Effect of Neurosteroid Modulation on Global Ischaemia-Reperfusion-Induced Cerebral Injury in Mice

Grewal, Amarjot Kaur,Jaggi, Amteshwar Singh,Rana, Avtar Chand,Singh, Nirmal The Korean Society of Pharmacology 2013 The Korean Journal of Physiology & Pharmacology Vol.17 No.6

The present study was designed to investigate the putative effect of neurosteroid modulation on global ischaemia-reperfusion-induced cerebral injury in mice. Bilateral carotid artery occlusion followed by reperfusion, produced a significant rise in cerebral infarct size along with impairment of grip strength and motor coordination in Swiss albino mice. Administration of carbamazepine (16 mg/kg, i.p.) before global cerebral ischaemia significantly attenuated cerebral infarct size and improved the motor performance. However, administration of indomethacin (100 mg/kg, i.p.) attenuated the neuroprotective effect of carbamazepine. Mexiletine (50 mg/kg, i.p.) did not produce significant neuroprotective effect. It may be concluded that the neuroprotective effect of carbamazepine may be due to increase in synthesis of neurosteroids perhaps by activating enzyme ($3{\alpha}$ HSD) as indomethacin attenuated the neuroprotective effect of carbamazepine. The sodium channel blocking effect of carbamazepine may not be involved in neuroprotection as mexiletine, a sodium channel blocker, did not produce significant neuroprotective effect.

Interplay between erodent concentration and impingement angle for erosion in dilute water–sand flows

Grewal, H S,Singh, H,Yoon, Eui-Sung Elsevier 2015 Wear: An international journal on the science and Vol.332 No.-

<P><B>Abstract</B></P> <P>Slurry erosion is a complex process with number of interacting variables (operating and material parameters). We study the interaction between erodent concentration and impingement angle using experimental and computational fluid dynamics (CFD) techniques. Experiments were performed using a high velocity slurry erosion test rig at a constant velocity with dilute slurries of water and sand particles. Concentration of sand in water was varied from 0.01wt% (100ppm) to 0.5wt% (5000ppm) at three sample orientations (30°, 60° and 90°). Six different targets, three bulk materials (aluminum, cast iron, and stainless steel) and three thermal sprayed coatings (Ni+20, 40, and 60wt% of Al<SUB>2</SUB>O<SUB>3</SUB>) were used for slurry erosion tests. Experimental results showed a significant interaction between erodent concentration and impingement angle. The concentration variation showed larger influence on erosion rate for sample held normal to the slurry jet compared to glancing angle. The degree of interaction was different for different materials. CFD simulations showed higher particle-to-particle interactions for sample at glancing angle compared to that at normal angle. This probably explains the low contribution of concentration variation at glancing angle compared to the normal angle. Further, the effect of concentration on erosion rates was also influenced by the restitution coefficient (function of material and impact parameters). For a high restitution coefficient materials, the change in slurry concentration showed minimum effect on erosion rate compared with low restitution coefficient materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Both Erodent concentration and impingement angle are highly interrelated. </LI> <LI> In slurry erosion, concentration effect is more evident at normal sample orientation. </LI> <LI> Flow field, particle and fluid properties influence concentration effect. </LI> <LI> High restitution coefficient reduces the concentration effect. </LI> </UL> </P>

The role of bio-inspired hierarchical structures in wetting

Grewal, H S,Cho, Il-Joo,Yoon, Eui-Sung IOP Publishing 2015 Bioinspiration & biomimetics Vol.10 No.2

<P>Superhydrophobicity facilitates the development of self-cleaning, anti-biofouling, and anti-corrosion surfaces. The leaves of the lotus (Nelumbo nucifera) and taro (Colocasia esculenta) plants are well known for their self-cleaning properties. A hierarchical structure comprising papillae epidermal cells superimposed with epicuticular wax crystalloids of varying shapes, sizes, and orientations is an important aspect of the surface of these plant leaves. We fabricated two types of hierarchical structures biomimicking the surface topography of the lotus leaf. The hierarchical patterns successfully demonstrated the superhydrophobic state in comparison with nano and micro patterns. We used the finite element method (FEM) to simulate and understand the wetting process. The FEM simulations showed good correlation with the experimental results. FEM was helpful in understanding the wetting of enormously complex biological surfaces with relative ease, and it qualifies as a potential tool for designing superhydrophobic surfaces. Using the FEM framework, we further designed surfaces to optimize the order of the shapes in hierarchy. The results showed that the superhydrophobic surface with the lowest wetted area was obtained by placing shapes with smaller geometric angles at the top of the hierarchy. This arrangement of shapes provides the optimum combination of superhydrophobicity and surface integrity. This observation explains why the hierarchical structure of many superhydrophobic leaves follows this order. We also investigated the complex hierarchical structure of Salvinia minima. Owing to its remarkable ability to entrap air and pin the contact line, it exhibits superhydrophobicity along with the much-required Cassie state. These properties of Salvinia minima make it an excellent candidate for developing omniphobic surfaces.</P>

Effect of topography on the wetting of nanoscale patterns: experimental and modeling studies.

Grewal, H S,Cho, Il-Joo,Oh, Jae-Eung,Yoon, Eui-Sung RSC Pub 2014 Nanoscale Vol.6 No.24

<P>We investigated the influence of nanoscale pattern shapes, contours, and surface chemistry on wetting behavior using a combination of experimental and modeling approaches. Among the investigated topographical shapes, re-entrant geometries showed superior performance owing to their ability to restrain the liquid-air interface in accordance with Gibbs criteria. The wetting state is also controlled by the surface texture in addition to the surface chemistry. Topographies with smaller intrinsic angles are better able to support the liquid droplet. Based on these observations, two geometrical relationships for designing superhydrophobic patterns exhibiting the Cassie-Baxter state are proposed. A detailed analysis of the simulation results showed the presence of viscous forces during the initial transient phase of the droplet interaction with the solid surface even at negligible normal velocity, which was verified experimentally using a high-speed imaging technique. During this transient phase, for a polystyrene surface, the liquid front was observed to be moving with a radial velocity of 0.4 m s(-1), which gradually decreased to almost zero after 35 ms. We observed that the viscous energy dissipation density is influenced by the surface material and topography and the wetting state. The viscous energy dissipation density is minimal in the case of the Cassie-Baxter state, while it becomes quite significant for the Wenzel state. The viscous effects are reduced for topographies with smooth geometries and surfaces with high slip length.</P>

Nanotribological behavior of bioinspired textured surfaces with directional characteristics

Grewal, H.S.,Pendyala, Prashant,Shin, Hyogeun,Cho, Il-Joo,Yoon, Eui-Sung Elsevier 2017 Wear: An international journal on the science and Vol.384 No.-

<P>Friction and adhesion becomes extremely important at nano and micro length scales, modulating the durability of several nano/micro electromechanical systems (NEMS/MEMS). Bio-mimicking the surface texture of different living organisms has helped improve the tribological performance of many such systems. In this study, we examined the friction and wetting behaviour of textured surfaces derived by mimicking the surface morphology of butterfly wing. Three different derivatives of mimicked structure with similar solid/air fraction but different contact aspect ratios were fabricated on Si wafer using photolithography and deep reactive ion-etching techniques. The textured surfaces patterns were sub-sequently coated with polytetrafluoroethylene (PTFE), diamond-like carbon (DLC), and fluorine incorporated diamond-like carbon (F-DLC) using plasma-enhanced chemical vapor deposition (PECVD) technique. Atomic force microscope was used to investigate the friction behaviour of the coated and un-coated samples at different applied normal load. Wetting behaviour of the textured and control surfaces was measured using sessile-drop method. Results showed that both wettability and friction were significantly influenced by the shape, orientation and surface chemistry of the textured structure. The PTFE and F-DLC coatings helped reduce the friction compared to Si control surface. The developed patterned displayed dual character with wetting and friction being function of the texture shape. The increase in aspect ratio of textured geometry enhanced directional wettability and friction. The wetting was controlled by the contact-line pinning phenomenon modulated by the texture geometry. The friction behaviour of the textured geometry varied in direct correlation with the contact area. Further, the edge-effect showed prominent influence leading to an increase in friction force in lateral direction. The effect of surface chemistry and texture geometry is explained on basis of intermolecular forces and contact mechanics. The directional friction and wetting characteristics of the developed surface would be of potential use for transport applications in different systems. (C) 2017 Elsevier B.V. All rights reserved.</P>

Effect of Cotton Stems Addition on the Chemical Composition and In Sacco Dry Matter Digestibility of Pearl Millet Silage

Grewal, R.S.,Saijpaul, S.,Kaushal, S. Asian Australasian Association of Animal Productio 2003 Animal Bioscience Vol.16 No.12

The possibility of using cotton stems as a roughage source in animal feeding was explored. Ground cotton stems (T2 and T3) or stems treated with 0.5% urea (T4 and T5) were ensiled with pearl millet green fodder in double lined plastic bags of 3 kg capacity for 50 days. Formic acid (0.4% v/v) was sprayed on T3 and T5 silages. The treatments were compared with pearl millet silage alone (T1) which constituted the control. All the bags were placed in the silo pit of pearl millet silage. Results indicated that urea treatment of cotton stems increased and formic acid application reduced dry matter loss of the silages. Inclusion of cotton stems in the silage significantly (p<0.05) increased CF, ADF, cellulose and ADL due to its higher cell wall content. The hemicellulose was significantly lower in T3 (16.7%) and T5 (22.52%) as compared to T2 (23.45%) and T4 (24.6%) due to formic acid application. Ammoniation significantly increased NH3-N content in T4 (0.202%) and formic acid controlled NH3-N level in T5 (0.107%).The in sacco dry matter digestibility was significantly higher (p<0.05) in formic acid preserved silages T3 and T5 (47.73 and 47.93%) as compared to silages without formic acid (44.94 and 41.22 %) in T2 and T4 respectively, but lower than T1 (54.39%). It is concluded that cotton stems can be ensiled with pearl millet fodder in 1:4 ratio with or without urea treatment. Formic acid application further increases the silage quality.

Nanotribological and wetting performance of hierarchical patterns

Grewal, H. S.,Piao, Shuxue,Cho, Il-Joo,Jhang, Kyung-Young,Yoon, Eui-Sung The Royal Society of Chemistry 2016 SOFT MATTER Vol.12 No.3

<P>Surface modification is a promising method to solve the tribological problems in microsystems. To modify the surface, we fabricated hierarchical patterns with different pitches of nano-scale features and different surface chemistries. Micro-and nano-patterns with similar geometrical configurations were also fabricated for comparison. The nano-tribological behavior of the patterns was investigated using an atomic force microscope at different relative humidity levels (5% to 80%) and applied normal loads (40 nN to 120 nN) under a constant sliding velocity. The results showed significant enhancement in the de-wetting and tribological performance of the hierarchical patterns compared with those of flat and micro-and nano-patterned surfaces. The PTFE-coated hierarchical patterns showed similar dynamic contact angles (advancing and receding) to those of the real lotus leaf. The influence of relative humidity on adhesion and friction behavior was found to be significant for all the tested surfaces. The tribological performance was improved as the pitch of the nano-scale geometry of the hierarchical pattern increased, even though the wetting property was not influenced significantly. A model was proposed based on the role of intermolecular force to explain the effect of the pitch of the hierarchical patterns on the adhesion and friction behavior. According to the model based on the molecular force, the contact between a ball and the patterned surface was a multi-asperity contact, contrary to the single-asperity contact predicted by the Johnson-Kendall-Roberts (JKR) and Maugis-Dugdale (MD) models. The strong intermolecular forces, which are activated in the confined spaces between the adjacent nano-pillars and the ball, contributed to the contact area and hence the adhesion and friction forces.</P>

Preserving Culture, Producing Culture : UNESCO’s Convention on the Protection and Promotion of the Diversity of Cultural Expression

Grewal, Inderpal Ewha Institute for the Humanities, Ewha Womans Uni 2009 탈경계인문학 Vol.1 No.-

The 2005 UNESCO Convention on the Protection and Promotion of the Diversity of Cultural Expression is an important project for rescuing cultural practices that are believed to be under attack by transnational corporations and a predatory globalization. However, the process of saving these practices and expressions by means of the UNESCO and its organizations will inevitably alter these practices and expressions, changing them from one cultural form to another that is marked by its transnational rescue.

The Changing Shape of Port Authorities in Australia

Devinder Grewal 한국물류협회 2006 물류혁신 컨퍼런스 Vol.14 No.2

Performance Evaluation of WiMAX Network with AMC and MCCDMA for Mobile Environments

Vinit Grewal,Ajay K. Sharma 보안공학연구지원센터 2012 International Journal of Multimedia and Ubiquitous Vol.7 No.4