bluuebunny/crossref_metadata_2025 huggingface dataset:
Failure of Timed Bright Light Exposure to Alleviate Age‐Related Sleep Maintenance Insomnia
Authors: Suhner Andrea G. , Murphy Patricia J. , Campbell Scott S.
Published: July 2002

OBJECTIVES:

To determine whether a twice‐weekly maintenance schedule of evening bright light exposure is effective in alleviating sleep maintenance insomnia on a long‐term basis, after the establishment of a more favorable phase relationship between the core body temperature (CBT) rhythm and sleep.

DESIGN:

Subjects underwent light treatment while living at home. Eleven to 13 consecutive days of acute light treatment (active) were followed by a 3‐month maintenance light treatment period (active or control). Subjects completed five laboratory sessions: before and after the acute phase and once a month during the maintenance period.

SETTING:

Sleep laboratory and subjects' homes.

PARTICIPANTS:

Fifteen older subjects (seven women, eight men; aged 63–84) with chronic (>1 year) complaints of sleep maintenance insomnia.

INTERVENTIONS:

During the acute phase, all participants were exposed to evening bright light (≈9:00 p.m. to 11:00 p.m.;>4,000 lux). During the maintenance phase, light treatment was reduced to a twice‐weekly schedule, in which the active group received bright light from ≈9:00 p.m. to 11:00 p.m. and the control group received bright light from 3:00 p.m. to 5:00 p.m.

MEASUREMENTS:

During each laboratory session, polysomnographic sleep and CBT were measured.

RESULTS:

Bright light exposure during the acute treatment resulted in an average phase delay in the temperature rhythm (Tmin) of 94 minutes. Sleep quality was not improved. No significant differences between active and control subjects were found during the maintenance phase; in both groups, Tmin gradually reverted to the baseline phase position, and sleep efficiency remained unchanged.

CONCLUSIONS:

Although a significant phase shift in CBT was achieved during the acute treatment phase, no improvement in sleep quality was observed. Twice‐weekly light exposure was not effective in maintaining the circadian phase shift over the subsequent 3 months. Issues of compliance and alternate etiologies for the sleep maintenance insomnia are discussed. J Am Geriatr Soc 50:617–623, 2002.
Wheelchair Users Are Not Necessarily Wheelchair Bound
Authors: Hoenig Helen , Pieper Carl , Zolkewitz Mike , Schenkman Margaret , Branch Laurence G.
Published: July 2002

OBJECTIVES:

To determine the patterns of wheelchair use in terms of locations of use, whether wheelchair use in one location was related to wheelchair use in other locations, and factors associated with wheelchair use in different locations.

DESIGN:

Longitudinal cohort study.

SETTING:

Patients prescribed wheelchairs by clinicians at one of two teaching hospitals (one Veterans Affairs hospital and one private hospital).

PARTICIPANTS:

One hundred fifty‐three consecutive persons who were prescribed a new wheelchair, resided in the community, had a Short Portable Mental Status Questionnaire score of greater than six out of 10, and who could be interviewed within 7 to 21 days of receiving the wheelchair.

MEASUREMENTS:

Patient, wheelchair, and environmental characteristics and self‐reported wheelchair use in life spaces.

RESULTS:

Wheelchair use in the 24 hours before the interview was inconsistent across life spaces. The correlation between wheelchair use in the bath and in the kitchen was 0.66, between locations near and far from home was −0.08, and between locations in the home and outside the home was 0.08. Predictors of wheelchair use in the home were using help from another person to propel the wheelchair (odds ratio (OR) = 0.14, 95% confidence interval (CI) = 0.04–0.45), the number of impairments (OR = 0.80, 95% CI = 0.67–0.96), a report that the wheelchair did not meet the subject's needs (OR = 3.71, 95% CI = 1.27–10.81), and having adapted the home to accommodate the wheelchair (OR = 3.75, 95% CI = 1.47–8.18). Having adapted the home was also positively associated with use of the wheelchair in areas near the home (OR = 4.77, 95% CI = 1.94–11.71). The only factor associated with wheelchair use in distant locations was older age (OR = 0.62, 95% CI = 0.46–0.83 per 10‐year increment).

CONCLUSIONS:

Personal factors (e.g., using help to propel the wheelchair) and environmental factors (e.g., home adaptations to accommodate the wheelchair) influenced wheelchair use. In addition, wheelchair use, and the factors influencing wheelchair use, differed by location. Wheelchair users appear to use their wheelchairs selectively, depending on their physical needs and the constraints of their environment. J Am Geriatr Soc 50:645–654, 2002.
Hardly Increased Oxidative Stress After Exposure to Low Temperature in Chilling‐Acclimated and Non‐Acclimated Maize Leaves
Authors: Leipner J. , Basilidès A. , Stamp P. , Fracheboud Y.
Published: July 2002

Abstract: Seedlings of Zea mays L. were grown at optimal (25 °C) and suboptimal (15 °C) temperature and then exposed to severe chilling temperature (6 °C) at their growth light intensity (450 ìmol quanta m−2 s−1) for 4 d. Photosynthetic parameters, hydrogen peroxide, antioxidant contents, and activity of scavenging enzymes were investigated before, during, and after chilling stress. This stress caused a stronger reduction in photosynthetic activity, maximum quantum efficiency of photosystem II primary photochemistry (Fv/Fm), and catalase activity in plants which had been grown at 25 °C rather than at 15 °C. Maize plants grown at suboptimal temperature de‐epoxidized their xanthophyll cycle pool to a greater extent and exhibited a faster recovery from chilling stress than plants which had not been acclimated to chilling. Antioxidant content, activity of scavenging enzymes, with the exception of catalase, hydrogen peroxide formation, and the size of the xanthophyll cycle pool were hardly affected by chilling stress. However, chilling induced a temporary increase in the glutathione content and triggered the synthesis of á‐tocopherol during the phase of recovery at 25 °C. The results indicate that leaves respond to chilling stress by down‐regulation of photosystem II accompanied by de‐epoxidation of the xanthophyll cycle pool, probably to prevent enhanced formation of superoxide radicals at photosystem I and, consequently, other reactive oxygen species.
Temporal and Spatial Expression of MADS Box Genes, FBP7 and FBP11, During Initiation and Early Development of Ovules in Wild Type and Mutant Petunia hybrida
Authors: Cheng X‐F. , Wittich P. E. , Kieft H. , Angenent G. , XuHan X. , van Lammeren A. A. M.
Published: July 2002

Abstract: The temporal and spatial distribution of the Petunia Floral Binding Proteins 7 and 11 (FBP7/11) were determined immunocytochemically during ovule initiation and development. In wild type plants, FBP7/11 were first detected in the placenta before ovule primordia were formed. At ovule primordium stage, FBP7/11 levels increased in the placenta and appeared in ovule primordia at the sites where integument primordia developed. At the megagametogenesis stage, FBP7/11 were present at high levels in the placenta, funicle and integument, but not in the nucellus or gametophyte. Transgenics with cosuppression of FBP7/11 formed normal ovule primordia on the placenta from which both normal ovules and carpel‐like structures developed. The amount of FBP7/11 was low in the ovules and undetectable in the carpel‐like structures. Plants with ectopic expression of FBP7/11 developed normal ovules on the placenta and, in addition, ovule‐ and carpel‐like structures on sepals. Placental and sepal ovules showed the same labeling pattern as observed in wild type ovules. FBP7/11 levels were, however, low or undetectable in the carpel‐like structures. The results indicate that FBP7/11 only have indirect roles in ovule primordium initiation. However, at least small quantities are needed for proper ovule differentiation. Thus, the amount of FBP7/11 is related to the type of development after primordium formation, i.e., towards the formation of real ovules or carpel‐like structures.
Soliton coupler
Authors: Heatley D. R. , Wright E. M. , Stegeman G. I.
Published: July 2002

We propose and examine the characteristics of a new device called a soliton coupler which exchanges energy between two adjacent waveguides by transfer of spatial solitons.
Time-resolved Raman spectrum of shock-compressed diamond
Authors: Gupta Y. M. , Horn P. D. , Yoo C. S.
Published: July 2002

A method has been developed for time-resolved Raman measurements under shock loading to examine the first-order Raman line of diamond (ω0=1333 cm−1). The diamond samples were subjected to uniaxial strain along the [110] direction to a longitudinal stress of 121 kbar. The observed spectral changes are consistent with frequency shifts calculated according to a phenomenological model used to describe stress effects on the zone center phonons of cubic materials.
Determination of the coordination number of Co atoms at the CoSi2(A,B)/Si(111) interface by transmission electron microscopy
Authors: Bulle-Lieuwma C. W. T. , de Jong A. F. , van Ommen A. H. , van der Veen J. F. , Vrijmoeth J.
Published: July 2002

The atomic structure of the (111) interface between CoSi2 (type A and B) and Si is investigated by high-resolution transmission electron microscopy, combined with image simulations. Type B interfaces of CoSi2 layers formed by thermal reaction of vapor deposited Co on (111) oriented Si, of Si/CoSi2/Si heterostructures, and of CoSi2 precipitates formed by high-dose Co implantation were examined. The coordination of the Co atoms at all B-type interfaces is found to be eightfold, in accordance with theoretical predictions. Type A interfaces of CoSi2 precipitates and continuous CoSi2 layers, formed by ion implantation and subsequent annealing, showed clear evidence for the presence of sevenfold coordinated interfacial Co.
Surface structure of (100) GaP grown by gas source molecular beam epitaxy
Authors: Baillargeon J. N. , Cheng K. Y. , Hsieh K. C.
Published: July 2002

I n situ reflection high-energy electron diffraction analysis was used to investigate the surface structure of the GaP epitaxial layers grown on (100) GaP substrates by gas source molecular beam epitaxy as a function of substrate temperature and V/III flux ratio. It was found that for GaP, column V and column III stabilized surfaces corresponded to the (2×4) and (4×2) reconstruction pattern, respectively, which is characteristic of most all III-V binary compound semiconductors. In the transition region, however, the surface exhibited a ((19)1/2 ×4 reconstruction pattern. At substrate temperatures below 660 °C and 685 °C for P- and Ga-stabilized surfaces, respectively, the surface structure was insensitive to temperature. Beyond 660 and 690 °C, the surface structure exhibited an exponential flux dependence with increasing substrate temperature.
cw laser irradiation of GaAs: Arsenic formation and photoluminescence degradation
Authors: Campbell I. H. , Fauchet P. M.
Published: July 2002

Low-power, cw laser irradiation of GaAs leads to the formation of solid arsenic at the sample surface and to the degradation of band-gap photoluminescence (PL) efficiency. In situ Raman scattering and PL are used to measure the lattice and carrier temperature in addition to monitoring the arsenic formation and PL efficiency. Both effects are athermal, do not involve surface oxidation, and occur in n,p and semi-insulating GaAs prepared by different growth techniques. These observations suggest that arsenic formation and PL decrease may both be the result of a nonradiative recombination process.
Pulsed excimer laser deposition Y1Ba2Cu3O7−x superconductor films on silicon with laser-deposited Y-ZrO2 buffer layer
Authors: Ogale S. B. , Vispute R. D. , Rao R. R.
Published: July 2002

The pulsed excimer laser ablation method is used to deposit both the buffer layer of Y-stabilized ZrO2 and the overlayer of Y1Ba2Cu3O7−x superconductor on (100) oriented single-crystal silicon. Process parameter optimization study is carried out and it is shown that a thin film of the superconductor (0.5–0.7 μm) having a zero resistance temperature of 86 K can be obtained using a 0.3 μm buffer layer deposited at substrate temperatures between 600 and 800 °C.
Optical properties of pyrolytic spray deposited electrochromic tungsten trioxide films
Authors: Zhang Jianping , Colbow Konrad
Published: July 2002

The measured reflectances of initial, colored and bleached polycrystalline WO3 films prepared by spray pyrolysis are presented and compared with the calculated reflectances using a theoretical model −Drude theory.
Anomalous Hall effect in (110)Fe/(110)Cr multilayers
Authors: Song S. N. , Sellers C. , Ketterson J. B.
Published: July 2002

We have studied the Hall effect and the magnetoresistance in [110] textured Fe/Cr multilayers grown by electron beam evaporation. We have observed a strong magnetic field dependence of the Hall coefficient as well as a large magnetoresistance. In all cases the Hall voltage is positive. The ordinary Hall coefficient is positive at room temperature and changes sign at low temperatures; this is similar to the behavior of an antiferromagnet but differs from that observed in Fe-Cr alloys. The extraordinary Hall coefficient Rs is positive and varies with the resistivity ρ as Rs∝ρ2.6, suggesting the importance of interface scattering.
Effect of Y2BaCuO5 inclusions on flux pinning in YBa2Cu3O7−δ
Authors: Jin S. , Tiefel T. H. , Kammlott G. W.
Published: July 2002

The effect of Y2BaCuO5 (211) inclusions on flux pinning in the YBa2Cu3O7−δ (123) superconductor has been investigated. Intragranular Jc has been measured on samples containing various amounts of dispersed (211) particles (0%–44%) with various particle sizes (1.3–10.4 μm). The results clearly show that the presence of (211) particles (at least down to the micron size level) neither significantly enhances the flux pinning nor deteriorates Jc. The observed insensitivity of Jc to the variation in the total particle surface area indicates that the likelihood of a substantial interface-pinning effect is minimal. While the (211) inclusions appear to assist in the peritectic reactions resulting in better microstructural perfection during melt processing, particle size needs to be controlled to a much finer scale in order for them to serve as efficient pinning centers.
Penetration depth and microwave loss measurements with a YBa2Cu3O7−δ/LaAlO3/YBa2Cu3O7−δ trilayer transmission line
Authors: Pond J. M. , Carroll K. R. , Horwitz J. S. , Chrisey D. B. , Osofsky M. S. , Cestone V. C.
Published: July 2002

A trilayer YBa2Cu3O7−δ/LaAlO3/YBa2Cu3O7−δ transmission line was fabricated to measure the penetration depth of the high-temperature superconducting layers, to determine the microwave losses, and to demonstrate the potential for practical high-temperature superconductor multilayer microwave circuits. All layers were deposited onto a (100) MgO substrate by pulsed laser deposition. The superconducting films are c-axis oriented with critical temperatures of 89 K. From the phase velocity measurements, the penetration depth was found to be consistent with weak-coupled BCS theory in the local limit with a zero-temperature value of 135 nm. A simple phenomenological temperature dependence for the penetration depth is also presented. This successful trilayer fabrication process, besides allowing the determination of the penetration depth and microwave loss, also expands the possible applications of the high-temperature superconductors.
In situ deposition of superconducting YBa2Cu3O7−x and DyBa2Cu3O7−x thin films by organometallic molecular-beam epitaxy
Authors: King L. L. H. , Hsieh K. Y. , Lichtenwalner D. J. , Kingon A. I.
Published: July 2002

Smooth, c-axis oriented, superconducting thin films of YBa2Cu3O7−x and DyBa2Cu3O7−x have been grown on (100) MgO by organometallic molecular-beam epitaxy. To our knowledge this is the first report of this technique for the fabrication of this class of high Tc superconductors. Y (or Dy) β-diketonate organometallic sources are utilized with Ba and Cu metallic sources. Films are grown in situ by codepositing from these sources in an ozone ambient with a substrate temperature of 700 °C. The use of an active oxygen source (ozone) is required for decomposition of the organometallic sources as well as for the attainment of superconducting films in situ. The films are characterized by Tc’s as high as 85 K and Jc’s of 1.2×106 A/cm2 at 12 K and 2.4×103 A/cm2 at 77 K. In addition to the four point Tc and Jc results, alternating-current susceptibility measurements are also reported. The composition of the films has been determined by Rutherford backscattering spectroscopy, Auger and secondary ion mass spectroscopy analysis, with the smoothness of the films characterized by scanning tunneling microscopy.
Si1−xGex/Si multiple quantum well infrared detector
Authors: Karunasiri R. P. G. , Park J. S. , Wang K. L.
Published: July 2002

A long-wavelength infrared detector is demonstrated using Si1−xGex/Si multiple quantum wells for the first time. A broad peak in the photoresponse is observed near 9 μm with a full width at half maximum of about 80 meV which provides the response in the 6–12 μm range. The position of the peak in the photoresponse is in good agreement with that observed in the absorption measurement using a waveguide geometry. A peak responsivity of about 0.3 A/W and detectivity of D*=1×109 cm √Hz/W at 77 K are achieved. This suggests the possibility of monolithic integration of Si1−xGex/Si multiple quantum well detectors with signal processing electronics for potential focal plane array applications.
k-space carrier dynamics in GaAs
Authors: Portella M. T. , Bigot J.-Y. , Schoenlein R. W. , Cunningham J. E. , Shank C. V.
Published: July 2002

We investigate the k-space scattering dynamics of carriers in GaAs by measuring the transient relaxation of an anisotropic population produced by a linearly polarized 9 femtosecond infrared pulse. The redistribution of carrier momentum is shown to occur in the first tens of femtoseconds after excitation, and the relaxation times are found to vary with carrier density, from 25 to 60 fs for a carrier density range from 8×1017 to 8×1016 cm−3. Our results indicate that carrier momentum is rapidly redistributed via carrier–carrier scattering, and the nature of the density dependence suggests that the scattering is mediated by a screened Coulomb interaction between the carriers.
Pyrochlore to perovskite phase transformation in sol-gel derived lead-zirconate-titanate thin films
Authors: Kwok Chi Kong , Desu Seshu B.
Published: July 2002

Pyrochlore to perovskite phase transformation in sol-gel derived lead-zirconate-titanate (PZT) films was studied by x-ray diffraction and transmission-electron microscopy (TEM). X-ray diffraction studies of PZT films on sapphire substrates indicated that the pyrochlore to perovskite phase transformation was completed at 650 °C. In contrast, TEM investigations of free-standing PZT films showed that the phase transformation was completed at much higher temperatures. This discrepancy in the behavior of free-standing films versus films on substrate can be related to the size effect.
Hydrogen treatment effect on shallow and deep centers in GaSb
Authors: Polyakov A. Y. , Pearton S. J. , Wilson R. G. , Rai-Choudhury P. , Hillard R. J. , Bao X. J. , Stam M. , Milnes A. G. , Schlesinger T. E. , Lopata J.
Published: July 2002

It is shown by spreading resistance and capacitance–voltage measurements that atomic hydrogen passivates shallow acceptors and donors in GaSb. Deep level passivation by hydrogen also occurs, as revealed by deep level transient spectroscopy measurements on Schottky diode structures. Effective diffusion coefficients for hydrogen were determined for both n+ and p+ GaSb; in the former case the diffusion is thermally activated with the relationship DH=3.4×10−5e−0.55 eV/kT, whereas in p+ material DH=1.5×10−6e−0.45 eV/kT over the temperature range 100–250 °C. Reactivation of passivated shallow and deep levels occurs for temperatures of 250–300 °C.
Microscopic nature of the metal to insulator phase transition induced through electroreduction in single-crystal KNbO3
Authors: Szot K. , Speier W. , Eberhardt W.
Published: July 2002

Electroreduction of the crystalline perovskite KNbO3 results in a change of the electrical resistivity by about 12–14 orders of magnitude from insulating to semimetallic at room temperature. This change is completely reversible through oxidation of the material. The semimetallic phase is characterized by a three-dimensional network of planar defects extending throughout the crystal. We have characterized the microscopic nature of this semimetallic phase by photoelectron spectroscopy after preparing the surface of the crystal to the same state. We also present evidence that at temperatures below 100 K these electroreduced materials may even become superconducting.
Focused ion beam imaging of grain growth in copper thin films
Authors: Gupta J. , Harper J. M. E. , IV J. L. Mauer , Blauner P. G. , Smith D. A.
Published: July 2002

Scanning ion microscopy (SIM) employing focused ion beam (FIB) imaging was used to study the grain structure of thin copper films as a function of annealing temperature from 20 to 500 °C. Accurate measurement of grain size is obtained for grains as small as 60 nm, allowing the microstructure of copper to be analyzed on small-grained samples which show poor contrast in scanning electron microscopy. Moreover, the short sample preparation time provides an advantage over transmission electron microscopy (TEM). The growth and coalescence of small (<100 nm) grains in the initially bimodal grain size distribution occurs in the temperature range of 250–350 °C in films of 1000 nm thickness. This grain growth takes place concurrently with the relaxation of compressive stress as observed by temperature-ramped stress measurement. Also, temperature-ramped in situ TEM examination confirms that coarsening of small grains is the dominant grain growth mechanism up to 500 °C.
Growth of stable dislocation-free 3-grain silicon ingots for thinner slicing
Authors: Martinelli G. , Kibizov R.
Published: July 2002

Using the CZ technique we have set up a 3-grain silicon ingot growing process which allows to obtain very large grains with a preselected orientation in order to facilitate thin slicing, a unanimously agreed upon requirement for photovoltaic applications. The 3-grain ingots we obtained are particularly suitable for this aim since no cleavage plane {111} crosses the crystal obliquely to the slicing direction. Furthermore, this type of ingot allows a high growth rate ascribable to the verticality of its {111} side planes and has electrical and structure properties very close to those of single-crystalline material.
Hopping conduction in a free-standing GaAs-AlGaAs heterostructure wire
Authors: Hasko D. G. , Cleaver J. R. A. , Ahmed H. , Smith C. G. , Dixon J. E.
Published: July 2002

We report on the fabrication and electron transport in a novel heterostructure in which layers of AlGaAs and GaAs have been grown after a submicron free-standing GaAs wire has been formed. Electronic conduction at low temperatures in this material is shown to be consistent with three-dimensional hopping conduction with a transition to one-dimensional hopping at temperatures below 1 K.
Resonant holographic interferometry of laser-ablation plumes
Authors: Lindley R. A. , Gilgenbach R. M. , Ching C. H.
Published: July 2002

Two-dimensional species-resolved, holographic interferometry has been used to measure absolute-line-density profiles of KrF laser ablation plumes in vacuum and gas. Laser ablation plumes are generated by focusing a KrF excimer laser (40 ns, 248 nm, ≤0.8 J) on a solid aluminum target at a fluence of 2–5 J/cm2. Aluminum neutral absolute-line-density profiles are measured to characterize the interaction of ablated material with background gases versus vacuum. The interferograms are made using a 20 ns pulsed dye laser tuned near (≤±0.020 nm) the 394.401 nm aluminum neutral transition from the ground state. Calculations have been performed to obtain absolute-line-density profiles from the resonant fringe shift data. Peak aluminum neutral line densities of up to 1×1015 cm−2 have been measured for plumes in backgrounds of 14 mTorr and 1 Torr argon and in vacuum.
Ultrafast exciton dynamics in highly oriented polydiacetylene films
Authors: Nisoli M. , Pruneri V. , Magni V. , De Silvestri S. , Dellepiane G. , Comoretto D. , Cuniberti C. , Le Moigne J.
Published: July 2002

The nonlinear optical response in uniaxially oriented films of poly[1.6-di(N-carbazolyl)-2, 4-hexadiyne], epitaxially grown on a potassium acid phthalate single crystal, has been measured by femtosecond pump and probe. A fast initial relaxation and the formation of long-lived species at high excitation intensities have been observed. A high third-order nonlinear optical susceptibility of 2×10−7 esu has been estimated at 627 nm. The effects of sample orientation on the relaxation dynamics have also been investigated.
Preparation of Cd1−xYxSb2O6 thin film on glass substrate by radio frequency sputtering
Authors: Yanagawa Kazuhiko , Ohki Yoshimichi , Omata Takahisa , Hosono Hideo , Ueda Naoyuki , Kawazoe Hiroshi
Published: July 2002

Cd1−xYxSb2O6 thin films were deposited onto a silica glass substrate by rf sputtering method. The highest conductivity observed for Cd0.95Y0.05Sb2O6 thin films was 4.1×10 S cm−1, with a carrier concentration of 1.3×1020 cm−3 and a Hall mobility of 1.9 cm2 V−1S −1. No distinct optical absorption band was observed from the visible to the infrared region. These observations show that Cd1−xYxSb2O6 thin films have characteristics of a transparent conductor, whose transparent wavelength region covers the near infrared.
Metalorganic chemical vapor deposition of TiO2:N anatase thin film on Si substrate
Authors: Lee Dong Heon , Cho Yong Soo , Yi Woul In , Kim Tae Song , Lee Jeon Kook , Jin Jung Hyung
Published: July 2002

Titanium dioxide thin film doped with nitrogen was deposited at 420 °C on p-type silicon substrate by metalorganic chemical vapor deposition using titanium tetra-isopropoxide and nitrous oxide. From an x-ray diffraction result, when deposited at 420 °C, only the anatase (101) peak and (200) peak were observed. Raman spectroscopy confirmed the presence of anatase phase without any rutile or TiN phase. X-ray photoelectron spectrum revealed that nitrogen was doped into the lattice of TiO2 anatase. In the bulk of the film nitrogen peak was observed, and the spectrum of Ti 2p core level confirmed titanium–nitrogen bonding due to nitrogen incorporation into the anatase lattice.
High reflectivity self-pumped phase conjugation in an unusually cut Fe-doped KTa1−xNbxO3 crystal
Authors: Mu Xiaodong , Shao Zongshu , Yue Xuefeng , Chen Jun , Guan Qingcai , Wang Jiyang
Published: July 2002

In this letter, a new type of self-pumped phase conjugation (SPPC) is demonstrated and a phase conjugate reflectivity as high as 83.8% is measured in an unusually cut Fe-doped KTa1−xNbxO3 (KTN:Fe) crystal with a He-Ne laser. Some novel characteristics of this type of device are found, which may reduce the need for special crystal qualities to obtain SPPC. Finally, a possible mechanism is postulated to reasonably explain this type of SPPC.
Formation of diamond during passage of a shock wave in a copper/graphite powder: Formation process and numerical simulation
Authors: Burkhard G. , Tamura H. , Tanabe Y. , Sawaoka A. B. , Yamada K.
Published: July 2002

A powder mixture of copper and graphite was dynamically shock-compressed by a rod-in-cylinder method. Structural characterization of the recovered specimen by transmission electron microscopy (TEM) showed the development of fine spherical diamond particles through shock-induced nuclei formation in the high pressure state and shock-assisted nuclei growth during unloading to ambient pressure via a solid–liquid–solid (SLS) phase transformation. A 2 μm large diamond particle was formed via a shock-induced martensitic path. Quantitative numerical simulation applying the two-dimensional computation code AUTODYN 2D was conducted to evaluate the pressure conditions during shock loading.
Improved electron emission by use of a cloth fiber cathode
Authors: Adler R. J. , Kiuttu G. F. , Simpkins B. E. , Sullivan D. J. , Voss D. E.
Published: July 2002

We have studied cloth fiber cold cathode emitters and have found them to be superior to many other types of cold cathode emitters. In this paper, the characteristics of this type of cathode are presented.
Frequency modulated (FM) time delay photoacoustic and photothermal wave spectroscopies. Technique, instrumentation, and detection. Part II: Mirage effect spectrometer design and performance
Authors: Mandelis Andreas , Borm Linda M. L. , Tiessinga John
Published: July 2002

FM time delay laser excitation has been implemented in a photothermal deflection spectrometric apparatus with fast rise-time optics. The performance of the system was studied in both frequency and time delay domains. The spectrometer was further used in the study of thin quartz layers on an opaque substrate. In this work we have demonstrated the operation of the first frequency modulated (FM) time delay photothermal deflection (mirage effect) spectrometer with a ns rise time spectrally flat beam position detector unit. It was established by use of a blackbody reference that the spectrometer is responsive to impulsive heat sources in the sample with no measureable instrumental distortion of the frequency or time delay domain responses. The sensitivity of the device was tested successfully in the measurement of thermal parameters of thin quartz layers on absorbing backings. It was further shown that our spectrometer is sensitive to thin SiO2 layers on Si wafers. The data were largely consistent with Green’s function models of heat conduction in the liquid interface and bulk. The ability of the spectrometer to perform high-quality frequency response measurements via fast Fourier transformations of the input data in very short time compared to the conventional lock-in detection is an extremely useful feature for thermal-wave applications.
Improved time-of-flight ion charge state diagnostic
Authors: Brown I. G. , Galvin J. E. , MacGill R. A. , Wright R. T.
Published: July 2002

A time-of-flight diagnostic for analysis of relatively low-energy ion beams is described. The system incorporates several novel features which improve its performance in a number of ways. The technique is simple and can provide an alternative to magnetic analysis of ion beams for the determination of ion charge state and beam composition.
Evaluation of a commercial, portable, ambient-temperature emissometer
Authors: Kollie Thomas G. , Weaver Freddie J. , McElroy David L.
Published: July 2002

The Devices&Services Company model AE emissometer was evaluated by measurements at ambient temperature on materials with emittances, ε, from 0.03 to 0.95, including plates of copper and stainless steel, aluminum foil, adhesive tape, wood, paper, and oxide coatings on a metal pipe. A repeatability of ±0.008 units was observed for measurements of ε of working standards over a one-year period. The accuracy of the emissometer was established by measurements on specimens of known ε; an uncertainty of ±0.014 units was determined. These repeatability and accuracy values were confirmed by a round-robin investigation using two working standards whose ε’s were measured by three independent laboratories using model AE emissometers and by four laboratories that used absolute methods. The instrument was shown to measure the total hemispherical ε, not the total normal ε. Experimental difficulties were encountered during measurements on a very anisotropic material and in determinations of ε’s of materials with transparencies less than 0.1. Critical procedural steps are discussed.
New portable photoacoustic and fluorescence photometer for field measurement of photosynthesis
Authors: Bélanger Raymond , Paquette André , N’soukpoé-Kossi Christophe N. , Leblanc Roger M.
Published: July 2002

A new portable photoacoustic and fluorescence photometer has been built. The instrument is especially made for field measurements but can also be used indoors. This new instrument has many advantages. It can measure the photosynthetic O2 evolution and energy storage, and the vitality index in the same sample. The system is very compact, which makes it easy to transport. A small electrical generator satisfies the 110 V power requirement for field applications. All manipulations are computer controlled including the data acquisition and treatment. The photoacoustic signal-to-noise ratio for carbon black is the same under field conditions as in the laboratory (∼2×104) at 130 Hz. Results obtained on declining sugar maple trees in the field are presented. The combination of photoacoustic and fluorescence measurements in one instrument represents a very powerful tool in photosynthesis research.
Preparation and characterization of tungsten tips for scanning tunneling microscopy
Authors: Cricenti A. , Paparazzo E. , Scarselli M. A. , Moretto L. , Selci S.
Published: July 2002

Tungsten tips obtained through electrochemical etching have been characterized by scanning electron microscopy, scanning Auger microscopy, and scanning tunneling microscopy. While such tips resulted to be very sharp, a thick oxide layer (∼10 nm) is present at the apex. High-vacuum annealing at 1800 K removes most of such oxide.
Parallel beam approximation for V-shaped atomic force microscope cantilevers
Authors: Sader John Elie
Published: July 2002

Due to its simplicity, the parallel beam approximation (PBA) is commonly used in the analytical evaluation of the spring constant of V-shaped atomic force microscope (AFM) cantilevers. However, the point of contention regarding the validity of the PBA is as yet an unresolved issue, which has been exacerbated by some recent contradictory reports. In this paper, we present a detailed investigation of the deflection properties of the V-shaped AFM cantilever, and in so doing, show that the PBA is in fact a valid and accurate approximation, provided the width and length of the parallel rectangular arms are chosen appropriately. As a direct consequence of this finding, we obtain exceedingly simple yet accurate formulas for the V-shaped cantilever, which will be of value to the users of the AFM.
Analysis of scanning tunneling microscopy feedback system
Authors: Oliva A. I. , Anguiano E. , Denisenko N. , Aguilar M. , Peña J. L.
Published: July 2002

A theoretical analysis of the feedback system in the scanning tunneling microscope (STM) is presented. The proposed model includes all the elements involved in the STM loop. The knowledge of its behavior allow one to accurately determine the region where the unstable STM operation could affect the measurements, and also to set the optimal working parameters. Each element of the feedback circuitry is analyzed and discussed as well as their mutual interactions. Thus the stability region of a STM has been obtained analytically, using all the possible elements in the feedback loop and without using simplifications or rare models for the system. The mathematical models for each element of the loop has been used and the problem has been solved using control theory. Different working conditions are simulated and analyzed. Some relations for stability conditions, considering the value of each component involved in the feedback loop, are proposed and analyzed. The good agreement between theory and experimentation is shown by comparing images taken under conditions of good stability and of instability.
Ferroelectric phase transition temperatures of KTiOPO4 crystals grown from self-fluxes
Authors: Angert N. , Tseitlin M. , Yashchin E. , Roth M.
Published: July 2002

The origin of diversity in the reported ferroelectric phase transition (Curie) temperatures Tc, of KTiOPO4 (KTP) crystals grown from self-fluxes has been studied. A series of crystals has been grown by the top-seeded solution method from fluxes of different K/P molar ratios and solute concentrations, covering most of the KTP crystallization field in the K2O–P2O5–TiO2 ternary system. Curie temperatures of as-grown and high-temperature annealed crystals have been measured using the standard dielectric technique and found to spread from 883 to 960 °C. We show that the actual Tc values depend on the solution chemical composition, and a functional representation of this dependence is given. Inherent gradients of the Tc in as-grown KTP crystals are discussed in terms of the nonuniformity of their physical properties.
Pulsed supersonic helium beams for plasma edge diagnosis
Authors: Diez-Rojo T. , Herrero V. J. , Tanarro I. , Tabarés F. L. , Tafalla D.
Published: July 2002

An experimental setup for the production of pulsed supersonic He beams to be used for plasma edge diagnosis in fusion devices is described. A compromise between compact design, low cost, and good quality of the probe beams has been met. The main characteristics of the generated beams, such as pulse shape, absolute flux intensity, and velocity distribution, differ in general from those expected for ideal beam performance and have been determined and optimized experimentally. A first test of this He beam source at the TJ-I UP Torsatron in Madrid is also reported.
A hybrid digital–analog long pulse integrator
Authors: Strait E. J. , Broesch J. D. , Snider R. T. , Walker M. L.
Published: July 2002

A digital–analog integrator has been developed for use with inductive magnetic sensors in long-pulse tokamaks. Continuous compensation of input offsets is accomplished by alternating analog-to-digital convertor samples from the sensor and a dummy load, while a RC network provides passive integration between samples. Typically a sampling rate of 10 kHz is used. In operational tests on the DIII-D tokamak, digital and analog integration of tokamak data show good agreement. The output drift error during a 1200 s integration interval corresponds to a few percent of the anticipated signal for poloidal field probes in International Thermonuclear Experimental Reactor, and bench tests suggest that the error can be reduced further.
Fetal magnetocardiography: Methods for rapid data reduction
Authors: Mosher John C. , Flynn Edward R. , Quinn A. , Weir A. , Shahani U. , Bain R. J. P. , Maas P. , Donaldson G. B.
Published: July 2002

Fetal magnetocardigraphy (fMCG) provides a unique method for noninvasive observations of the fetal heart. Electrical currents generated by excitable tissues within the fetal heart yield measurable external magnetic fields. Measurements are performed with superconducting quantum interference devices inductively coupled to magnetometer or gradiometer coils, and the resulting signals are converted to digital form in the data acquisition system. The measured fields are usually contaminated by fetal and maternal movements (usually respiration), other physiological fields such as skeletal muscle contraction, the maternal cardiac signal, and environmental electromagnetic fields. Sensitivity to relatively distant sources, both physiological and environmental, is substantially reduced by the use of magnetic gradiometers. Other contaminants may be removed by proper signal conditioning which may be automatically applied using “black box” algorithms that are transparent to the user and highly efficient. These procedures can rapidly reduce the complex signal plus noise waveforms to the desired fMCG with minimal operator interference.
Simple capacitive sensors for mass measurements
Authors: Golnabi Hossein
Published: July 2002

Design and operation of two simple capacitive transducer systems are described here. The first design uses a spring for the air-gap variations of a capacitor, while the second one employs a cantilever steel beam as a restoring element in a capacitive transducing arrangement. The reported setup makes it possible to detect mass changes of the order of 0.1 g in a 250 g range. A comparison has been made between the results of two sensors, and the second design shows a better performance in terms of repeatability, linearity, and sensitivity. It has a repeatability of better than 4% for this range of operation. This device is suitable for mass measurements of medium resolution and dynamic range and has the advantage of simplicity in design and construction.
Analysis of front contact heterojunction in a-Si:H one-dimensional position sensitive detectors
Authors: Topič M. , Smole F. , Furlan J. , Fortunato E. , Martins R.
Published: July 2002

The influence of different transparent conducting oxides (TCO) on the transverse photoelectrical properties of one-dimensional position sensitive detectors based on p-i-n amorphous silicon structures was studied. For both SnO2 and indium tin oxide, poor quality of the p layer was revealed by secondary ion mass spectroscopy measurements. Good agreement between experimental and simulation characteristics of TCO/p-i-n structure was additionally conditioned by a strong increase in defect states at the p layer surface which can be attributed to the reduction/oxidation process at the TCO/p interface. However, the analysis showed that under reverse bias the spectral response of the p-i-n structure is not significantly affected by different TCO layers and conditions at the TCO/p heterojunction. Nevertheless, indium tin oxide is less appropriate for a front TCO layer due to the poor reverse dark current-voltage characteristic, i.e., higher leakage current component leading to lower signal to noise ratio.
Mathematical modeling of disk reflector response as a contribution to the in situ ultrasonic inspection
Authors: Krstelj Vjera , Markuc̆ic̆ Damir
Published: July 2002

The possibility of mathematical modeling of ultrasonic beam, the most influencing factor in the ultrasonic methods in quality control of materials and constructions, is considered. We have focused attention on the distribution of acoustic energy in inspected material, since a reliable estimate of the reflector size is possible only if the former is known. In the experimental part we used an ultrasonic pulse-echo method and piezoelectric probes, as well as two basic types of reflectors that cross the ultrasonic beam and the reflectors that are within the beam, as representative for the flaw in inspected materials. In the modeling we have included real in situ conditions and factors influencing the results, and the results were selected using the proposed optimal criteria.
Pt resistor thermometry and pressure calibration in a clamped pressure cell with the medium, Daphne 7373
Authors: Murata Keizo , Yoshino Harukazu , Yadav Hari Om , Honda Yoshiaki , Shirakawa Naoki
Published: July 2002

Calibration of a Pt resistance thermometer (Netsushin) in magnetic fields and under pressure in the range of 1.5–300 K and below 1.5 GPa is presented. With the pressure medium, olefin olygomers, Daphne 7373, the pressure is continuous at its solidification and the pressure drop from 300 to 4.2 K by 0.15–0.17 GPa is constant, irrespective of the initial clamped pressure at 300 K. The applicability of the thermometer and the medium for precise study in field and pressure at low temperature is discussed.
Detection of small quantities of gaseous contamination in a gas by using a differential optical method
Authors: Djaozandry R. , St-Arnaud J.-M. , Bose T. K. , Fréchette M. F.
Published: July 2002

We present a differential optical method (DOM) based on an interferometric technique at λ=632.9 nm, for the detection of small amounts of gaseous contaminants in a gas. The DOM is based on comparative measurements of the refractive index of pure gas and mixtures of gaseous contaminant and the pure gas. This method allows detection of small amounts (ppmv) of contaminant as a function of pressure and temperature. The DOM was applied to gaseous SF6 contaminated with 0.49% and 10.5% of CO2 at 294.1±0.5 K, up to 0.5 MPa and 350, 700, 1244, and 1489 ppmv of water vapor at 304.1±0.1 K, up to 1 MPa. Comparative measurements with a hygrometer (MCM, Dewmatic 600 D) show good agreements at 350±25 and 700±50 ppmv of water.
Multidimensional fluorescence spectroscopy using a streak camera based pulse fluorometer
Authors: Bühler Christof A. , Graf Urs , Hochstrasser Remo A. , Anliker Max
Published: July 2002

Modern streak camera based pulse fluorometers readily allow data collection in two-dimensions. We have developed a modular instrument that is easily adapted for recording time-resolved emission spectra, fluorescence depolarization data, and time series of time-resolved fluorescence decays. The instrument is based on a synchroscan streak camera and a passively mode-locked Ti:Sapphire laser using second harmonic generation and third harmonic generation to extend the excitation wavelength range to the visible and ultraviolet. The performance of the instrument was tested using standard biological samples. The dynamic range is typically 600:1, and the detection limit is less than 1 fW. With respect to the fluorescence decay kinetic (first time axis), the temporal resolution is better than 10 ps, and rotational correlation times of 50 ps are measured routinely. For the second time axis, the maximum time resolution is approximately 2 ms.
Two types of ion gun equipped sputter-initiated resonant ionization and time-of-flight mass spectroscopy and its application in microanalysis of minerals
Authors: Jin L. , Dai S. T. , Dong G. X. , Li C. M. , Wang S. L. , Tian J. H. , Chen D. Y.
Published: July 2002

An apparatus, based on sputter-initiated resonant ionization spectroscopy and combined with time-of-flight mass spectroscopy, has been recently developed for microanalysis of mineral samples and other solid materials. This equipment has two kinds of ion gun, which make it possible to do more convenient and accurate microanalysis of complicated mineral samples. With this apparatus, detection and size measurement of fine gold grains trapped in pyrite at low concentrations have been carried out. The detection limit of this apparatus for gold is 73 ppb. The apparatus also has the function of secondary electron imaging. This gives very helpful information for geologists to evaluate the inborn state of gold in mineral samples and to improve the extraction rate of gold from minerals.
Pinhole camera imaging of x rays and energetic neutral atoms for hot plasma diagnostics
Authors: Kiwamoto Y. , Kikuchi Y. , Takahashi T. , Saito T. , Ichimura M. , Tatematsu Y. , Abe H. , Kajiwara K. , Koyama H. , Suzuki A. , Ito K. , Yamazaki A. , Tamano T. , Yatsu K.
Published: July 2002

A compact pinhole camera is found to be useful for observation of a spatial distribution of hot ions by imaging energetic charge-exchange neutral atoms. One can obtain images of neutral atoms and of x rays in the same geometry only by selecting filtering foils at the pinhole opening of a single camera. Easy comparison between the images associated with distributions of ions and electrons is quite beneficial for physical analyses of plasmas. The imaging technique is expected also to be useful to determine space–time-resolved energy spectra of hot ions.
Remote visual monitoring during time resolved in situ neutron diffraction study of recrystallization of melt-cast Bi1.6Pb0.4Sr2Ca3Cu4Oy by passage of dc current
Authors: Whitfield P. S. , Bhakta J. R. , Abell J. S. , Smith R. I. , Cywinski R.
Published: July 2002

The Polaris high intensity, medium resolution, time-of-flight neutron diffractometer at ISIS has been used in a real-time study to observe phase evolution in rods of melt-cast Bi1.6Pb0.4Sr2Ca3Cu4Oy in situ as they were recrystallized by passage of a dc current under a series of controlled atmospheres. Together with simultaneous measurement of current and resistance to facilitate control over sample heating, the experiment required visual monitoring of the sample during neutron diffraction data collection. This article describes the apparatus constructed to carry out these experiments, along with the necessary modifications made to Polaris and its control systems, and presents results which demonstrate the effectiveness of the technique. The results presented show that the initial appearance of the Bi-2201 phase occurred before hot zone formation. On formation of the hot zone, development of Bi-2212 took place at the expense of Bi-2201. Finally, passage of the zone saw the Bi-2212 redissolve and Bi-2201 reform.