Feedback-Topology Designs for Interference Alignment in MIMO Interference Channels

Interference alignment (IA) is a joint-transmission technique that achieves the capacity of the interference channel for high signal-to-noise ratios (SNRs). Most prior work on IA is based on the impractical assumption that perfect and global channel-state information(CSI) is available at all transmitters. To implement IA, each receiver has to feed back CSI to all interferers, resulting in overwhelming feedback overhead. In particular, the sum feedback rate of each receiver scales quadratically with the number of users even if the quantized CSI is fed back. To substantially suppress feedback overhead, this paper focuses on designing efficient arrangements of feedback links, called feedback topologies, under the IA constraint. For the multiple-input-multiple-output (MIMO) K-user interference channel, we propose the feedback topology that supports sequential CSI exchange (feedback and feedforward) between transmitters and receivers so as to achieve IA progressively. This feedback topology is shown to reduce the network feedback overhead from a cubic function of K to a linear one. To reduce the delay in the sequential CSI exchange, an alternative feedback topology is designed for supporting two-hop feedback via a control station, which also achieves the linear feedback scaling with K. Next, given the proposed feedback topologies, the feedback-bit allocation algorithm is designed for allocating feedback bits by each receiver to different feedback links so as to regulate the residual interference caused by the finite-rate feedback. Simulation results demonstrate that the proposed bit allocation leads to significant throughput gains especially in strong interference environments.Comment: 28 pages; 11 figures ; submitted to IEEE Trans. on Signal Processin

Molecular Probes to Evaluate the Synthesis and Production Potential of an Odorous Compound (2-methylisoborneol) in Cyanobacteria

The volatile metabolite, 2-Methylisoborneol (2-MIB) produced by cyanobacterial species, causes odor and taste problems in freshwater systems. However, simple identification of cyanobacteria that produce such off-flavors may be insufficient to establish the causal agent of off-flavor-related problems as the production-related genes are often strain-specific. Here, we designed a set of primers for detecting and quantifying 2-MIB-synthesizing cyanobacteria based on mibC gene sequences (encoding 2-MIB synthesis-catalyzing monoterpene cyclase) from various Oscillatoriales and Synechococcales cyanobacterial strains deposited in GenBank. Cyanobacterial cells and environmental DNA and RNA were collected from both the water column and sediment of a eutrophic stream (the Gong-ji Stream, Chuncheon, South Korea), which has a high 2-MIB concentration. Primer sets mibC196 and mibC300 showed universality to mibC in the Synechococcales and Oscillatoriales strains; the mibC132 primer showed high specificity for Pseudanabaena and Planktothricoides mibC. Our mibC primers showed excellent amplification efficiency (100–102%) and high correlation among related variables (2-MIB concentration with water RNA r = 689, p < 0.01; sediment DNA r = 0.794, p < 0.01; and water DNA r = 0.644, p < 0.05; cyanobacteria cell density with water RNA and DNA r = 0.995, p < 0.01). These primers offer an efficient tool for identifying cyanobacterial strains possessing mibC genes (and thus 2-MIB-producing potential) and for evaluating mibC gene expression as an early warning of massive cyanobacterial occurrence

Complete atrioventricular block as an initial manifestation of recurred oral cavity cancer: a case report

Abstract Background Intracardiac invasion of head and neck cancer is extremely rare. Here, we report a case of recurred oral cavity cancer presenting with complete atrioventricular (AV) block caused by cardiac metastasis. Case presentation A 70-year-old male presented with dizziness for 2 days. He had a history of oral cavity cancer a year ago, and the tumor was treated by surgical excision after induction chemotherapy and concurrent chemoradiation therapy. Electrocardiography showed complete AV block with ventricular escape rate of 43 beats per minute. Cardiac imaging revealed about 4.0 × 2.0 cm-sized mass invading interventricular septum and AV nodes and protruding into the right ventricle. Magenetic resonance imaging of head and neck demonstrated recurred mass in oral cavity and maxillary sinus. Fluorodeoxyglucose-positron emission tomography showed hypermetabolic lesion in both oral cavity and the heart around interventricular septum and atrioventricular node indicating recurred oral cavity cancer with cardiac metastasis. Permament pacemaker of DDD type was implanted for the symptomatic complete AV block, and palliative chemotherapy was initiated. Conclusion The present case demonstrated that oral cavity cancer can metastasize to the heart, and complete AV block may be an initial manifestation of the recurrence of extracardiac cancer with intracardiac invasion

Efficient Feedback Design for Interference Alignment in MIMO Interference Channel

Interference alignment (IA) is a joint-transmission technique that achieves the capacity of the interference channel for high signal-to-noise ratios (SNRs). However, most prior works on IA are based on the impractical assumption that perfect and global channel-state information(CSI) is available at all transmitters, resulting in overwhelming feedback overhead. To substantially suppress the feedback overhead, this paper proposes an efficient design of the feedback framework for IA in the K-user multiple-input multiple-output (MIMO) interference channel. The proposed feedback topology supports sequential CSI exchange (feedback and feedforward) between transmitters and receivers and reduces the feedback overhead from a cubic function of K to a linear one, compared to conventional feedback approaches. Given the proposed feedback topology, we consider the limited feedback channel from the receivers to corresponding interferers and analyze the effect of quantization error which generates the residual interference. Also, an efficient feedback-bit allocation algorithm that minimizes the upper-bound of sum residual interference is proposed

Comprehensive Electrokinetic-Assisted Separation of Oil Emulsion with Ultrahigh Flux

Many industries have a significant but largely unmet need for efficient and high-flux emulsion separation, particularly for nanoemulsions. Conventional separation membranes rely on size-based separation mainly utilizing a sieving mechanism plus a wetting phenomenon, resulting in a dramatic trade-off between separation efficiency and separation flux. Herein we address this challenge by adapting electrokinetics to membrane-based separation, using a charge-based mechanism capable of separating even nanoemulsions with a demonstrated separation efficiency of >99% and ultrahigh flux up to 40 000 L/H.m(2). Our device arrests nano-oil droplets, allowing them to coalesce into larger droplets which are then able to be filtered by coarser membranes. This hybrid technology makes electrokinetic-assisted filtration scalable and commercially viable and allows for a better understanding of the multiphysics underlying dynamic separation.11Nsciescopu

Tunable Ionic Transport for a Triangular Nanochannel in a Polymeric Nanofluidic System

Recently, tremendous engineering applications utilizing new physics of nanoscale electrokinetics have been reported and their basic fundamentals are actively researched. In this work, we first report a simple and economic but reliable nanochannel fabrication technique, leading to a heterogeneously charged triangular nanochannel. The nanochannel utilized the elasticity of PDMS when it bonded with a micrometer-scale structure on a substrate. Second, we successfully demonstrated novel ionic transportations by tweaking the micrometer structures: (1) the transition of nonlinear ionic conductance depending on the nanochannel properties and (2) the ionic field-effect transistor. Nanochannel conductance has two distinguishable nonlinear regimes called the "surface-charge-governed" and the "geometry-governed" regime and its only individual overlooks were frequently reported. However, the transition between two regimes by adjusting nanochannel properties has not been reported due to the difficulty of functional nanochannel fabrication. In addition, a gate voltage was comfortably applied to the triangular nanochannel so that the field-effect ion transportation was reliably achieved. Therefore, presenting triangular nanochannels have critical advantages over Its heterogeneous and tunable surface properties and thus, could be an effective means as an active fundamental to control and manipulate the ion-electromigration through a nanofluidic system.X115244sciescopu

Modeling Nonequilibrium Adsorption of MIB and Sulfamethoxazole by Powdered Activated Carbon and the Role of Dissolved Organic Matter Competition

This study demonstrates that the ideal adsorbed solution theory–equivalent background compound (IAST–EBC) as a stand-alone model can simulate and predict the powdered activated carbon (PAC) adsorption of organic micropollutants found in drinking water sources in the presence of background dissolved organic matter (DOM) under nonequilibrium conditions. The IAST–EBC represents the DOM competitive effect as an equivalent background compound (EBC). When adsorbing 2-methylisoborneol (MIB) with PAC, the EBC initial concentration was a similar percentage, on average 0.51%, of the dissolved organic carbon in eight nonwastewater impacted surface waters. Using this average percentage in the IAST–EBC model yielded good predictions for MIB removal in two nonwastewater impacted waters. The percentage of competitive DOM was significantly greater in wastewater impacted surface waters, and varied markedly in DOM size fractions. Fluorescence parameters exhibited a strong correlation with the percentage of competitive DOM in these waters. Utilizing such correlations in the IAST–EBC successfully modeled MIB and sulfamethoxazole adsorption by three different PACs in the presence of DOM that varied in competitive effect. The influence of simultaneous coagulant addition on PAC adsorption of micropollutants was also investigated. Coagulation caused the DOM competitive effect to increase and decrease with MIB and sulfamethoxazole, respectively

Carotid plaque rather than intima-media thickness as a predictor of recurrent vascular events in patients with acute ischemic stroke

Abstract Background To investigate the impacts of carotid plaque and intima-media thickness (IMT) on future vascular events (VEs) in the patients with acute ischemic stroke. Methods A total of 479 consecutive Korean patients with acute ischemic stroke were divided into 2 groups according to development of VEs; VE group (65.4 ± 10.9 years) vs no VE group (62.8 ± 13.2 years). VEs were defined as the development of recurrent stroke, coronary events, peripheral arterial disease, and death. Clinical, laboratory, and imaging findings were compared between the groups. Results During 105.5 ± 29.0 months of follow up, VEs were developed in 142 patients (29.6%). In univariate analysis, VEs were significantly associated with age, gender, diabetes, renal function, lipid levels, left ventricular function, carotid plaque or IMT. In multivariate analysis, the presence of carotid plaque, diabetes, renal function and male gender were independent predictors of future VEs in the patients with ischemic stroke, but carotid IMT was not a predictor of future VEs. Event free survival was significantly lower in patients with carotid plaque than without carotid plaque on Kaplan-Meier analysis (log rank p < 0.001). Conclusion The present study demonstrated that diabetes, impaired renal function, male gender, and the presence of carotid plaque rather than IMT were independent predictors of future VEs in Korean patients with acute ischemic stroke. Active medical management and careful monitoring for the development of recurrent VEs are strongly recommended in patients with acute ischemic stroke and carotid plaque