Xray computed tomography in Zernike phase contrast mode at 8 keV with 50-nm resolution using Cu rotating anode x-ray source

Abstract. High-resolution X-ray computed tomography (XCT) enables nondestructive 3D imaging of complex structures, regardless of their state of crystallinity. This work describes a sub-50 nm resolution XCT system operating at 8 keV in absorption and Zernike phase contrast modes based on a commercially available Cu rotating anode laboratory X-ray source. The system utilizes a high efficiency reflective capillary condenser lens and high-resolution Fresnel zone plates with an outermost zone width of 35 nm and 700 nm structure height resulting in a spatial resolution better than 50 nm currently. Imaging a fragment of the solid oxide fuel cells (SOFC) with 50 nm resolution is presented as an application example of the XCT technique in materials science and nanotechnology

A CLOSER LOOK AT SHALE: REPRESENTATIVE ELEMENTARY VOLUME ANALYSIS WITH LABORATORY 3D X-RAY COMPUTED MICROTOMOGRAPHY AND NANOTOMOGRAPHY

ABSTRACT Though naturally occurring in many regions of the world, shale rock microstructure continues to be much of a mystery. Pore sizes may be very small, typically low 100s of nanometers and even below 10s of nanometers. It is thus very important to determine the volume size that must be examined to understand the oil reserves in a macroscopic shale rock formation, as the small features require a very high resolution imaging system, which usually come with limited field of view. This makes precise quantification of the microstructure a daunting challenge, especially when the analysis needs to be performed in 3D to capture the tortuous paths taken by the pores. The introduction of ultra-high resolution imaging systems is now shedding light on the problem, with the commercialization of precise laboratory x-ray imaging tools. Here, a novel suite of x-ray computed tomography systems is shown to provide unique insight into shale microstructure. Large volumes are measured with as high as sub-1 m resolution using laboratory-based x-ray computed microtomography (VersaXRM) to localize regions-of-interest (ROIs) for further higher resolution analysis. A ROI of cubic volume with ~65 m on each side is isolated for precise analysis with a novel laboratorybased x-ray computed nanotomography system (UltraXRM) capable of 50 nm resolution for quantification of porosity within the shale sample. Using the multi-length scale resolution imaging systems described here, a representative elementary volume (REV) quantification has been performed, which identifies ~30 m as the minimum volume that must be considered in order to quantify pores in shale down to 150 nm linear dimensions. Using a 3D field of view capable of sampling ~4 of these REVs, a precise microstructure analysis is carried out, within which further calculations of pore tortuosity and connectivity are demonstrated. The non-destructive nature of x-ray imaging further opens the door to innovative experimentation, such as time-evolution and studies of microstructure response to varying environmental parameters, such as temperature cycling or surfactant treatment

Non Destructive Failure Analysis Technique With a Laboratory Based 3D X-ray Nanotomography System

ABSTRACT X-ray computed tomography (CT) is a powerful nondestructive 3D imaging technique, which enables the visualization of the three dimensional internal structure of opaque materials such as semiconductor devices. Reports of high resolution CT research on life science, materials and semiconductor has mainly been confined to synchrotron radiation centers. This severely limits the availability and accessibility of x-ray microscopes and the wide proliferation of this methodology. We describe a sub-50nm resolution nanoCT system operating at 8 keV in Zernike phase contrast mode based on a commercially available laboratory x-ray source. The system utilizes high-efficiency Fresnel zone plates with an outermost zone width of 35nm resulting in spatial resolution better than 50 nm. The technical description of the system and failure analysis applications notably in visualizing voids, residues in metal interconnects, and competitive analysis in semiconductor devices will be discussed

The association of two single nucleotide polymorphisms (SNPs) in growth hormone (GH) gene with litter size and superovulation response in goat-breeds

Two active mutations (A 781 G and A 1575 G) in growth hormone (GH) gene, and their associations with litter size (LS), were investigated in both a high prolificacy (Matou, n = 182) and a low prolificacy breed (Boer, n = 352) by using the PCR-RFLP method. Superovulation experiments were designed in 57 dams, in order to evaluate the effect of different genotypes of the GH gene on superovulation response. Two genotypes (AA and AB, CC and CD) in each mutation were detected in these two goat breeds. Neither BB nor DD homozygous genotypes were observed. The genotypic frequencies of AB and CC were significantly higher than those of AA and CD. In the third parity, Matou dams with AB or CC genotypes had significantly larger litter sizes than those with AA and CD (p < 0.05). On combining the two loci, both Matou and Boer dams with ABCD genotype had the largest litter sizes when compared to the other genotypes (p < 0.05). When undergoing like superovulation treatments, a significantly higher number of corpora lutea and ova, with a lower incidence of ovarian cysts, were harvested in the AB and CC genotypes than in AA and CD. These results show that the two loci of GH gene are highly associated with abundant prolificacy and superovulation response in goat breeds

Probing the effect of the non-active-site mutation Y229W in New Delhi metallo-β-lactamase-1 by site-directed mutagenesis, kinetic studies, and molecular dynamics simulations.

New Delhi metallo-β-lactamase-1 (NDM-1) has attracted extensive attention for its high catalytic activities of hydrolyzing almost all β-lactam antibiotics. NDM-1 shows relatively higher similarity to subclass B1 metallo-β-lactamases (MβLs), but its residue at position 229 is identical to that of B2/B3 MβLs, which is a Tyr instead of a B1-MβL-conserved Trp. To elucidate the possible role of Y229 in the bioactivity of NDM-1, we performed mutagenesis study and molecular dynamics (MD) simulations. Although residue Y229 is spatially distant from the active site and not contacting directly with the substrate or zinc ions, the Y229W mutant was found to have higher kcat and Km values than those of wild-type NDM-1, resulting in 1 ∼ 7 fold increases in k(cat) /K(m) values against tested antibiotics. In addition, our MD simulations illustrated the enhanced flexibility of Loop 2 upon Y229W mutation, which could increase the kinetics of both substrate entrance (kon) and product egress (koff). The enhanced flexibility of Loop 2 might allow the enzyme to adjust the geometry of its active site to accommodate substrates with different structures, broadening its substrate spectrum. This study indicated the possible role of the residue at position 229 in the evolution of NDM-1