Quantum-Cascade Lasers Generating at the 4.8-μm Wavelength at Room Temperature

We report on room-temperature generation at the 4.8-μm wavelength in a lattice-matched structure of a quantum cascade laser (QCL) grown on indium phosphide (InP) substrate. Laser heterostructures grown by molecular beam epitaxy (MBE) comprised 30 cascades and were designed to generate at the 4.80 μm wavelength corresponding to an atmospheric transparency window. Experiments demonstrated effective lasing at temperatures from 80 to 300 K on a wavelength coinciding with the calculated value, which confirmed the high quality of interfaces, high precision of layer thicknesses, and high accuracy of active region doping.     

Micromachinery rolling at last?

Suggestions that we are on the verge of a second industrial revolution, based on microsystems technology (MST), are apt to leave many of us unmoved. After all, the prospect of tiny machines, less than a hairsbreadth in dimension, that can go to work in optical systems, conventional and RF electronics, a wide range of sensors, robotics, or even our own bodies, has been dangled before us for decades. Yet there are signs that microelectromechanical systems (MEMS) might, at last, be about to take off. Could it be that these barely perceptible (to the human eye) syntheses of microelectronics with micromechanics are finally poised to make a big commercial impact?Market projections are increasingly bullish. For example, a survey by Europe’s Network of Excellence in Multifunctional Microsystems (NEXUS) suggests a world market of $68 billion by 2005, more than double the level of two years ago (Fig. 1

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Fig. 1. This NEXUS graph shows that total world market for microsystems is expected to grow from $30 billion in the year 2000 to $68 billion by the year 2005.

). NEXUS had to revise earlier projections because of runaway successes like that of the optical mouse (Agilent Technologies recently shipped its 50 millionth), an anticipated breakthrough later in the period for microoptoelectromechanical systems (MOEMS), enhanced prospects for RF switching systems, and the possible emergence of a market in domestic appliances. Analyst Venture Development Corporation goes further, concluding that the market will grow ‘exponentially’ for the next ten years. The first device to exceed $1 billion in sales is expected to be MEMS-based photonic switches, within about two years. Current breadwinning applications — desktop ink-jet printers, biomedical pressure sensors/systems, and automotive devices — continue to thrive.     

Neutron Scattering at Highest Magnetic Fields at the Helmholtz Centre Berlin

The Helmholtz Centre Berlin (HZB), formerly Hahn-Meitner Institute is a user facility for the study of structure and dynamics with neutrons and synchrotron radiation with special emphasis on experiments under extreme conditions. Neutron scattering is uniquely suited to study magnetic properties on a microscopic length scale, because neutrons have comparable wavelengths and, due to their magnetic moment, they interact with the atomic magnetic moments. At HZB a dedicated instrument for neutron scattering at extreme fields is under construction, the Extreme Environment Diffractometer ExED. It is projected according to the “time-of-flight” principle for elastic and inelastic neutron scattering and for the special geometric constraints of analysing samples in a high field magnet. The new magnet will not only allow for novel experiments, it will be at the forefront of development in magnet technology itself. The design of the magnet will follow the Series Connected Hybrid System Technology (SCH) developed at the National High Magnetic Field Laboratory (NHMFL) in Tallahassee, Florida. To compromise between the needs of the magnet design for highest fields and the concept of the neutron instrument, the magnetic field will be generated by means of a coned solenoid with horizontal field orientation. By using resistive insert coils, which are mounted in the room temperature bore of a superconducting cable-in-conduit (CIC) magnet, fields above 30 Tesla can be obtained in a geometry optimised for the demands of neutron scattering.     

Friction of Alloys at High Temperature

A brief review is given about the friction and wear properties of high temperature alloys. Above a critical temperature, if the oxide becomes ductile, it will flow over the surface and prevent metal-to-metat contact. In order to study the tribology of oxide lubrication. a series of tests were carried out using Cu(ReO4)2 as a lubricant. The effects of time. Surface finish. substrates. load and temperature were investigated. A mechanism of lubrication is proposed in which the surface slip predominates along with mechanical attachment of oxide to the surface.     

Reduction of Stibnite at Moderate Temperature

Reduction of stibnite with hydrogen in the presence of calcium oxide has been experimentally inves-tigated at moderate temperature. The results reveal that the effluent generated in the reduction pro-cess contains much less air-polluting substance H_2S, and that the reaction activation energy is63. 3 kJ/mol. The form of antimony changes considerably when the reaction temperature varies.     

The Diogene 4π detector at Saturne

Diogene, an electronic 4π detector, has been built and installed at the Saturne synchrotron in Saclay. The forward angular range (0°–6°) is covered by 48 time-of-flight scintillator telescopes that provide charge identification. The trajectories of fragments emitted at larger angles are recorded in a cylindrical 0.4-m³ Pictorial Drift Chamber (PDC) surrounding the target. The PDC is inside a 1-T magnetic field; the axis of the PDC cylinder and the magnetic field are parallel to the beam. Good identification has been obtained for both positive and negative π mesons and for hydrogen and helium isotopes. Multiplicities in relativistic nucleus-nucleus reactions up to 40 have been detected, limited mainly by the present electronics.     

Vortex dynamics at the superfluid λ-transition

A vortex-ring theory of the superfluid⁴He -transition is extended to include the dynamics of the transition. The response of the vortices to an oscillating superflow is found by solving the Fokker-Planck equation. This allows a calculation of the superfluid relaxation time, which is in agreement with Landau-Khalatnikov theory and with dynamic scaling. At high frequencies the transition becomes broadened, with both the superfluid density and the dissipation remaining finite at and above T. Comparison is made to earlier theories that use high-temperature expansions and renormalization-group expansions. Applications to other subjects such as mutual friction, high-T_c superconductors, and rapidly quenched systems are briefly discussed.     

Textured mullite at muscovite–kaolinite interface

Mullite crystallization was carried out by the inter-reaction of alternate layers of muscovite and kaolinite minerals. The nucleation and growth of mullite anisotropic crystals take place along the muscovite plane and specific structural relationships are observed, which confirm a topotactic effect with the high temperature form of muscovite. The [001]_mull axis is oriented parallel to [010]_musc, [310]_musc and axes. The mullite orientation is fully completed in a temperature range between the ternary eutectic at 985 °C and the ternary transition point at 1140 °C, of the SiO₂–Al₂O₃–K₂O system, which strongly suggests an influence of a small quantity of liquid phase at the interface. Along the kaolinite–muscovite interface, the realisation of highly textured ceramics can be achieved.     

An X-ray study of polyethylene at pressures up to 14 000 kg cm−2 at 298 K

The diamond piston-anvil method was used to make X-ray wide-angle diffraction studies of polyethylene at 298 K and at pressures up to 14 000 kg cm^–2. The data obtained were compared with the results of a study by Ito and Marui, and their observations (which were made at pressures up to 3000 kg cm^–2) were essentially confirmed. However, our data revealed that the linear compressibility in the [1 1 0] and [2 0 0] directions did not vary with pressure in a linear fashion over the entire range, and the empirical relation- _{hk l} =A _{h k l} – B _{hk l} ², where _{h k l} is the stress on h k l planes, was not found to be adequate for the planes (1 1 0) and (2 0 0) for pressures up to 14 000 kg cm^–2. With the addition of a third cubic term C _{h k l}³ to the relation, a better fit of the data could be achieved. By ignoring strains in the chain direction, the volumetric strains as a function of pressure were calculated, and the data agreed well with the equation of state derived by Pastine for the crystalline phase of polyethylene. A value for the Grüneisen constant ₀ at atmospheric pressure and 298 K was calculated and a value ₀=3.64 was obtained. This agrees well with values obtained by Ito and Marui, No phase transition was observed at 298° C for the pressure range reported.     

Microstructural simulation in spinodally-decomposed Cu–70 at.%Ni and Cu–46 at.%Ni–4 at.%Fe alloys

The microstructure simulation of spinodal decomposition was carried out in the isothermally-aged Cu–70at.%Ni and Cu–46at.%Ni–4at.%Fe alloys using the phase field method. The numerical simulation was based on the solution of the Cahn–Hilliard nonlinear partial differential equation by the explicit finite difference method. A slow growth kinetics of phase decomposition was observed to occur in the aged Cu–Ni alloy. The morphology of decomposed phases consisted of an irregular shape with no preferential alignment in any crystallographic direction at the early stages of aging in this alloy. The growth kinetics rate of phase decomposition in the aged Cu–46 at.%Ni–4 at.%Fe alloy was appreciably faster than that in the aged Cu–70 at.%Ni alloy. In the case of the aged Cu–46 at.%Ni–4 at.%Fe alloy, an irregular shape of the decomposed phases was also observed at the early stages of aging. A further aging caused the change of initial morphology to a cuboid and/or plate shape of the decomposed Ni-rich phase aligned in the elastically-softest crystallographic direction <100> of Cu-rich matrix.     

The DEAR Kaon Monitor at DAΦNE

Characteristics and performance of the Kaon Monitor of the DEAR experiment at the DAΦNE collider of Laboratori Nazionali di Frascati are described. The full TDC and ADC information collected from the detectors of the setup allows a clean observation of the charged kaon pairs from φ-decay by means of their different arrival times with respect to the background particles. The number of detected kaons can be used to obtain an absolute luminosity measurement in the DEAR interaction point at DAΦNE.     

Pulse shaping fiber laser at 1.5 μm

In this paper we present, for the first time to our knowledge, a new pulse shaping technology (modulation schemes for seed laser) used to mitigate pulse narrowing effect and SBS effect in a high energy Er:Yb codoped fiber master oscillator power amplifier system at 1.5 μm to obtain longer pulse duration and higher energy. An average power of over 1.3 W and a pulse energy of over 0.13 mJ were obtained at 10 kHz repetition rate with a pulse duration of 200 ns and near-diffraction-limited beam quality (M(2)<1.2).     

Polarization at metal–biomolecular interfaces in solution

Metal surfaces in contact with water, surfactants and biopolymers experience attractive polarization owing to induced charges. This fundamental physical interaction complements stronger epitaxial and covalent surface interactions and remains difficult to measure experimentally. We present a first step to quantify polarization on even gold (Au) surfaces in contact with water and with aqueous solutions of peptides of different charge state (A3 and Flg-Na3) by molecular dynamics simulation in all-atomic resolution and a posteriori computation of the image potential. Attractive polarization scales with the magnitude of atomic charges and with the length of multi-poles in the aqueous phase such as the distance between cationic and anionic groups. The polarization energy per surface area is similar on aqueous Au {1 1 1} and Au {1 0 0} interfaces of approximately −50 mJ m⁻² and decreases to −70 mJ m⁻² in the presence of charged peptides. In molecular terms, the polarization energy corresponds to −2.3 and −0.1 kJ mol⁻¹ for water in the first and second molecular layers on the metal surface, and to between −40 and 0 kJ mol⁻¹ for individual amino acids in the peptides depending on the charge state, multi-pole length and proximity to the surface. The net contribution of polarization to peptide adsorption on the metal surface is determined by the balance between polarization by the peptide and loss of polarization by replaced surface-bound water. On metal surfaces with significant epitaxial attraction of peptides such as Au {1 1 1}, polarization contributes only 10–20% to total adsorption related to similar polarity of water and of amino acids. On metal surfaces with weak epitaxial attraction of peptides such as Au {1 0 0}, polarization is a major contribution to adsorption, especially for charged peptides (−80 kJ mol⁻¹ for peptide Flg-Na₃). A remaining water interlayer between the metal surface and the peptide then reduces losses in polarization energy by replaced surface-bound water. Computed polarization energies are sensitive to the precise location of the image plane (within tenths of Angstroms near the jellium edge). The computational method can be extended to complex nanometre and micrometer-size surface topologies.     

Phase Equilibria in Zn-Al-Cu-Si System at 285℃

As a part of the systematic investigationon phase relationships of Zn-Al based alloyscontaining Cu and/or Si, the equilibrium phasetransformations of the quaternary Zn-Al-Cu-Sisystem at 285℃ were investigated by using X-raydiffracti on, scanning electron microscopy andelectron probe microanalysis techniques. A five-phase of (α+β+εT'+σ) and a four-phase of (β+ε+η+σ) were detected separatelycoexisting in the Zn-Al-Cu-Si system at 285℃.Then the 285℃ isothermal section of Zn-Al-Cu-Sisystem (with 0.1% -Si content) was established,and an equilibrium reaction was determined at286℃ as the following pattern, β+T'=α+ε     

Ionic Conduction in Cubic Zirconias at Low Temperatures

The ac conductivities of Y2O3 or CaO-stabilized cubic zirconias were obtained from complex impedance measurements in the temperature range from 373 to 473 K. By analyzing the temperature-dependence of the resultant dc conductivities, it was shown that the activation energies for conduction are lower than those reported previously for the same materials at high temperatures. Comparing the activation energy data with the theoretically estimated values revealed that there may exist a certain, although very small, amount of free oxygen vacancies in the test samples at low temperatures and the conduction in the test samples is a result of the migration of these free oxygen vacancies.     

Development of niobiumtin conductors at SLE

Superconductors Lips ECN is a recently formed company which produces NbTi and Nb₃Sn multifilament wires as well as superconducting cables. Multifilamentary Nb₃Sn wire, produced by the powder route, is developed commercially. About 30 km of strand material has been produced for the SULTAN 12 T project. These wires showed good performance. Developments are underway to reduce gradually the filament diameter at the same current performance to meet the full requirements for the NET and LHC conductors.     

Mechanical properties of polymer matrix composites at 77 K and at room temperature after irradiation with 60Co γ-rays

Ten different polymer matrix composites were irradiated with ⁶⁰Co γ-rays at room temperature, and were examined with regard to the mechanical properties at 77 K and at room temperature. The radiation-induced degradation of these composites is observed much more significantly in the ultimate strength and in the shear modulus than in the Young's modulus. The radiation resistance of these composites depends primarily on the radiation resistance of matrix resins, which increases in the order diglycidyl ether of bisphenol A < tetraglycidyl| diaminodiphenyl methane < Kerimid 601. Comparison of the mechanical properties tested at 77 K and at room temperature demonstrates that the extent of radiation-induced decrease in the composite strength is appreciably greater in the 77 K test than in the room temperature test. Interpretation of these results is based on the competition between the two opposing effects due to the hardness and brittleness of matrix resins.     

Kinetics of grain growth in 0·1 at.-%B doped nickel aluminide containing 23·2 at.-%Al

Abstract

Nickel aluminide containing 23·2 at.-%Al and 0·1 at.-%B was cold rolled and fully recrystallised at 825, 850, 875, 900, 925, 975, and 1000°C. Increase in grain size as a function of isothermal annealing time at these temperatures was measured. All the data showed excellent fit with the developed equations. The value of m, the exponent of the grain growth equation (D^m - D^m₀ = Kt), was 2·5. The activation energy for grain growth was 263 kJ g-atom^-1. Small changes in the boron content had an appreciable effect on the kinetic parameters. This was attributed to the solute drag effect of boron.