Biodegradable stereocomplex materials of polylactide‐grafted dextran exhibiting soft and tough properties in dry and wet states

Water‐swellable biodegradable materials exhibiting mechanically tenacious and tough characters in the wet state were prepared by a simple blend of two enantiomeric polylactide‐grafted dextran copolymers (Dex‐g‐PLLA and Dex‐g‐PDLA). DSC and WAXD analyses demonstrated the formation of SC crystals in the copolymer blend films. SC blend films showed lamellar‐type microphase‐separated structures. When swollen with water, these blend films showed the same level of tensile strengths and Young's modulus as the films in the dry state. SC blend films degraded gradually over a month under physiological conditions with a degradation rate faster than the corresponding Dex‐g‐PLLA films. The SC‐forming enantiomeric mixture of polylactide‐grafted polysaccharides should be a good candidate for an implantable biocompatible material exhibiting favorable mechanical properties and degradation behavior. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effect of fuel ratio of coal on the turbulent flame speed of ammonia/coal particle cloud co-combustion at atmospheric pressure

This study aims to clarify the effect of fuel ratio of coal on the turbulent flame speed of ammonia/coal particle cloud co-combustion at atmospheric pressure under various turbulence intensities. High-fuel-ratio coals are not usually used in coal-fired thermal power plants because of their low flame stability. The expectation is that ammonia as a hydrogen-energy carrier would improve the ignition capability of coal particles in co-combustion. Experiments on spherical turbulent flame propagation of co-combustion were conducted for various coal types under various turbulence intensities, using the unique experimental apparatus developed for the co-combustion. Experimental results show that the flame speed of co-combustion with a low equivalence ratio of ammonia/oxidizer mixture for bituminous coal case was found to be three times faster than that of pure coal combustion and two times faster than that of pure ammonia combustion. On the other hand, the flame speed of co-combustion for the highest-fuel-ratio coal case is lower than that of the pure ammonia combustion case, although the flame propagation can be sustained due to the ammonia mixing. To explain the difference of tendencies depending on the fuel ratio of coal, a flame propagation mechanism of ammonia/coal particle cloud co-combustion was proposed. Two positive effects are the increases of local equivalence ratio and the increases of radiation heat flux, which increases the flame speed. In opposite, a negative effect is the heat sink effect that decreases the flame speed. The two positive effects on the flame speed of co-combustion overwhelm a negative effect for bituminous coal case, while the negative effect overcomes both positive effects for the highest-fuel-ratio coal case. The findings of the study can contribute to the reduction of solid fuel costs when the ammonia is introduced as CO₂ free energy carrier and can improve the energy security through the utilization of high-fuel-ratio coals.     

Photoinduced electron transfer of N-[(3- and 4-diarylamino)phenyl]-1,8-naphthalimide dyads: orbital-orthogonal approach in a short-linked D-A system

The photoinduced electron transfer of a series of meta- and para-linked triphenylamine-naphthalimide dyads, N-{3- and 4-[bis(4-R-substituted phenyl)amino]phenyl}-1,8-naphthalimide, 1m,p (R = H), 2m,p (R = Me), 3m,p (R = OMe), and 4m,p (R = NMe2) was investigated in toluene and DMF. The singlet charge-transfer (CT) states were observed in all cases. The decay rates were found to be faster in DMF (tau = 6.5 ps to 100 ps) than those in toluene (tau = 190 ps to 7 ns). The long-lived triplet CT states were observed in toluene for 3 (ca. 10% contribution, tau = 670 ns for 3m, 240 ns for 3p). No long-lived species were detected in DMF. The decay rates were somewhat faster in the para-isomers than in the meta-isomers in most cases. The photolysis of 5 (p-phenylene extended analogue of 3, R = OMe) gave a singlet CT state and a locally excited triplet state on the naphthalimide chromophore.     

Current activities of ISO TC229/WG2 on purity evaluation and quality assurance standards for carbon nanotubes

The current standardization activities of ISO (International Organization for Standardization) TC229 on “Nanotechnology” are introduced with focus on the work of WG2 (Working Group 2) for “measurement and characterization”. Seven project groups of WG2 are actively preparing standard protocols (technical specifications) for characterization of single-wall carbon nanotubes (SWCNTs) by measurement methods such as TEM (transmission electron microscopy), SEM (scanning electron microscopy), EDX (energy-dispersive X-ray analysis), UV–Vis–NIR (ultraviolet-visible-near infrared) absorption spectroscopy, NIR-photoluminescence spectroscopy, EGA (evolved gas analysis)–GC–MS (gas chromatography–mass spectrometry), TGA (thermogravimetric analysis), and Raman spectroscopy; this work is described. The features of purity evaluation of SWCNTs by these methods are also briefly described and compared. Also described are two project groups of WG2 that are preparing standard protocols for characterization of multiwall CNTs (MWCNTs), aiming at the purity control by measurement of moisture content, ash content, metallic constituents, volatile content, polyaromatic hydrocarbon content, and carbon materials excluding MWCNTs. Other important properties for characterization of MWCNT, for example disorder, burning property, stacking nature, length, morphology, and inner/outer diameter, etc., are also mentioned. Finally, the importance and urgency of standardization for potential risk assessment of CNTs is briefly described, and current joint activity of ISO TC229 WG2 and WG3 for physicochemical characterization of engineered nanoscale materials for toxicological assessment is introduced.     

Magnetic moments and GT-type β-decay matrix elements in nuclei with a LS doubly closed shell plus or minus one nucleon

The magnetic moments and GT-type β-decay matrix elements of nuclei with an ¹⁶O core plus (minus) one nucleon and with a ⁴⁰Ca core plus(minus) one nucleon are studied from the point of view of configuration mixing in terms of second order perturbation theory. It is found that the effect of the mixing of highly excited configurations through a tensor force is essential to explain the large reduction of the GT-type β-decay matrix elements. It is also found that modulus of the isovector parts of the gyromagnetic ratio, g_τS and g_τl, are appreciably reduced by the configuration mixing.     

High-Resolution Reflectometry by Optical Multidigitized Coherence

We propose and confirm a novel technique of optical frequency domain reflectometry based on multidigitized coherence using a multimode laser. The proposed system can easily provide the potential for high resolution on the order of 10 μm without scanning frequencies as in frequency domain reflectometers of either continuous or stepwise sweep. The theoretical approach agrees well with the experimental results demonstrated using a commercially available multimode laser diode.     

A comparison of two single-pulse shock-tube techniques: The thermal decomposition of ethyl chloride and n-propyl chloride

This investigation presents a detailed examination of the relative reliability of the comparative and absolute rate methods as they are applied to kinetic studies in the single-pulse shock tube. For this purpose two previously studied reactions, the thermal elimination of HCl from ethyl chloride and n-propyl chloride, were selected and mixtures of these compounds were shock heated to temperatures in the range of 960°-1100°K. The experimental results were analyzed by both methods and the rate constants obtained from these analyses are compared with those of previous studies. The advantages and shortcomings of both methods are noted and it is concluded that reliable kinetic data can be obtained by the absolute rate (isolation technique) method with careful examination of the gas-dynamic flow conditions and taking cognizance of the incident shock deceleration. The limitations of the comparative rate technique encountered in the present study were similar to those detailed in previous investigations.     

Direct Monte Carlo simulation of scattering processes of kV electrons in aluminum; comparison of theoretical N(E) spectra with experiment

A Monte Carlo simulation of the scattering processes of kV electrons penetrating into aluminum was performed. The simulation is based on the use of different types of differential cross-sections for individual elastic and inelastic scattering: (i) Elastic scattering; the differential cross-sections derived by partial wave expansion method. (ii) Inelastic scattering; Gryzinski's excitation function for inner-shell electron excitation, Streitwolfs excitation function for conduction electron excitation, and Quinn's mean free path for plasmon excitation. For verification the energy loss spectra obtained from the Monte Carlo calculations were then compared with experiment done with commercial type Auger microprobes, JAMP-3, for angle of incidence 45° and JAMP-10 for normal incidence at primary electron energies of 1.5 and 3.0 keV, respectively. The results show satisfactory agreement between theory and experiment.     

Backscattering correction for quantitative Auger analysis: I. Monte Carlo calculations of backscattering factors for standard materials

The electron backscattering effect which is important for the quantitative interpretation of “matrix effects” in AES is investigated by applying the Monte Carlo calculation technique. The present calculation model is based on the use of a precise elastic scattering cross-section obtained by the partial wave expansion method, as well as on the combined use of Gryzinski's excitation function and Bethe's stopping power for inelastic scattering. Systematic calculations of the backscattering factors were performed for over 25 materials including pure elements, compounds, and alloys, which have been widely used as standard materials for practical Auger analysis. The results should enable the accuracy of quantitative analysis by AES to be improved.