The ATSC Digital Television System

The ATSC digital television standard describes a system designed to transmit high-quality video and audio, and ancillary data within a single 6-MHz terrestrial television broadcast channel. This paper outlines the overall architecture of the system and serves as an introduction to the papers that follow in this special issue of the Proceedings of the IEEE.     

Diffusion pathways of benzene, toluene and p-xylene in MFI

The diffusion of alkyl-substituted aromatic molecules in H-ZSM-5 was investigated by means of the frequency response method decoupling particle size effects and intracrystalline diffusion. For zeolite crystals above 5 μm average diameter, the transport in the zeolite pores exerts a significant effect on the overall transport causing anisotropic diffusion as the aspect ratio of the aromatic molecules increases. Diffusion of benzene is nearly isotropic, while p-xylene shows marked differences between the diffusive processes in the straight and sinusoidal channel system of ZSM-5. The isotropic diffusion of benzene is rationalized on the basis of its ability to reorient between the two channel systems without major hindrances. For p-xylene, switching between the channels is only possible by energetically unfavorable rotational motions leading to a low probability for changing between both channel systems.     

Sequential growths of AlN and GaN layers on as-polished 6H–SiC(0001) substrates

Microstructures of surfaces and defects generated during initial and subsequent growths via metalorganic vapor-phase epitaxy of AlN(0001) films on 6H–SiC(0001) substrates and GaN(0001) films on AlN/SiC(0001) substrates have been investigated using atomic force microscopy and cross-sectional and plan-view transmission electron microscopy. Scratches present on the SiC surfaces did not appear to bias the nucleation of AlN. The lateral growth rate of AlN was greater than the vertical growth rate, leading to almost planar layers at 15 and 100 nm thicknesses. Partially coalesced islands were observed after nominally ～15 nm of growth. Increasing the thickness to 100 nm resulted in complete island coalescence, formation of undulating films from the polishing scratches in the SiC substrate, a surface microstructure containing steps, terraces and small pits, and a reduced dislocation density relative to the 15 nm layers. The AlN/SiC interfaces contained steps and complex dislocation networks. GaN islands nucleated and grew on the AlN films. Complete coalescence of these islands occurred at thicknesses less than 100 nm. Dislocation density in the GaN films was reduced by increasing the thickness of either the AlN and or the GaN. Arguments are developed to account for these observations.     

The US HDTV standard

This standard for digital high-definition television has been submitted to the Federal Communications Commission for its approval. Based as it is on the MPEG-2 video compression and transport protocol, multiple transmission formats, Dolby AC-3 digital audio, and vestigial sideband digital modulation, this HDTV system will supply the home with superb images and spectacular sound while also, as part of the National Information Infrastructure (NII), relaying digital data. An HDTV system employing multiple transmission formats, digital compression, packetization, and modulation techniques is a marked advance over current world television standards such as NTSC, PAL, or SECAM     

Development of a polymerase chain reaction assay for detection of three canola transgenes

Many countries are developing or implementing regulatory requirements to monitor for the presence of genetically modified (GM) materials in seeds, grain, and derived food products using DNA and protein-based methods. There is no published report on the detection of different GM transgenes in canola, and this study is aimed at developing qualitative PCR methods for the three major GM transgenes commercially available in canola. Primer sequences were generated from Gen-Bank and previously published information to develop a polymerase chain reaction (PCR) detection method for Roundup Ready (glyphosate tolerance, GT73 event), Liberty Link (glufosinate ammonium tolerance, HCN92 event), and BX (Bromoxynil tolerance, OXY235 event) canola varieties. On using PCR, two primer pairs for each of the GT73 and HCN92 and one primer pair for OXY235 amplified specific amplicons for the three GM transgenes. All three GM transgenes were detected simultaneously by multiplexing the five primer pairs in a single PCR reaction. Multiplexing of the five primer pairs for DNA prepared at 1% (one GM seed in 99 non-GM seeds) and 0.5% (one GM seed in 199 non-GM seeds) levels generated the expected DNA fragments for GT73, HCN92, and OXY235. This information will lay the groundwork for the development of a quantitative PCR assay for canola transgenic events.     

Reduction of Escherichia coli O157:H7 counts on whole fresh apples by treatment with sanitizers

The objectives of this study were to determine if washing of whole apples with solutions of three different sanitizers (peroxyacetic acid, chlorine dioxide, or a chlorine-phosphate buffer solution) could reduce a contaminating nonpathogenic Escherichia coli O157:H7 population by 5 logs and at what sanitizer concentration and wash time such a reduction could be achieved. Sanitizers were tested at 1, 2, 4, 8, and 16 times the manufacturer's recommended concentration at wash times of 5, 10, and 15 min. Whole, sound Braeburn apples were inoculated with approximately 1 x 108 or 7 x 106 CFU per apple, stored for 24 h, then washed with sterile water (control) or with sanitizers for the prescribed time. Recovered bacteria were enumerated on trypticase soy agar. Washing with water alone reduced the recoverable population by almost 2 logs from the starting population; this can be attributed to physical removal of organisms from the apple surface. No sanitizer, when used at the recommended concentration, reduced the recovered E. coli population by 5 logs under the test conditions. The most effective sanitizer, peroxyacetic acid, achieved a 5-log reduction when used at 2.1 to 14 times its recommended concentration, depending on the length of the wash time. The chlorine-phosphate buffer solution reduced the population by 5 logs when used at 3 to 15 times its recommended concentration, depending on wash time. At no concentration or wash time tested did chlorine dioxide achieve the 5-log reduction.     

Processing of lipoxygenase-free soybeans and evaluation in foods

Lipoxygenase-free soybeans were processed into flour, concentrate, and isolate and compared to normal soybeans in bread, meat patties, and a beverage, respectively. Bread made with 20% normal or lipoxygenase-free soy flour had greater (P< 0.05) beany flavor than control yeast bread. There were no differences in beany flavor scores between soy flour types, normal and lipoxygenase-free. Ground beef patties made with 5% acid-washed or ethanol-washed soy protein concentrate had greater (P<0.05) beany flavor than control ground beef patties. Ground beef patties made with ethanol-washed concentrate were scored lower in beany flavor than those made with acid-washed concentrate from normal soybeans. There were no differences in beany flavor between normal and lipoxygenase-free soy isolate in 2%-fat or no-fat beverages. Comminuted meat products made with lipoxygenase-free soy proteins, especially ethanol-washed concentrate, have potential for making soy foods with less beany flavor than foods made with normal soy.