The mechanical response of Al–Si–Mg/SiCp composite: influence of porosity

The effect of porosity on the mechanical and fracture behaviour in Al–Si matrix alloy and composites reinforced with SiC particles of 10 and 20 vol.% in the as-cast state and after extrusion process has been studied. Matrix alloy and composites were fabricated by compocasting and extrusion. Samples were characterized by optical microscopy, image analyzer, scanning electron microscopy and tensile tests. The results demonstrate that hot extrusion considerably reduces the porosity, while size and distribution of the reinforcement particles are also affected. In the point of fracture behaviour, the existence of large porosity is more effective.     

Hard iron boride (Fe2B) on 99.97 wt% pure iron

Some properties such as hardness and fracture toughness of boride formed on the 99.97 wt% pure iron were investigated. Boronizing was carried out in a solid medium, consisting of Ekabor powders of 5% B₄C as donor, 5% KBF₄ as an activator and 90% SiC as diluent at 800 °C for 2, 4 and 8 h. The dominant phase formed on the substrate was found to be Fe₂B that had a finger-like shape morphology. The hardness of boride on the 99.97% pure iron was over 1700HVN, while the hardness of pure iron was about 130HVN. It was found that the fracture toughness of boride formed on surfaces of 99.97% pure iron, depending on the process time, ranged from 3.59 to 3.83 MPa m^1/2. Depending on process time and temperature, the depth of the boride layer ranges from 22 to 43 μm, leading to a diffusion-controlled process.     

Effect of electroless etching parameters on the growth and reflection properties of silicon nanowires

Vertically aligned silicon nanowire (Si NW) arrays have been fabricated over large areas using an electroless etching (EE) method, which involves etching of silicon wafers in a silver nitrate and hydrofluoric acid based solution. A detailed parametric study determining the relationship between nanowire morphology and time, temperature, solution concentration and starting wafer characteristics (doping type, resistivity, crystallographic orientation) is presented. The as-fabricated Si NW arrays were analyzed by field emission scanning electron microscope (FE-SEM) and a linear dependency of nanowire length to both temperature and time was obtained and the change in the growth rate of Si NWs at increased etching durations was shown. Furthermore, the effects of EE parameters on the optical reflectivity of the Si NWs were investigated in this study. Reflectivity measurements show that the 42.8% reflectivity of the starting silicon wafer drops to 1.3%, recorded for 10 μm long Si NW arrays. The remarkable decrease in optical reflectivity indicates that Si NWs have a great potential to be utilized in radial or coaxial p-n heterojunction solar cells that could provide orthogonal photon absorption and enhanced carrier collection.     

The Residual Stress Relaxation Behavior of Weldments During Cyclic Loading

Accurate measurement of residual stress is necessary to obtain reliable predictions of fatigue lifetime and enable estimation of time-to-facture for any given stress level. In this article, relaxation of welding residual stresses as a function of cyclic loading was documented on three common steels: AISI 1008, ASTM A572, and AISI 4142. Welded specimens were subjected to cyclic bending (R = 0.1) at different applied stresses, and the residual stress relaxation existing near the welds was measured as a function of cycles. The steels exhibited very different stress relaxation behaviors during cyclic loadings, which can be related to the differences in the microstructures of the specimens. A phenomenological model, which treats dislocation motion during cyclic loading as being analogous to creep of dislocations, is proposed for estimation of the residual stress relaxation.     

Normal liver, spleen, and kidney dimensions in neonates, infants, and children: evaluation with sonography

OBJECTIVE: The objective of this study was to determine the normal range of dimensions for the liver, spleen, and kidney in healthy neonates, infants, and children. SUBJECTS AND METHODS: This prospective study involved 307 pediatric subjects (169 girls and 138 boys) with normal physical or sonographic findings who were examined because of problems unrelated to the measured organs. The subjects were 5 days to 16 years old. All measured organs were sonographically normal. At least two dimensions were obtained for each liver, spleen, and kidney. Relationships of the dimensions of these organs with sex, age, body weight, height, and body surface area were investigated. Suggested limits of normal dimensions were defined. RESULTS: Dimensions of the measured organs were not statistically different in boys and girls. Longitudinal dimensions of all three organs showed the best correlation with age, body weight, height, and body surface area. Height showed the strongest correlation of all. This correlation was a polynomial correlation. CONCLUSION: Determination of pathologic changes in size of the liver, spleen, and kidney necessitates knowing the normal range of dimensions for these organs in healthy neonates, infants, and children. Presented data are applicable in daily routine sonography. Body height should be considered the best criteria to correlate with longitudinal dimensions of these organs.     

Prevalence of occupational asthma among automobile and furniture painters in the center of Eskisehir (Turkey): the effects of atopy and smoking habits on occupational asthma

BACKGROUND: Occupational asthma (OA) is a respiratory disorder characterized by airway hyperreactivity caused by agents present in the workplace. For determination of the prevalence of OA among car and furniture painters exposed to isocyanate in the center of Eskisehir, Turkey, a clinical and epidemiologic prospective study in three phases was done, incorporating 312 (89.4%) of the painters. METHODS: Of these subjects, 190 (61%) were furniture painters and 122 (39%) automobile painters. In the first phase of the study, a modified questionnaire and pulmonary function test (PFT) were done. During the second phase, peak expiratory flow rate (PEFR) was monitored in 52 subjects whose complaints were confirmed and who agreed to a month of such monitoring. In the third phase, nonspecific bronchial provocation tests (NSBPT) with histamine were done on 23 of the PEFR-monitored workers. RESULTS: Finally, through questionnaire, typical history, PFT, PEFR monitoring, and NSBPT, 30 workers (9.6%) were diagnosed as having OA. Smoking habits and atopy in the OA-diagnosed workers were found to be statistically significantly high in comparison to the other workers. CONCLUSIONS: It was concluded that OA is a common disorder among automobile and furniture painters, and smoking habits and atopy were seen to have a significant effect on OA occurrence.     

A case of split notochord syndrome: presence of dorsal enteric diverticulum adjacent to the dorsal enteric fistula

Like umblical enteric remnants (eg, umblical sinus and omphalomesenteric fistula), enteric remnants can be seen on the dorsal aspect of the body (dorsal enteric sinus, dorsal enteric fistula IDEF], dorsal enteric diverticulum) in conjunction with complete cleft of the vertebral column. Complete cleft of the vertebral column associated with gastrointestinal tract and central nervous system anomalies is known as "split notochord syndrome" (SNS). The authors present an unreported variant of SNS having dorsal enteric diverticulum adjacent to the DEF. The patient died 17 days after surgical repair.     

A new approach for measuring RMS value and phase angle of fundamental harmonic based on Wavelet Packet Transform

Traditional ways of calculating/measuring harmonics in power systems have been based on Fourier Transform and algorithms, such as Fast Fourier Transform and Goertzel that implements it. In this study, a novel approach based on Wavelet Packet Transform is presented to measure Root-Mean-Square (RMS) value and phase angle of the fundamental harmonic. To this end, analytical expressions were derived and using a Graphical User Interface (GUI) designed and experimental works the validity of analytical expressions was demonstrated.     

Microarchitectures for Managing Chip Revenues under Process Variations

As transistor feature sizes continue to shrink intothe sub-90nm range and beyond, the effects of process variationson critical path delay and chip yields have amplified. A commonconcept to remedy the effects of variation is speed-binning, bywhich chips from a single batch are rated by a discrete range offrequencies and sold at different prices. In this paper, we discussstrategies to modify the number of chips in different bins andhence enhance the profits obtained from them. Particularly, wepropose a scheme that introduces a small Substitute Cacheassociated with each cache way to replicate the data elementsthat will be stored in the high latency lines. Assuming a fixedpricing model, this method increases the revenue by as much as13.8% without any impact on the performance of the chips.     

Effect of SC-41930, a potent selective leukotriene B4 receptor antagonist, in the guinea pig model of middle ear inflammation

Arachidonic acid metabolites such as prostaglandins and leukotrienes have been shown to play an important role in the pathogenesis of otitis media (OM). Among these mediators, leukotriene B4 (LTB4) is one of the most potent inducers of inflammatory processes. SC-41930 has been shown to be a specific LTB4 receptor antagonist both in vitro and in vivo. In this study, anti-inflammatory effects of SC-41930 were investigated in a guinea pig model of OM induced by middle ear (ME) inoculation of killed Staphylococcus aureus. Outcome of treatment was determined by measurement of myeloperoxidase activity in the samples of ME mucosa, evaluation of temporal bone histopathology, and presence of ME fluids. Myeloperoxidase activity in the SC-41930-treated group was found to be significantly lower than that in the control group. Histopathology of temporal bones indicated decreased inflammation in the treated group as compared to the controls. In addition, ME fluids were absent in four out of six treated animals. These results demonstrate that SC-41930 can produce significant anti-inflammatory effects in this model of OM.