Kinetics Modeling of Mass Transfer Using Peleg’s Equation During Osmotic Dehydration of Seedless Guava (<Emphasis Type="Italic">Psidium guajava</Emphasis> L.): Effect of Process Parameters

Peleg’s equation was used to study the effect of process parameters on kinetics of mass transfer in terms of solids gain and water loss during osmotic dehydration using 30–50% (w/w) sucrose solution at 30, 40 and 50 °C. The experimental data were successfully fitted employing Peleg’s equation with the coefficient of determination (R ²) higher than 0.88, the root mean square error, and the mean relative percentage deviation modulus (E) of less than 0.003% and 6.40% for all treatments, respectively. In all cases, initial mass transfer rate parameter (K ₁) decreased significantly (p < 0.05) as the solution concentration and solution temperature increased suggesting a corresponding increase in the initial mass transfer rate. Initial mass transfer rate followed an Arrhenius relationship which showed that solids gain had the highest temperature sensitivity (E _a = 21.93–33.84 kJ mol⁻¹) during osmotic dehydration. Equilibrium mass transfer parameter (K ₂) decreased significantly (p < 0.05) as solution concentration increased demonstrating that the equilibrium solid and water contents increased with increase in solution concentration. The equilibrium solid and water contents were also estimated adequately using Peleg’s equation (R ² > 0.78). The results of this work allow estimating the kinetics of mass transfer during osmotic dehydration in order to obtain products with determined solid and water contents.     

In vitro and in situ antimicrobial action and mechanism of glycinin and its basic subunit

Glycinin, basic subunit and β-conglycinin were isolated from soybean protein isolate and tested for their antimicrobial action against pathogenic and spoilage bacteria as compared to penicillin. The three fractions exhibited antibacterial activities equivalent to or higher than penicillin in the next order; basic subunit>glycinin>β-conglycinin with MIC of 50, 100 and 1000 μg/mL, respectively. The IC(50%) values of the basic subunit, glycinin and β-conglycinin against Listeria\monocytogenes were 15, 16 and 695 μg/mL, against Bacillussubtilis were 17, 20, and 612 μg/mL, and against S. Enteritidis were 18, 21 and 526 μg/mL, respectively. Transmission electron microscopy images of L. monocytogenes and S. Enteritidis exhibited bigger sizes and separation of cell wall from cell membrane when treated with glycinin or basic subunit. Scanning electron microscopy of B. subtilis indicated signs of irregular wrinkled outer surface, fragmentation, adhesion and aggregation of damaged cells or cellular debris when treated with glycinin or the basic subunits but not with penicillin. All tested substances particularly the basic subunit showed increased concentration-dependent cell permeation assessed by crystal violet uptake. The antimicrobial action of glycinin and basic subunit was swifter than that of penicillin. The cell killing efficiency was in the following descending order; basic subunit>glycinin>penicillin>β-conglycinin and the susceptibility of the bacteria to the antimicrobial agents was in the next order: L. monocytogenes>B. Subtilis>S. Enteritidis. Adding glycinin and the basic subunit to pasteurized milk inoculated with the three bacteria; L. monocytogenes, B. Subtilis and S. Enteritidis (ca. 5 log CFU/mL) could inhibit their propagation after 16-20 days storage at 4 °C by 2.42-2.98, 4.25-4.77 and 2.57-3.01 log and by 3.22-3.78, 5.65-6.27 and 3.35-3.72 log CFU/mL, respectively.     

The Effect of Calcined Colemanite Addition on the Mechanical Strength of Magnetite Pellets Produced with Organic Binders

Iron ore pellets must have sufficient mechanical strengths against degradation in all stages of pellet production. Low strength is also a problem for product pellets since they abrade during transportation to the reduction furnaces. The use of a binder is necessary to provide sufficient strength to the pellets and for better operation and handling of pellets. Bentonite is the standard binder in the industry; however, it is considered an impurity due to its acid oxide contents. Organic binders have been tested for many years as alternative binder to bentonite. They have been found to give sufficient wet pellet properties. However, they failed to provide sufficient strength to the preheated and fired pellets due to lack of slag bonding. It has been assumed that one possible effective method to improve the preheated and fired pellet strengths is addition of a slag-bonding constituent. In this study, calcined colemanite was added to the pellet feed to overcome the lower strength problem encountered with organic binder use. The strength of pellets produced with organic binders and calcined colemanite alone and in combination was comparatively studied against the strength of pellets made with standard bentonite binder in magnetite concentrate pelletizing. The results showed that addition of calcined colemanite into the pellet mixture improved the preheated and fired pellet strengths of pellets produced with organic binders.     

Mechanical Performance of Ferritic Martensitic Steels for High Dose Applications in Advanced Nuclear Reactors

Ferritic/martensitic (F/M) steels are considered for core applications and pressure vessels in Generation IV reactors as well as first walls and blankets for fusion reactors. There are significant scientific data on testing and industrial experience in making this class of alloys worldwide. This experience makes F/M steels an attractive candidate. In this article, tensile behavior, fracture toughness and impact property, and creep behavior of the F/M steels under neutron irradiations to high doses with a focus on high Cr content (8 to 12) are reviewed. Tensile properties are very sensitive to irradiation temperature. Increase in yield and tensile strength (hardening) is accompanied with a loss of ductility and starts at very low doses under irradiation. The degradation of mechanical properties is most pronounced at <0.3T _M (T _M is melting temperature) and up to 10 dpa (displacement per atom). Ferritic/martensitic steels exhibit a high fracture toughness after irradiation at all temperatures even below 673 K (400 °C), except when tested at room temperature after irradiations below 673 K (400 °C), which shows a significant reduction in fracture toughness. Creep studies showed that for the range of expected stresses in a reactor environment, the stress exponent is expected to be approximately one and the steady state creep rate in the absence of swelling is usually better than austenitic stainless steels both in terms of the creep rate and the temperature sensitivity of creep. In short, F/M steels show excellent promise for high dose applications in nuclear reactors.     

Ag44(SR)30(4-): a silver-thiolate superatom complex

Intensely and broadly absorbing nanoparticles (IBANs) of silver protected by arylthiolates were recently synthesized and showed unique optical properties, yet question of their dispersity and their molecular formulas remained. Here IBANs are identified as a superatom complex with a molecular formula of Ag(44)(SR)(30)(4-) and an electron count of 18. This molecular character is shared by IBANs protected by 4-fluorothiophenol or 2-naphthalenethiol. The molecular formula and purity is determined by mass spectrometry and confirmed by sedimentation velocity-analytical ultracentrifugation. The data also give preliminary indications of a unique structure and environment for Ag(44)(SR)(30)(4-).     

EFFECT OF METHYL TERTIARY BUTYL ETHER (MTBE) AS A GASOLINE ADDITIVE ON ENGINE PERFORMANCE AND EXHAUST EMISSIONS

ABSTRACT

The effect of blending unleaded gasoline with different proportions of methyl-t-butyl ether MTBE (10, 15 and 20 vol % ) on engine performance was studied using a fixed compression ratio SI engine (Opel 4 -cylinder ). The exhaust gases were analyzed for carbon monoxide, carbon dioxide and the hydrocarbons emitted. The results have shown that MTBE blends gave slightly better engine performance than the unleaded gasoline as evidenced by the power output. Analysis of exhaust gases shows better carbon monoxide and hydrocarbon emissions for all MTBE blends tested than unleaded gasoline. A higher carbon dioxide exhaust emission of the blends than the unleaded gasoline also confirms their better combustion. The 20 vol % MTBE blend gave the lowest carbon monoxide and hydrocarbon emissions of all blends used. A comparison was also made between a     

THE EFFECT OF GASOLINE FUEL TYPE ON SI ENGINE NITROGEN-OXIDES AND CARBON MONOXIDE EMISSIONS UNDER PART-LOAD OPERATING CONDITIONS

ABSTRACT

Six different gasoline blends with different antiknock agents and aromatics content were investigated for its influence on SI engine nitrogen-oxides and carbon monoxide emissions at part- load operating conditions. The six fuel types used were leaded gasoline with 0·5 g Pb/1, commercial unleaded gasoline, unleaded synthetic gasoline and its blends with different proportions of methyl tertiary butyl ether MTBE l10, 15 and 20 vol%). A four- stroke, four- cylinder, spark- ignition Regata engine (type 138 B 3.000) was used for conducting this study. The exhaust gases were analyzed for nitrogen-oxides and carbon monoxide emitted at part-load operating conditions for the speed range of 1000 to 3000 rpm. The results of this investigation have shown that blending unleaded synthetic gasoline with ethers such as MTBE reduces the aromatic content of the fuel. The 20 vol% MTBE-fuel blend gave the lowest carbon monoxide emissions of all blends used at part load condition. On the other hand, the 10 vol% MTBE-fuel blend gave the lowest nitrogen-oxides emission of all blends at part-load condition. The carbon monoxide concentration in engine exhaust differs between increase and decrease at part-load condition when fuel aromatics content increases. It was also found that as the gasoline aromatics content increases in the blend, the nitrogen-oxides concentration in engine exhaust increases. So, substitution of MTBE for the higher aromatics gasoline blends may help improving state environment and air quality.     

7种云杉属树种花粉形态特征及其系统学的意义

通过扫描电镜观测了云杉属7个种的花粉形态,运用数据统计和图片分析的方法对花粉形态进行对比研究.结果显示:云杉属7个种的花粉大小变动范围为84.59～103.18 μm,均属于两气囊松科花粉;花粉体近极面与气囊过渡明显,形成帽沿;气囊表面纹理较平滑,在种间变异不显著.萌发沟位于花粉体远极面两气囊之间,呈现沟痕的形式.根据...     

Experimental research on heat transfer of water in tubes with conical ring inserts in transient regime

Forced convective of water in horizontal tubes with conical tube inserts has been studied experimentally. The transient flow regime has been used for the tests. Experimental results are validated with existing well established correlation. The turbulators were placed in two different arrangements: converging conical ring, referred to as CR array and diverging conical ring, DR array. Two correlations for the Nusselt number based on the experiment are introduced for practical use. It is found that the insertion of turbulators has enhanced the Nusselt number for the DR arrangement up to 521%, and for the CR arrangement up to 355%, although using the turbulators cause a significant increase in pressure drop.