Forty-two elderly patients (mean age, 66.2 +/- 5.1 yr) with hypertension, treated for an average of 17.3 years (standard deviation, 10.3), and 42 control subjects (mean age, 66.5 +/- 4.8 yr), matched ...for age, sex, and level of education, were studied with regard to the detection of lesions in the cerebral white matter with magnetic resonance imaging (MRI), particularly with axial T2-weighted images. The assessment of the MRI scans was blinded. Ten hypertensive patients showed confluent lesions in the white matter, versus only 1 control subject (Chi-square test, p = 0.01). The presence of diffuse lesions of the white matter was related to age but not to the known duration of hypertension, nor to the presence of any other cardiovascular risk factors. Cognitive function was measured in 34 hypertensive patients and in 18 control subjects. Results of the Mini-Mental State Examination, the Stroop color-word test, Trailmaking test, and the visual subtest of the Wechsler Memory Scale were worse in patients with confluent lesions of the white matter; there was no difference in mental functioning between hypertensive patients and control subjects with normal white matter or with only small focal lesions. Our findings suggest that long-standing hypertension in some patients may cause not only strokes but also chronic end-organ damage of the brain in the form of demyelination of the white matter, with cognitive decline.
Detailed P31 nuclear magnetic resonance (NMR) measurements are presented on well-characterized single-crystals of antiferromagnetic van der Waals Ni2P2S6. An anomalous breakdown is observed in the ...proportionality of the NMR shift K with the bulk susceptibility χ. This so-called K–χ anomaly occurs in close proximity to the broad peak in χ(T), thereby implying a connection to quasi-two-dimensional (2D) magnetic correlations known to be responsible for this maximum. Quantum chemistry calculations show that crystal field energy level depopulation effects cannot be responsible for the K–χ anomaly. Appreciable transferred hyperfine coupling is observed, which is consistent with the proposed Ni–S–Ni super- and Ni–S–S–Ni super-super-exchange coupling mechanisms. Magnetization and spin-lattice relaxation rate (T1−1) measurements indicate little to no magnetic field dependence of the Néel temperature. Finally, T1−1(T) evidences relaxation driven by three-magnon scattering in the antiferromagnetic state.
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68 5th graders studied a 125-word passage consisting of 18 statements about a fictional fox. Afterwards, Ss tried to reproduce the text and, 1 wk later, took a multiple-choice test. Prior to reading, ...half the Ss mobilized relevant preexisting knowledge. Results indicate that mobilizing significantly facilitated retention of information inconsistent with prior knowledge but did not affect retention of congruous information. A topically organized passage was not better remembered than a topically disorganized one. Results are discussed with reference to assimilation encoding theory and the failure of students to relate discourse to prior knowledge. (15 ref)
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