A mixed-signal RAM decision-feedback equalizer for disk drives

A mixed-signal RAM decision-feedback equalizer (DFE) that operates at 90 Mb/s is described. In the analog domain, the DFE subtracts intersymbol interference caused by the past four outputs. The equalized signal is fed into a nonuniform flash analog-to-digital converter (ADC) to produce the decision output and error signal used to adapt the RAM contents in the digital domain. With a 5 V supply voltage, the power dissipation is 260 mW during steady-state operation. The active area is 4.5 mm² in a 1 μm CMOS process     

Diode-Pumped Solid-State Lasers for Inertial Fusion Energy

We have begun building the Mercury laser system as the first in a series of new generation diode-pumped solid-state lasers for inertial fusion research. Mercury will integrate three key technologies: diodes, crystals, and gas cooling, within a unique laser architecture that is scalable to kilojoule and megajoule energy levels for fusion energy applications. The primary near-term performance goals include 10% electrical efficiencies at 10 Hz and 100J with a 2–10 ns pulse length at 1.047 m wavelength. When completed, Mercury will allow rep-rated target experiments with multiple chambers for high energy density physics research.     

A model for pattern perception with musical applications part II: The information content of pitch structures

This is the second paper of a series which begins by treating the perception of pitch relations in musical contexts and the perception of timbre and speech. The first paper discusses in some detail those properties of musical scales required in order for them to function as reference frames which provide for the measurement of intervals such that ([1], p. 270),Every melodic phrase, every chord, which can be executed at any pitch, can be also executed at any other pitch in such a way that we immediately perceive the characteristic marks of their similarity. Here we continue this discussion by developing quantitative measures of the degree to which different scales possess the above properties. Then that property of musical scales which permits a listener to code the pitches of which it is constituted into degrees is examined and a corresponding quantitative measure developed. Musical scales are shown to be optimal choices with respect to both the former and latter measures, and a theory limiting those scales which are musically useful to a small fraction of possible sets of pitches is proposed. Existing scales which have been examined fall within the theory, which links the techniques of composition which may be used (i.e., those which produce perceptible relations between musical segments) to the above properties of the scale structures. This paper is not self-contained—reading of the previous paper in this series is required.This research was supported in part by grants and contracts AF-AFOSR 881-65, AF 49(638)-1738 and AF-AFOSR 68-1596.     

Changes in the microbiological and shelf-life characteristics of beef tongues and livers following transcontinental and transoceanic shipment

The effects of transcontinental (interstate) transport and transoceanic shipment were determined on microbiological and shelf-life characteristics of beef tongues and livers. These variety meats were evaluated for both microbiological and shelf-life characteristics following slaughter in Guymon, Oklahoma, USA. The samples were then frozen and sent by refrigerated truck (4·5°C) to storage facilities in Jacksonville, Florida, USA. Further microbiological and shelf-life evaluations took place prior to overseas shipment at the University of Florida and following overseas shipment at The Institute CIVO-Technology, TNO, Zeist, The Netherlands. Aerobic plate counts (APCs) at 35°C for beef tongues showed a significant (P < 0·0.5) decrease following overseas shipment. Similar results were noted for beef livers. For both organs, the surface thawing in Florida, required for sampling, did not appear to affect the final bacterial counts. The 20°C APCs for beef tongues revealed a significant (P < 0·0.5) decrease following interstate transport but not transoceanic shipment. The 20°C APCs for beef livers did not differ significantly during the entire transportation period. The colour differences noted during transport of the product were probably the result of freezing and not of the actual shipping and storage conditions.     

Ultrafast picket fence pulse trains to enhance frequency conversion of shaped inertial confinement fusion laser pulses

A high-frequency train of 5-100-ps pulses (picket fence) is proposed to improve significantly the third-harmonic frequency conversion of Nd:glass lasers that are used to generate high-contrast-shaped pulses for inertial confinement fusion (ICF) targets. High conversion efficiency of the low-power foot of a shaped ICF pulse is obtained by use of a low duty cycle, multi-gigahertz train of ~20-ps pulses with high peak power. Even with less than 10% duty cycle, continuous illumination is maintained on the target by a combination of temporal broadening schemes. The picket fence approach is analyzed, and the practical limits are identified as applied to the National Ignition Facility laser. It is found that the higher conversion efficiency allows ~40% more third-harmonic energy to be delivered to the target, potentially enabling the larger drive needed for high-yield ICF target designs. In addition, the frequency conversion efficiency of these short pulses saturates much more readily, which reduces the transfer of fluctuations at the fundamental and thus greatly improves the power stability of the third harmonic.     

Model selection and optimal sampling in high-throughput experimentation

The practical difficulties encountered in analyzing the kinetics of new reactions are considered from the viewpoint of the capabilities of state-of-the-art high-throughput systems. There are three problems. The first problem is that of model selection, i.e., choosing the correct reaction rate law. The second problem is how to obtain good estimates of the reaction parameters using only a small number of samples once a kinetic model is selected. The third problem is how to perform both functions using just one small set of measurements. To solve the first problem, we present an optimal sampling protocol to choose the correct kinetic model for a given reaction, based on T-optimal design. This protocol is then tested for the case of second-order and pseudo-first-order reactions using both experiments and computer simulations. To solve the second problem, we derive the information function for second-order reactions and use this function to find the optimal sampling points for estimating the kinetic constants. The third problem is further complicated by the fact that the optimal measurement times for determining the correct kinetic model differ from those needed to obtain good estimates of the kinetic constants. To solve this problem, we propose a Pareto optimal approach that can be tuned to give the set of best possible solutions for the two criteria. One important advantage of this approach is that it enables the integration of a priori knowledge into the workflow.     

Synthesis and size-dependent properties of zinc-blende semiconductor quantum rods

Dimensionality and size are two factors that govern the properties of semiconductor nanostructures. In nanocrystals, dimensionality is manifested by the control of shape, which presents a key challenge for synthesis. So far, the growth of rod-shaped nanocrystals using a surfactant-controlled growth mode, has been limited to semiconductors with wurtzite crystal structures, such as CdSe (ref. 3). Here, we report on a general method for the growth of soluble nanorods applied to semiconductors with the zinc-blende cubic lattice structure. InAs quantum rods with controlled lengths and diameters were synthesized using the solution-liquid-solid mechanism with gold nanocrystals as catalysts. This provides an unexpected link between two successful strategies for growing high-quality nanomaterials, the vapour-liquid-solid approach for growing nanowires, and the colloidal approach for synthesizing soluble nanocrystals. The rods exhibit both length- and shape-dependent optical properties, manifested in a red-shift of the bandgap with increased length, and in the observation of polarized emission covering the near-infrared spectral range relevant for telecommunications devices.     

Librarian driven analysis with graphic user interface for nuclides quantification by gamma spectra

For a set of a priori given radionuclides extracted from a general nuclide data library, the authors use median estimates of the gamma-peak areas and estimates to produce a list of possible radionuclides matching gamma-ray line(s). An a priori determined list of nuclides is obtained by searching for a match with the energy information of the database. This procedure is performed in an interactive graphic mode by markers that superimpose, on the spectral data, the energy information and yields provided by a general gamma-ray data library. This library of experimental data includes approximately 17,000 gamma-energy lines related to 756 known gamma emitter radionuclides listed by ICRP.