Basis set limit electronic excitation energies, ionization potentials, and electron affinities for the 3d transition metal atoms: Coupled cluster and multireference methods

Recently developed correlation consistent basis sets for the first row transition metal elements Sc-Zn have been utilized to determine complete basis set (CBS) scalar relativistic electron affinities, ionization potentials, and 4s(2)3d(n-2)-4s(1)d(n-1) electronic excitation energies with single reference coupled cluster methods [CCSD(T), CCSDT, and CCSDTQ] and multireference configuration interaction with three reference spaces: 3d4s, 3d4s4p, and 3d4s4p3d'. The theoretical values calculated with the highest order coupled cluster techniques at the CBS limit, including extrapolations to full configuration interaction, are well within 1 kcal/mol of the corresponding experimental data. For the early transition metal elements (Sc-Mn) the internally contracted multireference averaged coupled pair functional method yielded excellent agreement with experiment; however, the atomic properties for the late transition metals (Mn-Zn) proved to be much more difficult to describe with this level of theory, even with the largest reference function of the present work.     

Synthesis of loliolide, actinidiolide, dihydroactinidiolide, and aeginetolide via cerium enolate chemistry

Loliolide, aeginetolide, actinidiolide, and dihydroactinidiolide were synthesized in racemic form from a single common intermediate, prepared through the 1,2 addition of the cerium enolate of ethyl acetate to 2,6,6-trimethylcylohexenone.     

High Frequency PMN-PT 1-3 Composite Transducer for Ultrasonic Imaging Application

Development of PMN-PT single crystal/epoxy 1-3 composites for high-frequency ultrasonic transducers application is presented. The composite was fabricated by using a DRIE dry etching process with a 45% volume fraction of PMN-PT. A 35 MHz ultrasound flat transducer was fabricated with the composite, which was found to have an effective electromechanical coupling coefficient of 0.81, an insertion loss of 18 db, and a -6 dB bandwidth as high as 100%. Tungsten wire phantom image shows that the transducer had an axial resolution of 30 μm, which was in good agreement with the theoretical expectation. The initial results showed that the PMN-PT/epoxy 1-3 composite has many attractive properties over conventional piezoelectric materials for medical imaging applications.     

On the affordances of the MaxEP principle

Optimality principles have long been popular in the natural sciences and enjoyed much successes in various applications. However these principles seem to be disparate, each applied in limited contexts and there are far too many of them causing some consternation among scientists and philosophers of science regarding the ad-hoc nature of the optimality arguments. In this paper, we discuss the Maximum entropy production (MaxEP) as a plausible over-arching principle to understand stable configurations in fluid mechanics and related problems. The MaxEP being based upon sound physical arguments and in the immutable laws of thermodynamics along with the fact that it has been successfully co-opted across disciplines makes it worthy of attention. We discuss various physical and metaphysical aspects of this principle and use it to analyze some model problems regarding patterns in particle sedimentation such as sedimentation of a particle in Newtonian and non-Newtonian fluids and stable deformation of a falling droplet.     

Efficacy of End-Only-Functionalized Oligo(arylene-ethynylene)s in Killing Bacterial Biofilms

Cationic end-only-functionalized oligo(arylene-ethynylene)s (EO-OPEs) have recently been found to be broad-spectrum and effective antimicrobial agents because of their unique structure and optical properties. In this study, we investigated their potential use for preventing and reducing Escherichia coli (E. coli) biofilms. The Calgary biofilm device (CBD) was used to form bacterial biofilms of E. coli; in these studies, the minimum inhibitory concentration (MIC) and the minimum biofilm eradication concentration (MBEC) were determined. E. coli biofilms uniformly grow on pegs of the CBD device lid. The MIC values determined for EO-OPEs are comparable to those found for standard antibiotics such as kanamycin (MIC = 11.2 μg/mL). About 10-30 times the concentration of EO-OPEs was required to eradicate E. coli biofilms and prevent regrowth in the dark. Near-UV irradiation of EO-OPEs enhanced their efficacy in killing biofilms.     

Shear localisation in stirred yoghurt

The shear flow behaviour of stirred yoghurt in the cone-and-plate and cylindrical Couette geometries was studied using diffusing wave spectroscopy (DWS) and nuclear magnetic resonance (NMR) velocimetry. Differences between the transmission and backscattering DWS correlations suggest the formation of a high shear rate band near the surface of a moving cone of a cone-and-plate geometry at low shear rates. At higher shear rates, homogeneous shear flow is indicated. NMR velocimetry unambiguously demonstrated that a high shear rate band forms at the moving inner wall of a cylindrical Couette geometry at low shear rates. At intermediate shear rate, a high shear rate band is formed at the stationary outer wall and plug-like flow is observed mid-gap. At higher shear rates, homogeneous shear flow is observed. Slip is seen at both walls. The three flow regimes appear to correlate loosely with transitions in the pseudo-steady-state flow curve and may reflect a break-up of the protein aggregates observed with confocal microscopy.     

Anomalous shear banding: multidimensional dynamics under fluctuating slip conditions

The strain-controlled flow of a wormlike micellar solution in cylindrical Couette geometries with smooth and rough glass inner walls is investigated using 2D ¹H NMR velocimetry. We find anomalous shear banding in which fluctuating slip dynamics in combination with surfactant properties lead to a non-lever rule behaviour where the interface position remains constant while the high and low shear rates change. Velocities in the flow direction are imaged in the flow-gradient/vorticity plane. The spatiotemporal resolution achieved reveals fluctuations in flow structure along the vorticity axis and instability of the high shear band.     

Fragmentation pathways of 2,3‐dimethyl‐2,3‐dinitrobutane cations in the gas phase

2,3‐Dimethyl‐2,3‐dinitrobutane (DMNB) is an explosive taggant added to plastic explosives during manufacture making them more susceptible to vapour‐phase detection systems. In this study, the formation and detection of gas‐phase [M+H]⁺, [M+Li]⁺, [M+NH₄]⁺ and [M+Na]⁺ adducts of DMNB was achieved using electrospray ionisation on a triple quadrupole mass spectrometer. The [M+H]⁺ ion abundance was found to have a strong dependence on ion source temperature, decreasing markedly at source temperatures above 50°C. In contrast, the [M+Na]⁺ ion demonstrated increasing ion abundance at source temperatures up to 105°C. The relative susceptibility of DMNB adduct ions toward dissociation was investigated by collision‐induced dissociation. Probable structures of product ions and mechanisms for unimolecular dissociation have been inferred based on fragmentation patterns from tandem mass (MS/MS) spectra of source‐formed ions of normal and isotopically labelled DMNB, and quantum chemical calculations. Both thermal and collisional activation studies suggest that the [M+Na]⁺ adduct ions are significantly more stable toward dissociation than their protonated analogues and, as a consequence, the former provide attractive targets for detection by contemporary rapid screening methods such as desorption electrospray ionisation mass spectrometry. Copyright © 2009 Commonwealth of Australia. Published by John Wiley & Sons, Ltd.