Does a monochromator improve the precision in quantitative HRTEM?

This paper addresses the question as to what extent the incorporation of a monochromator in an electron microscope can enhance the performance of high resolution transmission electron microscopy (HRTEM). The monochromator will reduce the chromatic aberration, and hence the information limit, at the expense of beam current, leading to a decrease in signal intensity and a corresponding decrease in signal-to-noise ratio (SNR). Both aspects, information limit and SNR, have been included in a quantitative evaluation based on the statistical precision with which the position of an atom column can be estimated. It is shown that the effect of a monochromator on the attainable precision depends on the microscope and monochromator parameters, as well as on the characteristics of the object.     

What can we learn from the GUM of 1995?

The Guide to the Expression of Uncertainty in Measurement (GUM) of 1995 is known to be flawed in aspects of it statistical theory and is now undergoing revision. This article considers three controversies faced in the development of such a document, namely (i) the acceptance of the existence of ‘true values’, (ii) the association of variances with systematic influences and (ii) the representation of fixed but unknown quantities by probability distributions, which is a step that separates Bayesian statistics from frequentist, i.e. classical, statistics. Particular attention is paid to Recommendation INC-1 of 1980, which is said to be the foundation of the GUM. This advocates that variances be associated with systematic effects in a manner according with frequentist statistics. However, the revision of the GUM is being carried out along Bayesian lines. A number of difficulties are identified with this approach.     

What does mean mean? – A systematic treatment of statistical methods for measurand estimation

Results of a study in statistical methods for point-wise estimation are presented. Estimation criteria based on unbiasedness, minimum-mean-square-error, maximum likelihood, least squares, and on decision theory are compared and contrasted. Decision theory emerges as a parsimonious and powerful rational, able to unify both ‘frequentist’ and ‘Bayesian’ estimation principles, and to reduce inflation of ad hoc solutions.     

Accounting of multicharged ions in the quantitative analysis of a substance on an ЭMAΛ-2 mass analyzer

Detials of a mass spectrometric analysis of a substance on an ЭMAΛ-2 laser mass analyzer are described. A monovalent-to-multivalent ion contribution ratio is studied. It is shown that the account of multivalent ions makes it possible to reduce the error down to 3–5%.     

How does antiseptic mouthwashes against SARS-COV-2 affect the bond strength of universal adhesive to enamel?

This study compares the effect of different mouthwashes that have been recommended during the Coronavirus disease 2019 (COVID-19) pandemic on shear bond strength (SBS) of universal adhesive to enamel in regards to self-etch (SE) and etch-and-rinse (ER) modes. Flat enamel surfaces were obtained from 100 sound human maxillary central incisors. They were randomly allocated to five groups according to the different mouthwashes (no mouthwash/control [Ctrl], 0.2% chlorhexidine 1.5% hydrogen peroxide [H₂O₂], 0.2% povidone-iodine [PVP-I], Listerine [L]), and adhesive application modes (ER and SE) (n = 10). After the application of a universal adhesive (single bond universal), composite resin (Filtek Z250) was bonded by a cylinder-shaped mold (height: 2 mm, diameter: 2.4 mm). They were subjected to SBS test using a universal testing machine (AGS-X, Shimadzu Corp.) (crosshead speed: 1 mm/min). The resin–enamel interfaces were observed with a scanning electron microscope (SEM). The semiquantitative chemical microanalyses were performed with energy-dispersive spectroscopy (EDS). The data were statistically analyzed by two-way analysis of variance and Bonferroni test (p < .05). In SE mode, Group Ctrl revealed significantly higher SBS than all mouthwash groups (p < .05). In ER mode, Group Ctrl showed significantly higher SBS than H₂O₂ and PVP-I groups (p < .05). ER mode caused significantly higher SBS than SE mode in all mouthwash groups (p < .05). The SEM observations highlighted that Group Ctrl had a regular and intact hybrid layer with resin tag formation while the H₂O₂ and PVP-I groups exhibited a thin hybrid layer in both modes. EDS analysis indicated that in SE mode, all mouthwash groups presented increased O content compared to Group Ctrl. H₂O₂ and PVP-I that were suggested for preprocedural use during the COVID-19 pandemic, reduced the enamel bond strength of the universal adhesive in ER mode.     

Is the Exponent 3/2 Justified in Analysis of Loading Curve of Pyramidal Nanoindentations?

Kaupp and Naimi‐Jamal (2010) claimed that the analysis of published loading curves reveals the exponent 3/2 to the depth for nanoindentations with sharp pyramidal or conical tips. To demonstrate this, they plotted the load vs. the penetration depth to the power 3/2. We show, through examples, the authors’ assertion is not credible because the methodology used is misleading and it cannot be asserted that the exponent 3/2 has a universal validity that applies to all kinds of materials. SCANNING 34: 410‐417, 2012. © 2012 Wiley Periodicals, Inc.     

Lost in reciprocal space? Determination of the scattering condition in spot profile analysis low-energy electron diffraction

The precise knowledge of the diffraction condition, i.e., the angle of incidence and electron energy, is crucial for the study of surface morphology through spot profile analysis low-energy electron diffraction (LEED). We demonstrate four different procedures to determine the diffraction condition: employing the distortion of the LEED pattern under large angles of incidence, the layer-by-layer growth oscillations during homoepitaxial growth, a G(S) analysis of a rough surface, and the intersection of facet rods with 3D Bragg conditions.     

Fragile X mental retardation: Misregulation of protein synthesis in the developing brain?

Fragile X mental retardation results from the absence of a selective RNA-binding protein, FMRP. Previous studies demonstrated that FMRP forms messenger ribonucleoprotein (mRNP) complexes to associate with translating polyribosomes, suggesting that FMRP is involved in regulating protein synthesis. We are now facing the changing questions: How does FMRP influence protein synthesis in the brain? What is the target for FMRP in learning and memory? How does the absence of FMRP cause misregulation of protein synthesis, which in turn leads to mental impairment in fragile X syndrome? Models for abnormal neuronal function as a result of misregulated translation due to the absence of FMRP are discussed. Microsc. Res. Tech. 57:145–147, 2002. © 2002 Wiley-Liss, Inc.     

Is there section deformation resulting in differential change of nuclear numerical densities along the z axis of thick methacrylate or paraffin sections?

The optical disector, a three‐dimensional counting frame or probe in stereology, is often positioned in the middle (depth) of a thick section for unbiased nuclear counting. Using 30–40 μm thick methacrylate or paraffin sections for nuclear counting of neurons with the optical disector, however, some studies showed markedly higher nuclear densities at 10% of the section thickness near the top or bottom surface of the section, suggestive of deformation of section along its z axis and thus affecting the number estimation. To verify the findings, this study obtained two sets of 12–14 methacrylate sections (average thicknesses 21.7 and 29.4 μm) and two sets of 12 paraffin sections (average thicknesses 13.8 and 29.2 μm) from mature rat testes. Each section was used to count round spermatid nuclei in the seminiferous epithelium densely packed with the cells, using 3–4 consecutive disectors placed vertically (along the z axis of the section) from the top surface of the section, through the whole section thickness (two sets of methacrylate and paraffin sections) or in 80–83% of the thickness (other sections). The results demonstrated that, overall, there were no considerable nonuniform changes of the nuclear densities along the z axis of the sections.     

Are the two polymorphic sites of anti-Marek’s disease in White Leghorn chickens also suitable for Partridge Shank chickens?

Background: The selection of Marek’s disease (MD)-resistant breeds in Partridge Shank chicken, a popularlocal chicken breed in Henan Province of China, has practical value. We hypothesized that the two polymorphic sites(rs14527240 located in SMOC1 and GGaluGA156129 located in PTPN3) related to MD resistance in White Leghornchickens are also applicable to Partridge Shank chickens. Methods: In this experiment, we screened 10 live hens and 2live roosters with the double GG genotype by genotyping the two sites from 6500 Partridge Shank chickens. Nineteenone-day-old chicks with the double GG genotype were obtained by artificial insemination. Seventy-two one-day-oldchickens (19 from the population expansion test and 53 randomly selected from chicken farms) were injected with2000 plaque-forming units of the Md5 virus strain. After 100 days of infection, all chickens were examined bypathological anatomical examination, histological sectioning, genotyping, and a quantitative polymerase chain reactionof SMOC1 and PTPN3. Results: There was only one site (rs14527240 located in SMOC1) associated with MD inPartridge Shank chickens (p < 0.05), but the GG genotype of SMOC1 in Partridge Shank chickens indicatedsusceptibility to MD. SMOC1 expression in MD-susceptible chickens was also significantly higher than that in MDresistant chickens (p < 0.05). Conclusion: Therefore, the MD resistance sites selected from White Leghorn chickenswere not completely suitable for Partridge Shank chickens, but they can be used as a reference. This study indicatedthat SMOC1 plays an important role in screening for MD resistance in poultry.