bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Interfacial Area in Unstable Emulsions by Light Transmission
Authors: Langlois Gordon E. , Gullberg Jonas E. , Vermeulen Theodore
Published: February 2005

Total interfacial area can be determined in agitated mixtures of transparent immiscible liquids by calculation from photoelectric measurements of their light transmission relative to clear fluids, with a probe of new design which is inserted into the emulsion. The probe is compact and rugged, and can be assembled from a simply constructed housing together with commercially available parts. A calibration obtained by high-speed photography of the emulsions is presented. The drop diameters measured were in the range of 0.01 to 0.10 cm, and, in this range, the specific area is found to depend only upon the light transmission and the ratio of refractive indexes of the dispersed and continuous phases.
Cyclotron Beam Energy Determination by a Time-of-Flight Method
Authors: Manley J. H. , Jakobson M. J.
Published: February 2005

A simple time-of-flight method has been employed as a means of measuring cyclotron beam energy. Through use of a movable and a fixed stilbene scintillation detector, a phase delay measured in terms of the cyclotron frequency is introduced by the flight time of the beam particles. Results good to 2 percent in energy have been obtained. These have less precision than the direct errors of the method, largely because of cyclotron instabilities.
Magnetic Deflector for the Bevatron
Authors: Wright Byron T.
Published: February 2005

A magnetic deflector for the bevatron is described. Particles initially circulating at some distance from the deflecting field are caused to enter the field during the course of a single turn because of a small energy loss in a suitable placed target. The estimated efficiency is about 1 percent in.−2 at a detector located twenty feet from the circulating current.
Electric Field Meters
Authors: Gunn Ross
Published: February 2005

The fundamental principles of electric field measurement by the use of inductors and vacuum tube amplifiers are reviewed. An electric field meter is described that employs a rotating inductor and a synchronous ac generator to provide a sign responsive meter reading proportional to the electric field. The synchronized circuits eliminate moving contact rectifiers and promote calibration stability.

A simplified field meter using rectified inductor currents to operate a high-impedance push-pull bridge circuit is also described. Design features are incorporated in both instruments that permit them to operate continuously under unusually severe storm conditions.
On the Temperature Dependence of BF3 Proportional Neutron Counters
Authors: Lockwood J. A. , Woods F. R. , Bennett E. F.
Published: February 2005

The results of an experimental study of the temperature dependence of commercial BF3 neutron counters are reported. The arrangement used for this investigation is described and the results analyzed. The conclusion is reached that during a given pulse there is an increase in the number of negative ions formed by electron attachment with an increase in temperature of the tube. This effect is an equilibrium process. Upon reduction of the tube temperature the tube characteristics return to their original values. The consequence of this temperature dependence on the resultant counting rate is discussed.
20-Kilovolt Delta-Function Generator
Authors: Heard Harry G.
Published: February 2005

An electronically triggered impulse generator has been developed which produces 20 kilovolt pulses having rise times of less than 0.6 millimicrosecond. When used with a shorting stub, this instrument produces delta-function pulses of less than 2.5 millimicrosecond total width at full amplitude. The functions of primary pulse generation and pulse sharpening are separated. A special 50-ohm coaxial switch was constructed of hydrogen thyratrons to produce 20 kilovolt primary pulses of arbitrary length and having rise times of less than 1.75 millimicroseconds. When triggered by a 2–500 volt pulse of 5 millimicroseconds rise time, the over-all jitter of the system is of the order of 1 millimicrosecond.
A Segmented-Mirror Solar Furnace for High-Intensity Thermal Radiation Studies
Authors: Gardon Robert
Published: February 2005

A solar furnace is described, in which an array of many small plane mirrors is used to produce radiation of practically uniform intensity (up to about 5.5 cal/cm2 sec) over an area 5 cm square. This relatively large area of irradiation is required for experiments in which edge effects must be kept to a minimum, and could not have been obtained by means of a conventional continuously curved mirror of reasonable focal length and of moderate cost.

The performance of the segmented-mirror furnace over a 15 month period is analyzed.
A One-Dimensional Fourier Analog Computer
Authors: Azaroff Leonid V.
Published: February 2005

A computer has been constructed to sum Fourier series having up to 30 terms. Although this is a one-dimensional computer it can be used for double and triple summations by using standard trigonometric expansions.

ODFAC sums Σn Fnsincos2πnx electrically. The trigonometric function is produced by a variable-angle transformer known as a resolver. Each amplitude is set by a variac which regulates the input to a particular resolver. The frequencies 2πnx for 31 values of n are arranged by gearing the rotors of the resolvers in ratios 0, 1, 2,…30. The resultant individual currents are added in parallel and the value at point x (in intervals of 1/60, 1/120, or 1/240 of a cell edge) is read on a voltmeter and the phase is read on an oscilloscope.

The relative speed of a computation is five to ten times faster than the standard strip methods. The average error in a computation compares favorably with the rounding-off error in conventional two-place strips.
Evacuating Photographic Materials for Use in Electron Optical Apparatus
Authors: Reisner John H.
Published: February 2005

Vacuum systems containing photographic materials may be most rapidly pumped if the materials have been desiccated previously. The primary factors influencing pumping time are the degree of preliminary desiccation and the amount of resorption of water vapor during the transfer of the material from the desiccator to the vacuum apparatus. Desiccation may be achieved by the use of a drying agent, evacuation, or the elevation of temperature. Resorption of water vapor may be minimized by rapid transfer of materials in tight containers from the desiccating means to the vacuum apparatus.
The Measurement of Two-Dimensional Fields. Part II: Study of a Quadrupole Magnet
Authors: Dayton I. E. , Shoemaker F. C. , Mozley R. F.
Published: February 2005

The characteristics of a dc quadrupole magnet have been measured using some of the techniques for measuring two-dimensional fields and gradients proposed by W. C. Elmore and M. W. Garrett in the preceding paper. Saturation curves and measurements of the flux distribution in the magnet are presented. The characteristics of the magnet have been determined both in the interior and in the fringing region at each end. It is shown that by using a pole tip of circular cross section and correctly chosen radius it is possible to produce a magnetic field with gradient constant to ±1 percent out to 0.8 of the radius of the gap.
An Apparatus for the Accurate Measurement of Internal Friction
Authors: Pattison John R.
Published: February 2005

This paper describes an electronic instrument which has been developed for the measurement of internal friction to a high level of accuracy. The device is actuated by an input signal consisting of a voltage-time decay wave form, with the necessary condition that the decay should follow an exponential law. The operation is both automatic and rapid so that the apparatus is suitable for investigating changes in damping when a given dependent parameter is varied.
An Adiabatic Apparatus for the Study of Self-Heating of Poorly Conducting Materials
Authors: Raskin Walter H. , Robertson Alexander F.
Published: February 2005

A small automatic furnace has been designed for the study of the thermal decomposition of wood and other combustible materials. After a sample has been brought nearly to thermal equilibrium at any desired temperature, the furnace temperature control system is automatically changed to allow the sample to self-heat up to a temperature of 500°C with small external heat loss or gain. Weight changes of the specimen during the test are continuously monitored and recorded. The control system is designed to stop the operation automatically after the specimen temperature has increased to some previously selected level.
Some Practical Aspects of Diffusion Cloud Chamber Operation
Authors: Alston Margaret H. , Crewe A. V. , Evans W. H.
Published: February 2005

Experimental problems which arise in the operation of diffusion cloud chambers are discussed. Particular attention is paid to methods of cooling the base of the chamber and design features of this type of chamber. Some of the limitations of the instrument are mentioned, and there is a discussion of symptoms which can arise when the conditions of operation are defective.
A Fast Neutron-Scintillation Spectrometer
Authors: Draper J. E.
Published: February 2005

A fast neutron-scintillation spectrometer employing two organic crystals in coincidence has been investigated experimentally. Considerations are made of some factors involved in the efficiency, resolution, neutron energy range, and background effects. The role of the carbon in the scintillation crystal is considered not to be important except in its increase of the plural scattering in the analyzing crystal. The D(d,n), T(d,n), and Li(d,n) spectra as taken with this instrument are presented.
A High-Speed Air-Driven Shutter for Controlling Exposures to a Convergent Beam of High-Intensity Thermal Radiation
Authors: Day R. P. , Hopton R. L. , Schmidt A. C.
Published: February 2005

A high-speed two-bladed shutter was built to deliver square-wave pulses of energy from a converging light beam with an average intensity of about 5 cal/cm2/sec, and a diameter of 3 in., in the plane of the shutter. The blades open or close in less than 0.01 sec. They move in the same direction, so that all parts of the target are exposed for very nearly the same length of time. The shutter makes use of a new type of air cylinder which is suitable for driving high-speed mechanisms, and has a dynamic shock absorbing system to stop the moving parts in a short distance with little rebound. It is electrically controlled and fully automatic. Exposure times may be varied from 0.07 to 5 sec by setting an electronic interval timer. Longer exposures are controlled manually. To date it has been used more than 15 000 times and has required only two overhauls.
Alternating Gradient Focusing of Cyclotron External Beam
Authors: Hubbard Edward L. , Kelly Elmer L.
Published: February 2005

The ¾-Mev external proton beam from the 20-inch cyclotron appeared to diverge horizontally from one point and vertically from another point. With a series of three alternately converging and diverging electro-static lens elements of hyperbolic cross section, it was possible either to focus the external beam to a point or to make it parallel.
Scintillation Spectrometers for Measuring the Total Energy of X-Ray Photons
Authors: Foote R. S. , Koch H. W.
Published: February 2005

X-ray spectrometers are described that operate on the principle of totally absorbing the energy of an individual x-ray photon in a scintillator. Experiments with scintillators of xylene containing terphenyl, and of sodium iodide activated by thallium, show that detection efficiencies better than 80 percent and energy resolutions better than 10 percent are attainable in the x-ray energy range from ½ to 50 Mev. Monte Carlo calculations and crude scaling laws that simplify extrapolations to other size scintillators are discussed.
Transient Response of the Glass Electrode to pH Step Variations
Authors: Distèche A. , Dubuisson M.
Published: February 2005

A dc amplifier with electrometer input stage is described making it possible to display pH changes on the oscilloscope screen for physiological applications. Sensitivity is 0.003 pH unit per cm beam deflection; noise 50 μv; drift 300 μv/hr(≃0.005 pH unit). A simple hydraulic mechanism is used to produce very fast pH steps under the electrode. The speed of the electrode response is shown to tend towards a finite limit when the speed of the pH change increases. The form of the transient in the fastest records is close to an exponential curve e−αt, with 1/α≃30 msec. The response is independent of the membrane thickness (5 to 10 μ). Some evidence exists to show that the response of the electrode to pH steps is analogous to the response of a low-pass RC-filter to a corresponding voltage step, where R and C are, respectively, the resistance and the capacity of the glass membrane. R and C values determined from the analysis of the electrode response to step voltages in series give RC≃30 msec in agreement with the experimental results.
Measurement of the Electrical Resistance of Metals and Alloys at High Temperatures
Authors: Chiotti P.
Published: February 2005

An alternating current potentiometric method for measuring the electrical resistance of metals and alloys at very high temperatures is described. The potential developed between two probes which make contact with the test piece is balanced against a potential developed across the secondary of a current transformer. The primary of the current transformer is connected in series with the test piece. The test piece in the form of a bar is mounted between water-cooled copper electrodes and is heated by passing a high 60-cycle current through it. The resistance is measured directly. A furnace and automatic recording and control instruments which can be used in conjunction with this method are described.
Wide-Band Amplitude Distribution Analysis of Voltage Sources
Authors: Orr Lyman W.
Published: February 2005

A method of wide-band amplitude distribution analysis is described which employs two commercial oscilloscopes and a phototube. The minimum set-up can be assembled quickly in the laboratory from standard equipment, and gives a rapid analysis accurate to better than 5 percent. It is free from the severe band-width restrictions of other methods (N. Knudtzon, Research Laboratory for Electronics, M. I. T. Tech. Rept. No. 115, July 15, 1949), and can often be employed up to 500 mc. Results on two noise sources are included for illustration, and a modification for improving the resolution and increasing the accuracy is presented.
Design of Extensometer for Creep Studies
Authors: Gossick Ben R.
Published: February 2005

The extensometer permits remote operation over a wide range of extensions. The creep specimen is mechanically coupled to a metal core within a mutual inductance bridge. The amount of deformation of the creep specimen determines the position of the core and thus the amount of bridge unbalance. The tolerances of mutual inductance bridges being imperfect, a residual voltage remains which is 90° out of phase with that produced by displacements of the core. A core which produces an output voltage 90° out of phase with the voltage produced by a steel core has been made with laminations of copper and steel. By connecting two bridges in series, one containing a steel core and the other the composite core, the null has been reduced to the noise level of the amplifier to which the bridge system is connected.

Requirements for making the phase angle of the bridge signal approximately independent of core position, over the extension range, are discussed.
Polar Cardioscope
Authors: Trank John W. , Schmitt Otto H.
Published: February 2005

In the polarcardioscope, the electrocardiogram is recorded radially on a circularly swept trace about ten inches in length. A long persistence screen cathode-ray tube is used, the angular sweep speed being adjusted to match the heart rate. Under these circumstances it becomes very simple to examine the details of the repeated beat, to compare successive superimposed beats, to detect arrhythmias, and to measure average frequency. The instrument is simple and comparable in bulk with an ordinary cathode-ray oscilloscope. It derives its input signal directly from any ordinary electronic electrocardiographic recorder.
Recording Integrating Photoelectric and Radioactive Scanner for Paper Electrophoresis and Chromatography
Authors: Durrum E. L. , Gilford S. R.
Published: February 2005

A versatile automatic scanner for paper strips which records directly optical density or radioactivity is built around a servo type recorder (Brown). Interference filters provide a narrow band light source. For scanning in the visible or ultraviolet where monochromatic light is desired the monochromator of a Beckman model DU spectrophotometer replaces the filters. The instrument incorporates positive synchronization of strip and recording paper, sequential scanning of strips to provide an optical density curve followed by superposition of the integral of this curve. Areas are easily calculated without the need for planimetry. The slits of varying size are interchangeable and are designed for either optical or radioactive scanning. For medium levels of activity a Geiger-Müller tube is interchangeable with the photocell, while for low activities, optical scanning of autoradiographs may be performed.
Focusing in Linear Ion Accelerators
Authors: Smith Lloyd , Gluckstern Robert L.
Published: February 2005

The results of the investigation of three methods of obtaining transverse stability in linear accelerators for ions are presented and discussed. For electric or magnetic quadrupole focusing the range of stable operation, oscillation amplitudes, and the effect of perturbing errors are treated. For grid focusing, the operation of an actual grid is analyzed from measurements of the field distribution. Finally, the formulas applicable to focusing by axial magnetic lenses are presented.
New Technique for Compressing Surface Films
Authors: Sher Irving H. , Chanley J. D.
Published: February 2005

A new method of applying continuous mechanical pressure to monomolecular films is presented. The advantages of the method include: simple and inexpensive apparatus, ability to produce continuously any desired pressure without adjustments, freedom from piston-oil contaminations and streaks, ease and speed of cleaning surface for next film, and full spreading of successive films.
Apparatus for Measuring the Thermal Conductivity of Metals in Vacuum at High Temperatures
Authors: Moss Marvin
Published: February 2005

The method of determining the thermal conductivity of a metal with this apparatus consists, essentially, of measuring both the axial temperature gradient and the transfer of heat under steady state conditions in a thermally shielded cylindrical rod of the metal which is heated at one end and cooled at the other. The objective was to make precise determinations of conductivity without reliance on previously established data for standard metals. In certain respects the apparatus embodies simplification of, and improvement over, other equipment of this type. A calorimetric measurement of heat flow constitutes a distinct advantage of the instrument both as to its simplicity and the fact that it supplies the data necessary for a direct rather than a comparative evaluation of thermal conductivity. Other features include vacuum operation and special instrumentation to facilitate the measurement of temperature differences. Tests have been made on nickel, zirconium, and a zirconium-3-percent-tin alloy from room temperature up to the range between 500 and 700°C. Where comparison is possible the results are in close agreement with some of the most accurate published data of this type.
Continuous Analysis of Ortho-Parahydrogen Mixtures
Authors: Weitzel D. H. , White L. E.
Published: February 2005

A Gow-Mac thermal conductivity unit has been utilized in the construction of a continuous flow analyzer for ortho-parahydrogen mixtures. No pump or vacuum system is required. The unit possesses adequate sensitivity for operation at room temperature, thus eliminating the need for low temperature baths. Parameters which influence reproducibility have been investigated and simple techniques for their control are suggested.
Absorption and Counting-Efficiency Data for X-Ray Detectors
Authors: Taylor Jeanne , Parrish William
Published: February 2005

Mass absorption coefficient data published by Allen, Bragg, and Victoreen for the wavelength region 0.1 to 50 A are plotted for several common x-ray tube and counter windows (Al, Be, and mica) and gases (Xe, Kr, A, and Ne) used in x-ray detectors. A graph of the calculated percentage transmission of the windows is presented. The calculated quantum-counting efficiencies for the range 0.1 to 15 A are shown for an end-window argon-filled Geiger counter, side-window Xe, Kr, A, and Ne proportional counters and an NaI·Tl scintillation counter. Some of the factors to be considered in the choice of detectors for x-ray diffractometry and x-ray spectroscopy are discussed particularly with respect to the spectral sensitivity.
Method of Correction for the α1 α2 Doublet in the X-Ray Diffraction Lines
Authors: Papoulis A.
Published: February 2005

In many applications it is necessary to determine the diffraction pattern due to monochromatic radiation. When the x-ray beam contains two frequencies α1 and α2, the experimental pattern P(2θ) equals the sum of the contributions f(2θ) and kf(2θ−δ) of the α1 and α2 components. In this paper a graphical method of determining f(2θ) from P(2θ) is given, with the assumption that f(2θ) is symmetrical. The area A(2θ) under the P(2θ) curve is plotted, from which the position of the maximum and the shape of f(2θ) is easily determined. In this construction it is not necessary for P(2θ) to have a well-defined zero.
Tuning of a Rectangular Parallelopiped Cavity Resonator with a Circular Metallic Post
Authors: Macdonald J. Ross
Published: February 2005

In radar T-R tubes and in ferromagnetic resonance experiments, it is often desirable to tune a rectangular cavity resonator by means of a circular metallic post projecting into one wall. Here it is shown how a perturbation formula due to Slater may be employed to calculate the relation between resonant frequency and small displacements of such a metallic post; the calculation is carried out to first order for a rectangular cavity operating in the TE110-mode and the result compared with a similar relation for a right circular cylinder whose length is varied by a plunger completely closing one end.
Characteristics of a High-Frequency Cockcroft-Walton Voltage Source
Authors: Peck R. A.
Published: February 2005

Direct voltage output and ripple from a conventional cascade rectifier voltage multiplier have been observed under various conditions of operating frequency, load current, and number of doubler stages. Four types of voltage ``loss'' and two of ripple are identified, and their dependence on the above parameters is discussed. For six units operated at 32 kc the ``voltage efficiency'' varies from 90 percent without load to 80 percent when 8 ma are drawn; at 60 cps it is 42 percent without load. From the nature of the loss and ripple components it is clear that there is a maximum fruitful operating frequency for a supply of this type, only slightly above 800 cps in the present case.
Use of Melamine as an X-Radiation Detector
Authors: Birnbaum Milton , Schulman James , Seren Leo
Published: February 2005

Melamine, in the form of a clear plastic material, can be used as an x-radiation detector in the range from hundreds to millions of roentgens. The effect of radiation is to increase the optical absorption of melamine for wavelengths from 330 to 480 millimicrons. The change in absorption produced by the radiation is greater at shorter wavelengths of light. However, in practice a compromise must be realized because the natural absorption of melamine also increases steeply as the wavelength of light is decreased. Preliminary experiments with 11-Mev bremsstrahlung radiation and with Co60 gamma rays indicate that the dosimeter properties are roughly independent of the x-ray energy.
Some Remarks as to Dark Current and Pulse-Height Distribution in E.M.I. 6260 Photomultipliers
Authors: Pelchowitch I.
Published: February 2005

Bias curves measured with an E.M.I. 6260 photomultiplier tube for dark current, and single photo-electrons emitted from the cathode under light stimulation, are discussed. It is shown that the dark current has a multi-electron emission component, the major part of which can be attributed to the K40 content of the glass. Pulse-height distributions are shown to be dependent on focusing characteristics of the multiplier and to broaden when space-charge limitation occurs.
Digital-Analog Magnetometer Utilizing Superconducting Sensor
Authors: Forgacs R. L. , Warnick A.
Published: February 2005

A magnetometer was developed which utilizes a superconducting quantum interference device (SQUID) as a sensor, and permits digital and analog measurements of magnetic fields. The digital mode permits measurement of large field changes with a constant accuracy of approximately 1/10 the natural periodicity of a SQUID. (The natural period is typically 10−6–10−3 G.) Thus, the precision of measurement of large field changes is high. The analog mode is advantageous for high precision measurement, of the order of 10−8 G, but for small field changes. Combined mode measurements permit the very high precision of the analog mode to be combined with the large range of the digital mode. The digital mode, which represents an improvement over the original lock-on magnetometer, utilizes two synchronous detectors to provide signals which uniquely determine the instantaneous magnetic bias of the SQUID. The synchronous detector outputs drive a novel logic circuit which produces appropriate add-subtract pulses to a digital counter, which reads out field changes in units equal to the periodicity of a SQUID.
Measuring Roundness in the Millimicron Range
Authors: Jurisson Jaan , Matthys Robert J. , Plasek Frank , Thompson Howard J.
Published: February 2005

This paper describes an instrument capable of measuring the roundness of an object with a resolution of 5 mμ. The instrument consists of a precision spindle with hydrostatic fluid bearings and a capacitance displacement transducer. In this scheme, the displacement transducer is part of a capacitance bridge, which is made self balancing by closing the servo loop to the nulling capacitor through the recorder pen motor. Also, an instrument using a multiple beam interferometer for the displacement transducer calibration is briefly described.
Optical Isolator for Near Infrared
Authors: DeShazer L. G. , Maunders E. A.
Published: February 2005

A Faraday effect optical isolator was constructed for the infrared region. The nonreciprocal element of the isolator was a lead glass rod in the magnetic field of a solenoid. A triple pass of the light beam through the glass decreased the magnetic field strength required for a 45° Faraday rotation. For 1.062 μ, the isolator had a 1.4 dB insertion loss, and a 29 dB isolation. Slight optical imperfections in the isolator components limited the isolator operation.
Piezoelectric and Mechanical Behavior of X-Cut Quartz Shock Loaded at 79°K
Authors: Jones O. E.
Published: February 2005

The piezoelectric and mechanical behavior at 79°K of uniaxially strained X-cut quartz has been experimentally investigated by an impact technique for stresses ranging between 6 and 21 kbar. Knowledge of this behavior is necessary to extend to liquid nitrogen temperature the use of large diameter-to-thickness ratio X-cut quartz disks as submicrosecond gauges for observing stress-time profiles induced in materials by plane wave shock loading. For stresses up to at least 21 kbar, elastic behavior is observed. The elastic wave velocity and mechanical impedance have constant values of 5.72 mm/μsec and 152 kbar/mm/(mm/μsec), respectively, which are within ±1% of 298°K values. From a least squares fit to the data, the piezoelectric factor at 79°K relating current and stress in uniaxial strain depends on stress σx and is given by (2.11×10−8+5.5×10−11σx) C/(cm2-kbar), as compared to (2.01×10−8+1.1×10−10σx) at 298°K. These expressions are based on 298°K values of the electrode area and thickness of the quartz disk. In the limit of zero stress, there is reasonable agreement between the e11/c11 piezoelectric coefficient determined from the 79°K expression and that obtained from low signal resonance measurements. A small apparent increase in the dielectric permittivity with stress is observed at 79°K.
Electrodeless Measurement of Resistivities over a Very Wide Range
Authors: Haisty R. W.
Published: February 2005

Resistivity of electronic conductors, from metals to semi-insulators, is determined from the change in grid current of a high frequency oscillator owing to the loading resulting from eddy currents in the sample. The signal appears as a pulse when the sample is dropped through the oscillator tank coil; greater amplification can be used than in previous eddy current methods where the sample was stationary during measurement; thus, higher resistivities can be measured. The samples can be sealed in ampoules and measured at high temperatures and pressures, limited only by the ampoule material. A typical calibration curve, made at 14 Mc and covering the range 10−6 Ω-cm to 108 Ω-cm is given; application to the estimation of sample homogeneity is discussed.
Growth-induced polarity formation in solid solutions of organic molecules: Markov mean-field model and Monte Carlo simulations
Authors: Wüst Thomas , Hulliger Jürg
Published: February 2005

A layer-by-layer growth model is presented for the theoretical investigation of growth-induced polarity formation in solid solutions H1−XGX of polar (H) and nonpolar (G) molecules (X: molar fraction of G molecules in the solid, 0<X<1). The model is characterized by the assumption of thermal equilibrium formation of adlayers, with respect to the up and down orientation of the dipoles of H molecules and to an exchange of H and G molecules, while previously attached layers are kept frozen. The model is analyzed by means of a Markov mean-field description and Monte Carlo simulations. In solid solutions, polarity results from a combined effect of orientational selectivity by H and G molecules with respect to the alignment of the dipoles of H molecules and miscibility between the two components. Even though both native structures (H,G) may be centrosymmetric, polarity can arise just from the admixture of G molecules in the H crystal upon growth. An overview of possible phenomena is given by random selection of molecular interaction energies within an assumed but realistic energy range. The analytical approach describes sufficiently basic phenomena and is in good agreement with simulations. High probabilities for significant vectorial alignment of H molecules are found for low (X⩽0.2) and high (X⩾0.8) fractions of G molecules, respectively, as well as for ordered HG compounds (X=0.5).
Representations of classical Lie subalgebras of quantum pseudodifferential operators
Authors: Boyallian Carina , Liberati José I.
Published: February 2005

We show that there is a family of anti-involutions σϵ,k (ϵ=±1 and k∊Z), up to conjugation, of the Lie algebra Sq of quantum pseudodifferential operators preserving the principal gradation. We classify the irreducible quasifinite highest weight modules over the Lie subalgebras of Sq, fixed by minus σϵ,k(keven), and we realize them in terms of irreducible highest weight representations of the Lie algebra of infinite matrices with finitely many nonzero diagonals and its classical Lie subalgebras of B, C, and D types.
Role of surface crossings in the photochemistry of nitromethane
Authors: Arenas Juan F. , Otero Juan C. , Peláez Daniel , Soto Juan
Published: February 2005

The photodissociation dynamics of nitromethane (CH3NO2) starting at the S3 excited state has been studied at the complete active space self-consistent field level of theory in conjunction with atomic natural orbital type basis sets. In addition, the energies of all the critical points and the energy profiles connecting them have been recomputed with the multiconfigurational second-order perturbation method. It is found that the key step in the reaction mechanism is a radiationless decay through an S3∕S2 conical intersection. The branching space spanned by the gradient difference and nonadiabatic coupling vectors of this crossing point comprises dissociation into excited nitromethane plus singlet atomic oxygen [CH3NO(1A″)+O(D1)] and S3→S2 deactivation, respectively. Furthermore, deactivated nitromethane Sn(n<3) can decompose in subsequent steps into CH3+NO2, where NO2 is generated at least in two different electronic states (1B22 and 1A12). It is shown that formation of excited nitric oxide NO(AΣ2) arises from CH3NO(1A″) generated in the previous step. In addition, four crossings between singlet and triplet states are localized; however, no evidence is found for a relevant role of such crossings in the photochemistry of CH3NO2 initiated at S3 state in the gas phase.
Effect of electron collisions on transport coefficients induced by the inverse bremsstrahlung absorption in plasmas
Authors: Bendib A. , Tahraoui A. , Bendib K. , Mohammed El Hadj K. , Hüller S.
Published: February 2005

The transport coefficients of fully ionized plasmas under the influence of a high-frequency electric field are derived solving numerically the electron Fokker–Planck equation using a perturbation method, parametrized as a function of the electron mean-free-path λei compared to the spatial scales L. The isotropic and anisotropic contributions of the inverse bremsstrahlung heating are considered. Electron-electron collision terms are kept in the analysis, which allows us to consider with sufficient accuracy to describe plasmas with arbitrary atomic number Z. Practical numerical fits of the transport coefficients are proposed as functions of Z and the collisionality parameter λei∕L.
Growth, structure, and properties of all-epitaxial ferroelectric (Bi,La)4Ti3O12∕Pb(Zr0.4Ti0.6)O3∕(Bi,La)4Ti3O12 trilayered thin films on SrRuO3-covered SrTiO3(011) substrates
Authors: Bao Dinghua , Lee Sung Kyun , Zhu Xinhua , Alexe Marin , Hesse Dietrich
Published: February 2005

All-epitaxial (Bi,La)4Ti3O12(BLT)∕Pb(Zr,Ti)O3(PZT)∕(Bi,La)4Ti3O12 trilayered ferroelectric thin films were prepared on SrRuO3 (SRO)-covered SrTiO3(011) substrates by pulsed-laser deposition. Epitaxial relationships were identified to be BLT(118)‖PZT(011)‖SrTiO3(011), and BLT[1¯1¯0]‖PZT[100]‖SrTiO3[100]. Atomic force microscopy observation of the surface showed that the upper BLT layer is composed of rod-like grains. Cross-sectional transmission electron microscopy investigations revealed ferroelectric 90° domains in the PZT layer, as well as a rather smooth morphology of the BLT/PZT interfaces. Remanent polarization and coercive field of the trilayered films were 28.1μC∕cm2 and 33.7kV∕cm, respectively. The thin films showed a high fatigue resistance at least up to 1010 switching pulse cycles. Obviously, a trilayered structure combines the advantages of PZT and BLT, indicating that the all-epitaxial BLT/PZT/BLT trilayered structure is a promising material combination for ferroelectric memory device applications.
Magnetic trap of a reaction zone
Authors: Digilov Rafael M. , Sheintuch M.
Published: February 2005

The reaction of ethylene glycol oxidation catalyzed by a colloidal suspension of iron oxide nanoparticles was monitored by IR thermography under an inhomogeneous magnetic field (with a spatial gradient ∼50T2∕m). The interaction of a reaction zone with the gradient magnetic field, in a way that the reaction zone could be trapped and manipulated at a desired position with the aid of the magnetic field effect, has been discovered. We explain this phenomenon by the magnetic buoyancy force arising from the variation in the magnetic susceptibility between the reaction zone and rest solution during the catalyzed redox process. These observations suggest the potential use magnetic fields for controlling chemical processes by the long-time localization of the reaction zone from the environment and enables complex problem solving to be performed in physics, chemistry, biology, chemical engineering, nanotechnology, and medicine.
Dendroclimatological potential of the Australian red cedar
Authors: Heinrich I. , Banks J. C. G.
Published: February 2005

We examined Toona ciliata M.Roemer (Australian red cedar) for its potential to deliver annually resolved tree-ring proxy data. Such proxies are valuable and sought-after sources for reconstructing climate beyond instrumental records, especially in Australia. T. ciliata was chosen because it is one of the few deciduous tree species in Australia experiencing a seasonally dormant period of the cambium. This was confirmed by a preliminary tree-ring analysis which revealed distinct growth rings. Because of initial uncertainties regarding reliable annual growth rings in the wood of T. ciliata, a dendrometer-band study was conducted in addition to the tree-ring analysis. Stem increments revealed a common period of dormancy during winter and the measurements were found to correlate with both precipitation and temperature, depending on the site. For the first time, our tree-ring analysis demonstrated that samples from different individuals can be cross-dated and the resulting site index from Upper Kangaroo Valley (New South Wales) has the potential to reconstruct early season temperatures and late-season rainfall.
Homeodomain-interacting protein kinase-2 mediates CtBP phosphorylation and degradation in UV-triggered apoptosis
Authors: Zhang Qinghong , Nottke Amanda , Goodman Richard H.
Published: February 2005

Homeodomain-interacting protein kinase-2 (HIPK2) is a serine/threonine kinase involved in transcriptional regulation and apoptosis. The transcriptional corepressor CtBP (carboxyl-terminal binding protein) also plays a fundamental role in these processes. Our previous studies indicate that HIPK2 participates in a pathway of UV-triggered CtBP clearance that results in cell death. HIPK2 phosphorylates CtBP at Ser-422
in vitro
. We developed a Ser-422 phospho-specific antibody to demonstrate that CtBP is phosphorylated on this residue in response to UV irradiation. HIPK2 knock-down blocked the UV-induced Ser-422 phosphorylation and degradation. The proteasomal inhibitor MG-132 treatment increased levels of ubiquitinated CtBP, which was induced by UV. Interference with HIPK2 function via the kinase-dead mutant decreased CtBP ubiquitination. Furthermore, a phosphopeptide spanning Ser-422 blocked UV-triggered CtBP degradation, confirming that Ser-422 phosphorylation marks CtBP for clearance. Consequently, interference with HIPK2 action in H1299 cells rescued UV-triggered apoptosis.
Near-infrared-emissive polymersomes: Self-assembled soft matter for
in vivo
optical imaging
Authors: Ghoroghchian P. Peter , Frail Paul R. , Susumu Kimihiro , Blessington Dana , Brannan Aaron K. , Bates Frank S. , Chance Britton , Hammer Daniel A. , Therien Michael J.
Published: February 2005

We demonstrate that synthetic soft materials can extend the utility of natural vesicles, from predominantly hydrophilic reservoirs to functional colloidal carriers that facilitate the biomedical application of large aqueous-insoluble compounds. Near-infrared (NIR)-emissive polymersomes (50-nm- to 50-μm-diameter polymer vesicles) were generated through cooperative self assembly of amphiphilic diblock copolymers and conjugated multi(porphyrin)-based NIR fluorophores (NIRFs). When compared with natural vesicles comprised of phospholipids, polymersomes were uniquely capable of incorporating and uniformly distributing numerous large hydrophobic NIRFs exclusively in their lamellar membranes. Within these sequestered compartments, long polymer chains regulate the mean fluorophore–fluorophore interspatial separation as well as the fluorophore-localized electronic environment. Porphyrin-based NIRFs manifest photophysical properties within the polymersomal matrix akin to those established for these high-emission dipole strength fluorophores in organic solvents, thereby yielding uniquely emissive vesicles. Furthermore, the total fluorescence emanating from the assemblies gives rise to a localized optical signal of sufficient intensity to penetrate through the dense tumor tissue of a live animal. Robust NIR-emissive polymersomes thus define a soft matter platform with exceptional potential to facilitate deep-tissue fluorescence-based imaging for
in vivo
diagnostic and drug-delivery applications.
Control of seed mass byAPETALA2
Authors: Ohto Masa-aki , Fischer Robert L. , Goldberg Robert B. , Nakamura Kenzo , Harada John J.
Published: February 2005

Arabidopsis APETALA2(AP2) encodes a member of the AP2/EREBP (ethylene responsive element binding protein) class of transcription factors and is involved in the specification of floral organ identity, establishment of floral meristem identity, suppression of floral meristem indeterminancy, and development of the ovule and seed coat. Here, we show that loss-of-functionap2mutations cause an increase in seed mass relative to that of wild-type seeds. Analysis of an allelic series ofap2mutations showed that increases in seed mass corresponded with the severity of defects in flower structure, indicating thatAP2activity directly influences seed mass. Experiments with male-sterile plants and deflowered wild-type plants showed that reduced fertility ofap2mutant plants due to abnormal flower structure accounted for only part of the increase in seed mass caused by strongap2mutant alleles. Reciprocal cross experiments showed thatAP2acts maternally to control seed mass. The maternal effect ofAP2on seed mass involves the regulation of both embryo cell number and cell size. We show further thatap2mutations cause changes in the ratio of hexose to sucrose during seed development, opening the possibility thatAP2may control seed mass through its effects on sugar metabolism. Together, these results identify a role forAP2in controlling seed mass.
Regulation of Secondary Cell Wall Development by Cortical Microtubules during Tracheary Element Differentiation in Arabidopsis Cell Suspensions
Authors: Oda Yoshihisa , Mimura Tetsuro , Hasezawa Seiichiro
Published: February 2005

Cortical microtubules participate in the deposition of patterned secondary walls in tracheary element differentiation. In this study, we established a system to induce the differentiation of tracheary elements using a transgenic Arabidopsis (Arabidopsis thaliana) cell suspension stably expressing a green fluorescent protein-tubulin fusion protein. Approximately 30% of the cells differentiated into tracheary elements 96 h after culture in auxin-free media containing 1 μ  m brassinolide. With this differentiation system, we have been able to time-sequentially elucidate microtubule arrangement during secondary wall thickening. The development of secondary walls could be followed in living cells by staining with fluorescein-conjugated wheat germ agglutinin, and the three-dimensional structures of the secondary walls could be simultaneously analyzed. A single microtubule bundle first appeared beneath the narrow secondary wall and then developed into two separate bundles locating along both sides of the developing secondary wall. Microtubule inhibitors affected secondary wall thickening, suggesting that the pair of microtubule bundles adjacent to the secondary wall played a crucial role in the regulation of secondary wall development.
Differential Expression and Evolution of the Arabidopsis CYP86A Subfamily
Authors: Duan Hui , Schuler Mary A.
Published: February 2005

Some members of the Arabidopsis (Arabidopsis thaliana) CYP86A and CYP94B cytochrome P450 monooxygenase subfamilies, which share some sequence homology with the animal and fungal fatty acid hydroxylases, have been functionally defined as fatty acid ω-hydroxylases. With these activities, these and other fatty acid hydroxylases have potential roles in the synthesis of cutin, production of signaling molecules, and prevention of accumulation of toxic levels of free fatty acids. The constitutive and stress-inducible patterns of the five Arabidopsis CYP86A subfamily members have been defined in 7-d-old seedlings and 1-month-old plant tissues grown under normal conditions, and 7-d-old seedlings treated with different hormones (indole-3-acetic acid, abscisic acid, gibberellin, methyl jasmonic acid, brassinosteroid, salicylic acid), chemicals (clofibrate, 1-aminocyclopropane-1 carboxylic acid), or environmental stresses (cold, wounding, drought, mannitol, etiolation). Very distinct expression patterns exist for each of these fatty acid hydroxylases under normal growth conditions and in response to environmental and chemical stresses. Analysis of the promoter sequences for each of these genes with their expression patterns has highlighted a number of elements in current databases that potentially correlate with the responses of individual genes.
Ligand‐binding regulation of LXR/RXR and LXR/PPAR heterodimerizations: SPR technology‐based kinetic analysis correlated with molecular dynamics simulation
Authors: Yue Liduo , Ye Fei , Gui Chunshan , Luo Haibin , Cai Jianhua , Shen Jianhua , Chen Kaixian , Shen Xu , Jiang Hualiang
Published: February 2005

Liver X receptor (LXR) and peroxisome proliferator‐activated receptor (PPAR) are two members of nuclear receptors involved in the nutrient metabolisms of dietary fatty acid and cholesterol. They are found to be of cross‐talk function in that LXR regulates fatty acid synthesis and PPAR controls fatty acid degradation. LXRs (LXRα and LXRβ) function by forming obligate heterodimers with the retinoid X receptor (RXR), and subsequently binding to specific DNA response elements within the regulatory regions of their target genes. In this work, the kinetic features concerning LXR/RXR and LXR/PPAR interactions have been fully investigated using surface plasmon resonance (SPR) technology. It is found that LXRs could bind to all the three PPAR subtypes, PPARα, PPARγ and PPARδ with different binding affinities, and such receptor/receptor interactions could be regulated by ligand binding. Moreover, molecular dynamics (MD) simulations were performed on six typical complex models. The results revealed that ligands may increase the interaction energies between the receptor interfaces of the simulated receptor/receptor complexes. The MD results are in agreement with the SPR data. Further analyses on the MD results indicated that the ligand binding might increase the hydrogen bonds between the interfaces of the receptor/receptor complex.
Advocacy in practice: the experiences of independent advocates on UK mental health wards
Authors: CARVER N. , MORRISON J.
Published: February 2005

Independent advocacy in mental health has become increasingly valued in the UK although little work has examined the day‐to‐day experiences of advocates themselves. This article reports on a small‐scale exploratory qualitative study of practising advocates’ experiences of their work in acute and continuing care wards. The project results from collaboration between members of the UK Advocacy Network and the Department of Mental Health and Learning Disability at the University of Sheffield. Although the findings will be of interest to any professional allied to these areas they are particularly relevant to mental health nurses wishing to increase their knowledge of advocacy and gain a fresh perspective on inpatient care. The findings reveal difficulties inherent in advocacy practice as well as the nature and importance of good working relationships between advocates and clinicians. Despite acknowledging such relationships frequently exist, advocates can still encounter ignorance of their role and opposition to their presence. The clearest implication of the findings is the need for greater training of nurses and other clinicians in the role of the advocate.