Analysis of Slot Characteristics in Slotted Single-Mode Semiconductor Lasers Using the 2-D Scattering Matrix Method

We use the two-dimensional (2-D) scattering matrix method (SMM) to analyze the slot characteristics in slotted single-mode semiconductor lasers and compare the results with those calculated by the one-dimensional transfer matrix method (TMM). The analysis shows that the 2-D SMM is required to accurately account for the measured results. Using the 2-D SMM simulation, we find that there is almost no reflection at the interface from slot to waveguide while a large reflection exists at the interface from waveguide to slot, and the power loss is much larger than the power reflected. For a single slot, the slot width has little influence on the slot reflectivity, which coincides with the measured results. The reflection and transmission of the slot are found to be exponentially dependent on the slot depth     

Simultaneous multigas detection with cascaded strongly gain coupledDFB laser by dual wavelength operation

Simultaneous detection of hydrogen sulphide and carbon dioxide by dual wavelength operation of a cascaded strongly gain coupled distributed feedback (DFB) laser in the 1575 to 1585 run region is reported for the first time. By precise dual wavelength tuning of the laser diode both gases were detected using wavelength modulation absorption spectroscopy     

Simultaneous multispecies gas sensing by use of a sampled grating distributed Bragg reflector and modulated grating Y laser diode

Widely tunable laser diodes operating at 1520 < or = lambda < or = 1570 nm are characterized and compared for use as sources for tunable laser diode gas absorption spectroscopy. Three gases, hydrogen cyanide, ammonia, and acetylene, with overlapping absorption features within the 50 nm tuning range of the devices were targeted by use of wavelength modulation spectroscopy with second-harmonic detection. In addition, a method for modulating the laser to improve sensitivity by taking advantage of the unique structure of these devices is reported.     

Widmanstätten ferrite plate formation in low-carbon steels

The mechanism by which Widmanstätten ferrite plates nucleate and grow in low-carbon steels has been studied. In-situ laser scanning confocal microscopy (LSCM) observations, optical microscopy, and electron backscattered diffraction (EBSD) techniques have been used to characterize the relationship between grain boundary allotriomorphs and Widmanstätten ferrite plates. The issue of where Widmanstätten ferrite plates nucleate is one of some debate, with theories including morphological instability and sympathetic nucleation. Evidence has been found that supports the theory of a sympathetic nucleation mechanism being responsible for the formation of Widmanstätten ferrite plates. The EBSD measurements have shown that low-angle misorientations of between 5 and 10 deg exist between ferrite allotriomorphs and Widmanstätten ferrite plates.     

Formation of intermetallic phases on 55 wt.%Al–Zn–Si hot dip strip

A study has been conducted to probe the formation of intermetallic phases on steel substrates immersed in 55 wt.%Al–Zn–Si hot dip baths as a function of dipping time and bath silicon content. Two bath compositions containing 1.3 and 1.5 wt.% Si, respectively, combined with two immersion times of 3 and 9 s were studied. It was found that the reaction rate and intermetallic phase formation varied in response to silicon content. Optical microscopy revealed a quantifiable difference in the development of the reaction layer between the two bath compositions. SEM-EDS revealed that the reaction layer that evolved on samples dipped in the 1.5 wt.% silicon bath were comprised of two intermetallic species, -AlFeSi/Fe₂Al₅, whilst in the 1.3 wt.% bath there were three clearly identifiable intermetallic species -AlFeSi/FeAl₃/Fe₂Al_5. A fourth phase appeared to be present in samples immersed in the 1.3 wt.% Si bath that, due to its fine structure, could not be conclusively identified. Experimental results from the literature and from this study have been assessed with reference to the phase stability predicted by MTDATA, a thermodynamic modelling package.     

Surface modification of a novel glass to optimise strength and deliverability of an injectable alginate composite

It is estimated that 1–6% of the adult population have an intracranial aneurysm. Aneurysm coiling is the current preferred treatment method; however, over 20% of coiled aneurysms recur. A novel glass–alginate composite hydrogel has been developed to treat aneurysms, which is designed to completely fill the aneurysm space and prevent aneurysm recurrence. This hydrogel is composed of a polymeric alginate, a novel bioactive glass and glucono-delta-lactone. This novel injectable hydrogel exhibits characteristics suitable for the treatment of cerebral aneurysms. However, poor hydrophilicity of the glass phase results in inhomogeneity and agglomerate formation within the composite, resulting in suboptimal deliverability and strength. This study examines the effect of surface modification of the glass particles using an acid washing technique, designed to increase glass surface hydrophilicity resulting in a homogeneous sample. This study found that acid washing of the glass not only decreased agglomeration and inhomogeneity but also lengthened working times and increased strength of the resultant hydrogel. This lengthened working time, allowed for an increased glass content and, as a result, further increased compressive strength and radiopacity of the resultant hydrogel. Glass particle size analysis revealed that the relative quantity of fine particles was reduced. Surface analysis of the glass particles revealed an increase in hydrophilic silanol groups and increased surface network connectivity. These factors, combined with a decreased surface calcium and an increased surface gallium content, are postulated as the likely reasons for the observed increased strength, working time and hardening time.     

Comprehensive dose survey of breast screening in Ireland

The primary purpose of this study was to evaluate the impact of digital mammography screening on breast dose by analysing the results of a patient dose survey of the Irish breast screening programme. Results from the survey were used to determine a dose reference level for the screening programme. Approximately, 100 examinations were acquired for each of the digital mammography systems operational in the screening programme. Each examination consisted of two standard views of each breast. The mean glandular dose for each acquired image was calculated. The dose reference level was established by calculating the 95th percentile of the average mean glandular dose for the average compressed breast thickness of the mediolateral oblique views. The overall average mean glandular dose per examination was 2.72 ± 0.04 mGy. The average compressed breast thickness was 61.4 ± 0.03 mm. The average compression force was 109 ± 7 N. A dose reference level value of 1.75 mGy was established for the screening programme. The results of this clinical dose survey provide a valuable indication of the dose performance of modern full field digital mammographic imaging systems. The results demonstrate clearly the dose benefits of digital mammography. The dose benefit of digital screening was further demonstrated by the establishment of a comparatively lower diagnostic reference level for the screening programme. The comparison of the dose performance of individual X-ray systems with the diagnostic reference level highlights the need for more optimisation within the service.     

Thermodynamic activities and phase boundaries for the alloys of the Ni3Al-Ni3Ti pseudobinary section in the Ni-Al-Ti system

The pseudobinary section Ni₃Al-Ni₃Ti of the ternary Ni-Al-Ti system has been investigated by ther-mal analysis and Knudsen effusion mass spectrometry. The solidus of the pseudobinary section and the thermodynamic activities of Ni and Al have been determined in the alloys Ni_0.75A1_0.25-xTi_x of the compositionsx = 0.00 to 0.21. Moreover, the thermodynamic activities of Ni and Ti in Ni₃Ti (x = 0.25) as well as the Gibbs energy of mixing of the Ni_0.75Ti_0.25 phase resulted. The ionization cross-sectional ratio Σ(Ni)/Σ(Ti) = 0.77 has been evaluated for the electron impact energy of 50 eV.     

Myomas and pregnancy

At this time, the growth of uterine myomas during pregnancy cannot be predicted. Major complications of pregnancy appear to be related to whether the placenta and the myoma are in contact. The location and number of myomas, especially in the lower uterine segment, increases the likelihood of cesarean birth and malpresentation. Frequent ultrasound evaluations to monitor fetal growth and presentation and the size of the myoma should be considered in pregnant women with uterine myomas. Surgical resection of myomas should be reserved for those pregnant women with symptomatic pedunculated myomas with a small stalk. In those women with a pregnancy complication owing to the myoma, resection should be considered prior to the next pregnancy.