Suppression of radiative losses of surface polaritons on nanostructured thin metal films

The strong electromagnetic coupling between surface plasmon polariton modes on opposite interfaces of a finite thickness periodically nanostructured metal film has been studied. Surface polariton dispersion and associated electromagnetic field distributions have been analyzed. It was shown that at a frequency that corresponds to the crossing of film Bloch modes of different symmetries, the radiative losses of surface polaritons that are related to the polaritons' coupling to light during propagation on the structured surface are suppressed.     

Enhancement of a 24.77-nm line emitted by the plasma of a boron nitride capillary discharge irradiated by a high-intensity ultrashort laser pulse

Investigations of plasma produced by a boron nitride capillary discharge irradiated with a guided 20-TW Ti: sapphire laser pulse at a peak intensity of 4 x 10(18) W/cm2 are presented. The guided laser radiation in the plasma channel generated He-like ions that, subject to suitable plasma temperature, recombined into Li-like nitrogen ions. Intense radiation at a wavelength of 24.77 nm was observed, indicating possible lasing at the 3d(5/2) - 2p(3/2) transition in Li-like nitrogen.     

Compaction of single-chain DNA by histone-inspired nanoparticles

We elaborated a versatile experimental model of chromatin which consists of a single chain of long duplex DNA that interacts with well-defined cationic nanoparticles of various sizes. We found that the DNA compaction by nanoparticles is stepwise and progressive at the single-chain level. It is controlled by the ability of DNA to wrap nanoparticles, which is more efficient for larger particles and, similar to DNA-histone interaction, is optimal at a physiological salt concentration.     

Superfluid-superfluid phase transitions in a two-component Bose-Einstein condensate

Depending on the Hamiltonian parameters, two-component bosons in an optical lattice can form at least three different superfluid phases in which both components participate in the superflow: a (strongly interacting) mixture of two miscible superfluids (2SF), a paired superfluid (PSF) vacuum, and (at a commensurate total filling factor) the super-counter-fluid (SCF) state. We study the universal properties of the 2SF-PSF and 2SF-SCF quantum phase transitions and show that (i) they can be mapped onto each other and (ii) their universality class is identical to the (d+1)-dimensional normal-superfluid transition in a single-component liquid. The finite-temperature 2SF-PSF(SCF) transitions and the topological properties of 2SF-PSF(SCF) interfaces are also discussed.     

Polarization control of optical transmission of a periodic array of elliptical nanoholes in a metal film

The spectral dependences of polarized optical transmission of a metal film with a periodic array of elliptical nanoholes have been studied. Such nanostructured metal films exhibit enhanced broadband optical transmission that one can control by selecting the polarization of incident and (or) transmitted light.     

Single-photon tunneling in photonic crystals with deep defect states

A new design for a single-photon tunneling device based on tunneling of light through a gap in a photonic crystal linear waveguide containing a deep defect state is suggested. Unlike recently observed single-photon tunneling through nanometer scale nonlinear pinholes in a thick gold film, in the device described here the photon current should be strictly conserved. By appropriate design of the barrier width, defect level position in the bandgap, and defect spatial position in the barrier, a desired photon tunneling rate can readily be engineered.     

Photodynamic inactivation of isolated crayfish neuron requires protein kinase C,PI 3-kinase and Ca2+

Involvement of some signalling pathways in response to photodynamic therapy (PDT) of sulfonated aluminium phthalocyanine Photosens has been studied in isolated nerve cell. Neurone photosensitisation with 10(-7) M Photosens gradually inhibited firing and irreversibly abolished neuronal activity. Activation of protein kinase C (PKC) by phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) precipitated PDT-induced abolition of neurone activity and caused nucleus swelling and impairment of the nucleus border. Elevation of cytosolic Ca(2+) concentration by ionomycin or thapsigargin also reduced neurone lifetime. In contrast, the PKC inhibitors staurosporine, hypericin or chelerythrine as well as the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitors wortmannin or LY294002 increased neurone lifetime. These results showed that PKC, PI 3-kinase and Ca(2+) are involved in PDT-induced neurone inactivation and following death.     

Neoglycoconjugates from synthetic tetra- and hexasaccharides that mimic the terminus of the O-PS of Vibrio cholerae O:1, serotype Inaba

A glycosyl acceptor and a glycosyl donor having the N-3-deoxy-L-glycero-tetronic acid side chain already attached have been prepared and used for the synthesis of the di-through to the hexasaccharide that mimic the upsteam terminus of the O-specific polysaccharide of Vibrio cholerae O:1, serotype Inaba. The target tetra- and the hexasaccharide, which were obtained in the form of 5-methoxycarbonylpentyl glycosides, were linked to BSA using squaric acid diester chemistry. The conjugation reactions were monitored by surface enhanced laser desorption ionization-time of flight mass spectrometry (SELDI-TOF MS). This allowed the progression of the conjugation of the synthetic oligosaccharides in a controlled way and termination of the reaction when the desired molar hapten/BSA ratio had been reached, yielding neoglycoconjugates with predetermined carbohydrate/carrier ratios. The ability to monitor the conjugation by the SELDI-TOF MS technique made it possible to prepare, from one hapten in a one-pot reaction, several neoglycoconjugates having different, predetermined carbohydrate/carrier ratios.     

Kinetics of amide and peptide cleavage by alkaline hydrogen peroxide

The hydroperoxide anion cleaves unactivated amides and peptides although it is completely unreactive toward ethyl esters. The cleavage by HO2(-) proceeds faster than by OH(-) and involves additional routes with general acid assistance by H2O2 and general base assistance by OH(-) and HO2(-). Cleavage of polypeptides occurs at the N-terminal peptide bond. [reaction: see text]