Controlled growth of flower-like,rod-like,and snowflake-like ZnO nanostructures using agarose as biotemplate and its photoluminescence property

Different nanostructures such as flower-like, rod-like, and snowflake-like of ZnO have been synthesized by varying the amount of agarose using sonochemical method. It is found that morphology is governed by amount of agarose as well as ultrasonic treatment. Three amounts of agarose 0.01, 0.1, and 1.00 g are used to investigate its effect on ZnO. X-ray diffraction (XRD) confirmed the formation of single phase with hexagonal structure. Scanning electron microscopy (SEM) showed flower-like, rod-like, and snowflake-like morphology for 1.00, 0.1, and 0.01 g agarose, respectively. UV/Visible absorption study showed blue shift at band-edge absorption in comparison to bulk ZnO. Photoluminescence spectra showed band-edge emission at 399 nm for lowest amount of agarose which quenched on increasing the agarose amount. These findings show a better and more environment friendly procedure for production of ZnO of readily adjustable morphology.     

Chemical constituents and in vitro antioxidant activity of Phyllanthus wightianus

The whole plant of Phyllanthus wightianus (PW) was investigated for the antioxidant effects of three successive extracts: hexane (PWHE), chloroform (PWCE) and methanol (PWME), using standard in vitro models. The PWME exhibited a strong scavenging effect on 2,2-diphenyl-2-picryl hydrazyl (DPPH) free radicals and nitric oxide radical inhibition activity, due to possessing the highest content of tannins. The free radical scavenging effect of PWME was comparable with that of reference antioxidants. The extracts were subjected to isolation of their compounds: isomeric sterol mixture (1) [stigmasterol (1a), compesterol (1b) and β-sitosterol (1c)], fredilin (2), lupeol (3), gallic acid (4), bergenin (5), geraniin (6), corilagin (7) and ellagic acid (8) were established through the use of column chromatographic methods and spectral data. The percentage of tannins was also determined and estimated using the HPLC method. The data suggest that tannins are the active antioxidant compounds of P. wightianus. This study provides proof for the ethnomedical claims and reported biological activities of this plant. The plant therefore has very good therapeutic potential.     

QM:QM embedding using electronic densities within an ONIOM framework: energies and analytic gradients

Accurate calculations of large systems remain a challenge in electronic structure theory. Hybrid energy techniques are a promising family of methods for treating such systems. Expanding on previous developments, we present a QM:QM electronic embedding model whereby the high-level region is polarized by the electron density of the low-level region within an ONIOM framework. A direct Coulomb embedding model as well a more computationally efficient model involving a density fitting expansion are considered. We also develop a generalized theory for the first derivatives of these classes of QM:QM electronic embedding schemes, which requires solution of a single set of self-consistent field response equations. Two initial test cases are presented and discussed.     

First-principles calculations of the structural and dynamic properties, and the equation of state of crystalline iodine oxides I2O4, I2O5, and I2O6

The structural and dynamical correlations, and the equation of state of crystalline I(2)O(4), I(2)O(5), and I(2)O(6) are investigated by first-principles calculations based on the density functional theory (DFT). The lattice dynamics results reveal distinctive features in the phonon density of states among the three crystals. The frequencies of the stretch modes in I(2)O(4) and I(2)O(5) are clearly separated from those of the other (e.g., bending) modes by a gap, with all stretch modes above the gap. In contrast, the gap in I(2)O(6) separates the highest-frequency stretch modes with other stretch modes, and there is no gap between the stretch and the other modes in I(2)O(6). The motion of iodine atoms is involved in all vibrational modes in I(2)O(5), but only in low-frequency lattice modes in I(2)O(6). In I(2)O(4), iodine atoms are involved in modes with frequency below 700 cm(-1). Van der Waals correction within our DFT calculations is found to reduce the overestimation of the equilibrium volume, with its effect on structure similar to the pressure effect. Namely, both effects significantly decrease the inter-molecular distances, while slightly increasing the bond lengths within the molecules. This causes the frequencies of some vibrational modes to decrease with pressure, resulting in negative "modes Gru?neisen parameters" for those modes. Thermodynamic properties, derived from the equation of state, of crystalline I(2)O(4), I(2)O(5), and I(2)O(6) are discussed within the quasi-harmonic approximation.     

A new three-component reaction: green synthesis of novel isoindolo[2,1-a]quinazoline derivatives as potent inhibitors of TNF-α

Concurrent construction of five and six membered fused N-heretocyclic ring was achieved via a conceptually new three-component reaction affording 6,6a-dihydroisoindolo[2,1-a]quinazoline-5,11-diones as novel inhibitors of TNF-αin vitro. This represents one of the few examples of direct TNF-α inhibition by small molecules.     

Influence of polarization and wavelength on two-photon excited luminescence of single gold nanospheres

The Brownian rotation of a nearly spherical gold particle capped with ligands can be observed in the correlation profile of the intensity of the two-photon excited luminescence. Here we report on a multi-parameter study of the luminescence properties, including spectral and polarization analysis of the signal at the single particle level. First, the data confirm the role of the radiative de-excitation of the surface plasmons in the luminescence process. Secondly, the results obtained at low power indicate that the capped particle in water can be approximatively described as a spherical rotor acting in the far-field as a point-like absorption and emission dipole of fixed directions. In addition, we show that the dynamics of the ligands, induced by the heat transfer from the particle to its environment, can be partly controlled by the choice of excitation wavelength.     

The quality of commercially available herbal products

Herbal products are believed to be safe as they are naturally occurring, however, this is a misconception. Currently, there are many herbal products which are not manufactured under the Good Manufacturing Practice (GMP) guidelines and hence the quality of the product is not controlled. Quality can be assessed by evaluation of data on levels of either active constituent(s) or chemical markers indicative of origin of plant material. Assessment of published data on levels of quality of herbal medicinal products revealed that only a percentage of the total number of products investigated were found to contain the levels of markers as stated on the label, and others had widely varying levels of constituents. Thus few products complied with acceptable quality control standards. Herbal products are increasingly self-prescribed for the treatment of minor ailments. Patients relying on herbal products for therapeutic effects may expose themselves to either low doses of active constituents causing insufficient effects or alternatively take higher levels than expected, with the increased risk of toxicity or adverse effects, or be affected by the inadvertent inclusion of unexpected components with associated potential health risks.     

Dietary Flavonoids: Cardioprotective Potential with Antioxidant Effects and Their Pharmacokinetic,Toxicological and Therapeutic Concerns

Flavonoids comprise a large group of structurally diverse polyphenolic compounds of plant origin and are abundantly found in human diet such as fruits, vegetables, grains, tea, dairy products, red wine, etc. Major classes of flavonoids include flavonols, flavones, flavanones, flavanols, anthocyanidins, isoflavones, and chalcones. Owing to their potential health benefits and medicinal significance, flavonoids are now considered as an indispensable component in a variety of medicinal, pharmaceutical, nutraceutical, and cosmetic preparations. Moreover, flavonoids play a significant role in preventing cardiovascular diseases (CVDs), which could be mainly due to their antioxidant, antiatherogenic, and antithrombotic effects. Epidemiological and in vitro/in vivo evidence of antioxidant effects supports the cardioprotective function of dietary flavonoids. Further, the inhibition of LDL oxidation and platelet aggregation following regular consumption of food containing flavonoids and moderate consumption of red wine might protect against atherosclerosis and thrombosis. One study suggests that daily intake of 100 mg of flavonoids through the diet may reduce the risk of developing morbidity and mortality due to coronary heart disease (CHD) by approximately 10%. This review summarizes dietary flavonoids with their sources and potential health implications in CVDs including various redox-active cardioprotective (molecular) mechanisms with antioxidant effects. Pharmacokinetic (oral bioavailability, drug metabolism), toxicological, and therapeutic aspects of dietary flavonoids are also addressed herein with future directions for the discovery and development of useful drug candidates/therapeutic molecules.     

Morphological explanation of the extraordinary fracture toughness of linear low density polyethylenes

The fracture toughness of commercial linear low-density polyethylenes (LLDPE) has been found to be extraordinarily high relative to commercial low-density (LDPE) and high-density (HDPE) polyethylenes in previously reported investigations. The present investigation shows that this extraordinary fracture toughness cannot be explained by differences in molecular structure variables, such as molecular weight, long-chain and short-chain branching, fractional crystallinity, and comonomer content. Instead, the presence of a second soft phase, which was extractable with a weak solvent, in a hard semicrystalline matrix was discovered by morphological investigations of LLDPE resins. This second phase arises from the extreme compositional heterogeneity of the copolymers which comprise these LLDPE resins. No evidence for a similar morphological entity was found in LDPE and HDPE resins. This finding provides persuasive evidence that this very-low-crystallinity second phase performs a function similar to that of the rubberlike second phase in other high impact resins and, thus, leads to the observed extraordinary fracture toughness of LLDPE resins. Evidence for the nature and existence of this second phase is given from temperature-rising elution fractionation and scanning electron microscopy investigations.     

Growth mechanism and optical property of CdS nanoparticles synthesized using amino-acid histidine as chelating agent under sonochemical process

Using amino-acid histidine as chelating agent, CdS nanoparticles have been synthesized by sonochemical method. It is found that by varying the ultrasonic irradiation time, we can tune the band gap and particle size of CdS nanoparticles. The imidazole ring of histidine captures the Cd ions from the solution, and prevents the growth of the CdS nanoparticles. The deviation in the linear relation in between cube of radius of nanoparticles and ultrasonic irradiation time confirms the growth of CdS nanoparticles occur via two process; one is the diffusion process of the reactants as well as reaction at the surface of the crystallite. CdS nanoparticles synthesized using histidine as organic chelating agent have band edge emission at 481 nm and have greater photoluminescence intensity with blue-shift to higher energy due to typical quantum confinement effect.