One-pot synthesis and third-order nonlinear optical properties of AgInS2 nanocrystals

Good quality colloidal nanocrystals of metastable orthorhombic phase of AgInS2 obtained by decomposing the single-precursor [(Ph3P)2AgIn(SCOPh)4] in a mixture of dodecanethiol and oleic acid at 125-200 degrees C, exhibit significant third order non-linear optical properties.     

Re-evaluation of the mechanical loss factor of hydroxide-catalysis bonds and its significance for the next generation of gravitational wave detectors

New measurements of the mechanical loss factors of hydroxide-catalysis bonds have been made and these have been found to be significantly lower than previously reported. We provide the first estimate for the resulting thermal noise limitation for a practical test mass geometry for next generation gravitational wave detectors.     

Mechanisms of heterogeneous crystal growth in atomic systems: insights from computer simulations

In this paper we analyze the atomic-level structure of solid/liquid interfaces of Lennard-Jones fcc systems. The 001, 011, and 111 faces are examined during steady-state growth and melting of these crystals. The mechanisms of crystallization and melting are explored using averaged configurations generated during these steady-state runs, where subsequent tagging and labeling of particles at the interface provide many insights into the detailed atomic behavior at the freezing and melting interfaces. The interfaces are generally found to be rough and we observe the structure of freezing and melting interfaces to be very similar. Large structural fluctuations with solidlike and liquidlike characteristics are apparent in both the freezing and melting interfaces. The behavior at the interface observed under either growth or melting conditions reflects a competition between ordering and disordering processes. In addition, we observe atom hopping that imparts liquidlike characteristics to the solid side of the interfaces for all three crystal faces. Solid order is observed to extend as rough, three-dimensional protuberances through the interface, particularly for the 001 and 011 faces. We are also able to reconcile our different measures for the interfacial width and address the onset of asymmetry in the growth rates at high rates of crystal growth/melting.     

Cosmological experiments in liquid He: status and prospects

A recent experiment, in which a small volume of liquid ⁴He is expanded rapidly through the lambda transition to model the mechanism of cosmic string creation in the early universe, is reviewed. New data are presented, suggesting that, although most of the quantized vortices generated in the expansion are created (like cosmic strings) by passage through the phase transition at a finite speed, a proportion of them are probably produced through more conventional processes. Possible ways of redesigning the experiment, so as to reduce the latter extraneous vortex creation processes, are discussed.     

Transport and geochemical controls on the distribution of solutes and stable isotopes in a thick clay-rich till aquitard, Canada

A comprehensive understanding of the transport and geochemical processes controlling solutes in clay-rich aquitard confining units is needed to accurately predict the long-term migration of contaminants into the subsurface. To this end, the geochemical and stable isotopic composition of porewaters in the upper 22 m of a thick, unoxidized and nonfractured clay-rich, till aquitard (Sutherland Group) was examined in detail. The aquitard is overlain by about 8 m of oxidized and fractured till (Floral Fm). Concentrations of TDS, SO4(2-), HCO3-, Cl-, Na+, Mg2+, Ca2+ and porewater deuterium were greater in the Floral Fm and decreased with depth through the aquitard. The elevated and seasonably variable solute concentrations in the oxidized Floral Fm were attributed to geochemical weathering and dynamic water movement through fractures. Good fits between measured delta2H, TDS, SO4(2-), Cl- and HCO3- profiles through the aquitard and simulated solute transport profiles were obtained by diffusion (without advection) with transport times of 4-6 ka. The deficiency of geochemical reactions affecting HCO3- and SO4(2-) in the aquitard was supported by delta13C(DIC) and delta34S(SO4) analyses. Geochemical and isotope mass balance modelling (NETPATH) indicated that diffusive mixing with minor calcite dissolution and ion exchange could account for the distribution of Na+, Ca2+ and Mg2+ in the aquitard. Results of this study further suggested that microbiological activity in the aquitard was limited. With minor exceptions, the solute and isotopic profiles, their transport and the controlling geochemical reactions in the Sutherland are similar to those determined at another clay-rich till aquitard, 160 km south of this site, suggesting that geochemical and biological processes in some clay-rich aquitards may have a minimal effect on the migration of dissolved constituents.     

On the hamiltonian path graph of a graph

The hamiltonian path graph H(F) of a graph F is that graph having the same vertex set as F and in which two vertices u and v are adjacent if and only if F contains a hamiltonian u ? v path. First, in response to a conjecture of Chartrand, Kapoor and Nordhaus, a characterization of nonhamiltonian graphs isomorphic to their hamiltonian path graphs is presented. Next, the maximum size of a hamiltonian graph F of given order such that K?_d ? H(F) is determined. Finally, it is shown that if the degree sum of the endvertices of a hamiltonian path in a graph F with at least five vertices is at least |V(F)| + t(t ? 0), then H(F) contains a complete subgraph of order t + 4.     

The two-body photodisintegration of the 3He nucleus

The two-body photodisintegration of ³He is calculated using ³He and proton-deuteron wave functions obtained by assuming a separable interaction for the two-nucleon t-matrix. We show that the isotropic component of the cross section is unlikely to yield useful information on the D-state probability densities of the deuteron and ³He. A detailed comparison is made with the data on the cross section at 90°. The separable approximation can account for some of the experimental results, but other experiments suggest that a more sophisticated treatment of the nuclear interactions and wave functions is necessary.     

A strengthening of Kikustapos;s theorem

We consider connected, locally connected graphs in which the maximum and minimum degrees differ by at most one and do not exceed five. It is shown that if C is a nonhamiltonian cycle in such a graph G, then there exists a cycle Capos; in G such that V(C) ? V(Capos;) and /V(Capos;) = /(C) + 1.     

Customer Enquiry Management: Part of a Hierarchical System to Control Lead Times in Make-to-Order Companies

The authors are currently developing a hierarchical production planning system specifically designed for the ‘make-to-order’ sector of industry. Its aim is to control the delivery and manufacturing lead times of all orders processed by a firm. Two major decision levels are identified - the customer enquiry stage and the order release stage. Input/output control is exercised at both stages. This paper is concerned with the control mechanisms used at the customer enquiry stage. Two important backlogs of work, along with their associated backlog lengths, are identified. The system aims to maintain these backlogs between predetermined minimum and maximum lengths in order to process all orders within an acceptable length of time. It is shown that the two backlogs are linked in a manner that enables them to be controlled simultaneously. Hence, a procedure for dealing with incoming customer orders is presented.