Rapidly mixed combustion of hydrogen/oxygen diluted by N2 and CO2 in a tubular flame combustor

In this study hydrogen flames have been attempted in a rapidly mixed tubular flame combustor for the first time, in which fuel and oxidizer are individually and tangentially injected into a cylindrical combustor to avoid flame flash back. Three different cases were designed to examine the effects of fuel and oxidizer feeding method, diluent property, oxygen content and equivalence ratio on the characteristics of hydrogen flame, including the flame structure, lean extinction limit, flame stability and temperature. The results show that by enhancing mixing rate through feeding system, the range of equivalence ratio for steady tubular flame can be much expanded for the N₂ diluted mixture, however, at the oxygen content of 0.21 (hydrogen/air) the steady tubular flame is achieved only up to equivalence ratio of 0.5; by decreasing oxygen content, the lean extinction limit slightly increases, and the upper limit for steady tubular flame establishment increases significantly, resulting in an expanded tubular flame range. For CO₂ diluted mixture, the stoichiometric combustion has been achieved within oxygen content of 0.1 and 0.25, for which the burned gas temperature is uniformly distributed inside the flame front; as oxygen content is below 0.21, a steady tubular flame can be obtained from the lean to rich limits; and the lean extinction limit increases from 0.17 to 0.4 as oxygen content decreases from 0.21 to 0.1, resulting in a shrunk tubular flame range. Laminar burning velocity, temperature and Damköhler number are calculated to examine the differences between N₂ and CO₂ diluted combustion as well as the requirement for hydrogen-fueled tubular flame establishment.     

Synthesis of the Orthorhombic Phase of 2Y˙ZrO2

A mixture of tetragonal and monoclinic 2Y˙ZrO₂ (2 mol% Y₂O₃–ZrO₂) powder was treated from 400° to 800°C and from 4 to 7 GPa for 30 min. The products were identified by powder XRD, Raman spectroscopy, and TEM. Results indicated that an orthorhombic phase was synthesized at T=400° to 600°C and P>4 GPa. The lattice parameters were obtained as a=0.505, b=0.525, and c=0.509 nm; the density was 6.17 Mg/m³. The orthorhombic phase always coexisted with the tetragonal phase in the products. The amounts of the tetragonal phase before and after treatment remained largely unchanged, whereas the amount of new orthorhombic phase was nearly the same as the decreased amount of the monoclinic phase. It was assumed, therefore, that only the monoclinic phase transformed into the orthorhombic phase.     

Modification of natural rubber tubes for biomaterials I. Radiation-induced grafting of N,N-dimethyl acrylamide onto natural rubber tubes

Radiation-induced simultaneous grafting of N,N-dimethyl-acrylamide (DMAA) onto natural rubber (NR) tubes has been studied to improve blood compatibility of the NR tubes. Concerning grafting of DMAA onto NR tubes, it was found that the grafting proceeds effectively in the presence of carbon tetrachloride (CCl₄) as a solvent. The degree of grafting was found to be saturated at about 26 wt%, but a higher degree of grafting can be obtained by either “so called two-step grafting” or “putting a standing time for a while before irradiation.” The initial grafting rate was proportional to 0.85 power of dose rate. The apparent activation energy of the graft-copolymerization was 7.42 kcal/mol. Evaluation of blood compatibility of DMAA-grafted NR tubes has been carried out by ex vivo test. According to the results, significant improvement of blood compatibility was obtained for the samples in which degree of grafting is higher than 30 wt%.     

Intrinsic stage i crack growth of directionally solidified Ni-Base superalloys during low-cycle fatigue at elevated temperature

Strain-controlled low-cycle fatigue tests of cylindrical smooth specimens of two kinds of directionally solidified Ni-base superalloys, RENé 80+Hf and CM 247LC, were carried out at a temperature of 873 K, and the successive process from the crack initiation to small crack propagation was investigated by employing a replication technique. Both materials exhibited typical features of stage I fatigue fracture; that is, the fracture occurred on the crystallographic 111 planes, the most important slip planes in face-centered cubic (fcc) materials. It was found that the rate of stage I crack growth, when not influenced by a nearby grain boundary, proportionally increased with the crack length. However, as the crack tip neared a grain boundary, the rate rapidly decreased. It was also shown that the crack growth rate fell when the crack deflection occurred due to secondary slip. Comparison was also made between the stage I crack growth rate and the long crack growth rate in polycrystalline Ni-base superalloys.     

A diurnal variation of hepatic acid cholesteryl ester hydrolase activity in the rat

The diurnal variation in lysosomal acid cholesteryl ester hydrolase (Acid CEH), (EC 3.1.1.13) has been examined in fed, fasted and adrenalectomized rats. The Acid CEH activity of normal rat liver exhibits a diurnal rhythm with maxima at 06.00 hours and minima at 18.00 hours, but such a rhythm was not observed in spleen and brain. This rhythm was abolished after fasting for two days, and the resulting Acid CEH activity remained constant at the minimum level. However, adrenalectomy did not abolish the diurnal rhythm. These results indicate that the Acid CEH activity varies according to a diurnal rhythm with maxima and minima separated by approximately 12 hr. Further, it is evident that the appearance of this rhythm is dependent upon dietary, but not adrenal hormone influence.     

Red blood cell tocopherol and liver tocopherol in hyperlipemic rats as compared with plasma tocopherol

In rats with hyperlipemia induced by Triton WR-1339, changes in tocopherol concentrations in plasma and RBC were compared with those in the liver and its subcellular fractions, microsomes and mitochondria. After daily injection with Triton, plssma total lipids at 3 days and 7 days, respectively, showed elevation 6.5 times and 15 times as high as those in the control rats, and triglycerides showed the most predominant elevation. With the hyperlipemia, the concentrations of tocopherol in RBC and the subcellular fractions decreased, as plasma lipids and plasma tocopherol increased, while no change occurred in tocopherol concentrations in liver homogenates. The changes in the ratio of tocopherol to total lipids in plasma coincided with changes in tocopherol concentrations in the RBC and subcellular fractions.     

Natural occurrence of deoxynivalenol in wheat from Paraná State,Brazil and estimated daily intake by wheat products

The occurrence of deoxynivalenol (DON) was evaluated in 113 wheat samples from the northern and central/southwestern regions of Paraná State, Brazil during the 2008 and 2009 growing seasons, and this rate of occurrence was used to estimate the DON dietary exposure. The DON determination was carried out by an indirect competitive enzyme-linked immunosorbent assay. DON was detected in 66.4% samples at levels ranging from 206.3 to 4732.3 μg/kg (mean 1894.9 μg/kg). The estimated daily intake (EDI) of DON through bread and pasta was evaluated in the inhabitants of Londrina City in northern Paraná State, Brazil. The average intake of these inhabitants was 0.79 μg/kg body weight (b.w.) for bread and 0.35 μg/kg b.w. for pasta. The total EDI was 1.13 μg/kg, which is above the Provisional Tolerable Daily Maximum Intake (PTDMI) of 1 μg/kg b.w. To our knowledge, this is the first report on natural DON occurrence in wheat and DON dietary exposure estimation from Paraná, Brazil.     

A mathematical model for computer simulation of a direct continuous esterification process between terephthalic acid and ethylene glycol: Part 1. Model development

A new mathematical model has been developed for the continuous esterification process of terephthalic acid (TPA) and ethlene glycol (EG) with consideration of oligomer characteristics. The liquid weight fraction in the reaction mixture, β, has been selected as a principal parameter in this model. The solubility of TPA in EG and bis β-hydroxyethyl terephthalate (BHET) has been measured in order to estimate more precisely the concentration of each component. Good agreement has been obtained by plotting the log of solubility data of TPA in EG and BHET against the reciprocal of the absolute temperature with correlation coefficients of 0.998 and 0.989, respectively. The validity of these data has been verified in comparison with other data.     

Flocculating activity of cross-linked poly-gamma-glutamic acid against bentonite and Escherichia coli suspension pretreated with FeCl3 and its interaction with Fe3+

Cross-linked poly-gamma-glutamic acid (C-L gamma-PGA) at 5 microg/ml flocculated bentonite suspension pretreated with polyaluminum chloride (PAC) at 2 microg/ml Al3+-PAC to a transparency of approximately 30% after 30 min and more than 90% after 4 h, while Al3+ concentration in the upper phase of the suspension decreased with incubation time. When pretreated with FeCl3 at 16 microg/ml Fe3+-FeCl3, similar results were obtained. In the case of Escherichia coli suspension, the combination of C-L gamma-PGA and FeCl3 demonstrated a more marked flocculating activity with a satisfactory transparency occurring after 30 min of treatment, accompanied by a decrease in residual Fe3+ concentration. In the above two suspensions pretreated with FeCl3, small visible floats appeared in the early stage of incubation. These floats were found to be due to the direct interaction between FeCl3 and C-L gamma-PGA, indicating the formation of a water-insoluble complex. After allowing the suspension to stand for a long time, elemental analysis and inductively coupled plasma spectroscopy of the precipitates produced suggested that not only the complex was formed due to the interaction between Fe3+ in FeCl3 and COO- in the C-L gamma-PGA molecule, but also Fe2O3 and Fe(OH)3 might be entrapped in this complex. This could be applied to scavenge metal ions including Fe3+ from polluted water.