A “cold” InP-based tunneling injection laser withgreatly reduced Auger recombination and temperature dependence

We have measured the Auger recombination rates in an InP-based quantum well tunneling injection laser from large signal modulation experiments. Measured values of the Auger coefficient, C_o=1.2±0.6×10^-29 cm⁶ s^-1 at 283 K, are a factor of over 10² smaller than those measured in similar multiple quantum well separate confinement heterostructure lasers. In effect, the tunneling injection mechanism keeps the carriers “cold” even at high injection levels. A maximum value of T_o=70 K is measured in the tunneling injection laser compared to 50 K for conventional quantum well structures,     

The use of hydrogen peroxide for the digestion and determination of total nitrogen in chickpea (Cicer arietinum L.) and pigeonpea (Cajanus cajan L.)

The use of hydrogen peroxide as an alternative to catalysts in the determination of nitrogen in plant materials has been investigated. Nitrogen determination in leaf, stem and seed samples of chickpea and pigeonpea was carried out by three digestion procedures, using hydrogen peroxide (H₂O₂ digestion) without a catalyst, and with mercury or selenium as catalysts (catalyst digestions). The nitrogen values obtained by the three digestion procedures did not differ significantly from each other when examined by microKjeldahl (MKJ) using mercury as a catalyst, and by a Technicon auto analyser (TAA) using selenium as catalyst. The gradual addition of H₂O₂, as recommended previously, was found to be unnecessary. In view of the cost and health hazards implicated with the use of mercury and selenium for digestion, the procedure based on H₂O₂ digestion is preferable for large scale N determinations in plant tissue and seed samples of these pulse crops. The results sugest that the H₂O₂ digestion technique can be conveniently adapted for total N analysis in plant tissues and grain samples by either TAA or MKJ method.     

Oil quality characteristics and headspace volatiles of newly released groundnut (Arachis hypogaea L) cultivars

Several groundnut (Arachis hypogaea L) cultivars developed by the International Crops Research Institute for the Semi-arid Tropics (ICRISAT), and one local cultivar for use as a control were grown in the post-rainy and rainy seasons at Patancheru, India. Free and bound lipids were extracted and their fatty acid compositions determined. Acid, peroxide, iodine and saponification values were determined. Flavour quality was evaluated using headspace analysis. The quantity of total lipids was significantly higher in the cultivars grown in the rainy season than those grown in the post-rainy season and was higher in the ICRISAT cultivars than in the control in both seasons. Oleic (O) to linoleic (L) acid ratio was lowest in the chioroform-methanol extract and highest in water-saturated butanol extract. One ICRISAT line, ICGS 21, showed the highest O/L ratio in all lipid fractions in both seasons. Among the flavour components, n-methyl pyrrole, associated with an objectionable musty flavour, was present in very high concentration in all the cultivars.     

Design studies for distributed Bragg reflectors for short-cavityedge-emitting lasers

In conventional edge-emitting lasers, mirror reflectivity is ~0.3-0.4 so that very short cavities have an unacceptable loss. To decrease the mirror losses, one can conceive of an external distributed Bragg reflector (DBR) structure produced by etching. We examine the design considerations for such mirrors. Using a finite-difference time-domain (FDTD) scheme, we numerically simulate the propagation of a Gaussian wave packet in a laser cavity with an external DBR structure on one end. We find that despite the divergence of light at the semiconductor-air interface, high reflectivities (>90%) can be obtained using only a few mirrors, provided a low refractive index material (such as air) is one of the components of the DBR period. In our modeling, we include fluctuations based on factors such as lithographical error, etch error, and off-design wavelength lasing. Our results indicate that the external DBR is highly tolerant of such factors. In addition, simulations done using material with higher refractive index than air in the DBR structure indicate that it is possible for insulators to be deposited in the DBR structure, yet allow high reflectivity     

Methods for the estimation of protein in pigeonpea [Cajanus cajan (L.) Millsp.] and the relationship between whole grain and dhal protein contents

Protein determinations of 172 grain and dhal (decorticated dry split seed) pigeonpea samples were carried out using three methods: (a) micro-Kjeldahl (MKJ), (b) colorimetric estimation of NH₄+ with phenol hypochlorite reagents using the Technicon Auto-Analyser (TAA), and (c) dye-binding capacity (DBC) method using Acid Orange 12 dye. Protein percentages determined by the TAA and MKJ methods were highly correlated for whole-grain (0.948**) and dhal (0.967**) samples. The DBC method gave reliable results for dhal samples only. In the DBC procedure, higher protein percentages were recorded with smaller flour particles and longer mixing time, but different temperatures and durations of heating had no effect. Positive and highly significant correlations were obtained between the protein values of whole-grain and dhal samples in all the methods. Small grains gave a lower correlation between whole-grain and dhal protein content due to the observed negative correlation between grain size and percentage of seed-coat.     

Uncooled performance of 10-Gb/s laser modules with InGaAlAs-InP and InGaAsP-InP MQW electroabsorption Modulators integrated with semiconductor amplifiers

Uncooled operation of long-reach high performance C-band 10 Gb/s of optical modulator modules is presented. Modules consisting of a distributed feedback laser and a chip with a monolithically integrated electroabsorption modulator and semiconductor optical amplifier based on multiquantum-well structures of both InGaAsP-InP and InGaAlAs-InP material systems are presented. Dispersion penalty of 1 dB over 94-km transmission, output power above 0 dBm, and low extinction ratio variation are demonstrated over an 80/spl deg/C temperature range. A simple analysis of the quantum confined Stark effect is employed to explain the temperature-dc bias voltage dependence.     

A decade''s experience in chemistry maintenance of once through steam generator of fast breeder test reactor

The steam generator of fast breeder test reactor (FBTR) at Kalpakkam (India) is a once through Steam Generator (OTSG) which requires the feed water at high purity level. Therefore, for maintaining feed water chemistry, all volatile treatment (AVT) is adopted along with a full-flow deep bed Condensate Polishing Unit (CPU) in the steam water system. Operational difficulties such as premature termination of operation cycle of the CPU, enhanced impurity pickup resulting in increased load for CPU, early silica breakthrough, etc. were observed on occasions. This paper describes the modifications carried out in the steam water circuit to overcome these problems. A decade's experience in operating the CPU and maintaining the feed water quality is also discussed.     

Surface temperature distributions along vertical recuperator pipes

Computer predictions are presented for the decay of the outer surface temperature along a cylindrical pipe through which previously heated oil flows. These have been corroborated by experimental observations.     

Evaluation of rapid methods for the estimation of protein in chickpea (Cicer arietinum L.)

Protein content in chickpea (Cicer arietinum L.) was determined by the following rapid procedures: (a) colorimetric estimation of ammonia with phenol-hypochlorite reagents using the Technicon auto-analyzer (TAA) method, (b) dye-binding capacity (DBC) method using acid orange-12 dye, and (c) modified biuret methods of Pinckney (B1) and Johnson and Craney (B2). Results obtained with the above procedures were compared statistically with the standard microKjeldahl (MKJ) procedure. Correlation of MKJ protein values with TAA, DBC, B1 and B2 methods were 0.99, 0.98, 0.96 and 0.95, respectively. Standard errors of estimation obtained by methods B1 (0.99) and B2 (0.95) were high when compared to the TAA (0.55) and DBC (0.69) methods. Possible interference of seed-coat pigments, effect of flour particle size, and time of shaking on protein estimation by the DBC and B1 methods were also studied. Implications of these results are discussed with reference to adapting any of these rapid methods as a routine screening procedure for the estimation of protein in large numbers of chickpea samples in a breeding programme.     

Characterization of a Bulk-Micromachined Membraneless In-Plane Thermopile

This paper describes the characterization method and results for bulk- micromachined in-plane thermopiles. Made of poly-Si or poly-SiGe, the thermocouple legs bridge the hot and cold side of a Si frame, which is formed by bulk micromachining. The characterization of the fabricated devices is carried out on a dedicated experimental setup, using which a uniform temperature difference can be imposed on all the thermocouples. Among design variations, the open-circuit output voltage reaches up to 95.0 mV/K and the corresponding output power on a matched external load is 2.34 × 10⁻³ μW/K². Two possible assembly schemes towards a fully fledged thermoelectric generator are illustrated as well. In the case of vertical assembly, the efficiency factor is expected to be 1.73 × 10⁻² μW/K²/cm².