Book reviews

Foley, James D., van Dam, Andrles, Feiner, Steven K., and Hughes, John. Computer Graphics: Principles and Practice (2nd Ed.), Reading, MA: Addison‐Wesley (1990), pp. 1774. $59.95 (U.S. dollars), ISBN 0–201–12110–7.

Berry, Dianne and Hart, Anna (Eds.). Expert Systems: Human Issues. Cambridge, MA: MIT Press (1990), pp. 263. $35.00 (U.S. dollars), ISBN 0–262–02307–5.     

A Review of “Dancing with Digital Natives: Staying in Step with the Generation That’s Transforming the Way Business is Done”

Abstract

A major initiative of the Sandia National Laboratories Technical Library is to provide desktop access to information for Sandia researchers. During 1995 the Library created a home page, with information about how to link to its client-server based OPAC. Through multiple access points Sandians can now search the catalog from their desks. A new and evolving initiative within Sandia Laboratories is to improve desktop access to Sandia-generated documents (full-text) by converting them to electronic form, placing them on Sandia's “internal Web,” and linking them to the OPAC bibliographic record, enabling desktop viewing and printing. This paper addresses the processes developed in the Library to accomplish the preceding activities. It also addresses procedures for cataloging these electronic reports, including identification of the bibliographic information and MARC tags to be used. Open issues and lessons learned are identified.     

A multiscale correlation of wavelet coefficients approach to spike detection

Extracellular chronic recordings have been used as important evidence in neuroscientific studies to unveil the fundamental neural network mechanisms in the brain. Spike detection is the first step in the analysis of recorded neural waveforms to decipher useful information and provide useful signals for brain-machine interface applications. The process of spike detection is to extract action potentials from the recordings, which are often compounded with noise from different sources. This study proposes a new detection algorithm that leverages a technique from wavelet-based image edge detection. It utilizes the correlation between wavelet coefficients at different sampling scales to create a robust spike detector. The algorithm has one tuning parameter, which potentially reduces the subjectivity of detection results. Both artificial benchmark data sets and real neural recordings are used to evaluate the detection performance of the proposed algorithm. Compared with other detection algorithms, the proposed method has a comparable or better detection performance. In this letter, we also demonstrate its potential for real-time implementation.     

Channelling effects in atomic resolution STEM

A Bloch wave theory for incoherent scattering of an incident plane wave has proved successful in predicting the fine detail in 2-D zone axis channelling patterns formed by ADF, BSE and characteristic X-ray detection in beam rocking mode. A previously published example of polarity determination of GaAs by channelling contrast is compared with simulations in order to illustrate the applicability of the theory. Modification of boundary conditions for a focused coherent probe allows lattice-resolution incoherent contrast based on ADF and EELS detection as well as X-ray emissions to be catered for within a similar theoretical framework. Mixed dynamic form factors constitute an integral part of this theory, where quantum-mechanical phase is a core issue. Simulations of lattice-resolution ADF and EELS are discussed with reference to various zone axis projections of GaAs. Issues of single versus double channelling conditions, and local versus nonlocal interactions, are discussed in relation to X-ray, ADF and EELS detection.     

Microwave-assisted proteomics

State-of-the-art proteomic analysis has recently undergone a rapid evolution; with more high-throughput analytical instrumentation and informatic tools available, sample preparation is becoming one of the rate-limiting steps in protein characterization workflows. Recently several protocols have appeared in the literature that employ microwave irradiation as a tool for the preparation of biological samples for subsequent mass spectrometric characterization. Techniques for microwave-assisted bio-catalyzed reactions (including sample reduction and alkylation, enzymatic and chemical digestion, removal and analysis of post-translational modifications and characterization of enzymes and protein-interaction sites) are described. This review summarizes the various approaches undertaken, instrumentation employed, and reduction in overall experimental time observed when microwave assistance is applied.     

Exit wave reconstruction at atomic resolution

An iterative method for exit wave function reconstruction based on wave function propagation in free space is presented. The method, which has the potential for application to many forms of microscopy, has been tailored to work with a through focal series of images measured in a high-resolution transmission electron microscope. Practical difficulties for exit wave reconstruction which are pertinent in this experimental environment are the slight incoherence of the electron beam, sample drift and its effect upon the defocus step size that can be utilised, and the number of image measurements that need to be made. To gauge the effectiveness of the method it is applied to experimental data that has been analysed previously using a maximum likelihood formalism (the MAL method).     

Structure determination at the atomic level from dynamical electron diffraction data under systematic row conditions.

We discuss a method to obtain structural information on crystals at the atomic level in high-resolution transmission electron microscopy from dynamical diffraction data under systematic row conditions. Working at a fixed incident energy and within an N-beam approximation, data is required at a well defined set of N incident beam orientations to determine the scattering matrix, one orientation for each column in the matrix. At each orientation the corresponding column of the scattering-matrix is obtained by Fourier transformation of the exit surface wave function. Thus, in addition to each exit surface image, we must recover the phase of the wave function for that orientation in the image plane. We show that retrieval of the phase using algorithms based on conservation of flux, which assume continuity of the phase, can yield incorrect solutions for the phase. This is because singularities can occur in the phase of the wave field at points where the intensity is zero, which can lead to edge dislocations in the phase. We demonstrate, using a model example, how these edge dislocations arise. We will show that phase retrieval from a through focal series of measurements or using the Gerchberg-Saxton algorithm (starting from measurements of an image and the corresponding diffraction pattern), correctly retrieves the phase and hence the exit surface wave function for all the orientations required to obtain the scattering-matrix. The dynamical (multiple) scattering can then be inverted to uniquely obtain the projected potential.     

PREDICTION OF CUTTING FORCES IN MACHINING WITH RESTRICTED CONTACT TOOLS

Abstract

A semi-empirical method is described for predicting cutting forces in orthogonal machining with restricted contact tools. The method uses a well-established machining theory to predict cutting forces and tool-chip contact length for the corresponding plane face tool, i.e., a tool having the same cutting-edge geometry but no restricted contact. These predicted parameters and a set of empirical relations are then used to calculate the cutting forces for the restricted contact tool. A comparison between predicted and experimental results for two plain carbon steel work materials and a range of tool geometries and cutting conditions shows good agreement.     

Quantitative Isotopomer Rates in Real-Time Metabolism of Cells Determined by NMR Methods

Tracer-based metabolism is becoming increasingly important for studying metabolic mechanisms in cells. NMR spectroscopy offers several approaches to measure label incorporation in metabolites, including ¹³C- and ¹H-detected spectra. The latter are generally more sensitive, but quantification depends on the proton–carbon ¹J_CH coupling constant, which varies significantly between different metabolites. It is therefore not possible to have one experiment optimised for all metabolites, and quantification of ¹H-edited spectra such as HSQCs requires precise knowledge of coupling constants. Increasing interest in tracer-based and metabolic flux analysis requires robust analyses with reasonably small acquisition times. Herein, we compare ¹³C-filtered and ¹³C-edited methods for quantification and show the applicability of the methods for real-time NMR spectroscopy of cancer-cell metabolism, in which label incorporations are subject to constant flux. We find an approach using a double filter to be most suitable and sufficiently robust to reliably obtain ¹³C incorporations from difference spectra. This is demonstrated for JJN3 multiple myeloma cells processing glucose over 24 h. The proposed method is equally well suited for calculating the level of label incorporation in labelled cell extracts in the context of metabolic flux analysis.     

Ammonium perchlorate decomposition: Neat and solution1

Abstract

The thermal decomposition of ammonium perchlorate (AP) was examined over a broad temperature range (215°C to 385°C) in solution and condensed phase. Over the entire temperature range, the decomposition, as monitored by loss of ammonium ion, appeared first-order out to 70% decomposition. Up to about 350°C the decomposition of AP in methanol (5wt% AP) proceeded at a rate similar to neat AP, but the AP in aqueous solution (20wt%) decomposed considerably slower than the neat material. Activation energies and frequency factors were determined for each experimental condition. In addition, decomposition products, both gaseous and condensed phase, were identified and quantified. For neat AP decomposition, the following reaction stoichiometries were determined.

At low temperatures, decomposition of ammonium perchlorate in methanol proceeded at a similar rate to that of neat AP. In contrast to decomposition of neat AP, the only nitrogen-containing decomposition product was nitrogen gas, while chlorine appeared only as chloride. The presence of CO and CO₂ as decomposition gases and chromatographic analysis of the solvent indicated interaction between methanol and AP. The decomposition of AP in water was slowed, but product distribution was not significantly different than that of neat AP.