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.     

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.     

Wear behaviour of thermal flame sprayed FeCr coatings on plain carbon steel substrate

The principle aim of this study is to investigate the wear behaviour of FeCr coatings on Ni-based bond deposited plain carbon steel substrate for several applications in power generation plants. For this purpose, FeCr and Ni-based powders were sprayed on plain carbon steel substrates using a thermal flame spray technique. Fabricated layers were characterized by using a X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), microhardness and surface roughness testers. FeCr coatings were subjected to sliding wear against AISI 303 stainless steel counter bodies under dry and acidic environments. A pin-on-plate type of apparatus was used with normal loads of 49 and 101 N and sliding speed of 1 Hz. XRD results revealed that FeCr, Fe, Cr, Fe–Cr–Ni, γ-Fe₂O₃ and Fe₃O₄ phases are exist in the coating. In addition, some inhomogenities such as oxides, porosity, cracks, unmelted particles and inclusions were observed by SEM. The surface morphologies of FeCr samples after wear experiments were examined by SEM and EDS. It was found that friction coefficients of the coatings in dry condition are higher than that in acidic environment.     

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.     

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.     

The dominant chloride channel mutant G200R causing fluctuating myotonia: clinical findings, electrophysiology, and channel pathology

Clinical, electrophysiological, and molecular findings are reported for a family with dominant myotonia congenita in which all affected members have experienced long-term fluctuations of the symptom of myotonia. In some patients myotonia is combined with myalgia. The myotonia-causing mutation in this family is in the gene encoding the muscular chloride channel, hCIC-1, predicting the amino acid exchange G200R. We have constructed recombinant DNA vectors for expression of the mutant protein in tsA201 cells and investigation of the properties of the mutant channel. The most prominent alteration was a +100-mV shift of the midpoint of the activation curve. Therefore, within the physiological range the open probability of the mutant channel is markedly smaller than in wild-type. This shift is likely to be responsible for the myotonia in the patients. The fluctuating symptoms of this chloride channelopathy are discussed with respect to short-term fluctuations of myotonia in the sodium channelopathy of potassium-aggravated myotonia.     

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.     

Cataract extraction comparative study of ocular Beh?et's disease and idiopathic uveitis

A retrospective clinical trial was performed to review the management and discuss the outcome of cataract extraction in eyes with complicated cataract due to ocular Beh?et's disease (BD) (n = 55) and idiopathic uveitis (IU) (n = 43). The aim was to find the best method of treatment in each pathology. The surgical methods were intracapsular cataract extraction (ICCE), extracapsular cataract extraction (ECCE), ECCE + intraocular lens (ECCE + IOL), and ECCE + trabeculectomy (ECCE + T). The postoperative visual prognosis was found to be significantly worse in eyes with ocular BD, than in those with IU because of the severe posterior segment complications of ocular BD, particularly optic atrophy (p < 0.05). When the outcome was evaluated with regard to the individual surgical techniques, the prognosis was found to be significantly better in eyes with IU undergoing ECCE than in those with BD undergoing the same operation (p < 0.05). No significant differences were observed between the groups with regard to the other surgical treatment modalities (p < 0.05).     

A Practical Space-Code Correlator Receiver for DSP Based Software Radio Implementation in CDMA2000

Development of practical algorithms for beamforming in 3G CDMA systems and their software radio implementations are still a challenging task, which will facilitate upgrading of traditional base stations into smart antenna capable 3G base stations. In this paper, we propose a practical space-code correlator (SCC) receiver structure for its software radio implementation a DSP. SCC’s advantage comes from the fact that it doesn’t require any training sequence or learning parameter as in other algorithms (LMS or CM). DSP implementations of the SCC are performed using Texas Instruments C67xx family platforms. In the simulations, reverse link base band signal format of CDMA2000 is used and the effects of different array topologies (uniform linear array-ULA or uniform circular array-UCA) are considered. The implementation results regarding beamforming accuracy, weight vector computation time (execution time), search resolution effect on DOA estimation accuracy, DSP resource utilization, and received SINR are presented. The results show that DSP based SCC beamformer can estimate weight vectors within less than 10 ms with DOA search resolution of 2° especially when C6713 DSP is used. With faster DSPs and larger search resolutions, execution time could be significantly reduced as well. It provides comparable SINR performance with LMS and CM algorithms.