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The pros and cons of oxidative dehydrogenation of propane are outlined and a new catalytic system based on metal-doped cerianite catalysts is introduced. These novel materials catalyze the selective combustion of hydrogen from a mixture of hydrogen, propane, and propene at 550 degrees C. This gives three key advantages: energy is supplied directly where needed, product separation is made easier, and the dehydrogenation equilibrium is shifted to the desired products. A set of eighteen doped cerianites was synthesized in parallel, characterized, and screened for activity, selectivity, and stability in a cyclic redox system. The best results were obtained with Ce(0.89)Cr(0.02)Fe(0.09)O(2), Ce(0.98)Sn(0.02)O(2), and Ce(0.96)Cu(0.02)Zn(0.02)O(2), which gave 98 %, 91 %, and 98 % selectivity, respectively. Ce(0.89)Cr(0.02)Fe(0.09)O(2) also shows excellent stability in over 120 cycles (66 h on stream at 550 degrees C). Importantly, these doped cerias are monophasic crystalline materials. The dopants are incorporated as solid solutions throughout the fluorite lattice. This means that these catalysts are very stable (they do not sinter during reduction) as opposed to traditional supported metal oxides. The results show that both activity and selectivity towards hydrogen combustion can be tuned (increased or decreased) by selecting the appropriate dopant. Furthermore, the trends in selectivity differ from those measured on supported oxides of the same elements, which indicates that these novel materials indeed contain unique active sites. The factors governing selectivity towards hydrogen oxidation and the nature of the active site are discussed.

Leaching of palladium species from Pd nanoparticles under C--C coupling conditions was observed for both Heck and Suzuki reactions by using a special membrane reactor. The membrane allows the passage of palladium atoms and ions, but not of species larger than 5 nm. Three possible mechanistic scenarios for palladium leaching were investigated with the aim of identifying the true catalytic species. Firstly, we examined whether or not palladium(0) atoms could leach from clusters under non-oxidising conditions. By using our membrane reactor, we proved that this indeed happens. We then investigated whether or not small palladium(0) clusters could in fact be the active catalytic species by analysing the reaction composition and the palladium species that diffused through the membrane. Neither TEM nor ICP analysis supported this scenario. Finally, we tested whether or not palladium(II) ions could be leached in the presence of PhI by oxidative addition and the formation of [Pd(II)ArI] complexes. Using mass spectrometry, UV-visible spectroscopy and 13C NMR spectroscopy, we observed and monitored the formation and diffusion of these complexes, which showed that the first and the third mechanistic scenarios were both possible, and were likely to occur simultaneously. Based on these findings, we maintain that palladium nanoparticles are not the true catalysts in C--C coupling reactions. Instead, catalysis is carried out by either palladium(0) atoms or palladium(II) ions that leach into solution.

The connection between quantum size effects and the surface plasmon resonance of metal nanoclusters is introduced and the pros and cons of in situ and ex situ cluster analysis methods are outlined. A new method for estimating the size of nanoclusters is presented. This method combines core/shell cluster synthesis, UV-visible spectroscopy, and Mie theory. The core/shell approach enables the estimation of metal cluster sizes directly from the UV-visible spectra, even for transition metal nanoclusters such as Pd that have no distinct surface-plasmon peak in UV-visible region. Pd/Au and Au/Pd core/shell clusters as well as Au-Pd alloy clusters are synthesized and used as test cases for simulations and spectroscopic measurements. The results of the simulations and UV-visible spectroscopy experiments are validated with transmission electron microscopy.

The formation of Pd nanoclusters in solution is studied. This system has two types of light-absorbing species: Pd ions which absorb light via electronic transitions and Pd clusters and aggregates which absorb light via valence-conduction transitions and also scatter light due to their nanometric dimensions. Here we monitor these dynamic changes using UV-visible spectroscopy. The reduction and clustering concentration profiles are extracted from the raw data using a combination of net analyte signal (NAS) and principal component analysis (PCA) methods. PdCl2, Pd(OAc)2 and Pd(NO3)2 are used as Pd2+ precursors and various tetra-n-octylammonium carboxylates are applied as reducing and stabilising agents. This in situ approach enables the quantification of both the reduction of the Pd2+ ions and the growth of the Pd clusters. Kinetic models that account for ion reduction, cluster growth and aggregation are presented and the influence of the counteranions and the reducing agents on these processes is discussed.

The problem of soot emissions from diesel engines is introduced and the possible solution of combining doped perovskites and microwave (mw) irradiation to "clean up" diesel soot filters is outlined. Eighteen doped perovskite catalysts are synthesized and tested for propane and CO oxidation, which are taken as model components for soot. The activity, selectivity, and SO2 tolerance are compared under conventional heating and mw irradiation. By combining mw irradiation and doped perovskites, one can create "hot spots" on the catalyst, resulting in efficient and selective heating of the active site, as well as less poisoning. Sr-doped and Ce-doped manganese perovskites show the highest activity. These catalysts are also the most selective, and have a high mw susceptibility. Optimal SO2 tolerance is displayed by Cr perovskites, from which the La0.8Ca0.2CrO3 combination uniquely converts propane before CO, and therefore can be used to remove >C2 hydrocarbons from a mix with CO. Possible mechanistic scenarios are presented and discussed.

The advantages of bimetallic nanoparticles as C-C coupling catalysts are discussed, and a simple, bottom-up synthesis method of core-shell Ni-Pd clusters is presented. This method combines electrochemical and 'wet chemical' techniques, and enables the preparation of highly monodispersed structured bimetallic nanoclusters. The double-anode electrochemical cell is described in detail. The core-shell Ni-Pd clusters were then applied as catalysts in the Hiyama cross-coupling reaction between phenyltrimethoxysilane and various haloaryls. Good product yields were obtained with a variety of iodo- and bromoaryls. We found that, for a fixed amount of Pd atoms, the core-shell clusters outperform both the monometallic Pd clusters and the alloy bimetallic Ni-Pd ones. THF is an excellent solvent for this process, with less than 2% homocoupling by-product. The roles of the stabiliser and the solvent are discussed.

The advantages of combining heterogeneous catalysis and aryl chloride substrates for cross-coupling are introduced. A heterogeneous Pd/C catalyst is used for activating aryl bromides and electron withdrawing aryl chlorides via a one-pot 'domino' HALEX-Sonogashira reaction. No ligand or co-catalyst is required, and the cross-coupling products are obtained in moderate to good yields. The influence of the solvent, base, iodide source and catalyst is evaluated. The catalyst is reusable for at least six consecutive reaction cycles. A variation on this reaction using catalytic amounts of KI is also proposed.

We show that polyelectrolyte shells may be perfect hosts and microreactors for catalysis. Using a layer-by-layer self-assembly process to form hollow polyelectrolyte capsules, we show that individual layers can be replaced by palladium and gold nanoclusters forming robust cell-type microcapsules. Testing the catalytic activity of those embedded nanoclusters using the Sonogashira cross-coupling reaction, we show that simple self-assembled polyelectrolyte shells are ideal as carrier of at least one expensive catalyst, and possibly several, opening the road to new cascade reactions.

High-throughput experimentation and screening methods are changing work flows and creating new possibilities in biochemistry, organometallic chemistry, and catalysis. However, many high-throughput systems rely on off-line chromatography methods that shift the bottleneck to the analysis stage. On-line or at-line spectroscopic analysis is an attractive alternative. It is fast, noninvasive, and nondestructive and requires no sample handling. The disadvantage is that spectroscopic calibration is time-consuming and complex. Ideally, the calibration model should give reliable predictions while keeping the number of calibration samples to a minimum. In this paper, we employ the net analyte signal approach to build a calibration model for Fourier transform near-infrared measurements, using a minimum number of calibration samples based on blank samples. This approach fits very well to high-throughput setups. With this approach, we can reduce the number of calibration samples to the number of chemical components in the system. Thus, the question is no longer how many but which type of calibration samples should one include in the model to obtain reliable predictions. Various calibration models are tested using Monte Carlo simulations, and the results are compared with experimental data for palladium-catalyzed Heck cross-coupling.

The importance of monitoring the transport of organic contaminants in soil and groundwater, and the pros and cons of existing sampling methods, are outlined. A new, alternative sampling method is proposed, using a passive sampler that functions as a water-permeable, semi-infinite sink for passing solutes of interest. Tracers integrated in the device store information on the volume of water passing through the sampler during the installation period. The conceptual basis of the sampling method is described. This device enables flux-proportional monitoring of the concentrations of mobile contaminants in the soil and groundwater. 14C-labeled phenanthrene (PHEN) and glyphosate (GLY) are used as case study compounds in laboratory experiments. The sorption capacities and uptake kinetics of 13 adsorbents are screened and compared, as well as the dissolution kinetics of three tracer salts: calcium citrate, calcium fluoride (CaF2), and calcium hydrogen phosphate (CaHPO4). The application of the passive sampler is then demonstrated in long-term laboratory experiments, using large soil columns under steady-state hydraulic conditions. The accumulated flux of PHEN was sampled with an accuracy of 3.6%-17.8%, using graphitized carbon, hexagonal mesoporous silica, and cross-linked polymers as adsorbents. The accumulated flux of GLY was sampled with an accuracy of 12.4%, using gamma-alumina as an adsorbent. The advantages and limitations of this new environmental monitoring method are discussed.

The practical difficulties encountered in analyzing the kinetics of new reactions are considered from the viewpoint of the capabilities of state-of-the-art high-throughput systems. There are three problems. The first problem is that of model selection, i.e., choosing the correct reaction rate law. The second problem is how to obtain good estimates of the reaction parameters using only a small number of samples once a kinetic model is selected. The third problem is how to perform both functions using just one small set of measurements. To solve the first problem, we present an optimal sampling protocol to choose the correct kinetic model for a given reaction, based on T-optimal design. This protocol is then tested for the case of second-order and pseudo-first-order reactions using both experiments and computer simulations. To solve the second problem, we derive the information function for second-order reactions and use this function to find the optimal sampling points for estimating the kinetic constants. The third problem is further complicated by the fact that the optimal measurement times for determining the correct kinetic model differ from those needed to obtain good estimates of the kinetic constants. To solve this problem, we propose a Pareto optimal approach that can be tuned to give the set of best possible solutions for the two criteria. One important advantage of this approach is that it enables the integration of a priori knowledge into the workflow.

The importance of small metal clusters in catalysis and the problems in understanding the clustering process in solution are outlined. A new analysis method for UV/Vis spectra is presented and applied to monitor the kinetics of ion reduction and cluster formation in situ. This method, which is based on a combination of two chemometric techniques, takes into account the entire UV/Vis spectrum and offers better interpretation possibilities than the traditional "band-assignment" approach. This is particularly true for nanoclusters because these have significant spectral contributions also outside the broad plasmon band that is usually associated with them. The reduction of palladium, gold, and silver ions and the formation of the corresponding clusters is monitored in the presence of two different reducing agents, sodium borohydride and tetraoctylammonium acetate. While Pd2+ is found to reduce and cluster directly, the spectral decomposition of the Au3+ reduction profiles shows two species corresponding to the Au+ intermediate and the Au0 clusters. The rates of reduction and clustering for Pd, Au, and Ag are compared and the possibilities of synthesising multimetallic clusters of these metals by coreduction are discussed.

The application of robotic systems to the study of complex reaction kinetics is considered, using the cascade reaction A --> B --> C as a working example. Practical problems in calculating the rate constants k1 and k2 for the reactions A --> B and B --> C from concentration measurements of CA, CB, or CC are discussed in the light of the symmetry and invertability of the rate equations. A D-optimal analysis is used to determine the points in time and the species that will give the best (i.e., most accurate) results. When exact data are used, the most robust solution results from measuring the pair of concentrations (CA, CC). The system's information function is computed using numeric methods. This function is then used to estimate the amount of information obtainable from a given cascade reaction at any given time. The theoretical findings are compared with experimental results from a set of two-stage cascade experiments monitored using UV-visible spectroscopy. Finally, the pros and cons of using a single reaction sample to estimate both k1 and k2 are discussed.

Combinatorial chemistry and high-throughput experimentation (HTE) have revolutionized the pharmaceutical industry-but can chemists truly repeat this success in the fields of catalysis and materials science? We propose to bridge the traditional "discovery" and "optimization" stages in HTE by enabling parallel kinetic analysis of an array of chemical reactions. We present here the theoretical basis to extract concentration profiles from reaction arrays and derive the optimal criteria to follow (pseudo)first-order reactions in time in parallel systems. We use the information vector f and introduce in this context the information gain ratio, chi(r), to quantify the amount of useful information that can be obtained by measuring the extent of a specified reaction r in the array at any given time. Our method is general and independent of the analysis technique, but it is more effective if the analysis is performed on-line. The feasibility of this new approach is demonstrated in the fast kinetic analysis of the carbon-sulfur coupling between 3-chlorophenylhydrazonopropane dinitrile and beta-mercaptoethanol. The theory agrees well with the results obtained from 31 repeated C-S coupling experiments.

A small library of copper and noble metal nanoclusters is designed and synthesized. These clusters are tested as catalysts in the Suzuki cross-coupling of various aryl halides with phenylboronic acid. It is found that copper and copper/noble metal combination nanoclusters are active catalysts for this reaction, the most active being the combined copper/palladium clusters. Iodo-, bromo-, and chloroarenes can be used. In the case of p-nitrobromobenzene, a one-pot cross-coupling and selective hydrogenation is achieved.

A new batch device that simulates the conditions in water and wastewater treatment plants and enables the study of low-concentration feeds is described. The application of this apparatus to the monitoring of the concentration of inorganic and/or biological contaminants is demonstrated, using kaolin particles and Cryptosporidium parvum oocysts, respectively. The rate of inorganic particle attachment to the static medium is found to be directly proportional to the initial influent concentration. On the other hand, Cryptosporidium parvum removal is found to be more effective in the presence of additional (kaolin) particles, and this is attributed to electrostatic interactions between oppositely charged layers on the absorbing medium. Accordingly, the addition of humic materials is found to inhibit the removal process, possibly by neutralizing the positive charge on the kaolin particles. The relevance of these results to existing water purification processes in general and to risk assessment of microbiological contamination in particular is discussed.

Data from 37 patients who underwent a transmetatarsal amputation from January 1993 to April 1996 were reviewed. The mean age and diabetes duration of the subjects were 54.9 (+/- 13.2) years and 16.6 (+/- 8.9) years, respectively. The follow-up period averaged 42.1 (+/- 11.2) months. At the time of follow-up, 29 (78.4%) of the 37 patients still had foot salvage, 8 (21.6%) had progressed to below-the-knee amputation, and 15 (40.5%) had undergone lower-extremity revascularization. Twelve (80%) of the 15 revascularized patients preserved their transmetatarsal amputation level at a follow-up of 36.4 months. The authors concluded that at a maximum of 3 years follow-up after initial amputation, transmetatarsal amputation was a successful amputation level.

The concept of an organic reaction between two macroscopic solid particles is investigated. Thus, we study several reactions that have been recently reported to proceed "in the solid phase" and clearly show that, in most cases, grinding the two solid reactants together results in the formation of a liquid phase. This is true both for catalytic transformations (e.g., aldol condensations and oligomerization of benzylic compounds) and for noncatalytic reactions (Baeyer-Villiger oxidations, oxidative coupling of naphthols using iron chloride, condensation of amines and aldehydes to form azomethines, homo-etherification of benzylic alcohols using p-toluenesulfonic acid, and nuclear aromatic bromination with NBS). This liquefaction implies the existence of a eutectic mixture with T(fusion) below ambient temperature (although both reagents have higher than ambient melting points). In cases where heating is required, it is again clear that a phase change (from solid to liquid) occurs, explaining the observed reaction kinetics. On the basis of 19 experimental examples, we discuss the possibility of solid-phase organic reactions and the implications of these findings to the reaction between two solid reagents. A general description of such reactive systems is proposed, based on a consideration of the potential for eutectic (or peritectic) formation between the constituents of the liquid phases that arise during the process of mechanical mixing of the solid reagents and products.

The in situ combination of oxidative coupling of benzene to biphenyl and reductive coupling of chlorobenzene (also to biphenyl) using palladium catalysts (Pd(2+)/Pd(0)) is described. In each cycle, the reductive process regenerates the catalyst for the oxidative process and vice versa. Kinetic investigations show that the reaction rate depends on [C(6)H(6)], [C(6)H(6)Cl], and catalyst loading, with E(a)() = 13 kcal mol(-)(1). The reduced palladium catalyst undergoes deactivation through aggregation and precipitation, but it is observed that during this deactivation process the Pd(0) becomes an active catalyst for the reductive coupling of chlorobenzene. Accordingly, while Pd(0)/C particles are inactive, Pd(0) colloids do catalyze the tandem reaction. Conversion is increased in the presence of a phase-transfer catalyst, presumably due to stabilization of the active Pd(0) clusters. The two halves of the catalytic cycle are examined in the light of previous research, regarding analogous oxidative and reductive coupling reactions, using stoichiometric amounts of PdCl(2) and Pd(0), respectively. The roles of homogeneous PdCl(2) and Pd(0) clusters are discussed.

Irreparable late lesions after a malaria infection are rare. They occur mainly after infection of tropical malaria. As ascertained late lesions are regarded cerebral disturbances, e.g. epilepsy after cerebral tropical malaria, cardiac disturbances, e.g. arrhythmia after cardiac tropical malaria and chronic renal insufficiency after quartan malaria. Chronic liver diseases, e.g. cirrhosis, are not known as ascertained late lesions of malaria. Bodily lesions may be recognized by experts as malaria-depending, when kind and form of the course of malaria may be considered as cause meanwhile appearing symptoms anticipate a connection and other causes were excluded with regard to these lesions.

The influence of intravenous noradrenalin infusions in increasing dosages lasting 60 minutes on the peripheral venous total T3- and total T4-concentrations of blood, blood pressure and heart rate was established on 5 test persons during a period of 110 minutes. Immediately after the addition of 0.12 micrograms NA/kg Kgw./min an increasing tendency of the T4-concentration in the venous blood occurred, respectively. Under influence of higher NA-doses (0.20 and 0.33 micrograms/kg Kgw./min) the noradrenergically induced T4-increase (p < 0.05) with average increases of the T4-level by 28.7 and 22.3%, respectively, in comparison to the initial values was statistically secured. The total T3-concentration did not show any statistically secure changes under NA-infusion. The fundamental possibilities of an influence of the intravenously applied NA on the production of the hormone of the thyroid gland, the secretion of the thyroid hormone and the peripheral conversion are discussed. Using findings of animal experiments the supposition of the immediate influence of the NA on the follicle cells of the thyroid gland and the secretory process gains importance. The clinical importance of the adrenergic modulation of the thyroxin secretion for the clinician is discussed.

Results and experiences of some immunodiagnostic methods for amebiasis. Experiences concerning the laboratory diagnosis of invasive amebiasis are described and discussed. Technics used include the Passive Hemagglutination Test with E. histolytica antigen (Behring FRG) and sheep erythrocytes as carrier and the Indirect Fluorescence Antibody Reaction (IFAR) with corpuscular antigen prepared from cultures of E. histolytica strain HK 9. Comparatively for a part infected hamster liver (Dr. Richle strain) has been used as antigen. We conclude that IFAR with HK 9 antigen is more sensitive than the other tests. It has been proved useful in the diagnosis of extraintestinal amebiasis (antibody titer greater than or equal to 1:160).