Laser cutting of thick-section circular blanks: thermal stress prediction and microstructural analysis

Laser cutting of thick-section circular mild-steel blanks of 10 mm thickness is examined. Thermal and stress fields developed in the cutting zone are predicted using finite element method and the simulation conditions are selected in line with the experimental parameters. An experiment is carried out to assess the geometric features of the cut surfaces. The morphology of the cut sections are examined using optical and scanning electron microscopes and energy dispersive spectroscopy is carried out for elemental composition of the cut surface. It is found that laser cutting of thick steel blanks results in substantial conduction loss from the cutting zone, which results in high-temperature gradients and large stress levels in the cutting section. The cut edge features such as local dross attachment, striation patterns, and microcrack formation in the cut section are also examined.     

Synthesis and polymerization of 1,5-bis( N -carbazolyl)pentane with its structural and behavioral highlights

Carbazole, the well-known electron donor and hole-transporting organic light-emitting molecule was modified into 1,5-bis[N-carbazolyl]pentane (1,5-BNCP) by introducing the saturated pentane spacer. Such insertion fixed the certain space between growing polymer chains and demonstrated π–π stacking effect over its morphology and structure. Its contribution in improving the thermal stability and photosensitization was also investigated. The FT-IR and 1H NMR was used to characterize monomer. Morphology of subsequently polymerized material was seen under SEM. The position of polymerization and structural change were studied by FT-IR and XRD, respectively. Thermal study with reference to glass transition temperature and stability was analyzed by DSC and TGA. Optical properties of monomer and polymer were investigated by UV–visible and photoluminescent spectrophotometer. The material was found crystalline, thermally stable, highly photosensitized and white light emitter.     

Synthesis and characterization of novel UV-curable polyurethane–clay nanohybrid: Influence of organically modified layered silicates on the properties of polyurethane

Nanohybrids based on UV-curable polyurethane acrylate (PU) and cloisite 20B (C-20B) have been synthesized by solution blending method using different loading levels of C-20B. The structures of PU/C-20B nanohybrids were confirmed by Fourier transform infrared spectroscopy (FTIR) while X-ray diffraction and transmission electron microscopy (TEM) showed the intercalation of PU into layer silicates. The thermal properties of PU and PU/C-20B nanohybrids were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetric (DSC). TGA tests revealed that the thermal decomposition temperature (T_d10%) of the nanohybrid containing 5 wt% of C-20B increased significantly, being 61 °C higher than that of pure PU while DSC measurements indicated that the introduction of 5 wt% of clay increased the glass transition temperature from 89.7 to 101 °C. Accordingly, the mechanical and anti-water absorption properties proved also to be enhanced greatly as evidenced by nanoindentation anylsis and water absorptions data in which the nanohybrid containing 5 wt% of clay have highest elastic modulus (4.508 GPa), hardness (0.230 GPa) and lowest water absorption capacity. Thus the formations of nanohybrids manifests through the enhancement of thermal, mechanical and anti-water absorption properties as compared with neat PU due to the nanometer-sized dispersion of layered silicate in polymer matrix.     

Glycemic Index and Chemical Composition of Traditional Omani Breads

This study evaluated the chemical composition and glycemic index (GI) of eight different types of traditional Omani breads made from wheat flour. Significant (P < 0.05) differences were observed in the proximate chemical composition, dietary fibre content, and gross energy value of these breads. The moisture, crude protein, total fat, ash, crude fibre and nitrogen free extract (NFE) contents ranged between 21.6–51.6, 4.3–10.5, 0.8–13.8, 1.2–2.3, 1.0–2.0, and 34.5–61.8 g/100 g of sample respectively. The values for dietary fibre were between 5.6, 9.6 g/100g, and the gross energy contents ranged between 897 and 1468 kJ/100 g. The GI value of these breads also differed significantly (P < 0.05). No significant differences were however observed among the GI values for White Toast Bread (local commercial bread), Brown Toast Bread (local commercial bread), White Khubz Lebanani (local commercial bread), Brown Khubz Lebanani (local commercial bread), and Chapati (local homemade bread), which were 63 ± 12, 58 ± 15, 63 ± 10, 57 ± 20, and 58 ± 10, respectively. Paratha (local restaurant made bread with fat), Goleh (local homemade soft bread), and Rekhal (local homemade thin bread) showed significantly (P < 0.05) lower GI values as compared to other breads, and these were 32 ± 13, 43 ± 13 and 39 ± 7, respectively. No specific correlation was observed in the chemical composition and glycemic index of these breads. These breads fall within low to medium GI category of foods.     

Extraction of incurred sulphamethazine in swine tissue by microwave assisted extraction and quantification without clean up by high performance liquid chromatography following derivatization with dimethylaminobenzaldehyde

A rapid and reliable method using microwave energy is described for the extraction of spiked and incurred (freeze-dried and fresh) sulphamethazine residues from swine tissues/organs (muscle, liver and kidney). Incurred tissues were obtained from an abattoir and freeze-dried pig tissue reference materials were produced as part of a reference material study for the Community Bureau of References, European Communities. The extraction was achieved by irradiating the sample in methanol for 25 s in a household microwave oven, commonly referred to as microwave-assisted extraction (MAE). The extracts were analysed without clean-up by high performance liquid chromatography (HPLC) using a C18 column and detected at 450 nm after derivatization with 4-dimethylaminobenzaldehyde (DMABA) in a heated rector at 40 degrees C. The limit of quantitation was 2.5 micrograms kg-1 of wet tissues. A comparison of MAE with an homogenization technique indicated that MAE worked extremely well for freeze-dried samples, while it showed significant variation for wet tissues. No sulphamethazine was detected in retail pork meat and liver samples when analysed by the MAE technique.     

Lubrication effectiveness of composite lubricants during P/M electrostatic die wall lubrication and warm compaction

The lubrication effectiveness of the composite lubricants, 50wt% ethylene bis-stearamide （EBS） wax ＋50wt% graphite and 50wt% EBS wax ＋ 50wt% BN, during the powder metallurgy （P/M） electrostatic die wall lubrication and warm compaction was studied. The results show that the combination of 50wt% EBS wax and 50wt% graphite has excellent lubrication performance, resulting in fairly high green densities, but the mixture of 50wt% EBS wax and 50wt% BN has less beneficial effect. In addition, corresponding die temperatures should be applied when different die wall lubricants are used to achieve the highest green densities.     

TiC-Maraging stainless steel composite： microstructure, mechanical and wear properties

Particulate TiC reinforced 17-4PH and 465 maraging stainless steel matrix composites were processed by conventional powder metallurgy （P/M）. TiC-maraging stainless steel composites with theoretical density 〉97% were produced using conventional P/M. The microstructure, and mechanical and wear properties of the composites were evaluated. The microstructure of the composites consisted of （core-rim structure） spherical and semi-spherical TiC particles depending on the wettability of the matrix with TiC particles. In TiC-maraging stainless steel composites, 465 stainless steel binder phase showed good wettability with TiC particles. Some microcracks appeared in the composites, indicating the presence of tensile stresses in the composites produced during sintering. The typical properties, hardness, and bend strength were reported for the composites. After heat treatment and aging, an increase in hardness was observed. The increase in hardness was at- tributed to the aging reaction in maraging stainless steel. The specific wear behavior of the composites strongly depends on the content of TiC particles and their interparticle spacing, and on the heat treatment of the maraging stainless steel.     

Frey''s syndrome following submandibular gland excision: an unusual postoperative complication

A coincidence of celiac disease and insulin-dependent diabetes mellitus has been described in several studies. Celiac disease appears to be more common among patients with IDDM than in general population. The diagnosis of celiac disease requires histologic evidence of villous atrophy and a positive antibody test result. Typical gastrointestinal complaints of celiac disease are rare in IDDM patients, while atypical isolated symptoms of celiac are more common. It is recommended that all young diabetic patients, even those asymptomatic, should be screened for celiac. Routine screening is recommended repeatedly during first years after the diagnosis of IDDM.