Effect of experimental conditions on the in vitro stability of99mTc (Sn)-pyrophosphate

The in vitro stability of^99mTc (Sn)-PyP as a function of experimental conditions of the preparation of the kit and time elapsed after labeling has been tested. The preparation was protected by using nitrogen-purged reactant solutions and kit vials and by ascorbic acid. The samples under nitrogen are stable for 6 h when the content of^99mTc-pertechnetate raises to 5%. The best stability was achieved by addition of 5 g of ascorbic acid per ml of the kit (content of^99mTc-pertechnetate about 0.5%). To accelerate the decomposition, exogenous hydrogen peroxide was used. In this case it was found that the presence of 10 g of ascorbic acid inhibits the effect both of oxygen and peroxide (6 g H₂O₂/ml of the kit). Radiochemical purity of^99mTc (Sn)-PyP remains practically unchanged for 6 h (content of^99mTc-pertechnetate about 0.5%).     

Effect of cuprous ion on labeling of three skeletal imaging agents with99mTc

The effect of increased content of copper on the radiochemical composition of three skeletal imaging agents:^99mTc(Sn)-methylene diphosphonate (MDP),^99mTc(Sn)-pyrophosphate (PYP) and^99mTc(Sn)-2,3-dicarboxypropane-1, 1-diphosphonate (DPD) was observed only in the case of^99mTc(Sn)-MDP. It was found that the radiochemical purity of this radiopharmaceutical falls to about 50% when the copper content reaches about 10^–5 mol dm^–3. According to the results of radiochemical and biological analyses, it could be concluded that with the increase of copper content, the content of free pertechnetate rises, too. The two other radiopharmaceuticals,^99mTc(Sn)-PYP and^99mTc(Sn)-DPD, were found to be stable under the given experimental conditions.     

Comparative quality control of some bone-seeking99mTc radiopharmaceuticals by gel chromatography

The radiochemical purity of the three osteopatic ligands:^99mTc(Sn)-PyP,^99mTc(Sn)-DPD and^99mTc(Sn)-MDP has been determined by gel chromatography on Sephadex. The results of the analyses strongly depend on the composition of the eluent. The dilution effect of pure saline as eluent was observed in all the preparations examined. The most sensitive was found to be^99mTc(Sn)-PyP. The retention of^99mTc activity bound to the gel matrix (^99mTc-hydrolyte) was over 30%. The diphosphonates were found to be more stable (retention 10–15%). The retention is substantially lower, i.e. a high recovery of the labeled complexes is obtained when the eluent contains the ligand. The best results are obtained when the eluent contains the same concentrations of ligand and reductant as in the labeled complex. There was no significant difference in the behavior of the given radiopharmaceuticals prepared as a fresh solution and in the freeze-dried kit.     

Highly functionalized organomagnesium reagents prepared through halogen-metal exchange

Organomagnesium reagents occupy a central position in synthetic organic and organometallic chemistry. Recently, the halogen-magnesium exchange has considerably extended the range of functionalized Grignard reagents available for synthetic purposes. Functional groups such as esters, nitriles, iodides, imines, or even nitro groups can be present in a wide range of aromatic and heterocyclic organomagnesium reagents. Also various highly functionalized alkenyl magnesium species can be prepared. These recent developments as well as new applications of organomagnesium reagents in cross-coupling reactions and amination reactions will be covered in this Review.     

New flavonoid and stilbene derivatives from the fruits of Macaranga balansae

Abstract

Two new prenylated flavonoids, 4´-methyl-8-prenyltaxifolin (1) and 6,8-diprenyl-4´-methyl-naringenin (2) and a new geranylated stilbene, 4′-deprenyl-4-methoxymappain (3) together with eight known flavonoids (4–11) were isolated from the fruits of Macaranga balansae Gagnep. Their chemical structures were determined by means of spectroscopic methods including 1D, 2D NMR, and MS data. Compound 2 showed the highest cytotoxic activity against PanC1, A549, KB and LU-1 cell lines with IC₅₀ values range from 7.89 to 22.81?µM.     

An algorithm for shakedown analysis of structures with temperature dependent yield stress

This work is an attempt to answer the question: How to use convex programming in shakedown analysis of structures made of materials with temperature‐dependent properties. Based on recently established shakedown theorems and formulations, a dual relationship between upper and lower bounds of the shakedown limit load is found, an algorithm for shakedown analysis is proposed. While the original problem is neither convex nor concave, the algorithm presented here has the advantage of employing convex programming tools. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Near optimal bounds for the Erdős distinct distances problem in high dimensions

We show that the number of distinct distances in a set of n points in ℝ ^d is Ω(n ^{2/d − 2 / d(d + 2)}), d ≥ 3. Erdős’ conjecture is Ω(n ^2/d ).     

Microstructure and fracture behavior of semicrystalline polymer–clay nanocomposites

The relationships between the microstructure and the fracture behavior of three polymer/clay nanocomposites were studied. Two different polymer matrices were chosen, namely polyamide‐6 and polyethylene (compatibilized with PE‐g‐MA or PE‐g‐PEo), to reach very different clay dispersion states. The microstructure was characterized in terms of polymer crystallinity, orientation of the polymer crystalline lamellae, clay dispersion state, and orientation of the clay tactoids. The mechanical behavior was characterized by tensile tests. The essential work of fracture (EWF) concept was used to determine the fracture behavior of the nanocomposites. Both tensile and EWF tests were performed in two perpendicular directions, namely longitudinal and transversal. It is shown that the fracture behaviors of the matrices mainly depend on the polymer crystalline lamellae orientation. For the nanocomposites, the relationships between the matrix orientation, the clay dispersion states, the values of the EWF parameters (w_e and βw_p), and their anisotropy are discussed. The results show that the lower the average clay tactoid thickness, the lower is the decrease of fracture performance for the nanocomposite and the more consumed energy as longer the path of the crack. Besides, a linear dependence of the anisotropy of the EWF parameters of the nanocomposites on the average clay aspect ratio is found. The more exfoliated the structure is, the less pronounced the anisotropy of the EWF parameters. Interestingly, it is thought that the average clay aspect ratio is the parameter representing the clay dispersion state that governs the fracture anisotropy of the nanocomposites (as the elastic properties determined by tensile tests). © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1820–1836, 2008     

Polyharmonic dirichlet problems

A certain Dirichlet problem for the inhomogeneous polyharmonic equation is explicitly solved in the unit disc of the complex plane. The solution is obtained by modifying the related Cauchy-Pompeiu representation with the help of a polyharmonic Green function. Dedicated to Prof. S.M. Nikol’skii on the occasion of his 100th birthday and to the memory of P.G.L. Dirichlet on the occasion of his 200th birthday