bluuebunny/crossref_metadata_2025 huggingface dataset:
Translational diffusion coefficients and hydrodynamic radii of normal corn starch in aqueous media from asymmetrical flow field-flow fractionation experiments
Authors: Juna Shazia , Huber Anton
Published: July 2024

Starch is a highly disperse material with broad distributions of molecular sizes and geometries. Its dissolution in aqueous media is difficult to achieve and it tends to form aggregates through both inter- and intra-molecular interactions. Asymmetrical flow field-flow fractionation (AF4) is a suitable technique for the separation of such macromolecular and colloidal systems. A major advantage of AF4 is the direct correlation of translational diffusion coefficients with retention time and experimental parameters. In this article, the hydrodynamic and diffusive mobility of normal corn starch dissolved in 0.035 M KSCN was investigated by systematically varying the cross flow rates (applied forces); the translational diffusion coeffcients for normal corn starch in aqueous medium were found to range between 9.9 x 10-9 cm2/s and ~2.5 x 10-7 cm2/s with varying Fcr rates. Diffusion coefficient ranges shifted to higher diffusion co-efficient values at higher cross flow rates (applied forces). This behaviour, which may be attributed to the increased retention of very large starch molecules/particles at high Fcr rates, is further confirmed by the decrease in apparent molar mass and mass recovery values.
Gas transport in aluminosilicate nanotubes by diffusion NMR
Authors: Dvoyashkin Muslim , Wood Ryan , Bowers Clifford R. , Yucelen Ipek , Nair Sankar , Katihar Aakanksha , Vasenkov Sergey
Published: July 2024

Diffusion of tetrafluoromethane in aluminosilicate nanotubes was studied by means of 13C pulsed field gradient (PFG) NMR at 297 K. The measured data allow the estimation of the diffusivity of tetrafluoromethane inside the nanotubes as well as the diffusivity for these molecules undergoing fast exchange between many nanotubes. The results support the assumption about the one-dimensional nature of the tetrafluoromethane diffusion inside nanotubes.
Velocity-sensitised Magnetic Resonance Imaging of foams
Authors: Bos Kevin J. , Wilson K. Gordon , Newling Benedict
Published: July 2024

Although flowing foams are used in a variety of technologies, foam rheology is still incompletely understood. In this paper we demonstrate the use of a velocity-sensitised magnetic resonance imaging (MRI) sequence for the study of flowing foam. We employ a constant-time (pure phase encode) imaging technique, SPRITE, which is immune to geometrical distortions caused by the foam-induced magnetic field inhomogeneity. The sample magnetisation is prepared before the SPRITE imaging with the Cotts 13-interval motion-sensitisation sequence, which is also insensitive to the effects of the foam heterogeneity. We measure the development of a power-law velocity profile in the foam downstream of a Venturi constriction (in which the cross-section of the tube decreases by 89% in area) in a vertical, cylindrical pipe.
Investigating pore to pore exchange in systems saturated with water and oil
Authors: Lewis Rhiannon T. , Nåden Susanne , Seland John Georg
Published: July 2024

Relaxation Exchange Spectroscopy (REXSY) has not previously been performed on samples containing different liquids. We present a pulse sequence that combines a Pulsed Gradient Spin Echo with REXSY, which we call PGSE-REXSY. Using this pulse sequence it is possible to separate the signals from two liquid components, here oil and water, simultaneously present within a sample due to the difference in diffusion properties. A REXSY analysis can then be performed on the individual liquids. The technique is very relevant to applications in petroleum research, and could potentially be used to determine how the mobility of one liquid is influenced by the presence of the other. We also show that compared to a two-dimensional Inverse Laplace Transform, a discrete multi-exponential component model is more robust when performing a quantitative analysis of REXSY data.
Effective diffusion tensor computed by homogenization
Authors: Nguyen Dang Van , Grebenkov Denis , Poupon Cyril , Bihan Denis Le , Li Jing-Rebecca Li
Published: July 2024

The convergence of the long-time apparent diffusion tensor of diffusion magnetic resonance imaging (dMRI) to the effective diffusion tensor obtained by mathematical homogenization theory was considered for two-compartment geometric models containing non-elongated cells of general shapes. A numerical study was conducted in two and three dimensions to demonstrate this convergence as a function of the diffusion time.
Inertial and memory effects in the hydrodynamic Brownian motion of rouse and zimm polymer coils
Authors: Tothova Jana , Lisy Vladimir
Published: July 2024

Traditional bead-spring models of the polymer dynamics are based on the Einstein theory of the Brownian motion (BM), valid only at the times much larger than the particle´s relaxation time. The reason is in neglecting the inertial and memory effects in the dynamics. In the present work we use a generalized theory of the BM to build models of the dynamics of flexible polymers in dilute solution. The equations of motion for the polymer segments include the friction force that follows from the linearized Navier-Stokes hydrodynamics. It has a form of a memory integral. To get a correct description of the short-time dynamics, inertial effects are included into the consideration. For negligible hydrodynamic interactions (HI) between the beads the motion of the polymer center of mass is not influenced by internal forces within the chain and has been considered exactly. Then we include the HI int the description of motion of chains, which are assumed Gaussian in equilibrium. Analytical solutions for the observable time correlation functions describing the movement of the polymer coils significantly differ from the classical results showing, in particular, algebraic long-time tails and ballistic motion at short times.
Diffusion and Brownian motion
analogies in the migration of atoms, animals, men and ideas
Authors: Vogl Gero
Published: July 2024

The macroscopic laws of diffusion were laid down for the case of liquids by Adolf Fick 150 years ago who realised the analogy of diffusion and heat conduction. 100 years ago Einstein and Smoluchowski put up the equation named after these scientists teaching us how to trace down the motion of a single diffusing particle and thus to understand long time unexplained Brownian motion as a fluctuation phenomenon. In the last fifty years these laws and their combination were boldly but successfully applied to the diffusion, migration, dispersion of single atoms, men, animals and ideas. We start by showing how the Einstein-Smoluchowski equation makes possible to induce diffusivity from microscopic information on details of the diffusion jump in solids. We then report on Brownian motion and diffusion of our fore-fathers in the Neolithicum following Cavalli-Sforza’s ideas and show how this diffusion must have been a mixture of demic diffusion, i.e. the diffusion of people, and the diffusion of technological ideas. Next we risk a glimpse to the immigration of early Americans. We point out the discrepancy a physicist faces in the conclusions of the Archaeologists. We finally discuss the ultra-fast dispersion of the horse-chestnut leaf miner throughout Europe following recent work of ecologists.
Anomalous conductance and diffusion in complex networks
Authors: Havlin Shlomo , López Eduardo , Buldyrev Sergey V. , Stanley H. Eugene
Published: July 2024

We study transport properties such as conductance and diffusion of complex networks such as scale-free and Erdős-Rényi networks. We consider the equivalent conductance G between two arbitrarily chosen nodes of random scale-free networks with degree distribution P(k) ~ k−⋋ and Erdős-Rényi networks in which each link has the same unit resistance. Our theoretical analysis for scale-free networks predicts a broad range of values of G (or the related diffusion constant D), with a power-law tail distribution ɸSF(G) ~ G−gG, where gG = 2⋋ − 1. We confirm our predictions by simulations of scale-free networks solving the Kirchhoff equations for the conductance between a pair of nodes. The power-law tail in ɸSF(G) leads to large values of G, thereby significantly improving the transport in scale-free networks, compared to Erdős-R´nyi networks where the tail of the conductivity distribution decays exponentially. Based on a simple physical “transport backbone” picture we suggest that the conductances of scale-free and Erdős-Rényi networks can be approximated by ckAkB/(kA + kB) for any pair of nodes A and B with degrees kA and kB. Thus, a single parameter c characterizes transport on both scale-free and Erdős-Rényi networks.
Computer simulation of the formation of hollow nanocrystals
Authors: Belova Irina V. , Murch Graeme E.
Published: July 2024

Experiments on the formation of hollow nanocrystals of cobalt sulphide by way of the Kirkendall effect have been reported recently by Yin et al. We perform a set of Monte Carlo simulations of the process to explore the phenomenon.
Solid-state diffusion and NMR
Authors: Heitjans Paul , Indris Sylvio , Wilkening Martin
Published: July 2024

Diffusion in solids, which requires the presence of crystal defects or disorder, has both microscopic and macroscopic aspects. Nuclear magnetic resonance techniques provide access to microscopic diffusion parameters like atomic jump rates and activation energies as well as to the tracer diffusion coefficient for macroscopic transport. Microscopic NMR methods include spin-lattice relaxation spectroscopy of stable and beta-radioactive nuclei, spin-spin relaxation or linewidth and spin alignment decay measurements, whereas macroscopic NMR methods are represented by the techniques of static and pulsed field gradient NMR. We recall some basic principles of the mentioned techniques and review case studies for their application to various solids like glassy and crystalline aluminosilicates, nanocrystalline composites, an intercalation compound and a simple bcc metal. Taken together, jump rates in solids are covered over about 10 decades by the microscopic, and diffusion coefficients over 3 decades by the macroscopic NMR methods.
Carbon Interstitial Diffusion in gamma-Fe
Authors: Belova Irina V. , Murch Graeme E.
Published: July 2024

n this paper, we employ a four-frequency model for carbon diffusion in austenite where interstitials can diffuse either as isolated species or pairs. We make use of the Okamura and Allnatt formalism that has recently been shown to be near exact. The general finding of a previous analysis of McKee is confirmed: the increase of both tracer and chemical carbon diffusion coefficients with carbon composition at 1000°C is largely a result of a much higher rate of rotation of an interstitial pair compared with isolated interstitials. However, we find that the carbon atoms move almost two times faster as a rotating pair than found originally by McKee.
technological impact of diffusion in nanopores
Authors: Ruthven Douglas M.
Published: July 2024

The impact of nanopore diffusion on the performance of adsorption separation processes is reviewed. Zeolite membrane processes and kinetically selective cyclic adsorption processes depend for their selectivity on differences in intracrystalline diffusion rates so these processes are designed to operate under conditions of intracrystalline diffusion control. In contrast, the performance of equilibrium based adsorption separation processes is adversely affected by diffusional resistance so in such processes the minimization of all resistances to mass transfer is a major design objective. Zeolite catalyzed reactions constitute a further important class of processes in which intrusion of diffusional resistance can be either advantageous or disadvantageous. Such effects are illustrated by considering in detail the conversion of methanol to light olefins (MTO) over SAPO34. Within the chemical process industries diffusion is important over a wide range of length scales. In this paper we focus only on diffusion at the nanometer scale since diffusional phenomena on this scale are critically important in adsorption separation processes as well as in many heterogeneous catalytic systems. Indeed membrane separations and molecular sieving adsorption processes (kinetic separations) are driven by differences in nanoscale diffusivities. For such processes the conditions of operation must therefore be selected so as to maximize the influence of nanoscale diffusion. This is true also for certain catalytic processes in which product selectivity can sometimes be improved by operating under conditions of diffusion control. More commonly, in equilibrium controlled adsorptive separations and in catalytic systems where activity rather than selectivity is the important feature, process performance is adversely affected by nanoscale diffusion, and in such systems it is obviously desirable to design the process in such a way as to minimize the intrusion of diffusional resistances. Some examples of both classes of process are discussed
below.
Applications of pulsed gradient spin-echo NMR diffusion measurements to solution dynamics and organization
Authors: Price William S.
Published: July 2024

The study of solution dynamics is a very fundamental area of research with wide ranging importance from physical chemistry through to the life sciences. A common theme is that the interactions which control the dynamics and organization of solutions are generally very weak. Translational diffusion provides a non-invasive, direct and natural probe of the dynamics and pulsed gradient spin-echo (PGSE) NMR is a convenient means of measuring diffusion. This paper gives a brief introduction to translational diffusion as a probe of solution dynamics and of the PGSE NMR method before presenting some representative examples illustrating the power of diffusion measurements for elucidating the molecular behaviour. The use of PGSE NMR to study solution dynamics and organization is a very active area of research and a very large literature already exists, consequently, the coverage of possible applications and the literature cited here is not comprehensive.
Diffusion imaging of the brain
Authors: Norris David G.
Published: July 2024

This chapter presents a brief introduction to the application of diffusion-weighted magnetic resonance imaging (MRI) to in vivo studies. Diffusion-weighted MRI has found application both in the clinic, and in basic neuroscience. In the former situation it is primarily used for the detection of brain lesions, in particular infarcted regions. The ability to follow fibre tracts in white matter via diffusion tensor imaging has also made this methodology of interest to the neurosurgeon wishing to avoid severance of essential fibre tracts, but also of interest to the cognitive neuroscientist exploring anatomical connectivity in the brain. The chapter starts with a brief recap of the theory of diffusionweighted MRI and moves on to examine the two major experimental confounds, eddy currents and bulk motion. Current correction schemes for these problems are touched upon. Diffusion anisotropy is introduced as a potential source of artefacts for lesion detection in white matter, and the diffusion tensor model presented. The chapter concludes with a short introduction to fibre tracking.
Magnetic resonance relaxation measurements using open-geometry sensors to assess the clog state of constructed wetlands
Authors: Hughes-Riley Theodore , Webber John Beau , Newton Michael Ian , Morris Robert H.
Published: July 2024

Monitoring the T1 relaxation of wetland clog matter has previously been identified as a gauge of its clogged state [1]. Magnetic resonance (MR) sensors explored in other work have typically been of a bore-whole configuration, which may not be ideal in a wetland environment where the sensitive volume of the sensor may become physically clogged and therefore inoperable. This work investigates two open-geometry sensor designs and a short study is presented to determine the suitability of the sensors for monitoring the clog state of wetlands. It was shown that a bar magnet geometry has a higher stray field than that of the four magnet surface sensor also presented, leading to a prohibitively short T2 eff. This means that the T1 values collected are notably shorter and not useful for distinguishing between clog state for the single magnet sensor. By contrast the four magnet surface sensor has a longer T2 eff, making it more suitable for T1 measurements; where T1= 915 ± 212 ms for a very thinly clogged sample, and T1= 127 ± 27 ms for a heavily clogged sample. This offers a clearly resolvable difference in the T1 values allowing the clogging state to be easily determined and making this sensor the desirable choice for long-term embedding.
New instrumental platform for the exploitation of the field-dependence of T 1 in rock core analysis and petroleum fluids
Authors: Korb Jean-Pierre , Ferrante Gianni , Bubici Salvatore , Mallett Mike
Published: July 2024

We propose using the latest wide bore fast field cycling NMR relaxometers for measuring the nuclear magnetic relaxation dispersion (NMRD) profiles of the logarithmic average proton-water <1/T1> in carbonate rock cores samples of 1 inch diameter and in different crude oil/brine mixings. The observed bilogarithmic frequency behaviours of the NMRD have been interpreted with a proposed theoretical model yielding a measurement of the water local wettability at the pore surface. We have also proposed a NMR platform that uses a variable wide-bore cryogen-free superconducting magnet to acquire 2D T1-T2 correlation spectrum of a mixing of bulk water and crude oil pools. Such a T1-T2 plot allows quantitative separation of mixed bulk water and crude oil. The 2D plot does not reveal any exchange between the different and independent pools.
Matrix factorisations for the estimation of NMR relaxation distributions
Authors: Teal Paul D.
Published: July 2024

The two most successful methods of estimating the distribution of NMR relaxation times from two dimensional data are firstly a data compression stage followed by application of the Butler-Reeds-Dawson (BRD) algorithm, and secondly a primal dual interior point method using a preconditioned conjugate gradient (PCG). Both of these methods have been presented in the literature as requiring a truncated singular value decomposition of matrices representing the exponential kernels. Other matrix factorisations are applicable to each of these algorithms, and which demonstrate the different fundamental principles behind the operation of the algorithms. In the case of the data compression approach the most appropriate matrix decomposition specifically designed for this task is the rank-revealing QR (RRQR) factorisation. In the case of the interior point method, the most appropriate method is the LDL factorisation with diagonal pivoting, also known as the Bunch-Kaufman-Parlett factorisation. The details of these differences are discussed, and the performances of the algorithms are compared numerically.
Driven diffusion in nanoscaled materials
Authors: Albers Tony , Bauer Michael , Borczyskowski Christian von , Gerlach Frank , Heidernätsch Mario , Kärger Jörg , Kondrashova Daria , Radons Günter , Schubert Sebastian , Shakhov Alexander , Täuber Daniela
Published: July 2024

Mass transfer processes in which specific interactions with environments lead to complex diffusion patterns, such as the occurrence of transient sub-diffusive behaviors or of heterogeneous diffusion, were studied by means of two different experimental techniques, namely single-particle tracking operating with single molecules and nuclear magnetic resonance operating with large molecular ensembles. As an important point, the combined application of these techniques allowed for a deeper insight into the microscopic diffusion mechanism in such complex systems, including those with broken ergodicity. Particle tracking concentrated on the “Influence of substrate surface properties on heterogeneous diffusion of probe molecules in ultrathin liquid films”. The mobility of liquids at solid-liquid interfaces is influenced by substrate heterogeneities. Here we study the distribution of surface silanols on differently treated silicon wafers with thermal oxide by confocal florescence microscopy of adsorbed Rhodamine G molecules. We further investigate the influence of the substrate properties on probe molecule diffusion in ultrathin liquid TEHOS films by single molecule tracking. The results are compared to simulations of two-layer diffusion employing heterogeneous substrates. Nuclear magnetic resonance has been applied to study translational diffusion of small organic molecules in nanopores and of polymer globules in the presence of larger polymer species. In both cases, the experiments revealed the occurrence of normal diffusion on the time scale of NMR experiments from ten to hundreds of milliseconds. While single particle tracking revealed the identical diffusivities for the former case, thus experimentally confirming the validity of the ergodicity theorem for diffusion, the discrepancies were noted for the latter case. More complex behavior revealing non-ergodic behavior for propagation of solid-liquid interfaces in disordered nanopores has further been studied using nuclear magnetic resonance cryoporometry. A common basis for comparing and analyzing the experimental observables accessed by the two methods is the distribution of diffusivities, which provides the probability of observing a given diffusivity fluctuation along a trajectory or in an ensemble. An overview of its properties is given and the advantages in analyzing heterogeneous, anisotropic, or anomalous diffusion processes are elaborated.
Transport of isopropanol in H-ZSM5 by impedance spectroscopy
Authors: Nguyen Tien Quang , Glorius Maja , Breitkopf Cornelia
Published: July 2024

Gas diffusion mechanisms and diffusion coefficients in microkinetic system of solid materials characterize the different performance of chemical and transport processes. These factors should be evaluated with respect to the range of diffusion coefficients based on the number of experimental methods. Here, impedance spectroscopy which is a powerful tool for understanding transport phenomena of gases in nanostructured porous solids is used. In this work, we developed a new approach to compare and evaluate diffusion coefficients of isopropanol in the zeolite H-ZSM5. Furthermore, FTIR spectroscopy was used to study the adsorption of isopropanol in H-ZSM5 at different temperatures to support the interpretation of diffusion regimes. The combination of EIS with FTIR enables to illustrate preferred interaction sites and their influence on transport processes. The activation energy for transport of molecules in the channels is also calculated. Results are compared to literature data and suggest improved applications of EIS to characterize transport processes.
effect of surface roughness on Nuclear Magnetic Resonance relaxation
Authors: Nordin Matias , Knight Rosemary
Published: July 2024

Most theoretical treatments of Nuclear Magnetic Resonance (NMR) measurements of porous media assume ideal pore geometries for the pores (i.e. slabs, spheres or cylinders) with welldefined surface-to-volume ratios (S/V). This same assumption is commonly adopted for naturally occurring materials, where the pore geometry can differ substantially from these ideal shapes. In this paper the effect of the roughness of the pore surface on the T2 relaxation spectrum is studied. By homogenization of the problem using an electrostatic approach it is found that the effective surface relaxivity can increase dramatically in the presence of rough surfaces. This leads to a situation where the system responds as a pore with a smooth surface, but with significantly increased surface relaxivity. As a result the standard approach of assuming an idealized geometry with known surface to-volume and inverting the T2 relaxation spectrum to a pore size distribution is no longer valid. The effective relaxivity is found to be fairly insensitive to the shape of the roughness but strongly dependent on the width and depth of the surface geometry.
Concentration dependent diffusivities of model solvents in heavy oil
Authors: Mohan Vijitha , Neogi P. , Bai Baojun
Published: July 2024

The rates of dissolution of heavy crude oil in liquid solvents and rates of desorption of solvents from oil have been measured. The crude oil used is a non-volatile heavy oil of 4253 mPa.s viscosity at room temperature. The solvents used are hexane, heptane and toluene. When the oil (black) is contacted with a solvent (transparent) an interface is seen which moves with time and takes a very long time to become fuzzy. The rate of movementof the front is measured. The dissolution experiments give very consistent results, but there are two parameters involved, Do, the diffusivity at infinite dilution and alpha which determines the concentration dependence. As a result it is necessary to do desorption experiments to be able to calculate both constants from the rate of movement of the front data. However, desorption experiments could not be performed under conditions of low concentrations suitable for the present case because of the very viscous nature of the oil. As a result, although the desorption experiments also showed good results, they could not be used to obtain good values of the parameters. When Stokes-Einstein equation was used to calculate Do, excellent results were obtained with alpha ~ 10 for the dissolution experiments and good deal smaller for the desorption experiments. That result is used to conclude that the above form for concentration dependent diffusivity is correct and concentration dependence is very high at low solvent concentrations explaining the sharp interfaces during dissolution.Other evidences have also been offered.
Characterizing Interactions of Ionic Liquid Based Electrolytes with Electrospun Gas Diffusion Electrode Frameworks by 1H PFG NMR
Authors: Merz Steffen , Jakes Peter , Tempel Hermann , Weinrich Henning , Kungl Hans , Eichel Rüdiger-A. , Granwehr Josef
Published: July 2024

Pulsed field gradient (PFG) 1H NMR was used to characterize the mobility of ionic liquid cations in porous gas diffusion electrode (GDE) frameworks for metal–air electrochemical systems. The carbon GDE frameworks were produced by electrospinning. It was found that the motion of ionic liquids in the highly porous hosts is more complex than what is commonly exhibited by conventional fluids, which makes a multimodal investigation essential for an adequate description of mobility and wetting of GDEs. Observed NMR diffraction-like patterns cannot be linked to the tortuosity limit but may serve as a proxy for structural features in the fibrous material. While the observed data were interpreted using standard theoretical models, alternative explanations and causes for artifacts are discussed.
sorption dynamics of C3 hydrocarbons over carbon nanotubes
Authors: Onyestyák György , Ötvös Zsolt , Kiricsi Imre , Rees Lovat V. C.
Published: July 2024

Carbon nanotubes obtained by the catalytic vapor deposition (CVD) method were purified by various procedures to obtain samples in pure and well-defined forms. The frequency response (FR) technique was employed to determine the sorption dynamics of C3-hydrocarbons in these samples. Two parallel sorption processes were found, characterized by different sorption capacities and time constants and were assigned to sorption on the convex and concave surfaces of the carbon tubes, respectively. Over a carbon nanotube sample at low coverage the mass transport is little influenced by the different chemical nature of the various C3 hydrocarbons. However the dynamic sorption properties of carbon nanotube preparations were shown to be strongly affected by the absence or presence of surface functional groups on the outer and inner surfaces of the tube walls. Different rate-determining mechanisms were observed for the samples functionalized to different extents.
Diffusive transport of adsorbed n-alkanes along e-beam irradiated plane surfaces and nanopillars
Authors: Zhdanov Gleb S. , Lozhkin Maksim S.
Published: July 2024

Diffusion of adsorbed n-alkanes was studied by means of electron beam induced deposition (EBID) technique. Carbon ring-like and pillar-like deposits were produced on bulk and thin substrates in a scanning electron microscope (SEM) operated in a “spot” mode. Residual nalkanes used as a precursor gas were delivered to the beam interaction region (BIR) via surface diffusion. The model of adsorbate diffusion along a heterogeneous surface with different diffusion coefficients D1 and D2 outside and inside the BIR, respectively, was proposed to explain the measured deposition rates. The estimates for diffusion coefficients ranging from ~1x10-10 to ~1x10-7 cm2s-1 at room temperature on surfaces with different roughness were obtained. These estimates most likely should be attributed to n-decane molecules expected to play the key role in the deposition process. Clusters of polymerized molecules produced by irradiation were assumed to act as effective traps hampering surface diffusion. For high D1/D2 ratios the deposition rates were found to be practically independent of the substrate material and initial roughness.
Diffusion NMR: From catalysts to gelatin, a useful tool for exploring structure and dynamics in porous networks
Authors: D’Agostino Carmine
Published: July 2024

In this work several applications of the technique to systems of industrial relevance, including catalysts and gelatinous materials, will be presented.
Diffusive phase transformations in metallic glasses
Authors: Louzguine Dmitri V.
Published: July 2024

A large set of experimental results obtained by the author and colleagues related to the diffusionrelated effects and phase transformation observed in metallic glasses will be presented and discussed.
Using Diffusion-Diffusion Exchange Spectroscopy to observe diffusion exchange in yeast
Authors: Breen-Norris James O , Siow Bernard , Hipwell Ben , Roberts Thomas , Lythgoe Mark F. , Ianus Andrada , Alexander Daniel C. , Walker-Samuel Simon
Published: July 2024

The permeability of cell membranes varies significantly across both healthy and diseased tissue, and changes in cell membrane permeability can occur during treatment response in tumours. Measurements of cell membrane permeability could therefore be useful for tumour detection and as biomarkers of treatment response in the clinic. As the diffusion of water across the cell membrane is directly dependent on cell membrane permeability, we have investigated the ability of diffusion-diffusion exchange spectroscopy to quantify the diffusion exchange of water in a suspension of yeast, as a first step towards its application in tumours.
new look towards the determination of parameters of Heine and Abarenkov model potential using only vacancy formation energy in fcc crystals
Authors: Ghorai Amitava
Published: July 2024

The Heine and Abarenkov model potential (HAP) parameters (rc, A) have been calculated in this paper for twenty face-centered cubic (fcc) closed pack crystals. From the minimization of the structure dependent energy of the pure crystal the inter-relation between the two parameters of HAP has been initially determined. The calculation uses pseudopotential technique with nine different exchange correlation functions (ECF), either the available experimental value of the vacancy formation energy (EF1v) or that obtained from an empirical relation based on other experimental parameters (melting temperature, cohesive energy or activation energy) as tool. The variation of EF1v with the parameter A of HAP and ECF shows a sharp fall in EF1v near a very small value of A after which it shows constancy for all fcc crystals, and the parameters (rc, A) are determined near the bend. Comparison is made with other calculations and parameters of the Ashcroft model also. For increase in valency the parameter A of HAP increases and shows distinctly different curves.
Grain Boundary Segregation: the New Sprouts
Authors: Bokstein Boris , Itckovich Alexei , Pokhvisnev Yury , Rodin Alexei
Published: July 2024

Some aspects of grain boundary segregation (GBS) are discussed. This paper adds two new sprouts. The first is connected with formation of the atomic complexes in boundary region and their effect on grain boundary diffusion (GBD). The second – with a nonhomogeneity of energy distribution between boundary sites.
Surface diffusion: defining a new critical effective radius for holes in thin films
Authors: Zigelman Anna , Novick-Cohen Amy
Published: July 2024

We explore a specific small geometry containing a single thin bounded grain on a substrate with a hole at its center. By employing a mathematical model based on surface diffusion, no flux boundary conditions, and prescribed contact angles, we study the evolution of the hole as well as the exterior surface of the grain, based on energetic considerations and dynamic simulations. Our results regarding the formation and evolution of holes in thin films in small geometries shed light on various nonlinear phenomena associated with wetting and dewetting.
Local Atomic Mechanism for the Diffusion Jump of Carbon Atom in Austenite
Authors: Semenov Michael , Kraposhin Valentin , Arestov Vitali , Korolev Ilya , Pancho-Ramires Antonio
Published: July 2024

A carbon atom diffusion jump in iron austenite was considered as a subsequence of transformations between the cementite structure and the regular FCC packing. A model of this transformation was based on a 2D model of the elemental act of a polymorph transformation in metals. The energy threshold of this transformation has been calculated using the Morse pair potential. It occurs that the estimated enthalpy of the transformation is equal to 149±20 kJ/mole which is in satisfactory agreement with experimental data.
Nonequilibrium field-induced phase separation in single-file diffusion
Authors: Tabatabaei Fatemeh , Schütz Gunter M.
Published: July 2024

Using an analytically tractable lattice model for reaction-diffusion processes of hard-core particles we demonstrate that under nonequilibrium conditions phase coexistence may arise even if the system is effectively one-dimensional as e.g. in the channel system of some zeolites or in artificial optical lattices. In our model involving two species of particles a steady-state particle current is maintained by a density gradient between the channel boundaries and by the influence of an external driving force. This leads to the development of a fluctuating but always microscopically sharp interface between two domains of different densities which are fixed by the boundary chemical potentials. The internal structure of the interface becomes very simple for strong driving force. We calculate the drift velocity and diffusion coefficient of the interface in terms of the microscopic model parameters.
Water self-diffusion studies in complex materials with fast-relaxing components
Authors: Gädke Achim , Friedemann Karen , Galvosas Petrik , Stallmach Frank , Kärger Jörg , Nestle Nikolaus
Published: July 2024

Field gradient NMR techniques have proved very useful for measurements of molecular self-diffusion coefficients in many materials ranging from simple liquids to more complex materials such as polymer melts, porous media and biological tissues. In such multicomponent systems, spin relaxation phenomena may not only lead to a reduction of the signal intensity available for the field gradient NMR experiment but also to systematical errors in the measured diffusion coefficient due to unwanted relaxation time weighting. While pulsed field gradient (PFG) techniques allow better separation of relaxation and diffusion effects, they require at the same time longer echo times. This in turn aggravates unwanted weighting by transverse relaxation. For materials containing fast-relaxing components such as clayey sediments or partially hydrated cement the use of static field gradient (SFG) techniques suggests substantial benefits due to shorter echo times (i.e. less transverse relaxation time weighting). However, the separation of relaxation and diffusion effects is more difficult in SFG. In this contribution, we present the echo ratio approach to separate both effects and discuss its limitations. As we will show on the basis of experimental and calculated results, the echo ratio technique works well for homogeneous samples and complex materials with sufficiently long longitudinal relaxation times. In materials with components for which T1 is comparable or shorter than the diffusion time, however, this approach also fails and no meaningful interpretation of the SFG data on the basis of simple fit functions is possible so far.
Exploring the influence of the surface resistance of nanoporous particles on molecular transport
Authors: Krutyeva Margarita , Vasenkov Sergey , Kärger Jörg
Published: July 2024

Molecular transport through the nanoporous particles, in particular, zeolite crystallites, is influenced both by intracrystalline diffusion and surface resistance. In comparison to zeolite crystallites with ideal structure, molecular transport in real-world zeolite particles may often be influenced by the surface barriers resulting from various defects at the surface of the crystallite. The potentials of the combined use of the pulsed field gradient NMR and dynamic Monte Carlo simulations for exploration of the surface permeability of nanoporous particles are demonstrated.
QENS and the benefit of diffusion measurements over different length scales
Authors: Jobic Hervé
Published: July 2024

The quasi-elastic neutron scattering (QENS) technique was first used to derive self-diffusivities of hydrocarbons in zeolites, but transport diffusivities of deuterated molecules and of molecules which do not contain hydrogen atoms can now be measured. The technique allows to probe diffusion over length scales ranging from an Å to hundreds of Å. The mechanism of diffusion can thus be followed from the elementary jumps between adsorption sites to Fickian diffusion. Since the space and time scales of the neutron techniques match closely the ones covered by molecular simulations, one expects, and usually finds, good agreement between neutrons and simulations. The neutron data give therefore reference values, so that lower values obtained by other techniques measuring diffusion over longer length scales have to be explained by additional transport barriers.
NMR diffusion diffraction and diffusion interference from cells
Authors: Kuchel Philip W. , Pages Guilhem
Published: July 2024

Pulsed field gradient spin-echo (PGSE) NMR spectroscopy is the definitive means for measuring translational motion of molecules in free solution and in heterogeneous systems. A unique ‘twist’ on the method is that in some systems in which diffusion is restricted the PGSE experiment yields information on the geometrical properties of the confining boundaries. When applied to red blood cells (RBCs) in suspensions, using intense magnetic field gradients (around 10 T m-1), the graph of normalized NMR-signal intensity versus the magnitude of the field gradients has the form of the diffraction and interference patterns that are seen in physical optics. We review here the nature of these so called q-space plots and discuss a data-processing method that adds objectivity to estimates of the mean RBC diameter. Convection potentially interferes with the veracity of these measurements so an experiment is reported in which a cell-free sample was deliberately made to flow. The very simple analysis of flow diffraction yielded estimates of flow that were in remarkable agreement with gravimetric measurements. Finally, in a theoretical study using a model of uniformly arrayed octagonal prisms that were ‘morphed’ in a systematic way, the dependence of the form of q-space plots on prism shape and packing density was obtained. This showed that elaborately shaped q-space plots can be obtained from simple periodic arrays of ‘cells’. The uniqueness or otherwise of shapes of q-space plots, and the prospect of generally solving the inverse problem whereby q-space analysis yields detailed information on packing arrangements is poised for further detailed investigations.
Diffusive thermal instabilities of C4H10-C3H8 / Air Laminar Premixed Flames
Authors: Abdulwahid Mazlan , Saqr Khalid M. , Sies Mohsin M. , Ujir Haffis
Published: July 2024

Preferential heat and mass transfer induces diffusive thermal instabilities in premixed laminar flames. Such instabilities in hydrocarbon flames are characterized by cellular structure and a tendency to promote flame extinction. We investigate the properties of such instabilities in C4H10-C3H8 /air flames. The adiabatic burning velocity of the laminar premixed flame was measured at different equivalence ratios while exhibiting cellular instabilities. Direct photographs have been captured to qualitatively asses the effect of burner plate temperature on the cellular structure of the flame. The present study preliminarily suggests a normal logarithmic correlation to predict the adiabatic burning velocity of diffusive thermal instabilities in laminar premixed C4H10-C3H8 /air flames.
La IA como herramienta de búsqueda de antecedentes de investigación económica: Perspectiva de estudiantes universitarios
Authors: Férez Vergara José Luis
Published: July 2024

El presente artículo abarca el impacto de la Inteligencia Artificial (IA) en la investigación económica universitaria, resaltando su capacidad para automatizar tareas metodológicas complejas. El objetivo de la investigación es analizar la perspectiva de los estudiantes de economía sobre la utilidad de la IA en la búsqueda de antecedentes para trabajos académicos, centrándose en la experiencia y la calidad de los resultados. Para su desarrollo se citaron estudios que sugieren que la IA puede mejorar la eficiencia y la calidad de los trabajos de investigación. La metodología del estudio es no experimental, con un enfoque cuantitativo y analítico. Se utilizó un alcance descriptivo y exploratorio, con un método de muestreo no probabilístico por conveniencia que abarcó 130 estudiantes de la Carrera de Economía de la Facultad de Ciencias Sociales y Derecho de la Universidad Laica Vicente Rocafuerte de Guayaquil, Ecuador. Se aplicó la técnica de la encuesta, con un cuestionario como instrumento diseñado en Google Form. La recopilación de datos se realizó en línea, a través del correo institucional de los discentes. Los resultados mostraron que el 58.5% de los estudiantes utiliza ocasionalmente la IA para buscar antecedentes, y el 41.5 % se muestra neutral en cuanto a la satisfacción con su efectividad. El estudio permitió identificar desafíos, como la dificultad para encontrar información relevante y problemas con la calidad de los resultados. Se concluyó que aunque la IA es ampliamente adoptada, la diversidad en la satisfacción y los desafíos identificados indican la necesidad de enfoques cuidadosos y programas de mejora continua.
EDUCATION ON THE IMPLEMENTATION OF ORGANIZATIONAL CITIZENSHIP BEHAVIORAL HEAD OF HAMLET IN THE MANAGEMENT OF SITULEUTIK TOURIST DESTINATION IN CIBEUREUM VILLAGE, BANJAR CITY
Authors: Muliawaty Lia , NR. Ruyani  , Fitri Farizah  , M. Yusuf
Published: July 2024

The behavior is carried out without coercion or expecting any reward. The extraordinary quality of service and the dedication to work with high standards are clear signs that OCB's behavior is present in every village apparatus in the organization. This behavior describes the added value of employees, a form of prosocial behavior, namely positive, constructive, and meaningful social behavior that helps the village organization progress. The approach method used to achieve the output, the community involvement PKM program in the Organizational Citizenship Behavior (OCB) mechanism taught, will be adapted through socialization. These goals can be achieved through 2 (two) approaches. The PkM team accompanied the PkM participants to make a presentation related to the importance of OCB being understood to reach an understanding regarding the authority and implementation of programs carried out by Village Heads, Urban Villages, and related agencies, including the Banjar City Youth, Sports, and Tourism Office. This understanding is related to OCB because it can increase the effectiveness and welfare of the organization. This voluntary behavior creates a positive work environment, reduces conflict, and increases team collaboration. The discussion of OCB usually involves the application of this concept in the context of human resource management (HRM) and organizational strategy. Understanding and managing OCB can help organizations create a productive and positive work environment.
SOCIALIZATION OF PREVENTION OF JUVENILE DELINQUENCY FOR THE REALIZATION OF A QUALITY YOUNG GENERATION
Authors: Rohaeti Titi , Muchammad Sape  , Cica Ratna Ningsih  , Dewi Anggita  , Ella Nur Amelia
Published: July 2024

The implementation of Community Service activities, especially in the SMP Negeri 2 Sumber school, is a form of our concern for students so that they avoid juvenile delinquency. According to Amdadi et al. (2021), adolescence is a transition period from childhood to adulthood, and during this period, there have been various physiological, social, and emotional changes. They want freedom so that they can cause conflicts within themselves, so they need a way to understand the essence and way of thinking of teenagers. We hope that this socialization can be a provision for students in facing their adolescence because, in this activity, we give them an overview of what they will face when they step on teenagers, the types of juvenile delinquency, the impact of juvenile delinquency, and solutions when facing a problem. This service involved field supervisors, pamong teachers, and PPL students. We carry out pretest (before) and posttest (after) this service to ensure our research's scientific rigor and validity. The results of the pretest and posttest that we conducted showed an increase in students' understanding of the impact of juvenile delinquency so they were more vigilant in socializing.
Penyuluhan Hukum Untuk Meningkatkan Kesadaran Tentang Bahaya Narkoba Dan Kekerasan Seksual Di Karang Taruna Desa Kebonsari Baru Jambangan – Surabaya
Authors: Ari Kosasih  , Rafli Hamzan Aryaputra  , Diva Faradhilla Ayu Amelia  , Wahyu Fadhilla Akbar  , Renalda Risdiyanti Putri
Published: July 2024

The problem of drug abuse and victims of sexual violence is something that has occurred in society from the past until now. Cases like this must be handled quickly because it is a case that causes a lot of victims who cannot be said to be in small numbers in the community. Actually in this case there is no target age desired by the perpetrator to carry out his actions in committing one of these criminal acts. As what is meant in this case is that there are still many children who are still minors who are the future generation of the nation in the future even become victims of drug abuse and sexual violence. Therefore, we should increase efforts to reduce or even stop cases like this. The community must also be careful of people they don't know to be aware of themselves so that they become victims of drugs and victims of sexual violence.