University of Nevada, Reno

About: University of Nevada, Reno is a education organization based out in Reno, Nevada, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 13561 authors who have published 28217 publications receiving 882002 citations. The organization is also known as: University of Nevada & Nevada State University.

Learning with case-injected genetic algorithms

Abstract: This paper presents a new approach to acquiring and using problem specific knowledge during a genetic algorithm (GA) search. A GA augmented with a case-based memory of past problem solving attempts learns to obtain better performance over time on sets of similar problems. Rather than starting anew on each problem, we periodically inject a GA's population with appropriate intermediate solutions to similar previously solved problems. Perhaps, counterintuitively, simply injecting solutions to previously solved problems does not produce very good results. We provide a framework for evaluating this GA-based machine-learning system and show experimental results on a set of design and optimization problems. These results demonstrate the performance gains from our approach and indicate that our system learns to take less time to provide quality solutions to a new problem as it gains experience from solving other similar problems in design and optimization.

Rangeland Monitoring Using Remote Sensing

Abstract: Monitoring vast landscapes has, from the beginning of rangeland management, depended on people's judgements. This is no longer tenable, but a more effective method has yet to be devised. The problem is how to do an economical inventory that will detect ecologically important change over extensive land areas with acceptable error rates. The error risk is a function of adequate sample numbers and distribution for each indicator monitored. Of all of the indicators identified for monitoring, ground cover and its inverse, bare ground, may be the most discussed. Ground-cover measurements address soil stability and watershed function which are first-priority ecological concerns; are well adapted to remote sensing frameworks thus allowing extensive, unbiased, economical sampling; and, the measurements, especially when done by computer image analysis, have the potential to reduce or avoid the human-judgement factor. Data collection through remote sensing appears the most logical approach to acquiring appropriately...

Prolonged suppression of ecosystem carbon dioxide uptake after an anomalously warm year

Abstract: Terrestrial ecosystems control carbon dioxide fluxes to and from the atmosphere through photosynthesis and respiration, a balance between net primary productivity and heterotrophic respiration, that determines whether an ecosystem is sequestering carbon or releasing it to the atmosphere. Global and site-specific data sets have demonstrated that climate and climate variability influence biogeochemical processes that determine net ecosystem carbon dioxide exchange (NEE) at multiple timescales. Experimental data necessary to quantify impacts of a single climate variable, such as temperature anomalies, on NEE and carbon sequestration of ecosystems at interannual timescales have been lacking. This derives from an inability of field studies to avoid the confounding effects of natural intra-annual and interannual variability in temperature and precipitation. Here we present results from a four-year study using replicate 12,000-kg intact tallgrass prairie monoliths located in four 184-m(3) enclosed lysimeters. We exposed 6 of 12 monoliths to an anomalously warm year in the second year of the study and continuously quantified rates of ecosystem processes, including NEE. We find that warming decreases NEE in both the extreme year and the following year by inducing drought that suppresses net primary productivity in the extreme year and by stimulating heterotrophic respiration of soil biota in the subsequent year. Our data indicate that two years are required for NEE in the previously warmed experimental ecosystems to recover to levels measured in the control ecosystems. This time lag caused net ecosystem carbon sequestration in previously warmed ecosystems to be decreased threefold over the study period, compared with control ecosystems. Our findings suggest that more frequent anomalously warm years, a possible consequence of increasing anthropogenic carbon dioxide levels, may lead to a sustained decrease in carbon dioxide uptake by terrestrial ecosystems.

Nitric oxide activates multiple potassium channels in canine colonic smooth muscle.

Abstract: 1. Nitric oxide (NO), an inhibitory neurotransmitter released from peripheral neurones, hyperpolarizes smooth muscle cells and inhibits contraction. The mechanism of this hyperpolarization is unknown. 2. We have identified three classes of K+ channels activated by NO and NO donors in colonic smooth muscle cells. NO and NO donors increased the open probability of 80 pS channels (KNO1), very small channels (< 4 pS, KNO2), and 270 pS Ca(2+)-activated K+ channels (BK channels) in cell-attached patches. 3. Dibutyryl cGMP and 8-bromo cGMP also increased the open probability of KNO1 and KNO2 in cell-attached patches. 4. In excised patches of membrane, direct application of NO or the NO donor, S-nitroso-N-acetyl penicillamine (SNAP), increased the open probability of KNO1 and KNO2, but cGMP or dibutyryl cGMP had no effect. SNAP had no effect on the open probability of BK channels in excised patches. 5. The reducing agent dithiothreitol and the alkylating agent N-ethylmaleimide blocked NO-induced channel openings. 6. In summary, the hyperpolarization response to NO in smooth muscles may be mediated by multiple K+ channels. At least two of these classes of channels may be activated by dual pathways involving direct activation by NO and cGMP-mediated mechanisms.