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Imaging biomarkers for Alzheimer's disease include medial temporal lobe
atrophy (MTLA) depicted on computed tomography (CT) or magnetic resonance
imaging (MRI) and patterns of reduced metabolism on fluorodeoxyglucose
positron emission tomography (FDG-PET).
To investigate whether MTLA on head CT predicts the diagnostic usefulness
of an additional FDG-PET scan.
Participants had a clinical diagnosis of Alzheimer's disease
(n = 37) or dementia with Lewy bodies (DLB;
n = 30) or were similarly aged controls
(n = 30). We visually rated MTLA on coronally
reconstructed CT scans and, separately and blind to CT ratings, abnormal
appearances on FDG-PET scans.
Using a pre-defined cut-off of MTLA ⩾5 on the Scheltens (0–8) scale, 0/30
controls, 6/30 DLB and 23/30 Alzheimer's disease had marked MTLA. FDG-PET
performed well for diagnosing Alzheimer's disease v. DLB
in the low-MTLA group (sensitivity/specificity of 71%/79%), but in the
high-MTLA group diagnostic performance of FDG-PET was not better than
In the presence of a high degree of MTLA, the most likely diagnosis is
Alzheimer's disease, and an FDG-PET scan will probably not provide
significant diagnostic information. However, in cases without MTLA, if
the diagnosis is unclear, an FDG-PET scan may provide additional
clinically useful diagnostic information.
We report the synthesis of a series of highly functional metal chelated silyl- and tert-butyl-protected 2, 3-diaminomethyl norbornene derivatives. Subsequent alterations to the previously synthesized norbornene adducts afford many other derivatives containing such functionalities as alkyl, cyano, esters, and ethers. These derivatives are then subjected to ring-opening metathesis polymerization (ROMP) employing a ruthenium homogeneous catalyst to afford phase separated block polymers. The block polymers formed serve as unique templates for the formation of size controlled metal nanoclusters having a narrow dispersion. These metal nanoclusters containing diblock polymers are evaluated as unique electrical and optical materials.
Sensitive measurements of electromigration-induced resistance changes in metallization interconnects have been previously interpreted as due to precipitation effects, vacancy concentration changes and local stress changes (due to the piezoresistance effect). The latter have the potential for characterizing the early stages of electromigration-induced diffusive phenomena prior to larger scale effects such as voiding and subsequent localized joule heating which seriously complicate the interpretation of small resistance changes. However the utility of such “early" measurements is also hindered by lack of an accurate knowledge of the stress coefficient of resistivity as a proper characterization of the change in strain state of the Al. We present measurements of the effects of volumetric strain on the resistivity of Al interconnects where the strain is induced by thermal expansion mismatch between the Al and surrounding passivations. The piezoresistance effect is characterized by properly accounting for the degree of interconnect constraint (and volumetric strain) induced by thermal expansion mismatch as a function of temperature for both passivated and unpassivated lines. Sensitive interconnect resistance versus temperature measurements for differently constrained interconnects (with different volumetric strains) thus allows for the measurement of the piezoresistance effect. Other effects such as solute or vacancy concentration changes with temperature are minimized since the measurements are performed by cooling the passivated and unpassivated lines from room temperature to approximately 70K, rather than by significant heating above room temperature. We determine the piezoresistance coefficient, defined as dρ/dɛv, where ρ = resistivity and ɛv = volumetric strain, to be approximately 1.5−5 Ω-cm, in rough agreement with previous work. The interpretation of sensitive resistance measurements as volumetric strains in isolated sections of interconnects undergoing electromigration-induced diffusion processes is described for specialized test structures.
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