Physicochemical properties of fermented Arabian mares' milk

Due to its numerous benefits, including health-promoting characteristics, there is increasing interest in finding product applications for mares' milk. In the present study, the physicochemical properties, turbidity and conductivity of Arabian mares' milk were studied during acidification by fermentation at 30 °C and compared with those of bovine milk. The data for the acidification rate were modelled using a logistic equation. Mares' milk showed a longer latency phase (284 min) and lower acidification rate (μ_max = 0.0052 dpH min^?1) compared with bovine milk (194 min and 0.0098 dpH min^?1 respectively). The general shape of the curves of the turbidity versus time and pH were similar in nature for the acidification of both milks. However, the characteristic points were different, due to the differences in casein micelle composition. Measurement of electrical conductivity during acidification showed that maximum demineralization of casein micelles started around pH 6.09 and 5.31, for mares' and bovine milk, respectively. In conclusion, the technological characteristics of mares' milk were very different from those of bovine milk, due to intrinsic physicochemical properties of both milks.     

Fretting wear characteristics of cold gas-dynamic sprayed aluminum alloys

Process selection for repair of mechanical components due to wear and corrosion, e.g. damage of aluminum casting housings of fuel injection systems, is based on cost and response time factors, provided that the mechanical performance is maintained within acceptable limits. One of the promising and emerging repair technologies is Cold Gas-Dynamic Spray (CGDS) coating, where a high-pressure gas propels fine powder particles to very high velocities to produce surface coating. It is essential to identify the optimum process conditions and powder composition to produce repaired surfaces with tribological properties close to those of the originally manufactured part (without coating). The objective of this work is to compare the dynamic friction and fretting wear properties of the repaired surfaces using various types of coating composition and spraying techniques. Eight types of CGDS coatings, applied to AMS 4260 aluminum specimens, were fretted against 440C stainless steel specimens at low and high nominal loads to assess their fretting wear resistance, dynamic friction properties and damping capacity. The optimum coating composition and process conditions were identified. In comparison to the uncoated specimen, this optimum coating offered tribological characteristics close to the uncoated material and even better dynamic friction properties.     

FLOW OF A NON-NEWTONIAN FLUID WITH HEAT TRANSFER ABOVE A ROTATING DISK CONSIDERING THE ION SLIP

The steady flow and heat transfer of a conducting non-Newtonian fluid due to the rotation of an infinite nonconducting disk in the presence of an axial uniform steady magnetic field are studied considering the ion slip. The governing nonlinear equations are solved numerically using finite differences, and the solution shows that the ion slip and the non-Newtonian fluid characteristics give some interesting results.     

A recursive method for the dynamic analysis of mechanical systems in spatial motion

Summary. In the present study, a recursive method for generating the equations of motion of mechanical systems that undergo spatial motion is presented. The method uses the force and moment equations to generate the rigid body equations of motion in terms of the Cartesian coordinates of a dynamically equivalent constrained system of particles, without introducing any rotational coordinates and the corresponding rotation matrices. For the open loop case, the equations of motion are generated recursively along the serial chains. Closed loop systems are transformed to open loop systems by cutting suitable kinematic joints and introducing cut-joint constraints. The method is simple and suitable for computer implementation. An example is chosen to demonstrate the generality and simplicity of the developed formulation.     

A synthetic strategy to a new class of cycloalkane ring-fused pyridine nucleosides as potential anti HIV agents

Condensation of cyanothioacetamide or cyanoacetamide with sodium salts of 2-formyl-1-cycloalkanones afforded the corresponding cycloalkane ring fused pyridine-2(1H)-thiones and -2-pyridones. The latter compounds served as a key intermediates for the synthesis of a new class of cycloalkane ring fused pyridine glycosides.     

Fatty acid composition of an oral load affects chylomicron size in human subjects

This paper outlines the demographic characteristics of the Baiga tribe, one of the most primitive of the aboriginal tribal groups of Central India. The Baiga population has grown steadily since the first anthropological study of the tribe in the 1930s. Age at menarche, age at marriage, breast-feeding, and time interval between marriage and first conception are natural. There are more females than males. Sub-tribe endogamy is common; consanguineous marriage is favoured (34% of marriages are between first cousins) and marital distance is low (mean 7.1 km). Though the mean menarcheal age is high (15.2 years), mean age at first marriage is low (16.6 years), giving a long reproductive period.     

Experiments on laminar flow and heat transfer in an elliptical duct

Experiments were performed to study the laminar developing and fully developed flow and heat transfer inside an elliptical duct having an aspect ratio of 0.5. The working fluid was air and two thermal situations were investigated, the first with the duct at a uniform temperature and the second when the wall temperature distribution is linear in the axial direction and does not vary transversely. The hydrodynamic results are presented in the form of a sequence of velocity profiles on the major and minor axes, measured at axial locations extending from the duct entrance to the fully developed regime. The axial drop in the static pressure due to the combined effect of the flow development and wall friction is also reported. The extended length necessary for static pressure development, expressed as x/Re D_h, was found to be 0.0345. The thermal information depicts the temperature development in the duct entrance by a series of temperature profiles on the major and minor axes. The thermal results encompass as well the Nusselt number and the thermal entrance length in each of the above two thermal situations. To the author's knowledge, theoretical solutions for the hydrodynamic flow development in the entrance of elliptical ducts do not exist. The present experimental fully developed dimensionless velocity and friction factor were compared to the analytic value of L. N. Toa [On some laminar-forced-convection problems, ASME J. Heat Trans. 83, 466–472 (1961)]. The percentage difference in the friction factor is 0.78%. The thermal development of the flow in the elliptical duct was studied analytically by N. T. Dunwoody [Thermal results for forced heat convection through elliptical ducts, J. appl. Meal. 29, 165–170 (1962)] and V. Javeri [Analysis of laminar thermal entrance region of elliptical and rectangular channels with the Kantorowich method, Wärme Stoffubert. 9, 85–98 (1976)] for the uniform and linear wall temperature ducts respectively. Both analyses assume either uniform or fully developed velocity profiles in the developing regime.     

Wear mechanisms of WC coated and uncoated tools in finish turning of Inconel 718

This paper presents the results of an experimental investigation on the wear mechanisms of uncoated tungsten carbide (WC) and coated tools (single-layer (TiAlN) PVD, and triple-layer (TiCN/Al₂O₃/TiN) CVD) in oblique finish turning of Inconel 718. Tool wear rate and wear mechanisms were evaluated for cutting speeds, 50<V<100 m/min, and feed rates, 0.075<f<0.125 mm/rev, at a constant depth of cut of 0.25 mm. It was concluded that abrasive and adhesive wear were the most dominant wear mechanisms, controlling the deterioration and final failure of the WC tools. While the triple layer CVD coated tools exhibited the highest wear resistance at high cutting speeds and low feeds, uncoated tools outperformed the single and multi-layer coated tools in the low range of cutting speeds and intermediate feeds. The cutting tool with single-layer PVD coating outperformed the other tools at the medium cutting speed.