Prosthetic urinary sphincter

A pump/valve unit for controlling the inflation and deflation of a urethral collar in a prosthetic urinary sphincter device is described. A compressible bulb pump defining a reservoir was integrated with a valve unit for implantation. The valve unit includes a movable valve member operable by depression of a flexible portion of the valve unit housing for controlling fluid flow between the reservoir and collar; and a pressure sensing means which operates the valve member to relieve an excess pressure in the collar should too much pressure be applied by the patient

Dynamics of protein-protein encounter: a Langevin equation approach with reaction patches

We study the formation of protein-protein encounter complexes with a Langevin equation approach that considers direct, steric and thermal forces. As three model systems with distinctly different properties we consider the pairs barnase:barstar, cytochrome c:cytochrome c peroxidase and p53:MDM2. In each case, proteins are modeled either as spherical particles, as dipolar spheres or as collection of several small beads with one dipole. Spherical reaction patches are placed on the model proteins according to the known experimental structures of the protein complexes. In the computer simulations, concentration is varied by changing box size. Encounter is defined as overlap of the reaction patches and the corresponding first passage times are recorded together with the number of unsuccessful contacts before encounter. We find that encounter frequency scales linearly with protein concentration, thus proving that our microscopic model results in a well-defined macroscopic encounter rate. The number of unsuccessful contacts before encounter decreases with increasing encounter rate and ranges from 20-9000. For all three models, encounter rates are obtained within one order of magnitude of the experimentally measured association rates. Electrostatic steering enhances association up to 50-fold. If diffusional encounter is dominant (p53:MDM2) or similarly important as electrostatic steering (barnase:barstar), then encounter rate decreases with decreasing patch radius. More detailed modeling of protein shapes decreases encounter rates by 5-95 percent. Our study shows how generic principles of protein-protein association are modulated by molecular features of the systems under consideration. Moreover it allows us to assess different coarse-graining strategies for the future modelling of the dynamics of large protein complexes

ACUPUNCTURE AND MEDICINE IN THE NEW MILLENNIUM

This is a transcript of the presentation given by Dr. Helms at the June 2000 ISSSEEM conference. He addresses the classical wisdom of acupuncture and the contemporary science of this medical discipline. The topics cover proposed mechanisms of action and clinical applications

Micronutrient Concentration Effects on Lettuce Growth and Susceptibility to Pythium

In hydroponic production waterborne pathogens such as Pythium are ubiquitous and continually threaten a wide range of Controlled Environment Agriculture (CEA) crops in hydroponic production, including but not limited to: lettuce, spinach, basil, arugula, cucumber, tomato, sweet pepper, roses, chrysanthemums, and cannabis (Sutton et al., 2006; Gull, 2002; McGehee and Raudales, 2021; Gillespie, 2020). Despite extensive sanitation measures, disease control in hydroponics is fallible and requires constant surveillance and management to minimize outbreaks (Sutton et al., 2006). A potential disease suppression strategy is to increase micronutrient concentrations within hydroponic systems to naturally strengthen plant defenses against pathogens such as Pythium. This thesis combines previous literature and research that looks at the effects of nutrient solution management and Pythium root rot disease on hydroponic lettuce. A series of preliminary studies were conducted to determine the correct Pythium species and strain, environmental parameters, and dosing methods in order to induce disease in hydroponic ‘Rex’ lettuce. These studies found that the Pythium strain and species P. myriotylum ‘PM1` had increased pathogenicity to cultivar ‘Rex’ lettuce and effectively caused root browning at concentrations of 1.80 × 104 oospores per L of solution or greater. Experiments in which preliminary findings were implemented looked at increasing Si and metal micronutrients iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) concentrations above standard hydroponic nutrient formulations for the effects on plant growth and susceptibility to P. myriotylum with hydroponic ‘Rex’ lettuce. Metal micronutrient/Si concentration and Pythium effects were measured with leaf SPAD chlorophyll content, shoot height and width, total plant fresh mass, percent reduction in lettuce growth, and root disease severity. It was found that increasing metal micronutrient and Si concentrations above standard hydroponic formulations resulted in decreased plant growth and yield. Overall, Pythium reduced plant growth and yield, however, increasing metal micronutrient and Si concentrations did not reduce Pythium disease severity compared to the standard solution, except for Cu at 10 mg·L-1. High concentrations of Cu have known fungicide and algaecide effects, however, can also be phytotoxic and reduce plant yield. Ultimately, combining proper sanitation, best management and cultural practices, appropriate hydroponic system design, and implementation of water treatment technologies will be the most effective strategy in controlling waterborne pathogens for hydroponic growers

ACUPUNCTURE AND MEDICINE IN THE NEW MILLENNIUM

This is a transcript of the presentation given by Dr. Helms at the June 2000 ISSSEEM conference. He addresses the classical wisdom of acupuncture and the contemporary science of this medical discipline. The topics cover proposed mechanisms of action and clinical applications

Micronutrient Concentration Effects on Lettuce Growth and Susceptibility to Pythium

In hydroponic production waterborne pathogens such as Pythium are ubiquitous and continually threaten a wide range of Controlled Environment Agriculture (CEA) crops in hydroponic production, including but not limited to: lettuce, spinach, basil, arugula, cucumber, tomato, sweet pepper, roses, chrysanthemums, and cannabis (Sutton et al., 2006; Gull, 2002; McGehee and Raudales, 2021; Gillespie, 2020). Despite extensive sanitation measures, disease control in hydroponics is fallible and requires constant surveillance and management to minimize outbreaks (Sutton et al., 2006). A potential disease suppression strategy is to increase micronutrient concentrations within hydroponic systems to naturally strengthen plant defenses against pathogens such as Pythium. This thesis combines previous literature and research that looks at the effects of nutrient solution management and Pythium root rot disease on hydroponic lettuce. A series of preliminary studies were conducted to determine the correct Pythium species and strain, environmental parameters, and dosing methods in order to induce disease in hydroponic ‘Rex’ lettuce. These studies found that the Pythium strain and species P. myriotylum ‘PM1` had increased pathogenicity to cultivar ‘Rex’ lettuce and effectively caused root browning at concentrations of 1.80 × 104 oospores per L of solution or greater. Experiments in which preliminary findings were implemented looked at increasing Si and metal micronutrients iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) concentrations above standard hydroponic nutrient formulations for the effects on plant growth and susceptibility to P. myriotylum with hydroponic ‘Rex’ lettuce. Metal micronutrient/Si concentration and Pythium effects were measured with leaf SPAD chlorophyll content, shoot height and width, total plant fresh mass, percent reduction in lettuce growth, and root disease severity. It was found that increasing metal micronutrient and Si concentrations above standard hydroponic formulations resulted in decreased plant growth and yield. Overall, Pythium reduced plant growth and yield, however, increasing metal micronutrient and Si concentrations did not reduce Pythium disease severity compared to the standard solution, except for Cu at 10 mg·L-1. High concentrations of Cu have known fungicide and algaecide effects, however, can also be phytotoxic and reduce plant yield. Ultimately, combining proper sanitation, best management and cultural practices, appropriate hydroponic system design, and implementation of water treatment technologies will be the most effective strategy in controlling waterborne pathogens for hydroponic growers

The Friendly Orange Glow: The Untold Story of the Rise of Cyberculture

Book review of The Friendly Orange Glow: The Untold Story of the Rise of Cyberculture by Brian Dear