Integrability and exact solution for coupled BCS systems associated with the su(4) Lie algebra

We introduce an integrable model for two coupled BCS systems through a solution of the Yang-Baxter equation associated with the Lie algebra su(4). By employing the algebraic Bethe ansatz, we determine the exact solution for the energy spectrum. An asymptotic analysis is conducted to determine the leading terms in the ground state energy, the gap and some one point correlation functions at zero temperature. (C) 2002 Published by Elsevier Science B.V.

Influence of wall stress and left ventricular geometry on the accuracy of Dobutamine stress Echocardiography

OBJECTIVES The goal of this study was to determine whether wall stress at rest and during stress could explain the influence of left ventricular (LV) morphology on the accuracy of dobutamine stress echocardiography (DSE). BACKGROUND The sensitivity of DSE appears to be reduced in patients with concentric remodeling, but the cause of this finding is unclear. METHODS We studied 161 patients without resting wall motion abnormalities who underwent DSE and coronary angiography. Patients were classified into four groups according to relative wan thickness (normal

Dry matter production and boron concentrations of vegetative and reproductive tissues of canola and sunflower plants grown in nutrient solution

Canola (Brassica napus L.) and sunflower (Helianthus annuus L.), two important oilseed crops, are sensitive to low boron (B) supply. Symptoms of B deficiency are often more severe during the reproductive stage, but it is not known if this is due to a decreased external B supply with time or an increased sensitivity to low B during this stage. Canola and sunflower were grown for 75 days after transplanting (DAT) in two solution culture experiments using Amberlite (IRA-743) B-specific resin to maintain constant B concentration in solution over the range 0.6 - 53 muM. Initially, the vegetative growth of both crops was good in all treatments. With the onset of the reproductive stage, however, severe B deficiency symptoms developed and growth of canola and sunflower was reduced with less than or equal to 0.9 and less than or equal to 0.7 muM B, respectively. At these concentrations, reproductive parts failed to develop. The critical B concentration (i.e. 90% of maximum shoot dry matter yield) in the youngest opened leaf was 18 mg kg(-1) in canola and 25 mg kg(-1) in sunflower at 75 DAT. The results of this study indicate that the reproductive stage of these two oilseed crops is more sensitive than the vegetative stage to low B supply.

Oral administration of a 12% sucrose solution did not decrease behavioural indicators of distress in piglets undergoing tail docking, teeth clipping and ear notching

Sucrose has been shown to attenuate the behavioural response to painful procedures in human infants undergoing circumcision or blood collection via heelstick. Sucrose has also been found to have a behaviour-modifying effect in neonatal rats exposed to a hot plate. The effect was abolished in neonatal rats by injection of the opioid antagonist naltrexone, suggesting that it was mediated by endogenous opioids. In this experiment, the behaviour of 571 newborn Large White x Landrace hybrid piglets in a specific-pathogen-free piggery of the University of Queensland was recorded during and after the routine management practices of tail docking, ear notching and teeth clipping. Piglets were randomly assigned to receive 1.0 ml of a 12% sucrose solution (treatment group) or a placebo (1.0 ml of air) administered via syringe in the mouth, 60 s before commencement of one of the management procedures. Behaviours were recorded at the time of the procedure, and then 2 min after completion of the procedure. Piglets that received the sucrose solution did not behave significantly differently from piglets receiving the placebo. Regardless of whether sucrose or placebo was administered, piglets undergoing the routine management procedures showed significantly greater behavioural responses than piglets undergoing no procedure. It was concluded that under commercial conditions, a 12% sucrose solution administered I min prior to surgery was not effective in decreasing the behavioural indicators of distress in piglets undergoing routine management procedures, Further research into methods of minimising distress caused to piglets by these procedures is recommended.

Applications of accurate, high-precision Pb isotope ratio measurement by multi-collector ICP-MS

The isotope composition of Ph is difficult to determine accurately due to the lack of a stable normalisation ratio. Double and triple-spike addition techniques provide one solution and presently yield the most accurate measurements. A number of recent studies have claimed that improved accuracy and precision could also be achieved by multi-collector ICP-MS (MC-ICP-MS) Pb-isotope analysis using the addition of Tl of known isotope composition to Pb samples. In this paper, we verify whether the known isotope composition of Tl can be used for correction of mass discrimination of Pb with an extensive dataset for the NIST standard SRM 981, comparison of MC-ICP-MS with TIMS data, and comparison with three isochrons from different geological environments. When all our NIST SRM 981 data are normalised with one constant Tl-205/Tl-203 of 2.38869, the following averages and reproducibilities were obtained: Pb-207/Pb-206=0.91461+/-18; Pb-208/Ph-206 = 2.1674+/-7; and (PbPh)-Pb-206-Ph-204 = 16.941+/-6. These two sigma standard deviations of the mean correspond to 149, 330, and 374 ppm, respectively. Accuracies relative to triple-spike values are 149, 157, and 52 ppm, respectively, and thus well within uncertainties. The largest component of the uncertainties stems from the Ph data alone and is not caused by differential mass discrimination behaviour of Ph and Tl. In routine operation, variation of sample introduction memory and production of isobaric molecular interferences in the spectrometer's collision cell currently appear to be the ultimate limitation to better reproducibility. Comparative study of five different datasets from actual samples (bullets, international rock standards, carbonates, metamorphic minerals, and sulphide minerals) demonstrates that in most cases geological scatter of the sample exceeds the achieved analytical reproducibility. We observe good agreement between TIMS and MC-ICP-MS data for international rock standards but find that such comparison does not constitute the ultimate. test for the validity of the MC-ICP-MS technique. Two attempted isochrons resulted in geological scatter (in one case small) in excess of analytical reproducibility. However, in one case (leached Great Dyke sulphides) we obtained a true isochron (MSWD = 0.63) age of 2578.3 +/- 0.9 Ma, which is identical to and more precise than a recently published U-Pb zircon age (2579 3 Ma) for a Great Dyke websterite [Earth Planet. Sci. Lett. 180 (2000) 1-12]. Reproducibility of this age by means of an isochron we regard as a robust test of accuracy over a wide dynamic range. We show that reliable and accurate Pb-isotope data can be obtained by careful operation of second-generation MC-ICP magnetic sector mass spectrometers. (C) 2002 Elsevier Science B.V. All rights reserved.

Corporate rumor activity, belief and accuracy

An integrated model relating workplace rumor activity, belief, and accuracy is proposed and tested. Senior VPs of Communications from a sample of Fortune-500 corporations and CEOs of established public relations firms were surveyed regarding rumor episodes that they had experienced. Results confirmed previous research on the role of uncertainty, anxiety, and belief in rumor activity. In addition, a reduced sense of control mediated the effects of uncertainty on anxiety, and anxiety mediated the effects of importance on rumor activity. Evidence was found for the roles of group bias in how strongly a rumor is believed. Rumor activity was also implicated in the formation of more accurate rumors. The significance of these results for rumor theory and for Public Relations practitioners is presented. (C) 2002 Elsevier Science Inc. All rights reserved.

Kinetics of adsorption on activated carbon: application of heterogeneous vacancy solution theory

The kinetics of single component adsorption on activated carbon is investigated here using a heterogeneous vacancy solution theory (VST) of adsorption. The adsorption isotherm is developed to account for the adsorbate non-ideality due to the size difference between the adsorbate molecule and the vacant site, while incorporating adsorbent heterogeneity through a pore-width-related potential energy. The transport process in the bidisperse carbon considers coupled mass transfer in both macropore and micropore phases simultaneously. Adsorbate diffusion in the micropore network is modeled through effective medium theory, thus considering pore network connectivity in the adsorbent, with the activation energy for adsorbate diffusion related to the adsorption energy, represented by the Steele 10-4-3 potential for carbons. Experimental data of five hydrocarbons, CO2 and SO2 on Ajax carbon at multiple temperatures, as well as three hydrocarbons on Norit carbon at three temperatures are first fitted by the heterogeneous VST model to obtain the isotherm parameters, followed by application of the kinetic model to uptake data on carbon particles of different sizes and geometry at various temperatures. For the hydrocarbons studied, the model can successfully correlate the experimental data for both adsorption equilibrium and kinetics. However, there is some deviation in the fit of the desorption kinetics for polar compounds such as CO2 and SO2, due to the inadequacy of the L-J potential model in this case. The significance of viscous transport in the micropores is also considered here and found to be negligible, consistent with recent molecular simulation studies. (C) 2002 Elsevier Science Ltd. All rights reserved.

Vacancy solution theory for binary adsorption equilibria in heterogeneous carbon

A heterogeneous modified vacancy solution model of adsorption developed is evaluated. The new model considers the adsorption process through a mass-action law and is thermodynamically consistent, while maintaining the simplicity in calculation of multicomponent adsorption equilibria, as in the original vacancy solution theory. It incorporates the adsorbent heterogeneity through a pore-width-related potential energy, represented by Steele's 10-4-3 potential expression. The experimental data of various hydrocarbons, CO2 and SO2 on four different activated carbons - Ajax, Norit, Nuxit, and BPL - at multiple temperatures over a wide range of pressures were studied by the heterogeneous modified VST model to obtain the isotherm parameters and micropore-size distribution of carbons. The model successfully correlates the single-component adsorption equilibrium data for all compounds studied on various carbons. The fitting results for the vacancy occupancy parameter are consistent with the pressure change on different carbons, and the effect of pore heterogeneity is important in adsorption at elevated pressure. It predicts binary adsorption equilibria better than the IAST scheme, reflecting the significance of molecular size nonideality.

Solution Structures of the cis- and trans-Pro30 Isomers of a Novel 38-Residue Toxin from the Venom of Hadronyche Infensa sp. that Contains a Cystine-Knot Motif within Its Four Disulfide Bonds

The primary sequence and three-dimensional structure of a novel peptide toxin isolated from the Australian funnel-web spider Hadronyche infensa sp. is reported. ACTX-HI:OB4219 contains 38 amino acids, including eight-cysteine residues that form four disulfide bonds. The connectivities of these disulfide bonds were previously unknown but have been unambiguously determined in this study. Three of these disulfide bonds are arranged in an inhibitor cystine-knot (ICK) motif, which is observed in a range of other disulfide-rich peptide toxins. The motif incorporates an embedded ring in the structure formed by two of the disulfides and their connecting backbone segments penetrated by a third disulfide bond. Using NMR spectroscopy, we determined that despite the isolation of a single native homologous product by RP-HPLC, ACTX-HI:OB4219 possesses two equally populated conformers in solution. These two conformers were determined to arise from cis/trans isomerization of the bond preceding Pro30. Full assignment of the NMR spectra for both conformers allowed for the calculation of their structures, revealing, the presence of a triple-stranded antiparallel sheet consistent with the inhibitor cystine-knot (ICK) motif.

The Three-dimensional Solution Structure of NaD1, a New Floral Defensin from Nicotiana alata and its Application to a Homology Model of the Crop Defense Protein alfAFP

NMR spectroscopy and simulated annealing calculations have been used to determine the three-dimensional structure of NaD1, a novel antifungal and insecticidal protein isolated from the flowers of Nicotiana alata. NaD1 is a basic, cysteine-rich protein of 47 residues and is the first example of a plant defensin from flowers to be characterized structurally. Its three-dimensional structure consists of an a-helix and a triple-stranded anti-parallel beta-sheet that are stabilized by four intramolecular disulfide bonds. NaD1 features all the characteristics of the cysteine-stabilized up motif that has been described for a variety of proteins of differing functions ranging from antibacterial insect defensins and ion channel-perturbing scorpion toxins to an elicitor of the sweet taste response. The protein is biologically active against insect pests, which makes it a potential candidate for use in crop protection. NaD1 shares 31% sequence identity with alfAFP, an antifungal protein from alfalfa that confers resistance to a fungal pathogen in transgenic potatoes. The structure of NaD1 was used to obtain a homology model of alfAFP, since NaD1 has the highest level of sequence identity with alfAFP of any structurally characterized antifungal defensin. The structures of NaD1 and alfAFP were used in conjunction with structure - activity data for the radish defensin Rs-AFP2 to provide an insight into structure-function relationships. In particular, a putative effector site was identified in the structure of NaD1 and in the corresponding homology model of alfAFP. (C) 2002 Elsevier Science Ltd. All rights reserved.

Accuracy of Mothers' Retrospective Reports of Smoking During Pregnancy: Comparison with Twin Sister Informant Ratings

Retrospective assessment of maternal smoking or substance use during pregnancy is sometimes unavoidable. The unusually close relationship of twin sister pairs permits comparison of self-report data versus co-twin informant data on substance use during pregnancy. Information about smoking during pregnancy has been gathered from a series of mothers from an Australian volunteer twin panel (576 women reporting on 995 pregnancies), supplemented in many cases by independent ratings of their smoking by twin sister informants (821 pregnancies). Estimates of the proportion of women who had never smoked regularly (56-58%), who had smoked but did not smoke during a particular pregnancy (16-21%), or who smoked throughout the pregnancy (16-18%), were in good agreement whether based on self-report or twin sister informant data. However, informants underreported cases who smoked during the first trimester but then quit (1-3% versus 7-9% by self-report). Women who smoked throughout pregnancy (by informant report) rarely denied a history of regular smoking (