Asymptotic SER and Outage Probability of MIMO MRC in Correlated Fading

This letter derives the asymptotic symbol error rate (SER) and outage probability of multiple-input multiple-output (MIMO) maximum ratio combining (MRC) systems. We consider Rayleigh fading channels with both transmit and receive spatial correlation. Our results are based on new asymptotic expressions which we derive for the p.d.f. and c.d.f. of the maximum eigenvalue of positive-definite quadratic forms in complex Gaussian matrices. We prove that spatial correlation does not affect the diversity order, but that it reduces the array gain and hence increases the SER in the high SNR regime.Comment: 10 pages, 2 figures, to appear in IEEE Signal Processing Letter

Open-Loop Spatial Multiplexing and Diversity Communications in Ad Hoc Networks

This paper investigates the performance of open-loop multi-antenna point-to-point links in ad hoc networks with slotted ALOHA medium access control (MAC). We consider spatial multiplexing transmission with linear maximum ratio combining and zero forcing receivers, as well as orthogonal space time block coded transmission. New closed-form expressions are derived for the outage probability, throughput and transmission capacity. Our results demonstrate that both the best performing scheme and the optimum number of transmit antennas depend on different network parameters, such as the node intensity and the signal-to-interference-and-noise ratio operating value. We then compare the performance to a network consisting of single-antenna devices and an idealized fully centrally coordinated MAC. These results show that multi-antenna schemes with a simple decentralized slotted ALOHA MAC can outperform even idealized single-antenna networks in various practical scenarios.Comment: 51 pages, 19 figures, submitted to IEEE Transactions on Information Theor

Centralizers of maximal regular subgroups in simple Lie groups and relative congruence classes of representations

In the paper we present a new, uniform and comprehensive description of centralizers of the maximal regular subgroups in compact simple Lie groups of all types and ranks. The centralizer is either a direct product of finite cyclic groups, a continuous group of rank 1, or a product, not necessarily direct, of a continuous group of rank 1 with a finite cyclic group. Explicit formulas for the action of such centralizers on irreducible representations of the simple Lie algebras are given.Comment: 27 page

Scaling Up Local Development Initiatives: Brazil's Food Acquisition Programme

__Abstract__ Global poverty largely remains a rural phenomenon. Close to 70 per cent of the developing world’s 1.4 billion people living in extreme poverty inhabit rural areas (IFAD, 2011). Further, agriculture is found to be a source of livelihood for over 80 per cent of rural people, highlighting the importance of supporting this activity as a means to fight poverty (World Bank, 2007; IFAD, 2011). This is darkly ironic: rural areas are where most of the world’s food is produced and also where the majority of the world’s extreme poor and malnourished reside. Poverty in rural areas stems from a diverse set of shortcomings such as: lack of adequate public investments in infrastructure, storage and market facilities coupled with disadvantages rooted in historical inequities, agricultural, land tenure and credit policies and economic factors that have a bearing on the distribution of assets, productive resources and access to credit and markets. Rural livelihoods are also based on a wide range of activities ranging from agricultural production to off-farm wage labour, and these vary across agro-climatic zones, land tenure arrangements, regions and cultures. The growing frequency of extreme weather events and recent increases in global financial and commodity price volatility—with sharp price rises particularly since 2006 (FAO et. al., 2011: 8)—have heightened the obstacles that rural producers, particularly poor, already face in many regions and have also contributed to severe localised food insecurity

On using a pyroclastic deposit as a manned lunar base site

Hawke et al. (1990) suggest that ilmenite found in Apollo 17-type pyroclastic glass may provide feedstock for the hydrogen reduction of ilmenite process for producing lunar oxygen. They also suggest that the ilmenite may help retain solar wind hydrogen and helium which can be extracted for use at a lunar outpost or even transported back to Earth for fusion fuel in the case of helium-3. Therefore, they suggest that ilmenite-rich material may be the best candidate. Here, researchers propose a somewhat different approach. They propose that the pyroclastic glass can be reduced directly to produce oxygen and one or more metals. Sulfur would be another important byproduct of the processing. This process would eliminate the need for having specific minerals such as ilmenite or for doing any mineral concentration. The bulk pyroclastic would provide the feedstock. Some recent experiments at the Johnson Space Center suggest that an iron-rich composition would be the most suitable for this direct feedstock reduction and that the titanium content may not be important. Also, the lunar pyroclastic deposits would be extremely useful in constructing and supporting a lunar base

The 'State' of Food Sovereignty in Latin America: Political Projects and Alternative Pathways in Venezuela, Ecuador, and Bolivia

__abstract__ The concept of food sovereignty has been enshrined in a number of countries’ Constitutions around the world without any clear consensus around what state-sponsored ‘food sovereignty’ initiatives might entail given the complexity and interconnectedness of the global food system. In the vanguard of this movement at the national level has been the so-called ‘pink tide’ of Latin America – namely Venezuela, Ecuador, and Bolivia. As a constitutional right, food sovereignty presents a significant opening to promote a citizen’s revolution of the food system, but is such a proposal possible or desirable as a top-down initiative? The concept itself is inherently peopleled as it implies constructing (or deconstructing) a food system that is defined, led, controlled, and accessed in a culturally appropriate and ecologically sustainable way by local people in a given territory. At the same time, state intervention is a necessary function to confront the global food system, dismantle unequal agrarian structures, and recognize the autonomy of people and communities in defining and controlling their food and agricultural systems. In different geographies and societies of food sovereignty, it is necessary to evaluate how state and social actors interact in the pursuit of a national food sovereignty strategy, with particular attention to the relations of control and access to decision-making and physical resources

Letting Go: Conceptualizing intervention de-implementation in public health and social service settings

The discontinuation of interventions that should be stopped, or de-implementation, has emerged as a novel line of inquiry within dissemination and implementation science. As this area grows in human services research, like public health and social work, theory is needed to help guide scientific endeavors. Given the infancy of de-implementation, this conceptual narrative provides a definition and criteria for determining if an intervention should be de-implemented. We identify three criteria for identifying interventions appropriate for de-implementation: (a) interventions that are not effective or harmful, (b) interventions that are not the most effective or efficient to provide, and (c) interventions that are no longer necessary. Detailed, well-documented examples illustrate each of the criteria. We describe de-implementation frameworks, but also demonstrate how other existing implementation frameworks might be applied to de-implementation research as a supplement. Finally, we conclude with a discussion of de-implementation in the context of other stages of implementation, like sustainability and adoption; next steps for de-implementation research, especially identifying interventions appropriate for de-implementation in a systematic manner; and highlight special ethical considerations to advance the field of de-implementation research

Sample preparation for point of care molecular diagnostics of STIs

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Brunel DoCLab is part of the esti2 consortium developing electronic self-testing instruments for sexually transmitted infections using nucleic acid amplification testing (NAAT). A proprietary sample collection device has been designed to integrate directly with a microfluidic cartridge. Cell lysis was conducted using a chemical method and nucleic acid purification was done on an activated cellulose membrane. The microfluidic device incorporates passive mixing of the lysis-binding buffers and sample. Preliminary results have shown extraction efficiencies for this new membrane of 69% and 57% compared to the commercial Qiagen extraction method of 85% and 59.4% for 0.1ng/μL and 100ng/μL salmon sperm DNA spiked in phosphate buffered solution. Preliminary extraction experiments in the passive mixer cartridges with lysis and nucleic acid purification showed extraction efficiency around 80% of the commercial Qiagen kit. Isothermal amplification was conducted using thermophillic helicase dependant amplification. A low cost benchtop real-time isothermal amplification platform has been developed capable of running six amplifications simultaneously. Work to integrate sample collection, nucleic acid extraction and isothermal amplification is currently underway