Light emission enhancement using randomly distributed plasmonic nanoparticle arrays

We have fabricated and characterised the optical properties of solution processed randomly distributed gold nanoparticle plasmonic arrays that are coated with a thin-film fluorescent dye. Three times enhancement in the emission intensity of the fluorescent dye Pyridine 2 has been observed. Our results are further supported by finite difference time domain simulations that predicted up to 7 times enhancements in the emission intensity as a result of the coupling between the molecular dipoles and the confined field in the underlying plasmonic array. Our results demonstrate the potential of using such structures in organic light emitting devices and chemical and bio-sensing applications

Investigagation of vibrations of variable cross-section linking elements

The applicability of analytical models for vibrations of variable cross-section two- layered cylindrical structural elements is investigated. Natural frequencies of longitudinal and lateral vibrations are calculated and validated experimentally. Natural frequency )( 0 n ? dependence on material properties (?, E) and geometric parameters (l, R, r, S) of structural element provide means for optimization of vibration amplitude characteristic

216 MHz repetition rate passively mode-locked electrically-pumped VECSEL

Electrically pumped vertical external cavity surface emitting laser is passively mode-locked at record-low repetition rate of 216 MHz demonstrating potential peak power scalability. A quantum dot saturable absorber is used to achieve stable operation

Vibration and noise measurements during silage thickening with inertia directional vibrator

Literature review and performed theoretical investigation indicates that it is environmentally and economically feasible for small and average size farms to use vibrational thickening method for silage preparation. However, the results need to be verified with experiments. This research work provides analysis and evaluation of flat surface inertia type vibrator, in which the excitation force is induced by turning the unbalanced mass. Directed action vibrator was manufactured and tested. Results indicate that application of inertia directional vibrator for thickening of finely chopped corn and Jerusalem artichoke stalk mixture, after 40 minutes thickening, allows to obtain a 114.6 kg m-3 density for both layers, while thickening the first 65 kg mass mixture layer after 10 minutes - a 197.9 kg m-3 density. Dry material densities correspond to 61.5 and 106.3 kg m-3 respectively. After examination of fodder quality it was determined that corn mixture silage, thickened by the inertia directional vibrator, satisfies highgrade silage requirements. Performed tests demonstrated that the effect of vibrations on whole body and the measured noise levels do not have detrimental effect on human health and the established acceptable limits are not exceeded while operating the inertia directional vibrator. The vibrator is suitable for silage preparation since it does not contaminate the fodder with dirt and gasoline products during operation. The proposed silage preparation method provides opportunities to use ecologically safe containers as well as sectional and other types of enclosure

Full characterization of vibrational coherence in a porphyrin chromophore by two-dimensional electronic spectroscopy

In this work we present experimental and calculated two-dimensional electronic spectra for a 5,15-bisalkynyl porphyrin chromophore. The lowest energy electronic Qy transition couples mainly to a single 380 cm–1 vibrational mode. The two-dimensional electronic spectra reveal diagonal and cross peaks which oscillate as a function of population time. We analyze both the amplitude and phase distribution of this main vibronic transition as a function of excitation and detection frequencies. Even though Feynman diagrams provide a good indication of where the amplitude of the oscillating components are located in the excitation-detection plane, other factors also affect this distribution. Specifically, the oscillation corresponding to each Feynman diagram is expected to have a phase that is a function of excitation and detection frequencies. Therefore, the overall phase of the experimentally observed oscillation will reflect this phase dependence. Another consequence is that the overall oscillation amplitude can show interference patterns resulting from overlapping contributions from neighboring Feynman diagrams. These observations are consistently reproduced through simulations based on third order perturbation theory coupled to a spectral density described by a Brownian oscillator model

Geometry-dependent electrostatics near contact lines

Long-ranged electrostatic interactions in electrolytes modify their contact angles on charged substrates in a scale and geometry dependent manner. For angles measured at scales smaller than the typical Debye screening length, the wetting geometry near the contact line must be explicitly considered. Using variational and asymptotic methods, we derive new transcendental equations for the contact angle that depend on the electrostatic potential only at the three phase contact line. Analytic expressions are found in certain limits and compared with predictions for contact angles measured with lower resolution. An estimate for electrostatic contributions to {\it line} tension is also given.Comment: 3 .eps figures, 5p