Kinetic Relationships Research Articles

UiO-66: An Advanced Platform for Investigating the Influence of Functionalization in the Adsorption Removal of Pharmaceutical Waste.

Highly efficient and selective removal of pharmaceuticals and personal care products (PPCPs) from wastewater is a great challenge and is significant. In this study, we chose UiO-66-R, which contains eight isostructural metal-organic frameworks (MOFs) with variable functional groups (-R), as a platform for systemically investigating the influence of functionalization on its adsorption behavior with respect to three classic PPCPs. We conducted kinetic, modeling, and structure-function relationship studies on PPCP removal using MOFs. The adsorption kinetics, including the adsorption rate, affinity, and separation factor ( RL), were comprehensively analyzed and simulated. The design and function of MOFs can greatly promote their adsorption capacity and the efficiency of PPCPs. The structure-function relationship study revealed that hydrogen bonding, electrostatic, and π-π interactions between MOFs and PPCP molecules played important roles in the adsorption process and significantly influenced the adsorption efficiency. This study paves a new way for the application of MOFs with respect to the removal of PPCP pollution and provides guidance for the design of new porous materials for environmental treatment and separation applications.

A micromechanical model for the growth of collagenous tissues under mechanics-mediated collagen deposition and degradation

In this study, we developed a micromechanical model for the growth and remodeling of a soft tissue based on the concurrent action of collagen deposition and degradation. We assumed in the model that collagen degradation causes a reduction in the fiber radius, while collagen deposition can increase both the radius and length of the collagen fibers growing under load. The latter arises from the assumption that collagen is deposited in an unstressed state, which increases the reference length of a fiber growing under mechanical load. The rate of collagen deposition and degradation can be stimulated and inhibited, respectively, by the fiber axial strain energy density. From these assumptions, we derived kinetic relationships for the fiber radial and axial growth stretch, and constitutive relations for the stress response and growth and remodeling of the tissues. We applied the model to study the growth of collagen fibers under a static and cyclic force. Cyclic force loading can drive the continual axial growth of collagen fiber, while the axial growth under a constant force eventually halts when an equilibrium state is reached. We then applied the model to investigate the development of stress and strain homeostasis of a spherical collagenous tissue membrane in response to a perturbation in the internal pressure. The model showed that an increase in the pressure produced growth in the tissue radius and thickness, such that the stress response was able to recover the equilibrium membrane stress before the pressure perturbation. Tissues composed of slender, or low-crimp collagen fibers also recovered the equilibrium mechanical stretch level before the perturbation. These results indicated that concurrent mechanics-stimulated collagen deposition and mechanics-inhibited degradation can produce stress homeostasis and for some fiber morphology strain homeostasis without prescribing a target stress or fiber strain.

Shelf-Life Prediction Model of Chitosan Coated Eggs at Different Storage Temperatures

Abstract In order to study the quality changes and shelf life of chitosan coated eggs during storage, the quality, gas chamber diameter, yolk coefficient and the quality change of Hough unit during storage were measured at temperature of 5, 20 and 35 ℃. The Pearson correlation between the quality indexes and the egg Hough’s unit value was analyzed, and the yolk coefficient was analyzed dynamically and the shelf life prediction model was based on the basis of the Arrhenius equation. The results showed that the quality of eggs, egg yolk coefficient, and Huff units all decreased with the extension of storage time, and the diameter of the air chambers of eggs showed an increasing trend with the extension of storage time. Moreover, the storage environment at high temperature (20 and 35 ℃) had a significant effect on the quality deterioration than the low temperature (5℃) storage environment; The correlation coefficient between egg yolk coefficient and Hough unit is the highest at all temperatures, which can be used as an important indicator for shelf life prediction; According to the changing rule of egg quality, the yolk coefficient can establish a first order kinetic model. According to the model established by the egg yolk coefficient, the coefficient R2 of the fitting curve of the predicted value and the measured value is 0.9825, and the average relative error P is 9.32% and less than 10%. The kinetic relationship between yolk coefficient and temperature is well described. At the same time, based on the dynamic model, the shelf life prediction model of chitosan-coated eggs based on yolk coefficient was determined by the dynamic model. The average relative error was 7.6%, less than 10%, which indicated that the egg shelf life prediction model based on the change of egg yolk coefficient was feasible.

Heat evolution and energy analysis of cyanide bioproduction by a cyanogenic microorganism with the potential for bioleaching of precious metals.

Precious metals were lost in the current technologies of recovering waste printed circuit boards (WPCBs). Microbe-produced cyanide is considered as an important lixiviant in bioleaching of precious metals from WPCBs. Enhancing cyanide production is the key to industrialization of bioleaching technology. This study identified the precursor form of biogenic cyanide, investigated the energy characteristics of cyanide synthesis, thermal change characteristics of cyanogenic culture, and the potential kinetic relationship between cyanide production and thermal change. We firstly found glycine anion [H2NCH2CO2]- was the precursor form of cyanide in microbial biocatalysis. The bond cleavage pathways from glycine anion to cyanide were analyzed by computation chemical. Results showed decomposition of glycine anion into cyanide was endothermic and non-spontaneous. Formations of [HN = CHCO2]- and -C≡N have an average energy barrier of 34.05 and 9.15 kcal/mol respectively, while formations of free radicals from anionic intermediates have an average barrier of 71.05 kcal/mol. Cyanide concentration began to increase from 0.48 to 5.27 mg/L when heat production was strongest. Temperature difference between sterile medium and cyanogenic culture reached 0.3 °C. Therefore, metabolic heat brought positive effect on cyanide biosynthesis.

Exploring the Kinetic and Thermodynamic Relationship of Charge Transfer Reactions Used in Localized Electrodeposition and Patterning in a Scanning Bipolar Cell.

Bipolar electrochemistry involves spatial separation of charge balanced reduction and oxidation reactions on an electrically floating electrode, a result of intricate coupling of the work piece with the ohmic drop in the electrochemical cell and to the thermodynamics and kinetics of the respective bipolar reactions. When paired with a rastering microjet electrode, in a scanning bipolar cell (SBC), local electrodeposition and patterning of metals beneath the microjet can be realized without direct electrical connections to the workpiece. Here, we expand on prior research detailing electrolyte design guidelines for electrodeposition and patterning with the SBC, focusing on the relationship between kinetics and thermodynamics of the respective bipolar reactions. The kinetic reversibility or irreversibility of the desired deposition reaction influences the range of possible effective bipolar counter reactions. For kinetically irreversible deposition systems (i.e., nickel), a wider thermodynamic window is available for selection of the counter reaction. For kinetically reversible systems (i.e., copper or silver) that can be easily etched, tight thermodynamic windows with a small downhill driving force for spontaneous reduction are required to prevent metal patterns from electrochemical dissolution. Furthermore, additives used for the bipolar counter reaction can influence not only the kinetics of deposition, but also the morphology and microstructure of the deposit. Cyclic voltammetry measurements help elucidate secondary parasitic reduction reactions occurring during bipolar nickel deposition and describe the thermodynamic relationship of both irreversible and reversible bipolar couples. Finally, finite element method simulations explore the influence of bipolar electrode area on current efficiency and connect experimental observations of pattern etching to thermodynamic and kinetic relationships.

Toward the elucidation of the mechanism for passive membrane permeability of cyclic peptides.

Toward the elucidation of the mechanism for passive membrane permeability of cyclic peptides.

Mechanism of Influence of Nanocrystal Sizes on the Parameters of the Curves of the Pseudoelastic and Thermoelastic Deformations of Alloys with the Shape Memory Effect

The data available in the literature on the influence of the nanocrystal sizes of alloys with the shape memory effect on the parameters of the curves of their pseudoelastic and thermoelastic deformation are analyzed in the framework of the theory of diffuse martensitic transitions (DMT). The peculiarity of the DMT theory is that it is based on both thermodynamic and kinetic relationships that make it sensitive to the alloy structure on the mesoscopic scale. This enables one to state the functional dependence of the parameter of the martensitic deformation of the nanocrystals on the size of their cross section D. As a result of the analysis, it is found that the coefficient of the strain (martensitic) hardening and the hysteresis of the pseudoelastic strain curves of submicrocrystals of the Ni54Fe19Ga27 are changed with D by law 1/D2. The temperature range (Ms – Mf) of the martensitic transition in TiNi alloy nanocrystals is changed by analogy law. These dependences are results of the constrained displacement of dislocations of the phase transformation by transverse sizes of the crystal. A kinetic mechanism of the appearance of the critical nanocrystal size Dk is established; the transition of austenite to martensite does not occur at transverse crystal sizes smaller than the critical size.

Wave based method (WBM) for free vibration analysis of cross-ply composite laminated cylindrical shells with arbitrary boundaries

In this paper, the wave based method (WBM) is presented to analyze the free vibration of composite laminated cylindrical shells with general classical and elastic restrained boundaries. The Reissner-Naghid’s theory is adopted to establish the equations of the motion force and moments, the displacement functions of composite laminated cylindrical shells are extended to wave functions which can accurately satisfy the equations of motion and boundary conditions. According to the kinetic relationship of the composite laminated cylindrical shell, the final equation of the composite shell will be obtained to calculate the free vibration results. To validate its accuracy, the vibration results of composite laminated cylindrical shells subject to various boundary conditions including the classical cases, elastic restraints and their combinations by WBM are compared with those published in the literature. The numerical values of the errors are used to prove the high precision and wide application of WBM. Furthermore, the effects of several important parameters, including boundary conditions, length to radius ratio, and elastic modulus on natural frequencies are discussed. Compared with other existing numerical methods, the present solution has the characteristics of complete matrix assembly and high calculation accuracy. When the boundary conditions change, only the initial parameters of the matrix need modifying to adapt.

TCR microclusters form spatially segregated domains and sequentially assemble in calcium-dependent kinetic steps

Engagement of the T cell receptor (TCR) by stimulatory ligand results in the rapid formation of microclusters at sites of T cell activation. Whereas microclusters have been studied extensively using confocal microscopy, the spatial and kinetic relationships of their signaling components have not been well characterized due to limits in image resolution and acquisition speed. Here we show, using TIRF-SIM to examine the organization of microclusters at sub-diffraction resolution, the presence of two spatially distinct domains composed of ZAP70-bound TCR and LAT-associated signaling complex. Kinetic analysis of microcluster assembly reveal surprising delays between the stepwise recruitment of ZAP70 and signaling proteins to the TCR, as well as distinct patterns in their disassociation. These delays are regulated by intracellular calcium flux downstream of T cell activation. Our results reveal novel insights into the spatial and kinetic regulation of TCR microcluster formation and T cell activation.

Механизм влияния размера нанокристаллов на параметры кривых псевдоупругой и термоупругой деформации сплавов с эффектом памяти формы

AbstractThe data available in the literature on the influence of the nanocrystal sizes of alloys with the shape memory effect on the parameters of the curves of their pseudoelastic and thermoelastic deformation are analyzed in the framework of the theory of diffuse martensitic transitions (DMT). The peculiarity of the DMT theory is that it is based on both thermodynamic and kinetic relationships that make it sensitive to the alloy structure on the mesoscopic scale. This enables one to state the functional dependence of the parameter of the martensitic deformation of the nanocrystals on the size of their cross section D . As a result of the analysis, it is found that the coefficient of the strain (martensitic) hardening and the hysteresis of the pseudoelastic strain curves of submicrocrystals of the Ni_54Fe_19Ga_27 are changed with D by law 1/ D ^2. The temperature range ( M _ s – M _ f ) of the martensitic transition in TiNi alloy nanocrystals is changed by analogy law. These dependences are results of the constrained displacement of dislocations of the phase transformation by transverse sizes of the crystal. A kinetic mechanism of the appearance of the critical nanocrystal size D _ k is established; the transition of austenite to martensite does not occur at transverse crystal sizes smaller than the critical size.

Tert-Butylphenylthiazoles with an oxadiazole linker: a novel orally bioavailable class of antibiotics exhibiting antibiofilm activity.

The structure–activity and structure–kinetic relationships of a new tert-butylphenylthiazole series with oxadiazole linkers were conducted with the objective of obtaining a new orally available antibacterial compounds. Twenty-two new compounds were prepared, purified and identified. Their activity against methicillin-resistant Staphylococcus aureus were examined. Compound 20 with 3-hydroxyazetidine as a nitrogenous side chain showed promising activity against twenty-four clinical isolates, including vancomycin-resistant staphylococcal and enterococcal species with MIC values ranging from 4–8 μg mL−1. Additional advantages of this compound include an ability to eradicate staphylococcal biofilm mass in a dose-dependent manner as well as high metabolic stability after an oral dose of 25 mg kg−1 with a biological half-life that exceeds 5 hours and a plasma concentration (Cmax) that exceeds the MIC values.

Analysis of Interdependent Kinetic Controls of Fatty Acid Synthases.

Biocatalytic systems (e.g., multienzyme pathways or complexes) enable the conversion of simple sugars into complex products under ambient conditions and, thus, represent promising platforms for the synthesis of renewable fuels and chemicals. Unfortunately, to date, many of these systems have proven difficult to engineer without a detailed understanding of the kinetic relationships that regulate the concerted action of their constituent enzymes. This study develops a mechanistic kinetic model of the fatty acid synthase (FAS) of Escherichia coli and uses that model to determine how different FAS components work together to control the production of free fatty acids-precursors to a wide range of oleochemicals. Perturbational analyses indicate that the modification or overexpression of a single FAS component can depress fatty acid production (a commonly observed phenomenon) by sequestering the proteins with which it interacts and/or by depleting common substrate pools. Compositional studies, in turn, suggest that simple changes in the ratios of FAS components can alter the average length of fatty acids but show that specialized enzymes (i.e., highly specific ketoacyl synthases or thioesterases) are required for narrow product profiles. Intriguingly, a sensitivity analysis indicates that two components primarily influence-and, thus, enable fine control over-total production, but suggests that the enzymes that regulate product profile are more broadly influential. Findings thus reveal the general importance of kinetic considerations in efforts to engineer fatty acid biosynthesis and provide strategies-and a kinetic model-for incorporating those considerations into FAS designs.

Investigation of Topological and Kinetic Characteristics of Catalytic Glass Fiber Materials

The structure and catalytic properties of glass fiber containing the oxides of transition metals were studied. Cobalt and copper ions were used to create the active part of the catalyst. The textural characteristics and kinetic relationships of the oxidation of organic substances were investigated.

A New Data Reconciliation Strategy Based on Mutual Information for Industrial Processes

In modern industrial processes, data reconciliation plays a significant role in reducing measurement errors and adjusting process measurements to meet conservation laws and constraints of process models. Most traditional data reconciliation methods are based on the weighted least-squares technique with diagonal weight matrix, in which the variable errors are assumed to be independent of each other. However, the measurement errors are often nonlinearly correlated due to reasons like kinetic relationships, external disturbances, and feedback control, etc. To deal with this problem, a new data reconciliation strategy based on mutual information is proposed in this paper. In the new method, mutual information is first utilized to measure the nonlinear variable correlations. Then, a new objective function is designed for data reconciliation with a full weight matrix, whose elements are the mutual information coefficients between different variables. Finally, the effectiveness of the proposed data reconciliatio...

Competition Between Crystallization‐Induced Expansion and Creep Compaction During Gypsum Formation, and Implications for Serpentinization

AbstractDeformation caused by reaction‐driven volume increases is an important process in many geological settings. The interaction of rocks with reactive fluids can change permeability and reactive surface area, leading to a large variety of feedbacks. Gypsum (CaSO4·2H2O) is an ideal material to study these processes. It forms rapidly at room temperature via bassanite (CaSO4·[1/2]H2O) hydration and is commonly used as an analog for rocks in high‐temperature, high‐pressure conditions. We conducted uniaxial deformation experiments on porous bassanite aggregates to study the effects of applied axial load σa on deformation during the formation of gypsum. While hydration of bassanite involves a solid volume increase, gypsum exhibits significant creep compaction when in contact with water. These two processes occur simultaneously. Samples exhibited an initial phase of deformation followed by a slower secondary phase. A particular value of σa separates expansion from compaction during each of the deformation phases. At σa≤150 kPa, samples expanded initially; for σa≥230 kPa, samples compacted initially. Up to σa≈3.2 MPa, samples expanded after compacting initially, while for σa≥3.6 MPa, no further deformation or continued compaction occurred. This behavior implies that crystallization‐induced stresses depend on porosity and reaction extent such that larger stresses cannot be generated by the reaction. We explain aspects of the observed behavior with a model that predicts strain evolution using kinetic relationships for the reaction and creep rates and consider the implications of our results for reaction‐induced fracturing during serpentinization.

Analysis of Electrochemomechanical Coupling in Non-Stoichiometric Oxide Thin Films

Non-stoichiometric oxides are used in a wide variety of applications including solid oxide fuel cells (SOFCs), lithium ion batteries (LIBs), gas sensors, and catalysis. Through the capacity of such materials to support large point defect concentrations, these functional oxides can readily store, transport, and exchange ions. An important consequence of this non-stoichiometry is a tendency toward chemomechanical coupling, particularly in the form of chemical expansion, or the coupling between material volume and defect concentration. Thin films of non-stoichiometric oxides are of particular interest in such device designs, given the potential for strain engineering. For example, it has been shown for several materials that tensile strain can increase the ionic conductivity or gas exchange reactivity for oxygen by up to an order of magnitude, potentially enabling enhanced device efficiency or decreased operating temperatures1. In electrochemical devices, chemical expansion can generate stress or strain that can lead to mechanical failure, and/or changes in mechanical properties including elastic moduli. Given the extreme environments and range of non-stoichiometric oxides in which chemical expansion can be expected, robust device design requires accurate, flexible, and rapid characterization of environmental conditions and materials that maximize (or minimize) chemical expansion in situ. However, methods used at present for characterizing chemomechanical expansion, such as dilatometry, synchrotron techniques, reflectometry, and others, are not amenable to thin films or are difficult to implement in standard laboratory settings. Recently, Swallow et al. described an approach for characterizing thin film non-stoichiometric oxide chemical expansion at high temperatures by way of electrochemically induced actuation that addresses the above needs2. That work characterized volume change within a fluorite film of PrxCe1-xO2-δ (PCO) and structural deflection of the PCO/YSZ (yttria-stablized zirconia) bilayer during electrochemical pumping of oxygen ions into the PCO film. It also demonstrated a positive attribute of such chemical expansion in the form of high temperature oxide actuators, which harness electrochemically generated chemical strain to produce measurable, nanoscale device deflections. The actuation produced ranged between 5-15 nm of displacement amplitude depending on the experimental conditions2. Here, we provide an extended and graphically rich analysis of electrical and mechanical response data from such experiments. We model the current and mechanical response of PCO to an electrochemical driving force using previously established defect equilibria and kinetic relationships for that oxide, demonstrating the contributions that material properties and sample geometries make to device deflection and electrochemical pumping. We also extend the measurement approach to an additional material system, the perovskite-structured oxide SrTi0.65Fe0,35O3-δ (STF) used as part of magnetic memory devices, gas transport membranes, and fuel cells. This case study demonstrates the broad applicability of this measurement method, as well as means to leverage chemical expansion effects at elevated temperatures for diverse actuating and functional devices. Yildiz, B. ‘Stretching’ the energy landscape of oxides—Effects on electrocatalysis and diffusion. MRS Bull. 39, 147–156 (2014).Swallow, J. G. et al. Dynamic chemical expansion of thin-film non-stoichiometric oxides at extreme temperatures. Nat Mater (2017). doi:10.1038/nmat4898

Introduction of Intrinsic Kinetics of Protein-Ligand Interactions and Their Implications for Drug Design.

Structure-kinetic relationship analyses and identification of dominating interactions for optimization of lead compounds should ideally be based on intrinsic rate constants instead of the more easily accessible observed kinetic constants, which also account for binding-linked reactions. The intrinsic rate constants for sulfonamide inhibitors and pharmacologically relevant isoforms of carbonic anhydrase were determined by a novel surface plasmon resonance (SPR) biosensor-based approach, using chemodynamic analysis of binding-linked pH-dependent effects. The observed association rates ( kaobs) were pH-dependent and correlated with the fraction of deprotonated inhibitor and protonated zinc-bound water molecule. The intrinsic association rate constants ( kaintr) were pH independent and higher than kaobs. By contrast, the observed and intrinsic dissociation rate constants were identical and pH-independent, demonstrating that the observed association and dissociation mechanisms are inherently different. A model accounting for the differences between intrinsic and observed rate constants was developed, useful also for other interactions with binding-linked protonation reactions.

Direct Observation of Oligomerization by Single Molecule Fluorescence Reveals a Multistep Aggregation Mechanism for the Yeast Prion Protein Ure2.

The self-assembly of polypeptides into amyloid structures is associated with a range of increasingly prevalent neurodegenerative diseases as well as with a select set of functional processes in biology. The phenomenon of self-assembly results in species with dramatically different sizes, from small oligomers to large fibrils; however, the kinetic relationship between these species is challenging to characterize. In the case of prion aggregates, these structures can self-replicate and act as infectious agents. Here we use single molecule spectroscopy to obtain quantitative information on the oligomer populations formed during aggregation of the yeast prion protein Ure2. Global analysis of the aggregation kinetics reveals the molecular mechanism underlying oligomer formation and depletion. Quantitative characterization indicates that the majority of Ure2 oligomers are relatively short-lived, and their rate of dissociation is much higher than their rate of conversion into growing fibrils. We identify an initial metastable oligomer, which can subsequently convert into a structurally distinct oligomer, which in turn converts into growing fibrils. We also show that fragmentation is responsible for the autocatalytic self-replication of Ure2 fibrils, but that preformed fibrils do not promote oligomer formation, indicating that secondary nucleation of the type observed for peptides and proteins associated with neurodegenerative disease does not occur at a significant rate for Ure2. These results establish a framework for elucidating the temporal and causal relationship between oligomers and larger fibrillar species in amyloid forming systems, and provide insights into why functional amyloid systems are not toxic to their host organisms.

Characterizing rainfall erosivity by kinetic power - Median volume diameter relationship

Kinetic power, i.e. kinetic energy per unit time and area, is the variable widely used to represent the rainfall erosivity which affects soil loss and sediment yield. This paper shows the results of an experimental investigation using the raindrop size distributions (DSDs) measured by an optical disdrometer installed at the Department of Agricultural, Food and Forestry Sciences of University of Palermo in Italy (June 2006–March 2014) and at the El Teularet experimental station in Spain (July 2015–May 2016). At first an analysis of the DSDs aggregated into intensity classes is carried out, then the measured kinetic power values are determined. The aggregated DSDs allowed to establish that the median volume diameter of the distribution is affected by raindrops characterized by the greatest values of the diameters that composes precipitation. The measured kinetic power values allowed to verify the reliability of kinetic power-rainfall intensity relationships proposed by Wischmeier and Smith and Kinnell. Finally, using all the available measurements of kinetic power, rainfall intensity and median volume diameter obtained in different climatic contexts and by different measurement techniques, this paper demonstrates that the ratio between kinetic power and rainfall intensity depends strictly only on median volume diameter of the distribution according to a single site-independent relationship. Therefore the estimate of the kinetic energy per unit volume of rainfall does not require the knowledge of the whole drop size distribution. The reliability of a theoretical relationship relating the kinetic power per unit volume of rainfall to median volume diameter is also positively verified using all available measurements.

A graphene oxide nanosensor enables the co-delivery of aptamer and peptide probes for fluorescence imaging of a cascade reaction in apoptotic signaling.

Cytochrome c (Cyt c) and caspase-3 are the key mediators in apoptotic signaling. As is known to all, the release of Cyt c from mitochondria is a vital caspase activation pathway and defines the point of no-return in cell apoptosis. However, it has not been reported that any fluorescence imaging tools could allow simultaneous visualization of Cyt c translocation and caspase-3 activation in apoptotic cells. Here, we develop a sensitive nanosensor that holds the capability of imaging of the released Cyt c from the mitochondria and a caspase-3 activation cascade reaction in apoptotic signaling. The nanosensor is constructed by the assembly of a fluorophore (Cy5)-tagged DNA aptamer on graphene nanosheets that have been covalently immobilized with a FAM-labeled peptide. After a spatially selective delivery into the cytoplasm, the Cy5-tagged DNA aptamer assembled on the nanosensor can bind with Cyt c released from the mitochondria to the cytoplasm and dissociate from graphene, triggering a red fluorescence signal. In addition, the caspase-3 activated by the Cyt c released to the cytoplasm can cleave the FAM-labeled peptide and result in a green fluorescence output. The nanosensor exhibits rapid response, high sensitivity and selectivity for in vitro assays, and high contrast imaging of Cyt c and caspase-3 in living cells. It also provides the method for the study of the kinetic relationship between the Cyt c translocation and caspase-3 activation through simultaneous imaging of Cyt c and caspase-3. The developed nanosensor described here will be an efficient and potential platform for apoptosis research.