Correction of non-linearity effects in detectors for electron spectroscopy

Using photoemission intensities and a detection system employed by many groups in the electron spectroscopy community as an example, we have quantitatively characterized and corrected detector non-linearity effects over the full dynamic range of the system. Non-linearity effects are found to be important whenever measuring relative peak intensities accurately is important, even in the low-countrate regime. This includes, for example, performing quantitative analyses for surface contaminants or sample bulk stoichiometries, where the peak intensities involved can differ by one or two orders of magnitude, and thus could occupy a significant portion of the detector dynamic range. Two successful procedures for correcting non-linearity effects are presented. The first one yields directly the detector efficiency by measuring a flat-background reference intensity as a function of incident x-ray flux, while the second one determines the detector response from a least-squares analysis of broad-scan survey spectra at different incident x-ray fluxes. Although we have used one spectrometer and detection system as an example, these methodologies should be useful for many other cases.Comment: 13 pages, 12 figure

An exploration of familial associations in spinal posture defined using a clinical grouping method

The primary aim of this study was to examine familial associations in spinal posture, defined using postural angles and a clinical classification method. A secondary aim was to investigate the reliability of clinical postural classification. Postural angles were calculated from sagittal photographs, while two experienced clinicians made use of standing sagittal images to classify participants into one of four postural groups (sway, flat, hyperlordotic, neutral). Parent-child associations in postural angles and postural groups were evaluated using Pearson\u27s correlation and Fisher\u27s exact test, respectively. Inter-rater reliability was expressed using percentage agreement and Kappa coefficients (K). Daughters whose father or mother had a hyperlordotic posture were 4.0 or 3.5 times, respectively, more likely to have a hyperlordotic posture than daughters whose parents did not have a hyperlordotic posture. These participants in the hyperlorotic group had a significantly higher body mass index than members of the other postural groups (p \u3c 0.03). Percentage agreement between clinicians was 63.5% (K = 0.48). These results provide preliminary evidence of a familial association in the hyperlordotic posture and support the use of postural classification. (C) 2011 Elsevier Ltd. All rights reserved

Cryopreservation of Human Adipose Tissues and Adipose-Derived Stem Cells with DMSO and/or Trehalose: A Systematic Review.

Adipose tissue senescence is implicated as a major player in obesity- and ageing-related disorders. There is a growing body of research studying relevant mechanisms in age-related diseases, as well as the use of adipose-derived stem cells in regenerative medicine. The cell banking of tissue by utilising cryopreservation would allow for much greater flexibility of use. Dimethyl sulfoxide (DMSO) is the most commonly used cryopreservative agent but is toxic to cells. Trehalose is a sugar synthesised by lower organisms to withstand extreme cold and drought that has been trialled as a cryopreservative agent. To examine the efficacy of trehalose in the cryopreservation of human adipose tissue, we conducted a systematic review of studies that used trehalose for the cryopreservation of human adipose tissues and adipose-derived stem cells. Thirteen articles, including fourteen studies, were included in the final review. All seven studies that examined DMSO and trehalose showed that they could be combined effectively to cryopreserve adipocytes. Although studies that compared nonpermeable trehalose with DMSO found trehalose to be inferior, studies that devised methods to deliver nonpermeable trehalose into the cell found it comparable to DMSO. Trehalose is only comparable to DMSO when methods are devised to introduce it into the cell. There is some evidence to support using trehalose instead of using no cryopreservative agent

A genome-wide RNAi screen identifies factors required for distinct stages of C-elegans piRNA biogenesis

In animals, piRNAs and their associated Piwi proteins guard germ cell genomes against mobile genetic elements via an RNAi-like mechanism. In Caenorhabditis elegans, 21U-RNAs comprise the piRNA class, and these collaborate with 22G RNAs via unclear mechanisms to discriminate self from nonself and selectively and heritably silence the latter. Recent work indicates that 21U-RNAs are post-transcriptional processing products of individual transcription units that produce similar to 26-nucleotide capped precursors. However, nothing is known of how the expression of precursors is controlled or how primary transcripts give rise to mature small RNAs. We conducted a genome-wide RNAi screen to identify components of the 21U biogenesis machinery. Screening by direct, quantitative PCR (qPCR)-based measurements of mature 21U-RNA levels, we identified 22 genes important for 21U-RNA production, termed TOFUs (Twenty-One-u Fouled Ups). We also identified seven genes that normally repress 21U production. By measuring mature 21U-RNA and precursor levels for the seven strongest hits from the screen, we assigned factors to discrete stages of 21U-RNA production. Our work identifies for the first time factors separately required for the transcription of 21U precursors and the processing of these precursors into mature 21U-RNAs, thereby providing a resource for studying the biogenesis of this important small RNA class

Quantum Rotor Engines

This chapter presents autonomous quantum engines that generate work in the form of directed motion for a rotor. We first formulate a prototypical clock-driven model in a time-dependent framework and demonstrate how it can be translated into an autonomous engine with the introduction of a planar rotor degree of freedom. The rotor plays both the roles of internal engine clock and of work repository. Using the example of a single-qubit piston engine, the thermodynamic performance is then reviewed. We evaluate the extractable work in terms of ergotropy, the kinetic energy associated to net directed rotation, as well as the intrinsic work based on the exerted torque under autonomous operation; and we compare them with the actual energy output to an external dissipative load. The chapter closes with a quantum-classical comparison of the engine's dynamics. For the single-qubit piston example, we propose two alternative representations of the qubit in an entirely classical framework: (i) a coin flip model and (ii) a classical magnet moment, showing subtle differences between the quantum and classical descriptions.Comment: Chapter of the upcoming book "Thermodynamics in the Quantum Regime - Recent Progress and Outlook

THE RELATIONSHIP OF TIBIAL BONE PERFUSION TO PAIN IN KNEE OSTEOARTHRITIS.

Objective To confirm altered perfusion within tibial bone marrow lesions (BMLs) and improve our understanding on the relationship between BMLs and pain in knee osteoarthritis (OA). Methods Participants with moderate to severe knee OA were recruited and pain was assessed using the pain subscale of the Western Ontario and McMaster Universities Arthritis Index (WOMAC). Subchondral tibial BMLs were identified and graded on magnetic resonance imaging (MRI) proton density-weighted (PDW) fat suppressed images. A pharmacokinetic model was used to analyze perfusion parameters on dynamic contrast enhanced (DCE) MRI which represent transfer rates in and out of the BMLs. The relation between perfusion and pain was evaluated using multivariable linear regression after adjustment for BML grade, age, gender and body mass index (BMI). Results There were 37 participants (mean age 64.9 years, range 46–86) with radiographic Kellgren and Lawrence grades of 3 and 4 in the study knee; 75.6% had BMLs that were classified grades 1 and 2. The mean WOMAC pain score was 10.3 (0–20 scale). There was a significant correlation between BML Kel (rate of contrast elimination) and BML grade (P = 0.001 univariate, P = 0.002 multivariate analyses), although we did not demonstrate any significant multivariate association between BML perfusion and pain. We also found an inverse relationship between pain at sleep and BML grade (P < 0.05). Conclusions The absence of any significant association between bone perfusion and pain implies that the relationship of tibial BMLs to pain in OA is still incompletely understood. BMLs are just one component of the whole knee joint and are formed from various causes, all of which interact and collectively contribute to the genesis of pain in OA

THE RELATIONSHIP OF TIBIAL BONE PERFUSION TO PAIN IN KNEE OSTEOARTHRITIS.

Objective To confirm altered perfusion within tibial bone marrow lesions (BMLs) and improve our understanding on the relationship between BMLs and pain in knee osteoarthritis (OA). Methods Participants with moderate to severe knee OA were recruited and pain was assessed using the pain subscale of the Western Ontario and McMaster Universities Arthritis Index (WOMAC). Subchondral tibial BMLs were identified and graded on magnetic resonance imaging (MRI) proton density-weighted (PDW) fat suppressed images. A pharmacokinetic model was used to analyze perfusion parameters on dynamic contrast enhanced (DCE) MRI which represent transfer rates in and out of the BMLs. The relation between perfusion and pain was evaluated using multivariable linear regression after adjustment for BML grade, age, gender and body mass index (BMI). Results There were 37 participants (mean age 64.9 years, range 46–86) with radiographic Kellgren and Lawrence grades of 3 and 4 in the study knee; 75.6% had BMLs that were classified grades 1 and 2. The mean WOMAC pain score was 10.3 (0–20 scale). There was a significant correlation between BML Kel (rate of contrast elimination) and BML grade (P = 0.001 univariate, P = 0.002 multivariate analyses), although we did not demonstrate any significant multivariate association between BML perfusion and pain. We also found an inverse relationship between pain at sleep and BML grade (P < 0.05). Conclusions The absence of any significant association between bone perfusion and pain implies that the relationship of tibial BMLs to pain in OA is still incompletely understood. BMLs are just one component of the whole knee joint and are formed from various causes, all of which interact and collectively contribute to the genesis of pain in OA

Framing and signalling effects of taxes on sugary drinks: a discrete choice experiment among households in Great Britain

Taxes on sugar-sweetened beverages (SSBs) are in place in many countries to combat obesity with emerging evidence that these are effective in reducing purchases of SSBs. In this study, we tested whether signalling and framing the price increase from an SSB tax explicitly as a health-related, earmarked measure reduces the demand for SSBs more than an equivalent price increase. We measured the demand for non-alcoholic beverages with a discrete choice experiment (DCE) administered online to a randomly selected group of n = 603 households with children in Great Britain (GB) who regularly purchase SSBs. We find a suggestive evidence that a price increase leads to a larger reduction in the probability of choosing SSBs when it is signalled as a tax and framed as a health-related and earmarked policy. Respondents who did not support a tax on SSBs, who were also more likely to choose SSBs in the first place, were on average more responsive to a price increase framed as an earmarked tax than those who supported the tax. The predictive validity of the DCE, to capture preferences for beverages, was confirmed using actual purchase data. The findings imply that a well-signalled and earmarked tax on SSBs could improve its effectiveness at reducing the demand

Evolution of spectral function in a doped Mott insulator : surface vs. bulk contributions

We study the evolution of the spectral function with progressive hole doping in a Mott insulator, $La_{1-x}Ca_xVO_3$ with $x$ = 0.0 - 0.5. The spectral features indicate a bulk-to-surface metal-insulator transition in this system. Doping dependent changes in the bulk electronic structure are shown to be incompatible with existing theoretical predictions. An empirical description based on the single parameter, $U/W$, is shown to describe consistently the spectral evolution.Comment: Revtex, 4 pages, 3 postscript figures. To appear in Phys. Rev. Let