On the concept of pressure in quantum mechanics

Heat and work are fundamental concepts for thermodynamical systems. When these are scaled down to the quantum level they require appropriate embeddings. Here we show that the dependence of the particle spectrum on system size giving rise to a formal definition of pressure can, indeed, be correlated with an external mechanical degree of freedom, modelled as a spatial coordinate of a quantum oscillator. Under specific conditions this correlation is reminiscent of that occurring in the classical manometer.Comment: 7 pages, 3 figure

Nutrient and fecal microbe assessment of the water quality of Tates Creek, Madison County, Kentucky

Tates Creek is a significant tributary to the Kentucky River that has shown high levels of microbial and nutrient pollution in the past (Kentucky River Watershed Watch). We sampled the waters of Tates Creek more comprehensively by collecting stream water at 25 stations along its 13-mile length from its headwaters to the Kentucky River. Most samples were collected at the confluence of major tributaries to also access the water quality of tributary streams. Samples were collected four times between May and August 2011 during dry periods as well as immediately after a rainfall event. We measured ammonium (NH4+), nitrate (NO3-), and phosphate (PO43-) concentrations using colorimetry. Microbial samples were measured for total coliform and Escherichia coli using IDEXX Colilert-18 media and methods. Background levels of NH4+, NO3- and PO4- are typically ~0.3 mg/L, 5 mg/L, and 1.0 mg/L, respectively. Thus, phosphate concentration almost always exceeds EPA criteria for freshwater (0.1 mg/L). Background levels of nutrient concentrations generally increase during rainfall events, presumably because nutrients are flushed into the stream. Background counts of E. coli are typically ~100 cfu/mL but E. coli counts reached 1,000 to 2,419 cfu/mL immediately following rain events. Some areas also show microbial counts far in excess of background levels. Microbe counts tend to be high in the headwaters of Tates Creek where we suspect leaky and/or broken sewage lines are responsible for high E. coli counts. Other high counts also occur adjacent to active pasture. Thus, fecal microbe pollution in Tates Creek occurs from both human and bovine sources. A sewage treatment plant existed approximately two miles from the headwaters of Tates Creek and noticeably affected water quality. Upstream of the plant, nutrient levels are low, whereas nutrient concentration, especially NH4+ and PO4-, are markedly increased at the plant’s outflow. These nutrients then decrease steadily in concentration downstream to background levels. In contrast, when the plant was operating fecal microbe counts are high upstream from the plant, but fall to near-zero levels at its outflow, and then increase anew downstream. The treatment plant went off line on 19 July 2011 and subsequent sampling showed nutrient levels no longer spike immediately downstream. E. coli counts remained high upstream and downstream of the plant because stream waters are no longer diluted by plant outflow that carried almost no microbes. A companion study sampled stream biota before and after the plant shut down. Thus, we will be able to note any changes in stream biota attributable to changing nutrient levels

Nutrient and fecal microbe assessment of the water quality of Tates Creek, Madison County, Kentucky

Tates Creek is a significant tributary to the Kentucky River that has shown high levels of microbial and nutrient pollution. We sampled the waters of Tates Creek comprehensively by occupying 25 stations along its 13-mile length, collecting stream water at the confluence of major tributaries from its headwaters to the Kentucky River. Samples were collected four times between May and August 2011 during dry periods as well as immediately after rainfall events. We measured ammonium (NH4+), nitrate (NO3-) and phosphate (PO4-) concentrations using colorimetry. Microbial samples were measured for total coliform and Escherichia coli using IDEXX Colilert-18 media. Background levels of NH4+, NO3- and PO4- are typically ~0.2 ppm, 13 ppm, and 1.0 ppm, respectively. Nutrient concentrations generally increase during rainfall events, presumably because nutrients are flushed into the stream. Background counts of E. coli are typically ~100 cfu/mL but microbe counts reached 1,000 – 2,419 cfu/mL immediately following rain events. A sewage treatment plant exists approximately two miles from the headwaters and noticeably affects water quality. Nutrient concentration, especially NH4+ and PO4-, are markedly increased at the plant’s outflow. These nutrients then decrease steadily in concentration downstream to background levels. In contrast, fecal microbe counts are high upstream from the plant, but fall to near-zero levels at its outflow, and then increase anew downstream. The treatment plant went offline on 19 July 2011, so we will be able to assess any changes in water quality and stream health in the future

Nutrient and fecal microbe contamination in Tates Creek, Madison County, Kentucky

Tates Creek is a significant tributary to the Kentucky River that has shown high levels of microbial and nutrient pollution. We sampled the waters of Tates Creek comprehensively by occupying 25 stations along its 13-mile length, collecting stream water at the confluence of major tributaries from its headwaters to the Kentucky River. Samples were collected four times between May and August 2011 during dry periods as well as immediately after a rainfall event. We measured ammonium (NH4+), nitrate (NO3-) and phosphate (PO4-) concentrations using colorimetry. Microbial samples were measured for total coliform and Escherichia coli using IDEXX Colilert-18 media. Background levels of NH4+, NO3- and PO4- are typically ~0.3 mg/L, 5 mg/L, and 1.0 mg/L, respectively. Background levels of nutrient concentrations generally increase during rainfall events, presumably because nutrients are flushed into the stream. Background counts of E. coli are typically ~100 cfu/mL but E. coli counts reached 1,000 – 2,419 cfu/mL immediately following rain events. A sewage treatment plant exists approximately two miles from the headwaters and noticeably affects water quality. Nutrient concentration, especially NH4+ and PO4-, are markedly increased at the plant’s outflow. These nutrients then decrease steadily in concentration downstream to background levels. In contrast, fecal microbe counts are high upstream from the plant, but fall to near-zero levels at its outflow, and then increase anew downstream. The treatment plant went off line on 19 July 2011 and nutrient levels downstream immediately decreased whereas E. coli counts remained high upstream and downstream of the plant. A companion study sampled stream biota before and after the plant shut down into 2012. This allows any changes in stream biota to be recognized and attributed to plant operations

Susceptibility testing for welding of AlMg alloys intended for extrusion

The objective of research was to determine the weldability, using Tungsten Inert Gas (TIG) of extruded sections made of hard-deformable 5xxx series aluminum alloys with differing magnesium content, i.e. AlMg3, AlMg4,5, AlMg5, AlMg7. Welded joints were obtained as a result of a welding process consisting of several steps. Only welds characterized by very good appearance and quality were selected for tests. As a result of conducted research, TIG welding parameters were determined for sections with a thickness of 8 mm. It was observed that alloys of differing Mg content are characterized by high weldability and do not exhibit a significant reduction of the yield point. Moreover, joints exhibit uniform hardness distribution in the welded joint and heat-affected zone. Tensile strength is reduced

Life in the Dark: Phylogenetic and Physiological Diversity of Chemosynthetic Symbioses

Possibly the last discovery of a previously unknown major ecosystem on Earth was made just over half a century ago, when researchers found teaming communities of animals flourishing two and a half kilometers below the ocean surface at hydrothermal vents. We now know that these highly productive ecosystems are based on nutritional symbioses between chemosynthetic bacteria and eukaryotes and that these chemosymbioses are ubiquitous in both deep-sea and shallow-water environments. The symbionts are primary producers that gain energy from the oxidation of reduced compounds, such as sulfide and methane, to fix carbon dioxide or methane into biomass to feed their hosts. This review outlines how the symbiotic partners have adapted to living together. We first focus on the phylogenetic and metabolic diversity of these symbioses and then highlight selected research directions that could advance our understanding of the processes that shaped the evolutionary and ecological success of these associations

A model of fasciculation and sorting in mixed populations of axons

We extend a recently proposed model (Chaudhuri et al., EPL 87, 20003 (2009)) aiming to describe the formation of fascicles of axons during neural development. The growing axons are represented as paths of interacting directed random walkers in two spatial dimensions. To mimic turnover of axons, whole paths are removed and new walkers are injected with specified rates. In the simplest version of the model, we use strongly adhesive short-range inter-axon interactions that are identical for all pairs of axons. We generalize the model to adhesive interactions of finite strengths and to multiple types of axons with type-specific interactions. The dynamic steady state is characterized by the position-dependent distribution of fascicle sizes. With distance in the direction of axon growth, the mean fascicle size and emergent time scales grow monotonically, while the degree of sorting of fascicles by axon type has a maximum at a finite distance. To understand the emergence of slow time scales, we develop an analytical framework to analyze the interaction between neighboring fascicles.Comment: 19 pages, 13 figures; version accepted for publication in Phys Rev