On Optimum End-to-End Distortion in MIMO Systems

This paper presents the joint impact of the numbers of antennas, source-to-channel bandwidth ratio and spatial correlation on the optimum expected end-to-end distortion in an outage-free MIMO system. In particular, based on an analytical expression valid for any SNR, a closed-form expression of the optimum asymptotic expected end-to-end distortion valid for high SNR is derived. It is comprised of the optimum distortion exponent and the multiplicative optimum distortion factor. Demonstrated by the simulation results, the analysis on the joint impact of the optimum distortion exponent and the optimum distortion factor explains the behavior of the optimum expected end-to-end distortion varying with the numbers of antennas, source-to-channel bandwidth ratio and spatial correlation. It is also proved that as the correlation tends to zero, the optimum asymptotic expected end-to-end distortion in the setting of correlated channel approaches that in the setting of uncorrelated channel. The results in this paper could be performance objectives for analog-source transmission systems. To some extend, they are instructive for system design.Comment: 35 pages, 10 figures, submitted to EURASIP Journal on Wireless Communications and Networkin

Soft Pilot Reuse and Multi-Cell Block Diagonalization Precoding for Massive MIMO Systems

The users at cell edge of a massive multiple-input multiple-output (MIMO) system suffer from severe pilot contamination, which leads to poor quality of service (QoS). In order to enhance the QoS for these edge users, soft pilot reuse (SPR) combined with multi-cell block diagonalization (MBD) precoding are proposed. Specifically, the users are divided into two groups according to their large-scale fading coefficients, referred to as the center users, who only suffer from modest pilot contamination and the edge users, who suffer from severe pilot contamination. Based on this distinction, the SPR scheme is proposed for improving the QoS for the edge users, whereby a cell-center pilot group is reused for all cell-center users in all cells, while a cell-edge pilot group is applied for the edge users in the adjacent cells. By extending the classical block diagonalization precoding to a multi-cell scenario, the MBD precoding scheme projects the downlink transmit signal onto the null space of the subspace spanned by the inter-cell channels of the edge users in adjacent cells. Thus, the inter-cell interference contaminating the edge users' signals in the adjacent cells can be efficiently mitigated and hence the QoS of these edge users can be further enhanced. Our theoretical analysis and simulation results demonstrate that both the uplink and downlink rates of the edge users are significantly improved, albeit at the cost of the slightly decreased rate of center users.Comment: 13 pages, 12 figures, accepted for publication in IEEE Transactions on Vehicular Technology, 201

OVERCOMING THE AGE-ASSOCIATED DECLINE IN NEURAL STEM CELL PROLIFERATION

poster abstractThe U.S. population is aging. Age-related cognitive decline is a major public health problem. Developing an approach to treat or delay cognitive decline is critical. Neurogenesis by neural stem/progenitor cells (NSCs) in the hippocampus is related to cognitive function, and is greatly affected by the aging process. The molecular signaling that regulates age-related decline in neurogenesis is still poorly understood. Here we took the advantage of a transgenic mouse, Nestin-GFP, to assess neurogenesis and molecular signal-ing related to age-related decline in neurogenesis. We found that the total number of NSCs, including quiescent neural progenitors (QNPs) and amplify-ing neural progenitors (ANPs) decreased as the mice aged, but more im-portantly, ANPs are more significantly affected than QNPs, leading to further reduction in number and proliferation of ANPs. We further found that the mTOR signaling pathway is impaired in NSCs as mice age. Activating the mTOR signaling pathway through Ketamine injections increased NSC prolif-eration in aged mice. In contrast, inhibiting the activity of the mTOR signal-ing pathway by rapamycin is sufficient to reduce ANP proliferation in young mice. These results indicate that NSCs becomes more quiescent when the activity of mTOR signaling is compromised in aged mice, and stimulating the activity of mTOR signaling can overcome the age-associated decline in NSC proliferation. This data suggests that promoting stem cell proliferation to en-hance neurogenesis may be a potential approach for attenuating cognitive decline in the aging brain.This work was supported by funding from the Ralph W. and Grace M. Showalter Research Award, Indiana University Biological Research Grant, NIH grants RR025761 and 1R21NS072631-01A, and Undergraduate Research Opportunities Program (UROP)

NEROPATHOLOGICAL APPROACH FOR BLAST-WAVE INDUCED MILD BRAIN INJURY

poster abstractVeterans of Iraq and Afghanistan are extremely susceptible to complica-tions derived from blast-wave induced mild traumatic brain injury (mTBI) sustained from road-side bombs and IEDs. Furthermore, there are 1.5 mil-lion civilian incidences of TBIs annually in the United States, and as many as nearly 75% of them are mTBIs. An mTBI is an important medical concern because it can lead to long-term cognitive, emotional difficulties and behav-ioral disturbances. Neuroimaging with CT or MRI is usually negative. That is why mTBI has been called an “invisible wound.” There are no effective treatments for these disorders, partially due to the fact that the pathological basis leading to neurological disorders are poorly understood. Using a blast-wave injury model, several mice were given injuries similar to those from the front lines. The damaged brains were collected, mounted, stained, and imaged to track the dendrite and spine degeneration, both over all and by type of spine. After quantification, the results showed that the injured brain is intact without showing dramatic lesion or cell death, however, when we further assessed the morphologies of the spared neurons by using Golgi staining to visualize the individual neurons including their processes and spines in a very high resolution, we found that the dendrites of the spared neurons in the injured cortex demonstrated dramatic swelling with beading, a hallmark of dendritic injury, and there was a significant decrease in the number of mature (mushroom) spines, as well as a significant decrease in the overall number of spines. The function of the central nervous system critically relies on the synaptic connection from the different neurons be-tween the spines. The widespread synapse loss disrupts neural circuitry fol-lowing mTBI and will certainly contribute to neurological disorders. Our re-sults showed that mild blast-wave induced injury led to extensive dendrite degeneration and synapse reduction in the cortex in an animal model. This experimental study sheds light on the neuropathology of mild TBI in humans, and suggests that neurodegeneration may be a novel target for developing diagnostic methods and therapeutic approaches for mTBI in the future

TRAUMATIC BRAIN INJURY LEADS TO ABERRANT MIGRATION OF ADULT-BORN NEURONS IN THE HIPPOCAMPUS

poster abstractTraumatic brain injury (TBI) is the leading cause of death in children and young adults, leading to substantial cognitive impairment, motor dysfunction and epilepsy. There is no effective treatment for these dis-orders. The discovery of neural stem/progenitor cells (NSCs) in the adult brain raises a potentially promising strategy for repairing CNS in-jury.Our previous study showed that TBI promotes NSC proliferation in an attempt to initiate innate repair and/or plasticity mechanisms. However, the spontaneously post-traumatic recovery of hippocampal-related cognitive and memory functions is very limited. Better under-standing of neurogenesis following TBI may provide additional inter-vention to further enhance neurogenesis for successfully repairing the damaged brain following TBI. Although newborn neurons generated from NSCs are continuously added to the brain throughout our life, they must migrate from their birthplace to their appropriate destina-tion to develop into mature neurons. When we tracked the migration of newly generated neurons in the adult hippocampus after TBI, we found that a large percentage of immature neurons migrate pass their normal stopping site at the inner granular cell layer, and misplace in the outer granular cell layer of the hippocampal dentate gyrus. The aberrant migration of adult-born neurons in the hippocampus occurs 3 days after TBI, and lasts for 10 weeks, resulting in a great number of newly generated neurons misplaced in the outer granular layer in the hippocampus. The newborn neurons at the displaced position will not be able to make correct connections with their appropriate targets, and may even make wrong connections with inappropriate nearby tar-gets in the pre-existing neural network. Abnormal migration can cause several diseases including epilepsy. These results suggest that stimu-lation of endogenous adult neural stem cells following TBI might offer new avenues for cell-based therapy. Additional intervention is required to further enhance successful neurogenesis for repairing the damaged brain

A fast topology optimization method of damping material layer for noise reduction to elastic curved plate-cavity structure

This paper presents a fast topology optimization method of damping material layer for noise reduction to elastic curved plate (shell)-cavity structure. Using less as far as possible the damping materials reach the maximum efficiency of one's vibration or noise reduction. Energy method is employed. The way to determine the location where the damping material pasted on is to find the location where damping material’s energy will lose more. The computational model is based on a finite element discretization. Assuming pasting a small amount of damping materials on the structure has little effect on vibration mode, the relationship between energy loss of the damping material on each element and the displacement of the nodes of the plate (shell) during a period of vibration was deduced. Damping material was laid out on the element location where damping layer energy will lose most, and then the second gradually, until optimization target was achieved. Commercial finite element software was used to obtain the finite element model of complex engineering structures. Nodes information, stiffness and mass matrix were read out by Matlab subroutines. A numerical result of topology optimization of damping material layer on the curved plate-cavity structure noise reduction was presented. The topology optimization method is approximate, simple and suitable for complex engineering applications

The Shapley Values on Fuzzy Coalition Games with Concave Integral Form

A generalized form of a cooperative game with fuzzy coalition variables is proposed. The character function of the new game is described by the Concave integral, which allows players to assign their preferred expected values only to some coalitions. It is shown that the new game will degenerate into the Tsurumi fuzzy game when it is convex. The Shapley values of the proposed game have been investigated in detail and their simple calculation formula is given by a linear aggregation of the Shapley values on subdecompositions crisp coalitions