An experimental study of neat and ionic liquid-aided ammonia borane thermolysis

This paper reports hydrogen (H₂) yield and reaction rate measurements of ammonia borane (AB) thermolysis in the neat form as well as facilitated by the presence of an ionic solvent, 1-butyl-3-methylimidazolium chloride (bmimCl). The measurements were conducted at various temperatures between 85 and 120 °C under quasi-isothermal conditions. The details of fast hydrogen evolution at the initial stage of the thermolysis process were captured for the first time. The presence of bmimCl led to significant increases in both the rate and the amount of hydrogen released, compared to the corresponding quantities at identical temperatures for neat AB thermolysis. Measurements reported in the literature are in qualitative agreement with this observation but lack the time resolution necessary for the quantitative comparisons. At 120 °C, the measured gravimetric H₂ storage capacity from the neat AB thermolysis was 9.9 wt% (material base) and that from the AB/bmimCl mixture (80/20 wt%) thermolysis was 11.2 wt%. Also, the reaction rate of the thermolysis of AB/bmimCl mixture (80/20 wt%) was twice as fast as that of the neat AB thermolysis at this temperature. In the bmimCl (20 wt%) aided AB thermolysis, a significant increase in the H₂ yield occurred at temperatures over 107 °C.     

Effect of treatment temperature on the performance of RuO2 anode electrocatalyst for high temperature proton exchange membrane water electrolysers

Ruthenium oxide catalysts were prepared by a sol–gel technique and calcined at different temperatures e.g., 400 °C, 500 °C and 600 °C. The catalysts performance for the oxygen evolution reaction was studied using cyclic voltammetry and their performance in a high temperature proton exchange membrane water electrolyser (PEMWE) examined. Physio-chemical characterization was carried out to study the thermal stability, oxygen-metal bond formation, crystallinity phase and crystallite size, particle size and elemental analysis by TGA, FTIR, XRD, TEM and EDX respectively. The electrolyte used for electrochemical characterisation was 1.0 M H₃PO₄ and 0.5 M H₂SO₄. Additionally, the effect of calcination and electrolyte temperature on oxygen evolution reaction of RuO₂ catalysts was studied and the apparent activation energy was determined using chronoamperometry. The prepared RuO₂ were tested as anode catalyst in PEMWE in the temperature range of 120–150 °C using phosphoric acid doped polybenzimidazole membrane electrolyte. The physio-chemical and electrochemical characterization results indicate that RuO₂ calcined at 500 °C gave the best performance with a current density of 0.875 A cm⁻² at 1.8 V in a PEMWE operated at 150 °C.     

Application of symbolic manipulation to inverse dynamics and kinematics of elastic robots

An inverse dynamics and kinematics of a flexible manipulator is derived in symbolic form based on the recursive Lagrangian assumed mode method. A PC-based program has implemented the algorithm to automatically generate the inverse dynamics and kinematics for an elastic robot in a symbolic form. A case study is given to illustrate how to use this program for inverse dynamic and kinematic generation. Simulation results for a case study by considering different mode shape are compared with the rigid case.Nomenclature A _i joint transformation relates systemi to systemi-1 - E _i link transformation relates the deflection of systemi to systemi - F _i joint torque acting on jointi - g gravity vector expressed at the base coordinates - J inertia = - K kinetic energy of the system - l _i length of linki - M _i a mass concentrated at the joint i - m _i number of modes used to describe the deflection of link i - n number of links - q _h joint variable of thehth joint - q _hk time-varying amplitude of mode k of link h - R vector of remaining dynamics and external forcing terms = - r _i vector locating the centre of mass of linki - R _j dynamics from the joint equation j, excluding second derivatives of the generalized coordinates - R _if dynamics from the deflection equation jf, excluding second derivatives of the generalized coordinates - V potential energy - W _i transformation from the base to theith link - transformation from the base to the systemî - z the vector of generalised coordinates = - link density     

Prevalence and characterization of antimicrobial resistance of foodborne Listeria monocytogenes isolates in Hebei province of Northern China, 2005-2007

A total of 2177 food samples collected from nine cities in northern China during 2005 to 2007 were screened for the presence of Listeria monocytogenes. All L. monocytogenes isolates were subjected to serotyping, antimicrobial susceptibility, pulsed-field gel electrophoresis (PFGE), as well as PCR screening to identify genes responsible for tetracycline resistance [tet(L), tet(M), tet(K), tet(S) and tet(B)], transposon Tn916, and class 1 integron. Contamination with L. monocytogenes was detected in 4.13% (90/2177) of the total samples representing various food products. The pathogen was mainly isolated from frozen food made of wheat flour or rice products (26/252, 10.32%) and raw meat products (46/733, 6.28%). Besides, 3.31% (10/302) of cooked meat, 1.17% (4/343) of seafood, 0.98% (2/204) of non-fermented bean products and 0.62% (2/323) of vegetables samples were contaminated by this bacterium. The L. monocytogenes isolates belonged to five serotypes (1/2a, 1/2b, 1/2c, 4b, and 3a), with serotype 1/2a being dominant (48.88%). Antimicrobial resistance was most frequently observed for ciprofloxacin (17.8%), tetracycline (15.6%) and streptomycin (12.2%). Overall, resistance was observed against 14 out of 18 antimicrobials tested while multiple resistances occurred among 18.9% (17/90) isolates. Interestingly, two isolates were resistant to more than five antimicrobials. Among 14 tetracycline-resistant isolates, 13 carried tet(M) gene including nine possessing Tn916, and one harbored tet(S) gene. PFGE analysis revealed genetic heterogeneity among individual serotypes as well as scattered occurrence of some genotypes without any clear-cut correlation to source or food type. The widespread distribution of epidemiologically important serotypes (1/2a, 1/2b and 4b) of L. monocytogenes, and their resistance to commonly used antibiotics indicate a potential public health risk. Our data also indicate that L. monocytogenes could act as a reservoir of mobile tet genes along the food chain.     

Spectral derivative feature coding for hyperspectral signature analysis

This paper presents a new approach to hyperspectral signature analysis, called spectral derivative feature coding (SDFC). It is derived from texture features used in texture classification to dictate gradient changes among adjacent bands in characterizing spectral variations so as to improve better spectral discrimination and classification. In order to evaluate its performance, two known binary coding methods, spectral analysis manager (SPAM) and spectral feature-based binary coding (SFBC) are used to conduct comparative analysis. Experimental results demonstrate that the proposed SDFC performs more effectively in capturing spectral characteristics than do SPAM and SFBC.     

Understanding the mechanical properties of hot pressed Ba-doped S-phase SiAlON ceramics

In this contribution, we report the analysis and interpretation of the mechanical property measurements for a new class of SiAlON ceramic. The hardness and indentation fracture toughness were measured on the hot pressed Ba-doped S-SiAlON ceramic using Vickers indentation at varying loads (up to 300 N). An important observation was that all the investigated S-SiAlON exhibited the characteristic rising R-curve behavior with a maximum toughness of up to 10–12 MPa m^1/2 for ceramics, hot pressed both at 1700 and 1750 °C. Crack deflection by large elongated S-phase grains and crack bridging by β-Si₃N₄ needles has been found to be the major toughening mechanisms for the observed high toughness. Theoretical estimates, using a toughening model based on crack bridging and deflection by platelet shaped ‘S’-phase grains and β-Si₃N₄ needles, reveal the interfacial friction of around 200 MPa. Careful analysis of the indentation data reveals the average (apparent) hardness modestly increases with indent load in all S-SiAlON samples, with more significant effect for S-SiAlON, hot pressed at 1600 °C. This effect has been analyzed in the light of the established model of ‘indentation-induced cracking’ phenomenon. Our experimental results suggest that a modest combination of average hardness of 15 GPa and indentation toughness of around 12 MPa m^1/2 could be achieved in Ba-S-SiAlON ceramic and further improvement requires microstructural tailoring.     

Serine-70 is one of the critical sites for drug-induced Bcl2 phosphorylation in cancer cells

Taxoids and other microtubule-damaging drugs are known to induce Bcl2 phosphorylation at the G2-M phase of the cell cycle, with concomitant apoptosis in malignant cells derived from a variety of human malignancies, including leukemia, lymphoma, and breast and prostate cancer. We have investigated the ability of another antineoplastic drug, dolastatin 10, in inducing Bcl2 phosphorylation and apoptosis. We also investigated the effects of a phosphatase inhibitor okadaic acid in the regulation of Bcl2 phosphorylation, cell cycle arrest, and programmed cell death. Moreover, site-directed mutagenesis studies were performed to determine the specific serine residue(s) responsible for drug-induced Bcl2 phosphorylation. Our results indicate that these antimicrotubule agents or okadaic acid can induce posttranslational modification (phosphorylation) of Bcl2 protein at multiple serine residues. Interestingly, mutation of a serine residue at position 70 to alanine can significantly decrease drug-induced posttranslational modification (phosphorylation) of Bcl2 protein. Apparently, Ser70 seems to be a critical site for drug-induced posttranslational modification (phosphorylation) of the Bcl2 protein.     

A theoretical analysis of non-isothermal flow in wire-coating co-extrusion dies

A theoretical study of non-isothermal superimposed flow of two polymer melts in wire coating co-extrusion dies has been carried out. Numerical methods have been employed to solve the coupled momentum- and energy-balance equations. Various combinations of three polymers—namely, high density polyethylene (HDPE), polystyrene (PS) and low density polyethylene (LDPE) have been studied and least squares curve fitted quadratic polynomials have been used for constitutive equations for all three polymers in non-Newtonian high shear rate regions. A multitude of thermal and mechanical boundary conditions can be treated by this algorithm. It was found that temperature and velocity profiles in the die depend significantly on the arrangement of the polymers. Maximum temperature rise has been noted to increase sharply with wire velocity but it can be reduced by increasing the die radius. When the thickness of the outer layer is increased from zero, the shear stress at the wall undergoes a dramatic change (if the viscosities of the polymers are different) at small values of the flow rate ratio and it reaches an asymptotic value at large values of flow rate ratio. It was also found that viscosity ratio at the interface can be reduced by changing the initial temperatures of the liquids. It was observed in some cases that large errors in the calculation of rheological and thermal variables for this problem can be made if temperature rise due to viscous dissipation is not considered.     

Evaluation of the suitability of data base management systems: a case study at the US Forest Service

A methodology for assessing the feasibility of a data base management system is described, and its use demonstrated in a specific situation: the U.S. Forest service. A series of questions to be answered at the test organization is formulated, aimed at quantifying the benefits of a DBMS. Results of attempting to answer these questions at two test sites are provided. Implications of these results are given for both forest and higher level management.