Kinetics Of Formation Research Articles

Tailoring the microstructure by prior treatment to achieve 37.6 GPa·% PSE in a room-temperature quenched and partitioned steel

In this work, different initial microstructures, including deformed cold-rolled structure, quenched martensite, granular bainite, and lathy bainite, were intentionally designed through cold rolling and prior treatment. Meanwhile, a novel room-temperature quenching and partitioning (RT-Q&P) process was proposed to further enhance strength-ductility combination of Cu-Ni bearing Q&P. The present study aims to investigate the influences of initial microstructures on the formation kinetics of austenite, the mechanical stability of RA, microstructure evolution, and mechanical performance in Q&P steel treated by RT-Q&P process. Compared to sample without prior treatment, samples with prior treatment showed a larger austenization degree due to more nucleation sites on martensite/bainite matrix. DICTRA simulation indicates the lathy bainite matrix with low C and low Mn is more conducive to the refinement of parent austenite, thus leading to fine and dispersive TM/A. During tensile deformation, the fine and dispersive lath-structures can effectively alleviate strain localization on the interfaces which resulted from the deformability difference between the soft and hard phases, thereby delaying crack initiation and propagation. After RT-Q&P treatment, the outstanding mechanical properties with UTS of 1152 MPa, TEL of 32.6 %, YS of 754 MPa, and PSE of 37.6 GPa·% was achieved in sample with lathy bainite matrix, far exceeding the properties of traditional Q&P steels, which was mainly attributed to higher work-hardening ability of fine and dispersive structure and sustained TRIP effect of RA.

Investigation of kinetics of passive layer formation on various microstructures in thermo-mechanically treated steel in simulated concrete pore solution

Carbon steel bars are critical in steel-reinforced concrete structures, and their corrosion can lead to significant deterioration. This research explored the passive layer formation on different carbon steel microstructures using a high throughput approach. Thermomechanically treated steel bars with three distinct microstructures, i.e., martensite in the outer layer, bainite in the middle, and pearlite in the center, were vertically cut and immersed in the simulated concrete pore solution. Scanning electrochemical microscopy was employed to study the formation of the passive layer, the kinetics of the passivation, and the effective rate constant of the species inside the solution on each microstructure. Results showed that the formation of the passive layer is a time-dependent process, and passivation was influenced by the local microstructure. Martensite demonstrated superior passivation behavior compared to pearlite and bainite.

Size-Dependent Nascent Sea Spray Aerosol Bounce Fractions and Estimated Viscosity: The Role of Divalent Cation Enrichment, Surface Tension, and the Kelvin Effect.

Viscosity, or the "thickness," of aerosols plays a key role in atmospheric processes like ice formation, water absorption, and heterogeneous kinetics. However, the viscosity of sea spray aerosols (SSA) has not been widely studied. This research explored the relationship between particle size and viscosity of authentic SSA particles through particle bounce, atomic force microscopy analysis, and predictive viscosity modeling from molecular composition. The study found that 40 nm SSA particles had estimated viscosities around 104 Pa·s and bounce fractions three times higher than 100 and 200 nm particles with less than 102 Pa·s at a relative humidity (RH) of 60%. Additional studies revealed the Kelvin effect and particle density, influenced by particle size, have a greater impact on size-dependent bounce fractions than changes in RH across impactor stages. While changes in the level of surfactants can impact particle bounce, the increased viscosity in smaller SSA is attributed to the formation of gel-like phase states caused by cation-organic cross-links between divalent calcium ions and organic anions enriched in the smaller particles. This work shows the smallest gel-like SSA particles observed in the field are highly viscous, which has implications for cloud formation, secondary aerosol growth, and pollutant transport in coastal environments.

In situ visualization of endothelial cell-derived extracellular vesicle formation in steady state and malignant conditions.

Endothelial cells are integral components of all vasculature within complex organisms. As they line the blood vessel wall, endothelial cells are constantly exposed to a variety of molecular factors and shear force that can induce cellular damage and stress. However, how endothelial cells are removed or eliminate unwanted cellular contents, remains unclear. The generation of large extracellular vesicles (EVs) has emerged as a key mechanism for the removal of cellular waste from cells that are dying or stressed. Here, we used intravital microscopy of the bone marrow to directly measure the kinetics of EV formation from endothelial cells in vivo under homoeostatic and malignant conditions. These large EVs are mitochondria-rich, expose the 'eat me' signal phosphatidylserine, and can interact with immune cell populations as a potential clearance mechanism. Elevated levels of circulating EVs correlates with degradation ofthe bone marrow vasculature caused by acute myeloid leukaemia. Together, our study provides in vivo spatio-temporal characterization of EV formation in the murine vasculature and suggests that circulating, large endothelial cell-derived EVs can provide a snapshot of vascular damage at distal sites.

Tuning the geometry of porous alumina layers via anodization in mixtures of different acids

AbstractPorous anodic aluminum oxide (AAO) layers have been obtained by two-step anodization of high-purity Al in two types of acid mixtures, i.e., in H2C2O4–H3PO4 and, for the first time, in H2SO4–H3PO4 systems. The kinetics of oxide formation was examined by monitoring the current vs. time curves while the morphology of the resulting layers was carefully verified by scanning electron microscopy (SEM). A special emphasis was put on establishing correlations between electrolyte composition, the kinetics and effectiveness of oxide growth, and the morphological features of AAO layers (pore and cell diameter, porosity), as well as pore arrangement. It was confirmed that the addition of H3PO4 to both H2C2O4 and H2SO4 electrolytes results in a significant decrease in oxide growth rate, and worsening of pore arrangement, while the values of pore diameter and interpore distance are much less affected. Moreover, the presence of a small amount of phosphoric acid in the reaction mixture allowed for a noticeable increase in pore ordering if anodization was carried out beyond the self-ordering regime, or performing controlled anodization even at voltages at which the burning phenomenon is typically observed. It is strongly believed that manipulating the electrolyte composition by adding another acid may provide another degree of freedom to control the morphology of the resulting nanostructured alumina layers.

Kinetics of pyrocarbon formation on the surface of carbon fiber filament

A kinetic model of the formation of a pyrocarbon layer on the surface of filaments of carbonized PAN fiber is proposed. The resulting kinetic model is confirmed by experimental data. Models for the formation of a pyrocarbon layer and an increasing of thickness of a pyrocarbon layer on a bundle of carbon fiber filaments after a long cycle of CVD are predicted.

Shish-kebab formation in the micro-injection molding of polyethylene: In-situ synchrotron small angle X-ray scattering study

The structural formation and evolution in high density polyethylene (HDPE) during the micro-injection molding process were investigated as a function of the mold temperature and injection speed utilizing an in situ synchrotron small angle X-ray scattering (SAXS) technique in conjunction with a portable micro-injection molding setup. It was found that shish-kebab structures were formed in all cases. The beginning of occurrence of shish is not much affected by the mold temperature, but the onset of the formation of kebab crystals is strongly dependent on the mold temperature. This mold temperature dependence of the kinetics of shish-kebab formation is attributed to the interplay between the crystallization rate in the outer layer and the formation rate of the shish-like structure, which was further evidenced by the multilayered structure of molded samples via ex situ microfocus scanning SAXS and wide angle X-ray diffraction (WAXD) measurements. On the other hand, the injection speed affects the long period of oriented lamellae and the dimension of the shish-like structure only slightly but influences the kinetics of structural formation evidently. The larger the injection speed, the earlier occurrence of oriented lamellae and shish formation is observed.

Evaluating the influence of the initial high molecular weight level on monoclonal antibody particle formation kinetics using a short-term chemical stress study

Protein formulations may form proteinaceous particles that vary in size from nanometers to millimeters. Monitoring the kinetics of protein particle formation, e.g., through accelerated degradation studies, is an attempt to understand and assess the rate and progression of particle populations. Little is known about whether the initial level of high molecular weight (HMW) species, or initial HMW level (IHL), of a protein solution influences the propagation of protein particle formation, and thus affects the storage stability of proteins.In this study, we have established a method to generate protein solutions of different IHLs by thermal stress. We have evaluated a 16-week thermal stability study at 40 °C of two monoclonal antibodies (mAb-A and mAb-B) at different IHLs using size exclusion chromatography (SEC) and sub-visible particle analysis. We have performed an isothermal stress study with guanidinium hydrochloride (GuaHCl) at room temperature for 300-min to evaluate the formation of HMWs analysed by SEC. The application of the Finke-Watzky (F-W) two-step nucleation model allowed us to mathematically describe the kinetics of HMW formation and to extract kinetic parameters of this process.For mAb-A, the IHLs had a marginal influence on the loss of monomer rate; instead, mAb-A exhibited fragmentation at 40 °C, which was independent of the IHL. Nevertheless, above a threshold of ≥ 7 % IHL, existing trimers/tetramers undergo conversion into higher-order oligomers at 40 °C, which is not observed at lower IHLs. In contrast, mAb-B exhibited an increased HMW formation rate above a threshold of ≥ 4 % IHL, which was reflected in the monomer decay rates at 40 °C and the F-W kinetic parameters of the chemical stress study.This case study shows that the initial level of HMWs exerts a differential influence on the progression of HMW formation. In one instance, there is a discernible acceleration in the formation of HMWs with rising IHLs. Conversely, in another example, the IHL exerts only a slight influence on HMW formation. Moreover, the results of our short-term chemical stress study are in accordance with those of a classical storage stability study conducted at 40 °C, which evaluated different IHLs. The analysis of HMW formation kinetics will enhance our understanding of the protein particle formation process and facilitate the formulation development of biotherapeutics.

Advances in Liquid-Phase Synthesis: Monitoring of Kinetics for Platinum Nanoparticles Formation, and Pt/C Electrocatalysts with Monodispersive Nanoparticles for Oxygen Reduction

The growing demand for hydrogen–air fuel cells with a proton-exchange membrane has increased interest in the development of scalable technologies for the synthesis of Pt/C catalysts that will allow us to fine-tune the microstructure of such materials. We have developed a new in situ technique for controlling the kinetics of the transformation of a platinum precursor into its nanoparticles and deposited Pt/C catalysts, which might be applicable during the liquid-phase synthesis in concentrated solutions and carbon suspensions. The technique is based on the analysis of changes in the redox potential and the reaction medium coloring during the synthesis. The application of the developed technique under conditions of scaled production has made it possible to obtain Pt/C catalysts with 20% and 40% platinum loading, containing ultra-small metal nanoparticles with a narrow size distribution. The electrochemically active surface area of platinum and the mass activity of synthesized catalysts in the oxygen electroreduction reaction have proved to be significantly higher than those of commonly used commercial analogs. At the same time, despite the small size of nanoparticles, the catalysts’ degradation rate turned out to be the same as that of commercial analogs.

Electrokinetics of Nitrite to Ammonia Conversion in the Neutral Medium Over A Platinum Surface.

Polycrystalline Pt electrode was employed to selectively convert nitrite ions ( ) into useful nitrogenous compound through electrochemical reduction reaction in neutral medium. According to adsorptive stripping analysis, the reduction process produced nitric oxide (NO) on the surface of Pt electrode. The spectroscopic test and gas chromatographic studies discovered the presence of ammonia (NH3) in the electrolyzed solution, suggesting the transformation of adsorbed NO into NH3 during the reverse scan. Scan rate dependent investigation was performed to elucidate kinetic information relating to this reaction on Pt surface. From Ep vs scan rate (υ) and jp vs υ (logarithmic plot), it was found that the conversion of ion into NO is an irreversible reaction which relies on the diffusion of ions to electrode surface. The Tafel analysis unveiled that the first electron transfer sets the overall reaction rate, having formal reduction potential, E0'=-0.46 V and standard heterogeneous rate constant, k0= cm s-1. Reductive transfer coefficient (α) is another kinetics parameter, which was found to be approximate 0.77 from the difference between Ep and Ep/2 of the voltammograms obtained over scan rate range 0.005 V s-1 to 0.250 V s-1, indicating a stepwise process. According to temperature-dependent voltammograms, the nitrite reduction reaction on Pt had a calculated activation energy of about 19.8 kJ mol-1 and a pre-exponential factor of about 8.39×103 mA cm-2.

Decomposition and Growth Pathways for Ammonium Nitrate Clusters and Nanoparticles.

Understanding the formation and decomposition mechanisms of aerosolized ammonium nitrate species will lead to improvements in modeling the thermodynamics and kinetics of aerosol haze formation. Studying the sputtered mass spectra of cation and anion ammonium nitrate clusters can provide insights as to which growth and evaporation pathways are favored in the earliest stages of nucleation and thereby guide the development and use of accurate models for intermolecular forces for these systems. Simulated annealing Monte Carlo optimization followed by density functional theory optimizations can be used reliably to predict minimum-energy structures and interaction energies for the cation and anion clusters observed in mass spectra as well as for neutral nanoparticles. A combination of translational and rotational mag-walking and sawtooth simulated annealing methods was used to find optimum structures of the various heterogeneous clusters identifiable in the mass spectra. Following these optimizations with ωB97X-D3 density functional theory calculations made it possible to rationalize the pattern of peaks in the mass spectra through computation of the binding energies of clusters involved in various growth and dissociation pathways. Testing these calculations against CCSD(T) and MP2 predictions of the structures and binding energies for small clusters demonstrates the accuracy of the chosen model chemistry. For the first time, the peaks corresponding with all detectable species in both the positive and negative ion mass spectra of ammonium nitrate are identified with their corresponding structures. Thermodynamic control of particle growth and decomposition of ions due to loss of ammonia or nitric acid molecules is indicated. Structures and interaction energies for larger (NH4NO3)n nanoparticles are also presented, including the prediction of new particle morphologies with trigonal pyramidal character.

Modulating Aggregation Behavior by Ternary Strategies for Efficient and Stable Thick-Film Organic Solar Cells.

Functional third components targeted to improve a specific property of organic solar cells is an effective strategy. However, introducing a third component to simultaneously improve efficiency and stability and achieve good performance in thick-film devices has rarely been reported. Herein, low diffusion third components IDCN and ID2CN are reported to achieve a power conversion efficiency (PCE)of 18.08% and a high short-circuit current (J SC)of 27.82mAcm-2, one of the highest values based on PM6:Y6. They increase light harvesting in the range of 400-500nm while enhancing energy transfer via Förster resonance energy transfer (FRET). A tightly ordered molecular arrangement is achieved by modulating the preaggregation and film formation kinetics of Y6, which enhance exciton dissociation and charge transport. Moreover, the low-diffusion third component can effectively restrict the diffusion of Y6 to improve the morphology stability, and the T90 lifetime is increased from 689 to 1545h. In 300nm thick-film devices, PM6:ID2CN:Y6 achieves a PCE of 15.01%, much higher than PM6:Y6's 12.83%, demonstrating the great potential of ID2CN in thick-film devices.

Water-in-oil emulsions as micro-reactors for achieving extremely rapid and high hydrogen uptakes into clathrate hydrates

As humanity transitions to a low-carbon future, hydrogen, with its high energy density and zero carbon emissions, is gaining prominence, and efficient hydrogen storage is thus a critical area of research. Storing hydrogen in a solid form by forming hydrates, ensuring straightforward formation and dissociation, environmental friendliness, and stability, is emerging as a new technology. In particular, the use of thermodynamic promoters such as tetrahydrofuran (THF) to form binary hydrogen hydrates enables hydrogen storage under much milder conditions compared to traditional compression and liquefaction processes. However, slow hydrate formation kinetics currently hinder commercialization, necessitating breakthroughs in this area. This study reports extremely rapid and high hydrogen uptake in binary hydrogen + THF hydrates by utilizing a water-in-oil emulsion. A hydrogen storage capacity of approximately 51.23 mmol H2/mol H2O and the hydrogen uptake rate of 91.71 mol min−1 m−3 water were achieved, significantly outperforming existing studies conducted at pressures below 15 MPa. This remarkable kinetics was achieved by controlling the distribution of THF within a ternary emulsion system composed of water, isooctane, and THF. Phase equilibrium measurements and a series of kinetic tests validated that using an excess of THF over stoichiometric amounts can lead to such high and rapid hydrogen uptake. Consequently, a hydrate formation mechanism in the emulsified system was suggested based on the results of a Raman analysis, water droplet size measurements, and 1H NMR analysis. These results will pave the way for further advances in practical hydrate-based hydrogen storage technology.

Ru Nanoparticles Encapsulated by Defective TiO2 Boost the Hydrogen Oxidation/ Evolution Reaction.

The development of efficient and durable electrocatalysts for the alkaline hydrogen oxidation/evolution reaction is crucial for anion exchange membrane fuel cells/water electrolyzers. However, designing such electrocatalysts poses a challenge due to the need for optimizing various adsorbates. Herein, highly dispersed Ru nanoparticles catalysts is reported encapsulated and supported by defective anatase phase of titanium dioxide (named as Ru NPs/def-TiO2(A)) for boosting hydrogen-cycle electrocatalysis with robust anti-CO-poisoning in alkaline conditions. The Ru NPs/def-TiO2(A) achieves a high-quality activity of 7.65 A mgRu -1, which is 23.2 and 9.5-fold higher than commercial Ru/C and Pt/C in alkaline HOR. Moreover, this catalyst exhibits an outstanding overpotential of 21mV at 10mAcm-2 in alkaline HER. Hydrogen underpotential deposition (Hupd) and CO stripping experiments demonstrate that Ru NPs/def-TiO2(A) has the optimized H*, OH*, and CO* adsorption strength, enabling the Ru NPs/def-TiO2(A) catalyst to display excellent and robust HOR/HER performance under alkaline conditions. Using density functional theory calculations, the enhanced HOR performance mechanism for the Ru NPs/def-TiO2(A) catalyst originates from the TiO2 step face in contact with the Ru nanoparticles, indicating that the kinetics of water formation are considerably more favorable at the Ru NPs/def-TiO2(A) interface.

An Overview of Microorganisms Immobilized in a Gel Structure for the Production of Precursors, Antibiotics, and Valuable Products.

Using free microorganisms for industrial processes has some limitations, such as the extensive consumption of substrates for growth, significant sensitivity to the microenvironment, and the necessity of separation from the product and, therefore, the cyclic process. It is widely acknowledged that confining or immobilizing cells in a matrix or support structure enhances enzyme stability, facilitates recycling, enhances rheological resilience, lowers bioprocess costs, and serves as a fundamental prerequisite for large-scale applications. This report summarizes the various cell immobilization methods, including several synthetic (polyvinylalcohol, polyethylenimine, polyacrylates, and Eudragit) and natural (gelatin, chitosan, alginate, cellulose, agar-agar, carboxymethylcellulose, and other polysaccharides) polymeric materials in the form of thin films, hydrogels, and cryogels. Advancements in the production of well-known antibiotics like penicillin and cephalosporin by various strains were discussed. Additionally, we highlighted cutting-edge research related to strain producers of peptide-based antibiotics (polymyxin B, Subtilin, Tyrothricin, varigomycin, gramicidin S, friulimicin, and bacteriocin), glusoseamines, and polyene derivatives. Crosslinking agents, especially covalent linkers, significantly affect the activity and stability of biocatalysts (penicillin G acylase, penicillinase, deacetoxycephalosporinase, L-asparaginase, β-glucosidase, Xylanase, and urease). The molecular weight of polymers is an important parameter influencing oxygen and nutrient diffusion, the kinetics of hydrogel formation, rigidity, rheology, elastic moduli, and other mechanical properties crucial for long-term utilization. A comparison of stability and enzymatic activity between immobilized enzymes and their free native counterparts was explored. The discussion was not limited to recent advancements in the biopharmaceutical field, such as microorganism or enzyme immobilization, but also extended to methods used in sensor and biosensor applications. In this study, we present data on the advantages of cell and enzyme immobilization over microorganism (bacteria and fungi) suspension states to produce various bioproducts and metabolites-such as antibiotics, enzymes, and precursors-and determine the efficiency of immobilization processes and the optimal conditions and process parameters to maximize the yield of the target products.

High Efficiency Alkaline Iodine Batteries with Multi-Electron Transfer Enabled by Bi/Bi2O3 Redox Mediator.

The multi-electron transfer I-/IO3- redox couple is attractive for high energy aqueous batteries. Shifting from an acidic to an alkaline electrolyte significantly enhances the IO3- formation kinetics due to the spontaneous disproportionation reaction, while the alkaline environment also offers more favorable Zn anode compatibility. However, sluggish kinetics during the reduction of IO3- persists in both acidic and alkaline electrolytes, compromising the energy efficiency of this glorious redox couple. Here, we establish the fundamental redox mechanism of the I-/IO3- couple in alkaline electrolytes for the first time and propose that Bi/Bi2O3 acts as a redox mediator (RM) to "catalyze" the reduction of IO3-. This mediation significantly reduces the voltage gap between charge/discharge from 1.6 V to 1 V with improved conversion efficiency and rate capability. By pairing the Zn anode and the Bi/Bi2O3 RM cathode, the full battery with I-/IO3- redox mechanism achieves high areal capacity of 12 mAh cm-2 and stable operation at 5 mAh cm-2 for over 400 cycles.

Simultaneous influences of hematocrit in the erythrocyte medium on erythrocyte aggregation and sedimentation: a kinetic study by a laser scattering technique

The erythrocyte aggregation is an important physiological phenomenon in the circulation of blood. It is a basic characteristic of normal blood that plays a major role in the cardiovascular system, especially in the microcirculation. This study explained the kinetics of single cells rouleaux formation one- dimensional aggregate and three- dimensional aggregate, during simultaneous, and the effect of hematocrit on the process of aggregation and sedimentation. The present study was done on forty one healthy subjects. Laser light is passed through a well mixed sample of blood and the forward scattered light intensities recorded continuously. The samples were prepared with different hematocrit, (10%, 15%, 20%, and 25%). Increasing the hematocrit, (10%, 15%, 20%, and 25%) had significantly decreased the rate of rouleaux formation (P< 0.005) but increase in the rate of one and three dimensional aggregate formation. On the other hand the sedimentation rate is decreased significantly (P

6656 Frequently sampled HbA1c Shows Low-Sodium, High-Carbohydrate Rice Diet To Be Effective in Type 2 Diabetes

Abstract Disclosure: F.A. Neelon: None. S. Sanoff: None. P. Lin: None. Hemoglobin and glucose react to form HbA1c, which persists until red blood cells (RBCs) are removed from circulation. Since RBCs survive approximately 122 days, HbA1c is usually measured at intervals of months to years, but more frequent measurement can illuminate changes in blood glucose (BG). We used Beach’s equation for the kinetics of HbA1c formation, to construct graphical depictions of how HbA1c should decline over the 122 days after a drop from constantly high to constantly normal BG levels. As part of routine patient care (not an experimental protocol), we measured HbA1c at 2-4-week intervals in a convenience sample of 10 patients (one of whom was evaluated on 2 occasions) with Type 2 diabetes, obesity, and elevated HbA1c who attended the now defunct Rice Diet Program (RDP) in Durham, NC. All were fed 3 meals/day, comprising 800-1000 kcal of rice, fruits, grains, and vegetables (70-90% carbohydrates) and 300 mg of sodium. Two patients were initially taking insulin; 1, glipizide; and 1, sitagliptin, exenatide, metformin; all hypoglycemic agents were eventually discontinued, and none added. Mean initial HbA1c of 9.7% (range, 8.3-11.7) fell to a mean of 6.2% (range 5.3-8.4) after a mean of 82 days (range, 41-139). Variability in final HbA1c values reflects, at least in part, variable duration of voluntary residence at the RDP. In 9 patients, HbA1c declined in close accordance with the course predicted for complete normalization of blood glucose from the very start of the diet; in 1 patient, HbA1c declined slowly for 25 days, after which the rate increased to near that for complete normalization of BG. Plots of Hb1c values extrapolate back through the point of origin, implying normalization of BG occurs within days of starting the RDP, and is maintained thereafter. Data from frequent measurement of HbA1c show: 1) Normalization of BG occurs almost immediately upon dietary restriction, implying that hyperglycemia in Type 2 diabetes is driven by daily calorie excess, not by accumulated calorie excess (ie, obesity). 2) Contrary to some misperceptions, a high-carbohydrate, sodium- and calorie-restricted diet is not deleterious to ― and may actually benefit ― glucose control in Type 2 diabetes. Presentation: 6/3/2024

Effect of Sodium Chloride on the Kinetics of Methane Hydrate Formation in Bulk Soy Lecithin Solutions

Effect of Sodium Chloride on the Kinetics of Methane Hydrate Formation in Bulk Soy Lecithin Solutions

Influence of Surfactants on Kinetics of Hydrate Formation in Powder Hydrogel Systems

Influence of Surfactants on Kinetics of Hydrate Formation in Powder Hydrogel Systems