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Structure of liquid equiatomic potassium–lead alloy: A neutron diffraction experiment (1987)

Saboungi, Marie-Louise ; Blomquist, R. ; Volin, K. J. ; [et al.]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 87 (1987), S. 2278-2281

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: Neutron diffraction measurements have been performed on liquid equiatomic potassium–lead alloy at T=870, 900, and 930 K to determine the influence of temperature on the structure. A well-defined first sharp diffraction peak (FSDP) at Q=0.96 A(ring)−1, similar to that found in glassy materials, was obtained in the total structure factors S(Q) at the three temperatures. While the position of the peak remained unaffected by temperature changes, its magnitude decreased with increasing temperature. The other features of S(Q) were almost unaltered by temperature, as expected. The FSDP can be related to the presence of chemical bonds or clusters whose stability decreases with increasing temperature. A molecular model based on the random packing of K4Pb4 structural units is shown to give a remarkable correspondence with the measured structure factors.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.453157

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Effects of scopolamine and physostigmine on recognition memory in monkeys with ibotenic-acid lesions of the nucleus basalis of Meynert (1987)

Aigner, T. G. ; Mitchell, S. J. ; Aggleton, J. P. ; [et al.]

Springer

Psychopharmacology 92 (1987), S. 292-300

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ISSN: 1432-2072

Keywords: Cholinergic system ; Drug effects ; Ibotenic acid ; Memory ; Monkeys ; Nucleus basalis of Meynert

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract Monkeys with bilateral ibotenic-acid lesions of the nucleus basalis of Meynert, an area rich in cholinergic neurons that innervate the cerebral cortex, were compared with unoperated control monkeys on a recognition memory task. Although animals with large lesions had substantial reductions of cortical choline acetyltransferase activity, none showed impairment in the task. Lesion effects were observed, however, when performance was assessed following administration of a muscarinic receptor blocker (scopolamine) or a cholinesterase inhibitor (physostigmine). Although scopolamine produced dose-related impairments in both groups, this effect was greater in the experimental animals. Conversely, whereas physostigmine produced modest improvement in performance in the control group, no such improvement was observed in the experimental animals. The altered sensitivity to the mnemonic effects of cholinergic agents in the experimental group suggests that the cholinergic neurons of the nucleus basalis of Meynert contribute to recognition memory.