Genetic Algorithm Optimization of Core-Shell Nanowire Betavoltaic Generators.

Numerical optimization has been used to determine the optimum junction design for core-shell nanowires used in betavoltaic generators. A genetic algorithm has been used to calculate the relative thickness, height, and doping of each segment within silicon, gallium arsenide, and gallium phosphide nanowires. Using the simulated spectra and energy deposition of nickel-63, nickel citrate, tritium, and tritiated butyl, devices with power output and overall efficiency up to 8 µW.cm-2 and 12%, respectively, have been predicted. Compared to previously investigated axial nanowires, the core-shell structures simulated here have realized drastic improvements by reducing surface recombination for longer nanowires. In addition, core-shell nanowires are shown to be capable of nearly matching the ideal performance predicted for this device structure. A new approach for calculating the practical upper limit of betavoltaic performance is presented and additional methods for improvement are discussed.

NEUDOSE: A CubeSat Mission for Dosimetry of Charged Particles and Neutrons in Low-Earth Orbit.

During space missions, astronauts are exposed to a stream of energetic and highly ionizing radiation particles that can suppress immune system function, increase cancer risks and even induce acute radiation syndrome if the exposure is large enough. As human exploration goals shift from missions in low-Earth orbit (LEO) to long-duration interplanetary missions, radiation protection remains one of the key technological issues that must be resolved. In this work, we introduce the NEUtron DOSimetry & Exploration (NEUDOSE) CubeSat mission, which will provide new measurements of dose and space radiation quality factors to improve the accuracy of cancer risk projections for current and future space missions. The primary objective of the NEUDOSE CubeSat is to map the in situ lineal energy spectra produced by charged particles and neutrons in LEO where most of the preparatory activities for future interplanetary missions are currently taking place. To perform these measurements, the NEUDOSE CubeSat is equipped with the Charged & Neutral Particle Tissue Equivalent Proportional Counter (CNP-TEPC), an advanced radiation monitoring instrument that uses active coincidence techniques to separate the interactions of charged particles and neutrons in real time. The NEUDOSE CubeSat, currently under development at McMaster University, provides a modern approach to test the CNP-TEPC instrument directly in the unique environment of outer space while simultaneously collecting new georeferenced lineal energy spectra of the radiation environment in LEO.

Host specificity of Lepidoptera in tropical and temperate forests.

For numerous taxa, species richness is much higher in tropical than in temperate zone habitats. A major challenge in community ecology and evolutionary biogeography is to reveal the mechanisms underlying these differences. For herbivorous insects, one such mechanism leading to an increased number of species in a given locale could be increased ecological specialization, resulting in a greater proportion of insect species occupying narrow niches within a community. We tested this hypothesis by comparing host specialization in larval Lepidoptera (moths and butterflies) at eight different New World forest sites ranging in latitude from 15 degrees S to 55 degrees N. Here we show that larval diets of tropical Lepidoptera are more specialized than those of their temperate forest counterparts: tropical species on average feed on fewer plant species, genera and families than do temperate caterpillars. This result holds true whether calculated per lepidopteran family or for a caterpillar assemblage as a whole. As a result, there is greater turnover in caterpillar species composition (greater beta diversity) between tree species in tropical faunas than in temperate faunas. We suggest that greater specialization in tropical faunas is the result of differences in trophic interactions; for example, there are more distinct plant secondary chemical profiles from one tree species to the next in tropical forests than in temperate forests as well as more diverse and chronic pressures from natural enemy communities.

Comparative oral bioavailability of azimilide dihydrochloride in the fed and fasted states.

AIMS: This study investigated the relative oral bioavailability of azimilide dihydrochloride following administration in the fed (high-fat meal) and fasted states. METHODS: This was a single-dose, randomized, two-way crossover study in 30 healthy, Caucasian, male subjects. Following oral administration, blood samples were collected over 27 days and analysed for azimilide using h.p.l.c. with u.v. detection. Pharmacokinetic parameters were determined using 'noncompartmental' analysis and compared using an ANOVA and 90% or 95% confidence intervals. RESULTS: The extent of absorption was equivalent in the fed and fasted states (ratio = 96.2%; 90% CI=90.5% -102.4%). However, Cmax was decreased 19% following a high-fat meal (ratio=81.4%; 90% CI= 76.2% -87.0%). No difference in tmax or t(1/2),z was observed. CONCLUSIONS: Azimilide dihydrochloride may be orally administered to patients without regard to the prandial state.

Azimilide pharmacokinetics following intravenous and oral administration of a solution and capsule formulation.

Azimilide dihydrochloride (NE-10064) is a novel class III anti-arrhythmic agent that blocks both the slowly and rapidly acting components of the delayed rectifier potassium current of human atrial and ventricular myocytes. In clinical studies, azimilide reduced the frequency of symptomatic episodes of atrial fibrillation, atrial flutter, and paroxysmal supraventricular tachycardia. This study was conducted to characterize azimilide pharmacokinetics following single-dose administration of a 1 mg/kg intravenous infusion (18 min), 2 mg/kg oral solution, and a 150 mg orally administered capsule. This was a three-period, randomized, crossover study in 27 healthy, drug-free (including caffeine and alcohol), non-smoking male volunteers (mean [SD]; age, 25.9 [1.0] years; weight 74.3 [0.7] kg; 23 Caucasians and 4 Hispanics). Blood and urine samples were collected for 27 days and analyzed for azimilide using HPLC with UV detection. Subjects were monitored for adverse events and abnormalities in clinical laboratory tests, vital signs, and electrocardiography (including Holter monitoring). Mean (%CV) azimilide parameters were total clearance = 0.143 L/h/kg (38%), renal clearance = 0.014 L/h/kg (35%), steady-state volume of distribution = 13.2 L/kg (23%), and terminal exponential half-life = 78.8 h (44%). Similar parameter estimates were obtained following oral administration. Both the oral solution and capsule formulations were completely absorbed. In addition, the rate (Cmax) and extent of absorption (AUC) following oral administration of the capsule dosage form were bioequivalent to the oral solution with means for times of maximum blood concentration of 7.08 and 7.18 hours for the oral solution and capsule, respectively. Azimilide dihydrochloride was generally well tolerated in all subjects.

Enhancing consumer independence through delegation.

Many forces are influencing the development of delegation options, and states are approaching the issue differently. In 1997 Oregon, Texas, New York, and Washington participated in a national symposium on delegation convened by The National Institute of Consumer-Directed Long-Term Services. These states do not necessarily represent four different approaches; however, each illustrates some of the issues involved and the ways that competing forces continue to work together to improve the policies and regulations governing delegation.

A nuclear gene for higher level phylogenetics: phosphoenolpyruvate carboxykinase tracks mesozoic-age divergences within Lepidoptera (Insecta).

The sequence of phosphoenolpyruvate carboxykinase (PEPCK) has been previously identified as a promising candidate for reconstructing Mesozoic-age divergences (Friedlander, Regier, and Mitter 1992, 1994). To test this hypothesis more rigorously, 597 nucleotides of aligned PEPCK coding sequence (approximately 30% of the coding region) were generated from 18 species representing Mesozoic-age lineages of moths (Insecta: Lepidoptera) and outgroup taxa. Relationships among basal Lepidoptera are well established by morphological analysis, providing a strong test for the utility of a gene which has not previously been used in systematics. Parsimony and other phylogenetic analyses were conducted on nucleotides by codon positions (nt1, nt2, nt3) separately and in combination, and on amino acids, for comparison to the test phylogeny. The highest concordance was achieved with nt1 + nt2, for which one of two most-parsimonious trees was identical to the test phylogeny, and with all nucleotides when nt3 was down-weighted sevenfold or higher, for which a single most-parsimonious tree identical to the test phylogeny resulted. Substitutions in nt3 approached saturation in many, but not all, pairwise comparisons and their exclusion or severe downweighting greatly increased the degree of concordance with the test phylogeny. Neighbor-joining analysis confirms this finding. The utility of PEPCK for phylogenetics is demonstrated over a time span for which few other suitable genes are currently available.

Ninety-seven million years of angiosperm-insect association: paleobiological insights into the meaning of coevolution.

From well preserved leaf damage of the mid-Cretaceous Dakota Flora (97 million years ago), three distinctive, insect-mediated feeding traces have been identified and assigned to two extant genera and one subfamily. These taxa are the leaf miners Stigmella and Ectoedemia of the Nepticulidae and Phyllocnistinae of the Gracillariidae. These fossils indicate that within 25 million years of early angiosperm radiation, the organs of woody dicots already were exploited in intricate and modern ways by insect herbivores. For Ectoedemia and its platanoid host, we document 97 million years of continuity for a plant-insect interaction. The early occurrence during the mid-Cretaceous of diverse and extensive herbivory on woody angiosperms may be associated with the innovation of deciduousness, in which a broadleafed angiosperm provided an efficient, but disposable, photosynthetic organ that with-stood the increased cost of additional insect herbivory. Moreover, the group represented in this study, the leaf-mining Lepidoptera, exhibits a wide range of subordinal taxonomic differentiation and includes the Gracillariidae, a member of the most derived lepidopteran suborder, the Ditrysia. Ditrysian presence during the mid-Cretaceous, in addition to lepidopteran body-fossil evidence from Early Cretaceous and Late Jurassic deposits, suggests that the radiation of major lepidopteran lineages probably occurred during the Late Jurassic on a gymnosperm-dominated flora.

Cross-allergenicity among celery, cucumber, carrot, and watermelon.

Cross-reactive allergens may be responsible for the clustering of food allergies seen in patients hypersensitive to fruits and vegetables. The pooled sera of six individuals were used to investigate cross-antigenicity among freshly prepared extracts of celery (Cy), cucumber (Cc), carrot (Ct), and watermelon (W). Each patient demonstrated clinical allergy to one or more study foods and, with the exception of Ct in two cases, had IgE to all four extracts by skin test or ELISA. In comparisons of each food against itself and the other three antigens, ELISA inhibition assays demonstrated allergenic similarity among Cy, Cc, Ct, and W by their similar slopes and 50% inhibition concentrations (2.0-7.3 micrograms/mL). In contrast, mountain cedar pollen (MC) produced at 50% inhibition of each food which was 10-fold higher (26.9-70.8 micrograms/mL) and had a flatter slope. Immunoblots of individual sera showed a 15-kD protein band common to all four foods. Pooled sera immunoblot inhibitions (100 and 5 micrograms/mL) demonstrated mutual inhibition of all bands in each of the four foods with the exception of a 28-kD protein of W uniquely inhibited by itself. We conclude that Cy, Cc, Ct, and W possess shared antigens that may account for clustering of these food allergies in patients.

Flightlessness in insects.

The evolution of wings is heralded as the most important event in the diversification of insects, yet flight-wing loss has occurred in nearly all pterygote insect orders. Flight loss is especially prevalent among taxa inhabiting historically stable habitats. Recent studies of wing-polymorphic species have revealed numerous selective trade-offs in the reproductive potentials of winged versus flightless forms. A diverse set of environmental factors, both biotic and abiotic, trigger flight loss in alary polyphenic taxa, presumably by influencing juvenile hormone titers. Phylogenetic comparisons promise to elucidate much about the historical contexts and consequences of flight loss.

Platelet MAO in subtypes of alcoholism.

A number of investigators have observed low platelet monoamine oxidase (MAO) activity in alcoholism. There is also preliminary evidence suggesting that low enzyme activity is principally associated with one of two putative subtypes of alcohol dependence, i.e., type II (male limited). The results of this study are consistent with two previous reports of reduced platelet MAO activity in type II male alcoholics as compared with type I male alcoholics and normal, healthy male controls. Type I (milieu-limited) alcoholics showed a smaller reduction in enzyme activity. The observed differences do not appear to be related to concurrent use of other psychoactive substances, characteristic differences in age between type I alcoholics and type II alcoholics, antisocial personality disorder, or variation in platelet size. Low platelet MAO activity in alcoholics is possibly related to both state and trait factors and may be a useful biochemical measure to assist with subtyping.

Shock in the operating room.

Many factors may contribute to producing a shock state within the surgical environment. The classic causes of shock--hypovolemia, cardiac failure, and sepsis--occur commonly in the operating room. Additionally, concurrent surgery and anesthesia may contribute to produce clinical shock. Surgery may produce hypovolemia from "third space" loss and/or from blood loss. Some anesthetic drugs, by inhibiting the autonomic nervous system, impair the body's ability to compensate for hypovolemia, cardiac failure, or sepsis. Other entities such as tension pneumothorax, drug allergy, or mechanical factors produced by surgical exposure may contribute to hemodynamic compromise of the patient. Shock that occurs outside the surgical suite may also be produced by a variety of insults. One or more factors may contribute to inadequate tissue perfusion, thus making diagnosis of the cause(s) of shock a clinical challenge. Presented in this review is an anesthesiologist's approach to shock on a macrocirculatory level. Two important concepts are vital to this approach. First, one must act immediately to restore adequate perfusion to the brain and heart when confronted with a patient in shock. This is possible without knowing the specific cause(s) of the poor perfusion. Second, a rapid, accurate diagnosis of the cause(s) must be made if the patient is slow to respond to the initial therapy. Through the use of pulmonary artery catheterization, the factors producing any given shock state may be identified, and appropriate therapy may be instituted and monitored.