Water dynamics in small reverse micelles in two solvents: two-dimensional infrared vibrational echoes with two-dimensional background subtraction

Water dynamics as reflected by the spectral diffusion of the water hydroxyl stretch were measured in w(0) = 2 (1.7 nm diameter) Aerosol-OT (AOT)/water reverse micelles in carbon tetrachloride and in isooctane solvents using ultrafast 2D IR vibrational echo spectroscopy. Orientational relaxation and population relaxation are observed for w(0) = 2, 4, and 7.5 in both solvents using IR pump-probe measurements. It is found that the pump-probe observables are sensitive to w(0), but not to the solvent. However, initial analysis of the vibrational echo data from the water nanopool in the reverse micelles in the isooctane solvent seems to yield different dynamics than the CCl(4) system in spite of the fact that the spectra, vibrational lifetimes, and orientational relaxation are the same in the two systems. It is found that there are beat patterns in the interferograms with isooctane as the solvent. The beats are observed from a signal generated by the AOT/isooctane system even when there is no water in the system. A beat subtraction data processing procedure does a reasonable job of removing the distortions in the isooctane data, showing that the reverse micelle dynamics are the same within experimental error regardless of whether isooctane or carbon tetrachloride is used as the organic phase. Two time scales are observed in the vibrational echo data, ~1 and ~10 ps. The slower component contains a significant amount of the total inhomogeneous broadening. Physical arguments indicate that there is a much slower component of spectral diffusion that is too slow to observe within the experimental window, which is limited by the OD stretch vibrational lifetime.     

Predicting thermal conductivity of liquid suspensions of nanoparticles (nanofluids) based on rheology

A methodology is proposed for predicting the effective thermal conductivity of dilute suspensions of nanoparticles (nanofluids) based on rheology.The methodology uses the rheological data to infer microstructures of nanoparticles quantitatively,which is then incorporated into the conventional Hamilton-Crosser equation to predict the effective thermal conductivity of nanofluids.The methodology is experimentally validated using four types of nanofluids made of titania nanoparticles and titanate nanotubes dispersed in water and ethylene glycol.And the modified Hamilton-Crosser equation successfully predicted the effective thermal conductivity of the nanofluids.     

On the g-circulant solutions to the matrix equation Am = λJ, II

Let g and n be positive integers and let $\text{k =}\text{n(g, n)}\text{(g}{}^{\mathrm{m}}\text{, n)}$. If θ(x) is a multiple of Σ_{i = 0}^{k ? 1}xⁱ, then the g-circulant whose Hall polynomial is equal to θ(x) satisfies the matrix equation in the title. If the g-circulant whose Hall polynomial is equal to Σ_{i = 0}^{h ? 1}xⁱ satisfies the matrix equation in the title, then h is a multiple of k.     

Novel 3-mono-<Emphasis Type="Italic">O</Emphasis>-hydroxyethyl cellulose: synthesis and structure characterization

The synthesis of 3-mono-O-hydroxyethyl cellulose using orthogonal protecting groups was realized. The reaction of 2,6-di-O-thexyldimethylsilyl cellulose with 2-(2-bromoethoxy)tetrahydropyran leads to a completely functionalized cellulose derivative. The complete removal of the protecting groups was possible by split off of the TDMS functions with tetrabutylammonium fluoride trihydrate and subsequently the tetrahydropyran moieties with hydrochloric acid. The structure of 3-mono-O-hydroxyethyl cellulose was confirmed by applying one and two-dimensional NMR spectroscopy. The novel polymer is soluble in water and does not show thermoreversible gelation.     

Competitive carbon emission yields the possibility of global self-control

Despite many international climate meetings such as Copenhagen 2009, it is still unclear how annual global emissions can be reduced without requiring governments to micro-manage the emitting companies within their individual jurisdictions. Here we examine a simple, yet highly non-trivial, computer model of carbon emission which is consistent with recent activity in the European carbon markets. Our simulation results show that the ongoing daily competition to emit CO₂ within a population of emitters, can lead to a form of collective self-control over the aggregated emissions. We identify regimes in which such a population spontaneously hits its emissions target with minimal fluctuations. We then focus on the emission dynamics induced by a governing body which chooses to actively manage the capping level. Finally we lay some formal stepping stones toward a complete analytic theory for carbon emissions fluctuations within this model framework – in so doing, we also connect this problem to more familiar theoretical terrain within computer science.     

Of protons or proteins

Mass analyses have been carried out on ions produced by an Electrospray (ES) source from dilute solutions of protein molecules with molecular weights (M) in the range from 5000 to nearly 40000. Each spectrum comprises a sequence of peaks corresponding to multiply charged intact parent species. The ions of each peak differ from those of their adjacent neighbors by one unit charge, H⁺ in these experiments. The maximum number of charges per ion generally increases with the molecular weight of the parent molecule, reaching a value of 45 in the case of alcohol dehydrogenase, atM=39830 the largest species in this study. Thus the resulting values ofm/z are within reach of a simple quadrupole mass filter whose nominal upper mass limit is 1500 daltons! The immediate application for the ES source is in mass spectrometric analysis of large fragile molecules of biochemical importance. But the multiply charged ions it produces are newcomers to the laboratory scene that constitute interesting subjects for study.     

Influence of the functionalization pattern of ethyl cellulose on the interactions with polystyrene latex particles in aqueous mixtures

The interactions between polystyrene latex particles and ethyl cellulose (EC) with different functionalization pattern have been investigated. 3-Mono-O-EC and EC with statistical functionalization pattern in the anhydroglucose units were studied in aqueous solutions and dispersions. EC belongs to a group of polymers that phase separate upon heating. The two types of EC showed large differences in phase separation temperature, which was explained as an effect of different interactions with water due to different functionalization pattern. Both types of EC did adsorb on polystyrene particles, which indicated a favorable interaction between EC and polystyrene latex particles, however, in a different manner depending on the structure of EC. The conventionally synthesized ethyl cellulose with statistical functionalization pattern formed much stronger networks with polystyrene latex particles than 3-mono-O-EC did. The lower phase separation temperature and the slightly higher molecular weight of the conventional ethyl cellulose gave it higher preference for interacting with polystyrene latex particles to form network. Throughout the study, comparison is made with other cellulose derivatives like ethyl(hydroxyethyl) cellulose (EHEC) and carboxymethyl cellulose (CMC).     

Nanoporous metal organic framework materials for hydrogen storage

Hydrogen is expected to play an important role in future transportation as a promising alternative clean energy source to carbon-based fuels.One of the key challenges to commercialize hydrogen energy is to develop appropriate onboard hydrogen storage systems,capable of charging and discharging large quantities of hydrogen with fast enough kinetics to meet commercial requirements.Metal organic framework (MOF) is a new type of inorganic and organic hybrid nanoporous particulate materials.Its diverse networks can enhance hydrogen storage through tuning the structure and property of MOFs.The MOF materials so far developed adsorb hydrogen through weak disperston interactions,which allow significant quantity of hydrogen to be stored at cryogenic temperatures with fast kinetics.Novel MOFs are being developed to strengthen the interactions between hydrogen and MOFs in order to store hydrogen under ambient conditions.This review surveys the development of such candidate materials,their performance and future research needs.