The computational model of nanofluid considering heat transfer and entropy generation across a curved and flat surface.

The entropy generation analysis for the nanofluid flowing over a stretching/shrinking curved region is performed in the existence of the cross-diffusion effect. The surface is also subjected to second-order velocity slip under the effect of mixed convection. The Joule heating that contributes significantly to the heat transfer properties of nanofluid is incorporated along with the heat source/sink. Furthermore, the flow is assumed to be governed by an exterior magnetic field that aids in gaining control over the flow speed. With these frameworks, the mathematical model that describes the flow with such characteristics and assumptions is framed using partial differential equations (PDEs). The bvp4c solver is used to numerically solve the system of non-linear ordinary differential equations (ODEs) that are created from these equations. The solutions of obtained through this technique are verified with the available articles and the comparison is tabulated. Meanwhile, the interpretation of the results of this study is delivered through graphs. The findings showed that the Bejan number was decreased by increasing Brinkman number values whereas it enhanced the entropy generation. Also, as the curvature parameter goes higher, the speed of the nanofluid flow diminishes. Furthermore, the increase in the Soret and Dufour effects have enhanced the thermal conduction and the mass transfer of the nanofluid.

Numerical simulation and mathematical modeling for heat and mass transfer in MHD stagnation point flow of nanofluid consisting of entropy generation.

The primary goal of this article is to explore the radiative stagnation point flow of nanofluid with cross-diffusion and entropy generation across a permeable curved surface. Moreover, the activation energy, Joule heating, slip condition, and viscous dissipation effects have been considered in order to achieve realistic results. The governing equations associated with the modeling of this research have been transformed into ordinary differential equations by utilizing appropriate transformation variable. The resulting system of equations was solved numerically by using Bvp4c built-in package in MATLAB. The impact of involved parameters have been graphically examined for the diverse features of velocity, temperature, and concentration profiles. Throughout the analysis, the volume fraction is assumed to be less than [Formula: see text] while the Prandtl number is set to be [Formula: see text]. In addition, the entropy generation, friction drag, Nusselt, and Sherwood numbers have been plotted for describing the diverse physical aspects of the underlying phenomena. The major outcomes reveal that the curvature parameter reduces the velocity profile and skin friction coefficient whereas the magnetic parameter, temperature difference parameter, and radiation parameter intensify the entropy generation.

Transport properties of two-dimensional dissipative flow of hybrid nanofluid with Joule heating and thermal radiation.

The important feature of the current work is to consider the pressure variation, heat transport, and friction drag in the hydromagnetic radiative two-dimensional flow of a hybrid nanofluid depending on the viscous dissipation and Joule heating across a curved surface. The curved surface has been considered with the binary heating process called as prescribed heat flux and surface temperature. The basic partial differential equation (PDEs) has been converted into the non-dimensional ordinary differential equations (ODEs) by applying some specified dimensionless transformations. The bvp4c built-in package in MATLAB has been considered to find the numerical solution of the consequential equations. The graphical results have been plotted in terms of pressure, friction drag, velocity, temperature, and heat transport. Several important results have also been plotted for the plan level surface [Formula: see text]The condition of [Formula: see text]. It is found that the heat transport rate respectively reduces and enhances with the enhancement of radiation parameter and Hartmann number as well as the friction drag is enhancing with the high-volume fraction of nanoparticles and Hartmann number. Moreover, enhancing curvature parameter, enhances the friction drag and declines the heat transport rate. The current work renders uncountable applications in several engineering and industrial systems like electronic bulbs, electric ovens, geysers, soil pollution, electric kettle, fibrous insulation, etc. Moreover, the heating as well as the cooling systems of electrical, digital, and industrial instruments, are controlled by the heat transport in fluids. Thus, it is important to use such flows in these types of instruments.

Comparative study on heat transfer and friction drag in the flow of various hybrid nanofluids effected by aligned magnetic field and nonlinear radiation.

The key purpose of the existing article is to discuss the effects of various hybrid nanofluids and a simple nanofluid over the heat transfer and friction drags along a stretched surface. The various kinds of hybrid nanofluids and a simple nanofluid together with the effects of aligned magnetic field, nonlinear radiation and suction have been taken into consideration. These hybrid nanofluids are prepared by suspending a couple of distinct nanoparticles [Formula: see text] and [Formula: see text] into the base fluids [Formula: see text] and [Formula: see text]. The comparison of various graphical results of skin friction coefficient, rate of heat transfer, velocity and temperature for two different hybrid nanofluids [Formula: see text]/[Formula: see text], [Formula: see text]/[Formula: see text] and a simple nanofluid [Formula: see text]/[Formula: see text] is considered. Moreover, the impact of surface stretching, aligned magnetic field and thermal radiation over the velocity, temperature, skin friction coefficient and local Nusselt number are also considered. The outcomes drawn from this modern research is that the hybrid nanofluid [Formula: see text]/[Formula: see text] is quite effective in cooling and heating in comparison to the other hybrid nanofluids [Formula: see text]/[Formula: see text], [Formula: see text]/[Formula: see text] and a simple nanofluid [Formula: see text]. Based on these findings we could say that the suspension of multiple particles in the composition of two or more base fluids provides a better rate of heat transfer and limits the friction drag.

New natural cholinesterase inhibiting and calcium channel blocking quinoline alkaloids.

During this study, one new coumarin; 7-O-beta-D-glucopyranoside-2H-1-benzopyran-2-one (1) and three quinoline alkaloids; 3-hydroxy, 2, 2, 6-trimethyl-3, 4, 5, 6-tetrahydro-2H-pyrano[3,2-c] quinoline 5-one (2), ribalinine (3) and methyl isoplatydesmine (4) were isolated from the aerial parts of Skimmia laureola and their structures established by spectroscopic studies. Compounds 2-4 were found to be linear mixed type inhibitors of acetylcholinesterase (K(i) = 110.0, 30.0 and 30.0 microM, respectively). Compounds 2 and 3 were also found to be linear mixed type inhibitors of butyrylcholinesterase, while compound 4 was a noncompetitive inhibitor of the enzyme (K(i) = 90.0, 70.0 and 19.0 microM, respectively). The inhibition of acetyl- and butyryl-cholinesterase enzymes persists as the most promising therapeutic strategy for activating the impaired cholinergic functions in Alzheimer's disease and related dementias. Compound 4 also showed dose-dependent spasmolytic activity in the isolated rabbit jejunum intestinal preparation by relaxing the spontaneous (EC50 = 0.1 mg/mL) and K(+)-induced contractions (EC50 = 0.4 mg/mL), suggesting that the spasmolytic effect of compound 4 is mediated through the blockade of voltage-dependent Ca2+ channels.

Kinetics and structure-activity relationship studies on pregnane-type steroidal alkaloids that inhibit cholinesterases.

The mechanism of inhibition of acetylcholinesterase (AChE, EC 3.1.1.7) and butyrylcholinesterase (BChE, EC 3.1.1.8) enzymes by 23 pregnane-type alkaloids isolated from the Sarcococca saligna was investigated. Lineweaver-Burk and Dixon plots and their secondary replots showed that the majority of these compounds, that is 1, 4, 5, 6, 9, 10, 12, 13, 15-19, and 21 were found to be noncompetitive inhibitors of both enzymes. Compounds 8, 20, 22, and 23 were determined to be uncompetitive inhibitors of BChE, while compounds 11 and 14 were found to be uncompetitive and linear mixed inhibitors of AChE, respectively. Ki values were found to be in the range of 2.65-250.0 microM against AChE and 1.63-30.0 microM against BChE. The structure-activity relationship (SAR) studies suggested that the major interaction of the enzyme-inhibitor complexes are due to hydrophobic and cation-pi interactions inside the aromatic gorge of these cholinesterases. The effects of various substituents on the activity of these compounds are also discussed in details.

Salsola pollen as a predominant cause of respiratory allergies in Kuwait.

BACKGROUND: Respiratory allergies are common in Kuwait, and the role of certain allergens has been previously documented. OBJECTIVE: To evaluate the results of skin prick tests to a range of allergens that were considered relevant to the vegetation surveys and aerobiological studies performed in Kuwait. METHOD: New patients attending our center during August 2002 to February 2003 with asthma or allergic rhinitis underwent skin prick tests to a battery of allergens. RESULTS: A total of 451 patients aged 5 to 60 years (mean age, 29.5 years) were tested. Of these patients, 403 (89.4%) had a positive test result to at least one allergen and were considered allergic. A total of 76.7% of the allergic patients had a positive reaction to Salsola pollen, with a mean wheal diameter of 8.25 mm (median, 8 mm). Chenopodium album was positive in 57.6% and Bermuda grass was positive in 38.2% of the allergic cases. Indoor allergens seemed to play a lesser role than pollens: Dermatophagoides pteronyssinus was positive in only 37.5%, and American and German cockroaches were positive in 33.2% and 22.3%, respectively. All the allergens other than Salsola elicited a mean wheal diameter of less than 6.25 mm (median, < or = 6 mm). CONCLUSIONS: Indoor allergens seem to play a lesser role in respiratory allergies in Kuwait. Most allergic patients become sensitized to pollens; the strongest and most frequent reaction is from Salsola pollen. Salsola imbricata is found growing extensively in most areas of the country, flowering mainly in autumn, when the most common pollen is of the Chenopod-Amaranth type and when most patients with seasonal allergic rhinitis become symptomatic.

New pregnane-type steroidal alkaloids from Sarcocca saligna and their cholinesterase inhibitory activity.

Five new steroidal alkaloids, 5,14-dehydro-N(a)-demethylsaracodine [3beta-N(a)-methyl-20S-N(b)-acetyl-N(b)-methylamino-pregn-5,14-diene] (1), 14-dehydro-N(a)-demethylsaracodine [3beta-N(a)-methyl-20S-N(b)-acetyl-N(b)-methylamino-5alpha-pregn-14-ene] (2), 16-dehydrosarcorine [(20S)-20-(N,N-dimethylamino)-3beta-(N(a)-acetylamido)-5alpha-pregn-16-ene] (3), 2,3-dehydrosarsalignone [(20S)-20-(N,N-dimethylamino)-3beta-(tigloylamino)-pregn-2,5-diene-4-one] (4), and 14,15-dehydrosarcovagine-D [(20S)-20-(N,N-dimethylamino)-3beta-(tigloylamino)-5alpha-pregn-2,14-diene-4-one] (5), were isolated from the ethanolic extract of Sarcococca saligna, along with two known bases, sarcovagenine-C (6) and salignarine-C (7). Their structures were elucidated on the basis of spectroscopic methods. All seven compounds were found to possess cholinesterase inhibitory potential in a concentration-dependent manner with the IC50 values ranging from 12.5 to 200 microM against acetylcholinesterase and from 1.25 to 32.2 microM against butyrylcholinesterase.

New steroidal alkaloids from Sarcococca saligna.

Two new steroidal alkaloids, salonine-A [(20S)-20-(N,N-dimethylamino)-3beta-(tigloylamino)-5alpha-pregn-14-en-2beta,4beta-diol] (1), and salonine-B [(20S)-20-(N,N-dimethylamino)-3beta-methoxy-pregn-5,16-diene] (2), were isolated from the MeOH extract of Sarcococca saligna, along with a known base, alkaloid-C (3). Their structures were elucidated on the basis of spectroscopic methods. All three compounds were found to be cholinesterase inhibitors.

Triterpene and coumarins from Skimmia laureola.

In the course of our studies on the chemical constituents of the leaves of Skimmia laureola, a new triterpene O-methyl cyclolaudenol (1) and a new coumarin, (+)-7-methoxy-6-(2'R-methoxy-3'-hydroxy-3'-methyl butyl) coumarin (2) were isolated. In addition five known coumarins, isogospherol (3), heraclenol (4), 5,8-dimethoxy coumarin-2H-1-benzopyran-2-one (5), 7-methoxy-6[2'-oxo-3'-methyl butyl] coumarin (6), and (+)-ulopterol (7) were also isolated for the first time from this plant. The structures were identified by spectroscopic studies and the stereochemistry at C-2' in compounds 3 and 4 were established by Horeau's procedure.