Influence of flow field on sedimentation efficiency in a circular settling tank with peripheral inflow and central effluent

The paper presents an experimental study of suspension flow patterns and velocity field inside a circular settling tank with continuous operation. Research was focused on the impact of a specific flow pattern on the sedimentation efficiency of the prototype settling tank. The latter differed from a common circular settling tank in that it was peripherally fed and had the central draw-off. Experiment was carried out on a settling tank section made of plexiglass and represented a radial slice of a prototype settling tank. The flow field and local suspension concentration was determined by computer-aided visualization. Sedimentation efficiency was assessed relatively by comparison of the amount of settled particles (sludge height measurements) between different types of flow in a certain time period of the settling tank operation. Results showed that there were two types of flow in the settling tank that were initiated by a horizontal or vertical inflow from the distribution ring. The type of inflow (horizontal or vertical) was a function of the suspension height in the settling tank. Significant differences in sedimentation efficiency were observed between both types of flow, particularly at lower inlet suspension concentrations. Horizontal inflow proved to be less efficient in terms of settling.     

Structure-activity relationship studies on the immune stimulatory effects of base-modified CpG toll-like receptor 9 agonists

Synthetic oligodeoxynucleotides containing unmethylated deoxycytidylyl-deoxyguanosine dinucleotide (CpG) motifs are able to stimulate potent immune responses through a signaling pathway involving Toll-like receptor 9 (TLR9). We have investigated the structure-activity relationship (SAR) of base-modified CpG oligonucleotides with TLR9 by measuring TLR9 activation by 20-mer oligonucleotides having just a single human recognition motif (5'-GTCGTT-3') in functional cell-based TLR9 assays. Substitution of guanine by hypoxanthine and 6-thioguanine resulted in activity similar to the unmodified parent molecule, whereas purine, 2-aminopurine, 2,6-diaminopurine, and 8-oxo-7,8-dihydroguanine substitution resulted in approximately 40-60 % reduction in activity, and 7-deazaguanine substitution led to the strongest (80 %) reduction in TLR9 stimulation. Furthermore, none of the investigated modifications at C5 and N4 of cytosine were well tolerated with respect to human TLR9 stimulation. Our results are compatible with a SAR model in which guanine is recognized by the Hoogsteen site, and C5 is most critical for recognition of cytosine. In addition, we found significant species-specific differences between human and murine TLR9 recognition, which demonstrates the importance of choosing appropriate assay systems for SAR studies.     

A TWO ZONE UNEQUAL VOLUME MODEL TO DESCRIBE MIXING IN CHEMICAL AND BIOCHEMICAL PROCESSES

The effect of imperfect mixing in a single batch reactor was studied using a two-tank system model with internal recycle and unequal volumes. The double-valued relationship between the reactant in each tank of the model for the A → B biochemical/chemical reversible and irreversible reactions was used to analyze mixing patterns in poorly mixed stirred-tank reactors.     

Hepatocellular carcinoma outcomes based on indicated treatment strategy

Hepatocellular carcinoma (HCC) in Western populations historically has been associated with poor survival. In this study, we conducted a 7-year retrospective analysis of patients evaluated at our institution with HCC to determine the effects of newer treatment strategies on outcome. During the period of study, 117 patients [86 (74%) male; mean age, 59 years (range, 16-85)] were evaluated with treatment as follows: surgical resection in 22 (19%), chemoembolization with or without systemic chemotherapy in 40 (35%), systemic treatment alone in 16 (13%), orthotopic liver transplantation in 8 (7%), and supportive care only in 31 (26%). Sixty-nine patients (59%) had documented cirrhosis, with hepatitis C being the most common cause in 27 of 69 (39%). In patients receiving no treatment, median survival was just under 3 months, with only two 1-year survivors. Patients with orthotopic liver transplantation had 1-, 2-, and 3-year survival rates of 87, 87, and 58 per cent compared with 69, 52, and 43 per cent in surgically resected patients. Survival after chemoembolization was 35, 20, and 11 per cent at 1, 2, and 3 years, whereas survival after systemic chemotherapy was 30 and 15 per cent at 1 and 2 years, respectively. One-year survival was improved in noncirrhotic patients compared with cirrhotics (47% vs 29%; P < 0.05) but was no different in patients younger than 55 years compared with older patients (38% vs 38%). When possible, surgical treatment strategies offer superior survival.     

Surgical clips: a cause of late recurrent gallstones

BACKGROUND: Oral iron supplements, which are usually in the form of ferrous (Fe2+) salts, are toxic to the gastrointestinal mucosa, and so intolerance is common, resulting in poor compliance and failure of treatment. The sugar derivative maltol strongly chelates iron, rendering it available for absorption and stabilized in the less toxic ferric (Fe3+) form. AIM: To test whether ferric trimaltol could correct iron deficiency anaemia in patients intolerant of ferrous sulphate. METHODS: Twenty-three patients were recruited from gastroenterology clinics, of whom 1 5 had inflammatory bowel disease, a group often difficult to treat with oral iron. Patients with iron deficiency anaemia and documented intolerance to ferrous sulphate were given 3 months of treatment with ferric trimaltol. RESULTS: Nineteen of 23 patients completed the treatment and anaemia was fully corrected in 14 of these, mean haemoglobin increased from 106 +/- 15 to 126 +/- 16 g/L, and there was a particularly low incidence of side-effects. Of 11 patients with inflammatory bowel disease who completed the study, nine fully corrected their anaemia. CONCLUSION: The results demonstrate that in patients intolerant of ferrous compounds, ferric trimaltol corrects iron deficiency and has a low incidence of side-effects.     

Numerical and experimental investigation of axial fan with trailing edge self-induced blowing

Axial fans often show adverse flow conditions at the fan hub and at the tip of the blades. In the present paper, a modification of conventional axial fan blades with numerical and experimental investigation is presented. Hollow blades were manufactured from the hub to the trailing edge at the tip of the blades. They enable the formation of self-induced internal flow through internal passages. The internal flow enters the internal radial flow passages of the hollow blades through the openings near the fan hub and exits through the trailing edge slots at the tip of the blade. The study of the influence of internal flow on the flow field of axial fan and the modifications of aerodynamic characteristics of the axial fan have been made. The numerical and experimental results show a comparison of integral and local characteristics of the axial fan with the internal flow, compared to characteristics of a geometrically equivalent fan without internal flow. The experimental results of local characteristics were performed with a five-hole probe and computer-aided visualization. A reduction of adverse flow conditions near the trailing edge at the tip of the blade was achieved, as well as boundary layer reduction on the blade suction side and the reduction of flow separation. The introduction of self-induced blowing led to the preservation of the direction of external flow, defined by blade geometry, and enabled maximal local energy conversion. The integral characteristic reached higher degree of efficiency.     

Time dependant measurements of cavitation damage

Due to the extremely long length of experiments, in most studies of cavitation erosion only damage in the incubation period is measured and the final damage (mass loss rate) is then predicted by extrapolation. The methods of extrapolation are usually very basic since there were almost no in depth time dependant measurements of cavitation erosion performed in the past. A rotating disc test rig that generates a very aggressive cavitation and pure copper specimens, as erosion sensors, were used to investigate the correlation between the damage within the incubation period and final mass loss. The damage was measured optically three times during the incubation period and by weighing the specimen during the rest of the experiment.The results confirmed that the same clear relationship between the damage in the incubation period and the final mass loss rate exists, what means, that the mass loss rate can indeed be qualitatively predicted on the basis of measurements performed within the incubation period. This is a good basis for developing laws of extrapolation from a short time scale (laboratory measurement within the incubation period) to the real time scale (machine operation).     

Mineral wool melt fiberization on a spinner wheel

In this paper, the formation of mineral wool fibres has been studied on a real industrial production process. Parametric dependence of the melt film structural dynamics on the spinner wheel rotational frequency was investigated. The results presented indicate the presence of the melt instability that is formed as a complex quasi-periodic oscillation of the structures on the melt film surface. In addition to the melt oscillations which coincide with the rotating frequency of the spinner wheel and its higher harmonics, aperiodic melt structures also appear. These structures result from the Taylor instability, which is inherent to liquid movement and is one of the basic mechanisms of the formation of melt ligaments that solidify into mineral wool fibres. Based on the results, a phenomenological model for structural instability as a function of the wheel rotational frequency was formed, indicating a characteristic influence of melt film dynamics on the fibre formation and indirectly, on the quality of the end product.     

Prediction of cavitation vortex dynamics in the draft tube of a francis turbine using radial basis neural networks

Application of radial basis neural networks (RBNN) for prediction of cavitation vortex dynamics in a Francis turbine draft tube is presented. The dynamics of the cavitation vortex was established by fluctuations of a void fraction in a selected region of the draft tube. The void fraction was determined by image acquisition and analysis. Pressure in the draft tube and images of the cavitation vortex were acquired simultaneously for the experiment. RBNN were used for prediction. The void fraction in the selected region of the cavitation vortex was predicted on the basis of experimentally provided pressure data. The learning set consisted of pressure – void fraction pairs. The prediction consisted in providing only the pressure. Regression coefficients r between the predicted and measured void fractions were in an interval of 0.82–0.98. A good agreement between power spectra and correlation functions of measured and predicted void fractions was shown.     

LDA Velocity Measurements of High‐Viscosity Fluids in Mixing Vessel with Vane Geometry Impeller

The object of this work was to measure the velocity field in non‐Newtonian fluids inside mixing vessel. The six‐bladed vane rotor used for mixing was designed from rotating vane geometry of a sensor system, commonly used for rheometrical measurements of complex fluids (Barnes and Nguyen, J. Non‐Newtonian Fluid Mech. 98 , 1‐14 (2001); Schramm, 1994). During mixing, the viscosity was determined by measuring the torque at different impeller speeds, and compared to rheologically obtained shear dependent viscosity. The velocity field was determined by LDA measurements at twelve places inside mixing vessel. It was observed that axial and radial component of the velocity were insignificant at all measurement points. On the other hand, the results showed the periodic nature of tangential component of the velocity, which was confirmed with computer‐aided visualization method.