Articoli di riviste: "Local desorption"

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Barbero, Giovanni, Antonio M. Scarfone e Luiz R. Evangelista. "The Kinetics of Sorption–Desorption Phenomena: Local and Non-Local Kinetic Equations". Molecules 27, n. 21 (5 novembre 2022): 7601. http://dx.doi.org/10.3390/molecules27217601.

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The kinetics of adsorption phenomena are investigated in terms of local and non-local kinetic equations of the Langmuir type. The sample is assumed in the shape of a slab, limited by two homogeneous planar-parallel surfaces, in such a manner that the problem can be considered one-dimensional. The local kinetic equations in time are analyzed when both saturation and non-saturation regimes are considered. These effects result from an extra dependence of the adsorption coefficient on the density of adsorbed particles, which implies the consideration of nonlinear balance equations. Non-local kinetic equations, arising from the existence of a time delay characterizing a type of reaction occurring between a bulk particle and the surface, are analyzed and show the existence of adsorption effects accompanied by temporal oscillations.

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Shen, Maoliang, Zhonggang Huo, Longyong Shu, Qixian Li, Pengxin Zhang e Weihua Wang. "The Pore Structure Multifractal Evolution of Vibration-Affected Tectonic Coal and the Gas Diffusion Response Characteristics". Processes 12, n. 8 (14 agosto 2024): 1701. http://dx.doi.org/10.3390/pr12081701.

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Vibrations caused by downhole operations often induce coal and gas outburst accidents in tectonic zone coal seams. To clarify how vibration affects the pore structure, gas desorption, and diffusion capacity of tectonic coal, isothermal adsorption-desorption experiments under different vibration frequencies were carried out. In this study, high-pressure mercury intrusion experiments and low-pressure liquid nitrogen adsorption experiments were conducted to determine the pore structures of tectonic coal before and after vibration. The pore distribution of vibration-affected tectonic coal, including local concentration, heterogeneity, and connectivity, was analyzed using multifractal theory. Further, a correlation analysis was performed between the desorption diffusion characteristic parameters and the pore fractal characteristic parameters to derive the intrinsic relationship between the pore fractal evolution characteristics and the desorption diffusion characteristics. The results showed that the vibration increased the pore volume of the tectonic coal, and the pore volume increased as the vibration frequency increased in the 50 Hz range. The pore structure of the vibration-affected tectonic coal showed multifractal characteristics, and the multifractal parameters affected the gas desorption and diffusion capacity by reflecting the density, uniformity, and connectivity of the pore distribution in the coal. The increases in the desorption amount (Q), initial desorption velocity (V0), initial diffusion coefficient (D0), and initial effective diffusion coefficient (De) of the tectonic coal due to vibration indicated that the gas desorption and diffusion capacity of the tectonic coal were improved at the initial desorption stage. Q, V0, D0, and De had significant positive correlations with pore volume and the Hurst index, and V0, D0, and De had negative correlations with the Hausdorff dimension. To a certain extent, vibration reduced the local density regarding the pore distribution in the coal. As a result, the pore size distribution was more uniform, and the pore connectivity was improved, thereby enhancing the gas desorption and diffusion capacity of the coal.

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Mori, G., M. Lazzarino, D. Ercolani, L. Sorba, S. Heun e A. Locatelli. "Desorption dynamics of oxide nanostructures fabricated by local anodic oxidation nanolithography". Journal of Applied Physics 97, n. 11 (giugno 2005): 114324. http://dx.doi.org/10.1063/1.1923165.

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Rosa, Luis G., P. A. Jacobson e P. A. Dowben. "Evidence for an Influence of Local Dipole Excitations in Thermal Desorption". Journal of Physical Chemistry B 110, n. 15 (aprile 2006): 7944–50. http://dx.doi.org/10.1021/jp054929n.

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Seyedvakili, Farnaz, e Mohammad Samipoorgiri. "Thermo-kinetic investigation of heavy metal ions adsorption onto lignin considering coupled adsorption–desorption mechanisms: Modeling and experimental validation". International Journal of Modeling, Simulation, and Scientific Computing 09, n. 02 (20 marzo 2018): 1850014. http://dx.doi.org/10.1142/s1793962318500149.

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A coupled adsorption–desorption thermo-kinetic model is developed incorporating both adsorption and desorption reactions. A local pseudo-equilibrium condition at the interface of adsorbent and adsorbate bulk phases was used as isotherm equation which can even be applied for multi-pollutants scenarios. The developed model is then validated using collected experimental data of heavy metal ions (Pb, Cu, Cd, Zn, and Ni). Comparisons were made for a number of isotherm and kinetic models to examine the performance of the proposed model. The developed model revealed desirable accuracy and superiority over other models in predicting the adsorption behavior and can be used for other systems of concern. The model correlates the adsorption kinetic with an [Formula: see text] value of 0.9391 and desorption kinetic with an [Formula: see text] value of 0.9383. By application of the proposed model to any available adsorption datasets, the individual characteristics of adsorption and desorption can be determined.

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Xia, Qibin, Zhong Li, Hongxia Xi e Kefeng Xu. "Activation Energy for Dibenzofuran Desorption from Fe3+/TiO2 and Ce3+/TiO2 Photocatalysts Coated onto Glass Fibres". Adsorption Science & Technology 23, n. 5 (giugno 2005): 357–66. http://dx.doi.org/10.1260/026361705774355469.

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In this work, TiO2, Fe3+/TiO2 and Ce3+/TiO2 photocatalytic films were respectively immobilized on glass fibres via the sol—gel technique to prepare supported photocatalysts. Temperature programmed desorption (TPD) experiments were conducted to measure the TPD curves for the removal of dibenzofuran from these photocatalysts, from which the activation energy for dibenzofuran desorption from the photocatalyst surfaces was estimated. The results showed that the activation energies for dibenzofuran desorption from the photocatalysts TiO2, Ce3+/TiO2 and Fe3+/TiO2 coated separately onto the glass fibres were 16.41 kJ/mol, 22.55 kJ/mol and 33.59 kJ/mol, respectively, while the hardness values of the ions Fe3+, Ce3+ and Ti4+ were respectively 13.1 eV, 11.9 eV and 10.6 eV. The data indicated that the use of Fe3+ or Ce3+ ions for doping a TiO2 photo-catalyst increased the local hardness of the doped TiO2 photocatalyst surface. This, in turn, increased the activation energy for the desorption of dibenzofuran from such a TiO2 photocatalyst surface.

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Zavorotynska, O., I. Saldan, S. Hino, T. D. Humphries, S. Deledda e B. C. Hauback. "Hydrogen cycling in γ-Mg(BH4)2 with cobalt-based additives". Journal of Materials Chemistry A 3, n. 12 (2015): 6592–602. http://dx.doi.org/10.1039/c5ta00511f.

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Hydrogen desorption and absorption properties of magnesium borohydride (Mg(BH₄)₂) were studied for three cycles. Effect of cobalt additives and their local structure upon cycling were investigated in detail.

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Sonobe, Satoshi, Yosuke Shibata, Yusuke Asakuma, Anita Hyde, Cuong Nguyen e Chi Phan. "A dimensionless number for microwave non-equilibrium local heating through surfactant desorption". Colloids and Surfaces A: Physicochemical and Engineering Aspects 591 (aprile 2020): 124560. http://dx.doi.org/10.1016/j.colsurfa.2020.124560.

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Бернацкий, Дмитрий Петрович, e Виктор Георгиевич Павлов. "FIELD DESORPTION MICROSCOPY OF CARBON-COATED FIELD ELECTRON EMITTERS". Physical and Chemical Aspects of the Study of Clusters, Nanostructures and Nanomaterials, n. 13 (23 dicembre 2021): 25–31. http://dx.doi.org/10.26456/pcascnn/2021.13.025.

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Полевые электронные эмиттеры в форме металлического острия с пленкой углерода на поверхности обладают рядом перспективных эксплуатационных свойств. Характеристики эмиттера зависят от фазового состава, толщины и однородности пленки. Определение параметров пленок толщиной в один или несколько моноатомных слоев представляет определённые трудности. В данной работе образование и характеристики углеродных наноструктур на поверхности полевых эмиттеров из иридия и рения исследуются с помощью полевой десорбционной микроскопии непрерывного режима. На полевых десорбционных изображениях области углеродных наноструктур проявляются в виде локальных вспышек (лавинообразная десорбция). При покадровом анализе видеозаписей вспышек обнаружено несколько стадий формирования вспышек и выявлены различия в протекании десорбции с углеродных наноструктур на иридии и на рении. Обнаруженные различия объясняются образованием на иридии однослойного, а на рении многослойного графена. Десорбционные изображения выявляют неоднородности и локальные различия толщины пленки. Показано, что полевая десорбционная микроскопия непрерывного режима позволяет определять закономерности формирования полевых десорбционных изображений различных углеродных наноструктур, в частности, однослойного и многослойного графена на поверхности полевого эмиттера, и проводить диагностику поверхности после науглероживания и контролировать однородность получаемого покрытия. Получаемые данные полезны для разработки технологии эффективных полевых электронных эмиттеров. Field electron emitters in the form of a metal tip with a carbon film on the surface have a number of promising operational properties. The characteristics of the emitter depend on the phase composition, thickness and uniformity of the film. Determining the parameters of films with a thickness of one or more monoatomic layers presents certain difficulties. In this paper, the formation and characteristics of carbon nanostructures on the surface of field emitters made of iridium and rhenium are studied using continuous-mode field desorption microscopy. In the field desorption images, the regions of carbon nanostructures appear as local flashes (avalanche-like desorption). Frame-by-frame analysis of flash video recordings revealed several stages of the flash formation and revealed differences in the desorption from carbon nanostructures on iridium and rhenium. The found differences are explained by formation of the single-layer graphene on iridium and a multilayer graphene on rhenium. Desorption images reveal inhomogeneities and local differences in the film thickness. It is shown that continuous-mode field desorption microscopy makes it possible to determine the regularities of formation of the field desorption images of various carbon nanostructures, in particular, the single-layer and multilayer graphene on the surface of the field emitter, and to diagnose the surface after carburization. Besides, control the uniformity of the resulting coating is possible. The obtained data are useful for developing technology of the effective field electronic emitters.

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Li, Chun, Zejun Zhang e Lars Heinke. "Mass transfer of toluene in a series of metal–organic frameworks: molecular clusters inside the nanopores cause slow and step-like release". Physical Chemistry Chemical Physics 24, n. 6 (2022): 3994–4001. http://dx.doi.org/10.1039/d1cp05560g.

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Toluene forms dimers in sufficiently large pores of MOFs of UiO-type. During the release process, the dimer break-up rather than the diffusion is rate limiting, causing a step-like desorption kinetics with a local maximum of the release rate.

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Xia, Tian Xiang, Jue Jun Yao, Mao Sheng Zhong e Xiao Yang Jia. "Field Study on Remediation of PAHs Contaminated Soil by Ex Situ Technologies at a Coking Site". Advanced Materials Research 773 (settembre 2013): 744–48. http://dx.doi.org/10.4028/www.scientific.net/amr.773.744.

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Decontamination level and residual amount of polycyclic aromatic hydrocarbons (PAHs) were investigated by ex-situ remediation technologies including biopile, soil washing and thermal desorption in a field level. After the remediation, 16 USEPA priority PAHs were decontaminated from 99.3% to 99.9% for thermal desorption, from 17.9% to 82.1% for biopile and from-27.6% to 84.3% for soil washing. Residual PAHs amount in soils by thermal desorption was below the local soil screening level, differently from that by biopile and soil washing. Especially for high molecular weight PAHs, i.e. 5-6 rings PAHs, residual amount exceeded over the screening lever 4 to 197 times for biopile and 17 to 421 times for soil washing. Additional factors, such as cost, time, operation and maintainance etc. for remedial technology selection and contaminant bioavailability in soil matrix for remediation target values, were proposed to be paid more attention for specific contaminated sites.

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Заика, Ю. В., Е. К. Костикова e Ю. С. Нечаев. "Пики термодесорбции водорода: моделирование и интерпретация". Журнал технической физики 91, n. 2 (2021): 222. http://dx.doi.org/10.21883/jtf.2021.02.50355.208-20.

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Various models of hydrogen thermal desorption peaks are analyzed. The dynamics model of the volume-averaged concentration with a continuum parameter allows integrally taking into account the degree of dominance of the limiting factors (diffusion and recombination of atoms into molecules during desorption). An analytical criterion for peaks symmetry is proposed in the context of comparison with the method of decomposing the component spectrum into the sum of Gaussian. Modifications of the Kissinger method for estimating the activation energy of desorption in experiments with several heating rates and procedures for solving the inverse problem of parametric identification of a unimodal peak using only one heating rate are presented. A comparative with a diffusion model with dynamic boundary conditions is performed. It is shown that the cause of local peaks can be not only capture with different binding energies but also the dynamics of interaction of bulk and surface processes, change in the surface structure during heating.

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Tong, S. Y., e H. Huang. "Time-Reversed Internal-Source Holography". Surface Review and Letters 05, n. 05 (ottobre 1998): 971–75. http://dx.doi.org/10.1142/s0218625x98001316.

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We have derived an expression for incident-beam-induced fine structures at a local site. We show that using time-reversal arguments, local incident-beam-induced fine structures are equivalent to photoelectron holography with an isotropic reference wave. We suggest that positron-beam-induced desorption or Auger fine structures offer attractive alternatives to using electron beams because the positron-atom scattering factor contains less angular anisortropy and the multiple scattering is weaker.

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Peksa, Ladislav, Tomas Gronych e Petr Řepa. "The influence of a local-induced desorption on pressure in an uhv system". Vacuum 43, n. 5-7 (maggio 1992): 695–98. http://dx.doi.org/10.1016/0042-207x(92)90111-9.

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Wilhelm, Thomas, e Gunther Wittstock. "Patterns of functional proteins formed by local electrochemical desorption of self-assembled monolayers". Electrochimica Acta 47, n. 1-2 (settembre 2001): 275–81. http://dx.doi.org/10.1016/s0013-4686(01)00566-7.

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Ageev, V. N., Yu A. Kuznetsov, B. V. Yakshinskii e T. E. Madey. "Electron stimulated desorption of alkali metal ions and atoms: Local surface field relaxation". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 101, n. 1-2 (giugno 1995): 69–72. http://dx.doi.org/10.1016/0168-583x(95)00286-3.

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Nechaev, Yury S., Evgeny A. Denisov, Alisa O. Cheretaeva, Nadezhda A. Shurygina, Ekaterina K. Kostikova, Andreas Öchsner e Sergei Yu Davydov. "On the Problem of “Super” Storage of Hydrogen in Graphite Nanofibers". C 8, n. 2 (29 marzo 2022): 23. http://dx.doi.org/10.3390/c8020023.

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This article is devoted to some fundamental aspects of “super” storage in graphite nanofibers (GNF) of “reversible” (~20–30 wt.%) and “irreversible” hydrogen (~7–10 wt.%). Extraordinary results for hydrogen “super” storage were previously published by the group of Rodriguez and Baker at the turn of the century, which been unable to be reproduced or explained in terms of physics by other researchers. For the first time, using an efficient method of processing and analysis of hydrogen thermal desorption spectra, the characteristics of the main desorption peak of “irreversible” hydrogen in GNF were determined: the temperature of the highest desorption rate (Tmax = 914–923 K), the activation energy of the desorption process (Q ≈ 40 kJ mol−1), the pre-exponential rate constant factor (K0 ≈ 2 × 10−1 s−1), and the amount of hydrogen released (~8 wt.%). The physics of hydrogen “super” sorption includes hydrogen diffusion, accompanied by the “reversible” capture of the diffusant by certain sorption “centers”; the hydrogen spillover effect, which provides local atomization of gaseous H2 during GNF hydrogenation; and the Kurdjumov phenomenon on thermoelastic phase equilibrium. It is shown that the above-mentioned extraordinary data on the hydrogen “super” storage in GNFs are neither a mistake nor a mystification, as most researchers believe.

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Опенов, Л. А., e А. И. Подливаев. "Влияние дегидрирования графана на его механические и электронные свойства". Физика и техника полупроводников 52, n. 6 (2018): 614. http://dx.doi.org/10.21883/ftp.2018.06.45925.8622.

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AbstractThe effect of the desorption of hydrogen on the mechanical characteristics and electronic structure of the armchair conformation of graphane is studied in the context of the nonorthogonal tight-binding model. It is shown that the mechanical stiffness and the Poisson ratio nonmonotonically depend on the hydrogen content and take minimum values at a hydrogen vacancy content of ~50% and ~30%, respectively. As hydrogen is desorbed, the characteristic peaks of the phonon density of states are rapidly reduced. In the initial stage of desorption, local energy levels are formed in the band gap. As the number of hydrogen vacancies is increased, these levels form an impurity band, in which the Fermi level is located.

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Костина, Ирина, Irina Kostina, Вера Молвинских, Vera Molvinskikh, Надежда Белоконова, Nadezhda Belokonova, Михаил Огнев e Mihail Ognev. "COMPARATIVE CHARACTERISTICS OF PHYSICO-CHEMICAL PROPERTIES OF DRUGS TOPICAL APPLICATION FOR THE PREVENTION OF COMPLICATIONS OF TOOTH EXTRACTION". Actual problems in dentistry 14, n. 4 (25 dicembre 2018): 64–70. http://dx.doi.org/10.18481/2077-7566-2018-14-4-64-70.

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Background. A comparative study of the dynamics of iodine desorption from drugs containing iodoform and used after tooth extraction to preserve blood clots and prevention, treatment of inflammatory complications. This took into account the type and form of drugs. The content and desorption of iodine determine the duration of local exposure to the drug on the tissues of the tooth well. Objectives. To study the physico-chemical properties of iodoform containing topical preparations for the prevention and treatment of alveolitis of the jaw. Methods. The objects of the study were complex multicomponent preparations of domestic production, presented in the dental market in the form of gauze bandage, collagen sponge, paste, powder containing iodoform. A standard titrimetric method was used to quantify the iodine content in aqueous systems. For the analysis of changes of iodine content in aqueous model systems applied to the spectrophotometric method in which the concentration of a substance was assessed according to the calibration chart from 0 minutes to 48 hours. In the model solution, the albumin and pH were changed, iodine concentration was determined in 1, 15 and 30 min. Results. Medications significantly differed in both the number of iodoform and desorption in the aquatic environment of the iodine. However, the content of iodoform in the preparations did not exceed the maximum permissible concentration. Desorption of iodine from the bandage after 15 minutes is significantly less than from the viscose flagellum. Desorption of iodine from the collagen sponge remains constant for 24 hours., but increases after 48 hours. Desorption of iodine from the powder is reduced after 45 minutes. Desorption of iodine from the paste gradually increases, reaches a maximum of 105 minutes and persists after 48 hours. In the albumin-bound state, iodine is more easily desorbed in an acidic medium, and at low concentrations of iodine, desorption in a neutral medium is significantly less. Conclusions. The duration of action of iodoform when applied topically affect the dosage form of the carrier (fiber, sponge, paste, powder), the concentration of the drug, the pH and albumin content in the aqueous medium.

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Helard, Denny, Shinta Indah, Chintia Maya Sari e Hestia Mariesta. "The Adsorption and Regeneration of Natural Pumice as Low-Cost Adsorbent for Nitrate Removal From Water". Journal of Geoscience, Engineering, Environment, and Technology 3, n. 2 (1 giugno 2018): 86. http://dx.doi.org/10.24273/jgeet.2018.3.2.1545.

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The potential of adsorption and regeneration of Indonesian natural pumice to remove nitrate from aqueous solution was studied in multiple adsorption-desorption cycles. Batch experiments were performed to examine the effect of various experimental parameters on the removal of nitrate. The optimum condition of nitrate removal by natural pumice were obtained at 3 of pH solution, 0.3 g/L of adsorbent dose, 30 min of contact time, <63 μm of particle size, and 90 mg/L of nitrate concentration with 54.79% of removal efficiency and 164.37 mg/g of nitrate uptake. The experimental data obtained were fitted with the Freundlich adsorption isotherm within the concentration range studied. Although complete desorption were not achieved, the result confirmed that HCl can be used as desorbing and recovery agent, which be desorbed 10-13% of nitrate ion. The used natural pumice also could be regenerated and reused up to three successive adsorption-desorption cycles. Overall results revealed that the ability of natural pumice to adsorb nitrate will create more interest to develop a new adsorbent from local mineral for pollutant removal from water

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Sekiguchi, T., Y. Baba, I. Shimoyama e K. G. Nath. "Local bonding states of ion-irradiated graphite characterized by photon-stimulated desorption (PSD) spectroscopy". Journal of Electron Spectroscopy and Related Phenomena 144-147 (giugno 2005): 437–41. http://dx.doi.org/10.1016/j.elspec.2005.01.156.

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Miyauchi, Naoya, Tomoya Iwasawa, Yoshiharu Murase, Taro Yakabe, Masahiro Kitajima, Shoji Takagi, Tomomi Akiyama, Satoka Aoyagi e Akiko N. Itakura. "Visualization of local hydrogen diffusion in stainless steel using time resolved electron stimulated desorption". Applied Surface Science 527 (ottobre 2020): 146710. http://dx.doi.org/10.1016/j.apsusc.2020.146710.

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Fan, Chao, Xin Ju e Chubin Wan. "Local and crystal structure of Mg1.9Al0.1Ni hydrogen storage alloys during hydrogen absorption–desorption cycling". International Journal of Hydrogen Energy 35, n. 15 (agosto 2010): 8044–48. http://dx.doi.org/10.1016/j.ijhydene.2010.02.117.

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Moghanloo, R. Ghanbarnezhad, e F. Javadpour. "Applying Method of Characteristics to Determine Pressure Distribution in 1D Shale-Gas Samples". SPE Journal 19, n. 03 (31 dicembre 2013): 361–72. http://dx.doi.org/10.2118/168218-pa.

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Summary This paper examines application of the method of characteristics (MOC) to determine pressure distribution in a 1D matrix of shale gas. Because of gas expansion and local desorption in shale gas, pressure distribution changes during production. We developed a semianalytic MOC solution of gas flow in shale by use of the analogous-continuum approximation (apparent permeability). The MOC solution is derived with the inclusion of compressibility, gas-slippage effect, and desorption. Through quantitative comparison of pressure profiles and history plots, we used a simulation approach to verify the accuracy of the analytic solution. Results suggest that the simulation results are consistent with our MOC solution, which can also be used to evaluate impacts of different parameters on pressure distribution. Prediction of pressure distribution over time will greatly enhance approximation of reservoir performance.

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Skakauskas, Vladas, e Pranas Katauskis. "On the kinetics of the Langmuir-type heterogeneous reactions". Nonlinear Analysis: Modelling and Control 16, n. 4 (7 dicembre 2011): 467–76. http://dx.doi.org/10.15388/na.16.4.14089.

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In this paper we investigate three two-dimensional in space mathematical models of the kinetics of unimolecular heterogeneous reactions proceeding onto planar surfaces. All models include the diffusion of the reactant from a bounded vessel towards an adsorbent, adsorption of the molecules of the reactant, their desorption, conversion (reaction) of the adsorbate into a product, instantaneous product desorption, and the diffusion of the product from the adsorbent into the same vessel. One of these models is based on the Langmuir-type kinetics of the surface reactions, the other one is based on the local steady-state value of the surface coverage, and the last one, in addition to the first model, involves the diffusion of the adsorbate along the adsorbent. Diffusivity of all species is assumed to be constant. Models were solved numerically by using the finite difference technique. By changing input parameters the effects of the rate constants of the reactant adsorption, desorption, and reaction and the influence of the surface diffusion of the adsorbate and approximation of the surface coverage by its steady-state value on the kinetics of surface reactions were studied numerically.

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Robinet, J. C., e M. Rhattas. "Détermination de la perméabilité non saturée des matériaux argileux à faible porosité". Canadian Geotechnical Journal 32, n. 6 (1 dicembre 1995): 1035–43. http://dx.doi.org/10.1139/t95-100.

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The presence of impermeable natural or artificial clayey layers plays a fundamental role in protecting ground water from pollution. In the case of low porosity and partially saturated clays, the experimental determination of transfer coefficient is particularly difficult because of a considerable reduction in hydraulic head and of water–particle interactions that reduce the interstitial water mobility. Experimental work was carried out to obtain, in a simple way, the hydrodynamic characteristics of two clayey formations: Boom and Bassin Parisien. The hydraulic profiles were determined by soaking tests on 300 mm high clayey columns and the sorption–desorption isotherms were evaluated by the saline solution technique on several samples of both clays. The spatio-temporal analysis of the hydraulic profiles reveals the variations in isothermal diffusion coefficient according to the water content. In accordance with the hypothesis of local equilibrium, the sorption–desorption isotherms give the characteristic curve of each formation in a potential versus water content relationship. The total diffusivity combined with retention curves allows to calculate the permeability as a function of the saturation. Key words : clay, sorption–desorption isotherms, soaking tests, diffusion coefficient, permeability.

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Čapek, Pavel, e Karel Klusáček. "Kinetically induced multiple steady states during acetylene hydrogenation". Collection of Czechoslovak Chemical Communications 55, n. 7 (1990): 1708–20. http://dx.doi.org/10.1135/cccc19901708.

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An isothermal reaction model of acetylene hydrogenation on palladium catalyst is described. Steady-state solutions of the mass balances in a CSTR display regions of multiplicity caused by the very distinct rate and strength of adsorption and desorption of acetylene and hydrogen, respectively. Uniqueness and local stability of this model are investigated numerically; oscillatory behaviour is predicted to be absent for typical conditions.

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Tosto, Sebastiano, Philippe Knauth e Maria Luisa Di Vona. "Proposed Model of Water Adsorption/Desorption in a PEM Membrane". Defect and Diffusion Forum 297-301 (aprile 2010): 209–14. http://dx.doi.org/10.4028/www.scientific.net/ddf.297-301.209.

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This paper describes the processes of water adsorption and desorption in PE membranes for fuel cells. A simple equation is inferred assuming that the surface of the membrane is uniformly covered by adsorbed molecules to an average depth of some monolayers. The adsorption depth is only controlled by diffusion of adsorbate from the surface towards the bulk through a two-layer or multi-layer mechanisms; so the empty sites formed at the surface can accept further molecules of water. If the diffusion rate is fast enough, cumulative water uptake occurs. The uptake kinetics is described considering the average penetration depth, i.e. neglecting the local concentration spikes below a random number and position of empty sites statistically formed at the surface of the membrane. The model also describes the desorption process, assumed to start at a prefixed time.

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Joyce, B. A., J. Zhang, A. G. Taylor e A. K. Lees. "A Reflection High Energy Electron Diffraction–Reflectance Anisotropy Spectroscopy Study of Silicon Growth Dynamics During Gas Source Molecular Beam Epitaxy from Silanes". Surface Review and Letters 05, n. 03n04 (giugno 1998): 761–67. http://dx.doi.org/10.1142/s0218625x98001146.

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Molecular beam epitaxy (MBE) provides an ideal experimental vehicle for the in situ study of thin film growth dynamics. By using a combination of reflection high energy electron diffraction (RHEED) and reflectance anisotropy (difference) spectroscopy [RA(D)S], it is possible to separate morphological (long range order) and local electronic structure effects, which we demonstrate with the growth of silicon films from disilane ( Si 2 H 6) on Si(001) (2 × 1)+(1 × 2) reconstructed surfaces. The rate-limiting step in Si growth from both monosilane ( SiH 4) and disilane is the desorption of molecular hydrogen and we have found using RAS that, over a significant range of temperature and coverage, hydrogen desorption follows zeroth order kinetics as the result of a step-mediated process. Finally, we show how this influences the growth rate on substrates of differing degrees of vicinality.

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Skryabina, N. E., Vladimir M. Pinyugzhanin e Daniel Fruchart. "Relationship between Micro-/Nano-Structure and Stress Development in TM-Doped Mg-Based Alloys Absorbing Hydrogen". Solid State Phenomena 194 (novembre 2012): 237–44. http://dx.doi.org/10.4028/www.scientific.net/ssp.194.237.

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In the most recent years, MgH2has attracted considerable attention for reversible hydrogen storage purposes because of a large 7.6 w% H-uptake, single plateau reaction at low pressure and abundance of metal. If the Mg ↔ H reactions take place at rather high temperature (> 300°C), the kinetic remains very low. However, early transition metal based additives (Ti, V, Nb...) improve dramatically the kinetics of hydrogen absorption/desorption, while having no essential impact on the reversible sorption capacity. Systematic analysis of many experimental data led to question chemical, physical, mechanical... parameters contributing significantly to improve the kinetics of absorption/desorption. Besides, results of theoretical and numerical computation enlighten the impact of structural and mechanical parameters owing to the local bonds of Mg/MgH2with of TM elements, in terms of total energy and electronic structure. More specifically, we found highly relevant to consider 1 - the impact of the crystallite sizes of Mg and the TM-phase, 2 - the role of internal and external stresses, as well as 3 - the role of texture on the kinetics of hydrogen absorption/desorption. Apart the previous considerations, we like to underline the role of specific TM in trapping intermediately hydrogen thus forming TMHxprior initiating the Mg ↔ MgH2nucleation process.

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Ju, Shin-Pon, e Cheng-I. Weng. "Investigation of the local structure variance of water molecules in laser-induced thermal desorption process". Applied Surface Science 230, n. 1-4 (maggio 2004): 179–90. http://dx.doi.org/10.1016/j.apsusc.2004.02.047.

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Lacin, Oral, Bahar Bayrak, Ozlem Korkut e Enes Sayan. "Modeling of adsorption and ultrasonic desorption of cadmium(II) and zinc(II) on local bentonite". Journal of Colloid and Interface Science 292, n. 2 (dicembre 2005): 330–35. http://dx.doi.org/10.1016/j.jcis.2005.05.092.

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33

Lenzi, Ervin K., Aloisi Somer, Rafael S. Zola, Luciano R. da Silva e Marcelo K. Lenzi. "A Generalized Diffusion Equation: Solutions and Anomalous Diffusion". Fluids 8, n. 2 (17 gennaio 2023): 34. http://dx.doi.org/10.3390/fluids8020034.

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We investigate the solutions of a generalized diffusion-like equation by considering a spatial and time fractional derivative and the presence of non-local terms, which can be related to reaction or adsorption–desorption processes. We use the Green function approach to obtain solutions and evaluate the spreading of the system to show a rich class of behaviors. We also connect the results obtained with the anomalous diffusion processes.

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Кузнецов, Ю. А., e М. Н. Лапушкин. "Влияние температуры на электронно-стимулированную десорбцию атомов лития с поверхности интерметаллидов Li-=SUB=-x-=/SUB=-Au-=SUB=-y-=/SUB=-". Физика твердого тела 65, n. 7 (2023): 1216. http://dx.doi.org/10.21883/ftt.2023.07.55848.64.

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The effect of temperature on the electron-stimulated desorption of lithium atoms from the surface of 2D semiconductor LixAuy intermetallic compounds in the temperature range from 160 to 300 K was studied. LixAuy intermetallic compounds were formed during the deposition of lithium atoms on gold film 2 monolayers thick at room temperature. An island mechanism for the formation of LixAuy intermetallic compounds has been proposed. The decrease in the yield of electronically stimulated desorption of lithium atoms from the surface of LixAuy 2D semiconductor intermetallic compounds with decreasing temperature is associated with a decrease in the probability of capturing an excited electron into the conduction band into a local state near the bottom of the conduction band. The calculation by the density functional method showed that 2D LiAu layers form semiconductor compounds, the band width of which decreases with increasing thickness of the 2D LiAu layer.

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Novickis, Richard W., Marcos V. Surmani Martins, Leila F. de Miranda, Roberto R. Ribeiro, Laureano Silva e Antônio Hortêncio Munhoz Jr. "Development of Nanosystems to Release Atenolol". Advances in Science and Technology 86 (settembre 2012): 102–7. http://dx.doi.org/10.4028/www.scientific.net/ast.86.102.

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Abstract: The structure of aluminum monohydroxide resulting from synthesis by ammonium hydroxide with aluminum chloride (or aluminum nitrate, for example) by a sol-gel process, gives a purified and chemically inert material with many applications possibilities because of its great specific surface area. A pseudoboehmite is the choice in this project for adsorption/desorption of atenolol. The molecular interaction with the pseudoboehmite substrate was studied by FTIR (Infrared Spectroscopy), DSC (Scanning electron /TG Thermogravimetry), UV-vis (Ultraviolet-visible spectroscopy) and SEM (Scanning Electron Microscopy). The SEM characterization has been used to quantify the local structural surface for the correlations with the synthesis process; and the Spectroscopies and Thermogravimetric techniques were used for measurements of the adsorption/desorption concentrations of the drug in physiological solution. This procedure gives information to the chemistry and surface of these fine ceramics material that would be applied like excipient in medications to control the drug delivery and plasmatic concentrations in optimal conditions.

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Swearer, Dayne F., Hangqi Zhao, Linan Zhou, Chao Zhang, Hossein Robatjazi, John Mark P. Martirez, Caroline M. Krauter et al. "Heterometallic antenna−reactor complexes for photocatalysis". Proceedings of the National Academy of Sciences 113, n. 32 (21 luglio 2016): 8916–20. http://dx.doi.org/10.1073/pnas.1609769113.

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Metallic nanoparticles with strong optically resonant properties behave as nanoscale optical antennas, and have recently shown extraordinary promise as light-driven catalysts. Traditionally, however, heterogeneous catalysis has relied upon weakly light-absorbing metals such as Pd, Pt, Ru, or Rh to lower the activation energy for chemical reactions. Here we show that coupling a plasmonic nanoantenna directly to catalytic nanoparticles enables the light-induced generation of hot carriers within the catalyst nanoparticles, transforming the entire complex into an efficient light-controlled reactive catalyst. In Pd-decorated Al nanocrystals, photocatalytic hydrogen desorption closely follows the antenna-induced local absorption cross-section of the Pd islands, and a supralinear power dependence strongly suggests that hot-carrier-induced desorption occurs at the Pd island surface. When acetylene is present along with hydrogen, the selectivity for photocatalytic ethylene production relative to ethane is strongly enhanced, approaching 40:1. These observations indicate that antenna−reactor complexes may greatly expand possibilities for developing designer photocatalytic substrates.

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Sarraj, Rihem, Amir Kessentini, Tarek Hassine, Ali Algahtani e Fehmi Gamaoun. "Hydrogen Effect on the Cyclic Behavior of a Superelastic NiTi Archwire". Metals 9, n. 3 (11 marzo 2019): 316. http://dx.doi.org/10.3390/met9030316.

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In this work, we are interested in examining the strain rate effect on the mechanical behavior of Ni–Ti superelastic wires after hydrogen charging and ageing for 24 h. Specimens underwent 50 cycles of loading-unloading, reaching an imposed deformation of 7.6%. During loading, strain rates from 10−4 s−1 to 10−2 s−1 were achieved. With a strain rate of 10−2 s−1, the specimens were charged by hydrogen for 6 h and aged for one day showed a superelastic behavior marked by an increase in the residual deformation as a function of the number of cycles. In contrast, after a few number of cycles with a strain rate of 10−4 s−1, the Ni-Ti alloy archwire specimens fractured in a brittle manner during the martensite transformation stage. The thermal desorption analysis showed that, for immersed specimens, the desorption peak of hydrogen appeared at 320 °C. However, after annealing the charged specimens by hydrogen at 400 °C for 1 h, an embrittlement took place at the last cycles for the lower strain rates of 10−4 s−1. The present study suggests that the embrittlement can be due to the development of an internal stress in the subsurface of the parent phase during hydrogen charging and due to the creation of cracks and local zones of plasticity after desorption.

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Esteve-Turrillas, Francesc A., Agustín Pastor e Miguel de la Guardia. "Low temperature headspace desorption of volatile organic compounds trapped in air sampling solid-supports". Environmental Chemistry 6, n. 5 (2009): 452. http://dx.doi.org/10.1071/en09013.

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Environmental context. The monitoring of volatile organic compounds (VOCs) in air is of great importance for air quality on both local and global scales. The determination of VOCs can be carried out by gas chromatography–mass spectrometry (GC-MS) after active or passive sampling and (high temperature) thermal desorption. An attractive alternative would be to combine GC-MS with headspace (HS) systems as it allows simpler, faster, low temperature desorption. We present here the first report of HS-GC-MS for the determination of VOCs in air sampled using solid supports. Abstract. The use of a headspace (HS) for low temperature desorption of VOCs, previously sorbed from indoor air on solid supports, has been evaluated in order to improve the GC-MS determinations in environmental studies. Graphitised carbon black (GCB), Porapak and Tenax were considered in this study. The HS injector does not allow temperatures higher than 150°C, so there is no a complete desorption of VOCs. However highly volatile compounds were completely desorbed from Porapak and Tenax, but compounds of low volatility showed a strong retention with recoveries of 71–100% for Porapak and 59–100% for Tenax. All studied VOCs were quantitatively desorbed from GCB. Only 100 μL of the HS volume is injected in the chromatographic system. So in spite of the reduced sensitivity we are able to make replicate analyses on the same sampler. Additional experiments were performed using the proposed methodology for the analysis of aforementioned supports in passive and active sampling modes. In short, the proposed methodology reduces the energy consumed and makes it possible to determine the VOCs in air with reduced cost media. The developed methodology permits the determination of 32 VOCs with limits of detection values around 1 μg m–3 when actively sampling air at 50 mL min–1 for 2 h and using 100 mg solid sorbent.

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Ledesma-Durán, Aldo, S. I. Hernández e Iván Santamaría-Holek. "Effect of Surface Diffusion on Adsorption–Desorption and Catalytic Kinetics in Irregular Pores. I. Local Kinetics". Journal of Physical Chemistry C 121, n. 27 (30 giugno 2017): 14544–56. http://dx.doi.org/10.1021/acs.jpcc.7b03652.

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40

Bartha, J. W., U. Barjenbruch e M. Henzler. "Thermal desorption spectroscopy of Xe at the Si(111) as a local probe for surface structures". Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 3, n. 3 (maggio 1985): 1588–91. http://dx.doi.org/10.1116/1.573137.

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41

Kwoka, Monika, Elisabetta Comini, Dario Zappa e Jacek Szuber. "Flower-like ZnO Nanostructures Local Surface Morphology and Chemistry". Nanomaterials 12, n. 15 (3 agosto 2022): 2666. http://dx.doi.org/10.3390/nano12152666.

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This work presents the results of comparative studies using complementary methods, such as scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS), and thermal desorption spectroscopy (TDS) to investigate the local surface morphology and chemistry of flower-like ZnO nanostructures synthesized by the thermal oxidation technique on native Si/SiO2 substrates. SEM studies showed that our flower-like ZnO nanostructures contained mostly isolated and irregular morphological low-dimensional forms, seen as rolled-up floss flowers, together with local, elongated, complex stalks similar to Liatris flowers, which contained joined short flosses in the form of nanodendrites. Beyond this, XPS studies showed that these nanostructures exhibited a slight surface nonstoichiometry, mostly related to the existence of oxygen-deficient regions, combined with strong undesired C surface contamination. In addition, the TDS studies showed that these undesired surface contaminations (including mainly C species and hydroxyl groups) are only slightly removed from the surface of our flower-like ZnO nanostructures, causing an expected modification of their nonstoichiometry. All of these effects are of great importance when using our flower-like ZnO nanostructures in gas sensor devices for detecting oxidizing gases because surface contamination leads to an undesired barrier for toxic gas adsorption, and it can additionally be responsible for the uncontrolled sensor aging effect.

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42

Mansurova, R. M., A. K. Umbetkaliev, N. K. Zhylybaeva, N. Erezhep, K. Dosumov e Z. A. Mansurov. "Ni-Carbon Mineral Sorbent - Catalyst of Sulfur Dioxide Sorption". Eurasian Chemico-Technological Journal 3, n. 2 (1 luglio 2017): 119. http://dx.doi.org/10.18321/ectj554.

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The morphology and structure of Ni-carbon mineral sorbent-catalysts on the basis of local mineral raw material were studied by methods of thermoprogrammed desorption and electron microscopy. The specific<br />surface, filamentary carbon diameter sizes and sorption characteristics of sulfur dioxide adsorption were determined. It was shown that the adsorption capacity of carboncontaining sorbents is influenced by: nature of metals of varying valence, specific surface and density of patterns. Physical and chemical sorption of sulfur dioxide was shown experimentally.

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Grau Turuelo, Constantino, Rebecca Grün e Cornelia Breitkopf. "Simulation of the Frequency Response Analysis of Gas Diffusion in Zeolites by Means of Computational Fluid Dynamics". Minerals 13, n. 10 (22 settembre 2023): 1238. http://dx.doi.org/10.3390/min13101238.

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Frequency response (FR) analysis allows the characterization of gas diffusion occurring within a porous solid system. The shape of the pressure response curves obtained after a volume modulation in the reactor gives essential information about the gas adsorption and desorption properties of the porous material, e.g., zeolites, which is in contact with a certain gas environment, as well as information about the transport phenomena such as diffusion. In this work, a simulation model developed in COMSOL Multiphysics® is introduced to reproduce the experimental behavior of the tested solid/gas systems. This approach covers, for the first time, a coupling of computational fluid dynamics (CFD), porous media flow, and a customized mass adsorption/desorption function to simulate the behavior of real frequency response systems. The simulation results are compared to experimental data obtained from the interaction of propane in MFI zeolites as well as additional data from the literature to evaluate the model validity. Furthermore, a small variation study of the effect of simulation parameters such as the mass of the sample, bed porosity, or geometry is performed and analyzed. The essential advantage of this model with respect to other analytical approaches is to observe the spatial pressure and adsorption distribution (along with other local effects) of the gas within the porous material. Thus, local environments can be visualized, and non-idealities can, therefore, be detected in contrast to the general integral simulation approach.

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Fiorani, Andrea, Stefania Rapino, Giulia Fioravanti, Giovanni Valenti, Massimo Marcaccio e Francesco Paolucci. "Local desorption of thiols by scanning electrochemical microscopy: patterning and tuning the reactivity of self-assembled monolayers". Journal of Solid State Electrochemistry 20, n. 4 (27 agosto 2015): 1037–42. http://dx.doi.org/10.1007/s10008-015-3020-7.

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45

Ebihara, Ken-ichi, Hideo Kaburaki, Tomoaki Suzudo e Kenichi Takai. "A Numerical Study on the Validity of the Local Equilibrium Hypothesis in Modeling Hydrogen Thermal Desorption Spectra". ISIJ International 49, n. 12 (2009): 1907–13. http://dx.doi.org/10.2355/isijinternational.49.1907.

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46

Sébenne, C. A., J. P. Lacharme, I. Andriamanantenasoa e M. Khial. "Local roughness and surface states on Si(001): Analysis of vacuum annealings and oxygen adsorption-desorption processes". Applied Surface Science 41-42 (gennaio 1990): 352–56. http://dx.doi.org/10.1016/0169-4332(89)90084-6.

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47

Dubey, Som Shankar, Battula Sreenivasa Rao, B. S. A. Andrews e B. Venkata Kiran. "Efficient Removal of Ce(III) and Eu(III) Ions from Aqueous Solutions by Local Clay -A Radiotracer Study". E-Journal of Chemistry 8, n. 2 (2011): 917–23. http://dx.doi.org/10.1155/2011/686592.

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Radiotracer technique has been used to study the removal behavior of Ce(III) and Eu(III) ions from aqueous solutions by local clay. Adsorptive concentration (10-4–10-6mol dm-3), pH (ca2.0-9.0) and temperature (303-333 K) were examined for assessing optimal conditions for removal of these ions. The adsorption phenomenon was highly dependent on the amount of the adsorbent concentrations. The uptake of ions, which fitted well for Freundlich isotherm, increased with increase in the temperature and no significant desorption took place in the studied temperature range. The energy of adsorption process for the both cations indicates that the adsorption phenomenon is of chemisorption type. The rate kinetics of the adsorption followed the first order rate kinetics.

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48

Alsawalha, Murad. "Overview of Current and Future Perspectives of Saudi Arabian Natural Clinoptilolite Zeolite: A Case Review". Journal of Chemistry 2019 (3 marzo 2019): 1–16. http://dx.doi.org/10.1155/2019/3153471.

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After a thorough review of existing studies of clinoptilolite zeolites, three areas for potential investigation of the Saudi Arabian zeolites were found. They are the characterizations, the catalytic activity, active sites, and uses of natural clinoptilolite zeolites. First, no analysis is available worldwide to compare the percentage weight of local zeolites with those sourced from other countries, nor does one exist for the establishment on the zeolite conversion of MBOH with water on acidic catalysts at lower temperatures. Secondly, a review of current literature on the topic revealed that basic and active sites of Saudi Arabian zeolites have yet to be examined. Future investigation of zeolite catalytic activity can be achieved by methyl butynol test reaction (MBOH) and absorption-desorption of ammonia. In the characterization of a range of international materials, the methyl butynol test reaction was utilized, including on natural zeolites, natural clays, and synthesized hydrotalcites. However, the catalytic performance of natural Saudi Arabian clinoptilolite zeolites by test reaction of MBOH conversion has not been yet investigated. Therefore, this article also includes an outline of the general testing conditions and parameters required to execute the accurate characterization of local Saudi clinoptilolite under optimal test conditions. Likewise, knowledge of the important active acidic centers of local materials is prescribed. This can be ascertained by determining the conditions together with the test parameters for the application of the “temperature-programmed desorption of ammonia” method in order to obtain an accurate determination of local Saudi clinoptilolite acidic centers. Additionally, an outline of the catalytic activity of worldwide clinoptilolite is given in this article together with kinetic investigations of other sources for the clinoptilolite zeolite in order to form the basis for the testing of local Saudi clinoptilolite. The percentage average of chemical composition (Wt.%) of natural clinoptilolite from various countries is also included. Finally, a future research plan is proposed here. This will form the basis for a complete study or survey to be compiled detailing the modifications needed to increase the surface areas for Saudi natural clinoptilolite zeolites using different methods of modifications. This could enhance its application as acid catalysts for use in the retardation of coke formation and for membrane separation on cationic exchange.

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Sgobba, Elvira, Yohann Daguerre e Marco Giampà. "Unravel the Local Complexity of Biological Environments by MALDI Mass Spectrometry Imaging". International Journal of Molecular Sciences 22, n. 22 (17 novembre 2021): 12393. http://dx.doi.org/10.3390/ijms222212393.

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Classic metabolomic methods have proven to be very useful to study functional biology and variation in the chemical composition of different tissues. However, they do not provide any information in terms of spatial localization within fine structures. Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI MSI) does and reaches at best a spatial resolution of 0.25 μm depending on the laser setup, making it a very powerful tool to analyze the local complexity of biological samples at the cellular level. Here, we intend to give an overview of the diversity of the molecules and localizations analyzed using this method as well as to update on the latest adaptations made to circumvent the complexity of samples. MALDI MSI has been widely used in medical sciences and is now developing in research areas as diverse as entomology, microbiology, plant biology, and plant–microbe interactions, the rhizobia symbiosis being the most exhaustively described so far. Those are the fields of interest on which we will focus to demonstrate MALDI MSI strengths in characterizing the spatial distributions of metabolites, lipids, and peptides in relation to biological questions.

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Charvat, Ales, Andreas Bógehold e Bernd Abel. "Time-Resolved Micro Liquid Desorption Mass Spectrometry: Mechanism, Features, and Kinetic Applications". Australian Journal of Chemistry 59, n. 2 (2006): 81. http://dx.doi.org/10.1071/ch05249.

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Liquid water beam desorption mass spectrometry is an intriguing technique to isolate charged molecular aggregates directly from the liquid phase and to analyze them employing sensitive mass spectrometry. The liquid phase in this approach consists of a 10 µm diameter free liquid filament in vacuum which is irradiated by a focussed infrared laser pulse resonant with the OH-stretch vibration of bulk water. Depending upon the laser wavelength, charged (e.g. protonated) macromolecules are isolated from solution through a still poorly characterized mechanism. After the gentle liquid-to-vacuum transfer the low-charge-state aggregates are analyzed using time-of-flight mass spectrometry. A recent variant of the technique uses high performance liquid chromatography valves for local liquid injections of samples in the liquid carrier beam, which enables very low sample consumption and high speed sample analysis. In this review we summarize recent work to characterize the ‘desorption’ or ion isolation mechanism in this type of experiment. A decisive and interesting feature of micro liquid beam desorption mass spectrometry is that — under certain conditions — the gas-phase mass signal for a large number of small as well as supramolecular systems displays a surprisingly linear response on the solution concentration over many orders of magnitude, even for mixtures and complex body fluids. This feature and the all-liquid state nature of the technique makes this technique a solution-type spectroscopy that enables real kinetic studies involving (bio)polymers in solution without the need for internal standards. Two applications of the technique monitoring enzyme digestion of proteins and protein aggregation of an amyloid model system are highlighted, both displaying its potential for monitoring biokinetics in solution.

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