Search

Motivated by recent experimental findings on the hyperfine signal of nitrogen donor (NC) in 4H and 6H SiC, we calculate the hyperfine tensors within the framework of density functional theory. We find that there is negligible hyperfine coupling with 29Si isotopes when NC resides at h site both in 4H and 6H SiC. We observe measurable hyperfine coupling to a single 29Si at k site in 4H SiC and k1 site in 6H SiC. Our calculations unravel that such Si hyperfine coupling does not occur at k2 site in 6H SiC. Our findings are well corroborated by our new electron paramagnetic resonance studies in nitrogen doped 6H SiC. [ABSTRACT FROM AUTHOR]

The carbon vacancy (Vc) has been suggested by different studies to be involved in the Z1/Z2 defect-a carrier lifetime killer in SiC. However, the correlation between the Z1/Z2 deep level with Vc is not possible since only the negative carbon vacancy (V-c) at the hexagonal site, V-c(h), with unclear negative-U behaviors was identified by electron paramagnetic resonance (EPR). Using freestanding n-type 4H-SiC epilayers irradiated with low energy (250 keV) electrons at room temperature to introduce mainly Vc and defects in the C sublattice, we observed the strong EPR signals of V-c(h) and another S = 1/2 center. Electron paramagnetic resonance experiments show a negative-U behavior of the two centers and their similar symmetry lowering from C3v to C1h at low temperatures. Comparing the 29Si and 13C ligand hyperfine constants observed by EPR and first principles calculations, the new center is identified as V-c(k). The negative-U behavior is further confirmed by large scale density functional theory supercell calculations using different charge correction schemes. The results support the identification of the lifetime limiting Z1/Z2 defect to be related to acceptor states of the carbon vacancy. [ABSTRACT FROM AUTHOR]

Dynamic nuclear polarization (DNP) is an attractive method for initializing nuclear spins that are strongly coupled to optically active electron spins because it functions at room temperature and does not require strong magnetic fields. In this Letter, we theoretically demonstrate that DNP, with near-unity polarization efficiency, can be generally realized in weakly coupled electron spin-nuclear spin systems. Furthermore, we theoretically and experimentally show that the nuclear spin polarization can be reversed by magnetic field variations as small as 0.8 Gauss. This mechanism offers new avenues for DNP-based sensors and radio-frequency free control of nuclear qubits.

We demonstrate optically pumped dynamic nuclear polarization of (29)Si nuclear spins that are strongly coupled to paramagnetic color centers in 4H- and 6H-SiC. The 99%±1% degree of polarization that we observe at room temperature corresponds to an effective nuclear temperature of 5  μK. By combining ab initio theory with the experimental identification of the color centers' optically excited states, we quantitatively model how the polarization derives from hyperfine-mediated level anticrossings. These results lay a foundation for SiC-based quantum memories, nuclear gyroscopes, and hyperpolarized probes for magnetic resonance imaging.

Organ anomalies and organ system transposition may cause diagnostic and therapeutic difficulties. We report a patient with situs inversus totalis and symptomatic cholelithiasis successfully treated via laparoscopic cholecystectomy. We present a laparoscopic and MR cholangiographic pictures of our patient with gallbladder agenesis.

Neurofibromatosis-1 is a here-do-familiar disorder that is associated with a variety of skeletal anomalies, mostly with spinal deformities in 10-50% of the patients. Intraoperatively, a poor vertebral bone quality has been observed. Efforts have been made to identify factors preventing curve progression, to optimize operational planning and to explain the pathomechanism. As part of the preoperative evaluation, the authors used a dual X-ray absorptiometry to assess the bone mineral density of the lumbar spine in 12 non operated patients with neurofibromatosis-1, supplemented by laboratory blood/urine investigations. A significant decrease in bone mineral density of lumbar spine was measured. An inverse relation was suggested between the severity of scoliosis and the lumbar spine Z-scores. No pivotal alterations were identified in the laboratory measurements. The bony tissue abnormality observed intraoperatively in neurofibromatosis-1 patients may be described as a diminution of the axial bone mineral density. The evaluation of bone mineral density in the course of the preoperative planning is proposed in neurofibromatosis-1.

We have performed 16 operations on 14 patients with primary hyperparathyoidism caused by a solitary parathyroid adenoma in our department between 1st jan. 1990-31 dec. 1999. In each case bilateral neck exploration was carried out. As in one case it was located in ectopic neck position, in the other case papillocarcinoma of the thyroid gland and ectopic parathyroid adenoma in mediastinal position were present, primary hyperparathyroidism persisted, so reoperation was needed. Histological examination proved the presence of adenomin all cases. Diffuse hyperplasia and parathyroid cancer did not occur. Before operation all patients underwent US and seven of them had radionuclide scintigraphy. CT scan aided in its localization with four patients. We did not make use of invasive methods, after the first operation 12 patients showed normal S-Ca levels very quickly. In two cases this level was too high after the operation and reoperation was necessary which resulted in normal Ca levels. Even though the number of our cases is rather modest, all the patients recovered. This may prove that we can successfully cure our patients of modern methods of diagnostics used for meticulous examination alongside with careful preparation of the patients by internal specialists are followed by the standard operative techniques available.

The anatomical patterns and frequency of occurrence of congenital coronary anomalies (CCA) in a Central European cohort has not yet been studied. The angiographic data of 7,694 consecutive patients undergoing coronary arteriography at the Albert Szent-Györgyi Medical University, Szeged, Hungary, from 1984 to 1994 were analyzed. CCA were found in 103 patients (1.34% incidence). Ninety-eight of them (95.2%) had anomalies of origin and distribution, and five (4.8%) had coronary artery fistulae. The incidence was the highest for the separate origin of left descending artery and left circumflex from the left sinus of Valsalva (52.42%). Anomalous origin of the left circumflex coronary artery from the right coronary was 8.7% while from the right sinus of Valsalva 18.4%. CCA, which may be associated with potentially serious events, such as ectopic coronary origin from the opposite aortic sinus (1.9%) and single coronary arteries (3.88%), were not frequent. The incidence of CCA in the Central European cohort under study was similar to that of the largest North American study. The anatomic classification presented can be useful from both clinical and surgical standpoints.

A case is presented where coronarography was complicated by coronary embolism. The acute circulatory failure could be controlled only by intraaortic balloon pump therapy. The authors emphasize the importance of the mechanical circulatory support devices in the cardiac catheterization laboratories as well as at the coronary care units.

The right ventricular ejection fraction was determined in 58 patients with simultaneous right and left ventricular myocardial infarction and in 77 patients with only left ventricular myocardial infarction. The results were analysed in four groups of patients (patients with anterior, anterior and right ventricular, posterior, posterior and right ventricular myocardial infarction). Furthermore, the relation between left and right ventricular ejection fraction, stress capacity and heart volume was investigated. There was no influence of the age and gender of patients on the observed values of right and left ventricular ejection fraction. In younger patients, after myocardial infarction, the heart volume was found to be less and the stress capacity to be higher then in elderly patients. The right ventricular ejection fraction was normal in patients with "poor" left ventricular infarction, and it was decreased in patients with right ventricular myocardial infarction. The right ventricular ejection fraction did not influence the stress capacity and the heart volume of the patients. The left ventricular ejection fraction found to be less in anterior, compared to posterior myocardial infarction. This difference was independent on the presence of right ventricular infarction. The authors consider the decreased right ventricular ejection fraction as a valuable indicator of the abnormal contractility of the right ventricle even at the time of the rehabilitation after myocardial infarction.

Hemodynamic data in 43 patients with right and left ventricular infarction and 39 with left ventricular infarction were compared. Right atrial pressure, pulmonary capillary wedge pressure, mean pulmonary artery pressure, left ventricular end-diastolic pressure before and after ventricular angiogram, cardiac index, left ventricular stroke volume index, right ventricular stroke work index were evaluated, as well as ratios of right atrial and pulmonary capillary wedge pressure, right and left ventricular end-diastolic pressure, right ventricular end-diastolic and pulmonary capillary wedge pressure, left ventricular ejection fraction calculated from left ventricular angiogram, Berentey's score, and cardiac volume index. Using ONEWAY analysis there was no significant difference between the two groups in period of rehabilitation. In 15 patients with right ventricular infarction regression of ECG changes was observed in lead V3R also without significant influence on hemodynamic data.

The authors have examined supposed causes of positive Th-201 stress scintigraphy. Patients were divided into two groups according to the presence of exercise-induced transitory hypoperfusion or in absence of it. In both groups negative coronarograms were verified. Results of two groups were compared according to parameters of the left ventricle function, pulmonary pressure, to the presence of disorder of system stimulus-conduction (LBBB, RBBB), mitral prolapsus, foramen ovale apertum, anomalous coronary anatomy, level of load during exercise, body weight, heart volume-index. Significant difference was found in disorder of left ventricle motion, ejection fraction and in comprehensive value of left ventricle function (F1).

1. It is a reliable nitroglycerin (NTG) form influencing circulation and haemodynamics like other nitroglycerin products, 2. It is easily applicable, 3. Its use is advantageous especially for the prevention of pressure elevation occurring in response to physical exercise thus for the prevention of effort angina as well, 4. It is a reliable drug to be used in haemodynamic laboratories for measuring nitroglycerin effect, 5. Due to the rapidly developing fall of end diastolic pressure caused by the product it is also of value in controlling cardiac asthma attacks.

Correlation between coronary anatomy and the presence or absence of chest pain was studied during bicycle exercise testing in 101 patients. All of them had significant ST segment depression during the stress test. ECG changes were accompanied by chest pain in 66 patients (group A). 35 patients were free of symptoms (group B). Coronary arteriography showed significant stenosis of one or more coronary artery branch in 50 patients of group A, and in 24 patients of group B, the difference was not significant statistically. The presence or absence of chest pain weren't valuable markers in the differential diagnosis of true and false positive ST segment depression. Frequency of three-vessel disease was significantly higher in group A (14 cases), than in the other group (1 case). In conclusion, if a significant ST segment depression occurs during exercise stress either with or without anginal pain coronary arteriography is recommended to perform.

A 6-month ECG follow-up was carried out in 65 patients with right-ventricular infarction accompanied by anterior (n = 17) and inferior (n = 48) left-ventricular necrosis. QRS morphology and ST-segment alterations were evaluated in the period of rehabilitation and 6 months later. By the end of the 6th month, QRS in V3-4R returned to normal in 12 patients (18%), and there was no ST elevation in any of the patients at that time. Normalizations of QRS in V3-4R was about the same in the two groups and it was independent of patients' ages.

6-month ECG follow-up was carried out in 65 patients with right ventricular infarction accompanied by anterior (n = 17) and inferior (n = 48) left ventricular necrosis. QRS morphology and ST segment alterations were evaluated in the period of rehabilitation and 6 months later. By the end of the 6th month QRS in V3-4R returned to normal in 12 patients (18%) and there was no ST elevation in none case by this time. Normalization of QRS in V3-4R was about the same in the two groups and it was independent from the age of patients.

Generally, right ventricle infarction is accompanied by left ventricle infarction. Isolated right ventricle necrosis is rare. Among 1707 patients with 6-week-old myocardial infarction there were 2 cases with isolated right ventricle infarction. Diagnosis based on pathologic Q waves in right precordial chest wall leads, radionuclide and echocardiographic observations. In one case, diagnosis was supported by coronary angiography, too.

In 29 patients with coronary artery disease (CAD) involving the proximal segment of left anterior descending coronary artery (LAD) and in 25 patients with normal coronary anatomy (control group) Q wave amplitude changes were studied in response to exercise with bicycle and treadmill. Decrease of the Q wave amplitude was observed only in the patient group. Increase in amplitude was found only in the control group. The sensitivity of bicycle test for a significant ST segment depression was 51.7%. The same value, obtained by treadmill exercise was 50%. When either a significant ST depression or decrease of Q wave amplitude was evaluated as an abnormal response to exercise, the sensitivity was 62% (bicycle) and 65% (treadmill). Taking both ST segment depression and reduction of Q wave amplitude, an increased sensitivity of exercise ECG examination can ben attained.

199 patients with myocardial infarction were divided into 4 groups according to the localisation of necrosis (anterior, inferior, anterior + right ventricle, inferior + right ventricle). Exercise capacity was determined by bicycle ergometer test at the beginning of rehabilitation and 3 weeks later. Exercise capacity and ejection fraction were better in case of inferior comparing with anterior infarction. There was no significant change in exercise capacity whether inferior or anterior left ventricle necrosis was accompanied by right ventricle infarction. In chronic phase of myocardial infarction exercise capacity of patients is not influenced by right ventricle necrosis accompanied by left ventricle infarction.

QRS complex, ST segment and T wave were investigated in V1R--V8R right chest wall leads in 122 healthy individuals (76 women, 46 men, mean age: 36.8 years). There was no Q wave in V1-3R. Going towards V8R, occurrence of QR and QS complexes increased. R/S ratio was the highest in V8R, while second r wave (r') was found to be most frequent (in 20.5%) in V6R. ST elevation at 80 msec after J point was found in all right chest wall leads, most frequently (in 91%) in V2R. All three forms of T wave morphology (positive, negative, isoelectric) were observed in these leads.

Authors performed in the Department of Traumatology of the County Hospital Kaposvár from 1979 to 1985 22 Matti-Russe-Zolczer operations for pseudoarthrosis of the navicular bone. The necessity of the strict observance of the conditions of indication is stressed. The results of operations were assessed in a follow-up. The time elapsed between the operation and control was 2 and 6 years. Good results were achieved after the use of Matti-Russe-Zolczer operation in 22 patients with navicular pseudoarthrosis.

QRS-complex and ST-segment were analyzed by ECG using 12 routine leads in three right chest wall leads (V3R, V4R, V5R) in patients with chronic anterior wall myocardial infarction. A QRS-complex was found in leads V3R and V4R in proximal occlusion of the LAD in all (n = 22) but four patients, where retrograde filling of the septal branch of the LAD was observed. When the medial LAD was occluded (n = 13), rS-complex was present in the right chest wall leads. Similar ECG findings were revealed in normal coronary arteries (n = 46). QS-complex in leads V3R and V4R refers to right ventricle infarction in the chronic phase of anterior wall myocardial infarction, when the proximal LAD is occluded.

The authors have undertaken controlled prospective clinical studies into Bricanyl treatment of 40 women with imminent abortion. Their conclusion has been that Bricanyl was an effective tocolytic for both intravenous and oral application. Thirty-eight cases were followed up to birth, with 30 mature infants being born plus seven premature birth (four of these immature). Abortion occurred in one case. Three foetuses were perinatally lost in the immature group. There were no side-effects which might have necessitated discontinuation of therapy. All tocolysed patients came under ECG control, and pathological changes were recorded from 17 in 31 women. Another checkup after birth revealed that all ECG findings had been restored to normal. Repeated warnings are given by the authors against application of betamimetics on an outpatient basis.