Phase diagrams of lyotropic cholesteric fluids

Experimental investigations of lyotropic cholesterics fluids are presented which show that changes in the shape anisotropy and chirality of the micellar population determine the topology of the temperature-concentration phase diagrams. For given amounts of the substances which induce the chirality and modify the shape anisotropy of the micelles, two distinct biaxial cholesteric phases are disclosed in the phase diagrams. This is interpreted in the framework of the catastrophe theory of phase transitions.     

Single-crystal Raman spectroscopy and X-ray crystallography at beamline X26-C of the NSLS

Three-dimensional structures derived from X-ray diffraction of protein crystals provide a wealth of information. Features and interactions important for the function of macromolecules can be deduced and catalytic mechanisms postulated. Still, many questions can remain, for example regarding metal oxidation states and the interpretation of `mystery density', i.e. ambiguous or unknown features within the electron density maps, especially at ～2 ? resolutions typical of most macromolecular structures. Beamline X26-C at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory (BNL), provides researchers with the opportunity to not only determine the atomic structure of their samples but also to explore the electronic and vibrational characteristics of the sample before, during and after X-ray diffraction data collection. When samples are maintained under cryo-conditions, an opportunity to promote and follow photochemical reactions in situ as a function of X-ray exposure is also provided. Plans are in place to further expand the capabilities at beamline X26-C and to develop beamlines at NSLS-II, currently under construction at BNL, which will provide users access to a wide array of complementary spectroscopic methods in addition to high-quality X-ray diffraction data.     

Investigation of Mg(OH)2 nanoparticles as an antibacterial agent

Our experimental results of using Mg(OH)₂ nanoparticles as an antibacterial agent are reported in this study. The antibacterial behavior of Mg(OH)₂ nanoparticles in liquid culture and in paper sheets was investigated. The colony forming units (CFU) counting and the headspace gas chromatography (HS-GC) measurement were used to determine the cell viability. Results indicate that Mg(OH)₂ nanoparticles are effective antibacterial agent against Escherichia coli (E. coli) and Burkholderia phytofirmans, and the OH^? and Mg²⁺ ions in Mg(OH)₂ water suspension were found not to be the reason for killing the bacteria. Mg(OH)₂ nanoparticles could be added directly to wood pulp to make paper sheets, whose antibacterial efficiency increased with the increase of the nanoparticle amount. The possible mechanism of antibacterial effect of Mg(OH)₂ nanoparticles is discussed.     

Potentiometric determination of enzyme activities with slopes computed with the savitzky-golay digital filter

The Savitzky-Golay least-squares differentiation digital filter is applied to the processing of potential/time response curves for quantifying enzyme activity with potentiometric membrane electrodes as detectors. The use of this filter avoids operator bias and provides a simple and rapid procedure for data processing.