Measurement of modal dispersion in optical fiber by means of acousto-optic coupling.

We show that frequency-wavelength tuning characteristics of acousto-optic coupling can be used for measuring the difference of effective index, group index, and chromatic dispersion between core and cladding modes in single-mode fibers. Chromatic dispersion measurements of a 30-cm-long conventional single-mode fiber, a nonzero dispersion-shifted fiber, and a dispersion-compensating fiber with this new method are presented for the wavelength range 1500-1600 nm. Qualitative agreement with independently measured data is obtained.

Structures of bromoalkanes' photodissociation in solution by means of ultrafast extended x-ray absorption fine-structure spectroscopy.

The structures of initial and final products of bromoalkanes' photodisociation reaction in cyclohexane solution have been measured with a bond length accuracy of 0.02 A by means of ultrafast time-resolved extended x-ray absorption fine structure spectroscopy. The photoredaction mechanism is also discussed.

Picosecond X-Ray Pulses Generated in a Diode Driven by 193-nm Picosecond Laser Pulses.

A new technique for the generation of picosecond x-ray pulses is presented. Picosecond laser pulses are used to generate ultrashort electron pulses in a conventional x-ray diode in which the cathode is replaced by a photocathode. In the experiments presented, 9-ps UV pulses are employed to produce characteristic x-ray pulses with duration in range of 20-90 ps at a repetition rate of 300 Hz. This technique is inherently capable of subpicosecond x-ray pulses and synchronization of the x-ray pulses with the laser pulses or other ultrafast devices with picosecond accuracy.

Third-harmonic generation in barium borate.

The cubic nonlinear susceptibility of barium metaborate was employed for the generation of phase-matched third-harmonic generation (THG) of 1.053-microm pump radiation. The various processes that are responsible for THG in this crystal are discussed and experimental results for types I and II phase matching are presented. THG power of 50 microW is recorded with an average pump power of 800 mW of 1-kHz repetition rate picosecond pulses.

[The prevention of postoperative suppurative complications in stomach cancer]. / Profilaktika na sledoperativnite gnoini uslozhneniia pri stomashen rak.

Bacteriologic studies of gastric juice and purulent drainage fluids in the event of complications were carried out in 80 patients who had undergone gastric resections and had been on conventional parenteral antibiotic treatment (control group). Another (experimental) group of 37 patient, having undergone the same operations, received prophylaxis of the suppurative complications with 5-nitrox and Flagyl solutions through nasogastric probe once in 3 hours for 6 to 8 days. The suppurative complications in the experimental group were reduced from 47.5 to 8.1 per cent and of the postoperative lethality due to suppurative complications from 22.5 to 0 per cent.

[Determination of the transaortic valve gradient in aortic stenosis by continuous Doppler echocardiography]. / Opredeliane na transaortniia klapen gradient pri aortna stenoza s neprekusnata doplerova ekhokardiografiia.

A correlative study was carried out between the transvalvular aortic gradient determined by continuous wave Doppler echocardiography and by cardiac catheterization (retrograde or transseptal) in 41 patients with proved by invasive methods aortic valvular stenosis of different degree with or without accompanying aortic incompetence (light, moderate or severe). A considerable correlation was found between the transvalvular aortic gradient determined by the two methods (r = 0.75). In spite of that in considerable number of cases there is overestimation or underestimation of the transvalvular aortic gradient determined by Doppler echocardiography compared with the one determined by cardiac catheterization. The overestimation of the transvalvular aortic gradient determined by Doppler echocardiography is due to the accompanying aortic incompetence of greater degree and to the condition that the gradient determined by Doppler echocardiography is maximum instantaneous while the one determined by cardiac catheterization is peak to peak and is principally of lower values. The underestimation of the transvalvular aortic gradient is due to the presence of considerable left ventricular dysfunction and technical faults in the Doppler echocardiographic examination.

[The potentials of pulse Doppler echocardiography for the diagnosis and determination of the degree of mitral stenosis]. / Vuzmozhnosti na pulsovata doplerova ekhokardiografiia za razpoznavane i opredeliane stepenta na mitralnata stenoza.

84 persons were examined: 61 patients with rheumatic mitral valve stenosis (21 men and 40 women), mean age 39.38 +/- 11.2 years and 23 healthy controls (14 men and 9 women), mean age 25.62 +/- 3.8 years. The morphologic and quantitative characteristics of the diastolic part of the pulse Doppler echocardiographic signal of mitral circulation analyzed by histogram of the time intervals show highly significant statistical differences between the patients with mitral valve stenosis and the healthy controls (100% specificity and sensitivity). The differentiation of mild and moderate from severe mitral stenosis by pulse Doppler echocardiography of mitral valve circulation, analyzed by histogram of the time intervals, is achieved with satisfactory precision by determination of the speed of the circulation fall in the early 1/3 of the diastole. The pulse Doppler echocardiograph performed by a transducer with 2.5 mHz frequency and the simultaneous M-echocardiography, the Doppler effect being analyzed by histogram of the time intervals, do not allow the precise determination of the degree of mitral valve stenosis.

[Effect of various factors on total serum cholesterol based on the data from an epidemiologic study in 4 large communities of Bulgaria]. / Vliianie na razlichni faktory vurkhu totalniia serumen kholesterol spored dannite na epidemiologichnoto prouchvane v chetiri golemi obshtini na Bulgariia.

The study includes 6243 persons--4051 women and 2192 men, mean age 37.9 +/- 14.2 years. The total serum cholesterol was examined and the factors related to the cholesterolemia were studied. A strong statistical correlation was found between the cholesterolemia and age, sex, body mass, smoking, degree of physical activity, alcohol consumption, feeding and diabetes mellitus. This multifactorial correlation of cholesterol serum level determines the need of complex population measures for reducing the high cholesterol level by correction of the mode of feeding and living and counteraction of the harmful habits (smoking), overfeeding, physical hypodynamia.

[Fibrinopeptide A and protein C in heart patients with acute coronary syndromes]. / Fibrinopeptid A i protein C pri surdechno bolni s ostri koronarni sindromi.

In order to determine the role of thrombosis in the acute coronary syndromes the blood levels of fibrinopeptide A and protein C were examined with an enzyme-immune test in 48 patients treated in the cardiological clinic of the National Centre for Cardiovascular Diseases. 27 patients were with transmural myocardial infarction and 21 patients were with non-transmural myocardial infarction. The average time of the test from the onset of pain is 18.4 +/- 12.2 hours (from 3 up to 72 hours). The mean level for fibrinopeptide A for the whole group of patients is 4.95 +/- 3.1 ng/ml and that of protein C is 70.1 +/- 9.8%. For the group of patients with transmural myocardial infarction the level of fibrinopeptide A is 6.09 +/- 3.49 ng/ml and of protein C is 65.3 +/- 8.0%. For the patients with nontransmural myocardial infarction the levels are respectively 3.49 +/- 1.7 ng/ml for fibrinopeptide A and 76.3 +/- 8.3% for protein C. The difference between the two groups is statistically significant (p less than 0.005). In the patients with non-transmural myocardial infarction from whom the blood for the test was taken before the 24th hour the fibrinopeptide A level is 4.8 +/- 2.4 ng/ml and the protein C level is 69.0 +/- 7.8%. The deviations from the reference group are statistically significant (p less than 0.04). The practical importance of these results is discussed.

[Indications for and the postoperative results of mitral valve prosthesis]. / Pokazaniia i sledoperativni rezultati pri protezirane na mitralnata klapa.

The influence of 20 hemodynamic and clinical indices on the postoperative results was studied in 528 patients with mitral valve prosthetics. One year after the operation 78.7% of the patients are with improved functional capacity, 18.8% are without change and 2.5% are in worse condition. The lack of improvement correlates moderately with the postoperative complications (r = 0.4701) and to a larger degree with the number of patients in the II functional class before the operations (r = 0.7342). The deterioration of the functional capacity is in relation to the complications by operations on the tricuspid valve (r = 0.8773), but there is also considerable correlation with the low ejection fraction (r = 0.6425), previous commisurotomy (r = 0.5871) and uncorrected tricuspid valvular disease (r = 0.6314). The operative lethality rate is 6.25%.

[Correlation of functional indices of the left ventricle with structural changes in the myocardium]. / Otnoshenie na funktsionalnite pokazateli na liavata kamera kum strukturnite izmeneniia y miokarda.

11 with dilatative cardiomyopathy, 9 with valvular disease and 3 with ischemic heart disease--a full intracardial examination including right ventricular endomyocardial biopsy was performed. The most severe disorders of the hemodynamic parameters were found in the group of patients with dilatative cardiomyopathy. The pressure in the pulmonary artery was the highest of all groups of patients. The initial meane values of the systolic, diastolic and the average pressure were 5.73, 2.53 and 3.73 kPa and after left ventriculography was performed they were 6.80, 3.60 and 5.07 kPa respectively. The values of the ejection fraction were the lowest of all groups of patients. The left ventricular volume was greatly increased. The average telediastolic volume index was 235 ml/m2 and the average telesystolic volume index was 173 ml/m2. The velocity indices were greatly decreased--the average velocity of the circumferential fibers contraction was 0.45 circ/s and the ratio dp/dt was 1062 mm Hg/s. All patients were with normal coronary arteries. The very poor indices of 4 patients indicates for cardiac transplantation are of special interest. In the patients with valvular disease various degree of lowered hemodynamic parameters were found corresponding to the structural changes of the myocardium. In the third group of 3 patients with ischemic heart disease and severe disorders in the left ventricular function massive fibrous changes in the myocardium were found.

[Hypertrophic cardiomyopathy--diagnostic significance of the disproportion of myocardial hypertrophy examined by two-dimensional echocardiography]. / Khipertrofichna kardiomiopatiia--diagnostichno znachenie na disproportsiiata na miokardnata khipertrofiia, ustanovena s dvurazmerna ekhokardiografiia.

34 patients with myocardial hypertrophy, mean age 44 years, were examined by two-dimensional echocardiography and the degree of disproportion of the hypertrophy of the different left ventricular segments was analyzed. Besides the classic index--ratio between the septum and the posterior ventricular wall--a new index for the asymmetry of the hypertrophic process is proposed: the ratio between the thickest, segment and the thinnest segment. The new index is more sensitive in determining the asymmetrical hypertrophy.

[Clinical and hemodynamic characteristics of patients with an aortic valve defect before the implanting of an aortic valve prosthesis]. / Klinichna i khemodinamichna kharakteristika na bolni s aorten klapen porok predi protezirane na aortnata klapa.

The clinical and hemodynamic characteristics, perioperative and early postoperative results were studied in 38 patients with aortic valve prosthesis in order to determine the indications for surgical treatment in isolated aortic valvular disease. The basic factors determining the need for surgical treatment are: severity of the aortic lesion--stenosis and/or incompetence, degree of the harmful action of the aortic valvular disease on the left ventricle (clinical data for left ventricular failure; hypertrophy and dilatation--telediastolic volume greater than 300 ml/m2, telesystolic volume greater than or equal to 50 ml/m2; myocardial lesion; hemodynamic data for left ventricular dysfunction) and functional class of the patients. Most of the patients were with severe aortic incompetence and/or aortic stenosis and considerably diminished functional capacity. Only few patients had a low degree valvular lesion but they also showed some of the signs of its harmful action on the left ventricle.