Novel combination of orientation measurements and transmission microscopy for experimental determination of grain boundary miller indices in silicon and other semiconductors.

The determination of grain boundary planes in multicrystalline material has only been restricted to transmission electron microscope investigations (Jang et al., 1992; Elgat et al., 1985) or to metallograpical investigations of the grain boundary (Randle et al., 1993). The first method is expensive, and both are complex and time consuming in grain boundary preparation. This paper proposes the determination of grain boundary planes in semiconductor wafer by a combined application of Electron Back Scatter Diffraction and Infrared Transmission Microscopy. In particular, the new method is demonstrated with directional solidificated multicrystalline silicon.

Neurosurgical strategies and operative results in the treatment of tumors of or extending to the petrous apex.

BACKGROUND: Tumors originating from or involving the petrous apex are considered to be an operative challenge due to their deep location and close relationship to critical neural and vascular structures. Extensive skull base approaches have been developed to deal with these lesions. The purpose of this study is to review an institutional series of 57 petrous apex tumors, to report our operative experiences and to address the usefulness and limits of standard approaches. MATERIAL AND METHODS: 57 patients (22 men, 35 women) with petrous apex tumors were treated microsurgically. We analyzed the type of surgical approach, histological diagnoses, pre- and postoperative clinical findings, diagnostic imaging and surgery-associated complications. RESULTS: According to the location and its predominant extension, a retromastoid approach (n=27), subtemporal approach (n=18), subtemporal/anterosigmoid approach (n=5), transnasal-transsphenoidal approach (n=2), pterional approach (n=2) or a subtemporal/retrosigmoid approach, biphasic approach (subtemporal and pterional), transmastoidal approach (n=1 each) was chosen. In the majority of cases, histological analysis revealed a meningeoma (n=31) or neurinoma (n=7). A total tumor resection was accomplished in 37 patients (64.9%). New permanent neurological deficits, mainly cranial nerve palsies, were found in 18 (31.6%), transient deficits in 5 patients (9.6%). Postoperative improvements of neurological deficits were observed in 17 patients (29.8%), and the neurological status remained unchanged in 17 patients (32.7%). CONCLUSION: Complete resection of petrous apex tumors using standard neurosurgical approaches without permanent surgery-associated neurological deficits is achievable in the majority of cases.

Dissociation of colonic apical Na/H exchange activity from bulk cytoplasmic pH.

Intracellular acidification by stimuli rather than CO2 fails to stimulate colonic apical Na/H ex-change and Na absorption. We examined whether Na absorption could be stimulated in the absence of changes in cytoplasmic pH (pHi). Distal colon of male Sprague-Dawley rats was used for pHi measurements with 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein and for flux measurements in Ussing chambers. In 21 mM HCO3-Ringer, increasing PCO2 from 20 to 70 mmHg decreased pHi from 7.51 to 7.03 and increased net Na flux (JnetNa) from 4.2 +/- 0.4 to 6.8 +/- 0.6 mu eq.cm-2.h-1. Similar increases in JnetNa occurred in the absence of mucosal CI and in the presence of phalloidin to inhibit microfilaments or penzolamide to inhibit membrane-bound carbonic anhydrase. sohydric increases in Pco2 did not alter pHi but stimulated JnetNa from 5.1 +/- 0.6 to 7.2 +/- 0.8 mu eq.cm-2.h-1. Carbonyl cyanide m-chlorophenylhydrazone (CCCP) decreased pHi from 7.45 to 7.35 but did not stimulate JnetNa. Butyrate (25 mM) decreased pHi from 7.15 to 7.02 with recovery to baseline within 6 min; however, JnetNa increased by 2.2 mu eq.cm-2.h-1 for 60 min. We conclude that apical Na/H exchange activity is unresponsive to changes in bulk pHi and is independent of Cl/HCO3 exchange, microfilaments, and membrane-bound carbonic anhydrase. The presence of an H-tight, CO2, and butyrate-permeable subapical domain is postulated.