Dry-sliding wear properties of 3D printed PETG/SCF/OMMT nanocomposites: Experimentation and model predictions using artificial neural network

In this article, an attempt has been made to experimentally investigate the synergistic effect of organically modified montmorillonite (OMMT) nanoclay and short carbon fibers (SCFs) on the tribological behaviour of additively manufactured Polyethylene Terephthalate Glycol (PETG) based nanocomposites. The tribo-specimens are 3D printed using fused deposition modelling (FDM). The tribological properties, that is, specific wear rate (SWR) and coefficient of friction (CoF) of various PETG/SCF/OMMT nanocomposites were assessed by performing dry-sliding wear test. In addition, an artificial neural network (ANN) methodology is proposed to accurately predict the wear performance of PETG nanocomposites. The ANN model is trained using the datasets obtained from the experimentation. For the training of the ANN model, the Levenberg–Marquardt optimisation algorithm with 10 neurons along with a tangent sigmoid activation function is utilised. Additional experimentation was performed for arbitrary load and sliding velocity which were not used for training the ANN model and the results were compared to assess the predictive capability of the ANN model on unseen data. The proposed ANN methodology predicted the SWR and CoF with agreeable accuracy. It is believed that by adopting the proposed ANN methodology, the experimentation costs and time can be significantly reduced without compromising on the accuracy of the results

Magnetoplasmons in quantum rings

We have studied the structure and dipole charge density response of nanorings as a function of the magnetic field using local-spin density functional theory. Two small rings consisting of 12 and 22 electrons confined by a positively charged background are used to represent the cases of a narrow and a wide ring. The results are qualitatively compared with experimental data existing on microrings and on antidots. A smaller ring containing 5 electrons is also analyzed to allow for a closer comparison with a recent experiment on a two electron quantum ring.Comment: Typeset using Revtex, 13 pages and 11 Postscript figure

Laughlin Wave Function and One-Dimensional Free Fermions

Making use of the well-known phase space reduction in the lowest Landau level(LLL), we show that the Laughlin wave function for the $\nu = {1\over m}$ case can be obtained exactly as a coherent state representation of an one dimensional $(1D)$ wave function. The $1D$ system consists of $m$ copies of free fermions associated with each of the $N$ electrons, confined in a common harmonic well potential. Interestingly, the condition for this exact correspondence is found to incorporate Jain's parton picture. We argue that, this correspondence between the free fermions and quantum Hall effect is due to the mapping of the $1D$ system under consideration, to the Gaussian unitary ensemble in the random matrix theory.Comment: 7 pages, Latex , no figure

Antibacterial activity of some selected medicinal plants of Pakistan

<p>Abstract</p> <p>Background</p> <p>Screening of the ethnobotenical plants is a pre-requisite to evaluate their therapeutic potential and it can lead to the isolation of new bioactive compounds.</p> <p>Methods</p> <p>The crude extracts and fractions of six medicinal important plants (<it>Arisaema flavum</it>, <it>Debregeasia salicifolia</it>, <it>Carissa opaca</it>, <it>Pistacia integerrima</it>, <it>Aesculus indica</it>, and <it>Toona ciliata</it>) were tested against three Gram positive and two Gram negative ATCC bacterial species using the agar well diffusion method.</p> <p>Results</p> <p>The crude extract of <it>P. integerrima </it>and <it>A. indica </it>were active against all tested bacterial strains (12-23 mm zone of inhibition). Other four plant's crude extracts (<it>Arisaema flavum</it>, <it>Debregeasia salicifolia</it>, <it>Carissa opaca</it>, and <it>Toona ciliata</it>) were active against different bacterial strains. The crude extracts showed varying level of bactericidal activity. The aqueous fractions of <it>A. indica </it>and <it>P. integerrima </it>crude extract showed maximum activity (19.66 and 16 mm, respectively) against <it>B. subtilis</it>, while the chloroform fractions of <it>T. ciliata </it>and <it>D. salicifolia </it>presented good antibacterial activities (13-17 mm zone of inhibition) against all the bacterial cultures tested.</p> <p>Conclusion</p> <p>The methanol fraction of <it>Pistacia integerrima</it>, chloroform fractions of <it>Debregeasia salicifolia </it>&<it>Toona ciliata </it>and aqueous fraction of <it>Aesculus indica </it>are suitable candidates for the development of novel antibacterial compounds.</p

Evaluation of Biologically Active Compounds from Calendula officinalis Flowers using Spectrophotometry

<p>Abstract</p> <p>Background</p> <p>This study aimed to quantify the active biological compounds in <it>C. officinalis </it>flowers. Based on the active principles and biological properties of marigolds flowers reported in the literature, we sought to obtain and characterize the molecular composition of extracts prepared using different solvents. The antioxidant capacities of extracts were assessed by using spectrophotometry to measure both absorbance of the colorimetric free radical scavenger 2,2-diphenyl-1-picrylhydrazyl (DPPH) as well as the total antioxidant potential, using the ferric reducing power (FRAP) assay.</p> <p>Results</p> <p>Spectrophotometric assays in the ultraviolet-visible (UV-VIS) region enabled identification and characterization of the full range of phenolic and flavonoids acids, and high-performance liquid chromatography (HPLC) was used to identify and quantify phenolic compounds (depending on the method of extraction). Methanol ensured more efficient extraction of flavonoids than the other solvents tested.</p> <p>Antioxidant activity in methanolic extracts was correlated with the polyphenol content.</p> <p>Conclusions</p> <p>The UV-VIS spectra of assimilator pigments (e.g. chlorophylls), polyphenols and flavonoids extracted from the <it>C. officinalis </it>flowers consisted in quantitative evaluation of compounds which absorb to wavelengths broader than 360 nm.</p

A neo-institutional perspective on ethical decision-making

Drawing on neo-institutional theory, this study aims to discern the poorly understood ethical challenges confronted by senior executives in Indian multinational corporations and identify the strategies that they utilize to overcome them. We conducted in-depth interviews with 40 senior executives in Indian multinational corporations to illustrate these challenges and strategies. By embedding our research in contextually relevant characteristics that embody the Indian environment, we identify several institutional- and managerial-level challenges faced by executives. The institutional-level challenges are interpreted as regulative, normative and cognitive shortcomings. We recommend a concerted effort at the institutional and managerial levels by identifying relevant strategies for ethical decision-making. Moreover, we proffer a multi-level model of ethical decision-making and discuss our theoretical contributions and practical implications

Wave propogation in and vibration of a travelling beam with and without nonlinear effects. Part II: Forced vibration

The wave propagation in a simply supported travelling beam, studied in Part I of this paper, has been used to derive the forced responses. Based upon the wave-propagation principles, a simple method for constructing the closed-form transfer function of such a beam has been presented. The use of this transfer function offers an easy alternative to the usual modal analysis for obtaining the steady-state harmonic response. The effects of non-linearities during the steady-state oscillation, maintained by a non-resonant hard harmonic excitation, have also been studied. The present method, when compared to the conventional Galerkin's technique, requires much less computational effort

Electrochemical Properties of Spinel Cobalt Ferrite Nanoparticles with Sodium Alginate as Interactive Binder

We introduce a process of making high-capacity and rate-capable metal-ferrite-based conversion anodes for lithium-ion batteries. Cobalt ferrite (CoFe2O4) exhibits a discharge capacity that is two-times higher compared to the state-of-the-art graphite anode, but at the same time it shows high volume change (ca. 95%) during conversion reaction with lithium in an electrochemical environment. This large volume expansion is responsible for the particle-particle and conductive-carbon particles-active materials detachment, which leads to cyclic instability during subsequent cycles. As observed in our earlier work, any kind of weak or strong chemical interaction between active materials and binder is necessary to achieve excellent electrochemical performance in case of conversion or alloying reactions. To compare the electrochemical activity of CoFe2O4 nanoparticles against lithium, we use conventional polyvinylidene fluoride and sodium alginate binder to fabricate electrodes. Fourier-transform infrared measurements reveal weak hydrogen-bond formation between surface -OH groups of CoFe2O4 and -COOH groups of the alginate binder. Indentation tests further confirm the increased hardness of the alginate/CoFe2O4-based electrode films. CoFe2O4-alginate-carbon anode exhibits a high specific capacity of 890 mAhg (1) at 0.1 C rate (91.4 mAg(-1)) after 50 charge-discharge cycles. Even at high rate cycling with current densities such as 18280 mAg(-1) (20 C), the same electrode material exhibits a specific capacity of 470 mAhg(-1), which is much higher than that of conventional graphite anode at the same electrochemical conditions