Milking Diatoms for Sustainable Energy: Biochemical Engineering versus Gasoline-Secreting Diatom Solar Panels

In the face of increasing CO2 emissions from conventional energy (gasoline), and the anticipated scarcity of Crude oil, a worldwide effort is underway for cost-effective renewable alternative energy sources. Here, we review a simple line of reasoning: (a) geologists claim that Much crude oil comes from diatoms; (b) diatoms do indeed make oil; (c) agriculturists Claim that diatoms could make 10-200 times as much oil per hectare as oil seeds; and (d) therefore, sustainable energy could be made from diatoms. In this communication, we propose ways of harvesting oil from diatoms, using biochemical engineering and also a new solar panel approach that utilizes genomically modifiable aspects of diatom biology, offering the prospect of ``milking'' diatoms for Sustainable energy by altering them to actively secrete oil products. Secretion by and milking of diatoms may provide a way around the puzzle of how to make algae that both grow quickly and have a very high oil content.

Modeling of Convection and Macrosegregation through Appropriate Consideration of Multiphase/Multiscale Phenomena during Alloy Solidification

Solidification processes are complex in nature, involving multiple phases and several length scales. The properties of solidified products are dictated by the microstructure, the mactostructure, and various defects present in the casting. These, in turn, are governed by the multiphase transport phenomena Occurring at different length scales. In order to control and improve the quality of cast products, it is important to have a thorough understanding of various physical and physicochemical phenomena Occurring at various length scales. preferably through predictive models and controlled experiments. In this context, the modeling of transport phenomena during alloy solidification has evolved over the last few decades due to the complex multiscale nature of the problem. Despite this, a model accounting for all the important length scales directly is computationally prohibitive. Thus, in the past, single-phase continuum models have often been employed with respect to a single length scale to model solidification processing. However, continuous development in understanding the physics of solidification at various length scales oil one hand and the phenomenal growth of computational power oil the other have allowed researchers to use increasingly complex multiphase/multiscale models in recent. times. These models have allowed greater understanding of the coupled micro/macro nature of the process and have made it possible to predict solute segregation and microstructure evolution at different length scales. In this paper, a brief overview of the current status of modeling of convection and macrosegregation in alloy solidification processing is presented.

Chemistry and biology of DNA methyltransferases

Recognition of a specific DNA sequence by a protein is probably the best example of macromolecular interactions leading to various events. It is a prerequisite to understanding the basis of protein-DNA interactions to obtain a better insight into fundamental processes such as transcription, replication, repair, and recombination. DNA methyltransferases with varying sequence specificities provide an excellent model system for understanding the molecular mechanism of specific DNA recognition. Sequence comparison of cloned genes, along with mutational analyses and recent crystallographic studies, have clearly defined the functions of various conserved motifs. These enzymes access their target base in an elegant manner by flipping it out of the DNA double helix. The drastic protein-induced DNA distortion, first reported for HhaI DNA methyltransferase, appears to be a common mechanism employed by various proteins that need to act on bases. A remarkable feature of the catalytic mechanism of DNA (cytosine-5) methyltransferases is the ability of these enzymes to induce deamination of the target cytosine in the absence of S-adenosyl-L-methionine or its analogs. The enzyme-catalyzed deamination reaction is postulated to be the major cause of mutational hotspots at CpG islands responsible for various human genetic disorders. Methylation of adenine residues in Escherichia coli is known to regulate various processes such as transcription, replication, repair, recombination, transposition, and phage packaging.

Modeling of Freezing Phenomena Induced by Chemical Reactions

Spatial variations in the concentration of a reactive solute in solution are often encountered in a catalyst particle, and this leads to variation in the freezing point of the solution. Depending on the operating temperature, this can result in freezing of the solvent oil a portion of catalyst, rendering that part of the active area ineffective Freezing call occur by formation of a sharp front or it mush that separates the solid and fluid phases. In this paper, we model the extent of reduction in the active area due to freezing. Assuming that the freezing point decreases linearly with solute concentration, conditions for freezing to occur have been derived. At steady state, the ineffective fraction of catalyst pellet is found to be the same irrespective of the mode of freezing. Progress of freezing is determined by both the heat of reaction and the latent heat of fusion Unlike in freezing of alloys where the latter plays a dominant role, the exothermicity of the reaction has a significant effect on freezing in the presence of chemical reactions. A dimensionless group analogous to the Stefan number could be defined to capture the combined effect of both of these.

Influence of surface chemistry of mesoporous alumina with wide pore distribution on controlled drug release

The crucial role of the drug carrier surface chemical moeities on the uptake and in vitro release of drug is discussed here in a systematic manner. Mesoporous alumina with a wide pore size distribution (2-7 nm) functionalized with various hydrophilic and hydrophobic surface chemical groups was employed as the carrier for delivery of the model drug ibuprofen. Surface functionalization with hydrophobic groups resulted in low degree of drug loading (approximately 20%) and fast rate of release (85% over a period of 5 h) whereas hydrophilic groups resulted in a significantly higher drug payloads (21%-45%) and slower rate of release (12%-40% over a period of 5 h). Depending on the chemical moiety, the diffusion controlled (proportional to time(-0.5)) drug release was additionally observed to be dependent on the mode of arrangement of the functional groups on the alumina surface as well as on the pore characteristics of the matrix. For all mesoporous alumina systems the drug dosages were far lower than the maximum recommended therapeutic dosages (MRTD) for oral delivery. We envisage that the present study would aid in the design of delivery systems capable of sustained release of multiple drugs.

Separation of Metallic and Semiconducting Single-Walled Carbon Nanotubes Through Fluorous Chemistry

Separation of metallic from semiconducting single-walled carbon nanotubes has been a major challenge for some time and some previous efforts have resulted in partial success. We have accomplished the separation effectively by employing fluorous chemistry wherein the diazonium salt of 4-heptadecafluorooc tylaniline selectively reacts with the metallic nanotubes present in the mixture of nanotubes. The resulting fluoroderivative was extracted in perfluorohexane leaving the semiconducting nanotubes in the aqueous layer. The products have been characterized by both Raman and electronic absorption spectroscopy. The method avoids the cumbersome centrifugation step required by some other procedures.

Oxide Particle Surface Chemistry and Ion Transport in "Soggy Sand" Electrolytes

The crucial role of oxide surface chemical composition on ion transport in "soggy sand" electrolytes is discussed in a systematic manner. A prototype soggy sand electrolytic system comprising aerosil silica functionalized with various hydrophilic and hydrophobic moieties dispersed in lithium perchlorate-ethylene glycol solution was used for the study. Detailed rheology studies show that the attractive particle network in the case of the composite with unmodified aerosil silica (with surface silanol groups) is most favorable for percolation in ionic conductivity, as well as rendering the composite with beneficial elastic mechanical properties: Though weaker in strength compared to the composite with unmodified aerosil particles, attractive particle networks are also observed in composites of aerosil particles with surfaces partially substituted with hydrophobic groups. The percolation in ionic conductivity is, however, dependent on the size of the hydrophobic moiety. No spanning attractive particle network was formed for aerosil particles with surfaces modified with stronger hydrophilic groups (than silanol), and as a result, no percolation in ionic conductivity was observed. The composite with hydrophilic particles was a sol, contrary to gels obtained in the case of unmodified aerosil, and partially substituted with hydrophobic groups.

Kinetics of photocatalytic reduction of NO by CO with Pd2+-Ion-Substituted Nano-TiO2

The objective of the present study is to develop the reaction mechanism and kinetics of photoreduction of NO by CO. For this purpose, the reactions were conducted in the presence of Pd-ion-substituted nano-TiO2, Ti1-xPdxO2-delta, which was synthesized via a solution combustion method. The photocatalytic activity was investigated with unsubstituted TiO2, 1% Pd/TiO2(imp), and Ti1-xPdxO2-delta (where x = 0.05-0.3). No appreciable NO conversion was observed over unsubstituted TiO2, although, despite competitive adsorption of NO and CO on the Pd2+ sites, there was a significant reduction of NO over Ti1-xPdxO2-delta. The kinetic model showed that the enhanced catalytic activity is due to the NO photodissociation at the oxide-ion vacancy.

Organometallic chemistry of diphosphazanes. Part 26. Ruthenium hydride complexes of chiral and achiral diphosphazane ligands and asymmetric transfer hydrogenation reactions

The half-sandwhich ruthenium chloro complexes bearing chelated diphosphazane ligands, [(eta(5)-Cp)RuCl{kappa(2)-P,P-(RO)(2)PN(Me)P(OR)(2)}] [R = C6H3Me2-2,6] (1) and [(eta(5)-Cp*)RuCl{kappa(2)-P, P-X2PN(R)PYY'}] [R = Me, X = Y = Y' = OC6H5 (2); R = CHMe2, X-2 = C20H12O2, Y = Y' = OC6H5 (3) or OC6H4'Bu-4 (4)] have been prepared by the reaction of CpRu(PPh3)(2)Cl with (RO)(2)PN(Me)P(OR)(2) [R = C6H3Me2-2,6 (L-1)] or by the reaction of [Cp*RuCl2](n) with X2PN(R)PYY' in the presence of zinc dust. Among the four diastereomers (two enantiomeric pairs) possible for the "chiral at metal" complexes 3 and 4, only two diastereomers (one enantiomeric pair) are formed in these reactions. The complexes 1, 2, 4 and [(eta(5)-Cp)RuCl {kappa(2)-P,P-Ph2PN((S)-*CHMePh)PPhY)] [Y = Ph (5) or N2C3HMe2-3,5 (SCSPRRu)-(6)] react with NaOMe to give the corresponding hydride complexes [(eta(5) -Cp)RuH {kappa(2)-P,P-(RO)(2)PN(Me)P(OR)(2)}] (7), [(eta(5)-Cp*)RuH {kappa(2)-P,P'-X2PN(R)PY2)] [R = Me, X = Y = OC6H5 (8); R = CHMe2, X-2 = C20H12O2, Y = OC6H4'Bu-4 (9)] and [(eta(5) -Cp)RuH(kappa(2)-P, P-Ph2PN((S)-*CHMePh)PPhY)][Y =Ph (10) or N2C3HMe2-3,5 (SCSPRRu)(11a) and (SCSPSRu)-(11b)]. Only one enantiomeric pair of the hydride 9 is obtained from the chloro precursor 4 that bears sterically bulky substituents at the phosphorus centers. On the other hand, the optically pure trichiral complex 6 that bears sterically less bulky substituents at the phosphorus gives a mixture of two diastereomers (11a and 11b). Protonation of complex 7 using different acids (HX) gives a mixture of [(eta(5)- Cp)Ru(eta(2)-H-2){kappa(2)-P, P-(RO)(2)PN(Me)P(OR)(2))]X (12a) and [(eta(5)-Cp)Ru(H)(2){kappa(2)-P, P-(RO)(2)PN(Me)P(OR)(2)}]X (12b) of which 12a is the major product independent of the acid used; the dihydrogen nature of 12a is established by T, measurements and also by synthesizing the deuteride analogue 7-D followed by protonation to obtain the D-H isotopomer. Preliminary investigations on asymmetric transfer hydrogenation of 2-acetonaphthone in the presence of a series of chiral diphosphazane ligands show that diphosphazanes in which the phosphorus centers are strong pi-acceptor in character and bear sterically bulky substituents impart moderate levels of enantioselectivity. Attempts to identify the hydride intermediate involved in the asymmetric transfer hydrogenation by a model reaction suggests that a complex of the type, [Ru(H)(Cl){kappa(2)-P,P-X2PN(R)PY2)(solvent)(2)] could be the active species in this transformation. (c) 2007 Elsevier B.V. All rights reserved.

Unlocking the potential of bile acids in synthesis, supramolecular/materials chemistry and nanoscience

The Maitra group has explored a variety of chemistry with bile acids during the past 15 years and these experiments have covered a wide variety of chemistry - asymmetric synthesis, molecular recognition, ion receptors/sensors, dendrimers, low molecular mass organo and hydrogelators, gel-nanoparticle composites, etc. Some of what excites us in this field is highlighted in this perspective article.

Ethylation of benzene: A statistical study

A central composite rotatable experimental design was constructed for a statistical study of the ethylation of benzene in the liquid phase, with aluminum chloride catalyst, in an agitated tank system. The conversion of benzene and ethylene and the yield of monoethyl- and diethylbenzene are characterized by the response surface technique. In the experimental range studied, agitation rate has no significant effect. Catalyst concentration, rate of ethylene Flow, and temperature are the influential factors. The response surfaces may be adequately approximated by planes.

Oxidation of acetaldehyde to acetic acid in a sparger reactor

The kinetics of oxidation of acetaldehyde to acetic acid was studied in a sparger reactor using manganese acetate as the catalyst. Data obtained in a stirred tank reactor are used for analyzing the sparger reactor data. The rate of chemical reaction is extremely fast and can be neglected for the rate equation of the sparger reactor. A kinetic model applicable at any temperature and concentration within the range of the variables studied is developed which predicts the performance of the sparger reactor satisfactorily.

Catalytic dehydrogenation of 2-propanol to acetone

Catalytic dehydrogenation of 2-propanol over Cu-SiO2 catalyst was investigated. The undesired side reaction of dehydration can be controlled by a selective catalyst and choice of proper operating conditions. The kinetics of the heterogeneous catalytic reaction can be adequately expressed by a forward first-order and reverse second-order mechanism. The rate-controlling step with chemically pure 2-propanol is single-site surface reaction, while for the technical grade alcohol the adsorption of alcohol is rate-controlling. The static bed data are compared with the fluidized bed dat

Studies on pneumatic atomization

A study of atomization has been made with an external mixing-type pneumatic atomizer. The drops were sampled on Vaseline-coated cells using a shutter arrangement and their sizes were measured under a microscope. The effects of liquid viscosity, liquid surface tension, liquid flow rate, air velocity, and nozzle angle on drop size have been studied. A model, which explains adequately the influence of various factors, has been proposed. This model predicts the values of average drop sizes over a wide range of operating conditions. The model also explains the data of other investigators who have used other kinds of pneumatic atomizers.