Thermal-Mechanical Properties of Polyurethane-Clay Shape Memory Polymer Nanocomposites

Shape memory nanocomposites of polyurethane (PU)-clay were fabricated by melt mixing of PU and nano-clay. Based on nano-indentation and microhardness tests, the strength of the nanocomposites increased dramatically as a function of clay content, which is attributed to the enhanced nanoclay–polymer interactions. Thermal mechanical experiments demonstrated good mechanical and shape memory effects of the nanocomposites. Full shape memory recovery was displayed by both the pure PU and PU-clay nanocomposites.

Naringin supplementation affects performance, carcass traits, meat quality and oxidative stability of finishing pigs

Naringin is a major flavanone derivate that has many important biological functions in animals. However, its effect on pigs is unknown. The aim of this study was to investigate the effect of naringin supplementation on performance, carcass traits, meat quality and oxidative stability in finishing pigs. Ninety-six pigs, with an average initial body weight of 66.2 ± 0.63 kg, were randomly divided into four groups. One group was fed a basal diet without supplementation (control), and the three others were fed diets supplemented with 0.5, 1.0 or 1.5 g naringin /kg DM of feed for 50 days. Each treatment was replicated six times with four pigs per replicate. Feed and water were available ad libitum. The 0.5 g/kg naringin treatment group had an improved loin eye muscle area, reduced serum triglycerides and were leaner compared with the other groups. Pigs in the 1.5 g/kg naringin treatment had higher pH45min values and inosine monophosphate concentrations, and lower MyHC IIb mRNA expression in muscle than the other groups. MyHC IIa mRNA expression was significantly up-regulated in all naringin-supplemented diet groups. Naringin significantly increased superoxide dismutase (SOD) activity and total anti-oxidative capacity in meat, as well as SOD and glutathione peroxidase activity in the liver. These results indicate that the dietary addition of naringin at 0.5 g/kg improved carcass characteristics, while 1.5 g/kg improved the oxidative stability and pork quality in finishing pigs. Keywords: antioxidant capacity; carcass characteristics; naringin-supplemented diets; pork qualit

Exchange coupling in CaMnO3_3 and LaMnO3_3: configuration interaction and the coupling mechanism

The equilibrium structure and exchange constants of CaMnO$_3$ and LaMnO$_3$ have been investigated using total energy unrestricted Hartree-Fock (UHF) and localised orbital configuration interaction (CI) calculations on the bulk compounds and Mn$_2$O$_{11}^{14-}$ and Mn$_2$O$_{11}^{16-}$ clusters. The predicted structure and exchange constants for CaMnO$_3$ are in reasonable agreement with estimates based on its N\'eel temperature. A series of calculations on LaMnO$_3$ in the cubic perovskite structure shows that a Hamiltonian with independent orbital ordering and exchange terms accounts for the total energies of cubic LaMnO$_3$ with various spin and orbital orderings. Computed exchange constants depend on orbital ordering. UHF calculations tend to underestimate exchange constants in LaMnO$_3$, but have the correct sign when compared with values obtained by neutron scattering; exchange constants obtained from CI calculations are in good agreement with neutron scattering data provided the Madelung potential of the cluster is appropriate. Cluster CI calculations reveal a strong dependence of exchange constants on Mn d e$_g$ orbital populations in both compounds. CI wave functions are analysed in order to determine which exchange processes are important in exchange coupling in CaMnO$_3$ and LaMnO$_3$.Comment: 25 pages and 9 postscript figure

High-resolution x-ray study of the nematic - smectic-A and smectic-A - smectic-C transitions in 8barS5-aerosil gels

The effects of dispersed aerosil nanoparticles on two of the phase transitions of the thermotropic liquid crystal material 4-n-pentylphenylthiol-4'-n-octyloxybenzoate 8barS5 have been studied using high-resolution x-ray diffraction techniques. The aerosils hydrogen bond together to form a gel which imposes a weak quenched disorder on the liquid crystal. The smectic-A fluctuations are well characterized by a two-component line shape representing thermal and random-field contributions. An elaboration on this line shape is required to describe the fluctuations in the smectic-C phase; specifically the effect of the tilt on the wave-vector dependence of the thermal fluctuations must be explicitly taken into account. Both the magnitude and the temperature dependence of the smectic-C tilt order parameter are observed to be unaffected by the disorder. This may be a consequence of the large bare smectic correlation length in the direction of modulation for this transition. These results show that the understanding developed for the nematic to smectic-A transition for octylcyanobiphenyl (8CB) and octyloxycyanobiphenyl (8OCB) liquid crystals with quenched disorder can be extended to quite different materials and transitions.Comment: 7 pages, 8 figure

Itinerant electron metamagnetism in LaCo9_9Si4_4

The strongly exchange enhanced Pauli paramagnet LaCo$_9$Si$_4$ is found to exhibit an itinerant metamagnetic phase transition with indications for metamagnetic quantum criticality. Our investigation comprises magnetic, specific heat, and NMR measurements as well as ab-initio electronic structure calculations. The critical field is about 3.5 T for $H||c$ and 6 T for $H\bot c$, which is the lowest value ever found for rare earth intermetallic compounds. In the ferromagnetic state there appears a moment of about 0.2 $\mu_B$/Co at the $16k$ Co-sites, but sigificantly smaller moments at the 4d and $16l$ Co-sites.Comment: 11 pages, 5 figures, PRB Rapid Communication, in prin

Primordial Trispectrum from Entropy Perturbations in Multifield DBI Model

We investigate the primordial trispectra of the general multifield DBI inflationary model. In contrast with the single field model, the entropic modes can source the curvature perturbations on the super horizon scales, so we calculate the contributions from the interaction of four entropic modes mediating one adiabatic mode to the trispectra, at the large transfer limit ($T_{RS}\gg1$). We obtained the general form of the 4-point correlation functions, plotted the shape diagrams in two specific momenta configurations, "equilateral configuration" and "specialized configuration". Our figures showed that we can easily distinguish the two different momenta configurations.Comment: 17pages, 7 figures, version to appear in JCA

Some (further) Comments on the Theta(1540) Pentaquark

Additional broader I=0 states in the KN channel near $\Theta^+$(1540) are expected in many models, making the absence of any signature in the K$^+$-deuteron scattering data even more puzzling. In an ideal "three-body" picture the $\Theta$ is viewed as two compact ud(1)ud(2) $\bar{3}$ color diquarks and an $\bar{s}$ quark. A "QCD-type" inequality involving $m(\Theta^+), m(\Lambda)$, the mass of the $\Lambda(1/2^-)$ L=1 excitation and that of a new I=0 tetraquark vector meson then follows. The inequality suggests a very light new vector meson, and is violated. We note that "associated production" of the pentaquark with another quadriquark or anti-pentaquark may be favored. This along with some estimates of the actual production cross sections suggest that the $\Theta$ can be found in BaBar or Belle e$^+$-e$^-$ colliders.Comment: 6 page

XUV digital in-line holography using high-order harmonics

A step towards a successful implementation of timeresolved digital in-line holography with extreme ultraviolet radiation is presented. Ultrashort XUV pulses are produced as high-order harmonics of a femtosecond laser and a Schwarzschild objective is used to focus harmonic radiation at 38 nm and to produce a strongly divergent reference beam for holographic recording. Experimental holograms of thin wires are recorded and the objects reconstructed. Descriptions of the simulation and reconstruction theory and algorithms are also given. Spatial resolution of few hundreds of nm is potentially achievable, and micrometer resolution range is demonstrated.Comment: 8 pages, 8 figure

Hyperfine structure of the ground state muonic He-3 atom

On the basis of the perturbation theory in the fine structure constant $\alpha$ and the ratio of the electron to muon masses we calculate one-loop vacuum polarization and electron vertex corrections and the nuclear structure corrections to the hyperfine splitting of the ground state of muonic helium atom $(\mu\ e \ ^3_2He)$. We obtain total result for the ground state hyperfine splitting $\Delta \nu^{hfs}=4166.471$ MHz which improves the previous calculation of Lakdawala and Mohr due to the account of new corrections of orders $\alpha^5$ and $\alpha^6$. The remaining difference between our theoretical result and experimental value of the hyperfine splitting lies in the range of theoretical and experimental errors and requires the subsequent investigation of higher order corrections.Comment: Talk on poster section of XXIV spectroscopy congress, 28 February-5 March 2010, Moscow-Troitsk, Russia, 21 pages, LaTeX, 8 figure

Finite element analysis and material sensitivity of Peltier thermoelectric cells coolers

In this work, a finite element simulation of a commercial thermoelectric cell, working as a cooling heat pump, is presented. The specially developed finite element is three-dimensional, non-linear in its formulation (using quadratic temperature-dependence on material properties) and fully coupled, including the Seebeck, Peltier, Thomson and Joule effects. Another special interface finite element is developed to prescribe the electric intensity, taking advantage of repetitions and symmetries. A thorough study of the distributions of voltage, temperature and the corresponding fluxes is presented, and the performance of the cell is compared with that of the manufacturer and with simplified analytical formulations, showing a good agreement. Combining the finite element model with the Monte Carlo technique, a sensitivity analysis is presented to take into account the performance dependence on the material properties, geometrical parameters and prescribed values. This analysis, which can be considered a first step to optimize these devices, concludes that the temperature-dependence of the material properties of electric conductivity and Seebeck coefficient is very relevant on cell performance.This research was partially supported by the Ministry of Education through Grant FPU AP-2006-02372 and also from Grants MICINN BIA-2008-00522, MCyT DPI 2002-04472-C02-02 and Excelencia Junta Andalucia P08-TEP-3641.Pérez-Aparicio, JL.; Palma, R.; Taylor, R. (2012). Finite element analysis and material sensitivity of Peltier thermoelectric cells coolers. International Journal of Heat and Mass Transfer. 55(4):1363-1374. https://doi.org/10.1016/j.ijheatmasstransfer.2011.08.031S1363137455