Extending the theory of Owicki and Gries with a logic of progress

This paper describes a logic of progress for concurrent programs. The logic is based on that of UNITY, molded to fit a sequential programming model. Integration of the two is achieved by using auxiliary variables in a systematic way that incorporates program counters into the program text. The rules for progress in UNITY are then modified to suit this new system. This modification is however subtle enough to allow the theory of Owicki and Gries to be used without change

Unbalanced reduction of nutrient loads has created an offshore gradient from phosphorus to nitrogen limitation in the North Sea

Measures to reduce eutrophication have often led to a more effective decline of phosphorus (P) than nitrogen(N) concentrations. The resultant changes in riverine nutrient loads can cause an increase in the N : Pratios of coastal waters. During four research cruises along a 450 km transect, we investigated how reductionsin nutrient inputs during the past 25 yr have affected nutrient limitation patterns in the North Sea. Thisrevealed a strong offshore gradient of dissolved inorganic N : P ratios in spring, from 375 : 1 nearshoretoward 1 : 1 in the central North Sea. This gradient was reflected in high nearshore N : P and C : P ratios ofparticulate organic matter (mainly phytoplankton), indicative of severe P deficiency of coastal phytoplankton,which may negatively affect higher trophic levels in the food web. Nutrient enrichment bioassays performedon-board showed P and Si limitation of phytoplankton growth nearshore, co-limitation of N and P ina transitional region, and N limitation in the outer-shore waters, confirming the existence of an offshore gradientfrom P to N limitation. Different species were limited by different nutrients, indicating that furtherreductions of P loads without concomitant reductions of N loads will suppress colonial Phaeocystis blooms,but will be less effective in diminishing harmful algal blooms by dino- and nanoflagellates. Hence, our resultsprovide evidence that de-eutrophication efforts in northwestern Europe have led to a large imbalance in theN : P stoichiometry of coastal waters of the North Sea, with major consequences for the growth, species composition,and nutritional quality of marine phytoplankton communities

The value of computed tomography in detecting distal radioulnar joint instability after a distal radius fracture

This study evaluated the value of computed tomography scans for the diagnosis of distal radioulnar joint instability. A total of 46 patients, conservatively treated for a unilateral distal radius fracture, were evaluated. Clinical instability was tested using the stress test and clunk test. A computed tomography scan of both wrists was performed in pronation and supination. Two independent observers reviewed the computed tomography scans using: the radioulnar line, subluxation ratio, epicentre and radioulnar ratio methods. Radiological distal radioulnar joint instability was assessed by comparing the measurements of the injured wrist with those of the contralateral uninjured wrists. A

Strong coupling between single-electron tunneling and nano-mechanical motion

Nanoscale resonators that oscillate at high frequencies are useful in many measurement applications. We studied a high-quality mechanical resonator made from a suspended carbon nanotube driven into motion by applying a periodic radio frequency potential using a nearby antenna. Single-electron charge fluctuations created periodic modulations of the mechanical resonance frequency. A quality factor exceeding 10^5 allows the detection of a shift in resonance frequency caused by the addition of a single-electron charge on the nanotube. Additional evidence for the strong coupling of mechanical motion and electron tunneling is provided by an energy transfer to the electrons causing mechanical damping and unusual nonlinear behavior. We also discovered that a direct current through the nanotube spontaneously drives the mechanical resonator, exerting a force that is coherent with the high-frequency resonant mechanical motion.Comment: Main text 12 pages, 4 Figures, Supplement 13 pages, 6 Figure

The Investigation of Silica Removal in Reverse Osmosis Concentrate by Changing Design Parameters

Silica at high concentrations can precipitate and polymerize, forming scales on heat exchangers, boilers and turbines in industrial equipment, and on the feed side of the semi-permeable membranes in Reverse Osmosis (RO). Silica scale can cause decreased efficiency, increased treatment costs and, in some cases, irreversible damage. The removal of silica scale is challenging because it requires the handling of dangerous and hazardous chemicals. Therefore, much research has gone into the removal of soluble silica. The purpose of this research was to compare the overall effectiveness of silica removal in RO concentrate water with freshly precipitated Mg(OH)2 and Fe(OH)3,and calcined Hydrotalcite (HTC) by changing the design parameters adsorbent dose and pH. To complete this work, 15 experiments (12 batch experiments and 3 flow through experiments) were performed. Initial batch studies investigated and compared the effects of changing the dose and on silica removal for freshly precipitated Mg(OH)2 and Fe(OH)3,and calcined HTC. The results showed that, for all materials, an increased dose at pH 10 led to increased silica removal. Then, using the three materials, the effect of pH was investigated on silica removal. When the pH was increased from 9 to 11, trends in silica removal varied for the three materials. Furthermore, batch studies were completed on the three materials to determine the sorption density and sorption kinetics onto the solids. The sorption densities were used to determine the most applicable isotherm (Freundlich or Langmuir) and identify isotherm parameters for the materials. All three materials fit the Freundlich isotherm model and based on isotherm parameters, the largest adsorption capacity was determined to be HTC and the most intense adsorption was determined to be Fe(OH)3. The sorption kinetics were examined for zero, first and second order kinetics to determine a rate constant for silica adsorption reactions. It was discovered that all three materials fit the second order kinetics models and the uptake rates were determined to be 3.0 X 10-4 mg/L×min for Mg(OH)2, 9.0 X 10-5 mg/L×min for Fe(OH)3 and 7.0 X 10-5 mg/L×min for HTC at various doses. Using the results of the batch tests, a flow through system was constructed and used to examine the material’s capacities on a larger scale and determine if 70% silica removal can be maintained. The results showed that when the materials were compared, HTC could achieve the target percent silica removal at a lower dose than Mg(OH)2 and Fe(OH)3 but, all three materials could maintain silica removal on a large scale. This study provides important information for water treatment industries looking to remove soluble silica from water

Comparison of anthropometric body features of highclass volleyball players

One of the factors determining skills of athletes in certain sport is body build features. Sport result depends a lot on morphologic features of the sportsman, that is one of the selective factors determining the sportsman's perspective. Purpose of research is studying of peculiarities anthropomentric and somatometric indices of super league, premier league and first league teams

Competition and facilitation between the marine nitrogen-fixing <i>cyanobacterium</i> Cyanothece and its associated bacterial community

N2-fixing cyanobacteria represent a major source of new nitrogen and carbon for marine microbial communities, but little is known about their ecological interactions with associated microbiota. In this study we investigated the interactions between the unicellular N2-fixing cyanobacterium Cyanothece sp. Miami BG043511 and its associated free-living chemotrophic bacteria at different concentrations of nitrate and dissolved organic carbon and different temperatures. High temperature strongly stimulated the growth of Cyanothece, but had less effect on the growth and community composition of the chemotrophic bacteria. Conversely, nitrate and carbon addition did not significantly increase the abundance of Cyanothece, but strongly affected the abundance and species composition of the associated chemotrophic bacteria. In nitrate-free medium the associated bacterial community was co-dominated by the putative diazotroph Mesorhizobium and the putative aerobic anoxygenic phototroph Erythrobacter and after addition of organic carbon also by the Flavobacterium Muricauda. Addition of nitrate shifted the composition toward co-dominance by Erythrobacter and the Gammaproteobacterium Marinobacter. Our results indicate that Cyanothece modified the species composition of its associated bacteria through a combination of competition and facilitation. Furthermore, within the bacterial community, niche differentiation appeared to play an important role, contributing to the coexistence of a variety of different functional groups. An important implication of these findings is that changes in nitrogen and carbon availability due to, e.g., eutrophication and climate change are likely to have a major impact on the species composition of the bacterial community associated with N2-fixing cyanobacteria