A New Model Compound for Studying Alkaline Cellulose Chain Cleavage Reactions

A conformationally rigid cellulose model, the 4′,6′-O-benzylidene derivative of 1,5-anhydrocellobiitol, has been studied to learn more about the mechanisms of chain cleavage reactions under alkaline pulping conditions. Heating the model at 170°C in 2.5N NaOH gave 55% glycon-oxygen (G-O) bond cleavage, and ～45% oxygen-aglycon (O-A) bond cleavage. The amount of observed O-A bond cleavage is significantly higher than that for 1,5-anhydrocellobiitol. The benzylidene model also degraded about ～35% faster than 1,5-anhydrocellobiitol; much of this rate increase can be attributed to a faster rate of O-A bond cleavage for the benzylidene model. The greater amount of O-A bond cleavage in the benzylidene case may be attributable to a more highly substituted glycosyl ring (making the ring a better anion leaving group) and/or to a more conformationally inflexible glycosyl ring. The inflexibility restricts one of the standard G-O bond cleavage mechanisms, namely the S_NicB(2′) mechanism. The results point out the value of choosing appropriate cellulose models.     

Oxygen,Nitrogen, and Sulfur Removal Reactions in Donor Solvent Coal Liquefaction

There are a number of ways coal can be converted to liquid fuel. It can be pyrolyzed to produce gas, liquid, and char. It can be first converted to carbon monoxide and hydrogen which can then be converted to liquid fuel via Fischer-Tropsch synthesis. It can be hy-dropyrolyzed to produce gases, naphtha range liquids, and heavy residues. Finally, it can be liquefied in the presence of a hydrogen donor solvent to produce liquid and gaseous products. This review is concerned with the last method for conversion of coal to liquid fuel.     

The Characterisation of Pluripotent and Multipotent Stem Cells Using Fourier Transform Infrared Microspectroscopy

Fourier transform infrared (FTIR) microspectroscopy shows potential as a benign, objective and rapid tool to screen pluripotent and multipotent stem cells for clinical use. It offers a new experimental approach that provides a holistic measurement of macromolecular composition such that a signature representing the internal cellular phenotype is obtained. The use of this technique therefore contributes information that is complementary to that acquired by conventional genetic and immunohistochemical methods.     

Response of real-time black carbon mass instruments to mini-CAST soot

Soot is a climate forcer and a dangerous air pollutant that has been increasingly regulated. In aviation, regulatory measurements of soot mass concentration in the exhaust of aircraft turbine engines are to be based on measurements of black carbon (BC) calibrated to elemental carbon (EC) content of diffusion flame soot. The calibration soot must currently meet only one criterion: minimum EC to total carbon (TC) ratio of 0.8. However, not including soot properties other than the EC/TC ratio may potentially lead to discrepancies between different BC measurements. We studied the response of two instruments, the AVL Micro-Soot Sensor (MSS) and the Artium Laser-Induced Incandescence 300 (LII), to soot from two miniature combustion aerosol standard (mini-CAST) burners. By changing the air-fuel ratio, premixing nitrogen into the fuel, and using a catalytic stripper to remove volatile compounds, we produced a wide range of particle morphologies and EC contents. As the EC content decreased, both the instruments underreported the EC mass, but the LII diverged more severely. Upon closer investigation of eight conditions with EC/TC > 0.8, the LII underreporting was found independent of primary particle size, but increased with decreasing geometric mean diameter of the soot agglomerates. As the geometric mean diameter decreased from 160 nm to 50 nm, the differences between the LII and MSS increased from 15% to 50%. The results suggest that in addition to EC content, calibration procedures for the regulatory BC measurements may need to take particle size distributions into account.

© 2016 American Association for Aerosol Research     

The Use of a Spreadsheet Program to Design Motors on a Personal Computer

The use of the personal computer and the wide availability of powerful spreadsheet programs has given the motor designer a very powerful but simple-to-use tool. The use of the Symphony spreadsheet program, presently used to design pancake-type and linear induction motors, is described. As the original design process involved the development of a Fortran program to obtain similar design capabilities, a direct comparison between the development time, using a high-level language, and a spreadsheet program is made. In addition, it is shown how the Fortran program results can be incorporated into the spreadsheet programs to use the graphics capability and documentation features. This topic will be of interest to motor designers and educators.     

Severity of delayed (“secondary”) cerebral energy failure after acute hypoxia-ischemia is related to the time integral of acute ATP depletion

The aim of this study was to reproduce the delayed (secondary) cerebral energy failure previously described in birth-asphyxiated newborn infants and to investigate relationships between primary insult severity and the extent of the delayed energy failure. Phosphorus (³¹P) magnetic resonance spectroscopy (MRS) at 7 T was used to study the brains of 12 newborn piglets during an acute, reversible, cerebral hypoxic-ischemic episode which continued until nucleotide triphosphates (NTP) were depleted. After reperfusion and reoxygenation, spectroscopy was continued for 48 h. High-energy metabolite concentrations returned to near normal levels after the insult, but later they fell as delayed energy failure developed. The time integral of NTP depletion in the primary insult correlated strongly with the minimum [phosphocreatine (PCr)]/[inorganic orthophosphate (P_i)] observed 24–48 h after the insult. (Linear regression analysis gave slope –8.04 h^–1; ordinate intercept=1.23;r=0.92;P<0.0001.) This model is currently being used to investigate the therapeutic potential of various cerebroprotective strategies including hypothermia.     

Efficient electrochemical decomposition of perfluorocarboxylic acids by the use of a boron-doped diamond electrode

The electrochemical decomposition of environmentally persistent perfluorooctanoic acid (PFOA) was achieved by the use of a boron-doped diamond (BDD) electrode. The PFOA decomposition follows pseudo-first-order kinetics, with an observed rate constant (k₁) of 2.4 × 10^− 2 dm³ h^− 1. Under the present reaction conditions, k₁ increased with increasing current density and saturated at values over 0.60 mA cm^− 2. Therefore, the rate-limiting step for the electrochemical decomposition of PFOA was the direct electrochemical oxidation at lower current densities. In the proposed decomposition pathway, direct electrochemical oxidation cleaves the C-C bond between the C₇F₁₅ and COOH in PFOA and generates a C₇F₁₅ radical and CO₂. The C₇F₁₅ radical forms the thermally unstable alcohol C₇F₁₅OH, which undergoes F⁻ elimination to form C₆F₁₃COF. This acid fluoride undergoes hydrolysis to yield another F⁻ and the perfluorocarboxylic acid with one less CF₂ unit, C₆F₁₃COOH. By repeating these processes, finally, PFOA was able to be totally mineralized to CO₂ and F⁻. Moreover, whereas the BDD surface was easily fluorinated by the electrochemical reaction with the PFOA solution, medium pressure ultraviolet (MPUV) lamp irradiation in water was able to easily remove fluorine from the fluorinated BDD surface.