Characterization of porosity in a 19th century painting ground by synchrotron radiation X-ray tomography

The enzyme 2,4′-dihydroxyacetophenone dioxygenase (or DAD) catalyses the conversion of 2,4′-dihydroxyacetophenone to 4-hydroxybenzoic acid and formic acid with the incorporation of molecular oxygen. Whilst the vast majority of dioxygenases cleave within the aromatic ring of the substrate, DAD is very unusual in that it is involved in C—C bond cleavage in a substituent of the aromatic ring. There is evidence that the enzyme is a homotetramer of 20.3 kDa subunits each containing nonhaem iron and its sequence suggests that it belongs to the cupin family of dioxygenases. By the use of limited chymotrypsinolysis, the DAD enzyme fromAlcaligenessp. 4HAP has been crystallized in a form that diffracts synchrotron radiation to a resolution of 2.2 Å.

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Static Atomic Displacements in Crystalline Solid Solution Alloys

MRS Proceedings ◽

10.1557/proc-437-181 ◽

1996 ◽

Vol 437 ◽

Cited By ~ 3

Author(s):

Gene Ice ◽

Cullie Sparks ◽

J. Lee Robertson ◽

J. Ernest Epperson ◽

Xiaogang Jiang

Keyword(s):

Synchrotron Radiation ◽

Crystalline Solid ◽

Local Order ◽

Chemical Order ◽

X Ray ◽

Atomic Displacements ◽

X Ray Scattering ◽

New Information ◽

Z Contrast

AbstractAtom size differences induce static displacements from an average alloy lattice and play an important role in controlling alloy phase stability and properties. The details of this role however, are difficult to study; chemical order and displacements are strongly interrelated and static displacements are hard to measure. Diffuse x-ray scattering measurements with tunable-synchrotron radiation can now measure element-specific static displacements with an accuracy of ± 0.1 pm and can simultaneously measure local chemical order out to 20 shells or more. Ideal alloys for diffuse scattering analysis with synchrotron radiation, are those that have previously been the most intractable: alloys with small Z contrast, alloys with only local order and alloys with small size differences. The combination of precise characterization of local chemical order and precise measurement of static displacement provides new information that challenges existing alloy models. We report on an ongoing systematic study of static displacements in the Fe/Ni/Cr alloys and compare the observed static displacements to the static displacements predicted by current theories. The availability of more brilliant 3rd generation hard x-ray sources will greatly enhance these measurements.

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Characterization of III-nitride Based Schottky UV Detectors with Wide Detectable Wavelength Range (360–10 nm) using Synchrotron Radiation

MRS Proceedings ◽

10.1557/proc-798-y6.6 ◽

2003 ◽

Vol 798 ◽

Author(s):

Atsushi Motogaito ◽

Kazumasa Hiramatsu ◽

Yasuhiro Shibata ◽

Hironobu Watanabe ◽

Hideto Miyake ◽

...

Keyword(s):

Synchrotron Radiation ◽

Schottky Barrier ◽

Wavelength Range ◽

Epitaxial Layer ◽

Device Performance ◽

Uv Detectors ◽

X Ray ◽

High Responsivity ◽

Vacuum Uv

ABSTRACTCharacterizations of transparent Schottky barrier GaN and AlGaN UV detectors in the vacuum UV (VUV) and soft X-ray (SX) region using synchrotron radiation are described. In the GaN UV detectors, the responsivity achieved about 0.05 A/W at 95 eV (13 nm). Thus, their device performance is shown between 3.4 and 100 eV (10 and 360 nm). Furthermore, the high responsivity spectra were realized by using AlGaN Schottky UV detectors consisting of Al0.5Ga0.5N on AlN epitaxial layer.

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