bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclooxygenase‐2 is induced in the endothelial cells throughout the central nervous system during carrageenan‐induced hind paw inflammation; its possible role in hyperalgesia
Authors: Ibuki Takae , Matsumura Kiyoshi , Yamazaki Yasuo , Nozaki Taiki , Tanaka Yoshifumi , Kobayashi Shigeo
Published: February 2004

Inflammation is often accompanied with hyperalgesia. This hyperalgesia is mediated partly by prostaglandin(s) produced in the CNS through the cyclooxygenase‐2 (COX‐2) dependent pathway. However, it remains unclear where COX‐2 is induced in the CNS during inflammation, and how it is involved in hyperalgesia. We studied the precise site of COX‐2 induction in the CNS, the relation between the time course of COX‐2 induction and that of hyperalgesia, and the effect of COX‐2‐selective inhibitor by using a carrageenan model. Carrageenan injection induced expression of COX‐2‐like immunoreactivity in vascular endothelial cells throughout the CNS. This response became evident by 3 h, and was most prominent at 6 h after carrageenan injection. This COX‐2 induction was associated with an elevation of prostaglandin E2 in the cerebrospinal fluid, being evident at 3 h, larger at 6 h, and alleviated by a COX‐2‐selective inhibitor. Thermal hyperalgesia became evident at 1 h, further increased thereafter, and remained elevated until 6 h. Intrathecal administration of COX‐2‐selective inhibitor 2 h after the carrageenan injection exerted a prominent therapeutic effect on hyperalgesia. These results demonstrate that, during carrageenan‐induced inflammation, endothelial cells are the major source of prostaglandin(s) in the CNS, and this endothelial expression of COX‐2 is involved in the inflammation‐induced hyperalgesia.
Characterization of chronic low‐level proteasome inhibition on neural homeostasis
Authors: Ding Qunxing , Dimayuga Edgardo , Martin Sarah , Bruce‐Keller Annadora J. , Nukala Vidya , Cuervo Ana Maria , Keller Jeffrey N.
Published: February 2004

Increasing evidence suggests that proteasome inhibition plays a causal role in promoting the neurodegeneration and neuron death observed in multiple disorders, including Alzheimer's disease (AD) and Parkinson's disease (PD). The ability of severe and acute inhibition of proteasome function to induce neuron death and neuropathology similar to that observed in AD and PD is well documented. However, at present the effects of chronic low‐level proteasome inhibition on neural homeostasis has not been elucidated. In order to determine the effects of chronic low‐level proteasome inhibition on neural homeostasis, we conducted studies in individual colonies of neural SH‐SY5Y cells that were isolated following continual exposure to low concentrations (100 nm) of the proteasome inhibitor MG115. Clonal cell lines appeared morphologically similar to control cultures but exhibited significantly different rates of both proliferation and differentiation. Elevated levels of protein oxidation and protein insolubility were observed in clonal cell lines, with all clonal cell lines being more resistant to neural death induced by serum withdrawal and oxidative stress. Interestingly, clonal cell lines demonstrated evidence for increased macroautophagy, suggesting that chronic low‐level proteasome inhibition may cause an excessive activation of the lysosomal system. Taken together, these data indicate that chronic low‐level proteasome inhibition has multiple effects on neural homeostasis, and suggests that studying the effects of chronic low‐level proteasome inhibition may be useful in understanding the relationship between protein oxidation, protein insolubility, proteasome function, macroautophagy and neural viability in AD and PD.
Alkali halide nanocrystal growth and etching studied by AFM and modeled by MD simulations
Authors: Garcia-Manyes Sergi , Verdaguer Albert , Gorostiza Pau , Sanz Fausto
Published: February 2004

NaCl hillocks have been grown on the NaCl(100) monocrystalline surface by simply making the tip of an atomic force microscope cantilever interact with the surface. A quantitative discussion about the hillock dissolution process as well as physical stability of these ionic surfaces has been made. Molecular dynamics simulations helped us to interpret the experimental data. An explanation for the hillock formation and dissolution phenomena is also discussed.
Analytical energy gradient of the symmetry-adapted-cluster configuration-interaction general-R method for singlet to septet ground and excited states
Authors: Ishida Mayumi , Toyota Kazuo , Ehara Masahiro , Frisch Michael J. , Nakatsuji Hiroshi
Published: February 2004

A method of calculating analytical energy gradients of the singlet and triplet excited states, ionized states, electron-attached states, and high-spin states from quartet to septet states by the symmetry-adapted-cluster configuration-interaction general-R method is developed and implemented. This method is a powerful tool in the studies of geometries, dynamics, and properties of the states of molecules in which not only one-electron processes but also two- and multielectron processes are involved. The performance of the present method was confirmed by calculating the geometries and the spectroscopic constants of the diatomic and polyatomic molecules in various electronic states involving the ground state and the one- to three-electron excited states. The accurate descriptions were obtained for the equilibrium geometries, vibrational frequencies, and adiabatic excitation energies, which show the potential usefulness of the present method. The particularly interesting applications were to the C′ 1Ag state of acetylene, the A 2Δu and B 2Σu+ states of CNC and the B14 and a 4Πu states of N3 radical.
Solid–fluid and solid–solid phase equilibrium in a model of n-alkane mixtures
Authors: Cao M. , Monson P. A.
Published: February 2004

Solid–fluid and solid–solid phase equilibrium for binary mixtures of hard sphere chains modeling n-hexane, n-heptane, and n-octane has been calculated using Monte Carlo computer simulations. Thermodynamic integration was used to calculate the Gibbs free energy and chemical potentials in the solid and fluid phases from pure component reference values. A multiple stage free energy perturbation method was used to calculate the composition derivative of the Gibbs free energy. Equation of state and free energy data for the fluid phase indicate ideal solution behavior. Nonideality is much more significant in the solid phase with only partial solubility of shorter chains in the longer chains and essentially no solubility at the other end of the composition range. The miscibility decreases with increasing chain length difference between the components. For the model of n-hexane/n-octane mixtures solid–solid phase separation has been observed directly in some of the simulations, with the components segregating between the layers of the solid structure. The behavior is similar to that seen in some binary n-alkane mixtures with longer chain lengths but comparable chain length ratios between the components. Such phase separation, although indicated thermodynamically, is not seen directly in the simulations of the n-heptane/n-octane mixture due to the difference in the pure component crystal structures.
Collision barrier effects on the bulk flow in a random suspension
Authors: Dance S. L. , Climent E. , Maxey M. R.
Published: February 2004

Simplified models are often used for the short-range interaction of spherical particles in dilute, liquid–solid suspensions. These may range from simple collision barriers to a more detailed inclusion of viscous lubrication forces. Results are given to illustrate the sensitivity of mean particle velocity, fluctuation levels, and microstructure to different parameters and barrier models.
Reaction pathway and potential barrier for the CaH product in the reaction of Ca(4s4p 1P1)+H2→CaH(X 2Σ+)+H
Authors: Song Yu-Wen , Chen Jye-Jong , Hsiao Ming-Kai , Lin King-Chuen , Hung Yu-Ming
Published: February 2004

The nascent CaH product in the reaction Ca(4s4p 1P1)+H2→CaH(X 2Σ+)+H is obtained using a pump–probe technique. The CaH(v=0,1) distributions, with a population ratio of CaH(v=0)/CaH(v=1)=2.7±0.2, may be characterized by low Boltzmann rotational temperature. According to Arrhenius theory, the temperature dependence measurement yields a potential barrier of 3820±480 cm−1 for the current reaction. As a result of the potential energy surfaces (PES) calculations, the reaction pathway favors a Ca insertion into the H2 bond along a (near) C2v geometric approach. As the H2 bond is elongated, the configurational mixing between the orbital components of the 4p and nearby low-lying 3d state with the same symmetry makes significant the nonadiabatic transition between the 5A′ and 2A′ surface in the repulsive limbs. Therefore, the collision species are anticipated to track along the 5A′ surface, then undergo nonadiabatic transition to the inner limb of the 2A′ surface, and finally cross to the reactive 1A′ surface. The observed energy barrier probably accounts for the energy requirement to surmount the repulsive hill in the entrance. The findings of the nascent CaH product distributions may be reasonably interpreted from the nature of the intermediate structure and lifetime after the 2A′–1A′ surface transition. The distinct product distributions between the Ca(4 1P1) and Mg(3 1P1) reactions with H2 may also be realized with the aid of the PES calculations.
Phase transformation in a lattice system in the presence of spin-exchange dynamics
Authors: Berim Gersh O. , Ruckenstein Eli
Published: February 2004

A joint action of the Glauber single-spin-flip and the Kawasaki spin-exchange mechanisms upon the processes of phase transformation is examined in the framework of the one-dimensional kinetic Ising model. It is shown that the addition of the Kawasaki dynamics to that of Glauber accelerates the process of phase transformation in the initial stage, but slows it down in later stages. For the truncated form of Glauber dynamics, which excludes the processes of splitting and coagulation of clusters, the addition of the Kawasaki dynamics always accelerates the phase transformation process. Acting alone, the Kawasaki mechanism provides a cluster growth proportional to t1/2 (where t is the time) in the initial stage and proportional to t1/3 (Lifshitz–Slyozov–Wagner law) in the intermediate stage. In the final stage, a cluster size approaches exponentially its equilibrium value.
The role of fluctuations in both density functional and field theory of nanosystems
Authors: Reguera David , Reiss Howard
Published: February 2004

The role of fluctuations in both the density functional theory (DFT) and the field theory (FT) of nanosystems is studied. It turns out that although fluctuations are rigorously incorporated into the general formalism of DFT, they are often omitted in the choice of an approximate free energy functional that must be constructed in order to solve the basic integral equation appearing in DFT. Aside from the analytical discussion, it is demonstrated, in connection with a particular system (fluid in a nanopore) that the effects of fluctuation are missing when one of the most common functionals for this system is used. The demonstration involves a comparison of the results of Monte Carlo simulation with the predictions of DFT when this free energy functional is used. The applicability of FT and DFT in the context of the theory of nucleation is also discussed.
Laser-induced fluorescence spectroscopy of NC3S
Authors: Nakajima Masakazu , Yoneda Yu , Sumiyoshi Yoshihiro , Endo Yasuki
Published: February 2004

In a discharged supersonic jet of acetonitrile and carbon disulfide, we have for the first time observed an electronic transition of the NC3S radical using laser-induced fluorescence (LIF) spectroscopy. A progression originating from the C–S stretching mode of the upper electronic state appears in the excitation spectrum. Each band of the progression has a polyad structure due to anharmonic resonances with even overtones of bending modes. Rotationally resolved spectra have been observed by high-resolution laser scans, and the electronic transition is assigned to Ã 2Πi–X̃ 2Πi. For the vibronic origin band, the position and the effective rotational constant of the upper level have been determined to be 21 553.874(1) and 0.046 689(4) cm−1, respectively. The dispersed fluorescence spectrum from the zero vibrational level of Ã 2Π3/2 has also been observed; its vibrational structure is similar to that of the LIF excitation spectrum, showing a prominent C–S stretching progression with polyad structures. The vibrational frequencies of the C–S stretching mode in the ground and excited electronic states are determined to be 550 and 520 cm−1, respectively. Fluorescence decay profiles have been measured for several vibronic levels of the Ã state.
Comparative studies of the photoinduced reactions in the Mg+–SCNC2H5 and Mg+–NCSC2H5 complexes
Authors: Hu Yihua , Liu Haichuan , Yang Shihe
Published: February 2004

The photoinduced reactions of the complexes Mg+–SCNC2H5 and Mg+–NCSC2H5 are studied comparatively in the spectral range of 230–440 nm. One-photon excitation of the complexes through the Mg+ chromophore (3 2P←3 2S) gives rise to the evaporative fragment as well as the molecular activation and charge transfer products. The action spectra of the complexes consist of three broad peaks for Mg+–SCNC2H5 and two for Mg+–NCSC2H5, which accord with the structures obtained from quantum mechanics calculations. These calculations reveal two association isomers for Mg+–SCNC2H5: one is with Mg+ being linked to the S atom and the other to the N atom. The former is more stable than the latter by only 0.23 eV. Both of the isomers have been shown to exist in the complex source employed in our experiments. On the other hand, only one stable structure is found for the complex Mg+–NCSC2H5 characterized by the Mg+–N linkage. In general, the photofragments are dominated by Mg+ at λ>400 nm, which decreases with decreasing wavelength accompanied by the increase in other photoproducts. In addition, the branching ratios of Mg+ to other photoproducts are nearly constant in the short wavelength region but decrease with decreasing wavelength. The observed photoreactions have been reasonably explained.
A fiber-optic diagnostic technique for mechanical detection of the laser–metal interaction underwater
Authors: Xu R. Q. , Chen X. , Shen Z. H. , Lu J. , Ni X. W.
Published: February 2004

A new fiber-optic force sensor based on optical beam deflection for the investigation of the mechanical effects during laser–metal interaction underwater is developed. This sensor is applied to detect the laser-induced plasma ablation force and liquid-jet impact during the cavitation bubble collapse near a solid boundary when a Q-switched laser is focused on a metal in water. The experimental results indicate the liquid-jet effect outweighs the well-known laser-induced plasma ablation force. This technique has the advantages of high-frequency response, simple structure, and nondestructive examination.
A time-integrated estimate of the entanglement mass in polymer melts in agreement with the one determined by time-resolved measurements
Authors: Padding J. T. , Briels W. J.
Published: February 2004

We make a critical examination of how the entanglement molecular mass Me is determined from various measurable quantities. We are guided by reptation theory, where it is assumed that characteristic relaxations abruptly change and become equal to those of a chain moving in a Gaussian tube, as soon as the corresponding length scales surpass the tube diameter d or similarly as soon as the corresponding mass surpasses a critical value. Taking this critical mass as a definition of the “reptational” entanglement mass, we observe that all methods based on time-resolved quantities, such as the single-chain dynamic structure factor S(q,t) and the zero-shear relaxation modulus G(t), give the same result. We observe that such a value differs, beyond error bars, from that obtained from the plateau modulus, which is a time-integrated quantity. We have investigated an alternative definition of entanglement mass in terms of time-integrated quantities and observe that the value of this specific entanglement mass is consistent with that obtained from the time-resolved observables. We comment on possible reasons for the plateau modulus discrepancy.
Switching processes and switching reproducibility in ferromagnetic ring structures
Authors: Kläui M. , Vaz C. A. F. , Bland J. A. C. , Sinnecker E. H. C. P. , Guimarães A. P. , Wernsdorfer W. , Faini G. , Cambril E. , Heyderman L. J. , David C.
Published: February 2004

We present an experimental study of the reproducibility of the different switching processes occurring in rings. Using superconducting quantum interference device and magnetoresistance measurements, we can measure hysteresis loops of arrays of rings and single structures at varying temperatures and thereby separate the influence of thermal excitations and defects (extrinsic and intrinsic). We find that the temperature dependence of the switching fields and their distributions can be correlated with the different physical processes occurring during different transitions. Measurements of the angular dependence of the switching fields of a single ring allow us to distinguish the contributions of extrinsic and intrinsic defects to the switching field distributions and, counterintuitively, it is established that transitions involving nucleation processes are less prone to defects and thermal excitations than processes involving domain-wall or vortex core depinning and propagation.
Low-temperature switching fatigue behavior of ferroelectric SrBi2Ta2O9 thin films
Authors: Yuan G. L. , Liu J.-M. , Zhang S. T. , Wu D. , Wang Y. P. , Liu Z. G. , Chan H. L. W. , Choy C. L.
Published: February 2004

The ferroelectric hysteresis and fatigue behavior over a wide temperature range from 290 to 50 K for SrBi2Ta2O9 thin films with Pt electrodes on silicon substrates, prepared by metalorganic decomposition (MOD) and pulsed-laser deposition (PLD), are investigated. It is found that given a fixed electrical field amplitude, the coercivity of all films increases with decreasing temperature T. The saturated hysteresis loop easily obtained for the MOD-prepared thin films has its remnant polarization enhanced with decreasing T, but the PLD-prepared samples exhibit minor loops whose remnant polarization decays with decreasing T. While the films prepared by MOD exhibit improved fatigue resistance at low T, significant fatigue effect at low T is observed for the films prepared by PLD. Although we cannot rule out the effect of strain, the experimental results can be explained by competition between pinning and depinning of domain walls, which are dependent of temperature and defect charges.
Dependence of the inverted temperature gradient phenomenon on the condensation coefficient
Authors: Meland Roar , Ytrehus Tor
Published: February 2004

This Brief Communication considers the effect of the condensation coefficient on the inverted temperature gradient phenomenon in a two-plate geometry, assuming diffuse reflection at the interfaces.
Contact-line dynamics and damping for oscillating free surface flows
Authors: Jiang Lei , Perlin Marc , Schultz William W.
Published: February 2004

New experimental data on the frequency and damping of Faraday water waves in glass tanks are presented to demonstrate the contact-line effect on free surface flows. We find a complicated nonlinear relationship between wave frequency and amplitude near contact lines: The amplitude dispersion for decaying standing waves directly progresses from a nonlinear regime due to large amplitude to a regime due to contact-line nonlinearity. The relative damping rate is also a function of the wave amplitude, increasing significantly at smaller wave amplitude. These results are discussed in relation to different formulations of contact-line conditions for oscillatory motions and free surface flows. A new model is proposed to explain the observed amplitude scaling in the frequency and damping rate, and to relate these behaviors to slip-length and other contact-line measurements by Ting and Perlin [J. Fluid Mech. 295, 263 (1995)].
Two-dimensional optical spectroscopy: Two-color photon echoes of electronically coupled phthalocyanine dimers
Authors: Prall Bradley S. , Parkinson Dilworth Y. , Fleming Graham R. , Yang Mino , Ishikawa Naoto
Published: February 2004

Two-color photon echo peak shift spectroscopy was used to study electronic coupling in a phthalocyanine homodimer. Two optical parametric amplifiers were used to produce pulses to excite the split lower states of LuPc2−. The existence of a two-color peak shift indicates the existence of correlation between these two dipole-allowed states. The nature of this correlation is discussed based on theoretical predictions of the interactions between exciton and charge resonance states.
Thickness and low-temperature conductivity of DNA molecules
Authors: Kasumov A. Yu. , Klinov D. V. , Roche P.-E. , Guéron S. , Bouchiat H.
Published: February 2004

We argue that interaction between molecules and substrate is a key parameter which determines the conducting or insulating behavior of DNA molecules. In this letter, we show that strongly deformed DNA molecules deposited on a substrate, whose thickness is less than half the native thickness of the molecule, are insulating, whereas molecules keeping their native thickness are conducting down to very low temperature with a non-ohmic behavior characteristic of a 1D conductor with repulsive electron–electron interactions.
Direct observation of magnetic depth profiles of thin Fe films on Cu(100) and Ni/Cu(100) with the depth-resolved x-ray magnetic circular dichroism
Authors: Amemiya K. , Kitagawa S. , Matsumura D. , Abe H. , Ohta T. , Yokoyama T.
Published: February 2004

A depth-resolved technique in the x-ray magnetic circular dichroism (XMCD) has been developed and applied to Fe/Cu(100) and Fe/Ni/Cu(100) in order to observe the magnetic depth profile directly. It was confirmed that the surface two layers of the 7 ML Fe/Cu(100) are ferromagnetically coupled, while the inner layers are in the spin density wave (SDW) state at 130 K. The technique enables one to extract the XMCD spectra from the surface ferromagnetic (FM) and inner SDW regions separately, indicating that the FM/SDW interface has an antiparallel magnetic coupling, and that the SDW region has the bulk-like feature. For Fe/Ni/Cu(100), we have observed magnetically live surface layers and some thickness dependent magnetic coupling between the Fe surface and Ni film.
Wavelength flipping in laser emission driven by a switchable holographic grating
Authors: Lucchetta D. E. , Criante L. , Francescangeli O. , Simoni F.
Published: February 2004

We report lasing from a simple wafer structure made of a thin layer of rhodamine 6G as active material and of a switchable holographic mirror, based on a reflection grating made of polymer dispersed liquid crystals. It is shown that switching-off the mirror reflectivity by application of a suitable voltage allows wavelength flipping of the laser emission by 10 nm.
Adaptive geometric optics derived from nonlinear acoustic effects
Authors: Higginson Keith A. , Costolo Michael A. , Rietman Edward A.
Published: February 2004

Tunable gradient index (GRIN) lenses were formed in a liquid-filled cavity supporting an ultrasonic standing wave. The refractive index gradient is based on the steady-state pressure component of the finite-amplitude acoustic signal. An acoustic lens was constructed which (1) focused and modulated a collimated light source and (2) formed an image. The properties of the lens are a function of the amplitude and frequency of the applied ultrasound. At the center of symmetry, the device can be approximated as a diverging lens with a single focal point of about −10 cm. In general, however, a series of focal lines are formed, to create a device resembling an axicon or an abberrating lens.
Controlled placement and electrical contact properties of individual multiwalled carbon nanotubes on patterned silicon chips
Authors: Hsiou Y. F. , Yang Y. J. , Stobinski L. , Kuo Watson , Chen C. D.
Published: February 2004

A scheme that allows on-chip growth of multiwalled carbon nanotubes at designed locations is demonstrated. The nanotubes were grown by thermal chemical vapor deposition and were contacted to nanoscaled Cr electrodes fabricated by standard e-beam lithography techniques. The contacts were found to be Ohmic with resistance values on the order of 103 Ω at room temperature. Remarkably, the contacts showed weak temperature dependence down to 40 mK and were insensitive to the magnetic field up to 5 T.
Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening
Authors: Fujii T. , Gao Y. , Sharma R. , Hu E. L. , DenBaars S. P. , Nakamura S.
Published: February 2004

Roughened surfaces of light-emitting diodes (LEDs) provide substantial improvement in light extraction efficiency. By using the laser-lift-off technique followed by an anisotropic etching process to roughen the surface, an n-side-up GaN-based LED with a hexagonal “conelike” surface has been fabricated. The enhancement of the LED output power depends on the surface conditions. The output power of an optimally roughened surface LED shows a twofold to threefold increase compared to that of an LED before surface roughening.
Highly directional emission from few-micron-size elliptical microdisks
Authors: Kim Sun-Kyung , Kim Se-Heon , Kim Guk-Hyun , Park Hong-Gyu , Shin Dong-Jae , Lee Yong-Hee
Published: February 2004

Few-micron-sized elliptically deformed InGaAsP–InP microdisk lasers are fabricated and highly directional emissions are observed along the direction perpendicular to the surface of highest curvature. As the size of the elliptical microdisk is reduced, both the azimuthal angular spreading and the number of lobes become smaller. The improved directionality of the smaller structure is attributed to the enhanced tunneling loss at the high curvature surfaces. The far-field radiation is linearly polarized. Charge-coupled-device images confirmed the existence of strong near-field emission in the vicinity of high curvature surfaces.
ELECTRIC FIELD CONTROL OF THE ELASTIC COMPLIANCE IN LITHIUM THALLIUM TARTRATE
Authors: Sawaguchi E. , Cross L. E.
Published: February 2004

In lithium thallium tartrate monohydrate it has been demonstrated that at temperatures close to the ferroelectric transition near 10 °K, the elastic compliance s44E may be controlled by an electric field applied in the [100] direction. The compliance changes by a factor of 25 for fields of order 10 kV/cm.
LIGHT MODULATIONS BY THIN CdS PLATELET OSCILLATORS
Authors: Preier H. , Kuzmany H.
Published: February 2004

The modulation of the light intensity of a He–Ne laser operating at 0.633 and 3.4μ, by an acousto-electric oscillator of photoconducting CdS with the c axis at 30° to the platelet normal was studied. A fast and a slow modulation effect was observed which were ascribed to an electro-optic and an elasto-optic effect, respectively. The elasto-optic effect was connected to the occurrence of current modulation. The acoustic flux was found to increase with time even after the current had reached a saturation value.
DETECTION OF SURFACE WAVES WITH GaAs BULK EFFECT DIODE
Authors: Hayakawa H. , Takada S. , Ishiguro T. , Mikoshiba N.
Published: February 2004

Surface waves propagating on LiNbO3 crystal have been detected in the frequency range 105–300 MHz using a subcritically doped GaAs bulk diode which is placed close to the surface of LiNbO3. When the diode is biased with high electric field for giving rise to an rf negative differential conductivity, the amplification of signals takes place in the diode and is responsible for the detection of the surface waves with sufficient sensitivity.
BIAS-DEPENDENT STRUCTURE IN EXCESS NOISE IN GaAs SCHOTTKY TUNNEL JUNCTIONS
Authors: Carruthers Tom
Published: February 2004

Large-amplitude excess noise has been observed in the tunneling current of degenerate p-type GaAs–Au Schottky junctions. At 4.2 K the noise voltage exhibits well-defined peaks as a function of bias voltage. The background noise exhibits a 1/f-type spectral response, but the spectral response of some of the peaks indicates that tunneling via surface states with a single average lifetime occurs. Peaks in the noise voltage correspond in bias voltage position with structure in d2I/dV2.
OPTICAL CONTRAST ENHANCEMENT IN LIQUID CRYSTAL DEVICES BY SPATIAL FILTERING
Authors: Caulfield H. J. , Soref R. A.
Published: February 2004

A spatial filtering technique has been demonstrated for contrast enhancement. Coherent light transmitted through a liquid crystal device is Fourier transformed. Undeviated (or deviated) light is spatially filtered at the Fourier transform plane, giving a high-contrast positive (or negative) image. The method is applicable to any type of liquid crystal whose light-deviating properties depend upon external stimuli.
EFFICIENT ELECTRON EMISSION FROM GaAs–Al1−xGaxAs OPTOELECTRONIC COLD-CATHODE STRUCTURES
Authors: Schade H. , Nelson H. , Kressel H.
Published: February 2004

An optoelectronic cold-cathode structure has been operated at pulsed (1% duty cycle emission current densities of 3 A/cm2 at an over-all efficiency of 1.6%. Continuous operation at a current density of 0.4 A/cm2 and an efficiency of 0.43% has been observed.
SYNTHESIS OF Nb3Sn BY SHOCK WAVES
Authors: Otto G. , Reece O. Y. , Roy U.
Published: February 2004

The energy of a converging shock wave has been used to form the intermetallic compound Nb3Sn from its elemental powders. A reaction pattern indicative of compound formation is observed when a critical shock pressure is exceeded. The compound is obtained in a ``pressure-temperature quenched state'' and exhibits a transition temperature to superconductivity of 16.3°K.
PHOTORESPONSE CHARACTERISTICS OF EXTENDED SURFACE-BARRIER DIODES
Authors: Seib D. H.
Published: February 2004

Surface-barrier diodes, which show a reversal of the photoresponse polarity with changing photon energy, have been fabricated by diffusing Cu into heavily n-type GaAs. The photoresponse is found to depend strongly upon applied bias. These properties are explained in terms of a model in which a thin compensated region at the semiconductor surface allows the simultaneous photoemission of both holes and electrons from the metal into the semiconductor.
CONTINUOUS SELF-MODE-LOCKING IN A CO–He–O2 LASER
Authors: Brechignac Ph. , Legay F.
Published: February 2004

Observation of self-locking of longitudinal and transverse modes in a cw CO–He–O2 laser is reported. Experimental results are given for different lengths of the optical cavity.
cw SELF-INDUCED FREQUENCY MODULATION AND SWITCHING OF A LASER BEAM IN LIQUIDS
Authors: Dabby F. W. , Paek U. C.
Published: February 2004

cw self-induced frequency modulation of a laser beam has been observed in liquids having a low surface tension. The modulation manifested itself as a time-varying thermal lens with a focal length which varied on a time scale of 1 Hz. The actual frequency change of the laser beam was much more rapid. At very high intensity, the laser beam deflected from the gravitational center to the forward direction (90°) in approximately 10 μsec. A simple phenomenological explanation is used to correctly predict the functional dependence of the modulation frequency.
EFFICIENT HIGH-GAIN PARAMETRIC GENERATION IN ADP CONTINUOUSLY TUNABLE ACROSS THE VISIBLE SPECTRUM
Authors: Yarborough J. M. , Massey G. A.
Published: February 2004

Coherent visible light, continuously tunable over the range from 4200 to 7300 Å, has been obtained by pumping an ammonium dihydrogen phosphate (ADP) crystal with the ultraviolet fourth harmonic of a Nd: YAG laser. Parametric gains sufficient to produce up to 25% average power conversion of the pump to the tunable visible output were obtained without the use of an external resonator. The output radiation typically had a 5-Å bandwidth, 2-nsec pulse duration, 100-kW peak power, and 5-mW average power at 30 pps. Wavelength tuning was accomplished either by varying the crystal temperature, or by varying its orientation with respect to the pump beam. Angle tuning allows the output to be rapidly tuned across the visible spectrum.
THIRD-ORDER NONLINEAR OPTICAL COEFFICIENTS OF LiIO3
Authors: Okada Masakatsu
Published: February 2004

The third-order nonlinear optical coefficients of LiIO3 have been measured by third harmonic generation. It has been found that the third-order nonlinear optical coefficient c35 is large. The coefficient c12 has a finite value, which shows that Kleinman's symmetry relations are not strictly valid in LiIO3.
VISUAL OBSERVATION OF SUBMILLIMETER WAVE LASER BEAMS
Authors: Keilmann F. , Renk K. F.
Published: February 2004

The operation of a thermal image converter for infrared and submillimeter wave laser radiation is reported. An energy density of 0.004 J/cm2 is sufficient for full contrast, independent of wavelength. Photographs taken with HCN laser radiation are shown.
cw LASER OSCILLATION IN SINGLY IONIZED MAGNESIUM
Authors: Hodges D. T.
Published: February 2004

Laser oscillation is reported for the first time in Mg II. cw lasing at the milliwatt level occurred in a He–Mg discharge at wavelengths of 0.9218, 0.9244, 1.0915, and 1.0952 μ. For helium pressures below 2 Torr, saturation of laser power with discharge current was not observed at currents up to 800 mA. The possibility of extending the lasing spectrum into the visible and ultraviolet is discussed.
SEALED-OFF OPERATION OF STABLE CO LASERS
Authors: Freed C.
Published: February 2004

Several watts of stable (Δf/f≤3×10−10) pure TEM00q-mode output power was obtained from completely sealed-off CO lasers at operating temperatures between +35 and −90°C. No deterioration of output powers has been seen after hundreds of hours of sealed-off operation.
NEW ELECTRON PARAMAGNETIC RESONANCE IN NITROGEN-ION-IMPLANTED CdS
Authors: Sugimoto Hiroshi , Shiraki Yasuhiro , Komatsubara Kiichi F.
Published: February 2004

The EPR of a new impurity center in nitrogen-implanted CdS has been observed. The observed fine and hyperfine structures show that this center is in the triplet state (S=1) and consists of a couple of N nuclei, which is similar to a nitrogen molecule. On the basis of the experimental data, the resonance spectrum is assigned to N2−− center substituted for sulfur ion in CdS. The molecular axis of the center was found to be coincident with the crystal c axis.
ELECTROMAGNETIC CYCLOTRON INSTABILITY
Authors: Lee Kai Fong
Published: February 2004

It is shown that in plasmas described by model velocity distributions of the ``ring'' or the loss-cone type, linearly polarized electromagnetic waves propagating across the magnetic field can be unstable around harmonics of the cyclotron frequencies. For suitable combinations of plasma and magnetic field parameters, the maximum growth rates of these electro-magnetic cyclotron instabilities are proportional to the plasma frequency and the average of the square of the parallel velocities.
OPTICAL SELF-PULSING OF JUNCTION LASERS OPERATING CONTINUOUSLY AT ROOM TEMPERATURE
Authors: Ripper José E. , Paoli Thomas L.
Published: February 2004

Pulsing of the output light intensity as a result of self-induced second-order mode locking is reported for double-heterostructure (DH) stripe-geometry junction lasers operating continuously at room temperature. In comparison with previously reported results for homostructure lasers operating at low temperatures, the self-induced pulsing in DH lasers occurs at a lower frequency and over a greater range of current and temperature. These differences are attributed to the lower dispersion and lower Q of the laser modes due to the increased temperature and not to the difference in laser structure. In addition, new effects associated with transitions of the mode locking from one modal family to another with different transverse spatial distribution are described.
STROBOSCOPIC INVESTIGATION OF THERMAL SWITCHING IN AN AVALANCHING DIODE
Authors: Sunshine Richard A. , Lampert Murray A.
Published: February 2004

A new stroboscopic technique for investigating thermal switching has been used to yield a new model describing the time and spatial development of a thermal-current constriction evolving out of a uniformly avalanching junction. The thermal instability was found to be caused by the buildup of thermally-generated reverse-bias diode current as the junction heated. The junction temperature at the time the constriction formed was a function of the applied bias. The constriction formed in less than 100 nsec in all cases. The ability of the constriction to penetrate the series material depended entirely upon whether this material was heated to its instrinsic temperature.
GENERAL CONDITIONS FOR GROWTH-INDUCED ANISOTROPY IN GARNETS
Authors: Gyorgy E. M. , Rosencwaig A. , Blount E. I. , Tabor W. J. , Lines M. E.
Published: February 2004

General symmetry conditions for models dealing with garnets exhibiting growth-induced noncubic magnetic anisotropies are presented. Under certain probable conditions all models are reduced to two parameters which can be related to the appropriate physical conditions.
PICOSECOND DYE LASER PULSES USING NITROGEN LASER PUMPING
Authors: von Gutfeld R. J.
Published: February 2004

The nitrogen laser has been used to obtain partial mode locking of rhodamine 6G. The resulting pulses are tunable over ∼ 200 Å with a pulse full width at half-power of ∼ 150 psec. The maximum modulation depth obtained is ∼ 80%.
TUNABLE ORGANIC DYE LASER AS AN EXCITATION SOURCE FOR ATOMIC-FLAME FLUORESCENCE SPECTROSCOPY
Authors: Denton M. B. , Malmstadt H. V.
Published: February 2004

A laser-pumped tunable organic dye laser is shown to excite atomic-flame fluorescence of the 5535. 5-Å barium resonance line. Ultrasonic nebulization reduces light scattering, producing a straight-line analytical working curve suitable for quantitative analysis.
CARBON MONOXIDE GAS DYNAMIC LASER
Authors: Watt William S.
Published: February 2004

cw laser oscillation has been obtained from supersonic flows of CO in argon which are expanded from a high-temperature reservoir. The maximum power observed was 20 W from a gas mixture which had been processed to 85 atm and approximately 2000°K. These results appear to confirm that vibrational exchange among the vibrational states of a single diatomic species can lead to preferential population of the upper states and thus produce inversions among these states.
POLARIZATION STUDIES OF RAMAN SCATTERING FROM InSb MAGNETOPLASMAS
Authors: Patel C. K. N. , Yang K. H.
Published: February 2004

We report investigations of polarization selection rules for Raman scattering from semi-conductor magnetoplasmas. Our results for the Δl = 1 and the spin-flip process do not agree with predictions, while those for the Δl = 2 process satisfy the predicted rules. The disagreement points to the need for further theoretical work.
VARIABLY SPACED GIANT PULSES FROM MULTIPLE LASER CAVITIES IN A SINGLE LASING MEDIUM
Authors: Landry M. J.
Published: February 2004

Multiple laser cavities have been established in a single lasing medium. Single giant pulses with a time duration of 40 nsec have been emitted from each cavity and spaced less than 80 nsec to 4 μsec apart. The 0.4-mm spatial separation between the cavities indicates that many cavities could be established in a single lasing medium. Sequentially switching large numbers of cavities, repumping depleted regions, and reswitching could result in a high-repetition-rate giant-pulse laser system for use in photography and holography.
ELECTRIC FIELDS FOR PREBREAKDOWN PARTIAL DISCHARGES IN LIQUID DIELECTRICS
Authors: Fafarman Alfred
Published: February 2004

The existence of prebreakdown collision-ionization processes in liquid dielectrics was observed reproducibly far below breakdown, using a coaxial cylindrical electrode geometry. Preliminary values of the critical electric fields, Epd, for ac prebreakdown partial discharges were measured for three liquid dielectrics: a silicate ester, Oronite Flowcool 180, Epd ≃ 520 ± 100 kV/cm rms; a mineral oil, Wemco C, Epd ≃ 610 ± 30 kV/cm rms; a dimethyl silicone, dc 331, Epd > 1000 kV/cm rms. However, prebreakdown partial discharges were not observed for the coaxial-cylindrical geometry with close spacings when the breakdown electric fields were lower than the above fields.
MODE LOCKING OF THE ARGON ION LASER IN THE ULTRAVIOLET
Authors: Heising S. J. , Jarrett S. M. , Kuizenga D. J.
Published: February 2004

The ultraviolet lines at 3511 and 3638 Å from an argon ion laser have been mode locked using an intracavity acousto-optic modulator. Pulses of 0.2 nsec and 10-mW average power have been obtained. Pulses of 0.17 nsec and 750-mW average power at the strong 5145-Å line are obtained in the same laser. These time durations and direct spectral observation demonstrate a larger bandwidth in the argon ion laser than previously reported.
DIRECT OBSERVATION OF LONG-RANGE MIGRATION OF SELF-INTERSTITIAL ATOMS IN STAGE I OF IRRADIATED PLATINUM
Authors: Pétroff P. , Seidman D. N.
Published: February 2004

The motion of single self-interstitial atoms (SIA's) in stage I of irradiated platinum was observed directly by field ion microscopy. A specimen irradiated at a temperature of 10°K with 20-keV Pt+ ions was found to contain immobile SIA's in the bulk at this temperature, as determined via pulse-field evaporation experiments. Direct observation of specimens, irradiated with 20- or 30-keV Pt+ ions, during warming experiments from 10 to 70°K showed that a flux of SIA's crossed the surface of the specimens between 13 and 25°K. Application of a diffusion model to the data yielded a value of ∼ 0.06 eV for the enthalpy change of migration and a diffusion coefficient of ∼ 0.5 exp(−0.06 eV/kT) cm2 sec−1 for the SIA.
SPECTRAL ANALYSIS OF THE BACKSCATTERED LIGHT FROM A LASER-PRODUCED PLASMA
Authors: Belland P. , DeMichelis C. , Mattioli M. , Papoular R.
Published: February 2004

The backscattered light from a laser-produced plasma has been spectrally analyzed by means of a grating monochromator. The incident-laser beam has a smooth spectrum of 37-Å half-width. For incident-power densities higher than 1.5 × 1012 W/cm2, the back-scattered spectrum consists of discrete lines, equally spaced, on the short-wavelength side of the maximum of the incident spectrum.
NEW INSTABILITY CRITERION FOR RECOMBINATION WAVE DIODES
Authors: Antognetti P. , Chiabrera A. , Ridella S.
Published: February 2004

We have introduced a new instability criterion for a recombination wave diode, e.g., golddoped silicon p+-i-n+ diode, irrespective of the type of injecting contacts. This criterion gives a class of sufficient conditions to obtain open-circuit oscillations, and substitutes the presently available instability condition. The theoretical results show a satisfactory agreement with known experimental data.
NEGATIVE ION EXTRACTION FROM THE PLASMA DURING ANODIZATION IN THE dc OXYGEN DISCHARGE
Authors: O'Hanlon J. F. , Pennebaker W. B.
Published: February 2004

This letter describes an experiment which demonstrates that negative ions in the oxygen discharge are the source of the oxygen incorporated in the anodic oxide. By use of time-varying electric fields, negative oxygen ions are eliminated from the anodizing current. Under this condition, film growth is not observed.
ELECTRON DENSITY IN ION-LASER DISCHARGES
Authors: Pleasance L. D. , George E. V.
Published: February 2004

A new analysis of the TE011 microwave-cavity mode applicable in the high-electron density range commonly found in ion-laser discharges is described. Measurements of the electron density in a cw argon-ion laser discharge in the pressure range where lasing action occurs are presented.
CONTROL OF FACET DAMAGE IN GaAs LASER DIODES
Authors: Ettenberg M. , Sommers H. S. , Kressel H. , Lockwood H. F.
Published: February 2004

Antireflecting films of SiO, applied to one facet of a laser diode, substantially increase the threshold for catastrophic facet failure. Tripling of the allowable peak power from one end of single-heterojunction ``close-confinement'' lasers is reported. The increase appears to be too large for a simple model of damage by optical absorption at an imperfection near the surface.
RAMAN SCATTERING OF ION-IMPLANTED GaAs
Authors: Peercy P. S.
Published: February 2004

We report measurements of Raman scattering in ion-implanted semiconductors. The broadening of the phonon modes produced by lattice strains on Xe ion implantation is measured for GaAs. The measurements show pronounced effects on the linewidth at moderate fluence levels and demonstrate that Raman scattering can provide a sensitive technique for probing stresses introduced by ion implantation. At higher-fluence levels where the material begins to transform from crystalline to amorphous, the linewidth is found to increase rapidly with fluence.
SUPERCONDUCTING PROPERTIES OF MULTIFILAMENTARY V3Ga WIRES
Authors: Suenaga M. , Sampson W. B.
Published: February 2004

Multifilamentary superconducting V3Ga wires in a Cu–Ca solid-solution matrix have been prepared. The superconducting critical temperature Tc and the critical current density Jc(H) are presented for wires with various heat treatments.
ANNEALING OF ELECTRON-IRRADIATED CdS
Authors: Kitagawa Michiharu , Yoshida Toshio
Published: February 2004

Isochronal annealing of radiation-induced changes in the conductivity, the carrier concentration, and the Hall mobility of CdS crystals has been studied over the temperature range 90–410 °K. High-conductivity crystals were irradiated by 10-MeV electrons near liquid-nitrogen temperature. The conductivity σ, the carrier concentration n, and the Hall mobility μ are decreased by irradiation. Three distinct annealing stages IN, IIN, and IIIN were found. The reverse annealing process slightly occurs in stage IN, 100–130 °K. Appreciable normal recovery occurs in stages IIN, 130–230 °K and IIIN, 330–410 °K. After the annealing at 410 °K the percentages of total recovery of σ, n, and μ amount to 74, 78, and 94% of the changes, respectively. The recovery in stage IIN and stage IIIN suggests that two kinds of induced acceptors which also act as charged scattering centers begin to migrate in the temperature ranges; one moves in stage IIN, and the other in stage IIIN.
ENERGY STORAGE OF CF3I PHOTODISSOCIATION LASER
Authors: Gensel P. , Hohla K. , Kompa K. L.
Published: February 2004

An experimental study of the time dependence of the Q-switched energy of a CF3I laser shows that the storage of energy can be increased in inhomogeneous magnetic fields. Chemical pumping adds to the photolytic generation of excited I atoms.
LOW-NOISE cw HOLLOW-CATHODE ZINC-ION LASER
Authors: Jensen R. C. , Collins G. J. , Bennett W. R.
Published: February 2004

A study of the noise spectra of cw zinc-ion lasers using hollow cathode and more conventional discharges is reported. It is found in the present work that the hollow-cathode mode of operation has two very attractive advantages over previous discharge tube designs for use in zinc-ion lasers: First, the noise on the output beam is at a very much lower level; second, there is a substantial improvement in gain per unit length on transitions from high-lying states of the ion.
INDUCED REVERSAL OF ELECTRETS
Authors: Jefimenko Oleg , Walker David K.
Published: February 2004

The reversal of electret polarity can be accelerated by temporarily unshielding the electret immediately after formation. As a result, the electret attains stable charge in a comparatively short time. Data on carnauba wax electrets with accelerated, or ``induced'', polarity reversal are presented and discussed.
LIQUID CRYSTAL DISPLAYS FOR MATCHED FILTERING
Authors: MacAnally R. B.
Published: February 2004

Displays utilizing dynamic scattering in a room-temperature nematic liquid crystal were found suitable as input planes both for recording matched filters and for correlating with matched filters. Autocorrelation spot intensities exceeding 13 dB above background and cross-correlation spot intensities less than 2 dB above background are easily obtained from target areas of only 20 mm2.