National Materials and Minerals Policy, Research, and Development Act of 1980 [microform] : hearing before the Committee on Science and Technology, U.S. House of Representatives, Ninety-seventh Congress, first session, July 28, 1981.

"No. 44."

Preliminary reports, memoranda and technical notes of the Materials Research Council Summer Conference

Mode of access: Internet.

Proceedings - American Society for Testing and Materials

Mode of access: Internet.

Scientific materials blue book; equipment and supplies for chemical, metallurgical and biological laboratories

Mode of access: Internet.

Measuring geometric phases of scattering states in nanoscale electronic devices

We show how a quantum property, a geometric phase, associated with scattering states can be exhibited in nanoscale electronic devices. We propose an experiment to use interference to directly measure the effect of this geometric phase. The setup involves a double-path interferometer, adapted from that used to measure the phase evolution of electrons as they traverse a quantum dot (QD). Gate voltages on the QD could be varied cyclically and adiabatically, in a manner similar to that used to observe quantum adiabatic charge pumping. The interference due to the geometric phase results in oscillations in the current collected in the drain when a small bias across the device is applied. We illustrate the effect with examples of geometric phases resulting from both Abelian and non-Abelian gauge potentials.

Population inversion of a driven two-level system in a structureless bath

We derive a master equation for a driven double quantum dot damped by an unstructured phonon bath, and calculate the spectral density. We find that bath-mediated photon absorption is important at relatively strong driving, and may even dominate the dynamics, inducing population inversion of the double-dot system. This phenomenon is consistent with recent experimental observations.

Simple microcavity for single-photon generation

A new design of an optical resonator for generation of single-photon pulses is proposed. The resonator is made of a cylindrical or spherical piece of a polymer squeezed between two flat dielectric mirrors. The mode characteristics of this resonator are calculated numerically. The numerical analysis is backed by a physical explanation. The decay time and the mode volume of the fundamental mode are sufficient for achieving more than 96% probability of generating a single-photon in a single-mode. The corresponding requirement for the reflectivity of the mirrors (similar to 99.9%) and the losses in the polymer ( 100 dB/m) are quite modest. The resonator is suitable for single-photon generation based on optical pumping of a single quantum system such as an organic molecule, a diamond nanocrystal, or a semiconductor quantum dot if they are imbedded in the polymer. (C) 2005 Optical Society of America.

Analysis of stroke patients' and carers' reading ability and the content and design of written materials: Recommendations for improving written stroke information

Objective: This study (a) evaluated the reading ability of patients following stroke and their carers and the reading level and content and design characteristics of the written information provided to them, (b) explored the influence of sociodemographic and clinical characteristics on patients' reading ability, and (c) described an education package that provides well-designed information tailored to patients' and carers' informational needs. Methods: Fifty-seven patients and 12 carers were interviewed about their informational needs in an acute stroke unit. Their reading ability was assessed using the Rapid Estimate of Adult Literacy in Medicine (REALM). The written information provided to them in the acute stroke unit was analysed using the SMOG readability formula and the Suitability Assessment of Materials (SAM). Results: Thirteen (22.8%) patients and 5 (41.7%) carers had received written stroke information. The mean reading level of materials analysed was 11th grade while patients read at a mean of 7-8th grade. Most materials (89%) scored as only adequate in content and design. Patients with combined aphasia read significantly lower (4-6th grade) than other patients (p = 0.001). Conclusion: Only a small proportion of patients and carers received written materials about stroke and the readability level and content and design characteristics of most materials required improvement. Practice implications: When developing and distributing written materials about stroke, health professionals should consider the reading ability and informational needs of the recipients, and the reading level and content and design characteristics of the written materials. A computer system can be used to generate written materials tailored to the informational needs and literacy skills of patients and carers. (c) 2005 Elsevier Ireland Ltd. All rights reserved.

An investigation of the mechanics of wire drawing with the superposition of an oscillatory drawing stress

A number of investigators have studied the application of oscillatory energy to a metal undergoing plastic deformation. Their results have shown that oscillatory stresses reduce both the stress required to initiate plastic deformation and the friction forces between the tool and workpiece. The first two sections in this thesis discuss historically and technically the devolopment of the use of oscillatory energy techniques to aid metal forming with particular reference to wire drawing. The remainder of the thesis discusses the research undertaken to study the effect of applying longitudinal oscillations to wire drawing. Oscillations were supplied from an electric hydraulic vibrator at frequencies in the range 25 to 500 c/s., and drawing tests were performed at drawing speeds up to 50 ft/m. on a 2000 lbf. bull-block. Equipment was designed to measure the drawing force, drawing torque, amplitude of die and drum oscillation and drawing speed. Reasons are given for selecting mild steel, pure and hard aluminium, stainless steel and hard copper as the materials to be drawn, and the experimental procedure and calibration of measuring equipment arc described. Results show that when oscillatory stresses are applied at frequencies within the range investigated : (a) There is no reduction in the maximum drawing load. (b) Using sodium stearate lubricant there is a negligible reduction in the coefficient of friction between the die and wire. (c) Pure aluminium does not absorb sufficient oscillatory energy to ease the movement of dislocations. (d) Hard aluminium is not softened by oscillatory energy accelerating the diffusion process. (e) Hard copper is not cyclically softened. A vibration analysis of the bull-block and wire showed that oscillatory drawiing in this frequency range, is a mechanical process of straining; and unstraining the drawn wire, and is dependent upon the stiffness of the material being drawn and the drawing machine. Directions which further work should take are suggested.

A rationale for the optimisation by computer methods of the efficient use of metals and materials

The aim of the research project was to gain d complete and accurate accounting of the needs and deficiencies of materials selection and design data, with particular attention given to the feasibility of a computerised materials selection system that would include application analysis, property data and screening techniques. The project also investigates and integrates the three major aspects of materials resources, materials selection and materials recycling. Consideration of the materials resource base suggests that, though our discovery potential has increased, geologic availability is the ultimate determinant and several metals may well become scarce at the same time, thus compounding the problem of substitution. With around 2- to 20- million units of engineering materials data, the use of a computer is the only logical answer for scientific selection of materials. The system developed at Aston is used for data storage, mathematical computation and output. The system enables programs to be run in batch and interactive (on-line) mode. The program with modification can also handle such variables as quantity of mineral resources, energy cost of materials and depletion and utilisation rates of strateqic materials. The work also carries out an in-depth study of copper recycling in the U.K. and concludes that, somewhere in the region of 2 million tonnes of copper is missing from the recycling cycle. It also sets out guidelines on product design and conservation policies from the recyclability point of view.

Optical linewidth of a passively mode-locked semiconductor laser

We measured the optical linewidths of a passively mode-locked quantum dot laser and show that, in agreement with theoretical predictions, the modal linewidth exhibits a parabolic dependence with the mode optical frequency. The minimum linewidth follows a Schawlow-Townes behavior with a rebroadening at high power. In addition, the slope of the parabola is proportional to the RF linewidth of the laser and can therefore provide a direct measurement of the timing jitter. Such a measurement could be easily applied to mode-locked semiconductor lasers with a fast repetition rate where the RF linewidth cannot be directly measured.

Decoherence of charge qubit coupled to interacting background charges

The major contribution to decoherence of a double quantum dot or a Josephson-junction charge qubit comes from the electrostatic coupling to fluctuating background charges hybridized with the conduction electrons in the reservoir. However, estimations according to previously developed theories show that finding a sufficient number of effective fluctuators in a realistic experimental layout is quite improbable. We show that this paradox is resolved by allowing for a short-range Coulomb interaction of the fluctuators with the electrons in the reservoir. This dramatically enhances both the number of effective fluctuators and their contribution to decoherence, resulting in the most dangerous decoherence mechanism for charge qubits.

Bistable regimes in an optically injected mode-locked laser

We study experimentally the dynamics of quantum-dot (QD) passively mode-locked semiconductor lasers under external optical injection. The lasers demonstrated multiple dynamical states, with bifurcation boundaries that depended upon the sign of detuning variation. The area of the hysteresis loops grew monotonically at small powers of optical injection and saturated at moderate powers. At high injection levels the hysteresis decreased and eventually disappeared.

Stabilization of a passively mode-locked laser by continuous wave optical injection

We investigate numerically and experimentally the properties of a passively mode locked quantum dot semiconductor laser under the influence of cw optical injection. We demonstrate that the waveform instability at high pumping for these devices can be overcome when one mode of the device is locked to the injected master laser and additionally show spectral narrowing and tunability. Experimental and numerical analyses demonstrate that the stable locking boundaries are similar to these obtained for optical injection in CW lasers. © 2010 American Institute of Physics.

Mode-locked semiconductor lasers with optical injection

We perform characterization of the pulse shape and noise properties of quantum dot passively mode-locked lasers (PMLLs). We propose a novel method to determine the RF linewidth and timing jitter, applicable to high repetition rate PMLLs, through the dependence of modal linewidth on the mode number. Complex electric field measurements show asymmetric pulses with parabolic phase close to threshold, with the appearance of waveform instabilities at higher currents. We demonstrate that the waveform instabilities can be overcome through optical injection-locking to the continues wave (CW) master laser, leading to time-bandwidth product (TBP) improvement, spectral narrowing, and spectral tunability. We discuss the benefits of single- and dual-tone master sources and demonstrate that dual-tone optical injection can additionally improve the noise properties of the slave laser with RF linewidth reduction below instrument limits (1 kHz) and integrated timing jitter values below 300 fs. Dual-tone injection allowed slave laser repetition rate control over a 25 MHz range with reduction of all modal optical linewidths to the master source linewidth, demonstrating phase-locking of all slave modes and coherence improvement.