Combined electrospray-scanning mobility particle sizer (ES-SMPS) and time-resolved synchrotron radiation-small-angle X-ray scattering (SR-SAXS) investigation of colloidal silica aggregation. Part II. Influence of aggregation initiator on gel stability.

The effect of ion specificity on the slow aggregation of silica nanoparticles with various initial morphology was investigated with an electrospray-scanning mobility particle sizer (ES-SMPS) and time-resolved synchrotron radiation-small-angle X-ray scattering (SR-SAXS). This combination provides a unique tool to monitor and resolve the early aggregate development in detail. Aggregation was induced by varying the K(2)CO(3) or KCl concentration to obtain a fixed gelation time of ∼40 min, and the results were compared with those obtained in a previous paper (Johnsson et al. J. Phys. Chem. B 2011, 115, 765-775) for NaCl. All dispersions produced gels that contained free primary particles well past the point of gelation (PoG). The initial aggregate formation and obtained gel morphologies were independent of the aggregation initiator. Nevertheless, ion-specific effects were observed for the rate of the stability increase of the 3-dimensional (3D) gel structure. The formation of a stable structure was fastest in the presence of the strongly hydrated counterions, and a clear anion effect was observed. The obtained gel stabilities were interpreted by relating the rate of formation of covalent siloxane bonds to the polarization of the water molecules surrounding structure-maker ions.

Combined electrospray-SMPS and SR-SAXS investigation of colloidal silica aggregation. Part I. Influence of starting material on gel morphology.

The slow aggregation of monodisperse, polydisperse, and preaggregated silica nanoparticles was studied with an electrospray-scanning mobility particle sizer (ES-SMPS) and time-resolved synchrotron radiation-small-angle X-ray scattering (SR-SAXS). Aggregation was induced by varying the NaCl concentration to obtain a fixed gelation time of ∼40 min. The combination of these techniques provides a unique tool to monitor and resolve the aggregate development in detail. The monodisperse spherical particles were converted to dimers, trimers, and eventually larger clusters as the aggregation proceeded, while the polydisperse spherical particles formed large clusters at an early stage. The initial particle shape and polydispersity had profound effects on the morphology of the aggregates; spherical primary particles produced compact spherical clusters, whereas the preaggregated dispersions formed open, elongated aggregates. All dispersions produced gels that contained free primary particles well past the point of gelation. The stability of the aggregates and the gel morphology were interpreted by relating to the structure of porous gel layers around the particles.

Detection of nodal micrometastases using immunohistochemistry and PCR in melanoma of the arm and trunk.

Sentinel node (SN) mapping and biopsy seems at present the best way to assess the nodal status in cutaneous melanoma without removing the lymphatic chain. The procedure is minimally invasive, safe and low cost, and allows selection of patients who can benefit from elective node dissection. From March 1997 up to July 1999 we examined 112 SNs excised after lymphatic mapping from 95 patients (48 males and 47 females) with stage I cutaneous melanoma affecting the trunk or limbs. Of these, 88 SNs from 74 patients were submitted to polymerase chain reaction (PCR) in order to detect tyrosinase mRNA. A new antibody (anti-tyrosinase, Clone T311, IgG2a type, Lab Vision Corporation) was used to detect nodal micrometastases. The search for micrometastases was histologically positive in 15 SNs and negative in 97. The 88 SNs examined using molecular biology were positive in 40 cases and negative in 48. In 28 only the PCR was positive. The new antibody used to detect micrometastases was shown to be very useful. Cases positive on both conventional histology and PCR were Clark level II or more and were thicker than 0.6 mm. No difference with regard to site or sex was observed. Lymphoedema and hypersensitivity reactions, nor the inability to work, did not occur. Only patients with histologically proven micrometastases underwent elective node dissection. Cases positive only on molecular biology were submitted to close follow-up.

[Mega-poly-calicosis. Apropos of a case with prenatal and postnatal diagnosis]. / Mégapolycalicose. A propos d'un cas avec diagnostic anté-natal et postnatal.

We report the first published case of megapolycalicosis with prenatal ultrasound diagnosis. Pyeloureteral junction dysplasia was observed only after delivery. The etiopathogenesis of megapolycalicosis (MPC) and its hypothetical association with uretero-pelvic junction obstruction are discussed. Presence of polycalicosis, good glomerular filtration and absence of compensatory controlateral renal hypertrophy are determinant in the diagnosis.

Scintigraphy of the parathyroid glands with 201TI: experience with 250 operated patients.

Parathyroid scintigraphy confirmed its validity in the preoperative localization of enlarged parathyroids, showing a sensitivity of 82% in a series of 250 patients suffering from primary hyperparathyroidism and successfully operated on. The glands better visualized were in an ectopic site or they were completely or partially outside the thyroid so that they were easily visible without employing digital image subtraction. This is nevertheless necessary to visualize parathyroids in a retrothyroid site but some problems arise, related not only to movements of the patient but also to the instrumentation to perform a correct image subtraction.

[Determination of glomerular filtration during sequential scintigraphy in the evaluation of separate renal function]. / La determinazione del filtrato glomerulare in corso di scintigrafia sequenziale nella valutazione della funzione renale separata.

The serial renal scan, a rapid series of images obtained with a scintillation camera, is explained; it visualizes the arrival to the kidneys and the passage through the parenchyma and the pelvocalyceal system of 99mTc-DTPA, a tracer cleared by glomerular filtration. Dynamic imaging of the kidneys provides more extensive information regarding anatomical structure and renal function that cannot be obtained by other noninvasive techniques. Computerized data analysis provides a lot of parameters, such as global and parenchymal transit times, useful in differentiating obstructive from non-obstructive uropathy, and total and separate glomerular filtration rate. 99mTc-DTPA computer-assisted scintigraphy is recommended as a routine method in nephro-urologic conditions where an accurate evaluation of separate renal function is required.

New perspectives in localizing enlarged parathyroids by technetium-thallium subtraction scan.

Double-tracer scanning (Tc-99m as pertechnetate and Tl-201 as chloride) with an Anger camera and computerized image subtraction was performed in 61 patients whose clinical and biochemical findings had suggested primary hyperparathyroidism. This study showed intra- or extrathyroidal focal uptake of thallium in 37 cases. Among these, 24 patients underwent surgery, and 18 parathyroid adenomas, five carcinomas, and one hyperplastic gland were found exactly in the sites predicted by scintigraphy. Among 24 patients with negative scans, only two underwent surgery; a hyperplastic parathyroid gland (diam less than 0.5 cm) was found in both. The success rate was 92% in the cases in which operation was performed. We believe that the new method may be useful in the preoperative detection of parathyroid enlargements.