The safety and durability of bridges designed from weathering steels are conditioned by the development of a sufficiently protective layer of corrosion products. Air pollution, microclimate around the bridge, time of wetness, structural solution of the bridge, and the position and orientation of the surface within the bridge structure all influence the development of protective layers on the surface of the weathering steel. In this article, attention is focused mainly on the microclimatic effects resulting from the road traffic under the bridge. The influence of chloride deposition on the development of corrosion products is evaluated using experimental in situ testing. Two neighboring bridges made of weathering steel and crossing different types of obstacles were selected for this experiment. Relations and dependences between the measured parameters  are evaluated and discussed. During the construction of the highway network of the Czech Republic between 2000 and 2010, a number of bridges with a weathering steel supporting structure were built. Most of these bridges are located on the D1 highway in Ostrava and its surroundings. The girder bridges are designed to be coupled with an upper concrete deck. The steel supporting elements of the bridges were made of S355J2W weathering steel [A static assessment should consider the effects of corrosion losses of the structural elements of the bridge . One of Defects of protective corrosion layers caused by leaking from the bridge drainage system can usually be removed without the application of anti-corrosion coatings. First of all, it is necessary to remove the leakage source and to clean the surface of the structure, including non-adherent corrosion products. A new sufficiently protective corrosion layer develops over time on this prepared surface. If the cause of unfavorable corrosion development is the microclimatic environment around the bridge, then the situation is more complex. Environmental parameters around the bridge cannot usually be changed. In order to ensure the required service life of the structure, it is therefore necessary to update the corrosion prediction model, and subsequently statically evaluate the effect of accelerated corrosion effects on the long-term reliability of the structure. If the prediction of expected corrosion losses is statically unacceptable, additional corrosion protection should be applied to corrosion-damaged surfaces, for example in the form of zinc-based coatings  in the cFor some bridge constructions, inspections have identified surfaces that are not exposed to direct leakage, yet they do not develop a sufficiently protective layer of corrosion products . In all 2 in the atmosphere as the main corrosion factor [2 concentration in the air reached maximum in Central Europe in the 1970s [Experiences with real bridge operations show that when designing a structure, it is necessary to pay more attention to the prediction of local microclimatic conditions that may be created around the planned building. The general classification of the site into a degree of corrosive category without linking to the dispositional and structural design of the proposed bridge and surrounding buildings is insufficient. The bridges on the D1 highway in Ostrava were designed based on corrosion maps, which mainly considered the concentration of SOn factor . The SO2he 1970s ,13. At t2 in the air has an impact on the development of corrosion products on the surface of weathering steel. Especially for sheltered surfaces , the development of corrosion products is very slow with a corrosion rate corresponding to the degree of corrosion category C1 to C2 [A low concentration of SOC1 to C2 . It turnC1 to C2 ,16.This article therefore pays attention to the development of corrosion products on the steel structure of the bridge protected by the upper concrete deck, which are affected by the increased deposition of chlorides. Attention is paid to the study of the microclimatic environment around the bridge and to the influence of the design and layout of the bridge on the development of corrosion products. The article further develops the findings described in previous publications of the authors, especially the reference . CompareBridge B1: Weathering steel bridge on the road No. 479 over highway D1 (built in 2001);Bridge B2: Weathering steel bridge on the road No. 479 over railway line (built in 1983).Two bridge structures were selected for the experimental measurement of the deposition of chlorides and their effect on the development of corrosion products. Both bridges are located in Ostrava (Czech Republic):The location of the bridges can be characterized in accordance with EN ISO 9223  as an urIn terms of the development of corrosion products, the two bridges compared differ only in the nature of the bridged obstacle. Bridge B1 is located above the highway and exposed to intense road traffic beneath the bridge. The fast-moving vehicles on the D1 highway are a significant source of chlorides spreading into the environment and onto the B1 bridge’s supporting girder structure. In winter, chlorides are dispersed over the surfaces of the structure mainly as an aerosol, while in the rest of the year, they are spread as dust deposits. Bridge B1 is specific in its construction design, however, with bridge supports forming perpendicular walls directly adjacent to the sides of the motorway. The environment under the bridge is also influenced by the geometric ground plan, the bridge having a large width (41.0 m) to length (51.4 m) ratio. In addition to 4 lanes for road transport, the bridge includes two tramway tracks. The aerosol and dust deposits stirred up by automobiles traveling on the highway therefore cannot spread in the transverse direction to the motorway axis. This means there is no dispersion of particles into the surrounding environment and the surfaces of the bridge structure are exposed to increased sedimentation of airborne impurities, including chlorides . Bridge Sd), in accordance with EN ISO 9225 [P1: Bridge B1—external girder, north orientation (in the direction of transport under the bridge);P2: Bridge B1—internal girder, north orientation (in the direction of transport under the bridge);P3: Bridge B1—internal girder, south orientation (opposite to the direction of transport under the bridge);P4: Bridge B1—external girder, south orientation (opposite to the direction of transport under the bridge);P5: Bridge B2—external girder, north orientation;P6: Bridge B2—internal girder, north orientation.Two basic methods were selected for measuring the deposition rate of chlorides ;Thickness of the corrosion product layer after one year of exposure (rcorr);Corrosion loss after one year of exposure ;Representation of individual phases in the corrosion layer.Corrosion coupons of S355J2WP steel (Corten A) were placed on the bridge structures to monitor the development of the corrosion layer on the selected positions. Coupons were made in standard sizes 150 × 100 × 1.5 mmISO 9226 . Only thVisual evaluation of the surface of the corrosion layer was supplemented by an evaluation of the proportions of adherent and non-adherent rust layers using the Scotch-tape test. In this method, Scotch-tape is pressed against the tested surface. The tape is pressed against the surface lightly and uniformly with a rubber roller or finger. After removal, the tape is attached to a sheet, such as a transparency, and kept in a record. Making a photocopy of the sheet is useful. The frequency and size of the captured rust particles is then evaluated. Fine and uniformly distributed rust particles less than 1 mm in size are typical on fully protective patina layers. A greater portion of rust particles larger than 5 mm is typical for corrosion layers that may have limited protective ability.The surface of the steel under the corrosion product layer was visually evaluated using the Keyence VHX-5000 3D microscope . Using the microscope, the frequency, diameter and depth of the pits on the surface of the steel under the corrosion layer were measured.tcorr) was measured using the magnetic-induction method with a PosiTector Smartlink and F-probe . The thickness of the corrosion products was determined as the average of the 15 measured sites on the surface of the corrosion layer. The measurement sites were selected evenly along the surface of the corrosion specimen. Corrosion losses (rcorr) were determined using standard gravimetric methods in accordance with ISO 8407 [The thickness of the corrosion products . Data evaluation was performed using the HighScore Plus 4.0. program. The monitored phases of the corrosion product layer included goethite (α-FeOOH), lepidocrocite (γ-FeOOH); akaganeite (β-FeOOH) and magnetite (Fe3O4). Based on the observed phase composition of the corrosion layer, the value of the PAIα and PAIβ indexes (protective ability index) were determined in accordance with [A layer of corrosion products was mechanically removed from the corrosion samples to determine the chemical composition and the representation of the individual phases in the corrosion layer. The representation of individual elements in the corrosion layer was determined using the atomic absorption spectroscopy with a Agilent 280 FS AA Spectrometer . The phase composition of the corrosion products was determined with a Philips X’pert Pro powder diffractometer  in a Bragg-Brentano paraphilic geometry using Co Kα radiation , and for the corrosion products developed on the surface of the exposed samples (exposure period of 1 year).A sufficiently protective layer of corrosion products, typical of sheltered exposures, has developed on bridge B1. An exception is on the upper surface of the bottom flanges of the inner girders see , where nAdhesion of corrosion products was assessed using the Scotch-tape test method. Imprints were collected after a one-year exposure of the corrosion samples see . Small, The frequency and size of the individual corrosion pits were evaluated using a Keyence VHX500 3D microscope. On each evaluated surface, four positions were focused at 500× magnification. The area under review was 670 μm × 500 μm. The average number of pits in the area under observation and average values of depth and diameter of pits are shown in Vertically-oriented surfaces give rise to a larger number of pits which, however, have a smaller diameter and depth than on the horizontal surface. For example, in the samples exposed at positions P1, 32 corrosive pits with an average depth of 35 μm and diameter of 69 μm were found on the vertically-oriented surface after removal of the corrosion layer. On the horizontally-oriented surface at P1, 18 pits with an average depth of 59 μm and diameter of 84 μm were identified.Chloride deposition has been monitored continuously on selected bridge structures since December 2016. Data for 24 months are available and can be separated into two periods (December 2016 to November 2017 and December 2017 to November 2018).Sd) was measured using the wet candle method  and the dry plate method in vertical and horizontal positions  in accordance with EN ISO 9225 [The deposition rate of chlorides (tcorr) of steel samples exposed at selected positions between December 2016 and November 2017 and between December 2017 and November 2018 (the average of 15 measurements is shown in the table).Position P5 was significantly affected by the failure of the bridge expansion joint. The horizontally-oriented steel coupon has been influenced by the direct flow of salt solution from the roadway. The 190.0 and 192.3 μm values therefore cannot be used to evaluate the effect of the deposition of chlorides in the form of aerosol or dust particles. Details on the development of corrosion products exposed to leaking from expansion joints are given in .Corrosion loss values for samples exposed for one year are listed in The amount of chlorides deposited in the corrosion products was determined in an elemental analysis of the corrosion layer. The analysis was performed on corrosion products that had formed on the steel coupons after one year of exposure. X-ray diffraction analysis revealed the representation of individual phases in corrosion product layers. The representation of individual phases, including the specified PA indexes, is given in The next chapter discusses the results of the measurements performed on two selected bridge structures in Ostrava. From the experimentally obtained data, the effect of microclimatic conditions under the bridge structure on the development of corrosion products on typical surfaces of the girder bridges can be evaluated. Bridge B1 conveys traffic over the busy D1 highway, which has chemical de-icing agents applied during the winter season. Bridge B2 conveys traffic over a railway line and is not affected by the negative impact of intense road traffic under the bridge. A comparison of the results from both bridges can therefore be used to evaluate the specific microclimatic influences of bridge structures spanning roads with high traffic volumes.tcorr) observed from the one-year exposures in the periods 2016/2017 and 2017/2018 show similar dependencies with respect to surface orientation. The thickness of corrosion products on the vertical surfaces (the webs of the main girders) of both bridge structures is much smaller compared to the horizontal surfaces (bottom flanges of the main girders). On horizontally-oriented surfaces, after a one-year exposure, up to three times the thickness of the corrosion layer was observed compared to the adjacent vertically-oriented surface. Similar ratios were also found between horizontal and vertical surfaces when evaluating corrosion losses (rcorr).The development of corrosion products on the surface of weathering steel is different for vertically and horizontally positioned surfaces of bridge constructions see . The thiSd,p) was found compared to the vertically-oriented dry plates (see mCl) was observed in corrosion products on the exposed samples  and corrosion losses (rcorr) after one year of exposure on corrosion samples, no significant differences were found between the outer and inner surfaces of the bridge . However, the differences between the outer and inner surfaces of the bridge were reflected in the weight of chlorine (mCl) in the corrosion products. Bridge B1 was found to have a higher weight of chlorine in the corrosion products at the P2 and P3 internal surfaces, although higher deposition rates , determined using the standard wet-candle method, were found on the outer surfaces at P1 and P4. The findings can be demonstrated on two comparable horizontal surfaces with the same orientation in the direction of traffic under the bridge ;Bridge B1, position P1 , 1-year exposure (2016/2017): mCl = 11.40 g·m−2; Sd = 9.80 mg/(m2·day).Bridge B1, position P2 , 1-year exposure (2016/2017): In evaluating corrosion products (idge see :Bridge BmCl) and the deposition rates of chlorides (Sd) can be explained by the fact that although the external surfaces of the bridge are more exposed to chlorides and impurities, the external surfaces are also regularly cleaned by wind and rainfall. The amount of chlorine found in the corrosion products of the external surfaces of bridge B1 was therefore less than the internal surfaces. This phenomenon negatively manifests in long-term development, where non-adherent layers of corrosion products with a large proportion of settled impurities form on the upper surfaces of the bottom flanges of the inner main girders (see inner surfaces shown in The apparent disproportion between the amount of chlorides found in the corrosion products (tcorr) and corrosion loss (rcorr) measurements after one year of exposure may not provide sufficiently accurate data about the future development of corrosion products. It is therefore very important to supplement the assessment of the development of corrosion products with other parameters: mainly visual assessment of the development of corrosion products, including evaluation of collected imprints (Scotch-tape test), and the results of chemical analysis of the corrosion layer, focusing on the elemental content that indicates increased deposition of chloride ions from road traffic. For example, corrosion loss values (rcorr) measured on horizontal surfaces of the B1 bridge correspond to corrosion category C3 according to EN ISO 9223 [From the above results, it follows that in predicting the long-term development of corrosion products based on year-long testing, it is necessary to analyze the sum of all information obtained from the corrosion tests. The results of corrosion thickness  for individual surfaces and measurement methods. The graphs show elevated deposition rates of chlorides occurring in the winter periods, when the roads are treated with chemical de-icing agents. Both observed winter periods show differences in the observed values. During winter 2016/2017, higher deposition values of chlorides were measured than in winter 2017/2018. These differences are mainly related to the current climatic conditions during the winter period. Data from two selected winter months are shown in For bridge construction B2, the deposition rates of chlorides in winter periods were found to be several times lower than on the bridge B1 . A comparison of the data obtained on bridges B1 and B2 shows a significant influence in the source of chlorides. The upper bridge deck with sufficient lateral overhang protects the main girders of both B1 and B2 bridges from the increased deposition of particles stirred up by traffic over the bridge. However, bridge B1 is located above a busy highway, and the construction of the bridge also creates tunnel-like conditions. The main source of elevated chloride deposition is road transport under the bridge structure.The influence of the environment under the bridge structure is also evident from the results of the elemental analysis of the exposed samples. On the horizontal surface of the B1 bridge spanning the motorway, more than six times the difference in the presence of chlorides in corrosion products was found after one year of exposure than on a comparable surface of the bridge B2 over the railway line. Large differences are also apparent in the representation of aluminum and silicon, i.e., elements indicating increased deposition of dust particles and other impurities. mCl = 11.40 g·m−2; mAl = 3.25 g·m−2; mSi = 16.33 g·m−2;Bridge B1, position P2 , 1-year exposure (2016/2017): mCl = 1.69 g·m−2; mAl = 0.49 g·m−2; mSi = 2.03 g·m−2.Bridge B2, position P6 , 1-year exposure (2016/2017): β to influence corrosion processes due to chlorides. The values of the PAIβ indexes were higher for bridge B1 than for bridge B2  and corrosion losses (rcorr) determined after one year of exposure of the corrosion samples. A more than double difference was found for both monitored variables:tcorr = 188.0 µm; rcorr = 45.8 µm;Bridge B1, position P2 , 1-year exposure (2016/2017): tcorr = 83.0 µm; rcorr = 20.4 µm.Bridge B2, position P6 , 1-year exposure (2016/2017): The different environments beneath both tested bridges also manifested in the values of corrosion thickness (The different development of corrosion products on the horizontal surfaces of both evaluated bridges can also be documented based on a visual evaluation. On the bridge B1 samples, bulkier and less adherent corrosion products developed with a higher proportion of settled impurities. Visual evaluation was supplemented by an evaluation of adherent and non-adherent rust layers using the Scotch-tape test. Imprints of horizontal surfaces from the bridge B1 show an uneven distribution of trapped particles of various sizes, whereas the size of the largest particles collected on the imprint were approximately 5 mm. For bridge B2, the collected particles were evenly distributed and the particle size was up to 2 mm. Imprints from the compared surfaces at positions P2 and P6 are shown in The evaluated bridge structures are made of structural steel S355J2W. The main corrosion risk associated with the use of this steel grade is the corrosion weakening of the structure or its parts. Stress corrosion cracking is very unlikely. During the inspection of the bridge over the D1 highway, the real thicknesses of the bottom flanges of the main girders were checked. The measurement was performed using the ultrasonic thickness gauge. Unfortunately, the original thicknesses of structural elements from the time of the bridge construction are not available. Real corrosion losses after 17 years of bridge operation are therefore unknown. However, the actual thicknesses are still within the range of rolling tolerances of the used sheets. Therefore, it is not necessary to carry out the reinforcement of structural elements with corrosion-negative development.From the static point of view, the greatest risk is the corrosion weakening of structural elements with low thickness: such typical components are fillet welds connecting webs and flanges of the main girders. For example, a corrosion weakening of 1 mm for a 7 mm thick filled weld can be very significant in terms of reducing the load-bearing capacity of the steel bridge structure. On the other hand, the same corrosion weakening of a 50 mm thick bottom flange does not significantly affect the load-bearing capacity of the bridge. A greater risk of failure of thin structural elements should be taken into account using suitable corrosion allowance already when designing the load-bearing structure. Corrosion allowances can be calculated in accordance with the recommendations given in .Regarding the local corrosion damage, it is important to evaluate its position within the bridge structure. For example, the corrosion weakening of the main girder in the area of outer hinged supports is not usually significant in terms of the bending resistance of the bridge, as there are no bending moments acting at the end of the main girders. On the other hand, the maximum shear forces act above the supports and therefore the fillet welds and the web of the main girders are significantly stressed. In the opinion of the authors of this article, it is therefore very important that the assessment of the detected corrosion failures is carried out by a structural engineer who is familiar with the static behavior of the bridge.The course of corrosion processes on bridges constructed with weathering steel is significantly influenced by the chosen structural solution of the bridge and the specifics of local microclimatic conditions. The results of the measurements performed show that the general classification of a locality according to the category of corrosion aggressiveness is not sufficiently indicative for the prediction of corrosion processes if the geometric parameters of the construction design and possible microclimatic influences are not taken into consideration.The course of corrosion processes can be very different for the different bridge structure surfaces under consideration. This fact should be reflected in designing structures  as well One of the decisive factors influencing the local microclimate in the vicinity of a bridge is the effect of chlorides, which are deposited on bridge structure elements mainly due to traffic on adjacent roads. De-icing salts used for winter road maintenance are a source of chlorides. Some significant findings have been determined from the results of measuring chloride deposition. Measurements show that in the case of bridges with suitable structural arrangements, it is possible to significantly eliminate the amount of deposited chlorides, the source of which is traffic over the bridge structure. Increased chloride deposition, however, may occur due to intense road traffic under the bridge structure. At present, not enough experimentally validated data is available to define the specific dimensional and structural requirements, which if applied, decreases chloride deposition from traffic under the bridge to a level that does not limit the beneficial development of patina on bridge structure components. Therefore, it is necessary to at least observe the basic rules: to design structures that allow the dispersal of pollutants and aerosols into the surrounding environment and, importantly, to implement basic maintenance consisting of regular cleaning of the steel structure after the end of winter.


Andropogon gerardi biomass as a precursor are presented. The tested samples were prepared at the temperature of 1000 °C under an inert gas atmosphere in the high-pressure thermogravimetric analyzer. The most developed porous structure was reported for carbon materials produced under 3 MPa. The highest volume of narrow micropores was characteristic for materials carbonized under 2 MPa.Various carbonaceous materials are valuable resources for thermochemical conversion processes and for production of materials of proven sorption properties, useful in environmental applications for gaseous and liquid media treatment. In both cases, the parameters of the porous structure of carbon materials are decisive in terms of their physical and mechanical properties, having direct effects on heat and mass transport as well as on sorption capacity and selectivity. The physical activation of carbon materials produced from various precursors is widely discussed in literature. In this respect, the effects of temperature and partial oxidation of carbonaceous materials with steam or carbon dioxide are mostly considered. The reports on the effects of pressure on the development of porous structures of carbon materials are, however, extremely limited, especially when biomass as a precursor is concerned. In this paper, the results of an experimental study on the effects of pressure in the range of 1–4 MPa on the specific surface area, the total pore volume, average pore diameter, and microporosity of carbon materials prepared with the use of  The effect of pressure on the specific surface area, the total pore volume, average pore diameter, and microporosity of biomass-derived carbon materials is discussed. The results prove pressure to be a parameter of considerable potential in shaping the porous structure of carbon materials.Depletion of natural resources and increasing energy demand imply the need for implementation of more sustainable technologies in all aspects of economic development. In particular, this concerns recycling and utilization of waste materials but also the wider use of biomass as a raw material of low carbon footprint. Biomass valorization has been widely discussed recently in terms of its utilization in thermochemical processing technologies, including pyrolysis and gasification . GasificH4)2S2O8 ,12,13,14H4)2S2O8 ,16,17,18H4)2S2O8 ,20. The H4)2S2O8 ,19, whilAndropogon gerardi is a grass of 1–2.5 m long blades cultivated mainly as an energy crop and animal feed crop, but is also applicable in anti-erosion and reclamation activities in post-industrial areas [The biomass sample was acquired from an experimental stand of M&D Farms Sp. z o. o. in Swierczow, Poland. al areas ,22. Its The biomass was carbonized with the use of a high-pressure thermogravimetric analyzer with the magnetic suspension balance mechanism , at the temperature of 1000 °C in an inert gas (Ar) atmosphere and under pressure of 1, 2, 3, or 4 MPa for 5 h see . A heatiThe results of the porous structure characterization are given in Micropore volume and area determined with the application of the V-t-deBoer method (pores width range 0.6–2.0) almost tripled with the increase in carbonization pressure from 1 to 3 MPa and slightly decreased from the maximum values (of about 14%) with further rise in pressure to 4 MPa. The data for micropore volume and area determined on the basis of the carbon dioxide isotherm (pore width range 0.4–1.5 nm) showed a 25% increase in micropore volume and 23% increase in micropore area with the pressure increase from 1 MPa to 2 MPa and a slight decrease of about 6% and 7%, respectively, with increase of pressure to 3 MPa, and of 6% with further rise in pressure to 4 MPa . The varThe DFT pore size distribution results showed the dominant role of microporosity (pores of a diameter below 2 nm), especially in the range of up to 1 nm, in shaping the pore volume of the carbon materials tested see b. MicropPore size distribution within the entire pore width range measured based on the nitrogen sorption isotherm as well as narrow micropore distribution measured on the basis of the carbon dioxide isotherm data showed comparable shares of pores of particular diameter ranges in carbon materials volume, irrespective of pressure applied . HoweverThe disintegration of carbon materials produced under pressure and at high temperature resulting mainly from moisture and volatiles release under low heating rates can be seen in The dominant role of micropores in the porous structure of chars generated under high pressure might imply that relatively low heating rates applied in this study enabled free swelling behavior of chars, which enhanced the development of microporosity. Intensive melting behavior, previously observed to be more pronounced with high heating rates applied in carbonization step, would lead to the development of macroporous materials . The sli3PO4 of cotton stalks (ratio of 0.3:1) followed by thermal activation at 500 °C for 2 h [The results observed proved that the pressure may be considered as an effective parameter shaping the porous structure of carbon materials, especially with lower heating rates. Similar values of the specific surface area as well as micropore area and volume were reported for the more complex and costly process of physical and chemical activation of peat with carbon dioxide at 750 °C and acid washing . Compara for 2 h . Carbon This proves that pressure may be considered as a practical tool for production of porous materials from various precursors, including non-lignocellulosic biomass, known to be less applicable in activated carbon production. It may replace, at least to some extent, the time-consuming and labor-intensive processes of chemical and physical activation. Clearly, the application of pressure itself is not sufficient to provide materials of the specific surface area and total pore volume comparable with commercial activated carbons or the materials after a complex cycle of physical and chemical activation of most suitable precursors ,8,12,14.Andropogon geraradi biomass were presented, enabling the following conclusions to be drawn:Carbonization of the selected biomass under 3 MPa gives carbon materials with the most developed porous structure in terms of the specific surface area, the total pore volume, and microporosity, as determined by nitrogen sorption isotherm;The pressure of 2 MPa was proved to enhance the development of narrow microporosity, as quantified by carbon dioxide isotherm;Application of pressure during carbonization enables tailoring of the porous structure of carbon materials.In this paper, the results of an experimental investigation of the effects of pressure on high temperature carbonization of


The purpose of this study was to compare the satisfaction of patients regarding retention, stability and accumulation of particles with a randomized, double-blind crossed method in users with complete dentures with and without adhesive.Seventeen edentulous individuals were randomized and received new upper and lower complete dentures. After a period of adaptation, they participated in some masticatory tests and clinical revisions, after use the protheses with and without the use of two denture adhesives: Adhesive A  and adhesive B  at 0, 7 and 14 days. Satisfaction was measured immediately after each test through a survey using a VAS scale (0-10) and data were analyzed with McNemar’s test with Bonferroni correction.p<.01) between the study groups with adhesive A - B and the group without adhesive, but no significant differences were found between the two stickers for any of the variables studied.The results showed significant differences (Complete denture adhesives significantly improved the satisfaction of patients because a better retention, stability and less accumulation of particles of the food substitute between the denture and the mucosa is obtained compared with non-use of complete denture adhesives. Key words:Complete dentures, patient satisfaction, denture adhesives, clinical trials. There are numerous alternatives of implant treatment for edentulous patients (EP) with good aesthetic and functional results, providing a higher quality of life -6, but sThe use of adhesives for complete dentures (CDAs) is relatively widespread among patients with complete denture which often use them without proper prescription by the dentist, causing dissatisfaction, as a result of not following the instructions of indication and use properly ,7.Numerous studies have shown that CDAs with proper prescription of the dentist help to improve the retention and stability of well developed ,8,12-20 The composition of the insoluble CDAs is a mixture of salts of polymers such as carboxymethyl cellulose (CMC) and polyvinyl ether Methyl Cellulose (PVM-MA) ,22,27 whGenerally dentists evaluate prosthesis using default criteria for the success based on the technique,The objective of this trial was to compare subjectively through a questionnaire, the feeling of retention, stability and accumulation of particles below the denture among patients with CDs without adhesive (WA) and with two CDAs  (AA) or adhesive B  (BA)). The null hypothesis was that the use of CDAs does not increase the patient satisfaction regarding the evaluation of the retention stability and accumulation of particles of the CDs.et al. with a method error of 95% confidence  and BA  were placed in similar white boats without identifying mark for the two products, having an investigator to performed the masticatory tests and a different one to perform data collection.In this way the double blind method was being applied, by ignoring both the clinician and the patient which of the two adhesives was being used. An irreversible hydrocolloid  Orthopr,41. The Mastication was performed in a standardized manner until completing 20 masticatory strokes ,12,41-43The EP carried out the masticatory tests and the satisfaction surveys as follows: day 0 the first test and survey, on day 7 the second test and survey and on day 14 the third test and survey Fig. ,12,25. IThe questionnaire had the three questions asked to each patient: 1) Lack of retention? . 2) Lack of stability? . 3) ¿Accumulation of particles? (If the patients felt the accumulation of particles of the substitute between the denture and mucosa). For the objectification of the answers to each of the questions relating to retention, stability and accumulation of particles under the denture, each patient was presented with a VAS scale (0-10), considering as a positive response when the patient marked 7 points or above 7 points and negative when 3 points or below 3 points were marked. (Responses between 3 and 7 were not considered).-Statistical analyzes The grouping variables of the study were WA, AA  BA . The results obtained, corresponding to the responses to the survey questions were collected in a file of IBM SPSS Statistics 22 (licensed from the University of Seville) , for appropriate processing ,12.The survey data and the subjective evaluation after masticatory tests by the EP with respect to retention, stability and accumulation of particles for the three studied groups  and BA (Corega GlaxoSmithKline)) was presented in It is observed how for the three variables, retention, stability and accumulation of particles, the percentage of “Yes” and “No” are very similar inverted in the case of the use of adhesive A and B , , .Compared to the values in the tests without the CDAs  those data are much better.p <0.01) The inferential analysis was planned to compare the variables Retention / Stability / Accumulation of particles among the three groups using the Cochran test which resulted statistically significant (p <0.01) between the study groups AA or BA and the group WA, but there were no significant differences between both groups of AA and BA together for any of the variables studied.To establish which particular groups appear among the above differences in each of the studied variables, pairwise comparisons were established by the McNemar test with Bonferroni correction. The result for each of the variables studied was the same, namely, there were significant differences  and (PVM-MA) have an action mechanism that achieves an increase in adhesive and cohesive properties, increasing the viscosity between CDs and the oral mucosa. In this way the CDAs used contribute to the reduction of movement ,12,22,25The results of this study are consistent with those of other authors -30,41,42Most authors show a recognized secondary benefit of CDAs in patients with CD, which properly used have the ability to act as a barrier to help prevent the migration of food particles under themselves. Unfortunately this could not be measured in an objective way to show numerical results ,34,35,37et al.  The CDAs significantly improved the satisfaction of EP because a better retention stability and accumulation of food substitute between the denture and mucosa was obtained compared with not using CDAs. 2) No significant differences exist in the satisfaction of EP in terms of retention, stability and accumulation of particles of food substitute between the denture and the mucosa when using the two CDAs of the clinical trial.


Nature Communications; 10.1038/s41467-018-05934-7; published online 29 August 2018Correction to: The original PDF version of this Article contained an error in which Fig. 3 and its legend were omitted and Equations 5 and 6 contained errors.This has been corrected in the PDF version of the Article. The HTML version was correct from the time of publication.Φ, and incorrectly read:Also in the original PDF version, there were errors in Equations 5 and 6. Both equations omitted all occurrences of The correct forms of Equations 5 and 6 are:This has been corrected in the PDF version of the Article. The HTML version was correct from the time of publication.


Both the activation and the inhibition of these receptors can have positive effects on several diseases, including viral pathologies and cancer, therefore prompting the development of new compounds. In order to provide new indications for the design of Toll-Like Receptor 7 (TLR7)-targeting drugs, the mechanism of interaction between the TLR7 and two important classes of agonists (imidazoquinoline and adenine derivatives) was investigated through docking and Molecular Dynamics simulations. To perform the computational analysis, a new model for the dimeric form of the receptors was necessary and therefore created. Qualitative and quantitative differences between agonists and inactive compounds were determined. The  The human immune system has been traditionally divided into the innate immune system and the adaptive immune system. The innate immune system’s main function is to recognize pathogen-associated molecular patterns (PAMPs) . This prToll-Like Receptor 7 (TLR7) is a transmembrane protein localized within the endosomal compartment. It is mainly expressed in lung, brain, stomach, placenta, and peripheral blood mononuclear cells (PBMCs), such as dendritic cells, monocytes, macrophages and B-lymphocytes. This receptor is involved in the innate immune system response  and natuIn humans the protein is composed of 1049 amino acids, divided into an ectodomain of twenty seven leucine-rich repeat (LRR) regions, a trans-membrane domain (TM) and a cytosolic Toll/interleukin-1 (IL-1) receptor (TIR) domain . The ect50 as 607 nM with a 240 nM standard deviation [et al. have generated variants of the compound 52455 (Sumitomo) by altering the pyrimidine/imidazole ring system or side group exchanges; the resulting small molecules are the 52455, 52457, 52459, 52763, 52542, and 52587; three of these compounds showed an effect on TLR7 in activating nuclear factor-kappaB (NF-κB) on HEK293 cells: compound 52455 showed an EC50 of 103 nM with a standard deviation of 12 nM, compound 52542 showed 353 nM with a standard deviation of 96 nM and compound 52763 showed 965 nM with a 283 nM standard deviation; the other compounds did not show any activity on TLR7 [The huge number of pathologies in which the TLR7 is involved has led to an increasing interest in developing new drugs able to bind with this protein; both the activation and the inhibition of the receptor could represent a fruitful therapeutic approach, depending on the disease characteristics. The activation can enhance the immune response to viral agents and cancer, while the inhibition of the receptor can be used in treatments of some chronic inflammatory diseases . Imidazoeviation . CL097 ieviation . These ceviation ,31,32,33 on TLR7 . 1V209 [ on TLR7  is anothin silico model, wherever an experimental (X-ray or NMR) one is not available (as the case of TLR7). It refers to constructing an atomic-resolution model of the target protein starting from the alignment of the amino acid sequence with the one of a related homologous (the template) having a defined experimental  three-dimensional (3D) structure. It is well accepted that the method can produce reliable models only if the similarity in amino acid chains between template and target is higher than 30%, with few exceptions [et al. produced a model for the TLR7 ectodomain, identifying putative binding residues [et al. homology modeling of TLR7 resulted in a prediction of the dimeric structure and the production of a pharmacophore [et al. was used in molecular docking experiments, assessing the residues involved in ligand binding. Furthermore putative dimeric structures were predicted and interestingly the most probable one was found to be very similar to TLR8 X-ray dimeric structure [Computational methods have been demonstrated to be powerful tools to study the behavior of proteins and small molecules at the atomistic scale. A pivotal requirement for computational analysis involving receptor studies is a reliable three dimensional structure of the protein. Homology modeling technique has become an important tool in drug design and discovery , as it aceptions . Recentlresidues . The samresidues . Yu et aacophore . Recentltructure . It is wIn order to better understand the mechanism of activation of the receptor by small molecules, and thus lay the basis for the development of novel therapeutic compounds, we built an all-atom model of the dimeric structure of the TLR7 based on a recently published TLR8 template, which includes two molecules of a dual agonist. This allowed us to obtain a realistic model also for the binding zone conformation, and nine compounds from two classes of known agonists were docked. Once the binding positions had been disclosed, we ran Molecular Dynamics simulations in order to equilibrate the complexes; this was made in order to introduce the full flexibility of the receptor, which was completely neglected during the docking procedure. Finally, to obtain a reliable energetic rank, the Molecular Mechanics Generalized Born Surface Area (MMGBSA) technique was employed, to verify the capability of our model to distinguish between TLR7 agonists and compounds that are unable to activate the receptor; in this manner, the weakness of the docking scoring function could be overcome. Moreover, this approach furnished quantitative indication about the importance of each residue in the binding zone on agonist recognition and interaction.479 is one of the probable sites of cleavage [543, Gly572, Thr574 in one monomer and Phe346, Tyr353, Gly376, Val378, and Phe405 in the other one for TLR8; in TLR7 the respective residues are Asp555, Gly584, Thr586, Phe349, Tyr356, Gly379, Val381, and Phe408; the modeling of the receptor resulted in 754 residues. The new TLR7 model is reported in The TLR8 endosomal domain consists of 817 residues for each monomer; residues from 434–458 are missed after the proteolytic cleavage; in TLR7, residues from 436–478 were deleted in each chain during the alignment procedure, as Asncleavage . The seqBinding energy results from Autodock are reported in 543/555 and Thr574/586 which participate with three hydrogen bonds in the binding with the two ligands. However, in TLR7 the C-H-π interaction between Leu557 and one of the aromatic rings is also present; it is worth highlighting that this residue is not conserved in TLR8 and that Leu557 has been already described as one of the most important residues for the ligand recognition in TLR7 [555, and two with Thr586, whereas Phe408 and Leu557 interact with the small molecules via arene-arene and C-H-π interactions, respectively  trend that reached a plateau around 3 Å . Moreove555 and Thr586; the agonists show a considerable contribution from these two residues, in particular Asp555 is the largest contributor for 1V209 and 52455, as expected by its similarities in chemical structure; in the case of both R-837 and R-848 it interacts with only one hydrogen bond. Regarding the 52459, the energetic contributions from Asp555 and Thr586 are negligible. It is worth mentioning that residues from the other chain played also an important role in receptor-ligand interactions, especially Phe408 was able to establish a hydrophobic interaction with all the ligands.The results from the MMGBSA calculations are reported in The work presented in this paper is a computational study focused on the activation of TLR7 dimer formation using several known agonists. It deals with known activators of TLR7 whose biological action has been previously investigated but no details of molecular action on the target have been given before. This is not intended to be a virtual screening effort since we knew which compounds already showed the desired activity. Our work elucidated their detailed mode of action at an atomistic level.555. Molecular modeling techniques were employed to find on our TLR7 model possible orientations of imidazoquinoline and adenine derivatives that work as activators of TLR7. Binding affinities calculated over the simulations allowed us to obtain a relative rank between compounds that was consistent with the experimental data about the activities; 1V209 demonstrated the best binding energy and agonists showed stronger binding energies compared to the inactive ones; taking into account the absence of activation of NF-κB and the less favorable binding energy of the 52457, 52459 and 52587 compounds observed in silico, we could hypothesize an extremely reduced affinity and incapability to bind with the target. These data not only confirmed our model as a powerful platform to find new candidates, but also highlighted a direct correlation between binding energy and agonist activity. It is worth mentioning that the described binding energies, obtained with the MMGBSA method, do not include the entropic contribution, so they are relative binding energies; however, the discussed results are not affected because our objective was to verify if the presented model was able to distinguish between agonists and inactive molecules. Finally, the importance of the residues in the binding pocket in terms of ligand binding contribution was assessed by a quantitative measure of the decomposition of free energies. Particularly, Asp555, Ile585, Thr586, and Phe408 were found to be the strongest contributors in agonist recognition; in addition Leu557 was established to be also important for the ligand recognition. This latter observation, and the related C-H-π interaction, could confirm the hypothesis of Tanji et al. [In this work, we proposed a novel structural model for the dimeric form of the Toll-like receptor 7. The lack of an experimental three-dimensional structure constituted an obstacle for using computational tools in order to accurately investigate the behavior of ligands within the protein. Although other homology models were published before for TLR7, we propose a model based on the recently disclosed TLR8 dimeric structure as template, which represents the most similar protein in terms of ligands, functions, cellular localization, and sequence similarity. Our structural evaluation confirms a good overall quality of this model, and a series of known ligands and inactive molecules were docked in the putative binding pocket around residue Aspi et al.  and explIn this work, different molecular modeling approaches were sequentially employed to investigate interactions between several small molecules and the TLR7 receptor. Homology modeling techniques were employed to obtain an all-atom structure of the protein, using as template one of the crystallographic structure of TLR8 . The strff12SB force field parameters for the protein [The structure of TLR8 containing two co-crystallized molecules of CL097 (Protein Data Bank id: 3W3J), an agonist of both TLR7 and TLR8 , was cho protein  and EHT  protein . The bes protein  and ETH  protein . The pro protein .2)) to the protein. Then we ran 2000 Steepest Descent steps, followed by 3000 Conjugate Gradients steps, reducing the restraint force to 4 kcal/mol/Å2 applied to the protein backbone and heavy atoms of the ligands only. The structural evaluation of the optimized model was then performed using ERRAT [A successive stage of minimization was performed using Amber12 pmemd.cuda with the goal of optimizing the shape of the binding pocket. Missing parameters for the small molecules were assigned using AmberTools12 antechamber ; ff12SB ng ERRAT , which eng ERRAT , which pNine compounds were docked, including two imidazoquinoline derivatives (R-837 and R-848), and the 52X series, divided into four adenine derivative agonists  and three inactive adenine derivatives , intended as unable to trigger the activation of the NF-κB. The structures of R-837 an R-848 were taken from PubChem  , spersion . Based ospersion ,65 forcespersion ,63; this Raccoon . Desolva Raccoon . Docking Raccoon .50 values were calculated for R-848, 52455, 52542 and 52763 using the following equation:Binding energies from experimental EC2 on the complexes, in order to allow the relaxation of the water molecules using 1000 steps of Steepest Descent method followed by 1000 steps of Conjugate Gradients method. Then, the restraints were removed and the whole system was minimized with 2000 steps of Steepest Descent followed by 3000 of Conjugate Gradients. The system was then heated up to 310 K in 100 ps using the Langevin thermostat with a time collision frequency of 2 ps and a time step of integration of 0.5 fs. Target temperature was reached after 150,000 steps and maintained for the last 50,000 in this step. An NVT ensemble was simulated, with a restraint of 2 kcal/mol/Å2 put on the protein backbone and on the heavy atoms of the small molecule. The restraints were slowly removed in four phases of 50 ps each with a step of 0.5 kcal/mol/Å2 and a production simulation for an NPT system was then performed for 10 ns with a time step of 2 fs at 1 atm, using Berendsen barostat; bonds involving hydrogens were blocked using the SHAKE algorithm. The trends of the RMSD between the protein backbone, the ligand and the residues included in the binding zone of the simulated systems and the initial conformations were calculated using AmberTools12 ptraj.Explicit hydrogens were reintroduced to the docked complexes using Protonate 3D. Missing parameters for the small molecules were assigned using antechamber; ff12SB and GAFF parameters were assigned for the protein and for the ligands, respectively with leap; the systems were inserted into an octahedral box with a buffer of 12 Å of TIP3P water molecules and neutralized with chlorine ions. in pmemd.cuda, two stages of minimization were performed: the first step was run with a restraint of 500 Kcal/mol/Å2 on the protein, in order to allow the relaxation of the water molecules using 1000 steps of Steepest Descent method followed by 1000 steps of Conjugate Gradients method. Then, the restraints were removed and the whole system was minimized with 2000 steps of Steepest Descent followed by 3000 of Conjugate Gradients; the system was heated up to 310 K in 100 ps using the Langevin thermostat [2 on the protein backbone. Afterwards the restraints were slowly removed in four phases of 50 ps each, with a step of 0.5 kcal/mol/Å2 and a production simulation (NPT ensemble) was run for 30 ns with a time step of 2 fs at 1 atm, using Berendsen barostat [A 30 ns long Molecular Dynamics simulation of the solvated receptor without any ligand was performed; ff12SB parameters were assigned for the protein with tleap. The system was inserted into an octahedral box with a buffer of 12 Å of TIP3P water molecules and neutralized with 43 chlorine ions. In pmemd.cuda, two stages of minimization were performed: the first step was run with a restraint of 500 kcal/mol/Åermostat  with a tbarostat . Bonds ibarostat . The treBinding free energies were calculated using the script MMPBSA.py  in AmberIn this work the Generalized Born model of solvation (MMGBSA) ,74 was uThe free energy is calculated with the equation :(4)ΔGbiThe in-vacuum contribution estimates the non-bonded interactions  between the two molecules and it can include the entropic term modeling the loss of entropy due to the bond, through the relation:It is possible to calculate the entropy contribution by performing normal mode  ,77 or quth atom has radius et al. in which Born radii are rescaled [As is possible to see from the free energy equation the energy of binding takes into account also the solvation contribution; the Generalized Born (GB) method is indeed a way to treat the modeling of the aqueous environment surrounding the systems by using an implicit solvent model, that is the replacement of explicit water molecules with an infinite continuum medium with the dielectric properties . This apximation  as(7)ΔGfunction ,80,81. ΔDynamics  thanks tDynamics ,84. ThesDynamics . The igbrescaled .Two hundred and fifty snapshots for each complex were evaluated from the last 5 ns of simulation in order to calculate the relative binding free energies using the MMGBSA method without considering the entropic contribution; igb flag was set to 5 . The pai555, Ile585, Thr586, Phe408 and Leu557, have been found to contribute mainly to the interactions with the ligands. The accurate description of the binding mode of the TLR7 agonists as well as the features of the binding pocket that we present in this paper can be a starting point for the design and the development of novel compounds targeting the human innate immune system for the treatment of a wide range of diseases.The TLR7 is a promising pharmaceutical target for the treatment of several diseases, including cancer and viral pathologies; a major obstacle for the development of novel compounds targeting this membrane protein is however the lack of an experimental three dimensional structure. In this work we employed the homology modeling technique to build a high quality three all-atom structure of the TLR7, using as template the recently published experimental structure of TLR8. The TLR7 dimeric model has been then used as target for molecular docking and Molecular Dynamics simulations, in order to study the binding poses of two classes of TLR7 activators. Free energy estimations have been performed in the final step in order to determine the quantitative characteristics of the binding as well as the single contributions from the residues in the binding zone: the active compounds showed higher stabilities and binding affinities compared with the inactive ones, demonstrating the reliability of our model as a platform for virtual screening. In addition five residues within the binding pocket, namely Asp


To understand the process of resilience  and the chance of mental health problems in children and adolescents (9–16 years) who have been victims of domestic violence, assisted in specialized services (Group 1 – G1) and in school services without reports of domestic violence (Group 2 – G2).Various semi-structured instruments were applied to the pairs (guardian and child or adolescent): the Strengths and Difficulties Questionnaire (SDQ); the Resiliency Scales for Children and Adolescents (RSCA), including Scale I (SI – sense of control), Scale II (SII – relationship skills) and Scale III ; the Social Support Appraisals; the Home Environment Resources Scale and a questionnaire created by the authors to characterize the population.There was no difference in the prevalence of resilience between G1 and G2. Children and adolescents of both groups had a higher chance of low resilience in the absence of perception of social support from the teacher  and other people in the community . Girls had higher chance of low resilience (SIII). The establishment of routine or rules in the lives of the children and adolescents facilitated the development of resilience (SIII). In G1, the prevalence of mental health problems was 65% for the self-application version of the SDQ for children and adolescents (SDQ/CA) and 54% for the version answered by the guardians (SDQ/G). In G2, it was 33% for SDQ/CA and 37.9% for SDQ/G. Domestic violence against children and adolescents was a risk factor for the development of mental disorders (SDQ/G). Subjects with low resilience (SI) had a higher chance of developing mental health problems (SDQ/CA). Despite originating from the same regions, the groups had socioeconomic differences, which showed no relationship with resilience.The quality and perception of social support and resources present in the home environment may have facilitated the development of resilience in the studied children and adolescents. Violence may have increased the chance of mental health problems, domestic violence being an aggravating factor. There is need for research on aspects that predict resilience and investment in intervention strategies for this population, as a way to promote mental health. Along with accidents, violence is the third cause of mortality in the general population and the first among children and adolescentsThe data on domestic violence are also concerning: one in four children suffers physical violence and one in five girls has suffered sexual abuse,,In Brazil, the limited structure of the services of assistance to victims of violence, in association with underreporting, makes it difficult to obtain safe incidence estimates. There are few complaints because family members, members of the community, professionals  and the victims themselves, out of fear or for other reasons, turn a blind eye to the abusive dynamics. This phenomenon is called “conspiracy of silence”-The recurring assaults and abuses have serious consequences for the child or adolescent and negatively affect their physical, cognitive, emotional, and social developmentExposure to situations of social violence at school or in the community may have a strong impact on the lives and health of children and adolescents, from physiological and psychological changes to impairment of their perspectives for the future and personal development. Some of the most commonly observed symptoms are behavioral and mood changes as well as post-traumatic stress disorder,,,Many subjects, however, manage to subdue these difficulties. Since 1950, longitudinal studies have revealed that some people, despite having been exposed to environments with multiple psychosocial risks, were able to stay emotionally healthy. A new field of study thus emerged, based on the concepts of resilience and vulnerability,,This study has as theoretical references the construct of resilience and the concept of safety or support network – or of child care services, even. The former is understood here as a phenomenon with a transitional character, mediated by individual capacities and associated with the subject's socio-cultural-history context, emphasizing the importance of sharing and redefining experiences. The latter refers to the group of people and systems with close and meaningful relationships with the subject, being either constant or dynamicThe objective of this research was to study a group of children or adolescents who had been victims of domestic violence assisted in specialized services, and a group of students without reports of domestic violence, to learn about the predictors of resilience, the quality and perception of social support, the resources present in the family environment and the chances of them developing mental health problems.Centro de Referência Especializado de Assistência Social  of the municipality of Campinas, state of São Paulo, constituting group 1 (G1). The remaining 66 were students of state schools located in the same regions as G1, without reports of domestic violence, constituting group 2 (G2). The children and adolescents of G1 suffered neglect of care or physical, psychological or sexual violence.This is a cross-sectional, descriptive and analytical study, with 166 pairs formed by children and adolescents (9–16 years old) and their respective guardians. Of these children and adolescents, 100 were characterized as victims of domestic violence served in specialized services associated with the In both groups, intentional sampling was conductedAs these were families in conditions of psychosocial vulnerability, many of which did not agree to participate in the research due to the theme, there was difficulty of adherence. Thus, at least 66 children or adolescents were chosen per group, 12 by region of the municipality, three by age group and one for each type of violence in G1.Participants with previous diagnosis of neurological disease or intellectual disabilities were excluded.To identify the subjects’ chances of developing mental health problems, the validated Brazilian version of the Strengths and Difficulties Questionnaire (SDQ) was usedTo learn about the characteristics of resilience, the validated Brazilian version of the Resiliency Scales for Children and Adolescents (RSCA) of Prince-EmburyTo learn about the subjects’ support network, the validated Brazilian version of the Social Support Appraisals (SSA)A semi-structured questionnaireThe Home Environment Resources Scale (HERS)Data were collected from March 2014 to February 2016. The interviews were carried out simultaneously with the pairs (with the consent of the children or adolescents and their guardians) by two psychologists with experience in applying the instruments. In G1, 50% occurred on the families’ visitation day at the services; due to the high absenteeism, some were also carried out at their houses (26%) and at the school or socio-educational center frequented by the children and adolescents (24%). In G2, the interviews were carried out with the pairs at the schools that agreed to participate in the research.This study was approved by the Research Ethics Committee of the School of Medical Sciences of Universidade Estadual de Campinas , by the Municipal Secretariat of Citizenship and Social Inclusion  and by the State Secretariat of Education .The data were processed using the SPSS software version 16.0To assess the association between the variables, the chi-square test or the Fisher-Freeman-Halton test were employed. In addition, the odds ratio (OR) was determined, the non-fitted OR having been calculated via univariate logistic regression (ENTER method). In this case, the dependent variable resilience, with its low, BlA, medium, AbA and high categories, was reduced to only two categories: low (low/BlA) and adequate (medium/ABa/high).The fitted OR values were determined via multivariate logistic regression , with p-value = 0.05 for inclusion and p-value = 0.10 for exclusion. All predicting variables with p-value < 0.20 were selected for the univariate analysis.Of the 166 children and adolescents in the study, 89 (53.6%) were female. All children and adolescents were studied, 100 in G1 and 66 in G2. In G1, 25 children of the total 100 belonged to each age group , whereas in G2, from 15 to 18 of the total 66 belonged to each of them; as for region, in G1, 20 of the total 100 belonged to each region  and in G2, from 12 to 14 of the total 66 belonged to each of them.In this study, 63% of the children or adolescents (G1) suffered more than one form of violence, psychological violence being the most frequent (82%), followed by neglect or abandonment (58%), sexual violence (26%) and physical violence (23%). The main aggressors were the parents, father and mother (50.9%) or only one of them (30%).The distribution, with differences between the groups in relation to socioeconomic status and number of people per residence, is presented in As for the prevalence of resilience, G1 featured 72% of adequate and 28% of low resilience in SI, 92% of adequate and 8% of low resilience in SII, and 87% of adequate and 13% of low resilience in SIII. G2 featured 74.2% of adequate and 25.8% of low resilience in SI, 89.4% of adequate and 10.6% of low resilience in SII, and 98.5% of adequate and 1.5% of low resilience in SIII.The prevalence of low resilience measured by the three resilience scales and distributed by group, socioeconomic conditions, number of people per residence, sex, age, SSA and RAF in the univariate analysis are presented in As in the analysis of resilience no other differences between G1 and G2 were found, it was decided to group them for studying the factors that could interfere in the construction of this skill.After the multivariate analysis, only variables SSA-teacher and SSA-other remained in SI; only SSA-other remained in SII; and only sex, SSA-teacher and HERS-routine remained in SIII. In all of them, a low perception of social support was associated with a higher chance of low resilience. As for emotional reactivity (SIII), girls were 15.49 times more likely to show low resilience than boys .SDQ-C/A was applied to 126 subjects (75 from G1 and 51 from G2), while SDQ-G was applied to all 166. The SDQ-C/A analysis showed that, in G1, 52% (39/75) could be placed in the abnormal (27/75) or borderline (12/75) categories, while in G2, this occurred in 33.3% (17/51) of the subjects  (p = 0.112).As for SDQ-R, 64% (64/100) of G1 could be placed in categories A (41/100) and L (23/100), while in G2, this occurred in 37.9% (25/66) of the subjects  (p = 0.002).In addition, the subjects of G1 and G2 with low resilience in SI of the RSCA were 4.9 times more likely to develop mental health problems (A) in SDQ-C/A [OR = 4.90 (95%CI 1.66–14.44) (p = 0.008)]. In the other scales, no association between low resilience and mental health problems was observed.,Despite advances in the research on resilience, they are recent, with controversies and disagreements as to the definitions, concepts and research methods, which complicates the comparison of data,In the results of this study, the children and adolescents who had been victims of violence (G1), although exposed to traumatic situations, showed a prevalence of adequate resilience corresponding to 72% (SI), 92% (SII) and 87% (SIII), and of low resilience corresponding to 28% (SI), 8% (SII) and 13% (SIII) , 3 and 4Another researchIn the multivariate analysis , low perSubjects with low perception of support by other people in the community had more chances of low resilience in the personal attributes of optimism, adaptability and self-efficacy (SI) and in relationship skills (SII) . AnotherThe school and the teachers were identified as major sources of protection for the subjects of this study . It was The literature indicates the family as the main source of social support,It was found that families in situation of domestic violence (G1) had higher socioeconomic vulnerability compared to those in G2, but these aspects are not associated with the predictors of resilience. Precarious socioeconomic conditions can aggravate the situations of violence and also the risk of problems in the psycho-emotional development of children and adolescents,,It was found through the RAF,The girls of this study had higher chances of low resilience in emotional reactivity (SIII). This index shows the ability to manage or regulate emotions, to maintain one's balance in stressful situationsThe literature shows that the prevalence of mental disorders in children and adolescents varies between 10% and 20%The prevalence of chances of mental health problems found in G1 using both versions of the SDQ were quite high (52% in SDQ-C/A and 64% in SDQ-G). In another research,However, the rates presented by G2 were also high (33.3% in SDQ-C and 37.9% in SDQ-G), compared to the average of the population. These rates can be associated with the fact that the children and adolescents of G2 had also been exposed to possible situations of social or community violence, poor health and housing conditions, economic and cultural difficulties, low educational level of the guardians, among other situations of vulnerability. These factors may affect the subjects’ global and emotional development, causing these high rates of emotional symptomsA research,,Domestic violence against children and adolescents was shown to be a risk factor for greater chance of mental health problems in the subjects studied, based on the evaluation of SDQ-G (p = 0.002), including in G2. This result is relevant for studies in the field of children's mental health,In addition, it was found that the children and adolescents from both groups with low resilience in SI (sense of control), which assesses individual strategies to deal with stressful events (optimism, self-efficacy and adaptabilityThe high absenteeism in the interviews in both groups, due to the social vulnerability of the population as a whole and to the theme chosen, was a limitation of the study. However, the importance of carrying out studies in the field of domestic and social or community violence should be emphasized, despite the difficulties of access to this population, for the construction of more effective public service policies.-,The resilience rates shown by the subjects of this study , 3 and 4,Therefore, reflecting about the aspects that influence the construction of resilience and situations of violence may contribute so that mental disorders are avoided or do not become chronicViolence may have increased the chance of development of mental health problems, domestic violence being an aggravating factor. In this study, it was identified that girls had higher chances of low resilience in emotional reactivity, i.e., difficulties to cope and recover emotionally from a situation of vulnerability. Children and adolescents with low resilience in relation to emotional reactivity were more likely to develop mental health problems.The absence of perception of social support from the teacher and other people in the community of the children and adolescents was also identified as vulnerability or risk factor, being associated with low resilience. On the other hand, the presence of routine or rules established by the guardians was considered a protective factor.The perception of adequate social or emotional support can be an important protective factor and facilitate the development of resiliency. Investments in psychosocial work and the strengthening of effective actions based on the concept of a care network for families in situation of violence can be strategies for the development of predictors of resilience.There is need for research on aspects that predict resilience and investment in intervention strategies for this population, as a way to promote mental health.


The process leading to the nanosystems comprises nanoparticles growth, their aggregation into necklace-like aggregates, and final fusion into nanowires. The fusion requires the consumption of H2O2. The nanowires can be passivated with an organic thiol, lyophilized, and resuspended in water without losing their dimensional and optical properties. The position of the broad surface plasmon band of the nanowires can be tuned from 630 to >1350 nm.The challenge to obtain plasmonic nanosystems absorbing light in the near infrared is always open because of the interest that such systems pose in applications such as nanotherapy or nanodiagnostics. Here we describe the synthesis in an aqueous solution devoid of any surfactant of Au-nanowires of controlled length and reasonably narrow dimensional distribution starting from Au-nanoparticles by taking advantage of the properties of glucosamine phosphate under aerobic conditions and substoichiometric nanoparticle passivation. Oxygen is required to enable the process where glucosamine phosphate is oxidized to glucosaminic acid phosphate and H In this latter case, Derjaguin, Landau, Verwey, and Overbeek (DLVO) suggested that the interactions between particles are governed by superposition of van der Waals forces and double layer forces ,2. It haFor several important applications like, for instance, surface-enhanced Raman scattering (SERS) for diagnostic purposes ,15 or th1, tris(hydroxymethyl)aminomethane (TRIS), H2O2, and solvents were obtained from Sigma-Aldrich  and used as received without further purification unless stated otherwise. Zwitterionic thiol 2 was prepared by following previously reported procedures ) AuNPs are stable as can be judged by the intensity and position of the SPR band monitored over several days. Phosphonic acid derivatives bearing an amino group like aminomethylene phosphonic acid are mild passivating agents of AuNPs [Our original idea was to find a mild capping agent for AuNPs that could allow them to remain stable in solution without aggregation even when used in stoichiometric concentration to passivate the nanoparticle surface. Glucosamine phosphate GAP,  proved sof AuNPs  and GAP of AuNPs . Howeverof AuNPs . They obof AuNPs  that hydof AuNPs ,39. Hydrof AuNPs . All theca. 30% of the gold atoms on the surface of the nanoparticles is not passivated in the “citrate-depleted” nanoparticles compared to none before the organic material removal protocol we performed. The Zeta potential of the as-prepared AuNPs is −25.5 mV while that of the citrate-depleted ones drops to −2.5 mV. The TGA experiments indicate that, when GAP is added, the amount of organic material remaining after the depletion process is higher  for prolonged times. However, when most of the citrate is removed  [1H-NMR analysis of the organic component of the AuNPs after several days reveals  or Au(III) ions and AuNPs, as well. It is able to reduce HAuClto AuNPs . The AuN to H2O2 ,38,39. Fto Au(0) ,46,47. Teals see  the disaeals see  derivatidoes see  and aggrThe overall process of formation of the nanowires requires the following steps: (a) the AuNPs growth and oxidation of GAP to GAP-COOH; (b) the formation of necklace-like aggregates; (c) the fusion of the aggregates into nanowires.ca. 25 nm from the 8.5 nm diameter of the original ones. We observe that nanoparticles growth is fast at the early stages of the process while it slows down considerably with time (4 followed by further reduction with NaBH4 still contain ca. 4% Au(I) [4 reduction, as in our case, the amount is expected to be larger. XPS analysis of our as-prepared-AuNPs reveals that ca. 9–10% Au(I) is still present  present in the aggregated nanoparticles leading to their fusion into NWs.The initial growth of the original nanoparticles B is a weith time B. Howeve4% Au(I) . In the  present . Cold werocedure . Their aWhen we examine in detail the formed nanowires, the “memory” of the original nanoparticles is manifested by their wavy aspect, which is not much different from that observed by Xia et al. . for nan2, which, in turn is reduced to H2O2. GAP-COOH is responsible for the aggregation of AuNPs into mostly necklace-like aggregates while the reduction of residual Au(I) to Au(0) by H2O2 is responsible for the fusion of the aggregates with formation of nanowires. It has been reported [2 to Au(I) under acidic conditions and high temperature in the presence of CTAB leading to their shortening. Although our conditions are much different from those reported for such a process to occur, we cannot rule out that a similar oxidation reaction could constitute an additional source of Au(I) for the fusion of our AuNPs.To sum up, the experimental evidence suggests that the small amount of GAP present after the partial depletion process is oxidized to GAP-COOH in the presence of Oreported  that gol2 to H2O2 and eventually, the reduction of remaining Au(I) ions present in the gold clusters by the H2O2 formed. The product of the oxidation of GAP, the gluconic acid derivative GAP-COOH, appears to drive the mostly linear aggregation of the AuNPs while their fusion requires the reduction of residual Au(I) to Au(0) by H2O2. Because of the small amount of passivating agent present at the onset of the experiments, nanoparticles grow quickly by interacting together and coalescing into bigger ones. At the early stages of the process, GAP exerts the double role of a reducing agent on one side and a source of the efficient crosslinking compound GAP-COOH on the other. Fusion of the linear aggregates into nanowires is then due to reduction of residual Au(I) by H2O2. The overall process is depicted in We report here a straightforward and mild procedure to induce the aggregation of AuNPs mostly in a linear fashion to form necklaces that eventually fuse into nanowires. Experimental evidence indicates that the evolution of the nanoparticles into nanowires is associated with a redox process catalyzed by the nanoparticles involving the oxidation of the glucose moiety of GAP, the reduction of OWe believe that our results are very important for several applications, particularly in the field of nanomedicine  in view


The effects of nano-SiO2 dopants and the crosslinked structure on the micro-structure and thermomechanical properties were investigated using molecular dynamics simulations. The results show that the increase of crosslinking density enhances the thermal and mechanical properties of pure EP and EP nanocomposites. In addition, doping nano-SiO2 particles into EP can effectively improve the properties, as well, and the effectiveness is closely related to the particle size of nano-SiO2. Moreover, the results indicate that the glass transition temperature (gT) value increases with the decreasing particle size. Compared with pure EP, the gT value of the 6.5 Å composite model increases by 6.68%. On the contrary, the variation of the Coefficient of Thermal Expansion (CTE) in the glassy state demonstrates the opposite trend compared with gT. The CTE of the 10 Å composite model is the lowest, which is 7.70% less than that of pure EP. The mechanical properties first increase and then decrease with the decreasing particle size. Both the Young’s modulus and shear modulus reach the maximum value at 7.6 Å, with noticeable increases by 12.60% and 8.72%, respectively compared to the pure EP. In addition, the thermal and mechanical properties are closely related to the Fraction of Free Volume (FFV) and Mean Squared Displacement (MSD). The crosslinking process and the nano-SiO2 doping reduce the FFV and MSD value in the model, resulting in better thermal and mechanical properties.Establishing the relationship among the composition, structure and property of the associated materials at the molecular level is of great significance to the rational design of high-performance electrical insulating Epoxy Resin (EP) and its composites. In this paper, the molecular models of pure Diglycidyl Ether of Bisphenol A resin/Methyltetrahydrophthalic Anhydride (DGEBA/MTHPA) and their nanocomposites containing nano-SiO With the growing expansion of electrical equipment applications, the disadvantages of the Epoxy Resin (EP) insulating materials such as Diglycidyl Ether of Bisphenol A resin/Methyltetrahydrophthalic Anhydride (DGEBA/MTHPA) have become increasingly obvious. Some of the properties, including mechanical and thermal properties, are often not able to meet the ever-increasing requirements of electrical equipment ,2,3,4; wgT) and the Coefficient of Thermal Expansion (CTE) of the composites is lower than that of the pure EP [In recent years, molecular simulation technologies have continued to progress and develop, which, at the molecular level, possess obvious advantages in the study of the microstructure and macro-properties of composite polymer materials ,14,15. I pure EP . Chen Sh pure EP  have con pure EP  investig pure EP  carried 2 is one of the most common fillers for the EP insulating materials. The EP composite filled with nano-SiO2 has improved mechanical and thermal properties [2/EP nanocomposites through experiments [SiOoperties ,24,25. Aeriments ,28,29,302. The SiO2 fillers were spherical, with particle radiuses of 6.5 Å, 7.6 Å, 8.8 Å and 10 Å, respectively. Based on the MD simulations, the parameters of the models, including the Fraction of Free Volume (FFV), Mean Square Displacement (MSD), gT, CTE and mechanical properties, were analyzed. The effects of crosslinking density and nano-SiO2 particle size on the microstructure, thermal and mechanical properties of EP were investigated. In addition, the relationship between the structure and properties of composite EP was analyzed. Furthermore, this paper provided theoretical guidance for the design and preparation of EP nanocomposites with enhanced performance.In this paper, MD simulations were performed on DGEBA/MTHPA EP filled with nano-SiO2; (2) construct the amorphous models of the crosslinked EP/SiO2 nanocomposites based on the practical crosslinking reaction mechanism; (3) perform MD simulations of DGEBA/MTHPA/SiO2 crosslinked models with different crosslinking densities and filler sizes. The models mentioned in this paper were built using Material Studio (developed by Accelrys).In this section, the simulation steps are synthesized as the following three parts: (1) mix DGEBA and MTHPA according to the actual proportion, and fill the models with nano-SiO2, nanofillers were also considered during the crosslinking reaction. The reaction mechanism is shown in Due to the existence of the numerous hydroxyl groups on the surface of nano-SiO2 was realized through programming. To simplify the process, the following assumptions have been made: (1) The crosslinking density is defined as the ratio of the reacted epoxy groups to the initial epoxy groups. (2) To start the crosslinking process, we introduce the partial product of (a) during the model construction stage  in the crosslinking process) as a crosslinking primer (denoted by DGEBA-MTHPA). As a result, the crosslinking density of the initial model is 10%. (3) The activity of each reaction group is the same. (4) The reaction is diffusion controlled. (5) The reactions are synchronized.Here, the crosslinking reaction between DGEBA, MTHPA and SiO2 composite is as follows:(1)2 with radiuses of 6.5 Å, 7.6 Å, 8.8 Å and 10 Å, respectively. Simulate the oxidation reaction of SiO2, so that the surface of fillers has massive hydroxyl groups [Construct the molecular models of DGEBA, MTHPA, DGEBA-MTHPA and spherical nano-SiOl groups ,32. Subs(2)2 particle to simulate the well-dispersed situation. The mass fraction of SiO2 in each system was maintained at 6.5% by adjusting the amount of the ingredients according to Considering that the actual molar ratio of DGEBA and MTHPA is about 1:2 ,33, we c(3)−4 GPa (which is one standard atmospheric pressure) respectively by applying the Andersen and Berendsen methodology [Perform a 200-ps MD simulation on each model under the NPT ensemble (the constant temperature and pressure ensemble). The specific details of the MD process are as follows. The time step was 1 fs. The temperature and pressure were controlled at 580 K and 1.0 × 10hodology . In addi(4)The scriptlet employed for the crosslinking reaction was written according to Epoxy prepolymer is regarded as a mixture of DGBEA with a polymerization degree of zero and one. In this paper, the polymerization degree of DGEBA was set to zero in the modeling process to simplify the composite model . The mod−4 GPa.Molecular models with crosslinking densities of 10%, 34%, 67% and 96% were further selected for MD processing. First, MD simulations of 200 ps were performed under the NVT ensemble (constant volume and temperature ensemble) and NPT ensemble successively, in order to eliminate the stress generated during the crosslinking process. The time step was 1 fs, and the temperature was 580 K. In addition, the pressure in the NPT ensemble was controlled at 1.0 × 10Subsequently, anneal simulations were performed on the above models from 580 K–280 K to extract the information of density, volume and temperature for thermal property analysis. The annealing rate was set to be 10 K/100 ps, i.e., an NPT ensemble MD simulation of 100 ps was performed after each temperature decrease by 10 K. The models of EP composite at 300 K are shown in TV, consists of two parts, i.e., the volume occupied by the molecule denoted as oV, and the free volume fV, where:The free volume theory  holds thfV is the intermolecular space, which disperses in the form of a hole among the materials and provides space for molecule movements. It also enables the movement of the molecular chain. The influence of nanoparticles on the free volume of the polymer was relatively complex in the following two aspects. First, the nanoparticle occupied a considerable part of the volume of the system and increased the distance between chain segments, which hindered the movement and stacking of molecular segments and reduced the free volume. Moreover, the nanoparticle can participate in the crosslinking reaction of the EP system and fix molecular chain segments, therefore expanding the crosslinked network and increasing the free volume. The above impacts existed in all the EP nanocomposite materials. Therefore, the increase or decrease of the free volume significantly depended on the properties of the nanoparticles.FFV) was introduced to characterize the relative size of the free volume. The expression is [The volumes of different models differed greatly due to the different numbers of molecules. As a result, the free volumes were different, as well. Therefore, to facilitate the comparison of the free volume characteristics of different systems, the fraction of free volume (ssion is :(2)FFV=VFFV of EP/nano-SiO2 composites with different particle sizes were calculated at 300 K. The variation trend of the FFV with the crosslinking density is shown in Here, the FFVs of pure EP and composites decrease first and then increased. The reason for the above trend is as follows. In the initial stage of the crosslinking reaction, the free volume in the crosslinking network was occupied by a dangling chain appearing [FFV of the system decreased slightly. Subsequently, the formation of a crosslinking network and the decrease of the dangling segment led to the increase of the free volume. On the other hand, the FFV of the nanocomposites was lower than that of the pure EP. The underlying cause is that the nanoparticles occupied a considerable part of the space in the system, resulting in a smaller range of segmental motion and a decrease in the FFV. Furthermore, the FFV decreased with the decreasing particle size. This was due to the final crosslinked network being generated by the covalent links between SiO2 and EP matrix in the system, and the interaction tended to enhance as the particle size decreased. Previous studies have suggested that the mechanical properties of the polymers depended on the free volume to a certain extent. The smaller the free volume was, the better the performance could be [According to ppearing ,37; thercould be ,38. TherMSD) is defined as a microscopic parameter to characterize the motion capability of each atom or molecular segment in the system, which is defined as the mean squared displacement of the molecules or segments, respectively. In general, the slope of the MSD curve indicates the strength of the polymer molecule segment motion. The MSD in a system containing N atoms can be described as follows [i at time t and the initial time in the system, respectively. In this paper, the MSD values of systems with different crosslinking densities, particle sizes and temperature in the first 30 ps of MD simulations under the NPT ensemble were investigated.The molecules of the models were constantly moving throughout the MD process. Some research has proven that there is a correlation between the strength of the segment motion and the mechanical properties of the polymer. Specifically, the enhancement of molecular segment motion may reduce the mechanical modulus of EP . Moreove follows :(3)MSD=1MSD values of the 6.5 Å system under different crosslinking densities are shown in MSD and crosslinking density in other systems were similar. As the crosslinking density increased, the MSD values of EP and its nanocomposites gradually decreased, which indicated that the crosslinked structure limited the molecular motion in the model. To analyze the effect of particle size on the segment motion, the MSD values of different particle size models were normalized based on the number of atoms in the pure EP system, as suggested in MSD values are shown in 2 dopants can significantly limit the movement of the molecular segment in the material, and the restriction will be more pronounced as the particle size increases. In addition, temperature had a significant effect on segmental motion. Particularly, temperature had an apparent effect on the segmental motion of EP and its composites, as well. With the increasing of temperature, MSD values increased continuously, as shown in MSD. Furthermore, in the temperature range of 400 K–410 K, the variation of MSD values was the most conspicuous, which was related to the glass transition of the materials.The gT) refers to the temperature for the transition from the glassy state to the rubbery state of the amorphous polymer or vice versa, which is a critical thermal performance index of EP materials. When EP transitions from the glassy state to the rubbery state at temperature gT, its performance completely changes due to the state conversion. Therefore, obtaining the accurate value of gT is an important prerequisite for thermal performance comparisons across different systems. In this paper, the density-temperature linear fitting and MSD curve method were used to accurately predict the gT of each system.The glass transition temperature  interval.The gT values obtained by the density-temperature linear fitting method and the gT intervals obtained by the MSD curve method are summarized in gT value of the pure EP with 67% crosslinking density was 382.68 K, which was highly close to the actual gT value of DGEBA/MTHPA epoxy [PA epoxy . It can gT values of EP and its composites for different particle sizes and crosslinking densities are summarized in gT value of pure EP and EP composite with 6.5 Å nano-SiO2 increased as the crosslinking reaction went on. Moreover, when the crosslinking density was greater than 34%, the increase rate of the gT value with crosslinking density was higher than that in the initial stage of the crosslinking process. Therefore, increasing the crosslinking density can significantly improve the gT value of EP and its composites. According to gT value.The gT value of pure EP and EP composite with different particle sizes at 67% crosslinking density. Nano-SiO2 can significantly improve the gT value of EP composites. Particularly, the gT value of composites doped with 6.5 Å SiO2 increased by 6.68%. Analysis suggested that the excellent thermal properties of nano-SiO2 can increase the gT value of the composites. On the other hand, the inorganic-organic interface integration between the filler and the EP matrix was an important factor to increase the gT value of the material. With the decrease of the particle size, the small size effect of nanoparticles was more intense, and the interface effect was strengthened. Therefore, the interfacial bonding between the nano-SiO2 and the matrix was stronger, resulting in higher gT values.V0 is the volume at 300 K and P is taken as the standard atmospheric pressure. The relationship between the volume and temperature of different EP systems was linearly fitted to obtain the values of Coefficient of Thermal Expansion (CTE) refers to the ratio of the increment in the length of the unit temperature and its length at 300 K, which is a critical index factor to measure the thermal stability of materials. The calculation formula is as follows :(4)CTE=12 crystal itself. In addition, the CTE in the glassy state was smaller than that in the rubbery state due to the different states of free volume, which is consistent with [Taking pure EP and the 6.5 Å composite as examples, the CTE at the glassy state and rubbery state obtained by Equation (4) are shown in ent with ,21,32. I2, the CTE in the glassy state decreased gradually. In the glassy state, the CTE of the 10 Å model was reduced by 5.70% compared to that of the 6.5 Å system and 7.70% compared to that of the pure EP; while the CTE in the rubbery state increased with the particle size. In general, the CTE in the glassy state provided a better referential value considering the fact that the actual working state of the EP materials was the glassy state.On the other hand, the CTE in the glassy and rubbery states showed different trends with the variation of the particle size. As shown in σ is the stress vector, ε is strain vector and C is the stiffness matrix. The EP models in the simulation can be regarded as an isotropic material; thus, C can be simplified as follows:λ and μ are elastic constants and can be obtained from the stiffness matrix. The parameters such as Young’s modulus E and shear modulus G of an EP system can be obtained from λ and μ:The static constant strain method  was used2 further enhanced the stiffness and mechanical properties of the material. Furthermore, according to the results shown in MSD and limited the molecular motion in the model, which may result in higher moduli, as well [The static mechanical properties of the pure EP and composites were investigated at 300 K.  as well . Moreove as well .2 with different particle sizes improved the mechanical properties of the DGEBA/MTHPA matrix to varying degrees. Among them, the 7.6 Å SiO2 had the best performance, where Young’s modulus and the shear modulus increased by 12.60% and 8.72%, respectively. The phenomena were basically consistent with the results of free volume analysis. The smaller the particle size was, the smaller the free volume was, the higher the moduli could be. However, when the particle size of SiO2 was less than 7.6 Å, the Young’s modulus and the shear modulus decreased slightly, which indicated that there were many factors affecting the mechanical properties of the nanocomposites. The interface characteristics produced by different particle sizes may be another factor affecting the mechanical properties, except the free volume.The Young’s and shear moduli of the pure EP and composites with different particle sizes at a crosslinking density of 67% are shown in 2 was developed, which effectively improved the accuracy of modeling and the molecular simulation efficiency of epoxy composites. The microstructure, thermal and mechanical properties of epoxy resin and its composites were studied by molecular dynamics. The results show that the crosslinking densities of epoxy resin and the doping of nano-SiO2 can influence the structure and properties of the materials in many ways. The obtained findings are as follows:gT) increased and the coefficient of thermal expansion (CTE) decreased; in addition, Young’s modulus and the shear modulus of the materials increased, and the mechanical properties were enhanced.The thermal and mechanical properties were improved by increasing the crosslinking density. With the increase of crosslinking density, the glass transition temperature  and Mean Squared Displacement (MSD). The crosslinking process and the nano-SiO2 doping reduced the FFV in the model, impeded the deformation and improved the elastic modulus of the system. Moreover, the decreasing FFV reduced the MSD of the model, limited the segment motion of the molecular chains and made it even harder for the glass transition.The thermal and mechanical properties are closely related to the Fraction of Free Volume (In this paper, an automatic crosslinking method for epoxy resin, anhydride curing agent and nano-SiO