Spherical Particles of Zirconia-Titania of Hexagonal Structure from a Neutral Amine Route

Through the sol–gel process, using the so-called neutral amine route, spherical particles of 1:1 zirconia–titania were synthesized from zirconium(IV) and titanium(IV) butoxides as well as 1,12-diaminododecane as precursor species. The obtained product exhibited a hexagonal structure, as determinated by X-ray diffraction data. The obtained material was also characterized by thermogravimetry, differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy, and surface area measurements. Despite the release of template molecules on heating, the spherical morphology was retained up to about 1200°C, at which the disruption of the spheres took place.     

Effects of Adsorbed Polyaniline on Redox Process on MoO3 Surface

The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press.     

A practical approach to assessment of sampling uncertainty

The paper reports the approach followed in the SOILSAMP project, funded by the National Environmental Protection Agency (ANPA)of Italy. SOILSAMP is aimed at assessing uncertainties associated with soil sampling in agricultural, semi-natural, urban, and industrial environments. The uncertainty assessment is based on a bottom-up approach, according to the Guide to the Expression of Uncertainty in Measurement published by the International Organization for Standardization (ISO). A designated agricultural area, which has been characterized in terms of elemental spatial distribution, will be used in future as a reference site for soil sampling intercomparison exercises. Received: 19 November 2001 Accepted: 6 January 2002     

Specific parametrisation of a hybrid potential to simulate reactions in phosphatases

Phosphatases are key biomolecules because they regulate many cellular processes. These enzymes have been studied for many years, but there are still doubts about the catalytic mechanism. Computer simulations can be used to shed light on these questions. Here we develop a new and specific parametrisation, and present extensive tests of a hybrid potential that can be used to reliably simulate reactions catalysed by phosphatases. High level ab initio data for phosphate ester thiolysis and alcoholysis is used in the training set. The parametrised quantum mechanical Hamiltonian reproduces ab initio energies with a root mean-squared deviation of 3 kcal mol(-1) for species along the pathway of various phosphate ester reactions. Preliminary results for simulation with the calibrated hybrid potential of catalysis by the phosphatase VHR indicate the calculated reaction barriers are in very good agreement with experiment.     

Thiolysis and alcoholysis of phosphate tri- and monoesters with alkyl and aryl leaving groups. An ab initio study in the gas phase

Phosphate esters are important compounds in living systems. Their biological reactions with alcohol and thiol nucleophiles are catalyzed by a large superfamily of phosphatase enzymes. However, very little is known about the intrinsic reactivity of these nucleophiles with phosphorus centers. We have performed ab initio calculations on the thiolysis and alcoholysis at phosphorus of trimethyl phosphate, dimethyl phenyl phosphate, methyl phosphate, and phenyl phosphate. Results in the gas phase are a reference for the study of the intrinsic reactivity of these compounds. Thiolysis of triesters was much slower and less favorable than the corresponding alcoholysis. Triesters reacted through an associative mechanism. Monoesters can react by both associative and dissociative mechanisms. The basicity of the attacking and leaving groups and the possibility of proton transfers can modulate the reaction mechanisms. Intermediates formed along associative reactions did not follow empirically proposed rules for ligand positioning. Our calculations also allow re-interpretation of some experimental results, and new experiments are proposed to trace reactions that are normally not observed, both in the gas phase and in solution.     

The boundary of the Milnor fibre of complex and real analytic non-isolated singularities

Let \(f\) and \(g\) be holomorphic function-germs vanishing at the origin of complex analytic germs of dimension three. Suppose that they have no common irreducible component and that the real analytic map-germ \(f\bar{g}\) has an isolated critical value at 0. We give necessary and sufficient conditions for the real analytic map-germ \(f\bar{g}\) to have a Milnor fibration and we prove that in this case the boundary of its Milnor fibre is a Waldhausen manifold. As an intermediate milestone we describe geometrically the Milnor fibre of map-germs of the form \(f\bar{g}\) defined in a complex surface germ, and we prove an A’Campo-type formula for the zeta function of its monodromy.     

Prodrugs for the treatment of neglected diseases

Recently, World Health Organization (WHO) and Medicins San Frontieres (MSF) proposed a classification of diseases as global, neglected and extremely neglected. Global diseases, such as cancer, cardiovascular and mental (CNS) diseases represent the targets of the majority of the R&D efforts of pharmaceutical companies. Neglected diseases affect millions of people in the world yet existing drug therapy is limited and often inappropriate. Furthermore, extremely neglected diseases affect people living under miserable conditions who barely have access to the bare necessities for survival. Most of these diseases are excluded from the goals of the R&D programs in the pharmaceutical industry and therefore fall outside the pharmaceutical market. About 14 million people,mainly in developing countries, die each year from infectious diseases. From 1975 to 1999,1393 new drugs were approved yet only 1% were for the treatment of neglected diseases[3]. These numbers have not changed until now, so in those countries there is an urgent need for the design and synthesis of new drugs and in this area the prodrug approach is a very interesting field. It provides, among other effects, activity improvements and toxicity decreases for current and new drugs, improving market availability. It is worth noting that it is essential in drug design to save time and money, and prodrug approaches can be considered of high interest in this respect. The present review covers 20 years of research on the design of prodrugs for the treatment of neglected and extremely neglected diseases such as Chagas' disease (American trypanosomiasis), sleeping sickness (African trypanosomiasis), malaria, sickle cell disease, tuberculosis, leishmaniasis and schistosomiasis.     

The catalytic acid in the dephosphorylation of the Cdk2-pTpY/CycA protein complex by Cdc25B phosphatase

The development of anticancer therapeutics that target Cdc25 phosphatases is now an active area of research. A complete understanding of the Cdc25 catalytic mechanism would certainly allow a more rational inhibitor design. However, the identity of the catalytic acid used by Cdc25 has been debated and not established unambiguously. Results of molecular dynamics simulations with a calibrated hybrid potential for the first reaction step catalyzed by Cdc25B in complex with its natural substrate, the Cdk2-pTpY/CycA protein complex, are presented here. The calculated reaction free-energy profiles are in very good agreement with experimental measurements and are used to discern between different proposals for the general acid. In addition, the simulations give useful insight on interactions that can be explored for the design of inhibitors specific to Cdc25.     

HL-2M 装置电子回旋共振加热及电流驱动系统设计与研制进展

根据 HL-2M 装置物理实验加热的需求,完成了总功率为 8MW 的电子回旋共振加热及电流驱动 (ECRH/ECCD)系统设计,开展了波源、传输及天线等关键部件研制。8MW ECRH/ECCD 系统,由 8 套 105GHz/  1MW/3s 波源系统、8 条内径为 63.5mm 的真空传输线及三套极向实时可控的发射天线构成。目前,已完成 ECRH/ECCD 系统关键部件研制及其相关的桌面与高功率性能测试。测试结果表明,微波源回旋管输出微波功率 达到1MW/3s,在真空度为 10^‒2Pa 的过模波纹圆波导传输线中能低耗稳定传输,发射天线极向全量程角度转动响 应时间在 50ms 以内。