Inclusion Compounds of Dehydrocholic Acid with Solvents

The host-guest inclusion of various organic solvents within dehydrocholic acid has been studied and the selectivity of enclathration determined by competition experiments.     

An Analysis of the Sensitivity of Digital Modulation Techniques to Frequency-Selective Fading

This Paper investigates the sensitivity to frequency-selective fading of different modulation techniques commonly used in digital radio systems. The modulation methods considered are phase-shift-keying (Mary PSK), nonoffset and offset quadrature amplitude modulation (M-ary QAM), and quadrature partial response signaling (QPRS). The performances of these methods during multipath fading are compared on the basis of the "signatures" calculated for idealized systems. Results are presented from which the relative outage probability was determined, assuming a propagation channel with frequency-selective Rician fading.     

Single-wall carbon nanotubes prepared with different kinds of Ni-Co catalysts: Raman and optical spectrum analysis

The addition of acetates and nitrates for the synthesis of single-wall carbon nanotubes via laser ablation was explored. Targets containing nominal amounts of acetates or nitrates in addition to Ni and Co catalysts were compared to a standard target containing only Ni and Co at temperatures ranging from 1000 to 1200 °C. The as produced web-like soot was characterized by transmission electron microscopy, Raman spectroscopy and optical absorption spectroscopy. All samples showed a linear increase in SWCNT mean diameter with temperature; however, the rate of mean diameter change with temperature differed for the various targets, more so at lower temperatures. The addition of nitrates improved the SWCNT relative yield over all the temperatures used, whereas the inclusion of acetates improved the relative yield only at lower temperatures. The above results were discussed and analyzed according to the porous structure of the targets resulting from the decomposition of the acetates and nitrates and consequential thermal diffusion changes.     

Optimisation of a thick-film 10–400 N force sensor

The ring-on-ring bending principle allows the fabrication of simple, low-cost thick-film piezoresistive sensors for compressive forces in the 10–400 N range. However, some imperfections are encountered in its basic embodiment, such as relatively high force-signal hysteresis and nonrepeatability (up to ca. 5%). These shortcomings were studied in this work, and major improvements have been achieved. Hysteresis was found to be mainly due to friction at the outer support ring, and was considerably reduced by inserting a compliant silicone glue ring. The same glue ring was used to permanently bond the sensor to a rigid base, thereby giving well-defined and constant boundary conditions and also considerably improving the repeatability of the sensitivity. Overall, hysteresis and repeatability error were reduced down to a level of ca. 1%.     

Chemical and biological variability of hot pepper fruits (Capsicum annuum var. acuminatum L.) in relation to maturity stage

The aim of the present work was to evaluate the chemical composition and the radical-scavenging and antioxidant activities of hot pepper fruits (Capsicum annuum L. var. acuminatum) at three maturity stages (small green, green and red). GC–MS analysis of n-hexane and chloroform fractions showed a different composition between the three stages of ripening. The first stage of maturation (small green) showed the highest radical-scavenging activity (IC₅₀ of 129 μg/ml). Using the bovine brain peroxidation assay, the methanolic extract of green pepper showed significant antioxidant activity (IC₅₀ of 522 μg/ml). Addition of methanolic extract of red and green pepper inhibited oxidation of linoleic acid. Methanolic extract of red pepper showed greater antioxidative potency than the others (IC₅₀ of 3 μg/ml). The different composition of lipophilic compounds and the various amount of phenolics, showed in the three stage of ripening of C. annuum var. acuminatum fruits, modifies the antioxidant activity.     

Viscosimetric studies on 2-methoxyethanol + 1,2-dimethoxyethane binary mixtures from −10 to 80°c

The kinematic viscosities (v) were measured for nine binary solvent mixtures of 2-methoxyethanol (ME) + 1,2-dimethoxyethane (DME) at nineteen temperatures ranging from ?10 to +80°C. The experimental data have been used to test some empirical equations of the type v = v(T), v = v(X₁) and v = v(T, X₁). The viscosities of all the mixtures increase from the values of pure DME to that of ME as the mole fraction of ME increases, and always yield a negative excess property (v^E) at all the investigated temperatures. Furthermore, thermodynamic parameters of viscous flow have been evaluated on the basis of the Eyring theory. The excess free energy of activation of viscous flow (ΔG^E) vs X₂ plot suggests the presence of a stable hetero-adduct, having ME : DME = 1 : 1 stoichiometric ratio.     

Fracture mechanics models applied to delayed failure of LVL beams

Several theories for modelling fracture and slow growth of a crack in wood have been developed. The various models may be differentiated by the specifically regarded stress levels, failure mechanisms and averaging procedures. This paper deals with the application of viscoelastic fracture mechanics models to predict delayed failure of a timber element in bending. Simulations are compared to experimental results of bending tests carried out on LVL (Laminated Veneer Lumber) notched beams. This analysis emphasizes the influence of the geometry and of the size of the beam as well as of the damage area on the delayed failure.     

Isolation of a hydroxytyrosol-rich extract from olive leaves (<Emphasis Type="Italic">Olea Europaea</Emphasis> L.) and evaluation of its antioxidant properties and bioactivity

In this research, a phenol extract of high hydroxytyrosol (OLPE) content was obtained from olive leaves (Olea europaea L.), and subsequently tested under different contexts. The method used to obtain the OLPE basically involved two steps: the use of strongly-acid aqueous steam, generated from 10% HCl (v/v) at 100°C, to directly hydrolyse the native complex phenols from integral olive leaves, and OLPE recovery by liquid–liquid extraction with ethyl acetate. Hydrolysis time was 1 h. Finally, the dried extract was dissolved in distilled water. The OLPE total phenols were determined by Folin–Ciocalteu’s method and by HPLC analysis. Hydroxytyrosol was about 92% of the total phenols present in OLPE, and the yield was about 0.2% on fresh leaves. OLPE showed antioxidant effects on different food lipids and did not inhibit lactic acid bacteria growth; however, it showed cytotoxicity on NIH/3T3 fibroblasts and human umbilical vein endothelial cells at concentrations higher than 0.32 mM (as hydroxytyrosol).     

Adsorption of Thin Liquid Helium Films on Cs Measured via Photoelectron Tunneling

The alkali metals Cs and Rb are the only surfaces which are not wetted by superfluid ⁴ He below a certain temperature. In our experiments, using the photoelectron tunneling method, we can highly resolve the growth of the non-wetting thin-film state of ⁴ He on a quench-condensed Cs surface. It turns out that far from coexistence there is little adsorption of helium. In contrast, close to coexistence a rapid growth up to two monolayers of helium is observed, but the surface is still non-wet under the usual convention.