Piezoresistivity is an electromechanical effect characterized by the reversible change in the electrical resistivity with strain. It is useful for electrical-resistance-based strain/stress sensing. ...The resistivity can be the volumetric, interfacial or surface resistivity, though the volumetric resistivity is most meaningful scientifically. Because the irreversible resistivity change (due to damage or an irreversible microstructural change) adds to the reversible change that occurs at lower strains, the inclusion of the irreversible effect makes the piezoresistivity appear stronger than the inherent effect. This paper focuses on the inherent piezoresistivity that occurs without irreversible resistivity changes. The effect is described by the gage factor (GF), which is defined as the fractional change in resistance per unit strain. The GF can be positive or negative. Strong piezoresistivity involves the magnitude of the fractional change in resistivity much exceeding the strain magnitude. The reversible effect of strain on the electrical connectivity is the primary piezoresistivity mechanism. Giant piezoresistivity is characterized by GF ≥ 500. This critical review with 209 references covers the theory, mechanisms, methodology and status of piezoresistivity, and provides the first review of the emerging field of giant piezoresistivity. Piezoresistivity is exhibited by electrically conductive materials, particularly metals, carbons and composite materials with conductive fillers and nonconductive matrices. They include functional and structural materials. Piezoresistivity enables structural materials to be self-sensing. Unfortunately, GF was incorrectly or unreliably reported in a substantial fraction of the publications, due to the pitfalls systematically presented here. The most common pitfall involves using the two-probe method for the resistance measurement.
We present the first joint analysis of cluster abundances and auto or cross-correlations of three cosmic tracer fields: galaxy density, weak gravitational lensing shear, and cluster density split by ...optical richness. From a joint analysis (4×2pt+N) of cluster abundances, three cluster cross-correlations, and the auto correlations of the galaxy density measured from the first year data of the Dark Energy Survey, we obtain Ω_{m}=0.305_{-0.038}^{+0.055} and σ_{8}=0.783_{-0.054}^{+0.064}. This result is consistent with constraints from the DES-Y1 galaxy clustering and weak lensing two-point correlation functions for the flat νΛCDM model. Consequently, we combine cluster abundances and all two-point correlations from across all three cosmic tracer fields (6×2pt+N) and find improved constraints on cosmological parameters as well as on the cluster observable-mass scaling relation. This analysis is an important advance in both optical cluster cosmology and multiprobe analyses of upcoming wide imaging surveys.
Summary Background Trial findings show cognitive behaviour therapy (CBT) and graded exercise therapy (GET) can be effective treatments for chronic fatigue syndrome, but patients' organisations have ...reported that these treatments can be harmful and favour pacing and specialist health care. We aimed to assess effectiveness and safety of all four treatments. Methods In our parallel-group randomised trial, patients meeting Oxford criteria for chronic fatigue syndrome were recruited from six secondary-care clinics in the UK and randomly allocated by computer-generated sequence to receive specialist medical care (SMC) alone or with adaptive pacing therapy (APT), CBT, or GET. Primary outcomes were fatigue (measured by Chalder fatigue questionnaire score) and physical function (measured by short form-36 subscale score) up to 52 weeks after randomisation, and safety was assessed primarily by recording all serious adverse events, including serious adverse reactions to trial treatments. Primary outcomes were rated by participants, who were necessarily unmasked to treatment assignment; the statistician was masked to treatment assignment for the analysis of primary outcomes. We used longitudinal regression models to compare SMC alone with other treatments, APT with CBT, and APT with GET. The final analysis included all participants for whom we had data for primary outcomes. This trial is registered at http://isrctn.org , number ISRCTN54285094. Findings We recruited 641 eligible patients, of whom 160 were assigned to the APT group, 161 to the CBT group, 160 to the GET group, and 160 to the SMC-alone group. Compared with SMC alone, mean fatigue scores at 52 weeks were 3·4 (95% CI 1·8 to 5·0) points lower for CBT (p=0·0001) and 3·2 (1·7 to 4·8) points lower for GET (p=0·0003), but did not differ for APT (0·7 −0·9 to 2·3 points lower; p=0·38). Compared with SMC alone, mean physical function scores were 7·1 (2·0 to 12·1) points higher for CBT (p=0·0068) and 9·4 (4·4 to 14·4) points higher for GET (p=0·0005), but did not differ for APT (3·4 −1·6 to 8·4 points lower; p=0·18). Compared with APT, CBT and GET were associated with less fatigue (CBT p=0·0027; GET p=0·0059) and better physical function (CBT p=0·0002; GET p<0·0001). Subgroup analysis of 427 participants meeting international criteria for chronic fatigue syndrome and 329 participants meeting London criteria for myalgic encephalomyelitis yielded equivalent results. Serious adverse reactions were recorded in two (1%) of 159 participants in the APT group, three (2%) of 161 in the CBT group, two (1%) of 160 in the GET group, and two (1%) of 160 in the SMC-alone group. Interpretation CBT and GET can safely be added to SMC to moderately improve outcomes for chronic fatigue syndrome, but APT is not an effective addition. Funding UK Medical Research Council, Department of Health for England, Scottish Chief Scientist Office, Department for Work and Pensions.
Micronutrient deficiencies are identified among obese individuals. Vitamin D deficiency (VDD) is prevalent in obese children, and is hypothesized to cause insulin resistance and metabolic ...abnormalities. This study aimed to determine the effect of vitamin D supplementation on obesity and related metabolic abnormalities among obese Sri Lankan children with VDD.
A triple-blind randomized controlled trial was conducted among vitamin D deficient (< 20 ng/ml), obese children (n = 96), randomly allocated to three intervention arms - treatment arm receiving weekly vitamin D
50,000 IU; supplementation arm receiving 2500 IU weekly and control arm, receiving placebo. Anthropometry, percentage fat mass (%FM) and blood pressure were assessed and fasting blood glucose, fasting insulin, lipid profile, aspartate transaminase (ALT), alanine transaminase (AST), vitamin D, parathyroid hormone (PTH) and hs-CRP and OGTT with 2-h random blood glucose and insulin was performed at baseline and after 24 weeks of treatment. Ethics Review Committee of Faculty of Medicine, University of Colombo approved the protocol.
Waist circumference Z-score, %FM and serum calcium significantly improved across all three arms, ALT significantly improved in treatment and supplementation arms while, BMI Z-score, PTH and vitamin D significantly improved in the treatment arm. Biceps (p = 0.035) and subscapular (0.048) skin fold thickness, vitamin D (p = 0.004) and ALT (p = 0.012) significantly improved in the treatment arm.
A strict dietary and physical activity regimen could improve some of the anthropometric, body composition and metabolic profiles, but high dose vitamin D, enhances those improvements. Therefore high dose vitamin D seems to potentiate management outcomes of obese children with vitamin D deficiency.
The study was registered at the Sri Lanka Clinical Trials Registry (SLCTR/2015/017) on 12th September 2015 at https://slctr.lk/trials/slctr-2015-017 .
review of exfoliated graphite Chung, D. D. L
Journal of materials science,
01/2016, Letnik:
51, Številka:
1
Journal Article
Recenzirano
Exfoliated graphite (EG) refers to graphite that has a degree of separation of a substantial portion of the carbon layers in the graphite. Graphite nanoplatelet (GNP) is commonly prepared by ...mechanical agitation of EG. The EG exhibits clinginess, due to its cellular structure, but GNP does not. The clinginess allows the formation of EG compacts and flexible graphite sheet without a binder. The exfoliation typically involves intercalation, followed by heating. Upon heating, the intercalate vaporizes and/or decomposes into smaller molecules, thus causing expansion and cell formation. The sliding of the carbon layers relative to one another enables the cell wall to stretch. The exfoliation process is accompanied by intercalate desorption, so that only a small portion of the intercalate remains after exfoliation. The most widely used intercalate is sulfuric acid. The higher concentration of residue in unwashed EG causes the relative dielectric constant (50 Hz) of the EG to be 360 (higher than 120 for KOH-activated GNP), compared to the value of 38 for the water-washed case. An EG compact is obtained by the compression of EG at a pressure lower than that used for the fabrication of flexible graphite. Compared to flexible graphite, EG compacts are mechanically weak, but they exhibit viscous character, out-of-plane electrical/thermal conductivity and liquid permeability. The viscous character (flexural loss tangent up to 35 for the solid part of the compact) stems from the sliding of the carbon layers relative to one another, with the ease of the sliding enhanced by the exfoliation process.
It is known that obesity is associated with vitamin D deficiency and observational studies have shown vitamin D deficiency to be linked with the development of type 2 diabetes. There are no ...comprehensive data regarding vitamin D deficiency in children with obesity in Sri Lanka and the objective of the study was to assess the prevalence of Vitamin D deficiency and its association with metabolic derangements among children with obesity.
Two hundred and two children between 5 and 15 years of age attending the obesity clinic Lady Ridgeway Hospital (LRH) were recruited excluding those having possible secondary causes for obesity. Blood was drawn after 12-h overnight fast for fasting blood glucose(FBG), lipid profile, serum insulin, alanine aminotransferase (ALT),aspartate aminotransferase(AST), Vitamin D, parathyroid hormone(PTH),high sensitivity C reactive protein(hs-CRP). Oral glucose tolerance test (OGTT) was done with 2 h random blood glucose. Anthropometry, blood pressure were measured, and body fat mass was assessed using bio-impedance.
Vitamin D deficiency (< 20 ng/ml) was seen in 152(75.2%) children and 43(21.3%) had insufficient (20-30 ng/ml) levels. Skin fold thickness, fasting and post-glucose insulin, HOMA-IR, PTH, LDL, Serum cholesterol and hs-CRP showed statistically significant negative correlations with Vitamin D levels.
Vitamin D deficiency was significantly high in Sri Lankan children with obesity and showed significant negative correlations with indicators of insulin resistance and adiposity.
We describe the procedure used to flux calibrate the three-band submillimetre photometer in the Spectral and Photometric Imaging Receiver instrument on the Herschel Space Observatory. This includes ...the equations describing the calibration scheme, a justification for using Neptune as the primary calibration source, a description of the observations and data processing procedures used to derive flux calibration parameters (for converting from voltage to flux density) for every bolometer in each array, an analysis of the error budget in the flux calibration for the individual bolometers and tests of the flux calibration on observations of primary and secondary calibrators. The procedure for deriving the flux calibration parameters is divided into two parts. In the first part, we use observations of astronomical sources in conjunction with the operation of the photometer internal calibration source to derive the unscaled derivatives of the flux calibration curves. To scale the calibration curves in Jy beam−1 V−1, we then use observations of Neptune in which the beam of each bolometer is mapped using a very fine scan pattern. The total instrumental uncertainties in the flux calibration for most individual bolometers is ∼0.5 per cent, although a few bolometers have uncertainties of ∼1-5 per cent because of issues with the Neptune observations. Based on application of the flux calibration parameters to Neptune observations performed using typical scan map observing modes, we determined that measurements from each array as a whole have instrumental uncertainties of 1.5 per cent. This is considerably less than the absolute calibration uncertainty associated with the model of Neptune, which is estimated at 4 per cent.
ABSTRACT
We present angular diameter distance measurements obtained by locating the baryon acoustic oscillations (BAO) scale in the distribution of galaxies selected from the first year of Dark ...Energy Survey data. We consider a sample of over 1.3 million galaxies distributed over a footprint of 1336 deg2 with 0.6 < $z$photo < 1 and a typical redshift uncertainty of 0.03(1 + $z$). This sample was selected, as fully described in a companion paper, using a colour/magnitude selection that optimizes trade-offs between number density and redshift uncertainty. We investigate the BAO signal in the projected clustering using three conventions, the angular separation, the comoving transverse separation, and spherical harmonics. Further, we compare results obtained from template-based and machine-learning photometric redshift determinations. We use 1800 simulations that approximate our sample in order to produce covariance matrices and allow us to validate our distance scale measurement methodology. We measure the angular diameter distance, DA, at the effective redshift of our sample divided by the true physical scale of the BAO feature, rd. We obtain close to a 4 per cent distance measurement of DA($z$eff = 0.81)/rd = 10.75 ± 0.43. These results are consistent with the flat Λ cold dark matter concordance cosmological model supported by numerous other recent experimental results.
Abstract
We present
Magellan
/IMACS spectroscopy of the recently discovered Milky Way satellite Eridanus II (Eri II). We identify 28 member stars in Eri II, from which we measure a systemic radial ...velocity of
and a velocity dispersion of
. Assuming that Eri II is a dispersion-supported system in dynamical equilibrium, we derive a mass within the half-light radius of
, indicating a mass-to-light ratio of
/
and confirming that it is a dark matter-dominated dwarf galaxy. From the equivalent width measurements of the Ca triplet lines of 16 red giant member stars, we derive a mean metallicity of Fe/H = −2.38 ± 0.13 and a metallicity dispersion of
. The velocity of Eri II in the Galactic standard of rest frame is
v
GSR
= −66.6
, indicating that either Eri II is falling into the Milky Way potential for the first time or that it has passed the apocenter of its orbit on a subsequent passage. At a Galactocentric distance of ∼370 kpc, Eri II is one of the Milky Way’s most distant satellites known. Additionally, we show that the bright blue stars previously suggested to be a young stellar population are not associated with Eri II. The lack of gas and recent star formation in Eri II is surprising given its mass and distance from the Milky Way, and may place constraints on models of quenching in dwarf galaxies and on the distribution of hot gas in the Milky Way halo. Furthermore, the large velocity dispersion of Eri II can be combined with the existence of a central star cluster to constrain massive compact halo object dark matter with mass ≳10
.
With the advent of the Heliophysics/Geospace System Observatory (H/GSO), a complement of multi-spacecraft missions and ground-based observatories to study the space environment, data retrieval, ...analysis, and visualization of space physics data can be daunting. The Space Physics Environment Data Analysis System (SPEDAS), a grass-roots software development platform (
www.spedas.org
), is now officially supported by NASA Heliophysics as part of its data environment infrastructure. It serves more than a dozen space missions and ground observatories and can integrate the full complement of past and upcoming space physics missions with minimal resources, following clear, simple, and well-proven guidelines. Free, modular and configurable to the needs of individual missions, it works in both command-line (ideal for experienced users) and Graphical User Interface (GUI) mode (reducing the learning curve for first-time users). Both options have “crib-sheets,” user-command sequences in ASCII format that can facilitate record-and-repeat actions, especially for complex operations and plotting. Crib-sheets enhance scientific interactions, as users can move rapidly and accurately from exchanges of technical information on data processing to efficient discussions regarding data interpretation and science. SPEDAS can readily query and ingest all International Solar Terrestrial Physics (ISTP)-compatible products from the Space Physics Data Facility (SPDF), enabling access to a vast collection of historic and current mission data. The planned incorporation of Heliophysics Application Programmer’s Interface (HAPI) standards will facilitate data ingestion from distributed datasets that adhere to these standards. Although SPEDAS is currently Interactive Data Language (IDL)-based (and interfaces to Java-based tools such as Autoplot), efforts are under-way to expand it further to work with python (first as an interface tool and potentially even receiving an under-the-hood replacement). We review the SPEDAS development history, goals, and current implementation. We explain its “modes of use” with examples geared for users and outline its technical implementation and requirements with software developers in mind. We also describe SPEDAS personnel and software management, interfaces with other organizations, resources and support structure available to the community, and future development plans.
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