bluuebunny/crossref_metadata_2025 huggingface dataset:
Cost‐effectiveness of analgesia after Caesarean section. A comparison of intrathecal morphine and epidural PCA
Authors: Vercauteren M. , Vereecken K. , La Malfa M. , Coppejans H. , Adriaensen H.
Published: July 2002

Background: Patient‐controlled analgesia (PCA) techniques and intrathecal morphine are the most widely used treatments for post‐Caesarean section pain. However these methods have not been compared with respect to analgesic quality and cost differences.

Methods: Fifty‐three patients scheduled for elective or semi‐urgent Caesarean section were randomized to receive for postoperative analgesia either epidural PCA with a mixture containing bupivacaine 0.06% and sufentanil 1 μg · ml−1 or intrathecal morphine 0.15 mg together with the spinal anaesthetic and to be supplemented with paracetamol and tramadol. Analgesic efficacy, side‐effects and costs were calculated during 48 h.

Results: VAS pain scores both at rest and during mobilization were lower in the PCA group, more particularly during the second postoperative day. Nausea and vomiting were more frequently registered in the morphine treated patients. PCA treated patients stayed longer in the recovery room but required fewer nurse interventions on the surgical ward. Manpower and drug costs were equal in both groups. The differences in total costs (Euro) amounted to €33 and were mainly caused by the more expensive equipment required for epidural PCA. Satisfaction and hospital discharge were similar for both treatments.

Conclusions: It was concluded that epidural PCA induced better pain relief, caused less nausea/vomiting but was more expensive than intrathecal morphine.
The Study of Cutaneous Melanomas in Camargue‐Type Gray‐Skinned Horses (2): Epidemiological Survey
Authors: Fleury Catherine , Bérard Frederic , Leblond Agnés , Faure Christine , Ganem Nathalie , Thomas Luc
Published: July 2002

An epidemiological survey was made on cutaneous melanomas occurring in Camargue‐type, gray‐skinned horses in southern France. The population investigated was composed of 264 horses, which were selected from the Camargue horse stud registry and were allowed to be examined by the owners. The presence of tumors was inspected macroscopically according to the standardized protocols of veterinary medicine specialists, and some tumors were subjected to macroscopic histopathological examination. The results indicated that: 1) the prevalence of melanomas in the overall population was 31.4%; 2) the odds ratio was obtained for an age class of 5–9 years, in which most melanomas were presumed to occur; 3) the incidence of melanomas was significantly correlated with age, giving a prevalence of 67% at ages> 15 years; 4) the size and number of tumorous lesions were significantly related to age; 5) little correlation was observed between melanoma incidence and gender; and 6) the most frequently occurring body site of these tumors was underneath the tail. Because of their frequent occurrence in shaded body regions, sun exposure was not likely to be a risk factor for melanoma formation in these horses. In view of the slightly darker skin pigmentation in these horses at younger ages, the unique characteristics of their melanocytes may be associated with melanoma formation.
Biochemical adaptations of two sugar kinases from the hyperthermophilic archaeon Pyrococcus furiosus
Authors: VERHEES Corné H. , KOOT Denise G.M. , ETTEMA Thijs J.G. , DIJKEMA Cor , de VOS Willem M. , van der OOST John
Published: July 2002

The hyperthermophilic archaeon Pyrococcus furiosus possesses a modified Embden—Meyerhof pathway, including an unusual ADP-dependent glucokinase (ADP-GLK) and an ADP-dependent phosphofructokinase. In the present study, we report the characterization of a P. furiosus galactokinase (GALK) and its comparison with the P. furiosus ADP-GLK. The pyrococcal genes encoding the ADP-GLK and GALK were functionally expressed in Escherichia coli, and the proteins were subsequently purified to homogeneity. Both enzymes are specific kinases with an optimal activity at approx. 90°C. Biochemical characterization of these enzymes confirmed that the ADP-GLK is unable to use ATP as the phosphoryl group donor, but revealed that GALK is ATP-dependent and has an extremely high affinity for ATP. There is a discussion about whether the unusual features of these two classes of kinases might reflect adaptations to a relatively low intracellular ATP concentration in the hyperthermophilic archaeon P. furiosus.
Bone resorption is increased in young adults with thalassaemia major
Authors: Voskaridou Ersi , Kyrtsonis Maria‐Christina , Terpos Evangelos , Skordili Maroussa , Theodoropoulos Ilias , Bergele Angeliki , Diamanti Evanthia , Kalovidouris Angelos , Loutradi Aphrodite , Loukopoulos Dimitris
Published: July 2002

Bone disease in patients with thalassaemia major is a multifactorial and still poorly understood process. The present study evaluated 45 thalassaemic patients using dual X‐ray absorptiometry at three sites (lumbar spine, head of femur and forearm) to assess bone mineral density, in parallel with a series of biochemical markers to measure bone formation and bone resorption. To identify possible interfering factors, our patients were grouped according to whether or not they needed transfusion therapy; the presence of hypogonadism was also considered. Our results showed that patients on regular transfusions had a markedly low bone mineral density in contrast to those not requiring blood support and that this finding was more pronounced in the hypogonadic group, irrespectively of sex. The decrease of bone mineral density values was more prominent in the forearm, thus making this site particularly interesting for such studies. Bone formation, as evidenced by the levels of serum alkaline phosphatase and osteocalcin, did not appear to be impaired, while bone resorption was grossly increased in all patient groups. The latter process was clearly evident using the recently introduced measurement of the urinary N‐terminal peptides of collagen type I, the sensitivity of which has already been established in other groups of osteoporotic patients. Our conclusion is that, in spite of the severe bone destruction that occurs in thalassaemia major, the fact that bone formation remains intact calls for a more intensive treatment comprising hormonal replacement, bisphosphonates and other agents.
An atypical contiguous gene syndrome: molecular studies in a family with X–linked Kallmann's syndrome and X‐linked ichthyosis
Authors: Maya‐Nuñez Guadalupe , Torres Leda , Ulloa‐Aguirre Alfredo , Carlos Zenteno Juan , Cuevas‐Covarrubias Sergio , Saavedra‐Ontiveros Dolores , Kofman‐Alfaro Susana , Pablo Méndez Juan
Published: July 2002

BACKGROUND AND OBJECTIVE

Kallmann's syndrome (KS) is characterized by hypogonadotrophic hypogonadism in association with anosmia or hyposmia. This entity can be associated with X‐linked ichthyosis (XLI) in a contiguous gene syndrome. Genetic defects have been demonstrated on the Xp22.3 region explaining the presence of one or both entities in affected individuals. In this report we describe the molecular findings in four patients, pertaining to a three generation family, with KS which was associated with XLI in two of them.

MEASUREMENTS

Enzymatic activity of steroid sulphatase was measured in leucocytes. Polymerase chain reaction of the 14 exons of the Kallmann gene (KAL) and of the 5′ and 3′ extremes of the steroid sulphatase gene was performed in genomic DNA. PCR products of the 14 exons of the KAL gene were purified and sequenced.

RESULTS

Absence of steroid sulphatase activity and a complete deletion of the STS gene were demonstrated in both patients with XLI. In all subjects, the 14 KAL gene exons amplified in a normal fashion; no mutation was documented after sequencing all exons.

CONCLUSIONS

Although it has been proposed recently that the X‐linked form of the disease accounts for the minority of patients with Kallman's syndrome, the pedigree chart of this family demonstrates this inheritance pattern. Various possibilities are mentioned in order to explain the absence of mutation in the KAL gene. The coexistence, in this family, of Kallman's syndrome individuals and patients with Kallman's syndrome and X‐linked ichthyosis is discussed.
Comparison of monthly intramuscular injections of Sandostatin LAR with multiple subcutaneous injections of octreotide in the treatment of acromegaly; effects on growth hormone and other markers of growth hormone secretion
Authors: Hunter  , Shaw  , Lee  , Wood  , Atkinson  , Bevan
Published: July 2002

OBJECTIVE

To compare the effects of monthly intramuscular injections of a long acting preparation of octreotide, Sandostatin LAR, with multiple daily subcutaneous injections of octreotide and to study the interrelationships between mean 24 h growth hormone profile, serum total and free IGF‐1 levels, 24 h urinary growth hormone levels and serum IGFBP‐3.

DESIGN

Patients were assessed by 24 h GH profile off octreotide or any other GH modifying drug therapy; on subcutaneous octreotide (200–600 μg daily in divided doses for six weeks); and 28 days after the second of two injections of Sandostatin LAR (20 mg by intra‐muscular injection) administered 28 days apart. Serum total and free IGF‐1, serum IGFBP‐3 and 24 h urinary GH were also measured on each occasion.

RESULTS

Sandostatin LAR was well tolerated. None of the patients reported any adverse effect and all completed the study uneventfully. Mean GH off treatment was 10.1 ± 3.0 μg/l falling equally significantly (P < 0.05) during therapy with subcutaneous octreotide to 3.0 ± 0.7 μg/l and Sandostatin LAR to 2.8 ± 0.7 μg/l. Fasting 0900 h GH was significantly reduced (P < 0.05) on Sandostatin LAR (3.0 ± 0.7 μg/l) compared with subcutaneous octreotide (5.1 ± 1.2 μg/l). Mean total IGF‐1 off treatment was 658.6 ± 56.1 μg/l and was reduced to a comparable extent with subcutaneous octreotide and Sandostatin LAR (466.0 ± 59.7 and 448.6 ± 59.5 μg/l respectively; both P < 0.05). Free IGF‐1 off treatment was 3.1 ± 0.6 μg/l and was reduced equally by subcutaneous octreotide and Sandostatin LAR (1.2 ± 0.2 and 1.2 ± 0.2 μg/l; both P < 0.05). IGFBP‐3 was reduced to a greater extent during Sandostatin LAR than during subcutaneous octreotide (4518.2 ± 247.3 vs 5132.8 ± 280.7 μg/l; P < 0.05). Twenty‐four hour urinary GH excretion was reduced to a comparable extent with both therapies. Highly significant positive correlations were found between mean 24 h GH levels and free IGF‐1 (r = 0.66, P < 0.0001) and 24 h urinary GH excretion (r = 0.94, P < 0.0001). The relationships between mean 24 h GH levels and total IGF‐1 and IGFBP‐3 although significant showed less powerful correlations.

CONCLUSIONS

These results suggest that Sandostatin LAR is well tolerated and as effective as subcutaneous octreotide. In addition, urinary growth hormone and serum free IGF‐1 may prove valuable for outpatient follow‐up of acromegalic patients, as both correlate well with mean 24 h serum growth hormone levels.
Estimating woody and herbaceous vegetation cover from time series satellite observations
Authors: Roderick Michael L. , Noble Ian R. , Cridland Shane W.
Published: July 2002

In this paper we test a method to estimate the tree and grass vegetation cover over Australia from satellite‐derived normalized difference vegetation index (NDVI) time series (monthly 1981–91, ≈5 km pixels) observations. The evergreen cover is assumed to track along the base of the NDVI time series, which is assumed to be equivalent to the woody vegetation cover. The base of the NDVI time series is estimated using modifications to a classical econometric model (i.e. time series is the sum of trend, seasonal and random components). Estimates of the average evergreen component during 1982–85 and 1986–89 were generally consistent with known vegetation distributions. Changes in evergreen cover were largely restricted to the south‐west and south‐east of Australia. Those changes were largely the result of differences in rainfall between the two periods. The proposed method for estimating woody vegetation cover is found to be generally robust. However, there are some regions where the grass (or pasture) is mostly evergreen. Some possible refinements are proposed to handle such cases.
Characterization of five tomato phospholipase D cDNAs: rapid and specific expression of LePLDβ1 on elicitation with xylanase
Authors: Laxalt Ana M. , Ter Riet Bas , Verdonk Julian C. , Parigi Lisa , Tameling Wladimir I. L. , Vossen Jack , Haring Michel , Musgrave Alan , Munnik Teun
Published: July 2002

Phospholipase D (PLD, EC 3.1.4.4.) has been implicated in a variety of plant processes, including signalling. In Arabidopsis thaliana a PLD gene family has been described and individual members classified into α‐, β‐ and γ‐classes. Here we describe a second PLD gene family in tomato (Lycopersicon esculentum) that includes three α‐ and two β‐classes. Different expression patterns in plant organs were observed for each PLD. In testing a variety of stress treatments on tomato cell suspensions, PLDβ1 mRNA was found to rapidly and specifically accumulate in response to the fungal elicitor xylanase. The greatest increase was found 2 h after treatment with 100 µg ml−1 xylanase (ninefold). In vivo PLD activity increased nearly threefold over a 1.5 h period of treatment. When the elicitor was injected into tomato leaves, PLDβ1 mRNA accumulation peaked at 2 h (threefold increase), before decreasing to background levels within 72 h. Mutant, non‐active xylanase was as effective as the active enzyme in eliciting a response, suggesting that xylanase itself, and not the products resulting from its activity, functioned as an elicitor. When chitotetraose was used as elicitor, no PLDβ1 mRNA accumulation was observed, thus it is not a general response to elicitation. Together these data show that PLD genes are differentially regulated, reflecting potential differences in cellular function. The possibility that PLDβ1 is a signalling enzyme is discussed.
Deep Wound Infection After Vagus Nerve Stimulator Implantation: Treatment Without Removal of the Device
Authors: Ortler Martin , Luef Gerhard , Kofler Alexandra , Bauer Gerhard , Twerdy Klaus
Published: July 2002

Summary: Effective treatment of deep wound infection without removal of a previously implanted foreign body is difficult. The Neurocybernetic Prosthesis (NCP) System (Cyberonics Inc., Webster, TX, U.S.A.), implanted for vagus nerve stimulation in patients with medically refractory epilepsy, uses coil‐like electrodes placed around the left vagus nerve after exposure of the nerve in the carotid sheath. Infection within this compartment endangers the contained structures and makes removal of the system hazardous. We report the case of one patient implanted with the NCP who underwent successful open wound treatment without removal of the system. A 35‐year‐old man had local signs of wound infection 5 weeks after implantation of a vagus nerve stimulator. Systemic signs of infection were absent. C‐reactive protein was slightly elevated, but all other laboratory values were normal. After open wound debridement and thorough rinsing with bacitracin‐containing solution, the wound was packed with 3% iodoformized gauze. The NCP was left in place. Systemic antibiotic therapy with fosfomycin and cefmenoxim was started. Cultures confirmed an infection with Staphylococcus aureus. The wound was rinsed daily with 3% hydrogen peroxide solution and 5% saline until cultures were sterile and granulation tissue started to fill the wound. Delayed primary closure was performed 2 weeks later. Wound healing was accomplished without removal of the device. No signs of recurrent infection were observed during a follow‐up of 1 year. Open wound treatment without removal of the implanted vagus nerve stimulator is feasible in cases of deep cervical wound infection and can be an alternative if removal of the device appears hazardous.
Chronic Idiopathic Hyponatremia in Older People Due to Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) Possibly Related to Aging
Authors: Anpalahan Mahesan
Published: July 2002

OBJECTIVE: To determine the prevalence of syndrome of inappropriate antidiuretic hormone secretion (SIADH) among older hyponatremic patients in a subacute geriatric facility, to identify patients with no apparent cause for the SIADH (idiopathic SIADH), and to determine their clinical characteristics.

DESIGN: Prospective analysis of a cohort of older patients over a period of 3 months.

SETTING: Two wards in a geriatric rehabilitation hospital.

PARTICIPANTS: Patients aged 65 and older.

MEASUREMENTS: All patients with hyponatremia (serum sodium <135 mmols/l) were clinically examined and relevant investigations were performed to determine the etiology of hyponatremia. Patients were observed for symptoms of hyponatremia. Hyponatremia was classified into possible SIADH and non‐SIADH types. Patients with SIADH type hyponatremia were screened for possible causes. Past medical histories were obtained from the general practitioners.

RESULTS: Of the 172 patients studied, 43 (25%) had hyponatremia. It was symptomatic in only four patients. Twenty‐two (51%) had SIADH etiology. In nine (mean age 84 ± 4), no cause for the SIADH was evident (presumed idiopathic SIADH) and in seven, hyponatremia (128–135 mmols/l) was chronic (12 to 72 months). Further reduction in serum sodium, which was symptomatic, was noted in two of these patients with the onset of pneumonia.

CONCLUSION: Most older hyponatremic patients in a rehabilitation setting seem to have SIADH etiology. This study confirms the presence of a group of older individuals with chronic idiopathic hyponatremia in whom the underlying mechanism may be SIADH related to aging. Hyponatremia is modest in these patients and has little clinical significance. However, they may be at increased risk of developing symptomatic hyponatremia with intercurrent illnesses.
Chemisorption-induced reflectivity changes in optically thin silver films
Authors: Butler M. A. , Ricco A. J.
Published: July 2002

The reflectivity of an optically thin metal film has been used to investigate its interactions with chemisorbed molecules. Reflectivity decreases for semitransparent, thin (50–250 Å) silver films vacuum evaporated on the end of multimode optical fibers were observed at 860 nm during chemisorption of various molecules. The magnitude of the decrease depends on the nature of the molecule/silver interaction. The dependence of this effect on film thickness is consistent with changes in the optical thickness as a result of chemisorption. This effect may lead to the development of new chemical sensors.
Ionized cluster beam deposition of Hg1−xCdxTe films and their optical properties
Authors: Takaoka Gikan H. , Murakami Satoshi , Ishikawa Junzo , Takagi Toshinori
Published: July 2002

The Hg1−x Cdx Te films with a small concentration of Cd and a narrow band gap have been prepared on GaAs(100) substrates by using the ionized cluster beam (ICB) technique. For the case of ionizing clusters of either CdTe or HgTe as source materials, the band gap can be controlled between 0.2 and 0.3 eV by adjusting the acceleration voltage for cluster ions. The kinetic energy and the ionic charge of the cluster ions are found to have much influence on the composition and the optical properties of the films.
Replacement of magnesium in InGaAs/InP heterostructures during zinc diffusion
Authors: Dildey F. , Treichler R. , Amann M.-C. , Schier M. , Ebbinghaus G.
Published: July 2002

Zn diffusions from spin-on films have been carried out into n-InP/p+-InGaAs/n-InP heterostructures, which were grown by metalorganic vapor phase epitaxy for heterojunction bipolar transistors with Mg as a p dopant. After diffusion, Mg was completely substituted by Zn and enriched in the spin-on film. In the presence of Mg, the indiffusion of Zn is strongly enhanced. By varying doping levels and diffusion conditions, the underlying mechanism is studied and compared to recent experiments with Be-doped AlGaAs/GaAs heterostructures.
Photorefractive effect in Ti-diffused channel waveguides using LiNbO3 substrates with reduced optical absorption
Authors: Fujiwara Takumi , Terashima Akira , Mori Hiroshi
Published: July 2002

We report a remarkably reduced photorefractive sensitivity in Ti:LiNbO3 channel waveguides using substrates with reduced optical absorption near the absorption edge. In addition, the intensity dependence of the saturated index change was measured, which indicates that, based on the Glass model, the saturated value of photoinduced index change is independent of irradiation intensity in the high intensity limit.
Growth of improved quality 3C-SiC films on 6H-SiC substrates
Authors: Powell J. A. , Larkin D. J. , Matus L. G. , Choyke W. J. , Bradshaw J. L. , Henderson L. , Yoganathan M. , Yang J. , Pirouz P.
Published: July 2002

Previously reported chemical vapor deposition of 3C-SiC on 6H-SiC has resulted in films with a high density of double positioning boundaries (DPBs). We have found that growth on as-grown faces of 6H-SiC crystals can yield films that are largely free of DPBs. The (111) 3C-SiC films, up to 12 μm thick, were evaluated by optical and electron microscopy and low-temperature photoluminescence (LTPL). The LTPL spectra of the films were similar to those of high quality Lely-grown 3C-SiC.
Total dose radiation hardness of diamond-based silicon-on-insulator structures
Authors: Landstrass M. I. , Fleetwood D. M.
Published: July 2002

Total dose radiation hardness measurements were performed on silicon-on-insulator (SOI) test structures where the insulator is chemical vapor deposited (CVD) diamond. These measurements represent a first look at the fundamental radiation response of low-pressure CVD synthetic diamond materials for SOI applications. Silicon/diamond metal-insulator-semiconductor (MIS) capacitors were subjected to both cobalt-60 and 10 keV x-ray irradiation up to doses of 1×107 rad (SiO2) while under positive, negative, and zero bias conditions. The diamond insulators used in these devices were found to be free from extensive hole or electron trapping. This behavior is consistent with the high electron and hole mobility of the polycrystalline diamond insulator.
Femtosecond thermal modulation measurements of electron-phonon relaxation in niobium
Authors: Yoo K. M. , Zhao X. M. , Siddique M. , Alfano R. R. , Osterman D. P. , Radparvar M. , Cunniff J.
Published: July 2002

Thermal modulation measurements using 120 fs/620 nm laser pulses were performed on niobium films. The electron-phonon relaxation time was found to be ultrafast and measured to be 360 fs, and the electron-phonon coupling constant was estimated to be (17±3)×1017 W m−3 K−1.
Epitaxial growth of aligned polydiacetylene films on anisotropic orienting polymers
Authors: Patel J. S. , Lee Sin-Doo , Baker G. L. , Shelburne J. A.
Published: July 2002

We report an epitaxial method for orienting thin films of polydiacetylenes on ordinary alignment polymers that have been stretched by rubbing. By selectively removing the alignment polymer using standard photolithographic techniques, we show that it is possible to obtain well-oriented polydiacetylene films in desired regions. Typical values for the birefringence are 0.14±0.01 for epitaxially grown films, enough to allow the formation of gratings and channel waveguides on patterned surfaces.
Reversible modification of CdTe surface composition by excimer laser irradiation
Authors: Brewer P. D. , Zinck J. J. , Olson G. L.
Published: July 2002

KrF excimer laser irradiation of CdTe at fluences below the melt threshold (≤75 mJ/cm2) removes surface layers and produces reversible changes in the surface composition that depend upon the laser fluence and number of laser pulses delivered to the surface. At fluences above ∼40 mJ/cm2 a Te-rich layer is obtained. A stoichiometric composition can be restored by irradiation at reduced laser fluence. The primary desorption products are Cd and Te2, and the velocities of these species are well described by a Maxwellian distribution. The fluence-dependent changes in CdTe surface composition are consistent with a photothermal mechanism based on the competition between formation and desorption of Te2 and desorption of Cd atoms from the laser-irradiated surface.
Tantalum as a diffusion barrier between copper and silicon
Authors: Holloway Karen , Fryer Peter M.
Published: July 2002

We have investigated the effectiveness and failure mechanism of thin tantalum layers as diffusion barriers to copper. 50 nm tantalum films were sputtered onto unpatterned single-crystal 〈100〉 Si wafers and overlaid with 100 nm Cu. Material reactions in these films were followed as a function of annealing temperature by in situ resistance measurements, and characterized by Rutherford backscattering spectroscopy and cross-section transmission electron microscopy. While pure Cu on Si reacts at 200 °C, the Ta film prevents Cu silicon interaction up to 600 °C. At higher temperatures, reaction of the Si substrate with Ta forms a planar layer of hexagonal TaSi2. Cu rapidly penetrates to the Si substrate, forming η″-Cu3Si precipitates at the Ta-Si2-Si interface.
Si impurity in chemical vapor deposited diamond films
Authors: Ruan J. , Choyke W. J. , Partlow W. D.
Published: July 2002

Cathodoluminescence (CL) and annealing studies of microwave plasma-assisted chemical vapor deposited (CVD) diamond films were carried out. The annealing behavior of the 1.681 eV (737.4 nm) line in the CL spectra of CVD diamond films grown on Si substrates is compared with that of the GR1 spectral line (1.673 eV) of natural diamond. We determine that these two lines have different origins. The comparison of CL spectra of diamond films grown on different substrates shows that the 1.681 eV peak is due to Si impurity in CVD diamond films.
Fiber optic magnetic field sensor based on domain wall motion in garnet film waveguides
Authors: Wolfe R. , Lieberman R. A.
Published: July 2002

A novel fiber optic magnetometer based on the Faraday effect in a magnetic garnet thin-film ridged waveguide is described. The single-mode film has planar magnetization aligned parallel and antiparallel to the light propagation direction by a gradient bias field, and a single domain wall crosses the light path. The motion of this wall in response to an applied field changes the Faraday rotation in the film. Operation of this field or current sensor in both the transmission mode and the single fiber reflection mode has been demonstrated. Optical output varying linearly with ac or dc fields up to 15 Oe, with a minimum detectable field of 0.05 Oe, has been observed. This domain wall motion scheme in a zero birefringence waveguide can also be used in a polarization controller.
Fundamental chemical differences among P
b defects on (111) and (100) silicon
Authors: Stathis J. H. , Dori L.
Published: July 2002

Using electron spin resonance, a single defect (called Pb0) is observed at the Si(111)/SiO2 interface, whereas two different defects (called Pb0 and Pb1) are observed at the Si(100)/SiO2 interface. While the structure of the Pb center is well established as a silicon dangling bond, the identities of Pb0 and Pb1 are controversial. We have discovered that under processing conditions where the hydrogen passivation reaction Si⋅+H0→Si-H passivates the Pb center at the Si(111)/SiO2 interface, the Pb1 center is likewise passivated but the Pb0 center is not. We conclude that the structure of Pb1 is a silicon dangling bond similar to the Pb on (111), and that the Pb0 is a fundamentally different defect, in agreement with recent theoretical calculations.
Study of diffusion and cluster formation of copper deposition on polyimide by optical second-harmonic generation
Authors: Zhang J. Y. , Shen Y. R. , Soane D. S. , Freilich S. C.
Published: July 2002

Optical second-harmonic generation is shown to be an effective means for in situ monitoring of two competing dynamic processes of Cu deposited on polyimide aggregation by surface diffusion and implantation by diffusion into the bulk. It is also explicitly demonstrated that a thin layer of Ti is able to completely block Cu diffusion into polyimide and promote the metal/polyimide.
Deposition of diamond-like carbon film using electron cyclotron resonance plasma
Authors: Kuo S. C. , Kunhardt E. E. , Srivatsa A. R.
Published: July 2002

Hard diamond-like carbon films were deposited on Si(100) substrates using a CH4 plasma created through electron cyclotron resonance (ECR) heating. The ECR plasma was excited by a Lisitano coil. These films could be deposited with a negative dc bias (−200 V) or a rf-induced negative self-bias (−100 V) on the substrates. The deposition rate of the film was about 2.3 Å/s. The deposited films were characterized by Raman spectroscopy and near-edge x-ray absorption fine structure analysis.
Ultraviolet radiation induced defect creation in buried SiO2 layers
Authors: Devine R. A. B. , Leray J-L. , Margail J.
Published: July 2002

The creation of oxygen-vacancy defects in amorphous SiO2 films produced by O+ implantation and annealing has been studied using radiation from a microwave excited Kr plasma. Photons having λ≤125 nm are found to create saturation densities ∼1.3×1019 cm−3 whereas for λ≥ (R18)200 nm the saturation density is ∼3.4×1017 cm−3. It is argued that simultaneous defect creation and annihilation may occur for long wavelength, sub-band-gap energy photons. Strongly enhanced defect creation (≤970 times) is observed as compared to bulk, amorphous SiO2 in the form of Suprasil 1 plate. It is suggested that this may be due to H sensitization of the defect precursors (O3≡Si—Si≡O3).
Experimental evidence of magnetostatic soliton propagation at microwave frequencies
Authors: Dragoman M. , Georgescu D.
Published: July 2002

The experimental results of magnetostatic soliton propagation at microwave frequencies are compared with a numerical nonlinear model. Despite the conclusions of the experimental results, it is shown that the output power behavior as a function of the input power represents the main signature of the soliton existence in the magnetic films.
Self-limitation in the surface segregation of Ge atoms during Si molecular beam epitaxial growth
Authors: Fukatsu S. , Fujita K. , Yaguchi H. , Shiraki Y. , Ito R.
Published: July 2002

Self-limitation in the surface segregation of Ge atoms in the Si epitaxial overlayers arising from the surface bond geometry on Si(100) during molecular beam epitaxy has been investigated theoretically. It was found that Ge surface segregation is strongly limiting when the Ge concentration exceeds 0.01 monolayer. As a result of this self-limitation, segregation profiles of Ge in Si overlayers are found to decay nonexponentially in the growth direction with a kink in the profile around 3×1020 cm−3, which is in close agreement with the experimental observation. The kinetic barrier of the Ge surface segregation is estimated to be 1.63±0.1 eV.
Vapor phase synthesis of crystalline nanometer-scale GaAs clusters
Authors: Saunders Winston A. , Sercel Peter C. , Atwater Harry A. , Vahala Kerry J. , Flagan Richard C.
Published: July 2002

We report the synthesis of crystalline nanometer-scale GaAs clusters in the 5–10 nm size regime. The clusters are formed by the homogeneous nucleation of a nonequilibrium vapor created by the explosive vaporization of a bulk GaAs sample in an inert atmosphere. High resolution electron microscopy and diffraction show that the clusters have zincblende crystal structure and are faceted. Optical measurements on the particles are suggestive of quantum confinement effects.
Microstructure of biepitaxial grain boundary junctions in YBa2Cu3O7
Authors: Rosner S. J. , Char K. , Zaharchuk G.
Published: July 2002

The microstructure of photolithographically defined 45° biepitaxial grain boundary junctions in YBa2Cu3O7 (YBCO) have been investigated by transmission electron microscopy. The junctions have been formed by growing YBCO and a buffer layer on a patterned MgO seed layer previously grown on r-plane sapphire or SrTiO3 coated (through the use of suitable buffer layers) (100) yttrium-stabilized-zirconia substrates. SrTiO3 or CeO2 buffer layers grown on these patterned MgO substrates reproduced the pattern with two variants crystallographically rotated 45° with respect to each other about the surface normal. The morphology of the YBa2Cu3O7 grown on these differently oriented patterned regions show marked differences; in particular, the ion milling damage to the sapphire surface during patterning causes the formation of low angle grain boundaries. The locations of the weak link grain boundaries with respect to the patterning in the MgO seed layer have been identified using electron diffraction.
Low-noise YBa2Cu3O7 rf SQUID magnetometer
Authors: Zhang Yi , Mück H.-M. , Herrmann K. , Schubert J. , Zander W. , Braginski A. I. , Heiden C.
Published: July 2002

A superconducting quantum interferometer device (SQUID) electronics with tank frequencies near 150 MHz was constructed to enhance the rf SQUID sensitivity. By these means we characterized our YBa2Cu3O7 thin-film rf SQUIDs with step-edge junctions immersed in liquid N2. We obtained transfer function values of over 40 μV/Φ0, at a 50 Ω input impedance, for both hysteretic and dispersive mode of rf SQUID operation. The rms white and 1/f flux noise levels were significantly lower than at the tank frequency of 20 MHz. The best magnetic field sensitivity at 77 K was 0.9 pT/Hz1/2, and the energy resolution 1.4×10−28 J/Hz, down to 0.3 Hz.
Solution-cast films of polyaniline: Optical-quality transparent electrodes
Authors: Cao Yong , Treacy George M. , Smith Paul , Heeger Alan J.
Published: July 2002

Optical-quality transparent conducting films of polyaniline (PANI) and of conducting polyblends of polyaniline with amorphous bulk polymers are described. Using functionalized protonic acids to induce solubility in common organic solvents, PANI and PANI polyblends can be cast from solution, in the conducting form, onto a variety of substrates. The resulting films are clear, and they combine low surface resistance with excellent transparency. By varying the thickness of the film and/or the volume fraction of PANI in the polyblend, the surface resistance can be controlled over an extraordinary broad range.
YBa2Cu3O7 nanobridges fabricated by direct-write electron beam lithography
Authors: Wendt J. R. , Martens J. S. , Ashby C. I. H. , Plut T. A. , Hietala V. M. , Tigges C. P. , Ginley D. S. , Siegal M. P. , Phillips J. M. , Hohenwarter G. K. G.
Published: July 2002

A direct method for nondamaging, nanometer-scale patterning of high Tc superconductor thin films is presented. We have fabricated superconducting nanobridges in high-quality, epitaxial thin-film YBa2Cu3O7 (YBCO) by combining direct-write electron beam lithography and an improved aqueous etchant. Weak links with both length and width dimensions less than 20 nm have exhibited critical currents at 77 K of 4–20 μA and IcRn products of 10–100 μV which compare favorably with results for other YBCO junction technologies. We have used this technique in the fabrication of a shock-wave pulse former as an initial demonstration of its applicability to monolithic superconductive electronics.
Novel measurements of high-dynamic crystal strength by picosecond x-ray diffraction
Authors: Wark J. S. , Woolsey N. C. , Whitlock R. R.
Published: July 2002

The fracture strength of many brittle materials is known to increase with the cubed root of the strain rate. At ultrahigh strain rates, the strengths should approach the ideal fracture strength. We have made direct measurements of the dynamic tension in laser-shocked silicon wafers at strain rates in excess of 108 s−1 by the use of picosecond x-ray diffraction. The elastic strains observed (3.4%±0.2%) correspond to tensile stresses of the order of 70 kbar, and are comparable to the highest fracture strengths observed in static measurements.
Smooth, low-bias plasma etching of InP in microwave Cl2/CH4/H2 mixtures
Authors: Constantine C. , Barratt C. , Pearton S. J. , Ren F. , Lothian J. R.
Published: July 2002

Electron cyclotron resonance microwave (2.45 GHz) discharges of Cl2/CH4/H2 with low additional dc biases (−80 to −150 V) on the sample are shown to provide smooth, anisotropic dry etching of InP at ∼150 °C. Rates of 2500 Å min−1 are obtained at a pressure of 0.5 mTorr and ∼80 V dc bias. SiO2 masks show no discernible erosion under these conditions, yielding a process that is extremely well suited for laser mesa fabrication. The CH4 addition promotes the anisotropy of the etching by a sidewall polymer mechanism, while the H2 addition significantly enhances the etch rate at low pressure.
Visible photoluminescence of silicon-based nanostructures: Porous silicon and small silicon-based clusters
Authors: Kanemitsu Yoshihiko , Suzuki Katsunori , Uto Hiroshi , Masumoto Yasuaki , Matsumoto Takahiro , Kyushin Soichiro , Higuchi Koichi , Matsumoto Hideyuki
Published: July 2002

We have studied and compared the optical properties of both porous Si and the chemically synthesized planar and cubic Si skeleton clusters. Broad photoluminescence with large Stokes shifts were observed at the visible region in both samples. Spectroscopic analysis suggests that the surface of porous Si is similar to a condensation of Si clusters. Small Si clusters play a key role in the strong room-temperature photoluminescence in porous Si.
Surface composition of Si-TaSi2 eutectic cathodes and its effect on vacuum field emission
Authors: Hickman James J. , Bergeron George , Czarnaski Mark , Kirkpatrick Douglas A.
Published: July 2002

Our research shows that the presence of an oxide layer on the surface of a field emission cathode is deleterious to its performance and that, for successful operation, removal of this layer is necessary before overcoating with another material. We further show that once the surface oxide is removed, cathodes can be protected with a Au overcoat and run in harsh environments. We have demonstrated stable emission for a Au-coated Si-TaSi2 cathode for over 100 h in an O2 atmosphere at 5×10−6 Torr.
Large temperature changes induced by molecular beam epitaxial growth on radiatively heated substrates
Authors: Shanabrook B. V. , Waterman J. R. , Davis J. L. , Wagner R. J.
Published: July 2002

We have performed optical transmission measurements on radiatively heated GaAs substrates as a function of molecular beam epitaxial growth of InAs, GaSb, AlSb, and GaAs films. The energy gap of the GaAs substrate is observed to decrease strongly in energy when materials with band gaps smaller than GaAs are deposited. This decrease in energy gap is a consequence of a substantial increase in growth temperature induced by the deposition of the film. We have observed increases in temperature of over 150 °C from the temperature measured before film growth. Because the thermocouple is weakly coupled to the radiatively heated substrate, conventional temperature controllers are ineffective at measuring or accounting for this change in temperature.
Triple quantum well electron transfer infrared modulator
Authors: Berger V. , Dupont E. , Delacourt D. , Vinter B. , Vodjdani N. , Papuchon M.
Published: July 2002

In this letter, we present a new bicolor infrared modulator using intersubband absorptions in quantum wells. The structure consists of two wells of different widths on either side of a reservoir of electrons. Depending on the sign of the electric field, the electrons transfer either into the wide well or into the narrow well, and then give rise to an intersubband absorption of the corresponding wavelength. With no applied bias, all the carriers are located in the reservoir and no absorption occurs in the midinfrared wavelength range of interest. Two samples are studied by transmission measurements in a Fourier transform infrared spectrometer. The great importance of the space charge effects in this type of device is evidenced and simulated by a self-consistent model.
Growth mechanisms and superconductivity of ultrathin Y1Ba2Cu3O 7−x epitaxial films on (001) MgO substrates
Authors: Zhu S. , Lowndes D. H. , Chakoumakos B. C. , Pennycook S. J. , Zheng X.-Y. , Warmack R. J.
Published: July 2002

Ultrathin YBa2Cu3O 7−x films grown on (001) MgO substrates by pulsed-laser ablation exhibit a transition from terraced-island growth to spiral growth at ∼4–5 unit cell thickness in films grown at 720 °C. The transition appears at greater thickness in films grown at higher growth temperatures. Observations of the morphology of ultrathin films indicate that the film–substrate interfacial interaction plays an important role when films are only several unit-cells thick. Plastic deformation and oxygen disorder both may affect the epitaxial quality and superconducting properties. However, superconducting properties can be improved by achieving a relatively strain-free state. Our observations of the growth transition and resistivity measurements show that this state occurs in the thicker grains of nominally 3.5 nm films grown at 800 °C and in nominally 7 nm films grown at both 720 and 800 °C. These results also imply that a strain-relieving buffer layer will improve the superconductive properties of ultrathin YBa2Cu3O7−x films grown on misfit substrates.
Second harmonic generation in disperse-red-labeled poly(methyl methacrylate) Langmuir–Blodgett film
Authors: Kajikawa Kotaro , Anzai Takeshi , Takezoe Hideo , Fukuda Atsuo , Okada Shuji , Matsuda Hiro , Nakanishi Hachiro , Abe Takashi , Ito Hiroshi
Published: July 2002

We have prepared a second harmonic (SH) active polymer LB film of copoly(2-{N-ethyl-N-[4-(4-nitrophenylazo)phenyl]amino}ethyl acrylate/methyl methacrylate) by means of horizontal deposition. Considerably high susceptibilities χzzz=41.9 pm/V (1.00×10−7 esu) and χzxx=7.33 pm/V (1.75×10−8 esu) were obtained without poling process. Although the initial 4 monolayers show no SH activity, the monolayers more than fifth have a SH active structure.
High quality epitaxy of YBa2Cu3O7−x on silicon-on-sapphire with the multiple buffer layer YSZ/CeO2
Authors: Copetti C. A. , Soltner H. , Schubert J. , Zander W. , Hollricher O. , Buchal Ch. , Schulz H. , Tellmann N. , Klein N.
Published: July 2002

High quality YBa2Cu3O7−x films on silicon-on-sapphire were grown using a multiple buffer layer, consisting of YSZ and CeO2. Ion channeling reveals the high crystalline perfection of the YBa2Cu3O7−x films. A channeling minimum yield for the Ba signal as low as 3% was measured. The normal state resistivity of 200 μΩ cm at 300 K, critical temperatures above 90 K, with transition widths down to 0.5 K, critical current densities above 2×106 A/cm2 at 77 K and surface resistance values of 1.4 mΩ at 18.9 GHz and 77 K confirm the high quality of the YBa2Cu3O7−x films. These results are very promising for integrated superconductor and semiconductor applications.
Vacancy controlled interdiffusion of the group V sublattice in strained InGaAs/InGaAsP quantum wells
Authors: Gillin W. P. , Rao S. S. , Bradley I. V. , Homewood K. P. , Smith A. D. , Briggs A. T. R.
Published: July 2002

In this letter we present the results of a photoluminescence study of the interdiffusion of arsenic and phosphorous in the In0.66Ga0.33As/In0.66Ga0.33As0.7P0.3 system over the temperature range 950–600 °C. We have shown that the diffusion is Fickian with no dependence of the diffusion coefficient on the substrate doping type or etch pit density. For both tin- and sulfur-doped substrates the diffusion can be described by a diffusion coefficient D, which is given by D=D0 exp(−EA/kT), where D0=23 cm2/s and EA=3.7 eV for temperatures greater than 675 °C. This activation energy is the same as that determined for the group III interdiffusion in In0.2Ga0.8As/GaAs. Below this temperature a lower activation energy process takes over with D0=5×10−10 cm2/s and EA=1.7 eV.
Noncontact force microscopy in liquids
Authors: Giles R. , Cleveland J. P. , Manne S. , Hansma P. K. , Drake B. , Maivald P. , Boles C. , Gurley J. , Elings V.
Published: July 2002

Force microscopy in liquids offers many advantages including the mitigation of capillary forces and the simulation of real environments for biological and technological processes. Noncontact force microscopy in liquids adds the advantage of probing electrical and magnetic fields above surfaces. Here we demonstrate magnetic force imaging of recorded bits on a computer hard disk in air and in liquid. A method of noncontact force microscopy (patent pending, Digital Instruments) is used in which the tip is first scanned in contact to image topography and then rescanned above the surface to image long-range forces.
New oxide phase Cd1−xYxSb2O6 with a wide band gap and high electrical conductivity
Authors: Yanagawa Kazuhiko , Ohki Yoshimichi , Ueda Naoyuki , Omata Takahisa , Hashimoto Takuya , Kawazoe Hiroshi
Published: July 2002

It was initially found that CdSb2O6, in which a small part of the Cd ions was substituted with Y ions, has characteristics of a transparent conductor. The electrical conductivity at room temperature of the Y-substituted CdSb2O6 ceramic was larger, by at least 1×100 S cm−1, while that of the nonsubstituted CdSb2O6 was smaller than 10−5 S cm−1. The optical band gap of CdSb2O6 was found to be larger than 4.1 eV by the measurements of diffuse reflectance spectra.
Characterization of a photorefractive phase conjugator by optical low-coherence reflectometry
Authors: Lambelet P. , Salathé R. P. , Garrett M. H. , Rytz D.
Published: July 2002

Optical low coherence reflectometry is applied to measure with μm precision the type, position and length of gratings inside a barium-titanate crystal producing self-pumped phase conjugation. In this particular crystal it shows the presence of an internal resonator due to reflections on faces of the crystal. Moreover, it was possible to measure the simultaneous presence of transmission and reflection gratings with conjugation efficiencies of 40% and 3%, respectively. The spectral reflectivity of the transmission grating is Gaussian-like with a full width at half-maximum=1.5 nm. The six reflection gratings, each with a length of 116±6 μm, are due to the multimode spectrum of the writing laser.
Growth mode evolution during homoepitaxy of GaAs (001)
Authors: Johnson M. D. , Sudijono J. , Hunt A. W. , Orr B. G.
Published: July 2002

Scanning tunneling microscopy studies have been performed on GaAs homoepitaxial films grown by molecular-beam epitaxy. After an initial transient regime, indicated by reflection high-energy electron diffraction oscillations, the system evolves to a dynamical steady state. This state is characterized by a constant step density and as such the growth mode can be termed generalized step flow.
Effect of the deposition sequence on the growth of YBa2Cu3O7−δ films by chemical vapor deposition
Authors: Matsubara M. , Morishita T. , Hirabayashi I.
Published: July 2002

We have investigated the possibility of layer-by-layer growth in the metalorganic chemical vapor deposition of YBa2Cu3O7−δ. In this study, the source gases were supplied alternately by various sequences in the form of a subunit cell block. Films deposited on MgO and SrTiO3 (STO) substrates were investigated by x-ray diffraction, scanning electron microscopy, and atomic force microscopy. We found the surface morphology and composition of the deposited films were highly dependent on the selection of the blocks and the deposition sequence. The best film on the MgO or STO substrates were obtained by sequence starting with the Ba layer, then followed by the /Cu,Y,Cu/ block, and ending up with the Cu-O chain layer. This result can be explained by the good wettability of Ba onto the substrates and the suppression of forming impurity phases such as barium cuprates.
Magnetic resonance of a small platinum particle using an integrated dc SQUID
Authors: Narasimhan L. R. , Takigawa M. , Ketchen M. B.
Published: July 2002

We report the detection of pulsed nuclear magnetic resonance in a single 50 μm particle of platinum metal at 4 K and in an applied field of 60 G. The flux from the precessing spins is detected directly by an integrated dc SQUID minisusceptometer. The device can operate in applied fields of up to 100 G without degradation of noise performance. The particle contains ≊1015 spin-active nuclei while the signal intensity corresponds to flux from 2.5×1014 spins all located at the center of the pickup loop. This result represents a significant improvement in the sensitivity of NMR and may be useful in the characterization of materials with small spin populations.