bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Markovian theories based on a decomposition of the spectral density
Authors: Kleinekathöfer Ulrich
Published: July 2004

For the description of dynamical effects in quantum mechanical systems on ultrashort time scales, memory effects play an important role. Meier and Tannor [J. Chem. Phys. 111, 3365 (1999)] developed an approach which is based on a time-nonlocal scheme employing a numerical decomposition of the spectral density. Here we propose two different approaches which are based on a partial time-ordering prescription, i.e., a time-local formalism and also on a numerical decomposition of the spectral density. In special cases such as the Debye spectral density the present scheme can be employed even without the numerical decomposition of the spectral density. One of the proposed schemes is valid for time-independent Hamiltonians and can be given in a compact quantum master equation. In the case of time-dependent Hamiltonians one has to introduce auxiliary operators which have to be propagated in time along with the density matrix. For the example of a damped harmonic oscillator these non-Markovian theories are compared among each other, to the Markovian limit neglecting memory effects and time dependencies, and to exact path integral calculations. Good agreement between the exact calculations and the non-Markovian results is obtained. Some of the non-Markovian theories mentioned above treat the time dependence in the system Hamiltonians nonperturbatively. Therefore these methods can be used for the simulation of experiments with arbitrary large laser fields.
Array of HgI2 detectors on the HL-1M Tokamak
Authors: Jinwei Yang , Wei Zhang , Shiqing Wang
Published: July 2004

An array of seven HgI2 detectors, which are suitable for detecting the time and space evolution of the x-ray radiation flux and energy spectrum in the range between 15–150 keV relevant to suprathermal electron and runaway electrons was installed on the HL-1M Tokamak (R0=1.02 m, a=0.26 m, BT=3.5 T, IP=350 kA, ne=3–6×1013 cm−3, Te=0.8–1.5 keV). Our iodine mercury (HgI2) semiconductor detectors possess the properties of low noise level, high detection efficiency, high counting rate, high energy resolution, and working at room temperature. Every detector is a high quality, high purity detector cut out of a big size HgI2 crystal. A new type of multichannel energy spectrometer with a high speed acquisition system was developed. Therefore, the spatial and temporal distribution of the x-ray energy spectrum induced by thermal and superthermal electrons can be observed.
Time-resolved measurements with a mercury resonance ionization imaging detector
Authors: Shepard M. R. , Temirov J. P. , Matveev O. I. , Chigarev N. V. , Smith B. W. , Winefordner J. D.
Published: July 2004

The recently developed mercury resonance ionization imaging detector (RIID) has many potential applications in the field of imaging science. We have demonstrated that useful information can be obtained from the time-resolved ionization signal detected along with the image of the object. Clearly distinguishable time-resolved signals from resonance ionization of mercury atoms and photoelectrons created within the channels of a microchannel plate by a UV signal transition of Hg at 253.7 nm were observed. Also, a new source of noise has been identified as low-mass ion desorption by 253.7 nm radiation from the inner parts of the Hg RIID. The time-resolved signal detection allowed temporal correction for the additional noises caused by nonresonant ionization processes inside the RIID, such as photoelectric effect and low-mass ion desorption. The temporal resolution of the RIID could be used for frequency shifted radiation detection and imaging.
Top-down topography of deeply etched silicon in the scanning electron microscope
Authors: Wells Oliver C. , Murray Conal E. , Rullan Jonathan L. , Gignac Lynne M.
Published: July 2004

It is proposed to measure the cross sections of steep-sided etched lines and similar deep surface topography on partially completed silicon integrated circuit wafers using either the backscattered electron (BSE) or the low-loss electron (LLE) image in the scanning electron microscope (SEM). These images contain regions where the collected signal is zero because there is no direct line of sight between the landing point of the electron beam on the specimen and the BSE or LLE detector. It is proposed to use the boundary of such a region in the SEM image as a geometrical line to measure the surface topography. Or alternatively, a shadow can be seen in the distribution of either BSE or LLE with an image-forming detector system. The use of this shadow position on the detector to measure deep surface topography will be demonstrated.
Low-noise computer-controlled current source for quantum coherence experiments
Authors: Linzen S. , Robertson T. L. , Hime T. , Plourde B. L. T. , Reichardt P. A. , Clarke John
Published: July 2004

We describe a dual current source designed to provide static flux biases for a superconducting qubit and for the Superconducting QUantum Interference Device (SQUID) which measures the qubit state. The source combines digitally programmable potentiometers with a stabilized voltage source. Each channel has a maximum output of ±1 mA, and can be adjusted with an accuracy of about ±1 nA. Both current supplies are fully computer controlled and designed not to inject digital noise into the quantum bit and SQUID during manipulation and measurement of the flux. For a 275 μA setting, the measured noise current is 2.6 parts per million (ppm) rms, in a bandwidth of 0.0017–10 Hz, from which we estimate dephasing times of hundreds of nanoseconds in the particular case of our own qubit design. By resetting the current every 10 min, we are able to reduce the drift to no more than 5 ppm at a current of 750 μA over a period of 3 days. The current source has been implemented without thermal regulation inside a radiofrequency-shielding room, and is used routinely in our quantum coherence experiments.
Performance summary on a high power dense plasma focus x-ray lithography point source producing 70 nm line features in AlGaAs microcircuits
Authors: Petr Rodney , Bykanov Alexander , Freshman Jay , Reilly Dennis , Mangano Joseph , Roche Maureen , Dickenson Jason , Burte Mitchell , Heaton John
Published: July 2004

A high average power dense plasma focus (DPF), x-ray point source has been used to produce ∼70 nm line features in AlGaAs-based monolithic millimeter-wave integrated circuits (MMICs). The DPF source has produced up to 12 J per pulse of x-ray energy into 4π steradians at ∼1 keV effective wavelength in ∼2 Torr neon at pulse repetition rates up to 60 Hz, with an effective x-ray yield efficiency of ∼0.8%. Plasma temperature and electron concentration are estimated from the x-ray spectrum to be ∼170 eV and ∼5·1019 cm−3, respectively. The x-ray point source utilizes solid-state pulse power technology to extend the operating lifetime of electrodes and insulators in the DPF discharge. By eliminating current reversals in the DPF head, an anode electrode has demonstrated a lifetime of more than 5 million shots. The x-ray point source has also been operated continuously for 8 h run times at 27 Hz average pulse recurrent frequency. Measurements of shock waves produced by the plasma discharge indicate that overpressure pulses must be attenuated before a collimator can be integrated with the DPF point source.
Optimal laser control of ultrafast photodissociation of I2− in water: Mixed quantum/classical molecular dynamics simulation
Authors: Nishiyama Yoshikazu , Kato Tsuyoshi , Ohtsuki Yukiyoshi , Fujimura Yuichi
Published: July 2004

A linearized optimal control method in combination with mixed quantum/classical molecular dynamics simulation is used for numerically investigating the possibility of controlling photodissociation wave packets of I2− in water. Optimal pulses are designed using an ensemble of photodissociation samples, aiming at the creation of localized dissociation wave packets. Numerical results clearly show the effectiveness of the control although the control achievement is reduced with an increase in the internuclear distance associated with a target region. We introduce effective optimal pulses that are designed using a statistically averaged effective dissociation potential, and show that they semiquantitatively reproduce the control achievements calculated by using optimal pulses. The control mechanisms are interpreted from the time- and frequency-resolved spectra of the effective optimal pulses.
Millimeter-wave, terahertz, and mid-infrared transmissionthrough common clothing
Authors: Bjarnason J. E. , Chan T. L. J. , Lee A. W. M. , Celis M. A. , Brown E. R.
Published: July 2004

This letter reports electromagnetic transmission measurements through cloth samples from eight types of fabrics common in garments and baggage. The transmission at millimeter-wave and terahertz frequencies was measured with a custom ErAs:GaAs tunable photomixing spectrometer. The IR transmission between 3 and 8μm was measured with a Fourier-transform infrared spectrometer. All samples were usefully transparent at millimeter-wave frequencies (up to 300GHz) based on a 3dB criterion, but became progressively opaque at higher frequencies in a highly sample-dependent manner. This is explained by the samples becoming “optically dense” in the THz region, so that the transmission becomes exponentially dependent on sample thickness. The attenuation in the IR region is very high (⩾25dB) except in two samples (rayon and nylon), whose exceptional transparency (e.g., −12dB in nylon) is attributed to pores intrinsic to the material.
AlGaN
-based 280nm light-emitting diodes with continuous wave powers in excess of 1.5mW
Authors: Sun W. H. , Zhang J. P. , Adivarahan V. , Chitnis A , Shatalov M. , Wu S. , Mandavilli V. , Yang J. W. , Khan M. A.
Published: July 2004

We report on AlGaN-based light-emitting diodes over sapphire with peak emission at 280nm. A modified active layer structure consisting of four multiple quantum wells, addition of an electron blocking magnesium doped p-AlGaN layer, improved contacts along with flip-chip packaging resulted in a cw power of 0.7mW at 230mA for a single 200μm×200μm device. Flip-chipping four 100μm×100μm devices in a parallel configuration improved the dc saturation current and enabled us to obtain a cw power of 1.53mW (at 450mA) and a pulse power as high as 24mW (at 1.5A). These powers translate to values of 0.36% and 0.12% for the external quantum efficiency and the wall plug efficiency.
Study of chemically induced pressure generation of hydrogels under isochoric conditions using a microfabricated device
Authors: Herber S. , Eijkel J. , Olthuis W. , Bergveld P. , van den Berg A.
Published: July 2004

A method is proposed to study the behavior of stimulus-sensitive hydrogels under isochoric conditions. Freedom of swell movement of such a hydrogel was restricted in all directions by enclosing the hydrogel between a micropressure sensor and a porous cover. Water and external stimuli can be applied to the hydrogel through the pores of the cover to provoke swelling, which results in pressure generation measured by the pressure sensor. The method was put to the proof by examining the response of a pH-sensitive hydrogel to changes in pH, ionic strength, and buffer concentrations of the surrounding solution. Both equilibrium and dynamic pressure generation were observed. The results show that higher pressures are obtained by incorporating more ionizable groups into the hydrogel network or by lowering the ionic strength of the external solution. Furthermore it was proven that pressures reach equilibrium faster when less titratable groups are incorporated or at the presence of higher buffer concentrations in the surrounding solution. By using microfabrication techniques the dimensions of the hydrogel could be kept small with the advantage that responses are fast. A DMAEMA-co-HEMA hydrogel with 2.5% protonable groups and a thickness of 15 μm generated a Δpressure of 0.67×105 Pa in 12 min when a pH step from 9 to 6 was applied. The presented method is a simple and fast manner to characterize the static and dynamic stimulus-dependent behavior of hydrogels.
Self-organized vertical superlattices in epitaxial GaInAsSb
Authors: Wang C. A. , Vineis C. J. , Calawa D. R.
Published: July 2004

Self-organized superlattices are observed in GaInAsSb epilayers grown nominally lattice matched to vicinal GaSb substrates. The natural superlattice (NSL) is detected at the onset of growth and is inclined by an additional 4° with respect to the (001) terrace of the vicinal GaSb substrate. This tilted NSL intersects the surface of the epilayer, and the NSL period is geometrically correlated with the periodicity of surface undulations. While the underlying driving force for this phase separation arises from solution thermodyamics, the mechanism for the self-organized microstructure is related to local strain associated with surface undulations. By using a template with surface undulations, the tilted NSL can be induced in layers with alloy compositions that normally do not exhibit this self-organized microstructure under typical growth conditions.
Stable field emission from tetrapod-like ZnO nanostructures
Authors: Li Q. H. , Wan Q. , Chen Y. J. , Wang T. H. , Jia H. B. , Yu D. P.
Published: July 2004

Stable field emission is realized from well-separated tetrapod-like ZnO nanostructures with high purity. The ZnO nanostructures are painted on a highly doped silicon substrate covered by a Au layer with a thickness of 300nm. An emission current density of 18mA∕cm2 is obtained and degradation was not observed over a three day period. The fluctuations of the emission current are less than 2%. These experimental results indicate that tetrapod-like ZnO nanostructures are promising materials as cold cathodes for mass production.
Charge decay characteristics of silicon-oxide-nitride-oxide-silicon structure at elevated temperatures and extraction of the nitride trap density distribution
Authors: Kim Tae Hun , Sim Jae Sung , Lee Jong Duk , Shin Hyung Cheol , Park Byung-Gook
Published: July 2004

We investigated the charge decay characteristics of a silicon-oxide-nitride-oxide-silicon type nonvolatile memory at elevated temperatures. Based on the amphoteric trap model and the thermal emission model of the trapped charge, we propose an advanced charge decay model which includes the effect of the bottom oxide, and apply it to extraction of the trap density distribution in energy levels of the nitride layer. The samples prepared have nitride films deposited simultaneously and are classified into two groups according to the thickness of the bottom oxide. The trap density distributions extracted from two groups showed good consistency.
Enhanced photoluminescence of InAs self-assembled quantum dots grown by molecular-beam epitaxy using a “nucleation-augmented” method
Authors: Chia C. K. , Chua S. J. , Miao Z. L. , Chye Y. H.
Published: July 2004

A two-stage “nucleation-augmented” growth method for producing InAs self-assembled quantum dots (QDs) using molecular-beam epitaxy on GaAs (100) substrates has been investigated in detail. Photoluminescence (PL) measurements show that a 1.8-monolayer-(MLs) InAs QD “nucleation” layer grown at a fast rate, followed by a 2.6-MLs-InAs “augmented” layer grown under pulsed conditions at a slow rate, dramatically increases the dot density and improves the PL intensity for the InAs QDs. It was found that, when the effective growth rate of the InAs augmented layer was reduced, the PL peak emission shifts to a longer wavelength and the PL intensity is enhanced. These changes in characteristics were attributed to improved optical quality and greater dot density.
Electric current enhanced defect mobility in Ni3Ti intermetallics
Authors: Garay Javier E. , Glade Stephen C. , Anselmi-Tamburini Umberto , Asoka-Kumar Palakkal , Munir Zuhair A.
Published: July 2004

The effect of the application of a dc current on the annealing of point defects in Ni3Ti was investigated by positron annihilation spectroscopy. An increased defect annealing rate was observed under the influence of the current and was attributed to a 24% decrease in the activation energy of mobility. The results are interpreted in terms of the electron wind effect and the complex nature of diffusion in ordered intermetallic phases. They provide direct evidence for an increase in defect mobility in ordered intermetallics under the influence of a current.
Spectral analysis of strongly enhanced visible light transmission through single C-shaped nanoapertures
Authors: Matteo J. A. , Fromm D. P. , Yuen Y. , Schuck P. J. , Moerner W. E. , Hesselink L.
Published: July 2004

We designed, fabricated, and characterized single C-shaped apertures in an Au film, resonant in the visible regime. Our C-shaped apertures showed transmission enhancement of 13–22 times over a square aperture of the same area and suggest as high as 106 enhancement over square apertures that are designed to produce the same near-field spot size. Spectra from individual apertures demonstrate the ability to tune this resonance over 70nm by scaling the dimensions of the apertures. This shows the C aperture to be a versatile tool for gaining high-resolution, enhanced transmission through single subwavelength apertures at optical wavelengths.
Traps spectroscopy of the Si3Ni4 layer using localized charge-trapping nonvolatile memory device
Authors: Lusky Eli , Shacham-Diamand Yosi , Shappir Assaf , Bloom Ilan , Eitan Boaz
Published: July 2004

A spectroscopy method is proposed and implemented for Si3Ni4 layer using the NROM® cell and the gate-induced-drain-leakage measurement. The proposed method allows probing of both electron and hole traps in the entire band gap with almost no fitting parameters. The energy levels of occupied charge traps are extracted following a thermionic emission model. It is found that the peak energy distribution of the electron traps is located ∼2.2eV below the nitride conduction band with a full width at half maximum (FWHM) of 0.16eV, while the peak energy distribution of the hole traps is located ∼1.5eV above the nitride valence band with a FWHM of 0.64eV. Based on these results, the retention loss of the NROM cell is successfully predicted over a wide range of temperatures and time scales.
Strain measurements by convergent-beam electron diffraction: The importance of stress relaxation in lamella preparations
Authors: Clément L. , Pantel R. , Kwakman L. F. Tz. , Rouvière J. L.
Published: July 2004

Local convergent-beam electron diffraction (CBED) patterns have been acquired on focus ion beam prepared samples in order to determine the strain field generated by a NiSi layer in a n-MOS transistor. A broadening of the high order Laue zone lines in the transmitted disk of CBED patterns is observed when approaching the NiSi∕Si interface. We show that this broadening is mainly due to the atomic plane bending that occurs as a result of the stress relaxation during the preparation of the thin lamella. From the analysis of this relaxation, we are able to determine the initial stress state of the bulk structure. The presented CBED procedure appears to be a promising tool to measure the strain and stress in any layer or structure deposited on a crystalline substrate.
Plasma wave detection of sub-terahertz and terahertz radiation by silicon field-effect transistors
Authors: Knap W. , Teppe F. , Meziani Y. , Dyakonova N. , Lusakowski J. , Boeuf F. , Skotnicki T. , Maude D. , Rumyantsev S. , Shur M. S.
Published: July 2004

We report on experiments on photoresponse to sub-THz (120GHz) radiation of Si field-effect transistors (FETs) with nanometer and submicron gate lengths at 300K. The observed photoresponse is in agreement with predictions of the Dyakonov–Shur plasma wave detection theory. This is experimental evidence of the plasma wave detection by silicon FETs. The plasma wave parameters deduced from the experiments allow us to predict the nonresonant and resonant detection in THz range by nanometer size silicon devices—operating at room temperature.
Oxygen as a surfactant for Al contact metallization of organic layers
Authors: Ivanco J. , Winter B. , Netzer F. P. , Ramsey M. G. , Gregoratti L. , Kiskinova M.
Published: July 2004

Valence band and spatially resolved x-ray photoemission studies of the Al growth on sexiphenyl films, in both an ultrahigh vacuum (UHV) and in a partial pressure of oxygen, are reported. We show that in an UHV, even for very high coverages, the Al balls up on the organic film and is discontinuous. In contrast, for growth in an oxygen partial pressure, similar to that in standard high-vacuum systems used in organic device production, very thin continuous conducting wetting layers are formed. We suggest that the oxygen acts like a surfactant that allows the high surface free-energy metal to wet low surface free-energy organic films.
Improved thermoelectric devices using bismuth alloys
Authors: Thonhauser T. , Scheidemantel T. J. , Sofo J. O.
Published: July 2004

We present first-principles transport calculations for bismuth utilizing the linearized-augmented plane-wave method. From the calculated transport distribution, we compute transport coefficients and our results agree well with experiment. Furthermore, we derive the power factor and find two pronounced maxima excelling even the power factor of Bi2Te3. These maxima can be related to the points of steepest slope in the transport distribution. This insight provides a very valuable guideline for the search of improved thermoelectric materials. The maximum in the power factor leads to a thermoelectric figure of merit of 1.44, which is considerably larger than the one for Bi2Te3.
All-sputtered 14% CdS∕CdTe thin-film solar cell with ZnO:Al transparent conducting oxide
Authors: Gupta Akhlesh , Compaan Alvin D.
Published: July 2004

Radio-frequency (rf)-sputtered Al-doped ZnO was used as the transparent front contact in the fabrication of high efficiency superstrate configuration CdS∕CdTe thin-film solar cells. These cells had CdS and CdTe layers also deposited by rf sputtering at 250°C with the highest processing temperature of 387°C reached during a post-deposition treatment. The devices were tested at National Renewable Energy Laboratory and yielded an efficiency of 14.0%, which is excellent for a CdTe cell using ZnO and also for any sputtered CdTe solar cell. The low-temperature deposition process using sputtering for all semiconductor layers facilitates the use of ZnO and conveys significant advantages for the fabrication of more complex multiple layers needed for the fabrication of tandem polycrystalline solar cells and for cells on polymer materials.
Ultrafast all-optical switching at 1.55μm using an organic multilayer device
Authors: Tatsuura Satoshi , Matsubara Takashi , Tian Minquan , Mitsu Hiroyuki , Iwasa Izumi , Sato Yasuhiro , Furuki Makoto
Published: July 2004

We report ultrafast all-optical switching at optical communication wavelength using a device with a layered structure containing organic films. Spin-coated layers of di(benzofuranonyl)methanolate (BM) derivative are formed alternately with vacuum evaporated layers of germanium (II) oxide. An optical Kerr shutter is constructed using this BM multilayer with 1.55μm signal and 1.63μm gate pulses of 100fs time durations. As a result, optical switching with signal-to-noise ratio over 20dB is attained at gate-pulse intensity above 30pJ∕μm2 and a response time comparable to pulse width is observed. The BM multilayer could be an efficient optical communication device for parallel data processing.
Negative effective permeability in polaritonic photonic crystals
Authors: Huang Kerwyn Casey , Povinelli M. L. , Joannopoulos John D.
Published: July 2004

We find that a two-dimensional photonic crystal composed of polaritonic materials behaves as an effective medium with negative permeability in the micron wavelength range. The resonance in μeff is due to the large values of ε(ω) attained near the transverse phonon frequency ωT. The minimal wavelength for achieving an effective permeability less than −1 in a LiTaO3 crystal, obtained by optimizing the rod size and the lattice constant, is around 12μm, a range previously inaccessible using dielectric metamaterials. For certain dissipation levels, we find that other polaritonic media also exhibit a resonant effect with μeff<−1 for wavelengths ranging from 2 to ∼100μm.
Photoacoustic determination of the plasmon enhanced electric field at a corrugated metal interface
Authors: Matelon R. J. , Newman D. M. , Wears M. L.
Published: July 2004

The intensity of the optical electric field in the vicinity of a corrugated Ni interface is evaluated in the presence of surface plasmons. A photoacoustic technique is used to measure the energy absorbed by the sample which together with a simultaneous conventional measurement of reflectance allows determination of the total energy flow into and out of the interface. The value of the optical electric field is then evaluated on the basis of energy conservation and found to be intensified by a factor of 2.5 as surface plasmons are resonantly generated.
Enhancement of ferromagnetic properties in Zn1−xCoxO by additional Cu doping
Authors: Lin Hung-Ta , Chin Tsung-Shune , Shih Jhy-Chau , Lin Show-Hau , Hong Tzay-Ming , Huang Rong-Tan , Chen Fu-Rong , Kai Ji-Jung
Published: July 2004

The high-temperature ferromagnetism in Co-doped ZnO samples fabricated by the standard solid-state reaction method is reported. Additional Cu doping into bulk Zn0.98Co0.02O is essential to achieve room-temperature ferromagnetism. Structure and composition analyses revealed that cobalt is incorporated into the lattice structure, forming a solid solution instead of precipitates. In the case of Zn0.97Cu0.01Co0.02O, the coercive field measured by a vibrating sample magnetometer at room temperature is 60Oe. The implication of the effect of Cu doping in bulk Zn0.98Co0.02O is also discussed.
Low-resistance gas sensors fabricated from multiwalled carbon nanotubes coated with a thin tin oxide layer
Authors: Liang Y. X. , Chen Y. J. , Wang T. H.
Published: July 2004

Gas sensors have been fabricated from multiwalled carbon nanotubes (MWNTs) coated with a thin tin oxide layer, and have been used to detect oxidizing and reducing gases down to a ppm level. The barriers between the tin oxide nanocrystal grains on the MWNTs dominate the sensor resistance in different gases, and the conducting carriers in the MWNTs have a low resistance, which make the resistance of the sensors much lower than that of SnO2 nanobelt sensors. The resistance is 130kΩ in air, 230kΩ in 2ppm NO2, and 2.8MΩ in 50ppm NO2, so that impedance matching with amplifying circuits can be easily achieved.
Electrostrictive resonances in (Ba0.7Sr0.3)TiO3 thin filmsat microwave frequencies
Authors: Tappe S. , Böttger U. , Waser R.
Published: July 2004

The bias-voltage-dependent permittivity of (Ba0.7Sr0.3)TiO3(BST) thin films with thicknesses ranging from 100 to 250nm is investigated in the frequency range from 500MHz to 40GHz by impedance spectroscopy of integrated BST capacitors. The dielectric spectra of the films exhibit resonance phenomena in the 4–7GHz range when a bias field is applied. It is shown that the main controlling parameter of the resonance frequency is the film thickness. Calculations based on the strong electrostrictive activity of the BST films underline the assumption that the emission of plane acoustic waves is the underlying mechanism for this behavior.
Thickness dependence of superconducting critical current densityin vicinal YBa2Cu3O7−δ thick films
Authors: Emergo R. L. S. , Wu J. Z. , Aytug T. , Christen D. K.
Published: July 2004

In YBa2Cu3O7−δ (YBCO) thick films, the superconducting critical current density (Jc) decreases with increasing film thickness (t). The mechanisms responsible for this Jc–t behavior remain unclear. To probe the correlation between the film microstructure and Jc-thickness behavior, we have deposited YBCO thick films up to 3.0μm in thickness on flat and surface-miscut (100) SrTiO3 substrates with 5°, 10°, and 15° vicinal angles. The microstructures of the YBCO films were found to evolve differently on flat and miscut substrates, resulting in different Jc–t behaviors. Surprisingly the small miscut angles of 5°–10° were favorable to obtain higher Jc and smaller Jc reduction at larger film thickness.
Chains of semiconductor nanoparticles templated on DNA
Authors: Dittmer Wendy U. , Simmel Friedrich C.
Published: July 2004

Towards the construction of DNA templated nanowires for self-assembled nanodevices, nanocrystals of the p-type semiconductor CuS were grown selectively and densely on DNA both in solution and stretched on a surface. Atomic force microscopy and transmission electron microscopy measurements display chains of CuS nanoparticles up to 10nm diameter separated by less than 40nm. By increasing the number of nucleation sites through the use of bundles of DNA, highly dense coverage of the DNA with nanocrystals is observed.
Ultrahigh-speed etching of SiO2 with ultrahigh selectivity over Si in microwave-excited non equilibrium atmospheric pressure plasma
Authors: Yamakawa Koji , Hori Masaru , Goto Toshio , Den Shoji , Katagiri Toshirou , Kano Hiroyuki
Published: July 2004

Etching of a SiO2 film [Boro-phospho silicate glass (BPSG)] has been performed in a continuous-wave microwave-excited nonequilibrium atmospheric pressure plasma using a microgap discharge. A NF3∕He gas mixture with added H2O was employed as the feed gas. An ultrahigh etch rate for SiO2 (BPSG) of 14μm∕min and an ultrahigh selectivity over Si(SiO2∕Si) of 200 was obtained. A mechanism for the selective etching is proposed based on results obtained using Fourier transform infrared spectroscopy and spatially imaged optical emission spectroscopy with an intensified charge-coupled device camera. This process could offer a breakthrough for ultrahigh-speed, damage-free micromachining of SiO2 in microelectromechanical system devices.
Refractive transmission of light and beam shapingwith metallic nano-optic lenses
Authors: Sun Zhijun , Kim Hong Koo
Published: July 2004

We have performed finite-difference time-domain (FDTD) analysis of optical transmission through a nanoslit array structure formed on a metal layer with tapered film thickness. The analysis result shows refractive transmission of light through the nanoslit array, opening up the possibility of creating metallic lenses that resemble glass lenses in their shape. Metallic lenses with curved surfaces are designed such that each nanoslit element transmits light with phase retardation controlled by the metal thickness in the aperture region. The FDTD analysis result demonstrates a focusing or collimating function of convex-shaped metal lenses.
Effect of Cu deficiency on the optical properties and electronic structure of CuInSe2 and CuIn0.8Ga0.2Se2 determined by spectroscopic ellipsometry
Authors: Han Sung-Ho , Hermann Allen M. , Hasoon F. S. , Al-Thani H. A. , Levi D. H.
Published: July 2004

Spectroscopic ellipsometry measurements of CuInSe2 (CIS) and CuIn0.8Ga0.2Se2 (CIGS) reveal that there are important differences in electronic properties between stoichiometric CIS (CIGS) and Cu-poor CIS (CIGS). We find a reduction in the absorption strength in the spectral region of 1–3eV. This reduction can be explained in terms of the Cu 3d density of states. Cu-poor CIS (CIGS) materials show an increase in band gap due to the reduction in repulsion between Cu 3d and Se 4p states. The experimental results have important implications for the function of polycrystalline optoelectronic devices.
Analytic representations based on su(3) coherent states and Robertson intelligent states
Authors: Daoud M.
Published: July 2004

Robertson intelligent states which minimize the Schrödinger–Robertson uncertainty relation are constructed as eigenstates of a linear combination of Weyl generators of the su(3) algebra. The construction is based on the analytic representations of su(3) coherent states. New classes of coherent and squeezed states are explicitly derived.
H atom elimination from the πσ* state in the photodissociation of phenol
Authors: Tseng Chien-Ming , Lee Yuan T. , Ni Chi-Kung
Published: July 2004

Photodissociation of phenol at 248 nm was studied using multimass ion imaging techniques. Photofragment translational energy distribution of H atom elimination was measured. The results demonstrate that H atom elimination occurs on the πσ* excited state which has repulsive potential-energy functions with respect to the stretching of OH bond. It supports the recent ab initio calculation.
Ischemic complications of transcatheter arterial chemoembolization in liver malignancies
Authors: Tarazov P.G. , Polysalov V.N. , Prozorovskij K.V. , Grishchenkova I.V. , Rozengauz E.V.
Published: July 2004

Objective: To determine the frequency, character, methods of treatment, and outcome of ischemic complications after transcatheter hepatic artery chemoembolization (TACE).

Material and Methods: Between 1985 and 1998, 827 sessions of TACE with Doxorubicin mixed with iodized oil, and gelatin sponge particles were performed in 282 patients with primary and metastatic liver cancer. Post-TACE monitoring included clinical observation, US and CT.

Results: Ischemic complications appeared in 13 (4.6%) and included the following: hepatic (n=6) and splenic abscess (n=1), cholecystitis (n=3), and bile duct necrosis (n=3). The treatment was US-guided drainage in 12 cases and systemic antibacterial therapy in 1. No negative influence of these complications on survival of patients was detected.

Conclusion: Serious ischemic complications of TACE occur in about 5% of patients and can be successfully managed without open surgery. These complications do not worsen the survival of patients.
Delayed presentation of traumatic left-sided diaphragmatic avulsion: A case report
Authors: Scaglione M. , Grassi R. , Pinto A. , Ragozzino A. , Romano S. , Pinto F.
Published: July 2004

We describe the case of a 35-year-old man who had suffered a severe multitrauma with blunt thoracic injury, left scapula and humerus fractures 5 years earlier. At the time of the trauma, a diaphragmatic lesion went unnoticed. Five years later, the patient had a 24-h history of increasingly severe abdominal pain with repeated vomiting. Helical CT showed a portion of the left hemidiaphragm avulsed from its insertions on the ribs with large-bowel loop obstruction herniated in the left hemithorax. The preoperative CT diagnosis was confirmed by surgery: reduction of the hernia and reinsertion of the hemidiaphragm to the lumbocostal arch were performed.
Factors influencing patient radiation doses from barium enema examinations
Authors: Vehmas T. , Lampinen J.S. , Mertjärvi A. , Rannikko S.
Published: July 2004

Purpose: To analyse factors behind the variation of patient doses from barium enema (BE) examinations.

Material and Methods: The patients' (n=89) organ and effective doses (E) due to BE examinations were computed with the ODS-60 program. An average risk factor for BE examinations was derived using the BEIR V schema. The correlation of E with several independent variables was analysed.

Results: Median Es at five hospitals were 4.4, 6.1, 7.1, 13 and 16 mSv. The E of the female patients (median 9.2 mSv) was higher than that of the males (median 5.4 mSv) ( p<0.001) due to the higher female doses to the gonads, bladder and uterus, resulting from different body structure. An average fatal risk factor of 0.02% per one BE examination was derived. Factors controlled by the radiologist (screening time, number of exposures) explained 40% and patient-related factors explained 16% of the total variation of E. The equipment-related factors are included in the residual 44%.

Conclusion: Due to the large contribution of the radiologists' examination technique in the value of E, an optimal examination technique is essential in reducing doses and the stochastic risk to patients.
Localization of insulinomas: Comparison of conventional arterial stimulation with venous sampling (ASVS) and superselective ASVS
Authors: Baba Y. , Miyazono N. , Nakajo M. , Kanetsuki I. , Nishi H. , Inoue H.
Published: July 2004

Purpose: To examine the value of superselective arterial stimulation venous sampling (ASVS) to localize insulinomas.

Material and Methods: Superselective ASVS (SS-ASVS) was performed in 9 patients with insulinoma. Injection of secretagogue (calcium gluconate: 0.01 mEq Ca++/kg) was performed into the gastroduodenal, splenic (proximal and distal), and superior mesenteric arteries in 9 patients and additionally into the dorsal pancreatic artery in 6 patients. Sampling from the hepatic vein was performed to measure serum insulin concentrations at 30, 60 and 120 s after each injection of secretagogue into these arteries. SS-ASVS results were correlated with surgical findings, compared to those of conventional ASVS.

Results: Insulinomas were correctly localized to the head, body or tail of the pancreas by SS-ASVS in 8 patients (89%). Conventional ASVS detected insulinomas in 7 patients (78%), although it could not distinguish whether the insulinoma was located in the pancreatic body or tail in 4 of the 7 patients. There were eight-fold or more increases in serum insulin levels in hepatic venous samples related to the artery supplying the tumor in 8 patients. Localization of the insulinomas was verified at surgery in all patients.

Conclusion: SS-ASVS is a useful method for detailed evaluation of overproduction of insulin from pancreatic insulinomas and their localization. When the pancreatic insulinoma is situated in the pancreatic body or tail, the localization is more accurately made by SS-ASVS than by conventional ASVS.
Quantitative bone scintigraphy: A methodological evaluation in prostate cancer
Authors: Rydh A. , Åhlström K. Riklund , Larsson A. , Johansson L. , Damber J.-E. , Tomiç R. , Hietala S.-O.
Published: July 2004

Purpose: To evaluate a simple method for quantification of focal activity in bone scintigraphy (BS).

Material and Methods: The gamma camera was calibrated using a phantom. Quantitative bone scintigraphy (QBS) was performed on 11 men recently diagnosed with prostate cancer (PCa), for whom routine BS showed involvement of the skeleton. Following endocrine therapy for 4 to 8 months, a second QBS was performed. Changes in QBS values were then compared to changes in serum levels of prostate-specific antigen (PSA).

Results: PSA response indicating regression of PCa was accompanied by a decrease in the QBS value in 8 of the 11 patients. The overall mean error of the QBS values was 15%.

Conclusion: QBS according to this method is a relatively simple procedure that might contribute to objective evaluation of therapeutic effects in skeletal metastases, although its validity must be tested in a larger clinical material.
Activity-based costing in radiology: Application in a pediatric radiological unit
Authors: Laurila J. , Suramo I. , Brommels M. , Tolppanen E.-M. , Koivukangas P. , Lanning P. , Standertskjöld-Nordenstam C.-G.
Published: July 2004

Purpose: To get an informative and detailed picture of the resource utilization in a radiology department in order to support its pricing and management.

Material and Methods: A system based mainly on the theoretical foundations of activity-based costing (ABC) was designed, tested and compared with conventional costing. The study was performed at the Pediatric Unit of the Department of Radiology, Oulu University Hospital. The material consisted of all the 7,452 radiological procedures done in the unit during the first half of 1994, when both methods of costing where in use. Detailed cost data were obtained from the hospital financial and personnel systems and then related to activity data captured in the radiology information system.

Results: The allocation of overhead costs was greatly reduced by the introduction of ABC compared to conventional costing. The overhead cost as a percentage of total costs dropped to one-fourth of total costs, from 57% to 16%. The change of unit costs of radiological procedures varied from −42% to +82%.

Conclusion: Costing is much more detailed and precise, and the percentage of unspecified allocated overhead costs diminishes drastically when ABC is used. The new information enhances effective departmental management, as the whole process of radiological procedures is identifiable by single activities, amenable to corrective actions and process improvement.
CT scores of emphysema and oxygen desaturation during low-grade exercise in patients with emphysema
Authors: Taguchi O. , Gabazza E.C. , Yoshida M. , Yasui H. , Kobayashi T. , Yuda H. , Hataji O. , Adachi Y.
Published: July 2004

Purpose: We evaluated the usefulness of CT for assessing oxygen desaturation during walking in patients with emphysema.

Material and Methods: The study comprised 32 patients with emphysema (mean age 67±6 years). Serial CT images of 5 mm were obtained from the apex to the basal regions of the lung during deep inspiration. The severity of emphysema was scored by four physicians according to a visual method. A six-minute walking test and oxygen desaturation (pSO2) measurements were performed.

Results and Conclusion: The mean CT score of the four observers was signfiicantly correlated with the nadir pSO2 and ΔpSO2, but did not correlate with the total distance walked. These results suggest that CT may be used for the assessment of oxygen desaturation during low-grade exercise in patients with emphysema.
Effect of CT digital image compression on detection of coronary artery calcification
Authors: Zheng L.-M. , Sone S. , Itani Y. , Wang Q. , Hanamura K. , Asakura K. , Li F. , Yang Z.-G. , Wang J.-C. , Funasaka T.
Published: July 2004

Purpose: To test the effect of digital compression of CT images on the detection of small linear or spotted high attenuation lesions such as coronary artery calcification (CAC).

Material and Methods: Fifty cases with and 50 without CAC were randomly selected from a population that had undergone spiral CT of the thorax for screening lung cancer. CT image data were compressed using JPEG (Joint Photographic Experts Group) or wavelet algorithms at ratios of 10:1, 20:1 or 40:1. Five radiologists reviewed the uncompressed and compressed images on a cathode-ray-tube. Observer performance was evaluated with receiver operating characteristic analysis.

Results: CT images compressed at a ratio as high as 20:1 were acceptable for primary diagnosis of CAC. There was no significant difference in the detection accuracy for CAC between JPEG and wavelet algorithms at the compression ratios up to 20:1. CT images were more vulnerable to image blurring on the wavelet compression at relatively lower ratios, and "blocking" artifacts occurred on the JPEG compression at relatively higher ratios.

Conclusion: JPEG and wavelet algorithms allow compression of CT images without compromising their diagnostic value at ratios up to 20:1 in detecting small linear or spotted high attenuation lesions such as CAC, and there was no difference between the two algorithms in diagnostic accuracy.
Intravascular ultrasound angioplasty in peripheral arterial occlusion: Preliminary experience
Authors: Goyen M. , Kröger K. , Buss C. , Rudofsky G.
Published: July 2004

Purpose: To determine if ultrasound angioplasty in a percutaneous approach was capable of recanalizing occluded arteries in acute and subacute peripheral arterial occlusions.

Material and Methods: We applied an ultrasound angioplasty device in a percutaneous approach in 9 patients with peripheral arterial occlusions. All patients suffered from severe leg ischemia due to subacute thrombotic occlusions.

Results: The ultrasound transmitter easily created a channel within the occlusive material. To further reduce the mass of the occlusive material, an aspiration thrombectomy was performed in all cases, leading to a complete recanalization in 7 cases. In 2 cases, a remaining stenosis was successfully dilated.

Conclusion: Intravascular ultrasonic devices can be useful for recanalization of occluded peripheral arteries. In particular, if thrombolytic therapy of longer peripheral arterial occlusions fails or is contraindicated, ultrasound angioplasty may be a new approach for recanalization.
Symptomatic peripheral vascular tree stenosis: Comparison of subtracted and nonsubtracted 3D contrast-enhanced MR angiography with fat suppression
Authors: Sueyoshi E. , Sakamoto I. , Matsuoka Y. , Hayashi H. , Hayashi K.
Published: July 2004

Objective: To determine the clinical feasibility of contrast-enhanced three-dimensional (3D) MR angiography (MRA) with fat suppression spectral inversion at lipids and to compare subtracted and nonsubtracted images.

Material and Methods: In 13 patients suspected of having lower extremity ischemia, 3D dynamic contrast-enhanced MRA of the iliac and femoral arteries was performed using the fat suppression technique. The validity of the MRA interpretations of the degree of stenoses was evaluated by comparing with conventional angiography as the gold standard. The contrast-to-noise (C/N) ratios of both subtracted and nonsubtracted maximum-intensity-projection (MIP) images were calculated.

Results: In the arteries with stenosis of 50% or greater, the sensitivity and specificity of the subtracted MR angiograms were 100% and 96.5%, respectively, not significantly different from the correponding values in nonsubtracted MRAs (100% and 94.1%, respectively). The C/N ratios of the subtracted images were significantly higher than those of the nonsubtracted images ( p<0.001).

Conclusion: With this technique, fat suppression can be performed with only a slight increase in the examination time. A lower dose of contrast material can be used in MRA with fat suppression than without it. Subtracted MRA improves the ease of interpretation compared to nonsubtracted MRA.
Patient radiation exposure during coronary angiography and intervention
Authors: Fransson S.-G. , Persliden J.
Published: July 2004

Purpose: To prospectively register fluoroscopic and cine times in a random fashion, and to measure patient radiation exposure from routine coronary angiography and coronary balloon angioplasty. We also evaluated an optional dose reduction system used during interventions.

Material and Methods: The incident radiation to the patient was measured as kerma area product (KAP) in Gycm2, obtained from an ionisation chamber mounted on the undercouch tube during 65 coronary angiography procedures and another 53 percutaneous transluminal coronary angioplasties (including 29 stent procedures), mostly directly following complete coronary angiography.

Results and Conclusion: The values from coronary angiography were comparable to other reports with a mean fluoroscopic time of 4.4 min and a mean KAP value of 62.6 Gycm2. The corresponding figures from coronary balloon angioplasty without stenting were lower than otherwise reported, with 8.2 min and 47.9 Gycm2, respectively. The use of coronary stents did prolong the mean fluoroscopic time (10.5 min) but did not significantly enhance the patient mean radiation dose (51.4 Gycm2). The dose reduction technique resulted in a significant KAP value reduction of 57%. In conclusion, with regard to radiation exposure, coronary angiography and balloon angioplasty are considered safe procedures.