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Stokes’ axisymmetrical translational motion of a slip sphere, located anywhere on the diameter of a virtual spherical fluid ‘cell’, is investigated. The fluid is micropolar and flows are parallel to the line connecting the two centres. An infinite-series solution is presented for the stream function, pressure field, vorticity, microrotation component, shear stress and couple stress of the flow. Basset-type slip boundary conditions on the sphere surface are used for velocity and microrotation. The Happel and Kuwabara boundary conditions are used on the fictitious surface of the cell model. Numerical results for the normalized drag force acting on the sphere are obtained with excellent convergence for various values of the volume fraction, the relative distance between the centre of the sphere and the virtual envelope, the vortex viscosity parameter and the slip coefficients of the sphere. In the special case when the spherical particle is in the concentric position with the cell surface, the numerical values of the normalized drag force agree with the available values in the literature.
A total of 3961 married couples from six major geographical areas representing the South Sinai governorates in Egypt were studied to assess the rate of consanguineous marriage. The population of six selected areas (St Catherines, Nuweiba, Abu Rudeis, Ras Sudr, El Tor and Abu Zenima) were subdivided into Bedouin, urban and mixed populations. A questionnaire-based interview was conducted showing that the consanguinity rate in this region is 37.5%, with the highest rate recorded in Abu Rudeis (52.3%) and lowest rate in Nuweiba (24.1%). Consanguinity was significantly higher among the Bedouin population compared with the urban population in Abu Rudeis, Ras Sudr, El Tor and Abu Zenima, while in St Catherines and Nuweiba there was no statistically significant difference. Among consanguineous couples, 5%, 60% and 35% were double first cousins, first cousins and second cousins respectively. The mean inbreeding coefficient α of the studied population was 0.01845.
Metal induced lateral crystallization (MILC) of hydrogenated amorphous silicon (a-Si:H) was studied and a model was developed based on the resistance measurement of the films. Hydrogenated amorphous silicon films of 300 nm thickness were deposited using plasma enhanced chemical vapor deposition (PECVD) on oxidized p-type (100) silicon wafers. Thermally evaporated 200 nm thick aluminum layer was deposited over amorphous silicon and patterned using photolithography. The samples were annealed at different temperatures for different time periods. After annealing the resistance of amorphous silicon between aluminum pads was measured. Based on these measurements, a model was developed to predict the lateral crystallization velocity. In this model, the resistance change due to loss of hydrogen from the film was also taken into account. For this purpose, another set of experiments was conducted. In this set, hydrogenated amorphous silicon films of 300 nm thickness were deposited on Corning 7059 glass. The samples were annealed for different period of time at different temperatures. After annealing, parallel bars of silver paint were formed on the samples and the resistance of each sample was measured. The theoretically determined lateral crystallization velocity was verified using optical microscope observations and X-ray diffraction analysis and was found to be in close agreement.
Property models have been developed for the major properties that need to be controlled in the production of borosilicate glasses for West Valley high-level nuclear waste immobilization. The chemical durability is the most important parameter for product performance, while melt viscosity is the most critical parameter in assuring the processability of the glass. Simple models for these properties are described that are based on data from numerous glasses which were prepared with compositions in the region around the West Valley reference glass. A scheme for optimization of the target glass and for predicting the acceptability of glasses resulting from natural process variations is illustrated. This involves integration of the product models with a process model that was described previously. This approach has guided the present placement of the West Valley reference glass.
Studies of the corrosion process of silicate and boro-silicate glasses under a broad range of contact times, surface-to-volume ratios and leachant compositions indicate that dissolution of such glasses in aqueous media can be interpreted in terms of activity of dissolving amorphous silica. This activity is modified by the presence of elements such as Al, Mg and Fe. The effects of these elements, when initially present in the glass or in the leachant, and, in general, the effects of glass composition on the course of the corrosion process can be viewed in terms of the formation of a surface layer on the leached glass. The type, composition and structure of this layer, which are determined by glass composition, control the dissolution behavior of the glass.
Determining the electronic and structural properties of semiconductor clusters is one of the outstanding problems in materials science. The existence of numerous structures with nearly identical energies makes it very difficult to determine a realistic ground state structure. Moreover, even if an effective procedure can be devised to predict the ground state structure, questions can arise about the relevancy of the structure at finite temperatures. Kinetic effects and non-equilibrium structures may dominate the structural configurations present in clusters created under laboratory conditions. We illustrate theoretical techniques for predicting the structure and electronic properties of small germanium clusters. Spefically, we illustate that the detailed agreement between theoretical and experimental features can be exploited to identify the relevant isomers present under experimental conditions.
We describe an outbreak of skin lesions due to Mycobacterium chelonae subsp. abscessus associated with injections of lidocaine (lignocaine) given by a ‘bioenergetic’ (a practitioner of alternative medicine) in Colombia. The lidocaine carpules and the lesions of the patients yielded mycobacteria with identical biochemical characteristics.
Using the methodology of Sartwell and a case control design we examined the incubation period and assessed risk factors. Of 667 potentially exposed individuals, a total of 298 patients were interviewed, of whom 232 had skin lesions. The median incubation period was 30·5 days (range 15–59 days). Male sex (OR 2·85, 95% CI 1·26–6·51), increasing age (OR 1·25, 95% CI 1·03–1·53), subcutaneous injection route (OR 3·72, 95% CI 1·09–12·7) and number of injections (OR 1·01, 95% CI 1·00–1·03) were risk factors for disease.
To our knowledge, this is the largest reported outbreak of M. chelonae infection, the first in which the organism has been isolated from the putative vehicle of infection, and the first in which the incubation period could be determined.
A binary Sn-5wt.%Sb solder alloy was chosen as a potential alternative to
Sn-Pb solder alloy to be subjected to many studies. It was casted from the
liquid state, cold drawn into wires of 1 mm diameters. The study includes
the structure, electrical resistivity, tensile strength, hardness and
indentation creep behavior using XRD, four probes electrical circuit,
conventional tensile testing machine, Vickers microhardness tester,
respectively. These properties were carried out for the cold worked alloy
and after annealing at 393 and 473 K for 60 min. It was found that annealed
samples exhibit more precipitations of the intermetallic compounds SnSb,
higher lattice parameters and higher crystallite size, while have lower
lattice-strain induced due to the cold working process. These structural
changes greatly affect the electrical resistivity and mechanical properties
of this alloy.
Protein malnutrition can adversely affect all tissues. The aim of the present study was to test the hypothesis that protein deprivation influences gastric ulcer formation, as well as metabolism and organ growth, in rats. In the present study, there was a significant reduction in the body and organ weight of rats fed a low-protein diet (P<0·001). Malnourished rats were less susceptible to ulceration of the gastric mucosa in ethanol and indomethacin models of acute gastric ulcers when compared with rats fed a normoproteic diet (17 % protein). Mucus production and prostaglandin E2 formation increased in malnourished rats, possibly explaining the lower number of acute ulcers in these animals. Pylorus ligature altered gastric juice composition (increased pH and gastric volume, and decreased total acid concentration) in the animal group fed a low-protein diet compared with the group fed a diet containing 17 % protein (P<0·05). The gastric mucosa was more damaged in malnourished rats than in normal rats evaluated for 14 d after acetic acid injection (P<0·001). Malnourished rats exhibited resistance to acute gastric lesions, owing to an increase in prostaglandin GE2 release and mucus secretion, which protected their gastric mucosa. This phenomenon was not seen in subchronic gastric ulceration.
The evolution toward equilibrium of the supersaturated Pb-1.5%Cd-0.15%Ag-1.25%Sn
alloy has been studied by various techniques, such as hardness, optical microscopy,
scanning electron microscopy and electron microprobe. The explored temperatures are
20 and 80°C. The precipitation hardening mechanisms of this alloy are similar
to those of silver-free alloys. The as-quenched structure transforms toward equilibrium
in a two stage process. In the first stage, called ageing, two transformations take place
at the same time: a continuous hardening precipitation and a discontinuous, incomplete,
softening transformation. The second stage is characterized by a discontinuous lamellar
reprecipitation. The microstructure of this alloy is characterized by the presence
of Ag5Cd8 precipitates and of zones corresponding to the eutectic mixture.
The main effect of silver is to increase hardness by about 2 HV.
Precipitation hardening in lead-cadmium-calcium alloys is a two stage process:
the first stage is a discontinuous hardening transformation without precipitation,
the second stage is a discontinuous lamellar precipitation of Pb3Ca. In order to
increase the mechanical and electrochemical properties of these alloys, we have studied
the influence of minor additions of tin on the precipitation hardening behaviour
of PbCaCd alloys, as this element is used to improve the electrochemical properties
of positive battery grids. The objective was to investigate in a systematic manner
the ageing and overageing behaviour of PbCdCaSn alloys in the case of two different
structural states: as-cast condition, rehomogenized state.
Despite an impressive amount of effort and extensive research, our knowledge of parturition remains scant. Although numerous scientists have investigated “the timing of birth”, we still have a limited understanding of the biological mechanisms that control events initiating delivery, or the availability of methods supposed to prevent these mechanisms from acting inappropriately. A multitude of factors and structures are involved; the myometrium, cervix, placenta and the fetus must act in concert to assure successful delivery. We do know that achievement of a “perfect” contractile force is not the sole factor. Successful delivery is also impacted by subtle differences in pelvic shape or size.
It is known that age-hardening in lead-calcium alloys proceeds in two stages. The first
corresponds to two concomitant hardening transformations of discontinuous type and without
precipitation. The second, is a lamellar reaction of precipitation of Pb3Ca. The ageing of
lead-cadmium alloys is characterized by a continuous precipitation and a discontinuous
transformation. The hardening process is followed by an overaging which consists of a
discontinuous transformation with a reprecipitation of the Cd from the fine hardening
precipitates of the same phases. With an aim of improving the mechanical and electrochemical
properties of Pb-Ca alloys, we undertook a study of the influence of minor additions of
cadmium on the age-hardening of these alloys. Two structural states were considered:
as-cast condition, rehomogenized condition.
Studies of the reactions between rare earth salts and phosphoric acid in aqueous or ethanolic media have shown that in both cases stable gels can be formed. Upon drying, gels prepared in aqueous environments yield macrocrystalline REPO4 products similar to those produced by conventional precipitation and drying. Gels prepared in ethanol, on the other hand, undergo dehydration to form dense microcrystalline products. This observation is based on optical and scanning electron microscopy, as well as on x-ray diffraction studies and infrared spectroscopy. These techniques, as well as differential thermal analysis, indicate that crystal growth of these products takes place around 600−700 °C. The composition of the dehydrated gels produced in both the aqueous and ethanolic systems corresponds to an orthophosphate structure. Other characteristics of the microcrystalline REPO4 products include high resistance to attack by water, absence of coloration upon exposure to gamma rays, and a high index of refraction.
After an initial attempt to close arterial ducts by the transcatheter insertion of an umbrella device had left significant residual patency, further attempts at closure were made in 14 patients by the insertion of an additional umbrella device. The ages of the patients ranged from four to 11 years. Overall, 17 attempts were made to insert additional devices at intervals of between six to 26 months after the insertion of the first umbrella. Successful insertion of a device was achieved in two patients only at a third attempt. One patient required the insertion of a third umbrella to achieve complete occlusion of the patent duct. Complete closure of the residual patency was achieved in 13 of the 14 patients. The remaining patient has been scheduled for insertion of a third umbrella.
Onchocerca raillieti is the only Onchocerca species infecting Sudanese donkeys; it occurs only in the ligamentum nuchae, especially in the lamellar part of the ligament. The morphological features of both uterine and skin microfilariae were determined. Skin microrilariae are shorter than uterine ones and tend to accumulate in the regions of Linea alba and withers of infected donkeys. The possible identity of the vector of this worm in the Sudan is discussed.
Seventy-three male alcoholics permitted information to be obtained from official sources about time recorded as lost from work in receipt of sickness or unemployment benefits and about their weekly state insurance contributions. The average yearly time loss was 121.7 working days per person, comprising an average yearly loss through sickness of 86.1 and through unemployment of 35.6 working days respectively. By contrast the recorded national sickness loss for men in a comparable twelve months period averaged 15.9 working days per person.
Thirteen alcoholics showed over five years, prolonged deficiency in work attendance. State benefits to the subjects, over twelve months during the early 1970s, totalled £18,434.80. Diagnoses on their medical certificates underestimated incapacity from alcoholism.
Speaking of comparative urbanization, Gideon Sjoberg noted that the Near East, the region in which cities first rose, has been understudied by urban sociologists. Few research projects have been realized on contemporary urbanization in the Arab World. This paper purports to examine recent trends of urbanization in the region; and their inter-relationship with the ‘modernization’ process.
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