Isolation and Crystal Structure of 6α,7α-Epoxy-5α,17α,27-trihydroxy-1-oxo-22R-witha-2,24-dienolide monohydrate-A Withasteroid from Withania somnifera Leaves

Abstract  

(5R,6S,7S,8S,9S,10R,13S,14S,17S,20R,22R)-6α,7α-epoxy-5α,17α,27-trihydroxy-1-oxo-22R-witha-2,24-dienolide has been isolated from Withania somnifera leaves. Three-dimensional X-ray intensity data were collected at 293 K on Bruker CCD area-detector diffractometer equipped with graphite-monochromated MoKα radiation (λ = 0.71073 ?). The compound crystallizes in monoclinic space group P21 with unit cell parameters: a = 6.4540(2), b = 11.3656(4), c = 17.4982(5) ?, β = 90.730 ^o(2), Z = 2. The crystal structure was refined to a final R-value of 0.0419 for 6122 observed reflections. One water solvent molecule was observed. All the rings of the steroid skeleton are trans connected. Rings A and B exists in a half-chair conformation, ring C a chair, and five membered ring D is intermediate between half-chair and envelope. The δ-lactone ring E adopts a distorted sofa conformation. The characteristic pattern observed in the packing diagram is the appearance of twisted chains of molecules. The packing of the molecules in the crystal is stabilized by intra- and intermolecular O–H···O and C–H···O interactions.     

Revisiting the shelf life constrained multi-product manufacturing problem

A multi-product manufacturing problem generally consists of the total cost minimization. In case where the shelf life constraint is imposed, various options to deal with the situation are widely discussed in the literature. These options include a reduction in the production rate and cycle time separately, and the simultaneous reduction of production rate and cycle time. When the production rate is decreased, the unit manufacturing cost increases and because of this the inventory holding costs need modification. In the existing literature, this has been ignored in the computation of cost and therefore a revisit to the problem has been justified. The present paper modifies the holding cost and this problem has been reformulated for the basic case. This has also been extended for an inclusion of shortages that are backordered completely or partially.     

Higher-Order Duality in Nondifferentiable Minimax Programming with Generalized Type I Functions

A unified higher-order dual for a nondifferentiable minimax programming problem is formulated. Weak, strong and strict converse duality theorems are discussed involving generalized higher-order (F,α,ρ,d)-Type I functions. The research of second author was supported by the Department of Atomic Energy, Government of India, under the NBHM Post Doctoral Fellowship Program 40/9/2005-R&D II/2398.     

Some variants of Hansen-Patrick method with third and fourth order convergence

Based on Hansen-Patrick method [E. Hansen, M. Patrick, A family of root finding methods, Numer. Math. 27 (1977) 257-269], we derive a two-parameter family of methods for solving nonlinear equations. All the methods of the family have third-order convergence, except one which has the fourth-order convergence. In terms of computational cost, all these methods require evaluations of one function, one first derivative and one second derivative per iteration. Numerical examples are given to support that the methods thus obtained are competitive with other robust methods of similar kind. Moreover, it is shown by way of illustration that the present methods, particularly fourth-order method, are very effective in high precision computations.     

Modeling the survival of a resource-dependent population: Effects of toxicants (pollutants) emitted from external sources as well as formed by its precursors

In this paper, a nonlinear mathematical model is proposed and analyzed to study the survival of a resource-dependent population. It is assumed that this population and its resource are affected simultaneously by a toxicant (pollutant) emitted into the environment from external sources as well as formed by precursors of this population. It is shown that as the cumulative rates of emission and formation of the toxicant into the environment increase, the densities of population and its resource settle down to lower equilibria than their initial carrying capacities, and their magnitudes decrease as rates of emission and formation of the toxicant increase. On comparing different cases, it is noted that when population is not affected directly by the toxicant but only its resource is affected, the possibility of its survival is greater than the case when both are affected simultaneously. But for large emission rate of toxicant, the affected resource may be driven to extinction under certain conditions and the population which wholly depends on it may not survive for long even if it is not affected directly by the toxicant.     

Near-resonant vibration-to-vibration energy transfer in the NO+-N2 collisions

First principles model calculations of the vibration-to-vibration (VV) energy transfer (ET) processes NO(+)(nu=1)+N(2)(nu=n-1)-->NO(+)(nu=0)+N(2)(nu=n)+(28.64n-14.67) cm(-1) and NO(+)(nu=n)+N(2)(nu=0)-->NO(+)(nu=n-1)+N(2)(nu=1)+(32.52(n-1)+13.97) cm(-1) for n=1-3 in the 300-1000 K temperature range are performed. The VV ET probability is computed for three mechanisms: (1) The charge on NO(+) acting on the average polarizability of N(2) induces a dipole moment in N(2) which then interacts with the permanent dipole moment of NO(+) to mediate the energy transfer. (2) The charge on NO(+) acting on the anisotropic polarizability of N(2) induces a dipole moment in N(2) which then interacts with the permanent dipole moment of NO(+) to mediate the energy transfer. (3) The dipole moment of NO(+) interacts with the quadrupole moment of N(2) to mediate the energy transfer. Because the probability amplitudes of the second and third mechanisms add coherently the ET probability for these two mechanisms is given as a single number. The probability of energy transfer per collision is in the 5 x 10(-3) range. The results of this calculation are compared with the available experimental data. This calculation should help quantify the role of NO(+) in the energy budget of the upper atmosphere.     

Arraying of intact liposomes into chemically functionalized microwells

Here, we describe a protocol to bind individual, intact phospholipid bilayer liposomes, which are on the order of 1 microm in diameter, in microwells etched in a regular array on a silicon oxide substrate. The diameter of the wells is on the order of the liposome diameter, so only one liposome is located in each well. The background of the silicon oxide surface is functionalized with a PEG oligomer using the contact printing of a PEG silane to present a surface that resists the adsorption of proteins, lipid material, and liposomes. The interiors of the wells are functionalized with an aminosilane to facilitate the conjugation of biotin, which is then bound to Neutravidin. The avidin-coated well interiors bind the liposomes whose surfaces contain biotinylated lipids. The specific binding of the liposomes to the surface using the biotin-avidin linkage, together with the resistant nature of the background and the physical confinement of the wells, allows the liposomes to remain intact and to not unravel, rupture, and fuse onto the surface. We demonstrate this intact arraying using confocal laser scanning microscopy of fluorophores specifically tagging the microwells, the lipid bilayer, and the aqueous interior of the liposome.     

Hydroxyapatite coating on stainless steel pre-coated with bovine serum albumin at ambient conditions

A biomimetic process for coating of nanosized hydroxyapatite on stainless steel, which capitalises the dual nature of the protein bovine serum albumin in both metal binding and a strong affinity for calcium ions, has been developed. The novelty of the process lies in pre-conditioning the metallic surface using the above protein prior to its mineralization with hydroxyapatite at ambient conditions. The microporous morphology of these coatings may provide favourable solubility and resorbability as desired by many orthopaedic and orthodontic applications.     

Phase behavior and preparation of mesoporous silica in aqueous mixtures of fluorinated surfactant and hydrophobic fluorinated polymer

The phase behavior and formation of self-assemblies in the ternary water/fluorinated surfactant (C(8)F(17)EO(10))/hydrophobic fluorinated polymer (C(3)F(6)O)(n)COOH system and the application of those assemblies in the preparation of mesostructured silica have been investigated by means of phase study, small angle X-ray scattering, and rheology. Hexagonal (H(1)), bicontinuous cubic (V(1)) with Ia3d symmetry, and polymer rich lamellar (L(alpha)(')) are observed in the ternary diagram. C(8)F(17)EO(10) molecules are dissolved in polymer rich aggregates, whereas (C(3)F(6)O)(n)COOH molecules are practically insoluble in the surfactant lamellar phase due to packing restrictions. Hence, two types of lamellar phases exist: one with surfactant rich (L(alpha)) and the other with polymer rich (L(alpha)(')) in the water/C(8)F(17)EO(10)/(C(3)F(6)O)(n)COOH system. As suggested by rheological measurements, worm-like micelles are present in C(8)F(17)EO(10) aqueous solutions but a rod-sphere transition takes place by solubilization of (C(3)F(6)O)(n)COOH. C(8)F(17)EO(10) acts as a structure directing agent for the preparation of hexagonal mesoporous silica by the precipitation method. The addition of (C(3)F(6)O)(n)COOH induces the formation of larger but disordered pores.