13,876 research outputs found

    Anatomy of a Governance Transformation: The Case of Daimler-Benz

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    Logue and Seward examine the evolutionary transformation in the corporate governance structure of Daimler-Benz AG, the largest German industrial company. Over the last several years, Daimler-Benz has taken numerous steps toward prioritizing shareholder value more intensely than ever before

    Construction and Software Design for a Microcomputer Controlled pH/Ion Titrator

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    The construction of an automated titration device is described. The major components include an Apple II+ Microcomputer and 8-bit parallel interface. Fisher Accumet, Model 520 Digital pH/lon Meter, Gilmont Micrometer Buret of 2.5 mL capacity, Sigma stepper motor, power supply and driver to operate the buret, and a constant temperature bath of ± 0.005 °C stability. The limitations of the system are 0.001 pH/0.1 mv for the pH/ion sensing system, and 0.125 μL per step for the buret. The system as described is designed to determine equilibrium constants for metal ion-amino acid complexes. By changing the software a variety of different pH and redox titration experiments may be performed. A computer program used to operate the stepper motor driven syringe buret and record the pH from a digital pH meter is described. The program uses both Apple BASIC and assembly language. This is a closed loop operation in which the data from the pH meter is used to control the amount of reagent delivered by the buret. The results are displayed graphically as the titration proceeds. The variance of the pH readings are calculated using an assembly language subroutine and the calculations are done with zero round-off error

    THE INVESTMENT POTENTIAL OF WARM-SEASON GRASSES FOR HILL-LAND BEEF PRODUCERS

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    The investment potential of warm-season grasses is compared with that of cool-season grasses, with special emphasis on hill-land beef production. In addition to evaluating relative costs and returns for various grazing systems, a sensitivity analysis is conducted. The results are then illustrated for a representative hill-land farm in West Virginia, and both an optimal and a set of quasi-optimal solutions are generated within the linear programming framework. In general, warm-season grasses are found to be a superior investment alternative for hill-land beef producers.Livestock Production/Industries,

    The hard X-ray burst spectrometer event listing 1980, 1981 and 1982

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    A comprehensive reference for the hard X-ray bursts detected with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission for the time of launch on February 14, 1980 to March 1983 is provided. Over 6300 X-ray events were detected in the energy range from 30 to approx 500 keV with the vast majority being solar flares. The listing includes the start time, peak time, duration and peak rate of each event

    Molecular Weight Dependence of Polymersome Membrane Elasticity and Stability

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    Vesicles prepared in water from a series of diblock copolymers and termed "polymersomes" are physically characterized. With increasing molecular weight Mˉn\bar{M}_n, the hydrophobic core thickness dd for the self-assembled bilayers of polyethyleneoxide - polybutadiene (PEO-PBD) increases up to 20 nmnm - considerably greater than any previously studied lipid system. The mechanical responses of these membranes, specifically, the area elastic modulus KaK_a and maximal areal strain αc\alpha_c are measured by micromanipulation. As expected for interface-dominated elasticity, KaK_a (\simeq 100 pN/nmpN/nm) is found to be independent of Mˉn\bar{M}_n. Related mean-field ideas also predict a limiting value for αc\alpha_c which is universal and about 10-fold above that typical of lipids. Experiments indeed show αc\alpha_c generally increases with Mˉn\bar{M}_n, coming close to the theoretical limit before stress relaxation is opposed by what might be chain entanglements at the highest Mˉn\bar{M}_n. The results highlight the interfacial limits of self-assemblies at the nano-scale.Comment: 16 pages, 5 figures, and 1 tabl

    Temporal and spectral characteristics of solar flare hard X-ray emission

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    Solar Maximum Mission observations of three flares that impose stringent constraints on physical models of the hard X-ray production during the impulsive phase are presented. Hard X-ray imaging observations of the flares on 1980 November 5 at 22:33 UT show two patches in the 16 to 30 keV images that are separated by 70,000 km and that brighten simultaneously to within 5 s. Observations to O V from one of the footprints show simultaneity of the brightening in this transition zone line and in the total hard X-ray flux to within a second or two. These results suggest but do not require the existence of electron beams in this flare. The rapid fluctuations of the hard X-ray flux within some flares on the time scales of 1 s also provide evidence for electron beams and limits on the time scale of the energy release mechanism. Observations of a flare on 1980 June 6 at 22:34 UT show variations in the 28 keV X-ray counting rate from one 20 ms interval to the next over a period of 10 s. The hard X-ray spectral variations measured with 128 ms time resolution for one 0.5 s spike during this flare are consistent with the predictions of thick-target non-thermal beam model

    RHESSI Observations of the Solar Flare Iron-line Feature at 6.7 keV

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    Analysis of RHESSI 3--10 keV spectra for 27 solar flares is reported. This energy range includes thermal free--free and free--bound continuum and two line features, at 6.7keV and 8keV, principally due to highly ionized iron (Fe). We used the continuum and the flux in the so-called Fe-line feature at 6.7keV to derive the electron temperature T_e, the emission measure, and the Fe-line equivalent width as functions of time in each flare. The Fe/H abundance ratio in each flare is derived from the Fe-line equivalent width as a function of T_e. To minimize instrumental problems with high count rates and effects associated with multi-temperature and nonthermal spectral components, spectra are presented mostly during the flare decay phase, when the emission measure and temperature were smoothly varying. We found flare Fe/H abundance ratios that are consistent with the coronal abundance of Fe (i.e. 4 times the photospheric abundance) to within 20% for at least 17 of the 27 flares; for 7 flares, the Fe/H abundance ratio is possibly higher by up to a factor of 2. We find evidence that the Fe XXV ion fractions are less than the theoretically predicted values by up to 60% at T_e=25 MK appear to be displaced from the most recent theoretical values by between 1 and 3 MK.Comment: To be published, Ap

    Inhibition of “self” engulfment through deactivation of myosin-II at the phagocytic synapse between human cells

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    Phagocytosis of foreign cells or particles by macrophages is a rapid process that is inefficient when faced with “self” cells that display CD47—although signaling mechanisms in self-recognition have remained largely unknown. With human macrophages, we show the phagocytic synapse at cell contacts involves a basal level of actin-driven phagocytosis that, in the absence of species-specific CD47 signaling, is made more efficient by phospho-activated myosin. We use “foreign” sheep red blood cells (RBCs) together with CD47-blocked, antibody-opsonized human RBCs in order to visualize synaptic accumulation of phosphotyrosine, paxillin, F-actin, and the major motor isoform, nonmuscle myosin-IIA. When CD47 is functional, the macrophage counter-receptor and phosphatase-activator SIRPα localizes to the synapse, suppressing accumulation of phosphotyrosine and myosin without affecting F-actin. On both RBCs and microbeads, human CD47 potently inhibits phagocytosis as does direct inhibition of myosin. CD47–SIRPα interaction initiates a dephosphorylation cascade directed in part at phosphotyrosine in myosin. A point mutation turns off this motor's contribution to phagocytosis, suggesting that self-recognition inhibits contractile engulfment
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