Dynamic effects in the scattering of electrons by small clusters of atoms

Dynamic scattering corrections were calculated for 40 kV electrons diffracted by randomly oriented fcc clusters of argon and of gold atoms ranging in size from 13 to 135 atoms. Computations were carried out according to several variants of two limiting theoretical approaches, namely, the direct summing up of atomic contributions calculated through single–single and single–double scattered waves by modifications of Glauber theory, and the extrapolation to limitingly small crystallites of conventional dynamic theory in the Blackman and Fujimoto formulations. For the small clusters studied, integrated intensities of diffraction rings (through single–double scatterings) calculated for three dimensional crystallites differ insignificantly from Glauber theory intensities calculated by projecting atomic potential energies onto a plane perpendicular to the mean direction of the incident and scattered wave vectors. The fractional dynamic correction increases with cluster size very nearly as N2/3 in both the Glauber and Blackman–Fujimoto limiting treatments. For crystalline clusters 8–20 Å in diameter, the dynamic effect calculated by summing single–double scatterings is an order of magnitude larger than that according to Blackman–Fujimoto theory. For argon clusters the dynamic effect is not serious; but according to our direct sums, dynamic corrections for 16 Å spheres of gold are surprisingly large, exceeding 25% for 111 reflections. Since the direct sums have been verified experimentally for several vapor‐phase molecules, the present work indicates that, in the limit of very small scatterers, extrapolations from conventional two‐beam dynamic theory may seriously underestimate the magnitude of dynamic effects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71250/2/JCPSA6-66-12-5387-1.pd

Entropic effects on the Size Evolution of Cluster Structure

We show that the vibrational entropy can play a crucial role in determining the equilibrium structure of clusters by constructing structural phase diagrams showing how the structure depends upon both size and temperature. These phase diagrams are obtained for example rare gas and metal clusters.Comment: 5 pages, 3 figure

Mitochondria of the Yeasts Saccharomyces cerevisiae and Kluyveromyces lactis Contain Nuclear rDNA-Encoded Proteins

In eukaryotes, the nuclear ribosomal DNA (rDNA) is the source of the structural 18S, 5.8S and 25S rRNAs. In hemiascomycetous yeasts, the 25S rDNA sequence was described to lodge an antisense open reading frame (ORF) named TAR1 for Transcript Antisense to Ribosomal RNA. Here, we present the first immuno-detection and sub-cellular localization of the authentic product of this atypical yeast gene. Using specific antibodies against the predicted amino-acid sequence of the Saccharomyces cerevisiae TAR1 product, we detected the endogenous Tar1p polypeptides in S. cerevisiae (Sc) and Kluyveromyces lactis (Kl) species and found that both proteins localize to mitochondria. Protease and carbonate treatments of purified mitochondria further revealed that endogenous Sc Tar1p protein sub-localizes in the inner membrane in a Nin-Cout topology. Plasmid-versions of 5′ end or 3′ end truncated TAR1 ORF were used to demonstrate that neither the N-terminus nor the C-terminus of Sc Tar1p were required for its localization. Also, Tar1p is a presequence-less protein. Endogenous Sc Tar1p was found to be a low abundant protein, which is expressed in fermentable and non-fermentable growth conditions. Endogenous Sc TAR1 transcripts were also found low abundant and consistently 5′ flanking regions of TAR1 ORF exhibit modest promoter activity when assayed in a luciferase-reporter system. Using rapid amplification of cDNA ends (RACE) PCR, we also determined that endogenous Sc TAR1 transcripts possess heterogeneous 5′ and 3′ ends probably reflecting the complex expression of a gene embedded in actively transcribed rDNA sequence. Altogether, our results definitively ascertain that the antisense yeast gene TAR1 constitutes a functional transcription unit within the nuclear rDNA repeats

Report from the fifth international consensus meeting to harmonize core outcome measures for atopic eczema/dermatitis clinical trials (HOME initiative)

This is the report from the fifth meeting of the Harmonising Outcome Measures for Eczema initiative (HOME V). The meeting was held on 12–14 June 2017 in Nantes, France, with 81 participants. The main aims of the meeting were (i) to achieve consensus over the definition of the core domain of long-term control and how to measure it and (ii) to prioritize future areas of research for the measurement of the core domain of quality of life (QoL) in children. Moderated whole-group and small-group consensus discussions were informed by presentations of qualitative studies, systematic reviews and validation studies. Small-group allocations were performed a priori to ensure that each group included different stakeholders from a variety of geographical regions. Anonymous whole-group voting was carried out using handheld electronic voting pads according to predefined consensus rules. It was agreed by consensus that the long-term control domain should include signs, symptoms, quality of life and a patient global instrument. The group agreed that itch intensity should be measured when assessing long-term control of eczema in addition to the frequency of itch captured by the symptoms domain. There was no recommendation of an instrument for the core outcome domain of quality of life in children, but existing instruments were assessed for face validity and feasibility, and future work that will facilitate the recommendation of an instrument was agreed upon. The Harmonising Outcome Measures for Eczema (HOME) initiative is an international group working together to develop a core outcome set (COS) for clinical trials in eczema (synonymous with atopic eczema and atopic dermatitis). HOME is coordinated from the Centre of Evidence Based Dermatology, University of Nottingham, U.K. Participation in HOME is open to anyone with an interest in outcomes for eczema. A COS is the agreed upon minimum set of instruments that should be included in all clinical trials for a particular condition. Use of a COS does not preclude using other instruments; other domains and instruments can also be included to meet the specific requirements of individual trials. COS initiatives are active across many fields of medicine and should enable better synthesis of trial data and reduce selective outcome reporting bias. The HOME initiative follows the best current guidance on developing a COS. Four core domains have been identified: clinician-reported signs; patient-reported symptoms; quality of life; and long-term control. The core outcome measurement instruments for clinician-reported signs and patient-reported symptoms have been established: the Eczema Area and Severity Index (EASI) for measuring clinician reported signs was agreed on at the HOME III meeting, and the Patient-Oriented Eczema Measure (POEM) was chosen to measure patient-reported symptoms at the HOME IV meeting. This is a report from the fifth consensus meeting of the HOME initiative (HOME V), which was held on 12–14 June 2017 in Nantes, France. The local organizers were Sebastien Barbarot and Jean-Francois Stalder of Nantes University Hospital, France

A Viable Hypomorphic Allele of the Essential IMP3 Gene Reveals Novel Protein Functions in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, the essential IMP3 gene encodes a component of the SSU processome, a large ribonucleoprotein complex required for processing of small ribosomal subunit RNA precursors. Mutation of the IMP3 termination codon to a sense codon resulted in a viable mutant allele producing a C-terminal elongated form of the Imp3 protein. A strain expressing the mutant allele displayed ribosome biogenesis defects equivalent to IMP3 depletion. This hypomorphic allele represented a unique opportunity to investigate and better understand the Imp3p functions. We demonstrated that the +1 frameshifting was increased in the mutant strain. Further characterizations revealed involvement of the Imp3 protein in DNA repair and telomere length control, pointing to a functional relationship between both pathways and ribosome biogenesis

Molecular dynamics study of orientational order and rotational melting in clusters of TeF 6

Molecular dynamics simulations of the behavior of molecules in crystalline clusters of TeF 6 were carried out on systems of 100, 150, 250, and 350 molecules. Several diagnostic functions were applied to investigate whether rotational melting occurred before translational melting. These functions included the coefficient of rotational diffusion D θ ( T ), the “orientational Lindemann index” δ θ ( T ), the “orientational angular distribution function” Q (θ, T ), and the “orientational pair-correlation function” g θ ( r, T ). All indicators implied that rotational melting occurred before translational melting, that it began with the outermost molecules, and that its onset for smaller clusters was at lower temperatures than for larger clusters. Results also showed that the rotational transition coincided with the transition from a lower symmetry phase (monoclinic) to cubic, a phenomenon that had been noted by others to occur with some regularity for systems of globular molecules.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43961/1/10053_2005_Article_BF01426586.pd

Genome-wide search for breast cancer linkage in large Icelandic non-BRCA1/2 families

Abstract Introduction: A significant proportion of high-risk breast cancer families are not explained by mutations in known genes. Recent genome-wide searches (GWS) have not revealed any single major locus reminiscent of BRCA1 and BRCA2, indicating that still unidentified genes may explain relatively few families each or interact in a way obscure to linkage analyses. This has drawn attention to possible benefits of studying populations where genetic heterogeneity might be reduced. We thus performed a GWS for linkage on nine Icelandic multiple-case non-BRCA1/2 families of desirable size for mapping highly penetrant loci. To follow up suggestive loci, an additional 13 families from other Nordic countries were genotyped for selected markers. Methods: GWS was performed using 811 microsatellite markers providing about five centiMorgan (cM) resolution. Multipoint logarithm of odds (LOD) scores were calculated using parametric and nonparametric methods. For selected markers and cases, tumour tissue was compared to normal tissue to look for allelic loss indicative of a tumour suppressor gene. Results: The three highest signals were located at chromosomes 6q, 2p and 14q. One family contributed suggestive LOD scores (LOD 2.63 to 3.03, dominant model) at all these regions, without consistent evidence of a tumour suppressor gene. Haplotypes in nine affected family members mapped the loci to 2p23.2 to p21, 6q14.2 to q23.2 and 14q21.3 to q24.3. No evidence of a highly penetrant locus was found among the remaining families. The heterogeneity LOD (HLOD) at the 6q, 2p and 14q loci in all families was 3.27, 1.66 and 1.24, respectively. The subset of 13 Nordic families showed supportive HLODs at chromosome 6q (ranging from 0.34 to 1.37 by country subset). The 2p and 14q loci overlap with regions indicated by large families in previous GWS studies of breast cancer. Conclusions: Chromosomes 2p, 6q and 14q are candidate sites for genes contributing together to high breast cancer risk. A polygenic model is supported, suggesting the joint effect of genes in contributing to breast cancer risk to be rather common in non-BRCA1/2 families. For genetic counselling it would seem important to resolve the mode of genetic interaction

Surface tensions and stress tensors of liquid and solid clusters by molecular dynamics

Surface tension and pressure (stress) tensors of Lennard-Jones clusters, in the size range $200\sim2700$ atoms/cluster, formed from evaporating liquid droplets were calculated in a Molecular Dynamics simulation. Icosahedral clusters have a much larger surface tension than decahedral, fcc, and hcp ones, meanwhile asymmetric icosahedral clusters have a lower surface tension. Fcc and hcp clusters have a very small surface tension. Decahedral clusters have a surface tension closer to that of fcc and hcp ones than to that of icosahedral ones, though both icosahedral and decahedral structures have five fold symmetry axis. Binary component clusters have a higher surface tension than single component ones