Addition Of High Concentrations Research Articles

CITRONELLA OIL AS BIOADDITIVES ON SI ENGINE PERFORMANCE CHARACTERISTICS

Current dynamics of world energy supply have driven various innovations by the industry as well as research communities. Fossil fuels, although experiencing a declining interest due to sustainability issues, remain undeniably crucial since they are nearly irreplaceable in some sectors including electricity generation, it is necessary to continuously establish efforts to improve efficiency of those kinds of fuel. In this work, the authors evaluate the potential of locally sourced essential oils, namely citronella, as a fuel additive in a vision of raising the fuel economy of gasoline RON 90. Citronella oil was selected based on a positive hypothesis deduced from its chemical properties, as mentioned in multiple published works. Tests were made on a generator-set powered by gasoline engine using the mixture of RON 90 and citronella oil of various concentrations as the fuels. In addition, a commercial synthetic additive was also tested alongside the essential oil to provide a comparative figure. Meanwhile other investigators suggest a favorable effect of essential oils, our results show that citronella oil additions lead to higher fuel consumption at the same power level. A similar negative effect was also demonstrated by the synthetic additive. The only sector showing positive results is in terms of exhaust temperature where experiments with citronella additives create lower exhaust temperature as compared to pure gasoline and synthetic additives. However, rooms for innovation remain open by exploring other variables such as higher additive concentrations or combining different kinds of essential oils.

Novel polyethersulfone mixed matrix adsorptive nanofiltration membrane fabricated from embedding zinc oxide coated by polyaniline

Novel mixed matrix polymeric membranes were prepared by incorporating self-produced zinc oxide coated by polyaniline (ZnO-PANI) nanoparticles into polyethersulfone (PES) matrix using phase inversion method. Nanoparticles were synthesized, characterized and incorporated in PES matrix with loadings from 0.05 to 0.6 wt%. ZnO-PANI demonstrated effectiveness as a low-cost adsorbent, especially at a loading of 0.2 wt%. ZnO-PANI was used for adsorbing total phenolic compounds (TPC) from olive leaf extract (OLE) at different initial adsorbate concentration (49.92–466.59 mg/L) and pH (2−6). ZnO-PANI proved to be an effective and low-cost adsorbent to remove TPC from OLE. Langmuir model described the adsorption of TPC better than Freundlich model. Effect of incorporated nanoparticles on membranes morphology and hydrophilic properties studied using contact angle measurement, water content, membrane pore size and porosity, SEM, FTIR and pure water flux. Prepared membranes showed a significant increment in porosity, pore size and hydrophilicity by addition of ZnO-PANI in the casting solution up to 0.2 wt%. This led to a considerable improvement in permeability, which decreased with higher additive concentration. During OLE filtration tests (10–30 bar) using bare PES and 0.2 wt% ZnO-PANI/PES membranes, 0.2 wt% ZnO-PANI/PES showed the highest permeate flux and good TPC rejection (83–87%). Bare PES exhibited impressive TPC value rejections (85–92%) and better fouling resistance. Using 0.2 wt% ZnO-PANI achieved a balanced permeate flux and TPC rejection. The research emphasizes the practical applicability of these membranes in various industries due to their enhanced efficacy in removing phenolic compounds from natural extracts, offering a balanced approach between permeate flux and TPC rejection.

Assessment of physical/mechanical properties and cytotoxicity of dual-cured resin cements containing Sr-bioactive glass nanoparticles and calcium phosphate.

The aim was to develop dual-cured resin cements containing Sr-bioactive glass nanoparticles (Sr-BGNPs; 5 or 10 wt%) and monocalcium phosphate monohydrate (MCPM; 3 or 6 wt%). Effects of additives on degree of monomer conversion (DC), biaxial flexural strength/modulus, shear bond strength (SBS), mass/volume change, color stability, ion release, and cytotoxicity were examined. Controls included material without reactive fillers and Panavia SA Plus (PV). Experimental cements showed higher DC than PV regardless of light activation (p<0.05). Mean SBS and color stability were comparable between experimental cements and PV. Cell viability upon the exposure to sample extracts of experimental cements was 80%-92%. High additive concentrations led to lower strength and modulus than PV (p<0.05). The additives increased mass change, reduced color stability, and promoted ion release. The experimental resin cements demonstrated acceptable mechanical/chemical properties and cytotoxicity. The additives reduced the strength but provided ion release, a desirable action to prevent recurrent caries.

Retarding ice recrystallization by tamarind seed polysaccharide: Investigation in ice cream mixes and insights from molecular dynamics simulation

Food hydrocolloids, such as naturally sourced polysaccharide stabilizers, are becoming potential candidates for retarding ice recrystallization in frozen desserts. Tamarind seed polysaccharide (TSP) and its depolymerized fraction (DTSP) possessed ice recrystallization retardation (IRR) activity by a splat cooling assay. This study is a follow-up work aiming to investigate their application effects to retard ice recrystallization in ice cream mixes (ICMs) and delve into the ice-binding behavior at the ice/water interface. Native TSP worked for or against IRR in the ICMs depending on the concentration, while DTSP possessed an increased IRR effect under the addition of higher concentration (3.0%). Compared to TSP, adding DTSP caused less of an increase in the viscosity of the ICMs. Molecular dynamics was used to simulate ice growth in the presence of TSP (oligomer) and showed that the TSP possessed activity for retarding ice growth along the prismatic planes. During the propagation of ice crystals, the TSP was bound onto the ice and caused evident structural defects of ice layers. The findings of this study proved that TSP and DTSP have a promising application to retard ice recrystallization in ice cream and shed new light on understanding the mechanism of natural polysaccharides to retard ice growth.

Polymer types and additive concentrations in single-use plastic products collected from Indonesia, Japan, Myanmar, and Thailand

Marine debris comprising single-use plastic products (SUPs) is ubiquitous in Asian coastal waters, but there is little information on the types of polymers and the concentrations of plastic additives such waste products contain. In this study, 413 SUPs randomly collected from 4 Asian countries between 2020 and 2021 were analyzed to obtain specific polymer and organic additive profiles. Polyethylene (PE), coupled with external polymers, was prominent in the inside of the SUPs, whereas polypropylene (PP) and polyethylene terephthalate (PET) were prevalent in both the insides and outsides of the SUPs. The use of different polymers in the insides and outsides of PE SUPs implies specific and complicated recycling systems are required to maintain the purity of the products. Phthalate plasticizers including dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DiBP), dibutyl phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP), and the antioxidant butylated hydroxytoluene (BHT) were prevalent in the SUPs (n = 68). High concentrations of DEHP were detected in PE bags from Myanmar (820,000 ng/g) and Indonesia (420,000 ng/g), which were an order of magnitude greater than the concentrations in PE bags collected in Japan. SUPs containing high concentrations of organic additives may be the primary source of harmful chemicals in the environment, and should be responsible for their ubiquitous distribution in ecosystems.

Incorporation of the Multi-Layer Plastic Packaging in the Asphalt Binders: Physical, Thermal, Rheological, and Storage Properties Evaluation.

The amount of residual Multi-layer Plastic Packaging (MPP) in Canada has greatly increased in the last two decades, which has economic and environmental consequences. MPP is primarily made up of two or more layers of Polyethylene (PE), Polyester (PET), Nylon (NY), and Metalized Polyester (METPET). While MPP has not been used as an asphalt modifier, some of the materials commonly found in MPP, such as PE and PET, have also been successfully used as asphalt modifiers. Nevertheless, a few recent studies have demonstrated the potential for reusing MPP as an asphalt modifier to improve asphalt pavement performance. Recycling post-industrial MPP instead of using raw polymers could lead to economic and environmental benefits. However, a comprehensive study to evaluate MPP as a viable asphalt additive is lacking. The main objective of this study is to evaluate the feasibility of using MPP as an asphalt modifier via the wet method, considering the physical, thermal, rheological, and storage properties of the MPP-modified binder at different MPP concentrations (2%, 4%, and 8%) in asphalt cement (PG 58-28). MPP-modified binders were evaluated using the following instruments: Differential Scanning Calorimeter (DSC), Thermogravimetric Analysis (TGA), Superpave Dynamic Shear Rheometer (DSR), Rotational Viscosity (RV), and Environmental Scanning Electron Microscopy (ESEM). Test results indicated that the incorporation of MPP has a strong potential to improve permanent deformation resistance at high temperatures. In addition, MPP shows a moderate impact on fatigue cracking performance at intermediate temperatures. Overall, in low-temperature climates, using less than 4% of MPP additives would offer higher fatigue damage resistance along with adequate permanent deformation. In high-temperature climates, higher concentrations of additives may be preferable to resist permanent deformation. Finally, MPP is a challenge for existing recycling systems, and its incorporation into asphalt applications may develop more sustainable materials that would contribute to circular economy principles.

A comparative photophysical study of molecular association of structurally similar phenothiazine dyes in aqueous solutions of caffeine

This paper comparatively reports the role of a molecular additive (caffeine) on the absorption and emission spectral characteristics and molecular association of a series of phenothiazine dyes in aqueous solutions. The studied dyes were five phenothiazine dyes (thionine, azure A, azure B, toluidine blue O, and methylene blue) with strong close molecular structures. The spectral data of the water-caffeine-dye systems were systematically analyzed and discussed based on the chemical structure of the constituent molecules. The aggregate structure and the dimer characteristics were analysed based on the exciton model. The additive was to act as strong water structure-breaker over the range of studied concentration. The main driving force for breaking the dye aggregation is water-caffeine or dye-caffeine interactions at low and moderate caffeine contain. At the high additive concentrations, the caffeine-caffeine, dye-dimer caffeine, and caffeine-water-caffeine might have crucial role in the spectral and aggregation behavior of the dyes. Caffeine induces markedly fluorescence quenching in emission spectra of the studied dyes.

Sensory and instrumental texture profile of gluten-free biscuit with different concentrations of carrot co-product flour

Instrumental texture profile analysis reproduces the chewing action and texture-related parameters. This, together with the sensory texture profile, allows the obtaining of representative results, characterizing the product under study in a more precise way. Therefore, this work aimed to evaluate the sensory and instrumental texture characteristics of gluten-free buttery biscuits with different proportions of carrot stems and leaf flour (CSLF). From the instrumental texture analysis and the texture profile by the Temporal Dominance of Sensations method, the results showed that the biscuits presented good instrumental quality. The hardness did not differ among the treatments studied, which shows that the increase in the concentration of CSLF did not interfere with this parameter, allowing the addition of higher concentrations of flour in the biscuits. The data from the Temporal Dominance of Sensations method showed positive attributes for the texture of biscuits with a higher concentration of flour, with the main dominant sensations being: crunchiness and low adhesiveness. The cookies showed good sensory quality, constituting a practical, affordable and healthy food alternative to serve the celiac public.

Citric acid enhances clean recycling of Chinese cabbage waste by anaerobic fermentation

The massive yield and putrefactive nature of Chinese cabbage waste inevitably threatens human and environmental health. Here, anaerobic fermentation technology featuring citric acid additions and high-throughput sequencing technology were performed to assist in the clean recycling of Chinese cabbage waste and reveal the related underlying microbiological mechanisms. The results demonstrated that citric acid additions lowered the pH value (3.89 vs. 4.06) and induced a 20.03% reduction in ammonia-N content, a 341.95% increase in acetic acid production and a 24.09% increase in water-soluble carbohydrate content during the anaerobic period. Moreover, high additive concentrations of citric acid (1.11% dry matter) inhibited pH enhancement (4.07 vs. 4.67), organic acid degradation, spoilage microorganism resuscitation, and ammonia-N formation after 9 days of aerobic exposure. Microbiologically, a 4.06%–10.46% increase in Lactobacillus abundance, 44.06%–84.10% decrease in Leuconostoc abundance and 55.78%–65.86% decrease in Sphingomonas abundance were found in the groups treated with citric acid during the anaerobic period. Moreover, high additive concentrations of citric acid (1.11% dry matter) reduced Naumovozyma and Lactobacillus abundances during aerobic exposure, which were the spoilage-induced microbes indicated by redundancy analysis. In addition, a shift in microbiome equilibrium and a small, simple and competition-enhanced microbiome were induced by citric acid addition, indicating the important role of the interactions between the microbes. Collectively, the present study suggested that citric acid addition at a concentration of 1.11% dry matter improves the clean recycling of Chinese cabbage waste, and the effect of citric acid on aerobic stability is dependent on the concentration, which is linked to variations in the microbiome.

Fabrication of Polyethersulfone (PES) Membrane Incorporated with Graphitic Carbon Nitride (g-C3N4) Nanoparticles in Palm Oil Mill Effluent (POME) Wastewater Treatment

Backed by the evolution in the nanotechnology field, membrane modified with nanoparticles as an additive has become increasingly prominent nowadays. The enormous potential of graphitic carbon nitride (g-C3N4) photocatalyst in wastewater treatment has been disclosed extensively. In this study, 4 Polyethersulfone (PES) membranes with different concentration of g-C3N4nanoparticles as additive were fabricated and their performances were investigated. Scanning Electron Microscopy (SEM) analysis showed that the membrane top surface layer was getting denser with the higher g-C3N4nanoparticles concentration which subsequently decreased the membrane mean pore size, porosity and flux. However the membrane with higher additive concentration was demonstrated a better improvement in anti-fouling properties where the flux recovery ratio (FRR) of the membranes showed an uptrend movement from 23.43% (membrane without additive) to 64.64% (membrane with 6 wt.% of additive). The enhancement of COD and colour removal rate from 61.50 % to 66.50 % and 78.75 % to 83.75 % was also observed in this study where the finding has signified the increased g-C3N4 nanoparticles concentration was constructive in PES membrane modification.

Experimental study on the preparation of binary ice by additives enhanced vacuum flash evaporation

Being a novel energy storage medium, ice slurry has the advantage of good fluidity, high latent heat and heat transfer efficiency, which has a broad application prospect. In this work, the ice making characteristics of different types of additives (MgCl2, ethylene glycol and magnetic iron oxide nanoparticles) in a binary ice system by vacuum flash evaporation under the action of solid adsorption were experimentally investigated. Subcooling, flash rate, ice packing factor, latent heat and thermal conductivity were measured to evaluate the performance of ice production. The results showed that 0.075% wt of iron oxide nanoparticles and 1% wt of MgCl2 are more suitable to be used as additives for binary ice preparation than ethylene glycol, with the former outperforming the latter. Under optimal conditions, compared with pure water for ice making, the subcooling degree of iron oxide nanofluid was reduced by 55.80%, and the thermal conductivity and ice packing factor were increased by 98.80% and 54.22%, respectively. The subcooling degree of the MgCl2 solution was reduced by 37.52% and the ice packing factor was improved by 59.51%. Meanwhile, DSC tests showed that the latent heat of the nanofluid was almost independent of the nanoparticle concentration. However, the increase of MgCl2 solution would cause the decrease of latent heat. In addition, high concentrations of additives can inhibit ice crystal nucleation and growth, but a certain concentration of additives facilitates ice crystal refinement in vacuum ice making process, which is conducive to the transportation of ice slurry.

Inhibiting Au nanoparticle aggregation in freeze-thawing by presence of various additives

After freezing aqueous suspensions of gold nanoparticles (AuNPs) in the presence of various substances, the resulting aggregation of the nanoparticles was evaluated and the anti-aggregation effects of the different additives were compared. Many of the additives exhibited an anti-aggregation effects during freeze-thawing, the extent of which was greater at higher additive concentrations and the effects were 5 ~ 35% less than during the actual freeze-drying. Dextran and polyvinylpyrrolidone highly inhibited the aggregation even at markedly low additive concentrations (2 µg/mL). The use of a combination of a disaccharide (2 mg/mL of sucrose) and a sugar ester (20 µg/mL of sucrose palmitate) successfully preserved the redispersibility of the product after freeze-thawing while using each separately did not. Regarding the influence freezing and thawing conditions, a higher thawing temperature (from 4˚C to 60˚C) resulted in 10 ~ 20% better redispersibility of the AuNPs whereas the freezing temperature had no significant affect. The effect of freezing/thawing cycles of suspensions of AuNPs was also examined. The concentration of additive molecules on the surfaces of the frozen particles was monitored by In-situ Fourier transform IR spectroscopy. The collective findings of this study indicate that the additives essentially exert an anti-aggregation effect by slowing down the movement of the AuNPs.

Enhanced Thermal Conductivity in Oriented Polyvinyl Alcohol/Graphene Oxide Composites.

Polymer composites have attracted increasing interest as thermal management materials for use in devices owing to their ease of processing and potential lower costs. However, most polymer composites have only modest thermal conductivities, even at high concentrations of additives, resulting in high costs and reduced mechanical properties, which limit their applications. To achieve high thermally conductive polymer materials with a low concentration of additives, anisotropic, solid-state drawn composite films were prepared using water-soluble polyvinyl alcohol (PVA) and dispersible graphene oxide (GO). A co-additive (sodium dodecyl benzenesulfonate) was used to improve both the dispersion of GO and consequently the thermal conductivity. The hydrogen bonding between GO and PVA and the simultaneous alignment of GO and PVA in drawn composite films contribute to an improved thermal conductivity (∼25 W m–1 K–1), which is higher than most reported polymer composites and an approximately 50-fold enhancement over isotropic PVA (0.3–0.5 W m–1 K–1). This work provides a new method for preparing water-processable, drawn polymer composite films with high thermal conductivity, which may be useful for thermal management applications.

Electrical Conductivity and Wettability of Nanofluids Prepared by Nanocomposite of MWCNTs and Dialkyl Pentasulfide

Background: Multi-walled carbon nanotubes (MWCNTs) were filled with dialkyl pentasulfide (DPS) to prepare MWCNTs-DPS composite (nanocomposite) additives for use in nanofluid- based machining. Methods: The nanocomposite was prepared by employing a liquid phase wet chemistry method, and was then added in pure water with a surfactant to form the nanofluids. The present study comprehensively reveals the effects of additive concentration, acid treatment time, testing temperature and electrowetting conditions on the electrical conductivity and wettability of nanofluids. Results: The nanocomposite was successfully produced with a maximum filling rate of 27.4%. Its additives displayed an optimal performance at a concentration of about 0.1%. Consequently, the electrical conductivity and wettability of the nanofluids were increased by over 13.7% and 6.35%, respectively in comparison with individual MWCNTs additives. Under the electro-wettability conditions, the wetting performance of the nanofluids produced by the nanocomposite increased with the increase in charging voltage. Moreover, due to higher conductivity and greater charge capacity, the nanofluids with a higher additive concentration displayed better wetting performance. Conclusion: The modification and filling enhanced properties such as the surface activity, electrical conductivity and capacitance of the MWCNTs, thereby improving the performance.

Polymorphic Phase Change of Calcium Carbonate with Glutamic Acid as an Additive

The calcium carbonate (CaCO3) crystals were successfully synthesized in the presence of glutamic acid used as an additive at 30 °C and at a pH of 8.5. The synthesized product was characterized in detailed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry and scanning electron microscopy (SEM) to identify the structure and habit of the crystals. Moreover, the size and surface charge of the crystals were measured by particle size and zeta potential analyzer. XRD and FTIR results showed that both calcite and vaterite in forms of apparently CaCO3 crystals were obtained in the presence of 50 ppm additive concentration at t=30 min. When increasing the glutamic acid concentration in the suspension, the formed CaCO3 were only in the vaterite form. The SEM analysis results pointed out that the addition of the glutamic acid significantly changed the shape of the CaCO3. At t=30 min the resulting product sample was found to contain two types of polymorphs; larger cubic shaped calcite crystals and smaller spherical-like vaterite crystals. Further addition of high concentrations of the additive enhanced the adsorption of the glutamic acid, resulting in the smaller spherical-like ellipsoidal vaterite crystals. Investigation of the zeta potential analysis indicated that higher additive concentration (100 ppm) resulted in a positive surface charge of the crystals, whereas lower concentration (50 ppm) gave negative electrical charge. Moreover, filtration analysis pointed out that adding glutamic acid additive resulted in a less specific cake resistance value (5.01 × 1011 m/kg) than that in pure media, which was 1.03 × 1012 m/kg.

Функциональные свойства пенобетона со сверхмалыми добавками углеродных нанотрубок

We studied the properties of foam concrete based on Portland cement, modified with of the ultra-low concentration carbon nanotubes addition. Carbon nanotubes (Taunit-24) with a mass percentage of 0.0004, 0.0006, 0.0008, 0.001 and 0.0012 % by weight of cement were used for the dispersed reinforcement of foam concrete based on Portland cement. To determine of the modified concrete samples strength characteristics an IP-M testing machine was used. The results of the study showed that the use of the carbon nanotubes additives in concentrations of 0.0004, 0.0006, 0.0008 % allows to gradually increase the compressive strength compared to the control sample. The compressive strength increase on 1, 12.4 and 68 %, respectively, and gradually decreases at concentrations of 0.001 and 0.0012 % from 55.5 to 45.7 %, respectively. A positive effect of the carbon nanotubes additive (0.0004, 0.0006 and 0.0008 %) is also noted when testing the bending strength by 3.7, 13.7 and 33.7%, respectively. With a further increase in the additive content (0.001 and 0.0012 %), the strength decreases to 20 and 14.8 %, respectively. When assessing water absorption, a decrease was showed with additives with concentrations of 0.0004 and 0.0006 %. However, at high concentrations of additives (0.0008, 0.001 and 0.0012 %), the highest percentage of water absorption was established.

Plastic additives and legacy persistent organic pollutants in the preen gland oil of seabirds sampled across the globe

Plastic pollution, and its associated impacts on marine fauna due to chemical contamination, is an area of growing global concern. We analyzed 145 preen gland oil samples from 32 seabird species belonging to 8 families with different foraging habits and life history strategies from around the world for plastic additives and legacy persistent organic pollutants. The additives included two brominated flame retardants (decabromodiphenyl ether, BDE209; decabromo diphenyl ethane, DBDPE) and six benzotriazole UV stabilizers (BUVSs; UVP, UV326, UV329, UV328, UV327, and UV234). Polychlorinated biphenyls (PCBs) and organochlorine pesticides (Dichlorodiphenyltrichloroethane and its metabolites: DDTs and hexachlorocyclohexane: HCHs) were detected ubiquitously. High concentrations of PCBs (up to 20,000 ng/g-lipid) were observed in the seabirds from higher-trophic level taxa. These patterns can be attributed to PCB exposure via their diet and associated biomagnification. DDT concentrations showed strong positive correlations with PCB concentrations, suggesting that DDTs in seabirds are also a result of diet and biomagnification. Plastic additives were detected sporadically as BDE209 and DBDPE were detected in 16 seabirds from 10 species (range: 3–379 ng/g-lipid) and BUVSs were detected in 46% (67) of the examined individuals (range: 2–7,055 ng/g-lipid). UV stabilizers were more frequently detected than flame retardants because UV stabilizers are more widely applied to plastic products. None of the plastic additives were correlated to the presence of PCBs, nor were they explained by the foraging area or trophic level. High concentrations of additives were detected in the species with high levels of plastic in their digestive tracts. In some of these species, such as Hawaiian petrels (Pterodroma sandwichensis) from Hawaii and flesh-footed shearwaters (Ardenna carneipes) from Western Australia, plastics were directly observed in the stomach. For other species, including great shearwaters (Ardenna gravis) from Gough Island, blue petrels (Halobaena caerulea) from Marion Island, and black-footed and Laysan albatrosses (Phoebastria nigripes and P. immutabilis) from Hawaii, plastic ingestion has been documented in literature. These patterns can be explained if the additives are mainly from ingested plastics rather than diet. The detection of BFRs and BUVSs demonstrated that a significant proportion of the examined seabirds accumulated chemicals from ingested plastics.

Effect of tip size and experimental conditions on nano-scale friction testing

Assessment of nano-tribological properties (friction and wear) on polymer surface helps to understand their scratch, mar and wear properties. More polymers are used now for automotive, electronics, appliances, and building and constructions industries due to aesthetics and design freedom. Owing to their lower mechanical properties, polymers are vulnerable to surface damage and deteriorate their morphology, functionality, and aesthetics with time. In this study, nano-indenter was used for measuring friction and wear properties varying test parameters and indenter tips. A Berkovich tip (B-tip) with radius of ∼50 nm and a conical tip (C-tip) with 60° cone angle and tip radius of 1000 nm were used. Polyoxy methylene (POM) with additives were chosen for friction testing. Higher coefficient of friction (COF) for C-tip was observed compared to B-tip and this explained based on the higher tip-material interactional area for C-tip. COF was decreased with higher additive concentration and same trend was followed for wear depth for the B-tip. For C-tip, COF was increased with the testing loads and corresponding wear depth were higher for higher load. Change of COF with test velocity was not showing any specific trend. Shallow wear depth using B-tip compared to C-tip may be better for probing top surface of the materials. Nano-scale tribo-mechanical evaluation techniques are uniquely suited for fundamental understanding and screening many additives quickly. Observed wear properties not only depend on the additives added to the formulation, but may also be influenced by the geometry of the tip.

P1052ASUPPRESSION OF BLOOD COAGULATION ON THE SURFACE OF A DIALYSIS MEMBRANE USING A DIALYSATE CONTAINING 800 PPM OF NITRIC OXIDE

Abstract Background and Aims Activation of platelets and leukocytes when blood comes in contact with a dialysis membrane surface leads to increased oxidative stress and release of proinflammatory cytokines, which may result in complications in dialysis patients. Within the blood vessels, nitric oxide (NO) generated by nitric oxide synthase on the endothelial cells suppresses both aggregation/activation of platelets and migration/adhesion of leukocytes. We previously showed in a rat hemodialysis model that NO (800 ppm) gas added to the dialysate can suppress blood coagulation on the surface of a dialysis membrane. The aim of the present study was to determine, using a rat hemodialysis model, the appropriate concentration of NO that would most effectively prevent blood coagulation without causing any adverse effects. Method Male Sprague Dawley rats weighing 300 to 400 g were used for the experiments. After the rats were anesthetized (isoflurane, 1.5%-3.0%), extracorporeal circulation was established by removal of blood from the carotid artery and returning it to the tail vein. During the experiment, the blood flow rate was kept at 1.0 mL/min, and the dialysate flow rate at 3 mL/min. Heparin was administered by bolus injection (0.7 unit/g-mouse) at the start of the hemodialysis, and no further heparin was added during the 4-hour hemodialysis session. A cellulose triacetate membrane and polymethylpentene membrane were used for making the small dialyzer and gas exchanger, respectively (the prototype module was manufactured by NIPRO, Co., Japan). NO (200 ppm, 400 ppm, or 800 ppm) was added to the dialysate via the gas exchanger in the NO groups, and N2 gas was added to the dialysate in the control group. During the experiment, the arterial pressure, dialyzer inlet pressure, venous pressure, activated whole blood clotting time (ACT) and methemoglobin (met-Hb) concentration were measured. After circulation, the amount of coagulated blood was measured by the hemoglobin (Hb) content and lactate dehydrogenase (LDH) activity in the eluate from the residual blood clotting in the dialyzer. Results The 4-hour hemodialysis session achievement rate was highest in the NO-800 ppm group (control, 54%; NO-200 ppm, 66%; NO-400 ppm, 77%; NO-800 ppm, 85%). The blood met-Hb content was below 10% in all the NO groups. The Hb content and LDH activity in the eluate were significantly lower in the NO groups than in the control group. These results indicate that addition of higher concentrations of NO was associated with a lower likelihood of coagulation on the dialyzer and in the dialysis circuit and a higher likelihood of smooth and successful 4-hour dialysis sessions. Addition of NO was associated with little risk of adverse effects such as met-Hb accumulation and reduction of blood pressure. Therefore, 800 ppm is considered as the most appropriate concentration of NO to be added to the dialysate for effectively inhibiting blood coagulation without causing any adverse effects. Conclusion Our experiment in a rat hemodialysis model showed that 800 ppm was the most appropriate concentration of NO to be added to the dialysate to suppress blood coagulation on the surface of the dialysis membrane without causing any adverse effects.

Amyloid Formation of α-Synuclein Based on the Solubility- and Supersaturation-Dependent Mechanism.

Amyloid fibrils are formed by denatured proteins when the supersaturation of denatured proteins is broken by agitation, such as ultrasonication, or by seeding, although the detailed mechanism of how solubility and supersaturation regulate amyloid formation remains unclear. To further understand the mechanism of amyloid formation, we examined α-synuclein (α-syn) amyloid formation at varying concentrations of SDS, LPA, heparin, or NaCl at pH 7.5. Amyloid fibrils were formed below or around the critical micelle concentrations (CMCs) of SDS (2.75 mM) and LPA (0.24 mM), although no fibrils were formed above the CMCs. On the other hand, amyloid fibrils were formed with 0.01-2.5 mg/mL of heparin and 0.5-1.0 M NaCl, and amyloid formation was gradually suppressed at higher concentrations of heparin and NaCl. To reproduce these concentration-dependent effects of additives, we constructed two models: (i) the ligand-binding-dependent solubility-modulation model and (ii) the cosolute-dependent direct solubility-modulation model, both of which were used by Tanford and colleagues to analyze the additive-dependent conformational transitions of proteins. The solubility of α-syn was assumed to vary depending on the concentration of additives either by the decreased solubility of the additive-α-syn complex (model i) or by the direct regulation of α-syn solubility (model ii). Both models well reproduced additive-dependent bell-shaped profiles of acceleration and inhibition observed for SDS and LPA. As for heparin and NaCl, participation of amorphous aggregates at high concentrations of additives was suggested. The models confirmed that solubility and supersaturation play major roles in driving amyloid formation in vitro, furthering our understanding of the pathogenesis of amyloidosis in vivo.