Physics Commons^™

Region-Of-Interest Material Decomposition From Truncated Energy-Resolved Ct, Taly Gilat Schmidt

Biomedical Engineering Faculty Research and Publications

Purpose: Energy-resolved CT using photon-counting detectors has the potential to provide improved material decomposition compared to dual-kVp approaches. However, available photon-counting detectors are susceptible to pulse-pileup artifacts, especially at the periphery of the field of view (FOV) where the object attenuation is low compared to the center of the FOV. Pulse pileup may be avoided by imaging a region-of-interest (ROI) where the dynamic range is expected to be limited. This work investigated performing material decomposition and reconstructing ROI basis images from truncated energy-resolved data.

Methods: A method is proposed to reconstructimages of basis functions primarily contained within the ROI, such …

Synthesis, Molecular Structure, And Reactivity Of Dinuclear Copper(Ii) Complexes With Carboxylate-Rich Coordination Environments, Richard C. Holz, John M. Bradshaw, Brian Bennett

Physics Faculty Research and Publications

The dinucleating ligand N,N‘-(2-hydroxy-5-methyl-1,3-xylylene)bis(N-(carboxymethyl)glycine) (CH₃HXTA) has been used to synthesize the dinuclear Cu(II) bis(pyridine) complex Na[Cu₂(CH₃HXTA)(Py)₂]·1.5(1,4-dioxane) (Na(1)):  triclinic space group P1̄ (a = 12.550(3) Å, b = 13.413(3) Å, c = 13.540(4) Å, α = 117.12(2)°, β = 104.70 (2)°, and γ = 92.13(2)°). The structure shows two distinct distorted square pyramidal Cu(II) centers with each Cu(II) ion bound by two carboxylate oxygen atoms, one amine nitrogen atom, a phenolate oxygen atom, and one pyridine nitrogen atom. The Cu--Cu separation is 3.531 Å, …

Spectroscopically Distinct Cobalt(Ii) Sites In Heterodimetallic Forms Of The Aminopeptidase From Aeromonas Proteolytica:  Characterization Of Substrate Binding, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

The Co(II)Zn(II)- and Zn(II)Co(II)-substituted derivatives of the aminopeptidase from Aeromonas proteolytica (AAP) were probed by EPR spectroscopy. EPR spectra of the high-spin S = ³/₂ Co(II) ions in [CoZn(AAP)] and [ZnCo(AAP)] indicated that each metal binding site provides a spectroscopically distinct signature. For [CoZn(AAP)], subtraction of EPR spectra recorded at pH 7.5 and 10 revealed that two species were present and that the relative contributions to each of the experimental spectra were pH-dependent. The first EPR species, predominant at lower pH values, was simulated as a relatively featureless axial signal with g_eff values of 2.20, 3.92, and …

Epr Studies On The Mono- And Dicobalt(Ii)-Substituted Forms Of The Aminopeptidase From Aeromonas Proteolytica. Insight Into The Catalytic Mechanism Of Dinuclear Hydrolases, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

The structure and function of the prototypical dinuclear hydrolase, namely, the aminopeptidase from Aeromonas proteolytica (AAP), was probed by EPR spectroscopy of the mono- and dicobalt(II)-substituted derivatives. A new systematic protocol for the interpretation of Co(II) EPR spectra is described and the S = ³/₂ spin states of the Co(II)-substituted forms of the enzyme have been characterized. This protocol allows the simulation of line shape using theoretically allowed g_eff values corresponding to an isotropic g_real value. In addition, the gross distortion of EPR spectra of high-spin S = ³/₂ Co(II) ions has been investigated, …

Evidence Favoring Molybdenum−Carbon Bond Formation In Xanthine Oxidase Action: 17O- And 13C-Endor And Kinetic Studies, Barry D. Howes, Robert C. Bray, Raymond L. Richards, Nigel A. Turner, Brian Bennett, David J. Lowe

Physics Faculty Research and Publications

The reaction mechanism of the molybdoenzyme xanthine oxidase has been further investigated by ¹³C and ¹⁷O ENDOR of molybdenum(V) species and by kinetic studies of exchange of oxygen isotopes. Three EPR signal-giving species were studied:  (i) Very Rapid, a transient intermediate in substrate turnover, (ii) Inhibited, the product of an inhibitory side reaction with aldehyde substrates, and (iii) Alloxanthine, a species formed by reaction of reduced enzyme with the inhibitor, alloxanthine. The Very Rapid signal was developed either with [8-¹³C]xanthine or with 2-oxo-6-methylpurine using enzyme equilibrated with [¹⁷O]H₂O. The Inhibited signal was …