小波包分析用于重叠分析化学信号的处理

对小波包分析的算法进行了改进,并将此算法成功地应用于多组分重叠色谱信号的解析.结果表明,本文提出的算法解决了MRSD算法的不足,更适合处理分析化学信号,用于重叠信号的解析时不需重构(逆变换),简化了数据处理步骤,加快了数据解析速度,具有较强的解析能力.对于重叠色谱信号的解析,小波包分析比小波分析具有更强的解析能力.     

Size-selective absorption and adsorption in anionic pigmented porous coating structures: case study cationic starch polymer versus nanofibrillated cellulose

The use of nano- or microfibrillar cellulose (NFC or MFC) in papermaking is generally hampered by high cost and potentially wasteful use in typical wet end applications. The solubility and fines nature of the material makes it inefficient to retain, and when retained it is generally inefficiently applied within the spatial distribution of the paper fibre matrix. The benefits of capturing the important NFC in a layer structure, to enhance surface and stiffness properties of paper, board and laminates whereby NFC is entrapped at the surface of a fibrous web by forming an in situ composite, were previously shown for the exemplified case of modified porous calcium carbonate, as might be used in an inkjet coating application (Ridgway and Gane in Cellulose 19(2):547–560, 2011). The NFC is seen to integrate itself within the larger interparticle porous structure providing excellent holdout and thin layer continuity, essential in developing an efficient concentration of the NFC at the surface of the substrate. The effect is likened to the well-known I-beam construction. The concept need not be confined to porous pigments, as any pigment coating structure that absorbs and holds the NFC, thus creating an in situ composite, could be used. The aim of this study is to look at a range of different pigments and investigate how these could be used as coating structures by measuring the effect on the pore structure before and after absorbing NFC. This is achieved by using model porous tablet blocks made from the respective anionic coating formulations. The penetration of cationic starch solution, as might be applied for surface sizing on paper, is studied for comparison. The use of cationic starch is considered in the industry to provide reasonably effective surface concentrations due to the electrostatically driven adsorption to the anionic pore surfaces. The effect of water alone on the coating structure has also been measured to allow for structural relaxation, considered to be mainly related to the swelling properties of the anionic polyacrylic coating pigment dispersant. The results illustrate the size-exclusion properties of the pore structure in relation to the material being absorbed and partial resistance to bulk penetration by pore wall adsorption in the case of oppositely charged species. The distribution of the absorbate throughout the pore network can be derived using mercury intrusion porosimetry and electron microscopy, and is deemed critical in respect to controlling the end performance properties, be they, for example, barrier, strength-enhancing applications, or both.     

Explicit finite difference simulations for accelerating cross diffusion flow over a perpendicular shield with parabolic motion

The heat transfer phenomenon subject to thermos-diffusion effects convey important applications in the heating processes, extrusion systems, chemical processes and various engineering systems. The objective of current work is to observe the contribution of Soret and Dufour effects in oscillating shield for cross diffusion flow. The perpendicular shield with oscillating motion induced the flow. The magnitude of oscillations is assumed to be small so that laminar flow due to oscillating shield has been resulted. The motivations for addressing the thermos-diffusion phenomenon due to oscillating of shield are due to applications in oscillatory pumps, moving surface, metal detectors, power systems etc. The dimensionless problem is obtained via introducing the appropriate set of variables. The numerical outcomes are suggested by using the most interesting explicit finite difference scheme. The physical illustration for flow parameters is presented. Moreover, the aspect of physical quantities involving the flow are graphically reported.     

19F NMR chemical shifts. 1. Aliphatic fluorides

The (19)F NMR shielding for the alkyl fluorides from methyl fluoride to tert-butyl fluoride has been calculated using IGAIM and has been separated into the contribution from each of the molecular orbitals. The relatively large change in fluorine shielding, in contrast to the adjacent carbon, was found to be due to the tensor components normal to the C-F bond axis. As the number of adjacent p-orbitals increases, the lone-pair p orbitals at fluorine become involved with MOs using these orbitals. The increase in the number of occupied orbitals associated with the fluorine leads to increased opportunities for mixing with virtual orbitals and to the increase in paramagnetic deshielding. The same pattern is seen on going from acetylene to 2-tert-butylacetylene and is also seen in the methyl (13)C shielding in the series ethane, propane, isobutane, and neopentane. The fluorine shielding in the series of fluoromethanes also decreases with increasing fluorine substitution. With carbon tetrafluoride, the decreased shielding arises from the highest occupied MO, which is a nonbonding linear combination of pure p functions at the fluorines.     

Self-Healing Molecular Biology for Microbial Concrete: A Review

The most extensively utilized material in construction is concrete, decreasing life of structure pointing toward loses in structural health. The crack is the major problem faced in the concrete construction. This causes the corrosion in the steel reinforcement. The structure gets deteriorated with the developing cracks; therefore need the proper attention toward this problem. The present work consists of the different self-healing techniques used by the researchers to inhibit the crack and prevent further deterioration in the structure. The self-healing mechanism proves advantageous in use of natural fibers to inhibit the corrosion process, to increase compressive strength, and to decrease water absorption is present in this study. The maximum strength increased and the width of crack get healed with the help of these techniques is also mentioned in the study.     

Characterization of micelle formation of dodecyldimethyl-N-2-phenoxyethylammonium bromide in aqueous solution

Aggregation behavior of dodecyldimethyl-N-2-phenoxyethylammonium bromide commonly called domiphen bromide (DB) was studied in aqueous solution. The Krafft temperature of the surfactant was measured. The surfactant has been shown to form micellar structures in a wide concentration range. The critical micelle concentration was determined by surface tension, conductivity, and fluorescence methods. The conductivity data were also employed to determine the degree of surfactant counterion dissociation. The changes in Gibb's free energy, enthalpy, and entropy of the micellization process were determined at different temperature. The steady-state fluorescence quenching measurements with pyrene and N-phenyl-1-naphthylamine as fluorescence probes were performed to obtain micellar aggregation number. The results were compared with those of dodecyltrimethylammonium bromide (DTAB) surfactant. The micelle formation is energetically more favored in DB compared to that in DTAB. The 1H-NMR spectra were used to show that the 2-phenoxyethyl group, which folds back onto the micellar surface facilitates aggregate formation in DB.     

Experimental and theoretical studies on the isomerization of allyl thiocyanate to allyl isothiocyanate

The mechanism of isomerization of allyl thiocyanate to allyl isothiocyanate has been investigated both experimentally and theoretically. The kinetic study indicates that the reaction is unimolecular and is not ionic. The entropy of activation suggests strongly that the mechanism involves a cyclic transition state. The rate of reaction was retarded to a small extent in polar solvents relative to that in nonpolar solvents. Ab initio MO calculations indicate, in agreement with the experimental results, that the reaction proceeds through a cyclic transition state, one in which the SCN moiety is almost linear. Thus, this is a [3,3] sigmatropic rearrangement. The charge separation in the transition state was substantial. The retardation of the reaction in polar solvents was attributed to the difference in solvation in the original state and in the transition state. © 1997 John Wiley & Sons, Inc.     

Permeation,sorption, and diffusion of water in ethyl cellulose

The permeability of ethyl cellulose to water vapor and liquid water was measured as a function of temperature. A change of slope was found in the Arrhenius plots at about 50°C., close to the glass transition. The sorption isotherms showed essentially zero heat of mixing in agreement with other workers. The diffusion constants were measured in four ways, viz., sorption, desorption, time lag, and by dividing the permeability constants by the equilibrium solubility coefficients. The time lag method gave diffusion constants which were independent of concentration, whereas the other three methods led to diffusion constants which steadily decreased with concentration. All the methods, however, extrapolated to about the same value at zero concentration. The decreasing diffusivities are believed to be due to the clustering of water molecules in the polymer. However, no clustering appeared to take place under the conditions of the time lag measurements.     

Ultrafast study of p-biphenylyldiazomethane and p-biphenylylcarbene

p-Biphenylyldiazomethane was excited by femtosecond pulses of UV light in acetonitrile, in cyclohexane, and in methanol. Ultrafast photolysis produces a singlet excited state of p-biphenylyldiazomethane with lambdamax = 490 nm, and lifetimes of less than 300 fs in acetonitrile, in cyclohexane, and in methanol. The decay of the excited state is accompanied by the growth of transient absorption with lambdamax = 360 nm. The carrier of this transient absorption is attributed to singlet p-biphenylylcarbene, a result that is consistent with the predictions of TD-DFT calculations. The singlet carbene lifetimes are 200 and 77 ps in acetonitrile and cyclohexane, respectively, and are controlled by intersystem crossing to the lower energy triplet state. The transient absorption does not decay to baseline in acetonitrile, because of the formation of nitrile ylide. The equilibrium mixture of singlet and triplet p-biphenylylcarbene reacts with acetonitrile to form a nitrile ylide (lambdamax = 370 nm), and with cyclohexane by C-H insertion 1-20 ns after the laser pulse. The singlet carbene lifetime is only 7.9 ps in methanol, owing to a rapid reaction with the solvent. Reaction with the solvent gives rise, in part, to a p-biphenylylbenzyl cation (lambdamax = 450 nm, tau = 6.3 ps) in methanol.     

Orientation of LDPE Crystals from Microscale to Nanoscale via Microlayer or Nanolayer Coextrusion

The microlayer or nanolayer coextrusion of hundreds or thousands of alternating low density polyethylene(LDPE)/polystyrene(PS) microlayers or nanolayers were used to study the orientation of LDPE crystals in the confined quasi-two-dimensional or two-dimensional space. The clear and continuous layer structures from microscale to nanoscale can be found in SEM images. The morphology evolution of LDPE crystals in the confined microlayer or nanolayer can be varied from 3D spherulites, 2D spherulites, stacked edge-on lamellar, to single edge-on lamellar. Due to the orientation of the LDPE crystals, the tensile strength of the films increases obviously when the layer thickness reduces to nanoscale. The 2D small angle X-ray scattering(SAXS) patterns can reflect the average degree of orientation of LDPE in the confined layers. The stacking of LDPE lamellae is suppressed in interlamination and oppositely in parallel to the extrusion direction. The specific orientation function f can be calculated from the patterns. The infrared dichroism further confirms the mutation of the orientation of LDPE crystals from microscale to nanoscale in the confined space.     

Basic Principles of Protease-Catalyzed Peptide Bond Formation

The stereospecific formation of peptide bonds under mild conditions and without side reactions is still a formidable task in peptide synthesis. One approach that springs to mind, namely the use of the naturally occurring catalyst involved in the biosynthesis of proteins, the ribosomal peptidyl transferase, cannot be realized in practice. The fact, however, that the natural cleavage of proteins is carried out by other enzymes, namely the proteases, together with the reversibility of these cleavage reactions in principle, has led to an interesting synthetic concept. Proteases normally catalyze the enzymatic degradation of proteins and peptides by hydrolytic cleavage of the peptide bond in an exergonic reaction. The use of physicochemical principles in order to influence the equilibrium, the concentration of products, and the kinetic parameters of the reaction results in the successful application of the catalytic properties of proteases to peptide synthesis. The purpose of this review is to describe and summarize the methods used in such approaches and to attempt a systematic categorization. The principles are applied to the synthesis of such practically relevant products as aspartame and human insulin.     

Preliminary evaluation of interactions between selected alcoholamines and model skin sebum components

The aim was to evaluate the interaction between selected alcoholamines and components of artificial skin sebum. The rate and depth of penetration into the lipophilic bead imitating pilosebaceous unit lumen was applied for alcoholamine penetration activity assay. The activity differentiation of 0.5% aqueous alcoholamine solutions with a potential cleansing effect on the pilosebaceous unit was performed. The depth of aminomethylpropanol penetration increased from 0.080 mm after 15 min to 3.049 mm after 72 h. The depth of aminomethylpropendiol penetration increased with time from 0.148 to 4.064, respectively, of diisopropanolamine from 0.481 to 4.626, triethanolamine from 0.236 to 4.342, triisopropanolamine from 0.275 to 2.392 and trometamol from 0.338 to 4.580. The products of alcoholamines reaction with the model skin sebum are easily dispersed in water. The rate of alcoholamines reaction with the model skin sebum depends on the alcoholamine, being the highest in the case of diisopropanolamine, decreasing to minimum for triisopropanolamine. Selected alcoholamines would be applied in ex vivo and in vivo research.     

Orientation of LDPE crystals from microscale to nanoscale <Emphasis Type="Italic">via</Emphasis> microlayer or nanolayer coextrusion

The microlayer or nanolayer coextrusion of hundreds or thousands of alternating low density polyethylene (LDPE)/polystyrene (PS) microlayers or nanolayers were used to study the orientation of LDPE crystals in the confined quasi-two-dimensional or two-dimensional space. The clear and continuous layer structures from microscale to nanoscale can be found in SEM images. The morphology evolution of LDPE crystals in the confined microlayer or nanolayer can be varied from 3D spherulites, 2D spherulites, stacked edge-on lamellar, to single edge-on lamellar. Due to the orientation of the LDPE crystals, the tensile strength of the films increases obviously when the layer thickness reduces to nanoscale. The 2D small angle X-ray scattering (SAXS) patterns can reflect the average degree of orientation of LDPE in the confined layers. The stacking of LDPE lamellae is suppressed in interlamination and oppositely in parallel to the extrusion direction. The specific orientation function f can be calculated from the patterns. The infrared dichroism further confirms the mutation of the orientation of LDPE crystals from microscale to nanoscale in the confined space.     

Detection of Vibrational Spectroscopic Biomarkers of the Effect of Gold Nanoparticles on Wheat Seedlings Using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy

The aim of this study is to evaluate the biochemical changes in the leaves of wheat seedlings exposed to gold nanoparticles (AuNPs) nondestructively and rapidly using attenuated total reflectance Fourier transform infrared spectroscopy and laser-induced fluorescence. The 18?nm size gold nanoparticles are synthesized by citrate reduction. For analyzing the effect of gold nanoparticles on wheat seedlings, the treatment of gold nanoparticles was applied to the seedlings through roots and following the spectroscopic measurement of biochemical signatures. The laser-induced fluorescence measurement has been performed to access the effect of gold nanoparticles on the chlorophyll concentration of wheat seedlings. The decrease in the fluorescence intensity and the fluorescence intensity ratio on the treatment of gold nanoparticles indicates increase in the concentration of chlorophyll in the leaves of wheat seedlings. The attenuated total reflectance Fourier transform infrarred spectroscopy in combination with principal component analysis has been used to visualize the biochemical changes in the cellulose, hemicellulose, pectin, lignin, amino acids, proteins, and lipid of the leaves of wheat seedlings by recording infrared spectra in the region from 4000 to 400?cm^?1. Principal component analysis applied to the preprocessed infrared data clearly distinguishes the spectral variability between control and gold nanoparticle treated seedlings. The study shows that exposure of gold nanoparticles increases the concentrations of cellulose, hemicelluloses, pectin, and lignin in the leaves of wheat seedlings. The increase in these chemicals indicates the modulation of cell walls of the wheat seedlings by the gold nanoparticle treatment. The exposure to gold nanoparticles also enhances the expression of lipid and proteins in the leaves of wheat seedlings.     

酸洗污泥与煤共燃烧过程中重金属的迁移分布研究

采用高温管式炉系统进行酸洗污泥与煤共燃烧实验。对共燃烧后As、Cr、Ni、Cd、Cu、Mn、Pb、Zn、Sb、Se重金属元素在烟气、飞灰及炉渣中的分配率进行分析。结果表明,Cd、Se、Zn是易挥发重金属,主要分布在烟气和飞灰中。Cd在烟气中的最大分配率为61%;Se在烟气中的分配率为38.58%~94.612%;Zn在低、高温段分别主要分布在烟气和飞灰中。As、Cu、Pb、Sb是半挥发重金属,Pb在炉渣中的分配率较稳定,分配率为42.67%~64.76%,在烟气和飞灰中的分配率波动较大,其分配率分别是14.176%~45.79%和9.78%~32.55%;Sb在烟气中的最大分配率为37.64%;温度升高反而会抑制As、Cu挥发,这与高温下As、Cu易与矿物质反应生成络合物有关。Ni、Cr、Mn属于难挥发重金属,绝大部分残留在炉渣中,且分配率对温度变化不敏感。赋存于炉渣中的Cr、Ni分别超过95%和97%;随着温度升高,Mn在炉渣中的分配率由71.46%增加到96.89%。     

Shear-driven release of a bud from a multicomponent vesicle

The authors study the response of a multicomponent budded vesicle to an imposed shear flow using dissipative particle dynamics. Under certain circumstances, phase separation in the vesicle membrane leads to the formation of a minority domain which deforms into a nearly spherical bud in order to reduce its interfacial energy. The authors show that an imposed shear force has a varying effect on the vesicle, tending either to separate the bud from the vesicle or to stretch the bud open, depending on the vesicle orientation. The authors examine the interplay of membrane bending rigidity, line tension, and shear in determining the behavior of the vesicle. With the appropriate design, vesicles can be made to release buds in a controlled manner in response to shear. The authors outline a regime in which bud release is favorable.     

Theory and practice of enzyme bioaffinity electrodes. Direct electrochemical product detection

The use of enzyme labeling techniques to convert biorecognition events into high sensitivity electrochemical signals may follow two different strategies. One, in which the current is the electrocatalytic response of a redox couple serving as cosubstrate to a redox enzyme label and another that consists in the detection of an electrochemically active product of the enzyme label. The theoretical relationships that link, in the latter case, the electrochemical current response to the amount of recognized labeled target analyte are established for steady-state diffusion-convection chronoamperometric regimes. Two governing parameters thus emerge. One measures the Michaelis-Menten competition in the enzyme kinetics. The other characterizes the competition between the enzymatic kinetics and the diffusion of the substrate. The electrochemical response is finally related to the labeled target analyte concentration in solution through the recognition isotherm. The direct electrochemical product detection thus provides a route to the characteristics of the recognition isotherm, which serves as a calibration curve in analytical applications. The establishment of further theoretical relationships allows one to surmise the increase in sensitivity that may be obtained by using cyclic voltammetry instead of steady-state chronoamperometry in standard electrochemical cells or by accumulation of the enzyme-product in cells of small volume/surface ratios. The theoretical predictions are tested with the example of the avidin-biotin recognition process in a system that involves alkaline phosphatase as enzyme label and 4-amino-2,6-dichlorophenyl phosphate as substrate, generating 4-amino-2,6-dichlorophenol as electrochemically active product. The advantages of the dichloro-substitution are discussed. The theoretical analysis is a requisite for a rational and realistic discussion of the analytical performances of the steady-state chronoamperometric and cyclic voltammetric approaches. These are shown to compare favorably with the best heterogeneous bioaffinity assays so far reported.     

Time-dependent alignment of molecules trapped in octahedral crystal fields

The hindered rotational states of molecules confined in crystal fields of octahedral symmetry, and their time-dependent alignment obtained by pulsed nonresonant laser fields, are studied computationally. The control over the molecular axis direction is discussed based on the evolution of the rotational wave packet generated in the cubic crystal-field potential. The alignment degree obtained in a cooperative case, where the alignment field is applied in a favorable crystal-field direction, or in a competitive direction, where the crystal field has a saddle point, is presented. The investigation is divided into two time regimes where the pulse duration is either ultrashort, leading to nonadiabatic dynamics, or long with respect to period of molecular libration, which leads to synchronous alignment due to nearly adiabatic following. The results are contrasted to existing gas phase studies. In particular, the irregularity of the crystal-field energies leads to persistent interference patterns in the alignment signals. The use of nonadiabatic alignment for interrogation of crystal-field energetics and the use of adiabatic alignment for directional control of molecular dynamics in solids are proposed as practical applications.     

Molecular dynamics studies of melting and solid-state transitions of ammonium nitrate

Molecular dynamics simulations are used to calculate the melting point and some aspects of high-temperature solid-state phase transitions of ammonium nitrate (AN). The force field used in the simulations is that developed by Sorescu and Thompson [J. Phys. Chem. A 105, 720 (2001)] to describe the solid-state properties of the low-temperature phase-V AN. Simulations at various temperatures were performed with this force field for a 4 x 4 x 5 supercell of phase-II AN. The melting point of AN was determined from calculations on this supercell with voids introduced in the solid structure to eliminate superheating effects. The melting temperature was determined by calculating the density and the nitrogen-nitrogen radial distribution functions as functions of temperature. The melting point was predicted to be in the range 445 +/- 10 K, in excellent agreement with the experimental value of 442 K. The computed temperature dependences of the density, diffusion, and viscosity coefficient for the liquid are in good agreement with experiment. Structural changes in the perfect crystal at various temperatures were also investigated. The ammonium ions in the phase-II structure are rotationally disordered at 400 K. At higher temperatures, beginning at 530 K, the nitrate ions are essentially rotationally unhindered. The density and radial distribution functions in this temperature range show that the AN solid is superheated. The rotational disorder is qualitatively similar to that observed in the experimental phase-II to phase-I solid-state transition.