Chitosan/anionic surfactant microparticles synthesized by high pressure spraying method for removal of phenolic pollutants

Biopolymeric microparticles were prepared by rapid expansion of high pressure CO₂-chitosan (Chi) solution in sodium bis-(2-ethyl hexyl) sulfosuccinate (AOT) solution. At pressures higher than 2 MPa, ultrafine particles were formed while under this value, wires were obtained. The formation of Chi/AOT complex was confirmed by Fourier Transform Infrared (FTIR) Spectroscopy, whereas scanning electron microscopy was used to characterize the morphology, size and shape of the particles. The FTIR spectrum proved the interaction between the sulfonate groups of AOT and the amino groups of Chi. Microparticles are quasi-spherical in wet conditions and irregular after freeze drying, presenting a rough surface with many pores. Lyophilized hydrophobic microparticles were used to remove phenol and o-cresol from aqueous solution, and the adsorption process showed a maximum efficiency in the 7–8 pH range. The uptake of phenol and o-cresol increased with the amount of particles and decreased with increasing the pollutant concentration. The adsorption occurred rapidly in the first 60–120 minutes, and leveled off thereafter.      

Mechanics of interfacial composite materials

Recent experiments and simulations have demonstrated that particle-covered fluid/fluid interfaces can exist in stable nonspherical shapes as a result of the steric jamming of the interfacially trapped particles. The jamming confers the interface with solidlike properties. We provide an experimental and theoretical characterization of the mechanical properties of these armored objects, with attention given to the two-dimensional granular state of the interface. Small inhomogeneous stresses produce a plastic response, while homogeneous stresses produce a weak elastic response. Shear-driven particle-scale rearrangements explain the basic threshold needed to obtain the near-perfect plastic deformation that is observed. Furthermore, the inhomogeneous stress state of the interface is exhibited experimentally by using surfactants to destabilize the particles on the surface. Since the interfacially trapped particles retain their individual characteristics, armored interfaces can be recognized as a kind of composite material with distinct chemical, structural, and mechanical properties.     

Microstructure, morphology, and lifetime of armored bubbles exposed to surfactants

We report the behavior of particle-stabilized bubbles (armored bubbles) when exposed to various classes and concentrations of surfactants. The bubbles are nonspherical, which is a signature of the jamming of the particles on the interface, and are stable to dissolution prior to the addition of surfactant. Armored bubbles exposed to surfactants, dissolve, and exhibit distinct morphological, microstructural, and lifetime changes, which correlate with the concentration of surfactant employed. For low concentrations of surfactant, an armored bubble remains nonspherical while dissolving, whereas for concentrations close to and above the surfactant cmc a bubble reverts to a spherical shape before dissolving. We propose a microstructural interpretation, supported by our experimental observations of particle dynamics on the bubble interface, that recognizes the role of interfacial jamming and stresses in particle-stabilization and surfactant-mediated destabilization of armored bubbles.     

Photoluminescence electron-transfer quenching of rhenium(I) rectangles with amines

Electron-transfer (ET) reactions from aromatic amines to excited states of rhenium(I)-based molecular rectangles [{Re(CO)3(mu-bpy)Br}{Re(CO)3(mu-L)Br}]2 (bpy = 4,4'-bipyridine, L = 4,4'-dipyridylacetylene (dpa), I; L = 4,4'-dipyridylbutadiyne (dpb), II; and L = 1,4-bis(4'-pyridylethynyl)benzene (bpeb), III) were investigated in a dichloromethane solution using luminescence quenching techniques. Direct evidence for the ET reaction was obtained from the detection of the amine cation radical in this system using time-resolved transient absorption spectroscopy. The values of the luminescence quenching rate constants, kq, of the 3MLCT excited state of Re(I) rectangles with amines were found to be higher than those for the monomeric Re(I) complexes and other Re(I)-based metallacyclophanes. The observed kq values were correlated well with the driving force (Delta G degrees) for the ET reactions. In addition, a semiclassical theory of ET was successfully applied to the photoluminescence quenching of Re(I) rectangles with amines.     

Synthesis and anticancer activity studies of alpha-aminoalkylated conjugated nitroalkenes

Novel alpha-aminoalkylated conjugated nitroalkenes which inhibit human cervical cancer (HeLa) cell proliferation by binding to tubulin were synthesized by imidazole/LiCl-mediated reaction of conjugated nitroalkenes with N-tosylimines.     

Surveillance for human Salmonella infections in the United States

Surveillance for human Salmonella infections plays a critical role in understanding and controlling foodborne illness due to Salmonella. Along with its public health partners, the Centers for Disease Control and Prevention (CDC) has several surveillance systems that collect information on Salmonella infections in the United States. The National Salmonella Surveillance System, begun in 1962, receives reports of laboratory-confirmed Salmonella infections through state public health laboratories. Salmonella outbreaks are reported by state and local health departments through the Foodborne Disease Outbreak Reporting System, which became a Web-based, electronic system (eFORS) in 2001. PulseNet facilitates the detection of clusters of Salmonella infections through standardized molecular subtyping (DNA "fingerprinting") of isolates and maintenance of "fingerprint" databases. The National Antimicrobial Resistance Monitoring System for Enteric Bacteria (NARMS) monitors antimicrobial resistance in Salmonella by susceptibility testing of every 20th Salmonella isolate received by state and local public health laboratories. FootNet is an active surveillance system that monitors Salmonella infections in sentinel areas, providing population-based estimates of infection rates. Efforts are underway to electronically link all of the Salmonella surveillance systems at CDC to facilitate optimum use of available data and minimize duplication.     

Thiourea catalyzed aminolysis of epoxides under solvent free conditions. Electronic control of regioselective ring opening

A reactant economizing process for the regioselective aminolysis of epoxides using equimolar quantities of reactants catalyzed by the double hydrogen bond donor N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea is reported. Regioselectivity of the reaction is controlled by the electronic nature of the substituent on the styrene oxide, which has been substantiated on the basis of ¹³C NMR data and DFT calculations.     

Exchange and correlation effects on density excitation spectra of metallic quantum wires at finite temperature

We have studied the effect of exchange and correlations on the density excitation spectra of metallic quantum wires at finite temperature. The correlations are treated by incorporating the first-order self and exchange contributions into the random-phase approximation (RPA). Numerical results are presented for the spectra of the density response function and the plasmon dispersion for the gold wire on Si(557) substrate-a system studied recently by Nagao et al. (2006 Phys. Rev. Lett. 97 116802) for plasmons using electron energy loss spectroscopy. Our results for plasmons are found to agree with the experimental data. Though the first-order correction is small at currently accessible wire parameters, it becomes significant with increasing coupling parameter r(s). The effect of temperature on plasmons is found to be small for the wire system investigated experimentally. However, temperature has a significant effect on the spectra of the response function. We have also calculated the static structure factor, the pair-correlation function and the correlation energy at zero temperature in the first-order theory to check its applicability in dealing with correlations. Results are compared directly with the available Monte Carlo simulation data. It is found that the static correlation functions improve significantly over the RPA with the increase of r(s). On the other hand, the correlation energy shows very good agreement for r(s) ≤ 5 and wire widths b ≥ a(0). For smaller b, the agreement is good up to relatively smaller r(s).     

Maps serving the combined coupling for use in environmental models and their behaviour in the presence of dynamical noise

Many physical, biological as well as the environmental problems, can be described by the dynamics of driven coupled oscillators. In order to study their behaviour as a function of coupling strength and nonlinearity, we considered dynamics of two maps serving the combined coupling (diffusive and linear) in the above fields. Firstly, we have considered a logistic difference equation on extended domain that is a part of the maps, that is discussed using its bifurcation diagram, Lyapunov exponent, sample as well as the permutation entropy. Secondly we have performed the dynamical analysis of the coupled maps using Lyapunov exponent and cross sample entropy in dependence on two coupling parameters. Further, we investigated how dynamical noise can affects the structure of their bifurcation diagrams. It was done (i) by the noise entering in two specific ways, that disturbs either the logistic parameter on extended domain or (ii) by an additive “shock” to the state variables. Finally, we demonstrated the effect of forcing by parametric noise, introduced in all maps’ parameter, on Lyapunov exponent of coupled maps.