Activities of oxygen in liquid thallium and indium from electrochemical measurements

Modified coulometric titrations on the galvanic cell;O in liquid Tl or In/ZrO₂(+CaO)/Air, Pt, were performed at 973, 1073, and 1173 K to determine the oxygen activities in liquid thallium and liquid indium. The standard Gibbs energies of solution of oxygen in liquid thallium and liquid indium for l/2 O₂ →O (1 at. pct) were determined respectively to be δG‡(in Tl) = -22000 + 0.74T (±300) cal/g-atom = -92000 + 3.10T (±1300) J/g-atom, δG‡(in In) = -42450+ 3.30T (±350) cal/g-atom = -177600 + 13.8T (±1500) J/g-atom, where the reference state for dissolved oxygen was an infinitely dilute solution. It was reconfirmed that the apparent initial oxygen concentration observed in the range of very low oxygen concentration in liquid metal was attributed to the oxygen released from the solid electrolyte.     

Density and viscosity of liquid Pu-U alloys

Density and viscosity determinations of liquid Pu-U alloys were made for five compositions, 5.5, 10.8, 16.6, 22.4, and 28.5 wt pct U, from near their liquidus temperatures to above 800°C. A vacuum pycnometric technique was used for the density determinations and an oscillating cup viscometer for the viscosity determinations. The partial molar volume of uranium was decreased approximately 15 pct in solutions containing up to 10.8 wt pct U and approached the normal molar volume at higher uranium concentration. The partial molar volume of plutonium changed by only 1 pct over the entire composition range. The viscosity of the alloys up to 10.8 pct U increased more rapidly than predicted from the pure components. Formerly with Monsanto Research Corp.     

The behavior of thallium during jarosite precipitation

Jarosite precipitation provides an effective means of eliminating thallium from zinc processing circuits, and a systematic study of the extent and mechanism of thallium removal during the precipitation of ammonium, sodium, and potassium jarosites was carried out. Thallium (as Tl⁺) substitutes for the “alkali” ion in the jarosite structure. Nearly ideal jarosite solid solutions are formed with potassium, but thallium is preferentially precipitated relative to either ammonium or sodium. Approximately 80 pct of the dissolved thallium precipitates during the formation of ammonium jarosite; the extent of thallium removal is virtually independent of thallium concentrations in the 0 to 3000 mg/L Tl range and of the presence of 75 g/L of dissolved Zn. Although the deportment of thallium is nearly independent of (NH₄)₂SO₄ or Na₂SO₄ concentrations >0.1 M, the precipitates made from more dilute media are relatively enriched in thallium. Likewise, the precipitates made from dilute ferric ion media are also Tl-rich. Low solution pH values or low temperatures both significantly reduce the amount of jarosite formed, but the precipitates made under these conditions are enriched in thallium. Furthermore, because thallium jarosite is more stable than the ammonium or sodium analogues, the initially formed precipitates are consistently Tl rich. The presence of jarosite seed accelerates the precipitation reaction, but dilutes the thallium content of the product. The results suggest that most of the thallium in a hydrometallurgical zinc circuit could be selectively precipitated in a small amount of jarosite, by carrying out the precipitation reaction for a short time in the absence of seed and from solutions having low alkali concentrations.     

Correlation of adenosine echocardiography and thallium scintigraphy

Echocardiography and thallium-201 imaging with coronary vasodilators such as dipyridamole have been shown to be useful in detecting the presence and prognostic significance of coronary artery disease. Adenosine, a potent and direct coronary vasodilator, has a shorter physiologic half-life than dipyridamole, which exerts its effect by blocking the cellular uptake of adenosine. Because of the potential advantage of dipyridamole, we undertook this study to determine the correlation of adenosine echocardiography with thallium scintigraphy. Forty-two patients (18 men and 24 women; mean age 64) who were unable to undergo treadmill exercise and were known or suspected to have coronary artery disease were studied. A baseline echocardiogram was obtained in four standard views followed by adenosine infusion at a rate of 140 micrograms/kg/min for 6 minutes. Thallium-201 was administered 3 minutes into the infusion while a second echocardiogram was performed. Thallium-201 imaging was begun immediately after the infusion of adenosine and repeated 4 hours later. Sixteen patients underwent coronary angiography within 1 month of the adenosine echocardiogram and thallium-201 study. At the peak infused dose of adenosine there was a significant increase in heart rate (12 beats/min; p = 0.0001) and rate-pressure product (1.3 x 10(3) beats/min x mm Hg; p = 0.02) and statistically insignificant decreases in systolic and diastolic blood pressures. Sixty-two percent of patients experienced side effects during the adenosine infusion, with chest pain, shortness of breath, and flushing occurring most frequently. These side effects resolved within 1 to 2 minutes after the infusion was stopped. Ischemic electrocardiographic changes occurred in 19% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

From thallium scan to molecular imaging

The diagnostic and prognostic evaluation of cardiovascular diseases has been improved considerably by the application of imaging procedures. Among many, scintigraphic procedures have emerged as important diagnostic tools to assess extent, severity, and prognosis in patients with coronary artery disease (CAD). For more than the last 30 years, however, the application of perfusion imaging has been extended to allow the combined evaluation of perfusion, perfusion reserve, and ventricular function. With positron emission tomography (PET), quantitative assessment of perfusion has become possible. In combination with pharmacological stress agents, the coronary flow reserve (CFR) can be quantitatively assessed as an early marker of endothelial dysfunction. PET in combination with metabolic tracers has added the evaluation of cardiac substrate metabolism, which has become an important clinical marker for ischemically jeopardized myocardium. The PET information is widely considered as the gold standard for tissue viability in the management of patients with advanced CAD and impaired left ventricular function (LVF). New tracer approaches include the assessment of cardiac innervation, which plays an increasingly recognized role in the pathophysiology of cardiac diseases. Radiolabeled catecholamine analogues provide visualization of sympathetic nerve terminals that are functionally altered in patients with diabetes mellitus and cardiomyopathy. In addition, this scintigraphic information allows the monitoring of physiological processes such as reinnervation of the transplanted heart. New methods, such as imaging of apoptosis and gene expression, are of interest in cardiology. Combining the therapeutic gene with a reporter gene, the transfection of cardiac tissue can be monitored noninvasively. First results employing the herpes simplex virus thymidine kinase reporter gene (HSV1-tk) are encouraging and represent an attractive approach for the use of PET imaging in the control of cardiac gene therapy.     

Comparison of persistent thallium perfusion defects by quantitative washout analysis with thallium reinjection in patients with coronary artery disease

Thallium reinjection can improve the detection of severely ischemic viable myocardium in patients with coronary artery disease. However, a disadvantage of this method is that it requires the acquisition of 3 separate sets of images and the administration of an additional dose of the radiotracer. Alternatively, quantitative analysis of the regional myocardial washout of thallium-201 can be easily obtained from the conventional postexercise and redistribution images without additional imaging time or radiation exposure to the patient. To determine whether this method can predict the results of thallium reinjection, this study analyzed thallium-201 images of 31 patients who had persistent perfusion defects in qualitative exercise/delayed redistribution single-photon emission computed tomographic thallium studies and who underwent thallium reinjection. The quantitative mean radioactive counts of each myocardial segment that had a persistent perfusion defect in the initial and delayed redistribution on 4-hour short-axis tomographic slices were measured to derive a delayed/initial ratio, and these values were compared with the results of thallium reinjection. The delayed/initial ratio was 1.06 +/- 0.22 in 39 segments that improved, versus 0.58 +/- 0.18 in 43 segments without improvement after reinjection (p < 0.001). Thirty-eight of the 39 segments that improved had a ratio of > or = 0.75, versus only 3 of the 43 segments that showed no improvement (sensitivity, 98%; specificity, 91%). The correlation between the delayed/initial ratio and reinjection results was equally high at any segment location or severity. It is concluded that quantitative regional thallium washout analysis predicts the results of thallium reinjection in segments with persistent thallium defects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Skin signs in the diagnosis of thallium poisoning

OBJECTIVES: We sought to determine the cost advantage of a strategy of same-sitting diagnostic catheterization and percutaneous transluminal coronary angioplasty (PTCA) (ad hoc) in comparison with staged PTCA. BACKGROUND: It is widely assumed that an ad hoc strategy lowers costs by reducing the length of hospital stay (LOS). However, this assumption has not been examined in a contemporary data set. METHODS: We studied 395 patients undergoing PTCA during 6 consecutive months. Cost analysis was performed using standard cost-accounting methods and a mature cost-accounting system. Costs were examined within three clinical strata based on the indication for PTCA (stable angina, unstable angina and after myocardial infarction [MI]). RESULTS: For the entire patient cohort, there was no significant cost advantage of an ad hoc approach within any of the strata, although there was a nonsignificant trend toward an ad hoc approach in patients with stable angina. For patients treated with conventional balloon PTCA alone, the lack of a significant difference between ad hoc and staged strategies persisted. For patients who received stents, there was a significant cost advantage of an ad hoc approach in all three clinical strata. An important cost driver was the occurrence of complications. Differences in the rates of complications did not reach statistical significance between ad hoc and staged strategies, but even a small trend toward greater complications in patients who had the ad hoc strategy negated cost and LOS advantages. Our study had the power to detect significant cost differences of $1,300 for patients with stable angina, $2,100 for patients with unstable angina and $2,500 for post-MI patients. It is possible that we failed to detect smaller cost advantages as significant. CONCLUSIONS: A cost savings with an ad hoc strategy of PTCA could not be consistently demonstrated. The cost advantage of an ad hoc approach may be most readily realized in clinical settings where the intrinsic risks are low (e.g., stable angina) or in which the device used carries a reduced risk of complications (e.g., stenting), because even a small increase in the complication rate will negate any financial advantage of an ad hoc approach.     

Are the results of thallium scintigraphy and coronary angiography equivalent? An evaluation of thallium scintigraphies performed at Vestfold Central Hospital

The value of exercise-redistribution thallium-201 perfusion scintigraphy (SPECT; single photon emission computed tomography) in the diagnosis of coronary artery disease was evaluated in 23 patients (one patient tested twice) who were subsequently submitted to coronary angiography. Reversible perfusion defects indicating myocardial ischemia were found in 22 patients, of whom 18 had angiographically significant coronary artery stenoses. Two patients had negative thallium scans, one had a normal angiogram and one had single vessel disease. Thus 18 of 19 patients with angiographically verified coronary heart disease had a positive thallium scan. The majority of patients with left main stenosis and triple vessel disease had scintigraphic evidence of double or triple vessel disease. The scintigraphic method identified the correct anatomical localization in 73% of the angiographically verified coronary artery stenoses. In conclusion, a positive exercise-redistribution thallium scan had a high predictive value in the diagnosis of coronary artery disease, whereas its value in estimating the number and localization of stenoses was more limited.     

火焰原子吸收光谱法测定粗铟中铊

粗铟样品中低含量铊的测定一般采用国家标准分析法 :甲基绿 -乙酸异戊酯萃取分光光度法。该方法操作繁冗 ,流程长 ,且有挥发性的有机溶剂乙酸异戊酯 ,危害分析人员健康。本文用原子吸收光谱法直接测定粗铟中低含量铊 ,测定结果与国家标准法一致 ,且操作简单、快速、选择性好 ,不使用有机试剂 ,改善了工作环境 ,节省了试剂。1　实验部分1 1　仪器和试剂WFX - 1C型原子吸收分光光度计。硝酸 (优级纯 ) :1 + 1 ;铊标准储备溶液 :1mg/mL ,称取 1 30 34g于1 0 5℃烘干的硝酸亚铊 (TlNO3,优级纯 )于 2 5 0mL烧杯中 ,加 1 5 0mL水溶解 ,移入 …