bluuebunny/crossref_metadata_2025 huggingface dataset:
Influência da obesidade na mortalidade, na duração da ventilação mecânica e na mobilidade de pacientes críticos com COVID-19
Authors: Martinato Luísa Helena Machado , Schmidt Débora , Piva Taila Cristina , Deponti Gracieli Nadalon , Graboski Maricene Colissi , Plentz Rodrigo Della Méa , Sbruzzi Graciele
Published: July 2024

RESUMO Objetivo Identificar a influência da obesidade na mortalidade, no tempo de desmame da ventilação mecânica e na mobilidade na alta da unidade de terapia intensiva em pacientes com COVID-19. Métodos Trata-se de estudo de coorte retrospectivo realizado entre março e agosto de 2020. Foram incluídos todos os pacientes adultos internados na unidade de terapia intensiva com necessidade de suporte ventilatório e diagnosticados com COVID-19. Os desfechos incluíram mortalidade, duração da ventilação mecânica e mobilidade na alta da unidade de terapia intensiva. Resultados Identificamos 429 pacientes, dos quais 36,6% estavam acima do peso e 43,8% eram obesos. Em comparação com os pacientes com índice de massa corporal normal, os pacientes com sobrepeso e obesidade apresentaram menor mortalidade (p = 0,002) e maior sobrevida na unidade de terapia intensiva (log-rank p < 0,001). Em comparação com pacientes com índice de massa corporal normal, aqueles com sobrepeso tiveram risco 36% menor de morte (p = 0,04), enquanto os pacientes com obesidade apresentaram risco 23% menor (p < 0,001). Não houve associação entre obesidade e duração da ventilação mecânica. O nível de mobilidade na alta da unidade de terapia intensiva não diferiu entre os grupos e apresentou correlação inversa moderada com o tempo de internação na unidade de terapia intensiva (r = -0,461; p < 0,001). Conclusão Os pacientes com sobrepeso e obesidade tiveram menor mortalidade e maior tempo de sobrevida na unidade de terapia intensiva. A duração da ventilação mecânica e o nível de mobilidade na alta da unidade de terapia intensiva não diferiram entre os grupos.
Application of low field and solid-state NMR spectroscopy to study the liquid/liquid interface in porous space of clay minerals and shales
Authors: Borysenko Artem , Clennell Ben , Burgar Iko , Dewhurst David , Sedev Rossen , Ralston John
Published: July 2024

In petroleum research understanding displacement, redistribution, and adsorption of oil and water plays an important role. To study complex multi-component systems such as liquid/liquid/mineral interactions in the porous space of clays and shales we applied low field (2 – 15 MHz) and high resolution (300 MHz) NMR spectroscopy. The detailed NMR analysis shows that the results from low field NMR measurements are in good correlation with the solid-state data. Consequently the process of liquid/liquid displacement can be characterised by considering the relaxation times, signal amplitudes and chemical shifts together.
Monte-Carlo simulations of the two-dimensional NMR T2-T2 exchange of fluids in porous media
Authors: Moldovan Daniel , Fechete Radu , Demco Dan Eugen , Culea Eugen , Blümich Bernhard
Published: July 2024

The effects of molecular exchange processes on the two-dimensional (2D) NMR T2-T2 distributions obtained by Laplace inversion were studied by numerical simulations. The Monte–Carlo technique is used to generate free random walks of a large number of molecules within space regions characterized by different relaxation times. Molecular exchange processes are considered during CPMG encoding periods as well as during the storage period, τstore. Systematic simulations were performed as function of NMR parameters like the storage period, τstore and geometric or physical system properties.
effect of framework flexibility on diffusion of small molecules in the metal-organic framework IRMOF-1
Authors: Ford Denise C. , Dubbeldam David , Snurr Randall Q.
Published: July 2024

Many efforts have been made to model adsorption and diffusion processes in metalorganic frameworks (MOFs) in the past several years. In most of these studies, the framework has been kept rigid. In this study, we examine the effect of using a flexible framework model on the self-diffusion coefficients and activation energies calculated for several short n-alkanes and benzene in IRMOF-1 from molecular dynamics simulations. We find only minor differences between flexible and rigid framework results. The selfdiffusion coefficients calculated in the flexible framework are 20-50% larger than the ones calculated in the rigid framework, and the activation energies differ by only 10-20%.
Contribution to the understanding of the point defect influence on some transport properties in UO2+x
Authors: Riahi Fatma , Laouar Sofiane , Mekki Djamel Eddine
Published: July 2024

A point defect model is developed in hyperstoichiometric uranium dioxide, UO2+x,in order to explain some experimental results of deviation from stoichiometry and electrical conductivity existing in the literature. This model takes into account both singly charged uranium vacancy, V'U , and two types of Willis clusters, characterized by two kinds of interstitial oxygen atoms that are located on two different sites and two oxygen vacancies, namely 2(Oi"Oi''Vȯ)4' and . The electron holes, ḣ , are also introcued to ensure the crystal global electroneutrality. An adjustment procedure of the most convincing experimental data of the literature, corresponding to the temperature and oxygen partial pressure dependencies of departure from stoichiometry,x, and electrical conductivity, [sigma] , has been undertaken. The fit model/experience obtained has been found fairly good, justifying, a posteriori, the relevance of the nature of the selected defects in the model.
Relation between self diffusion and interdiffusion in Al-Cu melts
Authors: Zhang Bo , Griesche Axel , Meyer Andreas
Published: July 2024

We compare the experimental interdiffusion constants DAlCu in liquid Al81.3Cu18.7 at% to the experimental Cu self diffusion constants DCu in a similar Al80Cu20 at% melt. DAlCu are measured by an X-ray radiography technique and DCu are measured by the quasielastic neutron scattering method. It was found that DAlCu is enhanced by a factor of 3 with respect to DCu. The relation between DAlCu and DCu is investigated in the context of Darken’s equation where the interdiffusion constant DAB in a binary A-B system is approximated by a simple linear combination of the self diffusion constants DA and DB, DAB = (DAXB + DBXA)Φ (with XA and XB the mole fractions of A and B particles, respectively, and Φ the thermodynamic factor representing the thermodynamic driving force for interdiffusion). We also present a calculation of Φ from the Gibbs free energy data in molten Al-Cu. With these calculated Φ and the DCu data, interdiffusion coefficients in liquid Al-Cu have been calculated. However, the experimental DAlCu are larger than the calculated ones by a factor of 2. These results suggest that the enhancement of interdiffusion in Al-Cu liquids can not be only attributed to the thermodynamic driving force. Here we propose that the missing factor of about 2 in the Darken equation comes from the contribution of cross correlations to interdiffusion in Al-Cu liquids.
Effect of catalyst pore size on styrene production rate
Authors: Zeynali Mohammad Ebrahim
Published: July 2024

In this study the diffusion coefficients for reaction components were determined for unimodal and bimodal pore size distribution and assuming transitional diffusion regime using a more realistic, Stewart-Johnson, method. It was found that determination of diffusion coefficient using the average pore size results in underestimated values. A comparison was made between the effects of unimodal and bimodal pore size distribution on diffusion coefficients. The governing differential equation for a single pellet for styrene production was solved by orthogonal collocation method. The effectiveness factor which is a key parameter in reactor design was determined for the reaction in practical range of pore size. It was found that the production rate and effectiveness factor are sensitive to pore size and pore size distribution and with certain pore size distribution a considerable improvement in production rate can be achieved.
Water diffusion in q-space imaging as a probe of cell local viscosity and anomalous diffusion in grey and white matter
Authors: Nicolas Renaud , Aubry Florent , Pariente Jérémie , Franceries Xavier , Chauveau Nicolas , Saint-Aubert Laure , Chollet François , Breil Stephane , Celsis Pierre
Published: July 2024

Extraction of accurate quantitative parameters to characterize water diffusion in complex porous media like brain tissue in neuroimaging is a challenging inverse problem, that depends on medium\''s structural and geometrical factors [1,3]. If the role of membranes is generally invoked, probe collisions with the insoluble cytoskeleton network and water hydrodynamic interactions with dissolved macromolecules and cytoskeleton occur as well [2]. The latter two interactions have been shown to determine the phenomenological “anomalous diffusion” of probes in the cytoplasm [4,5,6,7,8]. Additionally, the diffusion of small solutes in cytoplasm could be slowed by the local micro-viscosity of the aqueous phase, a phenomenon generally not taken into account in simulations. We suggest that the Grey and White Matter contrast in Diffusion Decay Imaging (DDI) could be caused by differences in cytoskeleton structures, composed respectively of actin and tubulin that could act by the elimination of one possible water diffusion pathlength by the volume occupied by the network phase. This could explain why anomalous DDI signal has been shown to be independent of membrane integrity [9]. Cytoplasm is able to rapidly shift from a sol (aqueous solutions embedded with insolubles particles) to a gel state (a colloidal solutions with a structured semi-solid and an aqueous fluid phase) or to a viscous solution when the insoluble particles become soluble. Does water have the ability of being a sensor of its local “self-viscosity” ? What is the length of the water diffusion\''s path compared to cells size ? Compared to this path length, how many cellular structures should be probed by water\''s translational diffusion ? We try to respond to these questions by investigating Diffusion Decay Imaging models and their effects on the hypothese-free q-space diffusion propagator shape [3], containing all informations concerning viscosity-slowed gaussian diffusion, structural informations [3] and restricted diffusion [1].
Structure-Transport relationship in organized soft matter systems by diffusion NMR
Authors: Hazelbaker Eric , Katihar Aakanksha , Sanders Monica , Menjoge Amrish , Vasenkov Sergey
Published: July 2024

In this paper we demonstrate and discuss the potentials of pulsed field gradient nuclear magnetic resonance (PFG NMR) at high magnetic field and high magnetic field gradients for uncovering the relationship between the structural and transport properties of soft matter systems. The reported diffusion studies are focused on room temperature ionic liquids and their mixtures with carbon dioxide or water as well as on multicomponent lipid bilayers. Both types of systems exhibit a well-defined structural organization on various length scales. Our experimental approach allows correlating this structural organization with the transport properties. The diffusion data were obtained by proton and carbon-13 PFG NMR. The experimental studies were in some cases complemented by dynamic Monte Carlo simulations.
Volume interdiffusion coeffcient and uncertainty assessment for polycrystalline materials
Authors: Léchelle Jacques , Noyau S. , Aufore Laurence , Arredondo Antoine , Audubert Fabienne
Published: July 2024

A method has been developed in order to assess small volume interdiffusion coeffcients from experimental Electron Probe MicroAnalysis concentration profiles of polycrystalline materials by means of Boltzmann-Matano or den Broeder methods and their complementary Hall method. These methods have been used as tools for the investigation of the quasi-binary UO2/U(1-y)PuyO(2-z) interdiffusion, for which obtaining a solid solution in the bulk of grains is of major interest. In this paper uncertainties on the interdiffusion coefficient as a function of concentration have been computed for each method. Small volume cofficient measurements were enhanced by means of a small angle acquisition profile line with respect to the interdiffusion interface.
Calculation of parameter of Ashcroft’s potential using vacancy formation energy for bcc metals like Cr, Mo, W, V, Nb, Ta, Tl, Eu and Zr
Authors: Ghorai Amitava , Choudhury Tirthankar , Das Arjun , Dey Rajesh , Ganguly Sourav
Published: July 2024

Variation of vacancy formation energy with the parameter of Ashcroft\''s model for nine different exchange and correlation functions show almost similar nature for the bcc metals like Cr, Mo, W, V, Nb, Ta, Tl, Eu and Zr. The mean value of this parameter for these bcc metals are respectively 1.173, 1.383, 1.458, 1.263, 1.478, 1.489, 1.802, 2.222 atomic unit.
Quantification of MRI sensitivity for mono-disperse microbubbles to measure subatmospheric fluid pressure changes
Authors: Alrwaili Amgad , Bencsik Martin
Published: July 2024

It would be very beneficial to perform MRI of fluids and sense the fluid pressure changes. Our aim is to demonstrate a contrast agent capable of MR sensitivity to sub-atmospheric pressure changes. To achieve this, monodisperse microbubbles were prepared with an optically measured mean radius of 1.4 ± 0.8 μm. A repeated pressure change cycle was applied on the microbubble contrast agent, until it produced an MR signal change solely due to the bubble radius change. The bubbles’ contribution to the relaxation rate before and after applying sub-atmospheric pressure changes was estimated and its echo time dependence modelled, so as to inform the mean radius change. The periodic subatmospheric pressure change was further applied until the MR signal change was only due to the bubble radius change. An excellent MR sensitivity of 28 % bar-1 is demonstrated, bubble radii of 2.4 and 1.8 μm are numerically estimated before and after the application of pressure, and the simulations are further used to estimate the optimum bubble radius maximising the MR sensitivity to a small change in radius.
1H and 19F FFC-NMR of catalyst layer materials for polymer electrolyte membrane fuel cells
Authors: Yamaguchi Makoto , Ohira Akihiro
Published: July 2024

1H and 19F spin lattice relaxation rates of catalyst layer materials (CLM) of polymer electrolyte membrane fuel cells were measured by the fast field cycling (FFC) method. In contrast to ionomer membranes, 1H relaxation rates of adsorbed water in both platinum-Ketjen black (Pt-KB) catalyst powder and CLM were strongly dependent on Larmor frequency approximated by a power law due to the strong surface interaction of adsorbed water. The difference in the frequency dependence in the Pt-KB and the CLM was attributed to higher acidity of the CLM.
Ion-Isotopic exchange reaction kinetics in characterization of anion exchange resins Dowex 550A LC and Indion-820
Authors: Singare Pravin U.
Published: July 2024

The present paper involves application of nondestructive radioactive tracer technique in characterization of Dowex 550A LC and Indion-820 anion exchange resins. The characterization study was based on kinetic of exchange reactions between inactive iodide/bromide ions on the resins with radioactive iodide/bromide ions in the solution. During iodide exchange reaction performed at a constant temperature of 40.00C, using 1.000 g of ion exchange resins and labeled iodide ion solution of concentration 0.003 mol/L, for Dowex 550A LC resin the specific reaction rate and initial rate of ion exchange was 0.271 min-1 and 0.141 mmol/min respectively, while the amount of iodide ions exchanged was 0.522 mmol, and log Kd was calculated to be 12.1. The above values calculated for Dowex 550A LC resin was higher than the respective values of 0.108, 0.330, 0.036 and 6.0 as obtained for Indion-820 resins. Similar results were obtained for the two resins during bromide exchange reactions, thereby indicating superior performance of Dowex 550A LC resin over Indion-820 resins.
Phenomenological coefficients in solid-state diffusion
Authors: Murch Graeme E. , Belova Irina V.
Published: July 2024

In this review, which is intended as an introduction to the subject, we introduce the phenomenological transport coefficients in solid-state diffusion and discuss their structure and physical meaning. Next, we discuss the Darken, the Manning, the Moleko, Allnatt and Allnatt and the Heumann expressions which relate the phenomenological coefficients to the (measurable) tracer diffusion coefficients. Finally, we discuss the relationships (sum-rules) among the phenomenological coefficients themselves in randomly mixed systems and note their applicability for simplifying collective diffusion problems.
Molecules dancing in membranes
Authors: Vattulainen Ilpo
Published: July 2024

In 1828, a botanist named Robert Brown found that small pollen particles suspended in water migrated in an erratic fashion. Later it was realized that the dance Brown observed was essentially a two-dimensional random walk driven by thermal fluctuations, thus this Brownian motion was more intense at higher temperatures. The pioneering ideas and observations by Brown have inspired people for a long time to think about the fascinating aspects of random walks, and hence of diffusion. In this brief contribution, we consider this topic at complex biological interfaces known as cellular membranes and discuss how the dance of lipids and small molecules can be quantified through experiments and theoretical approaches. Some illustrative examples of diffusion in membrane systems are discussed.
Investigating effects from restricted diffusion in multi-component diffusion data
Authors: Pavlin Tina , Seland John Georg
Published: July 2024

We have investigated model systems in which effects from non-Gaussian restricted diffusion could be separated from effects caused by multiple diffusion coefficients. We applied various models to analyze the experimental data. An analysis based on multi-exponential models does not account correctly for effects caused by restricted diffusion in a system with multiple compartments. However, separating the components due to differences in dynamic behavior prior to the diffusion analysis, combined with a diffusion analysis based on the second cumulant approximation, was more robust, and was able to handle effects from restricted diffusion in the presence of multi-component diffusion.
Reconstructing undersampled MR Images by utilizingprincipal-component-analysis-based pattern recognition
Authors: Zong Fangrong , D’Eurydice Marcel Nogueira , Galvosas Petrik
Published: July 2024

Compressed sensing technique is a recent framework for signal sampling and recovery. It allows signal acquisition with less sampling than required by Nyquist-Shannon theorem and reduces data acquisition time in MRI. When the sampling rate is low, prior knowledge is essential to reconstruct the missing features. In this paper, a different reconstruction method is proposed by using the principal component analysis based on pattern recognition. The experiments demonstrate that this method can reduce aliasing artefacts and achieve a high peak signal-to-noise ratio compared to a compressed sensing reconstruction.
Diffusion and conformational dynamics in locally perturbed model membrane systems
Authors: Petrov Eugene P. , Schwille Petra
Published: July 2024

In this article, we review our results on diffusion and phase separation in lipid membranes, as well as on interaction of membranes with colloidal particles, biomacromolecules, and supramolecular assemblies, which were obtained within the framework of the Saxon Research Unit FOR 877 “From Local Constraints to Macroscopic Transport”.
occurence of cocaine in Egyptian mummies
Authors: Görlitz Dominique
Published: July 2024

One of the unsolved problems of modern science is whether the pre-Columbian peoples of the New World developed completely independently of cultural influences from the Old World or if there was a trans-oceanic contact? A number of scientists agree that there are many – and often remarkable – similarities between the cultures of pre-Columbian America and those of the Mediterranean world. Nevertheless, there is no agreement, as yet, on how cultural diffusion can be differentiated from independent invention. Scientific analysis shows that scholarly positions are often strongly pre-formed from paradigms (scientific based assumptions), which tend to hinder consideration of solid scientific data offered by geo-biology and its trans-disciplinary examination of the subject under investigation here. An unambiguous answer to the question, what historical processes led to the emergence of the ancient American agriculture, hasn\''t been given. However, the archaeological discovery of crops with clear trans-oceanic origin, in addition to advances in molecular biology, increasingly support the hypothesis that humans from the distant past influenced each other across the oceans at a much earlier stage. The vegetation and zoo-geography indicate, by numerous examples that some species could only have spread through perhaps unintentional (passive) human transmission [1]. There are two very old crops found in the „New World‟, which contradict the paradigm of a completely independent origin for American agriculture. These are the African Bottle Gourd (Lagenaria siceraria L.) and the ancestral cotton species (Gossypium herbaceum L.) of the domesticated spin able sub-genus of tetraploid cotton. The historical spread of both types has been under discussion for decades, especially in respect of trans-oceanic human contact with the American continent. There has also been a debate in the \"Old World\" ever since the discovery of nicotine and cocaine in Egyptian mummies, centering around whether \"New World\" plants (or the ingredients) might have been transmitted in the reverse direction, back to the presumed start in centers of the Ancient World\''s oldest civilizations.
What are, and what are not, Inverse Laplace Transforms
Authors: Fordham Edmund J. , Venkataramanan Lalitha , Mitchell Jonathan , Valori Andrea
Published: July 2024

Time-domain NMR, in one and higher dimensionalities, makes routine use of inversion algorithms to generate results called \T2-distributions' or joint distributions in two (or higher) dimensions of other NMR parameters, T1, diffusivity D, pore size a, etc. These are frequently referred to as \Inverse Laplace Transforms' although the standard inversion of the Laplace Transform long-established in many textbooks of mathematical physics does not perform (and cannot perform) the calculation of such distributions. The operations performed in the estimation of a \T2-distribution' are the estimation of solutions to a Fredholm Integral Equation (of the First Kind), a different and more general object whose discretization results in a standard problem in linear algebra, albeit suffering from well-known problems of ill-conditioning and computational limits for large problem sizes. The Fredholm Integral Equation is not restricted to exponential kernels; the same solution algorithms can be used with kernels of completely different form. On the other hand, (true) Inverse Laplace Transforms, treated analytically, can be of real utility in solving the diffusion problems highly relevant in the subject of NMR in porous media.
Parameter dependence of ballistic velocity in deterministic diffusion in the form of devil's staircase
Authors: Miyazaki Syuji , Yoshida Masaomi , Fujisaka Hirokazu
Published: July 2024

By using simple extended mapping models showing chaotic diffusion, nonperturbative non-Gaussian characteristics of diffusive motion are examined in the framework of the large deviation statistical theory. Furthermore by rigorously solving the large deviation statistical quantities, it is found that the same type of anomalous, complex control parameter dependence as that for the diffusion coefficient reported by Klages and Dorfman is also observed in the large deviation statistical quantities such as the weighted average, the generalized diffusion coefficient and the generalized power spectrum densities.
Simulation of Fick’s verification of the 2nd law
Authors: DiDomizio Richard , Lupulescu Afina , Glicksman Martin E.
Published: July 2024

Adolph Fick’s original diffusion experiments used two vessels containing water and salt to establish a steady-state concentration gradient that demonstrated the validity of what is now called Fick’s second law of diffusion. The first vessel had a cylindrical shape creating a linear gradient. The second vessel was shaped like a funnel having a correspondent variable flow area. Using Fick’s second law, general solutions for any shape of the vessel are developed for steady diffusion in two and three dimensions, respectively. Two dimensional random walks were performed via computer simulations, and the numerical results are compared to continuum theory. Provided that a sufficiently large number of steps are simulated to allow the random walkers to traverse the total diffusion path, good agreement is achieved between discrete “molecular” motions (random walk) and the classical continuum description provided by scalar field theory (partial differential equations).
Boundary-induced bulk phase transition and violation of Fick's law
in two-component single-file diffusion with open boundaries
Authors: Brzank Andreas , Schütz Gunter M.
Published: July 2024

We study two-component single-file diffusion inside a narrow channel that at its ends is open and connected with particle reservoirs. Using a two-species version of the symmetric simple exclusion process as a model, we propose a hydrodynamic description of the coarse-grained dynamics with a self-diffusion coeffcient that is inversely proportional to the length of the channel. The theory predicts an unexpected nonequilibrium phase transition for the bulk particle density as the external total density gradient between the reservoirs is varied. The individual particle currents do not in general satisfy Fick''s first law. These results are confirmed by extensive dynamical Monte-Carlo simulations for equal diffusivities of the two components.
Mathematical modeling and visualization of gas transport in a
zeolite bed using a slice selection procedure
Authors: Petryk Mykhaylo , Leclerc Sebastien , Canet Daniel , Fraissard Jacques
Published: July 2024

We present the analytical solution of the equations of gas diffusion in a heterogeneous zeolite bed. The problem is handled by assuming that the bed consists of a large number of very thin layers of solid, perpendicular to the direction of propagation of the gas. Mass transfer by diffusion in such a material is determined by a system of differential equations with boundary and interface conditions. The results allow the theoretical determination of the time dependence of the concentration profiles and the inter- and intra-crystallite diffusion coefficients of a gas in each layer of the bed. A numerical application concerns the diffusion of benzene in a cylindrical bed of ZSM5 displaced vertically and rapidly, step by step, inside the NMR probe. Thus we can obtain the time dependence of the concentration of gas absorbed at the level of each slice. These coupled investigations give a better understanding of the diffusion process in this multilayer material.
Multiple correlation function approach
Authors: Grebenkov Denis S.
Published: July 2024

The multiple correlation function approach is briefly presented and applied to investigate spin-echo signal attenuation due to restricted diffusion in simple geometries (slab, cylinder, and sphere) in the presence of surface relaxation. Exact and explicit representations for the zeroth and second moments of the total phase accumulated by diffusing spins are derived by using the Laplace transform summation technique. Within the Gaussian phrase approximation, these two moments determine the reference and diffusion-weighted signals, respectively. In the slow-diffusion or short-time regime, the series expansion in half-integer powers of the diffusion coefficient is generalized to arbitrary temporal profile of a linear magnetic field gradient. In the motional-narrowing or long-time regime, it is shown how the presence of surface relaxation modifies the classical Robertson’s relation. Practical consequences of these findings are discussed.
Analytical solution for the time dependent self-diffusion coefficient of a liquid in a porous medium
Authors: Loskutov Valentin , Sevriugin Vyacheslav
Published: July 2024

The purpose of our work is to attempt to find the analytical expression approximating the experimentally obtained D(t) dependence of molecules of liquids or gases, in porous systems. The statement of the problem is based on the most general representations of self-diffusion processes in porous systems.
Long-term observation of adsorbed heavy metal ions in sediment samples by MRI
Authors: Nestle Nikolaus , Ebert Martin , Wunderlich Arthur , Baumann Thomas
Published: July 2024

Recently, we have reported studies of transport and sorption of heavy metal ions in water-saturated quartz sand columns under relatively fast water flow. In these experiments, clear indications for a fast and strong adsorption of the ions to the sediment could be found. Here we report the findings in a series of other experiments performed under static conditions. In this case, much higher concentrations of ions are adsorbed to the sand and remain immobile over time scales of more than a year. Changes in the MRI contrast observed for the sediment areas with the adsorbed ions indicate rearrangements in the distribution of the ions during the first days after administration to the sediment. EDX-studies of the ion distribution after several days indicate a spatially inhomogeneous distribution of adsorbed ions on the surface of the quartz sand. If the adsorbed ions are subjected to flow, a part of adsorbed ions moves away with the water flow. Also all ions are rapidly accessible to acid leaching.
Modeling brain extracellular space from diffusion data
Authors: Nicholson Charles
Published: July 2024

The extracellular space (ECS) of the brain is a thin region surrounding each cell that is filled with a medium resembling cerebrospinal fluid and an unknown amount of extracellular matrix. The ECS is difficult to study but diffusion measurements based on a point-source diffusion paradigm have begun to reveal the complex structure of this region. Despite the complexity, a modified version of Fick’s classical diffusion equation incorporating parameters for volume fraction and tortuosity has been shown to be valid. Using real-time iontophoresis and the small molecule tetramethylammonium, the volume fraction of typical brain tissue has been determined to be 0.2, i.e. 20% of the brain is ECS and the typical tortuosity is 1.6, which means that a small molecule has an effective diffusion coefficient that is 2.6 less than in free solution. Monte Carlo modeling, however, shows that a simple ensemble of convex cells, each surrounded by a uniform ECS cannot generate a tortuosity greater than 1.225. Further modeling suggests that the discrepancy between experiments and theory may be accounted for by the existence of dead-space microdomains in the ECS; a viscous extracellular matrix might also play a role. Diffusion measurements with integrative optical imaging of fluorescent macromolecules and quantum dots show that tortuosity is increased with macromolecular size and analysis based on the theory of restricted diffusion in pores suggests that the width of the ECS is in the range 38-64 nm.
Anomalous transport and diffusion in percolation systems
Authors: Bunde Armin , Heitjans Paul , Indris Sylvio , Kantelhardt Jan W. , Ulrich Markus
Published: July 2024

Many disordered systems can be modelled by percolation. Applications of this standard model range from amorphous and porous media to composites, branched polymers, gels and complex ionic conductors. In this brief review we give a short introduction to percolation theory and describe applications in materials science. We start with the structural properties of percolation clusters and their substructures. Then we turn to their dynamical properties and discuss the way the laws of diffusion and conduction are modified on these structures. Finally, we review applications of the percolation concept for transport in various kinds of heterogeneous ionic conductors.
Oxygen and cation diffusion processes in oxygen ion conductors
Authors: Martin Manfred
Published: July 2024

We discuss oxygen and cation diffusion processes in oxygen ion conductors. While the high oxygen diffusivity determines the proper oxygen ion conductivity, slow cation diffusion processes are important for sintering and degradation processes. In the first part of the paper we discuss an analytical model for the ionic conductivity of a strongly acceptor doped, fluorite-type oxygen ion conductor, i.e. a concentrated solution of AO2 and BB2O3. The model can be applied, e.g., to yttria doped zirconia (YSZ) and gives a qualitative explanation of the observed maximum of the conductivity as a function of the dopant fraction. The model considers nearest neighbor interactions between oxygen vacancies and dopant cations, which may be negligible, attractive or repulsive, and jump barriers that depend on the nature of the cation-cation edge that has to be crossed during a jump between adjacent oxygen sites. In the second part we discuss cation diffusion processes in doped lanthanum gallates (LSGM). The experimental results of nearly identical cation diffusion coefficients in the A- and B-sublattices of the perovskite LSGM can be explained by a bound defect cluster mechanism containing cation vacancies of both the Aand the B- sublattice and anion vacancies.
Comparison of 3D and 2D Li diffusion in cubic and hexagonal Li x TiS 2
Authors: Wilkening Martin , Heitjans Paul
Published: July 2024

Li diffusion in spinel-type structured cubic and hexagonal LixTiS2 with x = 0.6 and 0.7, respectively, was investigated by solid state NMR spectroscopy. In layered hexagonal LixTiS2, Li diffusion is known to be confined to the van-der-Waals gap between the TiS2 planes, i. e., it is two-dimensional (2D). In cubic LixTiS2, however, Li diffusion takes place in the three-dimensional (3D) interstitial space formed by the TiS6-polyhedra. Both polymorphs form a unique pair for studying the effects of dimensionality on Li diffusion within a host structure of the same chemical composition. 7Li spin-alignment echo and spin-lattice relaxation NMR methods were applied to measure Li jump rates. Additionally, solid echo NMR spectroscopy was used to estimate the Li diffusivity in cubic Li0.6TiS2. The activation energies for Li jumps in the two materials are very similar. Nevertheless, Li diffusion in the 3D host is slower than in the layered modification by a factor of about ten.
Anion diffusion processes in O- and N-mayenite investigated by neutron
powder diffraction
Authors: Boysen Hans , Kaiser-Bischoff Ines , Lerch Martin
Published: July 2024

The crystal structure of mayenite (ideal composition: Ca12Al14O33) consists of a (disordered) calcium-aluminate framework comprising 32 of the 33 oxygen anions. It contains large open cages, 1/6 of them being filled randomly by the remaining “free” oxygen which is available for diffusion and very high ionic conductivities. This extraframework oxygen could be substituted by nitrogen, opening up possibilities for a pure nitrogen ionic conductor. From high temperature neutron powder diffraction experiments, data analysis employing difference Fourier methods and anharmonic Debye-Waller factors and comparing pure O-mayenite with partly exchanged N/O-mayenite it is concluded that oxygen diffusion proceeds via jump-like processes, intimately coupled to relaxations of Ca and involving exchange of the “free” oxygen with framework oxygen, while nitrogen diffusion appears to proceed via an interstitial process.
High-temperature electrical conductivity and electromechanical properties of stoichiometric lithium niobate
Authors: Ohlendorf Gerd , Richter Denny , Sauerwald Jan , Fritze Holger
Published: July 2024

High temperature properties such as electrical conductivity (σ) and resonance behaviour of stoichiometric lithium niobate (LiNbO3) are determined in the temperature range from 20 to 950 °C. The activation energy of the conductivity is found to be 0.9 and 1.7 eV in the temperature range from 500 to 750 °C and from 800 to 950 °C, respectively. During thermal treatments in ambient air up to 950 °C and back, the conductivity remains unchanged at a given temperature, i.e., the crystal is stable under these conditions. The oxygen partial pressure (pO2) dependence of the conductivity shows two distinct ranges. At 750 °C, the property remains unchanged down to 10−15 bar. Below 10−15 bar, the conductivity increases according to σ ~ (pO2)−1/5. Z-cut LiNbO3 plates can be excited to thickness mode vibrations up to at least 900 °C. At this temperature, the quality factor Q is found to be between 30 and 100. As for changes of the conductivity, a decrease of the resonance frequency is observed below 10−15 bar indicating a correlation of both properties. In order to evaluate the lithium evaporation, the crystals are tempered at 900 °C in ambient air for 24 h. A depth profile of the constituents does not indicate lithium loss within the accuracy of the secondary ion mass spectroscopy. The preliminary results underline the potential of stoichiometric LiNbO3 for high-temperature applications and justify its closer investigation.
Assessing The Reliability of Module For Adolescence Psychological Well-Being In Malaysia Using The Application Of Sidek Model
Authors: Shahrul Mohd. , Nazihah Dayang Nurina , Nurafiqah Dayang , Ahmadi Raudhah , Salim Johari Md , Nadia Saidatul
Published: July 2024

In this study, a module of adolescence psychological well-being in Malaysia using the application of Sidek module development model was developed by the Counselling and Psychology Association of Malaysia (PEKAMARA) to optimize psychological well-being o teenagers aged 13-25 years. The assessment of the adolescence psychological well-being in Malaysia module was meticulously crafted following a systematic approach encompassing needs analysis, objective formulation, content development, strategy selection, module production, implementation, and evaluation. Rigorous psychometric measures adapted from the Sidek module were employed to assess the validity and reliability of the adolescence psychological well-being module. The findings reveal a good level of validity, with a coefficient of 0.80, indicating that the module has successfully targets and addresses the specific psychological challenges faced by teenagers in this age group. Furthermore, the overall reliability coefficient was impressively high, with an Alpha Cronbach value of 0.93, underscoring the module's consistency in measuring desired outcomes across different facets of psychological well-being. The Sidek module development model leverages evidence-based practices from cognitive-behavioural therapy, positive psychology, and mindfulness, offering tailored interventions to enhance stress management, emotional regulation, resilience, and overall life satisfaction among adolescents. By integrating these methodologies, the module of adolescence well-being in Malaysia provides comprehensive support to address the complex mental health needs of young individuals during their formative years. This study contributes to advancing the field of mental health interventions for adolescents by demonstrating the efficacy of a structured and systematic approach in promoting positive psychological outcomes. The results highlight the importance of integrating theoretical frameworks into practical modules that are not only effective but also adaptable to diverse cultural contexts and individual needs.
Antimicrobial property of the epidermal mucus of Tilapia Oreochromis spp.
Authors: Sajorne Recca , Mabuhay-Omar Jhonamie
Published: July 2024

This study was conducted to determine and compare the antimicrobial property of the epidermal mucus of Tilapia (Oreochromis spp.) from two environmental conditions, the fish tank and fishpond. The antimicrobial property was determined using Filter Paper Disc Diffusion Method with Amoxicillin and Nystatin as the positive controls and distilled water as the negative control. Results showed significant differences in the effects of the treatments when tested against Escherichia coli, Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Bacillus megaterium, Pseudomonas aeruginosa, Candida albicans, Aspergillus niger and Aspergillus flavus (p < 0.05). The Duncan’s Multiple Range Test further proved that the mucus of Tilapia from fishpond was significantly higher in terms of antibacterial property compared to mucus of Tilapia from fish tank. On the other hand, both of the epidermal mucus of Tilapia from fishpond and fish tank did not show any inhibitory effect against P. aeruginosa and A. niger. The epidermal mucus of Tilapia showed bacteriostatic fungistatic and bactericidal effects against test microorganisms. Based on the results, the mucus of Oreochromis spp. from fishpond and fish tank are potential sources of antimicrobial compounds.
Heavy oil degrading Burkholderia and Pseudomonas strains: insights on the degradation potential of isolates and microbial consortia
Authors: Bacosa Hernando , Inoue Chihiro
Published: July 2024

Bacterial strains were isolated from heavy oil degrading microbial consortia enriched from mangrove sediment. Among the 60 distinct isolates that formed colonies on heavy oil as a sole carbon and energy source, Pseudomonas sp. T2B and Burkholderia sp. T2C showed the best growth in heavy oil and in various aliphatic and aromatic hydrocarbons. The two isolates were tested in their abilities to degrade heavy oil. At 1% oil concentration, T2B and T2C degraded 19.6% and 16.7% of heavy oil within 21 days, respectively. These values were significantly lower than that of the source consortium T2, which degraded 24.2% of the oil. This indicates that the consortium is mor superior in degrading heavy oil than any of the isolates. The isolates can be used for biodegradation studies and can be utilized in producing an effective microbial consortium for bioremediation applications.
Growth and lipid levels of Tetraselmis tetrahele and Nannochloropsis sp. cultured under commercial fertilizers
Authors: Gonzales-Plasus Maria Mojena
Published: July 2024

Microalgae are aquatic photosynthetic organisms that contain high amounts of lipid and are potential sources of biofuels as well as feed additives for aquaculture. This study analyzed the growth and algal lipid content of two microalgae species (Tetraselmis tetrahele and Nannochloropsis sp.) using commercial fertilizers and nutrient enrichment. The samples were cultured for 5 days in 1 L dextrose bottles fertilized using Tongkang Marine Research Laboratory (TMRL) enrichment media, inorganic fertilizers such as 14-14-14, and a combination of 14-14-14 and 21-0-0. The relative growth rate of two algae were measured by computing the k value while the lipid components were extracted using the Bligh and Dyer Method, and the lipid content of each sample was determined using the gravimetric method. The use of 14-14-14 fertilizer produced the highest growth rates (k=1.810) and lipid composition (14.789%) for T. tetrahele. By contrast, Nannochloropsis sp., grew well under TMRL enrichment media (k=9.708), and the use of 14-14-14 fertilizer resulted to high lipid content (5.000%).
Speaking and listening proficiency of AB English students: basis for instructional material development
Authors: Palma Bonna , Pido Rosalie , Peralta Fernand , dela Gente Edgar , Baga-an Anabelle
Published: July 2024

This descriptive study sought to find the listening and speaking proficiency levels of the selected AB English students when their scores were taken as a whole and when categorized according to specific listening and speaking microskills. It also aimed to find out particular microskills the students needed to improve on. The research made use of listening and speaking tests patterned from Test of English as a Foreign Language (TOEFL) and Test of English for International Communication (TOEIC). Results showed that when taken as a whole, the students had Advanced speaking skills. When categorized according to specific microskill, their proficiency level in recognizing and producing vowel and consonant sounds was High Advanced, and Low Advanced in controlled and free speaking tests. Improvements may focus on specific microskills: (1) recognizing and producing consonant sounds, (2) employing appropriate vocal variety in rate, pitch and intensity, (3) selecting appropriate organizational pattern according to the topic, context, and purpose, (4) formulating substantial thesis statements supported by well-thought details, and (5) delivering the message in a clear, fluent manner using appropriate nonverbal behavior. In their listening skills, students exhibited Advanced Level of Proficiency when their scores were taken as a whole. When categorized according to specific microskills, their proficiency levels are as follows: Literal level- High Advanced, Inferential level– Low Advanced, and Evaluative level–Low Advanced. These results imply that review, planning, implementation of classroom activities and seminars must be carefully re-examined to polish the students’ listening and speaking skills. A well-designed instructional material should be planned out for this purpose.
Optimization of Combined Thermal Power Plant and Performance Analysis using Matlab/Simulink using Real Data: Kuwait as a Case Study
Authors: Alshammari Meshari F A F , Siti Fauziah Toha  , Hazleen Anuar  , Yose Fachmi Buys
Published: July 2024

To increase the overall plant efficiency, the Combined cycle power plant (CCPP), which is a combination of the Gas turbine (Brayton cycle) and steam turbine (Rankine cycle), is a highly efficient system for electricity generation.  In this paper, optimization and performance simulation analysis of Subiyah Combined Thermal Power Plant using real operating data is performed. The model is developed using MATLAB software. The main factors in the top and bottom cycles of the combined cycle are investigated and discussed. The simulation results demonstrate the exhaust of the Gas turbine reached up to 600°C. The net-power output based on the performance model using MATLAB (Simulink) is greater than the station's current real output by 20.5%. The overall thermal efficiency of the power plant is also raised from 50.5% to 55.2%.
IoT-Based Lab System for Teaching Methods in Times of Crisis
Authors: Syed Ridza Syed Ahmad Fawwaz Wafa , Motakabber S.M.A.
Published: July 2024

The revolution of communication technology has enabled people to communicate easily with others and perform many tasks from a distance. The Internet plays an important role in communication and helps to perform tasks and make people's lives easier. It led to the introduction of the Internet of Things (IoT) technology, where physical objects are connected to the Internet to perform a specific task. So that IoT can be a valuable tool in times of crisis, most modern industries can produce their products automatically and remote monitor and control the system. The same technique can be applied to overcome face-to-face teaching in science and engineering education during times of crisis. This research proposes the design and development of an IoT-based hands-on laboratory system that can be operated remotely. The methodology has been implemented and worked based on the concept of virtual reality. The research has been carried out for two simple electrical laboratory experiments: the basic logic gate and Ohm’s Law experiment. The experimental results show that the system can be implemented since the results obtained are satisfy their theoretical results. Furthermore, an improvement can be made so that the system can be integrated with the Internet and the system can function efficiently.