4,936 research outputs found

    Description of an experimental (hydrogen peroxide) rocket system and its use in measuring aileron and rudder effectiveness of a light airplane

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    A hydrogen peroxide fueled rocket system, which is to be used as a research tool in flight studies of stall and spin maneuvers, was installed on a light, four place general aviation airplane. The pilot controlled rocket system produces moments about either the roll or the yaw body axis to augment or oppose the aerodynamic forces and inertial moments acting on the airplane during various flight maneuvers, including the spin. These controlled moments of a known magnitude can be used in various ways to help analyze and interpret the importance of the various factors which influence airplane maneuvers. The rocket system and its installation in the airplane are described, and the results of flight rests used to measure rudder and aileron effectiveness at airspeeds above the stall are presented. These tests also serve to demonstrate the operational readiness of the rocket system for future research operations

    The tilting hygrometer: A new form of absorption hygrometer

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    Field theory of the inverse cascade in two-dimensional turbulence

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    A two-dimensional fluid, stirred at high wavenumbers and damped by both viscosity and linear friction, is modeled by a statistical field theory. The fluid's long-distance behavior is studied using renormalization-group (RG) methods, as begun by Forster, Nelson, and Stephen [Phys. Rev. A 16, 732 (1977)]. With friction, which dissipates energy at low wavenumbers, one expects a stationary inverse energy cascade for strong enough stirring. While such developed turbulence is beyond the quantitative reach of perturbation theory, a combination of exact and perturbative results suggests a coherent picture of the inverse cascade. The zero-friction fluctuation-dissipation theorem (FDT) is derived from a generalized time-reversal symmetry and implies zero anomalous dimension for the velocity even when friction is present. Thus the Kolmogorov scaling of the inverse cascade cannot be explained by any RG fixed point. The beta function for the dimensionless coupling ghat is computed through two loops; the ghat^3 term is positive, as already known, but the ghat^5 term is negative. An ideal cascade requires a linear beta function for large ghat, consistent with a Pad\'e approximant to the Borel transform. The conjecture that the Kolmogorov spectrum arises from an RG flow through large ghat is compatible with other results, but the accurate k^{-5/3} scaling is not explained and the Kolmogorov constant is not estimated. The lack of scale invariance should produce intermittency in high-order structure functions, as observed in some but not all numerical simulations of the inverse cascade. When analogous RG methods are applied to the one-dimensional Burgers equation using an FDT-preserving dimensional continuation, equipartition is obtained instead of a cascade--in agreement with simulations.Comment: 16 pages, 3 figures, REVTeX 4. Material added on energy flux, intermittency, and comparison with Burgers equatio

    Immunospecific Antibody Concentration in Egg Yolk of Chickens Orally Immunised with Varying Doses of Bovine Serum Albumin and the Mucosal Adjuvant, RhinoVax®, using Different Immunization Regimes

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    Antibody harvested from eggs of immunised chickens, IgY, has proven to be a non-invasive alternative to  antibodies purified from serum of mammals. Taking the non-invasive concept further, the development of  oral immunization techniques combined with IgY harvest from chicken eggs may subsequently eliminate  all regulated procedures from polyclonal antibody production. In the present study, we report the effects of  varying the temporal administration mode of the antigen (immunogen) comparing dosing on three consecutive  days with dosing on five consecutive days, and of incorporating a mucosal adjuvant. Two antigen  doses were compared: 30 mg bovine serum albumin (BSA) and 300 mg BSA, with and without the mucosal  adjuvant, RhinoVax®, administered to laying chickens. The egg yolk of chickens dosed with BSA in combination  with 20% RhinoVax®, contained significantly higher concentrations of immunospecific IgY than  did egg yolks of chickens fed with BSA without adjuvant. The most efficient dose in the RhinoVax®-treated  groups was 300 mg BSA regardless of whether the chickens were initially immunised daily for three or  five days. A 3-day dosing regime with BSA alone also induced immunospecific IgY production. This study  confirms that RhinoVax® is an efficient oral adjuvant. It also demonstrates the efficacy of daily immunizations  on three or five consecutive days on immunospecific IgY production. The chickens received oral  booster immunizations one and two months after the initial immunization. No real effect could be recorded  after the second and third immunization, although the study did provide some evidence of memory  based on an optimum IgY concentration recorded after the 2nd immunization.

    Across-wafer nonuniformity of long throw sputter deposition

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    A. A. Mayo et al., Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena 15, 1788 (1997) https://doi.org/10.1116/1.58952

    A structural study of Hypocrea jecorina Cel5A

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    Interest in generating lignocellulosic biofuels through enzymatic hydrolysis continues to rise as nonrenewable fossil fuels are depleted. The high cost of producing cellulases, hydrolytic enzymes that cleave cellulose into fermentable sugars, currently hinders economically viable biofuel production. Here, we report the crystal structure of a prevalent endoglucanase in the biofuels industry, Cel5A from the filamentous fungus Hypocrea jecorina. The structure reveals a general fold resembling that of the closest homolog with a high-resolution structure, Cel5A from Thermoascus aurantiacus. Consistent with previously described endoglucanase structures, the H. jecorina Cel5A active site contains a primarily hydrophobic substrate binding groove and a series of hydrogen bond networks surrounding two catalytic glutamates. The reported structure, however, demonstrates stark differences between side-chain identity, loop regions, and the number of disulfides. Such structural information may aid efforts to improve the stability of this protein for industrial use while maintaining enzymatic activity through revealing nonessential and immutable regions

    The Role of Ligand Steric Bulk in New Monovalent Aluminum Compounds

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    The article of record as published may be located at https://doi.org/10.1021/acs.jpca.7b02075The tetrameric Al(I) cyclopentadienyl compound Al4Cp*4 (Cp* = C5Me5) is a prototypical low-valence Al compound, with delocalized bonding between four Al(I) atoms and η5 ligands bound to the cluster exterior. The synthesis of new [AlR]4 (R = C5Me4Pr, C5Me4iPr) tetramers is presented. Though these systems failed to crystallize, comparison of variable-temperature 27Al NMR data with density functional theory (DFT) calculations indicate that these are Al4R4 tetramers analogous to Al4Cp*4 but with increased ligand steric bulk. NMR, DFT, and Atoms in Molecules analyses show that these clusters are enthalpically more stable as tetramers than the Cp* variant, due in part to noncovalent interactions across the bulkier ligand groups. Thermochemistry calculations for the low-valence metal interactions were found to be extremely sensitive to the DFT methodology used; the M06-2X functional with a cc-pVTZ basis set is shown to provide very accurate values for the enthalpy of tetramerization and 27Al NMR shifts. This computational method is then used to predict geometrical structures, noncovalent ligand interactions, and monomer/tetramer equilibrium in solution for a series of Al(I) cyclopentadienyl compounds of varying steric bulk

    Evolution Equation of Phenotype Distribution: General Formulation and Application to Error Catastrophe

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    An equation describing the evolution of phenotypic distribution is derived using methods developed in statistical physics. The equation is solved by using the singular perturbation method, and assuming that the number of bases in the genetic sequence is large. Applying the equation to the mutation-selection model by Eigen provides the critical mutation rate for the error catastrophe. Phenotypic fluctuation of clones (individuals sharing the same gene) is introduced into this evolution equation. With this formalism, it is found that the critical mutation rate is sometimes increased by the phenotypic fluctuations, i.e., noise can enhance robustness of a fitted state to mutation. Our formalism is systematic and general, while approximations to derive more tractable evolution equations are also discussed.Comment: 22 pages, 2 figure

    Organic amendment optimization for treatment of hydrocarbon contaminated soil using the chemicalbiological stabilization process

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    Sugar cane cachasse was tested as an organic soil amendment at 0, 2, 4 and 9% (dry weight), for the remediation of hydrocarbon contaminated soil (with an average initial concentration of 14,356 mg/Kg), which had been pre-treated by the incorporation of 4% (dry weight) calcium hydroxide according to the chemical-biological stabilization treatment method. Remediation efficiency was measured in terms of overall hydrocarbon reduction, hydrocarbon stabilization, soil leachates, microbial activity, acute toxicity and biomass production in a tropical forage grass (Brachiaria humidicola). Compared to the control, the over all half life for hydrocarbon degradation was optimal with 2 - 4% cachasse, reducing the half life from 301 days to about 195 days. The treatment with 9% cachasse presented reduced respiration rates, probably due to fermentation conditions, and a longer half life. Hydrocarbon availability (versus stabilization), and thus potential toxicity and leachability, was lowest in the treatments with 4 and 9% cachasse. In these treatments, there were no methanol extractable hydrocarbons after 19 months, although the TPH concentration was 1,000 - 1,500 mg/kg. In less than four months, toxicity, as  determined by the Microtox method, was reduced to regional background levels (Effective Concentration 50 > 100,000 mg/L), and soil leachates (TCLP) were reduced to < 1 mg/L in all treatments. Grass biomass production was related to the amendment concentration, being two to three times greater in the treatment with 9% cachasse during the major part of the treatment. According to these results, a 4% application rate is recommended to optimize the microbial response, with an additional 4% added after one year to further stimulate pasture growth.Key words: Soil remediation, petroleum, biodegradation, toxicity, biomass production, pasture
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