Comparison of plain and finned tubes during pool boiling of CaSO4 solutions

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.One of the most severe types of fouling occurs during pool boiling heat transfer. This has led some processes such as thermal desalination units, in particular, to be operated below saturation temperature to avoid rapid and severe formation of crystallized deposits e.g. CaSO4 on heat transfer surfaces. This has been despite superiority of pool boiling to other modes of heat transfer. This study investigates experimentally the formation of deposit on the finned tubes during pool boiling of CaSO4 solutions. The structured tubes are low finned tube type with a fin density of 19 fins per inch, 1.35 mm fin pitch and Cu-Ni as substrate. Fouling runs are carried out for different heat fluxes ranging from 100 to 300 kW/m2 and different salt concentrations at atmospheric pressure. For the sake of comparison, similar runs are also conducted for plain stainless steel tubes. Experimental results show for the finned tubes, substantial reduction of fouling compared to those of the plain tube. If any deposit forms on the surface then it is only a very thin and fragile layer of crystals which differs significantly to plain tubes which is characterized with a thick layer of deposit. In addition, the finned tubes perform much better at lower heat fluxes. Finally, the cleanability of finned tubes is also examined which show good performance.dc201

Ultrasonographic Diagnosis and Clinical Evaluation of the Foreign Body Complications in the Compound Stomach of Cattle and Buffaloes

This study was aimed to detect and record the clinical and ultrasonographic findings of the different complications resulted from the foreign bodies lodged in the compound stomach of cattle and buffaloes. A total of 105 animals (37 cattle and 68 buffaloes) were subjected to study. Based on the clinical and ultrasonographic examination, animals were classified into; acute local reticuloperitonitis (ALRP) (15 cattle and 28 buffaloes), chronic local reticuloperitonitis (CLRP) (6 cattle and 14 buffaloes), acute diffuse reticuloperitonitis (ADRP) (5 cattle and 3buffaloes), reticular abscesses (RA) (4 cattle and 7 buffaloes), traumatic pericarditis (TP) (6 cattle and16 buffaloes) and liver abscess (one cattle). Results revealed that ALRP represented the highest percentage of 40.5% in cattle and 41.2 % in buffalos between the different complications of TRP. TP represented the second complications of higher incidence (16.2% in cows and 23.5% in buffalos). Liver abscess represented the lowest percentage (2.8%) and was recorded in cows only. The pregnant animals were affected more than the non pregnant. Clinical findings represented in systemic reaction and pain tests were commonly encountered in TRP and its complications. Some of the affected animals were negatively respond to metal detector test. Results of the present study indicated that the ultrasonographic examination provide a specific echogenic pattern for the different complications of TRP. It was concluded that, clinical examination only is not efficient to give accurate diagnosis of foreign body lodged in the reticulum and rumen and their complications. Ultrasonography is a safe, non invasive diagnostic confirmatory method that could be used for early detection of such conditions

Effect of Narrow-Band Ultraviolet B Phototherapy and Methotrexate on MicroRNA (146a) Levels in Blood of Psoriatic Patients

Background. Recently, some miRNAs have been proven to show aberrant expression in psoriasis and play a role in the pathogenesis of the disease. Objective. To find out whether NB-UVB or methotrexate treatment affects whole blood levels of human miRNA (146a) in patients with psoriasis and demonstrate its correlation with disease severity. Methods. Blood samples were obtained from healthy control and from psoriatic patients before and 12 weeks after treatment with NB-UVB, methotrexate. Quantification of human miRNA (146a) by Real Time PCR (RT-PCR). Results. Blood human miRNA (146a) levels were higher in patients with psoriasis than those in healthy controls (P=0.001); it had no significant positive relation with PASI scores in patients (r=0.2, P=0.107). Real Time PCR showed that, after 12 weeks of treatment with NB-UVB phototherapy or treatment with methotrexate, there was significantly decreased level of miR146a (P=0.001; P=0.002, resp.). Conclusion. The expression of miRNA146a is increased in whole blood samples from psoriasis patients, so we can evaluate its possibility to work as a future therapeutic objective in the treatment of psoriasis. With these markers, it is able to screen therapeutics effect or changes to a further aggressive treatment for psoriasis

Immobilization of halophilic Aspergillus awamori EM66 exochitinase on grafted k-carrageenan-alginate beads

A novel extreme halophilic exochitinase enzyme was produced by honey isolate Aspergillus awamori EM66. The enzyme was immobilized successfully on k-carrageenan-alginate gel carrier (CA) with 93 % immobilization yield. The immobilization process significantly improved the enzyme specific activity 2.6-fold compared to the free form. The significant factors influencing the immobilization process such as enzyme protein concentration and loading time were studied. Distinguishable characteristics of optimum pH and temperature, stability at different temperatures and NaCl tolerance for free and immobilized enzyme were studied. The immobilization process improved optimum temperature from 35 to 45 °C. The immobilized enzyme retained 76.70 % of its activity after 2 h at 75 °C compared to complete loss of activity for the free enzyme. The reusability test proved the durability of the CA gel beads for 28 cycles without losing its activity

Bioprocess optimization for pectinase production using Aspergillus niger in a submerged cultivation system

Background: Pectinase enzymes present a high priced category of microbial enzymes with many potential applications in various food and oil industries and an estimated market share of $ 41.4 billion by 2020. Results: The production medium was first optimized using a statistical optimization approach to increase pectinase production. A maximal enzyme concentration of 76.35 U/mL (a 2.8-fold increase compared with the initial medium) was produced in a medium composed of (g/L): pectin, 32.22; (NH4)2SO4, 4.33; K2HPO4, 1.36; MgSO4.5H2O, 0.05; KCl, 0.05; and FeSO4.5H2O, 0.10. The cultivations were then carried out in a 16-L stirred tank bioreactor in both batch and fed-batch modes to improve enzyme production, which is an important step for bioprocess industrialization. Controlling the pH at 5.5 during cultivation yielded a pectinase production of 109.63 U/mL, which was about 10% higher than the uncontrolled pH culture. Furthermore, fed-batch cultivation using sucrose as a feeding substrate with a rate of 2 g/L/h increased the enzyme production up to 450 U/mL after 126 h. Conclusions: Statistical medium optimization improved volumetric pectinase productivity by about 2.8 folds. Scaling-up the production process in 16-L semi-industrial stirred tank bioreactor under controlled pH further enhanced pectinase production by about 4-folds. Finally, bioreactor fed-batch cultivation using constant carbon source feeding increased maximal volumetric enzyme production by about 16.5-folds from the initial starting conditions

Pool boiling of water-Al2O3 and water-Cu nanofluids on horizontal smooth tubes

Experimental investigation of heat transfer during pool boiling of two nanofluids, i.e., water-Al2O3 and water-Cu has been carried out. Nanoparticles were tested at the concentration of 0.01%, 0.1%, and 1% by weight. The horizontal smooth copper and stainless steel tubes having 10 mm OD and 0.6 mm wall thickness formed test heater. The experiments have been performed to establish the influence of nanofluids concentration as well as tube surface material on heat transfer characteristics at atmospheric pressure. The results indicate that independent of concentration nanoparticle material (Al2O3 and Cu) has almost no influence on heat transfer coefficient while boiling of water-Al2O3 or water-Cu nanofluids on smooth copper tube. It seems that heater material did not affect the boiling heat transfer in 0.1 wt.% water-Cu nanofluid, nevertheless independent of concentration, distinctly higher heat transfer coefficient was recorded for stainless steel tube than for copper tube for the same heat flux density

pKa Modulation of the Acid/Base Catalyst within GH32 and GH68: A Role in Substrate/Inhibitor Specificity?

Glycoside hydrolases of families 32 (GH32) and 68 (GH68) belong to clan GH-J, containing hydrolytic enzymes (sucrose/fructans as donor substrates) and fructosyltransferases (sucrose/fructans as donor and acceptor substrates). In GH32 members, some of the sugar substrates can also function as inhibitors, this regulatory aspect further adding to the complexity in enzyme functionalities within this family. Although 3D structural information becomes increasingly available within this clan and huge progress has been made on structure-function relationships, it is not clear why some sugars bind as inhibitors without being catalyzed. Conserved aspartate and glutamate residues are well known to act as nucleophile and acid/bases within this clan. Based on the available 3D structures of enzymes and enzyme-ligand complexes as well as docking simulations, we calculated the pKa of the acid-base before and after substrate binding. The obtained results strongly suggest that most GH-J members show an acid-base catalyst that is not sufficiently protonated before ligand entrance, while the acid-base can be fully protonated when a substrate, but not an inhibitor, enters the catalytic pocket. This provides a new mechanistic insight aiming at understanding the complex substrate and inhibitor specificities observed within the GH-J clan. Moreover, besides the effect of substrate entrance on its own, we strongly suggest that a highly conserved arginine residue (in the RDP motif) rather than the previously proposed Tyr motif (not conserved) provides the proton to increase the pKa of the acid-base catalyst