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While shell growth engineering to the atomic scale is important for tailoring semiconductor nanowires with superior properties, a precise knowledge of the surface structure and morphology at different stages of this type of overgrowth has been lacking. We present a systematic scanning tunneling microscopy (STM) study of homoepitaxial shell growth of twinned superlattices in zinc blende InAs nanowires that transforms {111}A/B-type facets to the nonpolar {110}-type. STM imaging along the nanowires provides information on different stages of the shell growth revealing distinct differences in growth dynamics of the crystal facets and surface structures not found in the bulk. While growth of a new surface layer is initiated simultaneously (at the twin plane interface) on the {111}A and {111}B nanofacets, the step flow growth proceeds much faster on {111}A compared to {111}B leading to significant differences in roughness. Further, we observe that the atomic scale structures on the {111}B facet is different from its bulk counterpart and that shell growth on this facet occurs via steps perpendicular to the ⟨112⟩B-type directions.

The nucleotide sequences at the 5' end of one actin cDNA and six actin genomic clones from Dictyostelium have been determined. The amino acid sequences derived from the nucleotide sequences show strong conservation for six of the seven genes relative to the NH2-terminal region of Physarum actin. The region 5' to the AUG initiating codon is greater than 90% A+T residues in all of the genes.

Two studies for proving the feasibility of AI-applications for space are presented. AI-systems that provide support in the areas of diagnosis and scheduling are deployed in operation centers and integrated with the operational environment

1. The juvenile phase of the nematode Echinocephalus pseudouncinatusoccurs commonly in the gonads of the sea urchin Centrostephanus coronatusoff Southern California. The gonads of about 78% of the urchins in Big Fisherman's Cove, Santa Catalina Island, were heavily infected with the juveniles. About 40% of the urchins at Pin Rock in Catalina Harbor, Santa Catalina Island, and at Whistler's Reef off Corona del Mar on the mainland coast of California were infected, although the infection was usually not as severe as in Big Fisherman's Cove. A juvenile, probably of E. psuedouncinatus,also was found in gonads of C. coronatuscollected from Bahia Tortola off west-central Baja California. Although juveniles of E. pseudouncinatusalso occur commonly in the foot of pink abalones, they only rarely infect other species of sea urchins in Southern California.2. The California horned shark Heterodontus francisciseems a likely host of the adult phase of E. pseudouncinatus. However, when specimens of the horned shark were examined, adult specimens of Echinocephaluswere found which do not seem to be the same species as our juvenile specimens.3. The juvenile nematodes were encysted mainly in the spaces (perihemal or hemal) between the perivisceral coelomic epithelium and the germinal epithelium of the Centrostephanusgonad. Large juveniles filled the host gonadal tubule and bulged into the perivisceral coelom. Host gametogenesis was suppressed in the infected gonadal tubule, especially in the oral parts of such tubules. Gametogenesis in adjacent tubules did not seem affected. When the juveniles were in major tubules of the host gonad, severe suppression of host gametogenesis occurred in the oral parts of the gonad. It is suggested that encysted juveniles block the passage through the gonadal tubules of some hormonal substance that regulates urchin gametogenesis.

This paper describes a procedure for simulating rigid link mechanisms on an analog computer. The computer circuit enables one to record all kinematic variables, i.e., displacements, velocities, and accelerations, for any point on the mechanism using conventional, commercially available computing elements. Also included in the paper is a scaled analog circuit for simulating velocities and displacements for the four-bar linkage, along with records of these parameters from the author’s simulation.

Presents letters to the editor referencing articles and topics discussed in previous issues. "The Institution That Saw No Evil," which criticized the role of the United Nations in the Bosnian war; "The Griz," which examined the campaign of U.S. political leader Morry Taylor in Iowa; "Jordan's Rules," which pays tribute to Barbara Jordan.

Due to its ability to absorb water molecules, graphene oxide (GO) is considered a promising material for sensitive coatings in fast surface acoustic wave (SAW) humidity sensors. In this work, we characterize GO films obtained by the SAW atomization technique. It is shown that the atomized submicroliter droplets of aqueous suspension of GO can be deposited onto the surface of Si, LiNbO3 or quartz substrates forming discrete or continuous films of nanometer thickness. The deposited films were examined using AFM and electron microscopy. We discuss the dependence of thickness and structure of the obtained GO films on the parameters of deposition: the number of atomized droplets, a volume of the initial droplet, a distance between the atomizer and the sample, etc. To evaluate the adsorption characteristics of the obtained GO films, we used them as sensitive coatings of the SAW humidity sensors. We found that the adsorption characteristics of the GO films are determined by fast adsorption on the surface of GO sheets and slow adsorption, attributed to limited penetration of water molecules between the sheets, and depend on the number of deposited layers.

The investigator using analog or hybrid computers in mechanism study encounters great complexity and a requirement for considerable equipment when a simulation is extended to accelerations and dynamics. This paper describes a resolver circuit which is a link analogy giving position, velocity, and acceleration terms in rectangular coordinates when driven with a voltage representing the angular acceleration of the link. It is an elaboration of former resolution methods dealing only with either position or velocity. Its utility involves a savings of computing components and it constitutes a fundamental building block when used in mechanism simulation.