Amplitude-distribution analysis of acoustic emission

Amplitude distribution of acoustic-emission events generated during fracture of materials contains the potential information about the fracture mechanisms. A methodology is developed for the analysis of acousticemission burst signals. Based on this, the amplitude distributions can be characterized from the cumulative counts and events data alone. This simplifies the equipment as well as the data analysis. A model for amplitude distribution is proposed here, which can potentially identify two mechanisms operating simultaneously. It is also shown analytically that cumulative counts (N) are linearly related to summation of amplitudes of events and thatN can be considered a measure of the total energy of acoustic emission only if the amplitude distribution does not change significantly.     

Differential inhibition of postnatal brain,spinal cord and body growth by a growth hormone antagonist

Background  

Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH.     

Solution phase photolysis of 1,2-dithiane alone and with single-walled carbon nanotubes

Photolysis of 1,2-dithiane (1) in acetonitrile with single walled carbon nanotubes (SWCNTs) was earlier reported to form thiol-functionalized SWCNTs via the butane-1,4-dithiyl diradical (2). The present study shows that 2 instead undergoes a facile rearrangement to thiophane-2-thiol (6). This photoreaction is clean, rapid, and irreversible under 313 nm irradiation. The secondary photolysis of 6 with SWCNTs at a shorter wavelength (254 nm) leads to 2-thiophanyl radicals 8, which derivatize SWCNTs by covalent attachment. Pyrolysis of the resulting "sulfurized SWCNTs" affords a mixture of organosulfur compounds, including thiophene formed by dehydrogenation. An unknown additional mechanism causes high TGA weight loss and a large incorporation of sulfur.     

Moments of the intensity of a non-circular Gaussian laser speckle pattern in the diffraction field

Statistics of the intensity of a non-circular Gaussian speckle field that arises in imaging and propagation geometries was analyzed in the past but no general expressions for the moments of intensity were given. In this paper general expressions for the moments of the intensity of a non-circular speckle field are derived and their dependence on the path and beam parameters is discussed.     

Effect of three-body forces on the lattice dynamics of noble metals

A simple method to generate an effective electron-ion interaction pseudopotential from the energy wave number characteristic obtained by first principles calculations has been suggested. This effective potential has been used, in third order perturbation, to study the effect of three-body forces on the lattice dynamics of noble metals. It is found that three-body forces, in these metals, do play an important role. The inclusion of such three-body forces appreciably improves the agreement between the experimental and theoretical phonon dispersion curves.     

Photochemical E-Z isomerization of meta-terphenyl-protected phosphaalkenes and structural characterizations

A series of phosphaalkenes, E-ArP=C(H)Ar' (Ar = 2,6-Mes2C6H3, Ar' = Ph (1a); Ar = 2,6-Mes2C6H3, Ar' = p-C6H4Br (2a); Ar = 4-Br-2,6-Mes2C6H2, Ar' = Ph (3a); Ar = 4-Br-2,6-Mes2C6H2, Ar' = p-C6H4Br (4a)) have been prepared by phospha-Wittig reactions and characterized. Exposure of these materials either to room light over an extended period of time (days) or to UV light (hours) produced equilibrium mixtures of the E and Z isomers (1b-4b) as indicated by 1H and 31P NMR spectroscopy. The structures of compounds 4a and 4b were determined by single-crystal X-ray diffraction methods. Variable-temperature (1)H NMR studies of 4b indicate hindered rotation about the P-CAr bond, with DeltaH(double dagger) = 13.8 kcal/mol and DeltaS(double dagger) = 1.3 eu. The electronic structures of E- and Z-PhP=C(H)Ph have been examined using density functional theory.