In-situ synthesis

Solubilization of vinylpyrrolidone, acrylic acid, and A,A -methylene-bis-acrylamide in AOT-reversed micelles allowed the synthesis in situ of a cross-linked polymer with narrow size distribution confined in the micellar domain. These particles displayed high entrapment efficiency of small hydrophilic drugs and have been considered interesting drug delivery systems [239],... 

Other works related to the use of platinum carbonyl species in the preparation of catalysts, which lie beyond the scope of this chapter, refer to the synthesis in situ of supported platinum carbonylate species. For this purpose, the impregnation or exchanging of Pt precursors as [Pt(NH3)4], [Ptcy and [PtCLt] " on an appropriate support is carried out. Then, the carbonylation renders a carbonylate species that could be naked to metal frameworks by appropriate decarbonylation. 

Vilchis et al. [81] presented a new idea to achieve better control of the particle size distribution by the synthesis in situ of a water-soluble copolymer of acrylic acid-styrene as suspension stabilizer without additional inorganic phosphate. Publications describe increasing the particle formation by using a physical (population balance, Maxwell fluid, power law viscosity, compartment mixing) modeling approach [22,60,98,105]. 

Supported zeolite membranes have been prepared using numerous procedures [4] such as alignment of crystals in electrical fields, electroplating, self-assembly, growth on organic molecular layers, covalent linkages, hydrothermal synthesis (in situ and ex situ), hydrothermal method microwave heating assisted, dry gel method (vapor-phase transport method and steam-assisted crystallization), synthesis at the interface between two fluid phases, etc. 

In this volume, we have already examined some alternatives to the synthesis in situ and/or to the use of methyl isocyanate. We thought that 1,3-dimethyl diazetidine dione (XII) (methyl isocyanate dimer) should be a suitable methyl isocyanate precursor which can release methyl isocyanate in safe conditions. This dimer was prepared from N-chlorocarbonyl-N-methyl N -methyl urea (XI) obtained by phosgenation of N,N -dimethyl urea as previously described in scheme 156, section 3-3-4. Cyclization of (XI) in a suitable solvent and in presence of a base such as DABCO afforded the expected dimer (XII) as depicted in scheme 220. 

Micro-arrays can be manufactured in two different ways, by synthesis in situ or by delivery. In the in situ synthesis approach, nucleic acids are synthesized directly on a chip surface. This is made possible by a light-directed chemical synthesis technology developed by scientists at Affymetrix. By using different sets of photolithographic masks, scientitsts can define the chip exposure sites and, thereby, the sequence of the oligonucleotides. In this way, arrays can be synthesized with up to 400,000 different oligonucleotides in an area of 1.6 cm. Every spot contains about... 

K. G. I. Nilsson, A simple strategy for changing the regioselectivity of glycosidase-catalysed formation of disaccharides Part II, Enzymic synthesis in situ of various acceptor glycosides,... 

An interesting way to make polymeric dispersions in liquid polyethers is the synthesis in situ of a polyamide by the polycondensation reaction between a dialkyl oxalate (for example, diethyl oxalate [91]) and a diamine, such as 1,6 hexamethylenediamine (reaction 6.28) ... 

The supply of oestrogen produced endogenously for the continued maintenance of tumour growth may be supplemented by the cancerous tissue itself (see review by Miller [30]). Over half [31] of human breast cancer cells synthesize oestrogen from androgen precursors in vitro [32-35]. Studies [35] on the synthesis in situ of oestrogens from human breast tumours by either the aromatase enzyme (from androstenedione) or a sulphatase enzyme (from oestrone sulphate) have shown that the latter pathway predominates. The sulphatase laromatase activity ratio is about 10 at normal in vivo concen-... 

X-ray diffraction can be used to identify the phases which are present in a catalyst. To follow the evolution of a catalyst during pretreatment or catalytic reaction (ammonia or methanol synthesis), in situ XRD experiments have been performed. For this purpose Nix et al. (1987) have built a high-pressure XRD cell operating up to 50 bar and temperatures up to 700 K. The reactant gases flow over the catalysts sample heated by conduction from a cartridge heater. The temperatures are measured and controlled using a thermocouple fixed into the copper support block (fig. 3). 

Intramolecular Heck reactions are particularly efficient and have been used considerably in organic synthesis.In situ reduction of palladium acetate and oxidative addition of the resulting palladium(O) into the aryl iodide 210 gave an... 

SAXS measurements are normally performed in situ and therefore require access to synchrotron radiation [21, 23, 27, 46]. SAXS is probably one of the most used in situ techniques for the study of zeolite synthesis. In situ cells, similar to those for WAXS or XRD measurements, can easily cope with elevated synthesis temperatures and pressures. It has been used to determine the activation energy of nucleation, where two independent studies show that it is around 70-85 kj mol [47, 48]. Also, three distinct particle sizes were observed in the reaction mixtures, being primary units of approximately 2.8 nm, their aggregates, and the actual zeolite crystals [47]. Other mechanistic studies include the effect of the precursor molecule, the chemical nature of which appears to be important in... 

As mentioned in the Introduction section, the adsorption of stabilizers to achieve stabilization of particle dispersions can not only be carried out in a separate step, but also already during the particle synthesis in-situ modifieation or in-situ functionalization), which... 

Several techniques such as intercalation of polymer from solution, in-situ intercalative polymerization, melt intercalation, direct mixture of polymer and particulates, template synthesis, in-situ polymerization and solgel process, are being employed for the preparation of polmer-layered silicate nanocomposites. Among them the most common and important approaches are in-situ polymerization, solution-induced intercalation method, and melt processing method, which are briefly discussed below. 

L. Motte, F. Billoudet and M. P. Pileni, Synthesis in situ of nanosize silver sulphide semiconduc-... 

Within a short period of time after fertilization, both egg and sperm nuclei are observed to begin DNA synthesis (Graham, 1966). This change in synthetic activity from a previously quiescent state is known to be induced by some cytoplasmic factor since adult nuclei, inactive in DNA synthesis in situ, are rapidly induced to synthesize DNA after transplantation into activated egg cytoplasm (Graham et al, 1966). Sev-... 

OMTOC can be prepared by two strategies. The organic groups can either be grafted to a preformed cluster (postsynthesis modification method) or introduced during the cluster synthesis (in situ method). 

Although roots, particularly the root apices, are a major site of cytokinin biosynthesis in plants, there is evidence now that other meristematic tissues and organs including the cambium, developing buds, seeds and fruits and the embryonic axis of germinating seed have the ability to synthesize cytokinins under optimal growth conditions [6, 14]. Recently, stem and leaves have also been shown to be additional sites of cytokinin production [6]. The view that root-produced cytokinins move in the xylem to the shoot to participate in the control of development and senescence is widely accepted [15]. The major question that remains to be clarified is under what conditions the observed cytokinin activity in other plant parts is derived solely from the roots, and when, and to what degree it is derived by synthesis in situ. 

Guodong Q., Minquan W., Mang W., Xianping F., Zhanglian H. Synthesis in situ of2,2 -dipyridyl-Tb (III) complexes in silica gel. J. Mater. Sci. Lett. 1997 16 322-323 Hao X., Fan X., Wang M. Luminescence behavior of Eu(TTFA)j doped sol-gel films. Thin Solid Films 1999 353 223-226... 

This suggests that in both species retinal taurine concentrations are maintained by uptake of taurine from the plasma and not by synthesis in situ in the retina. 

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