33—THE SNARLING OF HIGHLY TWISTED MONOFILAMENTS. PART II: CYLINDRICAL SNARLING

An account is given of an experimental investigation of the cylindrical snarling of highly twisted monofilaments.

The theory underlying cylindrical snarling is set out, and an expression is derived for calculating the critical twist level at which normal snarling will be replaced by cylindrical snarling. Experiments on rubber filaments are described, and it is shown that there is good agreement between the theoretical and experimental results. Further experiments, in which the specimen was allowed to contract freely or forced into other forms, are also described.

It is shown from these experiments that it is difficult to establish the true equilibrium behaviour, since the situation appears to be dominated by frictional effects or by direct barriers to relative movement.     

32—THE SNARLING OF HIGHLY TWISTED MONOFILAMENTS. PART I: THE LOAD–ELONGATION BEHAVIOUR WITH NORMAL SNARLING

An account is given of an experimental investigation of the normal snarling of highly twisted monofilaments, those used being vulcanized rubber and nylon.

An earlier theoretical analysis is corrected, and the experimental results show that, after this correction, the theory put forward for the mechanical properties of the snarling mechanism holds reasonably well for elastic filaments. Although, as would be expected, there are larger deviations from the theory for viscoelastic filaments, the theory still gives a good indication of the behaviour of these filaments under torsion.     

Effect of different denture adhesives on retention of complete dentures: an in vivo study

The increase in prevalence of tooth loss with the effect of population aging produces the growing need for complete dentures. The success and acceptance of complete dentures by the patient depends on sufficient retention and stability. Therefore, denture adhesives are regularly used by denture wearers to improve the function of complete denture. We evaluated the effect of three different denture adhesives (Corega, Protefix, Fittydent) on the retention of maxillary complete denture (MCD) using with digital dynamometer (DD). For this purpose, denture adhesives were applied on MCDs of 30 participants. After chewing procedure, the force was applied at 45° to the palatal surface of denture by DD. Dislodgement force was recorded by means of Newton. There were four measurements on each patient including; group of control: Group C; Group CR: Corega; Group F: Fittydent; Group P: Protefix. The result of the study was statistically evaluated by using analysis of variance (ANOVA) and Tukey HSD test. Statistics of ANOVA showed a significant difference among all the four groups (p = 0.00, <0.05). Tukey HSD test indicated that there was a statistical difference between Group F and the other groups, but there was not a significant difference between the other groups. The highest adhesive strength value was observed in group F, the lowest in group C. Use of denture adhesives improved the retentive strength of complete denture.     

Experimental validation of electromagnetic edge waves on a PEC wedge

The dyadic Green's function for electric and magnetic fields of a point current source radiating in close vicinity of a perfectly electric conducting wedge (PEC) has been derived through two independent means by Pearson (1986) and by Buyukdura , Goad, and Kouyoumjian (1996). Asymptotically, a so-called the edge wave may be identified when the source and the observation points are in proximity to the edge but widely separated along the edge, and has become part of the canonical problems in asymptotic diffraction theory. Both of the formulations indicated lead to identical asymptotic results. To corroborate the existence of edge waves, a series of measurements has been performed and the measured data are fit to a model based on the asymptotic results. The fit of the data supports the asymptotic form.     

Purification,structural characterization,and technological properties of an aspartyl proteinase from submerged cultures of Mucor mucedo DSM 809

An extracellular aspartyl proteinase from Mucor mucedo DSM 809 submerged cultures was purified by a two-steps chromatographic procedure. The enzyme had a molecular weight (MW) of 32.7 kDa, and an isoelectric point (pI) value of 4.29; no evidence of N-linked glycosylation was found. As judged by mass spectrometry, the primary structure of the M. mucedo enzyme presented homology with Rhizopus spp. proteinases. The secondary structure showed 4% α-helix, 48% β-sheet and 48% random coil structure in 20 mM phosphate buffer (pH 5.8), as evidenced by circular dichroism spectroscopy. When acting on milk to provoke curd formation, the proteinase showed maximum potency at pH 5.0 and at 40 °C. The enzyme was heat-sensitive and became completely inactivated after incubation at 55 °C for 10 min. These results indicate that the milk-clotting enzyme from M. mucedo can be considered as a potential substitute for bovine chymosin in cheese manufacturing.     

Phase formation and microstructure in sputter-deposited Ti-Mo-C and Ti-W-C thin films

Ti-Mo-C and Ti-W-C films were deposited by cosputtering from carbide targets in order to examine the phase formation, microstructure, and mechanical properties. A series of Ti-Mo-C films were deposited, with compositions ranging from TiC to Mo₂C. The X-ray diffraction (XRD) analysis showed that multiphase Ti-Mo-C films, containing the (Ti,Mo)C, Mo₂C, and Mo₃C₂ phases, were only obtained in highly Mo-rich films. The transmission electron microscopy (TEM) analysis showed a higher defect content in single-phase alloy Ti-Mo-C films in comparison to TiC alone. The hardness for most Ti-Mo-C films was in the range of 8 to 10 GPa, but even lower values were obtained in the multiphase films. Ti-W-C films deposited by cosputtering of TiC and WC formed only (Ti,W)C solid solutions. The X-ray photoelectron spectroscopy (XPS) analysis of peak positions showed that the W 4f _7/2 binding energy decreased with increasing W content. The hardness of most of the Ti-W-C coatings was in the range of 15 to 17 GPa; however, a sample with 40 pct W had a hardness of 29 GPa. The TEM analysis of this sample revealed an extremely small grain size and a higher film density. The high hardness of this specimen is attributed to Hall-Petch strengthening.     

Additively manufactured trapezoidal grooves for wideband and high gain Ku‐band antenna

Grooves around aperture antennas are known to be instrumental in obtaining directive antenna patterns. The shapes of the grooves are often restricted to rectangular or triangular due to manufacturing difficulties in traditional metal machining, and because of this reason, the effect of groove shape on antenna performance is often overlooked. The aim of this study is to analyze different groove shapes with the help of additive manufacturing. Waveguide slot fed, dual cavity aperture antenna with grooves is designed and the effect of groove shapes on antenna performance is studied at Ku band. Two antennas with and without grooves are built using 3D printing technology. Measured antenna performance reveals 5 GHz bandwidth covering 10 to 15 GHz for Ku‐band satellite communications and part of the X‐band applications. Proposed antenna achieves 13.25 dBi peak gain at 14 GHz and the gain is better than 11.25 dBi over the entire Ku‐band uplink and downlink frequency bands.     

Pectinase enzyme-complex production by Aspergillus spp. in solid-state fermentation: A comparative study

A comparative evaluation of three Aspergillus species according to their pectinase production in solid-state fermentation was performed. Solid-state fermentation offers several potential advantages for enzyme production by fungal strains. Utilization of agricultural by-products as low-cost substrates for microbial enzyme production resulted in an economical and promising process. The pectinolytic enzyme activities of two Aspergillus sojae strains were compared to a known producer, Aspergillus niger IMI 91881, and to A. sojae ATCC 20235, which was re-classified as Aspergillus oryzae. Evaluation of polymethylgalacturonase and polygalacturonase activity was performed as well as exo- vs. endo-enzyme activity in the crude pectinase enzyme-complex of the mentioned strains. Furthermore, a plate diffusion assay was applied to determine the presence and action of proteases in the crude extracts. A. sojae ATCC 20235 with highest polymethylgalacturonase activity and highest polygalacturonase activity both exo- and endo-enzyme activity, is a promising candidate for industrial pectinase production, a group of enzymes with high commercial value, in solid-state fermentation processes. Beside the enzymatic assays a protein profile of each strain is given by SDS-PAGE electrophoresis and in addition species-specific zymograms for pectinolytic enzymes were observed, revealing the differences in protein pattern of the A. sojae strains to the re-classified A. oryzae.     

Paclitaxel-loaded lipid nanoparticles prepared by solvent injection or ultrasound emulsification

Lipid nanoparticles were fabricated as an injectable carrier system for paclitaxel. The components for the lipid matrix were based on phospholipids, and sucrose fatty acid ester was used as an emulsifier. Formulation prepared with solvent injection has a slightly larger particle size (187.6 nm) than the formulation (147.7 nm) prepared with ultrasound emulsification. Differential scanning calorimetry results indicated that paclitaxel entrapped in the lipid nanoparticles existed in an amorphous state in the lipid matrix. In vitro drug release was rather slow; only 12.5-16.5% of the drug released from the formulations within 14 days. Lipid nanoparticles demonstrated their potential as a promising pharmaceutical formulation of paclitaxel.