bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Earned Value Management for More Sustainable Project Schedule Control
Authors: Avlijaš Goran
Published: November 2022

Research Question: The aim of this paper is to provide a state-of-science review and offer a critical analysis of contemporary schedule related Earned Value Management (EVM) approaches. Motivation: Since the introduction of the EVM as a tool for project control in the late 1960s, academics have tried to improve its best application. Although this method significantly contributed to efficient cost management, application of EVM to schedule management was falling behind. A significant effort has been made to improve its usability for project time management, which resulted in a dramatic evolution. The paper builds on existing literature and earlier studies, adding value with the inclusion of the cost-based and time-based approaches for assessing project schedule performance. Idea: The idea of this paper was to evaluate some of the most significant EVM schedule control methods and identify open issues. The main study hypothesis is that the most recent approaches provide a more reliable forecast and thus a solid ground for further improvements. Data: A case study in the form of a simplified project was used to illustrate how different contemporary approaches compare in terms of conceptualization, methodological issues, and theoretical underpinnings. Tools: A combination of statistical analysis and Monte Carlo simulation was used to evaluate the performance of different EVM approaches. Microsoft Excel was used for data processing, Microsoft Project and SATA software for data visualization, and Oracle Crystal Ball for Monte Carlo simulation. Findings: Quantitative analysis confirmed that the project-specific Earned Duration Management (EDM) and Earned Schedule (ES) approaches provide sustainable and more accurate results during the whole projects lifespan, while forecasts obtained by more traditional methods proved to be unreliable in the later stages of the project. While practical application generally lags after the growing theory, the latest literature paves the way to the integration of EVM and risk management making the contemporary EVM approaches stochastic and therefore more realistic. Contribution: The results of this study can be used as a basis for introducing advanced and generally more usable EVM models, which will improve the project schedule control.
Sarcopenia and echocardiographic parameters for prediction of cardiovascular events and mortality in patients undergoing maintenance hemodialysis
Authors: Zhang Mengyan , Zhang Liuping , Hu Yezi , Wang Ying , Xu Shengchun , Xie Xiaotong , Xu Tian , Li Zuolin , Jin Hui , Liu Hong
Published: November 2022

Background

Sarcopenia is prevalent and is associated with the occurrence of cardiovascular complications in patients undergoing maintenance hemodialysis (MHD). It is unknown how skeletal muscle may be associated with aspects of myocardial structure and function. This study aimed to evaluate the association between sarcopenia and cardiac structure and function in patients undergoing MHD. We also examined the prognostic role of sarcopenia for mortality and cardiovascular events (CVE) in this population.

Methods

Participants from a single center underwent bioimpedance body composition analysis to measure skeletal muscle and echocardiography to assess myocardial structure and function. Sarcopenia was diagnosed based on the Asian Working Group for Sarcopenia criteria. The end points were all-cause mortality and CVE.

Results

Of the 158 participants, 46 (29.1%) had sarcopenia, 102 (64.6%) had left ventricular diastolic dysfunction (LVDD), and 106 (67.0%) had left ventricular hypertrophy (LVH). Participants with sarcopenia had smaller right ventricular sizes (2.54 ± 0.77 vs 2.76 ± 0.28; P < 0.01), inter-ventricular thickness (1.07 ± 0.19 vs 1.14 ± 0.20; P = 0.039), and left ventricular posterior wall thickness (0.96, 0.89–1.10 vs 1.06, 0.95–1.20; P = 0.018). Skeletal muscle mass was strongly correlated with left ventricular mass (LVM) (r = 0.577; P < 0.0001). Furthermore, the risk of LVDD (OR: 4.92, 95% confidence interval (CI) [1.73–13.95]) and LVH (OR: 4.88, 95% CI [1.08–21.96]) was much higher in the sarcopenic group than in the non-sarcopenic group. During a follow-up period of 18 months, 11 (6.9%) patients died, of which seven died (4.4%) of CVE, and 36 (22.8%) experienced CVE. The presence of sarcopenia (adjusted hazard ratio (HR), 6.59; 95% CI [1.08–39.91]; P = 0.041) and low skeletal muscle index (HR, 3.41; 95% CI [1.01–11.57]; P = 0.049) and handgrip strength (HR, 0.88; 95% CI [0.78–0.99]; P = 0.037) independently predicted death. Sarcopenia was a significant predictor of CVE (HR, 10.96; 95% CI [1.14–105.10]; P = 0.038).

Conclusion

Our findings demonstrated that sarcopenia is associated with LVDD and LVH, and is associated with a higher probability of death and CVE.
Regulation of the MAP kinase cascade in PC12 cells: B‐Raf activates MEK‐1 (MAP kinase or ERK kinase) and is inhibited by cAMP
Authors: Peraldi P. , Frödin M. , Barnier J.V. , Calleja V. , Scimeca J.-C. , Filloux C. , Calothy G. , Van Obberghen E.
Published: July 2002

In PC12 cells, cAMP stimulates the MAP kinase pathway by an unknown mechanism. Firstly, we examined the role of calcium ion mobilization and of protein kinase C in cAMP‐stimulated MAP kinase activation. We show that cAMP stimulates p44mapk independently of these events. Secondly, we studied the role of B‐Raf in this process. We observed that NGF, PMA and cAMP induce the phosphorylation of B‐Raf as well as an upward shift in its electrophoretic mobility. We show that B‐Raf is activated following NGF and PMA treatment of PC12 cells, and that it can phosphorylate and activate MEK‐1. However, cAMP inhibits B‐Raf autokinase activity as well as its ability to phosphorylate and activate MEK‐1. This inhibition is likely to be due to a direct effect since we found that PKA phosphorylates B‐Raf in vitro. Further, we show that B‐Raf binds to p21ras, but more important, this binding to p21ras is virtually abolished with B‐Raf from PC12 cells treated with CPT‐cAMP. Hence, these data indicate that the PKA‐mediated phosphorylation of B‐Raf hampers its interaction with p21ras, which is responsible for the PKA‐mediated decrease in B‐Raf activity. Finally, our work suggests that in PC12 cells, cAMP stimulates MAP kinase through the activation of an unidentified MEK kinase and/or the inhibition of a MEK phosphatase.
Protective action of 17β‐estradiol and tamoxifen on glutamate toxicity in glial cells
Authors: Shy Hogan , Malaiyandi Latha , Timiras Paola S.
Published: July 2002

Estrogens influence differentiation, growth and function of neurons, but less is known of their effects on glia. In our experiments reported here, the ovarian steroid, 17β‐estradiol, and the “designer”, non‐steroidal estrogen, tamoxifen, effectively protected C‐6 glioma 2B clone cells from the cytotoxicity of the excitatory neurotransmitter, glutamate. Exposure of these cells to 10–20 mM glutamate induced 61–78% cell death. Pre‐treatment of the cells with 0.01 mM estradiol or with 2 μM tamoxifen significantly reduced the glutamate‐induced cell death, estradiol being the most effective in this regard. Estradiol‐ or tamoxifen‐treated cells that had survived glutamate damage appeared more mature than controls. Thus, estrogens often used in therapy (estradiol as replacement after menopause and tamoxifen for treatment/prevention of breast cancer) may significantly protect glial cells against glutamate toxicity and stimulate cell differentiation.
Psychopathology in treated Wilson's disease determined by means of CPRS expert and self‐ratings
Authors: Portala K. , Westermark K. , Von Knorring L. , Ekselius L.
Published: July 2002

Objective: To examine the occurrence and severity of psychopathological symptoms in patients with treated Wilson's disease (WD) and to evaluate the clinical utility of a self‐assessment.

Method: Twenty‐six consecutive patients with confirmed WD were investigated using the Comprehensive Psychopathological Rating Scale (CPRS) and the CPRS Self‐rating Scale.

Results: The total CPRS scores ranged from 2.5 to 59.0 (mean 29.4±15.5). Most common symptoms were: autonomic disturbances, observed muscular tension, fatiguability, reduced sexual interest, lack of appropriate emotion, concentration difficulties, reduced sleep, aches and pains, hostile feelings, apparent sadness and failing memory. Agreement between interview‐based ratings and self‐ratings was low.

Conclusion: The patients with treated WD have prominent psychopathology in the same range as in patients with moderate to severe depressive disorders. A specific symptom profile has been identified. If confirmed, the identification of the typical symptom profile might be of great importance. The patients with WD tend to underestimate the presence of psychopathological symptoms.
Developing laser‐induced glaucoma in rabbits
Authors: Johnson Bradley , House Philip , Morgan William , Sun Xinghuai , Yu Dao‐Yi
Published: July 2002

Purpose: An animal model of glaucoma is necessary for the study of its pathogenesis and treatment. The purpose of this study was to create open‐angle glaucoma using a laser in rabbits.

Methods: The trabecular meshwork of anaesthetized, adult, pigmented and albino rabbits was ablated internally using a diode laser via a gonioscopy lens, or externally through the limbus. In albino rabbits we used Chinese ink to pigment the angle and methylcellulose to open the iridocorneal angle. The eyes were examined weekly and histological assessment was performed.

Results: The success rate of intra‐ocular hypertension was low (15%) and a result of synechial angle closure. A narrow angle prevented access of the laser beam to the trabecular meshwork and promoted damage to the ciliary processes located on the posterior iris.

Conclusions: Due to the unique anatomy of the rabbit eye, laser‐induced glaucoma is difficult to achieve. To create a successful model it is necessary to widen the iridocorneal angle, selectively damage the trabecular meshwork and reduce inflammation.
A Phylogenetic Analysis of the Plastid matK Gene with Emphasis on Melanthiaceae sensu lato
Authors: Fuse S. , Tamura M. N.
Published: July 2002

Abstract: The presented matK tree primarily agrees well with the previously presented rbcL tree and combined rbcL +atpB + 18SrDNA tree. According to the matK tree, the monocotyledons are monophyletic with 100 % bootstrap support. Acorus diverges first from all other monocotyledons (90 % bootstrap support) in which two major clades are recognized: one (89 %) consisting of Alismatanae and Tofieldia (Nartheciaceae), and the other (< 50 %) comprising Lilianae, Commelinanae and Nartheciaceae other than Tofieldia. Within the latter major clade, Petrosavia and Japonolirion (Nartheciaceae) (82 %) diverge first from the remaining taxa (< 50 %) in which two clades are formed: one (81 %) consisting of Pandanales, Dioscoreales and Nartheciaceae‐Narthecioideae, and the other (< 50 %) comprising Liliales, Asparagales and Commelinanae. In the former clade, Dioscoreales and Narthecioideae are grouped together (88 %). In the latter clade, Asparagales and Commelinanae are grouped together (< 50 %). Differences between the matK and rbcL tree topologies appear in the positions of Tricyrtis (Calochortaceae) and Dracaenaceae. Differences between the matK and combined rbcL +atpB + 18SrDNA tree topologies exist in the positions of the Petrosavia‐Japonolirion pair (Nartheciaceae) and Pandanales. The stop codon position of the matK gene appears to be highly variable among the monocotyledons, especially in the Liliales.
Are Ectomycorrhizal Fungi Associated with Alnus of Importance for Forest Development in Wet Environments?
Authors: Baar J. , van Groenendael J. M. , Roelofs J. G. M.
Published: July 2002

Abstract: In the present paper we discuss the potential importance of ectomycorrhizal fungi associated with Alnus species for forest development in wet environments. We discuss the current state of knowledge and open questions about the ecology and functional role of ectomycorrhizal symbionts of Alnus under wet conditions. Possible approaches to investigate the ectomycorrhizal fungi in wet forest ecosystems are presented. Particularly, we concentrate on wet alder carr forests in Europe serving as a model forest ecosystem.
Windowless helium lamp assisted chemical vapor deposition of hydrogenated amorphous silicon
Authors: Zarnani H. , Yu Z. Q. , Collins G. J. , Bhattacharya E. , Pankove J. I.
Published: July 2002

A windowless helium lamp is employed to assist chemical vapor deposition of hydrogenated amorphous silicon from disilane feedstock gas at a film growth rate greater than 200 Å/min. Material properties in this preliminary study are comparable to the best hydrogenated amorphous silicon (a-Si:H) films produced by conventional bulk plasma CVD techniques. The amount of photoconductivity degradation under long-time illumination is more than plasma-deposited a-Si-H thin films. Photoconductivity as high as σp =4×10−4 (Ω cm)−1 has been obtained.
Optical-fiber-based photoluminescence spectrometer
Authors: Whalen M. S. , Martyak M. J. R.
Published: July 2002

An optical-fiber-based apparatus for measuring photoluminescence spectra has been demonstrated. The use of a variable ratio fiber directional coupler and an integral fiber microlens greatly simplifies the optical system for both photoluminescence excitation and collection and permits the attainment of high output power densities (40 kW/cm2) for modest fiber input powers (<5 mW). Spectra from several III-V semiconductor samples are shown which illustrate the sensitivity of the apparatus.
Equivalent circuit model for active-layer photomixing: Parasitic-free modulation of semiconductor lasers
Authors: Vahala Kerry J. , Newkirk Michael A.
Published: July 2002

Direct modulation of a laser diode by active-layer photomixing is studied in terms of an equivalent circuit model. The model shows that this modulation technique achieves nearly perfect immunity to package, chip, and junction-related parasitic effects so that the measured modulation response reflects the intrinsic carrier-photon dynamics. The nonlinear gain effect is included in the model.
Characterization of metastable AuxSi1−x alloys
Authors: Cros A. , Pierrisnard R. , Hewett C. A. , Lau S. S.
Published: July 2002

In this letter we report the observation of surface segregation of gold from AuxSi1−x alloys with 0.25<x<0.5. In view of the observed Au segregation and the known ability of gold-rich alloys to oxidize readily at low temperature, we propose a mechanism for oxidation of silicon in AuxSi1−x alloys with 0.4<x<0.7.
Effects of well width on the characteristics of GaAs/AlGaAs multiple quantum well electroabsorption modulators
Authors: Whitehead M. , Stevens P. , Rivers A. , Parry G. , Roberts J. S. , Mistry P. , Pate M. , Hill G.
Published: July 2002

We compare the characteristics of three electroabsorption modulators fabricated using GaAs/AlGaAs multiple quantum well structures with well widths 47, 87, and 145 Å. We find that the narrow well structure provides the largest change in transmission. The 87 Å well structure provides the largest contrast ratio, while the wide well sample offers the lowest operating voltage.
Laser photoablation of spin-on-glass
Authors: Hogan Michael , Lunney James G.
Published: July 2002

The photoablation of a phenylsiloxane spin-on-glass (SOG) (Allied Accuglass 204) in the precured state has been studied at 193 and 248 nm using an excimer laser. The ablation of a 400 nm layer of SOG on silicon was monitored interferometrically using a He-Ne laser. At 193 nm, where the absorption coefficient is high, the reflectivity shows the oscillation expected for uniform photoablation at the surface, but the SOG is not completely removed. At 248 nm the SOG film is nearly transparent, and for 0.53 J cm−2 only one shot is required for complete removal. At lower fluences more pulses are required to remove the SOG completely, but the reflectivity does not show the oscillation that would be expected for the uniform removal of material at the surface. The microlithographic capabilities of laser photoablation of SOG were investigated at 248 nm, and lines 2 μm wide with sloping sides 0.2 μm wide were obtained.
Angular dependence of preferential sputtering and composition in aluminum-copper thin films
Authors: Rudeck P. J. , Harper J. M. E. , Fryer P. M.
Published: July 2002

The copper concentration in aluminum-copper alloys can be altered by ion bombardment during film deposition. We have measured the sputtering yields of aluminum and copper in Al-Cu alloys as a function of the Cu concentration (5–13 at. %) and the angle of ion incidence (0°–40° from normal). During deposition, the films were partially resputtered by 500 eV Ar+ ion bombardment from a Kaufman ion source. We found that the Cu sputtering yield decreases by up to a factor of 10 in the alloy, relative to elemental Cu. The Al sputtering yield remains close to the elemental value. The net effect is a strong preferential sputtering of Al relative to Cu, which enhances the Cu concentration in an ion-bombarded film. The Al/Cu sputtering yield ratio for normal incidence ion bombardment ranges from 3 to 5 as a function of Cu concentration. This ratio decreases with increasing angle of incidence to as low as 2 for 40° incident ions. However, since a higher fraction of the film is resputtered from a sloping surface, a higher Cu concentration is found on a sloping surface relative to a flat surface. These results show that the film composition will vary as a function of the surface topography.
Electron spin resonance and transmission electron microscopy studies of solution-grown CdTe thin films
Authors: Padam G. K. , Gupta S. K.
Published: July 2002

The electron spin resonance (ESR) and transmission electron microscopy (TEM) of as-grown and air heat treated CdTe thin films deposited by the solution growth method are studied. A single isotropic ESR absorption line at g=2.0002 attributed to Cd+ (I=0) is obtained on heating the films in air at and above 300 °C. Line intensity increases from 300 °C and reaches maximum at 500 °C beyond which it decreases. Electron diffraction studies of the as-grown CdTe films showed the presence of both the zinc blende and the wurtzite phases, whereas those of the films heated in air showed only the zinc blende phase but along with additional phases: TeO2 (observed at 300 °C) and CdTeO3 (observed at 550 °C).
Enhanced electrical quality of low-temperature (Tdep≤800 °C) epitaxial silicon deposited by plasma-enhanced chemical vapor deposition
Authors: Ohi S. , Burger W. R. , Reif R.
Published: July 2002

We report in this letter the results of experiments comparing the electrical properties of low-temperature epitaxial silicon deposited by plasma-enhanced chemical vapor deposition (PECVD) and ultralow pressure chemical vapor deposition (U-LPCVD). Diode characteristics indicate a strong dependence of the electrical quality of the PECVD films on the plasma power. The data indicate that, in contrast to a purely thermal deposition (the U-LPCVD films), a low-power PECVD deposition (2.5–5 W) improves the electrical quality of the epitaxial layers and lowers the minimum epitaxy temperature. A high-power plasma (20 W), however, degrades the electrical characteristics in comparison to a strictly thermal deposition.
Reflection high-energy electron diffraction intensity oscillations in IV-VI compound semiconductors
Authors: Fuchs Jacob , Feit Ze’ev , Preier Horst
Published: July 2002

Reflection high-energy electron diffraction intensity oscillations were observed for the first time during layer-by-layer growth of IV-VI compound semiconductors. Epitaxial PbSe and PbTe layers were grown by molecular beam epitaxy on cleaved BaF2 (111) at a substrate temperature range of 210–350 °C. The growth rate for both compounds was measured using in situ intensity oscillations, and was verified by stylus thickness measurements. Very little variation in growth rate was observed while varying the substrate temperature in this range.
Amorphous-to-crystalline transformations in bismuth-oxide-based high T
c superconductors
Authors: Garzon Fernando H. , Beery Jerome G. , Raistrick Ian D.
Published: July 2002

The transformation of high-resistivity amorphous Bi1.5 SrCaCu2 Ox to superconductive material has been characterized by structural, thermochemical, transport, and magnetic measurements. X-ray powder diffraction confirmed that rapid solidification of Bi-Sr-Ca-Cu-O melts yields amorphous materials. Differential scanning calorimetry indicated an exothermic crystallization peak at ∼455 °C with a corresponding enthalpy of ∼50 J/g. Thermal cycling of the insulating glass to a temperature above that required for crystallization results in a transformation from an insulating to a partially superconducting material with an onset temperature of 85 K.
Intrinsic stress in narrow silicon metal-oxide-semiconductor field-effect transistors: Magnetotransport measurements
Authors: Paquin N. , Pepper M. , Gundlach A. , Ruthven A.
Published: July 2002

Measurements of the Hall (ρxy) and transverse (ρxx) resistivities in narrow polycrystalline silicon-gated Si(100) field-effect transistors have been obtained. The measurements were carried out both with and without externally applied uniaxial stress. Analysis of the results suggests the presence of large compressive intrinsic edge stresses. A model based on device fabrication is developed to explain the presence of these edge stresses.
Heteroepitaxial growth of Ga0.51In0.49P/GaAs on Si by low-pressure organometallic chemical vapor deposition
Authors: Horng R. H. , Wuu D. S. , Lee M. K.
Published: July 2002

In this letter we report on preliminary results of heteroepitaxial growth of Ga0.51In0.49P on Si with a GaAs interlayer by low-pressure organometallic chemical vapor deposition (OMCVD). The surface morphologies and crystalline quality of the films were found to be critically dependent on the growth parameters of the initial GaAs buffer layer. Under optimum conditions, specular single-crystal Ga0.51In0.49P epilayers can be reproducibly obtained. Capacitance-voltage measurements show that the carrier distribution in the grown layer is very uniform. The 77 K photoluminescence spectrum exhibits a strong near-band-edge emission with a half-width of 22 meV. These results can compete with those reported previously for the OMCVD-grown GaxIn1−xP on GaAs substrates.
All-optical routing networks based on bistable interferometers
Authors: Buller G. S. , Paton C. R. , Smith S. D. , Walker A. C.
Published: July 2002

The possibility of using bistable nonlinear Fabry–Perot interferometers as wide-band data transparent all-optical spatial switches has been investigated. It has been shown that three such devices, switching between transmitting and reflecting states, can form a 1×4 optical routing network: controlled purely by coded header pulses, preceding the data stream. The prospects for developing the performance of switches of this type towards the level required in practical telecommunications systems are discussed.
Effusion of deuterium from deuterated-fluorinated amorphous silicon under illumination
Authors: Weil R. , Busso A. , Beyer W.
Published: July 2002

Temperature-dependent deuterium effusion experiments were performed on deuterated-fluorinated amorphous silicon containing 25% D and 0.5% F. Evolution was made in the dark and under up to AM1 illumination. It was found that illumination enhanced effusion. The effect could be explained by an increased D diffusion, caused by enhanced SiD bond breaking resulting from energy supplied by the decay of photocarriers to midgap states.
Surface orientation transitions in surface stabilized ferroelectric liquid crystal structures
Authors: Xue Jiuzhi , Clark Noel A. , Meadows Michael R.
Published: July 2002

We provide direct evidence, using simultaneously total internal reflection and polarized optical microscopy, for the existence of two interface stabilized director n-polarization P orientation states at a ferroelectric liquid crystal (FLC)-solid interface. The states are separated by a first-order orientation transition, having n nearly parallel to the surface, opposite orientations of the component of P normal to the surface, with the state having P directed into the FLC being of lower energy. Any unswitched layer is less than 20 Å in thickness.
Electron energy-loss study of bonding in amorphous silicon-carbon alloy films prepared with hydrogen dilution
Authors: McKenzie D. R. , Bruley J. , Smith G. B.
Published: July 2002

Electron energy-loss spectroscopy was used to study the nature of chemical bonding in a-Si1−xCx:H films produced by rf glow discharge decomposition of SiH4/CH4 mixtures with hydrogen dilution. The low-loss region, the Si L edge, and the C K edge were studied. It was found that near stoichiometric films have a high degree of Si to C bonding and that substoichiometric films show some C to C sp2 bonding. A free-electron model was used to interpret the variation of plasmon energy of these films with composition.
Medium energy ion scattering analysis of reactive ion etched Si(001) surfaces
Authors: Copel M. , Tromp R. M. , Robey S. W. , Oehrlein G. S.
Published: July 2002

Silicon surfaces reactive ion etched in CF4/H2 plasmas have been examined using medium energy ion scattering and core level photoemission. Surfaces analyzed in ultrahigh vacuum have a significantly higher fluorine content than surfaces that have been exposed to air prior to analysis. In addition, an unusually large cross section exists for ion beam desorption of some, but not all, of the fluorine. Based on core level shifts, we demonstrate that fluorine desorption arises from both the fluorocarbon film and the underlying fluorosilyl layer.
InGaAs/InGaAsP distributed feedback quantum well laser with an intracavity phase modulator
Authors: Koren U. , Koch T. L. , Miller B. I. , Shahar A.
Published: July 2002

We demonstrate a distributed feedback laser with an integrated intracavity phase modulator based on advanced quantum well technology with applications to mode control, mode switching, and fast frequency modulation.
Monolithic GaAs/AlAs optical bistable étalons with improved switching characteristics
Authors: Kuszelewicz R. , Oudar J. L. , Michel J. C. , Azoulay R.
Published: July 2002

Compact bistable GaAs étalons with epitaxial GaAs/AlAs Bragg reflectors have been fabricated by metallorganic vapor phase epitaxy. Their monolithic structure is convenient for further technological steps. It has been found that the good thermal conductivity of the mirror layers allows more efficient heat sinking and leads to improved switching characteristics. A 2:1 contrast ratio and a 20 ns switching time have been obtained in the reflective mode, with a 4 mW threshold power and a strongly reduced dependence of the switch-off threshold upon incident pulse duration.
Tunable wavelength filters using λ/4-shifted waveguide grating resonators
Authors: Numai T. , Murata S. , Mito I.
Published: July 2002

We report on wide tuning range 1.5 μm wavelength filters using λ/4-shifted waveguide grating resonators. A tuning range of a transmission resonance wavelength as wide as 42 Å by carrier injection and two-channel wavelength signal switching was achieved.
Simultaneous two-band laser emissions and three primary color outputs in the superradiant mode from dye mixtures
Authors: Saito Y. , Nomura A. , Kano T.
Published: July 2002

A dye mixture of coumarin 460, disodium fluorescein, and nile blue 690 perchrolate was excited by a nitrogen laser. Simultaneous laser emissions in two spectra regions (blue and green, green and red, red and blue) were obtained in each of the two dye mixtures. Furthermore, simultaneous three primary color outputs in a superradiant mode from three dye mixtures were observed.
Fast photolytic laser writing of gold lines on a prenucleated substrate
Authors: Beeson K. W. , Clements N. S.
Published: July 2002

Laser written gold lines with resistivities as low as 4.5 μΩ cm and writing speeds up to 2.5 mm/s have been achieved by photolytic decomposition of gold metallopolymer thin films on alumina substrates prenucleated with a very thin (∼20 Å) nonconducting layer of sputtered gold. Laser writing is done at 257 nm with a frequency-doubled Ar+ laser and is followed by a subsequent annealing step at 250 °C for 30–200 min to produce conducting lines.
Highly collimated laser beams from grating coupled emission Pb1−xSnxSe/Pb1−x−yEuySnxSe diode lasers
Authors: Shani Y. , Katzir A. , Tacke M. , Preier H. M.
Published: July 2002

Grating coupled emission Pb1−xSnxSe/Pb1−x−yEuySnxSe double-heterostructure stripe-geometry diode lasers were fabricated using molecular beam epitaxy. Low-divergence far-field patterns of ∼5° for multimode operation and ∼2° for single-mode operation were obtained. These are the lowest values ever achieved with Pb salt lasers.
Elimination of light-induced effect in hydrogenated amorphous silicon
Authors: Chen Yang-Fang
Published: July 2002

Light-induced metastable defects in hydrogenated amorphous silicon can be eliminated by atomic hydrogen at the temperature below which the annealing effect occurs. The resulting material has a very high photosensitivity and stability.
Spectroscopic studies of the influence of intentionally increased CO partial pressure on the incorporation of residual C impurities in molecular beam epitaxy GaAs
Authors: Lee B. , Bose S. S. , Kim M. H. , Stillman G. E. , Calawa A. R.
Published: July 2002

High-purity Si-doped molecular beam epitaxy (MBE) GaAs layers grown with and without the intentional introduction of CO gas have been characterized by Hall effect measurements, photoluminescence, and photothermal ionization spectroscopy. The results indicate that CO itself is not the source of residual C acceptor impurities in MBE GaAs samples. The observations of the correlation of residual C impurity incorporation with the residual CO gas in the MBE growth chamber suggest that the partial pressure of CO, PCO , gives a quantitative indication of background levels of hydrocarbons which are the source of C acceptors.
Growth of lattice-mismatched stacked epitaxial CaF2-SrF2-BaF2 layers on (100) oriented Si substrates
Authors: Blunier S. , Zogg H. , Weibel H.
Published: July 2002

(100) oriented BaF2 has been grown epitaxially onto Si(100) despite its large lattice mismatch of 14% and preferred (111) growth mode. (100) epitaxy was achieved using thin intermediate CaF2 and/or SrF2 buffers to overcome the mismatch in a stepwise manner. Growth is three dimensional, and a roughness of the top surface in the 10 nm range was obtained. Ion channeling minimum yields are below 4% even for layers as thin as 3000 Å. Thermal misfit strains relieve due to movement of misfit dislocations. The layers are intended for use as epitaxial buffers for growth of compound semiconductors on Si(100) substrates with up to 20% total lattice mismatch.
Oriented high-temperature superconducting Bi-Sr-Ca-Cu-O thin films prepared by ion beam deposition
Authors: Lorentz Robert D. , Sexton J. H.
Published: July 2002

High-temperature superconducting Bi-Sr-Ca-Cu-O thin films have been prepared by ion beam sputter deposition. Films near the 2:2:1:2 and 4:3:3:4 compositions were deposited onto single-crystal MgO [100] substrates and annealed between 825 and 880 °C. Films with composition Bi2.00Sr2.09Ca0.75Cu2.44Ox have a transition beginning at approximately 85 K, with Tc(R=0) reached at 75 K. For films with composition Bi4.00Sr3.12Ca3.03Cu4.56Ox, a significant drop in the resistance is observed at about 110 K, with Tc(R=0) between 63 and 67 K. Films of both compositions have strong preferential c-axis orientation normal to the film plane.
Multiwavelength cw laser oscillation in a Nd3+ and Er3+ doubly doped fiber laser
Authors: Kimura Yasuo , Nakazawa Masataka
Published: July 2002

Nd3+ and Er3+ ions are doubly doped in the core part of a single-mode silica fiber. By end-pumping with an Ar ion laser at 514 nm, multiwavelength laser oscillations at 0.908, 0.932, 1.08, and 1.552 μm have been successfully achieved in the 1.5-m-long fiber with an adsorbed pump power of 70 mW.
Radiation damage effects in ion-implanted Bi-Sr-Ca-Cu-O superconducting thin films
Authors: Matsui S. , Matsutera H. , Yoshitake T. , Satoh T.
Published: July 2002

Transition temperature (Tc) control and annealing effects of Bi2.0Sr1.4Ca1.8Cu2.2Oy superconducting thin films implanted by 200 keV Ne+ have been investigated. Tc end points for 0.4-μm-thick Bi2.0Sr1.4Ca1.8Cu2.2Oy films for 0, 1×1012, and 1×1013 ions/cm2 doses are 78, 76, and 54 K, respectively. The ion dose, to achieve a nonsuperconductor for Bi2.0Sr1.4Ca1.8Cu2.2Oy films, is two or more orders of magnitude lower than that for YBa2Cu3O7−x films. The c-lattice constant increases were observed for the implanted films. Moreover, it was confirmed that the superconducting characteristics for the implanted films are recovered by annealing in O2 atmosphere.
New excitation method of surface polaritons
Authors: Nakagawa Yasuhiko , Kaneko Michihiro , Terunuma Noboru
Published: July 2002

We propose a new excitation method for surface polaritons of an evanescent mode which cannot be excited by the attenuated total reflection method. We designed and produced a thin-film waveguide to excite surface polaritons of evanescent modes at a Ag-SiO2 interface. If the wave number of the optical guided waves propagating in the dielectric thin-film waveguide (SiO2/Ta2O5/SiO2) is equal to the wave number of the surface polaritons, then a coupling between the two modes occurs. We can confirm the excitation of the surface polaritons by an attenuation of the optical guided waves.
Magnetization and critical currents of Bi-Sr-Ca-Cu-O and Ba2YCu3O7 superconductors
Authors: Gyorgy E. M. , van Dover R. B. , Jin S. , Sherwood R. C. , Schneemeyer L. F. , Tiefel T. H. , Waszczak J. V.
Published: July 2002

We have measured the critical currrent density Jc as a function of temperature for a Bi-Sr-Ca-Cu-O sample containing a substantial fraction of a phase with Tc≊110 K and for a Ba2YCu3O7 sample (TTc≊92 K). The behavior of Jc was deduced from magnetization measurements. For both samples the magnetization at fixed temperature and field decayed logarithmically with time. The values of Jc so derived, allowing for the decay to occur, went to zero for temperatures above 35 K for the Bi-Sr-Ca-Cu-O ceramic and to zero above 70 K for the Ba2YCu3O7 sample. These values are substantially lower than those deduced from dynamic M-H loops.
Synthesis of LaBa2Cu3O7−y through tetragonal to orthorhombic phase transition at high oxygen deficiency
Authors: Brass Stephen G. , Ghandehari Mohammad H.
Published: July 2002

Superconductive LaBa2Cu3O7−y materials which achieve zero resistivity at temperatures above 90 K have been synthesized using the appropriate sintering and annealing conditions. We find it necessary to sinter our samples in an inert atmosphere and to cool our samples from a high temperature to below the tetragonal to orthorhombic transition temperature in an inert atmosphere before the sample is further exposed to oxygen. We conclude that in order to produce amounts of orthorhombic LaBa2Cu3O7−y material sufficient to achieve zero resistivity at temperatures of 90 K or above, it is necessary to prevent the material from incorporating too much oxygen while it is at temperatures in excess of its tetragonal to orthorhombic transition temperature.
Limitations in low-temperature silicon epitaxy due to water vapor and oxygen in the growth ambient
Authors: Friedrich J. A. , Neudeck G. W. , Liu S. T.
Published: July 2002

Basic chemical equilibrium data for the Si/SiO2/O2/H2O system have been employed to compute critical epitaxial preclean and growth parameters. Preclean and growth experiments were conducted and compared with predicted behavior. A procedure is given that allows for the design of an epitaxial deposition process for most commercially available epitaxy reactor systems. Following this scheme, good crystal quality silicon was deposited at temperatures as low as 890 °C and at a deposition pressure of 150 Torr. For current commercially available reduced pressure reactor systems, a practical low-temperature limit of about 810 °C is predicted.
Grain growth of 〈100〉 textured Ge on a SiO2/Si3N4 stripe
Authors: Ogura Atsushi , Aizaki Naoaki , Terao Hiroshi
Published: July 2002

Grain growth enhancement in 〈100〉 textured Ge on a SiO2/Si3N4 stripe was investigated. Transmission electron microscope observation revealed 7-μm-diam (100) grains on a 1 μm periodic stripe after 20 h of 900 °C annealing. It is thought that the SiO2/Si3N4 stripe enhanced a grain growth similar to the grooved SiO2 case. However, since the stripe had no surface step, no grain growth interruptions were found at stripe boundaries.
Fast diffusion component of ion-implanted arsenic in thermally grown silicon dioxide
Authors: Lee S.-Tong , Fellinger P.
Published: July 2002

A fast diffusing species of ion-implanted arsenic has been observed in silicon dioxide annealed in a nitrogen annealing ambient. Below 1020 cm−3 concentration this arsenic diffuses 20× faster at 1100 °C than the slow arsenic found in oxidizing ambient. The effective activation energy of diffusion of this fast arsenic is 0.71 eV, in sharp contrast to 4.3 and 4.0 eV for the slow arsenic in O2 and O2 /H2 O, respectively. The fast species is believed to be arsenic occupying either the oxygen site or interstitial site in the SiO2 network.
Persistent currents in Tl-Ba-Ca-Cu-O superconductors
Authors: Grader G. S. , Gyorgy E. M. , Van Uitert L. G. , Grodkiewicz W. H. , Kyle T. R. , Eibschutz M.
Published: July 2002

We have demonstrated the presence of circulating circumferential currents in toroids of Tl-Ba-Ca-Cu-O superconductors at 77.3 and 90.2 K. The nominal composition was Tl1.5Ba2Ca2Cu3Ox; however, both the x-ray diffraction pattern and the Meissner effect indicate the presence of more than one phase. The circulating current was found to decrease by 27% in 3.8×103 s. The nature of the above time dependence is not consistent with the presence of a simple ohmic resistance but rather indicates that a process such as flux creep is the cause of this decay. An estimated upper limit of the resistivity is 1.3×10−14 Ω cm at 77.3 K.
Preparation of Bi-Sr-Ca-Cu-O superconductors from oxide-glass precursors
Authors: Hinks D. G. , Soderholm L. , Capone D. W. , Dabrowski B. , Mitchell A. W. , Shi D.
Published: July 2002

In this letter we report on efforts to synthesize the new Ca-Sr-Bi-Cu-O superconductors from amorphous glasses. These glasses are produced by quenching melts of the constituent oxides, followed by firing to produce the superconducting phase. This synthetic route produces denser, more uniform samples than those obtained from firing intimate mixtures of the constituent binary oxides and carbonates. Ultimately, this technique may yield pure materials with enhanced bulk properties.
Ba doping and rapid cooling effects on coercivity of Bi-Dy-Al-Fe garnet films for magneto-optical recording prepared by pyrolysis
Authors: Itoh Akiyoshi , Kryder Mark H.
Published: July 2002

Al-doped Bi-Dy iron garnet films have been fabricated by the pyrolysis method on glass substrates, and the effects of Ba doping and rapid cooling on the coercivity (Hc) were investigated. Films were quenched from 660 °C to room temperature within about 120 s. Rapid cooling causes a rise of Hc, and a small amount of Ba doping enhances this effect. Hc values near 4200 Oe at room temperature were obtained in rapidly cooled films with the composition Bi1Dy1.96Ba0.04Fe4.4Al0.6O12.
Photovoltage scanning electron microscopy
Authors: Flesner L. D. , O’Brien M. E.
Published: July 2002

A novel diagnostic technique utilizing secondary-electron energy analysis in a scanning electron microscope to image modulated photovoltages in semiconductor samples is reported. Contacts to the sample are not required, allowing nondestructive inspection of partially processed devices and isolated regions. Photovoltage decay following pulsed illumination, indicative of material and junction quality, can be observed. Applications to silicon on sapphire, InP, and GaAs devices are described.
Bistable operation of InGaAsP lasers using different absorber positions
Authors: Öhlander Ulf , Sahlén Olof
Published: July 2002

Experiments reveal that the physical characteristics related to absorptive bistability, such as lasing threshold, hysteresis width, and carrier redistribution, are greatly altered when the absorber position is changed from the middle section to one of the end-facet sections in a three-section laser diode.
Modeling of laser planarization of thin metal films
Authors: Marella Paul F. , Tuckerman David B. , Pease R. Fabian
Published: July 2002

The differences between excimer (≊30 ns pulse duration) and flashlamp-pumped dye (≊500 ns pulse duration) laser planarization are examined for 1.5–2 μm thick gold films over SiO2 layers. Test structures containing bar patterns (square waves) of 5000 Å peak-to-trough amplitude with spatial periods ranging from 10 to 100 μm were prepared and laser irradiated. A linear model is presented which described the time evolution of the film’s surface topography when melted with a dye laser pulse. Excimer laser planarization is found to be susceptible to evaporative recoil effects which may cause undesired pattern amplification.
Enhancement of free-carrier concentration in n-type AlxGa1−xAs grown by metalorganic vapor phase epitaxy in the temperature range 850–950 °C
Authors: Basmaji P. , Zaouk A. , Gibart P. , Gauthier D. , Portal J. C.
Published: July 2002

AlxGa1−xAs 0.2<x<0.4 epilayers were grown by metalorganic vapor phase epitaxy in the temperature range of 850–950 °C. It has been experimentally shown that epitaxial growth at high temperatures enhances the free-carrier concentration and causes unusual behavior of deep centers for Sn-doped AlxGa1−xAs. From the temperature dependence of the Hall carrier density, and assuming multivalley conduction, an activation energy of the donor of 10 meV was deduced. Furthermore, these samples did not exhibit persistent photoconductivity. Besides, when all parameters of the epitaxy were kept constant, the aluminum fraction in the epitaxial layers slightly increases as the growth temperature increases.
Visible-wavelength amplified spontaneous emission in a neodymium-doped optical fiber pumped at 1064 nm
Authors: Carruthers T. F. , Duling I. N. , Shaw C. M. , Friebele E. J.
Published: July 2002

A neodymium-doped single-mode fiber emits light at 496 and 633 nm, as well as at several near-infrared wavelengths, when pumped by a mode-locked, Q-switched Nd:YAG laser operating at 1064 nm. A threshold peak pumping power of approximately 50 kW is required for the process; peak emitted powers of several watts were observed. The blue line is more than 15 nm wide at high pumping levels and possesses large temporal pulse dispersion across its spectrum. Amplified spontaneous emission via a three-photon pumping process is proposed to account for the phenomenon.
Stimulated emission by ballistic electrons in semiconducting superlattices
Authors: Botton Mordechai , Ron Amiram
Published: July 2002

We investigate the radiation due to transitions of ballistic electrons in a superlattice. The equations of motion for the populations of photons and electrons are used to analyze the system both as an amplifier and as an oscillator. We then calculate the gain of the system and the threshold current needed to overcome electromagnetic losses. Finally, we compare our proposed infrared active system with other existing lasers.
New gettering using misfit dislocations in homoepitaxial wafers with heavily boron-doped silicon substrates
Authors: Kikuchi H. , Kitakata M. , Toyokawa F. , Mikami M.
Published: July 2002

The gettering mechanism due to misfit dislocations in P/P+ epitaxial wafers is clarified for copper-diffused epitaxial wafers. The epilayer thickness of the sample is 2.2 μm and the substrate resistivity of the sample is 0.0015–0.002 Ω cm. It is dipped in a Cu(NO3 )2 -HF solution and annealed at 900 °C for 30 min. The in-depth Cu profile obtained by secondary-ion mass spectroscopy shows a distinctive peak at the P+ -substrate side in the vicinity of the epi/sub interface. This peak coincides with that of dislocation density for their location in depth. Furthermore, from energy dispersive spectroscopy observation the diffused copper is found to be effectively gettered at misfit dislocations as copper silicide from moiré fringe.
Band-gap shifts in silicon-germanium heterojunction bipolar transistors
Authors: Sturm J. C. , Prinz E. J. , Garone P. M. , Schwartz P. V.
Published: July 2002

The band gap of the base of Si1−xGex strained-layer base heterojunction bipolar transistors has been investigated using minority-carrier transport measurements. We have found a band-gap reduction of 131 meV for a base of Si0.82Ge0.18, which is in reasonable agreement with theoretical calculations. Our measurements for a base of Si0.85Ge0.15 show a band-gap reduction less than predicted, suggesting a reduction of strain in the structure.
Light-scattering limitations for phase conjugation in optical Kerr media
Authors: McGraw R. , Rogovin D. , Gavrielides A.
Published: July 2002

It is shown that noise from light-scattering fluctuations inherent in an optical Kerr medium sets a lower limit on the incident probe power required to achieve meaningful phase conjugation by four-wave mixing. For visible wavelengths and room temperatures, we determine that about 10 μW of probe power is needed to obtain a signal-to-noise ratio of unity in the conjugate wave for reflectivities that are less than or near the first oscillation condition.
Supersaturated substitutional Ga+ ion implanted in silicon studied by x-ray photoelectron spectroscopy
Authors: Lu Z. H. , Sacher E. , Selmani A. , Yelon A.
Published: July 2002

Highly degenerate Ga-doped Si (100) has been prepared using 4 keV liquid-metal ion gun implantation and rapid thermal annealing, and has been studied using x-ray photoelectron spectroscopy. Si 2p core electron measurements provide the most direct experimental evidence of annealing-promoted tetrahedral SiGa bonds. The Ga, as high as 10 at. % after annealing at 500 °C, was found to occupy substitutional sites close to the surface. The surface concentration decreased with increasing annealing temperature. We find that the full width at half maximum of the Si 2p core levels increases with increasing substitutional Ga concentration. This can be explained by bond-length and bond-angle deviations of nearby SiSi bonds caused by SiGa bond formation and the resultant net static charge variations in the silicon lattice. We discuss the binding energy shift of both the Si 2p core level and the valence-band maximum produced by SiGa bonding.
Electronic structure of [110] Si-Ge thin-layer superlattices
Authors: Froyen Sverre , Wood D. M. , Zunger Alex
Published: July 2002

First-principles electronic structure calculations for SinGen superlattices ( for n=4, 6, and 8) grown epitaxially on a (110) Si substrate reveal a nearly direct band gap (to within ≊0.04 eV for n=4) despite the pronounced indirectness of its constituents. This is unlike superlattices grown in the [001] direction which are indirect when grown on Si and quasi-direct only on substrates with larger lattice constants, e.g., Ge. Transition dipole matrix elements for the lowest energy direct transition vanish for all repeat periods n but are finite for several other new low-energy transitions.
Focusing of particle beams using two-stage laser ablation
Authors: Kadar-Kallen M. A. , Bonin K. D.
Published: July 2002

We report a new technique for producing focused beams of neutrals, ions, and clusters using two-stage laser ablation. We have produced a collimated beam and beams which were focused in one and two dimensions. The on-axis density is 5×1015 atoms/cm3 for a barium beam focused in two dimensions over a distance of 10.7 cm. For a collimated beam the density is 1015 atoms/cm3 at the same distance.