Image coding by multistep, adaptive flux interpolation

The authors describe and discuss the new technique, multistep adaptive flux interpolation (MAFI), and its application to image data for coding. When applied to an image, MAFI produces an output which is also in an image form, but which has a more uniform feature density and a greatly reduced size. MAFI warps the input image by removing those rows and columns which contain a majority of redundant pixels. The side information required for reconstruction is minimal, and the image can be further compressed using conventional coders, making the compression ratio even higher. Because of its warped nature, the MAFI output's statistics are also more consistent with the properties assumed by block-based discrete cosine transform (DCT) methods     

Advantages of CDMA and spread spectrum techniques over FDMA andTDMA in cellular mobile radio applications

A unified theoretical method for the calculation of the radio capacity of multiple-access schemes such as FDMA (frequency-division multiple access), TDMA (time-division multiple access), CDMA (code-division multiple access) and SSMA (spread-spectrum multiple access) in noncellular and cellular mobile radio systems is presented for AWGN (additive white Gaussian noise) channels. The theoretical equivalence of all the considered multiple-access schemes is found. In a fading multipath environment, which is typical for mobile radio applications, there are significant differences between these multiple-access schemes. These differences are discussed in an illustrative manner revealing several advantages of CDMA and SSMA over FDMA and TDMA. Novel transmission and reception schemes called coherent multiple transmission and coherent multiple reception are briefly presented     

Application of Raman Spectroscopy to Retinal Proteins

Raman spectroscopic studies on photoreactive retinal proteins are comprehensively described, including the basic physics of Raman scattering and illustrative examples of the types of information on the structure and function of the retinal chromophore and its environment which can be obtained from the vibrational Raman spectra. In addition, practical advice and recipes are given which should enable the reader to plan and eventually perform a Raman experiment in a photolabile retinal protein. A dominant role is played by the resonance Raman (RR) experiment with visible laser excitation which selectively probes the retinal chromophore. Much discussion is devoted to bacteriorhodopsin (bR) and its photocycle as a paradigm for a light-induced reaction of a retinal protein. Various time-resolved techniques are described to study the temporal evolution of the bR chromophore by probing RR spectra of intermediate states. Vibrational Raman spectra are interpreted in terms of structure and structural changes of the chromophore. RR spectroscopic studies on halorhodopsin, sensory rhodopsin, and visual pigments are reported, as well as on modified proteins in which retinal analogues are incorporated, and on site-specific mutants. Results of ultraviolet RR experiments which selectively probe the aromatic side chains in the protein backbone are reported. In addition, a promising new technique of near-infrared Raman excitation is discussed. Finally, application of coherent anti-Stokes Raman spectroscopy (CARS) to retinal proteins is reported.     

Dynamic programming implementation on array processor architectures

Dynamic Programming (DP) applies to many signal and image processing applications including boundary following, the Viterbi algorithm, dynamic time warping, etc. This paper presents an array processor implementation of generic dynamic programming. Our architecture is a SIMD array attached to a host computer. The processing element of the architecture is based on an ASIC design opting for maximum speed-up. By adopting a torus interconnection network, a dual buffer structure, and a multilevel pipeline, the performance of the DP chip is expected to reach the order of several GOPS. The paper discusses both the dedicated hardware design and the data flow control of the DP chip and the total array.This work was supported in part by the NATO, Scientific and Environmental Affairs Division, Collaborative Research Grant SA.5-2-05(CRG.960201)424/96/JARC-501.     

Self-starting, passively mode-locked Fabry-Perot fiber solitonlaser using nonlinear polarization evolution

The authors demonstrate pure self-starting mode-locked operation in a fiber Fabry-Perot cavity. The laser produces 1.6 ps transform-limited soliton pulses by means of nonlinear polarization evolution in conjunction with an intracavity fiber polarizer. This laser system can be used for the generation and study of soliton pulses in the picosecond regime. With a careful choice of the fiber dispersion and fiber length, the system should also be able to operate in the femtosecond regime. The advantage of the system over existing self-starting fiber soliton lasers is that an optical isolator (an expensive component) is not required. The replacement of the two mirrors with fiber reflection gratings would make this configuration a truly all-fiber device     

The Deposition of Cubic Boron Nitride Fillms by Ion Beam Assisted Sputter Deposition

The relationship between film properties and assisting ion beam parameters such as the ion-to-atom arrival ratio, the mean energy transfer or the mean momentum transfer to a depositing atom has been established with a new method. We have made use of a focused assisting ion beam which generates zones of locally varying current densities on the film surface. By mapping these and the deposition rate, and measuring film properties as function of surface coordinates, we can determine their relationship from few samples. The: advantage is that the number of deposition runs can considerably be reduced, and errors can be avoided which may originate from slightly different deposition conditions (pressure, temperature, gas flow etc.) in different deposition runs.

This method has been applied to establish the relationship between the cubic phase formation of a boron nitride film and various assisting beam parameters. The BN films were characterized by transmission FTIR spectroscopy. The spectra were evaluated by fitting the absorption lines to Gaussian functions. The experiments show that the momentum transferred to a depositing atom is the relevant control parameter for the formation of the cubic phase and that a threshold exists at 250 (eV.amu)^1/2 above which the cubic phase is synthesized in accordance with results obtained by Kester and Messier. Below this threshold a small fraction of c-BN was also observed.     

Nanocrystalline iron sintering behavior and microstructural development

Nanocrystalline (20 nm) iron powder was closed-die sintered in a hydrogen atmosphere at a stress of 10.1 MPa and at temperatures between 670 and 1270 K. The maximum densification rate was approximately 6 × 10⁻⁴ s⁻¹. Density greater than 90 pct was obtained at sintering temperatures greater than 990 K. Densification was marked microstructurally by local gradients which appeared after initial cold compaction. Oxygen content in the starting powder was high but was effectively a monolayer of surface adsorbed oxygen. Despite the reducing sintering atmosphere, oxide was present in dense specimens as a fine dispersion of order 0.1 to 1μm. The extent of oxide formation can be controlled by closed-die sintering to a stable structure of interconnected porosity followed by open-die resintering in the reducing atmosphere. Final grain size in material sintered 1 hour at 1080 K was generally less than 200 nm, although scattered coarsening to approximately 5 μm was observed.     

QDA-a method for systematic informal program analysis

Formal verification of program properties may be infeasible or impractical, and informal analysis may be sufficient. Informal analysis involves the informal acceptance, by inspection, of the validity of program properties or steps in an analysis. Informal analysis may also involve abstraction. Abstraction can be used to eliminate details and concentrate on more general properties. Abstraction will result in informal analysis if it includes the use of undefined properties. A systematic, informal method for analysis called QDA (Quick Defect Analysis) is described. QDA is a comments analysis process based on facts and hypotheses. Facts are used to create an abstract program model, and hypotheses are selected, nonobvious program properties which are identified as needing verification. Hypotheses are proved from the facts that define an abstraction. QDA is hypothesis-driven in the sense that only those parts of an abstraction that are needed to prove hypotheses are created. The QDA approach was applied to a previously well tested operational flight program (OFP). The QDA method and the results of the OFP experiment are presented. The problems of incomplete or unsound informal analysis are analyzed, the relationship of QDA to other analysis methods is discussed, and suggested improvements to the QDA method are described     

Studies on the action of interleukin-1 on term human fetal membranes and decidua

The present study describes the development of an enzyme-linked immunosorbent assay capable of quantifying serum antibody of all four canine IgG subclasses. A panel of subclass-restricted and subclass-specific monoclonal antibodies was used to measure IgG subclasses in the serum of healthy dogs, as well as in dogs with a range of clinical diseases. The subclasses have been redefined as IgG1, IgG2, IgG3 and IgG4 based on a comparison with the relative concentration and electrophoretic mobilities of human IgG subclasses. In serum samples from healthy dogs, the concentration of IgG1 (mean, 8.17 +/- 0.95 mg ml-1) and IgG2 (mean, 8.15 +/- 3.16 mg ml-1) were very similar and considerably higher than the levels of IgG3 (mean, 0.36 +/- 0.43 mg ml-1) and IgG4 (mean, 0.95 +/- 0.45 mg ml-1). There was no apparent difference in the level of subclasses between the different breeds comprising this normal population. Sera from dogs with a range of immune-mediated or inflammatory diseases all had markedly elevated levels of IgG2 (more than 13 mg ml-1), but IgG1 decreased (less than 4 mg ml-1) to levels below the normal range.