Effect Of Long-term Immersion Research Articles

Fluid preservation in brain banking: a review.

Fluid preservation is nearly universally used in brain banking to store fixed tissue specimens for future research applications. However, the effects of long-term immersion on neural circuitry and biomolecules are not well characterized. As a result, there is a need to synthesize studies investigating fluid preservation of brain tissue. We searched PubMed and other databases to identify studies measuring the effects of fluid preservation in nervous system tissue. We categorized studies based on the fluid preservative used: formaldehyde solutions, buffer solutions, alcohol solutions, storage after tissue clearing, and cryoprotectant solutions. We identified 91 studies containing 197 independent observations of the effects of long-term storage on cellular morphology. Most studies did not report any significant alterations due to long-term storage. When present, the most frequent alteration was decreased antigenicity, commonly attributed to progressive crosslinking by aldehydes that renders biomolecules increasingly inaccessible over time. To build a mechanistic understanding, we discuss biochemical aspects of long-term fluid preservation. A subset of lipids appears to be chemical altered or extracted over time due to incomplete retention in the crosslinked gel. Alternative storage fluids mitigate the problem of antigen masking but have not been extensively characterized and may have other downsides. We also compare fluid preservation to cryopreservation, paraffin embedding, and resin embedding. Overall, existing evidence suggests that fluid preservation provides maintenance of neural architecture for decades, including precise structural details. However, to avoid the well-established problem of overfixation caused by storage in high concentration formaldehyde solutions, fluid preservation procedures can use an initial fixation step followed by an alternative long-term storage fluid. Further research is warranted on optimizing protocols and characterizing the generalizability of the storage artifacts that have been identified.

Effect of Long-Term Immersion on the Corrosion and Passivation Behavior of Lean Duplex Stainless Steel 2101 in 3.5 wt% NaCl Solution

Effect of Long-Term Immersion on the Corrosion and Passivation Behavior of Lean Duplex Stainless Steel 2101 in 3.5 wt% NaCl Solution

Investigation of waste clay brick as partial replacement in geopolymer binder

This study investigates waste clay brick (WCB) as partial binder replacement in geopolymers with fly ash and/or slag. The properties investigated include setting time, flowability, strength, water absorption, volume of permeable voids (VPV), water absorption rate, effect of long-term immersion in water, and sulfate attack. For all WCB-based geopolymer mortar samples tested, the short- and long-term compressive strengths remained between 42 MPa and 62 MPa. Water absorption and VPV were found to be between 6.4–7.1 % and 11.9–13 %, respectively. Compared to OPC, geopolymers investigated here showed enhanced resistance to sulfate attack considering both post-exposure length expansion and strength deterioration.

Experimental Investigation of Long Term Seawater Durability and Shear Properties of Pultruded GFRP Composite

The effect of long term immersion in seawater at different temperatures on the properties of pultruded glass fibre reinforced polymer (GFRP) composite rebar was investigated. Samples were conditioned in seawater and in dry at 23, 55 and 75 °C for 0, 8, 20, 30 and 36 months to analyse the changes in shear properties such as transverse shear strength (TSS) and short beam shear strength (SBSS). Both TSS and SBSS increased after conditioning in dry at 55 and 75 °C; on the other hand, TSS decreased gradually due to conditioning in seawater at 23, 55 and 75 °C, whereas SBSS decreased due to conditioning in seawater only at 75 °C. Microscopic analysis specified that the shear strength decreased due to fibre/matrix interfacial failure as a result of de-bonding and fibre pull-out. Compared to the short beam shear test, the transverse shear test was found to be a sensitive technique to measure the durability of pultruded GFRP rebar. FT-IR analysis indicated superficial hydrolysis reaction of polymer matrix occurred when the sample was conditioned at 75 °C. A reversible change in glass transition temperature (Tg) and in viscoelastic property of the polymer matrix was observed due to conditioning in seawater at 23 and 55 °C.

Durability and strength properties of particle boards from polystyrene–wood wastes

This paper presents the results of experimental study on the production of particle boards from wastes of wood and expanded polystyrene foam (EPS). Two different particle sizes of wood wastes and two different dosages of EPS resin were used as binders in the boards (WPP). Modulus of rupture (MOR), modulus of elasticity (MOE) and physical properties were analysed. Effects of long-term immersion in water for 7–28 days on the properties of the particleboards were similarly evaluated. SEM and FTIR were used to analyse the specimens. The results showed that water absorption decreased as EPS content was increased from 1.5 to 2.0 and thickness swelling indicated that WPP with 0.85 mm particle sizes and 1.5 resin dosages had the least value between 2.38 and 3.51% after 7–28 days of prolonged immersion in water. MOR and MOE indicated that the optimum performances of the WPP boards were recorded before the prolonged immersion in water at 4.3 MPa and 187.8 MPa. WPP with 0.85 and 1.75 mm particle sizes with 2.0 resin dosage had good post immersion performance. This study demonstrated that wood and EPS wastes are sustainable materials for producing composite wood based panels that are still durable in moist environment.

Effect of Long-term Immersion in Water and Artificial Saliva on the Flexural Strength of Two Heat Cure Denture Base Resins

The aim of the present study was to compare and evaluate the flexural strength of heat-polymerized Lucitone 199 and SR Ivocap denture base resin materials which uses polymerization techniques of compression molding and injection molding respectively and effect of artificial saliva and distilled water on long-term. Ninety specimens each from both the materials measuring 65 × 10 × 3 mm were prepared. After the polymerization, flexural strength was calculated after 24 hours (control group) without immersing in the liquid medium. The test group specimens immersed in saliva and distilled water at 37°C was calculated for the flexural strength at 2 weeks, 1 month, 2 months and 4 months. The flexural strength was measured using a universal testing machine. One-way analysis of variance (ANOVA) method was used to analyze the data, pairwise comparisons were done using Bonferroni post hoc test with a probability of less than 0.05 were considered to be statistically significant. The evaluation showed that, despite the duration of immersion and type of acrylic resin, high flexural strength was seen with specimens immersed in saliva than specimens under distilled water. The higher flexural strength was seen in SR Ivocap compared to that of Lucitone199 with the p value less than 0.05 which showed significant statistically. From the results, we can conclude that the higher flexural strength was shown in specimens of SR Ivocap fabricated through injection molding technique compared to specimens of Lucitone 199 fabricated through compression molding technique after immersion in artificial saliva and distilled water for long term. The homogeneous copolymer beads, the difference in the water sorption and powder to liquid ratios also affect the mechanical properties of the resins other than the type of resin used in the dentures base.

Segmental relaxation of water-aged ambient cured epoxy

The effects of long-term immersion on the viscoelastic characteristics of an ambient-temperature cured epoxy system, typical of systems used in infrastructure rehabilitation, are investigated using dynamic mechanical thermal analysis (DMTA). The study considers specimens aged at temperatures of immersion of 23, 37.8 and 60 °C. Time–temperature superposition principles were used to construct master curves of the storage modulus in the glass–rubber transition region for both wet and rejuvenated specimens. Viscoelastic parameters such as the relaxation time and the distribution parameters ( β) were determined using KWW curve fits to the master curves. The free-volume content determined through curve fitting of the WLF is higher by about 0.4% for wet specimens than the rejuvenated specimens. Consequently, the fragility index and the activation energy of the relaxation around T g are all reduced in the wet state. The viscoelastic properties of the aged epoxy specimens are strongly dependent on the temperatures of immersion although the level of water uptake in all cases is similar. Formation of multi-bound water molecules leads to the broadest glass–rubber relaxation in the wet state for specimens aged at 37.8 °C in deionized water, whereas the 60 °C aged specimens show the broadest relaxation in the rejuvenated state due to the formation of a heterogeneous network structure.

Effect of ageing on the bond strength of a permanent denture soft lining material.

Molloplast-B is a widely used, long-term, heat-cured silicone denture soft lining material. Adhesion failure of this material to poly (methyl methacrylate) denture base material is a problem that is encountered clinically. The purpose of this study was to investigate the effects of long-term immersion in water at 37 +/- 1 degrees C and of accelerated ageing in water at 50 +/- 1 degrees C on the tensile and shear bond strength values of this denture resilient lining material bonded to a heat-cured denture base material. Immersion in water for 1 week at 37 +/- 1 degrees C had no significant effect on the measured bond strength values. Longer immersion of specimens in water at 37 +/- 1 degrees C led to a significant reduction in the measured tensile and shear bond strengths. The present study has demonstrated that the reduction in Molloplast-B bond strength that occurs as a result of long-term ageing in water at 37 +/- 1 degrees C can be achieved in a shorter period of time by ageing the specimens in water at a higher temperature.