A model for two-phase turbulent mixing in a jet bubble column

Mixing behavior of the two phase air-water turbulent flow in a jet bubble column is examined. The time evolution of the mixing behavior of a liquid tracer in a turbulent air-water flow within a jet bubble column is predicted using a model based on the fundamental governing equations of fluid motion. The predictions of the model are compared with experimental measurements. Measured residence time distributions (RTD) of the liquid tracer within the cone agree well with the predicted values given by the model. For the range of parameters considered in the study, lack of radial mixing and large axial mixing are evident within the cone of the jet bubble column. Use of fundamental mathematical models for the study of hydrodynamics in a two-phase conventional bubble column has been reported earlier (Torvik, 1990; Jakobsen et al., 1993). The present paper extends the use of such models to predict the mixing characteristics in a jet bubble column.     

Dyeing of cotton with a bifunctional disulphide bis(ethylsulphone-sulphatoethylsulphone) disazo reactive dye

A new bifunctional disazo reactive dye of a temporarily high molecular structure based on a disulphide bis(ethylsulphone-sulphatoethylsulphone) reactive system was synthesised and applied to cotton fabric. This dye displayed good primary exhaustion under different neutral exhaustion conditions. The results assessed for the alkaline exhaust dyeing indicate that the disulphide bis(ethylsulphone-sulphatoethylsulphone) dye showed higher exhaustion and fixation values compared to those obtained with the commercial CI Reactive Black 5. The fastness properties of the disulphide dye were similar to those of the commercial dye. Received: 24 March 2005; Accepted: 15 June 2005.     

Surgical treatment of adenocarcinoma of the rectum

OBJECTIVE: The authors' aim was to determine survival and recurrence rates in patients undergoing resection of rectal cancer achieved by abdominoperineal resection (APR), coloanal anastomosis (CAA), and anterior resection (AR) without adjuvant therapy. SUMMARY BACKGROUND DATA: The surgery of rectal cancer is controversial; so, too, is its adjuvant management. Questions such as preoperative versus postoperative radiation versus no radiation are key. An approach in which the entire mesorectum is excised has been proposed as yielding low recurrence rates. METHODS: Of 1423 patients with resected rectal cancers, 491 patients were excluded, leaving 932 with a primary adenocarcinoma of the rectum treated at Mayo. Eighty-six percent were resected for cure. Surgery plus adjuvant treatment was performed in 418, surgery alone in 514. These 514 patients are the subject of this review. Among the 514 patients who underwent surgery alone, APR was performed in 169, CAA in 19, AR in 272, and other procedures in 54. Eighty-seven percent of patients were operated on with curative intent. The mean follow-up was 5.6 years; follow-up was complete in 92%. APR and CAA were performed excising the envelope of rectal mesentery posteriorly and the supporting tissues laterally from the sacral promontory to the pelvic floor. AR was performed using an appropriately wide rectal mesentery resection technique if the tumor was high; if the tumor was in the middle or low rectum, all mesentery was resected. The mean distal margin achieved by AR was 3 +/- 2 cm. RESULTS: Mortality was 2% (12 of 514). Anastomotic leaks after AR occurred in 5% (16 of 291) and overall transient urinary retention in 15%. Eleven percent of patients had a wound infection (abdominal and perineal wound, 30-day, purulence, or cellulitis). The local recurrence and 5-year disease-free survival rates were 7% and 78%, respectively, after AR; 6% and 83%, respectively, after CAA; and 4% and 80%, respectively, after APR. Patients with stage III disease, had a 60% disease-free survival rate. CONCLUSIONS: Complete resection of the envelope of supporting tissues about the rectum during APR, CAA, and AR when tumors were low in the rectum is associated with low mortality, low morbidity, low local recurrence, and good 5-year survival rates. Appropriate "tumor-specific" mesorectal excision during AR when the tumor is high in the rectum is likewise consistent with a low rate of local recurrence and good long-term survival. However, the overall failure rate of 40% in stage III disease (which is independent of surgical technique) means that surgical approaches alone are not sufficient to achieve better long-term survival rates.     

Polymerization of methyl methacrylate with Nickel(II)α‐benzoinoxime complex

Polymerizations of methyl methacrylate (MMA) monomer initiated by a novel Ni(II)α‐benzoinoxime complex have been achieved under homogeneous conditions in the 25–60°C temperature range. The activity for polymerization increases with reaction temperature and by carrying out the polymerization in solution of low‐polarity solvents without any induction time. The obtained polymers have weight‐average molecular weights about 10⁵ and slight broad polydispersity indexes (2.2 ≤ M_w/M_n ≤ 3.3). Dependence of rate constants polymerization and decomposition of initiator (k_app and k_d, respectively) on temperature was investigated and activation parameters were computed from Arrhenius plot. ¹H‐NMR analysis of PMMA revealed a syndio‐rich atactic microstructure in agreement with conventional radical process. Radical scavenger TEMPO effect together with microstructure and molecular weight distributions data supported that the polymerization proceed via free radical mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of acid-basic treatments of date stones on lead (II) adsorption

The effect of acid-basic treatments of date stones on lead adsorption was investigated. The physicochemical properties of this low-cost adsorbent were characterized by N₂ adsorption and mass titration. The date stones sample, treated with HNO₃, possess the highest surface oxygen containing functional groups (2.1 mmol/g), surface area (115 m²/g), and pore volume (0.048 cm³/g) and the more adsorption capacity to the lead(II) ions. The effect of contact time, initial concentrations of adsorbate, ionic strength, and adsorbent dose on the uptake of lead was studied in batch experiments. The sorption process was found to follow Redlich-Peterson isotherm and pseudo-second-order rate kinetics.     

A numerical and experimental study of the solidification rate in a twin-belt caster

A numerical and experimental study was carried out to investigate the solidification process in a twin-belt (Hazelett) caster. The numerical model considers a generalized energy equation that is valid for the solid, liquid, and mushy zones in the cast. Ak-ε turbulence model is used to calculate the turbulent viscosity in the melt pool. The process variables considered are the belt speed, strip thickness, nozzle width, and heat removal rates at the belt-cast interface. From the computed flow and temperature fields, the local cooling rates in the cast and trajectories of inclusions were computed. The cooling rate calculations were used to predict the dendrite arm spacing in the cast. The inclusion trajectories agree with earlier findings on the distribution of inclusion particles for near horizontally cast surfaces. This article also reports the results of an experimental study of the measurement of heat flux values at the belt-cast interface during the solidification of steel and aluminum on a water-cooled surface. High heat fluxes encountered during the solidification process warranted the use of a custom-made heat flux gage. The heat flux data for the belt surface were used as a boundary condition for the numerical model. Objectives of the measurements also included obtaining an estimate of the heat-transfer coefficient distribution at the water-cooled side of the caster belt. Y.G. KIM, formerly Graduate Student, Materials Engineering Department, Drexel University.     

Structural studies of some V2O5-P2O5-B2O3-Fe2O3 glass systems

X-ray diffraction and infrared measurements were performed on vanadium borophosphate glass containing different amounts of iron ranging from 0–7.5 mol % and heat treated at 300 °C for various times. The structure and phase separation could be determined for each glass composition. V₂O₅ was the main precipitated phase in all heat-treated samples, and its amount was dependent on the heat-treatment time and Fe₂O₃ content. Also FeP was detected in samples heat treated for 24 h. The infrared measurements showed the presence of both V⁴⁺ and V⁵⁺. The symmetry of V₂O ₇ ⁴⁻ and VO ₄ ³⁻ groups was found to increase with increasing Fe₂O₃ content. It was also found that some PO₄ changed to BO₃, forming a non-bridging oxygen.     

Structure and magnetic susceptibility of irradiated sodium borate glasses containing nickel oxide

The effect of introducing soda to boric oxide on the optical absorption infrared spectra and magnetic susceptibility of sodium borate glass system containing nickel oxide was studied. It was found that increasing of Na₂O helps in forming the BO₄ group and nonbridging oxygen and the nickel ions change from the octahedral state to the tetrahedral state. The magnetic susceptibility also increases rapidly with gradual increase of soda content up to 20 mol%, and then slightly increases, this may be due to the change in the coordination number of nickel ions. Also the effect of the addition of nickel oxide was studied, it was found that the values of magnetic susceptibility increases with the gradual increase of the nickel oxide, which is due to the increase of Ni²⁺ in octahedral coordination.     

Cholesterol secretion from hepatocytes induced by triacylglycerol and apolipoprotein E

The mechanism for the increase in plasma cholesterol levels in cholesterol-fed rats following chylomicron transport was investigated in intact animals, in isolated perfused liver, and in hepatocytes in monolayer cultures. Intravenous administration of egg phosphatidylcholine in amounts greater than those required to cause a plasma cholesterol response when given as chylomicrons was without effect. This makes it unlikely that increased plasma cholesterol levels resulted from the recruitment of tissue cholesterol by the plasma chylomicron phospholipids that persisted in the plasma after triacylglycerol clearance. The hepatic origin of the increased plasma cholesterol levels was directly confirmed by two hepatic perfusion experiments. When cholesterol-fed rats received intravenous chylomicrons prior to isolated hepatic perfusion, more cholesterol was secreted by the liver than when the rats were injected intravenously with buffer. Perfusion of apolipoprotein E (apo E)-rich triacylglycerol emulsions through the livers also enhanced cholesterol secretion. The increase in hepatocyte cholesterol secretion seen with cholesterol-fed rats was also noted in monolayer cultures following incubation with apo E rich-triacylglycerol emulsions. The apolipoprotein or the emulsion alone, or apo E-rich phosphatidylcholine liposomes, had no effect. The data confirm previous indirect observations that the liver is the source of cholesterol that appears in plasma following transport of chylomicrons or following a lipid-rich meal in cholesterol-fed rats. The data also re-emphasize the importance of providing apo E with triacylglycerol emulsions to initiate secretion of lower density lipoproteins by the liver.