Miracle-dz/UniFAR-FTUs huggingface dataset:
On the stability of fluorine ions in AlGaN/GaN heterostructures: A molecular dynamics simulation study

Fluorine ions can be effectively incorporated into AlGaN/GaN high electron mobility transistor (HEMT) structures, enabling the modulation of local potential and carrier density. The physical mechanism of fluorine incorporation in AlGaN/GaN heterojunctions is of fundamental importance to the stability of fluorine ions in AlGaN/GaN HEMTs. In this work, the molecular dynamic (MD) simulation method is used to calculate the potential energies of interstitial and substitutional fluorine atoms in AlGaN/GaN material system. Ziegler-Biersack-Littmark (ZBL), Lindhard-Sorensen (L-S) and Coulomb potential functions are applied in the MD simulation. The geometric lattice structures, spontaneous and piezoelectric polarizations, and temperature dependence are also included in the simulation. The activation energies associated with interstitial-substitutional and interstitial-interstitial diffusions are obtained. It is revealed that the fluorine ions are most likely located at the substitutional group-III cation sites S(III) and the diffusion of fluorine ions should be dominated by S(III)-interstitial process which exhibits an activation energy of 1.1 eV in Al0.25Ga0. 75N and 1.4 eV in GaN in the presence of group-III vacancies. It is expected that the removal of group-III vacancies can significantly suppress the fluorine diffusion, which in turn, leads to excellent fluorine stability in III-nitride materials. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
El congreso académico como espacio para la formación de investigadores. El caso del Encuentro Nacional de Estudiantes de Posgrado en Educación

espanolUno de los eventos mas importantes para la investigacion educativa mexicana es el Congreso Nacional de Investigacion Educativa, en el que, desde 2011, tiene lugar el Encuentro Nacional de Estudiantes de Posgrado (ENEPE). Tras una breve revision de la literatura en torno a la formacion para la investigacion educativa y los congresos academicos, planteamos que el analisis del ENEPE aporta informacion relevante sobre la formacion para la investigacion. Para ello abordamos las ultimas dos ediciones del encuentro (2015 y 2017) a partir del proceso de dictaminacion, el perfil de sus ponentes y la revision de las contribuciones no aceptadas. Se constata que los estudiantes con mejores resultados se afilian a un pequeno conjunto de instituciones, aunque tambien se advierten instituciones “emergentes”. Por ultimo, se apuntan algunos retos del ENEPE en lo que respecta a la formacion de investigadores educativos. EnglishOne of the most important events in Mexico’s educational research is the National Congress of Educational Research where, since 2011, the National Meeting of Graduate Students (ENEPE) has taken place. Following a brief review of the literature on training for educational research and academic congresses, we suggest that analyzing ENEPE will contribute relevant information on training for research. For this reason, we studied the last two publications of the meeting (2015 y 2017), focusing on the process of evaluating papers, the profile of speakers, and the revision of submissions that were not accepted. The results show that the students with the best results are affiliated with a small set of institutions, although “emerging” institutions are also present. In conclusion, attention is drawn to various challenges that ENEPE faces with respect to training educational researchers.
A Co‐Functionalization Approach to Soluble and Functional Single‐Walled Carbon Nanotubes

A new class of single-walled carbon nanotube (SWNT) derivatives have been synthesized by means of an oxidation route that leads to shortened nanotubes bearing carboxylic acid end groups. The simultaneous attachment of poly(ethylene glycol)amine (PEG–NH2) and amine derivatives of aromatic fluorophores was achieved through the formation of amide bonds. Different soluble products have been obtained from 2-aminofluorene, 2-aminoanthracene and 1-aminomethylnaphthalene. Basic spectroscopic characterization revealed peculiar features, such as quenching of the fluorescence, that suggest intramolecular interactions between the tubes and the attached aromatic moieties. The proposed co-functionalization procedure could be easily extended to obtain a wide range of soluble organic derivatives of SWNTs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
A marked improvement in the reliability of the measurement of trace moisture in gases

The reliability of the measurement of trace moisture in a gas was improved markedly owing to the establishment of a trace moisture standard at AIST. As a result, problems with conventional methods for measuring trace moisture in gases were revealed. This article presents the scenario which we adopted to improve the reliability of measurement of the trace moisture, the development of a national trace moisture standard, the provision of a metrological system traceable to a national standard for industrial measurements, and problems revealed of trace moisture analyzers available commercially through comparisons with the national standard. This improvement makes it possible to evaluate properly the quality of high purity gases used in industry.
UV-Ozone Generation from Modified High Intensity Discharge Mercury Vapor Lamps for Treatment of Indium Tin Oxide Films

In a homemade UV-Ozone generator, different ignition tubes extracted from HID mercury vapor lamps were investigated, namely: 80, 125, 250 and 400 watts. The performance of the generator in function of the type of the ignition lamp was monitored by the measurements of the ozone concentration and the temperature increment. The results have shown that the 400 W set up presented the highest ozone production, which was used in the treatment of indium tin oxide (ITO) films. Polymer light emitting diodes were assembled using ITO films, treated for 10, 20 and 30 min, as an anode. The overall results indicate improvement of the threshold voltage (reduction) and electroluminescence of these devices.
Emulsifier-free emulsion polymerization of N-butyl methacrylate

A cationic polymer of n-butyl methacrylate was prepared in an emulsifier-free system. Using, as a base, a 30% solid content, the variables studied were the monomer and initiator concentrations, the agitation, and the temperature. The molecular weight, the zeta potential, and the particle size were determined. The results are compared with earlier work done on similar systems. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1711–1719, 1998
Surface Electric Properties of Polypyrrole in Aqueous Solutions

The electric properties, for example, ζ potential and surface charge, of a solid in contact with an aqueous solution play an important role in various interfacial and colloidal phenomena, as well as in adsorption and filtration processes. In this study, the ζ potentials of chloride-doped polypyrrole (PPyCl) particles were investigated as a function of solution pH values. It was found that PPyCl particles had a zero point of ζ potential at about pH = 10, and the ζ potentials varied with solution pH values, which also greatly depended on the different pH ranges. With a treatment of PPyCl in a sodium hydroxide solution at pH = 14 (denoted as D-PPy), the ζ potentials of D-PPy at various solution pH values became significantly different from those of PPyCl and the zero point of ζ potential of D-PPy appeared at about pH = 3.5. A further treatment of D-PPy in a hydrochloric acid solution at pH = 0 (denoted as R-PPy), however, restored the ζ potentials of R-PPy at various solution pH values to almost the same as .
Applications and Environmental Aspects of Chitin and Chitosan

Abstract A survey on the properties of the natural nitrogen-containing polysaccharides chitin and chitosan is given. Outstanding features are the materials' mechanical and chemical properties which offer numerous, largely unexplored applications in technology, chemistry, medicine, and agriculture. Derivatives of chitin and chitosan are accessible by reactions of the hydroxy and amino groups with appropriate reagents. Various types of gels, membranes, and fibers, including polycationic and watersoluble materials, can be formed. Production of chitin and chitosan from waste crab shells involves environmentally safe processes. The polysaccharides are recycled in nature by enzymatic degradation and reuse of N-acetylglucosamine for biosynthesis and catabolism. Research deficits exist in economically competitive production technologies, construction of composite materials, and the ecological aspects of chemically modified chitosan.
CONTEMPORARY ANALYSES IN ASSESSING RESIDUAL STRESS TOPOGRAPHIC IMAGES ENCLOSING A COLD EXPANDED HOLE

Abstract Cold expansion of holes is a complex process; therefore, it is of prime importance to assess the three-dimensional nature of residual stresses surrounding a cold expanded hole. In the present work; the method of step drilling and a novel Fourier series solution were abridged to construct the through thickness residual hoop stress pattern available for any orientation around the hole. Secondly and based on the properties of the experimental data, Artificial Neural Network (ANN) modelling was employed to develop and then train the simulation of complete stress pattern encircling the bore. Results of the experimental technique and ANN prediction were collated by the use of statistical error analyzing methods where mean error percentages were remarkably small for training and testing indicating that these two entirely different approaches were in agreement. At a specific orientation at the bore, some results of the step drilling-Fourier series solution, diffraction methods and ANN modelling were in conformity and similitude was valid only for sections through the thickness at which stress gradient was not changing erratically. La dilatation à froid des ajours est un procédé complexe; il est donc de première importance d’évaluer la nature tri-dimensionnelle des contraintes résiduelles entourant un ajour dilaté à froid. Dans le présent travail, on a abrégé la méthode de perçage en étape ainsi qu’une nouvelle solution de la série de Fourier pour construire, au travers de l’épaisseur, le patron de contrainte périphérique résiduelle disponible pour toute orientation autour de l’ajour. Deuxièmement, en se basant sur les propriétés des données expérimentales, on a utilisé la modélisation de réseau neuronal artificiel (ANN) pour développer et ensuite entraîner la simulation de patron entier de contrainte entourant le trou. On a compilé les résultats de la technique expérimentale ainsi que la prédiction de l’ANN au moyen de méthodes d’analyse d’erreur statistique où les pourcentages d’erreur moyenne étaient remarquablement petits pour l’entraînement et l’évaluation, indiquant que ces deux approches complètement différentes étaient en accord. À une orientation spécifique en bordure du trou, certains résultats de perçage en étape-solution de la série de Fourier, méthodes de diffraction et modélisation d’ANN étaient en conformité et la similitude était valide seulement pour les sections au travers de l’épaisseur où le gradient de contrainte ne changeait pas de façon erratique.
Avaliação da resposta à eritropoetina no tratamento de pacientes portadores de síndrome mielodisplásica

O estudo teve como objetivo avaliar a resposta a Eritropoetina no tratamento de pacientes portadores de Sindrome Mielodisplasica (SMD). Durante a analise de variaveis que poderiam estar implicadas nessa resposta, foi possivel estabelecer uma forte associacao (Phi e Cramer’s V de 0,67) (p = 0,000) entre os pacientes que respoderam ao tratamento com eritropoetina e nao eram dependentes transfusionais e entre os que nao responderam ao tratamento e eram dependentes transfusionais. A hemoglobina pre tratamento apresentou uma mediana de 10,3 g/dl para os pacientes que responderam a eritropoetina e de 7,2 g/dl para os pacientes que nao responderam a eritropoetina (p = 0,001). A ferritina, dentre o grupo que apresentou resposta a EPO, tinha uma mediana de 297 ng/ml comparada a mediana de 653 ng/ml para o grupo que nao respondeu ao tratamento (p = 0,033). Os pacientes que responderam a EPO apresenetaram sobrevida media de 2376 dias (95% IC 2031 a 2722) e os que nao responderam, 1470 (95% IC 1184 a 1757) (p = 0,035), corroborando que resposta ao tratamento e capaz de alterar sobrevida de pacientes com SMD de baixo risco. Diante disso, concluimos que os niveis de concentracao de hemoglobina baixos, os niveis de ferritina elevados e a dependencia transfusional tem um impacto negativo na resposta a eritropoetina.
Vapor-Phase Lubrication: Reaction of Phosphate Ester Vapors with Iron and Steel

Aromatic phosphate esters such as triphenyl phosphate, tricresyl phosphate (TCP), and tri(tert-butylphenyl) phosphate, have been degraded in the presence of pure iron or metal alloys such as M-50 or 52100 steel. Among these volatile degradation products are those generated from the addition of an aromatic ring to the phosphate ester. Other products, which have been identified, include substituted biphenyls and diphenyl ethers derived from the decomposition of the above-mentioned addition product. Still other products are fused ring aromatic compounds such as anthracene, which arise from secondary reactions of the initial decomposition reactions. The decomposition reactions leave a nonvolatile phosphate film on the surface of the metal. Characterization of the film with Auger spectroscopy suggests iron phosphate as the product. X-ray photoelectron spectroscopy shows the presence of a bound organic layer at the surface. A mechanism that explains many of the decomposition products and the formation of a boun.
Isolation and Characterization of Pseudomonas stutzeri Capable of Reducing Fe(III) and Nitrate from Skarn-type Copper Mine Tailings

Nitrate and Fe(III) are two terminal electron acceptors in anaerobic respiration by microorganisms growing in the anoxic soil or sediment environment. In the current paper a facultative anaerobic dissimilatory Fe(III)- and nitrate-reducing bacterium was isolated from the Linchong tailings, a skarn-type copper mine tailings, located in Anhui. Skarn often formed at the contact zone between intrusions of granitic magma bodies into contact with carbonate sedimentary rocks. This made the tailings possessed strong acid neutralizing capacity and pH of the pore water was 6.8–8.6. The isolate, which was designated strain CW (CCTCC AB 2013114), was a gram-negative rod bacterium and belonged to the gamma subgroup p of the proteobacteria, closely (99.0%) related to Pseudomonas stutzeri. In defined medium, strain CW was shown to grow anaerobically with the acetate using the ferric iron or nitrate as the electron acceptors. Results also showed that strain CW could not grow in the presence of ferrous iron and nitrite.
Gas Permeation Through Poly(Ether‐b‐amide) (PEBAX 2533) Block Copolymer Membranes

Abstract The development of polymeric membranes for gas separations provides an alternative to traditional energy intensive processes, especially for hydrocarbon separations. We investigated the permeation behavior of several gases through poly(ether‐b‐amide) PEBAX 2533 copolymer membranes over a range of operating temperatures and feed pressures. Permeability coefficients were determined at temperatures ranging from 25°C to 75°C, and feed pressures from 25 to 200 psig for ethane, ethylene, nitrogen, propane, and propylene. Carbon dioxide was also studied to better appreciate the interaction between a polar gas and the membrane. The PEBAX 2533 membranes showed high hydrocarbon permeabilities. Plasticization effects on the membrane were pronounced with propane and propylene at elevated pressures. Activation energies of permeation were determined, which showed a linear decreasing trend with pressure increases for hydrocarbons.
Ryegrass Response to Mineral Fertilization and Organic Amendment with Municipal Solid Waste Compost in Two Tropical Agricultural Soils of Mali

Abstract A pot experiment was conducted to assess the effect of mineral fertilization and compost on the growth and chemical composition of ryegrass (Lolium perenne L.) grown on two Malian agricultural soils coming from Baguinéda, abbreviated as Bgda, (12°23′ S, 7°45′ W) and Gao (16°18′ N, 0°). Treatments included non‐fertilized control, NPK alone, NPK + C25, NPK + C50, NPK + C100, PK + C50, NK + C50, NP + C50, K + C50, P + C50, N + C50, and C50 alone, where NPK represents the non modified Hoagland's solution and C25, C50, and C100 represent the different rates (25, 50, and 100 T/ha) of compost. Compost and mineral fertilization significantly increased dry matter production. The application of 50 T/ha of compost alone increased the dry matter yield by 10 and 17.5% while mineral nitrogen–phosphorus–potassium (NPK) increased yield by 69.7 and 65% for Gao and Bgda, respectively. The combination of compost and mineral NPK (NPK + C25 for Gao and NPK + C50 for Bgda) affected the highest dry matter yield. For both soils, N concentrations in plants increased significantly with compost rate. Phosphorus and K concentrations in plants varied according to the soil. The application of compost increased the uptake of iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), and potassium (K from both soils). Increases in soil organic carbon, available P, calcium (Ca), magnesium (Mg), Fe, Mn, Zn, Cu, K, and pH were observed in treatments receiving compost. Therefore, compost appeared to be a good supplier of nutrients for tropical soils.
Thermal Oxidation of Silicon in Nitrous Oxide at High Pressures

Thermal oxidation of silicon in nitrous oxide (N 2 O) ambient at pressures from I to 4 atm has been studied. We show that the oxidation rate is different from the one predicted by the Deal-Grove model for normal oxidation in dry oxygen. In our case, the dependence observed for the oxide thickness as a function of the oxidation time is of the form x = x 0 + (γt) β , where x 0 is a native oxide thickness. For the temperature range between 900 and 1200°C, and 2 atm of pressure, the activation energy for γ is around 1.18 eV. In addition, the exponential factor β (at 1000°C) varies as the square root of the N 2 O pressure. These results indicate that thermal oxidation in N 2 O behaves in a completely different way than normal oxidation, very likely due to the influence of chemical reactions in the gas phase, to the catalytic influence of the N 2 O-SiO 2 interface, and to the incorporation of nitrogen into the oxide film itself. The results presented here establish the basis for the development of a more complete model for thermal oxidation of silicon in a N 2 O ambient.
On the synthesis and characterization of biodegradable dextran nanogels with tunable degradation properties

Hydrogels are widely investigated as carriers in drug delivery. To be suitable carriers for intracellular drug delivery, hydrogels should be small enough to be able to enter cells. This paper reports on the synthesis and characterization of both lipid coated and naked biodegradable hydroxyethyl methacrylated dextran (dex-HEMA) nanogels. Dynamic light scattering (DLS), atomic force microscopy, and transmission electron microscopy showed that lipid coated nanogels could be obtained by polymerization of an aqueous dex-HEMA solution entrapped in SOPC/DOTAP liposomes (SOPC and DOTAP, respectively, being l-stearoyl-sn-glycero-3-phosphocholine and 1,2-dioleolyl-3-trimethylamonium propane chloride). Naked dex-HEMA nanogels were prepared by removing the lipid coating by Triton X100. DLS measurements on dex-HEMA nanogels stored in buffer at 37 °C revealed that the degradation time depended on the cross-link density of the nanogels: dex-HEMA nanogel prepared from dextran lowly substituted with HEMA degraded quickly, while it took days to weeks for nanogels prepared from highly substituted dextran. Furthermore, confocal laser scanning microscopy showed that SOPC/DOTAP coated dex-HEMA nanogels can be taken up by VERO-1 cells.
Ion Concentrations of Particulate Matter in Yongin in Spring and Fall

Mass and ion concentrations of and were measured in Yongin, downwind of the Seoul metropolitan area. Twenty-four hour average samples were collected daily for a month or so in spring and fall of both 2007 and 2008. Asian dust occurred twice in each period except in the fall of 2007. During the Asian dust period, nitrate in fine particles decreased since large amount of cations in coarse particles of Asian dust absorbed it. In spring 2008, sulfate as well as ammonium also increased in coarse particles. In spite of occasional Asian dust events, the influence of secondary formation was dominant over the period. Excessive ammonium over sulfate was enough to neutralize nitrate as well. High correlation coefficients between and sulfate, nitrate, and ammonium indicate a close relationship between secondary formation and biomass burning. Biomass burning and open burning are considered to be important sources of chloride.
Charge Controlled Swelling of Microgel Particles

The swelling of cationic microgel particles has been studied experimentally, in the weak screening regime. The solution pH was selected as the external variable triggering the swelling, which was followed by dynamic light scattering. The particle charge was determined by conductometric and potentiometric titrations, leading to a good correlation between the charge of the microgel network and its size. This leads to the conclusion that the swelling is mainly charge controlled. The Flory−Huggins thermodynamic theory for gels, including a term accounting for the counterion distribution within the microgel, has been used to interpret the experimental data. The osmotic term associated with the counterions explains fairly well the observed behavior, and additional contributions due to the internal microgel microscopic structure are not necessary, as Pincus et al. have suggested.
Critical conditions for the binding of polyelectrolytes to small oppositely charged micelles

Mixed micelles associate with polyelectrolytes of opposite charge to form soluble or insoluble complexes. The interaction takes place abruptly-signaled by a sudden enhancement in scattering-upon an increase of micelle surface charge density, an increase in polymer linear charge density, or a decrease in ionic strength, and involves a microscopic or macroscopic phase change. Because the surface charge state and the dimensions of the mixed micelles may be varied over a wide range, the polyion-micelle system provides a useful model for polyelectrolyte-colloid interactions
Compiling a field manual from overhead photographs for estimating crop residue cover

A method is presented for compiling a manual for the estimation of crop residue cover in the field. The crop residue is a combination of standing stubble and the straw remaining on the ground after harvest. Field assessment of crop residue is important so that management decisions may be made in the field. Such decisions include selection of cultivation or sowing machinery, irrigation scheduling (for crusting materials), soil temperature control and grazing of crop residue. The manual consists of a graded set of colour photographs, taken from an overhead boom, and a sampling rate nomogram to determine the number of 1 m quadrats required in a given field to estimate the cover with a predetermined level of error. Two methods for calibration of the photographs are compared: (a) projection of slides onto a screen with manual counting, and (b) digital image analysis of the photographs. Image analysis is efficient, rapid and gives less error than counting from the projections because many more points are counted. The use of the manual in the field is described. It is an inexpensive piece of equipment for the field agronomist or farmer, and gives a reliable, rapid and semi-quantitative estimate of residue cover.