Non-aged Ones Research Articles

Membrane Order Effect on the Photoresponse of an Organic Transducer.

Non-genetic photostimulation, which allows for control over cellular activity via the use of cell-targeting phototransducers, is widely used nowadays to study and modulate/restore biological functions. This approach relies on non-covalent interactions between the phototransducer and the cell membrane, thus implying that cell conditions and membrane status can dictate the effectiveness of the method. For instance, although immortalized cell lines are traditionally used in photostimulation experiments, it has been demonstrated that the number of passages they undergo is correlated to the worsening of cell conditions. In principle, this could impact cell responsivity against exogenous stressors, including photostimulation. However, these aspects have usually been neglected in previous experiments. In this work, we investigated whether cell passages could affect membrane properties (such as polarity and fluidity). We applied optical spectroscopy and electrophysiological measurements in two different biological models: (i) an epithelial immortalized cell line (HEK-293T cells) and (ii) liposomes. Different numbers of cell passages were compared to a different morphology in the liposome membrane. We demonstrated that cell membranes show a significant decrease in ordered domains upon increasing the passage number. Furthermore, we observed that cell responsivity against external stressors is markedly different between aged and non-aged cells. Firstly, we noted that the thermal-disordering effect that is usually observed in membranes is more evident in aged cells than in non-aged ones. We then set up a photostimulation experiment by using a membrane-targeted azobenzene as a phototransducer (Ziapin2). As an example of a functional consequence of such a condition, we showed that the rate of isomerization of an intramembrane molecular transducer is significantly impaired in aged cells. The reduction in the photoisomerization rate translates in cells with a sustained reduction of the Ziapin2-related hyperpolarization of the membrane potential and an overall increase in the molecule fluorescence. Overall, our results suggest that membrane stimulation strongly depends on membrane order, highlighting the importance of cell passage during the characterization of the stimulation tools. This study can shine light on the correlation between aging and the development of diseases driven by membrane degradation as well as on the different cell responsivities against external stressors, such as temperature and photostimulation.

Abrasive wear performance of hygrothermally aged glass/PTFE composites

In the present study, abrasive wear tests were conducted to investigate the effect of hygrothermal ageing on the friction and wear resistance of glass/Polytetrafluoroethylene (PTFE) composites. Non-hybrid and hybrid composites were manufactured with PTFE coated two-dimensional plain weave (2D), three-dimensional knitted (3D), satin weave (SW) fabrics and a steel metal mesh (MM). Hybrid composites were manufactured with PTFE coated glass fabrics and MM by placing it on the top and bottom of the laminate. Specimens were aged in a distilled water at a temperature of 35 °C for 60 days. Abrasive wear tests were performed with 120 μm grit silicon carbide (SiC) paper using a plate on plate apparatus with loads ranging between 10 N and 50 N. Water absorption and kinetic parameters were determined and Fickian diffusion behaviour was observed. Differential Scanning Calorimetry (DSC) analysis showed that the crystallinity was sensitive to the hygrothermal ageing and decreased with an increase in water uptake. Hygrothermal ageing reduced the abrasive wear resistance of both the non-hybrid and hybrid composites as compared to the non-aged ones. For the same ageing conditions, the inclusion of MM improved the wear resistance of non-hybrid composites.

The Influence of Battery Acid on the Destruction of Acrylic Coatings of Car Bodies

Renovation coatings of car bodies undergo destruction under the influence of operational factors. Like ultraviolet radiation, erosion, and aggressive media (among others, battery acid). This article concerns the evaluation of the influence of battery acid on the destruction of acrylic coatings previously non-aged, as well as aged climatically for 2 years. Ageing of the coatings with battery acid contributed to a degradation increase of their chemical structure. It was supported by a considerable increase in the polar component of surface free energy (SFE) of the coatings. In the case of prior climate ageing, the increase in the polar component was even higher. Moreover, the coating’s ability to absorb battery acid increased, which induced blistering. The DSC method revealed that the action of battery acid caused more intense oxidation of coating material, and as a result, the brittleness increased, leading to chipping of the coating surface layers. This led to the increase in surface roughness, measured using an interferometric method. The coatings previously climatically aged for 2 years presented higher values of surface roughness parameters than the non-aged ones. The increase in the surface roughness contributed to a substantial decrease in the gloss of coatings. A sharp difference in colour escalating with the lengthening of the ageing period was also observed using the spectrophotometric method.

Comparative in-vitro study of marginal gap of four cad/cam all ceramic systems with thermal aging

Aim: Marginal fit evaluation of diverse all ceramic systems before and after thermal agingObjectives: To assess the impact of thermocycling on marginal adaptations of CAD/CAM ceramic crowns manufactured from distinctive prefabricated blocks. Background: Good marginal adaptation guarantees gingival health and comes about in less cement disintegration and few occasions of caries and discoloration improper marginal fit lead to plaque maintenance, microleakage and cement breakdown. Marginal accuracy can be measured via inspection, exploratory probing and radiographic examination. Glass ceramics are used to replace missing or damaged tooth structure because of their high translucency, superior biocompatibility and low thermal conductivity. However, they are brittle materials which display a high compressive and low tensile strength. Zirconia is a strong substitute veneering for glass ceramics, but it has more opacity. That opacity decreased recently by addition of more translucent feldspathic porcelain to achieve the desired esthetics.Methods: Four groups of 20 crowns each (Celtra DUO, e-max CAD, bilayered zirconia and monolithic zirconia) were cemented on identical all ceramic artificial teeth. Marginal gaps measured before and after thermal aging as half of specimens were thermocycled 500 times between the maximum and minimum temperatures that the mouth is subjected to (5±1°C and 55±1°C) respectively. Statistical analysis was performed using Graph-Pad In-Stat statistics software for Windows.Results: Marginal gaps of all tested materials within clinical range (<120 μm). The highest marginal gap mean value and standard deviation (SD) before and after thermal aging recorded with bilayered zirconia (39.73 ± 9.43) and (50.23 ± 14.6) respectively. E-max CAD showed the lowest values before thermal aging (19.65 ± 10.2) while Celtra DUO showed the lowest values after thermal aging (32.21 ± 7.88) with significance between all groups except Celtra DUO before and after thermal aging. Irrespective of material type, totally it was found that thermally aged groups recorded higher marginal gap mean value (41.56 μm) than non-aged ones mean value (28.94 μm) with statistical significance.Conclusion: Bilayered zirconia recorded the highest marginal gap in aged and non-aged subgroups among all tested all ceramic systems with statistical significance. E-max CAD and Celtra DUO recorded the lowest marginal gaps. Thermal aging increased marginal gap mean values as a total result of all ceramic systems.

Selective catalytic reduction of NO by NH3 over Fe2O3-promoted V2O5/TiO2-based catalysts with high Fe2O3-to-V2O5 ratios

Fe2O3-promoted V2O5-WO3/TiO2 catalysts with high Fe2O3-to-V2O5 ratios (3.4–6) have been prepared for the selective reduction of NO with NH3 (NH3-SCR) and extensively characterized using various spectroscopic measurements. No crystalline iron oxides were indicated even for 8% Fe2O3-promoted V2O5-WO3/TiO2 but α-Fe2O3 crystallites were observed in a XRD pattern for 7.04 % Fe2O3-promoted WO3/TiO2. Both Raman and XPS measurements suggest the formation of FeOV species which may make a better N2 selectivity in NH3-SCR reaction at high temperatures. All Fe2O3-promoted catalysts showed a great depression on N2O formation. At temperatures >400 °C, samples with 5.46 and 8% Fe2O3 (Fe2O3/V2O5 ratio = 3.4 and 5) gave significantly lower N2O production levels compared with the unpromoted and lower Fe2O3 loading catalysts. However, increasing in Fe2O3 loading resulted in a decrease in high temperature deNOx activity due to the oxidation of NH3 into NO. All the 3.4 and 5 ratio catalysts after a hydrothermal aging at 550 °C for 10 h gave NO removal activity and N2O formation similar to those measured over non-aged ones. However, such an aging at 750 °C could lead to a considerable increase in N2O formation even for the 5.46 % Fe2O3-promoted catalyst. Fe2O3-promoted V2O5/TiO2-based catalysts could catalyze the reduction of gas-phase N2O by NH3 adsorbed strongly, suggesting that this reaction may be a major route to greatly suppress N2O formation, consistent with infrared studies showing a reaction between N2O and surface NH3 species strongly adsorbed on the catalysts. This surface reaction could readily occur from a temperature as low as 250 °C.

Changes of asphalt fumes in hot-mix asphalt pavement recycling

Hot-mix asphalt pavement recycling is widely practiced for its economic and environmental benefits. Existing studies are mainly focused on the engineering properties of reclaimed asphalt pavement (RAP) materials, without considering their impacts on the generated asphalt fumes—a widely recognized environmental hazard. The effects of using RAP on asphalt fumes are systematically studied in this research. Asphalt binders from different sources were used to create RAP materials in three aging conditions. Asphalt fumes were generated and collected from non-aged asphalt materials as well as RAP materials, followed by gravimetric and chemical analysis of the collected asphalt fumes. RAP materials were found to generate greater amount of particulates in asphalt fumes as compared with non-aged ones. RAP materials are also associated with increase in the types and concentrations of polycyclic aromatic hydrocarbons (PAHs) in asphalt fumes, especially those PAHs with more than three aromatic rings. PAHs increase in asphalt fumes is particularly noticeable for RAP created in the natural aging condition. It is reasonable to conclude that asphalt fumes generated from RAP become more hazardous, hence deserving more attention from researchers and practitioners. The mechanisms of the increase in PAHs are discussed, in addition to field exposure studies and mitigation measures.

Effect of Hygrothermal Ageing on Tribological Behaviour of PTFE-Based Composites

The present study investigates the influence of hygrothermal ageing on the tribological behaviour of polytetrafluoroethylene (PTFE) polymer composites. Three PTFE composites along with unfilled PTFE were tested in sliding contact against Inconel 625 (a Ni-based alloy) plates in both dry and water-lubricated conditions, utilising a unidirectional pin-on-disc tribometer. The tribo-tests were performed at a constant sliding speed of 0.13 m/s with a normal load of 84N providing an apparent contact pressure of 5 MPa. Hygrothermal conditioning was carried out at two different temperatures, and the water absorption evolution and kinetic parameters were estimated. Various characterisation methods were used to identify the wear mechanisms and influence of hygrothermal ageing on the degradation of the filler/matrix. The different tribological behaviour for different PTFE composites was observed within the ageing timeframe. The wear resistance of the fibre-filled samples was reduced compared to the non-aged ones over the ageing timeframe. However, the friction and wear resistance of the bronze-filled PTFE were enhanced by hygrothermal ageing.

Molecular and structural changes in gelatin evidenced by Raman microspectroscopy

The gelatin used for the hard capsules manufacturing must meet strict dissolution specification to ensure the delivery of drugs at right time in the digestive tract. However, the environment of production and storage time affect the quality of gelatin dissolution. This study aimed to identify the mechanisms underlying the geographical environment of production and aging impact on the gelatin dissolution rate. Gelatins from 3 different origins of production (A, B & C), whose dissolution rate had been previously characterized, were analyzed by Raman microspectroscopy before and after aging. The principal component analysis (PCA) clearly separated the aged gelatins from non-aged ones. The spectra interpretation suggested the denaturation of gelatin triple-helices. In addition, the formation of cross-links such as dityrosine, glucosyl-galactosylhydroxylysinonorleucine and proteoglycan-like sugar adducts was strongly suspected. Whatever the gelatin aging state, PCA systematically separated the B-gelatins from A and C-gelatins. Pentosidine cross-link was likely to vary depending on the production origin. Finally, the quality of dissolution was discriminated for aged gelatins of A-origin: the non-compliant gelatins exhibited higher lipid content than the compliant ones.

Effect of low-temperature aging treatment on thermally- and stress-induced phase transformations of nanocrystalline and coarse-grained NiTi wires

The phase transformation behaviors of nanocrystalline NiTi alloys coupling with grain size poses a challenge in functional property configuration. To realize this configuration and simultaneously avoid undesirable grain growth, the low-temperature aging (LTA) treatment at 573K for 2h was applied to both the nanocrystalline and coarse-grained NiTi wires in this study and the effect of LTA on both the thermally- and stress-induced phase transformations was respectively investigated. The results show that, after LTA, B2↔R transformation temperature of nanograins was elevated when R→B19′ transformation was maintained suppressed. The stress hysteresis and residual strain of nanograins were increased while those of coarse grains were decreased. Nanograins required higher stress to activate stress-induced R-phase transformation than coarse grains. Aged NiTi coarse grains presented larger thermal hysteresis but smaller stress hysteresis compared with non-aged ones. To have an in-depth understanding of these differences, the microstructures and microhardness were further studied. It turns out that the nanoprecipitation, lattice recovery, as well as the preservation of the preformed grain size are responsible for the differences. This study thus suggests the potential of configuring the functional properties while simultaneously maintaining the constant grain size via LTA treatment, which may facilitate the application of NiTi nanocrystalline.

Effect of synthesis parameters on structural and mechanical properties of Ti3Al–Nb–Mo intermetallic compound obtained by powder metallurgy techniques

The influence of microstructure, heat treatment and alloying addition on mechanical and fracture properties of Ti3Al-based intermetallic at room and elevated temperatures was studied. Ti3Al–11Nb–1Mo (mole fraction, %) alloy was consolidated via powder metallurgy processing by mechanical alloying (MA) and hot pressing (HP). MA powders were characterized using XRD and SEM-EDS. Optimum MA duration was 25 h and HP conditions of 1350 °C, 2 h, 35 MPa. After HP, solution treatment at 1050 °C for 1 h and water quenching α2+β Widmanstätten microstructure is present, while subsequent aging at 800 °C during 24 h induces small content of O-phase. High fraction of β-phase is a direct consequence of Mo. Compression tests were performed from room temperature to 750 °C in vacuum. The yield strength of compacts increases with temperature up to 250 °C (pyramidal slip systems activation), after which it decreases. Ductility increases throughout the whole temperature range. The presence of O phase contributed to ductility increase in aged alloys, while negligibly lowering yield strength. Registered drop in the yield strength of aged alloys compared with non-aged ones was mostly influenced by precipitation of α″2 particles. Mixed fracture modes are operative at all temperatures.

Different Forms of Asphaltene Microstructures Discovered in Transmission Electron Microscopy

AbstractTwo forms of microstructures in different types of asphaltenes and asphalt binder samples were discovered by using transmission electron microscopy (TEM). The first type of the microstructures is needle-shaped with a crystalline structure, while the second type is plate-shaped without a regular pattern. The size of the microstructures ranges from a few nanometers to several micrometers. The microstructures are more prevalent in field-aged asphalt binder and asphaltenes samples than those in nonaged ones. Experimental results indicate that both forms of microstructures are not made of wax, but asphaltenes molecules. The two forms of asphaltenes microstructures differ in morphology, microscopic structure, chemical composition, and resistance to electron radiation damage, indicating that they are formed by different mechanisms and have different physicochemical properties. Both types of microstructures also show thermal stability at elevated temperatures. The prevalence, size, and shape of the micros...

Feasibility of different chemometric techniques to differentiate commercial Brazilian sugarcane spirits based on chemical markers

Chemometric techniques were used to assess the quality of 51 commercial Brazilian sugarcane spirits (cachaça) based on chemical markers. Benzo(a)pyrene, methanol, 2,3-methyl-1-butanol, acetaldehyde, isobutyl alcohol, n-propanol, density, alcoholic strength, and higher alcohols were quantified using chromatographic methods and results were subjected to Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA), and Linear Discriminant Analysis (LDA). No significant differences (p≥0.071) were observed in the chemical markers of Brazilian aged and non-aged cachaça samples. Besides non-significant (p=0.922), the content of benzo(a)pyrene in aged sugarcane spirits was 1.83 times higher than in non-aged ones. Differences in alcoholic strength (p=0.001) and n-propanol (p=0.015) were observed among cachaças produced by double distilling, alembic and in stainless steel columns. PCA was not suitable to separate the samples according to the provenance, aging and distilling process, while HCA was effective in separating alembic cachaças produced by from two distinct producing regions. LDA seemed to be very suitable to assess not only the provenance but also the distilling and aging processes that cachaça undergoes, yielding about 91% accuracy to discriminate non-aged from aged cachaça, 81.82% and 86.61% accuracy to discriminate samples from Minas Gerais and São Paulo, respectively.

Precipitation of Si and its Influence on Mechanical Properties of Type 441 Stainless Steel

In this study the precipitation of silicon in Type 441 steel (18%Cr-0.4%Nb-0.5%Si) was investigated and its influence on strength properties were determined. To simulate high-temperature service conditions, heat treatments with various ageing times up to 120 hours and temperatures up to 800 °C were performed. Following the aging treatments, micro-and macro-hardness and tensile properties were measured. Microstructure and precipitation were analyzed using scanning electron microscopy and energy-dispersive spectroscopy. Predictions for equilibrium pericipitation were calculated using the Factsage software. According to observations, coarse titanium nitrides (TiN) and niobium carbides (NbC, Fe3Nb3C) were present in all specimens including non-aged ones. These precipitates did not coarsen during ageing, which implies that their growth already occurred in the sheet production process. However, silicon started to precipitate in the course of prolonged annealing. Si contributed to the formation of a secondary phase resembling the Laves-phase (FeNbSi) on grain boundaries. Hardness and yield strength were found to decrease with prolonged ageing at high temperatures. Factors affecting the silicon precipitation are discussed.

Effect of long‐term natural aging on the thermal, mechanical, and viscoelastic behavior of biomedical grade of ultra high molecular weight polyethylene

AbstractIn the total joint prostheses, Ultra High Molecular Weight Polyethylene (UHMWPE) may undergo an oxidative degradation in the long term. The overall properties of UHMWPE are expected to be altered due to the oxidative degradation. The goal of this study is to investigate the effects of natural aging up to 6 years in air on the thermal, mechanical, and viscoelastic properties of UHMWPE that was used in total joint replacement. The changes in UHMWPE properties due to aging are determined using Differential Scanning Calorimetry (DSC), uniaxial tensile tests, and Dynamic Mechanical Analysis (DMA). The DSC results show that the lamellar thickness and degree of crystallinity of UHMWPE specimens increase by 38% and 12% due to aging. A small shoulder region in the DSC thermograms is remarked for aged specimens, which is an indication of formation of new crystalline forms within their amorphous region. The tensile properties of aged and nonaged UHMWPE specimens show a significant decrease in the elastic modulus, yield, fracture stresses, and strain at break due to aging. The DM testing results indicate that the storage modulus and creep resistance of UHMWPE specimens decrease significantly due to aging. Also, it is remarked that the α relaxation peak for aged UHMWPE specimens occurs at lower temperature compared to nonaged ones. The significant reduction in the strength and creep resistance of UHMWPE specimens due to aging would affect the long‐term clinical performance of the total joint replacement and should be taken into consideration during artificial joint design. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Study on the Failure Factors of Composite Insulation in High-Voltage Storage Capacitors

High-voltage storage capacitors, which have composite insulations of polypropylene film and paper impregnated with oil, are working under charge-discharge mode. The insulations are not only exposed to electrical stress but also to thermal stress. Failure factors of composite insulation in capacitors are analyzed from three aspects: partial discharge (PD), space charge, and thermal factors. In order to investigate the possible influences on the dielectric properties of materials in capacitors, aging tests were conducted on the capacitors. Some parameters were detected in aged capacitors compared with nonaged ones. Experimental results reveal that PD is the key factor leading to the breakdown of the capacitor, space charge is the direct factor that induces the breakdown, and thermal factor just accelerates the degradation process.

Fatigue analysis based on synthesis of psychological and physiological responses measured simultaneously in follow-up driving

The authors turned their attention to the changes of inner responses (drive burden) of the driver when the external burden of follow-up driving was given to him and conceptualized a method of estimating drive fatigue by synthetically evaluating psychological and physiological responses of the driver during follow-up driving. The authors conducted an experiment on six male and female drivers to simultaneously measure their psychological and physiological responses such as the distance from the car ahead, eye and head movement, heartbeat fluctuation, and subjective fatigue and developed a model expression for quantifying drive fatigue synthetically. It was elucidated by the analysis performed by using the model expression that drive fatigue differed between straight sections and corner ones, between aged drivers and non-aged ones, and between male drivers and female ones.

Effects of aging on latex film formation from polystrene particles: A photon transmission study

Aging due to the storage time on latex film formation was studied using the photon transmission method. The UV visible technique was used to monitor the evolution of transparency during film formation from two different polystyrene (PS) particles produced by using two different steric stabilizers, i.e., polyvinyl alcohol and polyvinyl pyrrolidone. The latex films were prepared from PS particles at room temperature before and after aging and annealed at elevated temperatures in various time intervals above glass transition (Tg). The increase in the transmitted photon intensity Itr was attributed to the increase in the number of disappeared particle–particle interfaces. Relative decrease in transparency and delay in film formation were observed in the aged latex films compared to the nonaged ones. The Prager–Tirrell model was employed to interpret the increase in crossing density at the junction surface. The back and forth activation energies (ΔE) were measured and found to be dependent on aging for a diffusing polymer chain across the junction surface. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2014–2021, 2001

Perservative errors in object discrimination learning by aged Japanese monkeys (Macaca fuscata).

To examine the nature of age-dependent cognitive decline, performance in terms of concurrent object discriminations was assessed in aged and nonaged Japanese monkeys (Macaca fuscata). Aged monkeys required more sessions and committed more errors than nonaged ones in the discriminations, even in simple object discriminations. Analyses of errors suggest that aged monkeys repeated the same errors and committed more errors when they chose a negative object at the 1st trial. A hypothesis analysis of behavior suggests that their incorrect choices were mainly due to object preference. Therefore, the impairment was probably caused by a failure to inhibit inappropriate responses. Together with previous neuropsychological findings, deficits of aged monkeys in the performance of object discriminations can be explained by dysfunction of the frontal cortex.

Microstructure and Electrical Properties of Mn-Ni-In Spinels

Microstructural investigations of negative temperature coefficient (NTC) ceramics in the Mn–Ni–In–O system have been performed using X-ray diffraction (XRD), scanning (SEM) and transmission electron microscopy (TEM). The electrical properties have been characterized by measurements of resistance, activation energy and aging. The replacement of Mn by In in Mn2.9—xNixIn0.1O4 (x = 0.50 — 0.66) leads to higher resistivities and thermal constants, both decreasing with increasing Ni content, and minimum aging of 0.1% for x = 0.58. Microstructural changes deduced from the a/c ratio and caused by aging are observable for Mn2.32Ni0.58In0.1O4 which is nearest to the tetragonal/cubic phase boundary. It is concluded that the Mn3+ concentration on octahedral sites increases due to aging. The domain configuration changes with increasing Ni content: samples with low Ni content reveal domain laths (∼100 nm width) with internal twinning (<10 nm), samples near to the boundary exhibit finer scaled (5–10 nm), weakly curved domains without twinning and for high Ni contents a slightly increased domain width of 5–15 nm is observed. With the exception of x = 0.58, all aged samples show the same microstructure as the corresponding non-aged ones, whereas aged Mn2.32Ni0.58In0.1O4 is more comparable with Mn2.40Ni0.50In0.1O4. Consequently, the choice of composition with respect to the phase boundary is decisive for the electrical and microstructural behaviour.