Non radiative transition probabilities in the statistical limit

In this paper we derive a general computational scheme for the calculation of the non radiative decay probability of a polyatomic molecule in the statistical limit. Within the framework of the Harmonic Approximation the relaxation rate of any polyatomic molecule can be expressed in terms of an infinite sum where each term consists of a medium distribution function and an intramolecular term. In the statistical limit the medium induced vibrational relaxation widths do not affect the non radiative decay characteristics. Numerical calculations are reported for the T ₁S ₀ intersystem crossing in the benzene molecule.     

Current-induced light emission and light-induced current in molecular-tunneling junctions

The interaction of metal-molecule-metal junctions with light is considered within a simple generic model. We show, for the first time, that light-induced current in unbiased junctions can take place when the bridging molecule is characterized by a strong charge-transfer transition. The same model shows current-induced light emission under potential bias that exceeds the molecular excitation energy. Results based on realistic estimates of molecule-lead coupling and molecule-radiation field interaction suggest that both effects should be observable.     

The Maximum Number of Edges in Geometric Graphs with Pairwise Virtually Avoiding Edges

Let G be a geometric graph on n vertices that are not necessarily in general position. Assume that no line passing through one edge of G meets the relative interior of another edge. We show that in this case the number of edges in G is at most 2n?3.     

From Exact Systems to Riesz Bases in the Balian�CLow Theorem

We look at the time–frequency localization of generators of lattice Gabor systems. For a generator of a Riesz basis, this localization is described by the classical Balian–Low theorem. We establish Balian–Low type theorems for complete and minimal Gabor systems with a frame-type approximation property. These results describe how the best possible localization of a generator is limited by the degree of control over the coefficients in approximations given by the system, and provide a continuous transition between the classical Balian–Low conditions and the corresponding conditions for generators of complete and minimal systems. Moreover, this holds for the non-symmetric generalizations of these theorems as well.     

Carbohydrate hydration: heavy water complexes of α and β anomers of glucose, galactose, fucose and xylose

The singly and doubly hydrated complexes of the α and β anomers of a systematically varied set of monosaccharides, O-phenyl D-gluco-, D-galacto-, L-fuco- and D-xylopyranoside, have been generated in a cold molecular beam and probed through infrared-ultraviolet double resonance ion-dip (IRID) spectroscopy coupled with quantum mechanical calculations. A new 'twist' has been introduced by isotopic substitution, replacing H(2)O by D(2)O to separate the carbohydrate (OH) and hydrate (OD) vibrational signatures and also to relieve spectral congestion. The new spectroscopic and computational results have exposed subtle aspects of the intermolecular interactions which influence the finer details of their preferred structures, including the competing controls exerted by co-operative hydrogen bonding, bi-furcated and OH-π hydrogen bonding, stereoelectronic changes associated with the anomeric effect, and dispersion interactions. They also reassert the operation of general 'working rules' governing conformational change and regioselectivity in both singly and doubly hydrated monosaccharides.     

Ionization-loss stimulated Raman spectroscopy for conformational probing of flexible molecules

The approach of studying structural and dynamical properties of flexible molecules is of substantial interest, as it allows decoding the shapes and intrinsic properties of isolated molecular constituents, which have an influence on the selectivity and functionality in biological processes. Combining quantum computation methods with double resonance or infrared hole burning techniques, mainly covering hydride stretch vibrations, recently led to great progress in understanding the structure of a variety of biological building blocks. Measurements of spectra in the lower frequency range, with relatively compact and convenient laser sources, still pose major challenges. For this reason, the method of ionization-loss stimulated Raman spectroscopy (ILSRS) has been developed and applied for monitoring the spectral features of the 2-phenylethanol prototype. The bands observed in the Raman spectra of its two conformers uniquely identify their structures and are in accord with anharmonic results obtained by density functional theory calculations. These findings point to future opportunities for ILSRS as a powerful conformational probe and set new standards for detailed interrogation of structure and intra- and inter-molecular interactions.     

A facile one-pot sonochemical synthesis of surface-coated mannosyl protein microspheres for detection and killing of bacteria

We report a remarkably facile one-pot sonochemical approach to prepare protein microspheres whose shells are covalently decorated with a mannosyl derivative to target Escherichia coli (E. coli), while their cores are encapsulated with tetracycline. Conjugated microspheres induced the agglutination of E. coli and increased the anti-bacterial activity of the encapsulated tetracycline by five fold.     

Direct imaging of carbon nanotubes spontaneously filled with solvent

For the first time, cryo-TEM imaging is used to directly show spontaneous filling of carbon nanotubes immersed in a solvent in the native state at ambient conditions. Multi-walled carbon nanotubes are dissolved in chlorosulfonic acid, and the high contrast between the acid and the carbon shows the difference between filled and unfilled nanotubes.