Ultrawide-band La-codoped Bi/sub 2/O/sub 3/-based EDFA for L-band DWDM systems

The demonstration of a 253-cm-long lanthanum-codoped Bi/sub 2/O/sub 3/-based erbium-doped fiber which provides gain of greater than 20 dB and noise figure less than 6.7 dB to 142 dense wavelength-division-multiplexing channels simultaneously over an extended wavelength range of 58 nm from 1554 to 1612 nm is reported. The 3-dB (gain of 17-20 dB) bandwidth of the erbium-doped fiber amplifier is 54 nm when it is pumped with 350 mW of 1480-nm light. The power conversion efficiency of the fiber is about 54%.     

Generating sub-1V reference voltages from a resistorless CMOS bandgap reference circuit by using a piecewise curvature temperature compensation technique

A piecewise curvature compensated CMOS voltage reference that is able to generate a sub-1V reference voltage is presented. The presented voltage reference circuit is operated at a minimum operating voltage of 1.5 V (theoretically 1.408 V) and generates a stable 0.658 V reference voltage with a temperature coefficient of 9.617 ppm/°C over the temperature range of −10 °C to 130 °C. When implemented in a 0.18 μm CMOS technology, the presented design occupies a compact silicon area of 0.022 mm². Spectre SPICE simulation showed that the presented design achieves a line regulation of 0.89%, a power supply rejection ratio of −42.3 dB, a power consumption of 0.449 mW at 1.8 V power supply and a high immunity to process variation.     

Mutual admittance characteristics for two-element parallel prolate spheroidal antenna systems

Spheroidal dipole antenna systems consisting of two thin center-fed parallel prolate spheroids in various configurations (side-by-side and collinear) are considered, The resultant EM fields are represented as modal expansions in terms of spheroidal vector eigenfunctions. The translational addition theorems for spheroidal functions developed by the authors in a previous paper play the central role in the formulation of a system matrix [G] which transforms the primary. EM excitations of the fed dipoles into their scattered responses. From the knowledge of the [G] matrix, the mutual admittances of the dipole system are obtained and plotted against center-to-center separation of the dipoles for side-by-side and collinear dipole configurations. The major to minor axial ratios of 10:1 and 100:1 of the prolate spheroidal dipoles are considered for presenting various curves. However, for the side-by-side configuration, due to a radius of convergence of the translational relation for outgoing wave to incoming wave transformation, the separationdof the spheroids is restricted tod > {a_{1}, a_{2}}_{max}, whosea_{1}anda_{2}are the semimajor axial lengths of the two spheroids.     

Effect of temperature and growth media on the attachment of Listeria monocytogenes to stainless steel

Listeria monocytogenes ATCC 19111 cultivated in nutrient-rich medium (brain heart infusion, BHI) or starved in minimal medium (10% filter sterilized pond water and 90% sterilized distilled water) were investigated for their initial attachment to austenitic stainless steel No. 4 with satin finish at 4 °C, 20 °C, 30 °C, 37 °C, or 42 °C. A droplet (10 μl) containing  10⁷ CFU/ml of L. monocytogenes suspended in BHI or minimal medium was placed on the stainless steel surface. After holding in saturated humidity for 3 h at the desired temperature the surface was washed and prepared for scanning electron microscopy (SEM). Using SEM, attachment of L. monocytogenes was determined by counting cells remaining on the surface. When L. monocytogenes cultivated in BHI were used, with the exception of the number of attached cells being lower at 42 °C than at 37 °C and 30 °C, the number of attached cells increased with increasing temperature (P < 0.05). When L. monocytogenes starved in minimal medium were used, the number of attached cells also increased with increasing attachment temperature (P < 0.05), but the number of attached cells at 42 °C was lower than that at the other temperatures. The attachment of L. monocytogenes to stainless steel surface was greater when cultivated in rich medium of BHI vs starved in the minimal medium.     

A novel partitioning method as a possible tool for investigating meat. I.

 This paper describes a practical application of the interfacial protein enrichment method, called three-phase partitioning (TPP), and outlines its significance in the differentiation of multicomponent protein systems, such as homogenates and drips of different meats (pork, beef, chicken, turkey and wild-boar). The results obtained using the single-protein model system are also reported to demonstrate the basic process and some characteristic features of TPP. For meat-protein-partitioning experiments, ammonium sulphate (41% relative saturation) and 23.7% tert-butanol were used at 20 – 25°C. Using this two-liquid system, a characteristic distribution of three phases (including a semi-solid midlayer) was obtained for homogenates of eight different meats following centrifugation. Compressibility, expressed as a ratio of layer thickness obtained by low-speed (200 g) and medium-speed (4500 g) centrifugation, allowed us to distinguish between beef and pork drips. A good correlation was found between layer thickness and storage time for wild-boar samples. The partitioning presented here can be considered as a rapid and simple method for comparison between raw meat samples of different origin. Received: 9 July 1997 / Revised version: 1 October 1997     

Thermal analysis of 9977 radioactive material package

The 9977 package is a certified type B transportation packaging that was designed to transport radioactive materials with a decay heat load of up to 19?W. The packaging was recently modified to accommodate increased content heat load (up to 38?W) by employing an aluminium heat dissipating sleeve outside the containment vessel (CV), as well as an aluminium spacer inside the CV holding two 3013 containers. This paper provides highlights of thermal analyses of the modified 9977 package that were performed to evaluate its compliance with the 10 CFR 71 regulatory safety requirements. Parametric studies were also performed to examine effects of (i) surface properties, e.g. light absorptivity and emissivity, of the packaging; (ii) total decay heat loads, ranging from 18 to 38?W; and (iii) distribution of decay heat load inside the CV on the temperature of the Viton O-ring seal. The results of thermal analyses show that for the normal condition of transport with insolation, increasing absorptivity and decreasing emissivity increase the temperature of the O-ring; decreasing heat load decreases the temperature of the O-ring, whereas changing heat load distribution has little effect on the temperature of the O-ring. Likewise, changing the thermal conductivity of the spacer inside the CVhas little effect on the temperature of the O-ring. Briefly discussed is the possible extension of the annual maintenance interval of the 9977 package, based on previous work and the data obtained in the long-term leak performance tests conducted by the Savannah River National Laboratory.     

Two-step purification strategy for enhanced recovery of recombinant hepatitis B surface antigen from Pichia pastoris

Univariate screening on factors affecting the purification performance of recombinant hepatitis B surface antigen (HBsAg) on ion exchange chromatography (IEC) and size exclusion chromatography (SEC) and the establishment of a two-step purification strategy were performed. Amongst four IEC adsorbents examined, the use of Q Sepharose XL IEC adsorbent under optimized conditions together with optimized SEC purification was able to efficiently purify HBsAg. An established purification strategy comprising the two techniques further demonstrated adaptability for scale-up operations with a final total purification factor (PF) of 94.82 ± 16.20, HBsAg purity of 95.48% and recovery yield of 78.07%.     

Heat transfer and fluid flow of nanofluids in laminar radial flow cooling systems

Nanofluids are considered as interesting alternatives to conventional coolants. It is well known that traditional fluids have limited heat transfer capabilities when compared to common metals. It is therefore quite conceivable that a small amount of extremely fine metallic particles placed in suspension in traditional fluids will considerably increase their heat transfer performances. A numerical investigation into the heat transfer enhancement capabilities of coolants with suspended metallic nanoparticles inside a radial, laminar flow cooling configuration is presented. Temperature dependant nanofluid properties are evaluated from experimental data available in recent literature. Results indicate that considerable heat transfer increases are possible with the use of relatively small volume fractions of nanoparticles. Generally, however, these are accompanied by considerable increases in wall shear-stress. Results also show that predictions obtained with temperature variable nanofluid properties yield greater heat transfer capabilities and lower wall shear stresses when compared to predictions using constant properties.     

Low energy electron storage ring with tunable compaction factor

A low energy electron storage ring is designed to have many desirable properties, such as varying momentum compaction factor, damping partition numbers, favorable betatron tunes for multiturn accumulations, and excellent dynamic aperture. This storage ring can be used for debunching rf linac beams in one turn, for compression of linac pulses, and more importantly for a compact photon source based on inverse Compton scattering of laser beams.