A Three-Dimensional Pattern-Space Representation for Volumetric Arrays

A three-dimensional pattern-space representation is presented for volumetric arrays. In this representation, the radiation pattern of an array is formed by the evaluation of the three-dimensional pattern-space on a spherical surface. The scan angle of the array determines the position of this surface within the pattern-space. This pattern-space representation is used in conjunction with a genetic algorithm to minimize the sidelobe levels exhibited by a thinned volumetric array during scanning

Grating Lobe Reduction in Aperiodic Linear Arrays of Physically Large Antennas

We present performance bounds obtained from the optimization of the sidelobe levels of aperiodic linear arrays. The antennas comprising these arrays are large compared to the distance between neighboring antennas, a case not addressed in previously published work. This optimization is performed in pattern-space and is applicable over a wide range of scan angles. We show that grating lobes can be suppressed even when the elemental antennas are several wavelengths in size, provided that the ratio of the antenna size to the average spacing between the antenna center-points does not exceed 80%

Scan Loss Pattern Synthesis for Adaptive Array Ground Stations

We present several techniques for maximizing the contact time between low Earth orbiting satellites (LEOs) and a ground station (GS). The GS comprises an adaptive array of electronically steered space-fed lenses (SFLs). Each SFL is manufactured as a low-cost printed circuit with the result that it exhibits scanning loss. By differently orienting the boresights of the SFLs in the adaptive array, the SFL\u27s scanning losses can be made to optimally complement the path loss of the LEO, thereby reducing the cost of the GS while maximizing the download capacity of the satellite link. The optimization, implemented with a genetic algorithm (GA), can be viewed as a kind of pattern synthesis. Such arrays will benefit Earth exploration satellite service (EESS) and telemetry applications, promising a decreased cost and increased reliability as compared with GSs consisting of a large dish antenna. We show that a network of these GSs comprising a total of fourteen small antennas can achieve an average daily data rate that is comparable with that of a single large dish antenna for the Earth Observing One (EO-1) satellite, without increasing the output power of the satellite. We also analyze the case in which the satellite transmits with a variable bit rate (VBR). Furthermore, we show that by selectively populating the focal surface of the SFL with feeds, simultaneous communications with multiple satellites can be achieved with a single ground station

Application of Millimeter Wave, Eddy Current and Thermographic Methods for Detection of Corrosion in Aluminum Substrate

Aluminum structures exposed to the elements are susceptible to corrosion. Corrosion may cause various mechanical and structural deficiencies such as material thinning. It is desirable to rapidly detect and evaluate the properties of an aluminum substrate early in the corrosion process to avoid costly maintenance actions later. There are several nondestructive testing methods for this purpose. To investigate capabilities of millimeter wave, conventional eddy current, and flash thermography techniques for detection of large corrosion areas in aluminum substrates, two corroded samples were inspected with and without dielectric coating (appliqué). This paper presents the results of the c-scan imaging of these samples using the methods mentioned above. The attributes of these methods for detection and evaluation of large, severe and non-uniform corrosion areas with and without a dielectric coating are discussed

Comparison of X-Ray, Millimeter Wave, Shearography and Through-Transmission Ultrasonic Methods for Inspection of Honeycomb Composites

Honeycomb composites are increasingly finding utility in a variety of environments and applications, such as aircraft structural components, flight control components, radomes, etc. In-service and environmental stresses can produce unwanted flaws that adversely affect the structural integrity and functionality of these composites. These flaws may be in the forms of disbonds, delaminations, impact damage, crushed honeycomb, moisture intrusion, internal cracks, etc. There are several nondestructive testing (NDT) methods that may be used to inspect these composites for the presence and evaluation of these flaws. Such NDT methods include X-ray computed tomography, near-field millimeter wave, shearography, and ultrasonic testing. To assess the capabilities of these methods for honeycomb composite inspection, two honeycomb composites panels were produced with several embedded flaws and missing material primarily representing planar disbonds at various levels within the thickness of the panels and with different shapes. Subsequently, the aforementioned NDT methods were used to produce images of the two panels. This paper presents the results of these investigations and a comparison among the capabilities of these methods

Genetic variation of Glucose Transporter-1 (GLUT1) and albuminuria in 10,278 European Americans and African Americans: a case-control study in the Atherosclerosis Risk in Communities (ARIC) Study

<p>Abstract</p> <p>Background</p> <p>Evidence suggests glucose transporter-1(<it>GLUT1</it>) genetic variation affects diabetic nephropathy and albuminuria. Our aim was to evaluate associations with albuminuria of six <it>GLUT1 </it>single nucleotide polymorphisms(SNPs), particularly <it>XbaI </it>and the previously associated <it>Enhancer-2(Enh2</it>) SNP.</p> <p>Methods</p> <p>A two-stage case-control study was nested in a prospective cohort study of 2156 African Americans and 8122 European Americans with urinary albumin-to-creatinine ratio(ACR). Cases comprised albuminuria(N = 825; ≥ 30 μg/mg) and macroalbuminuria(N = 173; ≥ 300 μg/mg). ACR < 30 μg/mg classified controls(n = 9453). Logistic regression and odds ratios(OR) assessed associations. The evaluation phase(stage 1, n = 2938) tested associations of albuminuria(n = 305) with six <it>GLUT1 </it>SNPs: rs841839, rs3768043, rs2297977, <it>Enh2</it>(rs841847) <it>Xba</it>I(rs841853), and rs841858. <it>Enh2 </it>was examined separately in the replication phase(stage 2, n = 7340) and the total combined sample (n = 10,278), with all analyses stratified by race and type 2 diabetes.</p> <p>Results</p> <p>In European Americans, after adjusting for diabetes and other <it>GLUT1 </it>SNPs in stage 1, <it>Enh2 </it>risk genotype(TT) was more common in albuminuric cases(OR = 3.37, P = 0.090) whereas <it>XbaI </it>(OR = 0.94, p = 0.931) and remaining SNPs were not. In stage 1, the <it>Enh2 </it>association with albuminuria was significant among diabetic European Americans(OR = 2.36, P = 0.025). In African Americans, <it>Enh2 </it>homozygosity was rare(0.3%); <it>XbaI </it>was common(18.0% AA) and not associated with albuminuria. In stage 2(n = 7,340), <it>Enh2 </it>risk genotype had increased but non-significant OR among diabetic European Americans(OR = 1.66, P = 0.192) and not non-diabetics(OR = 0.99, p = 0.953), not replicating stage 1. Combining stages 1 and 2, <it>Enh2 </it>was associated with albuminuria(OR 2.14 [1.20-3.80], P = 0.009) and macroalbuminuria(OR 2.69, [1.02-7.09], P = 0.045) in diabetic European Americans. The <it>Enh2 </it>association with macroalbuminuria among non-diabetic European Americans with fasting insulin(OR = 1.84, P = 0.210) was stronger at the highest insulin quartile(OR = 4.08, P = 0.040).</p> <p>Conclusions</p> <p>As demonstrated with type 1 diabetic nephropathy, the <it>GLUT1 Enh2 </it>risk genotype, instead of <it>Xba</it>I, may be associated with type 2 diabetic albuminuria among European Americans, though an association is not conclusive. The association among diabetic European Americans found in stage 1 was not replicated in stage 2; however, this risk association was evident after combining all diabetic European Americans from both stages. Additionally, our results suggest this association may extend to non-diabetics with high insulin concentrations. Rarity of the <it>Enh2 </it>risk genotype among African Americans precludes any definitive conclusions, although data suggest a risk-enhancing role.</p

LEO Download Capacity Analysis for a Network of Adaptive Array Ground Stations

To lower costs and reduce latency, a network of adaptive array ground stations, distributed across the United States, is considered for the downlink of a polar-orbiting low earth orbiting (LEO) satellite. Assuming the X-band 105 Mbps transmitter of NASA s Earth Observing 1 (EO-1) satellite with a simple line-of-sight propagation model, the average daily download capacity in bits for a network of adaptive array ground stations is compared to that of a single 11 m dish in Poker Flats, Alaska. Each adaptive array ground station is assumed to have multiple steerable antennas, either mechanically steered dishes or phased arrays that are mechanically steered in azimuth and electronically steered in elevation. Phased array technologies that are being developed for this application are the space-fed lens (SFL) and the reflectarray. Optimization of the different boresight directions of the phased arrays within a ground station is shown to significantly increase capacity; for example, this optimization quadruples the capacity for a ground station with eight SFLs. Several networks comprising only two to three ground stations are shown to meet or exceed the capacity of the big dish, Cutting the data rate by half, which saves modem costs and increases the coverage area of each ground station, is shown to increase the average daily capacity of the network for some configurations

Glycated Hemoglobin and the Risk of Kidney Disease and Retinopathy in Adults With and Without Diabetes

10.2337/db10-1198Diabetes601298-305DIAE

Serum adiponectin is positively associated with lung function in young adults, independent of obesity: The CARDIA study

<p>Abstract</p> <p>Rationale</p> <p>Adipose tissue produces adiponectin, an anti-inflammatory protein. Adiponectin deficiency in mice is associated with abnormal post-natal alveolar development.</p> <p>Objective</p> <p>We hypothesized that lower serum adiponectin concentrations are associated with lower lung function in humans, independent of obesity. We explored mediation of this association by insulin resistance and systemic inflammation.</p> <p>Methods and Measurements</p> <p>Spirometry testing was conducted at years 10 and 20 follow-up evaluation visits in 2,056 eligible young adult participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study. Body mass index, serum adiponectin, serum C-reactive protein (a marker of systemic inflammation), and insulin resistance were assessed at year 15.</p> <p>Main Results</p> <p>After controlling for body mass index, years 10 and 20 forced vital capacity (FVC) were 81 ml and 82 ml lower respectively (p = 0.004 and 0.01 respectively) in the lowest <it>vs</it>. highest adiponectin quartiles. Similarly, years 10 and 20 forced expiratory volume in one second (FEV₁) were 50 ml and 38 ml lower (p = 0.01 and 0.09, respectively) in the lowest <it>vs</it>. highest adiponectin quartiles. These associations were no longer significant after adjustment for insulin resistance and C-reactive protein. Serum adiponectin was not associated with FEV₁/FVC or peak FEV₁.</p> <p>Conclusions</p> <p>Independent of obesity, lower serum adiponectin concentrations are associated with lower lung function. The attenuation of this association after adjustment for insulin resistance and systemic inflammation suggests that these covariates are on a causal pathway linking adiponectin and lung function.</p