Search

Epitaxially laterally overgrown (ELO)-GaN substrates with dislocation-free regions can be prepared with a relatively small thickness using atmospheric pressure metal-organic chemical vapor deposition (MOCVD). In order to determine the effect of ELO-GaN layer on the reliability of blue–violet laser diodes (BV-LDs), we fabricated BV-LDs on the lateral-growth region of the ELO-GaN layer. The thickness of the ELO-GaN layer was maintained at 5 μm to inhibit wafer bending, so the total thickness of the BV-LDs was approximately 7 μm. The lifetime of the BV-LDs with a constant output power of 20 mW under CW operation at 25°C was more than 500 h. This lifetime is several times that of our conventional BV-LDs on sapphire substrates. The ELO-GaN layer was very effective in raising the lifetime of BV-LDs.

The well-number dependence of the optical pumping threshold power for stimulated emission of GaInN multiple quantum-well (MQW) laser structures was investigated. The pumping threshold power for a three GaInN MQW sample was found to be as low as 33 kW/cm 2 at room temperature. The room-temperature pulsed operation of a five GaInN MQW laser diode (LD), whose number of wells was determined based on the optical pumping experiment, was also demonstrated. The lowest threshold current density was 9.5 kA/cm 2 . The lasing wavelength was 417.5 nm with a full-width at half-maximum (FWHM) less than the spectrum resolution of 0.2 nm.

Pharmacologic stress tests are used to evaluate the significance of coronary arterial stenosis, and adenosine and dobutamine are often used for this purpose. The aim of this study was to examine coronary hemodynamics in 16 patients with stable exertional angina who had organic stenosis (> 90%) in the left anterior descending coronary arteries and in 13 control subjects at baseline and during separate intravenous infusions of dobutamine (20 micrograms/kg per min [corrected]) and adenosine (140 micrograms/kg per min [corrected]). Measurements of great cardiac vein blood flow and lactate and oxygen contents in the blood from the aortic root and great cardiac vein were analyzed in patients with ischemic signs of myocardial ischemia (ST-segment depression in the precordial ECG leads and/or myocardial lactate production) during the infusions (in 11 patients during adenosine infusion and in 12 patients during dobutamine infusion) and in control subjects. Myocardial oxygen consumption during adenosine infusion did not change compared with the baseline in both groups, whereas it increased during dobutamine infusion in both groups (p < 0.01 compared with the baseline in each case). However, great cardiac vein blood flow was significantly increased compared with the baseline during both infusions in both groups (p < 0.01 compared with baseline in each case), and the oxygen contents of great cardiac vein blood, which contains effluent from the ischemic region, showed no decrease but increased significantly during both infusions in the patients in comparison with control subjects. Although the global oxygen supply was excessive, myocardial ischemia occurred during dobutamine and adenosine infusions in the patients. As myocardial oxygen consumption remained unchanged during adenosine infusion, regional myocardial flow reduction, possibly as a result of flow maldistribution, may contribute, at least partly, to adenosine-induced myocardial ischemia. An increase in myocardial oxygen consumption may be the principal cause of myocardial ischemia during dobutamine infusion, but an inappropriate flow increase in normal myocardium may occur during dobutamine-induced ischemia.

Background: Plasma levels of B-type natriuretic peptide (BNP) are markedly increased in patients with heart failure and acute myocardial infarction. The changes in plasma BNP levels in the treatment of acute myocardial infarction with angiotensin-converting enzyme inhibitors have not been examined well. This study was designed to examine the effects of early angiotensin-converting enzyme inhibitor therapy on plasma BNP levels in patients with acute myocardial infarction. Methods and Results: We measured the plasma levels of B-type natriuretic peptide over the time course for 2 weeks in 30 patients with acute myocardial infarction in whom either imidapril (n = 15) or placebo (n = 15) was given at random immediately after admission. Plasma BNP levels increased and reached a peak of 192 ± 28 pg/ML 16 hours after admission; thereafter, the levels decreased and then again increased, forming the second peak of 217 ± 38 pg/ML on the fifth day (biphasic pattern). On the other hand, plasma BNP levels increased and reached a peak level of 190 ± 22 pg/ML 16 hours after admission and then decreased from 2 days after admission until the second week in the imidapril group (monophasic pattern). Left ventricular ejection fraction measured in the second week was significantly higher in the imidapril group than in the control group (62.2 ± 1.1% vs 51.2 ± 3.6%, P Conclusions: It is concluded that plasma BNP levels followed a monophasic pattern after imidapril treatment, whereas a biphasic pattern was followed after placebo, and that plasma BNP levels constitute a marker of ventricular dysfunction in the treatment of acute myocardial infarction with angiotensin-converting enzyme inhibitors.

Objectives. The present study was designed to compare the secretion patterns of two cardiac hormones—A-type (atrial) and B-type (brain) natriuretic peptides—from the ventricles in patients with old myocardial infarction. Background. Plasma levels of these two natriuretic peptides are increased, and their secretion from the ventricles is augmented, in patients with congestive heart failure. Methods. We measured the plasma levels of these two types of natriuretic peptides at the aortic root and the anterior interventricular vein in 42 patients with old myocardial infarction (anterior in 22 and inferior in 20) and 18 control subjects. Results. The difference between the plasma levels of both A- and B-type natriuretic peptide in the anterior interventricular vein and aortic root was significantly greater in the groups with anterior and inferior infarction than in the control group (A-type [mean ± SD] 380 ± 290 and 247 ± 205 pg/ml in the infarction groups vs. 11 ± 14 pg/ml; B-type 497 ± 445 and 75 ± 73 pg/ml vs. 23 ± 16 pg/ml, respectively). The difference between the plasma levels of each peptide at the anterior interventricular vein and aortic root had a significant negative linear correlation with left ventricular ejection fraction in both groups with infarction. The slope of the regression line of the arteriovenous difference of B-type natriuretic peptide at the anterior interventricular vein was significantly steeper in the anterior than in the inferior infarction group (left ventricular ejection fraction −12.801 vs. −1.891, p Conclusions. These results indicate that 1) the secretion of A-and B-type natriuretic peptide from the left ventricle increases in proportion to the severity of left ventricular dysfunction, and 2) secretion of B-type natriuretic peptide is much greater from the infarct than from the noninfarct region, suggesting that the regional ventricular wall stretch caused by infarction strongly stimulates secretion of B-type natriuretic peptide.

Atrial natriuretic peptide (ANP) is reported to dilate a major coronary artery in both experimental animals and humans. Spasm of a major coronary artery is the cause of variant angina pectoris and can be induced by hyperventilation. The effect of the ANP infusion on anginal attack induced by hyperventilation was studied in patients with variant angina pectoris. The study was performed in the early morning on 3 consecutive days in 11 patients with variant angina pectoris in whom the attacks were reproducibly induced by hyperventilation. On days 1 and 3 (saline solution infusion), and day 2 (ANP infusion), hyperventilation was started 14 minutes after beginning infusion of ANP (0.1 microgram/kg/min) or saline solution for 6 minutes. The attacks were induced in all 11 patients by hyperventilation on days 1 and 3. However, the attacks were not induced in any patient on day 2 of the ANP infusion. The plasma ANP level increased from 33 +/- 7 pg/ml to the peak level of 2,973 +/- 479 pg/ml (p0.01) at the end of the ANP infusion, and the plasma level of cyclic guanosine monophosphate (cGMP) increased from 5 +/- 1 pmol/ml to the peak level of 58 +/- 6 pmol/ml (p0.01) 5 minutes after the ANP infusion. The plasma levels of ANP and cGMP did not change after hyperventilation on days 1 and 3. It is concluded that the ANP infusion suppresses the attacks induced by hyperventilation in patients with variant angina pectoris, and cGMP is related to the mechanisms of suppression of the attacks.

The structure and the mechanism of the roughening of lattice-matched GaInP crystals grown on an exactly oriented (111)A and B and a misoriented (111)B GaAs substrate by MOCVD were studied. The overlayer on the (111)A surface was a mosaic crystal. The overlayer on the exactly oriented (111)B surface contained primary twins with a twin plane parallel to the substrate surface. The twin was identified as a “rotation twin” by high-resolution transmission electron microscopy. A multiple twin structure was revealed to form at the periphery of the primary twin, which was found to result in the rough surface of the exactly oriented (111)B GaInP. The suppression of a roughening by growth on an intentionally misorientated substrate surface would be responsible for the suppression of the primary rotation twinning and further multiple twinning by the preferential growth at steps, which follow the stacking sequence.

Isolated angiitis of the central nervous system (IAC) is an idiopathic type of vasculitis, exclusively affecting small to medium-sized blood vessels of the central nervous system. We report serial angiographical findings, mainly demonstrated with magnetic resonance angiography (MRA) in a case of IAC. A 58-year-old-female came to our hospital because of a sudden headache. Computed tomography (CT) did not show any particular findings. MRA 3 days after the onset revealed diffuse arterial dilatations and segmental stenoses of the middle and anterior cerebral arteries. However, these findings did not lead us to make a diagnosis of IAC. Two days later she was admitted with increased headache and subcortical hemorrhage in the left frontal lobe on CT. Subsequent MRA demonstrated remarkable changes such as dilatated main trunks with segmental stenoses. Steroid pulse therapy was started after definite diagnosis of IAC. She improved gradually and was headache-free 15 days after the onset. Nevertheless, follow-up MRA at 15 days revealed diffusely narrowed anterior and middle cerebral arteries with multiple segmental stenoses. Characteristic findings of angiitis showed improvement at 29 days and had disappeared at 73 days. The patient discontinued corticosteroids and has remained free from headache for the last 7 months.

Brainstem encephalitis is a rare form of encephalitis which should be differentiated from cerebrovascular and neoplastic diseases. The authors report a case of viral brainstem encephalitis mimicking malignant lymphoma. A 55-year-old female was admitted to our hospital with gradually progressive diplopia and left hemiplegia. CT scan revealed low density lesions in the right globus pallidus and the anterior limb of the internal capsule. MRI demonstrated high intensity signals extending into the right cerebral peduncle, temporal lobe, thalamus and the contralateral thalamus on FLAIR images. Petechial hemorrhages were seen in the affected lesions, but no enhancement was observed following administration of a contrast material. CSF examination revealed mild mononuclear cell dominant pleocytosis. Both early and delayed images of 123I-IMP SPECT revealed marked hot spots corresponding to the lesions on FLAIR images. CT-guided stereotactic biopsy was useful for early diagnosis.

In order to elucidate biosynthesis and secretion of natriuretic peptides in the early phase of acute myocardial infarction (AMI), we measured the plasma level of brain natriuretic peptide (BNP), a novel cardiac hormone secreted from the ventricle, in patients with AMI and compared with that of atrial natriuretic peptide (ANP). The plasma level of BNP increased rapidly (within hours from the onset of AMI) and markedly (greater than 100 times the normal level) as compared to that of ANP. The plasma ANP level correlated with pulmonary capillary wedge pressure (PCWP), whereas the plasma BNP level did not correlate with PCWP but highly correlated inversely with cardiac index. These results indicate that BNP is secreted from the heart much more acutely and prominently than ANP in the early phase of AMI, in association with left ventricular dysfunction.

BACKGROUND This study was designed to examine the hemodynamic, renal, and hormonal effects of brain natriuretic peptide (BNP) infusion in patients with congestive heart failure (CHF) and in control subjects. METHODS AND RESULTS We infused synthetic human BNP at a rate of 0.1 micrograms/kg/min. BNP infusion decreased pulmonary capillary wedge pressure (control, from 5 +/- 1 to 2 +/- 1 mm Hg, p less than 0.01; CHF, from 21 +/- 3 to 14 +/- 4 mm Hg, p less than 0.05) and systemic vascular resistance (control, from 1,264 +/- 75 to 934 +/- 52 dyne.sec.cm-5; CHF, from 2,485 +/- 379 to 1,771 +/- 195 dyne.sec.cm-5; p less than 0.01, respectively) and increased stroke volume index (control, from 49.9 +/- 2.7 to 51.5 +/- 2.3 ml/m2, p = NS; CHF, from 25.6 +/- 3.8 to 32.0 +/- 3.9 ml/m2, p less than 0.01). BNP infusion significantly increased urine volume (control, from 2.3 +/- 0.7 to 7.5 +/- 1.9 ml/min; CHF, from 0.8 +/- 0.2 to 5.3 +/- 1.0 ml/min; p less than 0.01, respectively), excretion of sodium (control, from 79.2 +/- 21.6 to 332.8 +/- 70.9 microEq/min; CHF, from 77.4 +/- 20.8 to 753.5 +/- 108.0 microEq/min; p less than 0.01, respectively), and excretion of chloride (control, from 72.5 +/- 18.4 to 256.0 +/- 43.3 microEq/min; CHF, from 74.0 +/- 19.6 to 708.8 +/- 103.3 microEq/min; p less than 0.01, respectively). Urinary excretion of sodium and of chloride in response to BNP infusion was higher in patients with CHF than in control subjects (p less than 0.01, respectively). BNP infusion increased the levels of plasma atrial natriuretic peptide (control, from 65 +/- 11 to 84 +/- 14 pg/ml; CHF, from 262 +/- 65 to 301 +/- 62 pg/ml; p less than 0.05, respectively) and decreased plasma aldosterone concentrations in both groups (control, from 43.3 +/- 12.1 to 27.3 +/- 7.1 pg/ml; CHF, from 91.1 +/- 34.3 to 66.3 +/- 27.2 pg/ml; p less than 0.05, respectively). CONCLUSIONS We conclude that BNP infusion improves left ventricular function in patients with CHF by vasodilation and prominent natriuretic action.

We applied transcoronary chemical ablation of the atrioventricular (AV) node to a patient with uncontrollable paroxysmal supraventricular tachycardia (PSVT). Through an angioplasty dilatation catheter. 99% ethanol at a dose of 1.0 ml was selectively infused into the AV nodal artery. Complete AV block with junctional escape rhythm occurred. Two weeks later, the treadmill exercise test was performed according to a modified Bruce protocol. The patient tolerated for 12 min, and the heart rate increased to 85 beats/min. His bundle electrocardiogram showed that the AV block resulted from atrio-Hisian block. Neither atrial nor ventricular extrastimulus could induce the tachycardia. It appeared that chemical ablation was a good method for controlling medically resistant PSVT. Elevation of serum creatine kinase was observed when ethanol overflowed during the ablation procedure. Occlusion of branches of the AV artery and mild hypokinesis in the inferobasal wall of the left ventricle were seen.

We have developed a new combined system of a field-ion scanning tunneling microscope (FI-STM) and a molecular beam epitaxy (MBE) growth chamber equipped with six Knudsen-cells and reflection high energy electron diffraction (RHEED). This system allows us to observe compound semiconductor surfaces such as GaAs while keeping their surfaces clean. In this paper, this system was applied to GaAs(100) and Si(110) surfaces. A GaAs sample was heated up to 550°C and a GaAs thin epitaxial film was grown by MBE. 2×, 4× structures were observed by RHEED and the sample was moved to the FI-STM chamber where STM images of 2×4 reconstructed GaAs(100) surfaces were obtained. Besides the observation of GaAs, FI-STM was also applied to the Si(110) surface. We have studied the change of the Si(110) surface structures at different conditions of heating and cooling.

The design and performance of an ion-sputtering gun for cleaning crystal surfaces in-situ in an ultra-high-vacuum electron microscope are reported. The electron microscopic aspects of ion-bombardment damage to ionic magnesium oxide, covalent germanium and silicon, and metallic gold and copper crystals, and the effects of annealing after and during sputtering are described. The growth of various kinds of films deposited in-situ on crystals cleaned by ion-sputtering are described and discussed.

Objectives . This study was performed 1) to examine the role of adenosine in the pathogenesis of syndrome X in patients with this syndrome and abnormal results on myocardial scintigrams during exercise, and 2) to determine the susceptibility to myocardial ischemia in this subset of patients with syndrome X. Background . A role for adenosine in the pathogenesis of syndrome X has recently been postulated, but there are few clinical data supporting this hypothesis. Methods . Exercise thallium-201 myocardial scintigraphy after intravenous administration of aminophylline, an adenosine receptor blocking agent, or saline solution and adenosine thallium-201 scintigraphy were performed in 26 patients with syndrome X. Hemodynamic variables during exercise and perfusion defect size after aminophylline and saline infusions were compared. At cardiac catheterization, coronary hemodynamic variables during separate infusions of adenosine and dobutamine were also examined and were compared among patients with abnormal or normal scintigrams and 10 control subjects. Results . Perfusion abnormalities on exercise-thallium-201 scintigraphy occurred in 14 of 26 patients with syndrome X. Intravenous infusion of aminophylline suppressed the scintigraphic perfusion defect and prolonged the time to 1-mm ST segment depression in patients with syndrome X with abnormal exercise scintigrams. Intravenous infusion of adenosine induced a perfusion defect in the same myocardial area where the perfusion defect was observed at exercise in 7 of the 14 patients with syndrome X. At cardiac catheterization, patients with syndrome X with abnormal exercise scintigrams had lower coronary flow reserve and a greater frequency of myocardial lactate production and ST segment depression in response to the infusions of adenosine and dobutamine than did the other two groups. During adenosine infusion, great cardiac vein blood flow and oxygen content were significantly increased and myocardial oxygen consumption and lactate extraction were significantly reduced from baseline without a significant increase in rate-pressure product in this subset of patients with syndrome X. Conclusions . Patients with syndrome X with abnormal exercise scintigrams have high susceptibility to myocardial ischemia during exercise or pharmacologic stress tests, probably owing to reduced coronary flow reserve. A heterogeneous response to endogenous adenosine may contribute to scintigraphic perfusion abnormalities and myocardial ischemia during exercise in this subset of patients with syndrome X.

GaAs substrates implanted selectively with 100 keV Zn ions to a dose of 5×1014 ions/cm2 were annealed at 700–850°C with an encapsulant of plasma CVD silicon nitride. Transmission electron microscopy revealed that gallium nitride is formed at the interface between the substrate and the encapsulant, and tends to grow epitaxially on (001) (GaAs in the process of 850°C annealing. Gallium nitride was observed in the implanted GaAs area, but not in the unimplanted area. Its formation may be attributable to the presence of the amorphous surface layer produced by ion implantation.