Effects of slots on the lateral vibration of a circular saw blade

In the majority of cases, wood is cut at a high feed rate and high rotational speed by circular saw blades with tungsten carbide tips brazed on the periphery of metal circular plates. Slots are made at several places from the periphery towards the center of a saw blade to prevent lateral vibration, both in idling and cutting, and to prevent a drop in critical rotational speed caused by heat expansion on the blade periphery during the cutting operation. In this paper, variations of lateral vibration mode, natural frequency and critical rotational speed of a slotted circular saw blade are investigated experimentally and by numerical calculations. The lateral deflection of a circular saw blade at the critical rotational speed and at the rotational speed near it is examined by a timber-cutting experiment.     

Oxidation of lipids: III. Oxidation of methyl linoleate in solution

The effects of oxygen pressure, substrate concentration and solvent on the rate and products of oxidation of methyl linoleate were studied at 50 C with azobisisobutyronitrile as a radical initiator. The absolute and quantitative numbers for oxygen uptake, substrate disappearance, and formation of conjugated diene and hydroperoxides were measured. Under the present conditions, 4 conjugated diene hydroperoxides, 13-hydroperoxy-9-cis, 11-trans-(2a), 13-hydroperoxy-9-trans, 11-trans-(3a), 9-hydroperoxy-10-trans, 12-cis-(4a), and 9-hydroperoxy-10-trans, 12-trans-(5a) octadecadienoic acid methyl esters, were formed almost quantitatively. The rate of oxidation decreased with decreasing oxygen pressure. However, the ratio ofcis,trans totrans,trans hydroperoxides, (2a+4a)/(3a+5a), was independent of oxygen pressure, and this ratio increased with increasing methyl linoleate concentration, as found recently by Porter. Further, the rate of oxidation and the ratio ofcis,trans/trans,trans hydroperoxides were dependent on solvent and increased with an increase in dielectric constant of solvent. A mechanism of methyl linoleate oxidation consistent with these results is discussed. Presented at the 15th Symposium on Oxidation Reactions, Nagoya, October 1981.     

Physical and mechanical properties of poly(L‐lactic acid) nucleated by dibenzoylhydrazide compound

Benzoylhydrazide compounds were evaluated as a nucleating agent for poly(L ‐lactic acid) (PLA). From the results of the differential scanning calorimetry, octamethylenedicarboxylic dibenzoylhydrazide (OMBH) was found to be most effective for acceleration of PLA crystallization under higher cooling rate of ?50°C min^?1. PLA with OMBH of 1 wt % exhibited very short crystallization half‐time with wide range of isothermal temperature from 90 to 130°C. The molding cycle time of PLA with OMBH in injection molding was less than 3 min, and the cooling time was one‐third of ethylenebis(12‐hydroxystearylamide)/talc system as a nucleating agent. Physical and mechanical properties improved extremely, and the heat distortion temperature of 124°C, flexural modulus of 4.1 GPa, and Izod impact strength of 7.9 kJ m^?2 were achieved. This indicates that the utilization of OMBH makes it possible to extend the application range of PLA as automotive parts and electric appliances, which require higher heat resistance and stiffness. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 244–250, 2007     

Distribution of tocopherols and tocotrienols to rat ocular tissues after topical ophthalmic administration

With increasing evidence suggesting the involvement of oxidative stress in various disorders and diseases, the role of antioxidants in vivo has received much attention. Chemically, tocopherols and tocotrienols are closely related; however, it has been observed that they have widely varying degrees of biological effectiveness. The present study has been carried out in an attempt to deepen our understanding of whether there is a significant difference in distribution between tocopherol and tocotrienol homologs to rat eye tissues. Rats were administered 5 μl of pure tocopherol or tocotrienol to each eye once a day for 4 d. Various tissues of the eyes were separated and analyzed for tocopherol and tocotrienol concentrations. The concentration of α-tocotrienol increased markedly in every tissue to which it was administered; however, no significant increase was observed in the case of α-tocopherol. The intraocular penetration of γ-tocopherol and γ-tocotrienol did not differ significantly. Additionally, a significant increase in total vitamin E concentration was observed in ocular tissues, including crystalline lens, neural retina, and eye cup, with topical administration using a relatively small amount (5 μL) of vitamin E, whereas no significant increase was observed when the same amount of vitamin E was administered orally. Topical administration of tocotrienols is thus an effective way to increase ocular tissue vitamin E concentration.     

The active site of carboxypeptidase Taq possesses the active-site motif His-Glu-X-X-His of zinc-dependent endopeptidases and aminopeptidases

Carboxypeptidase (CPase) Taq possesses the His–Glu–X–X–Hissequence, which is the consensus sequence in the active siteof zinc-dependent endopeptidases and amino-peptidases, at positions276–280. Amino acid replacement of the conserved His andGlu drastically diminished the activity of CPase Taq, and thezinc content of the enzyme was also greatly reduced when eitherof the two His residues was replaced with Arg or Tyr. The resultsindicate that this sequence actually functions as the activesite in CPase Taq, showing that CPase Taq is a novel type ofzinc-dependent CPase that possesses the His–Glu–X–X–Hisactive-site motif.     

Stoichiometric and kinetic studies on Ginkgo biloba extract and related antioxidants

Owing to increasing evidence showing the importance of lipid peroxidation in oxidative stress in vivo, the role and evaluation of antioxidants have received much attention. Ginkgo biloba extract (GBE), well-known as an efficient drug against diseases induced by free radicals, has been suggested to exert its effect by antioxidant action. A method was established to determine the activity of GBE as a hydrogen donor by stoichiometric and kinetic studies, and GBE was compared with several other antioxidants such as α-tocopherol, propyl gallate, and two kinds of flavonoids which are found in GBE, quercetin, and kaempferol. It was found that there were 6.62×10¹⁹ active hydrogens in 1g of GBE. Stoichiometric studies showed that one molecule of α-tocopherol reacted with one molecule of galvinoxyl radical. For quercetin, kaempferol and propyl gallate, the experimental stoichiometric numbers were 4.0, 1.9, and 3.1, respectively. The rates of reaction of antioxidants with galvinoxyl in ethanol were determined spectrophotometrically, using a stopped-flow technique. The second-order rate constant, k ₂, obtained at 25°C was 0.13 (g/l)⁻¹s⁻¹ for GBE and 5.9×10³, 2.1×10³, 1.2×10⁴, and 2.4×10³ M⁻¹s⁻¹ for quercetin, kaempferol, propyl gallate, and α-tocopherol, respectively. The second-order rate constant, k ₂′, on the molar basis of active hydroxyl groups in the tested substances obtained at 25°C decreased in the order of propyl gallate > α-tocopherol> quercetin>GBF∼kaempferol. This is the first study on GBE as an antioxidant which reports both stoichiometric and kinetic results.     

Perspectives and challenges of hydrogen storage in solid-state hydrides

Hydrogen has been widely considered as a clean energy carrier that bridges the energy producers and energy consumers in an efficient and safe way for a sustainable society. Hydrogen can be stored in a gas, liquid and solid states and each method has its unique advantage. Though compressed hydrogen and liquefied hydrogen are mature technologies for industrial applications, appropriate measures are necessary to deal with the issues at high pressure up to around 100 MPa and low temperature at around 20 K. Distinct from those technologies, storing hydrogen in solid-state hydrides can realize a more compact and much safer approach that does not require high hydrogen pressure and cryogenic temperature. In this review, we will provide an overview of the major material groups that are capable of absorbing and desorbing hydrogen reversibly. The main features on hydrogen storage properties of each material group are summarized, together with the discussion of the key issues and the guidance of materials design, aiming at providing insights for new material development as well as industrial applications.     

Molecular Properties of Propranolol Hydrochloride Prepared as Drug-Resin Complexes

Drug-resin complexes, as well as physical dispersions, containing varying contents of propranolol were prepared. The molecular properties of samples were investigated by differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), and infrared (IR) spectroscopy. In addition, the USP paddle method was used to determine the release behavior of drug from various formulations prepared from the samples. The data from DSC and XRPD indicated that the molecular state of drug in the complexes was amorphous, whereas that in the physical dispersions exhibited the crystalline state of pure drug. These results suggested that the molecule of drug prepared as drug-resin complexes was monomolecularly dispersed in the resin bead. The IR study provided evidence that demonstrated the interaction between the drug and resin in the complexes. The release behavior of drug from the complexes was governed by the cross-linkage structure and equilibrium treatment of drug exchange of resin.     

In-plane deformation observation of indentation along indenter surface

In this paper, the in-plane plastic deformation, which is perpendicular to the contacting load, of soft metal in contact with a hard spherical indenter is observed on a rolled aluminum surface. By measuring a displacement due to indentation of lattice points described on the aluminum surface, the in-plain deformation is obtained. Many small ferrous impurities are scattered on and in this aluminum specimen. When a hard spherical indenter is pressed onto this aluminum surface, the distance between impurities is changed by the surface plastic deformation. The change in distance between impurities is obtained using the image processing method, and it is demonstrated that the in-plane plastic deformation of surfaces caused by indentation can be observed. Results by both the lattice point method and the image processing method are compared quantitatively.     

Mechanism of lower oxidizability of eicosapentaenoate than linoleate in aqueous micelles

The aerobic oxidation kinetics of methyl eicosapentaenoate (20:5n-3) and methyl linoleate (18:2n-6) were compared in homogeneous chlorobenzene solution and in Triton X-100 aqueous micelles at 37°C. The rate of disappearance of 20:5n-3 was two times faster than that of 18:2n-6 in chlorobenzene, while the former was five times slower than the latter in aqueous micelles. It was also observed that ΔO₂=Δ18:2n-6 and ΔO₂=2Δ20:5n-3 in aqueous micelles. In the oxidation of a 1∶1 mixture of 20:5n-3 and 18:2n-6 in micelles, the rate of disappearance of 20:5n-3 was 3.6 times faster than that of 18:2n-6, and the rate of total substrate disappearance was reduced by a factor of 5 as compared with 18:2n-6 oxidation. These data suggest that the peroxyl radical derived from 20:5n-3 is more polar than that from 18:2n-6, and the former is likely to diffuse from the core to the micelle surface. This lowers the oxidizability for 20:5n-3 in aqueous micelles by enhancing the termination reaction rate for peroxyl radicals and by reducing the rate of propagation since there may be more 20:5n-3 peroxyl radicals at the surface than in the micelle core.