Mute Swans

Mute swans (Cygnus olor) are an invasive species originally brought to the United States in the late 19th and early 20th centuries for ornamental ponds and lakes, zoos and aviculture collections. Original populations were located in northeastern states along the Hudson Valley but have since expanded to several Midwestern states and portions of the western U.S. and Canada. Mute swan damage includes competing with native waterfowl, destroying native plants, spreading disease, and colliding with aircraft. They are also considered a nuisance in some areas due to their abundant fecal droppings and aggressiveness towards people. Mute swans can impact ecosystems by foraging on native plants and competing with native species for food and habitat. Mute swans forage primarily on submerged aquatic vegetation, and each swan consumes 4 to 8 pounds of vegetation per day. While feeding, mute swans use their feet to expose plant shoots and roots for foraging, and to help dislodge food for cygnets (i.e., young swans). This damages aquatic substrates and vegetation surrounding preferred foods. Mute swans typically consume less than 50 percent of what they remove. Results from one study showed their diet overlaps considerably with many native waterfowl species that overwinter in the lower Great Lakes or temporarily use the area during migration. Mute swans are known for their highly territorial behavior during their breeding season, and may compete with native wildlife for space and associated resources. Of particular concern are potential impacts on threatened and endangered species. During the breeding season, mute swans sometimes displace other native waterfowl from preferred nesting locations, and may kill adult and juvenile ducks and geese. During one incident in Maryland, a large molting flock of mute swans caused a colony of least terns (Sterna antillarum) and black skimmers (Rynchops niger) to abandon a nesting colony by trampling nests, eggs, and chicks. The mute swans also displaced nesting common terns (Sterna hirundo). In 2011 in Michigan, a mute swan nest was found in the middle of a black tern (Chlidonias niger) colony that had previously supported approximately 54 black terns in 2009. Only a few black tern nests remained, approximately 30 to 40 feet away from the swan nest

Computational polarimetric microwave imaging

We propose a polarimetric microwave imaging technique that exploits recent advances in computational imaging. We utilize a frequency-diverse cavity-backed metasurface, allowing us to demonstrate high-resolution polarimetric imaging using a single transceiver and frequency sweep over the operational microwave bandwidth. The frequency-diverse metasurface imager greatly simplifies the system architecture compared with active arrays and other conventional microwave imaging approaches. We further develop the theoretical framework for computational polarimetric imaging and validate the approach experimentally using a multi-modal leaky cavity. The scalar approximation for the interaction between the radiated waves and the target---often applied in microwave computational imaging schemes---is thus extended to retrieve the susceptibility tensors, and hence providing additional information about the targets. Computational polarimetry has relevance for existing systems in the field that extract polarimetric imagery, and particular for ground observation. A growing number of short-range microwave imaging applications can also notably benefit from computational polarimetry, particularly for imaging objects that are difficult to reconstruct when assuming scalar estimations.Comment: 17 pages, 15 figure

Identification of candidate genes affecting Delta9-tetrahydrocannabinol biosynthesis in Cannabis sativa.

RNA isolated from the glands of a Delta(9)-tetrahydrocannabinolic acid (THCA)-producing strain of Cannabis sativa was used to generate a cDNA library containing over 100 000 expressed sequence tags (ESTs). Sequencing of over 2000 clones from the library resulted in the identification of over 1000 unigenes. Candidate genes for almost every step in the biochemical pathways leading from primary metabolites to THCA were identified. Quantitative PCR analysis suggested that many of the pathway genes are preferentially expressed in the glands. Hexanoyl-CoA, one of the metabolites required for THCA synthesis, could be made via either de novo fatty acids synthesis or via the breakdown of existing lipids. qPCR analysis supported the de novo pathway. Many of the ESTs encode transcription factors and two putative MYB genes were identified that were preferentially expressed in glands. Given the similarity of the Cannabis MYB genes to those in other species with known functions, these Cannabis MYBs may play roles in regulating gland development and THCA synthesis. Three candidates for the polyketide synthase (PKS) gene responsible for the first committed step in the pathway to THCA were characterized in more detail. One of these was identical to a previously reported chalcone synthase (CHS) and was found to have CHS activity. All three could use malonyl-CoA and hexanoyl-CoA as substrates, including the CHS, but reaction conditions were not identified that allowed for the production of olivetolic acid (the proposed product of the PKS activity needed for THCA synthesis). One of the PKS candidates was highly and specifically expressed in glands (relative to whole leaves) and, on the basis of these expression data, it is proposed to be the most likely PKS responsible for olivetolic acid synthesis in Cannabis glands

An Optoelectronic Implementation of the Adaptive Resonance Neural Network

A solution to the problem of implementation of the adaptive resonance theory (ART) of neural networks that uses an optical correlator which allows the large body of correlator research to be leveraged in the implementation of ART is presented. The implementation takes advantage of the fact that one ART-based architecture, known as ART1, can be broken into several parts, some of which are better to implement in parallel. The control structure of ART, often regarded as its most complex part, is actually not very time consuming and can be done in electronics. The bottom-up and top-down gated pathways, however, are very time consuming to simulate and are difficult to implement directly in electronics due to the high number of interconnections. In addition to the design, the authors present experiments with a laboratory prototype to illustrate its feasibility and to discuss implementation details that arise in practice. This device can potentially outperform alternative implementations of ART1 by as much as two to three orders of magnitude in problems requiring especially large input field

HIV-Associated Neurocognitive Disorder: Pathogenesis and Therapeutic Opportunities

Human immunodeficiency virus type 1 (HIV) infection presently affects more that 40 million people worldwide, and is associated with central nervous system (CNS) disruption in at least 30% of infected individuals. The use of highly active antiretroviral therapy has lessened the incidence, but not the prevalence of mild impairment of higher cognitive and cortical functions (HIV-associated neurocognitive disorders) as well as substantially reduced a more severe form dementia (HIV-associated dementia). Furthermore, improving neurological outcomes will require novel, adjunctive therapies that are targeted towards mechanisms of HIV-induced neurodegeneration. Identifying such molecular and pharmacological targets requires an understanding of the events preceding irreversible neuronal damage in the CNS, such as actions of neurotoxins (HIV proteins and cellular factors), disruption of ion channel properties, synaptic damage, and loss of adult neurogenesis. By considering the specific mechanisms and consequences of HIV neuropathogenesis, unified approaches for neuroprotection will likely emerge using a tailored, combined, and non-invasive approach