Slow Step Research Articles

Innovative methodology for green synthesis of iridium nanoparticles of rod shapes by reduction of iridium (IV) using sustainable pectin with formation of keto-pectin derivatives

A prospective novel technique has been developed for green synthesis of iridium nanoparticles of rod shapes for the first time with simultaneous formation of keto-derivative oxidation product with a yield of 98.3 %. This takes place by reduction of hexacholoroiridate (IV) by using sustainable pectin as a powerful reducing agent biomacromolecule in acidic media. The formation of nanoparticles (IrNPS) was identified by Fourier transform infrared (FTIR), Transmission electron microscope (TEM), X-ray diffraction (XRD), and Scanning electron microscope (SEM) investigations. The TEM morphology showed that the iridium nanoparticles were of crystalline rod shapes on contrary to the spherical shapes reported on all synthesized IrNPS earlier. The rates of nanoparticles growth were followed kinetically using a conventional spectrophotometer. The kinetic measurements revealed a unity order reaction in [IrCl6]2− as oxidant and fractional first-order in [PEC] as a reducing agent, respectively. A decrease in the reaction rates was noticed with increasing the acid concentration. Kinetic evidence reveals the creation of intermediate complex as transient species prior to the slow step. Such complex formation may be facilitated by the participation of one chloride ligand from [IrCl6]2− oxidant forming a bridge between the oxidant and reductant in such formed intermediate complex. Plausible reaction mechanisms for electron transfer pathway routes consistent with the kinetics observations were discussed.

Kinetics Study of Hydrogen Combustion over Pt/Alumina Catalyst

Combustion of hydrogen releases energy but in many applications, catalytic combustion of hydrogen may prove advantageous over direct combustion. The main advantage of catalytic combustion of hydrogen is that heat can be obtained at lower temperatures as well. The activity of catalyst for combustion of lean mixtures (< 2%) of hydrogen was studied in the present work and the kinetics of catalytic combustion of hydrogen has been established. The combustion of hydrogen on alumina supported platinum catalyst starts at above 323 K. Two reaction models have been investigated for possible mechanism of the reaction. The kinetics follows Hougan-Watson model where both hydrogen and oxygen adsorb on same site; hydrogen undergoes dissociative chemisorption and surface reaction being the slowest step. However, a simplified power law type rate equation was also established which adequately fits the experimental data for temperature between 373 and 673 K.

Occupational Fall Risk Assessment Tool for older workers.

No easy-to-use fall risk assessment tools have been devised to assess occupational fall risk in older workers. To develop an Occupational Fall Risk Assessment Tool (OFRAT) and report its predictive validity and reliability in older workers. The baseline fall risk assessment was completed by 1113 participants aged ≥60 years who worked ≥4 days/month in Saitama, Japan. Participants were followed up for falls during occupational activities for 1 year, and 30 participants were assessed twice for test-retest reliability. The following assessment measures were summed to form the OFRAT risk score: older age, male sex, history of falls, physical work participation, diabetes, use of medications increasing fall risk, reduced vision, poor hearing, executive dysfunction and slow stepping. The scores were then classified into four grades (0-2 points: very low, 3 points: low, 4 points: moderate and ≥5 points: high). During follow-up, 112 participants fell 214 times during work. The negative binomial regression model showed that participants with higher grades had a higher incidence rate ratio [95% confidence interval] for falls than those with very low grades (low: 1.64 [1.08-2.47], moderate: 4.23 [2.82-6.34] and high: 6.12 [3.83-9.76]). The intraclass correlation coefficient for risk score was 0.86 [0.72-0.93], and the weighted kappa coefficient for grade assessment was 0.74 [0.52-0.95]. The OFRAT is a valid and reliable tool for estimating the occupational fall risk in older workers. It may assist occupational physicians implement strategies to prevent falls in this group.

Heterogeneous cobalt-catalyzed degradation of azo compounds using alcohols as the stoichiometric hydrogen source

Degradation of azo compounds is challenging but exciting to explore from both environmental and fundamental science aspects. Instead of using high H2-pressure, heterogeneous cobalt catalyzed efficient tandem transformation of azo compounds to the corresponding imines using stochiometric amount of alcohol is reported. Several cobalt-based heterogeneous catalysts were synthesized by varying the cobalt-ligand ratio, where the catalyst with cobalt:phenanthroline=1:6 was found to be the most active. Utilizing this protocol, selective degradation of a library of azo compounds was effectively carried out using various alcohols.The recyclability test revealed the catalyst could be recycled up to 6th times. In addition, the control experiments and the Hammett studies revealed this transformation was favorable, with the substrates having electron-donating substituents. The KIE study suggested the alcohol dehydrogenation was one of the slow steps. Moreover, the involvement of ordered transition states was demonstrated by the Eyring analysis.

Excess copper catalyzes protein disulfide bond formation in the bacterial periplasm but not in the cytoplasm.

Copper avidly binds thiols and is redox active, and it follows that one element of copper toxicity may be the generation of undesirable disulfide bonds in proteins. In the present study, copper oxidized the model thiol N-acetylcysteine in vitro. Alkaline phosphatase (AP) requires disulfide bonds for activity, and copper activated reduced AP both in vitro and when it was expressed in the periplasm of mutants lacking their native disulfide-generating system. However, AP was not activated when it was expressed in the cytoplasm of copper-overloaded cells. Similarly, this copper stress failed to activate OxyR, a transcription factor that responds to the creation of a disulfide bond. The elimination of cellular disulfide-reducing systems did not change these results. Nevertheless, in these cells, the cytoplasmic copper concentration was high enough to impair growth and completely inactivate enzymes with solvent-exposed [4Fe-4S] clusters. Experiments with N-acetylcysteine determined that the efficiency of thiol oxidation is limited by the sluggish pace at which oxygen regenerates copper(II) through oxidation of the thiyl radical-Cu(I) complex. We conclude that this slow step makes copper too inefficient a catalyst to create disulfide stress in the thiol-rich cytoplasm, but it can still impact the few thiol-containing proteins in the periplasm. It also ensures that copper accumulates intracellularly in the Cu(I) valence.

Secondary particle predictions in quasifree proton scattering reactions in the 100–250 MeV energy range

Results for observables related to the secondary particle production process in proton-nucleus spallation reactions at low beam incident energy (100--250 MeV) are shown. The energy and angular distributions of the residual nucleus are determined in the context of our multicollisional Monte Carlo intranuclear cascade model. The mechanism of proton-nucleus reactions is conventionally described as a sequence of two stages: the rapid intranuclear cascade phase and the slow particle evaporation step. In this work we focus on the rapid phase considering the nucleon effective mass as an effect of the many-body nuclear interactions and the intranuclear mean field. This procedure represents a more realistic scenario to obtain the particles' multiplicity generated in spallation reactions with light-mass target nuclei in a low-energy range. We focused our attention on target nuclei of macro elements, such as carbon, oxygen, phosphorus, sulfur, sodium, potassium, chlorine, and calcium, and trace elements such as iron, copper, zinc, bromine and selenium, which are the most frequent compounds of the organic material. The choice of these target nuclei is due to our expectancy that our results can work as a preliminary insight for further theoretical approaches, specially taking into account nuclear effects due to the interaction of the particles of the beam with the organic tissue.

Sorptive removal of phosphorus by flue gas desulfurization gypsum in batch and column systems

Phosphorus (P) over-loading is often a central topic due to its linkage to harmful algal blooms (HABs) and its importance in wastewater treatment that has fueled immediate remediation attempts to reduce P loading from point (e.g., wastewater) and nonpoint sources (e.g., fertilizers). Conventional remediation techniques (e.g., filtration) are often expensive, ineffective, and difficult to implement at large scales. The flue gas desulfurization (FGD) gypsum produced as an energy plant waste byproduct has recently been advocated as a physiochemical remediation strategy for P through sorptive removal. However, limited research is available on the practical applications of FGD gypsum for P removal from water. Herein, batch sorption experiments were performed to investigate the sorptive removal efficiency of P by FGD gypsum under environmentally relevant P concentrations (0.01–0.25 mM). In parallel, fixed-bed column experiments packed with FGD gypsum were performed using elevated P concentrations (0.1–1.0 mM) to understand the scalability of FGD gypsum for large-scale practical applications. During batch experiments, P sorption equilibrium was reached within 24 h that includes an initially fast step (via boundary layer diffusion), followed by a slow rate-determining step (via intraparticle diffusion). P sorption kinetics followed the pseudo second-order kinetics, indicating chemisorption. P sorption at equilibrium can be simulated by both the Freundlich and Langmuir sorption isotherms. The Langmuir sorption isotherm yielded a maximum sorption capacity (Qmax) of 36.1 mM kg−1. The fixed-bed column experimental results showed that sorption rate depends on the applied flow rate, irrespective of the tested P concentrations. Our findings can be extrapolated to evaluate the feasibility and scalability of FGD gypsum in removing P to counteract P runoff and mitigate HABs and P-loaded wastewater.

Effects of a key negatively charged residue mutation on the binding pathway of SH3 domain complex and ArkA peptide.

SH3 domains are common protein interaction domains found across all forms of life and serve important functions in cell signaling and cytoskeletal regulation. SH3 domains often bind to intrinsically disordered peptides (IDPs) which are peptides that lack a well-defined secondary structure. However, little is known about the binding mechanism in these complexes. Prior to this experiment, our lab has simulated the disordered ArkA peptide binding to the yeast SH3 domain AbpSH3, and it was observed that the binding proceeds through a flexible disordered encounter complex before reaching a fully bound state. While the encounter complex forms quickly, the slow step of binding is the transition from the disordered encounter ensemble to fully engaged state. We mutated glutamic acid to glutamine due to its interaction with the ArkA lysine (−3) in the bound state, a residue that is located at the center of 12-residue ArkA peptide and is required for binding. In this experiment, we used molecular dynamics simulations to simulate the binding between AbpSH3, which has a net negative charge, and ArkA, which has a net positive charge. We analyzed the effect a single residue mutation has on the transitioning of the ArkA peptide and AbpSH3 domain from the unbound stage to the disordered encounter complex and finally to the fully bound complex. We found that the mutated domain forms similar contacts with ArkA in both the encounter complex and bound state compared to the wild type, despite the disruption of the favorable interaction between glutamic acid and lysine. For future research, we will examine the effects of mutating the ArkA peptide on both the encounter complex and the fully bound state.

Making Heterometallic Metal–Metal Bonds in Keggin-Type Polyoxometalates by a Six-Electron Reduction Process

Polyoxometalates (POMs) represent a promising class of molecular electron reservoirs. However, their multielectron reduction gives rise to intricate physical-chemical phenomena that must be fully understood for their future use in energy-storage devices. Herein, we show that bulk electrolysis of the archetypal Keggin-type POM [Si(WVI2MoVIO10)(WVI3O10)3]4- in aqueous solution leads to the six-electron-reduced derivative [Si(WIV2MoIVO7(H2O)3)(WVI3O10)3]4- (notated SiW11Mo-VI') in which the mixed-metal triad acts as a storage unit for six electrons and six protons. X-ray diffraction analysis and multinuclear NMR (183W and 95Mo) studies reveal that this electron-rich species represents the first example of POMs containing heterometallic metal-metal bonds between addenda centers. This electron-rich POM can be further reduced through multielectronic events, while its full oxidation restores the structure of the oxidized parent ion. Remarkably, the formation of SiW11Mo-VI' results from a fast clustering process compared to that observed for the entirely W-based analogue, revealing that the formation of metal-metal bonds in the mixed-metal Mo/W POM is facilitated because the reaction rate is not limited by a slow disproportionation step. Last, we evaluate the supramolecular properties of SiW11Mo-VI' using a method based on the cloud-point measurement of a nonionic surfactant. This investigation demonstrates that the clustering process has dramatic consequences on the solution behavior of the POM, canceling its superchaotropic character due to a local structuring effect of the hydration shell. These fundamental results pave the way for applications using the massive electron-storage properties of mixed-metal POMs.

Faster SARS-CoV-2 sequence validation and annotation for GenBank using VADR.

In 2020 and 2021, >1.5 million SARS-CoV-2 sequences were submitted to GenBank. The initial version (v1.0) of the VADR (Viral Annotation DefineR) software package that GenBank uses to automatically validate and annotate incoming viral sequences is too slow and memory intensive to process many thousands of SARS-CoV-2 sequences in a reasonable amount of time. Additionally, long stretches of ambiguous N nucleotides, which are common in many SARS-CoV-2 sequences, prevent VADR from accurate validation and annotation. VADR has been updated to more accurately and rapidly annotate SARS-CoV-2 sequences. Stretches of consecutive Ns are now identified and temporarily replaced with expected nucleotides to facilitate processing, and the slowest steps have been overhauled using blastn and glsearch, increasing speed, reducing the memory requirement from 64Gb to 2Gb per thread, and allowing simple, coarse-grained parallelization on multiple processors per host. VADR is now nearly 1000times faster than it was in early 2020 SARS-CoV-2 sequence processing. It has been used to screen and annotate more than 1.5 million SARS-CoV-2 sequences since June 2020, and it is now efficient enough to cope with the current rate of hundreds of thousands of submitted sequences per month.

Slow O–H Dissociation in the First-Order Oxygen Evolution Reaction Kinetics on Polycrystalline γ-FeO(OH)

To unravel the reaction mechanism of the electrochemical oxygen evolution reaction (OER), analysis of the intrinsic activity parameters obtained via electrokinetic investigation remains effective. In this study, polycrystalline γ-FeO(OH), synthesized at room temperature, was used as a stable, albeit reactive, anode for OER, and electrokinetic studies were performed to unravel the oxygen evolution reaction pathway. The cell temperature, hydroxyl ion concentration, and the cation of the supporting electrolyte were varied, and the influence of external bias on the OER activity was recorded. Changes in the cell temperature from 30 to 65 °C lead to an enhanced OER activity due to small overpotential, Tafel slope, and charge-transfer resistance (Rct) values at high temperatures, which unambiguously highlights the influence of the thermodynamic barrier and electron-transfer kinetics. The calculated anodic charge-transfer coefficient (αa) and specific exchange current density (j0,s) values are 0.65 and 2.24 × 10–5 mA cm–2, respectively. The faster OER kinetics on polycrystalline γ-FeO(OH) can also be attributed to an appreciably low activation energy of 8.26 ± 2 kJ mol–1, where variation of the electrolyte concentration indicated a first-order dependence on [OH]−. Experimentally obtained intrinsic kinetic parameters such as the Tafel slope, anodic charge-transfer coefficient, exchange current density, activation energy (Ea), reaction order (m), and deuterium isotope effect implicate the dissociation of hydroxyl ions on the polycrystalline γ-FeO(OH) as the rate-determining step. The direct effect of cations such as Li+, Na+, and K+ of the electrolyte on OER highlights a weak interaction of the cations with the surface-active [FeIII-OH] species. A change in the electrode substance from three-dimensional highly conductive nickel foam (NF) to two-dimensional less conductive carbon cloth (CC) resulted in a change in the slow step, leading to the formation of a high-valency iron oxo intermediate from the iron hydroxy species.

Ruthenium(III) Catalyzed Oxidation of Hypoxanthine and Xanthine by Mn(VII) in Aqueous Brønsted Acid Solutions: A Kinetic and Mechanistic Study

Mn(VII) is broadly utilized as an oxidizing specialist, however it couldn’t oxidize hypoxanthine (HXAN) and xanthine (XAN) even in concentrated Brønsted acidic (HClO4, H2SO4) media and at raised temperatures. In any case, the responses went through flawlessly in presence of millimolar arrangements of ruthenium chloride (Ru(III) or RuCl3) in presence of fluid Brønsted acidic arrangements. Under synergist conditions, response complied with first request energy in [(Mn(VII)] and [Alkaloid] at steady causticity and temperature. Increase in [Ru(III)] dramatically sped up the reactions with a first order dependence on [catalyst] at constant acidity and temperature. The rate of oxidation was enhanced by an increase in the concentration of Brønsted acid (HClO4, H2SO4). The rate increases observed were examined using the acidity function criteria of Zucker-Hammett, Bunnett and Bunnett-Olsen. The most logical mechanism, involving the involvement of the water molecule in the slow step, has been proposed based on observed Bunnett-Olsen criteria of acidity functions (as proton transferring agent).

Palladium-catalyzed generation of CO from formic acid for alkoxycarbonylation of internal alkenes involves a PTSA-assisted NH-Pd mechanism: a DFT mechanistic study.

DFT calculations have been performed to find the mechanism of the alkyloxycarbonylation of an internal alkene with HCOOH catalyzed by a palladium complex with P,N hemilabile ligands. Four different cycles have been explored in detail, and a plausible catalytic cycle involves the decomposition of HCOOH/HCOOMe to CO, internal alkene isomerization, terminal alkene insertion, CO migratory insertion and methanolysis. It is shown that decomposition and isomerization processes involve a cooperative P,N hemilabile ligand and Pd(0) (NH-Pd) rather than the Pd(II) hydride (Pd-H) mechanism. Intriguingly, the simultaneous presence of PTSA acts as a hydrogen shuttle (H-shuttle), assisting CO generation and methanolysis. With such a mechanism, the rate-determining transition state corresponds to internal alkene isomerization, which is consistent with the experimental observation that isomerization was the slow step in this process. The back-bonding between palladium and olefin and rapid hydrogen transfer in the presence of a PTSA H-shuttle are responsible for the moderate barriers. In addition, a careful study of the solvent effect indicates that polar solvents, which are capable of hydrogen bonding, can promote the catalytic reactions. Mechanistic insights gained by this theoretical study have not only rationalized the experimental observations well but also have implications for new reaction development.

CETYL TRIMETHYL AMMONIUM BROMIDE ASSISTED OXIDATION OF HYPOXANTHINE AND XANTHINE USING Mn(VII) IN AQUEOUS BRONSTED ACID MEDIA: A KINETIC AND MECHANISTIC STUDY

Cetyl trimethyl ammonium bromide (CTAB) assisted Oxidation of hypoxanthine (HXAN), and xanthine (XAN) alkaloids by Mn(VII) occurred smoothly in presence of aqueous Bronsted acid (HClO4, H2SO4) media. The rate of oxidation of HXAN, XAN by Mn(VII) was enhanced due to an increase in [HClO4] / [H2SO4] in the presence of CTAB at a constant temperature. Reaction kinetics obeyed I-order in [Mn(VII)], [HXAN], or [XAN] at constant temperature and acid concentration in micellar (CTAB) conditions. In this present work, the acidity functions developed by Zucker-Hammett, Bunnett, and Bunnett-Olsen were used for analyzing rate enhancement, and the probable reaction mechanism that involves water moiety in the slow step has been proposed according to the criteria of Bunnett-Olsen.

Dual-Task Interference of Gait Parameters During Different Conditions of the Timed Up-and-Go Test Performed by Community-Dwelling Older Adults.

The Timed Up-and-Go (TUG) test has been combined with different verbal/cognitive tasks (i.e.,TUG dual task [TUGdt]) as a form of motor-cognitive testing. However, it is still unclear how different TUGdt conditions affect gait among older adults. Thirty community-dwelling older adults, with mean age of 73years, participated in the study. Data were collected using marker-free video recordings. Gait parameters were extracted using a semiautomatic deep learning system. Comparisons of execution time and gait parameter outcomes were made under TUG and three types of TUGdt test conditions: TUGdt-naming animals, TUGdt-months backwards, and TUGdt-serial 7s. Statistical analyses were based on mean values of the gait parameters for each participant and TUG condition, including TUGdt gait cost, that is, the relative difference between TUGdt and TUG. All the investigated TUGdt conditions resulted in varying degrees of gait parameter changes. Under TUGdt conditions, participants took shorter and slower steps, with TUGdt-serial 7s causing the largest interference.

Ag(I) catalyzed oxidation of hypoxanthine and xanthine by Mn (VII) in aqueous Bronsted acid solutions: A kinetic and mechanistic study

Mn (VII) is a widely used as an oxidizing agent, but it could not oxidize hypoxanthine (HXAN), and xanthine (XAN) even in concentrated aqueous Bronsted acid (HClO4, H2SO4) media, and at elevated temperatures. However, in the presence of an Ag(I) or AgNO3 catalyst, aqueous Bronsted acid medium, and Mn (VII), the oxidation of Xanthine and Hypoxanthine transpired smoothly. It was discovered that under catalytic circumstances, at constant acidity and temperature, both [(Mn (VII)] and [Xanthine / Hypoxanthine Alkaloid] reactions obeyed basic I - order kinetics. It was further noted that at constant acidity and temperature, increase in [Ag(I)] accelerated the reactions significantly. Rate acceleration observed in oxidation of Xanthine and Hypoxanthine using Mn (VII) at constant [Ag(I)], constant temperature was attributed to increase in concentration of aqueous Bronsted acid (HClO4, H2SO4). The acidity functions established by Bunnett-Olsen Zucker-Hammett, and Bunnett were used for analyzing rate enhancements in this present work. The observed Bunnett-Olsen criteria of acidity functions suggesting the involvement of H2O molecule as H+(proton) transferring agent in the slow step of most plausible mechanism proposed.

THE KEY DIRECTIONS OF THE STRATEGY AIMED AT OVERCOMING DEVELOPMENT DISPARITIES IN THE FIELD OF PUBLIC ADMINISTRATION

As a result of the analysis of the indicators of individual associations of RA territories and marzes, it was revealed that although the processes of shareholding in RA were fast, but due to the lack of innovations and investments, the companies could not enter the competitive field. Currently, marzes are taking very slow steps to move to the stage of development of competition based on innovations. Among the main reasons for this are the long-term freezing of production capacity, the breakdown of the structure, the termination of the SODDLC and the decline in the natural volume of production, as well as the lack of cooperation and integration of companies and the decline in exports. In this regard, the balanced development of regional associations requires the development of sectoral and regional programs for the development of competition, taking into account the provision of equal conditions of competition in the markets.

A clinical mutation in glucokinase causing maturity-onset diabetes in the young type 2 increases enzyme activity.

Glucokinase (GCK) is the pancreatic β-cell glucose sensor, and its kinetics are key to that purpose. A slow transition step, displayed as non-hyperbolic kinetics, and a low affinity for glucose characterize GCK. Mutations in GCK associated with maturity-onset diabetes of the young type 2 (MODY2) previously describedreduce the functionality of the human pancreatic β-cell, leading to diabetic clinical phenotypes. We present a kinetic characterization of the G448D mutation identified in a MODY2 patient, which is one of the first mutations to exhibit increased functionality. This mutant displays increased activity, high affinity for both Mg2+ -ATP and glucose, hyperbolic kinetics and increased phosphorylation potential. Hyperbolic kinetics and assays in the presence of glycerol indicate that G448D lacks the slow transition step crucial for the pancreatic β-cell glucose sensor function.

Eğitim Yöneticilerinin Eğitim Kurumlarındaki Özgün Önderlik Süreçlerinin İncelenmesi

In this study, it is aimed to examine the unique leadership processes of educational administrators working in educational institutions for the personnel in their institutions. The constant change of educational methods and techniques, educational processes, teaching programs also necessitates constant change in the concept of educational management, which is being reshaped within the framework of an authentic understanding of leadership. Today, the implementation of a student-centered educational program in educational planning directly affects the unique leadership processes of people who are educational administrators. This influencing factor generally brings with it the receipt of positive feedback in the original leadership processes of educational administrators, depending on the current situation and shaping of their internal motivational sources. This is a positive development in the process of implementing educational management. Original lead training managers who have adopted the stance resides in the understanding of educational management, continuous improvement hedeflenild as slow but steady steps forward were taken in achieving full participation and understanding of a concept that has been followed by the model of inclusive education practices in the integrity of the success of training management is inevitable. Key Words: Education Manager, Educational Institution, Original Leadership

Direct identification of the rotary angle of ATP cleavage in F1-ATPase from Bacillus PS3

F1-ATPase is the world’s smallest biological rotary motor driven by ATP hydrolysis at three catalytic β subunits. The 120° rotational step of the central shaft γ consists of 80° substep driven by ATP binding and a subsequent 40° substep. In order to correlate timing of ATP cleavage at a specific catalytic site with a rotary angle, we designed a new F1-ATPase (F1) from thermophilic Bacillus PS3 carrying β(E190D/F414E/F420E) mutations, which cause extremely slow rates of both ATP cleavage and ATP binding. We produced an F1 molecule that consists of one mutant β and two wild-type βs (hybrid F1). As a result, the new hybrid F1 showed two pausing angles that are separated by 200°. They are attributable to two slowed reaction steps in the mutated β, thus providing the direct evidence that ATP cleavage occurs at 200° rather than 80° subsequent to ATP binding at 0°. This scenario resolves the long-standing unclarified issue in the chemomechanical coupling scheme and gives insights into the mechanism of driving unidirectional rotation.