Activity of samarocene catalysts adsorbed on mesoporous silicates for the polymerization of methyl methacrylate

A samarocene complex, (C₅Me₅)₂SmMe(thf), was adsorbed on a series of mesoporous silicates of various pore sizes. Pre‐treatment of the latter with AlMe₃ before adding the complex was effective in deactivating the surface silanol functionalities. The silicates having relatively larger pore size tended to adsorb a larger amount of the complex. The polymerization of methyl methacrylate (MMA) by the complex adsorbed on the silicates with large pore sizes (>29 Å) quantitatively afforded highly syndiotactic poly(MMA)s with higher molecular weights compared with those obtained by the corresponding homogeneous system. Similar catalyst systems of smaller pore size were much less active. Copyright © 2004 Society of Chemical Industry     

Microwave Invasion Through Anti-Reflecting Layers of Dielectrics at a Millimeter Wave Irradiation to Living Bodies

Microwave invasion into living bodies through a millimeter wave catheter irradiation is described. As radiation sources for millimeter wave irradiation tests both Impatt oscillator (IO) and a Gunn oscillator were used. Irradiated samples are cow livers and living rats. A newly designed wave-guide vent antenna (WVA) with an anti-reflecting layer (ARL) is used as a launcher for the irradiation and the reflectance measurements. The correlation between the denaturation of thetissue and the reflectance from the WVA is studied in detail.     

Shape adaptive grinding of CVD silicon carbide

Because of the direct relationship between removal rate and surface roughness in conventional grinding, ultra-precision finishing of hard coatings produced by chemical vapour deposition (CVD) usually involves several process steps with fixed and loose abrasives. In this paper, an innovative shape adaptive grinding (SAG) tool is introduced that allows finishing of CVD silicon carbide with roughness below 0.4 nm Ra and high removal rates up-to 100 mm³/min. The SAG tool elastically complies with freeform surfaces, while rigidity at small scales allows grinding to occur. Since material removal is time dependent, this process can improve form error iteratively through feed moderation.     

Human cytoplasmic isoleucyl-tRNA synthetase: selective divergence of the anticodon-binding domain and acquisition of a new structural unit

We show here that the class I human cytoplasmic isoleucyl-tRNA synthetase is an exceptionally large polypeptide (1266 aa) which, unlike its homologues in lower eukaryotes and prokaryotes, has a third domain of two repeats of an approximately 90-aa sequence appended to its C-terminal end. While extracts of Escherichia coli do not aminoacrylate mammalian tRNA with isoleucine, expression of the cloned human gene in E. coli results in charging of the mammalian tRNA substrate. The appended third domain is dispensable for detection of this aminoacylation activity and may be needed for assembly of a multisynthetase complex in mammalian cells. Alignment of the sequences of the remaining two domains shared by isoleucyl-tRNA synthetases from E. coli to human reveals a much greater selective pressure on the domain needed for tRNA acceptor helix interactions and catalysis than on the domain needed for interactions with the anticodon. This result may have implications for the historical development of an operational RNA code for amino acids.     

Microbeam line with 1.5 MeV helium ions and protons at Osaka

A microprobe for Rutherford backscattering (RBS) and particle-induced X-ray emission (PIXE) measurements has been realized by focusing 1.5 MeV helium-ion or proton beams with a demagnification system consisting of piezo-driven objective slits and a magnetic quadrupole doublet. Minimum beam spot sizes of 1.3 × 2.2 μm² for helium ions and 2.2 × 4.0 μm² for protons have been achieved. The factors which may limit the minimum spot size are discussed using a Monte Carlo simulation procedure. Rutherford backscattering image mapping of 3-dimensional structures is demonstrated.     

Intra-arterial ACNU, CDDP chemotherapy for brain metastases from lung cancer: comparison of cases with and without intra-arterial mannitol infusion

To assess whether therapeutic efficacy is related to intra-arterial (IA) mannitol infusion prior to ACNU and cisplatin (CDDP) for brain metastases from lung cancer, clinical results of patients with and without IA mannitol infusion were compared. Thirty-nine patients were randomly assigned to either a mannitol infusion group (group A) or a non-mannitol infusion group (group B). There were 22 patients in group A and 17 in group B. During radiotherapy, ACNU and CDDP, at a dose of 100 mg/body, were given through the common carotid artery at a rate of 20 mg/min. In group A, 50 ml of 20% mannitol was injected intra-arterially at a rate of 50 ml/min immediately prior to the injection of chemotherapeutic agents. Major complications, such as seizure and neurotoxicity, were not observed. Complete response (disappearance of enhanced tumor mass) was obtained in 72% of group A and in 67% of group B. The median time to tumor progression was 40 weeks for group A and 22 weeks for group B. The median survival time (MST) was 45 weeks for group A and 30 weeks for group B. The survival time was significantly longer in group A as compared to group B (p < 0.05). When the patients who died of failure of vital organ systems other than brain complications were excluded in calculating the survival time, the MST was 69 weeks for 11 patients of group A and 34 weeks for 7 patients of group B. These data suggest that an effort to increase drug delivery to the brain tumor may indeed lengthen the survival time of patients with brain metastases from lung cancer.     

Bisphenol F Synthesis Over Mesoporous Aluminosilicate MCM-41 Molecular Sieves

Temperature-programmed desorption, X-ray photoelectron spectroscopy (XPS) spectroscopy and catalytic test reaction have been applied to investigate acid sites in a microporous activated carbon (Norit RX 1 Extra). Treatment with HNO₃ generates acid sites in the pristine carbon. XPS data show an increase of the amount of carboxyl and hydroxyl groups on the activated carbon surface. The thermodesorption profiles of the material corroborate the XPS data and indicate the presence of hydroxyl groups of carboxylic acids. The results obtained by these methods indicate the presence of acid sites. Thus, the acidity of the carbon was tested in the esterification of organic acids with alcohols. The pristine carbon presents no activity. By contrast, the treated carbon presents enough acidity to carry out the reaction achieving conversion values of around 45% for the reaction of benzoic acid with ethanol in a batch reactor. Such a value increases if the reaction is carried out under ultrasound activation, affording conversion values of around 85%. The selectivity of the reactions is high, around 95%. Only in the case of 1-octanol are some side-products observed, due to the oxidation of the alcohol.