Transients in the formation of nanowire heterostructures

We present results on the effect of seed particle reconfiguration on the growth of short InAs and InP nanowire segments. The reconfiguration originates in two different steady state alloy compositions of the Au/In seed particle during growth of InAs and InP. From compositional analysis of the seed particle, the In content in the seed particle is determined to be 34 and 44% during InAs and InP growth, respectively. When switching between growing InAs and InP, transient effects dominate during the time period of seed particle reconfiguration. We developed a model that quantitatively explains the effect and with the added understanding we are now able to grow short period (<10 nm) nanowire superlattices.     

<Emphasis Type="Italic">In situ</Emphasis> etching for total control over axial and radial nanowire growth

We report a method using in situ etching to decouple the axial from the radial nanowire growth pathway, independent of other growth parameters. Thereby a wide range of growth parameters can be explored to improve the nanowire properties without concern of tapering or excess structural defects formed during radial growth. We demonstrate the method using etching by HCl during InP nanowire growth. The improved crystal quality of etched nanowires is indicated by strongly enhanced photoluminescence as compared to reference nanowires obtained without etching.      

Decision making in the rat: Response-choice and response-time measures of discrimination reversal learning.

Tested 6 water-deprived male albino rats in 6 consecutive light-dark simultaneous discrimination reversals in a T maze. Measurements were obtained of (a) the animal's choices, (b) the time from the start box to the choice point, (c) the time in the choice point, and (d) the time from the choice point to the water spout at the end of the arm. Results indicate that response times were a reliable indicator of discrimination reversal learning and that the discrimination process was composed of separate prechoice, choice, and postchoice components. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Utopia or myopia? A reply to Fox.

Comments on the contribution of D. R. Fox (see record 1985-30567-001) whose central thesis was that psychological researchers have ignored radical decentralization as a possible solution to the global commons problem confronting society today. It is suggested that Fox's argument is weakened by inaccurate statements and logical flaws. In addition, it is asserted that Fox interpreted a single experiment without reference to the overall research program and assumed that most people would prefer to live in small autonomous communities. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Level crossing of nanometer sized InAs islands in GaAs

We used polarization spectroscopy to detect level crossings in the fine structure of excitons in strained InAs islands grown on [001] GaAs. The crossings gave rise to quasi-resonant peaks, when monitoring the circularly polarized photoluminescence (PL) as a function of magnetic field. The peaks could also be detected as increases of the PL intensity. The resonant magnetic field was strongly dependent on detection energy within the PL emission peak. This energy selection is equivalent to monitoring a specific size or small interval within the broader size and shape distribution inherent to the growth process. The resonance was observed to shift to a higher magnetic field, when increasing the angle between field and sample growth direction. Basic arguments based on quantum confinement and the exciton fine structure can qualitatively account for the observations. Together with hole effective g-values the level crossing fields can be used to calculate the zero magnetic field splitting of the exciton fine structure.     

Some issues in life assessment of longitudinal seam welds based on creep tests with cross-weld specimens

In order to reduce production costs, it is of great interest to use longitudinal seam welds when manufacturing large diameter pipes. The cost reduction can be as high as 30%. However, severe inservice accidents for this type of pipes working in the creep regime have occurred mainly due to mismatch in weldment creep properties.

In many cases, creep tests of cross-weld specimens, taken from the seam weld, are used to predict the behaviour of the seam weld, assuming that the creep behaviour of specimen and weldment is equivalent. Experiences of this procedure indicate that further knowledge is required before translation between specimen and component can be made.

In the present paper, both full scale seam welded pipes and cross-weld specimens are studied with the damage mechanics concept using finite element, FE, technique. The same mechanical model of multiple material zones is used for the two components. Both the influence of differences in creep properties between the weldment constituents and the size effect of the cross-weld specimen, are studied.

It is found that the cross-weld test results can not directly be translated to the full scale component. Factors such as the creep properties and the relative geometry of the weldment constituents and the size of the cross-weld specimen have to be considered when performing creep life assessment.     

High pressure and low temperature conducting properties of organic semiconducting metal-anthraquinones

High pressure and low temperature conducting properties of 1,4-diamino anthraquinone, with metals such as cobalt, nickel, copper, and silver, and reported. The complexes formed are oxidatively and thermally stable and are insoluble in common organic solvents. They possess interesting conducting properties. All are semiconductors, showing conductivity in the range 1.98 × 10^?1 to 1.36 × 10^?6 S/cm, depending upon the metal atom present in the complex. Low temperature (300 K to 30 K) and high pressure (up to 6 GPa) conductivity properties of these materials are reported. Copper complexes have been studied in detail, as they show interesting conducting properties. © 1993 John Wiley & Sons, Inc.