Metathesis as a versatile tool in oleochemistry

Olefin metathesis, awarded with the Nobel Prize in Chemistry 2005 for Chauvin, Grubbs and Schrock, has emerged as a powerful tool for organic as well as polymer chemistry. In oleochemistry, this reaction is well known and has been applied for many decades. Examples include the functionalization of the double bonds of different oleochemicals or the (direct) polymerization of plant oils via metathesis. More recent developments, particularly the development of better and more robust catalysts, allow for highly efficient cross‐metathesis reactions opening new possibilities for the direct introduction of chemical functionalities. Within this contribution, the development of metathesis in oleochemistry will be discussed, covering self‐metathesis as well as more recent developments in the field of cross‐metathesis that lead to desired platform chemicals.     

Chronic hypertrophic gastropathy in a child resembling adult Menetrier''s disease

N-(phosphonacetyl)-disodium L-aspartic acid (PALA) demonstrates a synergistic antitumor effect when combined with 5-Fluorouracil (5-FU) in in vitro studies. In a Phase II trial, 23 eligible patients with unresectable or metastatic adenocarcinoma of the stomach were treated with weekly i.v. bolus PALA (250 mg/M2) followed 24 hours later by a 24-hour infusion of 5-FU (2600 mg/M2) for an initial period of 8 weeks. No objective responses were noted. PALA and 5-FU is inactive against gastric adenocarcinoma at the doses and schedule used in this trial.     

Optical properties and laser performance of neodymium doped fluoroapatites SrxCa5−x(PO4)3F (x = 0, 1, 2, 3, 4, and 5)

Nd doped fluoroapatites Sr_xCa_5−x(PO₄)₃F(S_xC_5−xPF, X = 0, 1, 2, 3, 4, and 5) single crystals have been grown by the Czochralski technique. Their polarized absorption and emission spectra have been recorded at room temperature and used to calculate the absorption and stimulated emission cross sections. Broadening of the absorption and emission bands is observed for Nd³⁺ in the solid solutions SPF-CPF compared to Nd³⁺ in CPF or SPF. 1% Nd:S_xC_5−xPF, X = 0, 2, 3, 4, and 5, laser rods have been tested in a cavity longitudinally pumped by a 1 W AlGaAs laser diode and compared to Nd:YAG and Nd:YVO₄ rods. All fluoroapatites exhibit very good laser performance with low thresholds and high slope efficiencies, higher than in the case of YAG and equal to the YVO₄ samples. The dependance of the laser output power versus the diode temperature has also been measured for all materials. The laser output was found to be as sensitive to the diode temperature fluctuations for fluoroapatites as for YAG.     

Une architecture massivement parallèle intégrée

This paper presents a new massively parallel MIMD architecture, halfway between the Connection Machine and hypercubes based on 32-bit processors. It is built from specific 8-bit processors arranged in a 2-D grid and communicating by message transfers. We discuss the communication problems, the instruction set of the basic processing unit, the programmation of the whole array and the use of a high level data-flow language.     

An investigation of carbon nanotube jet grinding

Since their observation in 1976 and 1991, carbon nanotubes (CNTs) have generated much interest due to their properties and potential applications. CNTs are tubular carbon molecules with remarkable mechanical, electrical, chemical and thermal properties, which make them useful in various applications. Industries producing CNTs via the fluidized bed chemical vapor deposition technique face challenges related to the size of CNT bundles. The two main challenges are agglomeration and agglomerate size distribution control. A solution to these challenges involves the use of jet mills to grind the CNT agglomerates. The goal of this study was to determine whether the nanotubes could be ground with air jets using a commercial jet mill and apply a two-parameter model to describe the grinding process. The present study has indicated that air-jet grinding of CNTs is feasible with a typical commercial jet mill. This paper presents the effect of operational parameters on the arithmetic mean diameter of the ground product. Sonic velocity through the grinding nozzles was required to obtain reasonable grinding rates and relatively narrow particle size distributions. This occurs at high air to solids feedrate ratios. Additionally, a simple attrition model can describe the grinding process in the spiral jet mill.     

Electrophilic chlorination of methane over superacidic sulfated zirconia

Catalytic chlorination of methane was studied over SO ₄ ^2– /ZrO₂, Pt/SO ₄ ^2– /ZrO₂, and Fe/Mn/SO ₄ ^2– /ZrO₂ solid superacid catalysts. The reactions were carried out in a continuous flow reactor under atmospheric pressure, at temperatures below 240°C, with a gaseous hourly space velocity of 1000 ml/g h and a methane to chlorine ratio of 4 to 1. At 200°C with 30% chlorine converted the selectivity in methyl chloride exceeds 90%. At more elevated temperatures, the selectivity decreases but stays above 80% in methyl chloride at 225°C using the sulfated zirconia catalysts. The selectivity can be enhanced by adding platinum to sulfated zirconia catalysts. An iron and manganese-doped catalyst exhibited excellent selectivities at somewhat lower conversions. Methyl chloride is obtained at 235°C in selectivities greater than 85%. No chloroform or carbon tetrachloride is formed. The electrophilic insertion involves electron-deficient metal-coordinated chlorine into the methane C-H bond.Catalysis by solid superacids, 29. For part 28 see ref. [14].     

Representations by Contact and Intersection of Segments

A necessary and sufficient condition is given for a connected bipartite graph to be the incidence graph of a contact family of segments and points. We deduce that any four-connected three-colorable plane graph is the contact graph of a family of segments and that any four-colored planar graph without an induced C₄ using four colors is the intersection graph of a family of straight line segments.     

The influence of demineralisation and ammoxidation on the adsorption properties of an activated carbon prepared from a Polish lignite

The preparation of cheap nitrogen-enriched materials with large adsorptive capacities and selectivity towards volatile organic compounds remains a challenge. Ammoxidation has been used to prepare nitrogen-enriched activated carbons using a demineralised Polish lignite. The lignite samples were demineralised by two different methods before nitrogen-enrichment by ammoxidation and physical activation in steam. The surface chemistry was investigated by elemental analysis, Boehm titration, infrared and XPS spectroscopies and adsorptive properties by a linear solvation energy relationship approach. Results show a quasi-total demineralisation and a higher reactivity towards nitrogen for the demineralised samples. The BET surface is also higher than for the non-demineralised lignite. Active carbons previously ammoxidated and demineralised are more interesting in terms of selective removal of gaseous pollutants.     

Cracking and the Indentation Size Effect for Knoop Hardness of Glasses

The Knoop hardnesses of five glasses decreased with increasing load in accordance with the classic indentation size effect (ISE). At moderate loads, cracking dramatically altered the indentation sizes and the ISE trends in three of the five glasses. Cracked indentations were as much as 10 μm longer than uncracked indentations made under identical conditions. Diagonal length readings must be corrected for optical resolution limitations if low power lenses are used.     

Internal deterioration of concrete by the oxidation of pyrrhotitic aggregates

This paper presents research results on the causes of a severe concrete deterioration, which occurred in many building foundations approximately 2 years after construction. Concrete samples were investigated with X-ray diffraction (XRD) analysis, a scanning electron microscope (SEM) and a petrographic examination performed with a stereomicroscope. It was found that the early cracking of concrete stemmed from the oxidation of the pyrrhotite found in the anorthosite aggregates used to produce the concrete. The oxidation process led to the precipitation of iron hydroxides having a higher volume than the original pyrrhotite does. The presence of micas (biotite) close to the pyrrhotite seemed to promote and accelerate the oxidation process.