Comparison of gestational dating methods and implications Estimating gestational age is usually based on date of last menstrual period LMP or clinical estimation CE ; both approaches introduce potential bias.
Differences in methods of estimation may lead to misclassificat ion and inconsistencies in risk estimates, particularly if exposure assignment is also gestation-dependent. This paper examines a'what-if' scenario in which alternative methods are used and attempts to elucidate how method choice affects observed results. We constructed two week gestational age cohorts of pregnancies between and New Jersey, Pennsylvania, Ohio, USA using live birth certificates: RD divergences increased between cohorts as exposure period approached delivery.
Among births between 28 and 31 weeks, week 7 PM2. Different results from analyses restricted to births with both CE and LMP are most likely due to differences in dating methods rather than selection issues. Results are sensitive t. The invention employs a source of electromagnetic radiation having a known wavelength or wavelength distribution, which sends a beam of electromagnetic radiation through an object which causes it to be split hereinafter referred to as a "beamsplitter" , and then to a target. The beam is reflected from the target onto a screen containing an aperture spaced a known distance from the beamsplitter.
The aperture is sized so as to produce a Fresnel diffraction pattern. A portion of the beam travels through the aperture to a detector, spaced a known distance from the screen. The detector detects the central intensity of the beam. The distance from the object which causes the beam to be split to the target can then be calculated based upon the known wavelength, aperture radius, beam intensity, and distance from the detector to the screen. Several apparatus embodiments are disclosed for practicing the method embodiments of the present invention.
The invention employs a source of electromagnetic radiation having a known wavelength or wavelength distribution, which sends a beam of electromagnetic radiation through an object which causes it to be split hereinafter referred to as a beam splitter'' , and then to a target. The beam is reflected from the target onto a screen containing an aperture spaced a known distance from the beam splitter.
Absolute quantification methods in tissue near-infrared spectroscopy. Recent work aimed at providing an absolute measurement of tissue haemoglobin saturation and a new instrument development, the spatially resolved spectrometer SRS , are discussed. The theoretical basis of operation of this device and its hardware implementation are described and the results of validation studies on tissue simulating phantoms are presented as are preliminary measurements on human volunteers and observations on patients undergoing neurosurgery.
In its present form the instrument appears to produce absolute haemoglobin saturation values for resting human skeletal muscle and the normally perfused human head which are rather low based on physiological expectations. However, we obtained a tight correlation between the saturation values measured by the SRS instrument and those obtained from blood-gas analysis of samples drawn from a jugular bulb catheter in one neurosurgery subject during clamping of the right carotid arteries.
A Method for Geochronology. Gives historical background on the discovery of natural radiation and discusses various techniques for using knowledge of radiochemistry in geochronological studies. Absolute shape measurements using high-resolution optoelectronic holography methods. Characterization of surface shape and deformation is of primary importance in a number of testing and metrology applications related to the functionality, performance, and integrity of components. In this paper, a unique, compact, and versatile state-of-the-art fiber-optic-based optoelectronic holography OEH methodology is described.
This description addresses apparatus and analysis algorithms, especially developed to perform measurements of both absolute surface shape and deformation. The OEH can be arranged in multiple configurations, which include the three-camera, three-illumination, and in-plane speckle correlation setups. With the OEH apparatus and analysis algorithms, absolute shape measurements can be made, using present setup, with a spatial resolution and accuracy of better than 30 and 10 micrometers , respectively, for volumes characterized by a mm length.
Optimizing the experimental setup and incorporating equipment, as it becomes available, having superior capabilities to the ones utilized in the present investigations can further increase resolution and accuracy in the measurements. A MATLAB software tool has been developed to provide an easy to use graphical interface for the plotting and interpretation of paleomagnetic data.
The tool takes either paleomagnetic directions or paleopoles and compares them to a user defined apparent polar wander path or secular variation curve to determine the age of a paleomagnetic sample. Ages can be determined in two ways, either by translating the data onto the reference curve, or by rotating it about a set location e.
The results are then compiled in data tables which can be exported as an excel file. This data can also be plotted using variety of built-in stereographic projections, which can then be exported as an image file. This software was used to date the giant Sukhoi Log gold deposit in Russia. Sukhoi Log has undergone a complicated history of faulting, folding, metamorphism, and is the vicinity of many granitic bodies.
Absolute dating is the process of determining an age on a specified chronology in archaeology In historical geology, the primary methods of absolute dating involve using the radioactive decay of elements trapped in rocks or minerals. Geologists often need to know the age of material that they find. They use absolute dating methods, sometimes called numerical dating, to give.
Paleomagnetic analysis of Sukhoi Log allowed for the timing of large scale thermal or chemical events to be determined. Paleomagnetic analysis from gold mineralized black shales was used to define the natural remanent magnetization recorded at Sukhoi Log. The obtained paleomagnetic direction from thermal demagnetization produced a paleopole at This produced an age of We propose that this is the last major stage of activity at Sukhoi Log, and likely had a role in determining the present day state of mineralization seen at the deposit.
Determination of the absolute configuration of two estrogenic nonylphenols in solution by chiroptical methods. The absolute configurations of two estrogenic nonylphenols were determined in solution. Both nonylphenols, NP35 and NP could not be crystallized so that only solution methods are able to solve directly the question of absolute configuration. The conclusion based on experimental and calculated optical rotation and VCD data for the nonylphenol NP35 was independently confirmed by another study using a camphanoyl derivative and X-ray analysis of the obtained crystals. In case of NP, the experimental rotation data are inconclusive.
However, the comparison between experimental and calculated VCD data allowed the determination of the absolute configuration. Metrological activity determination of Ba by sum-peak absolute method. The National Laboratory for Metrology of Ionizing Radiation provides gamma sources of radionuclide and standardized in activity with reduced uncertainties. Relative methods require standards to determine the sample activity while the absolute methods , as sum-peak, not.
The activity is obtained directly with good accuracy and low uncertainties. Classical absolute methods don't calibrate Ba due to its complex decay scheme. The sum-peak method using gamma spectrometry with germanium detector standardizes Ba samples. Astigmatism error modification for absolute shape reconstruction using Fourier transform method. A method is proposed to modify astigmatism errors in absolute shape reconstruction of optical plane using Fourier transform method. If a transmission and reflection flat are used in an absolute test, two translation measurements lead to obtain the absolute shapes by making use of the characteristic relationship between the differential and original shapes in spatial frequency domain.
However, because the translation device cannot guarantee the test and reference flats rigidly parallel to each other after the translations, a tilt error exists in the obtained differential data, which caused power and astigmatism errors in the reconstructed shapes. In order to modify the astigmatism errors, a rotation measurement is added. Based on the rotation invariability of the form of Zernike polynomial in circular domain, the astigmatism terms are calculated by solving polynomial coefficient equations related to the rotation differential data, and subsequently the astigmatism terms including error are modified.
Computer simulation proves the validity of the proposed method. Volumetric vessel reconstruction method for absolute blood flow velocity measurement in Doppler OCT images. Doppler optical coherence tomography DOCT is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow velocity at a high accuracy.
However, the measurement of total absolute blood flow velocity BFV of major cerebral arteries is still a difficult problem since it not only relates to the properties of the laser and the scattering particles, but also relates to the geometry of both directions of the laser beam and the flow. In this paper, focusing on the analysis of cerebral hemodynamics, we presents a method to quantify the total absolute blood flow velocity in middle cerebral artery MCA based on volumetric vessel reconstruction from pure DOCT images.
Vessel skeletonization, followed by an averaging gradient angle calculation method , is then carried out to obtain Doppler angles along the entire MCA. Once the Doppler angles are determined, the absolute blood flow velocity of each position on the MCA is easily found. Given a seed point position on the MCA, our approach could achieve automatic quantification of the fully distributed absolute BFV. Based on experiments conducted using a swept-source optical coherence tomography system, our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches in the rodent brain.
Analytical methods for dating modern writing instrument inks on paper. This work reviews the different analytical methods that have been proposed in the field of forensic dating of inks from different modern writing instruments. The reported works have been classified according to the writing instrument studied and the ink component analyzed in relation to aging. The study, done chronologically, shows the advances experienced in the ink dating field in the last decades. Copyright Elsevier Ireland Ltd. An algorithm for error control absolute and relative in the five-point finite-difference method applied to Poisson's equation is described.
The algorithm is based on discretization of the domain of the problem by means of three rectilinear grids, each of different resolution. We discuss some hardware limitations associated with the algorithm,…. Absolute age Determinations on Diamond by Radioisotopic Methods: Gem-quality diamond contains such low abundances of parent-daughter radionuclides that dating the diamond lattice directly by isotopic measurements has been and will be impossible.
Absolute ages on diamonds typically are obtained through measurements of their syngenetic mineral inclusions: The application of the first two isotope schemes in the list requires putting together many inclusions from many diamonds whereas the latter isotope schemes permit ages on single diamonds. The key limitations on the application of these decay pairs are the availability and size of the inclusions, the abundance levels of the radionuclides, and instrumental sensitivity.
Practical complications of radioisotope dating of inclusions are fatal to the application of the technique for diamond provenance. In all mines, the ratio of gem-quality diamonds to stones with datable inclusions is very high. Thus there is no way to date the valuable, marketable stones that are part of the conflict diamond problem, just their rare, flawed cousins. Each analysis destroys the diamond host plus the inclusion and can only be carried out in research labs by highly trained scientists.
Thus, these methods can not be automated or applied to the bulk of diamond production. The geological problems with age dating are equally fatal to its application to diamond provenance. From the geological perspective, for age determination to work as a tool for diamond provenance studies, diamond ages would have to be specific to particular kimberlites or kimberlite fields and different between fields. The southern African Kaapvaal-Zimbabwe Craton and Limpopo Mobile Belt is the only cratonic region where age determinations have been applied on a large enough scale to a number of kimberlites to illustrate the geological problems in age measurements for diamond provenance.
However, this southern African example. A non-destructive method for dating human remains. The skeletal remains of several Native Americans were recovered in an eroded state from a creek bank in northeastern New Mexico. Subsequently stored in a nearby museum, the remains became lost for almost 36 years.
In a recent effort to repatriate the remains, it was necessary to fit them into a cultural chronology in order to determine the appropriate tribe s for consultation pursuant to the Native American Grave Protection and Repatriation Act NAGPRA. Because the remains were found in an eroded context with no artifacts or funerary objects, their age was unknown.
Having been asked to avoid destructive dating methods such as radiocarbon dating , the authors used Optically Stimulated Luminescence OSL to date the sediments embedded in the cranium. The OSL analyses yielded reliable dates between A. Accordingly, we conclude that the remains were interred somewhat earlier than A.
We believe the remains are from individuals ancestral to the Ute Mouache Band, which is now being contacted for repatriation efforts. Not only do our methods contribute to the immediate repatriation efforts, they provide archaeologists with a versatile, non-destructive, numerical dating method that can be used in many burial contexts.
Comparing alchemical and physical pathway methods for computing the absolute binding free energy of charged ligands. Accurately predicting absolute binding free energies of protein-ligand complexes is important as a fundamental problem in both computational biophysics and pharmaceutical discovery. Calculating binding free energies for charged ligands is generally considered to be challenging because of the strong electrostatic interactions between the ligand and its environment in aqueous solution.
In this work, we compare the performance of the potential of mean force PMF method and the double decoupling method DDM for computing absolute binding free energies for charged ligands. We first clarify an unresolved issue concerning the explicit use of the binding site volume to define the complexed state in DDM together with the use of harmonic restraints. We also provide an alternative derivation for the formula for absolute binding free energy using the PMF approach.
We use these formulas to compute the binding free energy of charged ligands at an allosteric site of HIV-1 integrase, which has emerged in recent years as a promising target for developing antiviral therapy. As compared with the experimental results, the absolute binding free energies obtained by using the PMF approach show unsigned errors of 1. According to the DDM decomposition of the binding free energy, the ligand binding appears to be dominated by nonpolar interactions despite the presence of very large and favorable intermolecular ligand-receptor electrostatic interactions, which are almost completely cancelled out by the equally large free energy cost of desolvation of the charged moiety of the ligands in solution.
We discuss the relative strengths of computing absolute binding free energies using the alchemical and physical pathway methods. Geological Survey experience with the residual absolutes method. Results show that the two methods compare very well with each other and both sets of baseline data were used to process the definitive data. The residual method will be implemented at the other USGS high-latitude geomagnetic observatories in the summer of and In this method , the sample refractive index can be deduced by refining n to maximize the agreement between the relative absorption spectrum calculated from bidirectional reflectance data calculated through a Hapke transform which depends on n and integrating sphere diffuse reflectance data calculated through a Kubleka—Munk transform which does not depend on n.
This new method can be quickly used to screen the suitability of emerging semiconductor systems for light-harvesting applications. The method is shown to work well for powders with a narrow size distribution exemplified by Fe 2O 3 and to be ineffective for semiconductors with a broad size distribution exemplified by Ge. As such, it provides a means for rapidly estimating the absolute optical properties of complex solids which are only available as loose powders. Effect of the absolute statistic on gene-sampling gene-set analysis methods.
Gene-set enrichment analysis and its modified versions have commonly been used for identifying altered functions or pathways in disease from microarray data. In particular, the simple gene-sampling gene-set analysis methods have been heavily used for datasets with only a few sample replicates. The biggest problem with this approach is the highly inflated false-positive rate. In this paper, the effect of absolute gene statistic on gene-sampling gene-set analysis methods is systematically investigated.
Thus far, the absolute gene statistic has merely been regarded as a supplementary method for capturing the bidirectional changes in each gene set. Here, it is shown that incorporating the absolute gene statistic in gene-sampling gene-set analysis substantially reduces the false-positive rate and improves the overall discriminatory ability. Its effect was investigated by power, false-positive rate, and receiver operating curve for a number of simulated and real datasets. The performances of gene-set analysis methods in one-tailed genome-wide association study and two-tailed gene expression data tests were also compared and discussed.
Absolute x-ray energy calibration and monitoring using a diffraction-based method. In this paper, we report some recent developments of the diffraction-based absolute X-ray energy calibration method. In this calibration method , high spatial resolution of the measured detector offset is essential. To this end, a remotely controlled long-translation motorized stage was employed instead of the less convenient gauge blocks. Examples of applications to pair distribution function PDF measurements and energy monitoring for high-energy X-rays are presented.
A new method to calibrate the absolute sensitivity of a soft X-ray streak camera. The calibrations are done in the static mode by using a small laser-produced X-ray source. A calibrated X-ray CCD is used as a secondary standard detector to monitor the X-ray source intensity. Results show that the calibrated spectrum covers the range from eV to eV.
The change of the absolute sensitivity in the vicinity of the K-edge of the carbon can also be clearly seen. Compared with previous calibration methods , the proposed method has several advantages: Our calibration results can be used to make quantitative X-ray flux measurements in laser fusion research. Assessment study of lichenometric methods for dating surfaces. In this paper, we discuss the advantages and drawbacks of the most classical approaches used in lichenometry. In particular, we perform a detailed comparison among methods based on the statistical analysis of either the largest lichen diameters recorded on geomorphic features or the frequency of all lichens.
To assess the performance of each method , a careful comparison design with well-defined criteria is proposed and applied to two distinct data sets. First, we study tombstones. This represents an ideal test bed because tombstone dates are known and, therefore, the quality of the estimated lichen growth curve can be easily tested for the different techniques. Secondly, 37 moraines from two tropical glaciers are investigated.
This analysis corresponds to our real case study. For both data sets, we apply our list of criteria that reflects precision, error measurements and their theoretical foundations when proposing estimated ages and their associated confidence intervals. From this comparison, it clearly appears that two methods , the mean of the n largest lichen diameters and the recent Bayesian method based on extreme value theory, offer the most reliable estimates of moraine and tombstones dates.
Concerning the spread of the error, the latter approach provides the smallest uncertainty and it is the only one that takes advantage of the statistical nature of the observations by fitting an extreme value distribution to the largest diameters. Air content of polar ice, V, depends primarily on air pressure, temperature and pore volume at close-off prevailing at the site of ice formation.
The first , years remarkably displays the fundamental Milankovitch orbital frequencies. But most of the variations observed in the V record cannot be explained neither by air pressure nor by temperature changes, and then should reflect properties influencing the porosity at close-off other than temperature. A wavelet analysis indicates a dominant period around 41 kyr, the period characteristic of the obliquity variations of the Earth's axis. We propose that the local insolation, via the solar radiation absorbed by the snow, leaves its imprint on the snow structure, then affects the snow-firn transition, and therefore is one of the controlling factors for the porosity at close-off.
Such mechanism could account for the observed anti-correlation between local insolation and V.
We estimate the variations of the absorbed solar flux in the near-surface snow layers on the basis of a simple albedo model Lemieux-Dudon et al. We compare the dating of the ice obtained using the local insolation signal deduced from the V record with a chronology based on ice flow modelling. We discuss the glaciological implications of the comparison between the two chronologies, as well as the potential of local insolation markers for approaching an absolute dating of ice core.
The latest results covering the period kyr BP will also be presented.
The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute -value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations.
Getting them to think differently about a concept that they…. Late Quaternary glacier fluctuations in the Macha Khola valley Gorkha Himal, Nepal were reconstructed using relative and absolute dating techniques. Our results indicate that younger moraine complexes were left by Late Holocene Laser interferometry method for absolute measurement of the acceleration of gravity. Gravimeter permits more accurate and precise absolute measurement of g without reference to Potsdam values as absolute standards. Device is basically Michelson laser beam interferometer in which one arm is mass fitted with corner cube reflector.
Teaching Absolute Value Meaningfully. What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students Wei ; Stallings-Roberts…. Method of self-consistent evaluation of absolute emission probabilities of particles and gamma rays. In assumption of well installed decay scheme the method provides a exact balance relationships, b lower compared to the traditional techniques uncertainties of recommended absolute emission probabilities of particles and gamma rays, c evaluation of correlations between the recommended emission probabilities for the same and different decay modes.
Application of the method for the decay data evaluation for even curium isotopes led to paradoxical results. Absolute gravimeters, based on laser interferometry, are widely used for many applications in geoscience and metrology. The measurement results for FG and FG5X clearly showed that the measured g-values depend on the size of the fringe signal and that this effect might be approximated by a linear regression with a slope of up to 0. However, these empirical results do not enable one to identify the source of the effect or to determine a reasonable reference fringe level for correcting g-values in an absolute sense.
The new systems use an analogue-to-digital converter HS5 to digitize the fringe signal and a new method of fringe signal analysis based on FFT swept bandpass filtering. We demonstrate that the source of the fringe size effect is connected to a distortion of the fringe signal due to the electronic components used in the FG5 X gravimeters.
To obtain a bias-free g-value, the FFT swept method should be applied for the determination of zero-crossings. The detector was held with a through-hole-type NaI Tl detector. The results include absolutely determined activity and its uncertainty especially about extrapolation. A comparison between the obtained and known activities showed agreement within their uncertainties.
Bu, Lintao; Beckham, Gregg T. Understanding the enzymatic mechanism that cellulases employ to degrade cellulose is critical to efforts to efficiently utilize plant biomass as a sustainable energy resource. A key component of cellulase action on cellulose is product inhibition from monosaccharide and disaccharides in the product site of cellulase tunnel. The absolute binding free energy of cellobiose and glucose to the product site of the catalytic tunnel of the Family 7 cellobiohydrolase Cel7A of Trichoderma reesei Hypocrea jecorina was calculated using two different approaches: For the SMD approach, three methods based on Jarzynski's equality were used to construct the potential of mean force from multiple pulling trajectories.
Analysis of the SMD pulling trajectories suggests that several protein residues Arg, Asp, Asp, Trp, and Tyr play key roles in cellobiose and glucose binding to the catalytic tunnel. The results demonstrated that all of the mutants tested can lower the binding free energy of cellobiose, which provides potential applications in engineering the enzyme to accelerate the product expulsion process and improve the efficiency of biomass conversion. The global reach of single, calibrated ELF receivers operating in the Schumann resonance SR band Hz has been verified by global maps of energetic Q-burst locations and vertical charge moment change, and by locations of independently verified transient luminous events in a wide variety of locations worldwide.
This inversion method involves a propagation model for the Earth-ionosphere cavity with day-night asymmetry. The Earth is now populated with more than 30 calibrated ELF receivers making continuous time series observations. This circumstance is exploited in the present study to verify the findings of the ELF inversion method. During the period May and , , two independent sets of nine ELF receivers each, in widely-separated geographical locations first set: Detailed comparisons will be shown over Universal Time for selected days.
Probabilistic performance estimators for computational chemistry methods: The empirical cumulative distribution function of absolute errors. Benchmarking studies in computational chemistry use reference datasets to assess the accuracy of a method through error statistics. The commonly used error statistics, such as the mean signed and mean unsigned errors, do not inform end-users on the expected amplitude of prediction errors attached to these methods.
We show that, the distributions of model errors being neither normal nor zero-centered, these error statistics cannot be used to infer prediction error probabilities. To overcome this limitation, we advocate for the use of more informative statistics, based on the empirical cumulative distribution function of unsigned errors, namely, 1 the probability for a new calculation to have an absolute error below a chosen threshold and 2 the maximal amplitude of errors one can expect with a chosen high confidence level.
Those statistics are also shown to be well suited for benchmarking and ranking studies. Moreover, the standard error on all benchmarking statistics depends on the size of the reference dataset. Systematic publication of these standard errors would be very helpful to assess the statistical reliability of benchmarking conclusions. Absolute flatness measurements of silicon mirrors by a three-intersection method by near-infrared interferometry.
Absolute flatness of three silicon plane mirrors have been measured by a three-intersection method based on the three-flat method using a near-infrared interferometer. The interferometer was constructed using a near-infrared laser diode with a 1,nm wavelength light where the silicon plane mirror is transparent.
The height differences at the coordinate values between the absolute line profiles by the three-intersection method have been evaluated.
The height differences of the three flats were 4. The three-intersection method using the near-infrared interferometer was useful for measuring the absolute flatness of the silicon plane mirrors. Tsunakawa-Shaw method - an absolute paleointensity technique using alternating field demagnetization. Among geologic materials volcanic rocks have been typically used to deduce an absolute paleointensity. In the last decade, however, there seems a becoming consensus that volcanic rocks are not so ideal materials due to such as magnetic grains other than non-interacting single domain particles.
One approach to obtain a good paleointensity estimate from the rocks is to reduce and correct the non-ideality, suppress alterations in laboratory and screen out suspicious results. This method is an AF alternating field -based technique and thus a paleointensity is estimated using coercivity spectra.
To reduce the non-ideality, all remanences undergo low-temperature demagnetization LTD before any AF demagnetizations to remove multi-domain like component. To correct the non-ideality, anhysteretic remanent magnetizations ARMs are imparted with their directions parallel to natural remanent magnetizations and laboratory-imparted thermoremanent magnetizations TRMs and measured before and after laboratory heating. These ARMs are used to correct remanence anisotropies, possible interaction effects originated from the non-ideal grains and TRM changes caused by laboratory alterations.
TRMs are imparted by heating specimens above their Curie temperatures and then cooling to room temperature at once to simulate nature conditions. These cycles are done in vacuum to suppress alterations in laboratory. Obtained results are judged by selection criteria, including a check for validity of the ARM corrections.
In case of old volcanic rocks, however, the method does not necessarily seem to be perfect. We will summarize these points in. Feature selection FS methods are widely used in grading and diagnosing prostate histopathological images. In this context, FS is based on the texture features obtained from the lumen, nuclei, cytoplasm and stroma, all of which are important tissue components. However, it is difficult to represent the high-dimensional textures of these tissue components. To solve this problem, we propose a new FS method that enables the selection of features with minimal redundancy in the tissue components.
We categorise tissue images based on the texture of individual tissue components via the construction of a single classifier and also construct an ensemble learning model by merging the values obtained by each classifier. Another issue that arises is overfitting due to the high-dimensional texture of individual tissue components.
The colon benchmark dataset requires a distinction between grades 1 and 2, which are the most difficult cases to distinguish in the colon domain. Thus, it makes possible the distinction between multiple Gleason grades e. The WOAV13 dataset comprises 3D global gridded climatological fields of absolute geostrophic velocity inverted It provides a climatological velocity field that is This small "n" observational study used a concurrent mixed methods approach to address a void in the literature with regard to the qualitative meaningfulness of the data yielded by absolute magnitude estimation scaling MES used to rate subjective stimuli.
We investigated whether respondents' scales progressed from less to more and…. The performance of different propensity score methods for estimating absolute effects of treatments on survival outcomes: Observational studies are increasingly being used to estimate the effect of treatments, interventions and exposures on outcomes that can occur over time. Historically, the hazard ratio, which is a relative measure of effect, has been reported. However, medical decision making is best informed when both relative and absolute measures of effect are reported.
When outcomes are time-to-event in nature, the effect of treatment can also be quantified as the change in mean or median survival time due to treatment and the absolute reduction in the probability of the occurrence of an event within a specified duration of follow-up. We describe how three different propensity score methods , propensity score matching, stratification on the propensity score and inverse probability of treatment weighting using the propensity score, can be used to estimate absolute measures of treatment effect on survival outcomes.
These methods are all based on estimating marginal survival functions under treatment and lack of treatment. We then conducted an extensive series of Monte Carlo simulations to compare the relative performance of these methods for estimating the absolute effects of treatment on survival outcomes. We found that stratification on the propensity score resulted in the greatest bias. When the prevalence of treatment was less extreme, then inverse probability of treatment weighting-based methods tended to perform better than matching-based methods.
Using new luminescence methods to date the Palaeolithic: The Palaeolithic site of Kalambo Falls in the north of Zambia was the subject of detailed study by J. Clark in the s with 4 excavations being located within 1 km of each other in a basin upstream of the falls. A rich palaeolithic tool record was recovered, but the value of this record was limited by the lack of chronological information available.
In , one of the excavation sites was re-investigated Barham et al. Many of the sediments in the Kalambo basin were deposited by fluvial activity. Dose distributions in the single grain quartz optically stimulated luminescence OSL measurements of the youngest sediments are consistent with incomplete bleaching. However, the residual doses obtained are typically less than 10 Gy, and so for older sediments the impact of incomplete bleaching becomes insignificant.
The oldest samples are affected by a different problem, namely saturation of the OSL signal, and many grains are saturated. However in all cases some grains give finite equivalent dose values, making it feasible to calculate single grain quartz OSL ages, but it is difficult to assess whether these ages are reliable or not. Only by using the two luminescence methods is it possible to create an absolute chronology for this key site stretching back over half a million years.
This study demonstrates the potential of using these two luminescence signals together for dating Palaeolithic sites throughout Africa and beyond. Recent excavations at Kalambo Falls, Zambia. Compared with the conventionally used photoabsorption method , this new method is free from the line saturation effect, which can seriously limit the accuracies of the measured photoabsorption cross sections for discrete transitions with narrow natural linewidths.
We present a comparative study of absolute distances to a sample of very nearby, bright Type Ia supernovae SNe derived from high cadence, high signal-to-noise, multi-band photometric data. Our sample consists of four SNe: For the highly reddened SN J the dispersion of the inferred distance moduli is slightly higher. These SN-based distances are in good agreement with the Cepheid distances to their host galaxies.
Generic method for the absolute quantification of glutathione S-conjugates: Application to the conjugates of acetaminophen, clozapine and diclofenac. Modification of cellular macromolecules by reactive drug metabolites is considered to play an important role in the initiation of tissue injury by many drugs. Detection and identification of reactive intermediates is often performed by analyzing the conjugates formed after trapping by glutathione GSH. Although sensitivity of modern mass spectrometrical methods is extremely high, absolute quantification of GSH-conjugates is critically dependent on the availability of authentic references.
Although 1 H NMR is currently the method of choice for quantification of metabolites formed biosynthetically, its intrinsically low sensitivity can be a limiting factor in quantification of GSH-conjugates which generally are formed at low levels. In the present study, a simple but sensitive and generic method for absolute quantification of GSH-conjugates is presented. The novel method was used to quantify the concentrations of GSH-conjugates of diclofenac, clozapine and acetaminophen and quantification was consistent with 1 H NMR, but with a more than fold lower detection limit for absolute quantification.
Published by Elsevier B. EIT Imaging of admittivities with a D-bar method and spatial prior: Electrical impedance tomography EIT is an emerging imaging modality that uses harmless electrical measurements taken on electrodes at a body's surface to recover information about the internal electrical conductivity and or permittivity.
The image reconstruction task of EIT is a highly nonlinear inverse problem that is sensitive to noise and modeling errors making the image reconstruction task challenging. D-bar methods solve the nonlinear problem directly, bypassing the need for detailed and time-intensive forward models, to provide absolute static as well as time-difference EIT images. Coupling the D-bar methodology with the inclusion of high confidence a priori data results in a noise-robust regularized image reconstruction method. In this work, the a priori D-bar method for complex admittivities is demonstrated effective on experimental tank data for absolute imaging for the first time.
Additionally, the method is adjusted for, and tested on, time-difference imaging scenarios. The ability of the method to be used for conductivity, permittivity, absolute as well as time-difference imaging provides the user with great flexibility without a high computational cost. Bringing the cross-correlation method up to date. In the new algorithm the correlation function itself, rather than the observed galaxy spectrum, is fitted by the model line profile: The standard reduced chi exp 2 is a good measure of the fit of the inferred velocity distribution, largely decoupled from the fit of the spectral template.
The updated XC method performs as well as other recently developed methods , with the added virtue of conceptual simplicity. The aim of this work is to make use of the mean of absolute deviation MAD method for the evaluation process of substitution boxes used in the advanced encryption standard. In this paper, we use the MAD technique to analyze some popular and prevailing substitution boxes used in encryption processes. Determination of the age of the dwellings of primitive man is of interest both from the point of view of the stratigraphy of quaternary deposits and for solving anthropogenetic problems.
For this reason, radiocarbon dating techniques were used for layers containing paleolithic residue of Molodova V, located in a m deep canyon at the right bank of the Dnester River in the Chernowith region. The measurements were carried out at a depth of 3. Thus, radiocarbon dating results confirmed earlier findings obtained by topological means concerning the age of the region near the Dnester River.
Absolute nuclear material assay. A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.
Method and apparatus for ultra-high-sensitivity, incremental and absolute optical encoding. An absolute optical linear or rotary encoder which encodes the motion of an object 3 with increased resolution and encoding range and decreased sensitivity to damage to the scale includes a scale 5 , which moves with the object and is illuminated by a light source The scale carries a pattern 9 which is imaged by a microscope optical system 13 on a CCD array 17 in a camera head The pattern includes both fiducial markings 31 which are identical for each period of the pattern and code areas 33 which include binary codings of numbers identifying the individual periods of the pattern.
The image of the pattern formed on the CCD array is analyzed by an image processor 23 to locate the fiducial marking, decode the information encoded in the code area, and thereby determine the position of the object. An absolute method for determination of misalignment of an immersion ultrasonic transducer.
An absolute methodology has been developed for quantification of misalignment of an ultrasonic transducer using a corner-cube retroreflector. The amplitude based and the time of flight TOF based C-scans of the reflector are obtained for various misalignments of the transducer. At zero degree orientation of the transducer, the vertical positions of the maximum amplitude and the minimum TOF in the C-scan coincide.
At any other orientation of the transducer with the horizontal plane, there is a vertical shift in the position of the maximum amplitude with respect to the minimum TOF. The position of the minimum TOF remains the same irrespective of the orientation of the transducer and hence is used as a reference for any misalignment of the transducer. With the measurement of the vertical shift and the horizontal distance between the transducer and the vertex of the reflector, the misalignment of the transducer is quantified.
Based on the methodology developed in the present study, retroreflectors are placed in the Indian MWe Prototype Fast Breeder Reactor for assessment of the orientation of the ultrasonic transducer prior to the under-sodium ultrasonic scanning for detection of any protrusion of the subassemblies. MRI-based methods using interleaved and combined hypercapnia and hyperoxia. Blood oxygenation level dependent BOLD functional magnetic resonance imaging FMRI is most commonly used in a semi-quantitative manner to infer changes in brain activity.
Despite the basis of the image contrast lying in the cerebral venous blood oxygenation level, quantification of absolute cerebral metabolic rate of oxygen consumption CMRO2 has only recently been demonstrated. The first approach is to apply hypercapnia and hyperoxia separately but interleaved in time and the second is a combined approach in which we apply hyperoxic challenges simultaneously with different levels of hypercapnia.
Eleven healthy volunteers were studied at 3T using a dual gradient-echo spiral readout pulsed arterial spin labelling ASL imaging sequence. Respiratory challenges were conducted using an automated system of dynamic end-tidal forcing. A generalised BOLD signal model was applied, within a Bayesian estimation framework, that aims to explain the effects of modulation of CBF and arterial oxygen content to estimate venous deoxyhaemoglobin concentration [dHb]0.
Current thermometry methods are either invasive or measure only temperature change, which limits the ability to study tissue responses to HT.
This study combines manganese-containing low-temperature sensitive liposomes Mn-LTSL with proton resonance frequency shift PRFS thermometry to measure absolute temperature in tumors with high spatial and temporal resolution using MRI. The release of manganese from Mn-LTSL in saline was characterized with inductively-coupled plasma atomic emission spectroscopy.
Accuracies of calibrated temperature measurements were in the range 0. A practical method of estimating standard error of age in the fission track dating method. The correlation, r, between spontaneous are induced track densities is a crucial element in the error analysis, acting generally to improve the standard error of age.
In addition, the correlation parameter r is instrumental is specifying the level of neutron dose, a controlled variable, which will minimize the standard error of age. The results from the approximation equation agree closely with the results from an independent statistical model for the propagation of errors in the fission-track dating method. Radar prediction of absolute rain fade distributions for earth-satellite paths and general methods for extrapolation of fade statistics to other locations.
The first absolute rain fade distribution method described establishes absolute fade statistics at a given site by means of a sampled radar data base. The second method extrapolates absolute fade statistics from one location to another, given simultaneously measured fade and rain rate statistics at the former. Both methods employ similar conditional fade statistic concepts and long term rain rate distributions. The extrapolation of fade distributions to other locations at 28 GHz showed very good agreement with measured data at three sites located in the continental temperate region.
Barnacles have never been successfully dated by electron spin resonance ESR. Living mainly in the intertidal zone, barnacles die when sea level changes cause their permanent exposure. Thus, dating the barnacles dates past sea level changes. From this, we can measure apparent sea level changes that occur due to ocean volume changes, crustal isostasy, and tectonics.
ESR can date aragonitic mollusc shells ranging in age from 5 ka to at least ka. By modifying the standard ESR method for molluscs to chemically dissolve 20 microm from off the shells, six barnacle samples from Norridgewock, Maine, and Khyex River, British Columbia, were tested for suitability for ESR dating. These ages agree well with 14C dates on the barnacles themselves and wood in the overlying glaciomarine sediment.
Although stability tests to calculate the mean dating signal lifetime and more ESR calibration tests against other barnacles of known age are needed to ensure the method 's accuracy, ESR can indeed date Balanus, and thus, sea level changes. Elatenyne is a marine natural product that was isolated in Despite its simple 2,2'-bifuranyl backbone, its relative structure was only recently determined. In this work, the structure of natural elatenyne was determined by the crystalline sponge method and the use of a porous coordination network a crystalline sponge capable of absorbing organic guests; in the sponge, the absorbed guests are ordered and crystallographically observable.
The crystalline sponge could differentiate between the two very similar alkyl side chains, and the absolute structure of elatenyne was thus reliably determined. Computational method for estimating boundary of abdominal subcutaneous fat for absolute electrical impedance tomography. Abdominal fat accumulation is considered an essential indicator of human health. Electrical impedance tomography has considerable potential for abdominal fat imaging because of the low specific conductivity of human body fat.
In this paper, we propose a robust reconstruction method for high-fidelity conductivity imaging by abstraction of the abdominal cross section using a relatively small number of parameters. Toward this end, we assume homogeneous conductivity in the abdominal subcutaneous fat area and characterize its geometrical shape by parameters defined as the ratio of the distance from the center to boundary of subcutaneous fat to the distance from the center to outer boundary in 64 equiangular directions.
To estimate the shape parameters, the sensitivity of the noninvasively measured voltages with respect to the shape parameters is formulated for numerical optimization. Numerical simulations are conducted to demonstrate the validity of the proposed method. A 3-dimensional finite element method is used to construct a computer model of the human abdomen. The inverse problems of shape parameters and conductivities are solved concurrently by iterative forward and inverse calculations.
A novel method is devised for estimating the boundary of the abdominal subcutaneous fat.
The fidelity of the overall reconstructed image to the reference image is significantly improved. The results demonstrate the possibility of realization of an abdominal fat scanner as a low-cost, radiation-free medical device. The purpose of this study was to establish a practical method to estimate the absolute boron concentrations in the tissues based on the standardized uptake values SUVs after administration of 4-borono-phenylalanine BPA using 4-borono 18 F-fluoro-phenylalanine 18 F-FBPA PET.
The absolute boron concentrations unit: Relatively large underestimation was observed for the lung In contrast, relatively large overestimation was observed for the kidney Method of excess fractions with application to absolute distance metrology: Multiwavelength interferometry MWI is a well established technique in the field of optical metrology.
Previously, we have reported a theoretical analysis of the method of excess fractions that describes the mutual dependence of unambiguous measurement range, reliability, and the measurement wavelengths. In this paper wavelength, selection strategies are introduced that are built on the theoretical description and maximize the reliability in the calculated fringe order for a given measurement range, number of wavelengths, and level of phase noise.
Practical implementation issues for an MWI interferometer are analyzed theoretically. Radiometric dating, or radioactive dating as it is sometimes called, is a method used to date rocks and other objects based on the known decay rate of radioactive isotopes. Different methods of radiometric dating can be used to estimate the age of a variety of natural and even man-made materials. The methods work because radioactive elements are unstable, and they are always trying to move to a more stable state.
So, they do this by giving off radiation. This process by which an unstable atomic nucleus loses energy by releasing radiation is called radioactive decay. The thing that makes this decay process so valuable for determining the age of an object is that each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life. So, if you know the radioactive isotope found in a substance and the isotope's half-life, you can calculate the age of the substance.
So, what exactly is this thing called a half-life? Well, a simple explanation is that it is the time required for a quantity to fall to half of its starting value. So, you might say that the 'full-life' of a radioactive isotope ends when it has given off all of its radiation and reaches a point of being non-radioactive. When the isotope is halfway to that point, it has reached its half-life. There are different methods of radiometric dating that will vary due to the type of material that is being dated.
For example, uranium-lead dating can be used to find the age of a uranium-containing mineral. It works because we know the fixed radioactive decay rates of uranium, which decays to lead, and for uranium, which decays to lead So, we start out with two isotopes of uranium that are unstable and radioactive. They release radiation until they eventually become stable isotopes of lead.
These two uranium isotopes decay at different rates. In other words, they have different half-lives. The half-life of the uranium to lead is 4. The uranium to lead decay series is marked by a half-life of million years. These differing rates of decay help make uranium-lead dating one of the most reliable methods of radiometric dating because they provide two different decay clocks. This provides a built-in cross-check to more accurately determine the age of the sample.
Uranium is not the only isotope that can be used to date rocks; we do see additional methods of radiometric dating based on the decay of different isotopes. For example, with potassium-argon dating , we can tell the age of materials that contain potassium because we know that potassium decays into argon with a half-life of 1. With rubidium-strontium dating , we see that rubidium decays into strontium with a half-life of 50 billion years.
By anyone's standards, 50 billion years is a long time. In fact, this form of dating has been used to date the age of rocks brought back to Earth from the moon. So, we see there are a number of different methods for dating rocks and other non-living things, but what if our sample is organic in nature?
For example, how do we know that the Iceman, whose frozen body was chipped out of glacial ice in , is 5, years old? Well, we know this because samples of his bones and hair and even his grass boots and leather belongings were subjected to radiocarbon dating. Radiocarbon dating , also known as carbon dating or simply carbon dating, is a method used to determine the age of organic material by measuring the radioactivity of its carbon content. So, radiocarbon dating can be used to find the age of things that were once alive, like the Iceman.
And this would also include things like trees and plants, which give us paper and cloth. So, radiocarbon dating is also useful for determining the age of relics, such the Dead Sea Scrolls and the Shroud of Turin. With radiocarbon dating, the amount of the radioactive isotope carbon is measured. Compared to some of the other radioactive isotopes we have discussed, carbon's half-life of 5, years is considerably shorter, as it decays into nitrogen Carbon is continually being created in the atmosphere due to the action of cosmic rays on nitrogen in the air.
Carbon combines with oxygen to create carbon dioxide. Because plants use carbon dioxide for photosynthesis, this isotope ends up inside the plant, and because animals eat plants, they get some as well. When a plant or an animal dies, it stops taking in carbon The existing carbon within the organism starts to decay back into nitrogen, and this starts our clock for radiocarbon dating.
A scientist can take a sample of an organic material when it is discovered and evaluate the proportion of carbon left in the relic to determine its age. Radiometric dating is a method used to date rocks and other objects based on the known decay rate of radioactive isotopes. The decay rate is referring to radioactive decay , which is the process by which an unstable atomic nucleus loses energy by releasing radiation. Each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life or, in other words, the time required for a quantity to fall to half of its starting value.
There are different methods of radiometric dating. Uranium-lead dating can be used to find the age of a uranium-containing mineral. Uranium decays to lead, and uranium decays to lead The two uranium isotopes decay at different rates, and this helps make uranium-lead dating one of the most reliable methods because it provides a built-in cross-check. Additional methods of radiometric dating, such as potassium-argon dating and rubidium-strontium dating , exist based on the decay of those isotopes.
Radiocarbon dating is a method used to determine the age of organic material by measuring the radioactivity of its carbon content. With radiocarbon dating, we see that carbon decays to nitrogen and has a half-life of 5, years. To unlock this lesson you must be a Study. Did you know… We have over college courses that prepare you to earn credit by exam that is accepted by over 1, colleges and universities. You can test out of the first two years of college and save thousands off your degree.
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