Luminescence of Gd2(WO4)3:Ln3+ at ambient and high hydrostatic pressure

This paper presents a spectroscopic characterization of Gd(2)(WO(4))(3):Ln(3+) (Ln=Eu, Pr, Tb and Dy). The luminescence and luminescence kinetics were measured under pressures up to 250 kbar. It was found that pressure quenches the luminescence of Pr(3+) and Tb(3+), whereas the emission of Eu(3+) and Dy(3+) was stable up to 250 kbar. This effect was related to a decrease in the ionization energy of Pr(3+) and Tb(3+) caused by pressure induced increase in energies of the Ln(2+) and Ln(3+) ions with respect to the band edges. Analysis of emission and excitation spectra allowed us to estimate the energies of the ground states of Ln(3+) and Ln(2+) with respect to the valence and conduction band edges of the Gd(2)(WO(4))(3) host. Differences between energies of the ground states of Ln(2+) and Ln(3+) have also been calculated.

High pressure luminescence spectra of CaMoO4:Pr3+

Steady state and time resolved luminescence measurements of CaMoO(4) doped with Pr(3+) as a function of hydrostatic pressure in the 1-175 kbar range are presented. It has been observed that with increasing pressure the spectral features shift towards lower energies, the decay times of both (3)P(0) and (1)D(2) emitting levels become shorter and the intensity of the (3)P(0) emission decreases to complete quenching at about 110 kbar, whereas that of the (1)D(2) emission increases in the 0-100 kbar range and then rapidly decreases when the pressure exceeds 127 kbar. A variation of the structure of the spectral manifolds indicates that a pressure induced phase transition of the host lattice occurs in the 80-100 kbar range. The quenching of the luminescence and the shortening of the decay times have been accounted for by means of a model that takes into account the role played by a praseodymium trapped exciton in the excited state dynamics of the investigated material.

Pressure-induced phase transition in LiLuF4:Pr3+ investigated by an optical technique

The luminescence and luminescence kinetics of LiLuF(4) doped with 1.5 at.% of Pr(3+) obtained at high hydrostatic pressure changing from ambient to 220 kbar applied in a diamond anvil cell are presented. It has been shown that pressure causes shift of the emission lines toward the red with rates of the order of single cm(-1) kbar(-1). The pressure-induced phase transition from tetragonal to fergusonite structure for pressure above 100 kbar was observed. The crystal field calculations performed showed that this phase transition reduces the point symmetry of the Pr(3+) site from the S(4) to the C(2) point group.

New Eu²+ sites in KMgF₃:Eu²+ crystal

The luminescence properties of KMgF(3):Eu(2 + ) are investigated at different pressures in the temperature range 25-292 K. Five new Eu(2 + ) luminescence (NEL) lines due to the [Formula: see text] transition are identified at 362.49 nm (L(1)), 362.53 nm (L(2)), 360.72 nm (L(3)), 360.15 nm (L(4)) and 359.59 nm (L(5)) together with the line at 359.32 nm (L(0)) which is well known in KMgF(3):Eu(2 + ). The emission lines under excitation at 325 nm show a strong dependence on temperature. At 25 K the emission spectrum consists of only two sharp lines, L(1) and L(2). Three additional lines (L(3), L(4) and L(5)) begin to appear with increasing temperature. With a further increase in temperature from 150 to 292 K all the lines disappear except for the single sharp line at 359.32 nm (L(0)). The zero-phonon transition of line L(0) is accompanied by vibronic sidebands. A pressure shift of five NELs is estimated to be about - 0.6 cm( - 1) kbar( - 1) similarly to the shift of line L(0), while the lifetimes of the NELs are about 0.7 ms which is shorter than that (5.2 ms) of L(0) at 80 K. The new luminescence lines are attributed to the Eu(2 + ) ions occupying the K( + ) sites with fluorine vacancy (F( - ) center) complexes.

Temperature and pressure dependence of the luminescence of Eu(2+)-doped fluoride crystals Ba(x)Sr(1-x)F(2) (x = 0, 0.3, 0.5 and 1): experiment and model

This paper summarizes experimental evidence of anomalous luminescence in Eu(2+)-doped fluoride crystals Ba(x)Sr(1-x)F(2) (x = 0, 0.3, 0.5 and 1). Luminescence, luminescence excitation spectra and luminescence kinetics obtained at ambient and high hydrostatic pressure at various temperatures are discussed. Hydrostatic pressure was shown to cause a redshift of normal [Formula: see text] emission and anomalous luminescence. The experimental data shows the existence of temperature- and pressure-induced spectral transformations where the anomalous luminescence is replaced by normal emission of Eu(2+) centers. We present a model that predicts a strong electron-lattice coupling of the trapped excitons as well as the pressure effect of the spectral transformation from anomalous to normal emission.

Pressure evolution of LiBaF(3):Eu(2+) luminescence

We investigated the single crystals of LiBaF(3) doped with Eu(2+) using high pressure spectroscopy, where high pressure was applied in a diamond anvil cell. Photoluminescence, time-resolved luminescence and luminescence kinetics at pressures from ambient to 200 kbar and at temperatures from 10 K to ambient were studied. At ambient conditions the luminescence spectra consisted of sharp lines peaked at 360 nm attributed to the [Formula: see text] transitions in the 4f(7) electronic configuration of Eu(2+) (the zero-phonon line and five single-phonon repetitions) and a broad band extending between 375 and 475 nm attributed to Eu(2+) trapped exciton recombination. When pressure was increased the Eu(2+) trapped exciton emission disappears and was replaced by the sharper band peaked at 355 nm, attributed to the [Formula: see text] transition in Eu(2+). To analyze the pressure dependence of luminescence spectra a model of impurity trapped excitons was developed. At temperatures lower than 50 K only the sharp lines related to [Formula: see text] transitions were observed for all pressures considered. Analysis of low temperature spectra allowed us to estimate the energies of the fifth phonon modes and the values of the Grüneisen parameters.

High pressure evolution of YVO(4):Pr(3+) luminescence

Photoluminescence and time-resolved photoluminescence spectra of YVO(4) doped with Pr(3+) obtained at high hydrostatic pressure up to 76 kbar applied in a diamond anvil cell are presented. At pressures lower than 60 kbar the steady state emission spectra consist of sharp lines related to the [Formula: see text] transition in Pr(3+). At pressures above 68 kbar the Pr(3+) emission intensity decreases and the corresponding bands are replaced by a broad band peaking at 19 500 cm(-1) attributed to perturbed VO(4)(3-) host luminescence. The quenching of the [Formula: see text] emission has been attributed to nonradiative transition to the charge transfer exciton trapped at Pr(3+) ion. The recovering of the VO(4)(3-) host luminescence at high pressure has been attributed to energy transfer from a Pr(3+) trapped exciton (PTE) to the host YVO(4). The kinetics of such a process is analyzed using the model of PTE considered as a Pr(4+) + electron bound by the Coulomb potential at the delocalized Rydberg states.

Repeated echocardiographic examinations of patients with suspected infective endocarditis

OBJECTIVE

To study the diagnostic contribution of repeated transthoracic (TTE) and transoesophageal echocardiography (TOE) among patients with suspected infective endocarditis.

METHODS

262 patients with 266 episodes of suspected infective endocarditis were referred for TTE and TOE over three years in a 423 bed university cardiology hospital. Patients were a mean (SD) of 47.6 (17.9) years old. 139 (52.3%) episodes occurred in men and 127 (47.7%) in women. The diagnostic information obtained from repeated TTE and TOE examinations was evaluated relative to the diagnosis of endocarditis.

RESULTS

TTE examinations were repeated in 192 (72.2%) and TOE examinations were repeated in 49 (18.4%) of 266 episodes. A mean of 2.4 TTE and 1.2 TOE examinations were performed for each episode of suspected endocarditis. The second and third TTEs added diagnostic information in 34 (26.7%) and the second and third TOEs added diagnostic information in 25 (19.7%) of 127 episodes with definite endocarditis. After the third TTE or TOE no additional diagnostic information was obtained.

CONCLUSIONS

The diagnostic contribution of repeated TTE or TOE for the diagnosis of endocarditis decreased as the number of repetitions increased. In this setting, the data do not substantiate more than three TTE or TOE examinations as an efficient strategy to increase the diagnostic yield for all but selected patients with suspected endocarditis.

Different familial transmission patterns in bipolar I disorder with onset before and after age 25

Gene identification in common disorders such as Alzheimer disease and breast cancer has greatly profited from the use of age of onset as criterion to delineate subgroups of disease characterized by different inheritance patterns. In bipolar affective disorder, where the majority of linkage studies have produced conflicting results, studies reporting clinical characteristics and familial occurrence of disease have suggested that age of onset might serve as an indicator for identifying more homogeneous subgroups of disease. Our study was the first to examine this hypothesis by the means of segregation analysis. We investigated a sample of 177 bipolar I probands recruited from consecutive admissions and their first- and second-degree relatives (2,407 subjects). Probands were subdivided into an early-onset (n = 107) and a late-onset group (n = 70) using an age of onset of 25 as a cut-off point. This age was chosen because the observed age of onset distribution was bimodal with a cut-off of 25 years. Morbid risks for affective disorder were found significantly higher (P = 0.01) in relatives of probands with an early onset than in probands with late onset of disease. The segregation analysis showed that the disease is transmitted differently in early- and late-onset groups. In the early-onset group, a non-Mendelian major gene with a polygenic component was favored while the data in the late-onset group were compatible with a multifactorial model. This result may have important implications for future molecular studies aiming at the identification of disease-associated genes.

Apolipoproteins AI, B, and E polymorphisms in severe aortic valve stenosis

Hypercholesterolemia has been related to aortic valve stenosis (AS). Polymorphisms of apolipoproteins (apo) AI, B, and E are associated with variable levels of plasma lipids, but the association between these polymorphisms and AS is unknown. In a case-control study of groups matched by age, sex, comparable body mass index, hypertension, triglycerides, high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) cholesterol, we analyzed the distribution of apo AI A/G mutation, apo B signal peptide insertion/deletion, apo B XbaI restriction fragment length. and apo E polymorphisms in 62 non-diabetic patients with severe aortic valve stenosis and 62 control subjects. All patients underwent echocardiographic analysis. Univariate analysis showed a higher prevalence of the XbaI X + /X + genotype (p = 0.007) of apo B and the apo E2 allele (p = 0.034) in patients with severe AS. Apo polymorphisms were not associated with lipid levels, left ventricular mass, or the aortic gradient.

SPECT dipyridamole scintigraphy for detecting coronary artery disease in patients with isolated severe aortic stenosis

BACKGROUND

The sensitivity and specificity of non-invasive methods--specifically single-photon emission computed tomography (SPECT) dipyridamole-thallium myocardial perfusion--for detecting coronary artery disease (CAD) in patients with severe aortic stenosis remains unclear. Occasionally, these patients present with atypical angina. Therefore, a CAD diagnosis must be excluded to prevent unnecessary cardiac catheterization.

METHODS

To determine the diagnostic value of SPECT dipyridamole-thallium imaging in this population, we compared the effectiveness of the imaging procedure with that of coronary angiography by prospectively analyzing patients who underwent both procedures. Group 1 included 59 patients who were asymptomatic or had atypical angina; group 2; 51 preoperative aged-matched patients with typical angina. SPECT acquisition was performed 15 min after 0.142 mg/kg/min of dipyridamole infusion completion, and redistribution images were performed 4 h after thallium injection. Two cut-off values of luminal diameter narrowing, >50 and >70%, defined significant CAD.

RESULTS

Coronary angiography with significant CAD (>50%) was present in 15 (25%) group 1 patients and in 16 (32%) group 2 patients (P=NS). The sensitivity was greater in group 2 than in group 1 (56 versus 26%; P=0.001). The specificity, positive and negative predictive value, and accuracy in the groups were similar. CAD of >70% luminal stenosis was present in 11 (19%) group 1 patients and in 12 (23%) group 2 patients (P=NS). The positive predictive value was greater in group 2 than in group 1 (75 versus 43%; P=0.001) but similar sensitivity, specificity, negative predictive value, and accuracy. The likelihood ratio for abnormal test increased in patients with CAD of >70%.

CONCLUSIONS

symptoms of typical angina had significant impact on test sensitivity, positive predictive value and likelihood ratio for abnormal test. Furthermore, SPECT dipyridamole-thallium imaging was a useful non-invasive method to exclude the diagnosis of significant CAD (high specificity) in asymptomatic and symptomatic patients with isolated severe aortic stenosis.

Arterial distensibility as a possible compensatory mechanism in chronic aortic insufficiency

OBJECTIVE

To evaluate elastic properties of conduit arteries in asymptomatic patients who have severe chronic aortic regurgitation.

METHODS

Twelve healthy volunteers aged 30+/-1 years (control group) and 14 asymptomatic patients with severe aortic regurgitation aged 29+/-2 years and left ventricular ejection fraction of 0.61+/-0.02 (radioisotope ventriculography) were studied. High-resolution ultrasonography was performed to measure the systolic and diastolic diameters of the common carotid artery. Simultaneous measurement of blood pressure enabled the calculation of arterial compliance and distensibility.

RESULTS

No differences were observed between patients with aortic regurgitation and the control group concerning age, sex, body surface, and mean blood pressure. Pulse pressure was significantly higher in the aortic regurgitation group compared with that in the control group (78+/-3 versus 48+/-1mmHg, P<0.01). Arterial compliance and distensibility were significantly greater in the aortic regurgitation group compared with that in the control group (11.0+/-0.8 versus 8.1+/-0.7 10(-10) N-1 m4, P=0.01 e and 39.3+/-2.6 versus 31.1+/-2.0 10(-6) N-1 m2, P=0.02, respectively).

CONCLUSION

Patients with chronic aortic regurgitation have increased arterial distensibility. Greater vascular compliance, to lessen the impact of systolic volume ejected into conduit arteries, represents a compensatory mechanism in left ventricular and arterial system coupling.

Mini-sternotomy for the treatment of aortic valve lesions

OBJECTIVE

To compare inverted-L mini-sternotomy performed above the sternal furcula with conventional sternotomy in patients with aortic valve diseases who undergo surgical treatment.

METHODS

We operated upon 30 patients who had aortic valve lesions that had clinical and hemodynamic findings. All patients underwent inverted-L sternotomy, which extended from above the manubrium of the sternum to the 3rd right intercostal space, without opening the pleural cavity. Their ages ranged from 32 to 76 years, and 18 were males and 12 were females. We used negative pressure in a venous 1/4-inch cannula, and the patients were maintained in Trendelemburg's position. Twenty-seven patients received bioprostheses with diameters ranging from 23 to 29mm. Three patients underwent only removal of the calcifications of the aortic valve leaflets and aortic commissurotomy.

RESULTS

The mean duration of anoxic cardiac arrest was 63.11min. Access was considered good in all patients. One death was due to pulmonary and renal problems not related to the incision. All patients had a better recovery in the intensive care unit, got out of bed sooner, coughed more easily, and performed prophylactic physiotherapeutic maneuvers for respiratory problems more easily and with less pain in the incision. Early ambulation was more easily carried out by all patients.

CONCLUSION

Mini-sternotomy proved to be better than the conventional sternotomy because it provided more comfort for the patients in the early postoperative period, with less pain and greater desire for early ambulation and all its inherent advantages.

Mitral valve repair in rheumatic patients

BACKGROUND

There is controversy regarding the role of reparative techniques for rheumatic-mitral valve disease. We have analyzed the late results of mitral valve repair in a group of patients with rheumatic mitral valve insufficiency.

METHODS

From March 1980 to December 1997, 201 patients with rheumatic fever underwent mitral valve repair at the Heart Institute, Hospital das Clínicas, Medical School, University of São Paulo. The mean age of patients was 26.9 +/- 15.4 years, with 59.7% of the patients being female. Other diagnoses were present in 67.7% of patients; the most common was tricuspid regurgitation (31.3%). Mitral valve repair techniques included: 1) Carpentier ring annuloplasty in 75 patients (37.3%); 2) posterior annuloplasty with bovine patch in 68 patients (33.8%); 3) posterior segmental annuloplasty in 16 patients (7.9%); 4) quadrangular resection of the posterior leaflet with ring plication in 11 patients (5.5%); 5) partial resection of the anterior leaflet in 6 patients (3%); 6) De Vega's annuloplasty in 6 patients (3%); 7) Kay's annuloplasty in 5 patients (2.5%); 8) Reed's annuloplasty in 4 patients (2%); and 9) miscellaneous techniques in 10 patients (4.9%). Combined techniques were used in 94 patients (46.8%), the most frequent of which was chordal shortening (48 patients, 23.9%). Other non-mitral cardiac procedures were performed in 113 patients (56.2%). Actuarial survival and event-free curves (Kaplan-Meier method) were compared by linear regression analysis.

RESULTS

The in-hospital mortality rate was 2.0% (four patients). The causes of death were multiorgan failure in two patients and low cardiac output in the other two patients. In the late postoperative period, 83.9% of the patients were in New York Heart Association (NYHA) functional class 1. The actuarial survival was 93.9% +/- 1.9% at a mean of 125 months. Twenty-three patients were reoperated in the postoperative period at a mean interval of 35.7 months. Survival free from reoperation was 43.3% +/- 13.7% at 125 months. When analyzing the patients according to age, actuarial survival was 91.3% +/- 3.8% in the group of patients younger than 16 years (Group 1), compared with 95.6% +/- 2.7% in the group older than 16 years (Group 2), with a statistically significant difference of p < 0.0001. Survival free from reoperation was 50.8% +/- 16.9% in Group 1 and 47.0% +/- 14.9% in Group 2 (p < 0.0001).

CONCLUSIONS

Late results obtained with mitral valve repair for rheumatic mitral valve insufficiency were satisfactory and exceeded those reported for mitral valve replacement in the same population.

Fisics-Incor bovine pericardial bioprostheses: 15 year results

BACKGROUND

From March 1982 to December 1995, 2,607 Fisics-Incor bovine pericardial bioprostheses were implanted in 2,259 patients. Mean age was 47.2 +/- 17.5 years, and 55% were male. Rheumatic fever was present in 1,301 (45.7%) patients.

METHODS

One thousand and seventy-three aortic valve replacements, 1,085 mitral replacements, 27 tricuspid replacements, 195 mitral-aortic replacements, and 16 other combined valve replacements were carried out. Combined procedures were performed in 788 (32.9%) patients, the most frequent being tricuspid valve repair (9.2%) and coronary artery bypass grafting (7.7%).

RESULTS

Hospital mortality was 8.6% (194 patients), 8.6% for the mitral group, 4.7% for the aortic group, and 12.8% for double-valve replacements. The linear rates for calcification, thromboembolism, rupture, leak and endocarditis were, respectively, 1.1%, 0.2%, 0.9%, 0.1% and 0.5% patient-year. The actuarial survival curve was 56.7 +/- 5.4% in 15 years. Survival free from endocarditis was 91.92%, survival free from thromboembolism was 95 +/- 1.7%, survival free from rupture was 43.7 +/- 9.8%, survival free from leak was 98.9 +/- 4.5%, and survival free from calcification was 48.8 +/- 7.9% in 15 years. In the late postoperative period, 1,614 (80.6%) patients were in New York Heart Association functional Class I.

CONCLUSIONS

We conclude that the results with the Fisics-Incor bovine pericardial prostheses were satisfactory in our group of patients.

Relapses, recurrences, valve replacements, and mortality during the long-term follow-up after infective endocarditis

BACKGROUND

Late prognosis after infective endocarditis has not been systematically studied in large series of patients with different underlying heart conditions in recent years.

METHODS

We studied an inception cohort study of 420 patients discharged after treatment of endocarditis from a university tertiary care hospital. The patients were aged 34.2+/-17.2 years (mean +/- SD), ranging from 2 months to 83 years; 270 (64.3%) were men and 150 (35.7%) were women. Mean follow-up was 6.1+/-4.3 years for survivors and 3.7+/-3.7 years for the patients who died during the follow-up. We studied the frequency and risk factors for relapses and recurrences of endocarditis, cardiac valve replacements, and deaths during the follow-up. Statistical analysis was performed through comparison of groups, of event-free survival, and risk ratios.

RESULTS

Relapses were observed in 14 (3.3%) patients. There was one recurrence of endocarditis in 48 (11.4%) patients, two (0.5%) in 2 patients, three in 1 patient (0.2%), and five (0.2%) in 1 patient. Valve replacement was performed in 83 (19.7%) patients. Ninety-eight (12.3%) patients died. Risk factors for recurrent endocarditis were increasing age (risk ratio 1.02) and male sex (risk ratio 1.61). Risk factors for valve replacement were recurrent endocarditis (risk ratio 1.62) and prosthetic valve endocarditis (risk ratio 1.61). Risk factors for death were increasing age (risk ratio 1.03) and recurrent endocarditis (risk ratio 2.06).

CONCLUSIONS

The long-term event-free survival for patients who survived their first episode of endocarditis was low. Recurrent endocarditis, prosthetic valve endocarditis, and increasing age contributed to the high rate of events during the follow-up.