Determination of Kinetic Parameters in the Biosorption of Cr (VI) on Immobilized <Emphasis Type="Italic">Bacillus cereus</Emphasis> M<Superscript>1</Superscript><Subscript>16</Subscript> in a Continuous Packed Bed Column Reactor

Due to technological advancement, environment suffers from untreated toxic heavy metal bearing effluent coming from different industries. Chromium (VI) is one of those heavy metals having adverse impact on ecological balance, human, and plant health because of its carcinogenic properties. Biosorption is presented as an alternative to traditional technologies which are costly and inefficient for treatment of industrial wastes containing low amount of heavy metals. In this study, bioremediation of Cr (VI) ions by immobilized Bacillus cereus M¹ ₁₆ was investigated in a laboratory scale packed bed up-flow column reactor. The effect of important parameters, such as the inlet flow rate, influent concentration, and effective bed height, has been studied. External mass transfer, surface adsorption, and intrabead mass transfer were also studied to conclude the rate limiting step for removal of Cr (VI) and to determine the process parameters which are important for biosorption optimization. The external mass transfer coefficient was calculated at different flow rates (6.51 × 10⁻² to 7.58 × 10⁻² cm/min). Using the model, the surface adsorption rate constant (k _ad) and the intrabead mass transfer coefficient (k _i) were predicted as 0.0267 × 10⁻³ and 0.7465 × 10⁻³ l/g/min, respectively. Both are much lower than the external mass transfer coefficient (k _e). The surface adsorption phenomenon is acting as the rate-limiting step due to its high resistance for removal of Cr (VI).     

Inventory model with stochastic lead-time and price dependent demand incorporating advance payment

Inventory model for an item is developed in stochastic environment with price-dependent demand over a finite time horizon. Here, probabilistic lead-time is considered and shortages are allowed (if occurs). In any business, placement of an order is normally connected with the advance payment (AP). Again, depending upon the amount of AP, unit price is quoted, i.e., price discount is allowed. Till now, this realistic factor is overlooked by the researchers. In this model, unit price is inversely related with the AP amount. Against this financial benefit, the management has to incur an expenditure paying interest against AP. Taking these into account, mathematical expression is derived for the expected average profit of the system. A closed form solution to maximize the expected average profit is obtained when demand is constant. In other cases model is solved using generalized reduced gradient (GRG) technique and stochastic search genetic algorithm (GA). Moreover, results of the models without and with advance payment are presented and solved. The numerical examples are presented to illustrate the model and the results for two models obtained from two methods are compared in different cases. Also, some parametric studies and sensitivity analyses have been carried out to illustrate the behavior of the proposed model. It is observed that advance payment has positive effect on the system.     

Inventory models for defective items incorporating marketing decisions with variable production cost

This paper investigates the finite replenishment inventory models of a single product with imperfect production process. In this process, a certain fraction or a random number of produced items are defective. These non-conforming items are rejected or reworked or if they reached to the customer, refunded. Here, a generalised unit cost function is formulated incorporating the several factors like raw material, labour, replenishment rate and others factors of the manufacturing system. The rate of replenishment is considered to be a variable. The selling price of an unit is determined by a mark-up over the production cost. Optimum production of the product is suggested to have maximum profit using a gradient based mathematical programming technique for optimization. Finally, numerical examples are given to illustrate the results and the significant features of the production system. As a particular case, the result of the perfect system (without defective items) are obtained. Also, the effect of changes in the selling rate, defectiveness, production cost and other parameters on the optimal average profit are graphically presented. Some interesting decisions regarding production policy are established.     

Structure of poly(propyl ether imine) dendrimer from fully atomistic molecular dynamics simulation and by small angle x-ray scattering

We study the structure of carboxylic acid terminated neutral poly(propyl ether imine) (PETIM) dendrimer from generations 1-6 (G1-G6) in a good solvent (water) by fully atomistic molecular dynamics (MD) simulations. We determine as a function of generation the structural properties such as radius of gyration, shape tensor, asphericity, fractal dimension, monomer density distribution, and end-group distribution functions. The sizes obtained from the MD simulations have been validated by small angle x-ray scattering experiment on dendrimer of generations 2-4 (G2-G4). A good agreement between the experimental and theoretical value of radius of gyration has been observed. We find a linear increase in radius of gyration with the generation. In contrast, Rg scales as approximately Nx with the number of monomers. We find two distinct exponents depending on the generations, x=0.47 for G1-G3 and x=0.28 for G3-G6, which reveal their nonspace filling nature. In comparison with the amine terminated poly(amidoamine) (PAMAM) dendrimer, we find that Rg of Gth generation PETIM dendrimer is nearly equal to that of (G+1)th generation of PAMAM dendrimer as observed by Maiti et al. [Macromolecules 38, 979 (2005)]. We find substantial back folding of the outer subgenerations into the interior of the dendrimer. Due to their highly flexible nature of the repeating branch units, the shape of the PETIM dendrimer deviates significantly from the spherical shape and the molecules become more and more spherical as the generation increases. The interior of the dendrimer is quite open with internal cavities available for accommodating guest molecules, suggesting the use of PETIM dendrimer for guest-host applications. We also give a quantitative measure of the number of water molecules present inside the dendrimer.     

Exploring DNA groove water dynamics through hydrogen bond lifetime and orientational relaxation

Dynamics of water molecules in the grooves of DNA are of great interest both for practical (functionality of DNA) and fundamental (as examples of confined systems) interest. Here the authors employ atomistic molecular dynamics simulations to understand varying water dynamics at the minor and the major grooves of a 38 base-pair long DNA duplex in water. In order to understand and quantify the diversity in the nature of hydrogen bond due to many hydrogen bond donors and acceptors present in the four bases, they have undertaken study of hydrogen bond lifetime (HBLT) correlation functions of all the specific hydrogen bonds between the base atoms and water molecules. They find that the HBLT correlation functions are in general multiexponential, with the average lifetime depending significantly on the specificity and may thus be biologically relevant. The average hydrogen bond lifetime is longer in the minor groove than that in the major groove by almost a factor of 2. Analysis further shows that water hydrogen bonds with phosphate oxygen have substantially shorter lifetimes than those with the groove atoms. They also compute two different orientational time correlation functions (OTCFs) of the water molecules present at the major and the minor grooves and attempt to correlate OTCF with HBLT correlation function. The OTCFs in the minor groove exhibit three time scales, with the time constant of the slowest component one to two orders of magnitude longer than what is observed for bulk water. A slow component is also present for the major groove water but with shorter time constant. Interestingly, correlation between reformations allowed HBLT correlation function [C(HB)(t)] and the OTCF markedly deviates from each other in the grooves, indicating enhanced rigidity of water molecules in the grooves.     

Ultrafast photoinduced deligation and ligation dynamics: DCM in micelle and micelle-enzyme complex

We report studies on diffusion controlled deligation and ligation dynamics of a probe ligand 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl) 4H-pyran (DCM) with cationic cetyltrimethylammonium bromide (CTAB) micelles. In order to investigate the effect of spatial heterogeneity on the dynamics we study the DCM labeled micelle upon complexation with an enzyme alpha-chymotrypsin (CHT). The variation of fluorescence line-width (Gamma(t)) of DCM in the complex and also in the micelle indicates the diffusion dynamics of DCM through various environments of different polarities. The temporal behavior of Gamma(t) reveals that at 50 mM CTAB concentration the excited DCM traverses 6.5 Angstrom distance from the surface of a host micelle (deligation) before entering to a stern layer of another adjacent micelle (ligation). From neutron scattering experiment the distance 6.5 Angstrom is found to be the thickness of a stern layer of CTAB micelle. No indication of ligation has been found at 2 mM CTAB concentration as the intermicellar distance is estimated to be very large (416 Angstrom) compared to the previous case. The dynamical behavior of Gamma(t) is also indicative of significantly slower diffusion of the ligand molecules (DCM) at the surface of the micelle in presence and absence of the enzyme compared to that in the bulk buffer. We have also studied the dynamics of solvation and local geometrical restriction on the probe DCM at the micellar surface with and without CHT. With picosecond time resolution, we found time constants of the solvation relaxation processes of the DCM labeled enzyme-micelle complex to be 230 ps (45%) and 870 ps (55%), which were comparable to those of the micelle without the enzyme. The time dependent anisotropy revealing local orientational motions of the probe in the complex was also found to be similar to that of DCM at the micellar surface in absence of CHT. These studies attempt to link the dynamical features for insight into the ligand mediated intercellular communication and the biological function of the enzyme alpha-chymotrypsin upon complexation with the CTAB micelle.     

Oxo- and oxoperoxo-molybdenum(VI) complexes with aryl hydroxamates: synthesis, structure, and catalytic uses in highly efficient, selective, and ecologically benign peroxidic epoxidation of olefins

A solution obtained by dissolving MoO3 in H2O2 reacts separately with secondary hydroxamic acids (viz., N-benzoyl N-phenyl hydroxamic acid (BPHAH), N-benzoyl N-ortho-, -meta-, -para-tolyl hydroxamic acids, (BOTHAH, BMTHAH, and BPTHAH, respectively), and N-cinnamoyl N-phenyl hydroxamic acid (CPHAH) affording [MoO(O2)(BPHA)2] (1), [MoO(O2)(BOTHA)2] (2), [MoO(O2)(BMTHA)2] (3), [MoO(O2)(BPTHA)2] (4), and [Mo(O)2(CPHA)2](5), respectively. The O and O2 are situated cis to each other in 2-4, but in each case, they are disordered and distributed over four sites. This disorder does not exist in the 6-coordinate cis dioxo complex 5, to which crude MoO(O2)(CPHA)2 (5') was converted during recrystallization. An aqueous molybdate solution readily reacts with all those hydroxamic acids producing [Mo(O)2(hydroxamate)2] (6). While 2, 3, and 4 possess a very distorted pentagonal bipyramidal structure, 5 has a distorted octahedral geometry. In the solid state, as well as in solution, 5 exists as two apparently enantiomerically related molecules differing in the orientation of the pendant phenyl rings. To emphasize that the formation and structural uniqueness of 5 compared to 1-4 is caused by the influence of the cinnamoyl residue, one compound of the 6 series, namely, [Mo(O)2(BPHA)2] (6A), was structurally characterized to prove directly that the special stereochemical properties of 5 rely on the special electronic structure of CPHA- ligand. Complexes 1-5, as well as 6, show high potential and selectivity as catalysts in the epoxidation of olefins at room temperature in the presence of NaHCO3 as a promoter and H2O2 as a terminal oxidant. A comparative epoxidation study has been performed to determine the relative efficiency of the catalysts. To make the epoxidation method cost effective, a study to optimize the use of H2O2 has also been performed. To obtain evidence in favor of our suggested mechanism to this homogeneous olefin --> epoxide conversion, it was necessary to synthesize a peroxo-rich compound, namely, [MoO(O2)2BMTHA]- (7), but the attempted synthesis culminated in the isolation of [MoO(O2)2(C6H5COO)]- (8), obviously, via the hydrolysis of coordinated BMTHA.     

1JCH correlates with alcohol hydrogen bond strength

The strength of the H-bond donation by alcohols is reflected in the carbon-hydrogen bond of the H-C-O-H functional group. The one-bond 13C-1H spin-spin coupling constant of hexafluoroisopropanol (HFIP) correlates with the strength of the H-bond in various HFIP-amine complexes with a slope of approximately -0.2 Hz in 1JCH per approximately 1 kJ mol(-1) increase in the H-bond enthalpy. The decrease in 1JCH is attributed to an increased overlap of the H-bonding sigma orbital with the antibonding sigma orbitals of the vicinal C-H bonds.     

Clove (Syzygium aromaticum Linn) extract rich in eugenol and eugenol derivatives shows bone-preserving efficacy

This study examined the efficacy of hydroalcoholic extract of dried clove buds, which is rich in phenolic compounds namely eugenol and eugenol derivatives (precursors of flavones, isoflavones and flavonoids), on different primary and secondary osteoporotic marker changes in an ovariectomised (OVX) rat model of osteoporosis. Female Wistar rats were randomly divided into three groups: sham-operated control (A), OVX (B) and OVX plus 50% hydroalcoholic extract of dried clove buds for 4 weeks (C). Results indicated that, compared to control, serum alkaline phosphatase (AP; 48.25%, p?相似文献   

Multifunctional magnetic calcium phosphate nanoparticles for targeted platin delivery

Magnetic mesoporous amorphous calcium phosphate nanoparticles with a size of 62 nm and abundant -COOH groups on the surface have been prepared by a simple method. The particles show excellent aqueous dispersion stability in physiological pH without any deterioration in hydrodynamic size and zetapotential. By virtue of the carboxylate groups on the surface, the platinum pharmacophore cis-diaquadiamine platinum(ii), folic acid and rhodamine isothiocyanate were conjugated on these magnetic calcium phosphate nanoparticles. The cytotoxicity and internalization efficiency of these nanocarriers have been evaluated on folate receptor overexpressed HeLa cells. These drug loaded nanoagents exhibit elevated cytotoxicity and induce apoptosis in HeLa cells.