Two-dimensional metallic photonic band-gap crystals fabricated by LIGA

 Two-dimensional metallic photonic band-gap crystals, consisting of square and triangular lattices of nickel pillars, were fabricated by the LIGA process. In particular, PMMA slabs with a thickness of up to 800 μm were irradiated with synchrotron radiation and the holes produced were then filled with nickel via electroforming. The lattice constant, i.e., the center-to-center distance between the pillars, is either 60 μm or 40 μm for the square and triangular structures respectively. The metal filling ratio is 10% for the square and 20% for the triangular structures. Transmission and reflection measurements demonstrate that the metallic photonic band-gap crystals show a cutoff frequency in the far infrared regime between 2 and 5 THz. It is concluded that LIGA is a promising method for the fabrication of 2-D metallic photonic band-gap structures, which could be potentially used as passive filters in THz devices. Received: 10 August 2001/Accepted: 24 September 2001     

Continuous countercurrent vacuum bleaching

Summary The Votator continuous countercurrent vacuum bleaching system has been described and compared with older methods of bleaching. Data have been presented, comparing the performance of batch open kettle-, batch vacuum-, and continuous countercurrent vacuum-bleaching systems. These data indicate that the vacuum methods of bleaching result in a superior quality bleached oil with the use of less adsorbent. They also prove the value of countercurrent contacting of oil and adsorbent as practiced in the Votator system. The economic aspects of bleaching have been discussed, proving that the continuous countercurrent vacuum-bleaching system, due to its automatic operation, compactness, and savings in adsorbent operates at a considerably lower cost than either batch method. Data have been offered to show the qualitative advantages of vacuum-bleached oils over atmospheric-bleached oils.     

Activation of low dose silicon implants in GaAs by multiply scanned electron beams

Low dose implants of Si+ into semi-insulating GaAs have been annealed with the multiply scanned electron beam processing system. The activation of ions was about 55%, with a high peak concentration and a carrier mobility of 3800 cm2/Vs. The samples were unencapsulated and showed no surface degradation after annealing.     

Embossing of 3D ceramic microstructures

 An embossing method based on the viscous polymer processed (VPP) ceramic tape has been used to fabricate 3D ceramic microstructures with high aspect ratios. Examples of lead zirconate titanate (PZT) microrod arrays with feature sizes of 10–150 μm and aspect ratios of 3–10 have been demonstrated. Advantages of the embossing technique over conventional casting and moulding methods are discussed. Received: 10 August 2001/Accepted: 24 September 2001     

Dilatometric investigations of fats

Summary 1. Dilatometric curves have been determined over the complete melting range for samples of prime steam lard, oleo oil, all-hydrogenated vegetable shortening, and partially hydrogenated cottonseed oil. From the dilatometric data estimates have been made of the percentages of solids and liquid in the fats at different temperatures. 2. Estimates of the percentages of solids and liquid in the hydrogenated cottonseed oil agreed with those previously reported on the same oil from calorimetric data when allowance was made for a lack of equilibrium conditions in the calorimetric experiment. Since a condition of equilibrium between solids and liquid is attained in the dilatometer, this instrument is to be preferred to the calorimeter for determining the composition of fats in terms of the two phases. 3. The consistency of the fats, as measured by micropenetrations, was different for different fats which contained equal percentages of solids. The consistency, therefore, is not determined solely by the amount of solids present, but also by the character of the solid particles. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Molecular distillation of a hydrogenated cottonseed oil and certain characteristics of the distilled fractions

Summary 1. A hydrogenated cottonseed oil has been molecularly distilled, and the distilled fractions examined. 2. Fractionation of a molecularly distilled oil occurs, as is to be expected, on the basis of variations in molecular weight of the glycerides. The composition of cottonseed oil is such that there is a considerable separation of the glycerides according to their degree of unsaturation. The composition of peanut oil is such that similar separation can only be slight. Soybean oil is in this respect intermediate between cottonseed oil and peanut oil. 3. Molecular distillation of hydrogenated cottonseed oil causes a segregation of tocopherols and related compounds similar to that observed in peanut oil. However, the fractions first distilled from the oil are relatively weak in antioxygenic properties. It appears probable that their lack of effectiveness is due to the presence of unknown substances capable of inhibiting or counteracting the action of tocopherols. However, the presence of substances other than tocopherols, which respond to or interfere with the Emmerie-Engel test is not to be excluded. The tocopherols in the potent fractions are more effective thana-tocopherol, but less effective than γ-tocopherol. This is one of four regional research laboratories operated by the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.