A possible explanation for the inconsistency between the Giotto grain mass distribution and ground-based observations

Giotto measured the in situ Halley dust grain mass distribution with 2 instruments, Particle Impact Analyzer and Dust Impact Detection System (DIDSY), as well as the total intercepted mass from the deceleration of the spacecraft (Giotto Radio-Science Experiment, GRE). Ground based observations made shortly before encounter have fluxes much higher than would be predicted from Giotto data. It is concluded that Giotto DIDSY and GRE data represent observations of dust originating from a narrow track along the nucleus. They are consistent with ground based data, if assumptions are made about the level of activity along this track. The actual size distribution that should be used for modeling of the whole coma should not include the large mass excess actually observed by Giotto. Extrapolation of the small grain data should be used, since for these grains the velocity dispersion is low and temporal changes at the nucleus would not affect the shape of the mass distribution

GEO debris and interplanetary dust: fluxes and charging behavior

In September 1996, a dust/debris detector: GORID was launched into the geostationary (GEO) region as a piggyback instrument on the Russian Express-2 telecommunications spacecraft. The instrument began its normal operation in April 1997 and ended its mission in July 2002. The goal of this work was to use GORID's particle data to identify and separate the space debris to interplanetary dust particles (IDPs) in GEO, to more finely determine the instrument's measurement characteristics and to derive impact fluxes. While the physical characteristics of the GORID impacts alone are insufficient for a reliable distinction between debris and interplanetary dust, the temporal behavior of the impacts are strong enough indicators to separate the populations based on clustering. Non-cluster events are predominantly interplanetary, while cluster events are debris. The GORID mean flux distributions (at mass thresholds which are impact speed dependent) for IDPs, corrected for dead time, are 1.35x10^{-4} m^{-2} s^{-1} using a mean detection rate: 0.54 d^{-1}, and for space debris are 6.1x10^{-4} m^{-2} s^{-1} using a mean detection rate: 2.5 d^{-1}. Beta-meteoroids were not detected. Clusters could be a closely-packed debris cloud or a particle breaking up due to electrostatic fragmentation after high charging.Comment: * Comments: 6 pages, 4 postscript figures, in Dust in Planetary Systems 2005, Krueger, H. and Graps, A. eds., ESA Publications, SP in press (2006). For high resolution version, see: http://www.mpi-hd.mpg.de/dustgroup/~graps/dips2005/GrapsetalDIPS2005.pd

Electromagnetic interferences from plasmas generated in meteoroids impacts

It is shown that the plasma, generated during an impact of a meteoroid with an artificial satellite, can produce electromagnetic radiation below the microwave frequency range. This interference is shown to exceed local noise sources and might disturb regular satellite operations.Comment: 6 pages, no figures. This version macthes the published versio

Energy Re-Investment

Despite worsening climate change threats, investment in energy—in the United States and globally—is dominated by fossil fuels. This Article provides a novel analysis of two pathways in corporate and securities law that together have the potential to shift patterns of energy investment. The first pathway targets current investments and corporate decision-making. It includes efforts to influence investors to divest from owning shares in fossil fuel companies and to influence companies to address climate change risks in their internal decision-making processes. This pathway has received increasing attention, especially in light of the Paris Agreement and the Trump Administration’s decision to withdraw from it. But, alone, it will not be enough to foster transition to a cleaner mix of energy sources. Key to achieving this goal of energy reinvestment is a second pathway focused on fostering investments in new companies innovating in clean energy. This pathway —which has received far less attention—uses emerging legal mechanisms to support greater investment in entrepreneurial clean energy ventures. The Article’s analysis of this pathway looks beyond the well-established ways in which subsidies support fossil fuels and renewable energy. It instead examines the significance for energy reinvestment of changes in U.S. securities regulation permitting greater crowdsourcing of investment and in state laws allowing for new types of corporations. This Article is the first to examine how these two pathways can synergistically promote energy reinvestment. The first pathway moves money away from fossil fuels, while the second helps to spur needed reinvestment. The Article proposes strategies for deploying the tools in the two pathways together, taking into account the motivations and constraints of diverse investors and corporations

Energy Re-Investment

Despite worsening climate change threats, investment in energy — in the United States and globally — is dominated by fossil fuels. This Article provides a novel analysis of two pathways in corporate and securities law that together have the potential to shift patterns of energy investment.The first pathway targets current investments and corporate decision-making. It includes efforts to influence investors to divest from owning shares in fossil fuel companies and to influence companies to address climate change risks in their internal decision-making processes. This pathway has received increasing attention, especially in light of the Paris Agreement and the Trump Administration’s decision to withdraw from it. But, alone, it will not be enough to foster transition to a cleaner mix of energy sources.Key to achieving this goal of energy reinvestment is a second pathway focused on fostering investments in new companies innovating in clean energy. This pathway — which has received far less attention — uses emerging legal mechanisms to support greater investment in entrepreneurial clean energy ventures. The Article’s analysis of this pathway looks beyond the well-established ways in which subsidies support fossil fuels and renewable energy. It instead examines the significance for energy reinvestment of changes in U.S. securities regulation permitting greater crowdsourcing of investment and in state laws allowing for new types of corporations.This Article is the first to examine how these two pathways can synergistically promote energy reinvestment. The first pathway moves money away from fossil fuels, while the second helps to spur needed reinvestment. The Article proposes strategies for deploying the tools in the two pathways together, taking into account the motivations and constraints of diverse investors and corporations

Frequency dispersion reduction and bond conversion on n-type GaAs by in situ surface oxide removal and passivation

The method of surface preparation on n-type GaAs, even with the presence of an amorphous-Si interfacial passivation layer, is shown to be a critical step in the removal of accumulation capacitance frequency dispersion. In situ deposition and analysis techniques were used to study different surface preparations, including NH4OH, Si-flux, and atomic hydrogen exposures, as well as Si passivation depositions prior to in situ atomic layer deposition of Al2O3. As–O bonding was removed and a bond conversion process with Si deposition is observed. The accumulation capacitance frequency dispersion was removed only when a Si interlayer and a specific surface clean were combined

GaAs interfacial self-cleaning by atomic layer deposition

The reduction and removal of surface oxides from GaAs substrates by atomic layer deposition (ALD) of Al2O3 and HfO2 are studied using in situ monochromatic x-ray photoelectron spectroscopy. Using the combination of in situ deposition and analysis techniques, the interfacial "self-cleaning" is shown to be oxidation state dependent as well as metal organic precursor dependent. Thermodynamics, charge balance, and oxygen coordination drive the removal of certain species of surface oxides while allowing others to remain. These factors suggest proper selection of surface treatments and ALD precursors can result in selective interfacial bonding arrangements