In vitro effects of urease inhibitors on rate of urea hydrolysis in soils

We studied the effect of urease inhibitors on the urea hydrolysis in some Sundanese soils belonging to the orders of Vertisol and Entisol. The hydrolysis showed a lag period of about 3 days and its rate (Y) per unit time (t) could be described by a two constants exponential equation of the general form Y = K₁t^K ₂. Statistical analysis showed that the intercept K₁ (rate of urea hydrolysis) was significantly affected by soil type rather than treatment. It seems that K₁ is associated with the soils' initial urease activity as it closely correlates with the Michaelis constant (km).The gradient, K₂, being significantly affected by soil type as well as treatment is probably associated with the induced urease activity with time and it, therefore, varied with variations in soils and treatments. Of the so-called urease inhibitors used in this study Ca(OH)₂, p-benzoquinone (PBQ) and orthophosphoric acid (OP) only PBQ reduced urea hydrolysis while the other chemicals have effects possibly related to modifying the soil pH. Inhibitor treated soils had substantial amounts of unacounted for N which was believed to be present, presumably, in the form of carbamate.Contribution from the Department of Biochemistry and Soil Science, Faculty of Agriculture, Shambat, Sudan.     

Experimental analysis of behavior and damage of sandwich composite materials in three-point bending. Part 2. Fatigue test results and damage mechanisms

The analysis of stiffness degradation and the identification of damage mechanisms during and after fatigue tests of sandwich panels with PVC foam cores have been performed. The sandwich panels with cross-ply laminates skins made of glass fiber and epoxy resin were manufactured by vacuum moulding and subjected to three-point bending tests. Two PVC cores of similar type but with differing densities were investigated. The effect of core density and thickness on the damage behavior was highlighted. Using the cyclic life criterion, fatigue curves were plotted according to two models and compared with those of the literature. It has been demonstrated that the sandwich SD 2, with the higher core density, withstands a higher load and possesses greater rigidity in static tests, combined with an enhanced fatigue resistance, when compared to sandwich SD 1 which has a lower core density. Translated from Problemy Prochnosti, No. 3, pp. 32–44, May–June, 2009.     

New separation method of metal/plastic micronized particles using travelling wave conveyors

The paper reports an experimental investigation for studying the movement dynamics and the separation of micronized particles on a poly-phase travelling wave conveyor (TWC). A digital balance and a sensitive electrometer controlled by Labview software were used to analyse the velocity and the material flow rate on a three-phase conveyor with respect to the variation of both the amplitude and the frequency of the applied voltage. It was found that about 80% of the particles mass move together in one single wave and that the electric charge gained by the particles increases with the intensity of the electric field. Moreover, preliminary experiments showed that it is possible to separate a granular mixture of plastic and copper micronized particles using a TWC. Successful experiments were carried out on micronized samples of both electric cable and electronic card wastes. High purity metal was recovered.     

Fault isolation in manufacturing systems based on learning algorithm and fuzzy rule selection

Neural Computing and Applications - This paper addresses the fault detection and isolation problem in manufacturing systems. Some of these systems can be affected by several faults, a first way of...     

Ferroelectric solid solution Li1 − xTa1 − xWxO3 as potential photocatalysts in microbial fuel cells: Effect of the W content

Microbial fuel cells (MFCs) are bio-electrochemical systems that can directly convert the chemical energy contained in an effluent into bioelectricity by the action of microorganisms. The performance of these devices is heavily impacted by the choice of the material that forms the cathode. This work focuses on the assessment of ferroelectric and photocatalytic materials as a new class of non-precious catalysts for MFC cathode construction. A series of cathodes based on mixed oxide solid solution of LiTaO₃ with WO₃ formulated as Li_1-xTa_1-xW_xO₃ (x=0, 0.10, 0.20 and 0.25), were prepared and investigated in MFCs. The catalyst phases were synthesized, identified and characterized by DRX, PSD, MET and UV-Vis absorption spectroscopy. The cathodes were tested as photoelectrocatalysts in the presence and in the absence of visible light in devices fed with industrial wastewater. The results revealed that the catalytic activity of the cathodes strongly depends on the ratio of substitution of W⁶⁺ in the LiTaO₃ matrix. The maximum power densities generated by the MFC working with this series of cathodes increased from 60.45 mW·m^-3 for x=0.00 (LiTaO₃) to 107.2 mW·m^-3 for x=0.10, showing that insertion of W⁶⁺ in the tantalate matrix can improve the photocatalytic activity of this material. Moreover, MFCs operating under optimal conditions were capable of reducing the load of chemical oxygen demand by 79% (COD_initial=1030 mg·L^-1).     

Crosslinking of Sericin on air atmospheric plasma treated polyester fabric

Durable and highly hydrophilic polyester fabric was produced by cross-linking Sericin on air-atmospheric plasma treated polyester fabric. Surface change properties were characterized by wettability measurements (water contact angle-WCA and % capillarity), Atomic Force Microscopy and zeta potential measurements. Chemical analyses using TBO dye were carried out to estimate surface functional groups after plasma treatment and Sericin cross-linking. Positive zeta potential values at low pH values, as well as AFM images confirm grafting of Sericin. With Sericin cross-linked onto both cleaned PET and plasma-treated PET, WCA reached that of PET subjected to plasma treatment alone, that is WCA between 40° and 46° compared to 81° for the hydrophobic untreated polyester fabric. However, plasma-treated polyester is readily subjected to aging, while cross-linked Sericin on plasma-treated PET yields a more durable hydrophilic finish with a high capillarity, 85% compared to 39% for Sericin on the untreated PET, and 3% for the untreated PET fabric. Plasma treatment creates chain-scissions at the polymer surface leading to the appearance of polar groups which promote the cross-linking of greater amount of Sericin.     

An analytical method for temperature-dependent free vibration analysis of functionally graded beams with general boundary conditions

Exact solutions are presented to study the free vibration of a beam made of symmetric functionally graded materials. The formulation used is based on a unified higher order shear deformation theory. Material properties are taken to be temperature-dependent, and vary continuously through the thickness according to a power law distribution (P-FGM), or an exponential law distribution (E-FGM) or a sigmoid law distribution (S-FGM). The beam is assumed to be initially stressed by a temperature rise through the thickness. Temperature field is considered constant in xy plane of the beam. Hamilton’s principle is used to derive the governing equations of motion. Free vibration frequencies are obtained by solving analytically a system of ordinary differential equations, for different boundary conditions.