Phase Behavior of Bent-Core Molecules

Recently, a new class of smectic liquid crystal phases (SmCP phases) characterized by the spontaneous formation of macroscopic chiral domains from achiral bent-core molecules has been discovered. We have carried out Monte Carlo simulations of a minimal hard spherocylinder dimer model to investigate the role of excluded volume interations in determining the phase behavior of bent-core materials and to probe the molecular origins of polar and chiral symmetry breaking. We present the phase diagram as a function of pressure or density and dimer opening angle $\psi$. With decreasing $\psi$, a transition from a nonpolar to a polar smectic phase is observed near $\psi = 167^{\circ}$, and the nematic phase becomes thermodynamically unstable for $\psi < 135^{\circ}$. No chiral smectic or biaxial nematic phases were found.Comment: 4 pages Revtex, 3 eps figures (included

Elevated levels of numerous cytokines in drainage fluid after primary total hip arthroplasty

As cytokines are involved in wound healing and other inflammatory processes, it could be valuable to measure their levels at the operative site. This study was conducted to investigate whether different cytokines are measurable in drainage fluid and, when measurable, whether we can find a difference in cytokine levels between one and six hours postoperatively. Samples from the drainage system in 30 consecutive patients undergoing primary total hip replacement were collected at one and six hours after closure of the wound. Levels of several cytokines were measured in the drainage fluids. A significant elevation of almost all cytokines was observed between the sample after one hour and six hours postoperatively. We found a strong correlation between the different pro-inflammatory cytokines. The IL-6 to IL-10 ratio were also raised, showing a pro-inflammatory predominance. Levels were much higher than those previously shown in serum

Label-free chemically specific imaging in planta with stimulated Raman scattering microscopy.

The growing world population puts ever-increasing demands on the agricultural and agrochemical industries to increase agricultural yields. This can only be achieved by investing in fundamental plant and agrochemical research and in the development of improved analytical tools to support research in these areas. There is currently a lack of analytical tools that provide noninvasive structural and chemical analysis of plant tissues at the cellular scale. Imaging techniques such as coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) microscopy provide label-free chemically specific image contrast based on vibrational spectroscopy. Over the past decade, these techniques have been shown to offer clear advantages for a vast range of biomedical research applications. The intrinsic vibrational contrast provides label-free quantitative functional analysis, it does not suffer from photobleaching, and it allows near real-time imaging in 3D with submicrometer spatial resolution. However, due to the susceptibility of current detection schemes to optical absorption and fluorescence from pigments (such as chlorophyll), the plant science and agrochemical research communities have not been able to benefit from these techniques and their application in plant research has remained virtually unexplored. In this paper, we explore the effect of chlorophyll fluorescence and absorption in CARS and SRS microscopy. We show that with the latter it is possible to use phase-sensitive detection to separate the vibrational signal from the (electronic) absorption processes. Finally, we demonstrate the potential of SRS for a range of in planta applications by presenting in situ chemical analysis of plant cell wall components, epicuticular waxes, and the deposition of agrochemical formulations onto the leaf surface

Raman spectroscopic insights into the chemical gradients within the wound plug of the green alga Caulerpa taxifolia

The invasive unicellular green macroalga Caulerpa taxifolia has spread dramatically in the Mediterranean Sea over the last decades. Its success is based on rapid plug formation after wounding, to prevent the loss of cell content. This quick and efficient process involves the rapid transformation of the secondary metabolite caulerpenyne to the reactive 1,4-dialdehyde oxytoxin 2, which acts as a protein crosslinker. The main metabolites of the wound plug were identified as proteins, caulerpenyne derivatives, and sulfated polysaccharides. Because of a methodological deficit, however, the detailed distribution of the compounds within the wound plug of C. taxifolia was unknown. This study demonstrates the suitability of FT-Raman spectroscopy for the noninvasive in vivo determination of caulerpenyne and its derivatives, as well as -carotene, from signals with special spectral features within the wound plug and the adjacent intact alga tissue, with a resolution of 100 m. FT-Raman spectra allowed four different zones with distinct chemical compositions around the region of wounds to be characterized. Gradients of the investigated metabolites within the wound plug and the alga could be determined. Moreover, various caulerpenyne derivatives could be identified spectroscopically, and this has led to a mechanistic proposal for the internal and the external wound plug formation