bluuebunny/crossref_metadata_2025 huggingface dataset:
IgM anti-myeloperoxidase antibody-secreting lymphocytes are present in the peripheral repertoire of lupus mice but rarely differentiate into IgG-producing cells
Authors: Vittecoq O , Brard F , Jovelin F , Le Loet X , Tron F , Gilbert D
Published: July 2002

Two IgM, κ anti-myeloperoxidase (MPO) monoclonal antibodies, 6D6 and 9B5, bound to MPO in a solid-phase enzyme-linked immunosorbent assay were derived from the splenocytes of (NZB × NZW) F1 and MRL/lpr-lpr mice, respectively. 6D6 gave a characteristic perinuclear immunofluorescence staining pattern on ethanol-fixed human neutrophils, bound to the native form of MPO by immunoblotting and had a high constant affinity for MPO as demonstrated by real-time specific interaction. 9B5 produced a cytoplasmic immunofluorescence staining pattern, reacted with the heavy chain of MPO and had a low constant affinity for MPO. The heavy-and light-chain variable region genes of monoclonal antibodies (mAb) 6D6 and 9B5 were sequenced and found to be highly homologous to germline genes and to contain negatively charged amino acids in the complementarity determining regions. IgM MPO-binding activity was observed in most BW and MRL/lpr-lpr mouse sera, which may correspond to polyclonal activation of B cells, whereas IgG anti-MPO antibodies could be rarely detected. Thus, this study indicates that (i) BW and MRL/lpr-lpr mice do not delete IgM anti-MPO secreting B cells, do not maintain these B cells in a state of anergy, but most individuals are not able to spontaneously induce the class-switching of this autoantibody population; (ii) IgM anti-MPO antibodies can recognize different epitopes on MPO and produce different immunofluorescence staining pattern on ethanol-fixed human neutrophils, as demonstrated by the immunochemical properties of the two lupus-mouse derived mAb.
Cervical length and funneling at 23 weeks of gestation in the prediction of spontaneous early preterm delivery
Authors: To M. S. , Skentou C. , Liao A. W. , Cacho A. , Nicolaides K. H.
Published: July 2002

Objectives

To establish the relationship of cervical length at 23 weeks of gestation to the risk of spontaneous delivery before 33 weeks and to determine the possible additional risk if funneling is present.

Methods

During a 36‐month period, 6819 women with singleton pregnancies underwent transvaginal sonographic cervical assessment at 22–24 weeks as a screening test for preterm delivery. The distribution of cervical length and the prevalence of funneling, defined as dilatation of the internal os of ≥ 5 mm in width, were established. Women who underwent cervical cerclage, iatrogenic preterm delivery or were lost to follow‐up were excluded from further analysis. In the remaining 6334 pregnancies, logistic regression was used to examine the contribution of cervical length and funneling to the risk of spontaneous preterm delivery before 33 weeks.

Results

The median cervical length was 36 mm and in 1.6% of cases the length was ≤ 15 mm. There was a significant inverse association between cervical length and percentage rate of spontaneous delivery before 33 weeks. Funneling of the internal os was present in about 4% of pregnancies and the prevalence decreased with increasing cervical length from 98% when the length was ≤ 15 mm to about 25% for lengths of 16–30 mm and less than 1% at lengths of > 30 mm. The rate of preterm delivery was 6.9% in those with funneling compared to 0.7% in those without funneling (
χ2 = 86.7; P < 0.0001). However, logistic regression analysis demonstrated that funneling did not provide a significant additional contribution to cervical length in the prediction of spontaneous delivery before 33 weeks (odds ratio for short cervix = 24.9, Z = 4.43, P < 0.0001; odds ratio for funneling = 1.8, Z = 0.84, P = 0.40).

Conclusion

In the prediction of preterm delivery, funneling does not provide any significant contribution in addition to cervical length. Copyright © 2001 International Society of Ultrasound in Obstetrics and Gynecology
Somatic Embryogenesis in Leguminous Plants
Authors: Lakshmanan P. , Taji A.
Published: July 2002

Abstract: This review examines recent advances in the induction and development of somatic embryos in leguminous plants. Emphasis has been given to identify the current trends and successful strategies for the establishment of somatic embryogenic systems, particularly in the economically important species. It appears that, in legumes, somatic embryogenesis can be realized relatively easily especially in young meristematic tissues such as immature embryos and developing leaves. In the majority of the species examined, chlorophenoxyacetic acids remained the most active inductive compounds; however, the new generation growth regulators such as thidiazuron are emerging as successful alternatives for high‐frequency direct regeneration of somatic embryos, even from well differentiated explant tissues. Low‐frequency embryo production, poor germination and conversion of somatic embryos into plantlets and somaclonal variation are the major impediments limiting the utility of somatic embryogenesis for biotechnological applications in legumes. These limitations, however, may be considerably reduced in the near future, as more newly developed growth regulators with specific morphogenic targets become available for experimentation. From the published data, it is apparent that more effort should be given to develop repetitive embryogenic systems with high frequency of germination and regeneration, since such systems will find immediate application in mass propagation and other crop improvement programmes. As our understanding of various morphogenic processes, including growth and differentiation of zygotic embryos, is fast expanding, it is conceivable that development of highly efficient somatic embryogenic systems with practical application can be anticipated, at least for the important leguminous crops, in the foreseeable future.
Die Behandlung der Angle Klasse II mit dem Herbstscharnier unter Berücksichtigung der Auswirkungen auf das Kiefergelenk
Authors: Richter F. , Richter U. , Küffer E. , Keil V.
Published: July 2002

Ziel der vorliegenden Arbeit war es, die Behandlung der Klasse-II-Malokklusion mit dem Herbstscharnier unter besonderer Berücksichtigung der posttherapeutischen
Kiefergelenksposition darzustellen.

Es sollte das Postulat überprüft werden, ob eine erreichte Klasse-I-Okklusion nach einer 6-8-monatigen Behandlung mit dem Herbstscharnier [ 21] wieder
dieselbe zentrische Kondylenposition zeigt [ 15, 16, 20], wie sie vor der Behandlung im Kiefergelenk vorgelegen hatte.

Eine kernspintomographische Untersuchung an 96 Kiefergelenken, die jeweils vor, unmittelbar nach Einsetzen und bei Abnahme des Herbstscharniers stattfand, belegte eindeutig, dass es
keine signifikanten Veränderungen der posttherapeutischen gegenüber der prätherapeutischen Kiefergelenksposition gab.

Die Kondylus-Diskus-Fossa-Relation war nach visueller Überprüfung unverändert. Auch die metrischen Werte, die die Breite des anterioren und posterioren Gelenkspaltes betrafen,
ließen statistisch keinerlei signifikante Veränderungen erkennen.

Eine Falldokumentation zeigt eine Patientin aus der untersuchten Gruppe, die eine 6-monatige Herbstscharnierbehandlung erfahren hat. Das Ergebnis zeigt eine stabile
Klasse-I-Okklusion, bei posttherapeutisch wiedererlangter zentrischer Kondylenposition. Die Kondylus-Diskus-Fossa-Relation ist unverändert. Eine 1 1/2 Jahre später erfolgte
Überprüfung der Gelenkposition und die Bisssituation belegen die mit der Herbstscharnier-Behandlung erreichte Stabilität.

Die vorliegende Arbeit soll der Beweisführung dienen, dass die Behandlung mit dem Herbstscharnier keinen negativen Einfluss auf die Kiefergelenke ausübt.
Die Behandlung der Angle Klasse II mit dem Herbstscharnier unter Berücksichtigung der Auswirkungen auf das Kiefergelenk
Authors: Richter U. , Richter F.
Published: July 2002

Ziel der Arbeit ist es, die Veränderung der Kodylenposition bei Patienten mit bestehender Diskusverlagerung zu evaluieren, die mit dem Herbstscharnier im Sinne einer Schienentherapie behandelt
wurden. Außerdem wurde die Häufigkeit der Diskusverlagerung bei einer konsekutiven Gruppe von Patienten der Angle Kl II-Anomalie untersucht. Es zeigte sich, dass bei 13%, in der Altersklasse von
10 bis 18 Jahren eine Diskusverlagerung vorlag.

Eine anteriore Diskusverlagerung, partiell oder total, ist verbunden mit einer Abdrängung des Kondylus nach dorsal, in den Bereich der bilaminären Zone, bei Verkleinerung des posterioren
Gelenkspaltes und entsprechender Verbreiterung des anterioren Gelenkspaltes [6, 28].

Mit Hilfe des Herbstscharniers (HS), das als rigide Schiene den Kondylus nach kaudal anterior einstellt, sollte es zu einer Entlastung der bilaminären Zone kommen, bei einer Vergrößerung des
posterioren Gelenkspaltes.

Auch nach den Remodellierungsvorgängen als Antwort auf die veränderte Kodylenposition während der 6-monatigen HS-Therapie bleibt ein - gegenüber dem Anfangsbefund - vergrößerter posteriorer
Gelenkspalt bestehen und damit eine bleibende Entlastung der bilaminären Zone.

Die HS-Behandlung wurde kernspintomographisch überwacht. Es wurden vor HS, nach Einsetzen des HS und vor Abnahme des HS jeweils MRTs angefertigt und ausgewertet [26].

Bei einer Gegenüberstellung von Patienten, die a priori ein gesundes KG aufwiesen, mit Patienten, bei denen eine bestehende anteriore Diskusverlagerung diagnostiziert worden war, zeigten sich
signifikante Unterschiede. Die Patienten mit der anfänglichen Diskusverlagerung zeigten am Ende der Behandlung sowohl einen signifikant verkleinerten anterioren als auch einen verbreiterten
posterioren Gelenkspalt.
Novel relaxation process in strained Si/Ge superlattices grown on Ge (001)
Authors: Wegscheider W. , Eberl K. , Abstreiter G. , Cerva H. , Oppolzer H.
Published: July 2002

A new mode of misfit defect formation has been observed for the first time in high quality Si/Ge strained-layer superlattices grown by molecular beam epitaxy on Ge(001). In order to investigate the transition from coherent to incoherent growth we have studied a set of samples with a varying number of superlattice periods by transmission electron microscopy. High-resolution lattice imaging reveals that strain relaxation occurs through successive glide of 90° (a/6)〈211〉 Shockley partial dislocations on adjacent {111} planes. The resulting microtwins represent the only relaxation mechanism we observed in the samples.
High-resolution transmission electron microscopy of GaAs/AlAs heterointerfaces grown on the misoriented substrate in the 〈110〉 projection
Authors: Ikarashi Nobuyuki , Sakai Akira , Baba Toshio , Ishida Koichi , Motohisa Junich , Sakaki Hiroyuki
Published: July 2002

Edge-on observations of the structures of vicinal interfaces of GaAs/AlAs heterostructures were carried out by high-resolution electron microscopy. In order to observe the interfacial steps running along the 〈110〉 direction edge-on, we demonstrate the imaging conditions for high-resolution observations in the 〈110〉 projection. Under these conditions, the structures of GaAs/AlAs interfaces, which were grown on the vicinal (001) substrate tilted toward [110], are examined in the [1̄10] projection. The interfacial structures are imaged edge-on, so that the monolayer height steps were observed. The results reveal fluctuations of terrace width and the roughness of step edges on an atomic scale.
Subpicosecond monolithic colliding-pulse mode-locked multiple quantum well lasers
Authors: Chen Y. K. , Wu M. C. , Tanbun-Ek T. , Logan R. A. , Chin M. A.
Published: July 2002

Ultrafast subpicosecond optical pulse generation is achieved by passive colliding-pulse mode locking of monolithic multiple quantum well InGaAsP semiconductor lasers. Transform-limited optical pulses with durations of 1.1, 0.83, 1.0, and 0.64 ps are achieved at repetition rates of 40, 80, 160, and 350 GHz, respectively, without using any external ac sources.
Power scaling of large-aperture photoconducting antennas
Authors: Darrow J. T. , Zhang X.-C. , Auston D. H.
Published: July 2002

We describe the power scaling and saturation properties of large-aperture planar photoconducting antennas which emit and detect ultrashort terahertz electromagnetic pulses. At high optical fluences, the radiated electric field saturates at a value comparable to the bias field in agreement with a simple model of the radiation mechanism.
Simulation of intervalley mixing in double-barrier diodes using the lattice Wigner function
Authors: Miller Douglas R. , Neikirk Dean P.
Published: July 2002

We demonstrate that through the use of the lattice Wigner function, band structure effects can be included explicitly in quantum kinetic simulations of double-barrier diodes. These band structure effects include Γ to X intervalley mixing and effective mass variations at the interface. In a simplified case which emphasizes the impact of broken translational symmetry, we have used this technique to calculate, for the first time, both Γ and X valley equilibrium Wigner functions for an AlAs/GaAs double-barrier diode.
Trap-enhanced electric fields in semi-insulators: The role of electrical and optical carrier injection
Authors: Ralph Stephen E. , Grischkowsky D.
Published: July 2002

We report extremely large field enhancement near the anode of an electrically biased metal/semi-insulator/metal structure. The large anode field results from a trap-enhanced space-charge region and is large enough to cause injection of holes at the anode. Our numerical simulations confirm this interpretation and show that for typical semi-insulating GaAs, large trap-enhanced fields (TEF) are to be expected. The TEF effect, contrary to that observed in doped materials, is enhanced by optical injection of carriers near the anode, and can be exploited for the efficient generation of ultrafast THz radiation.
Defects in organometallic vapor-phase epitaxy-grown GaInP layers
Authors: Feng S. L. , Bourgoin J. C. , Omnes F. , Razeghi M.
Published: July 2002

Nonintentionally doped metalorganic vapor-phase epitaxy Ga1−x InxP layers, having an alloy composition (x = 0.49) corresponding to a lattice matched to GaAs, grown by metalorganic chemical vapor deposition, have been studied by capacitance-voltage and deep- level transient spectroscopy techniques. They are found to exhibit a free-carrier concentration at room temperature of the order of 1015 cm−3. Two electron traps have been detected. The first one, at 75 meV below the conduction band, is in small concentration (∼ 1013 cm−3) while the other, at about 0.9 eV and emitting electrons above room temperature, has a concentration in the range 1014–1015 cm−3.
Influence of ionized impurities on the linewidth of intersubband transitions in GaAs/GaAlAs quantum wells
Authors: Dupont E. B. , Delacourt D. , Papillon D. , Schnell J. P. , Papuchon M.
Published: July 2002

In this letter, we report the influence of silicon donors on the linewidth of intersubband transitions 1–2 in GaAs/Ga0.75Al0.25As square quantum wells. We clearly demonstrate that the relative position between the ionized impurities and the center of the quantum wells is a major factor on the linewidth of the mid-infrared (10 μm) transitions. Besides, it is shown that the scattering processes are more influenced by temperature when donors are far from the quantum well (QW).
Fatigue and retention in ferroelectric Y-Ba-Cu-O/Pb-Zr-Ti-O/Y-Ba-Cu-O heterostructures
Authors: Ramesh R. , Chan W. K. , Wilkens B. , Gilchrist H. , Sands T. , Tarascon J. M. , Keramidas V. G. , Fork D. K. , Lee J. , Safari A.
Published: July 2002

Fatigue and retention characteristics of ferroelectric lead zirconate titanate thin films grown with Y-Ba-Cu-O(YBCO) thin-film top and bottom electrodes are found to be far superior to those obtained with conventional Pt top electrodes. The heterostructures reported here have been grown in situ by pulsed laser deposition on yttria-stabilized ZrO2 buffer [100] Si and on [001] LaAlO3. Both the a- and c-axis orientations of the YBCO lattice have been used as electrodes. They were prepared using suitable changes in growth conditions.
Disorder induced Raman scattering of nanocrystalline carbon
Authors: Li Fang , Lannin Jeffrey S.
Published: July 2002

Weak, low frequency disorder induced Raman scattering is observed in nanocrystalline, ‘‘glassy’’ carbon having an in-plane correlation length La≂30 Å. Similar, relatively more intense low frequency scattering is observed after the annealing of amorphous carbon films to 600 °C, suggesting the formation of quite small nanocrystallites of diameters estimated to be in the range of 10–15 Å. A comparison with the glassy carbon inelastic neutron scattering spectrum demonstrates that the Raman spectra represent a weighted phonon density of states of low frequency modes. The results confirm theoretically predicted low frequency, disorder induced scattering from nanocrystalline solids.
Auger recombination in intrinsic GaAs
Authors: Strauss U. , Rühle W. W. , Köhler K.
Published: July 2002

The recombination kinetics of the electron-hole plasma in strongly excited, intrinsic GaAs is investigated at room temperature by time-resolved photoluminescence using a line-shape analysis of transient spectra. Special structuring of the samples prevents stimulated emission and diffusion. Population of higher energetic subsidiary conduction-band valleys must be taken into account for densities ≳1.5×1019 cm−3. A significant influence of Auger recombination is detected for densities ≳2.5×1019 cm−3. The bimolecular recombination coefficient and an effective Auger coefficient are found to be B=(1.7±0.2)×10−10 cm3 s−1 and Ceff=(7±4)×10−30 cm6 s−1, respectively.
In-plane alignment of a-axis oriented YBa2Cu3Ox thin films
Authors: Mukaida Masashi , Miyazawa Shintaro
Published: July 2002

The in-plane orientation of a-axis oriented YBa2Cu3Ox thin films on SrLaGaO4 (100) substrates is studied by φ-scan (in-plane rotation) x-ray diffraction, reflection high energy electron diffraction, and planar-view transmission electron microscopy measurements. It is revealed that the thin films exhibit a twofold symmetry, indicating independent b- and c-axis orientations in the surface plane. There are no 90° domains, and the c-axis of a-axis oriented YBa2Cu3Ox thin films on SrLaGaO4 (100) is aligned to the [001] direction of the substrate azimuth. The resistivity in the c-axis direction at 290 K is 5.5 mΩ cm, about eleven times larger than that in the a-axis direction. The temperature differential of normalized resistivity, d[R(T)/R(300)]/dT, in the c-axis direction (1.1×10−3 K−1) is smaller than that in the b-axis direction (2.8×10−3 K−1).
Polymer optical fiber amplifier
Authors: Tagaya A. , Koike Y. , Kinoshita T. , Nihei E. , Yamamoto T. , Sasaki K.
Published: July 2002

Polymer optical fiber amplifiers (POFA) of graded-index (GI) type, which have a gain in visible region, were successfully prepared by the interfacial-gel polymerization technique. The gain of 27 dB was observed at 591 nm signal wavelength with 690 W launched pump power at 532 nm in a GI POFA with 0.5 m length.
Read-only optical disk with superresolution
Authors: Wu Yihong , Khoo Hock , Kogure Takuyo
Published: July 2002

The possibility of achieving superresolution in a read-only optical disk system with modified disk structures was investigated by simulation. The disk differs from the existing disks (such as compact disk) in addition of bilayer semiconductor materials. The absorption coefficient (α) of the semiconductor materials near band edge can be approximated by α∝(hν−EG)1/2 with hν as the photon energy and EG the band gap. Since the band gap EG within a certain range above room temperature decreases almost linearly with increasing the temperature, a strong nonlinearity of transmittance can be obtained by choosing a proper combination of EG and wavelength of the readout light source. Simulation results reveal that the spacial cutoff frequency can be significantly increased by the nonlinear transmittance of the additional semiconductor layers near the band edge.
Complete microcrystalline p-i-n solar cell—Crystalline or amorphous cell behavior?
Authors: Meier J. , Flückiger R. , Keppner H. , Shah A.
Published: July 2002

Complete μc-Si:H p-i-n solar cells have been prepared by the very high frequency glow discharge method. Up to now, intrinsic μc-Si:H has never attracted much attention as a photovoltaic active material. However, an efficiency of 4.6% and remarkably high short circuit current densities of up to 21.9 mA/cm2 due to an enhanced absorption in the near-infrared could be obtained. First light-soaking experiments indicate no degradation for the entirely μc-Si:H cells. Voltage-dependent spectral response measurements suggest that the carrier transport in complete μc-Si:H p-i-n cells may possibly be cosupported by diffusion (in addition to drift).
Carbon incorporation in silicon for suppressing interstitial-enhanced boron diffusion
Authors: Stolk P. A. , Eaglesham D. J. , Gossmann H.-J. , Poate J. M.
Published: July 2002

The effect of substitutional C on interstitial-enhanced B diffusion in Si has been investigated. Substitutional C was incorporated into B doped Si superlattices using molecular-beam-epitaxial growth under a background of acetylene gas. Excess Si self-interstitials were generated by near-surface 5×1013/cm2, 40 keV Si implants and diffused at 790 °C. The interstitial-enhanced diffusion of the B marker layers is fully suppressed for C concentrations of 2×1019/cm3, thus demonstrating that substitutional C acts as a trap for interstitials in crystalline Si. Uniform C incorporation of 5×1018/cm2 significantly reduces the transient enhanced diffusion of a typical B junction implant without perturbing its electrical activity.
Determination of the conduction-band discontinuities of In0.5Ga0.5P/In1−xGaxAs1−yPy by capacitance–voltage analysis
Authors: Cho Yong-Hoon , Kim Kwan-Shik , Ryu Sang-Wan , Kim Sang-Ku , Choe Byung-Doo , Lim H.
Published: July 2002

The conduction-band discontinuity ΔEc and interface charge density σ have been studied for In0.5Ga0.5P/In1−xGaxAs1−yPy (y<0.3) heterojunctions prepared by liquid phase epitaxy. The carrier concentration profiles of both normal (In0.5Ga0.5P on In1−xGaxAs1−yPy) and inverted (In1−xGaxAs1−yPy on In0.5Ga0.5P) structures are obtained by capacitance–voltage measurements, which agree well with the results of the self-consistent numerical calculations. The current–voltage and deep-level transient spectroscopy measurements confirm the validity of the result. It is found that ΔEc corresponds to 18% of the band-gap difference ΔEg, for both normal and inverted structures.
Hydrothermal epitaxy of highly oriented TiO2 thin films on silicon
Authors: Chen Qianwang , Qian Yitai , Chen Zuyao , Wu Wenbin , Chen Zhiwen , Zhou Guien , Zhang Yuheng
Published: July 2002

Highly oriented thin films (0.15 μm) of titania on Si (100) substrates have been prepared first by hydrothermal treatment of TiO42− solution (0.6–1.2M) at relatively low temperatures. Films made at 100–200 °C contain only the anatase phase with (112) orientation, adhere well to the substrates. The hydrothermal temperature, time, and the pH value of TiO42− solution are the critical parameters determining the formation of films.
Large format imaging photon detector for astronomical spectroscopy
Authors: Clampin M. , Edwin R. P.
Published: July 2002

We describe the design and development of a large format 40-mm active diameter imaging photon detector. The design comprises an S20 semitransparent photocathode proximity focused onto a stack of two microchannel plates clamped back to back having channel length to diameter ratios of 80:1. Event readout is facilitated by a circular arc terminated resistive anode. The theoretical performance of the design is discussed with reference to gain measurements of the microchannel plates. Experimental results give an optimum position resolution of 100 μm which is spatially nonuniform and degrades towards the edge of the imaging field. We discuss the role of signal processing in this nonuniformity and describe design modifications which would achieve optimum imaging performance.
Ultrafast emission spectroscopy in the ultraviolet by time-gated upconversion
Authors: Kahlow Michael A. , Jarzȩba Wl/odzimierz , DuBruil Thomas P. , Barbara Paul F.
Published: July 2002

We have built a new apparatus to time resolve ultrafast fluorescence following ultraviolet excitation. A synchronously pumped dye laser produces optical pulses of 1-ps or 70-fs full-width half-maximum, depending upon dyes and optical configuration. These pulses are amplified at a 8.2-kHz repetition rate using a copper vapor laser-pumped multipass amplifier. The resulting amplified laser pulses are frequency doubled to obtain ultrafast pulses in the ultraviolet. This ultraviolet light is used to electronically excite a sample; the resulting fluorescence is time resolved using fluorescence upconversion as the optical gating technique. A minimum 300-fs full-width half-maximum instrument response function is obtained. After a brief introduction, we discuss the principles involved in this method of time resolving fluorescence. We review special considerations for femtosecond laser experimentation, and discuss the construction of our apparatus. Finally, as an example, we show how this system can be used to study fundamental physical processes in solution.
First results on application of short-focus monochromators from formed pyrolytic graphite for x-ray fluorescent analysis using synchrotron radiation
Authors: Antonov A. A. , Baryshev V. B. , Grigoryeva I. G. , Kulipanov G. N. , Terekhov Ya. V. , Shipkov N. N.
Published: July 2002

A set of highly bent crystal monochromators made from formed pyrolytic graphite has been tested using synchrotron-radiation beams from the storage ring VEPP-3. These crystals were used in the following devices: short-focus wide-band monochromator and cylindrical dispersion filter of secondary (fluorescent) radiation.
A method of compensating for the friction of a rotating bearing
Authors: Smith H. J. T. , Smith M. D.
Published: July 2002

A torque converter and an electronic driver circuit are described that will generate a compensating applied torque that is equal and opposite to the frictional torque of a bearing over a range of angular velocities. The compensated bearing is effectively frictionless. The frictional torque is assumed to have a constant component and one that is proportional to the angular velocity.
Soft x-ray spectroscopy beamline 6 m high energy spherical grating monochromator at SRRC: Optical design and first performance tests
Authors: Chung S.-C. , Chen C.-I. , Tseng P.-C. , Lin H.-F. , Dann T.-E. , Song Y.-F. , Huang L.-R. , Chen C.-C. , Chuang J.-M. , Tsang K.-L. , Chang C.-N.
Published: July 2002

The layout and first data on the performance of the soft x-ray bending magnet beamline 6 m high energy spherical grating monochromator (6m-HSGM) at SRRC are described. The 6m-HSGM beamline, which covers photon energies from 110 to 1500 eV, is based on the Dragon concept with spherical gratings, and a movable exit slit. During the first performance tests, core-excitation thresholds of Ar and Ne, and K thresholds of N and O for gas phase CO, N2, and O2 have been recorded with resolutions which rank among the best reached so far in the soft x-ray region.
Design and operation of the pellet charge exchange diagnostic for measurement of energetic confined α particles and tritons on the Tokamak Fusion Test Reactor
Authors: Medley S. S. , Mansfield D. K. , Roquemore A. L. , Fisher R. K. , Duong H. H. , McChesney J. M. , Parks P. B. , Petrov M. P. , Khudoleev A. V. , Gorelenkov N. N.
Published: July 2002

Radially resolved energy and density distributions of the confined α particles in D–T experiments on the Tokamak Fusion Test Reactor (TFTR) are being measured with the pellet charge exchange (PCX) diagnostic. Other energetic ion species can be detected as well, such as tritons produced in D–D plasmas and H, He3, or tritium rf-driven minority ion tails. The ablation cloud formed by injected low-Z impurity pellets provides the neutralization target for this active charge exchange technique. Because the cloud neutralization efficiency is uncertain, the PCX diagnostic is not absolutely calibrated so only relative density profiles are obtained. A mass and energy resolving E∥B neutral particle analyzer (NPA) is used which has eight energy channels covering the energy range of 0.3–3.7 MeV for α particles with energy resolution ranging from 5.8% to 11.3% and a spatial resolution of ∼5 cm. The PCX diagnostic views deeply trapped ions in a narrow pitch angle range around a mean value of v∥/v=−0.048±10−3. For D–T operation, the NPA was shielded by a polyethylene–lead enclosure providing 100× attenuation of ambient γ radiation and 14 MeV neutrons. The PCX diagnostic technique and its application on TFTR are described in detail.
A low field superconducting quantum interference device magnetometer for dynamic measurements
Authors: Magnusson J. , Djurberg C. , Granberg P. , Nordblad P.
Published: July 2002

A superconducting quantum interference device magnetometer system designed for low field static and dynamic susceptibility measurements is described. Magnetic shields reduce the residual field in the sample space to about 0.04 A/m (0.5 mOe). A highly stable dc magnetic field is generated by a small superconducting solenoid working in the persistent mode. The temperature control system yields a resolution better than 10 μK in the range of 30–100 K. Combining ac susceptibility and dc magnetic relaxation measurements, the system allows dynamic susceptibility studies in a time window ranging from 3×10−6to 106 s. The sensitivity of the system is 10−12 Am2 (10−9 emu).
A simple, inexpensive, hyperthermal atomic oxygen sensor
Authors: Miller G. P. , Pettigrew P. J. , Raikar G. N. , Gregory J. C.
Published: July 2002

With the increasing duration of space flights, the development of a permanent facility in space, and the increasing use of ground-based hyperthermal atomic oxygen sources there is a need for a simple instrument to provide long-term monitoring of the beam flux. Such an instrument can also be used as a diagnostic tool to investigate the material degradation process. Reliance on models of the upper atmosphere to determine the fluence of atomic oxygen is not only necessarily complex but also imprecise due to the strong dependence of oxygen concentration on day/night, latitude, and solar activity. Mass spectroscopy, the traditional method for determining the gas phase species densities at low pressure, is not only expensive but is limited in the area that it can monitor as well as subject to effects of material degradation. Our group has developed a simple and inexpensive dosimeter to measure the atomic oxygen fluence via the change in resistance as the sensor element is gradually oxidized. The sensors consist of thin-film circuit elements of selected material deposited on a suitable substrate. Four-point resistance measurements are used to monitor the change in sensor resistance with respect to time. Results obtained from silver and carbon dosimeters flown on STS-46 (CONCAP-II-01) indicate that such sensors are sensitive enough to monitor the diurnal variations in atomic oxygen distribution and sufficiently durable to last the lifetime of a mission.
Escaping fast ion diagnostics in compact helical system heliotron/torsatron
Authors: Isobe M. , Darrow D. S. , Kondo T. , Sasao M. , Toi K. , Osakabe M. , Shimizu H. , Yoshimura Y. , Takahashi C. , Murakami S. , Okamura S. , Matsuoka K.
Published: July 2002

Escaping energetic ions have been measured with a scintillator-based probe which can provide both information of pitch angle and gyroradius of detected ions in compact helical system. The measurement was started in February 1997. It was confirmed that output signals are due to neutral beam-injected fast ions. A Lorentz orbit code was developed and fast ion orbits reaching the probe were computed to understand the loss process of detected ions. Birthplace and initial pitch angle of fast ions were calculated by a Monte Carlo beam deposition code HFREYA. From the comparison between pitch angle variation of computed fast ion orbits and pitch angle distribution of birth fast ions, it turns out that fast ions whose birthplace is in the core region cannot reach the detection point directly.
Enhancements to the Compact Helical System fast ion loss probe
Authors: Darrow D. S. , Isobe M. , Kondo T. , Sasao M. ,   the CHS Group
Published: July 2002

A scintillator-based fast ion loss probe has been used to measure 40 keV neutral beam ion loss from Compact Helical System plasmas. Modifications have recently been made to the probe to expand the range of gyroradius covered and to increase the probe acceptance at low pitch angles. In addition, a lamp has been installed inside the probe to facilitate calibration of the scintillator position within the field of view of the video camera. Finally, a Faraday cup structure, integral with the scintillator, has been added to allow direct measurement of the ion current to the probe. This last feature allows much easier absolute calibration of the diagnostic.
Measurement of the thermoelectric power of very small samples at ambient and high pressures
Authors: Polvani D. A. , Meng J. F. , Hasegawa M. , Badding J. V.
Published: July 2002

There is currently much interest in the thermoelectric properties of materials. A method for measuring the thermoelectric power of small single-crystal or polycrystalline samples is described. For high-pressure measurements, the small samples are loaded into a diamond anvil cell and compressed. An infrared laser system is used to induce a temperature gradient in the sample. The thermoelectric power is measured with a pair of small thermocouples contacting the sample. Reported here is the thermoelectric power of Ni and the previously reported intermetallic compound CePd3 up to 10 GPa. Other standards measured by this method included: Bi, Yb, and CeSn3.
Ultraviolet dosimetry using thermoluminescence of semiconductor-doped Vycor glass
Authors: Justus Brian L. , Huston Alan L.
Published: July 2002

Radiation dosimetry in the ultraviolet is described using the intrinsic ultraviolet response of a novel thermoluminescent semiconductor-doped Vycor glass. A linear response to 185 nm light was measured over the range 0.1 to 1000 μJ/cm2. The long wavelength limit of the sensitivity of the glass is ∼290 nm, indicating the utility of the glass as an effective solar blind dosimeter.
Dynamics of a piezoelectric tuning fork/optical fiber assembly in a near-field scanning optical microscope
Authors: Shelimov Konstantin B. , Davydov Dmitri N. , Moskovits Martin
Published: July 2002

Factors leading to a decrease in the resonance quality (the Q factor) of quartz microtuning fork/optical fiber assemblies used as sensing elements in near-field scanning optical microscopes were considered using a simple elastomechanical analysis. Experiments to test the predictions of the analysis were carried out and strategies for recovering high Q factors were proposed and tested. Three major factors affecting the magnitude of the Q factor are discussed. The first is the stiffness imparted to the tine of the microtuning fork by the optical fiber attached to it; the second is the location of the attachment point of the fiber along the tine; the third is the resonant vibrational excitation of the fiber tip which acts as an energy dissipative channel. For tapping mode operation using a standard 125 μm diameter fiber, the large longitudinal stiffness of the fiber results in a dramatic Q-factor degradation. This effect can be overcome by reducing the diameter of the fiber cladding, d, and by slightly bending the fiber. Under these conditions, bending rather than longitudinal stretching dominates the fiber dynamics. The effective bending force constant for a thinned fiber is predicted to be proportional to d4. A sharp upturn in the Q factor is observed for d⩽25 μm, consistent with this prediction. The effective stiffness and mass of the fiber are also expected to scale approximately as x3, where x is the distance from the point of attachment of the fiber to the fork’s base. Hence, the Q factor can be improved further by attaching the fiber closer to the tuning fork’s base. Vibrational coupling between the tuning fork and the probe tip can result in a substantial Q-factor degradation for tips of a certain size. By taking these insights into consideration, we were able to construct tapping mode tuning fork/optical fiber assemblies with Q factors of up to 9000.
Direct measurements of the true vibrational amplitudes in shear force microscopy
Authors: Wei Chih-Chun , Wei Pei-Kuen , Fann Wunshain
Published: July 2002

A new method to measure the tip’s true vibrational amplitude in the shear force microscopy is demonstrated. The measurements are based on modifications of the beam diffraction method. In addition to the dither vibration, the equilibrium position of the tip is set to move along the direction of the vibration. The ratio of ac amplitude to the derivative of dc amplitude gives the tip’s vibration. The sensitivity of this method is determined by the size of the laser focal spot times the ratio of the ac to dc signals of the diffracted light.
Thermally poled silica glass: Laser induced pressure pulse probe of charge distribution
Authors: Kazansky P. G. , Smith A. R. , Russell P. St. J. , Yang G. M. , Sessler G. M.
Published: July 2002

Charge distributions in thermally poled silica glass are mapped by using laser induced pressure pulse technique. The experimental results may be explained through postulating the formation of both real space charge layers and dipole polarization inside the depletion region.
Enhanced resistance to metal induced crystallization of amorphous Ge in contact with Bi
Authors: Missana T. , Afonso C. N. , Petford-Long A. K. , Doole R. C.
Published: July 2002

The metal-induced crystallization (MIC) of amorphous Ge (α-Ge) has been studied in two different Bi/α-Ge bilayer film systems prepared by dc sputtering: films with nm-size columnar Bi grains and films with micron-size laminar Bi grains produced by pulsed laser irradiation. Both systems were annealed in situ in a transmission electron microscope in order to determine the temperature at which the semiconductor crystallizes as a function of the metal grain size and the mechanism by which crystallization occurs. The results show that increasing the gram size by two orders of magnitude leads to an increase in the Ge crystallization temperature above the eutectic temperature of the Ge–Bi system and, thus, to a system with an enhanced resistance to MIC.
Dewetting of molten Sn on Au/Cu/Cr thin-film metallization
Authors: Liu C. Y. , Kim H. K. , Tu K. N. , Totta P. A.
Published: July 2002

On Au/Cu/Cr thin film surface, a drop of molten Sn first spreads out to wet the surface, but it then pulls back to dewet. The latter is due to the spalling of Cu–Sn compounds and exposing the Cr surface to the molten Sn when all of the Cu film has been consumed by the wetting reaction. Dewetting is clearly undesirable for solder joints in electronic packaging; the phenomenon is presented here.
Precise determination of the cholesteric pitch of a chiral liquid crystal in a circularly aligned configuration
Authors: Suh Seong-Woo , Joseph Kathy , Cohen Gil , Patel J. S. , Lee Sin-Doo
Published: July 2002

We propose a novel method of measuring the cholesteric pitch of a liquid crystal (LC) in a circularly aligned configuration. The LC cell is made with one homogeneously rubbed surface and one circularly rubbed surface so that it produces a disclination line passing through the singularity created by the circular rubbing. This disclination line is associated with two domains with different twist orientations. In such a geometry, the relationship between the angular deviation of the disclination line and the cholesteric pitch is analytically derived. The concept of a homogeneous-circular configuration is adopted to accurately measure the cholesteric pitch of LC in a broad range from 0.5 to 500 μm.
Evidence of annealing effects on a high-density Si/SiO2 interfacial layer
Authors: Kosowsky S. D. , Pershan P. S. , Krisch K. S. , Bevk J. , Green M. L. , Brasen D. , Feldman L. C. , Roy P. K.
Published: July 2002

Thermally grown Si(001)/SiO2 samples were studied by x-ray reflectivity. Fits of model electron density profiles to the data reveal the existence of an interfacial layer at the Si/SiO2 interface up to 15-Å-thick, with density higher than either the crystalline Si or the main oxide layer. This density of the layer is reduced by a postoxidation anneal.
Laser crystallization and structuring of amorphous germanium
Authors: Mulato M. , Toet D. , Aichmayr G. , Santos P. V. , Chambouleyron I.
Published: July 2002

The short-pulse laser crystallization and interference structuring of amorphous germanium films were investigated by time resolved reflection measurements and Raman spectroscopy. We demonstrate that submicrometer crystalline structures with very sharp lateral interfaces can be produced by laser interference crystallization of nonhydrogenated samples. In hydrogenated films, on the other hand, the film surface disrupts upon laser exposure leading to the formation of a free-standing crystalline membrane. The Raman spectra of laser crystallized germanium display effects of finite crystallite size and stress.
Heat capacity measurements of Sn nanostructures using a thin-film differential scanning calorimeter with 0.2 nJ sensitivity
Authors: Lai S. L. , Ramanath G. , Allen L. H. , Infante P.
Published: July 2002

We have developed a new thin-film differential scanning calorimetry technique that has extremely high sensitivity of 0.2 nJ. By combining two calorimeters in a differential measurement configuration, we have measured the heat capacity and melting process of Sn nanostructures formed via thermal evaporation with deposition thickness down to 1 Å. The equivalent resolution of the calorimeter is 1 nanogram in mass or 0.4 Å in thickness. We have observed a decrease of up to 120°C in the melting point of Sn nanostructures.
Amorphous-tetrahedral diamondlike carbon layered structures resulting from film growth energetics
Authors: Siegal M. P. , Barbour J. C. , Provencio P. N. , Tallant D. R. , Friedmann T. A.
Published: July 2002

High-resolution transmission electron microscopy (HRTEM) shows that amorphous-tetrahedral diamondlike carbon (a-tC) films grown by pulsed-laser deposition on Si(100) consist of three-to-four layers, depending on the growth energetics. We estimate the density of each layer using both HRTEM image contrast and Rutherford backscattering spectrometry. The first carbon layer and final surface layer have relatively low density. The bulk of the film between these two layers has higher density. For films grown under the most energetic conditions, there exists a superdense a-tC layer between the interface and bulk layers. The density of all four layers, and the thickness of the surface and interfacial layers, correlate well with the energetics of the depositing carbon species.
Low resistance Pd/Au ohmic contacts to p-type GaN using surface treatment
Authors: Kim Jong Kyu , Lee Jong-Lam , Lee Jae Won , Eoi Shin Hyun , Jo Park Yong , Kim Taeil
Published: July 2002

Ohmic contact to p-type GaN with the lowest contact resistivity was developed by the surface treatment prior to Pd/Au metal deposition. The contact resistivity drastically decreased from 2.9×10−2 to 4.3×10−4 Ω cm2 by the surface treatment using aqua regia. The surface treatment plays a role in removing the surface oxide formed on p-type GaN during epitaxial growth, and subsequently in reducing the barrier height for holes at the interface of Pd/p-type GaN, resulting in the good ohmic contacts to p-type GaN.
Controlled tuning of the radiative lifetime in InAs self-assembled quantum dots through vertical ordering
Authors: Colocci M. , Vinattieri A. , Lippi L. , Bogani F. , Rosa-Clot M. , Taddei S. , Bosacchi A. , Franchi S. , Frigeri P.
Published: July 2002

Multilayer structures of InAs quantum dots have been studied by means of photoluminescence techniques. A strong increase of the radiative lifetime with increasing number of stacked dot layers has been observed at low temperatures. Moreover, a strong temperature dependence of the radiative lifetime, which is not present in the single layer samples, has been found in the multistacked structures. The observed effects are nicely explained as a consequence of the electronic coupling between electrons and holes induced by vertical ordering.
Observation of neodymium electroluminescence
Authors: Kawamura Yuichiro , Wada Yuji , Hasegawa Yasuchika , Iwamuro Mitsunori , Kitamura Takayuki , Yanagida Shozo
Published: July 2002

Organic electroluminescence devices using a neodymium(III) complex as an emitting layer were fabricated. The cell structure of glass substrate/indium–tin–oxide/N,N′-diphenyl-N,N′-di(m-tolyl)-benzidine/tris(dibenzoylmethanato)(monobathophenanthroline)neodymium(III) complex/tris(8-quinolinolato)aluminum(III) complex/Mg:Ag was employed. Sharp near-infrared emission bands assigned to f–f transitions of neodymium ion were obtained at dc bias voltage of over 15 V.
Effect of growth conditions on surface morphology and photoelectric work function characteristics of iridium oxide thin films
Authors: Chalamala Babu R. , Wei Yi , Reuss Robert H. , Aggarwal Sanjeev , Gnade Bruce E. , Ramesh R. , Bernhard John M. , Sosa Edward D. , Golden David E.
Published: July 2002

The effect of thermal growth conditions on the morphology and surface work function of iridium oxide thin films grown by annealing Ir thin films in an O2 ambient is presented. The samples were analyzed using x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy, and photoelectric work function measurements. It is found that, with increasing temperature, IrO2 changes from (110) oriented to a mixture of (110) and (200) during the oxide growth. This is manifested as a sharpening of the photoelectric energy distributions at 800 °C. The surface work function was determined to be 4.23 eV using ultraviolet photoelectron spectroscopy. X-ray photoelectron spectroscopy analysis shows that IrO2 starts to form at 600 °C accompanied by surface roughening. Annealing the Ir film at 900 °C in O2 ambient leads to almost complete desorption of the film.
Light scattering from dipole and quadrupole nanoshell antennas
Authors: Oldenburg S. J. , Hale G. D. , Jackson J. B. , Halas N. J.
Published: July 2002

Metal nanoshells are nanoscale optical components that allow for the controllable redirection of electromagnetic radiation via careful engineering of their multilayer structures. By varying the core size and shell thickness of these nanoparticles, nanoscale “antennas” are constructed that can be selectively driven into a dipolar or quadrupolar oscillation pattern. With scattering cross sections many times larger than their physical cross section, these antennas efficiently couple to the incident electromagnetic wave. These structures can focus, redirect, or split the incident light with subwavelength precision, and may find useful applications in the remote coupling of electromagnetic signals into nanoscale machines or devices.
High-power laser light source for near-field optics and its application to high-density optical data storage
Authors: Partovi Afshin , Peale David , Wuttig Matthias , Murray Cherry A. , Zydzik George , Hopkins Leslie , Baldwin Kirk , Hobson William S. , Wynn James , Lopata John , Dhar Lisa , Chichester Rob , Yeh James H-J
Published: July 2002

A laser light source for high-resolution near-field optics applications with an output power exceeding 1 mW (104 times the power from previous sources) and small (300 nm square to less than 50 nm square) output beam size is demonstrated. The very-small-aperture laser (VSAL) tremendously expands the range of applications possible with near-field optics and increases the signal-to-noise ratios and data rates obtained in existing applications. As an example, 250-nm-diam marks corresponding to 7.5 Gb/in.2 storage density have been recorded and read back in reflection and transmission on a rewritable phase-change disk at 24 Mb/s with a 250-nm-square aperture VSAL. VSALs potentially enable data storage densities of over 500 Gb/in.2 (up to 100 times today’s magnetic or optical storage densities).