Regulating Growth of an Aquatic Plant: Lemna perpusilla

Growth rates of Lemna perpusilla 6746 can be regulated in axenic cultures by 6-benzylaminopurine (BA) . Concentrations of 10-BM BA significantly enhanced growth, while levels of 10-7M and Higher were inhibitory. These effects of BA on growth were evident when calculated as either fresh weight of frond number

Conversion Yields of Some Photographic Emulsions and Related Factors

Author Institution: Aerospace Research Laboratories, Wright-Patterson Air Force Base, OhioA method is presented for the determination of the effective average projected grain diameter (d-a) using visual analysis of enlargements of Kodak Tri-X Pan and Kodak Royal-X Pan emulsions. Each was exposed to three light sources of color temperatures 6100°K, 2850°K, and 2040°K, and was developed in Kodak developers HC-110, DK-50, and D-19 for 5, 8, 12, and 20 minutes at 68°F. For 5- to 20-minute developing times, dA was determined, from a total of over 12,000 counts, to be from ~ 2.1 to ~ 2.4 u for both films. A method for calculating the conversion yield -q (number of grains to total number of quanta focused on the emulsion) is derived. The value y is a function of film density (D); it was found that rj first increases and then decreases, and a theory which explains this behavior in connection with grain formation is proposed; that is, 77 is the result of a superposition of an increasing and a decreasing function. The first is caused by the fact that a photographic nucleus made up of three silver atoms has a lesser probability for development than a four-atom nucleus, where with the increased exposure (number of quanta per unit area), the ratio increases in favor of the latter, resulting in an increasing function. However, the photographic plate, unlike the photoemitter, is a "non-speciereplacing" device; as a result, the percentage of nonactivated silver halides decreases with exposure, making the latter a decreasing function. Typical values for 77 showing this behavior are: Tri-X Pan; 6100°K, spectral region 375 to 700 m/x; HC-110, 8 min, 68°F; ij~0.1% at D = 0.10, T7~O.3% at D = 0.30, rj~0.1% at D = 1.00, and' ^ 0 . 0 0 9% at D = 2.00. For A = 466 mn (peak of P-ll phosphor), r, increases from ~ 0.09% at D = 0.10 to ~ 0.4% at D = 0.40, then decreases to ~ 0.2% at D = 1.00 and ~ 0.01% at D = 2.00

General aviation piston-engine exhaust emission reduction

To support the promulgation of aircraft regulations, two airports were examined, Van Nuys and Tamiami. It was determined that the carbon monoxide (CO) emissions from piston-engine aircraft have a significant influence on the CO levels in the ambient air in and around airports, where workers and travelers would be exposed. Emissions standards were set up for control of emissions from aircraft piston engines manufactured after December 31, 1979. The standards selected were based on a technologically feasible and economically reasonable control of carbon monoxide. It was concluded that substantial CO reductions could be realized if the range of typical fuel-air ratios could be narrowed. Thus, improvements in fuel management were determined as reasonable controls

Report of the Terrestrial Bodies Science Working Group. Volume 5: Mars

Present knowledge of the global properties and surface characteraretics of Mars and the composition and dynamics of its atmosphere are reviewed. The objectives of proposed missions, the exploration strategy, and supporting research and technology required are delineated

Production of a Prompt Photon in Association with Charm at Next-to-Leading Order in QCD

A second order, $O(\alpha ^2_s)$, calculation in perturbative quantum chromodynamics of the two particle inclusive cross section is presented for the reaction $p +\bar{p}\rightarrow \gamma + c + X$ for large values of the transverse momentum of the prompt photon and charm quark. The combination of analytic and Monte Carlo integration methods used here to perform phase-space integrations facilitates imposition of photon isolation restrictions and other selections of relevance in experiments. Differential distributions are provided for various observables. Positive correlations in rapidity are predicted.Comment: 27 pages in RevTex plus 14 figures in one compressed PS fil

Collective dynamics in crystalline polymorphs of ZnCl2_{2}: potential modelling and inelastic neutron scattering study

We report a phonon density of states measurement of $\alpha$-ZnCl$_{2}$ using the coherent inelastic neutron scattering technique and a lattice dynamical calculation in four crystalline phases of ZnCl$_{2}$ using a transferable interatomic potential. The model calculations agree reasonably well with the available experimental data on the structures, specific heat, Raman frequencies and their pressure variation in various crystalline phases. The calculated results have been able to provide a fair description of the vibrational as well as the thermodynamic properties of ZnCl$_{2}$ in all its four phases.Comment: Accepted in J. Phys.: Condens. Matte

Use of clinical guidelines: Perspectives from clinicians in paediatric and maternity hospitals in Kabul, Afghanistan

© 2015, World Health Organization. All rights reserved. This study explored the perceived value, role and reported use of clinical guidelines by clinicians in urban paediatric and maternity hospital settings, and the effect of current implementation strategies on clinician attitudes, knowledge and behaviour. A total of 63 clinicians from 7 paediatric and maternity hospitals in Kabul, Afghanistan participated in structured focus groups; content analysis methodology was used for identification and analysis of key themes. Seven sets of guidelines, protocols or standards were identified (including 5 WHO-endorsed guidelines). However, most are failing to achieve high levels of use. Factors associated with guideline use included: clinician involvement in guideline development; multidisciplinary training; demonstrable results; and positive clinician perceptions regarding guideline quality and contextual appropriateness. Implementation activities should fulfil 3 major objectives: promote guideline awareness and access; stimulate motivation among clinical guideline users; and actively facilitate adherence to guidelines

Theoretical current-voltage characteristics of ferroelectric tunnel junctions

We present the concept of ferroelectric tunnel junctions (FTJs). These junctions consist of two metal electrodes separated by a nanometer-thick ferroelectric barrier. The current-voltage characteristics of FTJs are analyzed under the assumption that the direct electron tunneling represents the dominant conduction mechanism. First, the influence of converse piezoelectric effect inherent in ferroelectric materials on the tunnel current is described. The calculations show that the lattice strains of piezoelectric origin modify the current-voltage relationship owing to strain-induced changes of the barrier thickness, electron effective mass, and position of the conduction-band edge. Remarkably, the conductance minimum becomes shifted from zero voltage due to the piezoelectric effect, and a strain-related resistive switching takes place after the polarization reversal in a ferroelectric barrier. Second, we analyze the influence of the internal electric field arising due to imperfect screening of polarization charges by electrons in metal electrodes. It is shown that, for asymmetric FTJs, this depolarizing-field effect also leads to a considerable change of the barrier resistance after the polarization reversal. However, the symmetry of the resulting current-voltage loop is different from that characteristic of the strain-related resistive switching. The crossover from one to another type of the hysteretic curve, which accompanies the increase of FTJ asymmetry, is described taking into account both the strain and depolarizing-field effects. It is noted that asymmetric FTJs with dissimilar top and bottom electrodes are preferable for the non-volatile memory applications because of a larger resistance on/off ratio.Comment: 14 pages, 8 figure

Systems, interactions and macrotheory

A significant proportion of early HCI research was guided by one very clear vision: that the existing theory base in psychology and cognitive science could be developed to yield engineering tools for use in the interdisciplinary context of HCI design. While interface technologies and heuristic methods for behavioral evaluation have rapidly advanced in both capability and breadth of application, progress toward deeper theory has been modest, and some now believe it to be unnecessary. A case is presented for developing new forms of theory, based around generic “systems of interactors.” An overlapping, layered structure of macro- and microtheories could then serve an explanatory role, and could also bind together contributions from the different disciplines. Novel routes to formalizing and applying such theories provide a host of interesting and tractable problems for future basic research in HCI

Coherent Control for a Two-level System Coupled to Phonons

The interband polarizations induced by two phase-locked pulses in a semiconductor show strong interference effects depending on the time tau_1 separating the pulses. The four-wave mixing signal diffracted from a third pulse delayed by tau is coherently controlled by tuning tau_1. The four-wave mixing response is evaluated exactly for a two-level system coupled to a single LO phonon. In the weak coupling regime it shows oscillations with the phonon frequency which turn into sharp peaks at multiples of the phonon period for a larger coupling strength. Destructive interferences between the two phase-locked pulses produce a splitting of the phonon peaks into a doublet. For fixed tau but varying tau_1 the signal shows rapid oscillations at the interband-transition frequency, whose amplitude exhibits bursts at multiples of the phonon period.Comment: 4 pages, 4 figures, RevTex, content change