A Frequency Reconfigurable MIMO Antenna with Bandstop Filter Decoupling Network for Cognitive Communication.

A compact reconfigurable MIMO antenna was developed for cognitive radio applications in this research work. A bandstop filter-based decoupling network was employed in this MIMO antenna to keep mutual coupling at a minimum. A single PIN diode was connected in the filter configuration for the purpose of reconfiguration. Controlling the ON/OFF conditions of the PIN diode, it became possible to achieve a MIMO operating frequency of 4.75 GHz in mode 1 and 1.77 GHz in mode 2, respectively. At 4.75 GHz, isolation was 42.68 dB, while at 1.77 GHz, isolation was 26.52 dB. The proposed reconfigurable MIMO antenna achieved a peak gain and radiation efficiency of 6.63 dBi and 92.04 percent in mode 1 and 4.41 dBi and 89.64 percent in mode 2. MIMO characteristics such as an envelope correlation coefficient (ECC) less than 0.253, diversity gain (DG) greater than 9.675 dB, a mean effective gain (MEG) measurement ratio of less than 0.00388 dB, and channel capacity loss (CCL) of less than 0.06528 bits/s/Hz were measured for both operational frequency bands. To make it simple to integrate into small wireless devices, the overall size of the antenna is limited to 48 mm×24 mm 0.28 λ0×0.12 λ0.

Split Ring Resonator-Based Bandstop Filter for Improving Isolation in Compact MIMO Antenna.

The ever-growing expectation for high data rates has led to the introduction of multiple-input multiple-output (MIMO) technologies to wireless connectivity. Such a system requires an MIMO antenna with high isolation. At the same time, the MIMO dimension should not be compromised for achieving high isolation. Thus, isolation techniques that do not allow an increase in dimension need to be fostered for MIMO antenna design. In this paper, a novel low-profile, miniaturized MIMO antenna with high isolation was developed considering a split ring resonator (SRR)-based bandstop filter as a decoupling network. The bandstop filter was designed with a unit cell split ring resonator structure and was deployed between two closely spaced monopole MIMO antenna elements to obtain isolation as high as 39.25 dB at 2.61 GHz. Two open-circuit stub lines were attached with the MIMO feeding network to achieve good impedance matching at resonance frequency. The proposed antenna exhibited a peak gain of 3.8 dBi and radiation efficiency of 84%. It had a low envelop correlation coefficient (ECC < 0.12), high diversity gain (DG > 9.95 dB), low mean effective gain ratio (MEG 1/MEG 2 < 0.05 dB), and low channel capacity loss (CCL < 0.042 bits/s/Hz) at resonance frequency. The overall antenna dimension was restricted to 44 mm ×22 mm (0.38 λ0×0.19 λ0) for its easy integration in compact wireless devices.

Identification of a QTL for adipocyte volume and of shared genetic effects with aspartate aminotransferase.

Plasma levels of aspartate aminotransferase (AST), a liver enzyme, are elevated in patients with visceral obesity. This study examined whether adipocyte volume is under the influence of genetic factors and evaluated its genetic correlations with AST. Fasting plasma levels of 344 pedigreed baboons from the Southwest National Primate Research Center in San Antonio, TX, USA, were assayed for AST. Adipocyte volume was measured using biopsies of omental adipose tissue. Adipocyte volume, body weight, and plasma AST were heritable. Genetic correlations between the measured adiposity-related phenotypes and AST were significant. A quantitative trait locus (LOD score 3.2) for adipocyte volume was identified on the baboon homolog of human chromosome 6 near marker D6S1028. These results suggest that omental adipocyte volume is under genetic regulation and that shared genetic factors influence adiposity-associated traits and AST.

Quantitative loci regulating plasma levels of gamma glutamyl transferase and albumin and their genetic correlations with cardiovascular risk factors.

gamma Glutamyl transferase (GGT) and albumin (ALB) are two markers of liver function. These two proteins have been associated with non-alcoholic fatty liver disease and cardiovascular disease. The objectives of this study were to explore the genetic factors that influence variation in the plasma levels of GGT and ALB and to evaluate their genetic correlations with cardiovascular risk factors. Baboons from the Southwest National Primate Research Center at the Southwest Foundation for Biomedical Research, San Antonio, TX, were used as an animal model. The baboons were fed a standard monkey chow diet ad libitum. Fasting plasma concentrations of GGT, ALB, triglycerides, total cholesterol and LDL cholesterol were measured in 350 pedigreed adult baboons by standard assay procedures. A maximum likelihood-based variance decomposition approach implemented in the computer program SOLAR was used to conduct genetic analyses. The heritabilities of GGT (h(2) = 0.55; P < 0.0001) and ALB (h(2) = 0.42; P < 0.01) were significant. No statistically significant associations were found between GGT and the cardiovascular-related phenotypes. Genetic correlations between ALB and total cholesterol, LDL cholesterol and triglycerides were significant. A QTL (LOD = 2.8) for GGT plasma levels was identified on the baboon homologue of human chromosome 22 between markers D22S304 and D22S280. A QTL (LOD = 2.3) near marker D10S1432 was detected on the baboon homologue of human chromosome 10 for ALB. These results imply that variations in the plasma levels of GGT and ALB are under significant genetic regulation and that a common genetic component influences ALB and cardiovascular risk factor phenotypes.

Association of monocyte chemoattractant protein-1 with adipocyte number, insulin resistance and liver function markers.

BACKGROUND: Monocyte chemoattractant protein-1 (MCP-1) is an inflammatory chemokine known to induce adipocyte dedifferentiation and insulin resistance. Inflammation, insulin resistance, and obesity have been implicated in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). METHODS: Fasting plasma from 43 baboons were assayed for MCP-1, insulin, glucose, alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Adipocyte number and volume were measured via biopsies of omental adipose tissue. The homeostatic model assessment method (HOMA) was used to estimate systemic insulin resistance. RESULTS: Sex and age adjusted correlations were significant for MCP-1 with adipocyte number (r = -0.42; P = 0.01), adipocyte volume (r = 0.38; P = 0.02), HOMA (r = 0.45; P = 0.004), ALT (r = 0.46; P = 0.03) and AST (r = 0.45; P = 0.03). CONCLUSIONS: These results suggest that MCP-1 is related with adipocyte dedifferentiation and systemic insulin resistance, thereby potentially contributing to the development of NAFLD.