Microwave observations of sea state from aircraft

Airborne microwave radiometer measurements of thermal radiances over sea surface

The Importance of the Centrosomal Localization Sequence of Cyclin E for Promoting Centrosome Duplication: A Dissertation

This thesis comprises three separate studies that investigate the consequences of supernumary centrosomes, the effect of centrosome loss, and a control mechanism for regulating CDK2/cyclin E activity in centrosome duplication. The centrosome is the major microtubule-organizing center of the cell. When the cell enters mitosis, it is of critical importance that the cell has exactly two centrosomes in order to properly segregate the chromosomes to two daughter cells. Supernumary centrosomes are a problem for the cell in that they increase the incidence of chromosomal instability. Aberrant centrosome numbers are seen in a number of cancers, and there has been a proposed connection between the loss of function of p53 and multiple centrosomes. We investigated the consequences of multiple centrosomes in p53-null mouse embryonic fibroblasts (MEFs) to determine how cells with multiple centrosomes can continue to propagate and become cancer. We found that even in the face of extra centrosomes, p53-null MEFs are able to divide in a bipolar fashion by bundling extra centrosomes into two spindle poles. The centrosome has also been proposed to play a role in cell cycle control. We followed up on a previous study, which had suggested that centrosome loss causes a G1 arrest. We found that cells did not arrest in G1 due to centrosome removal as previously reported, but instead the arrest was viii dependent on additional stressors, namely the incident light used for our long-term live-cell observations. Our study showed that centrosome loss is a detectable stress that, in conjunction with additional stresses, can contribute to cell cycle arrest. It is known that CDK2/cyclin E activity is required to promote centrosome duplication. But with the discovery of a centrosomal localization sequence (CLS) in cyclin E, we wanted to know if centrosome duplication required a specific sub-cellular localization of CDK2 kinase activity. We found that centrosome duplication in Xenopus extract was dependent on CLS-mediated centrosomal localization of cyclin E, in complex with CDK2. Our results point to a mechanism for regulating centrosome duplication in the face of high cytoplasmic CDK2/cyclin E kinase activity

PHOSPHORUS-BASED NUTRIENT MANAGEMENT PLANNING ON DAIRY/POULTRY FARMS: IMPLICATIONS FOR ECONOMIC AND ENVIRONMENTAL RISKS

The effects of phosphorus (P)-based nutrient management plans on economic and environmental risks of dairy and dairy-poultry farms in Virginia were evaluated. Phosphorus-based nutrient management plans can greatly reduce P runoff risk but also reduce farmers' returns. P-based plans cause greater reductions in returns and P runoff on the dairy-poultry farm than on the dairy only farm.nutrient runoff, cost, mathematical programming, simulation, watershed, Environmental Economics and Policy, Livestock Production/Industries,

Predation risk is a function of alternative prey availability rather than predator abundance in a tropical savanna woodland ecosystem

Typically, factors influencing predation risk are viewed only from the perspective of predators or prey populations but few studies have examined predation risk in the context of a food web. We tested two competing hypotheses regarding predation: (1) predation risk is dependent on predator density; and (2) predation risk is dependent on the availability of alternative prey sources. We use an empirical, multi-level, tropical food web (birds–lizards–invertebrates) and a mensurative experiment (seasonal fluctuations in abundance and artificial lizards to estimate predation risk) to test these hypotheses. Birds were responsible for the majority of attacks on artificial lizards and were more abundant in the wet season. Artificial lizards were attacked more frequently in the dry than the wet season despite a greater abundance of birds in the wet season. Lizard and invertebrate (alternative prey) abundances showed opposing trends; lizards were more abundant in the dry while invertebrates were more abundant in the wet season. Predatory birds attacked fewer lizards when invertebrate prey abundance was highest, and switched to lizard prey when invertebrate abundance reduced, and lizard abundance was greatest. Our study suggests predation risk is not predator density-dependent, but rather dependent on the abundance of invertebrate prey, supporting the alternative prey hypothesis

Investigation of resin systems for improved ablative materials Interim report, 10 Jan. - 1 Jul. 1966

Preparation, and evaluation of polyimide sulfone resins, graphite-silica reinforced polyamide resins, and resin resistance to FLOX- methane, and fluorine-hydrogen fuel

Afraid of the Dark? The Influence of Natural and Artificial Light at Night on the Behavioral Activity of a Nocturnal Gecko

Both natural and artificial light at night can strongly influence animal behavior. Nocturnal animals often alter activity dependent on lunar light levels, to increase prey capture, minimize detection by predators, or both. Trade-offs among these ecological effects are likely to have a strong influence on behavior and fitness. Here, we examined the influence of light at night on nocturnal geckos that are both predators and prey, and use both natural and anthropogenic habitats. We tested the influence of illumination on the relative abundance and behavioral activity of native geckos in natural woodlands and under laboratory conditions. We hypothesized that Australian native house geckos (Gehyra dubia) would avoid activity on nights with high moon brightness, to minimize exposure to predators, consistent with the predation risk hypothesis. Counter to our prediction, we found a positive relationship between house gecko activity and moon brightness, i.e., house geckos were more active on bright nights. This behavior may allow house geckos to better see their prey while also increasing the visibility of approaching predators. In the laboratory, house geckos had shorter latency times to emerge from a shelter under low light conditions compared to darkness equivalent to a new moon, a trend consistent with higher activity under brighter conditions in the field. Light at night, from both natural and artificial sources, clearly influences the behavior and activity of geckos, but perhaps not in the ways we expect. Reducing the risk of attack from predators in darkness, and increasing prey capture success using vision, may increase the benefits of activity in lit conditions, compared to total darkness

Seasonal, environmental and anthropogenic influences on nocturnal basking in turtles and crocodiles from North-Eastern Australia

Many ectotherms bask in the sun as a behavioural mechanism to increase body temperature and facilitate metabolism, digestion or gamete production, among other functions. Such behaviours are common during the day, but some nocturnal species are also known to thermoregulate at night, in the absence of solar radiation, through shifts in body posture or microhabitat selection. Additionally, recent work has documented nocturnal basking in freshwater turtles in tropical Australia, though the purpose of the behaviour remains unknown. Here, we have built upon that work to test: 1. seasonal differences, 2. the influence of environmental factors and 3. the influence of anthropogenic development (e.g. river-front houses) on nocturnal basking behaviour. We visually surveyed transects repeatedly at night on the Ross River, Townsville, QLD, Australia from March to November 2020 and documented nocturnal basking in both freshwater turtles (Emydura macquarii krefftii) and freshwater crocodiles (Crocodylus johnstoni). For both taxa, we found significantly more nocturnal basking activity during the hotter months. Likewise, water surface temperature significantly influenced nocturnal basking in both taxa, especially when water temperatures were both high and warmer than air temperatures. We propose that nocturnal basking provides a mechanism for thermoregulatory cooling when water temperatures are high (e.g. 30°C) and above-preferred temperatures. After accounting for availability in basking habitat, both turtles and crocodiles basked more frequently on the undeveloped side of the river, suggesting avoidance of human activity or disturbance. This study is the first to document nocturnal basking activity temporally throughout the year as well as the first to identify the influences of environmental factors. Nocturnal thermoregulation has been documented in many reptiles, however, thermoregulatory cooling in tropical systems is less well-known

Performance Evaluation of RAKE Receiver for UWB Systems using Measured Channels in Industrial Environments

The industrial environments are an important scenario for ultra wideband (UWB) communication systems. However, due to large number of metallic scatterers in the surroundings, the multipath offered by UWB channels is dense with significant energy. In this paper, the performance of RAKE receivers operating in a non line-of-sight (NLOS) scenario in these environments is evaluated. The channels used for the evaluation are measured in a medium-sized industrial environment. In addition, a standard IEEE 802.15.4a channel model is used for comparison with the results of the measured data. The performance of partial RAKE (PRake) and selective RAKE (SRake) is evaluated in terms of uncoded bit-error-rate (BER) using different number of fingers. The performance of maximal ratio combining (MRC) and equal gain combining (EGC) is compared for the RAKE receiver assuming perfect knowledge of the channel state. Finally, based on the simulation results, conclusions are drawn considering the performance and complexity issues for system design in these environments