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Cation exchange capacity (CEC) characterizes the number of fixed
negative charges of plant cell walls and is an important parameter in
studies dealing with the uptake of ions into plant tissues, especially in
roots. Conventional methods of CEC determination use bulk tissue, the
results are the mean of many cells, and differences in the CEC of
different tissue types are masked. Energy-dispersive microanalysis (EDX)
in the transmission electron microscope allows CEC determinations on much
finer scales. Shoot and fine root tissue of Picea abies was acid
washed to remove exchangeable cations. Tissue blocks or semithin tissue
sections were loaded with 0.2 mM CaCl2, AlCl3, or
Pb(NO3)2 at pH 4.0. The amount of Ca, Al, or Pb
adsorbed to the exchange sites of cell walls was determined by EDX. The
CEC of cell walls of different tissue types was highly different, ranging
in shoot tissues from 0 to 856 mM Ca and 5.8 to 1463 mM Al (block loading)
or 4.3 to 1116 mM Ca and 0 to 2830 mM Al (section loading). In root
tissue, Pb adsorption to semithin sections yielded CEC values between 29.1
and 954 mM Pb. In most P. abies shoot tissues, the binding
capacity was clearly higher for Al than for Ca.
This special issue of Microscopy and Microanalysis contains
selected papers related to contributions presented during the 1st
International Conference on Environmental, Industrial, and Applied
Microbiology (BioMicroWorld-2005), held March 15–18, 2005 in
Badajoz, Spain (http://www.formatex.org/biomicroworld2005).
In February 2006, in conjunction with the 19th Australian Conference on Microscopy and Microanalysis held in Sydney, the 2nd Australian Workshop on Atom Probe Tomography was convened by S.P. Ringer, M.K. Miller, D.A. Saxey, and R. Zheng at the Australian Key Centre for Microscopy and Microanalysis at The University of Sydney. The topics covered at that workshop included specimen preparation; data acquisition and data analysis methods for atom probe tomography; applications to spinodal alloys, phase transformations, light metals, atomic clustering, and detection methods, as well as future directions of the science and technology of atom probe tomography. The presentations and discussions that took place at this workshop, which was attended by more than 30 people, provided the inspiration for this special issue of Microscopy and Microanalysis.
Our web submission system, Manuscript Central by ScholarOne, has been
in operation since September 1, 2006. The present issue of Microscopy
and Microanalysis contains the first paper to appear in print after
traversing this system electronically (see the paper by Fuseler et al.).
The time elapsed from submission to print publication was under seven
months. This is a significant improvement over the old paper-based methods
where a manuscript often took more than a year to appear in print.
This issue of Microscopy and Microanalysis contains papers
from the Seventh Regional Workshop of the European Microbeam Analysis
Society (EMAS) on Electron Probe Microanalysis of Materials
Today—Practical Aspects that took place May 13–16, 2006 in
Karlsruhe, Germany. The meeting was organized in collaboration with the
Institute for Transuranium Elements (ITU) of the Joint Research Centre of
the European Commission.
The Impact Factor data for 2006 is in, and we are pleased to announce that Microscopy and Microanalysis is ranked #2 among microscopy journals by the ISI Web of Science (Thomson Scientific). This ranking is based on the 2006 Impact Factor of 2.11 (an increase from the 2005 Impact Factor of 1.88).
Because of its applicability to biological specimens (nonconductors),
a single-molecule-imaging technique, atomic force microscopy (AFM), has
been particularly powerful for visualizing and analyzing complex
biological processes. Comparative analyses based on AFM observation
revealed that the bacterial nucleoids and human chromatin were constituted
by a detergent/salt-resistant 30–40-nm fiber that turned into
thicker fibers with beads of 70–80 nm diameter. AFM observations of
the 14-kbp plasmid and 110-kbp F plasmid purified from Escherichia
coli demonstrated that the 70–80-nm fiber did not contain a
eukaryotic nucleosome-like “beads-on-a-string” structure.
Chloroplast nucleoid (that lacks bacterial-type nucleoid proteins and
eukaryotic histones) also exhibited the 70–80-nm structural units.
Interestingly, naked DNA appeared when the nucleoids from E. coli
and chloroplast were treated with RNase, whereas only 30-nm chromatin
fiber was released from the human nucleus with the same treatment. These
observations suggest that the 30–40-nm nucleoid fiber is formed with
a help of nucleoid proteins and RNA in E. coli and chroloplast,
and that the eukaryotic 30-nm chromatin fiber is formed without RNA. On
the other hand, the 70–80-nm beaded structures in both E.
coli and human are dependent on RNA.
Among the microanalytical techniques, electron probe microanalysis
(EPMA) is one of the most powerful. Its performances can be used to
provide an accurate characterization. In the present article the
differences between the EPMA of highly irradiated materials and standard
EPMA are highlighted. It focuses on the shielded EPMA specificities. Then,
the article presents the difficulties encountered during the sample
preparation and the analysis (mainly due to the radioactive background).
In spite of these difficulties, some valuable results can be provided by a
shielded EPMA on the in-pile behavior of nuclear irradiated fuel. Some
results of specific examples analyzed by EPMA in nuclear fuel research are
In this article a method for determining errors of the strain values when applying strain mapping techniques has been devised. This methodology starts with the generation of a thickness/defocus series of simulated high-resolution transmission electron microscopy images of InAsxP1−x/InP heterostructures and the application of geometric phase. To obtain optimal defocusing conditions, a comparison of different defocus values is carried out by the calculation of the strain profile standard deviations among different specimen thicknesses. Finally, based on the analogy of real state strain to a step response, a characterization of strain mapping error near an interface is proposed.
The regular periodontal practice of scaling and root planing produces
a smear layer on the root surface that is detrimental to the readhesion of
tissues during subsequent regeneration therapy. Although it has been
demonstrated that gels containing the chelating agent
ethylenediaminetetraacetic acid (EDTA) can assist in the removal of this
contaminating layer, no quantitative method is yet available by which to
evaluate the efficiency of the treatment. In this article, the power of
atomic force microscopy (AFM) as a technique for monitoring and mapping
the surfaces of dentinal roots is demonstrated. Roughness parameters of
teeth that had been scaled and root planed were determined from AFM images
acquired both before and after treatment with EDTA. The results confirmed
that EDTA is an efficient cleaning agent and that dentinal samples free
from a smear layer are significantly rougher than the same samples covered
by a contaminating layer. AFM analysis is superior to alternative methods
involving scanning electron microscopy because the same sample section can
be analyzed many times, thus permitting it to be used as both the control
and the treatment surface.
For this analytical TEM study, nonmagnetic oxygen-rich boundaries were
introduced into Co-Pt-alloy perpendicular recording media by cosputtering
Co and Pt with TiO2. Increasing the TiO2 content
resulted in changes to the microstructure and elemental distribution
within grains and boundaries in these films. EFTEM imaging was used to
generate composition maps spanning many tens of grains, thereby giving an
overall depiction of the changes in elemental distribution occurring with
increasing TiO2 content. Comparing EFTEM with spectrum-imaging
maps created by high-resolution STEM with EDXS and EELS enabled both
corroboration of EFTEM results and quantification of the chemical
composition within individual grain boundary areas. The difficulty of
interpreting data from EDXS for these extremely thin films is discussed.
Increasing the TiO2 content of the media was found to create
more uniformly wide Ti- and O-rich grain boundaries as well as Ti- and
O-rich regions within grains.
Over the last few years there have been significant developments in the field of three-dimensional atom probe (3DAP) analysis. This article reviews some of the technical compromises that have led to different instrument designs and the recent improvements in performance. An instrument has now been developed, based around a novel reflectron configuration combining both energy compensation and focusing elements, that yields a large field of view and very high mass resolution. The use of laser pulsing in the 3DAP, together with developments in specimen preparation methods using a focused ion-beam instrument, have led to a significant widening in the range of materials science problems that can be addressed with the 3DAP. Recent studies of semiconductor materials and devices are described.
The performance of the pulsed-laser atom probe can be limited by both instrument and specimen factors. The experiments described in this article were designed to identify these factors so as to provide direction for further instrument and specimen development. Good agreement between voltage-pulsed and laser-pulsed data is found when the effective pulse fraction is less than 0.2 for pulsed-laser mode. Under the conditions reported in this article, the thermal tails of the peaks in the mass spectra did not show any significant change when produced with either a 10-ps or a 120-fs pulsed-laser source. Mass resolving power generally improves as the laser spot size and laser wavelength are decreased and as the specimen tip radius, specimen taper angle, and thermal diffusivity of the specimen material are increased. However, it is shown that two of the materials used in this study, aluminum and stainless steel, depend on these factors differently. A one-dimensional heat flow model is explored to explain these differences. The model correctly predicts the behavior of the aluminum samples, but breaks down for the stainless steel samples when the tip radius is large. A more accurate three-dimensional model is needed to overcome these discrepancies.
The mean-free-paths for inelastic scattering of high-energy electrons (200 keV) for AlAs and GaAs have been determined based on a comparison of thicknesses as measured by electron holography and convergent-beam electron diffraction. The measured values are 77 ± 4 nm and 67 ± 4 nm for AlAs and GaAs, respectively. Using these values, the mean inner potentials of AlAs and GaAs were then determined, from a total of 15 separate experimental measurements, to be 12.1 ± 0.7 V and 14.0 ± 0.6 V, respectively. These latter measurements show good agreement with recent theoretical calculations within experimental error.