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Electrocardiograms and radionuclide ventriculograms were obtained at rest and on exercise in 23 patients (20 men and 3 women, mean age 53.4 years) with exercise-dependent myocardial ischaemia after infarction, as well as in 22 persons (17 men and 5 women, mean age 43 years) without clinical, electrocardiographic and biochemical evidence of coronary heart disease. Among the ischaemia patients exercise-dependent loss of motility, as measured by regional ejection fraction and Fourier amplitude, occurred in 95% (50% of controls) in one sector, in 78% (4.5% of controls) in the two sectors with the highest contractility at rest, and in 74% (0% of controls) in three sectors. On exercise, phase shifts occurred in 87% (27% of controls). When combining the exercise-ECG, global ejection fraction as well as regional motility loss in one sector, in the two sectors with the highest contractility at rest and in three sectors, at least two of the five criteria of abnormality were present in 91.3% of the ischaemia patients, compared with at most one criterion in 90.9% of controls. The results indicate the greater diagnostic value of regional than global measures of ventricular function and emphasize the importance of radionuclide ventriculography as an addition to exercise electrocardiography in the pre-invasive diagnosis of coronary heart disease.

Between 1986 and 1992, pacemakers were implanted in 307 patients with symptoms caused by the sick sinus syndrome (SSS). 301 patients were regularly followed up (161 men, 146 women, mean age 72.9 [27-91] years) of whom 180 had a VVI, 65 and AAI and 58 a DDD/DDI pacemaker. Mean follow-up period was 58.3 months for VVI-stimulated patients and 35.6 months for atrial paced patients. The data were analysed retrospectively to ascertain whether a change in pacemaker treatment to a more physiological system produced any lowering in the mortality rate, incidence of permanent atrial fibrillation (AF), and thromboembolic phenomena. The annual mortality rate of the VVI-stimulated patients was 6.9%, that of atrial paced patients 2.8%. Age, abnormal ventricular function, survived resuscitation and diabetes mellitus each correlated with a shortened life expectancy already at the time of implantation, regardless of the pacemaker mode. Permanent AF was more frequent during VVI stimulation (16% vs 7%), especially if it had been preceded by intermittent AF (26% vs 13%). But there was no significant difference with regard to transitory cerebral ischaemic episodes and peripheral arterial emboli (15% vs 10%). Fewer patients with atrial pacing went into heart failure (20% vs 30%). Four patients developed a high-grade atrioventricular (a-v) block on AAI stimulation (annual incidence 2.4%). - These observations suggest that patients with SSS should always have atrial paced pacemaker systems. If a-v conduction is disturbed, a bifocal pacemaker is the system of choice.

A 60-year-old woman swallowed 2.4 g verapamil in a retard form (Isoptin retard). Depsite intensive efforts she died 44 hours later in a coma due to circulatory collapse. In contrast to other reported cases of poisoning, the verapamil concentration in plasma continued to rise. This atypical course with continuing absorption of verapamil was due to small-intestinal deposits of the drug, found at autopsy.

A 32-year-old woman without preceding illness or significant cardiovascular risk factors was admitted to hospital because of a syncope after physical exertion. Transoesophageal echocardiography, performed to exclude aortic dissection, showed as an incidental finding a cystic space-occupying mass, 5 x 6 cm in diameter, dorsal to the aortic root and main pulmonary artery. Exercise ECG had S-T segment depressions of about 0.3 mV, associated with anginal symptoms, so that inadequate coronary artery flow on exertion was suspected. Subsequent coronary angiography demonstrated a funnel-shaped 80% stenosis at the origin of the main left coronary artery, while all other coronary arteries were normal and smooth-walled. A causal connection between the two findings was assumed and quickly undertaken surgical intervention revealed an intrapericardial bronchogenic cyst which, presumably as a result of its size and location, had pressed on the main stem of the left coronary artery and caused the stenosis of its ostium. The cyst was completely resected and angioplasty of the coronary artery ostium was performed to ensure its patency. 3 months postoperatively the patient underwent an exercise test of up to 125 Watt without signs of ischaemia. This case presents a previously unreported complication of a bronchogenic cyst.

History and clinical findings A 53-year-old patient had a prosthetic valve (St. Jude Medical 25) 9 years ago because of a Staphylococcus aureus endocarditis with severe aortic regurgitation. An initially mild, progressively more severe, aortic regurgitation then developed as a result of an empty paravalvular abscess cavity, requiring another valve replacement. Fever started on the 3rd postoperative day and persisted despite combined treatment with beta-lactam antibiotics and aminoglycoside. Investigations At first no infectious focus could be identified radiologically or by echocardiography. But transoesophageal echocardiography revealed vegetations in the old abscess cavity. Several blood cultures were negative, while serological tests gave markedly raised antibody titers against Coxiella burnetii. Diagnosis, treatment and course Assuming Coxiella burnetii endocarditis the patient was given doxycycline, 2 x 100 mg daily and cotrimoxazole, 1 x 960 mg daily. The fever subsided and the vegetations had disappeared after four weeks. Because of the high risk of recurrence the antibiotic treatment was to be continued for two years. Conclusion Coxiella burnetii should be considered as a possible cause of fever of unknown origin, especially in patients with existing or operated cardiac valvar defects, when endocarditic vegetations have been demonstrated and several blood cultures have been negative.

OBJECTIVE To investigate prospectively the extent of potentially harmful interference of cardiac pacemakers by mobile phones in the C (analog) and D (digital) networks in use in Germany. PATIENTS AND METHODS 104 patients (54 men, 50 women; mean age 75.8 [40-100] years) with 58 different implanted pacemaker models (43 one-chamber and 15 two-chamber systems) underwent uniform tests at various functional states with three different telephones (D1 portable 8 Watt, D1 Handy model 2 Watt, C Handy model 0.5 Watt). The distances between telephone aerial and pacemaker, as well as reception sensitivity and polarity of the pacemaker were varied. All tests were done during continuous ECG monitoring. RESULTS 28 different pacemaker types (48.3%) in 43 patients (41.3%) showed interference in the form of pacemaker inhibition and switching to interference frequencies as well as triggering of pacemaker-mediated tachycardias in the DDD mode, as well as in the temperature-regulated frequency-adaptive function. D portables influenced pacemaker function more often and at greater distance than the D Handy model, which was little different from the c network hand phone. Reduction in pacemaker sensitivity as well as switching to bipolar reception only partly eliminated the interference. CONCLUSIONS Patients with implanted pacemakers should if possible not use mobile phones in the C and D networks. Individual testing with suitable programming of pacemaker sensitivity and polarity can reduce the risk of interference.

OBJECTIVE The factors that influence long-term survival after out-of-hospital resuscitations were investigated. PATIENTS AND METHODS Between 1985 and 1989, out of a total of 8403 responded emergency calls, 505 resuscitations were undertaken out of hospital by the emergency medical service in Goppingen. All emergency calls were recorded uniformly. Of the 505 resuscitations, 154 were primarily successful (30.5%), and 58 were secondarily successful, i.e. the patients were ultimately discharged from hospital. In 56 of them the further course could be followed at least 5 years after the resuscitation (45 males, 11 females; mean age 57 [10-83] years). The patients' charts were analysed; in 51 cases data could be obtained from the family doctor, from ambulant care or from home visits. RESULTS 34 patients (60.4%) were still alive 5 years after the resuscitation. The highest death rate (16%) was in the first post-resuscitation year. Prognostically unfavourable factors were: advanced age (P < 0.01), underlying cardiac disease (n = 49; P < 0.025), especially coronary heart disease (n = 34; P < 0.01). Patients with primary ventricular fibrillation and previous myocardial infarction (n = 10) had a poorer prognosis than those with acute infarction (n = 24; P < 0.05). Reduced survival chances occurred in those with impaired left ventricular function, as measured echocardiographically (P < 0.05), or with cardiac arrhythmias, Lown classes III and IV (P < 0.05), as well as in those with severe neurological sequelae (n = 8; P < 0.08). CONCLUSION Long-term prognosis depends, in the first instance, on the resuscitated patient's basic condition and not so much on the circumstances of the resuscitation.

HISTORY AND ADMISSION FINDINGS An 85-year-old woman was admitted because of frequent syncopes. She also reported slight weight loss, cough and dyspnoea. Chest auscultation revealed slight stridor and a cardiac arrhythmia, with an irregular ventricular rate between 120 and 140 beats/min. INVESTIGATIONS She had a thrombocytopenia (96 platelets/nl), and the ECG and long-term monitoring showed a tachyarrhythmia with atrial fibrillation, a bifascicular block (left anterior hemiblock and right bundle branch block), as well typical signs of sick-sinus syndrome with short periods of bradycardic sinus rhythm and pauses of up to 6 s on rhythm change. Echocardiography indicated moderately reduced left ventricular function. Chest radiogram revealed tracheal narrowing by a retrosternal goitre. No evidence of tumour was found on bronchoscopy. DIAGNOSIS, TREATMENT AND COURSE A VVI pacemaker was implanted. When the platelet count dropped to 30/nl idiopathic thrombocytopenic purpura was suspected, but administration of high doses of corticoids and immunoglobulin was without effect. Another echocardiogram, performed because of chest pain suspicious of pulmonary embolism, revealed a large bowl-shaped right ventricular thrombus with floating parts. Demonstration of anticardiolipin antibodies established the diagnosis of antiphospholipid syndrome (APLS), thought to be secondary to thyroid cancer suspected from the computed tomography. The patient died 2 months later from recurrent pulmonary embolism and progressive liver failure. Autopsy revealed a not previously diagnosed tracheal carcinoma with metastases to the thyroid, as well as haematogenous metastatic foci within the right ventricular thrombus. INTERPRETATION In case of thrombocytopenia of uncertain aetiology APLS should be included in the differential diagnosis, even in the absence of any early or acute thrombosis. If anticardiolipin antibodies and/or lupus anticoagulant are demonstrated, malignant neoplasm should be considered in addition to autoimmune disease.

History and admission findings A few days after uneventful surgical reconstruction of the mitral valve a 43-year-old man was found to have a systolic murmur due to prolapse of the posterior leaflet, suggesting renewed mitral regurgitation. Investigations Echocardiography revealed haemodynamically significant left ventricular outflow tract obstruction (LVOT) with a left ventricle to aorta systolic gradient of 83 mm Hg. In addition there was moderately severe mitral regurgitation as well as a pericardial effusion but no signs of tamponade. Treatment and course The obstruction was at first treated with verapamil, later with sotalol. The pericardial effusion was interpreted as part of a postcardiotomy syndrome. The effusion regressed under steroid administration, and the LVOT and mitral regurgitation also decreased. A provocation test five months postoperatively no longer brought about an outflow gradient. The good results were still present 12 months postoperatively. Conclusion The described, rarely seen form of LVOT was probably caused by a combination of a very large anterior mitral leaflet, postoperative pericardial effusion and pharmacological effects. If the obstruction first occurs postoperatively, appropriate medication may improve the cardiac status and reoperation may be avoided. Echocardiography is an important method of diagnosis and serial monitoring.

Myocardial infarction and coronary artery ventricular fistulas due to blunt chest trauma. HISTORY AND CLINICAL FINDINGS: An 18-year-old previously healthy, cigarette smoking man with no other risk factors for ischaemic heart disease, was admitted to hospital after being kicked in the chest by a horse. On arrival he complained about pain in the lower mediastinum. INVESTIGATIONS: The ECG showed sinus rhythm, right bundle branch block and convex bowed ST elevation in leads V1-V3. Sixty minutes after the incident the cardiac enzymes (creatinekinase-MB fraction, troponin I) were significantly raised. Despite an only slightly reduced left ventricular function documented by transthoracic echocardiography, SPECT-thallium scan showed large scintigraphic defects. Coronary heart disease was excluded by coronary angiography. Four small coronary-ventricular fistulas were identified. Laevocardiography showed a hypokinesia in the antero-septal region. DIAGNOSIS, TREATMENT AND COURSE: We assumed traumatic myocardial infarction of the anterior wall and rupture of multiple small coronary vessels, leading to coronary-ventricular fistulas. No interventional or surgical therapy was performed. Later on the left ventricular function became normal. Echocardiography merely outlined an akinetic scar in the middle of the septum. At exercise ECG test sixteen months later, the patient remained asymptomatic and was able to exercise without any signs of ischaemia up to a work load of 175 W. Furthermore, the fistulas could be seen by echocardiography. CONCLUSION: Cardiac involvement should be considered in all cases of blunt chest trauma. In addition to a traumatic myocardial infarction fistulas may also, though rarely, occur. Myocardial scintigraphy after cardiac contusion is not suitable for diagnosing myocardial ischaemia or vitability.

A full-scale compositional analysis of Yb3+-doped heavy metal fluoride glasses (HMFG) has been undertaken to determine potential hosts for use in the development of a first-generation optical cryocooler for space-borne remote sensing applications. By pumping to the lower levels of the Yb3+ 2F5/2 manifold, followed by a thermally-driven population redistribution to higher levels within the manifold, net cooling can be achieved by anti-Stokes fluorescence back to the ground state. This paper reports on fluoride glasses in the ZBLAN and BaF2–InF3–GaF3 (BIG) families which have shown promise for fluorescent cooling. ZBLANPb:Yb3+ is the first solid to actually exhibit net cooling due to anti-Stokes fluorescence. The BIG-derived hosts have been determined to contain similar mean emission photon energies and larger long-wavelength absorption tails than those of ZBLANPb:Yb3+. Low-temperature absorption and fluorescence spectra have indicated that the Yb3+-containing BIG glasses should have a cooling efficiency more than twice that of ZBLANPb at temperatures below 80 K and may attain a minimum temperature of 45 K compared to 55 K expected for the ZBLANPb.

Continual cooling of a material by anti-Stokes luminescence has been experimentally observed in a solid material. Net cooling was achieved by pumping to the lower levels of the 2F5/2 manifold of Yb3+, followed by population redistribution across this manifold via thermalization and fluorescence to the ground state. Fluoride glass hosts in the ZBLAN and BaF2–InF3–GaF3 (BIG) families have been used in these experiments. Temperature decreases of 0.33 K in a bulk glass sample and 16 K in a fiber sample were obtained in ZBLANPb:Yb3+. Net cooling was achieved when an electrochemical purification stage was incorporated into the glass fabrication process to decrease the extrinsic absorptive component of the host glass in the 1.0 μm region. Resonant laser ablation experiments showed the positive and negative effects of electrochemical processing on fluoride glasses in reducing transition metal content which is detrimental to successful fluorescent cooling. Reduction in copper, iron, and chromium content of 18, 4.2, and 5.5 were determined for the ZBLANPb sample via RLA. However, reductions in transition metal content were only 1.9 for copper and a negligible amount for iron and chromium in the BIG glasses.

The effects of the fiber drawing process and high power (170 mJ/pulse) ultraviolet excimer laser irradiation on defects and defect precursors of silica glasses have been investigated. This study has considered the defects induced by the fiberization process in low-OH silica fibers and their response to ultraviolet excimer laser irradiation. The principal change of the population of defects and defect precursors occurred in the neck-down region where severe conditions such as higher temperatures and shear stresses are encountered. The influence of fiber drawing conditions, in particular, the effect of drawing speed and drawing temperature on the concentration of oxygen-deficient centers (ODCs) has been studied. Drawing speeds ranging from 10 to 180 m/min and drawing temperatures ranging from 1950°C to 2150°C were evaluated. The 215 and 248 nm absorption bands and E′ electron spin resonance (ESR) signal intensity initially increased with drawing speed but eventually became invariant. However, both absorption bands and E′ ESR signal intensity were insensitive to drawing temperature variations. The photobleaching of a 248 nm absorption band, due to phototransformation of ODCs by ultraviolet excimer laser irradiation, in fibers is compared to the response of bulk rods from which they have been drawn. These data are interpreted in the context of the processing conditions employed during the investigation.

Metastable photoinduced anisotropy (PA) generated by linearly polarized sub-bandgap light is reported for undoped and Pr-doped Ge–S–I, Ge–Ga–S and As–Ga–S glasses with varying composition and Pr content. Compositional trends of PA are related to the light-stimulated reorientation of intrinsic anisotropic centers and their environments, which vary with composition. These centers can be modeled with pairs of over- and under-coordinated sulfur atoms: the valence alternation pairs (VAPs). The addition of Pr up to a level of about 1000 ppm affects PA, suggesting that this concentration is comparable with the concentration of VAPs. Microscopic models are proposed for the centers responsible for PA in these glasses.

The absorption and emission properties of Yb/sup 3+/-doped ZBLANP, BIGaZYT and QX/Yb phosphate glasses are studied to evaluate their potential for laser-induced fluorescent cooling or optical refrigeration. The efficiency of optical refrigeration increases with pump wavelength in the anti-Stokes region. The cooling efficiencies of the three glasses as a function of temperature are evaluated at the wavelength /spl lambda/p corresponding to the absorption coefficient of 10/sup -3/ cm/sup -1/. For temperatures

Undoped and Pr3+-doped GexSyIz glasses, with atomic concentrations of germanium 0.33 ≤ x ≤ 0.43 and iodine 0 ≤ z ≤ 20, respectively, were synthesized and their optical and thermal properties measured. The properties followed the same compositional trends as the binary GexS1 - x glasses, for which 0.33 ≤ x ≤ 0.43. The compositional dependences of the absorption edge and rare-earth solubility in GexSyIz glasses can be presented with a single parameter p = (y + z 2 ) x . Addition of iodine to the Ge-rich GexS1 - x-base glass system resulted in increasing the optical bandgap energy and decreasing the glass transition temperature. Thermal stability of the GexSyIz glasses is a function of both S Ge ratio and iodine concentration. XPS and Raman spectroscopic measurements were conducted to obtain information about the structural changes accompanying the compositional variations. Properties-structure correlations are discussed. The results of the present study were used for selection of a compositional range within the GexSyIz glass system with optimal properties required for Pr3+-doped fiber amplifier application.

The optical properties of several sulfur-based glasses doped with Pr3+ and Dy3+ have been measured, with emphasis on the 1.3 μm emission quantum efficiency. Glass hosts prepared using conventional methods include As2S3, As2S3 with 1.7 mol% I2, Ge30As10S60, Ge25Ga5S70, and Ge35S56.5I8.5 for Pr3+, and all but the As2S3 based compositions for Dy3+. Data obtained from optical absorption and fluorescence spectra and fluorescence lifetime measurements were used for theoretical predictions of quantum efficiency. These theoretical efficiencies were compared to absolute efficiency measurements using either an integrating sphere based system or a self-calibration technique (Pr3+ only, no As2S3-based glasses). The latter method produced erroneous values for glasses having electronic absorption edges beyond 500 nm, possibly due to a host sensitization phenomenon. A 100 ppm Pr2S3 doped GeGaS glass was the most efficient at 1.3 μm, measuring 93% via the integrating sphere technique. The measured efficiencies for Dy3+ doped glasses at 1.3 μm, the first reported to our knowledge, were less than those theoretically predicted. The most efficient Dy3+ doped sample, a 0.1 wt% Dy2S3 doped GeSI glass, was measured to be 6%.

Pr3+-doped Ge–S–I samples, with compositions having an S/Ge ratio between 1.5 and 1.7 and iodine concentrations between 5 and 20 at.%, have been prepared by well-established glass-melting techniques. The thermal and spectroscopic properties of these glasses have been measured and evaluated to assess their suitability for a fiber amplifier application at 1.3 μm. Pr3+ ions were successfully dissolved in Ge35S56.5I8.5 glass at doping levels as large as 0.2 wt%. The glasses within the investigated compositional range are transparent at the excitation (1.02 μm) and emission (1.34 μm) wavelengths for Pr3+ ions. The 1 G 4– 3 H 5 emission band of Pr3+ had a peak at 1.344 μm and an effective linewidth of 85 nm in this host. A 1 G 4 level fluorescence lifetime of 368 μs was measured in a 500 ppm/wt Pr3+-doped Ge35S56.5I8.5 samples. Glass rods of Pr3+-doped Ge35S56.5I8.5 composition, with typical 5 cm lengths and 10 mm diameters, were produced for fiber drawing.

Different concentrations of NdF 3 , PrF 3 , and PrF 3 , codoped with YbF 3 , ranging from 0.25 to 2.0 wt%, have been added to an AlF 3 -base glass with composition (mol%) 30.2AlF 3 –10.6BaF 2 –20.2CaF 2 –8.3YF 3 –3.5MgF 2 –3.8NaF–13.2SrF 2 –10.2ZrF 4 . The Avrami exponent, n , and activation energy, E , for the base glass, as well as the doped glasses, have been calculated by analyzing the differential scanning calorimetry curves, according to the amended Ozawa–Chen and Augis and Benett equations. In light of these results, we observe that the introduction of suitable amounts of rare-earth ions improved the thermal stability of the base glass.

New AlF 3 -based glasses with enhanced thermal stability have been synthesized and characterized using differential scanning calorimetry, spectroscopic and viscosity measurements. The HR values for these new glasses compare favorably with those of the base glass ((mol%) 30.2AlF 3 -10.6BaF 2 -20.2CaF 2 -8.3YF 3 -3.5MgF 2 -3.8NaF-13.2SrF 2 -10.2ZrF 4 ), ZBLAN and other compositions of halide glasses. Core and cladding glasses were synthesized using these compositions and evaluated for fiber drawing

The synthesis and optical properties of Pr-doped GeGaS glasses are reported. The radiative properties associated with the important 1G4 → 3H5 transition of Pr3+ at 1.3 μm have been determined by absorption and fluorescence measurements coupled with Judd-Ofelt analysis. As compared with ZBLAN glass, Pr-doped GeGaS glasses have a longer fluorescence lifetime and a larger stimulated emission cross-section, which are favorable for an efficient fiber amplifier. The concentration quenching of Pr3+ in these glasses has also been studied by fluorescence lifetime measurements.

Using a sol-gel process for rare-earth ions doping, a minimum optical loss of less than 2 dB/km in the region of 1.15μm has been reproducibly achieved in Er 3+ doped Al 2 O 3 SiO 2 glass single-mode fibers. A wide range of rare earth doping concentrations was successfully introduced into fibers using this technique. In the sol-gel dipcoating to deposit a thick film, the key to achievement of low loss fiber was found to depend critically on a process capable of providing a consistently crack-free film.

Rare-earth ions can easily be incorporated into fluoride glasses in moderate to large concentrations. Because these glasses possess low fundamental frequencies, they appear to have many advantages over oxide glasses as hosts for rare-earth ions used in optical amplifiers and lasers. We have investigated the optical properties (fluorescence, absorption, and excited-state lifetimes) of AlF(3)-based glass doped with Pr(3+), Yb(3+) and Lu(3+). The effects of different dopant levels on the optical properties of this glass system have also been investigated. These results are compared to those obtained for the same ions in other glass hosts.

Optical fibers with pure silica cores of both low and high water content and fluorine-doped silica claddings were irradiated with 248 nm (KrF) excimer-laser radiation. In addition to the differences in the spectra of luminescent emissions of the respective cores, spatial variance was observed in the luminescence behavior across cross sections of the cores. Photographic evidence of this phenomenon is presented along with the corresponding luminescence spectra. Spectral correlations of the spatial variances are made, and the defects that are responsible for the luminescence are discussed.

An infrared-transmitting chalcogenide fiber was used as an optical probe to analyze qualitatively and quantitatively various chemical substances in aqueous solutions. An unclad fiber with 380-microm diameter was combined with a Fourier transform infrared spectrometer to monitor the concentration of the analytes in solutions by measuring the changes in the absorbance of their fundamental vibration peaks. A linear relationship was observed between the absorption by the vanescent field and concentrations of various analytes. For this study low concentrations of acetone, ethyl alcohol, and sulfuric acid were detected in aqueous solutions. The minimum detection limit for these three chemical substances was 5, 3, and 2 vol. %, respectively, with a sensor length of 15 cm. It was also demonstrated that the same sensor design is capable of monitoring gaseous species such as dichlorodifluoromethane.

A new family of modified ZBLAN glass compositions has been synthesized which provides better stability against crystallization. A preliminary study of the Hruby factor HR shows higher values as compared to a ZBLAN glass prepared under the same conditions, utilizing similar high purity starting materials. Large rods of clear glass with a 1.5 cm diameter and up to 17 cm in length were easily obtained. Results will be presented on the physical properties and crystallization behavior of these high stability glasses.

Structural development of tellurite glasses with the addition of Li2O and Na2O has been studied using infrared, Raman, and X-ray photoelectron spectroscopies. The increase in intensity of the peak at 755 cm−1 in the infrared spectra as compared to the peak at 620 cm −1 suggests the transformation of TeO4 building units to TeO3 pyramids with the addition of alkali oxide. Proposed structural change is further supported by the strong compositional dependence of the 755-cm−1 peak in the Raman spectra as well as by the formation of a shoulder in the O 1s peak of X-ray photoelectron spectra. In contrast to alkali silicate glasses, formation of nonbridging oxygens with the addition of alkali oxide is not observed.

Although AlF3-based glasses have shown superior chemical durability and mechanical strength relative to ZrF4-based glasses, devitrification problems near the drawing temperature have limited their fiber applications. We have investigated the effect of atmosphere, particularly moisture, on the surface crystallization during the fiber drawing of these glasses. The crystallization behavior has been monitored by optical microscopy, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) techniques. Preforms of AlF3-based glasses have also been drawn into long fibers in a tower enclosed by a unique three-stage vertical glove box in which the moisture levels are maintained below 1 ppm.

The effect of starting materials purity, crucible material, and melting conditions on the optical scattering of AlF3-based glasses has been investigated. Platinum and vitreous carbon crucibles have been used to melt the glasses under nitrogen and reactive atmosphere (RAP) conditions. The optical quality of the bulk glass was evaluated by molecular light scattering in the Mie and Rayleigh regimes as a function of scattering angle and polarization at 0.647 μm. From an analysis of the angular scattering of both vertically and horizontally polarized beams, the sizes of the scattering sites have been estimated to be in the range of 0.02 to 2.0 μm. Glasses made with EM (BDH Limited) materials and melted in platinum crucibles without any reactive atmosphere exhibit lower values of scattering losses than those melted in the vitreous carbon crucibles under RAP.

A novel fiber-optic pH sensor has been developed with long-term stability and high sensitivity. The sensor is based on a porous cellulose triacetate fiber immobilized with Congo Red (pH indicator). This intrinsic fiberoptic pH sensor has shown excellent sensitivity, reversibility, and stability. It has also been demonstrated that the pH optrode is immune to metal-ion interferences.

Unclad, low-loss AlF(3)-based glass fibers with enhanced chemical durability have been successfully used for the first time to our knowledge as intrinsic evanescent infrared sensors for monitoring liquid chemicals. Different liquids with absorption bands between 1 and 4.5 microm, such as alcohol, acetonitrile, and mixtures of alcohol/acetonitrile and water/acetonitrile, have been tested. These fibers have also been used successfully as distributed sensors for simultaneous monitoring of different chemical species.

The attenuation of incoherent infrared radiation for wavelengths from 6 to 20 microm was investigated for hollow sapphire and silica waveguides suitable for applications in spectroscopy and thermometry. A low-attenuation region was exhibited between 9.6 and 17.2 microm for hollow sapphire fibers and between 7.25 and 9.5 microm for hollow silica fibers as a result of the cladding index of refraction dipping below that of the air core (n approximately 1). Losses have been characterized as a function of fiber diameter, launch conditions, and waveguide bend radius for cladding regions of both n1 and n1. In addition, the remote infrared sensing capability of the hollow waveguides was demonstrated by the detection of CO(2) in N(2) by utilizing hollow sapphire fibers capped with ZnSe windows.

A new technique has been demonstrated in the detection of low-frequency or dc magnetic fields in an optical-fiber interferometric sensor using the magnetostrictive approach. This technique permits magnetic-field measurements free of ambiguity associated with hysteresis effects of the material.

Fluorozirconate glasses are stable with respect to devitrification but have poor chemical durability and only fair mechanical strength. AlF3-based glasses with improved chemical durability and enhanced mechanical strength are reported here. The optical, mechanical, and thermal properties of these glasses are contrasted to the more familiar ZBLAN composition. The infrared edge of these glasses lies at shorter wavelengths than ZrF4-based glasses, but aluminum fluoride glasses offer some interesting opportunities for short-range IR fiber applications such as sensing, remote spectroscopy, and laser power propagation.

The effect on selected optical and physical properties of a fluoride glass doped with chloride was investigated. Four compositions were studied: 50%ZrF 4 -30%BaF 2 -5%ThF 4 -3%LaF 3 -12%Ab where A = NaCl, NaF, RbCl or RbF. The chlorine addition decreased the multiphonon absorption and its magnitude was determined to be dependent upon the molar concentration of ZrF bonds. The electronic absorption showed a substantial increase into the visible region. The index of refraction was increased by approximately 1.5% due to the more polarizable chlorine ion. There was a substantial change in the thermal stability of the glasses according to differential scanning calorimetric (DSC) analysis. The RbCl composition exhibited the largest ( T x − T g ) of 110°C whereas the RbF composition has the smallest value of 68°C. The chloride substitution increased the thermal expansion coefficient very slightly in the Na-containing glasses ( Δα ≈ 2 × 10 −6 ) and not at all in the Rb-containing glasses. However, the chloride containing glasses were found to be less chemically durable in water due to the higher solubility of chloride as compared with fluoride. These modifications in properties demonstrate the feasibility of a chlorofluoride core/fluoride clad fiber optic with high thermal stability, extended IR transparency, and large numerical aperture.

Recently a radon sensor using a glass scintillator in a fiber bundle structure was developed at Rutgers University. This instrument employs a flow of atmospheric air carrying the radon gas and its progeny in trace amounts through the bundle at room temperature. A central problem of interpretation is to distinguish whether the radioactive 222Rn atoms whose α decay is detected in the sensor are in the gas phase in the narrow spaces between the fibers or are adsorbed on the surfaces of the fibers. At the 43rd National Symposium of the American Vacuum Society (1996), calculated physical adsorption isotherms of radon were reported over a wide range of pressures, coverages, and temperatures. The latter explicitly included room temperature (300 K). The question arises as to whether this calculated isotherm is applicable to the Rutgers sensor. From radioactive considerations alone, in one experiment, it is estimated that there is either an upper bound of 5.5×10−10 Torr on the partial pressure of Rn or an upper bo...

We demonstrate nanostructural evolution resulting in highly increased photoluminescence in silicates doped with Er3+ ions. High-resolution transmission electron microscopy (HRTEM) imaging, nano-energy dispersed X-ray (NEDX) spectroscopy, X-ray diffraction (XRD) and photoluminescence analysis confirm the local composition and structure changes of the Er3+ ions upon thermal annealing. We studied two types of amorphous nanopowder: the first is of the composition SiO2/18Al2O3/2Er2O3 (SAE), synthesized by combustion flame-chemical vapor condensation, and the second is with a composition of SiO2/8Y2O3/2Er2O3 (SYE), synthesized by sol-gel synthesis (composition in mol%). Electron diffraction and HRTEM imaging clearly show the formation of nanocrystallites with an average diameter of approximately 8 nm in SAE samples annealed at 1000 degrees C and SYE samples annealed at 1200 degrees C. The volume fraction of the nanocrystalline phase increased with each heat treatment, eventually leading to complete devitrification at 1400 degrees C. Further XRD and NEDX analysis indicates that the nanocrystalline phase has the pyrochlore structure with the formula Er(x)Al(2-x)Si2O7 or Er(x)Y(2-x)Si2O7 and a surrounding silica matrix.

In this study, SiO 2 /Al 2 O 3 /Er 2 O 3 (SAE) nanopowders were fabricated by the Combustion Flame − Chemical Vapor Condensation (CF-CVC) technique with average primary particle sizes ranging from 10-30 nm. Fluorescence and lifetime measurements were made both on as-prepared powders, as well as heat treated powders, to compare the thermal annealing effects on optical properties. At an annealing temperature of 1000°C, the SAE became partially devitrified with extremely broad (FWHM ≈ 78 nm) and flat emission spectra, which is highly desirable for Wavelength Division Multiplexing (WDM) in optical amplifiers. The unique optical properties of the powders at this temperature, are attributed to the formation of a metastable phase consisting of an uniform nano-scale dispersion of a metastable intermediate SiO 2 (Al,Er) 2 O 3 phase in an amorphous SiO 2 matrix. At higher heat treatments (1400°C), a dual-phase equilibrium structure was formed, consisting of a pyrochlore phase in a crystobalite matrix.