Berry’s Phase in Pilot-Wave Theory

The projective-geometric derivation of Berry's adiabatic geometric phase for a single trajectory in the de Broglie-Bohm pilot-wave theory is given. The relation between this phase and the first order nature of pilot-wave theory is discussed. It is shown, in the case where the electromagnetic vector potential is a gradient, that the phase can be given in a locally phase invariant form. The appearance of the Berry connection is justified and its physical significance in pilot-wave theory is discussed.     

Magnetotransport in simple metals. An exactly soluble model

The magnetoconductivity tensors of a metal with a weakly anisotropic Fermi surface are determined from analytic solutions to the Boltzmann equation without any restrictions on the magnitude of the cyclotron frequency compared to the collision rate. Results are given for both a two- and a three-dimensional model, the former being analytically simpler to handle. The Hall coefficient and magnetoresistance are obtained as functions of the magnetic field, and we show by explicit calculation how the thermoelectric coefficients at high magnetic fields are determined by the thermodynamic entropy.     

Synthesis and characterisation of Gd2O3 nanocrystals functionalised by organic acids

Nanocrystals of Gd2O3 have been prepared by various methods, using, e.g., trioctylphosphine oxide (TOPO), diethylene glycol (DEG) or glycine. The crystalline particles were of sizes 5 to 15 nm. Different carboxylic acids, e.g., oleic acid or citric acid, were adsorbed onto the surface of the particles made with DEG. IR measurements show that the molecules coordinate to the Gd2O3 surface via the carboxylate group in a bidentate or bridging manner. The organic-acid/particle complexes were characterised by XRPD, TEM, FTIR, Raman, and XPS.     

A dimerization "switch" in the internalization mechanism of a cell-penetrating peptide

The internalization mechanism of a cell-penetrating peptide has been explored through combinatorial selection of a phage-displayed peptide dimer library, chemical synthesis, and biophysical characterization. Both energy-dependent and energy-independent modes for peptide uptake by the target mammalian cells were observed, suggesting a role for higher-order structure in modulating the action of this novel cell-penetrating peptide.     

Microporous organic crystals: an unusual case for L-leucyl-L-serine

Cocrystallized acetonitrile solvent molecules located inside 5.2 A channels in the crystal structure of L-leucyl-L-serine have been replaced by I2 molecules with full retention of the peptide scaffold.     

A Raman spectroscopic study of the low-frequency vibrations of o-dimethoxybenzene and its methyl deuterated analogues

The low-frequency (100–400 cm⁻¹) Raman spectra of liquid (at 300 K) and solid (at 130 K) veratrole (o-dimethoxybenzene), and its methyl deuterated analogues, have been measured. The methyl and methoxyl torsional transitions have been identified, and the corresponding rotational barriers have been determined. The interpretation of the spectra points to a conformationally mixed situation for solid veratrole, in which both planar and non-planar conformers may co-exist.     

Subcritical scattering from buried elastic shells

Buried objects have been largely undetectable by traditional high-frequency sonars due to their insignificant bottom penetration. Further, even a high grazing angle sonar approach is vastly limited by the coverage rate dictated by the finite water depth, making the detection and classification of buried objects using low frequency, subcritical sonar an interesting alternative. On the other hand, such a concept would require classification clues different from the traditional high-resolution imaging and shadows to maintain low false alarm rates. A potential alternative, even for buried targets, is classification based on the acoustic signatures of man-made elastic targets. However, the elastic responses of buried and proud targets are significantly different. The objective of this work is to identify, analyze, and explain some of the effects of the sediment and the proximity of the seabed interface on the scattering of sound from completely and partially buried elastic shells. The analysis was performed using focused array processing of data from the GOATS98 experiment carried out jointly by MIT and SACLANTCEN, and a new hybrid modeling capability combining a virtual source-or wave-field superposition-approach with an exact spectral integral representation of the Green's functions for a stratified ocean waveguide, incorporating all multiple scattering between the object and the seabed. Among the principal results is the demonstration of the significant role of structural circumferential waves in converting incident, evanescent waves into backscattered body waves, emanating to the receivers at supercritical grazing angles, in effect making the target appear closer to the sonar than predicted by traditional ray theory.