Solid-state time-to-pulse-height converter developed

Solid-state circuit produces an output pulse with an amplitude directly proportional to the time interval between two input pulses. It uses selected circuit options to achieve variable mode operation and a tunnel diode controls the charging time of a capacitor in proportion to the time interval being measured

Magnetic-Island Contraction and Particle Acceleration in Simulated Eruptive Solar Flares

The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. (2006) proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets. We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gains in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare current sheet. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magnetohydrodynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare current sheet is a promising candidate for electron acceleration in solar eruptions.Comment: Accepted for publication in The Astrophysical Journal (2016

Data acquisition system for NASA LaRC impact dynamics research facility

A data system is designed to permit the simultaneous recording of 90 data channels on one 28 track magnetic tape recorder using a constant bandwidth FM multiplexing technique. Dynamic signals from transducers located in the test aircraft are amplified and fed to voltage controlled oscillators where they are converted to discrete FM signals. The signals from each group of five VCO's are fed to a mixer/distribution amplifier where they are combined into one composite signal and recorded, using direct recording techniques, on one magnetic tape recorder track. Millivolt signals from the recorders reproduce heads are amplified to one volt and then electronically switched to an FM demultiplexing system where appropriate frequency discrimination and signal filtering recover the original analog information

Adaptive evolution of molecular phenotypes

Molecular phenotypes link genomic information with organismic functions, fitness, and evolution. Quantitative traits are complex phenotypes that depend on multiple genomic loci. In this paper, we study the adaptive evolution of a quantitative trait under time-dependent selection, which arises from environmental changes or through fitness interactions with other co-evolving phenotypes. We analyze a model of trait evolution under mutations and genetic drift in a single-peak fitness seascape. The fitness peak performs a constrained random walk in the trait amplitude, which determines the time-dependent trait optimum in a given population. We derive analytical expressions for the distribution of the time-dependent trait divergence between populations and of the trait diversity within populations. Based on this solution, we develop a method to infer adaptive evolution of quantitative traits. Specifically, we show that the ratio of the average trait divergence and the diversity is a universal function of evolutionary time, which predicts the stabilizing strength and the driving rate of the fitness seascape. From an information-theoretic point of view, this function measures the macro-evolutionary entropy in a population ensemble, which determines the predictability of the evolutionary process. Our solution also quantifies two key characteristics of adapting populations: the cumulative fitness flux, which measures the total amount of adaptation, and the adaptive load, which is the fitness cost due to a population's lag behind the fitness peak.Comment: Figures are not optimally displayed in Firefo

Optical Properties of Single-Crystal Cadmium

Measurements were made of the reflectivity and/or absorptivity of cadmium from 0.15 to 20 eV, using polarized light with the electric vector both perpendicular and parallel to the c axis of the crystal. In the visible and infrared spectra both polarizations yielded strong absorption peaks. For perpendicular polarization, the main peak was at 0.98 eV and was attributed mainly to transitions between bands along the L−H symmetry line. Also in this polarization there was an absorption edge at 0.29 eV. This may be due to transitions near the point K in the Brillouin zone. For parallel polarization, the main absorption peak was at 1.10 eV and was attributed to transitions between bands along Γ−K, Γ−M, and L−H. No low-energy absorption edge was found for parallel polarization. Agreement between the experimental data and the calculations of Kasowski based on a nonlocal-pseudopotential model was fairly good. There was no agreement between the data and calculations based on a local-pseudopotential model. At low temperatures, the long-wavelength absorptivities were approximately constant, in agreement with theory for the anomalous-skin-effect region. Using the theory of Kliewer and Fuchs and the experimental data, parallel and perpendicular effective masses were calculated to be 1.09m0 and 1.61m0, respectively. The weighted average of these is in good agreement with the thermal effective mass for cadmium. The low-energy data support the theory of Kliewer and Fuchs and tend to confirm the volume absorption process suggested by Holstein

The relationship between innovation culture and innovation outcomes: exploring the effects of sustainability orientation and firm size

Being sustainability oriented has become a key strategy for many firms. Equally, innovation culture and innovation outcomes have long been recognized as important contributors to the growth of firms. However, the literature on sustainability and innovation provides limited understanding of the important relationship between sustainability orientation, innovation culture and innovation outcomes. Given that large firms and small firms differ in building and employing their strategic assets, firm size matters in understanding the relationship. Through the lens of resource-based view, we develop a theoretical model embedding the four components and test it using data from a global survey: the 2012 Comparative Performance Assessment Study. Our research contributes to sustainability literature and innovation theory by providing an integrated framework to explicate the mechanism through which the innovation culture of the firm impacts on innovative performance through the sustainability orientation of the firm. The findings advance our understanding of the extent to which sustainable orientation can explain the relationship between innovation culture and innovation outcomes. Our evidence shows that the innovation culture of a firm facilitates the sustainability orientation of the firm and that the converse also applies. The research also contributes to our knowledge of the differences between large and small firms in leveraging their strategic assets in terms of innovation culture and sustainability orientation to facilitate superior innovation outcomes. Although firm size moderates the relationship between innovation culture and innovation outcomes, the research shows that this no longer holds when sustainability orientation is included in the relationship. A strong sustainability orientation can be a competitive advantage for firms in the delivery of superior innovation outcomes

Multiplet Structure below Threshold in Appearance-Potential Spectra—Lanthanum N4,5

We present the N4,5 appearance-potential spectrum of La. Structure exists at energies lower than the threshold energy for transitions terminating at the Fermi level. Several similarities between optical absorption spectra and our results are discussed. These results contradict the simple model usually used to interpret appearance-potential spectra and emphasize the need for a new theory