Durability of radiation-sterilized polymers. I. Estimation of oxidative degradation in polymers by chemiluminescence

In relation to sterilization of medical supplies, the degree of degradation by γ-ray and electron beam irradiations of homopolypropylene (HP), copolypropylene (CP, coplymer including 6% of ethylene unit) and polymethylpentene were compared, and chemiluminescence (CL) of irradiated polymers were measured. HP degraded extremely around the sterilization dose (2.5 Mrad) by either γ-ray or electron beam irradiations. In the case of CP and polymethylpentene, stabilities of polymers far differed between γ-ray and electron beam irradiations. The polymethylpentene was more stable than the polypropylenes against irradiation. The counts of CL emitted by recombination of peroxy radical (ROO ·) increased with increasing dose, reflecting degrees of oxidation of polymers. The degradation of polymers was independent of irradiation sources, rather it depended on the degree of oxidation. It was found that CL analysis are favorable for estimation of degradation in irradiated polymers.     

Compositions,flavour and antiradical properties of products from subcritical water treatment of raw Isada krill

Comparative analysis of subcritical water (SCW) treatment and ambient pressure boiling one of raw Isada krill was performed for the nutritive, flavour and antiradical properties of krill extracts and residues as well as the molecular mass and odour intensity of the extract. SCW treatment was performed for 10 min in a batch‐type vessel in the temperature range of 100–240 °C, using a 1:1 weight ratio of raw krill to water. Higher protein and lipid contents were obtained by SCW treatment relative to boiling. The lipid content of the SCW extracts increased with increasing treatment temperature. Protein was the main component in these extracts, and the highest protein content was achieved by SCW treatment at 200 °C. High‐molecular‐mass species decomposed under SCW treatment at high temperatures with consequent generation of smaller molecules. The antiradical activity of the SCW extract, determined by DPPH and ABTS assays, increased with increasing treatment temperature. The krill extracts and residues exhibited shrimp‐like flavour, and the most desirable flavour was obtained by SCW treatment at 140 °C or 160 °C for 10 min. The treatment would be applicable for the production of seasonings from Isada krill.     

Contents of eleven phthalates and di(2-ethylhexyl) adipate in retail packed lunches after prohibition of DEHP-containing PVC gloves for cooking purposes

Ten samples of retail packed lunches purchased from convenience stores were determined for 11 phthalates and di(2-ethylhexyl) adipate (DEHA) in August 2000, 2 months after the prohibition of DEHP-containing PVC gloves in Japan. Each homogenized sample was extracted with acetonitrile, partitioned with n-hexane, and cleaned up using Florisil and PSA columns. Phthalates in the extract were determined by GC/MS (SIM). The limits of detection were 14.9 ng/g for di(2-ethylhexyl) phthalate (DEHP) and 18.6 ng/g for dibutyl phthalate (DBP). Levels of phthalates in packed lunch samples were 45 to 517 ng DEHP/g (198 ng/g, average), ND to 90 ng DEHA/g, and ND to 10.0 ng BBP/g. Diisononyl phthalate (DINP) was detected in one sample at 76 ng/g. Average DEHP level in ten samples was 4% of that in 1999. The contents of other phthalates were also reduced. DBP was not detected in any sample. Recovery of deuterated isomers added as surrogates was 27.9% for DNP-d4, and 40.6 to 101.5% for the other phthalates.     

Membrane currents of the tunicate egg under the voltage-clamp condition

1. Ionic currents of the egg membrane of a certain tunicate. Halocynthia roretzi Drashe, were studied by the voltage-clamp technique. 2. The membrane depolarization beyond -55mV in standard artificial sea water induced mainly transient inward current and slight outward currents, when the holding potential was kept at -99 mV. 3. The transient inward current was composed of two components; the major one showed a faster time course, a more negative critical level of about -55 mV, and a reversal potential around +60 mV and the minor one showed a slower time course, a less negative critical level o -10 mV, and no definite reversal potential. 4. The major component became maximum at about -25 mV with the peak time of 6-9 msec at 15 degrees C, and the maximum currents ranged from 0-5 to 1-5 X 10(-5) A/cm2. 5. The major component of the inward current was abolished by the replacement of Na with choline or Tris or Cs ions, while it was almost unaltered by the replacement with Li. The minor component was independent of Na concentration in the external solution. 6. The major component showed the activation and inactivation identical with those of Na current of other excitable membranes. A conditioning depolarization over -90 mV inactivated the Na current and the half inactivation of the major inward current was obtained by a conditioning pulse to -56 mV, when the pulse duration was 400 msec and the temperature was at 15 degrees C. 7. The time course of the Na current was formulated with m and h parameters in the following equations: (see article). 8. The kinetic parameters taum and tauh of egg Na current were calculated and compared with those of the squid axon. The potential dependence of taum and tauh was almost identical with that of the axon, but the absolute values of both taum and tauh were ten- to twentyfold larger than those of the axon in any range of the membrane potential. 9. The temperature depdence of the kinetic parameters taum, tauh and of the chord conductance gNa was studied. The Q10's for taum and tauh were both 4-0, while the Q10 for gNa was 2-0 in the temperature range from 5 to 20 degrees C. 10. The outward and inward rectifying conductances of egg membrane were remarkably activated at the potential level above +100 mV and below -70 mV respectively in standard artificial sea water. Both increased currents were subsequently subject to inactivation. 11. It was suggested that Na, Ca, K inward rectifying and K outward rectifying conductances all exist separately in the egg cell membrane and the Na current was essentially identical with that through the Na channel in other excitable membranes.     

Analysis of pyridine extract from Sorachi coal. 1. Crystalline substances from its hexane-soluble portion

A gel-chromatographic separation was carried out on the hexane-soluble portion of pyridine extracts obtained at 50 °C from Sorachi coal (83.6% C), a Japanese caking coal, in order to extend knowledge of the composition of coal. Five crystalline substances were isolated from the different fractions, which were characterized by their infrared, ultraviolet, mass and nuclear-magnetic-resonance spectra, melting points and ultimate analyses. Three are likely to be alkyl derivatives of picene, one to be an alkyl derivative of chrysene, and a fifth to be a mixture of C₂₈–C₃₀ paraffins.     

Using the ring-shaped protein TRAP to capture and confine gold nanodots on a surface

The cavity of the toroidal protein TRAP (trp RNA-binding attenuation protein) is modified to capture gold nanodots in solution. By engineering a titanium-binding peptide onto one surface of the ring it is also possible to bind it specifically and tightly to a TiO2 surface. TRAP bound in this way is then used to capture gold nanodots and attach them to prepared surfaces. Gold-protein complexes are observed using atomic force microscopy and transmission electron microscopy. The modified TRAP is used to build gold nanodots into the SiO2 layer of a metal oxide semiconductor. This is the first use of a ring protein, rather than the more commonly used spherical protein cages, to constrain nanodots to a surface. This method is an important addition to the current range of bionanotechnology tools and may be the basis for future, multicomponent electronic devices.     

Effect of pre-irradiation on radiation stability of co-polypropylene

The radiation stability of the pre-irradiated copolymer of polypropylene containing 2.5 wt.-% ethylene units is compared with a copolymer of polypropylene with a nucleating agent with regard to radiation sterilization of medical devices. It is found that transparency property of the propylene-ethylene copolymer is improved through pre-irradiation processes. This finding was compared with the co-polypropylene with nucleating agent which also gives a better transparency property. In comparison, it is found that pre-irradiated copolymer exhibits better radiation stability during irradiation and during storage after irradiation. The radiation stability of the pre-irradiated copolymer is due to its lower crystallinity caused by the formation of branches during the pre-irradiation process.     

Encapsulation of sea buckthorn kernel oil in modified starches

Encapsulation of CO₂-extracted sea buckthorn kernel oil and the stability of the products were investigated. Maltodextrin and an emulsifying starch derivative were used for encapsulation by spray drying. Both shell materials significantly increased the storage stability of sea buckthorn kernel oil, even though in maltodextrin capsules 10% of the total oil was extractable from the surface of the capsule. The cornstarch sodiium octenyl succinate derivative capsules contained essentially no surface oil. After 9 wk storage at controlled conditions (20°C, RH 50%), PV of the unencapsulated oil was above 90 meq/kg, whereas in the encapsulated oils, the PV was still around 20 meq/kg. The PV of the encapsulated oil was dependent on the storage conditions. A small increase in temperature (from 20 to 25–30°C) and a significant increase in humidity (from RH 50 to RH 50–70%) decreased the stability of capsules. This was associated with the physical state of the microcapsule matrix and may be linked with glass transition of the wall polymers.     

Quantum distributed model of the resonant tunneling transistor

Two-dimensional simulation is crucial in the analysis of the transport characteristics of a resonant tunneling transistor that has a base electrode attached to the well region of a double barrier structure because of the transistor's two-dimensional heterogeneousness. We propose a novel numerical model of the resonant tunneling transistor that includes two-dimensional potential distribution and two-dimensional spatial current distribution. By using this mode in the present model, it is found that the transistor's I-V characteristics are strongly dependent on its internal well resistance