Surface Formate Research Articles

Study of Groove Formation in InP Surface During Zn Diffusion

Study of Groove Formation in InP Surface During Zn Diffusion

Karstic aquifer structure from geoelectrical modeling in the Ring of Sinkholes, Mexico

Groundwater models based on terrain resistivity can show the diverse properties and processes occurring between fractures, boreholes and conduits. Using electrical resistivity tomography, a conceptual model was created of the aquifer within the Ring of Cenotes, which surrounds the Chicxulub Crater on the Yucatan Peninsula, Mexico. Determining the hydrogeological parameters of an aquifer is vital since they determine flux and hydrodynamic patterns. In karstic environments, conventional techniques are not effective at recording heterogeneities such as fracture zones and conduits. Six transects were investigated among areas near cenotes (sinkholes) and aguadas (small surface-water bodies), as well as areas lacking these formations. The resulting profiles reached up to 30 m deep and showed an aquifer consisting of a fractured matrix saturated with freshwater. The matrix exhibiting resistivity values from 3 to 250 Ωm, lying under a vadose zone with values from 300 to 25,000 Ωm. Aguadas and cenotes are surface manifestations of the aquifer’s internal structure, which is a network of caves and conduits. In the Ring of Cenotes, the presence of these surface formations indicates increased hydraulic conductivity in their vicinity, with smaller conduits or fractures providing lesser conductivity in areas further away.

Methanol Synthesis from CO2 Hydrogenation.

In the future we will be phasing out the use of fossil fuels in favour of more sustainable forms of energy, especially solar derived forms such as hydroelectric, wind and photovoltaic. However, due to the variable nature of the latter sources which depend on time of day, and season of the year, we also need to have a way of storing such energy at peak production times for use in times of low production. One way to do this is to convert such energy into chemical energy, and the principal way considered at present is the production of hydrogen. Although this may be achieved directly in the future via photocatalytic water splitting, at present it is electrolytic production which dominates thinking. In turn, it may well be important to store this hydrogen in an energy dense liquid form such as methanol or ammonia. In this brief review it is emphasised that CO2 is the microscopic carbon source for current industrial methanol synthesis, operating through the surface formate intermediate, although when using CO in the feed, it is CO which is hydrogenated at the global scale. However, methanol can be produced from pure CO2 and hydrogen using conventional and novel types of catalysts. Examples of such processes, and of a demonstrator plant in construction, are given, which utilize CO2 (which would otherwise enter the atmosphere directly) and hydrogen which can be produced in a sustainable manner. This is a fast‐evolving area of science and new ideas and processes will be developed in the near future.

Improvement of Low-Alloy Pipe Steel Sulfide Stress Cracking Resistance

The influence of sheet microstructure formed by various thermomechanical processing schedules on sulfide stress cracking (SSC) resistance under uniaxial tension for low-alloy pipe steels grades X42–X65 is studied. A favorable role is established for substitution of a ferritic-pearlitic by a ferritic-bainitic microstructure and improvement of structural component dispersion is established. The favorable effect is facilitated by using high intensity post-deformation cooling from the austenite region. It is shown that segregation bands and non-metallic inclusions in a sheet axial zone do not affect the duration of specimens withstanding SSC, but they can lead to formation of hydrogen cracks (HIC) on a specimen surface that is a defective feature. In order to prevent crack formation in a specimen surface and premature failure it is necessary to lay down high specifications for specimen gauge length and fillet surface quality.

Enhanced bone regeneration capability of chitosan sponge coated with TiO2 nanoparticles

Chitosan has been a popular option for tissue engineering, however exhibits limited function for bone regeneration due to its low mechanical robustness and non-osteogenic inductivity. Here we hybridized chitosan with TiO2 nanoparticles to improve its bone regeneration capability. Morphology and crystallographic analysis showed that TiO2 nanoparticles in anatase-type were distributed evenly on the surface of the chitosan sponges. Degradation test showed a significant effect of TiO2 nanoparticles addition in retaining its integrity. Biomineralization assay using simulated body fluid showed apatite formation in sponges surface as denoted by PO4− band observed in FTIR results. qPCR analysis supported chitosan - TiO2 sponges in bone regeneration capability as indicated by DMP1 and OCN gene upregulation in TiO2 treated group. Finally, cytotoxicity analysis supported the fact that TiO2 nanoparticles added sponges were proved to be biocompatible. Results suggest that chitosan-50% TiO2 nanoparticles sponges could be a potential novel scaffold for bone tissue engineering.

Histological evaluation of platelet-rich fibrin for revascularization of immature permanent teeth in dogs

AimThe aim of this study was to evaluate the platelet rich fibrin as a scaffold for revascularization of immature root canals in dogs. Study designSixteen double rooted teeth divided into two main groups A and B (contaminated and non-contaminated). Each group included two sub groups, one experimental (platelet rich fibrin subgroup) and the other is control (calcium hydroxide subgroup). After six months, dogs were sacrificed and histological evaluation of prepared sections was done for apical closure, internal root thickness and new vital pulp tissue formation. ResultsIn contaminated root canals regarding all parameters used (apical closure, internal root thickness and new vital pulp tissue formation), PRF subgroup showed higher values than control subgroup with significant difference only in hard tissue formation in internal root surface. Non-contaminated PRF treated root canals showed better results than control subgroup and significant difference was in new intra canal vital pulp tissue formation only. No significant difference was clear between the two main groups. ConclusionPlatelet rich fibrin is a good intra-canal scaffold for revascularization of immature permanent teeth.

Elucidation of the Reaction Mechanism for High-Temperature Water Gas Shift over an Industrial-Type Copper-Chromium-Iron Oxide Catalyst.

The water gas shift (WGS) reaction is of paramount importance for the chemical industry, as it constitutes, coupled with methane reforming, the main industrial route to produce hydrogen. Copper-chromium-iron oxide-based catalysts have been widely used for the high-temperature WGS reaction industrially. The WGS reaction mechanism by the CuCrFeO x catalyst has been debated for years, mainly between a "redox" mechanism involving the participation of atomic oxygen from the catalyst and an "associative" mechanism proceeding via a surface formate-like intermediate. In the present work, advanced in situ characterization techniques (infrared spectroscopy, temperature-programmed surface reaction (TPSR), near-ambient pressure XPS (NAP-XPS), and inelastic neutron scattering (INS)) were applied to determine the nature of the catalyst surface and identify surface intermediate species under WGS reaction conditions. The surface of the CuCrFeO x catalyst is found to be dynamic and becomes partially reduced under WGS reaction conditions, forming metallic Cu nanoparticles on Fe3O4. Neither in situ IR not INS spectroscopy detect the presence of surface formate species during WGS. TPSR experiments demonstrate that the evolution of CO2 and H2 from the CO/H2O reactants follows different kinetics than the evolution of CO2 and H2 from HCOOH decomposition (molecule mimicking the associative mechanism). Steady-state isotopic transient kinetic analysis (SSITKA) (CO + H216O → CO + H218O) exhibited significant 16O/18O scrambling, characteristic of a redox mechanism. Computed activation energies for elementary steps for the redox and associative mechanism by density functional theory (DFT) simulations indicate that the redox mechanism is favored over the associative mechanism. The combined spectroscopic, computational, and kinetic evidence in the present study finally resolves the WGS reaction mechanism on the industrial-type high-temperature CuCrFeO x catalyst that is shown to proceed via the redox mechanism.

Absorbent Food PADS from Meat Packages-Potential Source of Contamination

The purpose of this study was to quantify the microbial load and to detect potentially pathogenic germs on the surface of absorbent food pads in the packaging of fresh chicken and minced meat marketed in the retail units in Romania. The load in E. coli, as an indicator of faecal contamination, was significantly lower than that of Enterobacteriacea and coliform germs. Congo red-binding E. coli strains have been identified. The affinity for the Congo red dye is considered a phenotypic marker for the presence of curli fibers. These surface formations give the bacterial strains the ability to form biofilm on various surfaces. Their presence also correlates with the property of these bacterial strains to trigger severe infections in humans. These strains showed 100% resistance to fourth-generation cephalosporins, 87.5% to third-generation cephalosporins and 75% to quinolones. A single strain was resistant to meropenem. All the tested strains were susceptible to gentamicin. Coagulase-positive staphylococci were identified in 40% of the analyzed samples. Of the 30 strains of Staphylococcus spp. tested (coagulase-positive and negative), 63.3% proved to be methicillin-resistant and 43.3% had resistance to sulfamethoxazole-trimethoprim. In one sample, it was detected Salmonella infantis. Thus, it can be appreciated that these absorbent food pads may be a source of direct contamination with potentially pathogenic and / or antibiotic-resistant germs for the persons who manipulates them in their domestic environment, as well as a source of cross-contamination of food and other surfaces in the kitchen.

SnO2/Al2O3 catalysts for selective reduction of NOx by propylene: On the promotional effects of plasma treatment in air atmosphere

Abstract To elucidate structure-reactivity relationship and promote the reaction performance of SnO2/Al2O3 for NOx-SCR, a series of catalysts have been prepared by impregnation method and treated by non-thermal dielectric barrier discharge (DBD) plasma. It is quantified that SnO2 disperses on γ-Al2O3 with a monolayer capacity of 0.262 mmol 100 m−2. The catalyst with a SnO2 loading close to the capacity displays the best activity, testifying the presence of a monolayer threshold effect. Plasma treating can improve SnO2 dispersion evidently, thus expanding the monolayer capacity to 0.340 mmol 100 m−2. As a result, the surface Sn cations are enriched, which improves the surface acidity of the catalysts, benefits the adsorption and activation of NO and C3H6 molecules, and eventually enhances the activity. It is concluded that the surface acidic site amount determines the reaction activity of catalysts. Over SnO2/Al2O3 catalysts, NOx-SCR by C3H6 follows a Langmuir-Hinshelwood mechanism. Surface monodentate nitrate and formate are found to be the major active intermediates for the reaction.

Active Surface Species Ruling Product Selectivity in Photocatalytic CO2 Reduction over Pt- or Co-Promoted TiO2

TiO2 is an active material for photocatalytic CO2 reduction. Its performance is improved by the addition of a metal or metal oxide as a cocatalyst. The enhanced electron-trapping capability is widely attributed to the function of these cocatalysts, but their precise roles are not fully understood. Here, we report how Pt and Co cocatalysts boost the formation of H2 and CH4 during photocatalytic CO2 reduction. More specifically, we used in situ diffuse reflectance infrared Fourier transform spectroscopy and multivariate spectral analysis to identify (in)active surface intermediates. Surface formates were identified as reactive intermediates common to all TiO2-based catalysts. The catalytic activity and product selectivity are determined by the unique function of the cocatalyst, which distinctly interacts with the TiO2 surface to produce and decompose formates to H2 or CH4. The evolution of the surface species also clarifies the transient nature of photocatalytic activities and how the TiO2 surface and cocat...

Acoustic emission method in the delayed fracture mechanics of structural materials

In the long-term load (static, cyclic, shunting, etc.) much smaller than the destroyed one, as well as during the influence of physical and chemical factors in the material of the structural element, there is the emergence of new and diffusion of existing physical microdefects (vacancies, dislocations), their unification and formation mechanical defects (pores, microcracks). Further development of the last ones leads to the emergence of macrocracks and their subcritical growth. The result of such process is the loss of structural element integrity. All these processes together form the basis of the delayed fracture mechanics of structural materials. An energy approach was used for mathematical models construction of the structural materials delayed fracture under the mechanical loading and physicochemical factors influence. On this basis, the residual life of the structural elements could be determined. The application of this approach is demonstrated on the example of the high-temperature creep crack propagation. At the same time it should be noted that elementary acts in the delayed fracture mechanics are accompanied by the elastic waves emission (acoustic emission) and the new small size surfaces formation that could not be registered by the existing non-destructive testing. Therefore, in our opinion, the acoustic emission (AE) method is the only one that makes it possible to effectively investigate the structural materials delayed fracture kinetics. Nowadays devices are well fitted to capture the AE events parameters (amplitude and total impulses count), but their connection with the delayed fracture acts characteristics (mechanism and size of the new formed surface) are not known. In the previous studies, the authors theoretically found that the newly formed surface size for one AE event is proportional to its amplitude. This made it possible to determine the crack nucleation period as the sum of the AE events amplitudes multiplied by the corresponding constants. On the basis of this and the aforementioned energy approach, mathematical models were created here through the averaged values of the acoustic emission events parameters for the determination of the precritical periods of the delayed cracks growth during the long-term loads and high temperature influence.

HOW DOES OUR BRAIN CHANGE DURING THE LEARNING PROCESS

This article is devoted to the brain changes during the leaning and teaching process. The results of the study present different tools and methods that equip modern educators and students. The author describes different aspects of the learning process and different learning styles. He provides some information about different stereotypes that appears on our way The author proposes the list of IT-competencies and methodological competences of teachers and students, necessary for been educator in the 21st century. Is it really different to teach in the 21st century than it was to teach in the 20th century or before? Many people saying, that the great evolution was in technologies, but teaching - is teaching and nothing more than that. Our students are digital multi-modal learners, who have different learning styles. They learn quantities of information in a structured surface format they record in working memory and stored in permanent memory for interactivity and reflection. Nowadays students ask more and more multimedia contents. And this is the real profile of our clients, our students, they are asking this to us. Multimodal learning has versus multimedia teaching and humans are multimodal learners. They learn through words, written sentences, images, audio. And all of this shows that our brain has different areas for different functions. We should present our contents in different formats and this modifies format that we should offer our contents, gives us the opportunity to make simultaneous and synchronize. This means that information can be presented four times or more easy understanding of our students. When students use several communication channels it is like we are multiplying the information to be presented. This is the challenge of today. And this stimulates us to create a new pedagogical and technological methods which will be in tune with our time and which will help our students to use their brains operate at its full potential and for this we will need new educational strategies in today’s digital environment

Phase transitions and critical phenomena of tiny grains carbon films synthesized in microwave‐based vapor deposition system

Different peak trends of tiny grains carbon film have been observed under the investigations of the Raman spectroscopy and energy loss spectroscopy. Carbon films known in nanocrystalline and ultrananocrystalline diamond films are synthesized by employing microwave‐based vapor deposition system. Carbon atoms exhibit several state behaviors depending on the incurred positions of their electrons. Different morphology of tiny grains under different chamber pressure is related to different rate of arriving typical energies at/near substrate surface. Those tiny grains of carbon film, which evolved in graphitic state atoms are converted to structure of smooth elements where elongation of atoms of one‐dimensional arrays is as per exerting surface format forces along opposite poles from their centers. Such tiny grains in the film are the cause of v1 peak under the investigation of the Raman spectrum because of the enhanced propagation of input laser signals through channelized inter‐state electron gaps of elongated graphitic state atoms. Those tiny grains of carbon film, which evolved in fullerene state are the cause of v2 peak. The tiny grains related to v1 peak possess a low intensity as compared with the ones which comprised atoms having state behaviors known in their exceptional hardness. Tiny grains representing v1 peak in the Raman spectrum are also the cause of field emission characteristic of a carbon film. Different peak recordings were made for the Raman at defined positions indicating a different state of carbon atoms for a different phase of deposited tiny grains, which is in line to their energy loss spectroscopy.

Mapping of the lubrication regimes in rough surface EHL contacts

Abstract Understanding film formation in rough surface elastohydrodynamically lubricated (EHL) contacts have been an ongoing pursuit in lubrication science for more than half a century. This study furthers that quest by establishing a single combined friction and electrical contact resistance map that forms a clear and comprehensive overview of the lubrication performance. A ball-on-disc machine was operated under a wide variety of heavily loaded rolling/sliding contact conditions. Results show that while sweeping the contact over the SRR- and entrainment speed-domain, the primary sweep direction significantly affects running-in and consequently the transition from EHL to the mixed lubrication regime. Such knowledge sheds new light into the mechanisms that governs EHL film formation and the concurrent interplay with the mixed lubricated friction coefficient.

Structure, chemical composition, mechanical properties of fluorine-containing coatings based on diamond-like carbon

The report contains the results of the study of structure and properties of coatings based on diamond-like carbon (DLC) containing fluorine atoms deposited from the products of pulsed vacuum cathodic-arc discharge with graphite cathode under the inflow of octafluorocyclobutane into the vacuum chamber. For the coatings deposited, the fluorine content reaches approximately 30 atomic %. The presence of C-F and C-F2 chemical bonds is shown. The morphology of the coatings is characterized by the presence of smooth regions and surface formations with increased content of fluorine chemically bonded to carbon. The hardness and Young’s modulus of the DLC-F coatings are lower in comparison with the undoped DLC coatings deposited under analogous conditions. The DLC-F coatings demonstrate low friction coefficient and high wear resistance in dry friction tests.

Investigation of oscillatory phenomena in the near electrode plasma of vacuum spark

A research of the vacuum spark plasma properties in the near-electrode area is considered. Results of the observations of the high-frequency electrical oscillatory discharges in the 1-110 MHz range are presented. Plasma element composition and temperature have been analyzed with a spectrometer. It contains the study of the microrelief of the electrode surface. Also observations of the 80-350 nm cellular structure formation are represented. Finally, it describes a proposed possible mechanism of the surface formations occurrence.

Investigation of Machine Tool Developed Settings Influence on Productivity and Quality of Simultaneous Double-Sided Lens Processing

The paper presents methodology for determining rational modes of abrasive processing for high-precision lenses while using a method of free lapping at finishing operations. Analytical expressions have been obtained to determine coordinates of reference points on a spherical surface which are necessary for mathematical modeling of its processing at pivotal machines. The paper contains results of a theoretical qualitative evaluation of high-precision operating lens surfaces formation in case of various combinations of setting parameters for technological equipment. In this case the most rational and unfavorable modes of processing have been identified. In particular, the last case presupposes shaping by changing rotational frequencies of an input link in an executive mechanism of the machine tool w2and the lens wл. An indicative feature is that a poor quality of processing has been obtained over the entire range of variation interval w2 at maximum value wл, and especially in the case when these frequencies are equal. It has been determined that the highest accuracy of processing is achieved with maximum amplitude of an oscillating tool motion, its diameter and frequency of part rotation and minimum rotational speed of the input link in the executive machine-tool mechanism. As such values of these setting parameters lead to an increased removal of an allowance in the marginal zone of a work-piece, then while processing a convex lens surface, its radius of curvature in each previous operation should be larger than a radius of curvature which is to be obtained in the process of subsequent operations. The inverse regularity of curvature radius values must be observed for a concave surface. The most advantageous values of the machine-tool setting parameters with various combinations have been proposed with the purpose to eliminate errors in the form of common as “knoll” and “hole” with due account of processing productivity and accuracy. The paper describes an influence of machine tool spindle wavering value on the processing accuracy of lenses having a wide range of diameters.

Theoretical and Experimental Studies of CoGa Catalysts for the Hydrogenation of CO2 to Methanol

Methanol is an important chemical compound which is used both as a fuel and as a platform molecule in chemical production. Synthesizing methanol, as well as dimethyl ether, directly from carbon dioxide and hydrogen produced using renewable electricity would be a major step forward in enabling an environmentally sustainable economy. We utilize density functional theory combined with microkinetic modeling to understand the methanol synthesis reaction mechanism on a model CoGa catalyst. A series of catalysts with varying Ga content are synthesized and experimentally tested for catalytic performance. The performance of these catalysts is sensitive to the Co:Ga ratio, whereby increased Ga content results in increased methanol and dimethyl ether selectivity and increased Co content results in increased selectivity towards methane. We find that the most active catalysts have up to 95% CO-free selectivity towards methanol and dimethyl ether during CO2 hydrogenation and are comparable in performance to a commercial CuZn catalyst. Using in situ DRIFTS we experimentally verify the presence of a surface formate intermediate during CO2 hydrogenation in support of our theoretical calculations.

Predictor Packing in Developing Unprecedented Shaped Colloidal Particles

Developing anisotropic particles of different shapes has been a hot topic of research since decades as they possess special features not possible to achieve through other means. It is considered challenging to control atoms for developing their particles of certain size and shape. In this study, different shapes of gold particles were developed while employing a pulse-based electron–photon–solution interface process. Gold atoms, when they are in certain transition state, develop their monolayer assembly around the light glow known in argon plasma generating at the bottom of copper capillary known in cathode. The rate of uplifted gold atoms to develop monolayer assembly at solution surface is controlled by electron streams and traveling photons of high-density entering the solution. Gold atoms dissociated from the precursor on transforming photons (propagating through immersed graphite rod known in anode) to heat energy. Double-packets of nanoshape energy are generated under tuned pulse protocol when they are placed over the compact monolayer assembly resulting in tiny-sized particles of own shape. On the separation of joined tiny particles into two equilateral triangular-shaped tiny particles, each atom of their one-dimensional array elongated on both sides from the centre while exerting opposite poles forces of surface format. This results in convertion of each array of atoms into a structure of smooth elements. Due to immersing force of solution surface and their termination at the centre of light glow, tiny-shaped particles pack from different zones where their structures of smooth elements assemble to develop monolayers of developing particle in a certain shape. Developing particles of one-dimension undertake assembling of structures of smooth elements where packing of their tiny-shaped particles is from the near regions belonging to rearward sides of north–south poles at the solution surface, whereas, developing particles of multi-dimension undertake assembling of structures of smooth elements where packing of their tiny-shaped particles is from the regions of east–west poles and near regions of east–west poles on the solution surface. Depending on the number and orientation of assembled structures of smooth elements nucleating monolayers for different particles, their different anisotropic shapes develop. At fixed precursor concentration, increasing the process time results in developing particles of low aspect ratio. Under tuned parameters, particles of unprecedented features developed.

Soils of Different Land Use Categories in the City of Petrozavodsk

In the territory of the city of Petrozavodsk, the following categories of land use were distinguished: lands of common use, lands of urban and rural development, natural recreation zone, and reserved land. In each area, soil pits were made, and each full profile was analyzed for its morphological structure and physicochemical properties. Among soils, urbostratozems (Urbic Technosols) predominate, urbistratified natural soils (Plaggic Cambisols, Technic Podzols), and technogenic surface formations are spread to a lesser extent. The undisturbed natural soil cover is preserved in suburban forests and on lands of reserve and rural development. The urban soils differ in their physicochemical properties from the zonal natural soils by the elevated base saturation and high content of mineral nutrients. Heavy metal concentrations are mainly at the level of regional background characteristics. Maximum/tentatively permissible concentrations of lead, copper and zinc are exceeded on the lands of common use, building areas, and in the natural recreational zone of the city, which was influenced in the past by the activity of the city-forming plant.