Gamma Ray Pulsars: Emission from Extended Polar Cap Cascades

We have used a Monte Carlo simulation of a Polar Cap (PC) model of gamma-ray pulsars to estimate light curves and phase-resolved spectra for sources whose rotational and magnetic axes are oriented so that only one of the magnetic poles produces emission directed at the Earth. In this Single Polar Cap (SPC) scenario, even sources whose light curves have two distinct peaks (Crab, Vela, Geminga, PSR B1951+32) are due to emission concentrated near the rim of a single PC. If the inclination alpha is comparable to the half-width of the PC gamma-beam, alpha ~ theta_{b}, the peak-to-peak phase separation can have the large values (0.4 - 0.5) observed from these sources. In the model presented here we attribute the observed interpeak emission to pair cascades above the PC interior. Our simulation assumes the physics of conventional PC models, in which the gamma rays are due to photon-pair cascades initiated by curvature radiation from the acceleration of electrons above the PCs. In this work we assume that the acceleration occurs over a finite region which may extend up to several radii above the neutron star surface. We find that the combined effects of moderately enlarged PC dimensions and extended acceleration zones resolve a major difficulty with earlier PC models, namely their small beam widths (and hence small detection probabilities). Our best fits to the observed light curves are obtained from models in which the accelerated electrons have a uniform surface density over the PC interior and a sharp density increase of 3 - 5 near the rim.Comment: 31 pages (AASTEX) + 9 figures (uuencoded, compressed ps), to be published in ApJ, Feb. 10 199

Contributions of Matrix Metalloproteinases to Neural Plasticity, Habituation, Associative Learning and Drug Addiction

The premise of this paper is that increased expression of matrix metalloproteinases (MMPs) permits the reconfiguration of synaptic connections (i.e., neural plasticity) by degrading cell adhesion molecules (CAMs) designed to provide stability to those extracellular matrix (ECM) proteins that form scaffolding supporting neurons and glia. It is presumed that while these ECM proteins are weakened, and/or detached, synaptic connections can form resulting in new neural pathways. Tissue inhibitors of metalloproteinases (TIMPs) are designed to deactivate MMPs permitting the reestablishment of CAMs, thus returning the system to a reasonably fixed state. This review considers available findings concerning the roles of MMPs and TIMPs in reorganizing ECM proteins thus facilitating the neural plasticity underlying long-term potentiation (LTP), habituation, and associative learning. We conclude with a consideration of the influence of these phenomena on drug addiction, given that these same processes may be instrumental in the formation of addiction and subsequent relapse. However, our knowledge concerning the precise spatial and temporal relationships among the mechanisms of neural plasticity, habituation, associative learning, and memory consolidation is far from complete and the possibility that these phenomena mediate drug addiction is a new direction of research

Pond Culture of Walleye Fingerlings

Walleye, Stitzostedion vitreum, has potential to be an aquaculture species in the North Central Region because: it is native to the region; it maintains optimum growth at temperatures lower than many other current aquaculture species (such as channel catfish); it is a highly-prized sport fish; its flesh is considered a delicacy; and the fillets are high in protein and . low in fat, making walleye an attractive food selection for today’s health conscious consumer

T Cell Adaptive Immunity Proceeds through Environment-Induced Adaptation from the Exposure of Cryptic Genetic Variation

Evolution is often characterized as a process involving incremental genetic changes that are slowly discovered and fixed in a population through genetic drift and selection. However, a growing body of evidence is finding that changes in the environment frequently induce adaptations that are much too rapid to occur by an incremental genetic search process. Rapid evolution is hypothesized to be facilitated by mutations present within the population that are silent or “cryptic” within the first environment but are co-opted or “exapted” to the new environment, providing a selective advantage once revealed. Although cryptic mutations have recently been shown to facilitate evolution in RNA enzymes, their role in the evolution of complex phenotypes has not been proven. In support of this wider role, this paper describes an unambiguous relationship between cryptic genetic variation and complex phenotypic responses within the immune system. By reviewing the biology of the adaptive immune system through the lens of evolution, we show that T cell adaptive immunity constitutes an exemplary model system where cryptic alleles drive rapid adaptation of complex traits. In naive T cells, normally cryptic differences in T cell receptor reveal diversity in activation responses when the cellular population is presented with a novel environment during infection. We summarize how the adaptive immune response presents a well studied and appropriate experimental system that can be used to confirm and expand upon theoretical evolutionary models describing how seemingly small and innocuous mutations can drive rapid cellular evolution

Do investors see through mistakes in reported earnings?

This study investigates whether investors see through materially misstated earnings, and whether they anticipate earnings restatements. For firms that restate at least one annual report, we find that investors are misled by mistakes in reported earnings at the time of initial earnings announcements. Investors react positively to the component of the favorable earnings surprise that will subsequently be restated, and attach the same valuation to it as to the true earnings surprise. We also find that investors anticipate the subsequent downward restatements and start marking stock prices down several months before a restatement announcement, so that the full impact of a restatement is about three times as large as the initial announcement effect. Overall our findings indicate that although investors anticipate restatements several months before its announcement, they are misled by misstated earnings for several years and therefore would benefit from better quality of financial information

A rotary mechanism for allostery in bacterial hybrid malic enzymes

This project was funded by BBSRC studentship 1500753 to C.J.H. and a BBSRC David Phillips fellowship to P.J.M. (BB/S010122/1).Bacterial hybrid malic enzymes (MaeB grouping, multidomain) catalyse the transformation of malate to pyruvate, and are a major contributor to cellular reducing power and carbon flux. Distinct from other malic enzyme subtypes, the hybrid enzymes are regulated by acetyl-CoA, a molecular indicator of the metabolic state of the cell. Here we solve the structure of a MaeB protein, which reveals hybrid enzymes use the appended phosphotransacetylase (PTA) domain to form a hexameric sensor that communicates acetyl-CoA occupancy to the malic enzyme active site, 60 Å away. We demonstrate that allostery is governed by a large-scale rearrangement that rotates the catalytic subunits 70° between the two states, identifying MaeB as a new model enzyme for the study of ligand-induced conformational change. Our work provides the mechanistic basis for metabolic control of hybrid malic enzymes, and identifies inhibition-insensitive variants that may find utility in synthetic biology.Publisher PDFPeer reviewe

Current HIV/AIDS end-of-life care in sub-Saharan Africa: a survey of models, services, challenges and priorities

BACKGROUND: In response to increased global public health funding initiatives to HIV/AIDS care in Africa, this study aimed to describe practice models, strategies and challenges to delivering end-of-life care in sub-Saharan Africa. METHODS: A survey end-of-life care programs was conducted, addressing the domains of service aims and configuration, barriers to pain control, governmental endorsement and strategies, funding, monitoring and evaluation, and research. Both closed and qualitative responses were sought. RESULTS: Despite great structural challenges, data from 48 programs in 14 countries with a mean annual funding of US $374,884 demonstrated integrated care delivery across diverse settings. Care was commonly integrated with all advanced disease care (67%) and disease stages (65% offering care from diagnosis). The majority (98%) provided home-based care for a mean of 301 patients. Ninety-four percent reported challenges in pain control (including availability, lack of trained providers, stigma and legal restrictions), and 77% addressed the effects of poverty on disease progression and management. Although 85% of programs reported Government endorsement, end-of-life and palliative care National strategies were largely absent. CONCLUSIONS: The interdependent tasks of expanding pain control, balancing quality and coverage of care, providing technical assistance in monitoring and evaluation, collaborating between donor agencies and governments, and educating policy makers and program directors of end-of-life care are all necessary if resources are to reach their goals

Effects of tissue hydration on nanoscale structural morphology and mechanics of individual Type I collagen fibrils in the Brtl mouse model of Osteogenesis Imperfecta

Type I collagen is the most abundant protein in mammals, and is a vital part of the extracellular matrix for numerous tissues. Despite collagen’s importance, little is known about its nanoscale morphology in tissues and how morphology relates to mechanical function. This study probes nanoscale structure and mechanical properties of collagen as a function of disease in native hydrated tendons. Wild type tendon and tendon from the Brtl/+ mouse model of Osteogenesis Imperfecta were investigated. An atomic force microscope (AFM) was used to image and indent minimally-processed collagen fibrils in hydrated and dehydrated conditions. AFM was used because of the ability to keep biological tissues as close to their native in situ conditions as possible. The study demonstrated phenotypic difference in Brtl/+ fibril morphology and mechanics in hydrated tendon which became more compelling upon dehydration. Dried tendons had a significant downward shift in fibril D- periodic spacing versus a shift up in wet tendons. Nanoscale changes in morphology in dry samples were accompanied by significant increases in modulus and adhesion force and decreased indentation depth. A minimal mechanical phenotype existed in hydrated samples, possibly due to water masking structural defects within the diseased fibrils. This study demonstrates that collagen nanoscale morphology and mechanics are impacted in Brtl/+ tendons, and that the phenotype can be modulated by the presence or absence of water. Dehydration causes artifacts in biological samples which require water and this factor must be considered for studies at any length scale in collagen-based tissues, especially when characterizing disease- induced differences

Silicone Applicator Cleaning Improvement

Cardinal Glass is a residential glass manufacturer for doors and windows. Cardinal glass was first founded in 1962 by a man named M.L. Gordon. Today, they employ 6,000 employees across 37 manufacturing plants throughout the United States. The Greenfield, Iowa, plant distributes to local large window manufacturers. Cardinal Glass is separated into five divisions. They are as followed:FG- Float & High Volume Tempered Glass; CT- Custom Tempered Glass; LG- Laminated Glass; CG- coated glass and optical mirrors; and IG- Insulating Glass. The Client is experiencing problems with silicone curing in applicator tips due to lack of a better process. The silicone cured tips are causing re-work that is costing the company thousands of dollars in labor