bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soft photo structuring of porous silicon in water
Authors: Juan M. , Bouillard J. S. , Plain J. , Bachelot R. , Adam P. M. , Lerondel G. , Royer P. 
Published: April 2007

AbstractWe report on local photo‐induced patterning of porous silicon in water. Scanning probe microscopy images of the sample surface after illumination show that the emission properties as well as the topography are modified according to the interferometric illumination pattern. Local photo‐oxidation is believed to be at the origin of these modifications. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New porosification of n‐InP and n‐GaAs in acidic liquid ammonia at 223 K: unusual morphologies associated to distinguished electrochemical behaviours
Authors: Gonçalves Anne‐Marie , Santinacci Lionel , Eb Alexandra , David Caroline , Mathieu Charles , Herlem Michel , Etcheberry Arnaud 
Published: April 2007

AbstractIn this paper we report on galvanostatic pore formation on both n‐InP and n‐GaAs in acidic liquid ammonia (223 K). Quantitative analyses by atomic absorption have revealed two different dissolution mechanisms (involving 6 or 8 holes) without secondary reaction. Electrochemical behaviours have also shown diverse evolutions. Potential oscillations were observed onto InP while a constant voltage is measured for GaAs. Distinguished pore morphologies observed by scanning electron microscopy have confirmed the different porosification processes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Alkaline etching of macroporous silicon
Authors: Lehmann Volker 
Published: April 2007

AbstractSquare pore cross‐sections and pore arrays of high porosity can be produced by subsequent alkaline etching of macroporous silicon membranes. The dependence of pore geometry on etching time, solution temperature and composition is investigated. The produced membranes offer new roads to investigate the formation of pyramidal hillocks during alkaline etching; an effect which is known for half a century, but not understood in detail. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control of charge carrier density in mesoporous silicon by adsorption of active molecules
Authors: Kashkarov P. K. , Osminkina L. A. , Konstantinova E. A. , Vorontsov A. S. , Pavlikov A. V. , Timoshenko V. Yu. 
Published: April 2007

AbstractWe demonstrate that adsorption of donor‐like and acceptor‐like molecules could be used to control the free charge carrier type and density in mesoporous silicon films. Fourier‐transform infrared spectroscopy and electron paramagnetic resonance technique are used to investigate the free charge carriers and surface defects (Pb‐like centers), respectively, in porous films formed from crystalline Si substrate of different conductivity type and doping level. It is shown that the carrier type (electron or hole) and concentration in mesoporous silicon are depended on (i) molecule partial pressure, (ii) doping level of the substrate; (iii) density of defects‐silicon dangling bonds. The free hole concentration in p‐type mesoporous silicon is found to be changed in the range from 1017 to 3 × 1019 cm–3 by the adsorption of acceptor‐like molecules. The donor‐like molecule adsorption can switch the type of major carriers from holes to electrons. The obtained results are explained by considering the adsorption‐induced formation of surface states in Si nanocrystals assembling mesoporous silicon. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Porous silicon as a cell interface for bone tissue engineering
Authors: Sun Wei , Puzas J. Edward , Sheu Tzong‐Jen , Fauchet Philippe M. 
Published: April 2007

AbstractA novel cell interface has been constructed on porous silicon. We have demonstrated that nano‐ to macro‐scale porous architectures have promising osteoconductive potentials. Macroporous silicon (pore opening 1–2 µm) is especially favorable for osteoblast adhesion, growth, protein synthesis and mineralization. An electronic/optoelectronic controllable medical implant with both scaffolding and drug delivery functions may be created for orthopaedic tissue engineering with this material. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Integrated inductors on porous silicon
Authors: Contopanagos H. , Nassiopoulou A. G. 
Published: April 2007

AbstractWe examine porous Si as a thick RF‐isolation layer for on‐chip inductors and separate the loss sources that downgrade the Q factors into their material components, namely Si substrate loss and metal types common to standard CMOS technologies. First we validate theoretical designs with measurements in standard 0.18 μm CMOS technology. Then we examine the effect of a porous Si substrate on a fixed metal layout of a 2‐metal optimized inductor design compatible either with 0.18 μm CMOS technology using Aluminum or with 0.13 μm CMOS technology using Copper metallization. For typical on‐chip inductor layouts of (200–300 μm)2, we show that a 50 μm thick porous Si layer produces negligible current distributions inside the underlying lossy Si substrate, compared to the ones without it, which maintain high values throughout a large lateral extent of the die. In Al technology, a fixed inductor layout produces Q ‐factor enhancements of the order of 50%, compared to the case where no porous Si layer is used. In a 0.13 μm‐compatible CMOS technology using Cu on porous Si, the resulting Q ‐factors increase by a factor of 2 and reach values of 30 or more in the 3 GHz frequency range. For porous‐Si‐isolated inductors we compare the effect of metal losses and show that the resulting Q ‐factors scale with the metal conductivity. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Novel microfluidic flow sensor based on a microchannel capped by porous silicon
Authors: Pagonis D. N. , Petropoulos A. , Kaltsas G. , Nassiopoulou A. G. , Tserepi A. 
Published: April 2007

AbstractThis work concerns the fabrication, modeling and characterization of a novel microfluidic flow sensor based on a microchannel capped with a porous silicon membrane, on top of which the sensor active elements are integrated. The microchannel is formed through a two‐step anodization process. In the first step a mesoporous silicon layer is formed on a lithographically defined area, while in the second step a channel is formed underneath the porous layer by electropolishing. The channel is buried into bulk silicon and capped with a free‐standing porous silicon layer, which is co‐planar with the Si substrate. The overall developed process for the formation of the device will be described and simulation and device characterization results will be presented. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The role of quantum confinement and surface chemistry in silicon nanocrystals at the strong confinement regime
Authors: Sa'ar A. , Dovrat M. , Jedrzejewsky J. , Popov I. , Balberg I. 
Published: April 2007

AbstractUsing infrared photo‐induced absorption (PIA) spectroscopy, we have found a remarkable correlation between inter‐sub‐level (ISL) optical transitions and the photoluminescence (PL) from silicon nanocrystals. Our results indicate that the quantized electronic sublevels of the nanocrystals are resonantly coupled to surface vibrational modes via a polarization field produced by coherent longitudinal polar vibrations. The model and the experimental results support our findings that the mechanism responsible for the efficient PL from silicon nanocrystals should be assigned to inhibition of nonradiative channels rather than enhancement of radiative transitions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Porous surface statistical characterization via fluorescence correlation spectroscopy
Authors: Plain J. , Jaffiol R. , Lerondel G. , Royer P. 
Published: April 2007

AbstractThe characterization of the porosity or of the pore density is a very important issue for porous materials. We report on a new technique allowing a direct measure of the surface pore density. The number of pores on porous silicon substrates has been measured using fluorescence correlation spectroscopy, a technique that is generally applied in solution to study molecules diffusing through a small observation volume. This technique is used to measure the surface density of luminescent pores in a mesoscopic porous silicon layer. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Integrated inductors on porous silicon
Authors: Contopanagos H. , Nassiopoulou A. G. 
Published: April 2007

AbstractThe cover picture illustrates the effective use of a thick porous silicon layer as an integrated micro‐plate for RF isolation on a silicon substrate, proposed by Harry Contopanagos and Androula Nassiopoulou in their Original Paper [1] in the current issue. What is plotted is the magnitude of the current distribution (colour coded from blue (low) to high (red) values) on the metallization and on a screen 50 µm underneath the bottom oxide layer of a 2‐metal integrated CMOS‐compatible inductor on bulk silicon (lower right) and on a 50 µm thick porous silicon layer (upper left) for a frequency of 2.5 GHz.Inductors were designed in a standard 0.13 µm CMOS technology. Efficient RF isolation is produced by the porous Si layer, as evidenced by the virtual elimination of surface currents relative to the case of standard CMOS, indicating virtually complete substrate shielding by a 50 µm thick porous Si layer for the relevant size scale. The quality factor of the inductor with the use of the porous Si layer is increased by 100%, reaching a maximum value of 33 for the design shown.The first author of the article is a visiting senior researcher at the Institute of Microelectronics (IMEL), National Center for Scientific Research “Demokritos” (Athens, Greece). His research focuses on electromagnetics and microwave engineering, artificial materials and photonic crystals, wireless front ends, antennas and high‐frequency analog integrated circuits.
An optical excitation study of Ru‐, Rh‐, Re‐ and Os‐doped Bi12SiO20 crystals
Authors: Skorikov V. M. , Milenov T. I. , Egorysheva A. V. , Rafailov P. M. , Dudkina T. D. , Veleva M. N. , Vasil'ev A. Ya. , Gospodinov M. M. 
Published: April 2007

AbstractWe studied the influence of doping with 4d and 5d elements on the optical and photo‐induced properties of Bi12SiO20 (BSO) crystals. Doping with Ru, Rh and Re does not significantly influence BSO absorption spectra as well as photo‐induced absorption and photocurrent in BSO. On the other hand, doping with Os with concentration of 0.0004 mass% increases by more than an order of magnitude the illumination response time, the strength of the photochromic effect and photocurrent, all this being accompanied by only a slight change of the absorption coefficient as compared to undoped BSO. The observed effects are explained in the framework of the Rose model assuming that doping with Os creates deep levels in the gap that act as recombination centers with a very little cross‐section of electron capture. We also studied the kinetic curves of photocurrent increase and decrease in BSO:Os which enabled us to determine the magnitude of the cross‐section of a photon capture at an impurity center. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mn2+ and band exciton luminescence in ZnMnTe/ZnMgTe quantum well structures
Authors: Agekyan V. F. , Akai I. , Filosofov N. G. , Karasawa T. , Karczewski G. , Serov A. Yu. , Vasiliev N. N. 
Published: April 2007

AbstractThe effect of excitation level on the luminescence of ZnMnTe/ZnMgTe quantum‐well (QW) structures has been studied. We find that result depend strongly on the QW width and manganese concentration. The increasing optical pumping implies a degradation of the Mn2+ intracenter luminescence (IL) due to the interaction of the strongly excited Mn2+ system with the high density of excitons. The spectral and kinetic properties of the IL reveal the contribution of the Mn2+ ions located on the interface and inside the QW as well as the Mn2+ IL decay dependence on the QW width. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Assessing the impact of a care innovation: telecare
Authors: Bayer Steffen , Barlow James , Curry Richard 
Published: April 2007

AbstractThe provision of health and social care for an increasing elderly population is a challenge facing many societies. Telecare, the delivery of health and social care to individuals within the home or wider community, with the support of information and communication technologies, has been advocated as an approach to reduce the rise in the number of elderly people in institutional care and to contain costs. A dynamic model is required to understand the systemic impact of telecare implementation over time. The paper cautions against overoptimistic expectations about the impact of telecare in the short term and emphasises that the benefits for healthcare systems may take a considerable time to be realised. Copyright © 2007 John Wiley & Sons, Ltd.
Small sample performance of tests of homogeneity of odds ratios in K 2 × 2 tables
Authors: Paul S. R. , Donner A. 
Published: April 2007

AbstractIn this note we study, by simulation, small sample performance in terms of size of ten procedures for testing the homogeneity of odds ratios in K 2 × 2 contingency tables. These ten statistics are derived for ‘largestratum’ settings. Our study concerns the behaviour of these statistics for ‘small‐stratum’ settings.
A comparison of several tests for censored paired data
Authors: Woolson Robert F. , O'Gorman Thomas W. 
Published: April 2007

AbstractThis paper reviews several tests for censored paired data and uses Monte Carlo methods to evaluate their sizes and powers. Each of the tests maintains its size. The Akritas test and the paired Prentice–Wilcoxon test are somewhat more powerful than the Gehan statistic or the generalized signed rank test for most of the distributions studied. If the survival times follow an exponential distribution, then the Gehan and the generalized signed rank tests are more powerful against a location shift alternative.
A semi‐bayes approach to the analysis of correlated multiple associations, with an application to an occupational cancer‐mortality study
Authors: Greenland Sander 
Published: April 2007

AbstractThomas et al.1 presented the application of empirical‐Bayes methods to the problem of multiple inference in epidemiologic studies. One limitation of their approach, which they noted, was the need to assume exchangeable log relative‐risk parameters, and independent relative‐risk estimates. Numerical integration was also required. Here I generalize their approach to allow for non‐exchangeable parameters and non‐independent estimates. The resulting method is Bayesian in so far as some feature of the prior distribution are specified from prior information, but is empirical Bayes in so far as some explicit parameters in the prior distribution are estimated from the data. Estimation is based on approximations to the posterior distribution; this allows one to implement the approach with standard software packages for matrix algebra. The method is illustrated in an occupational mortality study of 84 exposure‐cancer associations.
Cluster randomization in large public health trials: The importance of antecedent data
Authors: Duffy S. W. , South M. C. , Day N. E. 
Published: April 2007

AbstractLarge‐scale public health trials are often randomized by geographic or administrative clusters, for reasons of financial or organizational exigency. In this paper, we deal with the situation where the dependent variable is a count of events, such as mortality from, or incidence of a given disease. Simulation results show that this design may decrease power by more than 50 per cent. The lost power can largely be replaced by incorporating information on the dependent variable, within clusters, before the start of the trial. The pretrial and trial data can be analysed by negative trinomial models.
How many raters? toward the most reliable diagnostic consensus
Authors: Kraemer Helena Chmura 
Published: April 2007

AbstractWhen faced with a decision whether or not to treat a patient, to enter or to withdraw a patient from a clinical trial, or any other such binary decision, based on diagnosis with unsatisfactory reliability, can a consensus diagnosis be used to improve reliability? If so, exactly how? That is the question I address here. I draw comparisons and contrasts between the known results with an interval consensus and those with a binary consensus and suggest tactics for use in a pilot study to answer the above questions.
Adjustments to the mantel–haenszel test for data from stratified multistage surveys
Authors: Weerasekera D. R. , Bennett S. 
Published: April 2007

AbstractThe usual form of the Mantel–Haenszel test statistic assumes independent observations. This is inappropriate for data from a stratified multistage survey. Two alternative adjustments to the test statistic are developed to deal with this: (a) a modification of the effective sample size for each row of each table, using the design effects, extending a method proposed by Donald and Donner for familial aggregation studies; (b) a Taylor series approximation to the variance of the square root of the numerator of the Mantel‐Haenszel statistic. Both methods are evaluated by application to both simulated and real data. The two methods perform equally well, and offer a considerable improvement over the unadjusted test statistic when observations from the same cluster are highly correlated. A simplified adjustment is also considered, as is the need for correction to the variance of the odds ratio estimator.
Is the ‘simple carry‐over’ model useful?
Authors: Senn S. J. 
Published: April 2007

AbstractIt is argued that the models usually employed for carry‐over effects in cross‐over trials are not reasonable. The example of a non‐linear dose response for a dose‐finding trial arranged in a Williams square is developed to show that if carry‐over is present to any appreciable degree the usual statistical models provide no guaranteed protection against its effects. It is concluded that the most reasonably defended assumption about carry‐over effects is that no important carry‐over has taken place and that, where this assumption cannot be defended, statistical models provide no satisfactory substitute for it.
Clustering in sparse data and an analysis of rhabdomyosarcoma incidence
Authors: Grimson Roger C. , Aldrich Tim E. , Drane J. Wanzer 
Published: April 2007

AbstractTime series of epidemiologic events often contain periods of atypically low or high frequency. Correspondingly, for quite rare diseases there occur instances of long vacuous durations interrupted noticeably by periods of some disease activity. A recent community‐based observation of the incidence of rhabdomyosarcoma (RMS), and an investigation of it, yielded sparse data of this general description. We introduce a combinatorial test for patchy time series and apply it to the RMS data. We comment on the prevalent practice of post hoc data analysis of alleged clusters, and on scale effects.
Pre‐natal blood lead levels and learning difficulties in children: An analysis of non‐randomly missing categorical data
Authors: Conaway Mark R. , Waternaux Christine , Allred Elizabeth , Bellinger David , Leviton Alan 
Published: April 2007

AbstractThis paper presents an analysis of categorical variables subject to non‐response. We incorporate the incomplete data into the analysis by modelling the distribution of the variables of interest and the non‐response mechanism. We discuss issues of model selection and interpretation and the effect of discarding incomplete observations. In addition, we describe how to perform all of the computations with standard statistical software. We discuss the problem of incomplete categorical data within the context of a study of the effect of lead exposure on learning difficulties in children. In this study, many of the children are not observed on some of the variables of interest. It is particularly important in this study to incorporate the incomplete data, since there is evidence that non‐response is related to the variables of interest. We reach different conclusions when we incorporate the incomplete data into the analysis than we reach when we discard the incomplete data. We also examine the sensitivity of our conclusions to the choice of a model for the non‐response mechanism.
Applications of crude incidence curves
Authors: Korn Edward L. , Dorey Frederick J. 
Published: April 2007

AbstractCrude incidence curves display the cumulative number of failures of interest as a function of time. With competing causes of failure, they are distinct from cause‐specific incidence curves that treat secondary types of failures as censored observations. After briefly reviewing their definition and estimation, we present five applications of crude incidence curves to show their utility in a broad range of studies. In some of these applications it is helpful to model survival‐time distributions with use of two different time metameters, for example, time from diagnosis and age of the patient. We describe how one can incorporate published vital statistics into the models when secondary types of failure correspond to common causes of death.
Planned versus attained design in phase II clinical trials
Authors: Green Stephanie J. , Dahlberg Steve 
Published: April 2007

AbstractThe standard phase II trial problem is to decide whether or not to continue the testing of a new agent (or combination). Typically, one tests the null hypothesis Ho:p = po against the alternative HA:p = pA, where p is the probability of response. There is available a variety of two‐stage phase II designs, including optimal designs according to various criteria. Practical considerations in the conduct of multicentre trials, however, make it difficult to follow designs precisely. We investigate several approaches to adapting stopping rules when the attained sample size is not the planned size. We find that a simple approach of testing HA:p = pA at the 0·02 level at the first stage and Ho:p = po at the 0·055 level at the second stage works well across a variety of powers, pos and pAs.
A comment on replication,P‐values and evidence
Authors: Goodman Steven N. 
Published: April 2007

AbstractIt is conventionally thought that a smallp‐value confers high credibility on the observed alternative hypothesis, and that a repetition of the same experiment will have a high probability of resulting again in statistical significance. It is shown that if the observed difference is the true one, the probability of repeating a statistically significant result, the ‘replication probability’, is substantially lower than expected. The reason for this is a mistake that generates other seeming paradoxes: the interpretation of the post‐trialp‐value in the same way as the pre‐trial α error. The replication probability can be used as a frequentist counterpart of Bayesian and likelihood methods to show thatp‐values overstate the evidence against the null hypothesis.
Estimation, reference ranges and goodness of fit for the three‐parameter log‐normal distribution
Authors: Royston Patrick 
Published: April 2007

AbstractThe three‐parameter log‐normal distribution (3PL) is an appropriate model for many of the continuous variables encountered in medicine. It is shown how to obtain different types of estimate and approximate (sometimes conservative) confidence intervals for the parameters of the 3PL and for certain functions of them, particularly in the calculation of reference ranges of clinical measurements. A simple non‐iterative estimate of the shift parameter is described. The Shapiro–Wilk test of non‐normality is modified to allow it to be used for testing for departure from the 3PL. Its power is compared with that of other well‐known tests. The methods are illustrated using several data sets.