6,706 research outputs found
Weak Bond Screening System
The most commonly used nondestructive inspection (NDI) technique for adhesively bonded and composite structures is the ultrasonic C-scan technique operating in a pulse-echo or through-transmission mode. They are most effective in detecting disbonds, voids, delamination and foreign inslusions, but are ineffective for the detection of weak bonds at the adhesive points. Weak bonds are mostly caused by improper surface cleaning of substrates. There is no air space at the adhesive joints where the substrate and the adhesive are in intimate contact with each other. This results in a lack of interface for ultrasound reflection required for their detection by conventional ultrasonic NDI techniques. Other ultrasonic techniques such as ultrasonic spectroscopy and ultrasonic resonance testers also suffer from the same disadvantage
Quasiparticle-like peaks, kinks, and electron-phonon coupling at the (,0) regions in the CMR oxide LaSrMnO
Using Angle-Resolved Photoemission (ARPES), we present the first observation
of sharp quasiparticle-like peaks in a CMR manganite. We focus on the (,0)
regions of k-space and study their electronic scattering rates and dispersion
kinks, uncovering the critical energy scales, momentum scales, and strengths of
the interactions that renormalize the electrons. To identify these bosons we
measured phonon dispersions in the energy range of the kink by inelastic
neutron scattering (INS), finding a good match in both energy and momentum to
the oxygen bond-stretching phonons
Betel quid chewing as a risk factor for hepatocellular carcinoma: a case-control study
The role of betel quid chewing in the aetiology of hepatocellular carcinoma (HCC) was evaluated in a caseβcontrol study including 263 pairs of age- and sex-matched HCC patients and healthy controls. Serum hepatitis B surface antigen (HBsAg), and antibodies to hepatitis C virus (anti-HCV) were determined, and standardized personal interview conducted using a structured questionnaire. Multivariate analysis indicated that betel quid chewing (odds ratio (OR), 3.49; 95% confidence interval (CI), 1.74β6.96), HBsAg (OR, 16.69; 95% CI, 9.92β28.07), anti-HCV (OR, 38.57; 95% CI, 18.15β81.96), and educational duration of less than 10 years (OR, 1.71; 95% CI, 1.05β2.78) are independent risk factors of HCC. In addition, there was an additive interaction between betel quid chewing and chronic infection with either hepatitis B virus (synergy index, 5.37) or hepatitis C virus (synergy index, 1.66). Moreover, risk on HCC increased as duration of betel quid chewing increased, or amount of betel quid consumed (each P for trend < 0.0001). Β© 2001 Cancer Research Campaign http://www.bjcancer.co
Phase ordering in bulk uniaxial nematic liquid crystals
The phase-ordering kinetics of a bulk uniaxial nematic liquid crystal is
addressed using techniques that have been successfully applied to describe
ordering in the O(n) model. The method involves constructing an appropriate
mapping between the order-parameter tensor and a Gaussian auxiliary field. The
mapping accounts both for the geometry of the director about the dominant
charge 1/2 string defects and biaxiality near the string cores. At late-times t
following a quench, there exists a scaling regime where the bulk nematic liquid
crystal and the three-dimensional O(2) model are found to be isomorphic, within
the Gaussian approximation. As a consequence, the scaling function for
order-parameter correlations in the nematic liquid crystal is exactly that of
the O(2) model, and the length characteristic of the strings grows as
. These results are in accord with experiment and simulation. Related
models dealing with thin films and monopole defects in the bulk are presented
and discussed.Comment: 21 pages, 3 figures, REVTeX, submitted to Phys. Rev.
Electronic structure investigation of GdNi using X-ray absorption, magnetic circular dichroism and hard x-ray photoemission spectroscopy
GdNi is a ferrimagnetic material with a Curie temperature Tc = 69 K which
exhibits a large magnetocaloric effect, making it useful for magnetic
refrigerator applications. We investigate the electronic structure of GdNi by
carrying out x-ray absorption spectroscopy (XAS) and x-ray magnetic circular
dichroism (XMCD) at T = 25 K in the ferrimagnetic phase. We analyze the Gd
M-edge ( - ) and Ni L-edge ( - ) spectra using
atomic multiplet and cluster model calculations, respectively. The atomic
multiplet calculation for Gd M-edge XAS indicates that Gd is trivalent
in GdNi, consistent with localized states. On the other hand, a model
cluster calculation for Ni L-edge XAS shows that Ni is effectively
divalent in GdNi and strongly hybridized with nearest neighbour Gd states,
resulting in a -electron count of 8.57. The Gd M-edge XMCD spectrum
is consistent with a ground state configuration of S = 7/2 and L=0. The Ni
L-edge XMCD results indicate that the antiferromagnetically aligned Ni
moments exhibit a small but finite magnetic moment ( 0.12
) with the ratio 0.11. Valence band hard x-ray
photoemission spectroscopy shows Ni features at the Fermi level,
confirming a partially filled band, while the Gd states are at high
binding energies away from the Fermi level. The results indicate that the Ni
band is not fully occupied and contradicts the charge-transfer model for
rare-earth based alloys. The obtained electronic parameters indicate that GdNi
is a strongly correlated charge transfer metal with the Ni on-site Coulomb
energy being much larger than the effective charge-transfer energy between the
Ni and Gd states.Comment: 9 pages, 6 figures, text and figures revise
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