Purpose The purpose of this paper is to present a novel model on the unsteady MHD flow of heat transfer in carbon nanotubes with variable viscosity over a shrinking surface. Design/methodology/approach The temperature-dependent viscosity makes the proposed model non-linear and coupled. Consequently, the resulting non-linear partial differential equations are first reformed into set of ordinary differential equations through appropriate transformations and boundary layer approximation and are then solved numerically by the Keller box method. Findings Graphical and numerical results are executed keeping temperature-dependent viscosity of nanofluid. It is noted that, for diverse critical points, it is found that at one side of these critical values, multiple solutions exist; on the other side, no solution exists. A comparison is also computed for the special case of existing study. The temperature and pressure profiles are also plotted for various effective parameters. Originality/value The work is original.

Vitex negundo LINN. (syn: V. inesia LAM.) a deciduous shrub belonging to family Verbenaceae which comprises 75 genera and nearly 2500 species, chiefly occurring in Pakistan, India and Ceylon.1,2) Though almost all plant parts are used, the extract from leaves and the roots is the most important in the field of medicine and is sold as drugs.3) The leaf extract is used in Ayurvedic and Unani system of medicine. 4)The decoction of leaves is considered as tonic, vermifuge and is given along with long pepper in caterrhal fever. 3)Water extract of mature fresh leaves exhibited anti-inflammatory, analgesic and antihistamine properties.5) The methanolic root extract possessed potent snake venom neutralizing capacity. The plant extract significantly antagonized the Vipera russellii and Naja kaouthia venom-induced lethal activity both in in vitro and in vivo studies. V. russellii venom-induced haemorrhage, coagulant, defibrinogenating and inflammatory activity was neutralized by the plant extract.6) The acetone extract of Vitex negundo was found to possess insecticidal, ovicidal, feeding deterrence, growth inhibition and morphogenetic effects against various life stages of a noxious lepidoteron insect-pest, Spilarctia obliqua WALKER. 7)Literature survey of V. negundo revealed the presence of volatile oil, 8) triterpenes, 9) diterpenes, 10) sesquiterpenes, 11) lignan, 12) flavonoids, 13) flavone glycosides, 14) iridoid glycosides, [15][16][17] and stilbene derivative. 18) In the present investigation, a crude methanolic extract of the roots of Vitex negundo showed strong cytotoxicity in brine shrimp lethality test. Further biological screening of various fractions revealed significant inhibitory activity in the CHCl 3 extract against lipoxygenase and acetylcholinestrase enzymes. This prompted us to carry out isolation studies on the CHCl 3 soluble fraction of this plant. Herein we report the isolation and structure elucidation of two new lignans, 1 and 2 along with four known lignans which could be identified as (ϩ)-diasyringaresinol (3), (ϩ)-lyoniresinol (4), vitrofolal E (5) and vitrofolal F (6) through comparison of their physical and spectral data with those reported in literatures. 19-21) Results and DiscussionCompounds 1-6 were isolated from the CHCl 3 soluble fraction of the methanolic extract of ground and shade dried roots. Negundin A was found to have the molecular ion peak in HR-MS at m/z 352.0911 corresponding to the molecular formula C 20 H 16 , and 1241 cm Ϫ1 characteristic of phenolic groups, the carbonyl of g-lactone and the methoxyl groups, respectively. The 1 H-NMR spectrum showed two methoxyl groups at d 3.92 and 3.72 along with three aromatic signals at d 8.66, 7.72 and 7.62, respectively. The three other aromatic protons showed ABX type substitution pattern forming a doublet at d 7.36 (Jϭ7.9 Hz), a doublet at d 7.10 (Jϭ1.5 Hz) and a doublet of doublets at d 7.06 (Jϭ7.9, 1.5 Hz). In addition, a methylene singlet was observed at d 4.44. The 13 C-NMR and DEPT experiments displayed the signals for six met...

Emodinol, a new oleane type triterpene, has been isolated from the chloroform soluble fraction of Paeonia emodi. The structure 1beta, 3beta, 23-trihydroxyolean-12-en-28-oic acid 1 has been assigned on the basis of spectral studies including 2D NMR. It showed significant beta-glucuronidase inhibitory activity. In addition benzoic acid and 3-hydroxybenzoic acid have also been reported for the first time from this species.

Interface-resolved direct numerical simulations are performed to examine the combined effects of soluble surfactant and viscoelasticity on the structure of a bubbly turbulent channel flow. The incompressible flow equations are solved fully coupled with the FENE-P viscoelastic model and the equations governing interfacial and bulk surfactant concentrations. The latter coupling is achieved through a non-linear equation of state which relates the surface tension to the surfactant concentration at the interface. The two-fluid Navier-Stokes equations are solved using a front-tracking method, augmented with a very efficient FFT-based pressure projection method that allows for massively parallel simulations of turbulent flows. It is found that, for the surfactantfree case, bubbles move toward the wall due to inertial lift force, resulting in formation of wall layers and a significant decrease in the flow rate. Conversely, a high-enough concentration of surfactant changes the direction of lateral