Electronic structure and valence-bond band structure of cuprate superconducting materials

From ab initio calculations on various clusters representing the La2-xSrxCu(1)O(4) and Y(1)Ba(2)Cu(3)O(7) classes of high-temperature superconductors, it is shown that (i) all copper sites have a Cu(II)(d(9))oxidation state with one unpaired spin that is coupled antiferromagnetically to the spins of adjacent Cu(II) sites; (ii) oxidation beyond the cupric (Cu(II)) state leads not to Cu(III) but rather to oxidized oxygen atoms, with an oxygen ppi hole bridging two Cu(II) sites; (iii) the oxygen ppihole at these oxidized sites is ferromagnetically coupled to the adjacent Cu(II)d electrons despite the fact that this is opposed by the direct dd exchange; and (iv) the hopping of these oxygen ppi holes (in CuO sheets or chains) from site to site is responsible for the conductivity in these systems (N-electron band structures are reported for the migration of these localized charges).     

Feline nasal and paranasal sinus tumours: clinicopathological study, histomorphological description and diagnostic immunohistochemistry of 123 cases

Histological examination was performed in 123 cats with primary nasal and paranasal sinus tumours; 117 had undergone surgical biopsy and six necropsy. Special stains and immunohistochemistry were performed on poorly differentiated cases. Ninety-two percent (113/123) of the tumours were malignant. There was an increased risk for old cats (mean age of 10.9 years), and a male predilection (59% males). Clinical signs and breeds varied with the histological type of tumour. Thirty-nine percent (48/123) of the cases presented with nasal discharge, 21% (26/123) with dyspnea, 20% (24/123) with facial swelling, and 15% (19/123) with epistaxis. Forty-three percent (53/123) of the tumours were of epithelial origin. Adenocarcinomas (18/53) and squamous cell carcinomas (17/53) were the most common epithelial tumours. Fifty percent (26/53) of the epithelial tumours originated from the pseudo-stratified respiratory epithelium of the nasal cavity, 28% (15/53) from the stratified squamous epithelium of the vestibule, 9% (5/53) from olfactory epithelium, 9% (5/53) from submucosal glands and 4% (2/53) from minor salivary glands. Malignant lymphoma (35/123) was the most common tumour. Seventy-one percent (25/35) of the malignant lymphomas were B-cell tumours and 29% (10/35) were T-cell tumours. Six cases of malignant lymphomas were proved to be epitheliotropic T-cell lymphomas. This is the first report of a primary nasal epitheliotropic T-cell lymphoma in cats.     

EPIDEMIOLOGICAL AND GROSS PATHOLOGICAL STUDIES OF ONCHOCERCA GIBSONI INFECTION IN CATTLE

SUMMARY A total of 5712 cattle from 62 properties or localities in northern, central and eastern Australia were examined at abattoirs, and the presence of Onchocerca gibsoni infection was related to region, season when slaughtered, and breed, sex and age of slaughtered cattle. Additionally, these features were also related to nodule characteristics determined from macroscopic examination of all nodules in single (left or right) briskets from 1287 infected cattle selected at random from those examined in abattoirs. Infection rate was 86% and number of nodules per brisket was 3.7 ± 4.1 (Mean ± Standard Deviation). When adjusted for other variables infection rates varied from 18% in central New South Wales to a maximum of 96% in north western Queensland. Number of nodules per brisket in cattle from north western Queensland was 9 times greater than in cattle from central New South Wales. Most nodules (70%) were 1–2 cm in diameter and weighed less than 2 g. The occurrence of changes such as calcification and caseation indicated that 20–30% of nodules studied were undergoing advanced degeneration or resolution. More nodules were detected in autumn than during winter or spring and the proportions of nodules which were hard on palpation, or had thick capsules, both increased during the autumn-spring interval. Although inconclusive, breed differences observed suggested that Bos indicus and B. indicus crossbreds had slightly greater resistance to O. gibsoni infection than cattle of British breed. Infection rate and number of nodules per brisket were greater in bulls than in cows or steers but weight of nodules in steers was greater than in other groups. Percentage of animals infected, and nodule prevalence both increased with increasing age but annual increase in nodule prevalence was less in cattle over 5 years than in younger ones, suggesting development of some immunity in mature cattle.