Amplifier arrays for CMB polarization

Cryogenic low noise amplifier technology has been successfully used in the study of the cosmic microwave background (CMB). Monolithic millimeter wave integrated circuit (MMIC) technology makes the mass production of coherent detection receivers feasible. We have produced large numbers of MMIC amplifiers for CMB measurements. We have also demonstrated the viability of multi-function multi-chip modules as sensitive receiver front-ends. MMIC integration makes it possible to realize massive arrays of receivers suitable for measurements of the polarization of the CMB. We describe the development of the unit cell of such an array and the development plans for implementation.     

Bioremediation in Fractured Rock: 1. Modeling to Inform Design,Monitoring, and Expectations

Field characterization of a trichloroethene (TCE) source area in fractured mudstones produced a detailed understanding of the geology, contaminant distribution in fractures and the rock matrix, and hydraulic and transport properties. Groundwater flow and chemical transport modeling that synthesized the field characterization information proved critical for designing bioremediation of the source area. The planned bioremediation involved injecting emulsified vegetable oil and bacteria to enhance the naturally occurring biodegradation of TCE. The flow and transport modeling showed that injection will spread amendments widely over a zone of lower‐permeability fractures, with long residence times expected because of small velocities after injection and sorption of emulsified vegetable oil onto solids. Amendments transported out of this zone will be diluted by groundwater flux from other areas, limiting bioremediation effectiveness downgradient. At nearby pumping wells, further dilution is expected to make bioremediation effects undetectable in the pumped water. The results emphasize that in fracture‐dominated flow regimes, the extent of injected amendments cannot be conceptualized using simple homogeneous models of groundwater flow commonly adopted to design injections in unconsolidated porous media (e.g., radial diverging or dipole flow regimes). Instead, it is important to synthesize site characterization information using a groundwater flow model that includes discrete features representing high‐ and low‐permeability fractures. This type of model accounts for the highly heterogeneous hydraulic conductivity and groundwater fluxes in fractured‐rock aquifers, and facilitates designing injection strategies that target specific volumes of the aquifer and maximize the distribution of amendments over these volumes.     

Field verification of stable perched groundwater in layered bedrock uplands

Data substantiating perched conditions in layered bedrock uplands are rare and have not been widely reported. Field observations in layered sedimentary bedrock in southwestern Wisconsin, USA, provide evidence of a stable, laterally extensive perched aquifer. Data from a densely instrumented field site show a perched aquifer in shallow dolomite, underlain by a shale-and-dolomite aquitard approximately 25 m thick, which is in turn underlain by sandstone containing a 30-m-thick unsaturated zone above a regional aquifer. Heads in water supply wells indicate that perched conditions extend at least several kilometers into hillsides, which is consistent with published modeling studies. Observations of unsaturated conditions in the sandstone over a 4-year period, historical development of the perched aquifer, and perennial flow from upland springs emanating from the shallow dolomite suggest that perched groundwater is a stable hydrogeologic feature under current climate conditions. Water-table hydrographs exhibit apparent differences in the amount and timing of recharge to the perched and regional flow systems; steep hydraulic gradients and tritium and chloride concentrations suggest there is limited hydraulic connection between the two. Recognition and characterization of perched flow systems have practical importance because their groundwater flow and transport pathways may differ significantly from those in underlying flow systems. Construction of multi-aquifer wells and groundwater withdrawal in perched systems can further alter such pathways.     

Volatile C1C7 organic compounds in an anoxic sediment core from the Pettaquamscutt River (Rhode Island,U.S.A.)

Surface sediments from an anoxic marine environment, the Upper Basin of the Pettaquamscutt River, Rhode Island, were analyzed for volatile organic compounds in the C₁C₇ range. The compounds identified included methane, ethane, alkenes (C₂C₅), carbon disulfide, cyclopentane, 3-methylpentane, methylfuran, aldehydes and ketones. Ethane, methylfuran, and most of the aldehydes and ketones showed maxima at the sediment water interface. Methane levels were very high-10–100 times greater than observed in most other surface sediments examined in this laboratory.     

A neural network model for predicting aquifer water level elevations

Artificial neural networks (ANNs) were developed for accurately predicting potentiometric surface elevations (monitoring well water level elevations) in a semiconfined glacial sand and gravel aquifer under variable state, pumping extraction, and climate conditions. ANNs "learn" the system behavior of interest by processing representative data patterns through a mathematical structure analogous to the human brain. In this study, the ANNs used the initial water level measurements, production well extractions, and climate conditions to predict the final water level elevations 30 d into the future at two monitoring wells. A sensitivity analysis was conducted with the ANNs that quantified the importance of the various input predictor variables on final water level elevations. Unlike traditional physical-based models, ANNs do not require explicit characterization of the physical system and related physical data. Accordingly, ANN predictions were made on the basis of more easily quantifiable, measured variables, rather than physical model input parameters and conditions. This study demonstrates that ANNs can provide both excellent prediction capability and valuable sensitivity analyses, which can result in more appropriate ground water management strategies.     

Annual stability in the use of coves near inlets as settlement areas for winter flounder (Pseudopleuronectes americanus)

Coves near an ocean inlet in Little Egg Harbor in southern New Jersey may be important settlement areas for winter flounder (Pseudopleuronectes americanus), based on the high abundance of small postlarval individuals. During 1994–1996 we sampled in two coves and adjacent areas of this same estuary to determine if this pattern was annually consistent. Collections in spring and early summer indicated that small, recently-settled winter flounder (10–45 mm TL) were abundant in the coves from May to mid-June in every year with maximum mean densities ranging from 1.5–2.5 ind m⁻² and that these same size individuals were never collected at these densities in other habitats in the same estuary. Densities in the coves declined soon after settlement, usually by late June to early July in each year. In order to determine factors that may influence these high settlement rates we examined aspects of habitat quality by determining habitat-specific growth rates in cages for recently-settled individuals (17.5–38.3 mm TL) both inside and outside the coves during 1995. These rates (3.7–9.1 wt d⁻¹) overlapped those of other estuarine habitats (3.1–10.5 wt d⁻¹) suggesting that habitat quality, based on growth, does not differentiate the coves from other potential settlement habitats. Mark/recapture experiments for recently settled individuals (range 13–70 mm TL) in 1994 and 1996 had low recapture rates (1% in both years) suggesting that dispersal from the cove occurred soon after settlement. This pattern confirms that these coves are used as settlement areas but they are probably not used as nurseries because winter flounder, at least in this system, do not settle and stay and, as a result, use other habitats as primary nursery areas.     

Differentiation of clay resources on a limestone plain: The analysis of clay utilization during the Maya Formative at K'axob Belize

Differentiating clay resources in a uniform limestone plain, such as occurs in northern Belize, offers special challenges for the archaeologist. Combining data from soil mapping with petrographic and neutron activation analysis provides a mechanism for distinguishing possible resource areas. This study employed each of these differing avenues of analysis to determine possible clay resource areas used during the Maya Formative in northern Belize Central America. The results indicate that clay usage changed significantly from the Middle Formative period to the end of Late Formative period. These changes suggest a move to increased localized production and resource exploitation by the end of the period. © 2000 John Wiley & Sons, Inc.     

Cave bears and paleolithic artifacts in Yarimburgaz Cave,Turkey: Dissecting a palimpsest

This article addresses the taphonomic issues surrounding artifact-bear associations in Yarimburgaz Cave, northwestern Turkey. Our purpose is to evaluate the circumstances of bone assemblage formation in the Middle Pleistocene deposits of the cave, identifying the agencies responsible for the accumulations and the causes of bone damage before and following deposition. Pleistocene species representation, bone damage, body part representation, and mortality data indicate that cave bear remains in Yarimburgaz are unrelated to hominid use of the same site. None of the observations on the cave bear remains contradicts the expectations developed from modern wildlife accounts of modern bear behavior; these accumulations resulted from mortality normally associated with hibernation over many generations of den use. Nonursid carnivores also played roles in bone collection and/or modification. We conclude that at least three distinct biological processes contributed to the formation of the Middle Pleistocene faunas: hibernating bears, bone-collecting carnivores such as wolves, and hominids in descending order of importance. The Yarimburgaz faunas represent palimpsests or overlays of many short-term depositional events, the close spatial associations of which are explained by slow or uneven sedimentation rates inside the cave. Although occupations by hominids appear to have been ephemeral in nature, hominids ultimately discarded nearly 1700 stone artifacts in Yarimburgaz Cave. The hominids did not discard many ungulate bones in the same circumstances. These observations suggest that hominid foraging efforts focused on resources other than large game while at the cave. © 1996 John Wiley & Sons, Inc.