Inter-comparison on multi-feature bar calibration for determining machine-tool geometric errors

International audienceTo improve the accuracy of manufactured mechanical parts, the geometric errors of a machine-tool should be evaluated and compensated in order to better master the deviations between the actual and nominal tool positioning (volumetric accuracy). Thus, a novel Multi-Feature Bar (MFB) for machine-tool geometric errors' identification was designed and manufactured. The MFB standard is made of Invar material. The proposed design of the MFB allows extracting three intrinsic parameters: one linear positioning and two straightness errors. The calibration of the MFB was performed on an accurate coordinate measuring machine (CMM) when applying the reversal technique, in order to separate the MFB's error forms from the motion errors of the CMM's mechanical guiding systems. Furthermore, an intercomparison was conducted between four National Metrology Institutes (LNE, PTB, CMI, UM) to evaluate the reliability of the proposed calibration methodology. Findings resulting from this intercomparison reveal dimensional stability of the MFB standard for geometric errors identification on CMM and machine-tool. Therefore, the use on machine-tool of the calibrated MFB, regardless of the harsh environment, guarantees its metrology traceability to the SI metre definition of few micrometres (<5 µm)

Atomic and Electronic Structure of a Rashba pp-nn Junction at the BiTeI Surface

The non-centrosymmetric semiconductor BiTeI exhibits two distinct surface terminations that support spin-split Rashba surface states. Their ambipolarity can be exploited for creating spin-polarized $p$-$n$ junctions at the boundaries between domains with different surface terminations. We use scanning tunneling microscopy/spectroscopy (STM/STS) to locate such junctions and investigate their atomic and electronic properties. The Te- and I-terminated surfaces are identified owing to their distinct chemical reactivity, and an apparent height mismatch of electronic origin. The Rashba surface states are revealed in the STS spectra by the onset of a van Hove singularity at the band edge. Eventually, an electronic depletion is found on interfacial Te atoms, consistent with the formation of a space charge area in typical $p$-$n$ junctions.Comment: 5 pages, 4 figure

Picosecond fluctuating protein energy landscape mapped by pressure–temperature molecular dynamics simulation

Microscopic statistical pressure fluctuations can, in principle, lead to corresponding fluctuations in the shape of a protein energy landscape. To examine this, nanosecond molecular dynamics simulations of lysozyme are performed covering a range of temperatures and pressures. The well known dynamical transition with temperature is found to be pressure-independent, indicating that the effective energy barriers separating conformational substates are not significantly influenced by pressure. In contrast, vibrations within substates stiffen with pressure, due to increased curvature of the local harmonic potential in which the atoms vibrate. The application of pressure is also shown to selectively increase the damping of the anharmonic, low-frequency collective modes in the protein, leaving the more local modes relatively unaffected. The critical damping frequency, i.e., the frequency at which energy is most efficiently dissipated, increases linearly with pressure. The results suggest that an invariant description of protein energy landscapes should be subsumed by a fluctuating picture and that this may have repercussions in, for example, mechanisms of energy dissipation accompanying functional, structural, and chemical relaxation

Electronic Instability in a Zero-Gap Semiconductor: The Charge-DensityWave in (TaSe4)(2)I

We report a comprehensive study of the paradigmatic quasi-1D compound (TaSe4)(2)I performed by means of angle-resolved photoemission spectroscopy (ARPES) and first-principles electronic structure calculations. We find it to be a zero-gap semiconductor in the nondistorted structure, with non-negligible interchain coupling. Theory and experiment support a Peierls-like scenario for the charge-density wave formation below T-CDW = 263 K, where the incommensurability is a direct consequence of the finite interchain coupling. The formation of small polarons, strongly suggested by the ARPES data, explains the puzzling semiconductor-to-semiconductor transition observed in transport at T-CDW.open114sciescopu

Glass transition in biomolecules and the liquid-liquid critical point of water

Using molecular dynamics simulations, we investigate the relation between the dynamic transitions of biomolecules (lysozyme and DNA) and the dynamic and thermodynamic properties of hydration water. We find that the dynamic transition of the macromolecules, sometimes called a ``protein glass transition'', occurs at the temperature of dynamic crossover in the diffusivity of hydration water, and also coincides with the maxima of the isobaric specific heat $C_P$ and the temperature derivative of the orientational order parameter. We relate these findings to the hypothesis of a liquid-liquid critical point in water. Our simulations are consistent with the possibility that the protein glass transition results from crossing the Widom line, which is defined as the locus of correlation length maxima emanating from the hypothesized second critical point of water.Comment: 10 Pages, 12 figure

Isabel II. Reina de España. 1830-1904

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MAARS: a novel high-content acquisition software for the analysis of mitotic defects in fission yeast

Faithful segregation of chromosomes during cell division relies on multiple processes such as chromosome attachment and correct spindle positioning. Yet mitotic progression is defined by multiple parameters, which need to be quantitatively evaluated. To study the spatiotemporal control of mitotic progression, we developed a high-content analysis (HCA) approach that combines automated fluorescence microscopy with real-time quantitative image analysis and allows the unbiased acquisition of multiparametric data at the single-cell level for hundreds of cells simultaneously. The Mitotic Analysis and Recording System (MAARS) provides automatic and quantitative single-cell analysis of mitotic progression on an open-source platform. It can be used to analyze specific characteristics such as cell shape, cell size, metaphase/anaphase delays, and mitotic abnormalities including spindle mispositioning, spindle elongation defects, and chromosome segregation defects. Using this HCA approach, we were able to visualize rare and unexpected events of error correction during anaphase in wild-type or mutant cells. Our study illustrates that such an expert system of mitotic progression is able to highlight the complexity of the mechanisms required to prevent chromosome loss during cell division

Giant ambipolar Rashba effect in a semiconductor: BiTeI

We observe a giant spin-orbit splitting in bulk and surface states of the non-centrosymmetric semiconductor BiTeI. We show that the Fermi level can be placed in the valence or in the conduction band by controlling the surface termination. In both cases it intersects spin-polarized bands, in the corresponding surface depletion and accumulation layers. The momentum splitting of these bands is not affected by adsorbate-induced changes in the surface potential. These findings demonstrate that two properties crucial for enabling semiconductor-based spin electronics -- a large, robust spin splitting and ambipolar conduction -- are present in this material.Comment: 4 pages, 3 figure

Perceptions of people with mild intellectual disability and their family members about family-based social capital in the Netherlands

Families play an important role in the lives of people with intellectual disability as they do for everyone. However, little research has addressed the views of people with intellectual disability about their families by using self-report. Individual family members may hold different views about their family relationships. Therefore, we used a social capital theoretical perspective to examine (a) how perceptions of people with mild intellectual disability (MID) about their family support networks compare to those of their family members and (b) what factors are associated with any diverging perceptions. Randomly selected participants with MID (n = 111) and their family members (n = 111) were interviewed individually at their homes using the Family Network Method-Intellectual Disability (FNM-ID). The FNM-ID examines how people define their family groups and how they perceive existing supportive relationships within this group. The findings showed that participants with MID perceived that they had somewhat denser family networks (i.e., bonding social capital) than family members perceived them to have and were more likely to report bridging social capital. They reported more relationships that involved them providing support to family members. This difference in estimation was greater when the participant with MID displayed higher levels of externalizing behaviour problems. They also perceived more reciprocity in their relationships with family. No differences were found in the estimated numbers of significant family members and relationships in which support was received. It is concluded that people with MID and their family members have different perceptions on several aspects of the family support network. Family professionals and services should seek the views of people with intellectual disability and their family members when carrying out assessments or organizing supports. [Abstract copyright: © 2021 The Authors. Health and Social Care in the Community published by John Wiley & Sons Ltd.