bluuebunny/crossref_metadata_2025 huggingface dataset:
A data mining approach to developing the profiles of hotel customers
Authors: Min Hokey , Min Hyesung , Emam Ahmed
Published: September 2002

To stay competitive, hotels need to develop a viable customer retention strategy. Since a key to the successful development of such a strategy rests with customer relationship management, hotels should identify the most profitable ways to build and maintain a loyal customer relationship. In an effort to help hotels understand their customers’ preferences and the ways to interact with the customers, we propose data mining techniques. Based on a case study of luxury hotels in South Korea, this paper demonstrates the usefulness and practicality of the proposed data mining techniques.
The euro and public houses in the UK
Authors: Kevin Jenkins Andrew
Published: September 2002

The UK, unlike 12 of our fellow European countries, has decided not to join the euro. Indeed, the question of Britain’s membership of the single currency is unresolved. However, whether the UK decides to join or not, the British public house industry will be affected by the single currency. This article discusses the European Union and the euro, the impacts of the single currency on the British public house industry and a strategy for currency changeover in UK public house companies. The article includes a survey of finance directors of public house companies to ascertain their views of the euro. This is presented as a case study. The information contained in this article should be useful in helping public house firms develop a suitable strategic response to the euro. In this context, it is important that currency changeover is seen as an opportunity rather than a threat.
Robot systems reliability and safety: a review
Authors: Dhillon B.S. , Fashandi A.R.M. , Liu K.L.
Published: September 2002

This paper presents a review of published literature on robot reliability and safety. The literature is classified into three main categories: robot safety; robot reliability; and miscellaneous. Robot safety is further categorized into six classifications: general; accidents; human‐factors; safety standards; safety methods; and safety systems/technologies. The period covered by the review is from 1973 to 2001.
An artificial intelligence approach for improving plant operator maintenance proficiency
Authors: Edwards David J. , Holt Gary D. , Robinson Barry
Published: September 2002

Construction plant maintenance practice and its plant operators are inextricably linked. This is because, unlike plant operating within the manufacturing sector, construction plant is largely dependent upon operator skill and competence to maintain the item in a safe, fully operational condition. Research has previously successfully modelled machine breakdown, but revealed that the operator’s impact upon machine breakdown rates can be considerable. A conceptual model methodology with which to assess the maintenance proficiency of individual plant operators is presented. Specifically, an artificial intelligent classification model is proposed as a means of classifying plant operator maintenance proficiency into one of three bandings. These are good, average and poor. The results of such work will form the basis of new prescriptive guidelines, for incorporation into the new certificate of training achievement (CTA) scheme, available to inexperienced construction plant operators. The paper concludes with an indication of the palpable benefits of such research, to plant owners and the construction industry at large.
Packaging technologies for pressure‐sensors
Authors: Pavlin Marko , Belavic Darko , Santo Zarnik Marina , Hrovat Marko , Mozek Matej
Published: September 2002

Pressure‐sensor miniaturization requires high‐density packaging. This means that designers are constantly faced with all kinds of challenging, and sometimes impossible, requirements. In this paper we will present three examples with specific technologies and aspects of miniaturization and packaging. The first example is a pressure switch, the second a pressure sensor and the third a smart pressure sensor.
Angular disparity in ETACT scintimammography
Authors: Fahey Frederic H. , Rhyasen Kerry L. , Harkness Beth A. , Meltsner Michael A. , Webber Richard L.
Published: September 2002

Emission tuned aperture computed tomography (ETACT) has been previously shown to have the potential for the detection of small tumors (<1 cm) in scintimammography. However, the optimal approach to the application of ETACT in the clinic has yet to be determined. Therefore, we sought to determine the effect of the angular disparity between the ETACT projections on image quality through the use of a computer simulation. A small, spherical tumor of variable size (5, 7.5 or 10 mm) was placed at the center of a hemispherical breast (15 cm diameter). The tumor to nontumor ratio was either 5:1 or 10:1. The detector was modeled to be a gamma camera fitted with a 4‐mm‐diam pinhole collimator. The pinhole‐to‐detector and the pinhole‐to‐tumor distances were 25 and 15 cm, respectively. A ray tracing technique was used to generate three sets of projections (10°, 15°, and 20°, angular disparity). These data were blurred to a resolution consistent with the 4 mm pinhole. The TACT reconstruction method was used to reconstruct these three image sets. The tumor contrast and the axial spatial resolution was measured. Smaller angular disparity led to an improvement in image contrast but at a cost of degraded axial spatial resolution. The improvement in contrast is due to a slight improvement in the in‐plane spatial resolution. Since improved contrast should lead to better tumor detectability, smaller angular disparity should be used. However, the difference in contrast between 10° and 15° was very slight and therefore a reasonable clinical choice for angular disparity is 15°.
Independent monitor unit calculation for intensity modulated radiotherapy using the MIMiC multileaf collimator
Authors: Chen Zhe , Xing Lei , Nath Ravinder
Published: September 2002

A self‐consistent monitor unit (MU) and isocenter point‐dose calculation method has been developed that provides an independent verification of the MU for intensity modulated radiotherapy (IMRT) using the MIMiC (Nomos Corporation) multileaf collimator. The method takes into account two unique features of IMRT using the MIMiC: namely the gantry‐dynamic arc delivery of intensity modulated photon beams and the slice‐by‐slice dose delivery for large tumor volumes. The method converts the nonuniform beam intensity planned at discrete gantry angles of 5° or 10° into conventional nonmodulated beam intensity apertures of elemental arc segments of 1°. This approach more closely simulates the actual gantry‐dynamic arc delivery by MIMiC. Because each elemental arc segment is of uniform intensity, the MU calculation for an IMRT arc is made equivalent to a conventional arc with gantry‐angle dependent beam apertures. The dose to the isocenter from each 1° elemental arc segment is calculated by using the Clarkson scatter summation technique based on measured tissue‐maximum‐ratio and output factors, independent of the dose calculation model used in the IMRT planning system. For treatments requiring multiple treatment slices, the MU for the arc at each treatment slice takes into account the MU, leakage and scatter doses from other slices. This is achieved by solving a set of coupled linear equations for the MUs of all involved treatment slices. All input dosimetry data for the independent MU/isocenter point‐dose calculation are measured directly. Comparison of the MU and isocenter point dose calculated by the independent program to those calculated by the Corvus planning system and to direct measurements has shown good agreement with relative difference less than ±3%. The program can be used as an independent initial MU verification for IMRT plans using the MIMiC multileaf collimators.
Computer aided classification of masses in ultrasonic mammography
Authors: Dumane V. A. , Shankar P. M. , Piccoli C. W. , Reid J. M. , Forsberg F. , Goldberg B. B.
Published: September 2002

Frequency compounding was recently investigated for computer aided classification of masses in ultrasonic B‐mode images as benign or malignant. The classification was performed using the normalized parameters of the Nakagami distribution at a single region of interest at the site of the mass. A combination of normalized Nakagami parameters from two different images of a mass was undertaken to improve the performance of classification. Receiver operating characteristic (ROC) analysis showed that such an approach resulted in an area of 0.83 under the ROC curve. The aim of the work described in this paper is to see whether a feature describing the characteristic of the boundary can be extracted and combined with the Nakagami parameter to further improve the performance of classification. The combination of the features has been performed using a weighted summation. Results indicate a 10% improvement in specificity at a sensitivity of 96% after combining the information at the site and at the boundary. Moreover, the technique requires minimal clinical intervention and has a performance that reaches that of the trained radiologist. It is hence suggested that this technique may be utilized in practice to characterize breast masses.
Reproducibility of mammary gland structure during repeat setups in a supine position
Authors: Klein Zeggelink William F. A. , Deurloo Eline E. , Muller Sara H. , Schultze Kool Leo J. , Gilhuijs Kenneth G. A.
Published: September 2002

Purpose: In breast conserving therapy, complete excision of the tumor with an acceptable cosmetic outcome depends on accurate localization in terms of both the position of the lesion and its extent. We hypothesize that preoperative contrast‐enhanced magnetic resonance (MR) imaging of the patient in a supine position may be used for accurate tumor localization and marking of its extent immediately prior to surgery. Our aims in this study are to assess the reproducibility of mammary gland structure during repeat setups in a supine position, to evaluate the effect of a breast immobilization device, and to derive reproducibility margins that take internal tissue shifts into account occurring between repeat setups. Materials & Methods: The reproducibility of mammary gland structure during repeat setups in a supine position is estimated by quantification of tissue shifts in the breasts of healthy volunteers between repeat MR setups. For each volunteer fiducials are identified and registered with their counter locations in corresponding MR volumes. The difference in position denotes the shift of breast tissue. The dependence on breast volume and the part of the breast, as well as the effect of a breast immobilization cast are studied. Results: The tissue shifts are small with a mean standard deviation on the order of 1.5 mm, being slightly larger in large breasts and in the posterior part (toward the pectoral muscle) of both small and large breasts. The application of a breast immobilization cast reduces the tissue shifts in large breasts. A reproducibility margin on the order of 5 mm will take the internal tissue shifts into account that occur between repeat setups. Conclusion: The results demonstrate a high reproducibility of mammary gland structure during repeat setups in a supine position.
An empirical model for independent dose verification of the Gamma Knife treatment planning
Authors: Phaisangittisakul Nakorn , Ma Lijun
Published: September 2002

A formalism for an independent dose verification of the Gamma Knife treatment planning is developed. It is based on the approximation that isodose distribution for a single shot is in the shape of an ellipsoid in three‐dimensional space. The dose profiles for a phantom along each of the three major axes are fitted to a function which contains the terms that represent the contributions from a point source, an extrafocal scattering, and a flat background. The fitting parameters are extracted for all four helmet collimators, at various shot locations, and with different skull shapes. The 33 parameters of a patient's skull shape obtained from the Skull Scaling Instrument measurements are modeled for individual patients. The relative doses for a treatment volume in the form of 31×31×31 matrix of points are extracted from the treatment planning system, the Leksell GammaPlan (LGP). Our model evaluates the relative doses using the same input parameters as in the LGP, which are skull measurement data, shot location, weight, γ‐angle of the head frame, and helmet collimator size. For 29 single‐shot cases, the discrepancy of dose at the focus point between the calculation and the LGP is found to be within −1% to 2%. For multi‐shot cases, the value and the coordinate of the maximum dose point from the calculation agree within ±7% and ±3 mm with the LGP results. In general, the calculated doses agree with the LGP calculations within ±10% for the off‐center locations. Results of calculation with this method for the dimension and location of the 50% isodose line are in good agreement with results from Leksell GammaPlan. Therefore, this method can be served as a useful tool for secondary quality assurance of Gamma Knife treatment plans.
Demonstrating optical beat notes through heterodyne experiments
Authors: Razdan K. , Van Baak D. A.
Published: September 2002

The interference between two independent beams of light, often called optical heterodyne detection, is of considerable theoretical and practical importance. This note concentrates on considerations of instrumentation and technique that arise in demonstrating optical heterodyning, and describes three experimental demonstrations of the phenomenon.
Averaging of harmonic physical fields over an annular region enclosing field sources
Authors: Li Lin
Published: September 2002

Fields such as temperature, current density, and static electromagnetic fields in regions with no field sources are harmonic functions that satisfy the Laplace equation. Such functions on a sphere have a well-known mean value property. A new mean value property is derived for fields that are harmonic on an annular region, with the field sources enclosed by the inner boundary. Some examples are discussed.
Heat capacity of an ideal gas along an elliptical PV cycle
Authors: Velasco S. , González A. , White J. A. , Calvo Hernández A.
Published: September 2002

The heat capacity CΠ of an ideal gas along an elliptical cycle Π in a PV diagram is analyzed. We find that CΠ can take values between −∞ and +∞. The conditions CΠ=0 and CΠ=±∞ are used to determine the parts of the cycle where the transfer of heat has a positive or negative sign. The knowledge of CΠ allows us to do an analytical calculation of the transfer of heat during a process between two points along the cycle. The corresponding TS diagram is also discussed.
Multiple scattering of a plane scalar wave from a uniform dielectric slab
Authors: Guo Wei
Published: September 2002

The multiple scattering method is used to model the propagation of a plane scalar wave through a uniform dielectric slab extending from z=0 to z=d. The slab is assumed to be formed by evenly distributed dipoles characterized by an isotropic polarizability α. Expressions for the diffracted, transmitted, and reflected waves are derived and compared to the corresponding transmission and reflection coefficients for a linearly polarized vector wave whose amplitude vector is perpendicular to the plane of incidence. It is found that, when energy is lost, the amplitude of the familiar periodic variation of the intensity of the reflected wave becomes a decreasing function of the slab thickness while the intensity of the transmitted wave ceases to vary as a function of the slab thickness.
Roller ball dynamics revisited
Authors: Heyda P. G.
Published: September 2002

The rotor in a hand held gyroscopic device can be accelerated to high revolutions by simple movements of the hand. The dynamics of the device is presented with straightforward mathematics while maintaining realistic physics.
Does the Euler Disk slip during its motion?
Authors: Petrie D. , Hunt J. L. , Gray C. G.
Published: September 2002

The motion of a disk that is spun on a smooth flat surface slowly damps out due to friction. To help identify the nature of the friction, we test experimentally whether the disk slips during its motion. We find that, at least during the early stages, the disk rolls without slipping, thus ruling out sliding friction as the cause of the damping. Together with the results of the experiments of van der Engh et al. that rule out air friction, our results establish that rolling friction is mainly responsible for the damping in the early stages of the motion. Student projects are suggested that could establish whether our conclusion of rolling without slipping holds for the later stages of the motion.
The air bubble: experiments on an unusual harmonic oscillator
Authors: Leroy Valentin , Devaud Martin , Bacri Jean-Claude
Published: September 2002

We discuss a series of easily reproducible experiments with one and two air bubbles immersed in water, and we show that these systems can be analyzed in terms of harmonic oscillators.
A Role for CD40 Expression on CD8
+
T Cells in the Generation of CD8
+
T Cell Memory
Authors: Bourgeois Christine , Rocha Benedita , Tanchot Corinne
Published: September 2002

The delivery of CD4 help to CD8
+
T cell responses requires interactions between CD40 and CD40 ligand and is thought to occur through antigen-presenting cell (APC) activation. Here we show that generation of memory CD8
+
T cells displaying an enhanced capacity for cell division and cytokine secretion required CD4 help but not CD40 expression by the APCs. Activated CD4
+
and CD8
+
T cells expressed CD40; and in the absence of this protein, CD8
+
T cells were unable to differentiate into memory cells or receive CD4 help. These results suggest that, like B cells, CD8
+
T cells receive CD4 help directly through CD40 and that this interaction is fundamental for CD8
+
T cell memory generation.
Macrophage Apoptosis by Anthrax Lethal Factor Through p38 MAP Kinase Inhibition
Authors: Park Jin Mo , Greten Florian R. , Li Zhi-Wei , Karin Michael
Published: September 2002

The bacterium
Bacillus anthracis
causes the death of macrophages, which may allow it to avoid detection by the innate immune system. We found that
B. anthracis
lethal factor (LF) selectively induces apoptosis of activated macrophages by cleaving the amino-terminal extension of mitogen-activated protein kinase (MAPK) kinases (MKKs) that activate p38 MAPKs. Because macrophages that are deficient in transcription factor nuclear factor κB (NF-κB) are also sensitive to activation-induced death and p38 is required for expression of certain NF-κB target genes, p38 is probably essential for synergistic induction of those NF-κB target genes that prevent apoptosis of activated macrophages. This dismantling of the p38 MAPK module represents a strategy used by
B. anthracis
to paralyze host innate immunity.
Parasites as a Viability Cost of Sexual Selection in Natural Populations of Mammals
Authors: Moore Sarah L. , Wilson Kenneth
Published: September 2002

Sexual selection in mammals has resulted in the evolution of sexual size dimorphism (SSD), with males usually being the larger sex. Comparative analyses indicate that the evolution of SSD is associated with the evolution of male-biased mortality, suggesting a possible causal link between the two. Here, we use a comparative approach to investigate the possible role of parasites in generating this relation. We show that there is a robust association between male-biased parasitism and the degree of sexual selection, as measured by mating system (monogamous or polygynous) and by the degree of SSD. There is also a positive correlation, across taxa, between male-biased mortality and male-biased parasitism. These results are consistent with the hypothesis that parasites contribute to the observed association between SSD and male-biased mortality.
Physical One-Way Functions
Authors: Pappu Ravikanth , Recht Ben , Taylor Jason , Gershenfeld Neil
Published: September 2002

Modern cryptographic practice rests on the use of one-way functions, which are easy to evaluate but difficult to invert. Unfortunately, commonly used one-way functions are either based on unproven conjectures or have known vulnerabilities. We show that instead of relying on number theory, the mesoscopic physics of coherent transport through a disordered medium can be used to allocate and authenticate unique identifiers by physically reducing the medium's microstructure to a fixed-length string of binary digits. These physical one-way functions are inexpensive to fabricate, prohibitively difficult to duplicate, admit no compact mathematical representation, and are intrinsically tamper-resistant. We provide an authentication protocol based on the enormous address space that is a principal characteristic of physical one-way functions.
Nucleotide Control of Interdomain Interactions in the Conformational Reaction Cycle of SecA
Authors: Hunt John F. , Weinkauf Sevil , Henry Lisa , Fak John J. , McNicholas Paul , Oliver Donald B. , Deisenhofer Johann
Published: September 2002

The SecA adenosine triphosphatase (ATPase) mediates extrusion of the amino termini of secreted proteins from the eubacterial cytosol based on cycles of reversible binding to the SecYEG translocon. We have determined the crystal structure of SecA with and without magnesium–adenosine diphosphate bound to the high-affinity ATPase site at 3.0 and 2.7 angstrom resolution, respectively. Candidate sites for preprotein binding are located on a surface containing the SecA epitopes exposed to the periplasm upon binding to SecYEG and are thus positioned to deliver preprotein to SecYEG. Comparisons with structurally related ATPases, including superfamily I and II ATP-dependent helicases, suggest that the interaction geometry of the tandem motor domains in SecA is modulated by nucleotide binding, which is shown by fluorescence anisotropy experiments to reverse an endothermic domain-dissociation reaction hypothesized to gate binding to SecYEG.
Critical Role for STAT4 Activation by Type 1 Interferons in the Interferon-γ Response to Viral Infection
Authors: Nguyen Khuong B. , Watford Wendy T. , Salomon Rachelle , Hofmann Sigrun R. , Pien Gary C. , Morinobu Akio , Gadina Massimo , O'Shea John J. , Biron Christine A.
Published: September 2002

Interferons (IFNs) are essential for host defense. Although the antiviral effects of the type 1 IFNs IFN-α and IFN-β (IFN-α/β) have been established, their immunoregulatory functions, especially their ability to regulate IFN-γ production, are poorly understood. Here we show that IFN-α/β activate STAT4 directly (STAT, signal transducers and activators of transcription) and that this is required for IFN-γ production during viral infections of mice, in concert with T cell receptor–derived signals. In contrast, STAT1 appears to negatively regulate IFN-α/β induction of IFN-γ. Thus, type 1 IFNs, in addition to interleukin-12, provide pathways for innate regulation of adaptive immunity, and their immunoregulatory functions are controlled by modulating the activity of individual STATs.
Biomolecules and the Bomb
Authors: Rasmussen Nicolas
Published: September 2002

Designs for Life
Molecular Biology after World War II. Soraya de Chadarevian. Cambridge University Press, New York, 2002. 443 pp. $55, £35. ISBN 0-521-57078-6.

De Chadarevian examines the birth and growth of molecular biology through the prism of an account of the Medical Research Council Laboratory of Molecular Biology at Cambridge.
FABRICATION AND OPTICAL AND MORPHOLOGICAL CHARACTERIZATION OF n+-ZnO/i-ZnO AND n+-ZnO/ZnSe BILAYERS USED AS OPTICAL WINDOWS IN SOLAR CELLS
Authors: CALDERÓN C. , INFANTE H. , GORDILLO G.
Published: September 2002

This work presents results concerning the development of n +- ZnO/i-ZnO and n +- ZnO/ZnSe bilayer structures with adequate properties to be used as optical windows in solar cells based on CuInSe 2 thin films. The optical and morphological properties of each of the layers constituting the bilayer structures were studied through spectral transmittance and atomic force microscopy (AFM) measurements. The studies revealed that windows of this type allow a significant increase of the spectral range of absorbed radiation by the solar cell in comparison with those using ZnO/CdS as optical window.
A STUDY OF THE ELECTRICAL PROPERTIES OF Al2O3 FILMS DEPOSITED ON GaAs SUBSTRATES BY SPRAY PYROLYSIS
Authors: CHAVEZ-RAMIREZ J. , AGUILAR-FRUTIS M. , GARCIA M. , MARTINEZ E. , ALVAREZ-FREGOSO O. , LOPEZ S. , BURILLO G. , FALCONY C.
Published: September 2002

Electrical characteristics of high quality aluminum oxide thin films deposited by the spray pyrolysis technique on GaAs substrates are reported. The films were deposited using a spraying solution of aluminum acetylacetonate in N,N-dimethylformamide and an ultrasonic mist generator. The substrates were (100) GaAs wafers Si-doped (1018 cm -3). The substrate temperature during deposition was in the range of 300–600°C. The electrical characteristics of these films were determined by capacitance and current versus voltage measurements by the incorporation of these films into metal-oxide-semiconductor structures. The interface state density resulted in the order of 1012 1/ eV-cm 2 and the films can stand electric fields higher than 5 MV/cm, without observing a destructive dielectric breakdown. The refractive index, measured by ellipsometry at 633 nm, resulted close to 1.64. The determination of the chemical composition of the films was achieved by energy dispersive X-ray spectroscopy; it resulted close to that of stoichiometric aluminum oxide (O/Al = 1.5) when films are deposited at substrate temperatures of 300–350°C.
PHOTOLUMINESCENCE STUDIES OF GaInArSb HIGHLY DOPED WITH TELLURIUM GROWN BY LIQUID PHASE EPITAXY ON (100) GaSb
Authors: DÍAZ-REYES J. , CORONA-ORGANICHE E. , HERRERA-PÉREZ J. L. , ZARATE-CORONA O. , MENDOZA-ALVAREZ J.
Published: September 2002

Tellurium-doped GaInArSb epitaxial layers with electron concentration in the range of 3 × 1017 – 2 × 1020 cm -3 are grown at 530°C on (100) GaSb substares by liquid phase epitaxy (LPE). To dope the layers we used pellets of Sb 3 Te 2 in preparing growth melts. The low temperature photoluminescence (PL) spectra (20 K) showed a dominant peak composed of three transitions associated to excitons bound to residual acceptor impurities. For highly Te-doped layers the excitonic transitions related to exciton bound to neutral acceptor, BE 2, disappears.
NEW PHYSICAL PRINCIPLES OF CONTACT THERMOELECTRIC COOLING
Authors: GUREVICH YU. G. , LOGVINOV G. N. , TITOV O. YU. , GIRALDO J.
Published: September 2002

We suggest a new approach to theory of contact thermoelectric cooling (Peltier effect). The metal–metal, metal–n-type semiconductor, metal–p-type semiconductor, p–n junction contacts are analyzed. Both degenerate and nondegenerate electron and hole gases are considered. The role of recombination in the contact cooling effect is discussed for the first time.
CHARGE TRAPPING IN SOL–GEL-DERIVED COATINGS ON Si WAFERS
Authors: DIAZ T. , JUÁREZ H. , CUAMATZI M. , OLVERA J. , MARTINEZ J. , JUÁREZ R.
Published: September 2002

Sol–gel techniques are particularly useful for the formation of thin oxide films on various substrates, which can be important for many technological applications. In microelectronic technology these films can be used as passivation layers, diffusion and oxidation barriers, intermetal dielectrics (IMD) and so on. Sol–gel-derived oxides are obtained from tetraethoxysilane, which is used as precursor and a two-step process involving acid catalysts. Varying the composition of the sol–gel solution, optical and electrical properties of the resulted films can be changed. In the present work, HF and HNO 3 were used as catalyst in order to vary the electrical properties of the films. Oxides were deposited on Si substrates and MIS (metal–insulator–semiconductor) structures were fabricated. Electrical properties of the coatings were studied by the C–V (capacitance–voltage) method. Fourier transform infrared spectroscopy (FTIR) measurements ware employed to investigate the chemical bonding structure. The results show evidence of the existence of charge trapping in the TEOS/HNO 3 films when MIS capacitors are biased from accumulation to inversion condition. This fact can be applied in the semiconductor device technology.
INTERACTION BETWEEN Zn AND Cd ATOMS DURING THE ATOMIC LAYER EPITAXY GROWTH OF CdZnTe/ZnTe QUANTUM WELLS
Authors: LARRAMENDI ERICK M. , LÓPEZ-LUNA EDGAR , DE MELO OSVALDO , HERNÁNDEZ-CALDERÓN ISAAC
Published: September 2002

Layers of 6 and 16 Cd–Te–Zn–Te periods were grown by atomic layer epitaxy (ALE) within ZnTe thin films. Different samples were grown at substrate temperatures of 260 and 290°C. Information about the kinetics of growth and surface reconstruction during the ALE growth of CdTe and ZnTe films, and Cd–Te–Zn–Te periods was obtained by means of reflection high-energy electron diffraction (RHEED) experiments and through the analysis of the temporal behavior of the intensities of several features of the RHEED patterns. The photoluminescence of the sample grown at 260°C presents two narrow and intense peaks corresponding to emission from quantum wells (QWs). However, the spectrum of the samples grown at 290°C does not show any feature associated with QWs, the spectrum resembling that of a ZnTe film. Cd replacement by Zn atoms explains the absence of the CdZnTe QWs at 290°C and a lower Cd content than expected at 260°C. The replacement of Cd atoms by Zn atoms in the CdTe surface was clearly demonstrated by Auger experiments.
BINDING ENERGY FOR A SHALLOW DONOR IMPURITY IN GaAs–(Ga, Al)As QUANTUM WELLS UNDER HYDROSTATIC PRESSURE AND APPLIED ELECTRIC FIELD
Authors: MONTES A. , MORALES A. L. , DUQUE C. A.
Published: September 2002

The present work investigates the effects of the hydrostatic pressure and the external applied electric field on the binding energy for shallow donor impurities in GaAs–Ga 1 - x Al x As quantum wells. The effective mass approximation is used and a trial envelope wave function is adopted for the impurity carrier. For fixed well width and applied electric field, the binding energy of the shallow donor impurity is enhanced by increasing the external hydrostatic pressure, and for fixed well width and hydrostatic pressure, the binding energy decreases by increasing the external electric field.
STUDY OF MICROSTRUCTURE AND CATALYTIC ACTIVITY OF γ-Bi2MoO6 AND Bi2WO6 COMPOUNDS
Authors: RANGEL R. , BARTOLO-PÉREZ P. , GÓMEZ-CORTÉZ A. , DÍAZ G. , GALVÁN D. H.
Published: September 2002

Bi 2 MO 6 (M=Mo, W) compounds were prepared for low-temperature oxidation. The catalysts were prepared by solid-state reaction. The structural changes were followed by X-ray diffraction, scanning electron microscopy, Auger electron spectroscopy and BET nitrogen absorption. Auger analysis shows that Bi 2 WO 6 catalysts have more bismuth on the surface than γ- Bi 2 MoO 6, although both samples are bismuth deficient as compared to the stoichiometric compound. The results regarding catalytic activity show that Bi 2 WO 6 prepared at 1073 K reaches total conversion of CO (100%) at a lower temperature when compared to γ- Bi 2 MoO 6. This indicates that Bi 2 WO 6 is a potential candidate to be used as catalyst in the CO to CO 2 oxidation.
STARK EFFECT IN A FINITE REGION FOR A 1D COULOMB POTENTIAL
Authors: VÁZQUEZ G. J. , AVENDAÑO C. , REYES J. A. , DEL CASTILLO-MUSSOT M. , SPECTOR H.
Published: September 2002

We calculate the states of a one-dimensional hydrogen atom under the effect of an electric field (Stark effect) in the strong field regime being the field confined in a finite region of width 2a (capacitor region). We find numerically the solution inside the capacitor and match it to an analytical solution outside the capacitor. Although the electric field tends to separate the two opposite charges particles, the total energy of the system decreases with increasing electric field strength. Our results are useful as a guideline to study strong electric field effects in electronic states of impurities or excitons in 1D systems.
HYDROXYAPATITE COATINGS ON METALS OF ORTHOPEDIC INTEREST
Authors: SÁENZ A. , MONTERO M. L. , CASTAÑO V. M.
Published: September 2002

Hydroxyapatite coatings on metallic surfaces of orthopedic interest are achieved, with a chemical bond metal–hydroxyapatite established by the chemical process known as functionalizing. Two different functionalizing agents were used and the pH of the solutions was varied. Results show that crystal size and morphology depend on pH.
Phosphorylation and Putative ER Retention Signals Are Required for Protein Kinase A-Mediated Potentiation of Cardiac Sodium Current
Authors: Zhou Jingsong , Shin Hyeon-Gyu , Yi Jianxun , Shen Wangzhen , Williams Christine P. , Murray Katherine T.
Published: September 2002

Activation of protein kinase A (PKA) increases Na
+
current derived from the human cardiac Na
+
channel, hH1, in a slow, nonsaturable manner. This effect is prevented by compounds that disrupt plasma membrane recycling, implying enhanced trafficking of channels to the cell membrane as the mechanism responsible for Na
+
current potentiation. To investigate the molecular basis of this effect, preferred consensus sites (serines 483, 571, and 593) and alternative sites phosphorylated by PKA in the rat heart isoform (serines 525 and 528) were removed in the I-II interdomain linker, a region in the channel previously implicated in the PKA response. Our results demonstrate that the presence of either serine 525 or 528 is required for Na
+
current potentiation. The role of amino acid sequences that can mediate channel-protein interactions was also examined. Removal of a PDZ domain-binding motif at the carboxy terminus of hH1 did not alter the PKA response. The I-II interdomain linker of the channel contains 3 sites (479RKR481, 533RRR535, and 659RQR661) with the sequence RXR, a motif known to mediate retention of proteins in the endoplasmic reticulum (ER). The PKA-mediated increase in Na
+
current was abolished when all 3 sites were eliminated, with RRR at position 533 to 535 primarily responsible for this effect. These results demonstrate that both α-subunit phosphorylation and the presence of putative ER retention signals are required for the PKA-mediated increase in cardiac Na
+
current, an effect that likely involves interaction of the I-II interdomain linker with other proteins or regions of the channel.
L-Type Ca
2+
Channel Density and Regulation Are Altered in Failing Human Ventricular Myocytes and Recover After Support With Mechanical Assist Devices
Authors: Chen Xiongwen , Piacentino Valentino , Furukawa Satoshi , Goldman Bruce , Margulies Kenneth B. , Houser Steven R.
Published: September 2002

Ca
2+
influx through the L-type calcium channel (LTCC) induces Ca
2+
release from the sarcoplasmic reticulum (SR) and maintains SR Ca
2+
loading. Alterations in LTCC properties, their contribution to the blunted adrenergic responsiveness in failing hearts and their recovery after support with LV assist devices (LVAD) were studied. L-type Ca
2+
current (
I
Ca,L
) was measured under basal conditions and in the presence of isoproterenol (ISO), dibutyryl-cAMP (db-cAMP), Bay K 8644 (BayK), Okadaic acid (OA, a phosphatase inhibitor), and phosphatase 2A (PP2A) in nonfailing (NF), failing (F), and LVAD-supported human left ventricular myocytes (HVMs). Basal
I
Ca,L
density was not different in the 3 groups but
I
Ca,L
was activated at more negative voltages in F- and LVAD- versus NF-HVMs (V
0.5
: −7.18±1.4 and −7.0±0.9 versus 0.46±1.1 mV). Both ISO and db-cAMP increased
I
Ca,L
in NF- and LVAD- significantly more than in F-HVMs (NF >LVAD> F: ISO: 90±15% versus 77±19% versus 24±12%; db-cAMP: 235%>172%>90%). ISO caused a significant leftward shift of the
I
Ca,L
activation curve in NF- and LVAD- but not in F-HVMs. After ISO and db-cAMP, the
I
Ca,L
activation was not significantly different between groups. BayK also increased
I
Ca,L
more in NF- (81±30%) and LVAD- (70±15%) than in F- (51±8%) HVMs. OA increased
I
Ca, L
by 85.6% in NF-HVMs but had no effect in F-HVMs, while PP2A decreased
I
Ca, L
in F-HVMs by 35% but had no effect in NF-HVMs. These results suggest that the density of LTCC is reduced in F-HVMs but basal
I
Ca,L
density is maintained by increasing in LTCC phosphorylation.
Myofilament Calcium Sensitivity and Cardiac Disease
Authors: Westfall Margaret V. , Borton Andrea R. , Albayya Faris P. , Metzger Joseph M.
Published: September 2002

The heightened Ca
2+
sensitivity of force found with hypertrophic cardiomyopathy (HCM)–associated mutant cardiac troponin I (cTnIR145G; R146G in rodents) has been postulated to be an underlying cause of hypertrophic growth and premature sudden death in humans and in animal models of the disease. Expression of slow skeletal TnI (ssTnI), a TnI isoform naturally expressed in developing heart, also increases myofilament Ca
2+
sensitivity, yet its expression in transgenic mouse hearts is not associated with overt cardiac disease. Gene transfer of TnI isoforms or mutants into adult cardiac myocytes is used here to ascertain if expression levels or functional differences between HCM TnI and ssTnI could help explain these divergent organ-level effects. Results showed significantly reduced myofilament incorporation of cTnIR146G compared with ssTnI or wild-type cTnI. Despite differences in myofilament incorporation, ssTnI and cTnIR146G expression each resulted in enhanced myofilament tension in response to submaximal Ca
2+
under physiological ionic conditions. Myofilament expression of an analogous HCM mutation in ssTnI (ssTnIR115G) did not further increase myofilament Ca
2+
sensitivity of tension compared with ssTnI. In contrast, there was a divergent response under acidic pH conditions, a condition associated with the myocardial ischemia that often accompanies hypertrophic cardiomyopathy. The acidic pH-induced decrease in myofilament Ca
2+
sensitivity was significantly greater in myocytes expressing cTnIR146G and ssTnIR115G compared with ssTnI. These results suggest that differences in pH sensitivities between wild-type ssTnI and mutant TnI proteins may be one factor in helping explain the divergent organ and organismal outcomes in TnI HCM- and ssTnI-expressing mice.
Evoked and Spontaneous Purinergic Junctional Ca
2+
Transients (jCaTs) in Rat Small Arteries
Authors: Lamont Christine , Wier W. Gil
Published: September 2002

Confocal microscopy of fluo-4 fluorescence in pressurized rat mesenteric small arteries subjected to low-frequency electrical field stimulation revealed Ca
2+
transients in perivascular nerves and novel, spatially localized Ca
2+
transients in adjacent smooth muscle cells. These muscle Ca
2+
transients occur with a very brief latency to the stimulus pulse (most <3 ms). They are wider (≈5 μm) and last longer (t
1/2
, 145 ms) than Ca
2+
sparks. They are abolished by the purinergic receptor (P2X) antagonist suramin, but they are totally unaffected by the α
1
-adrenoceptor antagonist prazosin or by capsaicin (which inhibits the function of perivascular sensory nerves). We conclude that these novel Ca
2+
transients represent Ca
2+
entering smooth muscle cells through P2X receptors activated by ATP released from sympathetic nerves, and we therefore call them “junctional Ca
2+
transients” or jCaTs. As expected from spontaneous neurotransmitter release, jCaTs also occur spontaneously, with characteristics identical to evoked jCaTs. Visualization of sympathetic neurotransmission shows that purinergic components dominate at low frequencies of sympathetic nerve fiber activation.
Tubulovascular Nitric Oxide Crosstalk
Authors: Dickhout Jeffrey G. , Mori Takefumi , Cowley Allen W.
Published: September 2002

Studies were designed to determine the source of NO responsible for buffering of the angiotensin II (Ang II)–mediated decrease of blood flow in the renal medulla. Intracellular Ca
2+
concentration ([Ca
2+
]
i
) and NO production ([NO]
i
) of pericytes and endothelium of the vasa recta were independently measured with the use of fura 2-AM and 4,5-diaminofluorescein diacetate (DAF-2DA), respectively, in microtissue strips of the vascular bundles of the outer medullary vasa recta. Disruption of the endothelium of the vasa recta by perfusion with latex microspheres enabled imaging of the pericytes. Ang II (1 μmol/L) produced an increase of [NO]
i
of 19±6 U in pericytes of the vasa recta when the vessels were adjacent to medullary thick ascending limbs (mTALs). Pericytes of isolated vasa recta without surrounding mTALs showed a rapid peak increase in [Ca
2+
]
i
of 248±107 nmol/L, with a sustained elevation of 107±75 nmol/L, but did not show an increase in [NO]
i
to either Ang II (1 μmol/L) or the Ca
2+
ionophore 4-bromo-A23187 (5 μmol/L). These observations indicated the lack of Ang II and Ca
2+
-sensitive NO production in pericytes of the vasa recta. In isolated vasa recta with intact endothelium, Ang II reduced [Ca
2+
]
i
from 128±28 to 62±13 nmol/L and failed to increase [NO]
i
. However, the Ca
2+
ionophore did increase [NO]
i
in the endothelium (47±8 U), indicating the presence of Ca
2+
-sensitive NO production. Significant increases of [NO]
i
were observed in single isolated mTALs in response to both Ang II (33±6 U) and the Ca
2+
ionophore (51±18 U). We conclude that Ang II increases [Ca
2+
]
i
in pericytes of the descending vasa recta as part of its constrictor action and that this vasoconstriction is buffered by the NO from the surrounding tubular elements, such as mTALs.
Reduced Apoptosis and Increased Lesion Development in the Flow-Restricted Carotid Artery of p75
NTR
-Null Mutant Mice
Authors: Kraemer Rosemary
Published: September 2002

Apoptosis of neointimal smooth muscle cells is a well-recognized component of the pathogenesis of vascular lesions. In recent studies, we have identified the neurotrophin receptor, p75
NTR
, as a mediator of apoptosis of neointimal smooth muscle cells. Neurotrophin ligands and p75
NTR
are selectively expressed in areas of atherosclerotic lesions with increased smooth muscle cell apoptosis and the neurotrophins are potent apoptotic agents for p75
NTR
-expressing smooth muscle cells in vitro. In the present study, we directly assess the role of p75
NTR
in lesion development in the flow-restricted carotid artery, a model of murine vascular injury. Ligation of the left carotid artery resulted in a 3- to 4-fold increase in lesion development in p75
NTR
-null mutant mice as compared with wild-type mice. The increase in lesion size was associated with a 70% decrease in apoptosis of neointimal smooth muscle cells, as assessed by in situ TUNEL analysis. These data suggest that under conditions of flow restriction, p75
NTR
activation impairs lesion formation by promoting smooth muscle cell apoptosis. These results further implicate p75
NTR
as an important regulator of smooth muscle cell apoptosis and lesion development after vascular injury.
p21-Activated Kinase Increases the Calcium Sensitivity of Rat Triton-Skinned Cardiac Muscle Fiber Bundles via a Mechanism Potentially Involving Novel Phosphorylation of Troponin I
Authors: Buscemi Nina , Foster D. Brian , Neverova Irina , Van Eyk Jennifer E.
Published: September 2002

Phosphorylation of myofilament proteins by kinases such as cAMP-dependent protein kinase and protein kinase C has been shown to lead to altered thin-filament protein-protein interactions and modulation of cardiac function in vitro. In the present study, we report that a small GTPase-dependent kinase, p21-activated kinase (PAK), increases the calcium sensitivity of Triton-skinned cardiac muscle fiber bundles. Constitutively active PAK3 caused an average 1.25-fold (25.0±6.0%, n=6) increase in force at pCa 5.75, 1.44-fold (44.0±7.78%, n=6) at pCa 6.25, and 2.41-fold (141.2±23.7%, n=4) at pCa 6.5, representing a change in pCa
50
value of approximately 0.25. Constitutively active PAK3 produced no change in force under conditions of relaxation (pCa 8.0) or maximal contraction (pCa 4.5). Furthermore, an inactive, kinase-dead form of PAK3 failed to produce any change in force development at any pCa value. The myofilament proteins phosphorylated by PAK3, at pCa 6.5, are desmin, troponin T, troponin I, and an unidentified 70-kDa protein. Importantly, cardiac troponin I was found to be phosphorylated at serine 149 of human cardiac troponin I, representing a novel phosphorylation site. These findings suggest a novel mechanism of modulating the calcium sensitivity of cardiac muscle contraction.
3‐D tomographic seismic inversion of a paleochannel system in central New South Wales, Australia
Authors: Deen Tara , Gohl Karsten
Published: September 2002

Buried paleochannels are of significant interest for understanding hydrological mechanisms and their potential as alluvial gold deposits. Seismic tomographic methods are a suitable solution for resolving the vertical and horizontal structure of such features. We assess a method for seismic 3‐D tomographic inversion from refraction arrivals with reflection control over a suspected paleochannel adjacent to the Wyalong gold fields in the Lachlan fold belt of central New South Wales, Australia. A standard multichannel engineering seismic recording and cable–receiver system was used on a 3‐D field geometry of multiple linear arrays. More than 3000 P‐wave first‐arrival traveltime values were inverted using a regularized inversion scheme for which simplified 2‐D models served as initial velocity–depth models for the complete 3‐D inversion. Seismic reflection arrivals provided additional depth estimates to the bedrock and compensated for a lack of refraction phases at that depth. Correlating the 3‐D seismic velocity–depth data with existing drillhole and nonseismic geophysical data resulted in a detailed structural and compositional interpretation of the paleochannel and the incised regolith. The model suggests the presence of a system of deposits from meandering channels overlying a metasedimentary bedrock formation. The general paleodrainage deposit is relatively conductive in electromagnetic surveys, indicating a potential saline storage or transport mechanism.
A new approach to depth determination from magnetic anomalies
Authors: Abdelrahman El‐Sayed M. , El‐Araby Hesham M. , El‐Araby Tarek M. , Essa Khalid S.
Published: September 2002

We have developed a semiautomatic method to determine the depth to shallow and deep‐seated structures from a magnetic anomaly profile. It involves using a relationship between the depths to two coaxial sources obtained by combining observations at symmetric points with respect to the coordinate of the sources center. For five established, fixed data points, the depth to the shallow structure is determined for each preassigned depth of the deep‐seated structure. The computed depths to the shallow structure are plotted against the computed depths to the deep‐seated structure, yielding a continuous, monotonically increasing depth curve. The spacing between the observations is then modified, producing several curves. The accepted estimates for the depths to both structures are read at the common intersection of these curves. The effective intensity and the angle of magnetization of both structures are also estimated.

The proposed method was tested both on noisy synthetic and real magnetic data. In the case of synthetic data, the depth curves method determined the correct depths of both coaxial and laterally offset sources. In the case of practical data (vertical component anomaly over a chromite body in the Guleman concession, Turkey), the method suggested the shape of the buried shallow structure resembles a horizontal cylinder model buried at a depth of 31 m and the shape of the buried deep seated structure resembles a dike model buried at a depth of 62 m. The estimated shape and depth of the shallow structure are in very good agreement with the results obtained from drilling and surface geology. The area appears to still hold promise for chromite exploration from the deeper structure.