Charge Transfer and Built-in Electric Fields between a Crystalline Oxide and Silicon.

We report charge transfer and built-in electric fields across the epitaxial SrNb_{x}Ti_{1-x}O_{3-δ}/Si(001) interface. Electrical transport measurements indicate the formation of a hole gas in the Si and the presence of built-in fields. Hard x-ray photoelectron measurements reveal pronounced asymmetries in core-level spectra that arise from these built-in fields. Theoretical analysis of core-level spectra enables built-in fields and the resulting band bending to be spatially mapped across the heterojunction. The demonstration of tunable charge transfer, built-in fields, and the spatial mapping of the latter, lays the groundwork for the development of electrically coupled, functional heterojunctions.

Engineered Unique Elastic Modes at a BaTiO_{3}/(2×1)-Ge(001) Interface.

The strong interaction at an interface between a substrate and thin film leads to epitaxy and provides a means of inducing structural changes in the epitaxial film. These induced material phases often exhibit technologically relevant electronic, magnetic, and functional properties. The 2×1 surface of a Ge(001) substrate applies a unique type of epitaxial constraint on thin films of the perovskite oxide BaTiO_{3} where a change in bonding and symmetry at the interface leads to a non-bulk-like crystal structure of the BaTiO_{3}. While the complex crystal structure is predicted using first-principles theory, it is further shown that the details of the structure are a consequence of hidden phases found in the bulk elastic response of the BaTiO_{3} induced by the symmetry of forces exerted by the germanium substrate.

Breast biopsy techniques and adequacy of margins.

The change toward breast-conserving surgery for cancer has altered the role of the initial biopsy. We retrospectively analyzed two methods, traditional excisional biopsy (n = 47) and lumpectomy (n = 44) to evaluate their usefulness as the initial procedure for breast-conserving surgery. Lumpectomy required more time (mean +/- SEM, 53 +/- 3 minutes) than traditional biopsy (37 +/- 2 minutes). Margins were verified by microscopic examination to be clear in 73% of the patients in the lumpectomy group and in only 17% of patients in the traditional biopsy group. Patients in the lumpectomy group subsequently underwent more axillary dissections than patients in the traditional biopsy group (31% vs 4%, respectively) and fewer modified radical mastectomies (49% vs 71%, respectively). A correlation between extensive intraductal components and positive margins was found in the lumpectomy group. These data suggest that as the initial biopsy method, lumpectomy more often provides adequate margins and may decrease the number of subsequent procedures on the breast for breast-conserving surgery.

Effects of endothelium on basal tone and agonist and O2 sensitivity in porcine coronary artery.

Paired rings of porcine left anterior descending artery, with and without endothelium as determined by thrombin-induced relaxation, were suspended for isometric force measurement in Krebs solution (95% O2-5% CO2). The response to 50 mM KCl was similar in both preparations, averaging 59.3 +/- 2.5 mN/mm2 (n = 28). In the absence of any treatment, de-endothelialized rings (-E) spontaneously contracted; i.e., a basal tone of 21.8 +/- 2.0% of the control 50 mM KCl contraction was measured against the base line after an N2-induced relaxation. Intact rings (+E) developed a basal tone of only 1.8 +/- 0.7% (n = 14). Upon decreasing PO2 in the bath from 95 to 20%, (approximately 665-140 Torr) -E showed a 12.9 +/- 2.8% increase in force compared with only 1.5 +/- 0.6% for +E (n = 10). Norepinephrine also preferentially constricted the -E rings (1 x 10(-6) M: -E = 13.6 +/- 2.0%, +E = 0.6 +/- 0.3%; 3 x -6 M: -E = 21.7 +/- 3.1%, +E = 3.3 +/- 1.1%, n = 8). A similar increase in sensitivity of the -E compared with the +E ring was observed for methoxamine, a nonmetabolized, alpha-1-selective agonist, KCl, Bay K 8644 and histamine, suggesting that the level of tone and not the endothelium per se underlies the changes in sensitivity. To test this hypothesis, the vasoconstrictive effects of decreasing PO2 and norepinephrine were also studied with tone altered by 10 mM KCl which increased the tone in both -E and +E.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on mechanisms of diltiazem-induced protection of the ischemic myocardium: selective myocardial depressant action of diltiazem on an ischemic isolated blood-perfused canine papillary muscle preparation.

The effect of diltiazem on the contractile and vascular responses to 2 min of total occlusion and reperfusion was investigated in isolated blood-perfused canine papillary muscle preparations. Diltiazem, in doses (3 and 10 micrograms/min) that increased coronary blood flow but did not change developed tension and maximum rate of tension development (dT/dt) in papillary muscle before occlusion, attenuated tension development between 40 and 120 sec of ischemia. At-60 sec postocclusion, developed tension was at 36 +/- 4, 37 +/- 5 and 44 +/- 4% below preocclusion levels for 3, 10 and 100 micrograms/min of diltiazem, respectively (nondiltiazem treated = 24 +/- 3%). The dT/dt increased to 22 +/- 6% above preocclusion value during ischemia in nondiltiazem-treated preparations. This was blocked by diltiazem in a dose-dependent fashion. Propranolol and nitroprusside did not modify the developed tension and the increase in dT/dt of the papillary muscle during occlusion. On reperfusion, an overshoot in developed tension to 22 +/- 4% above preocclusion level was observed. This was significantly reduced by diltiazem and propranolol but not by nitroprusside. Diltiazem inhibited the maximal peak reactive hyperemia response after 2 min of occlusion by 30 to 38%. Both propranolol and nitroprusside did not change this response. The results show that diltiazem selectively depresses the inotropic state of the ischemic myocardium and suggest that a diltiazem-induced reduction in myocardial oxygen consumption during ischemia may contribute to the protection of ischemic myocardium and the reduction in reactive hypermia response in the ischemic heart.

Contractile performance, mitochondrial function and blood flow distribution in porcine heart with induced coronary collateral circulation.

Progressive stenosis of the proximal left anterior descending coronary artery in young pigs was surgically induced over eight weeks and was accompanied by the development of a coronary collateral circulation originating from the right coronary artery. The antero-apical left ventricular myocardium dependent on this induced collateral blood supply became hypokinetic compared with the other regions of the left ventricle in the same hearts, and compared with the same region in different hearts, where the native circulation exists. Regional myocardial mechanics determined as fractional systolic shortening was 12.5 +/- 1.5% in normal regions, 0.7 +/- 2.4% in collateral-dependent myocardium, and in acutely ischemic myocardium was -2.0 +/- 1.3%, indicative of systolic lengthening. The rate of state 3 respiration of isolated mitochondria was depressed by 20% in collateral regions and by 64% in acutely ischemic regions relative to values obtained in mitochondria from respective normal myocardium (300 natoms of oxygen/min/mg mitochondria protein). Regional myocardial blood flow determined by 15 mu radionuclide labelled spheres revealed subendocardial hypoperfusion of 0.34 +/- 0.11 ml/min/g tissue in the collateral-dependent regions compared to 1.06 +/- 0.26 ml/min/g tissue in the normal regions. Transmural ischemia was observed (less than 0.10 ml/min/g tissue) in regions subjected to acute coronary artery ligation. Light microscopy revealed patchy fibrotic lesions predominately associated with the subendocardial half of the collateral dependent myocardial wall. Accordingly, the hypokinesia of collateral-dependent myocardium is more likely the result of blood flow abnormalities and loss of contractile elements than from mitochondrial dysfunction.