Anatomical Studies of Two Jatropha Species with Importance for Biodiesel Production

Jatropha curcas L. and Jatropha macrocarpa Griseb. (Euphorbiaceae) are perennial species adapted to marginal conditions not suitable for agriculture, and have been recently exploited for oil and biodiesel production. The anatomy of different organs in members of this family exhibits a wide range of variations. However, knowledge of anatomical features is still incomplete. The aim of the present work was to analyze the anatomical structure of stem, leaf and root of J. curcas and J. macrocarpa seedling cultivated in a greenhouse. Fixed samples were properly treated using triple stain hematoxylin, safranin and fast green. Primary roots were diarch and triarch in J. curcas, whereas in J. macrocarpa were diarch and the cortex showed parenchyma cells, larger in J. macrocarpa than J. curcas. Stem cortex was thicker in J. macrocarpa than in J. curcas. Both species had parenchyma cells with cystolith, chloroplasts, laticifers and starch granules, these being more abundant in J. macrocarpa. Leaves were characterized by dorsoventral anatomy, with the epiderm showing amphistomatic condition with high stomata density at the lower surface. Both Jatropha species had paracytic stomata. Druses and non-articulated branched laticifers were recorded in the mesophyll. Some of the different anatomical features of J. curcas and J. macrocarpa could explain the different tolerance to abiotic stress

Fluoride degradable and thermally debondable polyurethane based adhesive

We report the one-pot, solvent free synthesis of a stimuli-responsive polyurethane (PU) adhesive. The hard domains within the supramolecular PU network contain a silyl protected phenol ‘degradable unit’ (DU). The DU undergoes rapid decomposition (<30 minutes) upon treatment with fluoride ions which causes depolymerisation of the linear PU adhesive. The mechanism of depolymerisation was investigated in solution using 1H NMR spectroscopy by following the degradation of the polymer in the presence of tetra-butylammonium fluoride (TBAF). In the absence of fluoride ions, the material behaves as a typical thermoplastic adhesive, and underwent four adhesion/separation cycles without loss of strength. The fluoride initiated depolymerisation of the PU adhesive in the solution state was verified by GPC analysis, showing reduction in Mn from 26.1 kg mol−1 for the pristine PU to 6.2 kg mol−1 for the degraded material. Degradation studies on solid samples of the PU which had been immersed in acetone/TBAF solution for 30 minutes exhibited a 91% reduction in their modulus of toughness (from 27 to 2 MJ m−3). Lap shear adhesion studies showed the fluoride responsive PU was an excellent material to join metallic, plastic, glass and wood surfaces. Pull adhesion tests confirmed that immersing the adhesive in TBAF/acetone solution resulted in a reduction in strength of up to 40% (from 160 N to 95 N at break) after drying

Anomalous Diffusion in Infinite Horizon Billiards

We consider the long time dependence for the moments of displacement < |r|^q > of infinite horizon billiards, given a bounded initial distribution of particles. For a variety of billiard models we find ~ t^g(q) (up to factors of log t). The time exponent, g(q), is piecewise linear and equal to q/2 for q2. We discuss the lack of dependence of this result on the initial distribution of particles and resolve apparent discrepancies between this time dependence and a prior result. The lack of dependence on initial distribution follows from a remarkable scaling result that we obtain for the time evolution of the distribution function of the angle of a particle's velocity vector.Comment: 11 pages, 7 figures Submitted to Physical Review

Using Resonances to Control Chaotic Mixing within a Translating and Rotating Droplet

Enhancing and controlling chaotic advection or chaotic mixing within liquid droplets is crucial for a variety of applications including digital microfluidic devices which use microscopic ``discrete'' fluid volumes (droplets) as microreactors. In this work, we consider the Stokes flow of a translating spherical liquid droplet which we perturb by imposing a time-periodic rigid-body rotation. Using the tools of dynamical systems, we have shown in previous work that the rotation not only leads to one or more three-dimensional chaotic mixing regions, in which mixing occurs through the stretching and folding of material lines, but also offers the possibility of controlling both the size and the location of chaotic mixing within the drop. Such a control was achieved through appropriate tuning of the amplitude and frequency of the rotation in order to use resonances between the natural frequencies of the system and those of the external forcing. In this paper, we study the influence of the orientation of the rotation axis on the chaotic mixing zones as a third parameter, as well as propose an experimental set up to implement the techniques discussed.Comment: 15 pages, 6 figure

Relative dispersion in fully developed turbulence: The Richardson's Law and Intermittency Corrections

Relative dispersion in fully developed turbulence is investigated by means of direct numerical simulations. Lagrangian statistics is found to be compatible with Richardson description although small systematic deviations are found. The value of the Richardson constant is estimated as $C_2 \simeq 0.55$, in a close agreement with recent experimental findings [S. Ott and J. Mann J. Fluid Mech. {\bf 422}, 207 (2000)]. By means of exit-time statistics it is shown that the deviations from Richardson's law are a consequence of Eulerian intermittency. The measured Lagrangian scaling exponents require a set of Eulerian structure function exponents $\zeta_{p}$ which are remarkably close to standard ones known for fully developed turbulence