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This document contains 395 abstracts of presentations on the theme of changing the image of chemistry, made at a conference on chemical education. Included with the abstracts are the presenters' names and addresses. The conference included the following sessions: Lecture and Learning: Are They Compatible?; ChemSource; Relevant Chemistry for the Non-Science Major; Industry-Education Initiatives; Innovative Outreach Programs; Breaking the Bubble: New Thoughts on Testing and Evaluation; Enhancing the Role of the High School Laboratory; Empowering Student Success; New Courses in Chemistry; Finding and Retaining Future Scientists; Bringing Women into Chemistry; and Writing in the Curriculum. (AA)

Within high school chemistry the topic of acids, bases, and pH is particularly challenging because robust understanding of the topic depends heavily on the student possessing deep concepts of atoms, molecules, ions, and chemical reactions. Since knowledge is acquired and stored in a dynamic structure, it was investigated in this study how knowledge changed as a result of the student's exposure to a particular type of learning task. Two areas of interest were targeted: the change in the students' understanding of acids, bases, and pH over the course of the treatment and the type of thought processes in which the students engaged while performing the treatment tasks. These understandings and thought processes were followed as a function of three levels of information presented by the technology: low level as represented by the use of chemical indicator solutions, intermediate level as represented by the use of a pH meter, and high level as represented by the use of a microcomputer-interfaced electronic pH probe. Reported in this paper are students' understandings prior to and after interacting with these technologies. Verbal data and drawings obtained in clinical interviews were used to construct concept maps and to analyze students' molecular concepts. Experts were also interviewed, and their concept maps were analyzed to identify critical nodes on their understanding of acids, bases, and pH. The concept maps and drawings were analyzed and two general conclusions reached: (1) students using microcomputer-based laboratory (MBL) activities appeared to construct more powerful and more meaningful chemical concepts; (2) the microcomputer group's high rates of both erroneous and acceptable links provide evidence that these students were positively engaged in restructuring their chemical knowledge. MBL appears to help students develop deeper understanding of acids, bases, and pH concepts, as indicated by the concept maps showing more detailed differentiation and integration. Examples of student's and expert's concept maps are appended. (KR)

Thirty-two computer-based lesson modules in organic chemistry were developed at the University of Texas (Austin) over an 18-month period and evaluated in varying classroom situations for three semesters starting in the Fall of 1972. The modules were designed as supplements to the traditional organic chemistry course of the University. As such, they emphasized tutorial-drill and experiment simulation applications in some of the basic organic chemistry concepts including nomenclature, classes of organic compounds, syntheses, reactions, preparations, laboratory exercises, and spectral interpretations. This paper includes descriptions of the modules together with a summary of their initial use and evaluation. (Author/DGC)

Computers have effected a comprehensive transformation of chemistry. Computers have greatly enhanced the chemist's ability to do model building, simulations, data refinement and reduction, analysis of data in terms of models, on-line data logging, automated control of experiments, quantum chemistry and statistical and mechanical calculations, and information storage including retrieval and the capacity for dynamic visual display. A recent conference addressed itself to the following aims: (1) provide a national forum for the impact of computers on chemistry; (2) encourage more investigation on computers; (3) make known the present status and the potential of computer-assisted instruction (CAI) in chemistry; and (4) inspire further examination of the chemistry curriculum in light of recent advances in computer technology. The conference report is a collection of 80 papers divided into the following categories: data fitting; curve fitting and band analysis of spectra; structure determination; CAI; computer technology in theoretical chemistry; chemistry curriculum development; communications in the field of chemistry; computer control of experiments; the use of A Programing Language (APL) in the undergraduate curriculum; and information systems. (EMH)

The formation of carbon via the triple alpha process is a key step in stellar production reactions of light ions and heavily impacts the life-cycle of red giant stars. Here, we propose a novel theoretical approach for sequential mechanism of the helium burning process, based on the Imaginary Time Method (ITM) and semiclassical models. We compare our results to those of the NACRE collaboration, which has set the standard for the past decades. Our calculations differ by several orders of magnitude in the low temperature region, which may seriously affect the early evolution of helium burning stars. [ABSTRACT FROM AUTHOR]

In this work, we report the measurement of elastic and Coulomb break-up channels in 6He+208Pb collisions at Elab = 19.3 MeV, close to the Coulomb barrier of this system ∼ 19 MeV. In the context of the astrophysical r-process, the reaction 4He(2n,γ)6He has been proposed to be a key reaction in the path of synthesizing seed nuclei for the r-process, as 12C, in an environment composed mainly of alpha particles and neutrons. Based on a theoretical approach for treating three body reactions by means of which its reaction rate can be inferred, our experimental approach aims to obtain an indirect measurement of the reaction rate of 4He(2n,γ)6He by measuring the Coulomb breakup of 6He under the intense electric field produced by a 208Pb target nucleus. The experiment was carried out at the TriSol facility operated in the Nuclear Science Laboratory of the University of Notre Dame, USA, which delivered a 6He beam together with other contaminants. Particular care must be taken for the alpha particles produced in the production reaction. [ABSTRACT FROM AUTHOR]

Benzene-d6 has been the scintillation material of choice for performing most of the neutron-capture cross-section measurements at CERN n_TOF for more than 20 years. Recently a revamping of solidstate Stilbene scintillators has been justified by their good timing performances, lack of toxicity and excellent neutron-gamma discrimination by Pulse-Shape Analysis. Consequently, several measurements were recently performed at the n_TOF facility at CERN and INFN-Catania to characterize their performance. We benchmarked both regular and deuterated stilbene scintillation crystals in EAR2@CERN. Based on these results, we are developing and designing a new generation of detectors with enhanced detection sensitivity and improved safety and maintenance conditions. [ABSTRACT FROM AUTHOR]

The present work is inherent to the NUMEN project that aims at providing data-driven information for the nuclear matrix elements of the neutrinoless double beta decay through the study of heavy-ion induced double charge exchange reactions. This is a formidable task since during a nuclear collision, the same final states may be populated through various reaction mechanisms. In this respect, understanding the degree of competition between successive nucleon transfer and charge exchange reactions is crucial for the proper description of the meson-exchange mechanism. To this purpose, the reaction dynamics in the 18O+48Ti collision were sought by measuring a plethora of reaction channels under the same experimental conditions. The 48Ti was chosen as target since it is the daughter nucleus of 48Ca in double beta decay. The relevant experiment was performed at the MAGNEX facility of INFN-LNS in Catania. In this contribution, the status of the analysis for the 48Ti(18O,18F)48Sc single charge exchange reaction will be presented. [ABSTRACT FROM AUTHOR]

Many observations strongly support the hypothesis that nuclei may fission through several independent fission modes (multimodal fission) interpreted as different prescission shapes and fission paths in a multidimensional potential energy landscape where shell effects are dominant. Mass distributions of the fission fragments are sensitive to the potential energy landscape and appear to be single humped (symmetric) or double humped (asymmetric). In many cases a mixture of both modes is observed. We propose here our study on 180Hg. Binary fission fragments formed in the reaction 68Zn + 112Sn → 180Hg at different excitation energies around the Coulomb barrier were detected using the double-arm time-of-flight technique with the spectrometers CORSET. The experiment was performed at JYFL (Jyvaskyla, Finland). We will discuss an analysis of the mass distributions in terms of fission modes predicted by a five-dimensional fission model. We have found out that the mass distributions can be well reproduced by considering a symmetric fission mode and two asymmetric modes at (AL ≈ 80, AH ≈ 100) and (AL ≈ 70 and AH ≈ 110). [ABSTRACT FROM AUTHOR]

The addition of aluminum to an explosive mixture can result in a discrepancy between the experimentally observed detonation velocity and the calculated Chapman-Jouguet (CJ) detonation velocity. CJ theory assumes that chemical reaction reaches completion at the sonic point in the flow, but that is generally not the case for aluminized explosives. A more suitable model to consider is eigenvalue detonation, as described by Fickett and Davis in "Detonation Theory and Experiment", 1979. In eigenvalue detonation theory, the explosive is modeled at a minimum by two sequential reactions; an exothermic reaction followed by a net endothermic reaction. Then the progress of reaction at the sonic point, is not complete, and is dependent on the reaction rates. The reaction zone of an eigenvalue detonation has two potential paths to complete reaction. If the detonation is unsupported, the flow passes through the sonic point and reaches complete reaction at the weak state (known as weak detonation). But, if the reaction zone is supported at the eigenvalue speed, the flow reaches the sonic point then recompresses up to the strong state resulting in a strong detonation with much higher pressure and temperature at the end of the reaction zone than a weak detonation. The reaction zone structure of strong and weak branch detonation are explored analytically through steady eigenvalue detonation theory, and validated by reverse impact and flyer impact numerical simulations. [ABSTRACT FROM AUTHOR]

Mesoscale simulations of the Shock to Detonation Transition (SDT) of heterogeneous explosives provide a means to better understand the SDT at the macroscale. In literature, there has been efforts to determine how hot spots form in an explosive microstructure after the impact of a flyer plate. However, studies that focused on hot spot growth and its influence on the shock acceleration are scarcer. In recent experimental studies by Johnson et al. [1, 2], hot spots in HMX monocrystals and polycrystals were observed. These studies suggested that hot spots developed mainly on the surface of the crystals and that the grains were consumed by the propagation of a deflagration front. In this present work, mesoscale simulations of an explosive composed of HMX were performed. Chemical reactions in the explosive were modelled through the propagation of a deflagration front at the surface of the crystals, based on [1, 2]. Accordingly, the simulations did not focus on the effects of the explosive microstructure on the hot spot formation, but essentially on their growth and its influence on the SDT. The wedge test configuration was employed on a microstructure generated by a 2D-Voronoï scheme. The shock/detonation position was post-processed from the simulations and used to determine the run-to-detonation distance (RDD) for different impact velocities. The Pop-plot obtained from these RDD was then compared to experimental Pop-plot data. [ABSTRACT FROM AUTHOR]

Shock initiation of energetic materials produces cations and anions that can contribute to the initial endothermic chemical reactions leading to detonation. Despite their potential importance, these transient charged species are difficult to detect in detonation experiments and often ignored in molecular dynamics modeling of shocked energetic materials. The pump-probe technique of femtosecond time-resolved mass spectrometry (FTRMS) and complementary theoretical calculations can unravel initial unimolecular dissociation reactions of transient cationic species on femtosecond-picosecond timescales. Here, we report the insights gained into sub-picosecond reaction timescales from FTRMS measurements and quantum chemical modeling for three ionized energetic molecules: nitromethane cation, multiply charged para-nitrotoluene cations, and ethylene glycol dinitrate (EGDN) cation. Each of these cationic species undergoes one or more decomposition reactions within hundreds of femtoseconds. [ABSTRACT FROM AUTHOR]

Understanding early chemical reaction steps in detonation environments is critical to the development of robust detonation theories and non-phenomenological models. Towards this end, we present initiation studies of 3,4-bis(3-nitrofurazan-4-yl)furoxan (BNFF), a hydrogen-free explosive with the chemical formula C6N8O8. BNFF is of interest for its unique chemistry, high detonation temperature, and formation of nanoscale carbon structures upon detonation. These studies are performed on Sandia's High Throughput Initiation (HTI) experimental platform, using laser-driven flyer plates to rapidly investigate the reaction threshold of vapor-deposited BNFF samples as a function of thickness using photonic Doppler velocimetry diagnostics. Initial cut-back style experiments, where the thickness of the sample is reduced in order to see how far along a reaction is at a given distance into the explosive, indicate that BNFF is sub-detonative at a depth of 25 µm up to our upper limit of impact velocity at around 4200 m/s using a 25 µm thick Parylene C flyer. When thicker films, 100 – 150 µm thick, are impacted, growth to detonation begins to occur more promptly at impact velocities below 3000 m/s. Future work will involve incorporation of streak spectroscopy into the HTI platform for emission spectroscopy to further elucidate initial chemistry. [ABSTRACT FROM AUTHOR]

In order to predict explosive behavior in new energetics, it is necessary to evaluate the chemical reactions that lead to the formation of localized ignition sites. Because explosive safety tests tend convolute the mechanics of heat generation at the mesoscale with the thermal stability and reaction rates of the explosive at the molecular level, we have sought to deconvolute the physics and mechanics of heat generation from the underlying chemistry of the molecules through i) state-of-the-art modeling and simulation at the meso- and atomic scales, ii) targeted synthetic modifications of the molecular properties that matter, iii) statistical analyses of historical datasets of sensitivity data, and finally iv) the development of carefully designed experiments with new diagnostics. In this review, we discuss the multi-step, multi-disciplinary process involved in probing and modifying the formation of an explosive ignition site, and the new diagnostics necessary to understand explosive ignition site formation and propagation with an emphasis on nitrate ester explosives like pentaerythritol tetranitrate (PETN). [ABSTRACT FROM AUTHOR]

Chemists balance chemical processes by modifying reactant and product stoichiometric coefficients to save mass. This method was done manually by chemists through examination and trial and error. New machine learning (ML) techniques have automated and optimized this critical process. The stoichiometric coefficient affects the balancing process chemistry. Using manual balancing, chemists tested equations. Modern ML motivates academics to automate and enhance it computationally. This thorough systematic review covers cyclical reaction balancing experiments and ML approaches. Examination of literature technique, dataset, and evaluation measure pros and disadvantages. We investigate chemical reaction balancing concerns using ML. [ABSTRACT FROM AUTHOR]

In order to study the thermal stability of fullerene С50 in a nitrogen atmosphere during the transition from the condensed phase to the gas phase and further reactions in the vapor phase, the method of thermodynamic modeling is used. The study was carried out with an excess and deficiency of nitrogen. Based on the results of the calculation, the chemical reactions in the С50−N2 system are compiled and the temperature intervals are distinguished for each reaction. In this work, a comparative study of the thermal stability intervals of C50 fullerenes in the condensed and gas phases was carried out. This study is one of series of papers on the properties of nanoparticles in a nitrogen atmosphere. [ABSTRACT FROM AUTHOR]

Battery is an electrical component which is capable of storing energy in the form of chemical reactions. In the process of receiving (charging) and releasing (discharging) energy, some of the energy can be lost and turned into heat. Excessive heat can impair performance and shorten battery life. Immersion cooling is one of the direct contact cooling methods for Battery Thermal Management Systems (BTMS), where the battery modules are immersed in a pool of dielectric coolant. The present work will discuss the cooling performance of immersion or direct contact method for a battery module by CFD code analysis. The simulated battery model is a Lithium-Ion type with a capacity of 50 Ah, and the coolant used is Novec 7300. The immersion will be varied based on the surface area of the battery module immersed: 100%, 90%, and 50% immersion. From the simulation results, it is found that 100% immersion and 90% immersion can keep the battery temperature below 308.15 K, which is the upper threshold of the safe operating temperature for lithiumion battery. 100% immersion can keep the average battery temperature at 300.40 K. 90% immersion can keep the average battery temperature at 301.89 K. 50% immersion can keep the battery temperature at 308.40 K. [ABSTRACT FROM AUTHOR]

The complex reaction network connected to the 19F stellar abundance is very sensitive to the physical condition in stars. To overcome difficulties present in the direct measurements, mainly the very low cross section in the astrophysical energy range due to the Coulomb repulsion, an indirect measurement of the 19F(p, α) reaction, with the Trojan Horse Method (THM), was performed at INFN-LNS. While the method had been successfully used to study α0 channel, in the present analysis focus was given to the α1,2 channels, where better knowledge of the reaction rates at low energies is required, obtainable by employing the THM method. [ABSTRACT FROM AUTHOR]

The chemical reaction between a fuel and an oxidizer at micro level, exothermic in nature, is known as micro-combustion is studied, as well as the flame stability and characteristics of combustion of a lean and premixed methane and air combination in a micro combustor with different heat production and chemical species conversion. Shapes of bluff bodies (half ellipse, crescent, wall-blade, and triangle) under different physical and chemical conditions are examined by solving governing equations in two dimensions. For intake mixture velocities of 10 m/s and 20 m/s and 0.59 equivalence ratio, blow-off limit of various bluff bodies, emitter efficiency, effect on flame structure and exhaust gas temperature of micro-combustor are investigated. The micro-combustor is made out of steel with 20 W/m.K conductivity. Existing literature suggests that geometry of wall blade produces the highest flame temperature for non-hydrocarbon - air mixtures. [ABSTRACT FROM AUTHOR]

This paper deals with a steady flow model of Reiner-Rivlin nanofluid due to a stretchable rotating disk. Entropy optimization in Reiner-Rivlin nanofluid flow model consists of a system of non-linear differential equations. These non-linear equations are solved using Homotopy Analysis Method (HAM). A simple and closed form of an analytical expression for the nanofluid's velocity, temperature, concentration and entropy rate is derived. Impact of Radiation variable (Rd), Brinkman variable (Br), Prandtl number (Pr), Schmidt number (Sc), Thermophoretic variable (Nt), Brownian diffusion parameter (Nb), and chemical reaction parameter(γ) on the resultant kinetic expressions is discussed. Testing the label of convergence between the HAM solution and numerical (MATLAB) solution gives good agreement. Furthermore, numerical values of entrainment velocity, moment coefficient, and skin friction coefficient are computed and given in tabular form. [ABSTRACT FROM AUTHOR]

The measurement of the breakup of the radioactive nucleus 7Be on 12C at 5 MeV/u is reported for the first time. Significant coincidence counts of α and 3He from 7Be breakup have been identified. Analysis is ongoing to identify the breakup events from a direct or sequential process. [ABSTRACT FROM AUTHOR]

Astrophysical reactions involving radioactive isotopes (RI) often play an important role in high-temperature stellar environments. The experimental information on those reactions is still limited mainly due to the technical difficulties in producing high-quality and intense RI beams. Although a direct measurement of those reactions at astrophysical energy would be still challenging, we may take several alternative approaches to determine the reaction rates, by applying other mesurement methods or improving the target and detectors. Here we mainly discuss the thick-target method in inverse kinematics (TTIK) based on the successful examples of experimental studies performed at Center for Nuclear Study, the University of Tokyo, using the low-energy RI beam separator CRIB. [ABSTRACT FROM AUTHOR]

Nuclear reaction study is important to understand elemental abundance in the universe and stability of stars. For several reactions due to the paucity of experimental data or diffculties in performing the direct measurements, we depend upon theoretical estimates and therefore one needs reliable theoretical models with minimum inputs. This paper is a short review of our work on nuclear reactions and their applications to astrophysics. In particular, we discuss the nuclear transfer and breakup reaction while focusing on our theoretical modelings and techniques involved. [ABSTRACT FROM AUTHOR]

Nuclear reactions within stars typically occur at energies significantly below 1 MeV. Consequently, the Coulomb barrier exponentially suppresses the cross section, reducing it to values as small as a few nanobarns for charged particles. This challenge in obtaining accurate input data for astrophysics has led to the introduction of indirect methods. Specifically, techniques such as ANC and THM have been employed to derive cross sections for reactions involving photons and charged particles in the exit channel, respectively, eliminating the need for extrapolation. The discussion delves into recent results from the application of these methods. For instance, the 6Li(3He,d)7Be measurement is utilized to deduce the ANC's of the 3He+4He→ 7Be and p+6Li→ 7Be channels, along with their corresponding radiative-capture cross sections. Additionally, the THM measurement of the 27Al(p, α)24Mg cross section via the 2H(27Al,α24Mg)n reaction is highlighted. In both cases, the cross section at astrophysical energies has been established with unprecedented accuracy. [ABSTRACT FROM AUTHOR]

Advection-diffusion-reaction (ADR) equations are useful to model real-life phenomena in which transport phenomena and chemical reactions take place. Here, these equations are used to predict the amount of total dissolved solids extracted in the espresso coffee percolation process. The corresponding initial-boundary value problem is solved by using the Crank-Nicolson scheme, with respect to the time, whereas the spatial derivatives are approximated via radial basis functions (RBFs). The reliability of the proposed solving strategy is assessed experimentally, by comparing real and simulated extractions conducted under different physico-chemical conditions. [ABSTRACT FROM AUTHOR]

Chemistry, especially in the chapter on reaction rates, studies the composition of matter, changes in matter, basic laws, and abstract concepts. The reaction rate chapter is considered difficult bystudents, so the source and learning media are needed to make it easier for students to learn it. One of the sources of learning media is teaching material. Teaching material has an important role because it is a tool to achieve learning objectives. Therefore, new reaction rate teaching material needs to be created to accommodate abstract concepts. These concepts can be described by chemical representationandthen explained through representational competence. Based on the description above, this study aimed to 1) develop valid and appropriate teaching materials for reaction rate-based chemical concepts, chemicalrepresentation, and representational competencies and 2) analyze the validity and legibility tests of the developed teaching materials. The research and development design used was the defining stage, designing stage, developing stage, and disseminating stage, which refers to the 4-D model by Thiagarajan et al. (1974). However, the dissemination stage was not carried out due to time and cost considerations. The research instruments used were a validation questionnaire sheet and a legibility questionnaire sheet. The product was validated by two validators from the lecturers of the Department of Chemistry, Universitas NegeriMalang, and then tested for legibility by 32 students of class XI-MIPA at SMA Negeri 3 Kediri. Quantitative data were analyzed using descriptive statistical techniques with the percentage formula. The data analysis was then interpreted according to the range of criteria according to the Likert scale. Meanwhile, qualitative data were analyzed using descriptive analysis techniques. The teaching material validation results obtained an overall average value of 93.5% with a very valid category. Meanwhile, the results of the legibility test of teaching material obtained an overall average value of 87.5% with a very decent category. Based on the research results, it was known that the teaching material developed was categorized as very feasible with few revisions to be used. Therefore, this teaching material can be further developed for dissemination. [ABSTRACT FROM AUTHOR]

Modified chitosan have received significant attention that considered as useful biocompatible materials to remove Sutra Bugis textile heavy metal ions. The reactive functional groups of chitosan, -NH2 and -OH can form chelates and prone to chemical reaction with heavy metal ions so that it can be modified. Chitosan has drawback that unstable in acid or base, it can be modified to carried out by crosslinked with citric acid and tripolyphosphate which respect to concentration or crosslinker. The optimal result from the concentration of citric acid and tripolyphosphate for removal Pb(II) ion and Cd(II) ion are 1% and 2%, respectively for each Sutra Bugis textile waste heavy metal ions. The modified chitosan have been characterized by FTIR. The adsorbent based on modified chitosan allows for better adsorption of Sutra Bugis textile waste heavy metal ions is chitosan-citric acid-tripolyphosphate than chitosan-citric acid. [ABSTRACT FROM AUTHOR]

One of the largest issues in our society is the energy crisis. Although we are shifting to renewable energy, petroleum is still going to be our main energy source in the decades to come. Moreover, global oil demand is expected to rise in the next decades. One of the promising enhanced oil recovery schemes is polymer flooding. A polymer solution can be hundreds of times more viscous than water, and its shear-thinning property could also improve viscosity as the fluid travels further from the injection well. To compensate for the high-pressure burden for the fluid injection, an in-situ chemical reaction can also be incorporated. In this work, polymer flooding experiments were performed in porous media generated from granular packing. Micro-tomography and image processing techniques were used to monitor and assess the fluid in the porous media. Three experiments with different fluid systems were performed under two different flow rates to investigate the effects of polymer flooding, shear-thinning properties, and in-situ chemical reaction of viscosity improvement. We found that polymer flooding improved oil production significantly than water flooding. Due to its shear-thinning property, oil production improved with lower injection velocity. In addition, the in -situ chemical reaction was also found to improve the oil production although only slightly. [ABSTRACT FROM AUTHOR]

In this article, we have discussed the effects of gyrotactic microorganisms on electrically conducting carreau nanofluid across an exponentially stretching surface over a thermal radiation in the presence of chemical reaction. The governing partial differential equations and boundary conditions are converted into a system of non-linear ordinary differential equations by the using of similarity transformations which are then solved numerically using shooting technique with the help of MATLAB program. The fluid velocity is an increasing function of the local Weissenberg number, according to this research. Magnetic field influence reduces the thickness of the momentum boundary layer. Due to increased values of thermophoresis and Brownian motion effects, there is an increasing trend in carreau fluid temperature. Brownian motion causes the concentration field to decrease, whereas thermophoresis causes it to increase. The concentration profile is enhanced by activation energy, but the Schmidt number is reduced. Present results are compared with the previously published results in some limiting cases and results are found to be in an excellent agreement. [ABSTRACT FROM AUTHOR]

The rapidly growing population in the world demands an increase in the support of human life by providing massive production of food and medicine. As a result, the catalyst used in the production of the material plays a key role leading to intensive research. Synthesis of nanomaterials is becoming an important way to discover new catalysts by changing sizes and combining two or more metals on the nanoscale. Pd-based catalysts are well-known catalysts such as Pd-Pt, Pd-H, and Pd-Au for many chemical reactions such as the direct synthesis of hydrogen peroxide. Therefore, the provision of nanocluster bimetallic catalysts offers more benefits such as the rearrangement of surfaces to suit characteristics and lower material costs. However, the stability of the catalyst challenges researchers beyond reactivity and selectivity. In this paper, we predict the structural stability of Pd-based catalysts using a density functional theory approach. We use the 38-atom model in the M6@Pd32 core shell, where M is Hg, Pt, Au, Cu, Ni, Cu, Zn, Ag, Pd, and Cd, Pt. We prepared and investigated a series of structures such as truncated octahedral (TO) and polyhedral (PH) by calculating the excess energy. Based on our calculations and placing the monometallic Pd38 nanocluster as a reference, the TO structure is more stable than that of PH. The Zn6@Pd32 system showed the most stable followed by Cd6@Pd32 and Hg6@Pd32 was the worst. [ABSTRACT FROM AUTHOR]

The aim of this research paper is to study numerically the behavior and manifestations of chemical reaction cycles. A simple model demonstrating how a chemical reaction-diffusion process can be controlled by a thermal gradient is developed. The reaction-diffusion equation system consists in the coupling of chemical equations—describing a first order chemical transformation whose kinetics follow the Arrhenius' law—with chemical diffusion. Two kinds of gradients of temperatures are imposed (linear and Heaviside profile) in order to study a reaction in nonequilibrium steady state. The numerical modeling of equations governing the problem of this work is performed by integrating the corresponding PDEs using XMDS2 open source code. The steady state spatial distribution of the chemical fluxes are investigated for two use cases: whether the diffusion coefficient is dominant in reference to the kinetic constant of the reaction(δ/ρ>1), or the kinetic constant of the reaction is dominant in reference to the diffusion coefficient (δ/ρ<1). The phenomenology related to chemical reaction-diffusion cycles is studied as a function of the different thermodynamic parameters associated with the problem, in order to understand the spatial distribution of the chemical fluxes induced by the external temperature gradient. [ABSTRACT FROM AUTHOR]

Recently, utilization of nanoparticles has been increasing due to their wide range of capability to act as catalyst in chemical reactions, carrier for certain molecules, or additives that would alter certain materials' properties. One way to produce nanoparticles is by utilizing microfluidics technology. Passive micromixing using serpentine microchannel can be utilized to generate nanoparticles in a simple, automated, and high-throughput manner. Here, we design and validate a serpentine microchannel in computational simulation environment prior to realization by stereolithography. The serpentine microchannel has a footprint area of 2 cm x 2 cm with 300 micrometer-wide microchannel. Simulation result shows that the serpentine microchannel is capable of operating under the specified fluid flow parameters. The serpentine microchannel has been successfully realized by stereolithography using standard resin. Metrological measurement shows that the geometrical tolerance is around 18% which is still acceptable for DLP product. Chip assembling is performed by bonding between the serpentine microchannel with rigid transparent acrylic plate. Functional flow test demonstrates the product can perform successfully. [ABSTRACT FROM AUTHOR]

The shrinking core model (SCM) has been widely used to model the kinetics of solid-liquid reactions such as metal extraction from ore minerals. Most studies considered a single-sized grain, and the particle size variation of the ore was disregarded. In the present study, the kinetics analysis of limonitic nickel ore in sulfuric acid by incorporating the effect of particle size distribution in SCM was made. The approach was used to evaluate the effects of leaching temperature (65 to 95°C) and agitation speed (250 to 400 rpm) on the leaching kinetics of nickel from limonite ore. The analysis showed that the rate-determining step was shifted from diffusion through unreacted core to an interface chemical reaction. the increase in the extracted nickel by the increase in agitation speed also indicated that the leaching rate is chemical reaction-controlled. This investigation results give an insight into incorporating particle size distribution's effect in the shrinking core model on the rate-determining step in the leaching of limonite ore in sulfuric acid at atmospheric pressure. [ABSTRACT FROM AUTHOR]

Graphene quantum dots (GQDs) attract huge scientific attention ever since they were discovered. They are the only 0-dimensional, water-dispersible graphene-based nanomaterial. They show (i) excellent biocompatibility; (ii) stable and tunable photoluminescence in the visible part of the spectrum resistive to photobleaching; (iii) large surface area; (iv) good solubility in water and polar organic solvents. Their astonishing properties stem from the structure: graphene in the core and a vast number of different oxygen-containing functional groups such as carboxyl, carbonyl, epoxy, hydroxyl, and lactone. Their lateral size is below 100 nm, and the height is from 0.5 to a few nm. Thanks to different oxygen groups, they have very reach chemistry; they can be easily processed, modified, and functionalized. GQDs can be modified after their synthesis using different chemical reactions, which lead to changes in oxygen content, the addition of heteroatoms, binding of target molecules. Heteroatoms can be built-in GQDs structure during the process of synthesis and usually, N, S, and P are selected. They can be produced in many different ways and starting materials and all of them are dived into two main groups: bottom-up and top-down methods. Due to a large number of diverse functional groups and high surface area, GQDs create complexes with ions, cations, biomolecules, organic molecules, etc. Thanks to this feature, GQDs are studied for the application in sensing heavy metal ions, selected anions, proteins, metabolites, hormones, enzymes, pesticides, organic colors, etc. Another exciting feature of GQDs is their ability to produce reactive oxygen species under visible light. [ABSTRACT FROM AUTHOR]

The accurate prediction of flow characteristics and thermal response characteristics is one of most vital criterion for space vehicles which are flying at very high speeds. These vehicles undergoes severe aerothermodynamics loads during their ascent and descent trajectories. In the present work, we have carried out the DSMC simulation of chemically reacting hypersonic flow over a Crew module Atmospheric Re-entry Experiment (CARE) capsule with five chemical species. A DSMC solver called SPARTA which provide accurate results similar to the Boltzmann equation is used for the present simulation. We have utilized the hybrid chemical reaction model for our simulation which invokes Quantum Kinetic (QK) and Total Collision Energy (TCE) model for modeling the chemical reaction such as dissociation and exchange. The VHS and Larsen-Borgnakke model is used for the modeling of collision and energy exchange reaction. The simulation is carried out with the transitional Knudsen number of 0.1 and the free stream Mach number of 20. The dissociation of N2 is faster for Hybrid TCE-QK. The independent QK model have higher chemical composition especially for NO composition. The present work demonstrates the hybrid chemical reaction model ensure the faster vibrational equilibrium and better chemistry compared to the independent chemical reaction model. [ABSTRACT FROM AUTHOR]

The choice of materials for thermal protection systems (TPS) is crucial during re-entry flows, as the material must shield the vehicle from extreme aerothermal heating. Exothermic heterogeneous reactions catalyzed by the porous micro-structure of the TPS lead to a major increase of this heat flux. In addition, the catalytic reactions can lead to alterations in the gas phase composition, with the formation of eventually otherwise not present reactive and radiative species. As a result, radiative heating must be considered as well. Furthermore, the surface structure might be changed by the interaction with the gas, due to oxidation or ablation processes. The gas-and plasma simulation code PICLas has been extended by a catalysis model, to include chemical reactions occurring on a surface. A variety of reaction mechanisms have been implemented, including the pre-cursor mediated adsorption according to the Kisliuk model, desorption and Langmuir-Hinshelwood recombination. The model uses macroscopic reaction rate data and surface parameters, taken from experiment. In this study, the heterogeneous reaction model is verified by application to selected test cases and evaluation of the surface coverage and the gas-phase composition, together with the heat flux on the reactive surface. The results obtained from the newly implemented catalytic model are compared to a fully catalytic surface treatment, which makes use of a simple recombination model as an extension of the Maxwell scattering process. [ABSTRACT FROM AUTHOR]

Groundwater containing pyrite and dissolved ferrous ions may oxidize, potentially producing acidic and metal-rich water that is harmful to ecosystems and human health. Groundwater conditions, which are affected by both chemical reactions and hydrogeological factors, that have been the subject of an intensive numerical investigation because of their impact on pyrite oxidation. The solubility of ferrous ions, which act as catalysts in the oxidation process, and the kinetics of pyrite oxidation are both properly modeled in the numerical simulation. The model considers hydrogeological factors including pH, temperature, and flow rates for a more accurate representation of the real world. The numerical model accurately represents pyrite oxidation kinetics and ferrous ion solubility, making it possible to investigate temporal and spatial variations in water quality. According to our findings, groundwater acidity and metal pollutant formation are both accelerated by dissolved ferrous ions, which in turn accelerates pyrite oxidation. The study also highlights the rise in ferrous ion concentration with depth because of pyrite's increasing oxidation rate. Water quality is shown to vary across time and place because of pyrite oxidation in a series of simulations. The findings demonstrate that groundwater acidity and metal pollutant generation are both accelerated by the presence of dissolved ferrous ions, which are produced during the oxidation of pyrite. Potential factors on oxidation rates are also investigated, including groundwater flow patterns, the reactive surface area of pyrite, and the initial concentrations of ferrous ions. Exploration provides insights into the primary causes of pyrite oxidation in different hydrogeological conditions, which is critical for designing effective countermeasures. The need of considering both chemical and hydrogeological criteria to effectively predict the degree of pyrite oxidation and its potential ramifications on water resources. The findings of this research are helpful in formulating efficient plans for dealing with pyrite's harmful effects on groundwater quality. It is essential to consider both chemical and hydrogeological characteristics to appropriately forecast the degree of pyrite oxidation and its prospective effects on water resources. The findings of this research may be utilized to gain a greater understanding of pyrite's role in polluting groundwater. [ABSTRACT FROM AUTHOR]

Most nuclei far from the valley of stability, and typically near the drip lines, exhibit exotic features that have challenged our current understanding of nuclear structure. The question we pose concerns the effect of these exotic nuclei on stellar reaction rates and nucleosynthesis. Consequently, this may significantly affect the pattern of astrophysical abundances relevant to r-process nucleosynthesis by a considerable margin. We show the effect of improved calculations for nuclear structure, especially of possible bubble structure in 20N on abundances in explosive nucleosynthesis. [ABSTRACT FROM AUTHOR]

The cross section measurement of 144Sm (p, γ) 145Eu has been carried out around proton energies 2.6–6.8 MeV using the activation technique. Measured cross sections are compared with the previous measurement and theoretical predictions using TALYS 1.96. The molecular deposition method was used to prepare the enriched 144Sm targets of thickness 100–350 μg/cm2 on Al backing. [ABSTRACT FROM AUTHOR]

The aim of this study is to implement a Semi Analytical Iterative Method (SAIM) to solve a non-linear chemical kinetics system. To determine the reliability and effectiveness of the method, the result obtained by SAIM was compared with an existing result by the Runge-Kutta method (RK4). Both results showed good agreement in terms of precision. Consequently, this method provided a simple and efficient technique which requires less computational work. [ABSTRACT FROM AUTHOR]

The effect of a nickel oxide supported silica oxide (NiO/SiO2) catalyst on temperature programmed reduction (TPR) with 40% (v/v) carbon monoxide (CO) in nitrogen atmosphere as reductant agent was investigated. The conventional impregnation method was used to create the NiO/SiO2 catalysts. The reduction characteristics of NiO to Ni were investigated up to 700 °C, followed by isothermal reduction. The TPR profile of 9% NiO/SiO2 slightly shifted to lower temperature from 412 to 392 °C. Whereas the undoped NiO was reduced at a lower temperature of 387 °C. XRD diffractogram of the catalysts showed a complete reduction of NiO to Ni and have different intensities for each different loading of NiO catalyst on SiO2 support. The TEM images indicated that the carbon nanotubes were deposited on the NiO surfaces indicating some chemical reactions occur on NiO. It was found that the addition of 3% of NiO on SiO2 also exhibited a larger BET surface area (532.8 m2g−1) and insignificant pore diameter (5.9-6.0 nm). Based on these results, it is interesting to note that the addition of a small amount of NiO to SiO2 has a remarkable influence by reducing the temperature in the reduction process. The 9% NiO/SiO2 was found sufficient could enhance the reducibility of NiO at a lower temperature. [ABSTRACT FROM AUTHOR]

In this paper, we present the mechanisms of water droplet absorption into the cellulose-based fabric from a molecular viewpoint. A 5×5×5-unit-cells of cellulose Iβ model and a water molecule model have been developed to represent fabric and water droplet. The climbing-image nudged elastic band method was used to find the minimum energy path and the energy barrier of a water molecule when absorbed into three different cellulose surfaces, i.e. [100], [010], and [001] surfaces. The [010] has the lowest calculated energy barrier compared to the other surfaces, thus it is the easiest surface to be penetrated by water molecules. The other surfaces have larger energy barrier values due to the temporary binding of an oxygen atom of the water molecule on cellulose molecules when the water molecule penetrates the surface. For all surfaces, there is not any chemical reaction taking place when the water molecule is adsorbed on the surface or when it is absorbed in the subsurface. Thus, the absorption processes observed in this study is physical absorption. [ABSTRACT FROM AUTHOR]

A more general, but also more difficult task in combustion methane-air mixture in the combustion chamber (СС) of gas diesel (GD) is to find the composition of the components in the flame developing in the boundary layer. In order to solve it, it is necessary, in our opinion, to consider more aerodynamically simple cases for which the results of the theory of turbulence could be used, to identify the influence of turbulence characteristics on the course of chemical combustion reactions in these conditions, to outline ways of transition to solving the problems of turbulent diffusion combustion in the difficult conditions of the CC of GD. [ABSTRACT FROM AUTHOR]

The explosive atmosphere may be caused by flammable gases, vapors, or combustible dust. In the event that the material is combined with air in an adequate proportion, an ignition source is required to produce an explosion. Fuels and other liquids, as well as solvents from industrial items, release volatile vapors that can catch fire or explode when they come into contact with the air. At normal temperatures, flammable liquids can emit enough vapor to form combustible mixtures with air, heat, and often thick, black, and toxic clouds of smoke. The potential causes of explosions within work systems are represented by the intrinsic properties of flammable/combustible chemical substances and preparations used, dangerous chemical reactions, energy sources, or the ability of technical equipment, work methods, or techniques to cause human or material damage. Understanding the characteristic explosive parameters in regulated settings is essential to evaluating the risk of explosion and the evolution of explosion in such mixtures. In this paper maximum explosion pressure pmax and maximum rate of pressure rise (dp/dt)max for gasoline-air mixtures were determined in a standard 20 dm³ spherical explosion vessel in order to validate in the laboratory the method of determining the explosion parameters of air-vapor mixtures. [ABSTRACT FROM AUTHOR]

The numerical study presents the effect of heat generation and chemical reaction on the problem of magnetohydrodynamics mixed convective flow of power-law nanofluid using Buongiorno's model. Adiabatic non-conducting solid square block is located at the center of the cavity and both vertical walls are moving with uniform velocity. The governing dimensional equations in vector form are transformed into non-dimensional form. Then, the dimensionless equations are solved numerically by finite element method (FEM) using automated solution technique which is FEniCS. The effects of different parameters such as Richardson number, power-law index, magnetic field, heat generation/absorption, chemical reaction and size of square block on velocity, temperature, and concentration profiles are performed and discussed in this paper. It is found that rising both Richardson number and power-law index lead to increase the velocity and temperature profiles (right side of cavity). Besides, rising both magnetic parameter and size of square block lead to decrease the velocity and temperature profiles (right side of cavity). Adding the heat generation/absorption parameter has increased the temperature profile. In addition, increasing chemical reaction parameter has reduced the concentration profile. [ABSTRACT FROM AUTHOR]

In this paper, steady two-dimensional magnetohydrodynamics mixed convective flow of non-Newtonian power-law nanofluid with the presence of heat generation/absorption and chemical reaction effects is investigated. The nanofluid incorporates the effects of Brownian motion and thermophoresis using Buongiorno's model. The flow is studied in a cavity with a moving top wall and contains isothermal solid circular cylinder at the center. The governing dimensional equations in a vector form are transformed into non-dimensional form. Then, the dimensionless equations are solved numerically by finite element method (FEM) using automated solution technique which is FEniCS. The influence of various parameters such as Richardson number, power-law index, magnetic field, heat generation/absorption, chemical reaction and size of solid circular cylinder on velocity, temperature, and concentration profiles are presented and discussed in this study. The results show that increasing Richardson number and power-law index has enhanced the velocity and the temperature profiles (left side of cavity). Meanwhile, both profiles reduce when the magnetic parameter and the size of solid circular cylinder are added. The temperature profile is increased with the rising of heat generation/absorption parameter. Besides that, declining trend is observed on the concentration profile with increasing chemical reaction parameter. [ABSTRACT FROM AUTHOR]

The associative property of addition facilitates the change of the group member. If the group members are molecules, can we apply this property to study a chemical reaction? The aim of this paper is to use the associative property of addition to design reaction pathways of methyl acetate hydrolysis in the acid environment. The reaction is found in Alzheimer's Disease. We evaluate the designed pathways using activation energy obtained from density functional theory calculation. The results show the associative property of addition can be used to design four reaction pathways of the hydrolysis. The calculations show the acidity significantly affected the activation energy. This result agrees with the common knowledge. Hence, we have demonstrated the usefulness of the associative property of addition in designing chemical reaction pathways. [ABSTRACT FROM AUTHOR]

Dynamics of thermal radiation and the Lorentz force on the free convective flow of hybrid nanofluid (H2O + Fe3O4 + MWCNT) flow by a solid sphere with chemical reaction are examined in this paper. Non-Fourier heat flux (Cattaneo-Christov heat flux) model is included in the energy equation. Matlab's built-in function, bvp4c, is used to solve governing equations after they have been transformed into ordinary differential equations. Graphs are used to display results (such as changes in the temperature profile caused by thermal radiation). Major findings are, as the volume fraction of nanoparticles increases, the shear stress decreases by 0.16509, while the shear stress increases by 4.593595 with respect to magnetic field. It is noticed that the fluid temperature rises when thermal radiation upsurges. Temperatures drop as a function of thermal relaxation parameter, which is also observed. The data also shows that as Schmidt number rises, so does the mass transfer rate, with an increment rate of 3.356359. [ABSTRACT FROM AUTHOR]

A predator-prey model with an epidemic model of SEIR (Susceptible-Exposed-Infected-Recovered) and SIERS (Susceptible-Exposed-Infected-Recovered-Susceptible) in the prey population is introduced. The epidemic disease had been described by the SEIR and the SEIRS models. A logistical growth function appears in the susceptible prey population. The predation function is given in the five nonlinear ordinary differential equations. They present the dynamics' of the species' population. The main focus of this article is to propose an eco-epidemiological model that can be implemented by a chemical reaction network. The studied chemical reaction network is a mathematical-chemical apparatus through which a parallel between the change of reactant concentrations and the dynamics of the populations can be made. The authors present a chemical reaction network which describes the considered model indicating the obtained differential equations. The main law that is used is the law of mass action kinetics. Some numerical experiments are given. [ABSTRACT FROM AUTHOR]

The high levels of all air pollutants are of great importance for human health. Especially dangerous are particulate matter (PM) contaminants. PM is a mixture of solid particles and liquid droplets found in the air. Particle pollution includes: PM10: inhalable particles, with diameters that are between 2.5 and 10 micrometers; and PM2.5: fine particles, with diameters that are generally 2.5 micrometers and smaller. These particles are emitted in air directly from a source, such as construction sites, unpaved roads, fields, smokestacks, volcanos or fires. Most particles form in the atmosphere as a result of complex reactions of chemicals such as sulphur dioxide and nitrogen oxides, which are pollutants emitted from power plants, industries and automobiles. For all European countries there are many regulations aimed against the air contamination and for the monitoring of pollution. Bulgaria, as a part of EU has to follow all these regulations. Still in Bulgaria there are many places and periods of time during the years with PM10 contamination, bigger than the daily norm of 50µg/m3. This study is to investigate the PM10 air pollution in the city of Svishtov, Bulgaria for the period 2012–2021. Svishtov is located in northern Bulgaria, on the bank of the river Danube – the north Bulgarian border with Romania. For the study we use official data from the monitoring of PM10 air contamination in Svishtov region, Bulgaria. We apply statistic methods to study data and to predict future PM10 pollution in the city of Svishtov. All results of the study are graphically presented and commented. [ABSTRACT FROM AUTHOR]