Correction Of Such Effects Research Articles

Impact of aerobic reworking of biomass on steroid and hopanoid biomarker parameters recording ecological conditions and thermal maturity

Steranes and hopanes are the biomarkers of eukaryotic sterols and bacterial hopanols. Extracted from sedimentary rock, they are widely used to assess burial temperatures and palaeoecological conditions. The relative proportion of steranes and hopanes is commonly applied as a measure of the flux of eukaryotic versus bacterial biomass into sediments, and the relative abundances of C27, C28 and C29 steranes are proxies for shifts in eukaryote ecology. In Recent sediments, intact sterols provide additional information about particular eukaryotic origins. However, biological lipid distributions are not always recorded faithfully in sediments. Based on observations on modern algae and plants, and on 558 million year old fossil macroalgae from the Ediacaran of the White Sea, we suggest that these biomarker proxies can be severely altered by aerobic microbial reworking, to the extent that a complete loss of primary ecological information may occur. Network analysis on the biomarker data suggests that oxic degradation also affects isomer and homolog distributions of saturated and aromatic steroids, hopanes, cheilanthanes and n-alkanes, generating anomalies in apparent thermal maturity indicators and other proxies. In our dataset, between Ediacaran macroalgae that experienced the least and the most oxic degradation, the absolute concentration of biomarkers decreases 80-fold, and at the same time the proportion of steranes over hopanes decreases by a factor of 82, while the proportion of C29 steranes among total steranes decreases from 91% to 47%. Such redox dependent offsets may explain the recurrently erratic behaviour of numerous biomarker parameters. While these results impart constraints on the interpretation of biomarker distributions, they do provide a tool for evaluating the effects of oxygen exposure and microbial degradation on organic matter preservation in recent and ancient environments and may point towards a solution for the correction of such effects.

Seismic-Q Compensation by Iterative Time-Domain Deconvolution

Attenuation is often significant during seismic wave propagation in the subsurface, leading to the reduced resolution and narrower bandwidth of seismic images. Traditional corrections for such effects are inverse-Q filtering and deconvolution, which require a high signal-to-noise ratio (SNR) to avoid noise boost-up. Here, we propose a time-domain method offering advantages in the resolution and interpretational quality of the resulting images. Similar to wavelet transforms, the iterative time-domain deconvolution (ITD) represents the seismogram by a superposition of non-stationary source wavelets modeled in the appropriate attenuation model. Arbitrary frequency-dependent Q and velocity dispersion laws can be used and non-Q type attenuation can be caused by focusing, defocusing, scattering, effects of fine layering, and fluctuations of the wavefield. Compared to inverse-Q filtering and some deconvolution methods, the method does not boost high-frequency noise and is less sensitive to the accuracy of the Q model. We illustrate and compare this method to inverse-Q filtering by using several synthetic and real data examples. The tests include noise-contaminated data, inaccurate Q models, and variable source wavelets. The examples show that the ITD is a practical and effective tool for Q-compensation with a broad scope of potential applications, albeit with some defects. An important benefit of ITD that other methods may not possess could be the ability to utilize geological information, such as locations and sparseness of major reflectors or the presence of interpreted Q contrasts, which might be able to further improve the performance of ITD.

Interfacial ion solvation: Obtaining the thermodynamic limit from molecular simulations.

Inferring properties of macroscopic solutions from molecular simulations is complicated by the limited size of systems that can be feasibly examined with a computer. When long-ranged electrostatic interactions are involved, the resulting finite size effects can be substantial and may attenuate very slowly with increasing system size, as shown by previous work on dilute ions in bulk aqueous solution. Here we examine corrections for such effects, with an emphasis on solvation near interfaces. Our central assumption follows the perspective of Hünenberger and McCammon [J. Chem. Phys. 110, 1856 (1999)]: Long-wavelength solvent response underlying finite size effects should be well described by reduced models like dielectric continuum theory, whose size dependence can be calculated straightforwardly. Applied to an ion in a periodic slab of liquid coexisting with vapor, this approach yields a finite size correction for solvation free energies that differs in important ways from results previously derived for bulk solution. For a model polar solvent, we show that this new correction quantitatively accounts for the variation of solvation free energy with volume and aspect ratio of the simulation cell. Correcting periodic slab results for an aqueous system requires an additional accounting for the solvent's intrinsic charge asymmetry, which shifts electric potentials in a size-dependent manner. The accuracy of these finite size corrections establishes a simple method for a posteriori extrapolation to the thermodynamic limit and also underscores the realism of dielectric continuum theory down to the nanometer scale.

Criminal Mind or Inculpable Adolescence? A Glimpse at the History, Failures, and Required Changes of the American Juvenile Correction System

This Comment provides an historical analysis of the principles, understandings and laws that have formed and altered the American juvenile correction system. Part I offers an historical synopsis of the societal understanding that juvenile offenders are less culpable than their adult counterparts and explains the process by which this concept came to permeate early American common law. By discussing the early nineteenth-century juvenile correction reformation movement and the cases that followed, Part I also illustrates the development and early failures of the American juvenile correction system. Part II explains the history of juvenile waiver laws, from their early presence in the American juvenile correction system to their stringent nationwide alteration during the 1980s and 90s. In Part III, this Comment discusses the unconstitutional results of increased juvenile waiver legislation and examines the United States Supreme Court’s judicial correction of such effects. Part IV concludes that despite the roadblocks to effectuating necessary changes within the juvenile correction system, the interaction among various omnipresent and undeniable forces requires that the States and their judiciaries do so.

DEM shading method for the correction of pseudoscopic effect on multi-platform satellite imagery

The pseudoscopic effect in satellite imagery causes perception problems for rugged terrain. The topographic relief is perceived in reverse in images with southeast illumination because of the position of land shadows and the mechanisms of human vision and depth perception. This article presents a correction method for false topographic perception phenomena. Superposition of the orthoimage and the correctly shaded digital elevation model (DEM) provides the correct three-dimensional visualization of the relief. This study demonstrates the applicability of this processing technique for the correction of such effects to provide cartography with a more useful interpretation. The resolution of the DEM employed should be in accordance with the spatial resolution of each image. The opacity level proposed for the overlapping DEM is 50%, 30% and 45% for each image type. The selection of the most appropriate local incidence angle is determined by the level of terrain roughness in the work area.

Note: Quantitative (artifact-free) surface potential measurements using Kelvin force microscopy

The measurement of local surface potentials by Kelvin force microscopy (KFM) can be sensitive to external perturbations which lead to artifacts such as strong dependences of experimental results (typically in a ∼1 V range) with KFM internal parameters (cantilever excitation frequency and/or the projection phase of the KFM feedback-loop). We analyze and demonstrate a correction of such effects on a KFM implementation in ambient air. Artifact-free KFM measurements, i.e., truly quantitative surface potential measurements, are obtained with a ∼30 mV accuracy.

High-resolution magnetic analysis of sediment cores: Strengths, limitations and strategies for maximizing the value of long-core magnetic data

Narrow-access long-core cryogenic magnetometers enable measurement of a range of magnetic parameters at a speed and resolution that cannot be matched by other techniques. Despite the revolutionary impact that these instruments have had on paleomagnetic and environmental magnetic investigations, some fundamental constraints limit their usefulness. First, the pick-up coils have different response functions for the transverse and axial measurement axes. Transverse coils typically have regions of negative response on either side of the main response peak, whereas the axial coil usually lacks the negative response lobes. Zones of negative response affect the measured remanence intensity, for which corrections can be made by normalizing the measured magnetic moment by the area under each respective response curve. This correction works adequately for homogeneously magnetized cores. Second, in cores with significant changes in remanence intensity, the ratio of axial to transverse moment varies with intensity change, which can introduce spurious artefacts into the paleomagnetic directional record. Deconvolution is required to remove such effects. Third, measurements of non-centred samples with irregular cross-section (e.g., split core measurements), cause geometric effects that can introduce small but paleomagnetically important artefacts. Corrections for such effects are only possible if spatial variability of the magnetometer response is known throughout the entire measurement volume rather than solely along the centre-line of the magnetometer. Fourth, analysis of cores deposited at rates >10 cm/ky is desirable to minimize the effects of measurement smoothing. Finally, measurements of magnetic susceptibility should be conducted using loop sensors with a similar response function as a u-channel magnetometer to ensure comparability of data. Routine adoption of these five strategies should help to maximize the value of long-core magnetic measurements.

Study of bandwidth effects in monochromator-based spectral responsivity measurements.

The errors caused by monochromator bandwidth in spectral responsivity measurements with a monochromator-based apparatus are discussed. Bandwidth effects are not negligible in high-accuracy cryogenic radiometer-based calibrations. A simple numerical method is used to calculate bandwidth effects for different types of detectors, monochromator slit scattering functions, and monochromator output spectral distributions. The method uses low-order Lagrange polynomials fitted segmentwise to measured spectral responsivity and monochromator spectral distribution data in order to make the calculations. It is shown that the shape of the slit function has only a small influence on the bandwidth errors, whereas the output spectral distribution of the monochromator can strongly affect bandwidth errors. It is also shown that in most cases the magnitude of bandwidth effects will vary as the square of the bandwidth. Bandwidth error calculations are presented for various types of detectors (silicon, silicon trap, germanium, InGaAs), for a V(X) detector, and for a typical filter radiometer. A comparison is made between calculated and measured bandwidth effects to validate the method used. In general, calculations of bandwidth effects will be mostly useful for determining uncertainties associated with monochromator bandwidth in spectral responsivity measurements; however, in certain cases the calculations can be used to apply corrections for such effects.

Software for X-ray fluorescence and scattering tomographic reconstruction

Computer tomography is commonly based on transmitted radiation, i.e. the part of the radiation that does not interact with the sample. In recent years the scientific community has demonstrated a growing interest in alternative tomographic techniques, based on fluorescence or on scattered radiation. These kinds of tomography provide complementary information about the sample, e.g., information concerning the spatial distribution of particular elements. Furthermore, they can be applied on experimental situations where a complete turn of the apparatus around the object is not possible. However, fluorescence tomography presents certain additional difficulties in comparison to transmission tomography. This is mainly due to self-absorption effects in the sample. Few algorithms for the correction of such effects are reported in the literature. The solution proposed by Hogan et al. provides a good compromise between image quality and reconstruction speed. In this paper we report an implementation of such an algorithm and also several examples. It is our intention that this paper and the included software represent the first part of a complete set of tools for scattering and fluorescence tomography, which we intend to present in the near future.

Composition and chemical width of ultrathin amorphous films at grain boundaries in silicon nitride

Two different electron energy loss spectroscopy (EELS) quantitative analytical methods for obtaining complete compositions from interface regions are applied to ultrathin oxide-based amorphous grain boundary (GB) films of ∼ 1 nm thickness in high-purity HIPed Si3N4 ceramics. The first method, 1, is a quantification of the segregation excess at interfaces for all the elements, including the bulk constituents such as silicon and nitrogen; this yields a GB film composition of SiN0.49±1.4O1.02±0.42 when combined with the average film thickness from high resolution electron microscopy (HREM). The second method, II, is based on an EELS near-edge structure (ELNES) analysis of the Si–L2,3 edge of thin GB films which permits a subtraction procedure that yields a completeEELS spectrum, e.g., that also includes the O–K and N–K edges, explicitly for the GB film. From analysis of these spectra, the film composition is directly obtained as SiN0.63±0.19O1.44±0.33, close to the one obtained by the first method but with much better statistical quality. The improved quality results from the fewer assumptions made in method II; while in method I uniform thickness and illumination condition have to beassumed, and correction of such effects yields an extra systematic error. Method II is convenient as it does not depend on the film thickness detected by HREM, nor suffer from material lost by preferential thinning at the GB. In addition, a chemical width for these films can be deduced as 1.33 ± 0.25 nm, that depends on an estimation of film density based on its composition. Such a chemical width is in good agreement with the structural thickness determined by HREM, with a small difference that is probably due to the different way in which these techniques probe the GB film. The GB film compositions are both nonstoichiometric, but in an opposite sense, this discrepancy is probably due to different ways of treating the surface oxidation layers in both methods.

Proximity Effects in Electron Lithography: Magnitude and Correction Techniques

Proximity effects due to electron scattering in the resist and substrate seem to set a fundamental limit to the areal density that can be achieved in electron lithography. This work briefly reviews the form and the magnitude of the proximity function and its extent as evidenced by deviations in designed linewidths. It also discusses methods to decrease the proximity effect as well as the algorithms used for correction of such effects.

A graphical correction procedure for inner filter effect in fluorescence quenching titrations

Inner filter effects constitute a serious limitation for fluorescence quenching titrations with absorbing ligands. In most cases, the conventional methods employed for correction of such effects yield reliable results only at low total absorbance and, hence, titration is often restricted to relatively low ligand concentrations. To attain accurate corrections also in samples of elevated absorbance, a simple procedure based on graphical extrapolation has now been developed. The new method extends the accessible range of absorbance by nearly one order of magnitude and was successfully applied in the determination of the dissociation constants of the complexes of creatine kinase with MgADP and MgATP.

On the use of neutron spin-echo to separate inelastic scattering from elastic scattering at high energy resolution

Generally the measured intensity of a Bragg peak or of elastic diffuse scattering contains an inelastic component (thermal diffuse scattering, low-lying phonon branches). Theoretical corrections for such effects are only possible in the limited number of cases where appropriate data are available. An experimental correction is difficult because the high energy resolution imposed reduces the beam intensity in a conventional experiment. In the case of neutron diffraction, the spin-echo technique proposed by Mezei [Z. Phys. (1972), 255, 146-160] for neutron spectroscopy can be used as a filter for inelastic scattering without significant loss in elastic intensity. The application of the technique to an elastic neutron-scattering experiment is described, and it is shown that for a neutron wavelength of 1.5 Å an energy resolution of better than 50 μeV can be obtained. With this energy band-pass, scattering even from very soft phonons or magnons can be avoided when studying critical scattering near phase transitions. Simple estimates also imply that more than 90% of the TDS contribution can be removed even for soft materials.