Effect of Boundary Constraints on the Nonlinear Flapping of Filaments Animated by Follower Forces

Elastically driven filaments subjected to animating compressive follower forces provide a synthetic way to mimic the oscillatory beating of active biological filaments such as eukaryotic cilia. The dynamics of such active filaments can, under favorable conditions, exhibit stable time-periodic responses that result due to the interplay of elastic buckling instabilities, geometric constraints, boundary conditions, and dissipation due to fluid drag. In this paper, we use a continuum elastic rod model to estimate the critical follower force required for the onset of the stable time-periodic flapping oscillations in pre-stressed rods subjected to fluid drag. The pre-stress is generated by imposing either clamped-clamped or clamped-pinned boundary constraints and the results are compared with those of clamped-free case, which is without pre-stress. We find that the critical value increases with the initial slack--that quantifies the pre-stress, and strongly depends on the type of the constraints at the boundaries. The frequency of oscillations far from the onset, however, depends primarily on the magnitude of the follower force, not on the boundary constraints. Interestingly, oscillations for the clamped-pinned case are observed only when the follower forces are directed towards the clamped end. This finding can be exploited to design a mechanical switch to initiate or quench the oscillations by reversing the direction of the follower force or altering the boundary conditions

APPLICATION OF ARTIFICIAL NEURAL NETWORK TECHNIQUES FOR DESIGN OF MODULAR MINICELL CONFIGURATIONS

Artificial neural networks, so far, have not been used for designing modular cells. Therefore, Self-organizing neural network (SONN) is used in the present research to design minicell-based manufacturing system. Two previously developed methods were studied and implemented using SONN model. Results obtained are compared with previous results to analyze the effectiveness of SONN in designing minicells. A new method is then developed with the objective to design minicells more effectively and efficiently. Results of all three methods are compared using machine-count and materialhandling as performance measuring criteria to find out the best metho

Follower Forces in Pre-Stressed Fixed-Fixed Rods to Mimic Oscillatory Beating of Active Filaments

Flagella and cilia are examples of actively oscillating, whiplike biological filaments that are crucial to processes as diverse as locomotion, mucus clearance, embryogenesis and cell motility. Elastic driven rod-like filaments subjected to compressive follower forces provide a way to mimic oscillatory beating in synthetic settings. In the continuum limit, this spatiotemporal response is an emergent phenomenon resulting from the interplay between the structural elastic instability of the slender rods subjected to the non-conservative follower forces, geometric constraints that control the onset of this instability, and viscous dissipation due to fluid drag by ambient media. In this paper, we use an elastic rod model to characterize beating frequencies, the critical follower forces and the non-linear rod shapes, for prestressed, clamped rods subject to two types of fluid drag forces, namely, linear Stokes drag and non-linear Morrison drag. We find that the critical follower force depends strongly on the initial slack and weakly on the nature of the drag force. The emergent frequencies however, depend strongly on both the extent of pre-stress as well as the nature of the fluid drag

In vitro studies on quality assessment and ethnobotany of Acampe rigida (Buch.-Ham. ex Sm.) P.F.Hunt encountered in Ultapani Forest Range, Assam

Acampe rigida (Buch.-Ham.ex Sm.) P.F.Hunt (Family: Orchidaceae), locally known as ‘Miral Baha’ among the Santhal community of Ultapani Forest Range, BTR, Assam, blooms in the month of July to November. The present study was aimed to carry out the ethnobotanical studies, macroscopic, pharmacognostic, preliminary phytochemical and heavy metal analysis of A. rigida. Apart from being an eye-catching ornamental plant, it has a number of medicinal potentialities as folk medicine among the Santhal community where the leaves are used for recovering throat cancer and epilepsy and the paste helps in relieving rheumatism, healing wound as tonic to strengthen the body and increase blood in the body. Parenchyma cells, stomata, fibre were observed in the microscopic examination of powdered plant part. The pulverised leaves colour, odour, flavor/taste and texture were all satisfactory. Preliminary phytochemical screening of A. rigida leaves aqueous extract confirmed the presence of alkaloids, carbohydrates, flavonoids, glycosides, phenols, steroids, saponins, tannins, terpenoids, whereas phlobatannins was absent. Heavy metal tests revealed that the samples were free from bismuth, cadmium and lead. The present studies might be significant to establish the pharmacognostic and phytochemical standards of this orchid species and may help in the identification, to ensure quality and purity and standardization of the herbal drug

Characterisation of indigenous plants for herbal formulations preparation based on pharmacognostic and physiochemical data

The use of plant-based drugs has increased considerably in the modern world for their efficiency in managing diseases with lesser side effects than synthetic drugs. The current study was aimed to confirm the identity, quality and purity of some locally available potential medicinal plants such as Alstonia scholaris (bark), Centella asiatica (whole plant), Drymaria cordata (whole plant), Hydrocotyle sibthorpioides (whole plant), Oroxylum indicum (bark), Senna hirsuta (leaf), Senna occidentalis (leaf), Solanum indicum (root), Stephania japonica (tuber) in powdered form. The powdered plant parts were evaluated for preliminary phytochemicals, pharmacognostical studies, physical characteristics and heavy metals. Preliminary phytochemical screening of the different extracts inferred the existence of carbohydrates, phenolics, alkaloids and amino acids while triterpenoids were absent. Microscopical study of the powder revealed the diagnostic qualities such as stone cells, trichomes, stomata, calcium oxalate crystal, fibres, xylem vessel, pitted spiral vessels, etc. The colour, odour, flavour/taste and texture of the pulverized plant were overall acceptable. The physical characteristics which determine the flow rate of the powder with respect to Carr’s index and Hausner’s ratio were found to be good to passable except for Hydrocotyle sibthorpioides (whole plant), Oroxylum indicum (bark), which were not easily passable. The heavy metal test showed the absence of bismuth, cadmium and lead. Thus the present study may serve as a standard reference for the quality control analysis of the herbal drug either singly or in synergy

Pharmacognostic and physicochemical characterisation of potential plants for antidiabetic herbal formulations

In recent years, mankind has relied largely on herbal medicines to treat a variety of ailments. The aim of the current study is to investigate the pharmacognostic and physicochemical characterisation of some medicinal plants such as Bambusa balcooa (leaf) (BBL), Phyllanthus emblica (fruit) (PEF), Hodgsonia heteroclita (fruit pulp) (HHP), and Punica granatum (fruit peel) (PGP) used by the local Bodo tribe for the treatment of diabetes, which can be combined together to develop a novel polyherbal formulation. The preliminary phytochemical screening, microscopic evaluation, organoleptic and flow properties and qualitative heavy metal estimation was carried out usimng standard protocols. The preliminary phytochemical screening revealed the existence of carbohydrates, phenolics, alkaloids in all. However, amino acids were present in P. granatum and P. emblica, whereas triterpenoids were inferred in P. officinalis. Microscopical analysis of crude showed the presence of stone cells (BBL, HHP and PGP), xylem (PEF, HHP and PGP), trichome (PGP), fibres (all) and epidermis (PEF). The macroscopical study of crushed powder was overall acceptable to sense organs. The physical evaluation of flow properties was found to be good for P. emblica fruit when compared to others which was fair to passable. The heavy metal test showed the absence of bismuth, cadmium and lead in all species. Accordingly, the results obtained from the study is endowed with essential information for the authentication and quality assessment of these herbal drugs