bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of optical scanner to switching of x-ray photon helicities at kHz range
Authors: Suzuki Motohiro , Kawamura Naomi , Ishikawa Tetsuya
Published: January 2003

A new method for fast helicity switching of x-ray circular polarization in the kHz range is described. An optical scanner was used to sinusoidally oscillate a diamond crystal, functioning as an x-ray quarterwave-phase plate, with a 55.5″ angular amplitude around the Bragg condition up to 3 kHz. The oscillation accuracy and stability with respect to frequency variations were evaluated in situ to be better than ±1.5″, within the angular acceptance of the phase plate. All of the Stokes components of the produced circular polarization were determined as the helicities were switching at an x-ray energy of 8388 eV. A degree of circular polarization of greater than 97% was obtained for both helicities up to 2 kHz. Absolute values of the S3/S0 between right- and left-circular polarizations agreed within the experimental errors.
Determination of thermophysical parameters of porous silicon using a photothermal technique
Authors: Abdalla S. , Easawi K. , Negm S. , Youssef G. M. , El-Brolossy T. A. , Talaat H.
Published: January 2003

The effective thermophysical properties, diffusivity (α), effusivity (e), and thermal conductivity (k) have been measured by photoacoustic (PA) and photothermal interferometry (PTI) for silicon samples of varying porosities. The experimental results show a reduction in the thermal conductivity with increasing the porosity, by two orders of magnitude. The results obtained by PTI are compared to those obtained by the PA technique.
Geodesic compatibility and integrability of geodesic flows
Authors: Topalov Peter
Published: January 2003

We give a natural geometric condition called geodesic compatibility that implies the existence of integrals in involution of the geodesic flow of a pseudo-Riemannian metric. We prove that if two metrics satisfy the condition of geodesic compatibility then we can produce a hierarchy of metrics that also satisfy this condition. A lot of metrics studed in Riemannian and Kählerian geometry satisfy such conditions. We apply our results for obtaining an infinite family (hierarchy) of completely integrable flows on the complex projective plane CPn.
The extended surface forces apparatus. Part III. High-speed interferometric distance measurement
Authors: Zäch M. , Vanicek J. , Heuberger M.
Published: January 2003

In this communication, we describe a photoelectric setup used to monitor the wavelength of a spectral line at sampling rates exceeding 1 kHz. A split photodiode was chosen as the position-sensitive element. Its operation, calibration, and performance are discussed in terms of the interferometric distance measurement in the surface forces apparatus. We demonstrate how the normalized difference signal from the photodiode can be transformed into surface separation and that the extension of the experimental window allows for the acquisition of up to ten force-versus-distance curves per second. Provided that the detector is sufficiently small, we find a linear relationship between the surface separation and the normalized photodetector signal. We illustrate the experimental setup in detail, including the necessary signal-evaluation circuitry. The main difficulties associated with this high-speed approach are low light levels and noise. Optimizing the spectral intensity, keeping the detector area small, designing the evaluation circuits carefully, as well as normalizing the photodetector signal are some of the measures that were found to improve overall performance. Calibration of the device against an absolute distance measurement using a charge coupled device camera as well as its statistical and systematic errors are discussed. The curved nature of the interference fringes and associated implications on the distance determination are considered.
Apparatus for illuminating the tip-sample interface of an atomic force microscope
Authors: Thoreson E. J. , Burnham N. A.
Published: January 2003

An apparatus for the delivery of radiation to the tip-sample interface of an atomic force microscope (AFM) is demonstrated. The pulsed light delivery system (PLDS) was fabricated to probe photoinduced conformational changes of molecules using an AFM. The system is 67 mm long, 59 mm wide, and 21 mm high, leaving clearance to mount the PLDS and a microscope slide coated with a thin film of photoactive molecules beneath the cantilever tip of a stand-alone AFM. The PLDS is coupled into a fiber pigtailed Nd:yttrium–aluminum–garnet frequency doubled laser, operating at a wavelength of 532 nm. The radiation delivered to a sample through the PLDS can be configured for continuous or pulsed mode. The maximum continuous wave power delivered was 0.903 mW and the minimum pulse width was 12.3 μs (maximal 401 μs), corresponding to a minimal energy of 0.150 nJ (maximal 362 nJ), and had a cycle duration of 10.0 ms. The PLDS consists of micro-optical components 3.0 mm and smaller in diameter. The optical design was inspired by the three-beam pickup method used in CD players, which could provide a method to focus the pulse of light onto the sample layer. In addition, the system can be easily modified for different operational parameters (pulse width, wavelength, and power). As proof that the prototype design works, we observed a photoinduced ‘bimetallic’ bending of the cantilever, as evidenced by observing no photoinduced bending when a reflective-coated cantilever was replaced by an uncoated cantilever. Using the apparatus will allow investigation of many different types of molecules exhibiting photoinduced isomerization.
Lifetime measurement and calibration from pressure-sensitive paint luminescence images
Authors: Drouillard T. F. , Linne M. A. , Goss L. P. , Gord J. R. , Fiechtner G. J.
Published: January 2003

A dual-image lifetime technique for acquiring surface pressure measurements from pressure-sensitive paint image data has been developed. This technique eliminates the need to acquire a “wind-off” reference image as required by the traditional radiometric technique, which is known to corrupt results. Here a luminescence lifetime-versus-pressure calibration experiment was conducted. Uncertainty was nominally less than ±4% and decreased as signal level increased. The nominal sensitivity was less than ±5 Torr at 100 Torr, less than ±50 Torr at 700 Torr, and improved with signal level.
Physics of the expanding plasma ejected from a small spot illumined by an ultraviolet pulsed laser
Authors: Nassisi V. , Pedone A.
Published: January 2003

We present the results concerning the physics of the expanding plasma produced by a laser ion source. An efficient source of multiple charged ions was realized by means of an excimer laser. The analysis of the generated plasma was performed for three different laser spot sizes, determining the threshold conditions of the ablation process for a Cu target. Two typologies of Faraday cups were developed in order to detect the plasma current and the ion current along the propagation tube. The time-of-flight measurements were performed inserting in front of the cup an adjustable voltage electrostatic barrier that allowed us to get quantitative information about the ion flux and the kinetic energy of the produced ions. To study the plasma characteristics we measured the total etched material per pulse, 0.25 μg, and the fractional ionization, 12%. The ablated material distribution was monitored by optical transmission analysis of a deposited film. Applying a high voltage to the extraction gap, an ion beam containing Cu+1 (0.44 mA), Cu+2 (0.34 mA), Cu+3 (0.09 mA), and Cu+4 (0.01 mA) ions was obtained.
Rare-earth doped optical fiber approach to an alarm system for fire and heat detection
Authors: Sun T. , Grattan K. T. V. , Sun W. M. , Wade S. A. , Powell B. D.
Published: January 2003

A fluorescence based optical fiber fire alarm system has been further refined in this work to determine the presence of a localized temperature excursion (as low as 50–100 °C) against a varying background at temperatures up to 500–600 °C.
Development of a spring ring for microchannel plate stack fastening in the cosmic hot interstellar plasma spectrometer detector
Authors: Marckwordt Mario
Published: January 2003

This article describes the development of the spring ring used to fasten the microchannel plate (MCP) stack of the cosmic hot interstellar plasma spectrometer (CHIPS) detector. Fastening criteria specific to the CHIPS detector is developed, although the method is applicable to any MCP detector design with cylindrical symmetry. The basic equations from spring disk theory are presented along with appropriate simplifying approximations. Design criteria and test data of the final CHIPS flight version is reviewed, including comparison to results obtained with different materials and processing steps.
Wigner measures and codimension two crossings
Authors: Fermanian Kammerer Clotilde , Lasser Caroline
Published: January 2003

This article gives a semiclassical description of nucleonic propagation through codimension two crossings of electronic energy levels. Codimension two crossings are the simplest energy level crossings, which affect the Born–Oppenheimer approximation in the zeroth order term. The model we study is a two-level Schrödinger equation with a Laplacian as kinetic operator and a matrix-valued linear potential, whose eigenvalues cross, if the two nucleonic coordinates equal zero. We discuss the case of well-localized initial data and obtain a description of the wavefunction’s two-scaled Wigner measure and of the weak limit of its position density, which is valid globally in time.
Advanced high-temperature ultracentrifuge apparatus for mega-gravity materials science
Authors: Mashimo Tsutomu , Huang Xinsheng , Osakabe Toyotaka , Ono Masao , Nishihara Masamichi , Ihara Hirotaka , Sueyoshi Masanori , Shibasaki Koji , Shibasaki Shiro , Mori Nobuo
Published: January 2003

An ultracentrifuge apparatus, which can generate an ultra-strong gravitational field even >1 000 000 (1 million) G (1 G=9.8 m/s2) over a wide temperature range up to >500 °C with high stability control, was developed for new materials science research. The system consists of an air turbine motor with ceramic ball bearings and dumper section, a sample rotor with an outer diameter of up to 160 mm, a vacuum chamber, and a heating system. The nonbored rotor and the double-structural dumper bushing are used to raise the maximum rotational speed and to improve the stability. The samples can be heated by radiant heat. A maximum rotational speed of 190 000 rpm using a 70 mm diam rotor was recorded despite a short time where the maximum gravitational field was >1 2000 000 G. Long and high-temperature ultracentrifuge experiments using 70 and 80 mm diam rotors made of titanium alloy with rotational speeds of up to 170 000 rpm even at temperatures of over 200 °C for 100 h with ripples of <0.05% and <1°, respectively, were successfully performed, where the maximum gravitational field of the sample was >1 000 000 G. The potential energy and sample volume were increased by factors of >2 and >4, respectively, compared with those in the Kumamoto University study [T. Mashimo, S. Okazaki, and S. Tashiro, Rev. Sci. Instrum. 67, 3170 (1996)].
Completely explosive pulsed power minisystem
Authors: Talantsev E. F. , Shkuratov S. I. , Dickens J. C. , Kristiansen M.
Published: January 2003

It is demonstrated that it is feasible to produce pulsed power using an autonomous completely explosive system that harnesses two physical phenomena successively: the transverse shock wave demagnetization of Nd2Fe14B high-energy hard ferromagnets and magnetic cumulation.
Martin–Puplett multichannel far infrared heterodyne interferometer on the Helicity Injected Torus II
Authors: Jewell Patrick D. , Smith Roger J. , Jarboe Thomas R.
Published: January 2003

A novel multichannel implementation of the Martin–Puplett interferometer (MPI) configuration designed for plasma density measurements on the Helicity Injected Torus II (HIT-II) device is described. It is believed that the system represents the first use of a Martin–Puplett interferometer as a plasma density diagnostic in the far infrared (FIR) range and the first MPI system with a frequency-encoded, polarized laser source. The system uses a continuous wave difluoromethane FIR laser (185 μm) with an output power of 70 mW. The MPI replaces a Mach–Zehnder interferometer used on HIT-II while retaining the existing heterodyne scheme which employs a rotating grating wheel that selectively frequency shifts one polarization component of the laser. The advantages of the Martin–Puplett system over the Mach–Zehnder system are (1) the capability to expand to multiple channels, (2) the ability to easily scan through various impact parameters on a shot-to-shot basis, (3) minimization of refractive misalignments due to edge density gradients, and (4) doubling the phase sensitivity using the double pass probe arm. The advantages of the MPI over a modified Michelson system using corner cubes include (1) isolation of the laser source from the detector by the polarizing beam splitter, (2) suppression of spurious reflections at the detector, and (3) a twofold increase in power obtained at the output of a Martin–Puplett interferometer relative to a Michelson interferometer. Two tangentially viewing channels are presently in operation, and each channel is capable of scanning through six impact parameters. This has enabled, for the first time, acquisition of density profile information on both coaxial helicity injection plasmas and inductively driven plasmas on the HIT-II device. Phase sensitivities of 10−2 fringe and bandwidths as high as 250 kHz have been achieved.
256-anode channel plate device for simultaneous ion detection in time of flight measurements
Authors: Bouneau S. , Cohen P. , Della Negra S. , Jacquet D. , Le Beyec Y. , Le Bris J. , Pautrat M. , Sellem R.
Published: January 2003

A 256-anode channel plate device with dedicated electronics has been built for the detection and accurate timing of a large number of simultaneous particle impacts in counting mode. In addition, a method is described which extends the performance of this detector by providing access to the amplitude response without any encoding. This experimental amplitude is extracted for each pixel using a threshold discriminator variation procedure. A detailed description of the detection processes allows calculation of the detector output signal amplitude for single as well as for multiple impacts per pixel. These calculations take into account the geometrical design of the pixelated anode structure. From a comparison between calculated and experimental amplitudes the number of incident particles per pixel can be deduced and thus the total number of particles impinging on the MCP surface. An illustration is given that uses the spatial distribution of swift C60 carbon constituents that exit a thin carbon foil.
Method for the study of semiconductor device operation using scanning capacitance microscopy
Authors: Nakakura C. Y. , Tangyunyong P. , Hetherington D. L. , Shaneyfelt M. R.
Published: January 2003

A new method for studying semiconductor device operation with cross-sectional scanning capacitance microscopy (SCM) is described. The technique uses a modified, commercial SCM system to image device cross sections while dc voltages are incrementally applied to bias test structures between nonconducting and conducting states. The novel test structure design and packaging simplify sample preparation while enabling the application of voltages to discrete regions of the semiconductor device. By recording sequential SCM images as a function of bias voltage, the process of switching a device “off” and “on” can be visualized to study carrier movement in the active region of the device. Two sample SCM sequences of metal–oxide–semiconductor field-effect transistors, one fabricated on a bulk silicon substrate and the other on a silicon-on-insulator substrate, are presented to show typical carrier movement in these devices.
Interacting fermions and domain wall defects in 2+1 dimensions
Authors: Da Rold L. , Fosco C. D. , López A.
Published: January 2003

We consider a Dirac field in 2+1 dimensions with a domain wall like defect in its mass, minimally coupled to a dynamical Abelian vector field. The mass of the fermionic field is assumed to have just one linear domain wall, which is externally fixed and unaffected by the dynamics. We show that, under some general conditions on the parameters, the localized zero modes predicted by the Callan and Harvey mechanism are stable under the electromagnetic interaction of the fermions.
Flux-across-surfaces theorem for a Dirac particle
Authors: Dürr D. , Pickl P.
Published: January 2003

We consider the asymptotic evolution of a relativistic spin-12 particle, i.e., a particle whose wave function satisfies the Dirac equation with external static potential. We prove that the probability for the particle crossing a (detector) surface converges to the probability, that the direction of the momentum of the particle lies within the solid angle defined by the (detector) surface, as the distance of the surface goes to infinity. This generalizes earlier nonrelativistic results, known as flux across surfaces theorems, to the relativistic regime.
Direct generation of a tunable nearly transform-limited picosecond pulse in the ultraviolet region using a distributed-feedback dye laser
Authors: Hoa D. Q. , Takeyasu N. , Imasaka T. , Hung N. D.
Published: January 2003

A new design and the characteristics of operating a distributed-feedback dye laser (DFDL) pumped by the fourth-harmonic emission of a Q-switched Nd:YAG laser are described. An ultraviolet nearly transform-limited picosecond pulse was generated by means of two right-angle prisms in the pumping geometry, and the laser wavelength was continuously tunable from 318 to 369 nm using two dye solutions (BM-terphenyl and BMQ). The application of this DFDL to the lifetime measurement of a fluorescent dye is also presented.
±30 μK temperature controller from 25 to 103 °C: Study and analysis
Authors: Madhavan Unni P. K. , Gunasekaran M. K. , Kumar A.
Published: January 2003

A simple two-stage metal thermostat, having a wide tolerance, has been built for performing light scattering studies in multicomponent liquid systems. It gives a temperature stability of ±30–45 μK for 112 h and ±60–90 μK for 7–14 h over a broad range of 25–103 °C. A detailed profile of thermal gradients within the sample recess is provided. The parameter ΔTeff [i.e., the difference between the maximum (minimum if ΔTeff has a negative value) temperature within the sample recess and the temperature just outside the sample recess] seems to be more relevant than ΔT (i.e., the temperature difference between the inner and the outer stages) in understanding the behavior of our thermostat. The thermal gradients can be tuned by varying ΔTeff (or by varying ΔT). The least values of horizontal and vertical thermal gradients, i.e., 250 and 100 μK/mm, respectively, are observed for ΔTeff=4.46 mK. The transient response of the controller is almost invariant for ΔTeff>0, but it shows a dramatic decrease of almost 50% when ΔTeff<0. On the whole, the limit ΔTeff → 0, provides the best operating condition from all standpoints. A simple and effective compensation scheme to null the effect of extraneous parameters is employed. The importance of the stability of the bridge excitation source in improving the long-term stability of the controller is established.
Study of electron identification in a few GeV region by an emulsion cloud chamber
Authors: Kodama K. , Hoshino K. , Komatsu M. , Miyanishi M. , Nakamura M. , Nakamura T. , Nakano T. , Narita K. , Niwa K. , Nonaka N. , Sato O. , Toshito T. , Uetake T.
Published: January 2003

We have performed an experimental study of electron identification using an emulsion cloud chamber detector with electron-enriched π− beams at 2 and 4 GeV/c produced by the proton synchrotron source at CERN. This study shows that the efficiency of electron identification is about 90% with little (6%) contamination from pions. These results are in agreement with those obtained using a Cherenkov counter and are reproduced well by the simulation.
Add-on transmission attachments for the scanning electron microscope
Authors: Khursheed A. , Karuppiah N. , Osterberg M. , Thong J. T. L.
Published: January 2003

This article presents simulation and experimental results for add-on transmission attachments that have been developed for the scanning electron microscope (SEM). A primary beam energy of around 30 keV is used to irradiate thin test specimens (<100 nm). A transmission lens attachment enables a conventional field emission SEM to improve its image resolution by an order of magnitude, providing an image magnification of several million and a spatial resolution down to 0.3 nm. In addition, a compact energy electron loss spectrometer attachment has been developed that uses the SEM’s built-in secondary electron detector.
Low-shear-rate capillary viscometer for polymer solution intrinsic viscosity determination at varying temperatures
Authors: Rushing T. S. , Hester R. D.
Published: January 2003

A low-shear capillary viscometer has been designed, constructed, and used to measure polymer solution intrinsic viscosities over temperatures ranging from 10 to 75 °C. The instrument is capable of detecting the small shear stress forces produced when low-viscosity fluids are subjected to very low-shear rates. Instrument performance and sensitivity were evaluated using deionized water at temperatures between 10 and 75 °C. The measured water viscosity values differed from the literature values by less than 1%. The viscometer was also used to determine that the intrinsic viscosity of a poly(acrylamide) aqueous solution at 29 °C was 17.7 dL/g. This value was in agreement with the value obtained using a Contraves Low-Shear 30 cup and bob rheometer, 17.9 dL/g.
Characterization of a high-intensity unipolar-mode pulsed ion source with improved magnetically insulated diode
Authors: Zhu X. P. , Lei M. K. , Dong Z. H. , Ma T. C.
Published: January 2003

A magnetically insulated ion diode (MID) with an improved external-magnetic field system has been developed and installed onto a TEMP-6-type high-intensity pulsed ion source in order to produce a high-intensity pulsed ion beam (HIPIB) for surface modification of materials. The external-magnetic field MID is operated in unipolar mode based on dielectric high-voltage flashover, and a double coaxial pulse-forming line (PFL) powered with a Marx generator is used to form the unipolar pulse of nanosecond width. A specially designed cathode has been constructed with a forked connection to two symmetrically installed transformers to improve the effect of the magnetic field and thus increase the stability of generation and propagation of the ion beam. It was found that the efficient generation of HIPIB mainly depended on the magnetic field strength, the gas pressures in reverse and output switches of PFL, and the anode–cathode (A–K) gap of the external-magnetic field MID. A proper magnetic field strength was found with magnetic field power system at dc charging voltage of 8 kV. The proper A–K gap distance is not uniform with the value varied from 6 to 8 mm. Suitable gas pressures for reverse and output switches were about 1.2 and 2.4 atm, respectively, at a charging voltage of 40 kV to the Marx generator. The most efficient plasma generation and ion extraction led to a maximum output of HIPIB with a peak ion current density of 300 A cm−2 and a beam pulse width of 80 ns (full width at half maximum), at an accelerating pulse of 300–350 kV with a pulse width of 70 ns.
Simultaneous multicolor fluorescence imaging by scanning near-field optical/atomic force microscopy
Authors: Muramatsu H. , Kim J. M. , Sugiyama S. , Ohtani T.
Published: January 2003

We have developed an easily operable scanning near-field optical microscope for multicolor fluorescence imaging by applying a highly sensitive charge-coupled-device (CCD) camera. The CCD camera is used as a variable area photosensor, and a mean intensity of a selected area in the CCD camera is converted to a numerical value. By combining a spectrometer with the CCD camera, arbitrary wavelength ranges can be selected to provide plural fluorescence images separated by fluorescence wavelength. The function of the system is demonstrated by imaging mixed fluorescence particles and a two-color stained chromosome sample of Hordeum vulgare treated with a two-color fluorescent banding stain method.
Fast auroral snapshot satellite observations of very low frequency saucers
Authors: Ergun R. E. , Carlson C. W. , McFadden J. P. , Strangeway R. J. , Goldman M. V. , Newman D. L.
Published: January 2003

Wave and charged particle observations of quasielectrostatic whistler emissions known as “VLF saucers” (very low frequency, or kilohertz radio range) from the Fast Auroral SnapshoT (FAST) satellite demonstrate that the majority (∼85%) of VLF saucer emissions are generated on flux tubes that carry antiearthward, energetic (>10 eV) electrons in the downward current region of the aurora. In most cases, the VLF saucers are nested, that is, they have two or more clearly discernible “arms” that indicate several distinct source regions at differing altitudes. These observations verify previous interpretations that the individual source regions are highly localized both in latitude and altitude. In some cases, the individual source regions are localized in three dimensions. An important new finding is that the FAST satellite frequently detects solitary structures identified as electron phase-space holes at the vertex of VLF saucers. Electron phase-space holes were identified in ∼79% of the VLF saucer events in the downward current region. This finding implies either a common energy source or a direct association between the two phenomena. Furthermore, the observations now show a direct association with the VLF saucer source flux tube and diverging dc electric field structures. An interpretation is put forth that the VLF saucer source region is in or near parallel electric fields in the downward current region of the aurora.
Non-Abelian braid statistics versus projective permutation statistics
Authors: Read N.
Published: January 2003

Recent papers by Finkelstein, Galiautdinov, and co-workers [J. Math. Phys. 42, 1489 (2001); 42, 3299 (2001)] discuss a suggestion by Wilczek that non-Abelian projective representations of the permutation group can be used as a new type of particle statistics, valid in any dimension. Wilczek’s suggestion was based in part on an analysis by Nayak and Wilczek (NW) of the non-Abelian representation of the braid group in a quantum Hall system. We point out that projective permutation statistics is not possible in a local quantum field theory as it violates locality, and show that the NW braid group representation is not equivalent to a projective representation of the permutation group. The structure of the finite image of the braid group in a 2n/2−1-dimensional representation is obtained.
Modified braid equations, Baxterizations and noncommutative spaces for the quantum groups GLq(N), SOq(N), and Spq(N)
Authors: Chakrabarti A. , Chakrabarti R.
Published: January 2003

Modified braid equations satisfied by generalized R̂ matrices (for a given set of group relations obeyed by the elements of T matrices) are constructed for q-deformed quantum groups GLq(N), SOq(N), and Spq(N) with arbitrary values of N. The Baxterization of R̂ matrices, treated as an aspect complementary to the modification of the braid equation, is obtained for all these cases in particularly elegant forms. A new class of braid matrices is discovered for the quantum groups SOq(N) and Spq(N). The R̂ matrices of this class, while being distinct from the restrictions of the universal R̂ matrix to the corresponding vector representations, satisfy the standard braid equation. The modified braid equation and the Baxterization are obtained for this new class of R̂ matrices. Diagonalization of the generalized R̂ matrices is studied. The diagonalizers are obtained explicitly for some lower dimensional cases in a convenient way, giving directly the eigenvalues of the corresponding R̂ matrices. Applications of such diagonalization are then studied in the context of associated covariantly quantized noncommutative spaces.
Belov–Chaltikian and Blaszak–Marciniak lattice equations: Recursion operators and factorization
Authors: Sahadevan R. , Khousalya S.
Published: January 2003

A systematic investigation on the construction of recursion operators for partial differential–difference equations (PDDEs) with two independent variables (one continuous and one discrete) using its generalized symmetries is presented. Also it is explained how to factorize the obtained recursion operators. The applicability of the above procedure have been illustrated for the relativistic toda (RT), Belov–Chaltikian (BC) and Blaszak–Marciniak (BM) lattice equations and shown that the former two lattice equations admit (2×2) matrix recursion operators while the latter one possesses a (3×3) matrix recursion operator. Furthermore, the constructed recursion operators can be written as a factor of 2 distinct invertible matrix operators in each of the lattice equations. It is also proved explicitly that the factorized operators are Hamiltonian and hence RT, BC and BM lattice equations are bi-Hamiltonian systems.
Some integrable systems in nonlinear quantum optics
Authors: Horowski Maciej , Odzijewicz Anatol , Tereszkiewicz Agnieszka
Published: January 2003

In the paper we investigate the theory of quantum optical systems. As an application we integrate and describe the quantum optical systems which are generically related to the classical orthogonal polynomials. The family of coherent states related to these systems is constructed and described. Some applications are also presented.
The effect of the ambient plasma conditions on the variation of charge on dust grains
Authors: Chakraborty M. , Kausik S. S. , Saikia B. K. , Kakati M. , Bujarbarua S.
Published: January 2003

An experimental study has been performed into the variation of charge on dust grains with change in the ambient plasma conditons. A dust beam containing submicron sized silver grains was passed through plasma. The dust grains were charged by the plasma particles as well as by primary electrons from the filament. An increase in the filament current increased both the plasma density and the number density of the primary electrons. The grain charge was found out both from the deflection of the dust grains and also from the floating potential. The experimental observations shows that the secondary emission caused by the primary electrons significantly influenced and played a prominent role in the establishment of charge on the grains.
On dimensional regularization of sums
Authors: Contino Roberto , Gambassi Andrea
Published: January 2003

We discuss a systematic way to dimensionally regularize divergent sums arising in field theories with an arbitrary number of physical compact dimensions or finite temperature. The method preserves the same symmetries of the action as the conventional dimensional regularization and allows an easy separation of the regulated divergence from the finite term that depends on the compactification radius (temperature).
Trigonometric osp(1|2) Gaudin model
Authors: Kulish P. P. , Manojlović N.
Published: January 2003

The problems connected with Gaudin models are reviewed by analyzing model related to the trigonometric osp(1|2) classical r-matrix. The eigenvectors of the trigonometric osp(1|2) Gaudin Hamiltonians are found using explicitly constructed creation operators. The commutation relations between the creation operators and the generators of the trigonometric loop superalgebra are calculated. The coordinate representation of the Bethe states is presented. The relation between the Bethe vectors and solutions to the Knizhnik–Zamolodchikov equation yields the norm of the eigenvectors. The generalized Knizhnik–Zamolodchikov system is discussed both in the rational and in the trigonometric case.
Effect of nonlinear coupling of right and left circularly polarized Hall magnetohydrodynamic modes on filamentation processes in the solar wind
Authors: Shukla Anita , Sharma R. P.
Published: January 2003

This paper presents the model equations, governing the coupling of the right and left circularly polarized Alfvén waves, using Hall magnetohydrodynamics (MHD) equations. The solution of these model equations has been obtained by using analytical and numerical methods to study the effect of their mutual nonlinear interaction on filament formation, the critical size of the filaments and the threshold in the compressible Hall MHD case. The coupling between the two modes may be so effective that the formation of periodic filaments, separated by a distance of the order of 900 kms and a transverse size of the order of 2.3×105 kms, can be predicted for typical solar wind parameters. The effect of coupling on Faraday rotation and ellipticity has also been studied. Its effect on solar wind turbulence has been pointed out.
Induced representations of Uqso(5)
Authors: Parashar Preeti
Published: January 2003

We study the reduction of the left regular representation of the quantum algebra Uqso(5). This yields induced representations of Uqso(5) on some quotient space of the matrix quantum group SOq(5). To facilitate the construction of a suitable basis the Gauss decomposition of SOq(5) is worked out explicitly. We then investigate the behavior of these representations for a generic q as well as when q is an Nth root of unity leading to some finite dimensional irreducible representations of Uqso(5). Two basic intertwining operators are also constructed via the right action.
Casimir energy of a relativistic perfect fluid confined to a D-dimensional hypercube
Authors: Edery Ariel
Published: January 2003

Compact formulas are obtained for the Casimir energy of a relativistic perfect fluid confined to a D-dimensional hypercube with von Neumann or Dirichlet boundary conditions. The formulas are conveniently expressed as a finite sum of the well-known gamma and Riemann zeta functions. Emphasis is placed on the mathematical technique used to extract the Casimir energy from a D-dimensional infinite sum regularized with an exponential cutoff. Numerical calculations show that initially the Dirichlet energy decreases rapidly in magnitude and oscillates in sign, being positive for even D and negative for odd D. This oscillating pattern stops abruptly at the critical dimension of D=36 after which the energy remains negative and the magnitude increases. We show that numerical calculations performed with 16-digit precision are inaccurate at higher values of D.
Compression effects in inductively coupled, high-power radio-frequency discharges for negative hydrogen ion production
Authors: Wilhelm Rolf
Published: January 2003

In the paper we present a simplified model description of inductively coupled plasma discharges operating at a rather high radio-frequency (rf) power. In this case the induced high plasma currents can cause periodic compressions over a substantial radial distance. Such conditions are obviously given in rf driven 1 MHz/150 kW plasma sources developed at the Institute for Plasma Physics Garching for negative (hydrogen) ion production in future neutral beam injection (NBI) systems for nuclear fusion research, such as the 1 MeV/50 MW NBI system for the International Thermonuclear Experimental Reactor [T. Inoue, R. Hemsworth, V. Kulygin, and Y. Okumura, Fusion Eng. Design 55, 291 (2001)]. The given model describes quite well the compression and other features of the discharge. The results include the Ohmic power input (i.e., electron heating), the resulting density build-up, and—as a new feature—periodical plasma compressions, leading to a direct energy input also into the plasma ions. The model also explains the strange effect of small argon admixtures, which improve the negative ion yield in rf sources by a factor of up to 2–3 (but which have no effect in conventional dc arc sources). With the calculated dependencies from external parameters (e.g., rf-power and frequency, gas pressure, ion mass or the specific geometry), the modeling may help for the further optimization of the rf source.
Mechanisms responsible for improvement of 4H–SiC/SiO2 interface properties by nitridation
Authors: Afanas’ev V. V. , Stesmans A. , Ciobanu F. , Pensl G. , Cheong K. Y. , Dimitrijev S.
Published: January 2003

An analysis of fast and slow traps at the interface of 4H–SiC with oxides grown in O2, N2O, and NO reveals that the dominant positive effect of nitridation is due to a significant reduction of the slow electron trap density. These traps are likely to be related to defects located in the near-interfacial oxide layer. In addition, the analysis confirms that the fast interface states related to clustered carbon are also reduced by nitridation.
A Laplace operator and harmonics on the quantum complex vector space
Authors: Iorgov N. Z. , Klimyk A. U.
Published: January 2003

The aim of this article is to study the q-Laplace operator and q-harmonic polynomials on the quantum complex vector space generated by elements zi,wi, i=1,2,…,n, on which the quantum group GLq(n) [or Uq(n)] acts. The q-harmonic polynomials are defined as solutions of the equation Δqp=0, where p is a polynomial in zi,wi, i=1,2,…,n, and the q-Laplace operator Δq is determined in terms of q-derivatives. The q-Laplace operator Δq commutes with the action of GLq(n). The projector Hm,m′:Am,m′→Hm,m′ is constructed, where Am,m′ and Hm,m′ are the spaces of homogeneous (of degree m in zi and of degree m′ in wi) polynomials and homogeneous q-harmonic polynomials, respectively. By using these projectors, a q-analog of the classical zonal spherical and associated spherical harmonics are constructed. They constitute an orthogonal basis of Hm,m′. A q-analog of separation of variables is given. The quantum algebra Uq(gln), acting on Hm,m′, determines an irreducible representation of Uq(gln). This action is explicitly constructed. The results of the article lead to the dual pair (Uq(sl2),Uq(gln)) of quantum algebras.
Comment on “Low frequency dusty plasma modes in a uniform magnetic field” [Phys. Plasmas 9, 4396 (2002)]
Authors: Shukla P. K. , Salimullah M. , Sandberg I.
Published: January 2003

It is shown that Wang et al. [Phys. Plasmas 9, 4396 (2002)] have not properly treated low-frequency dusty plasma waves in a uniform magnetic field. Their electron and ion susceptibilities are dubious. An improved description of the low-frequency dusty plasma wave spectra is presented.
Estimates on the mean current in a sphere of plasma
Authors: Núñez Manuel
Published: January 2003

Several turbulent dynamo models predict the concentration of the magnetic field in chaotic plasmas in sheets with the field vector pointing alternatively in opposite directions, which should produce strong current sheets. It is proved that if the plasma is contained in a rigid sphere with perfectly conducting boundary the geometry of these sheets must be balanced so that the mean current remains essentially bounded by the Coulomb gauged mean vector potential of the field. This magnitude remains regular even for the sharp field variations expected in a chaotic flow. For resistive plasmas the same arguments imply that the contribution to the total current of the regions near the boundary compensates the current of the central part of the sphere.
On the invariants of some solvable rigid Lie algebras
Authors: Campoamor-Stursberg Rutwig
Published: January 2003

We determine fundamental systems of invariants for complex solvable rigid Lie algebras having nonsplit nilradicals of characteristic sequence (3,1,…,1), these algebras being the natural followers of solvable algebras having Heisenberg nilradicals. A special case of this allows us to obtain a criterion to determine the number of functionally independent invariants of rank one subalgebras of (real or complex) solvable Lie algebras. Finally, we give examples of the inverse procedure, obtaining fundamental systems of an algebra starting from rank one subalgebras, and a criterion for the nonexistence of nontrivial invariants.
A connection between distributivity and locality in compound P-lattices
Authors: Watanabe Teppei
Published: January 2003

A P-lattice is a σ-complete, orthomodular atomic lattice ℒ which is formed by the set of propositions of a physical system. A composition of physical systems is considered, and some concept of locality in a compound physical system is represented in terms of P-lattices. We give a remark toward necessary and sufficient conditions for it to hold, which have been provided implicitly in antecedent studies, and we show that it can be provided under weaker conditions.
Bound states in one and two spatial dimensions
Authors: Chadan K. , Khuri N. N. , Martin A. , Tsun Wu Tai
Published: January 2003

In this article we study the number of bound states for potentials in one and two spatial dimensions. We first show that in addition to the well-known fact that an arbitrarily weak attractive potential has a bound state, it is easy to construct examples where weak potentials have an infinite number of bound states. These examples have potentials which decrease at infinity faster than expected. Using somewhat stronger conditions, we derive explicit bounds on the number of bound states in one dimension, using known results for the three-dimensional zero angular momentum. A change of variables which allows us to go from the one-dimensional case to that of two dimensions results in a bound for the zero angular momentum case. Finally, we obtain a bound on the total number of bound states in two dimensions, first for the radial case and then, under stronger conditions, for the noncentral case.
Category of nonlinear evolution equations, algebraic structure, and r-matrix
Authors: Qiao Zhijun , Cao Cewen , Strampp Walter
Published: January 2003

In this paper we deal with the category of nonlinear evolution equations (NLEEs) associated with the spectral problem and provide an approach for constructing their algebraic structure and r-matrix. First we introduce the category of NLEEs, which is composed of various positive order and negative order hierarchies of NLEEs both integrable and nonintegrable. The whole category of NLEEs possesses a generalized Lax representation. Next, we present two different Lie algebraic structures of the Lax operator: one of them is universal in the category, i.e., independent of the hierarchy, while the other one is nonuniversal in the hierarchy, i.e., dependent on the underlying hierarchy. Moreover, we find that two kinds of adjoint maps are r-matrices under the algebraic structures. In particular, the Virasoro algebraic structures without a central extension of isospectral and nonisospectral Lax operators can be viewed as reductions of our algebraic structure. Finally, we give several concrete examples to illustrate our methods. Particularly, the Burgers’ category is linearized when the generator, which generates the category, is chosen to be independent of the potential function. Furthermore, an isospectral negative order hierarchy in the Burgers’ category is solved with its general solution. Additionally, in the KdV category we find an interesting fact: the Harry–Dym hierarchy is contained in this category as well as the well-known Harry–Dym equation is included in a positive order KdV hierarchy.
Dirichlet forms and symmetric Markovian semigroups on CCR algebras with respect to quasi-free states
Authors: Bahn Changsoo , Ko Chul Ki , Park Yong Moon
Published: January 2003

Employing the construction method of Dirichlet forms on standard forms of von Neumann algebras developed in Infinite Dimensional Analysis, Quantum Probability and Related Topics, 2000, Vol. 3, No. 1, pp. 1–14 (Ref. 1), we construct Dirichlet forms and associated symmetric Markovian semigroups on CCR algebras with respect to quasi-free states. More precisely, let A(h0) be the CCR algebra over a complex separable pre-Hilbert space h0 and let ω be a quasi-free state on A(h0). For any normalized admissible function f and complete orthonormal system (CONS) {gn}⊂h0, we construct a Dirichlet form and corresponding symmetric Markovian semigroup on the natural standard form associated to the GNS representation of (A(h0),ω). It turns out that the form is independent of admissible function f and CONS {gn} chosen. By analyzing the spectrum of the generator (Dirichlet operator) of the semigroup, we show that the semigroup is ergodic and tends to the equilibrium exponentially fast.
Piezoresistive detection of acoustic waves
Authors: Passian A. , Evans P. G. , Varma V. K. , Ferrell T. L. , Thundat T.
Published: January 2003

A simple and cost-effective method for detecting propagation of acoustic waves based on the harmonic oscillations of a piezoresistive microcantilever is presented. Monitoring the Fourier amplitude of the microcantilever’s fundamental frequency, the dependence of the detected amplitude upon the acoustic source location, is measured. At a fixed probe–source distance, the solid angular dependence of the cantilever plane relative to the source is studied. The potential use of a microelectromechanical cantilever as an acoustic leak sensor for pressurized gas reservoirs is addressed.
Effects of poloidal variation of neutral density on Pfirsch–Schlüter transport near the tokamak edge
Authors: Simakov Andrei N. , Catto Peter J.
Published: January 2003

Effects of neutral particles on plasma flows and radial transport in a collision-dominated plasma are discussed, with a particular attention given to the modifications due to a poloidal variation of the neutral density. It is found that neutrals are of no importance if the radial particle transport is on a Pfirsch–Schlüter level. If, on the other hand, anomalous effects increase this transport to the Pfirsch–Schlüter radial heat transport level or higher, neutral effects become important in determining the radial heat transport, radial electric field, and the ion parallel flow velocity.
Damping of waves in helicon-wave range of frequency in molecular- and rare-gas plasmas
Authors: Kikuchi H. , Fukui Y. , Sakawa Y. , Shoji T.
Published: January 2003

The damping of electromagnetic waves in helicon-wave range of frequency in molecular- and rare-gas plasmas is investigated. Test waves are excited by applying 144 MHz of rf to a single-loop antenna in H2 and He plasmas under the external magnetic field B0⩽1 kG. High-density H2 plasmas are produced at an optimum frequency for a fixed B0. Axial structures of the wave magnetic field are measured. The pressure dependence of k∥ and ki on B0 is investigated, where k∥ and ki are, respectively, the real and imaginary parts of wave number parallel to B0. The measured values of k∥ agree well with the ones calculated from the cold plasma theory in H2 and He plasmas. The effective collision frequency νeff=kiωce/k⊥ is evaluated from the measured ki, where k⊥ and ωce are the perpendicular component of wave vector and electron cyclotron frequency, respectively. As a result, whereas νeff in He plasmas is consistent with the calculated value, that in H2 is nearly a factor of 3 larger than the calculated one.