Validation of analytical capillary electrophoresis methods for use in a regulated environment

Since its introduction into the analytical laboratory, CE has had to prove that it was capable of generating results comparable to HPLC or GC techniques in the six areas (specificity, precision, accuracy, linearity, ruggedness, and range) typically required of validated methods intended for submission to governmental agencies. This paper will showcase the development and validation of two analytical methods: one for specific identification of HEPES (N-[2-hydroxyethyl]piperazine-N'-[2-ethane sulfonic acid]) and the other to quantitate millimolar concentrations of tris (tris[hydroxymethyl]aminomethane) in high electrolyte solutions. Utilizing neutral markers and internal standards, results for HEPES demonstrate that migration time reproducibility, expressed as %RSD of 2% or less on a variety of capillaries, is obtainable. Additionally, for quantitation of tris, the values obtained for accuracy (%relative mean bias), precision (%RSD), and linearity (r2) over multiple days and capillaries meet the rigorous standards we require of HPLC or GC methods.     

Failure probability and optimum microstructure of pressure vessel steels

This paper presents a method for assessing the probability of brittle fracture in steels used for nuclear power generating equipment. The method is based on a statistical analysis of microstructural parameters and on physical models of the initiation and propagation of cleavage microcracks. The least probability of brittle failure ascertained by this method has been utilized for determining the optimum ferrite grain size. This method represents a foundation for systematic control of the brittle fracture characteristics of engineering steels employed for the components of nuclear power stations.     

Germanium-antimony-selenium-tellurium thin films: Clusters formation by laser ablation and comparison with clusters from mixtures of elements

Quaternary germanium-antimony-selenium-tellurium (Ge-Sb-Se-Te) thin films deposited from Ge_19.4Sb_16.7Se_63.9−xTe_x (x = 5, 10, 15, and 20) glass-ceramics targets by radio frequency magnetron sputtering were studied using laser ablation quadrupole ion trap time of flight mass spectrometry. Binary, ternary, and quaternary Ge_aSb_bSe_cTe_d clusters were formed and their stoichiometry was determined. By comparison of the clusters obtained from quaternary Ge-Sb-Se-Te thin films and those from ternary Ge-Sb-Te materials, we found that Ge-Te species are not detected from the quaternary system. Furthermore, Ge-Se and Se-Te species are missing in mass spectra generated from Ge-Sb-Se-Te thin films. From the Ge-Sb-Se-Te thin films, 16 clusters were detected while ternary Ge-Sb-Se glasses yielded 26 species. This might be considered as a signal of higher stability of Ge-Sb-Se-Te thin films which is increasing with a higher content of Te. The missing (Se₂⁺, Ge_aSb⁺ (a = 1–4), and GeSe_c⁺ (c = 1, 2)) and new (Ge⁺ and Sb_bTe⁺ (b = 1–3)) clusters may indicate that some of the structural features of the films (Ge₂Se_6/2 and Se₂Sb-SbSe₂) were replaced by (GeSe_4−xTe_x and SbSe_3−xTe_x) ones. In addition, when comparing the stoichiometry of clusters formed from Ge-Sb-Se-Te thin films with those from the mixtures of the elements, only Sb₃⁺ and SbSe⁺ were observed in both cases. The knowledge gained concerning clusters stoichiometry contributes to the elucidation of the processes proceeding during plasma formation used for the chalcogenide thin films deposition.     

Endovascular stent graft repair for aneurysms on the descending thoracic aorta

BACKGROUND: The traditional treatment of aneurysms of the descending thoracic aorta includes posterolateral thoracotomy and aortic replacement with a prosthetic graft. In this study, we report our experiences and results in endovascular stent graft placement as an alternative to surgical repair. METHODS: Between January 1989 and July 1997, a total of 68 patients (24 women) underwent replacement of the thoracic aorta. Mean age at operation was 51 years. Fifty-eight patients underwent conventional surgical treatment. All of these patients were suitable candidates for endovascular stenting; however, no stent graft material was available at the time of operation. Ten patients (1 chronic dissection, 9 atherosclerotic aneurysm) received in the past 8 months the first commercially manufactured endovascular stent graft. The mean diameter of the aneurysms in this group was 7 cm (range, 6 to 8 cm). Two stent patients were operated on using only spinal cord analgesia. All stent grafts were custom designed for each of the 10 patients. RESULTS: The 30-day mortality in the conventional group was 31% versus 10% in the stent group. Mean length of intervention was 320 minutes in the conventional group versus 150 minutes in the endovascular group. Spinal cord injury occurred in 5 patients (12%) in the surgical group, whereas none of the stented patients developed any neurologic sequelae. Mean intensive care unit stay was 13 days, followed by a mean of 10 days on a ward in the first group compared to 4 days in the intensive care unit and 6 days on the ward in the stent group. One stent was required in 2 patients, two stents were required in 3 patients, and four stents were deployed in 5 patients of our series. Five patients required transposition of the left subclavian artery to achieve a sufficient neck for the proximal placement of the stent. There was complete thrombosis of the thoracic aortic aneurysm surrounding the stent graft in 8 patients (80%). Two patients required restenting as a result of leakage (20%). Stent graft placing was performed through the femoral artery in 8 patients, whereas access was only achieved through the abdominal aorta in 2 patients. CONCLUSIONS: These preliminary results demonstrate that endovascular stent graft replacement might be a promising, cheaper, and safe alternative method in selected patients with descending thoracic aneurysms.     

Fracture toughness and other mechanical metallurgy characteristics of pressure vessel steels

The objective of this work is to investigate the effect of specimen size and evaluation method on estimates of fracture toughness for three commercial pressure vessel steels in different heat treatment conditions. It is found that the fracture toughness values K_C recorded on large, 150 mm thick, specimens were consistently close to the lower bound envelope of the K_δC, K_JC and K_E values established on 20 mm thick specimens. Comparison of the various elasto-plastic fracture criteria ascertained on a single specimen shows that the variations in these values are relatively slight which implies that the evaluation techniques used in this study can be considered as giving results that are, for practical purposes, the same.     

‘Smart’ Raman/Rayleigh imaging of nanosized SiC materials using the spatial correlation model

Non-destructive Raman and Rayleigh microspectrometries were used to map nanostructural and topological variations across the diameter of the SCS-6 Textron SiC fibre. It is shown for the first time that Rayleigh imaging offers a competitive alternative to AFM measurements for materials containing carbon as a second phase. The Spatial Correlation Model has been used to decompose the SiC Raman spectra into amorphous and crystalline components. Smart Raman images, which contain the calculated structural parameters revealed the nanostructure distribution. A good agreement has been obtained at the nanoscale between these smart images and transmission electron microscopy (TEM) data. A major asset of Raman smart images is to give a non destructive and global view on the crystal quality, grain size and residual stress. The potential and the limitations of the procedure are discussed.     

"Healthy Dubec" -design of a joint Czech-American community project for the reduction of cardiovascular and cerebrovascular disease (adapted from American experience)

A case of renal angiomyolipoma composed primarily of smooth muscle element is presented. It was a solitary small tumor without evidence of tuberous sclerosis. The imaging findings including ultrasonography, computerized tomography, magnetic resonance imaging, and angiography were not characteristic of angiomyolipoma, but suggestive of atypical renal cell carcinoma, and a simple nephrectomy was performed. The diagnostic considerations, particularly imaging features of angiomyolipoma, are discussed.     

Elevated free fatty acids induce uncoupling protein 3 expression in muscle: a potential explanation for the effect of fasting

The newly described uncoupling protein 3 (UCP3) may make an important contribution to thermogenesis in humans because of its high level of expression in skeletal muscle. Contrary to expectations, fasting, a condition that reduces resting energy expenditure, has been reported to increase UCP3 expression in muscle. We have confirmed that a 10-fold increase in UCP3 mRNA levels occurs in rat quadriceps muscle between 12 and 24 h of food removal. A less consistent twofold increase in muscle UCP2 mRNA levels was observed in animals fasted for up to 72 h. Administration of recombinant leptin to prevent a fall in circulating leptin levels did not eliminate the fasting-induced increase in quadriceps UCP3 expression. Administration of a high dose of glucocorticoid to fed animals to mimic the increase in corticosterone induced by fasting did not reproduce the increase in UCP3 expression observed in fasted animals. In contrast, elevation of circulating free fatty acid levels in fed animals by Intralipid plus heparin infusion caused significant increases in the UCP3/actin mRNA ratio compared with saline-infused fed controls in both extensor digitorum longus (2.01 +/- 0.34 vs. 0.68 +/- 0.11, P = 0.002) and soleus muscles (0.31 +/- 0.07 vs. 0.09 +/- 0.02, P = 0.014). We conclude that free fatty acids are a potential mediator of the increase in muscle UCP3 expression that occurs during fasting. This seemingly paradoxical induction of UCP3 may be linked to the use of free fatty acid as a fuel rather than an increased need of the organism to dissipate energy.