Hysteresis and first-order phase transition in the two-dimensional electron gas

We report experimental evidence of the first-order phase transitions in the two-dimensional electron gas formed in a gated wide GaAs/AlGaAs quantum well at even-integer quantum-Hall states. At the filling factor values of ν=2,4 and low temperatures, crossing of Landau levels through the application of the gate bias yields a suppression of the quantum-Hall-state excitation gap and hysteretical behaviour of the diagonal resistivity in up and down sweeps of the magnetic field. Detailed many-body calculations indicate the occurrence of a first-order phase transition and allow the determination of the exact properties of the electron ground states involved in the transition.     

Counting and the Base‐Ten Concept

Herein is presented an approach to the teaching of the rudiments of counting and the base‐ten concept to primary school children and remedial classes.     

Determination of number of dedicated OR's and supporting pricing mechanisms for emergent surgeries

Inefficient management of emergent surgeries in hospitals can, in part, be attributed to a lack of rigorous analysis appropriate to capturing the underlying uncertainties inherent to this process and a pricing mechanism to ensure its financial viability. We develop a non-preemptive multi-priority queueing model that optimally manages emergent surgeries and supports the resource allocation decision-making process. Specifically, we utilize queueing and discrete event simulation to develop empirical models for determining the required number of emergent operating rooms for a hospital surgical department. We also present algorithms that estimate the appropriate pricing for patient surgeries differentiated by priority level given the patient demand and the resources reserved to meet this demand.     

Discovery of bioactive small-molecule inhibitor of poly adp-ribose polymerase: implications for energy-deficient cells

Poly (ADP-ribose) polymerase (PARP1) is a nuclear protein that, when overactivated by oxidative stress-induced DNA damage, ADP ribosylates target proteins leading to dramatic cellular ATP depletion. We have discovered a biologically active small-molecule inhibitor of PARP1. The discovered compound inhibited PARP1 enzymatic activity in vitro and prevented ATP loss and cell death in a surrogate model of oxidative stress in vivo. We also investigated a new use for PARP1 inhibitors in energy-deficient cells by using Huntington's disease as a model. Our results showed that insult with the oxidant hydrogen peroxide depleted cellular ATP in mutant cells below the threshold of viability. The protective role of PARP1 inhibitors against oxidative stress has been shown in this model system.     

Fiber-optic scanning two-photon fluorescence endoscope

We report on the development of a miniature, flexible, fiber-optic scanning endoscope for two-photon fluorescence imaging. The endoscope uses a tubular piezoelectric actuator for achieving two-dimensional beam scanning and a double-clad fiber for delivery of the excitation light and collection of two-photon fluorescence. Real-time imaging of fluorescent beads and cancer cells has been performed.     

Problem-structuring methods and project management: an example of stakeholder involvement using Hierarchical Process Modelling methodology

Project Management has gained in importance over the last few decades and it isincreasingly common in many types of organisations. Today there is a concernover the relevance of the more conventional project management approaches toproblems that are increasingly complex and constrained and involve large numbersof interested parties or stakeholders. This paper examines the relevance ofproblem-structuring methods to project management, focusing on the front-end ofmanaging complex projects and discusses stakeholder involvement usingHierarchical Process Modelling methodology.     

The orbital splitting patterns for the first and second-row elements

OPHF calculations for first and second-row elements have been performed and the results compared with the corresponding HF values. Systematic trends in the splitting of s and p-orbitals within, and between, rows are observed; in addition the splitting ratios decrease by at least an order of magnitude as one proceeds from a given shell to the next innermost shell.     

Mechanism of lactide polymerization in the presence of stannous octoate: The effect of hydroxy and carboxylic acid substances

The effect of hydroxy and carboxylic acid substances on lactide polymerization in the presence of stannous octoate was investigated. A polymerization mechanism was postulated to attempt to explain the controversies existing in the literature and also to explain our experimental observations. Stannous alkoxide, a reaction product between stannous octoate and alcohol, is proposed as the substance initiating the polymerization through coordinative insertion of lactide. Alcohol can affect the polymerization through the reactions of initiator formation, chain transfer, and transesterfication. Carboxylic acid affects the polymerization through a deactivation reaction. Experiments showed that alcohol increased PLLA production rate while carboxylic acid decreased it. Both alcohol and carboxylic acid reduced PLLA final molecular weight. The higher the alcohol concentration, the lower the polymer molecular weight. However, the final molecular weight of PLLA was not sensitive to the carboxylic acid concentration. A polymerization induction period was observed at high carboxylic acid concentration, due to the deactivation reaction caused by carboxylic acid. © 1994 John Wiley & Sons, Inc.     

Mono- and bivalent ligands bearing mannose 6-phosphate (M6P) surrogates: targeting the M6P/insulin-like growth factor II receptor

[reaction: see text] Mannose 6-phosphate mimics locked into the alpha-configuration and bearing hydrolase-resistant phosphate surrogates were synthesized and evaluated for binding affinity to the mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGF2R). Affinity increases as the phosphate surrogate is varied in the order malonyl ether < malonate < phosphonate. An alkene cross-metathesis approach to sought-after bivalent M6P-bearing ligands is also described. These compounds were designed to map onto biantennary sectors of high-mannose-type oligosaccharides carried by glycoprotein M6P/IGF2R ligands.