EFFECTS OF END CAP AND ASPECT RATIO ON TRANSMISSION OF SOUND ACROSS A TRUSS-LIKE PERIODIC DOUBLE PANEL

Transmission of sound across 2-D truss-like periodic double panels separated by an air gap and in contact with an acoustic fluid on the external faces is analyzed. Each panel is made of repeated cells. Combining the transfer matrices of the unit cell forms a set of equations for the overall elastic frequency response. The acoustic pressure in the fluids is expressed using a source boundary element method. Adding rigid reflecting end caps confines the air in the gap between panels which influences sound transmission. Measured values of transmission loss differ from the 2-D model by the wide low-frequency dip of the mass-spring-mass or “msm” resonance also termed the “air gap resonance”. In this case, the panels act as rigid masses and the air gap acts as an adiabatic air spring. Results from the idealized 3-D and 2-D models, incorporating rigid cavities and elastic plates, reveal that the “msm” dip is absent in 2-D models radiating into a semi-infinite medium. The dip strengthens as aspect ratio approaches unity. Even when the dip disappears in 2-D, TL rises more steeply for frequencies above the “msm” frequency.     

PHOTOCHROMIC SYNERGISM OF BACTERIORHODOPSIN- and HALORHODOPSIN-MEDIATED PHOTOPHOSPHORYLATION IN Halobacterium halobium*

Quantitative action spectroscopy was performed in Halobacterium halobium. using four suited pigment mutants, namely the bacteriorhodopsin and halorhodopsin positive mutant strain M-l (BR⁺, HR⁺), the bacteriorhodopsin positive but halorhodopsin negative strain M-18 (BR⁺, HR^-), the bacteriorhodopsin negative but halorhodopsin positive strain L-33 (BR^-, HR⁺), and the bacteriorhodopsin and halorhodopsin negative strain L-07 (BR^-, HR⁺). The approached questions were: First, photoenergetic synergism of halorhodopsin and bacteriorhodopsin in intact cells; second, photochromism and cellular function of the blue light-absorbing intermediates, i.e. M-412 and HR-410 in bacteriorhodopsin and in halorhodopsin, respectively. Dark-adapted cells of mutant strain M-l show wavelength-dependency of quantum yield of photo-phosphorylation, φ_ATP. An 1.4-fold enhancement was found at 575 nm wavelength where the long wavelength absorbance bands of bacteriorhodopsin and halorhodopsin intersect. The enhancement vanished after a 30 min pulse of orange light (600 Wm^-2 bandpass from 495 to 750 nm), but was restored after a 30 min pulse of blue light (100 Wm^-2 bandpass from 325 to 480 nm). Photoreversibility of this enhancement probably reflects phototransformation of halorhodopsin from its ground state into its inactive intermediate, HR-410, and vice versa. The halorhodopsin-mediated enhancement with maximum quantum yield of photophosphorylation, φ_ATP= 0.06, i.e. a quantum requirement of = 17 photons/ATP, is partly substituted by a rise in phosphate potential and explained in terms of a voltage-regulated gating effect on the H⁺-driven ATP-synthase, superimposed on the chemiosmotic mechanism of energy coupling. The blue-absorbing photochromic intermediate, M-412 of bacteriorhodopsin, dissipates light energy upon photoexcitation that is reflected by a spectral decline in quantum yield of photophosphorylation to a minimum value of = 0.01 at 415 nm, i.e. a quantum requirement of = 100 photons/ATP.     

Procedurally Rational Volunteers

The mixed-strategy equilibrium applied to the volunteer's dilemma (Diekmann, 1985 Diekmann , A. ( 1985 ). Volunteer's dilemma . Journal of Conflict Resolution , 29 , 605 – 610 .[Crossref], [Web of Science ®] , [Google Scholar]) predicts that the probability that at least 1 bystander volunteers decreases, if the number of bystander increases. I argue that this prediction lacks empirical support and demonstrate that an alternative solution concept from the literature on bounded rationality, the procedurally rational equilibrium (Osborne &; Rubinstein, 1998 Osborne , M. J. &; Rubinstein , A. ( 1998 ). Games with procedurally rational players . American Economic Review , 88 , 834 – 847 .[Web of Science ®] , [Google Scholar]), yields alternative predictions. I supply some empirical evidence that the alternative solution concept fares better in explaining observed behavior in the volunteer's dilemma.     

Error estimates and extrapolation for the numerical solution of Mellin convolution equations

In this paper we consider a quadrature method for the numericalsolution of a second-kind integral equation over the interval,where the integral operator is a compact perturbation of a Mellinconvolution operator. This quadrature method relies upon a singularitysubtraction and transformation technique. Stability and convergenceorder of the approximate solution are well known. We shall derivethe first term in the asymptotics of the error which shows that,in the interior of the interval, the approximate solution convergeswith higher order than over the whole interval. This implieshigher orders of convergence for the numerical calculation ofsmooth functionals to the exact solution. Moreover, the asymptoticsallows us to define a new approximate solution extrapolatedfrom the dilated solutions of the quadrature method over mesheswith different mesh sizes. This extrapolated solution is designedto improve the low convergence order caused by the non-smoothnessof the exact solution even when the transformation techniquecorresponds to slightly graded meshes. Finally, we discuss theapplication to the double-layer integral equation over the boundaryof polygonal domains and report numerical results.     

Microwave heating of carbon-coated ceramic fibres: A mathematical model

The microwave heating of a thinly carbon-coated ceramic fibreis modelled and analysed in the small Biot number regime. Theelectric field is assumed known and uniform throughout the cross-section,and constant along the axis of the cylinder. The mathematicalmodel consists of a nonlinear heat equation with an idealizedsource term that models the thin carbon coating and simplifiedreaction kinetics. The analysis yields an asymptotic approximationof the heating process on two time scales. The first capturesthe initial heating of the carbon coating and the ceramic, andthe carbon reaction, while the second determines the long timebehaviour of the sample. The results show a qualitative relationshipbetween the coating thickness and the final temperature of thefibre. If the coating thickness is not uniform along the fibreaxis, then the model explains the mechanism for the formationand propagation of hot-spots.     

PHOTO-OXIDATION OF THYMINE SENSITIZED BY 2-METHYL-1,4-NAPHTHOQUINONE: ANALYSIS OF PRODUCTS INCLUDING THREE NOVEL PHOTO-DIMERS

Abstract —The near-UV photosensitization of thymine by 2-methyl-1,4-naphthoquinone in oxygenated aqueous solution leads to the formation of nine major thymine-derived products. Six of the photoproducts, representing 70% of the initial thymine loss, are also known to be formed by γ-ray or X-ray irradiation of oxygenated water solutions of thymine. They include the cis and trans isomers of 5-hydroperoxy-6-hydroxy-5,6-dihydrothymine, the cis and trans thymine glycols, 5-hydroxy-5-methylhydantoin, and N-formyl-N'-pyruvylurea. The three remaining major products, accounting for a further 25% of the initial thymine loss, are thymine di-adducts of a type not previously reported. Preliminary characterization of these novel photoproducts, based on their UV absorption, mass spectra, and proton and carbon-13 nuclear magnetic resonance spectra, suggests that in each of the three, the thymine moieties are linked by an N(1)-C(5) or N(1)-C(6) bond. A thymine cation radical is implicated as the common precursor of all 9 products. Accordingly. pyrimidine photosensitization by 2-methyl-1,4-naphthoquinone serves as a model system for studying the chemical consequences of radiation-induced ionization of the DNA bases.     

ChemInform Abstract: Fe4Si2Sn7O16: A Combination of FeSn6-Octahedra with Layers of (Fe3Sn)O6-Octahedra; Preparation,Properties, and Crystal Structure.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Spin-orbit matrix elements for internally contracted multireference configuration interaction wavefunctions

An efficient method for the calculation of Breit-Pauli spin-orbit matrix elements for internally contracted multireference configuration interaction wavefunctions is presented. Instead of taking all two-electron contributions of the wavefunction explicitly into account, the most important two-electron contributions of the spin-orbit operator are incorporated by means of an effective one-electron Fock operator. As a further refinement, explicit two-electron contributions can be reinstated for the dominant all-internal parts of the wavefunctions.     

Charged-lepton flavour physics

This write-up on a talk at the 2011 Lepton?CPhoton symposium in Mumbai, India, summarizes recent results in the charged-lepton flavour sector. Searches for charged-lepton flavour violation, lepton electric dipole moments and flavour-conserving CP violation are reviewed here. Recent progress in ??-lepton physics and in the Standard Model prediction of the muon anomalous magnetic moment is also discussed.