Fractal capacitors

A linear capacitor structure using fractal geometries is described. This capacitor exploits both lateral and vertical electric fields to increase the capacitance per unit area. Compared to standard parallel-plate capacitors, the parasitic bottom-plate capacitance is reduced. Unlike conventional metal-to-metal capacitors, the capacitance density increases with technology scaling. A classic fractal structure is implemented with 0.6-μm metal spacing, and a factor of 2.3 increase in the capacitance per unit area is observed. It is shown that capacitance boost factors in excess of ten may be possible as technology continues to scale. A computer-aided-design tool to automatically generate and analyze custom fractal layouts has been developed

Low-frequency current variability and spin-off eddies along the shelf off Southeast Florida

Time series analyses of current meter records from a 6-element box array installed on the narrow shelf (\u3c5 km) off Miami, Florida revealed two distinct current regimes. Current oscillations at the shelf break (30m isobath) appeared to be primarily produced by Florida Current spawned events, such as low frequency (periods of 2 days to 2 weeks) wave-like meanders of the Florida Current and the transient occurrence of small diameter spin-off eddies, both of which may be indirectly related to wind forcing...

Low-Frequency Current and Temperature Variability From Gulf Stream Frontal Eddies and Atmospheric Forcing Along the Southeast U.S. Outer Continental Shelf

Low‐frequency current and temperature time series from the outer shelf between Cape Canaveral, Florida, and Cape Romain, South Carolina, are compared with shipboard hydrographic data, satellite VHRR, coastal and buoy winds, and coastal sea level during the period from February to June 1980. Low‐frequency current and temperature variability along the shelf break was primarily produced by cyclonic, cold core Gulf Stream frontal eddies. These disturbances traveled to the north at speeds of 50 to 70 cm s−1 with periods of 5 to 9 days throughout the experiment and produced cold cyclonic perturbations of the northward mean flow and temperature fields over an along‐shelf coherence scale of 100 km. Frontal eddies appear to be an important mechanism in the observed eastward transport of northward momentum and heat along the shelf edge. They also appear to play a key role in the transfer of eddy kinetic and potential energy back to the mean flow, which suggests an upstream formation region and shear‐induced dissipation. Upwelling velocities of about 10−2 cm s−1 in the cold core provide the major source of new nutrients to the outer shelf. Subtidal flow variability at the 40‐m isobath was a mixed response to Gulf Stream and wind forcing. Barotropic along‐shelf current oscillations were coherent with the local winds and coastal sea level at periods of 3–4 and 10–12 days over along‐shelf scales of 400 km with small phase lags, suggesting a nearly simultaneous frictional equilibrium response to coherent wind‐induced sea level slopes

Stage 1 Geotechnical Studies for Interstate 15 Reconstruction Project, Salt Lake County, Utah

Interstate 15 Reconstruction Project includes rebuilding of 137 bridges; widening the existing three general purpose lane roadway to four general purpose lane with a HOV lane and an auxiliary lane roadway, and other associated work such as converting the existing diamond interchanges to single point urban interchanges (SPUI). The project will be built under a design-build procurement process and is anticipated to be completed in 4 ½ years by October of 2001. The subsurface soils beneath the corridor consist of lake deposits (Lake Bonneville), namely soft to medium stiff plastic clays, silts and loose to medium dense sands ranging in thickness over 150 meters. The shallow water table is generally 5 to 10 feet below natural grade. The soft clays have low shear strengths and are highly compressible under embankment loads. The Salt Lake segment of the Wasatch fault is approximately 3.5 kilometer to the cast of the highway corridor. The structures will have to be designed to meet the seismic criteria and take into account the high liquefaction potential of some of the saturated sand lenses. Stage 1 efforts included identification of the various subsurface conditions; evaluation of soil parameters; establishing guidelines for field investigations, laboratory testing; analysis; reporting etc. In addition, various project specific studies were carried out for the proposed reconstruction project, details of which are presented in the paper

Purine nucleoside phosphorylase: A new marker for free oxygen radical injury to the endothelial cell

The effect of ischemia and reperfusion on purine nucleoside phosphorylase was studied in an isolated perfused rat liver model. This enzyme is localized primarily in the cytoplasm of the endothelial and Kupffer cells; some activity is associated with the parenchymal cells. Levels of this enzyme accurately predicted the extent of ischemia and reperfusion damage to the microvascular endothelial cell of the liver. Livers from Lewis rats were subjected to 30, 45 and 60 min of warm (37° C) no flow ischemia that was followed by a standard reperfusion period lasting 45 min. Purine nucleoside phosphorylase was measured at the end of the no flow ischemia and reperfusion periods as was superoxide generation (O2‐). Bile production was monitored throughout the no flow ischemia and reperfusion periods. Control perfusions were carried out for 120 min. A significant rise in purine nucleoside phosphorylase levels as compared with controls was observed at the end of ischemia in all the three groups. The highest level, 203.5 ± 29.2 mU/ml, was observed after 60 min of ischemia. After the reperfusion period, levels of purine nucleoside phosphorylase decreased in the 30‐ and 45‐min groups 58.17 ± 9.66 mU/ml and 67.5 ± 17.1 mU/ml, respectively. These levels were equal to control perfusions. In contrast, after 60 min of ischemia, levels of purine nucleoside phosphorylase decreased early in the reperfusion period and then rose to 127.8 ± 14.8 mU/ml by the end of reperfusion (p < 0.0001). Superoxide generation at the beginning of reperfusion was higher than in controls with similar values observed at the end of 30, 45 and 60 min of ischemia. During reperfusion, production of superoxide continued. Bile production was significantly lower at the end of 30 min (0.044 ± 0.026 μl/min/gm), 45 min (0.029 ± 0.0022 μ/min/gm) and 60 min of ischemia (0.022 ± 0.008 μ/min/gm) when compared with bile production by control livers during the corresponding time (0.680 ± 0.195, 0.562 ± 0.133 and 0.480 ± 0.100 μ/min/gm respectively; p < 0.001). During reperfusion, rates of bile production were normal after 30 and 45 min of ischemia. In contrast, significantly lower rates of bile production, 0.046 ± 0.36 μ/min/gm (p < 0.001) occurred during reperfusion after 60 min of ischemia. Control livers during the same period produced 0.330 ± 0.056 μl/min/gm of bile. The results indicate that purine nucleoside phosphorylase levels may be a good index of oxidative injury to the liver in ischemia reperfusion and reliably predict the functional state of the organ after reperfusion. Copyright © 1990 American Association for the Study of Liver Disease

Review of Upwelling Off the Southeastern United States and Its Effect on Continental-Shelf Nutrient Concentrations and Primary Productivity

Gulf Stream induced upwelling occurs along the length of the southeastern United States continental shelf break. Upwelling events are produced by northward propagating Gulf Streams frontal meanders and eddies and travel northwards with these features. Meanders and eddies occur throughout the year in a period band of 2-14 days; however, resultant upwellings can affect the shelf quite differently. During fall, winter, and spring, upwelling is restricted to the outer shelf by cross-shelf density distributions, but in the summer upwelled water may penetrate across as a subsurface intrusion if aided by upwelling-favorable winds. If water does penetrate across the shelf, it may become stranded, detached from its deep-water Gulf Stream source, and may reside on the shelf for many weeks. The mass of nitrate within stranded water masses has been observed to be over 2500 metrick tonnes nitrate-nitrogen covering an area of 2500 km2. Gulf Stream upwelling-induced nutrient inputs dominate all other sources to the south atlantic bight (SAB) and have a profound effect of phytoplankton production. During the fall, winter, and spring, high phytoplankton, coincides with outer shelf upwelling, while in the summer production also occurs in the lower layer over the inner and middle shelf. Over one-half the phytoplankton production is considered “new” production

Gulf Stream Frontal Eddy Influence on Productivity of the Southeast United States Continental Shelf

Weekly period meanders and eddies are persistent features of Gulf Stream frontal dynamics from Miami, Florida, to Cape Hatteras, North Carolina. Satellite imagery and moored current and temperature records reveal a spatial pattern of preferred regions for growth and decay of frontal disturbances. Growth regions occur off Miami, Cape Canaveral, and Cape Fear due to baroclinic instability, and decay occurs in the confines of the Straits of Florida between Miami and Palm Beach, between 30° and 32°N where the stream approaches the topographic feature known as the Charleston bump and between 33°N and Cape Hatteras. Eddy decay regions are associated with elongation of frontal features, offshore transport of momentum and heat, and onshore transport of nutrients. Onshore transport of new nitrogen from the nutrient-bearing strata beneath the Gulf Stream indicates that frontal eddies serve as a nutrient pump for the shelf. New nitrogen flux to the shelf due to Gulf Stream input could support new production of 7.4 x 1012 g C yr-1 or about 8 million tons carbon per year if all nitrate were utilized. Calculations indicate that approximately 70% of this potential new production is realized, yielding an annual new production for the outer shelf of 4.3 x 1012gC