Molecular Modeling of High-performance Polymers

High-performance polymers are extensively used in the aerospace and aeronautics industries due to their low density, high specific strength, and high specific stiffness. These properties along with better infiltration with reinforcements [carbon nanotubes (CNTs), glass, etc.] capability make them an excellent candidate to fabricate Polymer Matrix Composites (PMCs) tailored for specific applications. The applications range from products used daily to deep space exploration. These materials are subjected to varying temperatures and pressures during fabrication and in service. Therefore, the evolution of their intrinsic properties needs to be studied and their ability to sustain extreme environmental conditions in outer space needs to be investigated. Utilizing experimental techniques for this purpose is time-consuming and expensive. Predictive computational tools like molecular dynamics (MD) can be used for such studies as they are quick and inexpensive relative to experiments. Furthermore, it reduces the overall time in designing and deploying the next generation of composite materials. In this work, MD is implemented to model self-assembled stacks of flattened CNTs (flCNTs) and polyimide composites to investigate the interfacial properties at the interface between flCNT and polyimides. Fluorinated and non-fluorinated polyimides are compared based on interaction energy, friction force, and transverse strength. The reactive interface force field (IFF-R) is validated to predict thermo-mechanical properties of epoxies for varying degrees of cure. These nanoscale properties provide a set of inputs for microscale analysis to predict the evolution of residual stresses for the process modeling of composites. In order to use nanoscale mechanical properties as inputs, they need to be corrected for the strain-rate discrepancy associated with several orders of magnitude difference between experimental and simulated strain rates. A phenomenological approach to account for this strain-rate difference is developed based on experimental characterization data. Once the MD properties are corrected, they can be used in microscale analysis to accurately predict residual stresses

The interpretative options of anaphoric complex demonstratives

In this paper, we present experimental evidence from a ‘yes’/‘no’ judgement task and two acceptability rating studies (Experiments 1a-c) for the claim made in Hinterwimmer (2019) that sentences with two anaphorically interpreted complex demonstratives are less acceptable than sentences with two anaphorically interpreted definite descriptions and sentences where one of the two previously introduced referents is picked up by a complex demonstrative, while the other one is picked up by a definite description. The results of Experiment 1a and 1b are in principle compatible with the account argued for in Hinterwimmer (2019), according to which the (potentially abstract) demonstrations presupposed by demonstratives may not have overlapping trajectories. However, sentences with two anaphorically interpreted complex demonstratives are not judged as unacceptable as would be expected if they involved a presupposition violation. Therefore, we propose an alternative, economy-based pragmatic account that builds on Ahn (2019) and Nowak (2019). The question of whether the observed pattern is more compatible with the account proposed by Hinterwimmer (2019) or the alternative pragmatic account is directly addressed in a further acceptability rating study (Experiment 1c). The design of that study is similar to that of Experiment 1b, but it includes as fillers both sentences clearly violating a presupposition and sentences violating a pragmatic constraint. Since the ratings for sentences containing two anaphorically interpreted complex demonstratives are closer to the ratings for sentences violating a pragmatic constraint than for sentences violating a presupposition, we conclude that the alternative pragmatic account is preferable to the account by Hinterwimmer (2019)

The effects of acute aerobic exercise on choice reaction time in young adults

Background:Exercise, especially aerobic exercise thought to have a positive impact on cognitive and brain function which mainly involved in acquisition, processing, storage and executive functions. Executive control processes are important in sport and occupational settings where a person is being asked to make decisions while performing physical work. We have done this study, to determine the effects of acute moderate intensity exercise on cognitive domains and to apply this knowledge in various fields where cognition and executive functions are important. Study and control population each consists of 60 apparently healthy subjects in the age group of 18-30 years.Methods:The material used for study Cosco Upright Exercise Bike and Reaction Time apparatus. Visual Choice Reaction Time, the examiner presented visual stimuli at random to the subject. The subject saw the light displayed on his side and pressed the appropriate corresponding button as quickly as possible and the reading was noted. The same procedure was repeated for auditory choice reaction time for auditory stimuli. After that each subject from study population underwent acute moderate intensity aerobic exercise on for 10 minutes. Starting within 5 minutes after the exercise, subjects were assessed for the same cognitive test as above, for the second time. Control population rested for 10 minutes and then was assessed again for the same cognitive test.Results:There was no significant difference between the pre- values of study population and pre- values of control population. There was no significant difference between the pre- values of control population and post values of control population. Thus, there was no improvement in cognitive functions on account of repetition of tests. There was a significant difference between the post values of study population and post values of control population. There was a significant difference between the pre- values of study population and post values of study population.Conclusions:There was a decrease in reaction time following exercise in the study population, suggests that there was an improvement in the cognitive functions post exercise

Structural Evolution In Mechanically Alloyed Fe-based Powder Systems

A systematic study of iron-based binary and multi-component alloys was undertaken to study the structural evolution in these powders as a function of milling time during mechanical alloying. Blended elemental powders of Fe100-XBX (where x = 5, 10, 17, 20, 22, 25, 37.5 and 50 at. %) and a bulk metallic glass (BMG) composition (Fe60Co8Zr10Mo5W2B15) were subjected to mechanical alloying in a SPEX 8000 mixer mill. X-ray diffraction technique was employed to study the phase evolution, crystallite size, lattice strain and also to determine the crystal structure(s) of the phases. Depending on the milling time, formation of supersaturated solid solutions, intermetallics, and amorphous phases was noted in the binary Fe-B powder mixtures. A maximum of about 22 at. % B was found to dissolve in Fe in the solid state, and formation of FeB and Fe2B intermetallics was noted in some of the powder blends. However, an interesting observation that was made, for the first time, related to the formation of a crystalline phase on continued milling of the amorphous powder in the BMG composition. This phenomenon, termed mechanical crystallization, has been explored. Reasons for the mechanical crystallization of the amorphous powder using the X-ray diffraction and electron microscopy methods have been discussed. External heat treatments of the milled powder were also conducted to study the complete crystallization behavior of the amorphous phase. Preliminary attempts were made to consolidate the milled BMG powder to bulk shape by hot isostatic pressing (HIP) and magnetic compaction techniques. Full densification was not achieved. Nanoindentation and microhardness tests were performed to characterize the mechanical properties of the glassy alloy. Nanoindentation results gave an elastic modulus of 59 GPa, lower than the expected value of 184 GPa; due to the presence of porosity in the consolidated sample. Optimization of the consolidation parameters is required to achieve a fully dense material

Demonstrative Pronouns as Anti-Logophoric Pronouns: An Experimental Investigation

In this paper we report the results of two experimental studies in which we tested the claim of Hinterwimmer and Bosch (2017) that German demonstrative pronouns are anti-logophoric pronouns: They avoid discourse referents as antecedents that function as perspectival centers. In both experiments we tested the interpretative options of demonstrative pronouns in text segments which were either perspectivally neutral or in which the narrator’s or a topical protagonist’s perspective was foregrounded. Taken together, the experimental results are most compatible with a slightly modified version of the analysis argued for in Hinterwimmer and Bosch (2017) according to which topical discourse referents in neutral narration automatically become perspectival centers.&nbsp

A novel fluorescent "turn-on" chemosensor for nanomolar detection of Fe(III) from aqueous solution and its application in living cells imaging

An electronically active and spectral sensitive fluorescent “turn-on” chemosensor (BTP-1) based on the benzo-thiazolo-pyrimidine unit was designed and synthesized for the highly selective and sensitive detection of Fe³⁺ from aqueous medium. With Fe³⁺, the sensor BTP-1 showed a remarkable fluorescence enhancement at 554 nm (λex=314 nm) due to the inhibition of photo-induced electron transfer. The sensor formed a host-guest complex in 1:1 stoichiometry with the detection limit down to 0.74 nM. Further, the sensor was successfully utilized for the qualitative and quantitative intracellular detection of Fe³⁺ in two liver cell lines i.e., HepG2 cells (human hepatocellular liver carcinoma cell line) and HL-7701 cells (human normal liver cell line) by a confocal imaging technique

The amidine based colorimetric sensor for Fe³⁺, Fe²⁺, and Cu²⁺ in aqueous medium

An amidine based chemosensor AM-1 was synthesized and characterized by various spectroscopic (FT-IR, 1H-NMR and mass) data and elemental analyses. Sensor AM-1 exhibited high selectivity and sensitivity towards Fe³⁺, Fe²⁺ and Cu²⁺ in the presence of other surveyed ions (such as Sr²⁺, Cr³⁺, Co²⁺, Ni²⁺, Zn²⁺, Ag⁺, Al³⁺, Ba²⁺, Ca²⁺, Cd²⁺, Cs⁺, Hg²⁺, K⁺, Li⁺, Mg²⁺, Mn²⁺, Na⁺ and Pb²⁺) with a distinct naked-eye detectable color change and a shift in the absorption band. Moreover, the emission of AM-1 was quenched selectively only in the presence of Fe³⁺

EXPERIMENTAL EVALUATION OF MOORVA AS A NON ABSORBABLE MONO FILAMENT SUTURE

Suturing material plays a very important role in surgical procedures. The purpose of suturing (Seevankarma as called in the Ayurvedic terminology) is to approximate the wound edge for faster healing. This study was an attempt to assess Moorva mono filament fiber for the suturing purpose. An attempt to compare it with ethilon3-0 as non-absorbable suture in rats was done. Fully grown Moorva leaves were taken. Its fibers were separated under running water and subjected to autoclave. Moorva fiber tensile strength and thickness was measure before and after autoclave. Ethilon 3-0 tensile strength and thickness was measured. Rats were Anesthetized intramuscularly using 1ml syringe, after that suturing was done on prepared area. Redness, Discharge, Temperature, Approximation, Odema were observed for eight days and biopsy was taken on day eight. Temperature was measured on infrared thermometer. 12 rats were used for this study Trial group and control group skin closures were done on the same rat on different sites. Both the groups shows equivalent results for Redness, Odema, Discharge, Approximation, Temperature. Histopathological changes for inflammatory infiltrate, vascularity, fibrosis were same in both the groups. Moorva fibers tensile strength and thickness was less than ethilon 3-0 and this tensile strength and thickness was sufficient to hold the wound edges. The study proves that the Moorva fiber can be made and acceptable suturing material and it can be used for skin closures. Scope for further study Along term study on tissue absorbability property of Moorva fiber suturing material and detail chemical study of Moorva fiber

Virgin coconut oil prepared by protease-assisted process : Characteristics and application

Doctor of Philosophy (Food Science and Technology), 2018Coconut milk and meat at three different maturity stages including immature coconut (IMC), mature coconut (MC) and overlay mature coconut (OMC) had varying proximate compositions. Compositions of coconut milk generally were in accordance with those found in coconut meat. Cocosin with molecular weight of 55 kDa was observed as the major protein in all coconut milks but its band intensity slightly decreased with increasing maturity stages. Oil droplet size increased as maturity stages increased. Nevertheless, virgin coconut oil (VCO) extracted from coconut with three different maturity stages had no impact on fatty acid composition and physicochemical properties. VCO separated using Alcalase showed the highest recovery (95.64%) when coconut milk from OMC was used as starting material. All VCO samples had waterlike appearance and contained medium chain fatty acid (MCFA), especially lauric acid as a major fatty acid, (49.74-51.18 g/100g). Myristic acid in the range of 18.70-19.84 g/100g was present in all VCO. All VCO samples had low lipid hydrolysis and oxidation, indicating that maturity stages had no influence on oil stability. Albumin and globulin were the predominant protein fractions in defatted coconut meat. Both fractions showed the differences in protein patterns and amino acid compositions. Varying emulsifying property was obtained between both fractions. Albumin, water-soluble protein fraction, exhibited lower emulsifying properties, compared to globulin (salt-soluble) counterpart. However, globulin fraction was more susceptible to hydrolysis by Alcalase, leading to the higher collapse of emulsion of coconut milk after being hydrolyzed. This contributed to the higher oil recovery from coconut milk. Difference was observed in degree of hydrolysis (DH), oil recovery, microstructure and protein pattern of coconut milk hydrolyzed by partially purified protease from seabass pyloric caeca (PPSP) and commercial trypsin (CT) at different proteolytic levels (5 and 10 units/g protein) at 60 °C for various hydrolysis times (0-150 min). The highest VCO yield (77.35%) was found when sample was hydrolyzed by PPSP (10 units/g protein) for 150 min. Based on DH and electrophoretic study, proteins in coconut milk were more prone to hydrolysis by PPSP, compared to CT. Therefore, PPSP could be used as an alternative processing aid and the efficiency was higher than CT. PPSP was further used in combination with different treatments including microfluidization, chill-thawing and freeze-thawing for extraction of VCO. Coconut milk hydrolyzed by PPSP at 10 units/g protein, followed by freeze-thawing showed the highest yield among other samples (p<0.05). Conversely, the lowest VCO yield was attained for coconut milk homogenized at 4000 psi, followed by hydrolysis using PPSP (5 units/ g protein). Hydrolysis by PPSP, followed by freeze-thawing of 5 cycle rendered the highest yield of VCO (98.6%). However, no marked difference was observed in fatty acid profile, moisture content, free fatty acid content (FFA) and oxidative stability among all VCO extracted from aforementioned methods. Because of high stability and various health benefits, VCO in combination with fish oil (FO) rich in n-3 fatty acids at different ratios (95:5, 90:10, 85:15, v/v) was used to prepare a functional mayonnaise. Chemical and physical changes were monitored during the storage of 30 days at room temperature (30-32 °C) in comparison with those of mayonnaise prepared using soybean oil (SO). Addition of FO up to 10% in VCO/FO blend could yield the mayonnaise with sensorial acceptability. Oxidative stability varied with mayonnaises containing different oils. Mayonnaise sample with VCO was less prone to lipid oxidation throughout storage of 30 days. Types of oil used for preparation of mayonnaise and storage time affected the color, textural and rheological properties of resulting mayonnaise. In general, mayonnaise containing VCO/FO (90:10) blend showed the property equivalent to that prepared using SO. Thus, VCO could be incorporated in combination with FO at appropriate level to prepare a functional mayonnaise with acceptability and oxidative stability. Therefore, VCO could be successfully produced with the aid of fish trypsin in conjunction with repeated freeze-thawing cycles. The resulting VCO could be employed as food ingredient or other applications