Trace Decomposition Research Articles

Structure-adapted Multichannel Matching Pursuit for Seismic Trace Decomposition

While the single-channel matching pursuit decomposes a seismic trace into a series of wavelets, the multichannel matching pursuit examines the lateral coherence of the seismic traces as a constraint to improve the lateral continuity of the decomposition. However, the presence of structures in the subsurface negatively affects the performance of the multichannel matching pursuit. We proposed a structure-adapted matching pursuit method that combines with a dynamic time-warping (DTW) algorithm to estimate the similarity between adjacent seismic traces and extract an optimal wavelet along the dip plane. This structure-adapted implementation would significantly speed up the convergence of the decomposition process. We modified the DTW algorithm by combining the Euclidean distance of the seismic trace and the first-order temporal derivative of the seismic trace. We also updated the amplitudes of all extracted wavelets simultaneously based on the least-squares principle. This DTW-based, structure-adapted, least-squares, multichannel matching pursuit method would improve the robustness and accuracy of seismic trace decomposition.

Aerobic pyruvate metabolism sensitizes cells to ferroptosis primed by GSH depletion

Ferroptosis is a non-accidental, regulated form of cell death operated by lipid peroxidation under strict control of GPx4 activity. This is consistent with the notion that lipid peroxidation is initiated by radicals produced from decomposition of traces of pre-existing lipid hydroperoxides. The question, therefore, emerges about the formation of these traces of lipid hydroperoxides interacting with Fe2+. In the most realistic option, they are produced by oxygen activated species generated during aerobic metabolism. Screening for metabolic sources of superoxide supporting ferroptosis induced by GSH depletion, we failed to detect, in our cell model, a role of respiratory chain. We observed instead that the pyruvate dehydrogenase complex -as other α keto acid dehydrogenases already known as a major source of superoxide in mitochondria- supports ferroptosis. The opposite effect on ferroptosis by silencing either the E1 or the E3 subunit of the pyruvate dehydrogenase complex pointed out the autoxidation of dihydrolipoamide as the source of superoxide. We finally observed that GSH depletion activates superoxide production, seemingly through the inhibition of the specific kinase that inhibits pyruvate dehydrogenase. In summary, this set of data is compatible with a scenario where the more electrophilic status produced by GSH depletion not only activates ferroptosis by preventing GPx4 activity, but also favors the formation of lipid hydroperoxides. In an attractive perspective of tissue homeostasis, it is the activation of energetic metabolism associated to a decreased nucleophilic tone that, besides supporting energy demanding proliferation, also sensitizes cells to a regulated form of death.

Enhancing the resolution of time–frequency spectrum using directional multichannel matching pursuit

Matching pursuit is able to decompose signals adaptively into a series of wavelets and has been widely applied in signal processing of the geophysical fields. Single-channel matching pursuit could not take into account the lateral continuity of seismic traces, and the recent multichannel matching pursuit exploits the lateral coherence as a constraint, which helps to improve the stability of decomposition results. However, atoms searched by multichannel matching pursuit currently are just shared by lateral seismic traces at the same time slicers. The lack of directionality in multichannel search strategies leads to irrationality in dealing with large dip angle seismic traces. Considering that the waveforms of reflection events are relatively continuous and similar, an improved multichannel matching pursuit is proposed to realize the directional decomposition of adjacent signals. Based on the principle of seismic reflection events tracking and identification, directional multichannel decomposition of seismic traces is realized. The seismic channel to be decomposed is correlated with the time shift of the optimal atom determined by the previous seismic channel. The time position of the maximum correlation indicates the center time of the optimal atom. Optimal atoms identified by one iteration of multichannel decomposition have the same frequency and phase parameters, different center time and amplitude parameters. The center time of the optimal atoms is consistent with seismic reflection events. Tests illustrate that the algorithm can successfully reconstruct 2D seismic data without reducing accuracy. Besides, the application of field data is of great significance for reservoir exploration and hydrocarbon interpretation.

Surface and catalyst driven singlet oxygen formation in Li-O2 cells

Large overpotentials upon discharge and charge of Li-O2 cells have motivated extensive research into heterogeneous solid electrocatalysts or non-carbon electrodes with the aim to improve rate capability, round-trip efficiency, and cycle life. These features are equally governed by parasitic reactions, which are now recognized to be caused by formation of the highly reactive singlet oxygen (1O2). However, the link between the presence of electrocatalysts and 1O2 formation in metal-O2 cells is unknown. Here, we show that, compared to pristine carbon black electrodes, a representative selection of electrocatalysts or non-carbon electrodes (noble metal, transition metal compounds) may both slightly reduce or severely increase the 1O2 formation. The individual reaction steps, where the surfaces impact the 1O2 yield are deciphered, showing that 1O2 yields from superoxide disproportionation as well as the decomposition of traces of H2O2 are sensitive to catalysts. Transition metal compounds in general are prone to increase 1O2. The results highlight the importance of 1O2 in metal-O2 cells and to use a comprehensive set of metrics to judge the impact of catalysts on reversibility.

Detection of decomposition products of C4F7N-CO2 gas mixture based on infrared spectroscopy

Heptafluoroisobutyronitrile (C4F7N)-carbon dioxide (CO2) gas mixture has been gradually applied as an excellent environment-friendly insulating medium. The research on the decomposition characteristics of C4F7N-CO2 gas mixture not only helps to better understand its decomposition mechanism under insulation fault, but also provides effective basis for monitoring the insulation state of electrical equipment based on decomposition products analysis. Due to infrared spectroscopy has good potential for on-line monitoring of electrical equipment, this paper studies the feasibility of the decomposition products detection by infrared spectroscopy. The infrared spectrum of C4F7N and its decomposition products were obtained by theoretical calculation. The possibility of detection by infrared spectroscopy was theoretically analyzed. The experimental platform for overheating decomposition of C4F7N-CO2 gas mixture was built, and a long path gas cell with 4 m light path was developed for the detection of trace decomposition products. The results show that C3F6, COF2 and CO can be effectively detected by infrared spectroscopy with the long path gas cell. At last, the decomposition experiments under different temperature and pressure have been employed and the decomposition products growth trend has been analyzed. The study illustrates the detection feasibility of decomposition products of C4F7N-CO2 gas mixture by infrared spectroscopy, and lays a foundation for future on-line monitoring technology of electrical equipment with the gas mixture based on infrared spectroscopy.

Peak Colocalized Orthogonal Matching Pursuit for Seismic Trace Decomposition

Orthogonal matching pursuit (OMP) is an efficient method for decomposing a seismic trace with regard to an atom dictionary. The original OMP optimizes one unique single objective in terms of successively maximizing the inner product between an atom and its corresponding residual at different approximating levels. Though the inner product effectively measures signal similarity at a global time scale, it tends to neglect localizing an atom whose peak position plays a key role in seismic reconstruction. To address this limitation, we propose a peak colocalized orthogonal matching pursuit (PCOMP) strategy that optimizes two objectives, i.e., signal correlation and peak colocalization, both of which are defined based on signal residuals and atoms. Compared with the original OMP, the PCOMP extends a much larger search space in favor of more accurate seismic reconstruction. In this scenario, the genetic algorithm (GA) used for solving the original OMP is not suitable for the PCOMP. Therefore, we propose to solve the two objective optimization problem by exploiting an improved nondominated sorting genetic algorithm (NSGA-II) algorithm, which not only increases the diversity of searching for optimization and but also reduces the reconstruction error over the GA. Furthermore, the constrained atom positions obtained from the peak colocalization objective enable efficient convergence. Experiments for seismic data validate the advantages of the proposed PCOMP.

The attenuated Ricker wavelet basis for seismic trace decomposition and attenuation analysis

ABSTRACTThe widely used wavelets in the context of the matching pursuit are mostly focused on the time–frequency attributes of seismic traces. We propose a new type of wavelet basis based on the classic Ricker wavelet, where the quality factor Q is introduced. We develop a new scheme for seismic trace decomposition by applying the multi‐channel orthogonal matching pursuit based on the proposed wavelet basis. Compared with the decomposition by the Ricker wavelets, the proposed method could use fewer wavelets to represent the seismic signal with fewer iterations. Besides, the quality factor of the subsurface media could be extracted from the decomposition results, and the seismic attenuation could be compensated expediently. We test the availability of the proposed methods on both synthetic seismic record and field post‐stack data.

A genetic system for biasing the sex ratio in mice.

Biasing the sex ratio of populations of different organisms, including plants, insects, crustacean, and fish, has been demonstrated by genetic and non-genetic approaches. However, biasing the sex ratio of mammalian populations has not been demonstrated genetically. Here, we provide a first proof of concept for such a genetic system in mammals by crossing two genetically engineered mouse lines. The maternal line encodes a functional Cas9 protein on an autosomal chromosome, whereas the paternal line encodes guide RNAs on the Y chromosome targeting vital mouse genes. After fertilization, the presence of both the Y-encoded guide RNAs from the paternal sperm and the Cas9 protein from the maternal egg targets the vital genes in males. We show that these genes are specifically targeted in males and that this breeding consequently self-destructs solely males. Our results pave the way for a genetic system that allows biased sex production of livestock.

Improved Delivery of CRISPR/Cas9 System Using Magnetic Nanoparticles into Porcine Fibroblast

Genetically modified pigs play an important role in agriculture and biomedical research; hence, new efficient methods are needed to obtain genetically engineered cells and animals. The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas (CRISPR-associated) system represents an effective genome editing tool. It consists of two key molecules: single guide RNA (sgRNA) and the Cas9 endonuclease that can be introduced into the cells as one plasmid. Typical delivery methods for CRISPR/Cas9 components are limited by low transfection efficiency or toxic effects on cells. Here, we describe the use of magnetic nanoparticles and gradient magnetic field to improve delivery of CRISPR/Cas9 constructs into porcine fetal fibroblasts. Polyethylenimine-coated nanoparticles with magnetic iron oxide core were used to form magnetic plasmid DNA lipoplexes. CRISPR/Cas9 construct was prepared to induce site-specific cutting at the porcine H11 locus. Quantitative assessment of genomic cleavage by sequence trace decomposition demonstrated that the magnetofection efficiency was more than 3.5 times higher compared to the classic lipofection method. The Tracking of Indels by Decomposition web tool precisely determined the spectrum of indels that occurred. Simultaneously, no additional cytotoxicity associated with the utilization of magnetic nanoparticles was observed. Our results indicate that magnetofection enables effective delivery of the CRISPR/Cas9 construct into porcine fetal fibroblasts with low cell toxicity.

Electrocatalytic Hydrogen Production by a Nickel Complex Containing a Tetradentate Phosphine Ligand

A nickel complex has been synthesized using the P4N2 ligand, a tetradentate phosphine ligand with two pendant amines in the ligand backbone. The rigidly square pyramidal [Ni(P4N2)(CH3CN)]2+ complex is an electrocatalyst for the reduction of protons to hydrogen. Using N,N-dimethylformamidium ([DMF(H)+]) as the acid in an acetonitrile/water solution, [Ni(P4N2)(CH3CN)]2+ displays a turnover frequency of 1.6 × 106 s–1, which is among the fastest rates reported for any molecular electrocatalyst. This high catalytic rate comes at the cost of a 1200 mV overpotential at the catalytic half-wave potential. The Ni(II) state of the catalyst was found to be stable under strongly acidic conditions, with only trace decomposition observed over 2 weeks in the presence of 0.1 M trifluoromethanesulfonic acid (HOTf). The catalyst was less stable in the Ni(0) state due to the inability of the rigid P4N2 ligand to adopt a tetrahedral geometry. Using variable scan rate cyclic voltammetry, a first-order rate constant of ∼1 s–1 w...

On the shift of acoustic characteristics of compression-ignited engines when operating with gasoline partially premixed combustion

As the focus of research and development is put into innovative combustion concepts with the goal of reducing harmful chemical pollutants while keeping or even improving the efficiency of conventional Diesel combustion, it is necessary to consider the impact on noise pollution brought by those innovative concepts. However, the question arises as to what extent the noise characterization and optimization strategies currently applied to conventional Diesel compression-ignited engines are applicable to these innovative combustion concepts. In this paper, we apply experimental noise characterization techniques based on pressure trace decomposition to two compression-ignited engines: a baseline conventional Diesel engine and an innovative 2-stroke engine operating with the gasoline partially premixed combustion concept. Analysis of the results reveals that the underlying physical phenomena responsible for the spectral signature of the noise are still shared between the new and the conventional concepts. However, results evince a significant change in the relevance of these physical sources, leading to necessary changes in optimization strategies for future compression-ignited engine development.

Seen as different, soil clays become more important to soils and also beyond soils

ABSTRACTUsing data from the literature, we pose the question of the extent to which a knowledge of soils is contributed by that of its clay fraction. In the past, soil characteristics have not related well to mineralogical analyses but we have redefined clays and also used a computer programme to more closely analyse X-ray diffraction (XRD) profiles. It was found that cation exchange capacities and specific surface areas of soil kaolinites almost always exceed those of standard kaolinites. The surfaces of soil clays are often coated by organic matter, which reduces their capacity to adsorb dissolved organic carbon (DOC). Oxidised iron is closely associated with phyllosilicate clays and enhances their capacity to adsorb DOC. Computer-aided decomposition of XRD traces show that phyllosilicates may contain several phases and react dynamically with potassium-containing solutions. Clays should be regarded as natural products with as yet undiscovered applications, including for cancer treatment.

Genotyping of CRISPR/Cas9 Genome Edited Xenopus tropicalis.

The targeted nuclease revolution (ZFN, TALEN, and CRISPR/Cas9) has led to a myriad of reports describing genotyping methodologies for genome edited founders (F0-crispants) and their offspring (F1). As such, choosing a specific genotyping methodology for your Xenopus CRISPR/Cas9 experiments can be challenging. In this chapter we will discuss, with emphasis on Xenopus tropicalis (X. tropicalis), different methods for assessing genome editing efficiencies within F0 CRISPR/Cas9 founders and for identification of their hetero-, compound hetero-, and homozygous mutant F1 offspring. For F0 crispants, we will provide the protocols and the respective (dis)advantages of genotyping with heteroduplex mobility assay (HMA), subclone Sanger sequencing, and sequence trace decomposition. Furthermore, we provide a previously unpublished pipe-line for rapid genotyping of F1 offspring-high resolution melting analysis (HRMA) and sequence trace decomposition-procured from breeding with F0 crispants. As such, we report here the current state-of-the-art cost- and time-effective approaches to perform genotyping of CRISPR/Cas9 experiments for the Xenopus tropicalis researcher.

Single-channel and multi-channel orthogonal matching pursuit for seismic trace decomposition

The conventional matching pursuit (MP) algorithm can decompose a 1D signal into a set of wavelet atoms adaptively. As to reflection seismic data, some applicable algorithms based on the MP decomposition has been developed, such as single-channel matching pursuit (SCMP) and multi-channel matching pursuit (MCMP). However, these algorithms cannot always select the optimal atoms, which results in less meaningful decompositions. To overcome this limitation, we introduce the idea of orthogonal matching pursuit into a multi-channel decomposition scheme, which we refer to as the multi-channel orthogonal matching pursuit (MCOMP). Each iteration of the proposed MCOMP might extract a more reasonable atom among a redundant Morlet wavelet dictionary, like the MCMP decomposition does, and estimate the corresponding amplitude more accurately by solving a least-squares problem. In order to correspond to SCMP, we also simplified the MCOMP decomposition to single-channel orthogonal matching pursuit (SCOMP) for decompositions of an individual seismic trace. We tested the proposed SCOMP algorithm on a synthetic signal and a field seismic trace. Then a field marine dataset example showed relative high resolution of the proposed MCOMP method with applications to the detection of low-frequency anomalies. These application examples all demonstrate more meaningful decomposition results and relative high convergence speed of the proposed algorithms.

Multiwavelet prestack Kirchhoff migration

The problems of stretching and aliasing usually occur in prestack Kirchhoff migration. A multiwavelet-based approach is proposed to provide an alternative approach to resolve these problems. Two steps are involved in the multiwavelet-based algorithm: The first step is the decomposition of the seismic traces with a series of wavelets of different dominant frequencies. This step is based on the principle of basis pursuit and is enhanced for more accurate and sparse decomposition by adding an adaptive subdictionary that is associated with the minima and maxima of a seismic trace. The second step is wavelet migration based on the Kirchhoff formulation using a novel approach. The outer iteration is the wavelets of the input seismic traces, which ensures that an input wavelet is only used once in the entire migration process. This enables output of multiple migrated images of different wavelets of dominant frequency ranges, elimination of noisy images, and composition of images for specific interpretation and reservoir characterization purposes with very little extra computational cost. The stretching and aliasing problems are naturally resolved because interpolation on the seismic trace is not required in the migration. We tested the algorithm using a synthetic model with a dipping layer and a 2D real seismic section. We compared our results with results obtained by conventional Kirchhoff migration.

Decomposition of atrazine traces in water by combination of non-thermal electrical discharge and adsorption on nanofiber membrane

In recent decades, several types of persistent substances are detected in the aquatic environment at very low concentrations. Unfortunately, conventional water treatment processes are not able to remove these micropollutants. As such, advanced treatment methods are required to meet both current and anticipated maximally allowed concentrations. Plasma discharge in contact with water is a promising new technology, since it produces a wide spectrum of oxidizing species. In this study, a new type of reactor is tested, in which decomposition by atmospheric pulsed direct barrier discharge (pDBD) plasma is combined with micropollutant adsorption on a nanofiber polyamide membrane. Atrazine is chosen as model micropollutant with an initial concentration of 30 μg/L. While the H2O2 and O3 production in the reactor is not influenced by the presence of the membrane, there is a significant increase in atrazine decomposition when the membrane is added. With membrane, 85% atrazine removal can be obtained in comparison to only 61% removal without membrane, at the same experimental parameters. The by-products of atrazine decomposition identified by HPLC-MS are deethylatrazine and ammelide. Formation of these by-products is more pronounced when the membrane is added. These results indicate the synergetic effect of plasma discharge and pollutant adsorption, which is attractive for future applications of water treatment.

Easy quantitative assessment of genome editing by sequence trace decomposition.

The efficacy and the mutation spectrum of genome editing methods can vary substantially depending on the targeted sequence. A simple, quick assay to accurately characterize and quantify the induced mutations is therefore needed. Here we present TIDE, a method for this purpose that requires only a pair of PCR reactions and two standard capillary sequencing runs. The sequence traces are then analyzed by a specially developed decomposition algorithm that identifies the major induced mutations in the projected editing site and accurately determines their frequency in a cell population. This method is cost-effective and quick, and it provides much more detailed information than current enzyme-based assays. An interactive web tool for automated decomposition of the sequence traces is available. TIDE greatly facilitates the testing and rational design of genome editing strategies.

High Resolution Time-Frequency Analysis Base on Ricker Atom Matching Pursuit Decomposition

The high accuracy time-frequency representation of non-stationary signals is one of the key researches in seismic signal analysis. Low-frequency part of the seismic data often has a higher frequency resolution, on the contrary it tends to have lower frequency resolution in the high frequency part. It’s difficult to fine characterize the time-frequency variation of non-stationary seismic signals by conventional time-frequency analysis methods due to the limitation of the window function. Therefore based on the Ricker wavelet, we put forward the matching pursuit seismic trace decomposition method. It decomposes the seismic records into a series of single component atoms with different centre time, dominant frequency and energy, by making use of the Wigner-Ville distribution, has the time-frequency resolution of seismic signal reach the limiting resolution of the uncertainty principle and skillfully avoid the impact of interference terms in conventional Wigner-Ville distribution.

Trace decompositions of tensor spaces

The trace decomposition theory of tensor spaces, based on duality, is presented. The trace decomposition equations for tensors, symmetric in some sets of superscripts, and antisymmetric in the subscripts, are derived by means of the trace operations and appropriate symmetrizations and antisymmetrizations. Commutation relations for the corresponding linear operators are also derived. Trace decompositions of various concrete tensor spaces are discussed.

Application of the Haar wavelet transform to detect microseismic signal arrivals

A discrete wavelet transform is applied for the time-scale representation of raw seismic data and subsequent identification of events of interest. The wavelet transform properties such as localization, which is essential for the analysis of transient signals, provide a filter to extract characteristics of interest such as energy and predominant time scales. This information is subsequently exploited for microseismic events detection. The sample sum of squares is partitioned on a scale-by-scale basis and analysed across the time scales to emphasise the signal phase arrival, retaining the scales at which the seismic events have larger energy. The orthonormal decomposition of the signal energy estimated by the wavelet variance into the retained scales provides a useful means of describing the change in the signal magnitude associated with the triggering events. This type of analysis discriminates between signal phase arrival and spurious signal triggering by the different magnitude of local relative energy, which is much smaller in the latter case. The relative energy across the scales also changes, with greater magnitudes at coarser resolutions in the pattern expected in a trace decomposition with only a random noise component.