Design, fabrication and calibration of alpha particle densitometers for measuring planetary atmospheric density

An alpha particle densitometer was developed for possible application to measurement of the atmospheric density-altitude profile on Martian entry. The device uses an Am-241 radioactive-foil source, which emits a distributed energy spectrum, located about 25 to 75 cm from a semiconductor detector. System response - defined as the number of alphas per second reaching the detector with energy above a fixed threshold - is given for Ar and CO2. The altitude profile of density measurement accuracy is given for a pure CO2 atmosphere with 5 mb surface pressure. The entire unit, including dc-dc converters, requires less than 350 milliwatts of power from +28 volts, weighs about 0.85 lb and occupies less than 15 cubic inches volume

Flight of a UV spectrophotometer aboard Galileo 2, the NASA Convair 990 aircraft

An ultraviolet interference-filter spectrophotometer (UVS) fabricated for aircraft-borne use on the DOT Climatic Impact Assessment Program (CIAP) has been successfully tested in a series of flights on the NASA Convair 990, Galileo II. UV flux data and the calculated total ozone above the flight path are reported for several of the flights. Good agreement is obtained with the total ozone as deducted by integration of an ozone sonde vertical profile obtained at Wallops Island, Virginia near the time of a CV-990 underpass. Possible advantages of use of the UVS in the NASA Global Atmospheric Sampling Program are discussed

Aharanov-Bohm excitons at elevated temperatures in type-II ZnTe/ZnSe quantum dots

Optical emission from type-II ZnTe/ZnSe quantum dots demonstrates large and persistent oscillations in both the peak energy and intensity indicating the formation of coherently rotating states. Furthermore, the Aharanov-Bohm (AB) effect is shown to be remarkably robust and persists until 180K. This is at least one order of magnitude greater than the typical temperatures in lithographically defined rings. To our knowledge this is the highest temperature at which the AB effect has been observed in semiconductor structures

Reversed Dickson polynomials over finite fields

AbstractReversed Dickson polynomials over finite fields are obtained from Dickson polynomials Dn(x,a) over finite fields by reversing the roles of the indeterminate x and the parameter a. We study reversed Dickson polynomials with emphasis on their permutational properties over finite fields. We show that reversed Dickson permutation polynomials (RDPPs) are closely related to almost perfect nonlinear (APN) functions. We find several families of nontrivial RDPPs over finite fields; some of them arise from known APN functions and others are new. Among RDPPs on Fq with q<200, with only one exception, all belong to the RDPP families established in this paper

Implementing the Simple Biosphere Model (SiB) in a general circulation model: Methodologies and results

The Simple Biosphere MOdel (SiB) of Sellers et al., (1986) was designed to simulate the interactions between the Earth's land surface and the atmosphere by treating the vegetation explicitly and relistically, thereby incorporating biophysical controls on the exchanges of radiation, momentum, sensible and latent heat between the two systems. The steps taken to implement SiB in a modified version of the National Meteorological Center's spectral GCM are described. The coupled model (SiB-GCM) was used with a conventional hydrological model (Ctl-GCM) to produce summer and winter simulations. The same GCM was used with a conventional hydrological model (Ctl-GCM) to produce comparable 'control' summer and winter variations. It was found that SiB-GCM produced a more realistic partitioning of energy at the land surface than Ctl-GCM. Generally, SiB-GCM produced more sensible heat flux and less latent heat flux over vegetated land than did Ctl-GCM and this resulted in the development of a much deeper daytime planetary boundary and reduced precipitation rates over the continents in SiB-GCM. In the summer simulation, the 200 mb jet stream and the wind speed at 850 mb were slightly weakened in the SiB-GCM relative to the Ctl-GCM results and equivalent analyses from observations

To What Extent Can Vegetation Mitigate Greenhouse Warming? A Modeling Approach

Climate models participating in the IPCC Fourth Assessment Report indicate that under a 2xCO2 environment, runoff would increase faster than precipitation overland. However, observations over large U.S watersheds indicate otherwise. This inconsistency suggests that there may be important feedbacks between climate and land surface unaccounted for in the present generation of models. We postulate that the increase in precipitation associated with the increase in CO2 is also increasing vegetation density, which may already be feeding back onto climate. Including this feedback in a climate model simulation resulted in precipitation and runoff trends consistent with observations and reduced the warming by 0.6OC overland. This unaccounted for missing water may be linked to about 10% of the missing land carbon sink. A recent compilation of outputs from 19 coupled atmosphere-ocean general circulation models used in the IPCC Fourth Assessment Report (AR4) shows projected increases in air temperature, precipitation and river discharge for 24 major rivers in the world in response to doubling CO2 by the end of the century (1). The ensemble mean from these models also indicates that, compared to their respective baselines overland, the global mean of the runoff change would increase faster (8.9% per year) than that of the precipitation (5% per year). We analyze century-scale observed annual runoff time-series (1901-2002) over 9 hydrological units covering large regions of the Eastern United States (Fig.1) compiled by the United States Geological Survey (USGS)(2). These regions were selected because they are the most forested; the least water-limited and are not under extensive irrigation. We compare these time-series to similar time-series of observed annual precipitation anomalies spanning the period 1900-1995 (3). Both time-series exhibit a positive longterm trend (Fig. 2); however, in contrast to the analysis of (I), these historic data records show that the rate of precipitation increase is 5.5 % per year, roughly double the rate of runoff increase of 3.1 % per year

Natality and calf mortality of the Northern Alaska Peninsula and Southern Alaska Peninsula caribou herds

We studied natality in the Northern Alaska Peninsula (NAP) and Southern Alaska Peninsula (SAP) caribou (Rangifer tarandus granti) herds during 1996-1999, and mortality and weights of calves during 1998 and 1999- Natality was lower in the NAP than the SAP primarily because most 3-year-old females did not produce calves in the NAP Patterns of calf mortality in the NAP and SAP differed from those in Interior Alaska primarily because neonatal (i.e., during the first 2 weeks of life) mortality was relatively low, but mortality continued to be significant through August in both herds, and aggregate annual mortality was extreme (86%) in the NAP Predators probably killed more neonatal calves in the SAP, primarily because a wolf den (Canis lupus) was located on the calving area. Despite the relatively high density of brown bears (Ursus arctos) and bald eagles (Haliaeetus leucocephalus), these predators killed surprisingly few calves. Golden eagles (Aquila chrysaetos) were uncommon on the Alaska Peninsula. At least 2 calves apparently died from pneu&not;monia in the range of the NAP but none were suspected to have died from disease in the range of the SAP. Heavy scav&not;enging by bald eagles complicated determining cause of death of calves in both the NAP and SAP

DNA metabarcoding reveals the dietary profiles of a benthic marine crustacean,Nephrops norvegicus

Norwegian lobster, Nephrops norvegicus, are a generalist scavenger and predator capable of short foraging excursions but can also suspension feed. Existing knowledge about their diet relies on a combination of methods including morphology-based stomach content analysis and stable isotopes, which often lack the resolution to distinguish prey items to species level particularly in species that thoroughly masticate their prey. DNA metabarcoding overcomes many of the challenges associated with traditional methods and it is an attractive approach to study the dietary profiles of animals. Here, we present the diet of the commercially valuable Nephrops norvegicus using DNA metabarcoding of gut contents. Despite difficulties associated with host amplification, our cytochrome oxidase I (COI) molecular assay successfully achieves higher resolution information than traditional approaches. We detected taxa that were likely consumed during different feeding strategies. Dinoflagellata, Chlorophyta and Bacillariophyta accounted for almost 50% of the prey items consumed, and are associated with suspension feeding, while fish with high fisheries discard rates were detected which are linked to active foraging. In addition, we were able to characterise biodiversity patterns by considering Nephrops as natural samplers, as well as detecting parasitic dinoflagellates (e.g., Hematodinium sp.), which are known to influence burrow related behaviour in infected individuals in over 50% of the samples. The metabarcoding data presented here greatly enhances a better understanding of a species’ ecological role and could be applied as a routine procedure in future studies for proper consideration in the management and decision-making of fisheries

Robust Magnetic Polarons in Type-II (Zn,Mn)Te Quantum Dots

We present evidence of magnetic ordering in type-II (Zn, Mn) Te quantum dots. This ordering is attributed to the formation of bound magnetic polarons caused by the exchange interaction between the strongly localized holes and Mn within the dots. In our photoluminescence studies, the magnetic polarons are detected at temperatures up to ~ 200 K, with a binding energy of ~ 40 meV. In addition, these dots display an unusually small Zeeman shift with applied field (2 meV at 10 T). This behavior is explained by a small and weakly temperature-dependent magnetic susceptibility due to anti-ferromagnetic coupling of the Mn spins