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Search Results: 1 - 10 of 248488 matches for " R. Z. Clardy "
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Incremental Investment Value of Waterfowl Impoundments in the Upstate of South Carolina, USA
R. Z. Clardy,W. M. Smathers, Jr.,T. J. Straka
Wildlife Biology in Practice , 2012,
Abstract: Financial incentives and economic factors play a role in expansion and survival of waterfowl in the Upstate of South Carolina. Satisfying a basic biological need, waterfowl impoundments are an effective way to ensure that migrating ducks have a food source, cover, and water on their journey south during the winter months (duck hunting season), but also year-round to ensure these birds return annually. Development of the region’s rural areas has resulted in a decrease in total area of flooded wetlands designated to waterfowl and a decline in waterfowl populations. At the same time, the willingness to pay to hunt ducks has escalated. South Carolinians drive across the United States in search for duck hunting when the same hunting experience could be created in their own backyard. The incremental value of creating a waterfowl impoundment was determined on five different properties in the Upstate of South Carolina (the study area). A discounted cost flow analysis approach was used that considered initial costs (a pond leveler, site preparation work, and blind building), recurring costs, and hunter revenue. The model also considered the opportunity cost of foregoing the harvest of planted crops on the land. Realistic examples are provided with corresponding net present values and geographic information system generated maps illustrate the layout of these impoundments. Waterfowl impoundments were found to produce significant financial return.
The Next Opportunity in Anti-Malaria Drug Discovery: The Liver Stage
Emily R. Derbyshire,Maria M. Mota,Jon Clardy
PLOS Pathogens , 2011, DOI: 10.1371/journal.ppat.1002178
Using genomics to deliver natural products from symbiotic bacteria
Jon Clardy
Genome Biology , 2005, DOI: 10.1186/gb-2005-6-9-232
Abstract: Natural products - small molecules derived from living organisms - have long been objects of fascination and utility, and they have provided most of the motivation for developing organic chemistry [1]. An example is given by morphine, the most active of the sleep-inducing compounds in opium, which was isolated in pure form in 1806 but was known thousands of years earlier [2]. Collaboration between chemists and biologists led to the identification of the opioid receptor and the isolation of its endogenous ligands (enkephalins). The story of morphine and related compounds has been repeated many times, and natural-products research still contributes important small molecules to medicine. Between 2000 and 2003, 15 new drugs derived from natural products were introduced for the treatment of disorders such as malaria, fungal infections, bacterial infections, cancer, blood clots, premature labor, infertility, and stimulation of the central nervous system, such as Alzheimer's disease [3,4]. Two recent papers [5,6] describe the identification and cloning of genes encoding the biosynthetic pathway of patellamide, a potential anticancer agent, highlighting the profound changes that genomic approaches are bringing about in what is arguably the oldest scientific discipline.Natural-products research was transformed in the 1940s by the establishment of the actinomycete group of Gram-positive filamentous soil bacteria as the premier source of medically useful natural products. The actinomycete group produces the antibiotics streptomycin, actinomycin, erythromycin, and vancomycin; the antifungal agents nystatin and amphotericin; the anticancer agents doxorubicin and calicheamicin; the immunosuppressive agents FK506 and rapamycin; and many other useful molecules. In addition to their ability to produce this staggering array of important natural products, the biosynthetic genes of bacteria have an organization that has greatly simplified genetic studies: all of the instructions for ma
Integrating Course and Instructional Evaluation with a Learning History Approach
Alan Clardy
The Journal of Scholarship of Teaching and Learning , 2003,
Chemical Analyses of Wasp-Associated Streptomyces Bacteria Reveal a Prolific Potential for Natural Products Discovery
Michael Poulsen,Dong-Chan Oh,Jon Clardy,Cameron R. Currie
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016763
Abstract: Identifying new sources for small molecule discovery is necessary to help mitigate the continuous emergence of antibiotic-resistance in pathogenic microbes. Recent studies indicate that one potentially rich source of novel natural products is Actinobacterial symbionts associated with social and solitary Hymenoptera. Here we test this possibility by examining two species of solitary mud dauber wasps, Sceliphron caementarium and Chalybion californicum. We performed enrichment isolations from 33 wasps and obtained more than 200 isolates of Streptomyces Actinobacteria. Chemical analyses of 15 of these isolates identified 11 distinct and structurally diverse secondary metabolites, including a novel polyunsaturated and polyoxygenated macrocyclic lactam, which we name sceliphrolactam. By pairing the 15 Streptomyces strains against a collection of fungi and bacteria, we document their antifungal and antibacterial activity. The prevalence and anti-microbial properties of Actinobacteria associated with these two solitary wasp species suggest the potential role of these Streptomyces as antibiotic-producing symbionts, potentially helping defend their wasp hosts from pathogenic microbes. Finding phylogenetically diverse and chemically prolific Actinobacteria from solitary wasps suggests that insect-associated Actinobacteria can provide a valuable source of novel natural products of pharmaceutical interest.
Catecholate Siderophores Protect Bacteria from Pyochelin Toxicity
Conrado Adler, Natalia S. Corbalán, Mohammad R. Seyedsayamdost, María Fernanda Pomares, Ricardo E. de Cristóbal, Jon Clardy, Roberto Kolter, Paula A. Vincent
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046754
Abstract: Background Bacteria produce small molecule iron chelators, known as siderophores, to facilitate the acquisition of iron from the environment. The synthesis of more than one siderophore and the production of multiple siderophore uptake systems by a single bacterial species are common place. The selective advantages conferred by the multiplicity of siderophore synthesis remains poorly understood. However, there is growing evidence suggesting that siderophores may have other physiological roles besides their involvement in iron acquisition. Methods and Principal Findings Here we provide the first report that pyochelin displays antibiotic activity against some bacterial strains. Observation of differential sensitivity to pyochelin against a panel of bacteria provided the first indications that catecholate siderophores, produced by some bacteria, may have roles other than iron acquisition. A pattern emerged where only those strains able to make catecholate-type siderophores were resistant to pyochelin. We were able to associate pyochelin resistance to catecholate production by showing that pyochelin-resistant Escherichia coli became sensitive when biosynthesis of its catecholate siderophore enterobactin was impaired. As expected, supplementation with enterobactin conferred pyochelin resistance to the entE mutant. We observed that pyochelin-induced growth inhibition was independent of iron availability and was prevented by addition of the reducing agent ascorbic acid or by anaerobic incubation. Addition of pyochelin to E. coli increased the levels of reactive oxygen species (ROS) while addition of ascorbic acid or enterobactin reduced them. In contrast, addition of the carboxylate-type siderophore, citrate, did not prevent pyochelin-induced ROS increases and their associated toxicity. Conclusions We have shown that the catecholate siderophore enterobactin protects E. coli against the toxic effects of pyochelin by reducing ROS. Thus, it appears that catecholate siderophores can behave as protectors of oxidative stress. These results support the idea that siderophores can have physiological roles aside from those in iron acquisition.
Bioassessment of the Rio Grande Upstream and Downstream of Los Alamos National Laboratory,New Mexico, USA  [PDF]
Philip R. Fresquez, Gerald Z. Jacobi
Journal of Environmental Protection (JEP) , 2012, DOI: 10.4236/jep.2012.311176
Abstract: Benthic macroinvertebrates (aquatic insects) were collected from the Rio Grande upstream and downstream of Los Alamos Canyon (LAC), a major drainage that crosses Los Alamos National Laboratory (LANL) lands in northern New Mexico, USA. LAC contains legacy waste, including radionuclides and polychlorinated biphenyls, and occasionally discharges storm water and snowmelt flows to the Rio Grande. The Rio Grande is the major waterway that flows southward across the state. In 2009, rock baskets were placed in waters 61- to 76-cm-deep within each reach (five per reach), and, after approximately 6 weeks of colonization, the rock baskets were retrieved. All samples were sorted completely and organisms were identified to the lowest possible taxonomic level. Both reaches in 2009 were dominated by the collector filtering net-spinning caddisfly, Hydropsyche occidentalis. In 2011, benthic macroinvertebrates were collected using D kick nets from shallow riffle locations (15- to 31-cm depth) from each reach (six per reach). These samples were collected after post- (Las Conchas) fire flooding events moved sediment and ash through the two study areas—the downstream reach, however, was affected by higher flows and greater number of flooding events than those affecting the upstream reach. Each kick net sample consisted of ten 1-m (kick) samples. The 10 subsamples were composited and organisms were picked from randomly selected cells in a sorting pan until 500 organisms had been identified to the lowest possible taxonomic level. Both reaches in 2011 were dominated by the collector-gathering mayfly, Baetis tricaudatus. A bioassessment of the downstream reach compared with the upstream (reference) reach was conducted by scoring 10 metrics related to the structure and function of the benthic macroinvertebrate community. While 2009 ranked at the highest level (nonimpaired), 2011 ranked a level lower (slightly impaired). The slightly lower bioassessment score of the downstream reach in 2011 may be a result of flooding impacts following the Las Conchas fire rather than of LANL operations. Overall, based on the similarity of benthic macroinvertebrate metrics between reaches and the composition of benthic macroinvertebrates favoring pollution intolerant taxa, LANL influences, if any, via the LAC system to the Rio Grande are not significantly impacting water quality of the Rio Grande.
Evaluate Tectonic Activity of Tehran City (Iran) Based on Geomorphic Indices, Field Investigation and Remote Sensing Study  [PDF]
Z. Mohammadi Asl, M. R. Abbassi
Open Journal of Earthquake Research (OJER) , 2019, DOI: 10.4236/ojer.2019.81002
Active tectonics in the south part of Alborz Mountain (Iran) has greatly influenced the drainage system and geomorphic expressions. The metropolis of Tehran is located at the southern foothills of the Alborz Mountains at the abrupt topographic boundary between the mountain range and the northern border of the central Kavir Desert. The presence of active faults and tectonic activity, threatens the area and shows the vulnerability of this Tehran city. So the evaluation of active tectonics of Tehran City is necessary because of vast human activity, which has hidden geomorphic feature. Active tectonics of Tehran City was evaluated by using Digital elevation model (DEM) derived drainage network and three geomorphic indices basin (asymmetry factor (AF), basin shape index (Bs) and mountain front sinuosity (Smf)). The average of the three measured geomorphic indices was used to evaluate the distribution of relative tectonic activity in the study area. Furthermore to overcome some inevitable error in this method, field investigation was carried out also remote sense was studied, and finally the obtained results were compared with existing seismic data. The result confirms that the East South, East North and West North Tehran have high rate of relative tectonic activity (RTA) respectively.
Two-dimensional Ising model and local nonuniversality of critical exponents
Bariev, R. Z.;
Brazilian Journal of Physics , 2000, DOI: 10.1590/S0103-97332000000400008
Abstract: we obtain the local magnetization of a planar ising model with defects of different types. it is shown that near the critical point the local magnetization has a nonuniversal behavior that manifests itself in the fact that its critical exponent is a continuous function of the microscopic parameters of the system.
Magnetic reconnection associated fluctuations in the deep magnetotail: ARTEMIS results
Z. V r s
Nonlinear Processes in Geophysics (NPG) , 2011,
Abstract: On the basis of ARTEMIS two-probe mission magnetic reconnection (MR) outflow associated magnetic fluctuations and turbulence are analyzed on 19 February 2011. In the deep-tail, at distances between X = 45 – 51 RE, evidence for reconnection associated plasma sheet thinning was found, accompanied by heating of the plasma sheet. Correlated flow and field reversals and the large-scale Hall-effect signatures indicated the presence of the reconnection X-line. Within fast reconnection plasma outflows, magnetic fluctuations exhibit the same spectral scaling features and kinked spectra as magnetic fluctuations in the solar wind or in various parts of geospace. It was shown that the proton scale magnetic fluctuations are constrained by oblique firehose, proton cyclotron and mirror instability thresholds. For parallel plasma β|| > 1, where the thresholds converge, perpendicular magnetic fluctuations are enhanced. Magnetic compressibility decreases with the distance to the neutral sheet, however, near the instability thresholds it is comparable to the values obtained in the solar wind.
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