Continuous-time feedforward SD modulators with robust lowpass STF

Continuous-time sigma-delta modulators are often implemented using the feedforward structure. This type of architecture is prone to large out-of-band peaking and degraded anti-aliasing filtering owing to its sensitivity to process variation. Two alternative continuous-time delta- sigma modulators, which exhibit significantly lower signal transfer function (STF) sensitivity, are described.     

Microwave Synthesis and Characterization of Spinel-type Zinc Aluminate Nanoparticles

In the present work, ZnAl₂O₄ nanoparticles have been synthesized with the aid of Zn(OAc)₂·2H₂O and Al(NO₃)₃·9H₂O as starting reagents in the presence of microwave irradiation. Besides, the effect of preparation parameters such as microwave power and irradiation time on the morphology and particle size of products was studied by SEM images. The as-prepared ZnAl₂O₄ nanoparticles were characterized extensively by techniques like XRD, TEM, SEM, FT-IR, PL, and EDS. Photoluminescence studies of the ZnAl₂O₄ nanoparticles displayed quantum confinement behavior with band gap of 3.2 eV. The XRD studies showed that pure orthorhombic ZnAl₂O₄ nanoparticles have been produced after calcination.     

Optimization of the water-based road-marking paint by experimental design, mixture method

The main purpose of this research is formulating and optimizing a new road-marking paint which is an environmentally friendly product. This paint is produced with an emulsion of an acrylic copolymer and contains the least of the volatile organic compounds. The formulation and optimization procedure is carried out on the base of experimental design by the method of mixture in which the important paint properties are modeled by using special cubic model. The present method has the capability of investigation the effect of raw materials at different levels with fewer experiments than factorial and fractional factorial design.

In this research, the main parameters such as resin, pigment and filler were selected at different levels, and different samples were prepared by combination of additives and other required reagents. The properties of wet and dry films of the samples were determined using ASTM test methods. Different responses such as pigment volume concentration (PVC), latex critical pigment volume concentration (LCPVC), abrasion resistance, hardness, gloss, no pick up time and surface drying time, were selected as the objective functions of this study. By running DX6 software, using special cubic model and selection of desired range of end-use properties, the region of optimum paint formula was determined.

The accuracy of the model was examined by preparing a sample in optimized region and by determining its final properties, experimentally. The results exhibit a good agreement between the model and experimental measurements. This product was compared with commercial solvent based traffic paint and good quality was reported in end-use properties.     

Vascularized fascial patch for repair of suboccipital dural defect

The capabilities of current protein structure prediction methods have been assessed from the outcome of a set of blind tests. In comparative modeling, many of the numerical methods did not perform as well as expected, although the resulting structures are still of great practical use. The new methods of fold identification ('threading') were partially successful, and show considerable promise for the future. Except for secondary structure data, results from traditional ab initio methods were poor. A second blind prediction experiment is underway, and progress in all areas is expected.     

Microvascular soft-tissue coverage and distraction osteosynthesis for lower-extremity salvage

In our attempts to salvage massive lower-extremity injuries, even in the presence of severe peripheral vascular pathology, adequate soft-tissue coverage is no longer a limiting factor due to recent advances in microvascular composite tissue transfer. Restoration of tibial continuity without shortening has emerged as the last obstacle in the formidable task of salvaging lower extremities with grade III B and III C defects. Proposed solutions to this problem include conventional free cancellous bone-grafting applicable to small defects only, vascularized bone grafts, or shortening of the leg with subsequent elongation using the Ilizarov technique. We present our experience with 3 consecutive cases of lower-limb salvage, utilizing a new approach in which microsurgical soft-tissue reconstruction has been combined with bony reconstruction by distraction osteosynthesis. Bone transport by distraction osteosynthesis under a free flap performed while preserving the initial limb length throughout the treatment period proved to be superior to other methods in selected cases and is presented as a new technique for the management of problematic lower-limb injuries.     

Intestinal absorption in Saudi Arabia: an evaluation of the one hour blood xylose test

The screening value of the one-hour blood xylose test, corrected for body surface area, was prospectively studied in Saudi Arabian adults and children under investigation for suspected intestinal malabsorption. Sensitivity of discrimination between patients with and without upper small bowel disease was 91%, compared to 85% for the five-hour urine xylose test. Primary small bowel disorder was rare. In a three-year review, no cases of adult coeliac disease or tropical sprue were found. The most common causes of malabsorption were intestinal tuberculosis, abdominal lymphoma and immunoproliferative small intestinal disease. Despite its acceptability as an index of proximal small bowel function, the blood xylose test alone is an inadequate screening test for any of these conditions.     

DC and AC electrical conductivity of electro-deposited carbon-black–epoxy composite films

Carbon-black–epoxy composite films were prepared by cathodic electro-deposition of a dispersion containing carbon black and epoxy resins. The films, after baking at elevated temperature, show a semi-conducting behavior. Using DC conductivity measurements it was possible to determine the glass transition temperature of the samples, the conductivities of which lie in the sensitivity range of the instrument. Conductive samples show a positive temperature coefficient both below and above T_g. Based on the electrical impedance data extracted from the electrochemical impedance spectra, the exponents x and y were determined for the frequency dependence of the complex conductivity and complex dielectric constant as 0.8 and 0.2, respectively. These values are in good agreement with the classical values of x = 0.72 and y = 0.28. It was also found that these exponents are the same for all the CCB contents studied.     

Enhanced optical and hydrophilic properties of Si and Cd co-doped TiO<Subscript>2</Subscript> thin films

In this study, preparation of Si and Cd co doped (5 mol% Si and 5–20 mol% Cd) TiO₂ dip-coated thin films on glass substrates via sol–gel process have been investigated. The samples were characterized by X-ray diffraction (XRD) and Scanning electron microscopy analysis after heat treatments. XRD results suggested that adding dopants has a great effect on crystallinity and particle size of TiO₂. Titania rutile phase formation was inhibited by Si⁴⁺ and promoted by Cd²⁺ doping. But the effect of Cd doped appeared at high concentration. Accordingly, the thin films showed various water contact angles. The water contact angles changed from 69.0° to 9.6° by changing the content of Cd doped.     

Influence of preheating of fly ash precursors to produce geopolymers

This study has been focused on the effect of pretreatment of FA and POFA after geopolymerization on the mechanical properties. The aim of this work was to simplify the pretreatment that it can easily industrial be applied, using existing technology. Previous work has shown that a reduction in particle size increases the mechanical properties. However, this method involves a milling process which is not applicable for a wide industrial application. Hence, FA and POFA particles have been heated to 300°C, 500°C, and 800°C but applying different pretreatments: (i) predried at 110°C (reference sample); (ii) as received; (iii) prewetted; (iv) prewetted and later quenched in cold water. It was found that during the treatment the particle size increased due to thermal stress cracking. During fast heating, trapped pore water cannot be removed as fast as it evaporates and hence the particles crack. This increase in particle size caused an increase in compressive strength. In addition, heating to 300°C and 500°C caused a dehydroxylation of FA and POFA. This dehydroxylation resulted in a higher initial reactivity, reducing the setting time and improved mechanical strength.     

Tuning the conditions for the deposition of nanocrystalline diamond by hot filament chemical vapour deposition

Although large focus has been placed into the deposition of nanocrystalline and ultra-nanocrystalline diamond films, most of this research uses microwave plasma assisted CVD systems. However, the growth conditions used in microwave systems cannot be directly used in hot-filament CVD systems. This paper, aims to enlarge the knowledge of the diamond film depositing process. H2/CH4/Ar gas mixtures have been used to deposit micro, nano and ultra-nanocrystalline diamond films by hot-filament CVD systems. Additionally, the distance between the filaments array and the substrate was varied, in order to observe its effect and consequently the effect of a lower substrate temperature in the nucleation density and deposition. All the samples were characterized for microstructure and quality, using scanning electron microscopy and Raman spectroscopy.