Akhil.P Chandran - Profile on Academia.edu (original) (raw)

Papers by Akhil.P Chandran

Hip International, 2008

This study discusses the definition of operative, anatomic and radiographic acetabular anteversio... more This study discusses the definition of operative, anatomic and radiographic acetabular anteversion and their effect on a long posterior wall cup. In this cadaveric study, anteversion was modelled radiographically with a Charnley double wire marker Long Posterior Wall (LPW) cup and the position of the long posterior wall was studied with relation to different anteversion angles, and also correlated with computer generated line diagrams of the acetabular cup. The position of a long posterior wall varies when different types of anteversion are applied. By increasing the operative anteversion the long posterior wall comes to lie inferiorly and the advantage of the long posterior wall is lost. In light of prior confusion with definitions and in an attempt to make the terms more relevant to the surgical technique we propose the simplified alternate terms of 'flexion-anteversion' previously called 'operative anteversion', 'internal rotation-anteversion' previously called 'anatomic anteversion' and 'combined anteversion' previously called 'radiographic anteversion'. If the surgeon elects to use LPW it is important to understand the effect of each type of anteversion on eventual position of the raised wall.

Simulating change in soil organic carbon in two long term fertilizer experiments in India: with the RothCmodel

Climate Change and Environmental Sustainability, 2013

Global importance of total organic carbon (TOC) in soil is due to its role in the global carbon c... more Global importance of total organic carbon (TOC) in soil is due to its role in the global carbon cycle and, thus, the part it plays in influencing the atmospheric levels of greenhouse gases (GHGs). It is also of local importance as it determines ecosystem and agro-ecosystem function, influencing various soil parameters. The objective of the present study was to evaluate RothC model (26.3) to estimate TOC changes under two long term fertilizer experimental (LTFE) sites representing humid (Mohanpur) and semi-arid (Akola) climate in India. Five treatments each at the LTFE sites of Mohanpur representing alluvial soils (Alfisol) of the Indo-Gangetic Plains (IGP) and of Akola dominated by black soils (Vertisols) in the Black Soil Region (BSR) were selected. Mohanpur site was modelled for 3 layers (0–13, 13–23, and 23–39 cm) while Akola for surface layer (0–15 cm) only. The root mean square error (RMSE), considered as modelling error, ranged from 3.34 to 17.85%, 6.87 to 14.22% and 6.66 to 24.34% in the 3 soil layers of Mohanpur site respectively. For Akola, RMSE ranges from 1.79 to 13.28. The simulation biases expressed by M (relative error) for all treatments at these sites were non-significant. In Mohanpur, observed trends in TOC show marginal increase in control (T1) and 100% NPK (T2) while the increase was nearly 17 to 35% when organic amendments were applied along with inorganics during 1999 to 2010. For the same period in Akola, control (T1), 50% NPK (T2), and 100% NPK (T4) recorded decrease in TOC while 26 to 29% increase was registered without inorganics and with the combination of inorganics and organics respectively. The calculation of modelled TOC stock to find out effect of global warming indicated that treating the entire soil pedon as a homogenous unit will overestimate effects of global warming in accelerating decomposition of soil carbon.

Physical (nine characteristics) and chemical (14) properties of red and black soils are described... more Physical (nine characteristics) and chemical (14) properties of red and black soils are described: sand, silt, clay, fine clay, BD, COLE, HC (hydraulic conductivity) and WDC; pH (H 2 O and KCl), EC, OC, CaCO 3 , clay CO 3 , extractable Ca, Mg, Na, K, CEC, clay CEC, BS and ESP are described in three ecosystems, namely sub-humid (moist and dry) [SH (m) and SH (d)], semi-arid (moist and dry) [SA (m) and SA (d)] and arid in SAT, India. Clay contents vary between 30% in arid system to 82% in sub-humid (dry) system and 79% in semi-arid (dry) system. The red soils contain 8-55% clay. Fine clay (<0.2 μm) content ranges between 9-54% in red soils; for black soils nearly 50% of total clay (<2 μm) remains in finer (<0.2 μm) fractions. The overall relation between SOC and BD is negative; however, the correlation between SIC and BD within a depth of 0-30 cm soil depth is positive. Increase in relative proportion of coarse fragments increases the pore space, effecting decrease in BD values. The inherent relation between total clay and COLE in different bioclimatic systems indicates a positive correlation with a relatively high value (r = 0.83) in arid bioclimatic system. Except sub-humid (moist) and arid bioclimates, a positive correlation between COLE and slickensides is observed in most of the Vertisols in SAT India. A general decreasing trend of SOC with increase in HC is observed. Conversely, an increasing trend of HC has been found with decrease in SIC. In all the bioclimates, there is an increasing trend of SOC with decrease in ESP and an increasing trend of SIC with increase in ESP. This is due to preferential release of Ca 2+ ions and their precipitation as CaCO 3 in soil, thereby increasing the relative concentration of Na + ions in the exchange complex effecting high value of ESP. In general, a positive correlation between amount of fine clay and SOC in surface soils has been found. The SOC values in the surface (0-30 cm) follow the trend of forest system > permanent fallow (grassland), horticultural system > agricultural system > wasteland. Surface soils of agricultural and horticultural systems store higher SIC as compared to other systems. The surface soils of semi-arid (moist) show higher SOC under agricultural system due to inclusion of sun hemp for green manuring in crop rotation. The average SOC values follow the trend of SA (m) (0.825%) > SH (d) (0.804%) > SH (m) (0.642%) > SA (d) (0.633%) > arid (0.594%) for black soils under agricultural system. The values of SOC follow the trend of SH (m) (1.35) > SA (d) (0.84) > SA (m) (0.70) for the red soils used for cultivation. The level of SIC values in surface soils under agricultural system followed the trend of arid (2.34%) > SH (d) (1.06%) > SA (m) (0.99%) > SA (d) (0.94%) > SH (m) (0.54%) for black soils. In red soils, CaCO 3 in general is not found except in soils of semi-arid (dry) bioclimatic system. The SOC in surface horizon under agricultural systems shows higher values for cereal-based system (0.79%), followed by soybean systems (0.70%) and cotton-based systems (0.68%). Interestingly, the SIC values have been found to be the highest in cotton-based systems (1.53%), followed by soybean-based systems (0.66%) and cereal-based systems (0.29%). This trend is opposite to that of the corresponding SOC values. With the help of data generated, 14 systems (five in cotton, three in soybean, four in cereals, one in horticulture and one under forest) have been identified as ideal for organic carbon sequestration, keeping in view the existing level of management practices vis-à-vis soil health. This publication is part of the research project "Identifying Systems for Carbon Sequestration and Increased Productivity in Semi-Arid Tropical Environments (RNPS-25)" funded by the National Agricultural Technology Project (NATP) through

Crystal Growth & Design, 2014

Hot-injection techniques are currently the state-ofthe-art method for the synthesis of high-quali... more Hot-injection techniques are currently the state-ofthe-art method for the synthesis of high-quality colloidal nanocrystals (NCs) but have typically been limited to small batch reactors. The nature of this method leads to local fluctuations in temperature and concentration where inhomogeneity due to mixing makes precise control of reaction conditions very challenging at a large scale. Therefore, development of methods to produce high-quality colloidal NCs with highthroughput is necessary for many technological applications. Herein, we report a high-quality and high-throughput NC synthesis method via a continuous microwave-assisted flow reactor where separation of nucleation and growth is demonstrated. A significant issue of microwave heating in a single-phase continuous flow microwave reactor is the deposition of in situ generated NCs on the inner wall of the reactor in the microwave zone. This deposited material leads to significantly enhanced microwave absorption and rapid heating and can result in sparking in the reactor. A gas−liquid segmented flow is used to avoid this problem and also results in improved residence time distributions. The use of this system allows for finely tuned parameters to achieve a high level of control over the reaction by separating the nucleation and growth stages. C olloidal nanocrystals (NCs), exhibiting a wide range of size-and shape-dependent properties, have gained attention for a number of applications including light emitting diodes, 1,2 lasers, 3,4 and solar cells. 5−9 Each of these applications depends critically on the ability to synthesize "high-quality" NCs as judged by their uniformity in size, shape, composition, and crystal structure. 9,10 The development of a high-throughput method to produce colloidal NCs with the aforementioned properties is also a key step in the commercialization process. NCs are generally synthesized by thermal decomposition of precursors in a mixture of solvents and coordinating ligands. One of the key factors for synthesizing high-quality NCs is the temporal separation of nucleation and growth stages of the reaction which is most commonly accomplished using a hotinjection technique. 11 In a typical hot-injection reaction, a solution containing one or more precursors at lower temperature is rapidly injected into a hot (i.e., above nucleation temperature) solution containing the remaining precursor(s), resulting in burst nucleation. The mixed solution naturally decreases rapidly in temperature (thus confining nucleation to a short time period following injection) and is finally held at

Sodicity in smectite dominant shrink-swell soils (Vertisols and vertic intergrade) is common in t... more Sodicity in smectite dominant shrink-swell soils (Vertisols and vertic intergrade) is common in the semi-arid region. It is not known whether long-term sodicity in soils changes the layer charge of smectites as layer charge is an important fundamental property of smectitedominated soils and most of the soil properties depends upon the layer charge. Understanding the importance of layer charge of soil clay smectites, two benchmark Vertisols, one Paral soils (sodic) and the other Boripani soils (non-sodic) from Akola and Nagpur districts of Maharashtra were chosen for the study. The study intended to show whether long-term sodicity causes hydroxy-interlayering in smectites which result in an increase in layer charge. The soils had high clay and smectite content and the smectite charge was distributed in both tetrahedral and octahedral layers. The layer charge of both the soil fine clays are the lowest reported till date for Indian smectites and varied from 0.307 to 0.353 and 0.328 to 0.360 mol(-)/{Si, Al) 4 O 10 (OH) 2 } in a soil profile for Paral and Boripani soils respectively. Hydroxy-interlayering in smectites was also negligible. The study discussed that sodicity may not be responsible for the formation of hydroxy-interlayering in smectites and thus not likely to increase the layer charge. Shrink-swell soils of the Upper Peninsular India are mainly formed from the weathering of Deccan basalt, rich in plagioclase feldspars and yield dioctahedral smectite as the first weathering product (Pal and Deshpande, 1987; Bhattacharyya et al., 1993). These smectites are dominated by beidellite-nontronite type of minerals (Ghosh and Kapoor, 1982). It was later confirmed by diagnostic methods that smectites of Indian shrink-swell soils are nearer to montmorillonite of the montmorillonite-nontronite series (Pal and Deshpande, 1987). To characterize the shrink-swell soils which contain dominant proportions of smectites, determination of their layer charge is fundamental to all physical and chemical properties of soils. The properties include soil structure, drainage, aeration, water retention (Laird et al., 1987), cation exchange reactions, specific surface area and degree of hydration (Bailey, 1980; Wilding and Tessier, 1988). The layer

Special section: Soil information system: use and potentials in humid and semi-arid tropics

Current science

The articles presented in this special section emanated from the researches of consortium members... more The articles presented in this special section emanated from the researches of consortium members of the National Agricultural Innovative Project (NAIP, Component 4) of the Indian Council of Agricultural Research (ICAR), New Delhi. These researches have helped develop a soil information system (SIS). In view of the changing scenario all over the world, the need of the hour is to get assistance from a host of re-searchers specialized in soils, crops, geology, geogra-phy and information technology to make proper use of the datasets. Equipped with the essential knowledge of data storage and retrieval for management recom-mendations, these experts should be able to address the issues of land degradation, biodiversity, food

Pedogenetic processes in a shrink–swell soil of central India

ABSTRACT In view of lack of precise information on the factors and processes in clay illuviation,... more ABSTRACT In view of lack of precise information on the factors and processes in clay illuviation, pedoturbation and slickenside formation in shrink-swell soils, a study on a <100 years old shrink-swell soil (Vertic Haplustalf) of Central India was undertaken. The soil has typical physical, chemical and mineralogical properties of Vertisols but lack in slickensides. Detailed physical, chemical and micromorphological data indicate the presence of argillic horizon characterized by impure clay pedofeatures in voids and poorly separated plasma. The study proves a fact that clay illuviation is more important pedogenetic process than pedoturbation. A time of a century is not adequate for the formation of slickensides that are hitherto considered to be a rapid pedogenetic process for structure formation in Vertisols. The study suggests a highly probable pathway for the formation of Vertisols with time from Vertic Alfisols in sub-humid and semi-arid climatic conditions of central India.

Authenticated and persistent skip graph

Proceedings of the International Conference on Advances in Computing, Communications and Informatics, 2012

Cloud computing has evolved as a popular computing environment. In data centric applications host... more Cloud computing has evolved as a popular computing environment. In data centric applications hosted on the cloud, data is accessed and updated in a purely distributed manner. The distributed data structures used for dynamic storage of the data for such applications require two fundamental qualities, authentication and persistence, which are not completely met by existing distributed data structures. Authentication is

Inflammatory bowel disease: dysfunction of GALT and gut bacterial flora (II)

The Surgeon, 2003

The precise cause(s) of Crohn's disease and ulcerative colitis are unknown. From animal m... more The precise cause(s) of Crohn's disease and ulcerative colitis are unknown. From animal models and human studies it is well established that gut bacterial flora are essential for inducing the bowel inflammation. Animal models, when kept in a germ-free environment, do not develop colitis until the gut flora is reconstituted. It is not clear whether the bacterial antigens (Ags) from the normal flora or some other pathogenic bacterial Ags induce/propagate the inflammatory process in inflammatory bowel disease (IBD). Despite extensive research it has not been possible to identify any specific bacteria or virus as a credible cause of IBD. Recent understanding of quorum sensing molecules (QSMs) secreted by bacteria helps to explain the community behaviour in bacterial species. When QSMs reach a defined concentration, they activate bacterial proliferation and a number of virulence genes. Also, these molecules have been found to modulate the immune system to the advantage of the gut bacteria. They have not been well studied, however, in the gut. Inappropriate secretion of QSMs may alter the gut-associated lymphoid tissue (GALT) and, thereby, deregulate the immune tolerance normally present. Usefulness of probiotics and their immune modulating effects are being increasingly reported. Probiotics are also being used in the treatment of IBD. The interaction between the epithelial cells and the gut flora is very important as this is the first line of contact; this interaction may determine the induction of tolerance and mucosal integrity or immune activity, tissue inflammation and abnormal permeability. The latter is documented in patients with IBD and their healthy relatives. This may be an important factor in disruption of mucosal integrity and GALT dysfunction.

Soil Research, 2005

In this study, we report the chemical and mineralogical characteristics of 4 benchmark Ultisols o... more In this study, we report the chemical and mineralogical characteristics of 4 benchmark Ultisols of Kerala to elucidate their genesis and taxonomy. The taxonomic rationale of the mineralogy class of Ultisols and other highly weathered soils on the basis of the contemporary pedogenesis is also explained. The Ultisols of Kerala have low pH, low cation exchange capacity, low effective cation exchange capacity and base saturation, with dominant presence of 1 : 1 clays and gibbsite. Presence of gibbsite along with 2 : 1 minerals discounts the hypothesis of anti-gibbsite effect. Since the kaolins are interstratified with hydroxy-interlayered vermiculites (HIV), the formation of gibbsite from kaolinite is not tenable. Thus, gibbsite is formed from primary minerals in an earlier alkaline pedo-environment. Therefore, the presence of gibbsite does not necessarily indicate an advanced stage of weathering. On the basis of a dominant amount of gibbsite, a mineralogy class such as allitic or gibbs...

Pharmacological modulation of brain activity in a preclinical model of osteoarthritis

NeuroImage, 2013

The earliest stages of osteoarthritis are characterized by peripheral pathology; however, during ... more The earliest stages of osteoarthritis are characterized by peripheral pathology; however, during disease progression chronic pain emerges-a major symptom of osteoarthritis linked to neuroplasticity. Recent clinical imaging studies involving chronic pain patients, including osteoarthritis patients, have demonstrated that functional properties of the brain are altered, and these functional changes are correlated with subjective behavioral pain measures. Currently, preclinical osteoarthritis studies have not assessed if functional properties of supraspinal pain circuitry are altered, and if these functional properties can be modulated by pharmacological therapy either by direct or indirect action on brain systems. In the current study, functional connectivity was first assessed in order to characterize the functional neuroplasticity occurring in the rodent medial meniscus tear (MMT) model of osteoarthritis-a surgical model of osteoarthritis possessing peripheral joint trauma and a hypersensitive pain state. In addition to knee joint trauma at week 3 post-MMT surgery, we observed that supraspinal networks have increased functional connectivity relative to sham animals. Importantly, we observed that early and sustained treatment with a novel, peripherally acting broad-spectrum matrix metalloproteinase (MMP) inhibitor (MMPi) significantly attenuates knee joint trauma (cartilage degradation) as well as supraspinal functional connectivity increases in MMT animals. At week 5 post-MMT surgery, the acute pharmacodynamic effects of celecoxib (selective cyclooxygenase-2 inhibitor) on brain function were evaluated using pharmacological magnetic resonance imaging (phMRI) and functional connectivity analysis. Celecoxib was chosen as a comparator, given its clinical efficacy for alleviating pain in osteoarthritis patients and its peripheral and central pharmacological action. Relative to the vehicle condition, acute celecoxib treatment in MMT animals yielded decreased phMRI infusion responses and decreased functional connectivity, the latter observation being similar to what was detected following chronic MMPi treatment. These findings demonstrate that an assessment of brain function may provide an objective means by which to further evaluate the pathology of an osteoarthritis state as well as measure the pharmacodynamic effects of therapies with peripheral or peripheral and central pharmacological action.

Journal of Mathematical Analysis and Applications, 1989

Effect of Carbon Nanotube Dispersion on Mechanical Properties of Aluminum-Silicon Alloy Matrix Composites

Journal of Materials Engineering and Performance, 2013

ABSTRACT This study has been carried out to reinforce the commonly believed fact that the dispers... more ABSTRACT This study has been carried out to reinforce the commonly believed fact that the dispersion of carbon nanotubes in a composite has a profound effect on the properties of the composite. In this study, ball milling was carried out using two different parameters to obtain distinctly different degrees of dispersion of carbon nanotubes (4 wt.%) in Al-9 wt.% Si powders. Composite disks, 80 mm in diameter, having good and bad dispersions of carbon nanotubes were obtained by hot pressing. Optical micrographs and Raman spectroscopy images showed the presence of larger carbon nanotube clusters in the bad dispersion sample. Transmission electron microscopy images confirmed the presence of large clusters in the bad dispersion sample, while the good dispersion sample showed individual carbon nanotubes in the Al matrix. Nanoindentation results indicated a 41% increase in the hardness and a 27% increase in the elastic-to-plastic work ratio, while compression tests indicated a 185% increase in compression yield strength and a 109% increase in fracture strength with improvement in carbon nanotube’s dispersion.

International Journal of Engineering Science, 1977

Ahakaet-Using the characteristic coordinate system, a unifi$ analysis has been carrkd out for the... more Ahakaet-Using the characteristic coordinate system, a unifi$ analysis has been carrkd out for the decay of plane, cylindricaI and spherical weak waves in a ga+parGck system. A general decay law has been presented for a system undergoing an arbitrary number of relaxation processes. For each geometry of the weak wave considered, the decay term exhibits a simpk additive character and the ratio of decay factors for a non-steady and steady weak wave is independent of the nonzquiltMum effects.

Flow and heat transfer in the boundary layer due to rotating spheres, spheroids and paraboloids

International Journal of Engineering Science, 1986

Abstract The effects of rotating spheres, spheroids and paraboloids on the flow and heat transfer... more Abstract The effects of rotating spheres, spheroids and paraboloids on the flow and heat transfer in the boundary layers have been investigated. The field functions corresponding to the polynomial profiles have been determined numerically. The nonlinear boundary value ...