Development of a portable immunoextraction-reversed-phase liquid chromatography system for field studies of herbicide residues

A portable system based on immunoextraction and reversed-phase HPLC was developed for the field analysis of herbicides in groundwater and surface water. Atrazine, simazine, and cyanazine were used as model analytes for this work. These were measured in water by using three coupled columns: an anti-atrazine antibody column for the selective extraction of these analytes, a reversed-phase precolumn for their reconcentration, and a reversed-phase analytical column for their separation. Various factors were considered in the optimization of this system, including the binding properties of the immunoextraction column, the effect of flow rate on the performance of each column, the selection of sample volume, and the choice of mobile phases for the RPLC columns. A typical analysis with this system allowed the injection of one sample every 7.5 min and provided results for all three of the tested herbicides in less than 10 min. In the analysis of atrazine alone, samples could be injected every 4 min and results were obtained within 8 min. There was good correlation between this technique and a comparable benchtop system. The lower limits of detection for the given analytes were approximately 0.2-0.25 microg/L, with a linear range that extended to 20 microg/L and a dynamic range that went up to at least 100 microg/L. The use of this technique in the field was demonstrated through applications that involved the development of time and location profiles for triazine herbicides in environmental samples.     

Clinical image quality criteria for full field digital mammography: a first practical application

In order to quantify the clinical quality of full-field digital mammography, a set of image quality parameters is developed. The set consisted of 12 image quality criteria and 8 physical characteristics of the image. The first set interrogates the visibility of anatomical structures and typical characteristics of a digital image, such as noise and saturation of dark and white areas. The second set of criteria evaluates contrast, sharpness and confidence with the representation of masses, microcalcifications and the image. The use of these criteria is reported in a retrospective study, in which the impact of dose on the radiological quality of digital mammograms is evaluated. Fifty patients acquired in a low-dose mode were retrieved and compared with 50 patients acquired in a dose mode that was set 41% higher. The dose affects, more than expected, contrast and sharpness of the image, whereas the visibility of the anatomical structures remains unchanged. With these parameters, quantification of the image quality is possible; however, because of subjectivity of the parameters, only intra-observer comparison and evaluation of the individual parameters rather than the overall results are advised. Together with physical tests of image quality, critical radiological evaluation of the quality should be included in the acceptance process of digital mammography.     

A quantitative method for evaluating the detectability of lesions in digital mammography

This study presents a quantitative method for evaluating the detectability of microcalcifications in digital mammography. Four hundred and twenty microcalcifications (with various morphology, size and contrast), simulated with a previously validated method, were used for the creation of image datasets. Lesions were inserted into 163 regions of interests of 59 selected raw digital mammograms with various anatomical backgrounds and acquired with a Siemens Novation DR. After processing, these composite images were scored by experienced radiologists, who located multiple simulated lesions and rated them under conditions of free-search. For statistical analysis, free-response receiver-operating characteristic curves are plotted; the use of jackknife free-response receiver-operating characteristic method has also been investigated. The main advantage of this methodology is that the exact number of inserted microcalcifications is well known and that the lesions are fully characterised in terms of pathology, size, morphology and peak contrast. A first application has been the evaluation of the effect of anatomical background on microcalcifications detection. Preliminary findings in this study indicate that this method may be a promising tool to evaluate factors that have an influence on the detectability of lesions, such as the clinical processing or the viewing conditions.     

Redox enzymes immobilized on electrodes with solution cosubstrates. General procedure for simulation of time-resolved catalytic responses

In view of the existing and potential applications of electrochemical enzymatic catalysis with redox enzymes immobilized on the electrode surface in biosensors, a numerical calculation procedure for simulating their cyclic voltammetric responses is presented. It is applicable to systems involving a redox cosubstrate in solution. The cosubstrates, substrates, products, and inhibitors are assumed to diffuse linearly (planar electrode) between the electrode and the solution. The reactions in which the various forms of the immobilized enzyme participate may be as numerous and intricate as required by the simulation with no other restriction than the computing time. They may, at will, follow or not follow Michaelis-Menten kinetics. Slow charge-transfer cosubstrates are treated in the framework of Butler-Volmer kinetic law.     

Lymphatic staging by laparoscopic surgery

Lymphadenectomy is mandatory in vesical and prostatic tumours for a precise staging of candidates to radical surgery. Presentation of our series of 18 ilioobturative lymphadenectomies between May 1992 and February 1993, performed in 14 prostate carcinoma and 4 vesical tumours. As most interesting results, the average number of nodes removed, which was 8, and the discovery of nodular affectation in 5 cases, understaged by the non-invasive procedures, are highlighted; likewise, the reduction in surgery duration up to the current frame of 80 to 120 minutes must be emphasized. Mortality due to the procedure was null. We believe that laparoscopic lymphadenectomy should be the choice technique in the staging of tumoral dissemination in the ilioobturative domain.     

Dedicated microprocessors for realtime identification of multivariable systems

In this paper, an algorithm is proposed for identifying multivariable systems in state-space form from noisy data, which is suitable for implementation on dedicated microprocessor systems. The proposed algorithm uses the normalized stochastic approximation criterion which reduces the computational complexity and memory requirements. It is shown that the overall performance of the proposed stochastic approximation algorithm when using a dedicated microprocessor with fixed point arithmetic is superior to the extended least-squares method in terms of memory requirements, execution speed per iteration, and the estimation results.     

Renin-secreting tumor detected by MRI]

We report an uncommon case of small renin secreting tumor of the kidney located in the medulla. The tumor was primarily detected by MRI and subsequently studied by spiral CT. The results and limitations of both techniques are discussed.     

Texture as a reflection of microstructure

The perception of texture has been correlated to the microstructure of particulate whey protein gels. A full, two-level, factorial experimental design was used in which the processing conditions, pH, heating rate and addition of salt were used as design factors. The texture of the gels was analysed by a sensory panel, and the microstructure was analysed by light and electron microscopy. The microstructure was quantified by using different types of image analysis.

In this study of particulate whey protein gels, the test principles of analysing texture were divided into two groups: destructive tests and non-destructive tests. The microstructural parameters can also be divided into two groups: overall network dimensions (pore size and particle size) and strand characteristics. The texture as measured with destructive methods was sensitive to overall network dimensions, whereas texture as measured with non-destructive methods was sensitive to the strand characteristics of particulate protein gels.     

Influence of SDZ-PSC833 on daunorubicin intracellular accumulation in bone marrow specimens from patients with acute myeloid leukaemia

From August 1987 through February 1995 we performed 42 surgical procedures in 29 patients with occluded or stenotic radiocephalic arteriovenous fistulae. Operations were designed to preserve native veins for cannulation (Group I) or to preserve access in the same forearm, bypassing the failed fistula (Group II). For 27 procedures in 22 Group I patients, cumulative primary patency was 70%, 57%, and 47% at 6, 12, and 18 months, respectively. A subgroup of patients was identified, however, in whom excellent results could be reliably predicted. Among 19 hemodynamically stable patients with mature fistulae amendable to more proximal arteriovenous anastomoses, cumulative primary patency was 100%, 81%, and 67% at 6, 12, and 18 months, respectively. Secondary patency for 17 such patients was 100%, 89% and 89% for these same intervals. In Group II only two of ten patients required use of other access sites (9 1/2, 18 1/2 months). We believe that all occluded or stenotic radiocephalic arteriovenous fistulae should be considered for surgical salvage. Excellent results can be predicted for (1) hemodynamically stable patients with (2) mature fistulae that (3) fail near the arterial anastomosis and are (4) amendable to new more proximal arteriovenous anastomoses.