Different Groups Of Materials Research Articles

New development of compact magnetic separator for on-site material screening in various geological survey

AbstractMagnetic separation has been recognized as a valuable technique for extracting or separating target materials from mixed heterogeneous particles. In conventional geological research, it has been used to separate ferro- and ferri-magnetic minerals such as Fe–Ni metal, magnetite and ilmenite. Recently, a mixture of diamagnetic and weak paramagnetic particles has been successfully separated into groups of different materials using a compact magnetic circuit; however, the resolution was not sufficiently high to analyze various heterogeneous particles studied in geological research. Here, we show that the resolution has remarkably improved by developing new magnetic separator. Accordingly, the separation efficiency of particles due to magnetic translation increased by a factor of ~ 2.5, and two different materials were definitely resolved when their variance of the magnetic susceptibility exceeded ~ 2 × 10−7 emu/g; previously, limit of the resolution was above 7 × 10–7 emu/g. We also established the orbit simulation program in magnetic and gravitational field, which accurately predicted the actual trajectory due to magnetic translation. The improved separation resolution of the new separator has significantly increased the range of solid materials that can be magnetically separated, and the range of applications has been considerably expanded to include the matrix of primitive meteorites, surface soils of solid planets and satellites, volcanic ash and sedimentary rocks. The newly developed device is compact and requires little electric power, allowing on-site material screening in various geological research.

Impact response of different materials for sports mouthguards

Up to this moment, there is no guideline regarding the materials to produce mouthguards. The most used is Ethylene-Vinyl Acetate (EVA). Studies indicate that laminating EVA sheets with rigid components could increase the protection capacities of the mouthguards whereas other studies suggest that only replacement of the material within it structure can increase energy absorption. The aim of this work is to evaluate the impact response of four different foils when compared to a 4 mm thickness EVA sheet. Five groups of different materials were subjected to impact tests with energies of 1.72 J, 2.85 J and 4.40 J. In this context was considered the following materials: EVA foils (G1), EVA foils with an EVA foam core (G2), EVA foils with an acetate core (G3), Foils of Erkoloc-pro (G4) and Foils of Ortho IBT resin (G5). Comparisons between the materials were made by qualitative analysis of the average energy-time and load-displacement curves, as well as by comparison of the peak load, maximum displacement, contact time and absorbed energy using the Kruskal-Wallis test. It was possible to conclude that statistically significant differences were found in the energy absorbed (p=0.001). Laminated foils with a soft core (G2) are a good option to produce mouthguards, while EVA foils with an acetate core (G3) and foils of Ortho IBT resin (G5) were declared unsuitable.

Bond strength of zirconia- or polymer-based copings cemented on implant-supported titanium bases – an in vitro study

Purpose To evaluate the bond strength between polymer-based copings and zirconia copings as positive control, cemented on implant-supported titanium bases with different adhesive cement systems. Moreover, to evaluate if airborne-particle abrasion of polymethylmetacrylate (PMMA) would enhance the bond strength. Methods Four groups of different materials were used to fabricate the copings, 30 in each group: airborne-particle abraded milled zirconia (TAZirconia, control group), milled PMMA (TPMMA), airborne-particle abraded milled PMMA (TAPMMA) and 3 D-printed micro filled hybrid resin (TAMFH). Each group of copings was cemented on titanium bases by three different adhesive cement systems, 10 each: Multilink Hybrid Abutment, Panavia V5, RelyX Ultimate. The specimens were stored dry at room temperature for 24 h, subjected to thermocycling for 5000 cycles followed by evaluating the bond strength by tensile strength test. Results TPMMA and TAPMMA cemented with Multilink Hybrid Abutment showed statistically significant lower bond strength in comparison to TAZirconia and TAMFH. No difference was observed between the latter two. TPMMA, TAPMMA and TAMFH had a statistically significant lower bond strength compared to the control group when cemented with Panavia V5. TPMMA and TAPMMA cemented with Rely X Ultimate showed statistically significant lower bond strength in comparison to the control group. Conclusion Almost all experimental groups, except 3 D-printed MFH, performed inferior than the positive control group where the highest bond strength was reported for the cementation of zirconia copings cemented with Panavia V5 or Rely X Ultimate. Airborne-particle abrasion did not improve the bond strength of the PMMA, except when Multilink Hybrid Abutment was used.

The stress dependence anisotropic elastic properties of shale

The stress dependence anisotropic elastic properties of shale is experimentally evident. It is well explained by the homogenization theory for a medium containing imperfect contact areas (ICA) of which the elastic properties are functions of the effective confining stress. For practical purpose, a minimum number of parameters related to the ICA is considered and calibrated on experimental data. It is observed that the trends of the five transversely isotropic elastic stiffnesses versus the effective confining stress can be well captured by four microscopic parameters: (1) a parameter that characterizes the orientation distribution of the contacts; (2) a ratio between the normal and in-plane compliances of the contacts; (3) the magnitude of the contact compliance at the stress-free condition; and (4) a curvature parameter that defines the dimensionless evolution of the contact compliance versus the effective confining stress. More importantly, these parameters can be fixed for different groups of materials: e.g. wet shale, dry shale, kerogen-rich shale, etc. therefore, a strong predictive capacity of the proposed method is approved. It is then used to predict the effective stiffnesses of shale at a high stress range using the measured data at a low stress range. It can also be used to explain the difference between the elastic properties of in-situ shale and shale samples at a stress-free or a modified stress condition in laboratory. Taking into account the stress dependence contact effect can also offers a capacity to analyze the relationship between its dynamic and static elastic properties.

Application of Soft Relining Materials in Dental Medicine - Clinical Results.

The objective of this study was to carry out an in vivo investigation of patients wearing dentures relined with soft materials, assuming their positive and negative alterations in time. A direct survey method was used to gather data from 23 patients included in this study (11 male and 12 female patients). Twenty-seven dentures were made (12 partial and 15 total dentures) 9 of which in chairside procedures, 11 - in a laboratory, and 7 were made using the direct-indirect method. Patients were included in regular follow-ups at one month and six months, and at one, two, and three years after dentures delivery. The study started in 2014 and continued till 2017. All participants completed questionnaires which included questions related to changes in retention and stability of the relined dentures, changes in color and softness, in bond strength, and inflammation. There were no significant differences in the behavior of the different groups of materials at six months. After six months we observed decline in the bond strength of the vinyl-polysiloxane (VPS) materials, as well as increased staining and hardness in the poly-methyl-methacrylate (PMMA).

Gamma dose rate effects in luminescence signals of various artificial, well established dosimetric phosphors

The present work attempts to study tentative gamma dose rate effects for the stable TL and OSL signals of specific, well established artficial luminescence dosimeters. Two different dose rates of gamma radiation (2 and 31 Gy/h) were used. The study has been performed to the stable TL peaks of 5 different TL phosphors (LiB4O7:Cu,In; MgB4O7:Dy,Na; LiF:Mg,Ti; CaF2:Dy; BeO) as well as to both OSL components of BeO. Tentative dose rate effects were studied for both dosimetric dose response features as well as kinetic parameters after deconvolution for both signals. Two different groups of materials were revealed. The first one includes materials such as LiF: Mg,Ti, BeO and MgB4O7: Dy,Na; for these, both TL dose response features and TL kinetic parameters are independent on the dose rate. This is also the case for both OSL components of BeO besides the linearity index of the dose response of the fast OSL component; the latter seems to mildly depend on the dose rate. At the same time, experimental arguments based on both dosimetric as well as deconvolution features suggest the presence of tentative dose rate effects for the cases of LiB4O7:Cu, In and CaF2:Dy. Moreover, the effective use of these aforementioned features as probes for identification of dose rate effects is also discussed. The results of the present study suggest that the basic postulate of most phenomenological TL models that traps pre-exist and they are simply filled during irradiation has to be reconsidered.

Step-wise transient method for analysis of thermal properties of materials Part 2. Experimental investigations

The subject of the paper which is a continuation of part 1 are issues related to the implementation of the stepwise transient plane source method. Both the measuring device and the testing methodology were developed. Measurements of thermophysical properties k, a and cp of selected materials from the group of thermal insulating foams (polyurethanes, polystyrenes), organic glass polymers and metals, including high thermal conductivity ones, i.e. duralumin at one measurement, were carried out. The measurement time was on the order of a few to several hundred seconds. Procedures for calculating thermal effusivity b and thermal diffusivity a were illustrated. Parameters of the thin-layer heater used in the measurement system were studied, i.e. measurements of the resistance change of the heater in the function of the voltage of the power supply and examination of the heater homogeneity were performed using a thermal imaging camera. The method requires that the thermocouples should be mounted on the faces of the samples. According to authors, this is an advantage of the method, because it allows to limit the applied pressure of the measuring stack on the accuracy of materials thermophysical properties measurements, especially metals. The measurements confirmed the suitability of the method for testing the thermophysical parameters of different groups of materials. The obtained experimentally accuracy of thermophysical parameters of testing materials in relation to reference values did not exceed 10%. The usefulness of the analytical solution of 2D transient heat conduction problem in the considered measuring stack has been confirmed by the results of numerical simulation, which includes heat transfer in a sample and in a flexible thin layer Kapton-nichrome heater.

Comparative Study Clarifying the Usage of PEEK as Suitable Material to Be Used as Partial Denture Attachment and Framework.

BACKGROUND:Utilization of attachments in a removable partial denture is highly essential not only as a line of treatment but also as it has a remarkable impact on the denture’s durability during the function. The attachment should act as a stress breaking system preserving the abutment teeth.AIM:This consideration aimed to verify the convention of polyether ether ketone (PEEK) material as an attachment.MATERIAL AND METHODS:Four groups of different materials for both attachments and partial denture framework were fabricated and tested using strain gauges to compare between them according to the strains originated around both the abutment teeth and edentulous area.RESULTS:PEEK material is one of the esthetic materials used for fabrication of the framework of the RPD. On using it as a precision attachement is shows favorable stress distribution decreasing the strains around the abutment teeth and the alveolar ridge especially distal to the abutment teeth that was significantly reduced in comparison with the other treatment options.CONCLUSION:Utilization of PEEK material as both an attachment and framework decline the strains performed around the abutment teeth and over the edentulous ridge.

Effect of materials and superstructure designs on the passive fit of implant-supported fixed prostheses

This study aimed to compare the passive fits of implant-supported cement-retained computer aided design/computer aided manufacturing (CAD/CAM) bridges fabricated with different implant superstructure designs from zirconia and titanium. A total of 32 cubic clods with the same dimensions and with elastic modulus similar to that of mandibles were used. Each clod received two one-stage implants to simulate a partially edentulous jaw that was missing teeth between the lower left second premolar and second molar. Four linear strain gauges were bonded on the region surrounding each implant on the mesial, buccal, distal, and lingual aspects. A total of 32 identical frameworks were fabricated through CAD/CAM after scanning. The frameworks were allocated into four different groups (n=8) in accordance with material types and superstructure designs. Group A included zirconia ceramic implant-supported fixed prostheses with regular marginal designs. Group B comprised zirconia ceramic implant-supported fixed prostheses with full circumferential zirconia-collar marginal designs. Group C consisted of titanium ceramic implant-supported fixed prostheses with regular marginal designs. Group D included titanium ceramic implant-supported fixed prostheses with full circumferential titanium-collar marginal designs. Strain development before and after ceramic veneering was recorded during cement setting. Data were statistically analyzed by using SPSS software. Before ceramic veneering, material types affected the strains of prostheses, and zirconia frameworks showed lower strain than other frameworks (P<0.01). Designs affected the strains of prostheses, and frameworks with full collar marginal design showed lower strain than other frameworks (P<0.01). These two factors showed interactions (P<0.01). The strain of decorative porcelain increased after sintering. The two groups of different materials did not significantly differ (P>0.05). Nevertheless, the full circumferential collar marginal design reduced discrepancies among groups (P<0.01). The passive fits of zirconia prostheses were better than those of titanium-based porcelain-fused-to-metal restorations. The full circumferential collar marginal design can help reduce fit inaccuracy, as well as the adverse effects of ceramic veneering.

Effects of marginal adaptation with different materials on restoring dental wedge-shaped defects

Objective To evaluate the effects of marginal adaptation with different materials on restoring dental wedge-shaped defects. Methods From January 2016 to July 2016, 80 patients with 172 wedge-shaped defect teeth in Stomatological Hospital of Haishu District were chosen and randomly divided into three groups according to random number table method, 26 patients with 55 defect teeth were treated with Fuji glass ionomer(group A), 23 patients with 59 defect teeth were treated with Carey charismatic light-cured composite resin(group B), and the other 31 patients with 58 defect teeth were treated with beautifil flow plus reinforced polymer F03(group C). Marginal adaptation of three groups of different materials of the teeth were measured. Results The micro-leakage depth among the three groups had statistically significant difference(H=7.036, P=0.035). The micro-leakage depth of group A, B and C were (1.10±0.05)mm, (0.96±0.05)mm, (0.78±0.06)mm, respectively.There was statistically significant difference among the three groups(F=22.371, P=0.005). Conclusion The marginal adaptation of beautifil flow plus reinforced polymer F03 is superior to FujiⅡglass-ionome and Charisma composite resin, and has benefits for treatment of wedge-shaped defects. Key words: Dental prosthesis repair; Fuji glass ionomer; Carey charismatic light-cured composite resin; Beautifil flow plus reinforced polymer; Marginal adaptation

Contribution of the Kinetics of Inelastic Deformations to the Summation of Fatigue Damage to Steels

We propose a method for the evaluation of the accumulation of fatigue defects and variations of inelastic strains under cyclic loading with variable stress amplitudes. This method is based on the earlier developed model of ultimate exhaustion of cyclic plasticity. It is shown that, for materials with unstable inelastic deformations under cyclic loading, the fatigue damage does not obey the law of linear summation. We discovered a difference between the accumulation of fatigue defects in cyclically hardened and softened materials. This difference and nonlinearity are caused by the kinetics of inelastic deformations in different groups of materials. Hence, it is proposed to take this fact into account in estimating the degree of fatigue damage in order to decrease the computation error. In addition, we propose a scheme for the improvement of the results of evaluation of the total fatigue life under irregular loading by using the individual fatigue curves for the specimens with an aim of minimization of errors caused by the spread of experimental results.

General European Legislation for Food Contact Materials

Background: Food contact materials are regulated in the European countries through the horizontal Regulation 1935/2004, on materials and articles intended to come into contact with food, and the Regulation 2023/2006, on good manufacturing practice for materials and articles intended to come into contact with food. Specific measures have to be implemented regarding different groups of materials and presence of specific substances. Until now, only plastic, ceramic, intelligent and active materials and regenerated cellulose film, materials intended to come into contact in food, have been regulated. Methods: In an attempt to protect human health from the exposition of contaminants which might impair toxic effects, several Regulations and Directives have to be implemented to control food contact materials. Results: Plastic materials are well described in the Regulation 10/2011. This paper is intended to provide the implementation procedure of this Regulation regarding the overall and specific migration of plastic materials in contact with foodstuff. It also describes the concept and use of simulants and the assay conditions. Emphasis is given to mineral oils and Bisphenol A migration, because of their novelty or impact in the media, as a risk evaluation is still a matter of discussion. Regulations are continuously being amended according to the European Food Safety Authority (EFSA) opinions, and include authorization of new substances, according to toxicity studies. It is expected that in the near future all groups of materials are going to be regulated by specific legislations, and not only the polymeric materials. Non-intentionally added substances (NIAS) is another hot topic to consider as they represent a group of substances that are present in a material but have not been added for a technical reason during the production process. Conclusion: Whereas regulatory guidelines provide data on maximum levels of plasticizers in a specific type of food, scientific and academic studies are equally important to determine the toxicity of the different chemicals and define the effects and impact on the organisms. Keywords: European legislation, food contact, Regulatory framework, human health, Non-intentionally added substances (NIAS), plasticizers.

Эколого-экономическая оценка загрязнения атмосферы в результате пожаров на объектах техносферы Иркутской области

On the example of Russia’s Irkutsk region the problem of air basin pollution as a result of fires in technosphere objects is considered. Has been proved the necessity for assessment of air pollution as a result of fires, and importance of such assessment has been demonstrated. It has been noted that the ecological assessment of air pollution from fires, which are the sources of pollution, previously had not been calculated at regional level. The method for phased determination of burnt materials’ quantitative and qualitative characteristics has been proposed. As a result of fires effects monitoring in 2000–2015 have been determined average values of burnt materials’ mass. Taking into account specific indicators for the toxicants emission during combustion of different groups of materials, have been determined mass values for priority products of combustion, that has allowed perform subsequently the ecological and economic assessment of air pollution from fires in the region. It has been established that every year in the Irkutsk region the ecological and economic damage from air pollution by combustion products was on the average 5,73 million rubles.

Improved correlation for elastic modulus prediction of metallic materials in the Small Punch Test

Generally, the correlation factors of parameters obtained from the load-displacement curve of small punch tests and the mechanical properties of materials are only acceptable for the materials tested in each investigation. Although the standardization of the correlation factors for different groups of materials is the objective in much of the research on the Small Punch Test (SPT), there are not many studies focused on the physical sense of these correlation factors. Consequently, the applicability of these factors needs the prior knowledge of the material to be tested with comparisons between SPT's and standardized tensile tests.This investigation, through finite element modeling and a theoretical analysis, goes in depth into the understanding of the first zone of the SPT curve and the study of an unloading/loading cycle introduced into this zone in order to obtain an improved correlation factor for the elastic modulus. This factor is acceptable for most isotropic and homogeneous metallic alloys and depends only on the geometrical setup of the test. Experimental tests (tensile tests and SPT's) were added to these numerical/theoretical analyses to demonstrate the suitability of this correlation.

Multispectral X-ray imaging to distinguish among dental materials.

PurposeDual-energy X-ray imaging is widely used today in various areas of medicine and in other applications. However, no similar technique exists for dental applications. In this study, we propose a dual-energy technique for dental diagnoses based on voltage-switching.Materials and MethodsThe method presented in this study allowed different groups of materials to be classified based on atomic number, thereby enabling two-dimensional images to be colorized. Computer simulations showed the feasibility of this approach. Using a number of different samples with typical biologic and synthetic dental materials, the technique was applied to radiographs acquired with a commercially available dental X-ray unit.ResultsThis technique provided a novel visual representation of the intraoral environment in three colors, and is of diagnostic value when compared to state-of-the-art grayscale images, since the oral cavity often contains multiple permanent foreign materials.ConclusionThis work developed a technique for two-dimensional dual-energy imaging in the context of dental applications and showed its feasibility with a commercial dental X-ray unit in simulation and experimental studies.

Polarimetric Image Discrimination With Depolarization Mueller Matrix

Polarimetric imaging techniques exploit the polarization characteristics of objects and, thus, can achieve a better discriminative performance. In this paper, an adaptive discrimination method based on the classification of depolarization Mueller matrix is proposed. According to the Mueller–Jones theory, the general formula of Mueller matrix for depolarization optical system is analyzed. In addition, a two-channel imaging platform is constructed to obtain a polarization-difference image with certain states of polarization. Under this methodology, every pixel of the image can be expanded as a combination of independent entries of the Mueller matrix, with polarization states as the representative coefficients. Thus, the optimal polarization states can be obtained via support vector machine (SVM), and a high contrast image is achieved. Finally, experiments on two groups of different materials are conducted to demonstrate the applicability and performance of the proposed method. The related criteria (e.g., Fisher ratio) are introduced to quantitatively evaluate the results. Experimental results indicate that the proposed method shows advantages for image discriminations.

In Vitro Analysis of the Tribological Behaviour of Different Material Combinations for Telescopic Crowns

Telescopic crowns are used to connect removable dental prostheses with the remaining dentition. Several material combinations are used for manufacturing primary and secondary crowns. The present experimental study analysed the influence of different material combinations on the long-term development of surface roughness and pull-off forces. Six different material combinations were tested. Secondary crowns were manufactured either by casting or electroforming. Each material combination was tested with n = 10 specimens. A material testing device with integrated power sensors was used for 10,000 cycles per test. Signs of wear were identified by surface roughness measurements, and visualized by a scanning electron microscope (SEM) and X-ray spectroscopy (EDX) technologies. Statistical significances were tested by using the U-Test with Bonferroni correction. The choice of materials and the manufacturing process were found to influence the long-term development of pull-off forces as well as wear-associated surface roughness. Combinations of different groups of materials for primary and secondary crowns showed favourable results. Worse results were found for the combination pure titanium and pure titanium and the combination high gold alloy and electroformed gold. Wear-associated surface roughness was higher for combinations of similar or identical groups of materials. For manufacturing telescopic crowns, combinations of different groups of materials are preferred. For secondary crown manufacturing, electroforming is superior to casting.

A Study on the Grindability of Engineering Plastics and Metals

In this study, the surface grinding was performed at different feed rates and depth of cuts. Grindability of engineering thermoplastics and metals was evaluated. Further, important process parameters influencing surface quality were determined using analysis of variance (ANOVA). Experimental results compared two significantly different groups of materials in order to emphasize common variables. Finally, further research directions were presented to seek for functional relation between process parameters and grindability.

Evaluation of rhizomania-resistance segregating sequences and overall genetic diversity pattern among selected accessions of Beta and Patellifolia. Potential implications of breeding for genetic bottlenecks in terms of rhizomania resistance

AbstractSugar beet is hypothesized to have a narrowed genetic base due to its origin as White Silesian Beet and from numerous breeding selections and practices. High sugar quality, yield of recoverable sugar, cytoplasmic-male sterility system, monogermity, pests and disease resistance and bolting resistance constitute some of the adaptations that significantly influenced the existing genetic background of the crop. In this study we aimed to evaluate the extent of genetic diversity existing in wild beet representatives of Beta and Patellifolia and sugar beet cultivars, with a special focus on the complex Beta vulgaris. Another purpose was to determine the potential usefulness and conformity of selected molecular markers in different groups of materials in the context of rhizomania resistance. To reach these goals, molecular RAPD, ISSR techniques, literature-selected rhizomania resistance-segregating sequences as well as mitochondrial markers were used. The comparison of genetic diversity in wild and cultivated Beta forms shows that the population differentiation values and distance values are relatively high in cultivars. Moreover, the diversity component seemed to be compromised rather on the level of population (Hs) than in total (Ht) in cultivars. Our results shed a new light on the expected genetic bottlenecks existing in cultivars and revealed features specific for individual taxa (Patellifolia, Corollinae). Some degree of distinctiveness was suggested between genetic determinants of rhizomania resistance in modern cultivars in comparison with wild resistance sources. In addition, we document here an internal heterogeneity existing in selected wild/weedy accessions at the level of crucial sequences using high resolution melting.

Transparent electrodes for organic optoelectronic devices: a review

Transparent conductive electrodes are one of the essential components for organic optoelectronic devices, including photovoltaic cells and light-emitting diodes. Indium-tin oxide (ITO) is the most common transparent electrode in these devices due to its excellent optical and electrical properties. However, the manufacturing of ITO film requires precious raw materials and expensive processes, which limits their compatibility with mass production of large-area, low-cost devices. The optical/electrical properties of ITO are strongly dependent on the deposition processes and treatment conditions, whereas its brittleness and the potential damage to underlying films during deposition also present challenges for its use in flexible devices. Recently, several other transparent conductive materials, which have various degrees of success relative to commercial applications have been developed to address these issues. Starting from the basic properties of ITO and the effect of various ITO surface modification methods, here we review four different groups of materials, doped metal oxides, thin metals, conducting polymers, and nanomaterials (including carbon nanotubes, graphene, and metal nanowires), that have been reported as transparent electrodes in organic optoelectronic materials. Particular emphasis is given to their optical/electrical and other material properties, deposition techniques, and applications in organic optoelectronic devices.