Search Results - (Author, Cooperation:C. D. Williams)

2013-04-27

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; *Cold Temperature ; *Elasticity ; *Energy Metabolism ; Flight, Animal ; Manduca ; Motion ; *Muscle Contraction ; Muscle, Skeletal/*physiology ; Myofibrils/metabolism/*physiology ; X-Ray Diffraction

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] The analogy2 4 between liquid helium and the early Universe arises because they both undergo phase transitions that can be considered as being of second order, describable in terms of Ginzburg-Landau theory6. In each case, the potential contribu-tion to the free energy density can be written as ...

Electronic Resource

0392-6737

General theories and computational techniques

Springer Online Journal Archives 1860-2000

Physics

Riassunto Si considera il problema di due loci atomici tipo idrogeno (statis solamente) accoppiati con una matrice hopping. Si impiega un nuovo formalismo, il metodo risolutore dell’operatore di Liouville, per valutare la funzione termodinamica di Green per la particella singola per questo sistema. Si discutono anche dettagli del metodo.

Summary The problem of two hydrogenlike atomic sites (s-shells only) coupled via a hopping matrix is considered. We employ a new formalism, the Liouville operator resolvent method, to evaluate the single-particle thermodynamic Green’s function for this system. Details of the method are also discussed.

Electronic Resource

1572-8943

cobalt ; isomorphous substitution ; manganese ; tetraalkylammonium cations

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Abstract Pure silica zeolite ZSM-5 has been synthesised in a slightly acidic aqueous fluoride medium which produces the protonated form of the zeolite ZSM-5 [1]. Tetrahalometallate [2] species of cobalt and manganese have been synthesised and increasing mole fractions incorporated into the zeolite synthesis gel. The products have been analysed and characterised using simultaneous thermogravimetric-derivative thermogravimetric analysis (TG-DTG). The thermal decomposition, under nitrogen of the associated tetraethylammonium (TEA+) and tetrapropylammonium (TPA+) cations occluded within the zeolite channels is indicative and characteristic of the incorporation of the heteroatoms into the zeolitic framework. Analysis by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR) has confirmed the reliability of thermogravimetric (TG) and derived thermogravimetric analysis (DTG) as a diagnostic tool.

Electronic Resource

1573-4811

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Electronic Resource

1573-4803

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Abstract The permittivities (ε′) of undoped MgO and iron-doped Fe-MgO single crystals have been measured over the temperature range 20 to 650

Electronic Resource

1573-7357

67.70.+n ; 68.15.+e ; 68.45.Gd ; 41.20.Cv

Springer Online Journal Archives 1860-2000

Physics

Abstract Prompted by the recent striking experimental results reported by Babkin and Hakonen that appeared to show that liquid helium-II does not wet magnesium fluoride, we have examined the effects that an inhomogeneous electrostatic field has on thin films of liquid helium at temperatures below 0.5K. Our model includes the influence of gravity, surface tension, the electric field and the van der Waals interaction between the helium and its supporting substrate. We show that, an inhomogeneous charge on the substrate can produce effects that mimic the surface profiles between wetted and non-wetted areas. The calculations also indicate that some special precautions may be necessary when studying films of liquid or solid helium on insulators.

Electronic Resource

1573-7357

Springer Online Journal Archives 1860-2000

Physics

Abstract Zurek suggestedNature 317 , 505; 1985) that the Kibble mechanism, through which topological defects such as cosmic strings are believed to have been created in the early Universe, can also result in the formation of topological defects in liquid 4 He, i.e. quantised vortices, during rapid quenches through the superfluid transition. Preliminary experiments (Hendry et al., Nature 368 , 315; 1994) seemed to support this idea in that the quenches produced the predicted high vortex-densities. The present paper describes a new experiment incorporating a redesigned expansion cell that minimises vortex creation arising from conventional hydrodynamic flow. The post-quench line-densities of vorticity produced by the new cell are no more than 10 10 m −2 , a value that is at least two orders of magnitude less than the theoretical prediction. We conclude that most of the vortices detected in the original experiment must have been created through conventional flow processes.

Electronic Resource

1573-7357

Springer Online Journal Archives 1860-2000

Physics

Abstract A fast (∼ 3 ms) adiabatic expansion of a volume of liquid 4 He through the lambda transition is being used to study the nature of the transition and to model the cosmological false vacuum to true vacuum phase transition of the early universe. Preliminary results are reported showing that, in accordance with theoretical predictions by W H Zurek (Nature 317, 505; 1985), there is copious production of quantized vortex lines, which represent the superfluid analogue of cosmic strings. The line density after the expansion appears to decay in two distinct stages, with a fast decay being followed by a much slower one, in agreement with earlier work on the decay of quantum turbulence created in thermal counterflow. Extrapolation of the initial fast decay suggests an initial line density, immediately following the expansion, of ∼107 cm−2 . Smaller, but still substantial, vortex densities are also found to occur when the system is expanded from below the lambda transition, and the physical implications are discussed.

Electronic Resource

1572-8943

copper ; fluoride ; isomorphous substitution ; nickel ; ZSM

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Abstract The synthesis of pure silica ZSM-5 has been modified to produce highly crystalline material in the protonated form, necessary for catalytic activity, directly from a low water fluoride gel. Tetrahedrally co-ordinated divalent species of nickel and copper have been synthesised as salts of large organic cations and increasing mole fractions incorporated into the zeolite gels. The products have been analysed and characterised using simultaneous thermogravimetric and derivative thermogravimetric analysis (TG-DTG). The thermal decomposition under nitrogen of the metal associated cations, tetraethylammonium (TEA+), occluded within the zeolite channels is indicative and characteristic of the incorporation of heteroatoms into the zeolite framework. Anomalous losses in the systems can be explained by Jahn–Teller distortions. The mass losses increased with increased metal loading and were consistent with those reported in full water system, analysis also confirmed that the material was hydrophobic and thermally stable. Analysis by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR) and Atomic Absorption Spectroscopy (AAS) has confirmed the reliability of TG-DTG as a diagnostic tool. The maximum levels of substitution achieved were (mass%) Ni 3.93 and Cu 4.38.

Electronic Resource