Pulsed radiolysis of model aromatic polymers and epoxy based matrix materials

Models of primary processes leading to deactivation of energy deposited by a pulse of high energy electrons were derived for epoxy matrix materials and polyl-vinyl naphthalene. The basic conclusion is that recombination of initially formed charged states is complete within 1 nanosecond, and subsequent degradation chemistry is controlled by the reactivity of these excited states. Excited states in both systems form complexes with ground state molecules. These excimers or exciplexes have their characteristics emissive and absorptive properties and may decay to form separated pairs of ground state molecules, cross over to the triplet manifold or emit fluorescence. ESR studies and chemical analyses subsequent to pulse radiolysis were performed in order to estimate bond cleavage probabilities and net reaction rates. The energy deactivation models which were proposed to interpret these data have led to the development of radiation stabilization criteria for these systems

Sustainable Cropping Systems

Global crop production must substantially increase to meet the needs of a rapidly growing population. This is constrained by the availability of nutrients, water, and land. There is also an urgent need to reduce the negative environmental impacts of crop production. Collectively, these issues represent one of the greatest challenges of the twenty-first century. Sustainable cropping systems based on ecological principles are the core of integrated approaches to solve this critical challenge. This special issue provides an international basis for revealing the underlying mechanisms of sustainable cropping systems to drive agronomic innovations. It includes review and original research articles that report novel scientific findings on improvement in cropping systems related to crop yields and their resistance to biotic and abiotic stressors, resource use efficiency, environmental impact, sustainability, and ecosystem services

Mathematical ConceptiΦns

The author completed four original works in order to illustrate the connection between writing creatively and mathematics. It is her belief that the two share a symbiotic relationship. The selections published here include two haikus, a short story, and a blank verse narrative poem. Mathematical concepts incorporated into the works include zero vector, Gaussian surfaces, matrices, and contain vibrant descriptions of mathematics

In vivo and in vitro models of demyelinating diseases. V. Comparison of the assembly of mouse hepatitis virus, strain JHM, in two murine cell lines.

The developmental sequence of a neurotropic strain (JHM) of mouse hepatitis virus was examined by transmission electron microscopy and immunocytology. The nucleoprotein core of this coronavirus, which contains RNA of positive polarity and is helical in configuration, becomes incorporated into enveloped particles in the same manner as the nucleocapsids of the orthomyxo- and paramyxoviruses. However, JHM virus is assembled intracellularly by budding at surfaces of smooth membranous vacuoles. A comparison of JHM virus replication in L2 and 17Cl-1 cell lines revealed that L2 cells undergo more rapid cytopathology and cease virus production much sooner than 17Cl-l cells. In L2 cells the accumulation of core material appears to continue after the abrupt cessation of virus assembly. This is evident by the massive cytoplasmic accumulation of structure resembling nucleocapsids, which react with hybridoma antibody to the nucleocapsid antigen as demonstrated by the immunoperoxidase procedure. The current findings are consistent with our previously published demonstration, using cells of neural and other deviation, of the fundamental role of the host cell type in regulating the replication and expression of coronaviruses

4D printing inflatable silicone structures

This article details steps in creating low-power artificial muscles using 3D printing. It describes a manufacturing system that can be used to fabricate seamless tubular dielectric elastomer actuators (DEA), for eventual use in biorobotic devices. The focus is on producing passive elastomeric components of DEA and the dimensional changes that occur after printing is complete. A four-axis printing system is described, capable of spray depositing multilayer tubular silicone membranes onto an air-permeable mandrel. Mechanical strain was imparted in the membranes by means of inflation. A laser measurement system was constructed to act as a 3D scanner, which measured the shape of the inflated ‘‘balloon.’’ The surface shape was reconstructed in software using the parametric modeling tool Grasshopper. Seamless auxetic tessellations were calculated across the entire surface, and then converted to CNC GCode. These toolpaths were then physically extruded over the surface of the balloon, stacked five layers high. When the extruded silicone structure was completely cured, the pneumatic strain was released, allowing the structure to collapse evenly. The compression in the printed structure was balanced by the tension in the stretched membranes, thus producing a minimum energy structure

Classroom Structure as an Environmental Effect on Creative Production of College Students

Little research has been done to explore creativity in the classroom environment. The present study investigated the effects of three classroom settings (formal, intermediate, and informal) on the creative production of college students. Ninety students were tested using Sternberg and Lubart\u27s (1995) Creativity Assessments both before and after participation in a teaching session. No significant changes were found between classes mean creativity scores after the experimental session. In the intermediate classroom, there was a significant decrease in scores before and after the session; however, in the other two classrooms, formal and informal, there was no significant change found

The United States Chiropractic Workforce: An alternative or complement to primary care?

UnlabelledBackgroundIn the United States (US) a shortage of primary care physicians has become evident. Other health care providers such as chiropractors might help address some of the nation's primary care needs simply by being located in areas of lesser primary care resources. Therefore, the purpose of this study was to examine the distribution of the chiropractic workforce across the country and compare it to that of primary care physicians.MethodsWe used nationally representative data to estimate the per 100,000 capita supply of chiropractors and primary care physicians according to the 306 predefined Hospital Referral Regions. Multiple variable Poisson regression was used to examine the influence of population characteristics on the supply of both practitioner-types.ResultsAccording to these data, there are 74,623 US chiropractors and the per capita supply of chiropractors varies more than 10-fold across the nation. Chiropractors practice in areas with greater supply of primary care physicians (Pearson's correlation 0.17, p-value < 0.001) and appear to be more responsive to market conditions (i.e. more heavily influenced by population characteristics) in regards to practice location than primary care physicians.ConclusionThese findings suggest that chiropractors practice in areas of greater primary care physician supply. Therefore chiropractors may be functioning in more complementary roles to primary care as opposed to an alternative point of access

The effects of energetic proton bombardment on polymeric materials: Experimental studies and degradation models

This report describes 3 MeV proton bombardment experiments on several polymeric materials of interest to NASA carried out on the Tandem Van De Graff Accelerator at the California Institute of Technology's Kellogg Radiation Laboratory. Model aromatic and aliphatic polymers such as poly(1-vinyl naphthalene) and poly(methyl methacrylate), as well as polymers for near term space applications such as Kapton, Epoxy and Polysulfone, have been included in this study. Chemical and physical characterization of the damage products have been carried out in order to develop a model of the interaction of these polymers with the incident proton beam. The proton bombardment methodology developed at the Jet Propulsion Laboratory and reported here is part of an ongoing study on the effects of space radiation on polymeric materials. The report is intended to provide an overview of the mechanistic, as well as the technical and experimental, issues involved in such work rather than to serve as an exhaustive description of all the results

The Thermal Environment of the Fiber Glass Dome for the New Solar Telescope at Big Bear Solar Observatory

The New Solar Telescope (NST) is a 1.6-meter off-axis Gregory-type telescope with an equatorial mount and an open optical support structure. To mitigate the temperature fluctuations along the exposed optical path, the effects of local/dome-related seeing have to be minimized. To accomplish this, NST will be housed in a 5/8-sphere fiberglass dome that is outfitted with 14 active vents evenly spaced around its perimeter. The 14 vents house louvers that open and close independently of one another to regulate and direct the passage of air through the dome. In January 2006, 16 thermal probes were installed throughout the dome and the temperature distribution was measured. The measurements confirmed the existence of a strong thermal gradient on the order of 5 degree Celsius inside the dome. In December 2006, a second set of temperature measurements were made using different louver configurations. In this study, we present the results of these measurements along with their integration into the thermal control system (ThCS) and the overall telescope control system (TCS).Comment: 12 pages, 11 figures, submitted to SPIE Optics+Photonics, San Diego, U.S.A., 26-30 August 2007, Conference: Solar Physics and Space Weather Instrumentation II, Proceedings of SPIE Volume 6689, Paper #2