Coupled whispering gallery modes in a multilayer-coated microsphere

Whispering gallery modes in a microsphere coated with three layers of high, low, and high refractive indices (RIs) are considered. Coastal modes and inland modes, centered on the outer and inner high-RI layers, exist as different radial modes. At right values of RI and thickness of the three layers, an inland mode and a coastal mode couple to produce a radial distribution of the photonic field that resembles bonding and antibonding orbitals. The coupling occurs across a layer of the middle low-RI layer, much thicker than the wavelength of light. The coupling is analyzed in a quantum-mechanical analog of a one-dimensional particle in a double-well potential.     

Turbulent vortex rings in weakly turbulent and in turbulent ambient flow

Turbulent vortex rings were investigated in weakly turbulent flow and in three different grid generated turbulent flows to clarify the reciprocal action of the vortex ring with defined external turbulence. Assuming self-similarity and turbulent viscosity as proportional to V₀D₀ the equations for the ring diameter D(t) and the velocity of propagation V(t) were derived. The time difference Δt between the virtual origins of 1/V(t) respectively D²(t) led to an invariant term. The equation of momentum is fulfilled. – Position and diameter of the vortex rings were determined till their decay by means of an optical system, which did not disturb the vortex rings. The experimental results in weakly turbulent ambient flow obtained by the author and by others confirm the theory very well. The ambient turbulence was nearly constant in the measuring region; its effect could be described by simply adding its viscosity to the vortex ring’s internal turbulent viscosity. The results could be represented in unified non-dimensional diagrams. Moreover, an explanation was found as to why the mean internal turbulent viscosity is constant.     

The mechanical pre-stressing in ultrasonic piezotransducers

Composed piezotransducers submitted to mechanical pre-stressing present shifts on resonance and anti-resonance frequencies. Changes on characteristic parameters of the ceramic and in the coupling between the parts of the transducer can be the causes for this behavior. In applications where the level of pre-stressing is low (up to 50 MPa) the parameters of the ceramic are not altered, therefore, the shifting on frequencies are attributed to coupling between parts. This paper describes a mathematical model to explain this effect based on difference of effective cross-section between transducers parts under pre-stressing. The results show a proportional relation between pre-stressing and effective coupling of the parts.     

Examining the possibilities of applying high pressure to preserve yoghurt supplemented with probiotic bacteria

Natural yoghurt was subject to pressures of 200 and 250 MPa/4 and 18°C/15 min, after which milk-activated inocula of Lactobacillus acidophilus and Bifidobacterium sp. were added. The yoghurts were stored for 4 weeks at refrigeration temperature. After preparation and each week of storage, the count of bacteria, acidity, antibacterial property and an organoleptic assessment was determined. The highest survival rate was demonstrated by the bacteria of Lactobacillus delbrueckii ssp. bulgaricus, Streptococcus thermophilus and Bifidobacterium sp. in the yoghurt pressurised 200 MPa/15min at 4°C. Acidity increases in the control yoghurts were higher than in the pressurised ones. Pressurised yoghurts demonstrated weaker antibacterial effect in comparison to control yoghurts. Slight changes in the smell and taste were observed after pressurisation. Yoghurts pressurised at 18°C were characterised by more favourable organoleptic properties. Better conciseness of the curd and lower whey seep out were observed in pressurised yoghurt.     

The MTE continuum relation with application to an argon arc at atmospheric pressure

The continuum emission coefficient relation for a plasma in Multithermal Equilibrium (MTE) is derived using the partial-MTE ionization equation. The results are presented in a form using the nonhydrogenic free-bound Gaunt factors of Schlüter. Measurements on a 200 A, 1 atm, constricted argon arc indicate that electron densities calculated from the MTE continuum relation and Schlüter's ξ_fb values exceed electron densities from the Stark broadening of H_β by 15–30%. Experimental values of ξ_fb are up to 3 times larger than Schlüter's values, but are in agreement with the values of Morris and Krey at 5 atm, which is probably one of the few similar experiments actually in or near complete LTE. In the present experiment at the arc axis: N_e(H_β) = 1.00 × 10¹⁷cm^-3 (±8%); T_e = 34,000 K (±20%); T_exa = 12,000 K (±3%); T_exβ = 9000 K (±5%); and T_a = T_i = 10,000 K (±68%). The probable errors reflect the need for more accurate transition probabilities which had an uncertainty of 25%.     

Preface

In life sciences,molecules are categorized into biological macromolecules(protein,DNA,RNA etc.)and small molecules(neurotransmitters,vitamins,drugs,natural products,water etc.).The main methodology of chemistry for life sciences is using chemical techniques and tools to explore and manipulate the functions of biological macromolecules.This methodology can be traced back to W hler’s synthesis of urea from"inorganic"compounds in 1828.Today,we realize that chemistry can advance a molecular understanding of biology,and the harnessing of biology can advance chemical knowledge as well[1–4].Chemicals are widely used as probes to investigate biological functions[5–7].     

DI-(2,2,2-Trichloroethyl)-Carbonate: Byproduct in Reactions with 2,2,2-Trichloroethyl Chloroformate

2,2,2-Trichloroethyl chloroformate (1) in higher boiling solvents, particularly in the presence of potassium carbonate and potassium bicarbonate, affords undesired di-(2,2,2-trichloroethyl)-carbonate (2) as a byproduct. When chemically pure chloroformate was used, addition of carbonates was found to be unnecessary in N-demethylation reactions.     

POLAR INTERACTIONS OF HYALURONIC ACID -EXPERIMENTS AND MOLECULAR DYNAMICS SIMULATIONS-

ABSTRACT

To study the polar interactions of the cartilage component hyaluronate (HA) contact angle measurements of polymer films of sodium hyaluronate and of the free hyaluronic acid with different probe liquids and theoretical investigations with molecular dynamics simulation (MD) on polymer segments in aqueous environment were performed. For the designation of contact angles water, formamid, glycerol and α-bromnaphthalene as probe liquids were used. The surface tension components were calculated on the basis of the theory of van Oss using the Young equation. Experimental investigations were done with air dried layers of the sodium salt of HA whose surface has been formed at the interface to the air resp. glass support. Whereas the surface polymer/air is characterized by small, but non-zero values for γ^? and γ^-the surface polymer/glass tends to have γ^-monopolar properties. In opposite to the salt form of HA a strong repulsion of chains and high γ^- monopolarity was measured for the protonated form.

The molecular dynamics simulation (MD) on HA in water were carried out employing the force field CHARMM and the water model TIP3P. MD trajectories of HA tetramer subunit surrounded by approximately 950 water molecules were produced up to 3 ns. The interaction energies of HA and water, hydrogen bonding, and the orientation of water molecules at different solute atom groups were calculated. On the basis of energy and geometry criteria, the number of hydrogen bonds between the water molecules and the polymer acceptor atoms was determined to be between 10 and 15 per dimer unit.     

Nonstoichiometry in steps on AB crystals (I). General aspects,including bulk imperfections

Starting with a quasichemical treatment, simple model calculations are given for the equilibrium composition in surface steps containing A and B kinks, the amount and ratio of which is varied by changing the adjacent gas composition. In connection with deviations from step stoichiometry, the total amount of kinks increases strongly. A nearest neighbour approximation has been applied to the attachment of A or B atoms at kinks from the gas phase, and also from the bulk by formation of vacancies V_A or V_B. These processes can be formulated separately for the two elements, taking into account the effective formation of bulk atoms of the other kind (B_B or B_A).     

Synthesis of stereoregular poly(alkyl malolactonates)

Optically pure methyl, ethyl, isopropyl, and benzyl (R)-malolactonate were prepared from (S)-(-)-malic acid and were polymerized in the bulk with tetraethylammonium benzoate as the initiator to yield high-molecular-weight, crystalline polymers. The optical purity of methyl and benzyl malolactonate was determined by ¹H NMR spectroscopy of the β-lactone complexed with a chiral europium shift reagent. Enantiomeric excesses of 100% were found (the experimental error was 3%). Optically active poly(β-malic acid) was obtained from optically active poly[benzyl (S)-malate] by catalytic hydrogenolysis of the pendent benzyl esters. Ethyl and benzyl (R)-malolactonate were also copolymerized, and the benzyl esters of the resulting copolymer were converted into carboxylic acid units by hydrogenolysis.