Design and testing of SMA temperature-compensated cavity resonators

In this paper, we present a method for designing temperature-compensated cavity resonators using shape memory alloys (SMAs). This paper gives an expression for the temperature drift of resonant frequency, which is valid for any conductor-loaded cavity regardless of its shape. This formula, combined with a field perturbation model, is used to derive the resonant frequency of an SMA-compensated resonator subject to temperature fluctuation. Experimental results are given that confirm the feasibility of the proposed design approach. A design method is proposed for specifying SMA alloys to build the actuator. An expression is derived to accurately predict the performance of an actuator design.     

Removal of oil from oil/water emulsions using electroflotation process

Dispersed oil was separated from oil–water emulsions in an electroflotation cell equipped with insoluble electrodes: titanium coated with ruthenium oxide as anode and stainless steel screen as cathode. The effect of operating parameters such as current density, oil concentration, flotation time and coagulant concentration, on the performance of the electroflotation cell was examined. Oil removal reached 70% at optimum conditions; 75% in the presence of NaCl (3.5% by wt); and 99.5% in the presence of both NaCl and an optimum concentration of coagulant. Electrical energy consumption varied from 0.4 to 1.6 kWh m⁻³ according to experimental conditions. The performance of the oil removal process was also represented by a first order kinetic rate model. The constants obtained fit the experimental data well. Good correlation was found for the change in percentage oil removal within a wide range of operating parameters.     

Obstructed nasolacrimal duct system in epiphora: long-term results of dacryocystoplasty by means of balloon dilation

PURPOSE: To evaluate the long-term results of balloon dacryocystoplasty in the treatment of epiphora due to obstruction of the nasolacrimal ducts. MATERIALS AND METHODS: One hundred eyes in 84 patients with complete or incomplete obstruction of the lacrimal sac and duct were selected for dacryocystoplasty. A catheter with a balloon diameter of 3 mm was used. Follow-up was 5-48 months. No stents were placed. A Kaplan-Meier analysis was used to evaluate patency. RESULTS: The long-term primary patency rate was 70% +/- 7 (+/- standard error). Repeat dacryocystoplasty was successful in 10 of the 11 cases with initial failure or reobstruction during follow-up, which yielded a long-term secondary patency rate of 81% +/- 7. There was no association between the length of the obstruction or the duration of symptoms before dacryocystoplasty and the initial and long-term success. Initial and long-term success was statistically significantly higher in dacryocystoplasty for an incomplete obstruction rather than for a complete obstruction. CONCLUSION: The long-term results of dacryocystoplasty, followed if necessary by repeat dacryocystoplasty, are good. Dacryocystoplasty is a safe and simple procedure and could become the treatment of choice for epiphora due to obstruction of the nasolacrimal ducts. Dacryocystorhinostomy is indicated when dacryocystoplasty or repeat dacryocystoplasty fails or when dacryocystoplasty is contraindicated (e.g., in anatomic malformations in the lacrimal duct or bony canal).     

Thermodynamics of oxygen behaviour in cobalt-nickel alloys

In this study the concentration and chemical potential of oxygen in liquid Co-Ni alloys equilibrated with cobalt-nickel aluminate spinel solid solutions and alumina have been determined at 1773, 1823 and 1873K as a function of nickel concentration. The oxygen content of the melt has been measured by suction sampling and inert gas fusion analysis. The corresponding oxygen potential has been determined with the following solid state cell: Mo, Mo+MoO₂ | (MgO)ZrO₂ | (Co, Ni) melt + AI₂O₃ + (Co, Ni)O·(1+x)Al₂O₃, Mo. The effect of nickel on the activity coefficient of oxygen in Co-Ni alloys has been determined. The results for the activity coefficient have been modelled with Wagner's interaction parameters and also the more recent exponential method of St. Pierre et al. at the three temperatures.     

Mutations in SOX9, the gene responsible for Campomelic dysplasia and autosomal sex reversal

Campomelic dysplasia (CD) is a skeletal malformation syndrome frequently accompanied by 46,XY sex reversal. A mutation-screening strategy using SSCP was employed to identify mutations in SOX9, the chromosome 17q24 gene responsible for CD and autosomal sex reversal in man. We have screened seven CD patients with no cytologically detectable chromosomal aberrations and two CD patients with chromosome 17 rearrangements for mutations in the entire open reading frame of SOX9. Five different mutations have been identified in six CD patients: two missense mutations in the SOX9 putative DNA binding domain (high mobility group, or HMG, box); three frameshift mutations and a splice-acceptor mutation. An identical frameshift mutation is found in two unrelated 46,XY patients, one exhibiting a male phenotype and the other displaying a female phenotype (XY sex reversal). All mutations found affect a single allele, which is consistent with a dominant mode of inheritance. No mutations were found in the SOX9 open reading frame of two patients with chromosome 17q rearrangements, suggesting that the translocations affect SOX9 expression. These findings are consistent with the hypothesis that CD results from haploinsufficiency of SOX9.     

New relations between the Schur-Cohn-Fujiwara and Nour Eldinstability criteria

The authors demonstrate relationships between two different stability criteria, including reduced-order versions of these criteria. Modifications of the criteria can also be used for root counting. The various matrices whose signatures are the key to obtaining root distributions are related by congruency transformations with triangular structure, implying that the sign patterns of the leading principal minors are identical     

Iterative simplex-finite difference method for the characterizationof optical waveguides

A new method is presented for reconstructing smooth refractive index profiles of optical waveguides from measured effective indexes. It is based on the semivectorial finite difference method to solve the polarized wave equation for a given refractive index profile. An iterative simplex algorithm is used to find the best refractive index parameters that give, as a solution, effective indexes close to the measured ones. The method is applied successfully to Ag⁺-Na ⁺ ion-exchanged glass slab waveguides and to diffused Mg/Ti:LiNbO₃ slab waveguides. Dopant concentration profiles are obtained by using secondary ion mass spectrometry. The relationship between the refractive index change and the dopant concentration is determined for both cases. The iterative simplex algorithm-finite difference method (ISA-FDM) is compared to other index profile reconstruction methods, and the advantages with respect to WKB-based methods are pointed out     

Lignocellulose–polymer composite. I

Bagasse grinded to different mesh sizes was used for the production of lignocellulose polymer composites. Samples of different polymer loads were prepared from crude-grafted bagasse with polymethyl methacrylate. A sodium bisulfite–soda lime glass system was used as an initiator for the grafting reaction. The properties of the resulting composites have been found to be affected by both the polymer load and the mesh size of the ground bagase. Grafting in the absence of soda lime glass from the initiator system was successful, and the properties of the composite produced from the prepared samples differed greatly from those containing glass. Other oxides, namely, copper (cupric) oxide and iron (ferric) oxide, were used in replacing glass in the initiator system. Some of the properties of the composite containing the latter were deteriorated. A composite from the true-grafted sample (homopolymer free) showed improvement in some of the properties, while the others deteriorated. Composites prepared from impregnated bagasse with polymer or homopolymer behaved differently in their properties and from those from crude-grafted samples, depending on the mesh size of the ground bagasse they are made from.     

Dielectric investigation of the molecular dynamics of blends (II): polymers with dissimilar molecular architecture (PS/TMPC blend)

The molecular dynamics of polystyrene/tetramethyl polycarbonate (PS/TMPC) blends were investigated using dielectric spectroscopy in the frequency and temperature ranges 10^?2?10⁷ Hz and 50–220°C, respectively. Blends with different compositions, namely 12.5, 25, 50, 75 and 87.5 wt% PS/TMPC were found to be compatible over the entire composition range and showed one glass relaxation process corresponding with the transition observed by calorimetric measurements. It was found that neither the kinetics or the distribution of relaxation times of the local process observed in pure TMPC were affected by blending. This fact implies that the local environment of the segments is not changed upon blending. Furthermore, these blends showed that the blending of TMPC with weakly polar polystyrene does not cause any change in the dipolar interaction of the TMPC segments, so that the relaxation strength varies linearly with composition. It is concluded that the polymeric chains of the TMPC and PS are not mixed at a segmental level, but at a higher structural level lying somewhere between segmental and molecular. This conclusion is in good agreement with that obtained in the case of blends composed of polymers with similar molecular architecture.