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Today's terminal operators are facing several challenges related to the profitability of their bulk terminal, petrochemical and oil field storage sites. First, they are under pressure to increase margins by [...]

Present study investigates the stiffening effect on the behavior of tubular T-joints in offshore platform jacket structures subjected to axial compression. Stiffening is crucial to enhance the structures' strength and lifetime. Tubular cross section structures are preferred due to their mechanical properties and cost-efficiency. The study introduces an innovative technique by adding stiffeners at the interface between braces and chords to effectively distribute loads from multiple directions. The T-joint specimen used has specific dimensions: Chord length 400 mm, brace length 200 mm, chord diameter 100 mm, brace diameter 50 mm, chord thickness 4 mm, and brace thickness 3 mm. Experimental tests and Numerical simulations were conducted to measure failure loads for both stiffened and unstiffened T-joints. Stiffened configurations (4, 6, and 8 strips) has a notable impact on the ultimate capacity of the T-joint, showcasing an increase in strength compared to the unstiffened joint. Stiffened joints showed a significant increase in ultimate strength compared to unstiffened joints, with improvements ranging from 67.18 to 73.33% for different stiffener configurations. Joint local stiffness also improved substantially, with percentage increases ranging from 67.03 to 140.80% for various stiffener configurations. Present research work demonstrates the positive impact of stiffeners on tubular T-joints, improving their strength and stiffness while showing strong agreement between numerical simulations and experimental results and the study also concludes that the addition of stiffeners effectively enhances the ultimate capacity and local stiffness of tubular T-joints. These findings emphasize the effectiveness of the proposed reinforcement strategies for optimizing tubular T-joints in offshore structures.

ABSTRACTThe application of artificial neural network (ANN) to predict the wear rate of the surface composites produced using a solid-state technique called friction stir processing (FSP) is presented in this work. The copper surface composites were prepared by incorporating different sort of ceramic particles such as SiC, TiC, Al2O3, WC and B4C. The design of experiments (DOE) strategy was utilised to direct the experimental work. The considered operating parameters were sort of ceramic particle, traverse speed, tool rotational speed and groove width, whereas wear rate is the response. An approximation mechanism having an arbitrary function, the ANN was consequently used for simulating the wear rate of the surface composites. The feedforward back propagation technique was employed to alter the weights of the network to minimise the mean squared error for the development of ANN models. The predicted trends were explained and studied the influence of the considered factors with the aid of observed micro structures. The lower wear rate was observed with B4C-reinforced surface composites.

ABSTRACT Contemporary TQM models seem to be oriented towards tools/practitioner's perception/ international standards with an objective of achieving materialistic results. However, the moral and ethical means of reaching the goals [...]

ABSTRACT Adoption of total quality management (TQM) is an essential element for the success of business. In spite of many industries implementing TQM, quite a few organizations have eventually lost [...]

Wire arc additive manufacturing is a promising reliable free-form fabrication technique suitable for producing large-scale components that feature a very low buy-to-fly ratio. This research work is aimed to fabricate a rectangular prototype Inconel-625 alloy slab using a robotic metal inert gas welding system. The microstructure and mechanical properties of as-deposited and solution-annealed (SA) alloys were investigated. It was found that the as-deposited alloy exhibited a columnar dendritic structure and the presence of intermetallic phases such as the Laves phase, NbC and carbides were observed in the gamma-nickel matrix. In SA deposit, the intermetallic phases were dissolved in the NiCr-matrix and the secondary carbides M23C6, M6C were also observed in the microstructure. It was found that the ultimate tensile strength and microhardness of the as-deposited alloy were higher than that of SA deposit.

Monoamine oxidase B (MAO-B) is a potential biomarker for Parkinson’s disease (PD), a neurodegenerative disease associated with the loss of motor activities in human subjects. The disease state is associated with dopamine deprival, and so the inhibitors of MAO-B can serve as therapeutic drugs for PD. Since the expression level of MAO-B directly correlates to the disease progress, the distribution and population of this enzyme can be employed to monitor disease development. One of the approaches available for estimating the population is two-photon imaging. The ligands used for two-photon imaging should have high binding affinity and binding specificity toward MAO-B along with significant two-photon absorption cross sections when they are bound to the target. In this article, we study using a multiscale modeling approach, the binding affinity and spectroscopic properties (one- and two-photon absorption) of three (Flu1, Flu2, Flu3) of the currently available probes for monitoring the MAO-B level. We report that the binding affinity of the probes can be explained using the molecular size and binding cavity volume. The experimentally determined one-photon absorption spectrum is well reproduced by the employed QM/MM approaches, and the most accurate spectral shifts, on passing from one probe to another, are obtained at the coupled-cluster (CC2) level of theory. An important conclusion from this study is also the demonstration that intrinsic molecular two-photon absorption strengths (δ2PA) increase in the order δ2PA(Flu1) > δ2PA(Flu2) > δ2PA(Flu3). This is in contrast with experimental data, which predict similar values of two-photon absorption cross sections for Flu1 and Flu3. We demontrate, based on the results of electronic-structure calculations for Flu1 that this discrepancy cannot be explained by an explicit account for neighboring residues (which could lead to charge transfer between a probe and neighboring aromatic amino acids thus boosting δ2PA). In summary, we show that the employed multiscale approach not only can optimize two-photon absorption properties and verify binding affinity, but it can also help in detailed analyses of experimental data.

In this investigation, Friction stir welding (FSW) was performed to join 3 mm-thick AISI 321 stainless steel sheets. The rectangular sheets of size 100 mm × 50 mm were butt joined to contemplate the impact of tool rotational speeds for the steady welding traverse speed of 55 mm/min, axial force of 13 kN and tool tilt angle of 1.5°. The present assessment aims to correlate the relationship between the weld joint properties and important FSW parameter, the tool rotational speed. Microstructural investigation on the FS welded joints was performed using optical microscope and scanning electron microscopy (SEM). Transverse tensile test was undertaken to ascertain the quality and strength of the welded joints such as yield strength, ultimate tensile strength, etc. The microstructural features reveal evolution of fine equiaxed austenite grain structures in the weld stir zone dominated by discontinuous dynamic recrystallization mechanism. The weld joints fabricated at 500 rpm and 700 rpm had significantly better strength about 88% and 93% compared to the base metal. Subsequently, the hardness of the weld stir zones was significantly greater than the hardness of the base metal. All the welds fractured at a distance to that of the weld stir zone and dimple structures were observed at the fracture locations.

Ambidextrous supergelators are developed through structure-gelation screening of rationally designed cyclic dipeptides (CDPs). The organo- and hydrogels of CDPs were thoroughly characterized by their minimal gelation concentration (MGC) for organic and aqueous solvents, thermal stability (Tg), and viscoelastic properties. Intermolecular hydrogen bonding, the major driving force for gelation was evaluated using temperature-dependent nuclear magnetic resonance (NMR) spectroscopy. The contribution of attractive van der Waals interaction of tBoc group in driving CDP gelation was ascertained using β-cyclodextrin (β-CD)-adamantane carboxylic acid (AC)-based host–guest gelation and 1H NMR studies. The self-assembled fibrous network of CDPs in organic and aqueous solvents responsible for the molecular gelation was elucidated using field emission scanning electron microscopy (FESEM) analysis. Among the CDPs studied CDP-2 found to be supergelator with MGC of 0.3 wt % and form in situ hydrogels under simulated physiological conditions. The in situ gelation property was evaluated by the incorporation of curcumin, as a model study to demonstrate the drug delivery application. Furthermore, supergelator CDP-2 was found to exhibit in cellulo cytocompatibility. Moreover, density functional theory (DFT) calculations were carried out to propose the microscopic structure for the self-assembly of CDP compounds and intermolecular N–H···O hydrogen bonding interactions appear to stabilize the fibrous network. The hydrophobic interactions among the tert-butyloxycarbonyl (tBoc) groups and π–π stacking interactions between phenyl rings contribute to the further stabilization of self-assembled 2D fibrous networks of CDPs. Overall, the present study highlights the in situ gelation property of CDP-based supergelators and their potential for biomedical and regenerative medicine applications.

Sirtuins are a family of nicotinamide adenine dinucleotide (NAD+)-dependent enzymes, which undergo robust deacetylase activity, resulting in the production of nicotinamide. It is well known that nicotinamide, which is one of the products, can also act as an inhibitor for further deacetylation process by forming NAD+again. Hence, the removal of nicotinamide from sirtuins is a demanding process, and the mechanistic understanding of the process remains elusive. In this investigation, we have made an attempt to unravel the unbinding pathways of nicotinamide from SIRT1, SIRT2, and SIRT3 (SIRT1–3) using Random Acceleration Molecular Dynamics (RAMD) Simulations, and we have successfully identified various unbinding channels. The selectivity of the egression channel is determined by using a thorough analysis of the frequency of egression trajectories. Similarly, various inhibitors have been docked with the active sites of SIRT1–3, and their egression pathways have been investigated to understand whether they follow the same egression pathway as that of nicotinamide. The residues that are responsible for the unbinding pathways have been determined from the analysis of RAMD trajectories. From these results, it is clear that phenylalanine and histidine residues play major roles in the egression of inhibitors. Additionally, the key residues Leu, Pro, Met, Phe, Tyr, and Ile are found to control the release by acting as gateway residues. The role of these residues from different egression channels has been studied by carrying out mutations with alanine residue. This is the first report on sirtuins, which demonstrates the novel unbinding pathways for nicotinamide/inhibitors. This work provides new insights for developing more promising SIRT1–3 inhibitors.

6-mm-thick pure copper and dual-phase brass plates were joined using friction stir welding (FSW). The role of plate location prior to welding and the tool rotational speed on the microstructure evolution was evaluated and correlated to the tensile properties of the joint. All the joints with copper on advancing side produced defects. Typical zones commonly found in FSW joints were observed. TMAZ was not found on the copper side, and no coarsening of grains was noticed in the HAZ on the brass side. The microstructure of the weld zone was heterogeneous and grouped into three categories. The plate position and the tool rotational speed influenced the material flow and the formation of different structures. The weld zone was further characterized by ultra-fine grains, dislocations and annealing twins. The hardness across the weld zone was varying considerably. The process parameter had an opposite effect on the hardness of brass and copper portion of the weld zone. The joints with brass on advancing side showed higher tensile strength. The fracture location and surfaces were further reported.

This work is focused on developing AA2124/4wt.%B4C nano-composite coatings on Ti−6Al−4V using friction surfacing to improve the wear resistance. The composite was produced using conventional stir casting method and coatings were laid using an indigenously-developed friction surfacing machine. The rotational speed of the mechtrode was varied. The microstructure of the composite coating was observed using conventional and advanced microscopic techniques. The sliding wear behavior was evaluated using a pin-on-disc apparatus. The coating geometry (thickness and width) increased with increased rotational speed. The interface was straight without thick intermetallic layer. Homogenous distribution of nano B4C particles and extremely fine grains was observed in the composite coating. The interfacial bonding between the aluminum matrix and B4C particles was excellent. The composite coating improved the wear resistance of the titanium alloy substrate due to the reduction in effective contact area, lower coefficient of friction and excellent interfacial bonding.

To address drug resistance to HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs), a series of novel diarylpyrimidine (DAPY) derivatives targeting “tolerant region I” and “tolerant region II” of the NNRTIs binding pocket (NNIBP) were designed utilizing a structure-guided scaffold-hopping strategy. The dihydrofuro[3,4-d]pyrimidine derivatives 13c2and 13c4proved to be exceptionally potent against a wide range of HIV-1 strains carrying single NNRTI-resistant mutations (EC50= 0.9–8.4 nM), which were remarkably superior to that of etravirine (ETV). Meanwhile, both compounds exhibited comparable activities with ETV toward the virus with double mutations F227L+V106A and K103N+Y181C. Furthermore, the most active compound 13c2showed favorable pharmacokinetic properties with an oral bioavailability of 30.96% and a half-life of 11.1 h, which suggested that 13c2is worth further investigation as a novel NNRTI to circumvent drug resistance.

Friction stir welding (FSW) was applied for the joining of 3-mm-thick AISI 316L stainless steel sheets. The investigation was aimed to explore the relationship between weld joint characteristics and one of the very important primary FSW parameters, the welding speed. The soundness of the fabricated joints was tested by x-ray radiography technique initially. The microstructural studies of the joints were carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD). Discontinuous dynamic recrystallization was the suggestive dominant recrystallization mechanism in the weld stir zone (SZ). The presence of fine equiaxed austenite grain boundaries and the consequent increase in hardness at the weld SZ resulted in joint strength superior to that of the base steel at higher welding speeds. But, at lower welding speeds, the evolution of delta ferrite decreased the toughness and strength of the joints owing to higher heat generation (higher peak temperature). However, the delta ferrite formed in the weld SZ has not transformed into sigma phase, probably due to fast cooling of the weld zone.

Understanding the mechanism of fibrillization of amyloid forming peptides could be useful for the development of therapeutics for Alzheimer’s disease (AD). Taking this standpoint, we have explored in this work the free energy profile for the interconversion of monomeric and dimeric forms of amyloid forming peptides into different secondary structures namely beta-sheet, helix, and random coil in aqueous solution using umbrella sampling simulations and density functional theory calculations. We show that the helical structures of amyloid peptides can form β sheet rich aggregates through random coil conformations in aqueous condition. Recent experiments (Chem. Eur. J.2018, 24, 3397–3402 and ACS Appl. Mater. Interfaces2017, 9, 21116–21123) show that molybdenum disulfide nanosurface and nanoparticles can reduce the fibrillization process of amyloid beta peptides. We have unravelled the free energy profile for the interconversion of helical forms of amyloid forming peptides into beta-sheet and random coil in the presence of a two-dimensional nanosurface of MoS2. Results indicate that the monomer and dimeric forms of the peptides adopt the random coil conformation in the presence of MoS2while the helical form is preferable for the monomeric form and that the beta-sheet and helix forms are the preferable forms for dimers in aqueous solution. This is due to strong interaction with MoS2and intramolecular hydrogen bonds of random coil conformation. The stabilization of random coil conformation does not lead to a β sheet like secondary structure for the aggregate. Thus, the confinement of MoS2promotes deaggregation of amyloid beta peptides rather than aggregation, something that could be useful for the development of therapeutics for AD.

The widespread interest in phase recognition of lipid membranes has led to the use of different optical techniques to enable differentiation of healthy and not fully functional cells. In this work, we show how the combination of different (non)linear optical methods such as one-photon absorption (OPA), two-photon absorption (TPA), and second harmonic generation (SHG) as well as the study of the fluorescence decay time leads to an enhanced screening of membrane phases using a fluorescent 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine (DiD) probe. In the current study we consider the pure liquid disordered phases of DOPC (dioleoyl-sn-glycero-3-phosphocholine, room temperature) and DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 323 K), the solid gel phase of DPPC (298 K), and the liquid ordered phase of a 2:1 binary mixture of sphingomyelin and cholesterol. By means of extensive hybrid quantum mechanics–molecular mechanics calculations and based upon the (non)linear absorption of the embedded probes, it is found that DiD can be used to identify the lipid bilayer phase. The joint TPA and SHG as well as fluorescence analyses qualifies DiD as a versatile probe for phase recognition. In particular, the SHG data obtained by means of hyper-Rayleigh scattering and by electric field induced second harmonic generation reveal differences in polarization of the probe in the different environments. The TPA results finally confirm the particular location of the probe in between the polar headgroup region of the 2:1 SM:Chol mixture in the liquid ordered phase.

The social network, by the name which has popularised in today's world and growing rapidly at all times and controlling over mankind. The social networks like Twitter, Facebook, and LinkedIn, etc., have become a regular and daily usage of many people. It becomes a good mediator for the people who would like to share some posts, are some of their own videos, or some messages. But there has been major issues that the particular user of the social networks like Twitter and Facebook have the problem of indiscipline actions which we call as spam, by the third person who is knowingly doing this to spoil their intention and good opinion upon each other. Also, these spams help to steal information about the people who using social networks. In this paper, we study and analyse about the spam in social networks and machine learning algorithms to detect such kind of spams. This paper also focuses on the ML algorithms detection rate and false positive rate over different datasets.

Friction stir welding (FSW) is one of the new technique for welding materials in solid state welding process. In this proposed work we are using FSW to join the two dissimilar alloys of aluminium. The 6mm thick aluminum plates of aluminium 5086 and aluminum 7075 plates are considered for welding. These have been considered due to their application in various fields. In this experimental process Taguchi’s L9 orthogonal array method is used for optimizing the three process parameters namely rotational speed, axial force and welding speed. To produce a better joint the tensile strength is predicted for the optimum welding parameters and also their percentage of contribution is calculated, by applying the effect of analysis of variance. Depends upon the experimental study, the rotational speed is found better over the other process parameters, which enhances the quality of the weld. The tensile strength has been found for the optimum parameters and the result found during the experiment was 290Mpa which was higher than the base metal strength of aluminium 5086 alloy. The SEM fractograph analysis was done on the optimum parameters welded joints to show the fracture behaviour of tensile test which justifies the visual inspection results of brittle and ductile failures.

The fluorescent marker Laurdan and its new derivative, C-Laurdan, have been investigated by means of theoretical calculations in a DOPC lipid bilayer membrane at room temperature, and a comparison is made with results from fluorescence experiments. Experimentally, the latter probe is known to have a higher sensitivity to the membrane polarity at the lipid headgroup region and has higher water solubility. Results from Molecular Dynamics (MD) simulations show that C-Laurdan is oriented with the carboxyl group toward the head of the membrane, with an angle of 50° between the molecular backbone and the normal to the bilayer, in contrast to the orientation of the Laurdan headgroup whose carbonyl group is oriented toward the polar regions of the membrane and which describes an angle of ca. 70–80° with the membrane normal. This contrast in orientation reflects the differences in transition dipole moment between the two probes and, in turn, the optical properties. QM/MM results of the probes show little differences for one- (OPA) and two-photon absorption (TPA) spectra, while the second harmonic generation (SHG) beta component is twice as large in Laurdan with respect to C-Laurdan probe. The fluorescence anisotropy decay analysis of the first excited state confirms that Laurdan has more rotational freedom in the DOPC membrane, while C-Laurdan experiences a higher hindrance, making it a better probe for lipid membrane phase recognition.

Friction stir back extrusion (FSBE) is emerging as a novel method to produce high strength fine grained metallic tubes. The objective of the present work is to produce aluminum seamless tubes from solid cylindrical bars using FSBE and to report the microstructure and mechanical characterization. A die, tool and fixture were designed to carry out FSBE. A conventional friction stir welding machine was utilized for FSBE. A cylindrical bar of aluminum alloy AA6061-T6 was kept inside the hole in the die and extruded by plunging the rotating tool. The microstructure of the produced tube was studied using optical microscopy. The microstructure was found to be homogeneous along the tube. The microhardness and compressive strength of the tube have been presented in this paper. The results indicated that the FSBE process was capable of producing sound aluminum seamless tubes.

The design of novel fibril imaging molecules for medical diagnosis requires the simultaneous optimization of fibril-specific optical properties and binding specificity toward amyloid fibrils. Because of the possibility to monitor internal organs and deep tissues, the two-photon probes that can absorb in the infrared (IR) and near-IR (NIR) region with a significant two-photon absorption cross section are of immense interest. To contribute to this exploration of chemical compounds suitable for two-photon fibril imaging, we have computationally studied the one- and two-photon properties of a donor–acceptor-substituted DANIR-2c probe, which was used for in vivo detection of β-amyloid deposits using fluorescence spectroscopy. In particular, a multiscale computational approach was employed involving molecular docking, molecular dynamics, hybrid QM/MM molecular dynamics, and coupled-cluster/MM to study the binding of the studied probe to amyloid fibril and its one- and two-photon absorption properties in the fibrillar environment. Multiple binding sites are available for this probe in amyloid fibril, and the one corresponding to the largest binding affinity exhibits also the largest and experimentally meaningful two-photon absorption cross section, thus demonstrating the potential of the studied probe in two-photon microscopy.

Friction stir welding provides an alternative method of joining aluminum in a reliable way. Anticipation of the joint efficiency is then a necessary step to optimize the process of the welding operation. In the light of this, artificial neural network (ANN) technique may then be applied as a reliable method for simulating and predicting the durability of the joints for different process parameters. In the present work, an ANN model is presented that predicts the ultimate tensile strength of friction stir-welded dissimilar aluminum alloy joints. Four parameters were considered including tool pin profile (straight square, tapered square, straight hexagon, straight octagon and tapered octagon), rotational speed, welding speed and axial force. Experimental tests were conducted according to a four-parameter five level central composite design. A feed-forward back propagation ANN with a single hidden layer comprising 20 neurons was employed to simulate the ultimate tensile strength (UTS) of the joints. The neural network was trained using the data obtained from the experimental work. A comparison between the experimental and simulated data showed that the ANN model reliably predicted the UTS of dissimilar aluminum alloy friction stir-welded joints. The models developed were capable of predicting values with less than 5 % error. Furthermore, the effect of different process parameters on the tensile behavior of dissimilar joints was also investigated and reported upon.

The extraordinary ligand binding properties of albumin makes it a key player in the pharmacokinetics and pharmacodynamics of many vital drugs. Albumin is highly susceptible for nonenzymatic glycation mediated structural modifications, and there is a need to determine structural and functional impact of specific AGEs modifications. The present study was aimed toward determining the AGE mediated structure and function changes, primarily looking into the effect on binding affinity of drugs in the two major drug binding sites of albumin. The impact of the two most predominant AGEs modifications, i.e., carboxyethyllysine (CEL) and argpyrimidine (Arg-P), was studied on the basis of the combination of in vitroand in silicoexperiments. In vitrostudies were carried out by AGEs modification of bovine serum albumin (BSA) for the formation of Arg-P and CEL followed by drug interaction studies. In silicostudies involved molecular dynamics (MD) simulations and docking studies for native and AGEs modified BSAs. In particular the side chain modification was specifically carried out for the residues in the drug binding sites, i.e., Arg-194, Arg-196, Arg-198, and Arg-217, and Lys-204 (site I) and Arg-409 and Lys-413 (site II). The equilibrated structures of native BSA (n-BSA) and glycated BSA (G-BSA) as obtained from MD were used for drug binding studies using molecular docking approach. It was evident from the results of both in vitroand in silicodrug interaction studies that AGEs modification results in the reduced drug binding affinity for tolbutamide (TLB) and ibuprofen (IBP) in sites I and II. Moreover, the AGEs modification mediated conformational changes resulted in the shallow binding pockets with reduced accessibility for drugs.

We establish the relationships between the metric of charge transfer excitation (Δr) for the bright ππ* state and the two-photon absorption probability as well as the first hyperpolarizability for two families of push–pull π-conjugated systems. As previously demonstrated by Guido et al. (J. Chem. Theory Comput.2013, 9, 3118–3126), Δris a measure for the average hole–electron distance upon excitation and can be used to discriminate between short- and long-range electronic excitations. We indicate two new benefits from using this metric for the analyses of nonlinear optical properties of push–pull systems. First, the two-photon absorption probability and the first hyperpolarizability are found to be interrelated through Δr; if β ∼ (Δr)k, then roughly, δTPA∼ (Δr)k+1. Second, a simple power relation between Δrand the molecular hyperpolarizabilities of push–pull systems offers the possibility of estimating properties for longer molecular chains without performing calculations of high-order response functions explicitly. We further demonstrate how to link the hyperpolarizabilities with the chain length of the push–pull π-conjugated systems through the metric of charge transfer.

Friction stir processing (FSP) is a novel technique used to fabricate surface composites. This investigation is an attempt to made Al/Al2O3 and Al/SiC surface composite using FSP and compare the mechanical and metallurgical properties influenced by the types of reinforcement particles. Two plates were grooved with 0.8 mm in width, 5 mm in depth and 100 mm in length in the middle of the aluminium plate using wire EDM and compacted with Al2O3 and SiC powder. The FSP was carried out automatically on an indigenously built FSW machine at tool rotational speed of 1200 rpm, processing speed of 60 mm/min and axial force of 10 kN. The optical and Scanning Electron microstructures are precisely revealed the homogeneous distribution of Al2O3 and SiC particles in the stir zone of surface composite layer (SCL). The microhardness was measured across the cross section of SCL layers of Aluminium and Aluminium with SiC and Al2O3. The higher microhardness was obtained in Aluminium with SiC and Al2O3 composites fabricated by FSP. This is because of the higher hardness value of SiC particles than Al2O3 particles.

The present investigation is carried out to investigate on mechanical and metallurgical properties of Friction stir (FS) / Underwater Friction stir (UFS) welded 3 mm thick AISI 316 L stainless steel joints. Experiments were carried out at a tool rotational speed of 700 rpm, welding speed of 45 mm/min and axial force of 12 kN. Defect free joints were confirmed by visual inspection. A marginal rise of about 4.5 % increase in the joint strength is achieved in water cooling than by gas cooling technique. Reduced peak temperature in water cooled joint led to better grain refinement in the weld nugget enhancing FSW tool life. No sign of secondary phase precipitation was observed in the weld joints which was confirmed by Energy Dispersive Spectroscopy (EDS) spectrums and micro etchants like Groesbeck and modified Murakami reagents in the weld nugget.

In the preset investigation, aluminum alloy, AA5052 and HSLA steel are successfully butt welded using a modified FSW process wherein the work pieces submerged in a liquid medium are stirred by the FSW tool. The trials are conducted by varying the tool rotational speed from 400 rpm to 900 rpm while keeping the other parameters constant. The welded joints are tested for ultimate tensile strength (UTS) and the joint interface microstructure is analyzed using SEM and EDS. The results show that when compared to the normal FSW process, the peak value of UTS is marginally low but the range of tool rotational speed that could produce defect free joints with good joint strength is almost doubled in the modified FSW process.

In the present work 3mm thick aluminium alloy AA5052 and HSLA steel were successfully butt joined using friction stir welding (FSW) technique. The FSW trials were carried out by varying the tool traverse speed while keeping the other parameters constant. The joint characteristics such as ultimate tensile strength (UTS), microhardness, microstructure at the joint interface and fracture surface of fractured tensile specimens were investigated. SEM and EDS analysis suggest that in all cases intermetallic compound (IMC) layer is formed at the joint interface and its thickness is critical in the tensile strength of the joint. For a given tool rotational speed, axial load and tool tilt angle, the tool traverse speed has significant influence on the thickness of IMC layer formed and hence on the joint strength. The highest joint strength of about 91% of UTS of the base aluminium alloy is obtained at tool traverse speed of 45mm/min and the UTS follow approximately a centre peak type variation against tool traverse speed.

The aim of the present study is to investigate on mechanical and microstructural properties of Friction Stir Welded 316 L austenitic stainless steel. Defect free weld were produced at a tool rotational speed (N) of 600 rpm, transverse speed (V) of 45 mm/min, axial force (F) of 11 kN and tool tilt angle (T) of 1.50.Mechanical properties such as Ultimate Tensile strength (UTS), Percentage Elongation (PE), Impact Strength (IS) were evaluated on the welded specimen. Further,micro hardness and microstructural analysis were carried out the transverse direction to the welded specimen. No significance of HAZ in the welded joint with observation of sigma phase precipitation revealed by Groesbeck and Modified Mukrami reagent. Further,FESEM with Electron Dispersive Spectroscopy (EDS) were obtained at the stir zone to ensure constituent of alloying elements present and ensuring no secondary phases found in the stir zone.

Friction stir processing (FSP) has evolved as a novel solid state technique to fabricate aluminium matrix composites (AMCs) in the recent years. FSP technique was applied to synthesis AA6082/TiC AMCs in order to analyze the effect of TiC particles, its volume fraction on the microstructure, mechanical and the sliding wear behaviour. A single pass FSP was carried out using a tool with 1200rpm rotational speed, whose travel speed of 60mm/min and an axial force of 10kN to produce the composite. AMCs with five different volume fractions (0, 6, 12, 18 and 24vol.%) were synthesized. The microstructure of the AA6082/TiC AMCs was studied using optical and scanning electron microscopy. The microhardness and ultimate tensile strength (UTS) were measured and the sliding wear behaviour was evaluated using a pin-on-disc apparatus. Thus the results revealed that the TiC particles significantly influenced the area of the composite, dispersion, grain size of matrix, microhardness, UTS and sliding wear behaviour of the AA6082/TiC AMCs. With this the effect of TiC particles on fracture surface and worn surface is also reported in this paper.

Understanding the interaction of gold nanoclusters with proteins has important ramifications in various fields. We present a study of the interaction between gold nanoclusters and lysozyme investigated using classical molecular dynamics and center-of-mass pulling simulations. The results reveal that the gold nanoclusters induce significant structural changes in lysozyme. Because the internal motions of lysozyme are related to its function, the changes in these internal motions have been quantified using principal component analysis of the molecular dynamics trajectories. The internal motions of lysozyme that are important for its function have been altered because of the interaction with the gold nanocluster. We have also explored how these induced changes in the lysozyme structure affect specific optical properties of the gold nanocluster using the complex polarization propagator method within the time-dependent density functional theory framework, which is of relevance for studies of the optical imaging of lysozyme using gold nanoclusters as molecular probes.

AbstractThe present study involves the screening of actinomycetes for enzymes and antimicrobial activities from the soil sediments of Northern Tamil Nadu, South India. Actinomycetes from the soil samples were isolated by pour plate technique on Actinomycetes Isolation Agar. Morphological characteristics of the isolates were studied based on microscopic appearance. Actinomycetes isolates was screened for the production of different extracellular enzymes like amylase, protease and lipase. In the screening for enzyme activity, the actinomycetes strains showed amylase activity, protease activity and lipase activity. Preliminary screening for antimicrobial activity of actinomycetes isolates were performed by cross streak plate method. Active form of 82 isolated strains showed activity against one or more bacteria and exhibited potential antifungal activity. The active strain was subjected to cultural, molecular identification and optimization of fermentation medium, solvent extraction and antimicrobial activity for crude extracts. Based on the primary antimicrobial proficiency, Loyola AR1 strain was selected for further studies. Ethyl acetate extract showed good antimicrobial activity when compared to butanol extract. The partial 16s rRNA sequence analysis of Loyola AR1 isolate identified to be Streptomycessp. and the sequence was submitted to the Gene Bank (HM163569).

An attempt was made to synthesize Cu/B4C surface composite using friction stir processing (FSP) and to analyze the influence of tool rotational speed on microstructure and sliding wear behavior of the composite. The tool rotational speed was varied from 800 to 1200 r/min in step of 200 r/min. The traverse speed, axial force, groove width and tool pin profile were kept constant. Optical microscopy and scanning electron microscopy were used to study the microstructure of the fabricated surface composites. The sliding wear behavior was evaluated using a pin-on-disc apparatus. The results indicate that the tool rotational speed significantly influences the area of the surface composite and the distribution of B4C particles. Higher rotational speed exhibits homogenous distribution of B4C particles, while lower rotational speed causes poor distribution of B4C particles in the surface composite. The effects of tool rotational speed on the grain size, microhardness, wear rate, worn surface and wear debris were reported.

pH sensors play a key role in many industrial and diagnostic applications. Mostly their usage is based on experience, and in many cases the working mechanisms of these sensors are not known in detail, thereby hindering a systematic improvement of such sensors for specific applications. In this report, we present results from combined quantum chemical and molecular mechanics calculations of molecular structures and optical absorption properties of bromocresol green (BRG) in aqueous solution with varying pH value. In the acidic pH range, this chromophore has an intense band with absorption maximum at 444 nm and in the basic pH regime the absorption spectra show a redshift toward 613 nm. In order to identify the molecular structures responsible for this pH dependent optical behavior the closed and open forms of BRG are studied using static approaches considering in each case the three possible protonated states namely, neutral, anionic, and dianionic. For the most significant forms, i.e. the open forms of BRG, extensive modeling based on the integrated approach has been carried out, where the structure and dynamics were studied using hybrid QM/MM molecular dynamics, while the excitation energy calculations were carried out using time dependent density functional theory wherein the surrounding solvent was described as polarizable continuum, semicontinuum, or via a molecular mechanics force-field. The anionic and dianionic forms of BRG have been recognized as molecular forms responsible for its acidic and basic pH behavior, respectively. In contrast to the case of solvatochromic probes, the different protonation states determine the optical behavior in different pH values for pH probes. Hence, the level of solvent description appears to be of minor importance. Independent of the level of theory used to describe the solvent, all models reproduce the spectral features of BRG in different pH and also the pH induced redshift in good agreement with experiment.

The dry sliding wear behavior of AA6061 matrix composite reinforced with aluminium nitride particles (AlN) produced by stir casting process was investigated. A regression model was developed to predict the wear rate of the prepared composite. A four-factor, five-level central composite rotatable design matrix was used to minimize the number of experimental runs. The factors considered in this study were sliding velocity, sliding distance, normal load and mass fraction of AlN reinforcement in the matrix. The developed regression model was validated by statistical software SYSTAT 12 and statistical tools such as analysis of variance (ANOVA) and student's ttest. It was found that the developed regression model could be effectively used to predict the wear rate at 95% confidence level. The influence of these factors on wear rate of AA6061/AlNpcomposite was analyzed using the developed regression model and predicted trends were discussed with the aid of worn surface morphologies. The regression model indicated that the wear rate of cast AA6061/AlNpcomposite decreased with an increase in the mass fraction of AlN and increased with an increase of the sliding velocity, sliding distance and normal load acting on the composite specimen.

The aim of this study is to identify the responsible molecular forms for the pH dependent optical properties of the deGFP1 green fluorescent protein mutant. We have carried out static and dynamic type calculations for all four protonation states of the chromophore to unravel the contributions due to finite temperature and the flexible protein backbone on the pH dependent optical properties. In particular, we have used a combined molecular dynamics and density functional–molecular mechanics linear response approach by means of which the optical property calculations were carried out for the chromophore in the explicitly treated solvent and bioenvironment. Two different models were used to describe the environmentelectronic embedding and polarizable electronic embeddingaccounting for the polarization of the chromophore and the mutual polarization between the chromophore and the environment, respectively. For this purpose a polarizable force field was derived quantum mechanically for the protein environment by use of analytical response theory. While the gas-phase calculations for the chromophore predict that the induced red shift going from low to high pH is attributed to the change of molecular forms from neutral to zwitterionic, the two more advanced models that explicitly account for the protein backbone attribute the pH shift to a neutral to anionic conversion. Some ramifications of the results for the use of GFPs as pH sensors are discussed.

Friction Stir Welding (FSW) as a joining technique with regard to low melting temperature materials such as aluminum alloys has already been established and implemented in the industry. But, with regard to high melting temperature metals and alloys the major issue still to get successfully addressed is a pertinent tool material for a class of work materials and to get their operating parameters optimized. This paper presents a detailed assessment on the FSW of high melting temperature (HMT) materials, giving emphasis on the tool materials, tool geometry and FSW equipment aspects based on the information gathered from experimental studies and research publications.

Friction stir processing (FSP) is as a novel modifying technique to synthesize surface composites. An attempt has been made to synthesis AA6082/TiC surface composite using FSP and to analyze the effect of tool rotational speed on microstructure and microhardness of the same. The tool rotational speed was varied from 800 rpm to 1600 rpm in steps of 400 rpm. The traverse speed, axial force, groove width and tool pin profile were kept constant. Scanning electron microscopy was employed to study the microstructure of the fabricated surface composites. The results indicated that the tool rotational speed significantly influenced the area of the surface composite and distribution of TiC particles. Higher rotational speed provided homogenous distribution of TiC particles while lower rotational speed caused poor distribution of TiC particles in the surface composite. The effect of the tool rotational speed on microhardness is also reported in this paper.

In this present work the influence of Cenosphere filler material in thermal and mechanical properties of Epoxy resin is discussed. For comparative study, pure resin and composites made with different compositions (1, 3 and 5 wt% of Cenosphere) were prepared. The specimens were submitted to thermal analysis (DMA) and mechanical test (Tensile and Flexural) as well. Dynamic mechanical analysis (DMA) revealed an enhancement in the energy dissipation ability of the composite with 1wt%, wt3%, wt5% of Cenosphere and an increase in stiffness relative to the pure matrix phase. It was generally observed that the tensile strength found to increase with the inclusion of Cenosphere as filler material. Maximum value of tensile stress and strain of resin is not sensitively increased by filler material.

This paper discusses the influence of Flux Cored Arc Welding Process parameters such as welding current, travel speed, voltage on bead profile, metallurgical and mechanical properties of welds of 2 mm thick 409M ferritic stainless steel sheets. The study reveals that, grain coarsening, volume fraction of martensite, hardness of heat affected zone and % of delta ferrite in ER 309 weld metal increases with increase in heat input. However, the results show that variation of heat input does not make any significant effect on tensile strength of the joint. Hence, welding parameters that provide uniform bead profile for the weld are recommended for fabrication.

Imaging of metal ion concentration, distribution, and dynamics can pave the way to diagnose a number of diseases and to identify the normal functioning of the human body. Recently, two-photon microscopy-based imaging of metal ions has become popular due to several favorable factors as compared to fluorescence-based imaging. However, much has to be investigated in order to design probes with large two-photon absorption cross sections and yet with selective binding affinity toward metal ions. In particular, it is crucial to recognize the mechanisms of metal ion-induced changes of the two-photon absorption intensity. The present paper contributes to this effort and reports on the results of extensive studies carried out to define a reliable computational protocol that can account for sampling, solvent, and finite temperature effects for one- and two-photon properties of metal probes, using azacrown ether substituted distyrylbenzene embedded in solvents as a testbed. We employ a selection of theoretical approaches to model the structure of the probe alone and in the presence of Mg2+ion in acetonitrile solvent, including static quantum-chemical calculations, rigid- and flexible-body molecular dynamics, and hybrid QM/MM molecular dynamics. For a set of solute–solvent configurations, the one- and the two-photon properties are computed using the recently developed polarizable embedding response approach. It is found that the hybrid QM/MM molecular dynamics based approach is the most successful one among other employed computational strategies, viz. reproduction of the metal ion-induced blue shift in the absorption wavelength and decrease in the two-photon absorption cross section, which actually is in excellent agreement with experimental data. The mechanism for such metal ion-induced changes in the optical properties is put forward using a few-state model. Possible design principles to tune the two-photon absorption properties of probes are also discussed.

The microstructure and mechanical characterization of dissimilar friction stir welded AA5083-H111 and AA6351-T6 aluminum alloys were studied. Three different welding speeds (36, 63 and 90 mm/min) were used to weld the dissimilar alloys. The effect of welding speed on mechanical and metallurgical properties was analyzed. It is found that the welding speed of 63 mm/min produces better mechanical and metallurgical properties than other welding speeds. The weld zone is composed of three kinds of microstructures, namely unmixed region, mechanically mixed region and mixed flow region. The fracture mode was observed to be a ductile fibrous fracture.

AbstractMost of the manufacturing enterprises indulge in the bonding of metals during the production process. This makes welding one of the most important processes in industries. Subsequently, due to the high usage of welding process, industrial engineers desire to optimize the parameters concerned to achieve the desired weld bead characteristics. This paper focuses on optimization of flux cored arc welding process parameters, which are used for deposition of duplex stainless steel on low carbon structural steel plates. Experiments were conducted based on central composite rotatable design and mathematical models were developed using multiple regression method. Further, optimization with objectives as minimizing percentage dilution, maximizing height of reinforcement and bead width was carried out using genetic algorithm and memetic algorithm. This problem was formulated as a multi objective, multivariable and non-linear programming problem. The algorithms were implemented using basic functions of C language making it highly reliable, adoptable, very user friendly and extendable to other welding processes such as GMAW, GTAW, robotic welding, etc. The adopted optimization techniques were further compared based on various computational factors.

Motion is an essential and fundamental feature of any living organism. The evolved organisms have developed sophisticated and perfect machineries and highly delicate mechanisms to carry out directional and coordinated movements which eventually lead to motion at the macroscopic length scale. By mimicking these natural machineries, attempts to design and synthesize similar molecular motors are made in relevance to their applications in drug delivery, data storage, and molecular sensing. It is highly desirable to establish the rules for controlling the conformational states of molecular motors by tuning some of the external variables which can be used for the design strategies. We contribute to this subject by looking into the solvent influence on the conformational states of a synthetic molecular rotor, namely, diketopyrrolopyrrole (DPP) based [2]rotaxane, using the force-field molecular dynamics approach. We study this system in three different solvents, and we report a strong solvent dependence in the population of three different translational isomers. In chloroform solvent we report the dominant population of the 2-P isomer which is in excellent agreement with experimental results based on H NMR spectra (Org. Lett.2013, 15, 1274). However, there is a striking difference seen in the population of translational isomers in DMSO solvent, and we attribute these features to negligence of solvent hydrogen bonding induced upfield and downfield effects in the interpretation of experimental proton NMR spectra. In addition, we also report a solvent-polarity-induced fully unstretched to folded conformational transition in the [2]rotaxane system. On the basis of the molecular mechanics Poisson–Boltzmann (and generalized Born) surface area approach, we identify the driving force for the formation of the supramolecular guest–host [2]rotaxane system. Finally, we calculate the relative binding free energies for the macrocycle at different binding sites of the DPP skeleton using the molecular dynamics simulations performed for the macrocycle–rotaxane system in water solvent which suggests the increased stability of the 2-O isomer in polar solvent.

The design of novel protein–nanoparticle hybrid systems has applications in many fields of science ranging from biomedicine, catalysis, water treatment, etc. The main barrier in devising such tool is lack of adequate information or poor understanding of protein–ligand chemistry. Here, we establish a new strategy based on computational modeling for protein and precursor linkers that can decorate the nanoparticles. Moringa oleifera(MO2.1) seed protein that has coagulation and antimicrobial properties was used. Superparamagnetic nanoparticles (SPION) with precursor ligands were used for the protein–ligand interaction studies. The molecular docking studies reveal that there are two binding sites, one is located at the core binding site; tetraethoxysilane (TEOS) or 3-aminopropyl trimethoxysilane (APTES) binds to this site while the other one is located at the side chain residues where trisodium citrate (TSC) or Si60binds to this site. The protein–ligand distance profile analysis explains the differences in functional activity of the decorated SPION. Experimentally, TSC-coated nanoparticles showed higher coagulation activity as compared to TEOS- and APTES-coated SPION. To our knowledge, this is the first report on in vitroexperimental data, which endorses the computational modeling studies as a powerful tool to design novel precursors for functionalization of nanomaterials; and develop interface hybrid systems for various applications.

Presently, there is a great demand for small probe molecules that can be used for two-photon excitation microscopy (TPM)-based monitoring of intracellular and intraorganelle activity and pH. The candidate molecules should ideally possess a large two-photon absorption cross section with optical properties sensitive to pH changes. In the present work, we investigate the potential of a methoxy napthalene (MONAP) derivative for its suitability to serve as a pH sensor using TPM. Using an integrated approach rooted in hybrid quantum mechanics/molecular mechanics, the structures, dynamics, and the one- and two-photon properties of the probe in dimethylformamide solvent are studied. It is found that the protonated form is responsible for the optical property of MONAP at moderately low pH, for which the calculated pH-induced red shift is in good agreement with experiments. A 2-fold increase in the two-photon absorption cross section in the IR region of the spectrum is predicted for the moderately low pH form of the probe, suggesting that this can be a potential probe for pH monitoring of living cells. We also propose some design principles aimed at obtaining control of the absorption spectral range of the probe by structural tuning. Our work indicates that the integrated approach employed is capable of capturing the pH-induced changes in structure and optical properties of organic molecular probes and that such in silico tools can be used to draw structure–property relationships to design novel molecular probes suitable for a specific application.

Friction stir processing (FSP) has evolved as a potential candidate to fabricate surface composites. This paper investigates the influence of traverse speed on microstructure and microhardness of Cu/B4C surface composite fabricated using FSP. The traverse speed was varied from 20 to 60 in steps of 20 mm/min. The tool rotational speed, axial force and groove width were kept constant. Optical microscopy and scanning electron microscopy were employed to study the microstructure of the fabricated surface composites. The results indicated that the traverse speed significantly influenced the area of the surface composite and distribution of B4C particles. The area of the surface composite was found to bear an inversely proportional relationship to traverse speed. Lower traverse speed exhibited homogenous distribution of B4C particles while higher traverse speed caused poor distribution of B4C particles in the surface composite.