bluuebunny/crossref_metadata_2025 huggingface dataset:
PARAFAC with splines: a case study
Authors: Reis Marlon M. , Ferreira Márcia M. C.
Published: October 2002

The PARAFAC model has been used in several applications in chemistry, e.g. for overlapped spectra resolution and second‐order calibration. In general, the PARAFAC method uses a vector space approach by considering the matrices resulting from the decomposition as a collection of vectors. This paper presents a PARAFAC application where the factors resulting from the decomposition are considered as functions. The functional objects used for this are spline functions. The methodology used performs the Spline‐PARAFAC decomposition based on the Bro–Sidiropoulos approach for the unimodality constraint. One of the advantages of using splines is the possibility of achieving a controlled degree of smoothing on the decomposed components. The amount of smoothing applied on the components in the presented methodology is controlled by a penalty parameter or by the number of basis functions. Thus Spline‐PARAFAC requires the calculation of the parameter λ and the number of basis functions, which were determined in this work by using ordinary cross‐validation (OCV). Spline‐PARAFAC was applied to a carbon monoxide data set comprising concentrations measured every hour during the years 1997 and 1999 in the city of São Paulo, Brazil. Each data set was arranged in a three‐way array of dimension (24 hours × 5 days × 52 weeks). Spline‐PARAFAC showed a good performance, producing smoothed profiles describing the daily variations in emitted gas and the seasonal effects during the year. Copyright © 2002 John Wiley & Sons, Ltd.
Dealing with missing data in MSPC: several methods, different interpretations, some examples
Authors: Arteaga Francisco , Ferrer Alberto
Published: October 2002

This paper addresses the problem of using future multivariate observations with missing data to estimate latent variable scores from an existing principal component analysis (PCA) model. This is a critical issue in multivariate statistical process control (MSPC) schemes where the process is continuously interrogated based on an underlying PCA model. We present several methods for estimating the scores of new individuals with missing data: a so‐called trimmed score method (TRI), a single‐component projection method (SCP), a method of projection to the model plane (PMP), a method based on the iterative imputation of missing data, a method based on the minimization of the squared prediction error (SPE), a conditional mean replacement method (CMR) and various least squared‐based methods: one based on a regression on known data (KDR) and the other based on a regression on trimmed scores (TSR). The basis for each method and the expressions for the score estimators, their covariance matrices and the estimation errors are developed. Some of the methods discussed have already been proposed in the literature (SCP, PMP and CMR), some are original (TRI and TSR) and others are shown to be equivalent to methods already developed by other authors: iterative imputation and SPE methods are equivalent to PMP; KDR is equivalent to CMR. These methods can be seen as different ways to impute values for the missing variables. The efficiency of the methods is studied through simulations based on an industrial data set. The KDR method is shown to be statistically superior to the other methods, except the TSR method in which the matrix to be inverted is of a much smaller size. Copyright © 2002 John Wiley & Sons, Ltd.
Resolution of on‐flow LC/NMR data by multivariate methods — a comparison
Authors: Shen Hailin , Airiau Christian Y. , Brereton Richard G.
Published: October 2002

Data from LC/NMR have some distinct characteristics, differing from those of LC/MS and LC/DAD. This paper compares several approaches for resolution on both a three‐component and a seven‐component case study. Non‐iterative methods based on principal component analysis (EFA, WFA, HELP) and iterative approaches using constraints (ALS, Gentle) are compared with a new proposed method, constrained key variable regression (CKVR), which involves refining key variables and then using constraints of non‐negativity and equality to obtain optimized spectral resolution. In LC/NMR the reconstruction of detailed spectral profiles is important, requiring specific refinement of existing tools. Copyright © 2002 John Wiley & Sons, Ltd.
Multivariate biological profiling and principal toxicity regions of compounds: the PCB case study
Authors: Eriksson Lennart , Andersson Patrik L. , Johansson Erik , Tysklind Mats
Published: October 2002

The chemometric QSAR strategy, as applied in environmental sciences and drug design, is based on (1) multivariate characterization of chemical structure, (2) multivariate design in the principal properties of a set of compounds to select a representative training set, and (3) multivariate modelling of the structure–activity relationships. A multivariate QSAR investigation is often commenced by applying a screening design, and the selected compounds are tested biologically in a broad battery of test systems (‘multivariate biological profiling’). In many cases the result is such that for certain biological end‐points only some of the tested compounds are active, while for another set of biological end‐points other tested chemicals are active. In other words, when looking at the chemical property space, there may be both responding and non‐responding toxicity regions, or even regions of very specific toxicity mechanisms. This may lead to loss of resolution and balance in the resulting QSAR models. Therefore it might sometimes be worthwhile to focus the QSAR modelling on parts of the chemical space where high toxicity is expected or known to be the case. In this paper we describe a multi‐stage modification of the chemometric QSAR strategy, aimed at identifying focused sets of compounds that provide a good mapping of such principal toxicity regions. This strategy is based on PCA, PLS and multivariate design in several stages. The strategy is illustrated using a data set of polychlorinated biphenyls, a set of compounds for which seven biological end‐points were determined. Copyright © 2002 John Wiley & Sons, Ltd.
Feasibility study of NIR for surveillance of a pharmaceutical process, including a study of different preprocessing techniques
Authors: Stordrange Laila , Libnau Fred Olav , Malthe‐Sørenssen Dick , Kvalheim Olav M.
Published: October 2002

Multivariate calibration models for predicting the initial reactant and an impurity in a synthesis of contrast media have been developed using near‐infrared (NIR) spectroscopy. The reaction is presently monitored off‐line by HPLC. The calibration models are based on spectra measured on‐line. The process solution is chemically complex and the intention of this study was to enhance knowledge about the predictive ability of the models. Different data‐preprocessing and variable selection methods reported in the literature have been tested in order to enhance chemical information and reduce irrelevant variability due to physical influences on measured spectra such as scattering and temperature. In addition to standard preprocessing methods such as normalization, differentiation and multiplicative scatter correction, orthogonal signal correction and optimized scaling were tested. The modelling was performed by partial least squares (PLS), except for optimized scaling which uses principal component regression (PCR). Optimized scaling on differentiated data gave the lowest prediction error. The NIR region from 1100 to 1900 nm gave better models than variable selection and fewer variables. Models with correlation coefficients for best fit equal to 0.998 and 0.961 were obtained for the initial reactant and the impurity, respectively. Copyright © 2002 John Wiley & Sons, Ltd.
Reconstruction of smooth distributions within unsmooth circumferences from limited views using filtered‐backprojection algorithm
Authors: Feng J. , Bao S.L.
Published: October 2002

This study demonstrates the feasibility of reconstruction of smooth distributions within unsmooth circumferences from limited views using the filtered‐backprojection algorithm with angular interpolation in Fourier domain, which leads to noniterative reconstruction of smooth distributions within skulls in diagnostic medicine. Two phantoms with a circular and an elliptic circumference are numerically tested. This speedy approach has great advantages in applications when swift reaction is necessary or when result of reconstruction is indispensably navigational to its following detection. © 2002 Wiley Periodicals, Inc. Int J Imaging Syst Technol 12, 93–96, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10015
An accelerated multiplicative iterative algorithm in image reconstruction
Authors: Liu Li , Wang Yuan‐mei
Published: October 2002

Based on the ML‐EM (maximum likelihood expectation maximization) algorithm and AWLS (one kind of multiplicative weighted least square) reconstruction, a new algorithm named RMITC (rapid multiplicative iteration with total‐count conservation) is proposed. The new method assumes a higher order correction factor and incorporates a total‐count conservation constraint to obtain better images reconstructed while achieving a higher speed of convergence. Computer simulated phantom data and real positron emission tomography (PET) transmission data were used to compare the new method with other reconstruction algorithms, such as ML‐EM and AWLS. Results demonstrated that the new method is faster and better quantitatively than both ML‐EM and AWLS. © 2002 Wiley Periodicals, Inc. Int J Imaging Syst Technol 12, 97–100, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10016
Position‐dependent defocus processing for acoustic holography images
Authors: Yin Ruming , Flynn Patrick J. , Broschat Shira L.
Published: October 2002

Acoustic holography is a transmission‐based ultrasound imaging method that uses optical image reconstruction and provides a larger field of view than pulse‐echo ultrasound imaging. A focus parameter controls the position of the focal plane along the optical axis, and the images obtained contain defocused content from objects not near the focal plane. Moreover, it is not always possible to bring all objects of interest into simultaneous focus. In this article, digital image processing techniques are presented to (1) identify a “best focused” image from a sequence of images taken with different focus settings and (2) simultaneously focus every pixel in the image through fusion of pixels from different frames in the sequence. Experiments show that the three‐dimensional image information provided by acoustic holography requires position‐dependent filtering for the enhancement step. It is found that filtering in the spatial domain is more computationally efficient than in the frequency domain. In addition, spatial domain processing gives the best performance. © 2002 Wiley Periodicals, Inc. Int J Imaging Syst Technol 12, 101–111, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10017
Analysis of the compatibility conditions for the radon projections, with an application to seismology
Authors: Bindi Dino , Caponnetto Andrea
Published: October 2002

In the context of the Radon approach to tomographic imaging, we face the problem of ascertaining whether or not a set of functions can be considered a set of reliable projections of an unknown function. We first review some results about the singular system of the Radon operator. Then, we define a set of parameters that allows us to evaluate the degree of compatibility of a set of projections. We apply our analysis to the seismic source imaging problem. In particular, we show that the compatibility conditions can be used for the empirical Green function retrieval. © 2002 Wiley Periodicals, Inc. Int J Imaging Syst Technol 12, 112–116, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10018
On estimation of the number of image principal colors and color reduction through self‐organized neural networks
Authors: Atsalakis A. , Papamarkos N. , Andreadis I.
Published: October 2002

A new technique suitable for reduction of the number of colors in a color image is presented in this article. It is based on the use of the image Principal Color Components (PCC), which consist of the image color components and additional image components extracted with the use of proper spatial features. The additional spatial features are used to enhance the quality of the final image. First, the principal colors of the image and the principal colors of each PCC are extracted. Three algorithms were developed and tested for this purpose. Using Kohonen self‐organizing feature maps (SOFM) as classifiers, the principal color components of each PCC are obtained and a look‐up table, containing the principal colors of the PCC, is constructed. The final colors are extracted from the look‐up table entries through a SOFM by setting the number of output neurons equal to the number of the principal colors obtained for the original image. To speed up the entire algorithm and reduce memory requirements, a fractal scanning subsampling technique is employed. The method is independent of the color scheme; it is applicable to any type of color images and can be easily modified to accommodate any type of spatial features. Several experimental and comparative results exhibiting the performance of the proposed technique are presented. © 2002 Wiley Periodicals, Inc. Int J Imaging Syst Technol 12, 117–127, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10019
Robust estimation of 3D trajectories from a monocular image sequence
Authors: Pang Chung‐Yi Chan , Guesalaga Andrés R. , Roda Valentín Obac
Published: October 2002

This article describes a new method for object trajectory estimation that uses sequences of images taken from a monocular camera. The method integrates a Kalman filter to estimate the three‐dimensional (3D) parameters of the optical system and a lineal projective model to determine 3D point coordinates projected on the retinal plane. It works with at least three distinctive points in the image, and they are updated with correlation methods. The result is an estimation of the rotation and translation parameters between successive images within the sequence and yield to the 3D coordinates of the points selected for correspondence. The scaling problem related to 3D reconstruction is tackled via a priori information of the objects being observed. The method is tested with synthetic images to evaluate its accuracy, and later, an interesting application in autonomous navigation is presented. © 2002 Wiley Periodicals, Inc. Int J Imaging Syst Technol 12, 128–137, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10020
Detection, Distribution, and Quantification of Carbon in
Steel Microstructures by PEELS
Authors: Menon E.S.K. , Fox A.G.
Published: October 2002

This work concerns the use of parallel electron energy loss
spectroscopy (PEELS) to investigate the detection, distribution,
and quantification of carbon in various steel microstructures
generated by rapid cooling rates or by isothermal transformation.
The feasibility of detecting C in steels containing very small
amounts of carbon was first examined by calculating the minimum
detectable mass fraction for a variety of binary Fe-C alloy
specimen thicknesses and microscope conditions. These theoretical
studies indicated that the detection of carbon in steel
microconstituents containing about 0.01 wt.% (or even less)
was easily possible with an analytical transmission electron
microscope equipped with a LaB6 emitter and a PEEL
spectrometer. These theoretical calculations seemed to be
reasonable, as it proved possible to make a quantitative PEELS
study of the partitioning between the microconstituents ferrite,
retained austenite, and martensite found in an ultralow carbon
(0.03 wt.%) steel weld metal provided care was taken to avoid
hydrocarbon contamination. Studies of both carbon and molybdenum
segregation to ferrite/martensite interfaces in an isothermally
transformed Fe-C-Mo alloy were also carried out in order to
investigate the nature of the “solute drag” effect
in this alloy system.
Measuring Thickness Changes in Thin Films Due to Chemical
Reaction by Monitoring the Surface Roughness with In Situ
Atomic Force Microscopy
Authors: Beaulieu L.Y. , Rutenberg A.D. , Dahn J.R.
Published: October 2002

Measuring the changing thickness of a thin film, without a
reference, using an atomic force microscope (AFM) is problematic.
Here, we report a method for measuring film thickness based
on in situ monitoring of surface roughness of films as
their thickness changes. For example, in situ AFM
roughness measurements have been performed on alloy film electrodes
on rigid substrates as they react with lithium electrochemically.
The addition (or removal) of lithium to (or from) the alloy
causes the latter to expand (or contract) reversibly in the
direction perpendicular to the substrate and, in principle,
the change in the overall height of these materials is directly
proportional to the change in roughness. If the substrate on
which the film is deposited is not perfectly smooth, a correction
to the direct proportionality is needed and this is also discussed.
The Pros and Cons of Apoptosis Assays for Use in the Study
of Cells, Tissues, and Organs
Authors: Watanabe Michiko , Hitomi Midori , van der Wee Kathy , Rothenberg Florence , Fisher Steven A. , Zucker Robert , Svoboda Kathy K.H. , Goldsmith Edie C. , Heiskanen Kaisa M. , Nieminen Anna-Liisa
Published: October 2002

Programmed cell death or apoptosis occurs in many tissues during
normal development and in the normal homeostasis of adult tissues.
Apoptosis also plays a significant role in abnormal development
and disease. Increased interest in apoptosis and cell death
in general has resulted in the development of new techniques
and the revival of old ones. Each assay has its advantages and
disadvantages that can render it appropriate and useful for
one application, but inappropriate or difficult to use in another.
Understanding the strengths and limitations of the assays would
allow investigators to select the best methods for their needs.
HRTEM Image Simulations for the Study of Ultrathin Gate Oxides
Authors: Taylor Seth T. , Mardinly John , O'Keefe Michael A.
Published: October 2002

We have performed high resolution transmission electron microscope
(HRTEM) image simulations to qualitatively assess the visibility
of various structural defects in ultrathin gate oxides of MOSFET
devices, and to quantitatively examine the accuracy of HRTEM
in performing gate oxide metrology. Structural models contained
crystalline defects embedded in an amorphous 16-Å-thick
gate oxide. Simulated images were calculated for structures
viewed in cross section. Defect visibility was assessed as a
function of specimen thickness and defect morphology, composition,
size, and orientation. Defect morphologies included asperities
lying on the substrate surface, as well as “bridging”
defects connecting the substrate to the gate electrode.
Measurements of gate oxide thickness extracted from simulated
images were compared to actual dimensions in the model structure
to assess TEM accuracy for metrology. The effects of specimen
tilt, specimen thickness, objective lens defocus, and coefficient
of spherical aberration (Cs) on measurement accuracy
were explored for nominal 10-Å gate oxide thickness. Results
from this work suggest that accurate metrology of ultrathin
gate oxides (i.e., limited to several percent error) is feasible
on a consistent basis only by using a Cs-corrected
microscope. However, fundamental limitations remain for
characterizing defects in gate oxides using HRTEM, even with
the new generation of Cs-corrected microscopes.
Characterization of Magnetic Nanoparticles Using Energy-Selected
Transmission Electron Microscopy
Authors: Sayagués María J. , Rojas Teresa C. , Fernández Asunción , Dunin-Borkowski Rafal E. , Doole Ron C. , Hutchison John L.
Published: October 2002

Fe, Co, and Ni magnetic nanoparticles have been characterized
using energy-selected imaging in a high-resolution transmission
electron microscope. The samples comprised Fe/FeOx
and Co/CoOx nanoparticles synthesized by inert gas
evaporation and a Ni/C nano-composite prepared by a sonochemical method.
All of the particles examined were found to be between 5 and
30 nm in size, with the Fe and Co crystals coated in 5–10
nm of metal oxide layer and the Ni metallic crystallites embedded
in an amorphous carbon spherical matrix.
Compositional Averaging of Continuum Intensities in Multielement
Compounds
Authors: Donovan John J. , Pingitore Nicholas E.
Published: October 2002

We find no physical basis for traditional mass-fraction weighted
averaging of X-ray continuum measured in pure elements to estimate
continuum production from compounds. Measurements of continuum
from pairs of stable isotopes demonstrate that mass alone (the
presence of more or fewer neutrons) has no effect on continuum
production in electron probe microanalysis. Electron-fraction
weighted averaging, which is based on the relative contribution
of each constituent element to the electron (or proton) composition
of a compound, proved superior to mass-fraction weighted averaging,
in predicting the continuum of a compound from the measured
continuum of its elements.
Ordering Energies and Occupancies in Doped TiAl, and Dedicated
ALCHEMI Instrumentation
Authors: Spence J.C.H. , Jiang N. , Weierstall U.
Published: October 2002

Alloy design has been a lifelong interest of Gareth Thomas,
and modern design algorithms include atomistic parameters which
are obtainable from new electron microscope techniques such
as ALCHEMI. In this paper, we discuss the relevance of ALCHEMI
site occupancy measurements to intermetallic alloys, and summarize
prior work. The results are found to lie in regions of a
site-occupancy diagram (SOC) relating ordering energies to
occupancy, as predicted by the Bragg–Williams theory of
short-range order. These predictions also explain previous
inconsistencies in the ALCHEMI measurements. A diffraction camera
and X-ray detector system of novel design is proposed for dedicated
ALCHEMI analysis for substitutional and interstitial dopant
site-occupancy measurement, and details of the design given.
Using this novel hardware design, the data-collection times
for two-dimensional ALCHEMI patterns should be reduced by an
order of magnitude or more, and the full data collection process
automated. The resulting occupancy information can provide
essential input parameters for atomistic alloy design algorithms,
and can provide entirely new information on interstitial
occupancies in minerals, ceramics, semiconductors, and alloys.
Electron Microscopy Observations on the Role of Twinning
in the Evolution of Microstructures
Authors: Dahmen U. , Hetherington C.J.D. , Radmilovic V. , Johnson E. , Xiao S.Q. , Luo C.P.
Published: October 2002

Twinning plays an important role in phase transformations and
can have significant effects on microstructural evolution.
Different roles of twinning in the development of microstructures
during precipitation and phase transformations are reviewed
and illustrated with examples from investigations by
high-resolution electron microscopy, including the effect of
multiple twinning on the development of Ge precipitates in Al-Ge
and Ag-Ge alloys, the twin dissociation of grain boundaries
in Au, the formation of hexagonal Si at twin intersections and
the effect of twin boundaries on the equilibrium shape of Pb
inclusions in Al.
Dewetting of Liquids on Ceramic Surfaces at High Temperatures
Authors: Ravishankar N. , Gilliss Shelley R. , Carter C. Barry
Published: October 2002

The influence of surface structure and chemistry on
high-temperature dewetting of silicate liquids on ceramic surfaces
has been investigated. Model systems based on well-defined
crystallography and known chemistry have been used to illustrate
the effect of surface roughness and chemistry on the dewetting
process. Reconstructed ceramic surfaces provide ideal substrates
to study effects of surface roughness. It has been shown that
the morphology of dewet droplets depend on the length scale
and the crystallography of the facets on the surface. Complex
pattern formation due to solute redistribution during dewetting
is illustrated in the case of SiO2 dewetting on (001)
rutile substrates. The role of kinetics on the dewetting process
has also been clarified.
Structural Evolution in Amorphous Silicon and Germanium Thin Films
Authors: Chen L.J. , Cheng S.L. , Yu C.H. , Su P.Y. , Lin H.H. , Chi K.S.
Published: October 2002

The structural evolution in amorphous silicon and germanium
thin films has been investigated by high-resolution transmission
electron microscopy (HRTEM) in conjunction with autocorrelation
function (ACF) analysis. The results established that the structure
of as-deposited semiconductor films is of a high density of
nanocrystallites embedded in the amorphous matrix. In addition,
from ACF analysis, the structure of a-Ge is more ordered than
that of a-Si. The density of embedded nanocrystallites in amorphous
films was found to diminish with annealing temperature first,
then to increase. The conclusions also corroborate well with
the results of diminished medium-range order in annealed amorphous
films determined previously by a variable coherence microscopy
method.
Ultrasoft Magnetic Films Investigated with Lorentz Tranmission
Electron Microscopy and Electron Holography
Authors: De Hosson Jeff Th.M. , Chechenin Nicolai G. , Alsem Daan-Hein , Vystavel Tomas , Kooi Bart J. , Chezan Antoni R. , Boerma Dik O.
Published: October 2002

As a tribute to the scientific work of Professor Gareth Thomas
in the field of structure-property relationships this paper
delineates a new possibility of Lorentz transmission electron
microscopy (LTEM) to study the magnetic properties of soft magnetic
films. We show that in contrast to the traditional point of
view, not only does the direction of the magnetization vector
in nano-crystalline films make a correlated small-angle wiggling,
but also the magnitude of the magnetization modulus fluctuates.
This fluctuation produces a rapid modulation in the LTEM image.
A novel analysis of the ripple structure in nano-crystalline
Fe-Zr-N film corresponds to an amplitude of the transversal
component of the magnetization ΔMy
of 23 mT and a longitudinal fluctuation of the magnetization of the
order of ΔMx = 30 mT. The nano-crystalline
(Fe99Zr1)1−xNx
films have been prepared by DC magnetron reactive sputtering with
a thickness between 50 and 1000 nm. The grain size decreased
monotonically with N content from typically 100 nm in the case
of N-free films to less than 10 nm for films containing 8 at%.
The specimens were examined with a JEOL 2010F 200 kV transmission
electron microscope equipped with a post column energy filter
(GIF 2000 Gatan Imaging Filter). For holography, the microscope
is mounted with a biprism (JEOL biprism with a 0.6 μm diameter
platinum wire).
In Situ TEM Studies of Metal–Carbon Reactions
Authors: Sinclair Robert , Itoh Toshio , Chin Richard
Published: October 2002

The reactions which occur between amorphous carbon and a number
of first transition metals (Ti, Cr, Fe, Co, Ni, and Cu) have
been studied by transmission electron microscopy (TEM). The
materials are in thin-film form with the metal layer sandwiched
between thicker carbon layers. In four cases, the predominant
reaction is the graphitization of the amorphous carbon, at
temperatures well below 800°C. This is brought about by
the elements themselves in the case of Co and Ni, and by metastable
carbides in the case of Fe (Fe3C) and Cr
(Cr3C2−x). The Ti–C and
Cu–C systems do not exhibit graphitization. For the former,
only TiC is produced up to 1000°C, while the carbon does not react
at all with copper. In situ TEM studies show the mechanism to
be of the dissolution-precipitation type, which is equivalent to the
metal-mediated crystallization process for amorphous silicon and
germanium. The heat of graphitization is found to be 18–19
kcal/mol-C by differential scanning calorimetry.
Early Stages of Carbon Segregation and Precipitation in a
Σ = 5 (310)[001] Molybdenum Tilt Boundary
Authors: Pénisson Jean-Michel , Bacia Maria
Published: October 2002

A Σ = 5 (310)[001] tilt grain boundary in molybdenum
has been annealed at high temperature in the presence of carbon
and observed in high-resolution electron microscopy. The carbon
is located at the grain boundary in a 1-nm slab. Two different
morphologies coexist. The first one is a grain boundary
precipitation while the second one can be considered as a segregation.
Nanometric Scale Investigation of Local Strain in GaInAs
Islands by High Resolution and Analytical TEM
Authors: Laval J.Y. , Kret S. , Delamarre C. , Bassoul P. , Benabbas T. , Androussi Y.
Published: October 2002

The continuous displacement field within elastically relaxed
GaInAs islands was calculated from digitized HREM images of
{110} cross sections of In0.35Ga0.65As
layers grown on GaAs by molecular beam epitaxy. Experimental maps
of the deformations parallel to the interface
(εx) and along the growth direction
(εz) were drawn and compared with the ones
calculated via the finite element method. It was found that
εx exp was systematically higher than
εx calc and the significant maximum observed
for εz exp within the island could not be
found for εz calc. These discrepancies were
attributed to a variation of the chemical composition in the island.
The maps showing the indium concentration gradient drawn from HREM and
FE calculations were compared to quantitative profiles for indium
concentration obtained by nanometric X-ray microanalysis in TEM. The
measured gradient within the island backs our assumption.
Physical and Magnetic Modification of Co/Pt Multilayers by
Ion Irradiation
Authors: Kusinski G.J. , Thomas G.
Published: October 2002

The microstructure of Co/Pt multilayers with large perpendicular
magnetic anisotropy (PMA) was investigated before and after
energetic ion irradiation. No pronounced microstructural changes
were detected at ion doses sufficient to completely reduce the
PMA and cause a spin reorientation transition to in-plane.
Ion-induced displacement of Co and Pt atoms near Co/Pt interfaces
lead to local “roughening” and Co layer strain
relaxation, reducing the PMA. The magnetic domain confinement
induced by ion irradiation and magnetic patterning by selective
ion irradiation were also investigated.
Nanoscale Phenomena in Synthetic Functional Oxide Heterostructures
Authors: Nagarajan V. , Ganpule C.S. , Stanishevsky A. , Liu B.T. , Ramesh R.
Published: October 2002

This paper reviews nanoscale phenomena such as polarization
relaxation dynamics and piezoelectric characterization in model
ferroelectric thin films and nanostructures using voltage-modulated
scanning force microscopy. Using this technique we show the
three-dimensional reconstruction of the polarization vector
in lead zirconate titanate (PZT) thin films. Second, the
time-dependent relaxation of remanent polarization in epitaxial
PZT ferroelectric thin films, containing a uniform two-dimensional
grid of 90° domains (c-axis in the plane of the
film), has been investigated extensively. The 90° domain
walls preferentially nucleate the 180° reverse domains during
relaxation. Relaxation occurs through the nucleation and growth
of reverse 180° domains, which subsequently coalesce and
consume the entire region as a function of relaxation time.
In addition we also present results on investigation of the
relaxation phenomenon on a very local scale, where pinning and
bowing of domain walls has been observed. We also show how this
technique is used for obtaining quantitative information on
piezoelectric constants and by engineering special structures,
and how we realize ultrahigh values of piezoconstants. Last,
we also show direct hysteresis measurements on nanoscale
capacitors, where there is no observable loss of polarization
in capacitors as small as 0.16 μm2 in area.
Use of Plasmon Spectroscopy to Evaluate the Mechanical
Properties of Materials at the Nanoscale
Authors: Oleshko Vladimir P. , Murayama Mitsuhiro , Howe James M.
Published: October 2002

Relationships between volume plasmon excitations and mechanical
properties of various materials are considered. Based on systematic
evaluation of available data, correlations between the volume
plasmon energy, Ep, Young's modulus,
Ym, bulk modulus,
Bm, shear modulus, Gm, and microhardness,
Hm, are established. The resulting
correlations indicate that plasmon energies potentially can be used
to predict and/or determine the local mechanical properties of
technologically important materials, such as metal alloys, semiconductors,
and ceramics at the nanometer level.
Introduction: A Symposium Dedicated to Gareth Thomas on the
Occasion of his 70th Birthday
Authors: Howitt D.G.
Published: October 2002

This symposium, and the special issue of Microscopy &
Microanalysis that Barry Carter and Uli Dahmen have put
together, provides us with a glimpse of a career that has not
only spanned the development of electron microscopy of materials
but also helped to drive it. Over the last 40 years Gareth has
guided more than a hundred graduate students and over forty
post-doctoral fellows, building a foundation for the application
of transmission electron microscopy in the United States including
the creation of the National Center for Electron Microscopy.
It is with great pleasure that we celebrate his 70th
birthday, gratified that he is still going strong and marveling at
how he does it.
Electron Microscopy, Second Edition, John J. Bozzola
and Lonnie D. Russell. Jones and Bartlett Publishers, Inc.,
Sudbury, MA, 1999, 670 pages (hardback, $56.25). ISBN 0-7637-0192-0
Authors: Price Bob
Published: October 2002

Electron Microscopy by John Bozzola and Lonnie Russell
continues to be a text of choice for instruction in classes
that cover beginning electron microscopy for biologists and
should also be on the bookshelf of all technologists that work
with biological specimens for transmission or scanning EM. The
first chapter in the book presents a brief, but interesting,
history of the development of instrumentation and techniques
for specimen preparation and sets the stage for the wealth of
practical information that is presented in the remaining twenty
chapters. These chapters are laid out in a logical chronological
fashion of exactly what one must do to start with an unfixed
specimen and end with a publication quality micrograph.
High‐Cell‐Density Fermentation of Recombinant Saccharomyces cerevisiae Using Glycerol
Authors: Raj A. Eugene , Kumar H. S. Sathish , Kumar S. Umesh , Misra M. C. , Ghildyal N. P. , Karanth N. G.
Published: October 2002

To obtain a high cell density of recombinant Saccharomyces cerevisiae (INVSc 1 strain bearing a 2 μm plasmid, pYES2 containing a GAL1 promoter for expression of the β‐galactosidase gene), the yeast was grown with glycerol as the substrate by fed‐batch fermentation. The feeding strategy was based on an on‐line response of the medium pH to the consumption of glycerol. The approach was to feed excess carbon into the medium to create a benign environment for rapid biomass buildup. During cell growth in the presence of glycerol, the release of protons in the medium caused a decrease in pH and the consumption rate of ammonium phosphate served as an on‐line indicator for the metabolic rate of the organism. The extent of glycerol feeding in a fed‐batch mode with pH control at 5.0 ± 0.1 was ascertained from the automatic addition of ammonium phosphate to the medium. The glycerol feeding to ammonium phosphate addition ratio was found to be 2.5–3.0. On the basis of the experiments, a maximum dry cell biomass of 140 g per liter and a productivity of 5.5 g DCW/L/h were achieved. The high cell density of S. cerevisiae obtained with good plasmid stability suggested a simple and efficient fermentation protocol for recombinant protein production.
Control of Secondary Metabolite Congener Distributions via Modulation of the Dissolved Oxygen Tension
Authors: Frykman Scott A. , Tsuruta Hiroko , Starks Courtney M. , Regentin Rika , Carney John R. , Licari Peter J.
Published: October 2002

Many secondary metabolites, including various polyketides, require complex enzymatic pathways for modification into their final biologically active forms. Limitation of the dissolved oxygen supplied during cultivation of various microbial strains can decrease the activity of cytochrome P‐450 monooxygenases required for the processing of pathway intermediates into their final forms, resulting in the accumulation of these intermediates as the primary products. Here, a generalized oxygen‐limited cultivation strategy is specifically demonstrated with a myxobacterial strain engineered to heterologously express the epothilone polyketide synthase (PKS) gene cluster under either an excess (the dissolved oxygen tension is maintained at 50% of saturation) or a depleted (no residual dissolved oxygen detected) level of oxygenation during cultivation. Cultivation of this myxobacterial strain with excess oxygenation resulted in the production of epothilones A and B as the primary products, while cultivation of this same strain under depleted oxygenation resulted in the production of epothilones C and D as the primary products. Additionally, the peak cell density in the oxygen‐depleted cultivations was 60% higher than that observed in oxygen‐excess cultivations. Finally, an active EpoK epoxidase was found to catalyze the production of a novel epothilone (Epo506) with an unexpected structure during the cultivation of another myxobacterial strain expressing a genetically modified epothilone PKS under excess oxygenation. The structure of Epo506 was determined by high‐resolution mass spectrometry and one‐ and two‐dimensional NMR.
Bactericidal Properties of Flat Surfaces and Nanoparticles Derivatized with Alkylated Polyethylenimines
Authors: Lin Jian , Qiu Shuyi , Lewis Kim , Klibanov Alexander M.
Published: October 2002

We previously discovered that covalently coating glass and plastic slides with certain long poly(vinyl‐ N‐alkylpyridinium) chains enables the resultant surfaces to kill a variety of airborne and waterborne bacteria on contact. In the present study, these findings have been extended to an unrelated polymer class, polyethylenimines (PEIs). Alkylated PEIs attached to flat macroscopic surfaces and to those of nanoparticles make these materials highly bactericidal toward both Gram‐positive and Gram‐negative pathogenic bacteria. Systematic chemical modifications of the immobilized PEI conducted herein shed light on the relationship between the structure of the polymer and the antibacterial efficiency of the resultant coating.
Purines and pyrimidines are not involved in NANC relaxant responses in the rabbit vaginal wall
Authors: Ziessen Tom , Cellek Selim
Published: October 2002

Non‐adrenergic non‐cholinergic (NANC) relaxant responses were elicited by electrical field stimulation (EFS) in rabbit vaginal wall strips after treatment with guanethidine and scopolamine and raising smooth muscle tone with phenylephrine. Under these conditions treatment with NOS inhibitors revealed a non‐nitrergic NANC relaxant response. The possible role of purines and pyrimidines in these non‐nitrergic NANC responses was investigated.

Exogenous application of ATP, ADP, adenosine, UTP, or UDP (all at 0.03–10 mM) induced concentration‐dependent relaxant responses.

Responses to exogenous application of ATP were reduced by the general P2 antagonist cibacron blue (500 μM), but not by suramin (100 μM) and were unaffected by L‐NAME (500 μM), ω‐conotoxin GVIA (ω‐CTX, 500 nM) or tetrodotoxin (TTX, 1 μM).

Responses to exogenous application of adenosine were reduced by the A2A antagonist ZM‐241385 (30 μM).

ATP‐ and ADP‐induced responses were unaffected by the G‐protein inhibitor pertussis toxin (100 ng ml−1), whilst ADP‐ but not ATP‐induced responses were reduced by GDPβS (100 μM), which stabilizes G‐proteins in their inactive state.

EFS‐induced non‐nitrergic NANC relaxant responses were unaffected by suramin, cibacron blue, ZM‐241385, pertussis toxin or GDPβS, but were completely inhibited by TTX.

Exogenous application of ATP (10 mM) and adenosine (10 mM) increased intracellular cyclic adenosine‐3′, 5′‐monophosphate (cAMP). However, non‐nitrergic NANC responses were not associated with increased cAMP. Neither non‐nitrergic NANC responses nor responses to ATP or adenosine were associated with increased intracellular cyclic guanosine‐3′, 5′‐monophosphate (cGMP) concentrations.

These results suggest that adenosine A2A receptors and P2 receptors are present in the rabbit vaginal wall, but that they are not involved in non‐nitrergic NANC relaxant responses.

British Journal of Pharmacology (2002) 137, 513–521. doi:10.1038/sj.bjp.0704898
Optimizing the use of donated cadaver livers: Analysis and policy development to increase the application of split-liver transplantation
Authors: Emond Jean C. , Freeman Richard B. , Renz John F. , Yersiz Hasan , Rogiers Xavier , Busuttil Ronald W.
Published: October 2002

The American Society of Transplant Surgeons and the American Society of Transplantation jointly sponsored a conference in Crystal City, Virginia, on March 28th and 29th, 2001, to explore mechanisms for maximizing the cadaver-organ donor pool. Participants from transplantation medicine, surgery, organ procurement organizations, the general public, and government convened to address expanding utilization of each organ type. The committee assigned to review liver organ utilization identified multiple practices that could expand the potential donor pool including non-heart beating donors, marginal grafts, efficient allocation of cadaver organs, and wider application of split-liver transplantation. This article details the data reviewed by the liver committee and their recommendations on policy development for the expanded application of split-liver transplantation.
Slowly tapering off steroids protects the graft against hepatitis C recurrence after liver transplantation
Authors: Brillanti Stefano , Vivarelli Marco , De Ruvo Nicola , Aden Ardo Abdiueli , Camaggi Valeria , D’Errico Antonia , Furlini Giuliano , Bellusci Roberto , Roda Enrico , Cavallari Antonino
Published: October 2002

Chronic hepatitis C represents a major clinical problem after liver transplantation, but factors influencing the recurrent disease have not been well characterized. We analyzed the clinical records of all the patients transplanted for hepatitis C virus (HCV)-related liver disease in our Center between 1991 and 1997. Eighty consecutive HCV-positive (+) patients (60 men, ages 28 to 64) survived more than 1 month after transplantation and were followed for a median of 45 months. Diagnosis of recurrent chronic hepatitis C was made in 38 patients (47.5%), of whom 22 had moderate/severe chronic hepatitis. Decompensated cirrhosis occurred in six patients (7.5%). No difference in patient survival was found between patients with and without hepatitis C recurrence. No association was found between recurrent hepatitis C and presumed risk factors. The method of tapering off corticosteroids was significantly associated with both hepatitis C recurrence and the severity of hepatitis. In patients receiving a higher daily prednisone dose, 12 months after transplantation, the proportion of recurrent hepatitis C was 35.7% versus 66.6% (P = .02; odds ratio [OR], 3.6; 95% confidence interval (CI): 1.25 to 10.36), and among patients receiving a higher daily prednisone dose, 6 months after transplantation, the proportion of moderate/severe chronic hepatitis C was 40% versus 89% (P = .03; OR: 0.08, 95% CI: 0.008 to 0.84). Finally, prednisone dose at month six was significantly associated with disease-free survival of the liver graft. In conclusion, our results seem to indicate that in HCV-infected liver transplant recipients, a long-term treatment with corticosteroids, slowly tapered off over time, may prevent the more aggressive forms of recurrent liver disease.
Liver transplantation for hepatocellular carcinoma: Analysis of survival according to the intention-to-treat principle and dropout from the waiting list
Authors: Yao Francis Y. , Bass Nathan M. , Nikolai Bev , Davern Timothy J. , Kerlan Robert , Wu Victor , Ascher Nancy L. , Roberts John P.
Published: October 2002

A major obstacle for orthotopic liver transplantation (OLT) as treatment for hepatocellular carcinoma (HCC) is tumor growth resulting in dropout from the waiting list for OLT. There is a paucity of data on survival according to intention-to-treat analysis and the rate of dropout from the waiting list for OLT among patients with HCC. To further evaluate these issues, we analyzed the outcome of 46 consecutive patients with HCC listed for OLT between January 1998 and January 2001. Exclusion criteria for OLT were tumor size greater than 5 cm for one to three lesions or four lesions or greater of any size. Twenty-one patients underwent OLT. There were 11 dropouts because of tumor progression and six deaths, including three deaths after dropout. Kaplan-Meier 1- and 2-year intention-to-treat survival rates were 91.7% and 72.6%, respectively. Monthly dropout rates were 0% from 0 to 3 months, 1.5% from 3 to 6 months, 1.0% from 6 to 9 months, 4.9% from 9 to 12 months, and 5.6% from 12 to 15 months. One dropout occurred beyond 15 months among 4 patients remaining at risk. Cumulative probabilities for dropout at 6, 12, and 24 months were 7.3%, 25.3%, and 43.6%, respectively. Predictors for dropout included two or three tumor nodules or a solitary lesion greater than 3 cm at initial presentation and previous hepatic resection. Our results support recent changes in the scheme of organ allocation aimed at reducing the dropout rate and improving outcome for patients with HCC awaiting OLT.
Late acute rejection after liver transplantation: The Western Canada experience
Authors: Ramji Alnoor , Yoshida Eric M. , Bain Vincent G. , Kneteman Norman M. , Scudamore Charles H. , Ma Mang M. , Steinbrecher Urs P. , Gutfreund Klaus S. , Erb Siegfried R. , Partovi Nilufar , Chung Stephen W. , Shapiro James , Wong Winnie W.S.
Published: October 2002

Acute rejection usually occurs within 3 months posttransplantation. Most centers reduce immunosuppression over 6 to 12 months to minimize opportunistic infection, malignancy, and drug toxicity. Pretransplant disease and low immunosuppression have been reported in association with late acute rejection (LAR). The objective of this study was to determine the incidence, predictive factors, and outcomes of LAR via retrospective review of adult liver transplant recipients in Western Canada from 1989 to 2000. LAR was defined as biopsy-proven acute rejection occurring more than 180 days posttransplantation. Patient characteristics, immunosuppression, and outcome were determined. Both a univariate and multiple logistic regression analysis were performed. LAR occurred in 97 (23%) of 415 patients more than 180 days posttransplantation. Median follow-up was 402 days (range, 180 to 3137 days); 79% of LAR episodes were graded mild. At the time of LAR, 33% were on a steroid taper. A total of 73% of LAR episodes were treated with pulse intravenous steroids, and 5% were steroid-resistant. In the univariate analysis, patients undergoing transplantation for viral etiologies and older age were associated with less LAR. Immunosuppression was significant in a multiple logistic regression model, but not with a proportional hazards model. On multivariate analysis, only patients undergoing transplantation for viral etiologies remained resistant to LAR (hazard ratio, 0.52; range, 0.34 to 0.93, P = .02). There was a trend toward increased chronic rejection in patients who developed LAR (P = .04). LAR is common and occurs after more than 1 year posttransplantation. Patients undergoing transplantation for viral etiologies seem to have a lower risk of LAR. There may be an increased risk of chronic rejection in those developing LAR.