bluuebunny/crossref_metadata_2025 huggingface dataset:
Successfully increasing technological control through minimizing workplace resistance: understanding the willingness to telework
Authors: Wicks David
Published: September 2002

Technological change has permitted organizations to design jobs in different ways and control work performed in remote locations. This article examines how telework can be used to provide benefits to organizations and their members. In it I present the findings of a study of a large Canadian financial services organization preparing to introduce telework into its sales and customer service operations. These findings highlight the role of expectancy in forming attitudes toward telework, most importantly: the extent to which face‐to‐face communication prevents important social needs from being satisfied and prevents workers from developing a sense of belonging and commitment to the organization; and the belief that telework will bring improved performance results by creating a work environment with fewer distractions and new, more objective performance measures based on output. This exploration of individuals’ willingness to telework is apt because it points to potential sources of resistance to the implementation of new technologies of production and control in the workplace.
Global ethics and the Alien Tort Claims Act: a summary of three cases within the oil and gas industry
Authors: Olsen Janeen E.
Published: September 2002

Three recent cases within the oil and gas industry point to the trend to prosecute companies in the USA for alleged human rights and environmental degradation abroad. The Alien Tort Claims Act has been used with varying degrees of success to bring claims against multinational companies. The examples of Texaco in Ecuador, Chevron in Nigeria, and Unocal in Burma are presented as case studies of the use of the Alien Tort Claims Act. Implications for global ethics are discussed and recommendations for managerial actions to lessen the potential harm brought about by legal charges under the Act are proposed.
An analysis of teleworking centres in Spain
Authors: Rosa del Águila Obra Ana , Bruque Cámara Sebastián , Padilla Meléndez Antonio
Published: September 2002

In this paper, we present the concept of telecentres as an aid to socio‐economic development in deprived rural and urban areas, and analyse the use of information technology in these workplaces. Numerous public and not‐for‐profit organisations are subsidising these initiatives as pilot development aid projects on a international scale. We have undertaken an empirical study on a Spanish scale with the following objectives: to know how many telecentres exist in Spain; to identify their state, category and organizational characteristics; to discover what services they offer; to determine the marketing strategies they employ; and to identify the principal factors that determine their success.
Threats to brand integrity in the hospitality sector: evidence from a tourist brand
Authors: Mangan Emir , Collins Alan
Published: September 2002

This paper investigates the threats to brand integrity in the hospitality sector where the brand owner is separated from the service provider and runs the risk of falling foul of cheating behaviour. It takes the case of the Shamrock bed and breakfast brand in the Irish tourist market. The analysis uses both the perceived risk literature and the “lemons” model developed by Akerlof to highlight potential dangers to the brand emerging on both the demand and supply sides of the bed and breakfast market. The findings suggest that quality variations may encourage the suppliers of high quality services to exit the brand, thereby reducing the average level of quality within the brand. The analysis also demonstrates that as consumers’ perceptions of quality variations increase, their trust in the Shamrock diminishes.
Food safety in school catering in the People’s Republic of China
Authors: Kivela Jaksoa , Ling Lam Mei , Inbakaran Robert
Published: September 2002

As a result of inadequate safe food handling and food safety procedures, school catering organisations take tremendous risks with people who are arguably more vulnerable to food poisoning than adults. Food poisoning can be a serious affliction, the symptoms of which usually start between one and 36 hours after ingestion of food and can last for days. As noted, some segments of the population face a greater risk and have a higher incidence of food‐borne illness. These are identified as the “vulnerable groups”, and include: children and infants; senior citizens; pregnant women; and people with diabetes, AIDS sufferers, and chemotherapy patients. This study was undertaken in the Hong Kong Special Administrative Region in the People’s Republic of China (PRC) and it examined the extent of food safety gaps in the provision of school meals. Findings of the study suggest that considerable food safety gaps exist, and specific managerial recommendations about how to narrow some of these gaps is given.
CatExpress for small libraries
Authors: Floer Sheila
Published: September 2002

After a short introduction to OCLC’s copy cataloging service CatExpress, the service is explained in more detail. Then use of CatExpress at the Perrot Memorial Library in Old Greenwich, Connecticut is examined to demonstrate the value of this service for smaller libraries. The article concludes with the major advantages, as well as the limitations of CatExpress.
Personal capital and virtual selves
Authors: Harkins Arthur , Fiala Brenda
Published: September 2002

Invention arises from creativity, while innovation arises from invention. Innovation is not the last step in this sequence; innovations must be implemented through small and large changes in organizational practices before they can become operationally successful. The comparatively higher frequency and wider distribution of this process defines an innovation society and its economy. This article proposes a focus on the individual as the first beneficiary of preparatory and on‐the‐job‐services to help evolve innovation societies for coping with five major “divides” currently driving the unequal distribution of global opportunity. To this end, the article proposes developing personal capital through role evolution, rehearsal, and assessment processes supported by “virtual” selves.
On becoming an entrepreneur: an evolving typology
Authors: Alstete Jeffrey W.
Published: September 2002

This paper examines the perceptions of prospective entrepreneurs in light of the possible influence of the post‐Internet boom awareness and the slowing growth of the economy on their attitudes toward founding a business. The study presents and analyzes the responses and ensuing discussion to questions posed to 54 individuals in three college entrepreneurship courses. Using a controlled Internet discussion board, an interactive dialogue developed among participants. According to the qualitative research findings, a majority of participants in the study perceive there is a slight decline in entrepreneurial activity after the widely publicized failure of new e‐businesses that were created in recent years, and the subsequent slowing of the economy. However, there are several reasons why individuals considering entrepreneurship would continue with their goal of founding a business, including greater control of their destiny, increased satisfaction, more money, and creating a legacy for their family and children. Recommendations are made for further qualitative and empirical research of prospective entrepreneurs in follow‐up to these findings.
Neurokinin B Induces Oedema Formation in Mouse Lung Via Tachykinin Receptor‐Independent Mechanisms
Authors: Grant Andrew D. , Akhtar Roksana , Gerard Norma P. , Brain Susan D.
Published: September 2002

The tachykinin neurokinin B (NKB) has been implicated in the hypertension that characterises pre‐eclampsia, a condition where tissue oedema is also observed. The ability of NKB, administered intradermally or intravenously, to induce oedema formation (assessed as plasma extravasation) was examined by extravascular accumulation of intravenously injected 125I‐albumin in wild‐type and tachykinin NK1 receptor knockout mice. Intradermal NKB (30‐300 pmol) caused dose‐dependent plasma extravasation in wild‐type (P < 0.05) but not NK1 knockout mice, indicating an essential role for the NK1 receptor in mediating NKB‐induced skin oedema. Intravenous administration of NKB to wild‐type mice produced plasma extravasation in skin, uterus, liver (P < 0.05) and particularly in the lung (P < 0.01). Surprisingly, the same doses of NKB led to plasma extravasation in the lung and liver of NK1 knockout mice. By comparison, the tachykinin substance P induced only minimal plasma extravasation in the lungs of wild‐type mice. The plasma extravasation produced by NKB in the lungs of NK1 receptor knockout mice was unaffected by treatment with the NK2 receptor antagonist SR48968 (3 mg kg−1), by the NK3 receptor antagonists SR142801 (3 mg kg−1) and SB‐222200 (5 mg kg−1) or by the cyclo‐oxygenase (COX) inhibitor indomethacin (20 mg kg−1). L‐Nitro‐arginine methyl ester (15 mg kg−1), an inhibitor of endothelial nitric oxide synthase (eNOS), produced only a partial inhibition. We conclude that NKB is a potent stimulator of plasma extravasation through two distinct pathways: via activation of NK1 receptors, and via a novel neurokinin receptor‐independent pathway specific to NKB that operates in the mouse lung. These findings are in keeping with a role for NKB in mediating plasma extravasation in diseases such as pre‐eclampsia.
Effects of Perfusion Rate on Permeability of Frog and Rat Mesenteric Microvessels to Sodium Fluorescein
Authors: Montermini D. , Winlove C. P. , Michel C. C.
Published: September 2002

The permeability, PS, to sodium fluorescein (Stokes‐Einstein radius = 0.45 nm) has been measured in single mesenteric capillaries of pithed frogs and anaesthetised rats as perfusion velocity, U, was varied over a range from 400 up to 2000–10 000 μm s−1. PS increased linearly with U. In 20 frog capillaries, mean (± S.E.M.) PS (in μm s−1) = 9.35 (± 1.55)U× 10−5+ 0.244 (± 0.0291). Similarly, in nine rat venules, mean PS= 1.62 (± 0.385)U× 10−4+ 0.375 (± 0.025). The flow‐dependent component of permeability could be reversibly abolished in frog capillaries by superfusing with 100 μM noradrenaline and by superfusing rat venules with the nitric oxide synthase inhibitor, NG‐nitro‐L‐arginine (20 μM). It was shown that changes in microvascular pressure accompanying changes in U during free perfusion could account for only 15 % of the changes in PS, i.e. 85 % of the changes in PS were changes in the permeability coefficient itself. A comparison between the changes in PS with U and the previously described changes in microvascular permeability to K+ with U, suggest that if the flow‐dependent component of permeability is modelled as a population of pores of constant size, these have radii of 0.8 nm. Such a pathway would limit flow‐dependent permeability to small hydrophilic molecules and have minimal effect on net fluid exchange.
NO‐ and non‐NO‐, Non‐Prostanoid‐Dependent Vasodilatation in Rat Sciatic Nerve During Maturation and Developing Experimental Diabetic Neuropathy
Authors: Thomsen Kirsten , Rubin Inger , Lauritzen Martin
Published: September 2002

This study examined NO‐ and non‐NO‐, non‐prostanoid‐dependent pathways of agonist‐induced vasodilatation in streptozotocin (STZ)‐induced diabetic rats and their age‐matched controls at 1–2, 8–10 and 18–20 weeks after induction of diabetes. Using laser Doppler flowmetry, vasodilatory responses to acetylcholine (ACh; 0.1 mM) and morpholino‐sydnonimine (SIN‐1) were determined in the presence of Ringer solution, during inhibition of NO synthase (NOS) and cyclo‐oxygenase (COX) with Nω‐nitro‐L‐arginine (L‐NNA; 1 mM) + indomethacin (10−5 M), and during inhibition of K+ channels, NOS and COX with tetraethylammonium (TEA; 10 mM) + L‐NNA + indomethacin. Basal NOS activity and nerve conduction velocity were also determined. In age‐matched controls, SIN‐1‐induced vasodilatation in the presence of TEA + L‐NNA + indomethacin, basal NOS activity and the initial vasodilatory response to ACh during NOS and COX inhibition all decreased with maturation. In STZ‐induced diabetics, SIN‐1‐induced vasodilatation in the presence of TEA + L‐NNA + indomethacin was impaired immediately after induction of diabetes, but not at 18–20 weeks. NOS activity in STZ‐induced diabetics displayed a transient 2‐fold increase at 8–10 weeks, decreasing to age‐matched control levels at 18–20 weeks. At 18–20 weeks of STZ‐induced diabetes, ACh‐induced vasodilatation during NOS and COX inhibition was prolonged due to increased K+ channel activity and experimental diabetic sensory neuropathy (EDN) had developed. Thus, in sciatic nerve microcirculation of STZ‐induced diabetic rats: (1) diabetic impairment of vasodilatation in response to exogenous NO was transient; (2) non‐NO‐, non‐prostanoid‐dependent vasodilatation and K+ channel activity were augmented in STZ‐induced diabetes; and (3) alterations in NO bioactivity were not related to the development of EDN.
Contribution of a Calcium‐Activated Non‐Specific Conductance to NMDA Receptor‐Mediated Synaptic Potentials in Granule Cells of the Frog Olfactory Bulb
Authors: Hall Benjamin J. , Delaney Kerry R.
Published: September 2002

We studied granule cells (GCs) in the intact frog olfactory bulb (OB) by combining whole‐cell recordings and functional two‐photon Ca2+ imaging in an in vitro nose‐brain preparation. GCs are local interneurones that shape OB output via distributed dendrodendritic inhibition of OB projection neurones, the mitral‐tufted cells (MTCs). In contrast to MTCs, GCs exhibited a Ca2+‐activated non‐specific cation conductance (ICAN) that could be evoked through strong synaptic stimulation or suprathreshold current injection. Photolysis of the caged Ca2+ chelator o‐nitrophenol‐EGTA resulted in activation of an inward current with a reversal potential within the range ‐20 to +10 mV. ICAN in GCs was suppressed by the intracellular Ca2+ chelator BAPTA (0.5–5.0 mM), but not by EGTA (up to 5 mM). The current persisted in whole‐cell recordings for up to 1.5 h post‐breakthrough, was observed during perforated‐patch recordings and was independent of ionotropic glutamate and GABAA receptor activity. In current‐clamp mode, GC responses to synaptic stimulation consisted of an initial AMPA‐mediated conductance followed by a late‐phase APV‐sensitive plateau (100–500 ms). BAPTA‐mediated suppression of ICAN resulted in a selective reduction of the late component of the evoked synaptic potential, consistent with a positive feedback relationship between NMDA receptor (NMDAR) current and ICAN. ICAN requires Ca2+ influx either through voltage‐gated Ca2+ channels or possibly NMDARs, both of which have a high threshold for activation in GCs, predicting a functional role for this current in the selective enhancement of strong synaptic inputs to GCs.
Measurement of Hydraulic Conductivity of Single Perfused Rana Mesenteric Microvessels between Periods of Controlled Shear Stress
Authors: Neal C. R. , Bates D. O.
Published: September 2002

A new method for the determination of hydraulic conductivity in individually perfused microvessels in vivo is described. A vessel is cannulated at both ends with glass micropipettes and the fluid filtration rate across the vessel wall measured from the velocities of red cells when the pressure in the micropipettes is balanced. Hydraulic conductivity measured using this double‐cannulation method (2.6 (± 0.9) × 10−7 cm s−1 cmH2O−1) was not significantly different from that measured using a previously described technique in the same vessel (2.4 (± 0.9) × 10−7 cm s−1 cmH2O−1 using the Landis‐Michel method). Shear stress on the vessel wall was controlled by changing the difference between the inflow and outflow pressures during periods of perfusion. The volume flow through the vessel, calculated from red cell velocity either in the vessel or in the pipette, was linearly proportional to this pressure difference. Higher flow rates could only be calculated from red cell velocities in the micropipette. There was no relationship between the imposed shear stress and intervening measurements of hydraulic conductivity (r= 0.029). This novel technique has advantages over the Landis‐Michel method, which include the control of outflow resistance, the measurement of shear stress under conditions of controlled pressure, the elimination of compression damage to the vessel (since vessel occlusion is not necessary) and assessment of hydraulic conductivity over the same length of vessel throughout the experiment. The measurement of solute concentrations by indwelling micropipette electrodes and the collection of perfusate for analysis are other possibilities.
A new approach to off‐line setup corrections: Combining safety with minimum workload
Authors: de Boer J. C. J. , Heijmen B. J. M.
Published: September 2002

Off‐line patient setup correction protocols based on electronic portal images are an effective tool to reduce systematic patient setup errors. Recently, we have introduced the no action level (NAL) protocol which establishes a significant error reduction at a very small workload. However, this protocol did not include an explicit verification of the applied setup corrections. Systematic mistakes in the execution of setup corrections (e.g., a setup correction is always executed in the direction whereas a correction in the direction was prescribed) may introduce large systematic setup errors (irrespective of the setup protocol) and may seriously impair treatment outcome. We have therefore extended the NAL protocol with a correction verification (COVER) stage, solely aimed at detecting such mistakes. In short, COVER tests the magnitude of the postcorrection setup error in each relevant direction. If these residue errors are below the acceptance threshold T, no more electronic portal images are required and the protocol has finished. If not, the origin of this result should be investigated; if no obvious mistakes are present, the procedure is repeated for one more treatment fraction. If the residue setup errors are confirmed to be larger than T, the entire protocol is restarted. Using both Monte Carlo simulations and analytical calculations, we performed a risk analysis and evaluated the workload for various choices of T. A threshold where is the mean standard deviation of the random setup errors, ensured that (1) COVER introduces only a small additional workload (1.05 measurement per patient, while the absolute minimum is 1.0) and (2) serious correction mistakes are detected with high probability. Even if setup corrections are wrongly applied in each patient (worst case scenario), COVER ensures that the final distribution of systematic errors is not wider than the precorrection distribution of systematic errors; for realistic frequencies of correction mistakes (≪1 per patient) this distribution becomes much more narrow. The combination of NAL and COVER thus provides a highly efficient as well as safe method to reduce systematic setup errors.
Simultaneous iterative reconstruction of emission and attenuation images in positron emission tomography from emission data only
Authors: Landmann M. , Reske S. N. , Glatting G.
Published: September 2002

For quantitative image reconstruction in positron emission tomography attenuation correction is mandatory. In case that no data are available for the calculation of the attenuation correction factors one can try to determine them from the emission data alone. However, it is not clear if the information content is sufficient to yield an adequate attenuation correction together with a satisfactory activity distribution. Therefore, we determined the log likelihood distribution for a thorax phantom depending on the choice of attenuation and activity pixel values to measure the crosstalk between both. In addition an iterative image reconstruction (one‐dimensional Newton‐type algorithm with a maximum likelihood estimator), which simultaneously reconstructs the images of the activity distribution and the attenuation coefficients is used to demonstrate the problems and possibilities of such a reconstruction. As result we show that for a change of the log likelihood in the range of statistical noise, the associated change in the activity value of a structure is between 6% and 263%. In addition, we show that it is not possible to choose the best maximum on the basis of the log likelihood when a regularization is used, because the coupling between different structures mediated by the (smoothing) regularization prevents an adequate solution due to crosstalk. We conclude that taking into account the attenuation information in the emission data improves the performance of image reconstruction with respect to the bias of the activities, however, the reconstruction still is not quantitative.
Comparison of four methods for assessing patient effective dose from radiological examinations
Authors: Theocharopoulos Nicholas , Perisinakis Kostas , Damilakis John , Varveris Haralambos , Gourtsoyiannis Nicholas
Published: September 2002

Three methods of indirect effective dose estimation were reviewed and compared to a direct effective dose determination method. An anthropomorphic phantom and thermoluminescence dosimetry were used to obtain dosimetric data associated with anterior–posterior (AP) abdominal radiography, posterior–anterior (PA) chest radiography, PA head radiography, and AP heart fluoroscopy. Effective dose was determined using: (i) organ specific dose values directly determined by thermoluminescence dosimeters, (ii) data published by National Radiological Protection Board (NRPB) and entrance surface dose (ESD), (iii) NRPB data and dose area product (DAP), (iv) energy imparted derived from DAP. The effective dose values estimated from the Rando phantom measurements were 161, 32.3, and 8.4 μSv/projection for the abdomen, chest, and head radiographs, respectively. Cardiac fluoroscopy yielded an effective dose value of 111 μSv/min. The effective dose values obtained indirectly using NRPB data and DAP were in good agreement with directly assessed values in all simulated exposures (difference <8%). The effective doses using NRPB data and ESD values differed from directly assessed values by less than 15% for the radiographic exposures and 60% for heart fluoroscopy. The energy imparted method yielded 136, 31, and 6.6 μSv/projection for the abdomen, chest, and head radiographs, respectively, and 111 μSv/min for heart fluoroscopy. Indirect patient effective dose determination using the NRPB dosimetric data and the measured value of incident radiation allows for reliable patient effective dose estimates. The use of DAP rather than ESD is recommended because it yields accurate results even for complex radiologic exposures involving fluoroscopy. The value of energy imparted may be used for the accurate determination of patient effective dose, especially when specific organ dose values are not of interest. The calculation of energy imparted with the use of EAP provides a reliable starting point for estimation of effective dose from radiologic examinations for which dosimetric data are not provided by NRPB.
Algorithms for modeling anatomic and target volumes in image‐guided neurosurgery and radiotherapy
Authors: Alakuijala Jyrki
Published: September 2002

The use of image‐guidance in surgery and radiotherapy has significantly improved patient outcome in neurosurgery and radiotherapy treatments. This work developed volume definition and verification techniques for image‐guided applications, using a number of algorithms ranging from image processing to visualization. Stereoscopic visualization, volumetric tumor model overlaid on an ultrasound image, and visualization of the treatment geometry were experimented with on a neurosurgical workstation. Visualization and volume definition tools were developed for radiotherapy treatment planning system. The magnetic resonance inhomogeneity correction developed in this work, possibly the first published data‐driven method with wide applicability, automatically mitigates the radio‐frequency (RF) field inhomogeneity artifact present in magnetic resonance images. Correcting the RF inhomogeneity improves the accuracy of the generated volumetric models. Various techniques to improve region growing are also presented. The simplex search method and combinatory similarity terms were used to improve the similarity function with a low additional computational cost and high yield in region correctness. Moreover, the effects of different priority queue implementations were studied. A fast algorithm for calculating high‐quality digitally reconstructed radiographs has been developed and shown to better meet typical radiotherapy needs than the two alternative algorithms. A novel visualization method, beam's light view, is presented. It uses texture mapping for projecting the fluence of a radiation field on an arbitrary surface. This work describes several improved algorithms for image processing, segmentation, and visualization used in image‐guided treatment systems. These algorithms increase the accuracy of image‐guidance, which can further improve the applicability and efficiency of image‐guided treatments.
A Newton–Faraday approach to electromagnetic energy and angular momentum storage in an electromechanical system
Authors: Gauthier N.
Published: September 2002

The dynamical behavior of a simple rotating mechanical system that carries a charge on its surface and is accelerated by a falling mass is considered. It is shown that a fraction of the total kinetic energy is missing and that exactly this fraction of energy has been stored in the magnetic field distribution. The conservation of electromagnetic angular momentum is also discussed on the same basis. The concept of an electromagnetic moment of inertia is introduced to establish a close parallel with the concept of mechanical moment of inertia in classical dynamics. It is suggested that the present mechanical system can be used as a teaching tool at the early-to-intermediate level of an undergraduate physics program to ease the transition from the dynamics of rigid bodies to that of more abstract fields.
The homopolar motor: A true relativistic engine
Authors: Guala-Valverde Jorge , Mazzoni Pedro , Achilles Ricardo
Published: September 2002

This article discusses experiments which enable the identification of the seat of mechanical forces in homopolar-machines reported earlier in this journal [J. Guala-Valverde and P. Mazzoni, Am. J. Phys. 63, 228–229 (1995); J. Guala-Valverde, P. Mazzoni, and K. Blas, ibid. 65, 147–148 (1997)]. We provide a suitable variation on a recent work “The Unipolar Dynamotor: A Genuine Relational Engine” [J. Guala-Valverde and P. Mazzoni, Apeiron 8, 41–52 (2001)], where “relational” implies “absolutely relativistic.” Our view agrees with both Weber’s recognition in the 19th century of the importance of relative motion in electromagnetic phenomena [A. K. T. Assis, Electrodynamics (Kluwer, Dordrecht, 1994)] and Einstein’s 1905 statement concerning electromagnetism [Ann. Phys. 17, 891–921 (1905)].
An "Endless" Route to Cyclic Polymers
Authors: Bielawski Christopher W. , Benitez Diego , Grubbs Robert H.
Published: September 2002

A new synthetic route to cyclic polymers has been developed in which the ends of growing polymer chains remain attached to a metal complex throughout the entire polymerization process. The approach eliminates the need for linear polymeric precursors and high dilution, drawbacks of traditional macrocyclization strategies, and it effectively removes the barrier to producing large quantities of pure cyclic material. Ultimately, the strategy offers facile access to a unique macromolecular scaffold that may be used to meet the increasing demand of new applications for commercial polymers. As a demonstration of its potential utility, cyclic polyethylenes were prepared and found to exhibit a variety of physical properties that were distinguishable from their linear analogs.
COHERENT DYNAMICS OF AN ASYMMETRIC DOUBLE QUANTUM WELL
Authors: CAMACHO B. A. S. , GUTIERREZ R. M.
Published: September 2002

Coherent optical effects coming from two excited levels in an engineered asymmetric double quantum well have been detected with duration of picoseconds.1 This short decoherence time is related with the dephasing time. Although dephasing is mainly due to electron–electron scattering and LO phonons in polar semiconductor provide the dominant inelastic scattering mechanism, a study of the elastic scattering with phonons during the coherent stage is also needed to understand the coherent electron dynamics. In this work is presented a microscopic study of the elastic scattering rates due to electron–LO-phonon interaction, which are obtained for each of the three conduction subbands on a tailored double asymmetric quantum well by using the imaginary part of the polaron self-energy within a many-body formalism. Both absorption and emission rates are calculated. The dephasing times for different electronic states in a given heterostructure can be very different, depending on the material, geometry, temperature, carrier density, etc. As an important geometric parameter is chosen the barrier width, which tunes the energy differences between the two upper levels or tunneling times. Electron density effect is studied through screening. Two limits are presented — unscreened and static screening. It is found that after an ultrashort pulse the absorption and emission scattering rates in each level are very different from the scattering rates in equilibrium and that screening effects can be used as coherent control mechanism.
POROUS SILICON DIELECTRIC FUNCTION MODELING FROM EFFECTIVE MEDIUM THEORIES
Authors: CAMPOS A. M. , TORRES J. , GIRALDO J. J.
Published: September 2002

The spectral variation of the effective dielectric constant in porous silicon thin films is modeled using effective medium theories. The pores in the material are supposed to be spheroid prolate inclusions in a homogeneous matrix. We employ modified Maxwell–Garnett and Bruggeman expressions obtained from previous work. Fitting to experimental reflectance spectra and the refractive index at the visible spectral range is satisfactory. Best results in both models are obtained using the spheroidal inclusions of 0.9 eccentricity. The best adjusted porosity values for two samples with different parameters of preparation are 47% with Bruggeman's expression and 67% with Maxwell–Garnett's expression, which are very close to the experimental ones of 44% and 67% respectively, obtained through gravimetric methods. Our model is useful for determining and for checking the influence of the preparation parameters on the optical and structural properties.
FIRST PRINCIPLES CALCULATIONS OF THE ADSORPTION OF GROUP III METALS ON Si(001) AT HIGH TEMPERATURE
Authors: COTZOMI-PALETA J. , COCOLETZI GREGORIO H. , TAKEUCHI NOBORU
Published: September 2002

First principles total energy calculations are performed to investigate the Si(001)-(3 × 4) reconstruction induced by the adsorption of group III metals (Ga, Al and In) when deposited at high temperatures. We have considered different models in our study and we have found that the pyramid-like structure proposed by Bunk et al. for In on Si(001) yields the most stable atomic configuration in all cases. We present a detailed description of this surface reconstruction, and compare the structural parameters for Al, Ga and In.
OPTICAL AND ELECTRICAL PROPERTIES OF PURE AND RARE-EARTH-DOPED nc-Si/SiO2 COMPOSITES PREPARED BY RF COSPUTTERING
Authors: FONSECA LUIS F. , RESTO OSCAR , NERY GUILLERMO , POSADA YURY , WEISZ ZVI , LIU HUIMIN , MAHFOUD AZIZ
Published: September 2002

Photoluminescence and optical absorption spectra from silicon nanoparticles embedded in SiO 2 are presented. The material was synthesized by RF cosputtering. The samples were prepared with a variety of Si volume concentrations and annealing temperatures. The results are discussed by correlating them with the preparation conditions, the nanostructure, and comparing them with the results obtained for porous silicon. The conductivity, photoconductivity and minority carriers diffusion length were also obtained for samples with different Si content and average size of the nanostructure. The study gives information about the percolation threshold and the electrical transport mechanisms in the composite. Eu- and Er-doped samples were finally prepared and studied for their PL response. A clear correlation between the enhancement of the Er +3 infrared emission and the presence of the silicon nanostructure is shown. In the case of Eu-doped samples, emissions from Eu +3 or Eu +2 are observed depending on the characteristics of the host (when exciting with 514.5 nm laser radiation). Degenerate four-wave mixing signals suggest a strong interaction between the free carriers of the silicon nanostructure and the Eu ions that can promote the emission from Eu +2 under illumination.
CHEMICAL AND STRUCTURAL CHARACTERIZATION OF Co–Ni SILICIDE THIN FILMS
Authors: GARCIA-MENDEZ M. , ELIZONDO-VILLARREAL N. , FARIAS M. H. , HIRATA G. A. , BEAMSON G.
Published: September 2002

By means of pulsed laser deposition we prepared Co–Ni/p-Si thin films upon a Si(100) substrates. Samples were thermally treated in vacuum in order to promote silicide formation. From X-ray photo-electron spectroscopy (XPS) analysis, we detected chemical shifts of the Co2p and Ni2p transitions, characteristic of silicide binding energy, at the respective ranges of 778.3–778.6 and 853.2–853.6 eV. By means of high resolution transmission electron microscopy (HRTEM) we identified some nanocrystalline regions belonging to CoSi 2, Ni 2 Si and NiSi 2 structures. We also appreciate that the resulting films are of a polycrystalline nature.
NEW MATERIALS USED AS OPTICAL WINDOW IN THIN FILM SOLAR CELLS
Authors: GORDILLO G.
Published: September 2002

The purpose of this work is to investigate new materials which present good properties to be used as optical window and buffer layer in thin film solar cells based on CdTe and CuInSe 2. As potential candidates for optical windows, two different bilayer systems were studied: ZnO/In x Se y and ZnO/ZnSe. They are planned to be used later in the fabrication of solar cells with structures CuInSe 2/ In x Se y/ ZnO and ZnO/ZnSe/CdTe.

The methods used to prepare the different window materials, as well as the technological stages of the solar cell fabrication, will be described. Additionally, the optical and morphological properties of the window systems will be studied through transmittance and atomic force microscopy (AFM) measurements.

Preliminary results obtained with Cu(In,Ga)Se 2 solar cells, fabricated using ZnO/In x Se y as optical window, will be reported. They will be compared with those obtained using ZnO/CdS as optical window, which is regularly used in this type of cells.
EFFECT OF THE CdCl2 TREATMENT ON THE MORPHOLOGY AND STRUCTURAL PROPERTIES OF CdTe THIN FILMS DEPOSITED BY THE CSS METHOD
Authors: INFANTE H. , GORDILLO G.
Published: September 2002

CdTe thin films deposited by the CSS (close spaced sublimation) method, with adequate properties to be used as absorber layer in solar cells, were submitted to a chemical treatment in a saturated CdCl2 solution, followed by thermal annealing in air at 400°C, in order to improve the electronic properties. The effect of chemical and thermal treatments on the morphological and crystallographic properties was studied through atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements.

The studies revealed that the CdTe grows in the cubic phase and that the postdeposition treatments affect the morphology as well as the crystallographic properties; the effect on the morphology is significantly stronger. Increase of the grain size and roughness was observed in samples treated chemically and thermally. On the other hand, no effects were identified on the crystalline structure as induced by the treatments, although recrystallization was observed after thermal annealing.
DEPOSITION, OPTICAL AND STRUCTURAL CHARACTERIZATION OF SnO2:F/CdS AND ZnO/CdS STRUCTURES USED AS OPTICAL WINDOWS IN SOLAR CELLS
Authors: CAICEDO L. M. , MORENO L. C. , SANDINO J. W. , GORDILLO G.
Published: September 2002

The purpose of this work is to find the conditions for fabricating SnO 2: F/CdS and ZnO/CdS bilayer structures with adequate properties to be used as optical windows in solar cells based on CdTe and CuInSe 2 thin films. In both types of structures the CdS layer is deposited by chemical bath deposition (CBD) and by the evaporation method; the SnO 2: F and ZnO layers are deposited by spray pyrolysis and reactive evaporation, respectively. The influence of the preparation methods on the optical and structural properties of each of the layers constituting the bilayer structures, was studied through spectral transmittance and X-ray diffraction (XRD) measurements.

The studies revealed that the spectral transmittance of the ZnO/CdS system is significantly greater than that of the SnO 2: F/CdS structure, indicating that the first type of structure is more suitable for using as optical window in solar cell fabrication.
EFFECTS OF FINITE REACTION RATES ON THE KINETIC PHASE TRANSITIONS IN THE CATALYTIC OXIDATION OF CARBON MONOXIDE
Authors: LÓPEZ-CARREÑO L. D.
Published: September 2002

Oxidation of carbon monoxide is one of the most extensively studied heterogeneous catalysis reactions, being important among other applications in automobile-emission control. Catalytic oxidation of carbon monoxide on platinum (111) surface was simulated by the Monte Carlo technique following an extended version of the model proposed by Ziff, Gulari and Barshad (ZGB). In the simulation, a simple square two-dimensional lattice of active sites replaces the surface of the catalyst. Finite reaction rates for (i) diffusion of the reactive species on the surface, (ii) reaction of a CO molecule with an oxygen atom in a nearest neighbor site, and (iii) desorption of unreacted CO molecules, have been taken into account. The produced CO 2 desorbs instantly. The average coverage of O, CO and the CO 2 production rate for a steady state configuration, as a function of the normalized CO partial pressure (P CO ), shows two kinetic phase transitions. In the ZGB model these transitions occur at P CO ≈ 0.39 and P CO ≈ 0.53. For 0.39 < P CO < 0.53 a reactive ( CO 2 production) steady state is found. Outside of the interval, the only steady state is a poisoned catalyst of pure CO or pure O. Our results show that finite reaction rates shift the values in which these phase transitions occur.
LOCAL MAGNETIC MOMENTS OF Fe1/CrN NANOINCLUSIONS EMBEDDED IN BULK Fe
Authors: MORÁN-LÓPEZ J. L. , ALVARADO-LEYVA P. G. , MONTEJANO-CARRIZALES J. M.
Published: September 2002

Local magnetic moments of Fe 1/ Cr N inclusions in an Fe matrix are calculated as a function of the Cr number of atoms N at zero temperature, and for N ≤ 64. We use a realistic spd-band Hamiltonian to determine their magnetic properties. The local magnetic moments μ(i) at the various cluster sites i are calculated self-consistently in the unrestricted Hartree–Fock approximation. The matrix Fe atoms couple always antiferromagnetically with the Cr atoms. The μ(i) of Cr atoms at the interface are enhanced by the presence of Fe atoms in their first nearest neighbor shell. In most cases the Fe moments close to the cluster are reduced. A remarkable interplay between the antiferromagnetism of Cr and the ferromagnetism of Fe is obtained.
SPACE-CHARGE LAYERS AND SURFACE STATES IN p-TYPE CRYSTALLINE SILICON
Authors: RAMÍREZ-PORRAS A. , MANY A. , GOLDSTEIN Y. , WEISZ S. Z.
Published: September 2002

Pulse measurements on the silicon/electrolyte interface have been used to study space-charge layers and surface states on the (100) faces of p-type silicon. The techniques used enable both the creation and study of space-charge layers at the semiconductor surface, ranging from large-depletion to strong-accumulation conditions. They also permit a straightforward separation of the different components of the induced charge at the silicon/electrolyte interface, so as to yield the variation of both the free-electron density in the space-charge layer and the density of occupied surface states with barrier height. The measured space-charge characteristics are in very good agreement with theory. The data in strong-accumulation layers indicate the presence of an insulating buffer layer (such as an oxide), 3–4 monolayers thick. As to surface states, we find that for CP-4-etched silicon, a distribution of states exists ~ 0.34 eV above the valence-band edge, with total density ~ 6 × 1011 cm -2.
ABSORPTION SPECTRUM OF AN EXCITON IN AN InxGa1 - xAs/GaAs QUANTUM DOT IN THE PRESENCE OF A MAGNETIC FIELD
Authors: RODRÍGUEZ J. C. , FONSECA K. , REY-GONZÁLEZ R. R.
Published: September 2002

We calculate the absorption spectrum of a single exciton, confined in an In x Ga 1 - x As/GaAs disk-shaped quantum dot, as a function of the strength of an applied magnetic field. Exciton eigenstates are obtained by numerical diagonalization of the Hamiltonian, within the effective mass approximation. A correction in the expression of the Coulomb interaction matrix elements is verified.
GROWTH EQUATIONS, DISCRETE MODELS AND MBE EXPERIMENTS
Authors: SÁNCHEZ J. R. , MIRABELLA D. A. , ALDAO C. M.
Published: September 2002

The question of the validity of the scaling ansatz in discrete deposition models and their connection with the scaling exponents of continuum differential equations is addressed. We specifically focus on the scaling properties of the Wolf–Villain type models and, as an extension of this model, on the influence of attractive and repulsive interactions up to second neighbors on the scaling relation. As an example of technological relevance, we present the evolution of steps in the vicinal (100) surface of Si during deposition at relatively low temperatures. We have found that, in general, one should not expect that discrete models, as well as real crystals, exhibit scaling.
Delineation of the Role of Pre-β
1
-HDL in Cholesterol Efflux Using Isolated Pre-β
1
-HDL
Authors: Sviridov Dmitri , Miyazaki Osamu , Theodore Kally , Hoang Anh , Fukamachi Isamu , Nestel Paul
Published: September 2002

Objective—

The role of pre-β
1
-high density lipoprotein (pre-β
1
-HDL) in cholesterol efflux was investigated by separating human plasma into purified pre-β
1
-HDL and pre-β
1
-HDL–deficient plasma by using a monoclonal antibody specifically reacting with pre-β
1
-HDL.

Methods and Results—

When compared with whole plasma, pre-β
1
-HDL–deficient plasma was equally efficient in promoting cholesterol efflux from human skin fibroblasts and THP-1 human macrophage cells. When added at the same apolipoprotein A-I concentration, pre-β
1
-HDL was less effective than whole plasma in promoting cholesterol efflux from fibroblasts but equally effective in promoting cholesterol efflux from THP-1 cells. However, pre-β
1
-HDL–deficient plasma reconstituted with 16% pre-β
1
-HDL was more active than whole plasma, demonstrating that pre-β
1
-HDL does promote cholesterol efflux actively. The amount of cellular cholesterol present in reisolated pre-β
1
-HDL was 1.5- to 2-fold greater after incubation of the cells with whole plasma than after incubation of the cells with pre-β
1
-HDL–deficient plasma or plasma treated with the anti–pre-β
1
-HDL antibody. However, the anti–pre-β
1
-HDL antibody did not inhibit cholesterol efflux.

Conclusions—

We conclude that whereas pre-β
1
-HDL is capable of taking up cellular cholesterol, its presence in plasma is not essential for cholesterol efflux, at least in vitro. Instead, pre-β
1
-HDL may be the first product of apolipoprotein A-I lipidation during the formation of HDL but may not play a major role in transferring cellular cholesterol to HDL.
Effects of Continuous Combined Hormone Replacement Therapy on Inflammation in Hypertensive and/or Overweight Postmenopausal Women
Authors: Koh Kwang Kon , Ahn Jeong Yeal , Jin Dong Kyu , Yoon Byung-Koo , Kim Hyung Sik , Kim Dae Sung , Shin Mi-Seung , Son Ji Won , Choi In Suck , Shin Eak Kyun
Published: September 2002

Objective—

We observed that estrogen did not show cardioprotective benefits in type 2 diabetic postmenopausal women. We hypothesized that hypertensive and/or overweight women may be less likely to realize cardiovascular benefits from estrogen.

Methods and Results—

We administered micronized progesterone (MP) 100 mg or medroxyprogesterone acetate (MPA) 2.5 mg with conjugated equine estrogen (CEE) 0.625 mg daily during 2 months to 35 hypertensive and/or overweight postmenopausal women with a randomized, double-blind, crossover design. With significant changes of lipoproteins, CEE+MP or MPA significantly improved flow-mediated dilation and reduced plasma E-selectin, intercellular adhesion molecule type-1, monocyte chemoattractant protein-1, and tumor necrosis factor-α levels (
P
<0.001,
P
<0.001,
P
=0.021,
P
<0.001, and
P
<0.001 by ANOVA, respectively), but not C-reactive protein and fibrinogen levels. Of note, there were no significant differences between each therapy regarding these effects. However, the magnitude of improvement of flow-mediated dilation in these women was less than in healthy postmenopausal women and more than in diabetic postmenopausal women reported by our previous studies. The effects of CEE+MP or MPA on inflammatory markers were comparable to healthy postmenopausal women, but not comparable to diabetic postmenopausal women.

Conclusions—

Estrogen combined with synthetic progestin significantly improved flow-mediated brachial artery dilator response and reduced inflammation markers in hypertensive and/or overweight women, comparable to estrogen combined with natural progesterone.
Postprandial Enrichment of Remnant Lipoproteins With ApoC-I in Healthy Normolipidemic Men With Early Asymptomatic Atherosclerosis
Authors: Björkegren Johan , Silveira Angela , Boquist Susanna , Tang Rong , Karpe Fredrik , Bond M. Gene , de Faire Ulf , Hamsten Anders
Published: September 2002

Objectives—

Recently, we reported that exaggerated postprandial triglyceridemia in normolipidemic patients with coronary artery disease is associated with enrichment of remnant lipoproteins with apolipoprotein C-I (apoC-I). In this study, the number and composition of chylomicron remnants and very low density lipoproteins (VLDLs) were examined in 30 asymptomatic normolipidemic 50-year-old men with and without early carotid atherosclerotic lesions.

Results and Methods—

Intima-media thickness of the far wall of the common carotid artery was determined by B-mode ultrasound. Triglyceride-rich lipoproteins were subfractionated by density gradient ultracentrifugation and separated into VLDL and chylomicron remnant fractions by immunoaffinity chromatography. The postprandial triglyceridemia and increase in triglyceride-rich lipoprotein particle number (ie, apolipoprotein B concentrations) were not exaggerated in men with early atherosclerosis. In contrast, their large (Svedberg flotation rate 60 to 400) and small (Svedberg flotation rate 20 to 60) chylomicron remnants and VLDL were greatly enriched with apoC-I, and their small chylomicron remnants and VLDL particles were relatively enriched with cholesterol. Moreover, the number of apoC-I molecules on small chylomicron remnants was strongly associated with the degree of atherosclerosis.

Conclusions—

Early asymptomatic atherosclerosis in normolipidemic men without exaggerated postprandial triglyceridemia is associated with the enrichment of postprandial chylomicron and VLDL particles with apoC-I. Therefore, it is conceivable that the apoC-I content of lipoprotein remnants may serve as an early marker of coronary artery disease risk.