiated and poorly differentiated carcinomas (mean values: 535, 436, 252 and 45 vessels mm−2, respectively, P<0.0001). Well-differentiated tumours had high cytoplasmic VEGF and HIF-1α expression. Poorly differentiated carcinomas were associated with nuclear HIF-1α and membranous CA9 expression. Low MVD (P=0.0001) and membranous CA9 expression (P=0.0004) were associated with a poorer survival. Contrary to other types of cancer, PETs are highly vascularised, but poorly angiogenic tumours. As they progress, VEGF expression is lost and MVD significantly decreases. The regulation of HIF signalling appears to be specific in pancreatic endocrine tumours