A Branch-and-Bound Algorithm for Quadratically-Constrained Sparse Filter Design

This paper presents an exact algorithm for sparse filter design under a quadratic constraint on filter performance. The algorithm is based on branch-and-bound, a combinatorial optimization procedure that can either guarantee an optimal solution or produce a sparse solution with a bound on its deviation from optimality. To reduce the complexity of branch-and-bound, several methods are developed for bounding the optimal filter cost. Bounds based on infeasibility yield incrementally accumulating improvements with minimal computation, while two convex relaxations, referred to as linear and diagonal relaxations, are derived to provide stronger bounds. The approximation properties of the two relaxations are characterized analytically as well as numerically. Design examples involving wireless channel equalization and minimum-variance distortionless-response beamforming show that the complexity of obtaining certifiably optimal solutions can often be significantly reduced by incorporating diagonal relaxations, especially in more difficult instances. In the case of early termination due to computational constraints, diagonal relaxations strengthen the bound on the proximity of the final solution to the optimum.Texas Instruments Leadership University Consortium Progra

Sparse Filter Design Under a Quadratic Constraint: Low-Complexity Algorithms

This paper considers three problems in sparse filter design, the first involving a weighted least-squares constraint on the frequency response, the second a constraint on mean squared error in estimation, and the third a constraint on signal-to-noise ratio in detection. The three problems are unified under a single framework based on sparsity maximization under a quadratic performance constraint. Efficient and exact solutions are developed for specific cases in which the matrix in the quadratic constraint is diagonal, block-diagonal, banded, or has low condition number. For the more difficult general case, a low-complexity algorithm based on backward greedy selection is described with emphasis on its efficient implementation. Examples in wireless channel equalization and minimum-variance distortionless-response beamforming show that the backward selection algorithm yields optimally sparse designs in many instances while also highlighting the benefits of sparse design.Texas Instruments Leadership University Consortium Progra

Speech Communication

Contains research objectives, summary of research and reports on three research projects.U. S. Navy - Office of Naval Research (Contract N00014-67-A-0204-0064)U. S. Navy - Office of Naval Research (Contract N00014-67-A-0204-0069)National Science Foundation (Grant GK-31353)National Institutes of Health (Grant 5 RO1 NS04332-10)Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DAAB07-71-C-0300Bell Telephone Laboratories Fellowshi

Correlation with basic differentiation processes of neurons

The development of the spinal cord involves the proliferation of neurons, their migration to well-defined areas, fiber outgrowth and synapse formation. The present study was designed to correlate the spatiotemporal pattern of expression of synaptophysin, an integral membrane protein of small synaptic vesicles, with these basic processes occurring during the embryonic development of the rat spinal cord. Thoracic segments of spinal cords from embryonic days 12, 14, 16, 18, 20 and of adult spinal cords were studied. S1 nuclease protection assays and immunoblots revealed minute amounts of specific mRNA and synaptophysin at embryonic day 12. There was a steep increase of mRNA between embryonic days 14 and 16, after which levels reached a plateau. A rise in the amount of synaptophysin in the spinal cord occurred between embryonic days 12 and 14, and the levels changed only slightly until the end of embryonic development. Even higher levels of synaptophysin, found in the adult spinal cord, may indicate that its biosynthesis continued after birth. In situ hybridization histochemistry revealed the localization of specific synaptophysin mRNA in the neuroepithelium. However, immunocytochemistry failed to detect synaptophysin in the neuroepithelial cells. Following migration of the neuroblasts, synaptophysin was found in neurons concomitantly with the onset of fiber outgrowth. Thus, already at embryonic day 12, outgrowing fibers of the dorsal root sensory neurons and of motoneurons were synaptophysin positive. From embryonic day 14 throughout the prenatal period, strong synaptophysin immunoreactivity was seen in the ventrolateral and dorsal parts of the marginal layer. Most likely this staining pattern indicates transient functional synaptic contacts because, in the adult spinal cord, the corresponding region, the white matter, exhibited only faint synaptophysin immunoreactivity. In the intermediate layer of the embryonic spinal cord, which corresponds to the gray matter of the adult spinal cord, synaptophysin-positive fibers were observed prior to the formation of functional synapses. The latter are most likely permanent, since synaptophysin in the adult spinal cord is mainly confined to the gray matter. Our data (i) show transcription and translation of synaptophysin within the neurons of the spinal cord and correlate these processes with proliferation, migration, fiber outgrowth and the formation of transient or permanent synapses, and (ii) prove that synaptophysin is a marker for fiber outgrowth in addition to synapse formation

Digital Signal Processing

Contains an introduction and reports on fourteen research projects.National Science Foundation FellowshipNational Science Foundation (Grant ECS84-07285)U.S. Navy - Office of Naval Research (Contract N00014-81-K-0742)Sanders Associates, Inc.U.S. Air Force - Office of Scientific Research (Contract F19628-85-K-0028)Advanced Television Research ProgramAmoco Foundation FellowshipHertz Foundation Fellowshi

Financing of International Collective Action for Epidemic and Pandemic Preparedness.

The global pandemic response has typically followed cycles of panic followed by neglect. We are now, once again, in a phase of neglect, leaving the world highly vulnerable to massive loss of life and economic shocks from natural or human-made epidemics and pandemics. Quantifying the size of the losses caused by large-scale outbreaks is challenging because the epidemiological and economic research in this field is still at an early stage. Research on the 1918 influenza H1N1 pandemic and recent epidemics and pandemics has shown a range of estimated losses (panel).1; 2; 3; 4; 5; 6 ; 7 A limitation in assessing the economic costs of outbreaks is that they only capture the impact on income. Fan and colleagues8 recently addressed this limitation by estimating the “inclusive” cost of pandemics: the sum of the cost in lost income and a dollar valuation of the cost of early death. They found that for Ebola and severe acute respiratory syndrome (SARS), the true (“inclusive”) costs are two to three times the income loss. For extremely serious pandemics such as that of influenza in 1918, the inclusive costs are over five times income loss. The inclusive costs of the next severe influenza pandemic could be US$570 billion each year or 0·7$1 billion over 5 years, is developing vaccines against known emerging infectious diseases as well as platforms for rapid development of vaccines against outbreaks of unknown origin. The WHO R&D Blueprint for Action to Prevent Epidemics12 is a new mechanism for coordinating and prioritising the development of drugs and diagnostics for emerging infectious diseases. Consolidating and enhancing donor support for these new initiatives would be an efficient way to channel resources aimed at improving global outbreak preparedness and response. Crucial components of the global and regional system for outbreak control include surge capacity (eg, the ability to urgently deploy human resources); providing technical guidance to countries in the event of an outbreak; and establishing a coordinated, interlinked global, regional, and national surveillance system. These activities are the remit of several essential WHO financing envelopes that all face major funding shortfalls. The Contingency Fund for Emergencies finances surge outbreak response for up to 3 months. The fund has a capitalisation target of $100 million of flexible voluntary contributions, which needs to be replenished with about$25–50 million annually, depending on the extent of the outbreak in any given year. However, as of April 30, 2017, only $37·65 million had been contributed, with an additional$4 million in pledges.13 The WHO Health Emergencies and Health Systems Preparedness Programmes face an annual shortfall of $225 million in funding their epidemic and pandemic prevention and control activities.14 Previous health emergencies have shown that it can take time to organise global collective action and provide financing to the national and local level. In such situations, a global mechanism should offer a rapid injection of liquidity to affected countries. The World Bank\u27s Pandemic Emergency Financing Facility (PEF) is a proposed global insurance mechanism for pandemic emergencies.15 It aims to provide surge funding for response efforts to help respond to rare, high-burden disease outbreaks, preventing them from becoming more deadly and costly pandemics. The PEF currently proposes a coverage of$500 million for the insurance window; increasing the current coverage will require additional donor commitments. In addition, the PEF has a $50–100 million replenishable cash window. As the world\u27s health ministers meet this month for the World Health Assembly, we propose five key ways to help prevent mortality and economic shocks from disease outbreaks. First, to accelerate development of new technologies to control outbreaks, donors should expand their financing for CEPI and support the WHO R&D Blueprint for Action to Prevent Epidemics. Second, funding gaps in the WHO Contingency Fund for Emergencies and the WHO Health Emergencies Programme should be urgently filled and the PEF should be fully financed. Third, all nations should support their own and other countries\u27 national preparedness efforts, including committing to the JEE process. Fourth, we believe it would be valuable to create and maintain a regional and country-level pandemic risk and preparedness index. This index could potentially be used as a way to review preparedness in International Monetary Fund article IV consultations (regular country reports by staff to its Board). Finally, we call for a new global effort to develop long-term national, regional, and global investment plans to create a world secure from the threat of devastation from outbreaks. This article summarises the recommendations of a workshop held at the National Academy of Medicine, Washington, DC, USA, co-hosted by the Center for Policy Impact in Global Health at Duke University, Durham, NC, USA and the Coalition for Epidemic Preparedness Innovations, Oslo, Norway. Participants\u27 travel and accommodation were supported by the Center for Policy Impact in Global Health. BO is a consultant to Metabiota, a private company engaged in infectious disease risk modelling and analytical services. In this capacity, he has led the development of an index measuring national capacity to respond to epidemic and pandemic disease outbreaks