Computer controlled-flow injection potentiometric system based on virtual instrumentation for the monitoring of metal-biosorption processes

A completely automated flow-injection system was developed for the monitoring of biosorption studies of Cu(II) ion on vegetable waste by-products. The system employed flow-through Cu(II)-selective electrodes, of epoxy-resin-CuS/Ag₂S heterogeneous crystalline type, and computer controlled pumps and valves for the flow operation. Computer automation was done through a specially devised virtual instrument, which commanded and periodically calibrated the system, allowing for the monitoring of Cu(II) ions between 0.6 and 6530 mg L⁻¹ at a typical frequency of 15 h⁻¹. Grape stalk wastes were used as biosorbent to remove Cu(II) ions in a fixed-bed column with a sorption capacity of 5.46 mg g⁻¹, obtained by the developed flow system, while the reference determination performed by FAAS technique supplied a comparable value of 5.41 mg g⁻¹.     

Using Berry's phase to detect the Unruh effect at lower accelerations

We show that a detector acquires a Berry phase due to its motion in spacetime. The phase is different in the inertial and accelerated case as a direct consequence of the Unruh effect. We exploit this fact to design a novel method to measure the Unruh effect. Surprisingly, the effect is detectable for accelerations 10(9) times smaller than previous proposals sustained only for times of nanoseconds.     

Zn-doping effect on the energy barrier to magnetization reversal in superparamagnetic nickel ferrite nanoparticles

Measurements of ac-susceptibility and dc-magnetization were carried out on samples of Ni_1-xZn_xFe₂O₄ nanoparticles (x=0, 0.25, 0.5, 0.75) with average diameters 〈D〉≈7 nm. Values of the superparamagnetic blocking temperature T̄_B were obtained from the characteristic temperature behavior of the imaginary susceptibility χ_imag. An Arrhenius-type law, which accurately describes the relationship between the observation time τ_obs and the blocking temperature, was used to determine the effective energy barrier to magnetization reversal U_eff. A Zn-content dependence of the energy barrier is observed, where U_eff changes little for 0≤x≤0.25, it peaks at x=0.5, and decreases back upon further Zn-doping. The large increase of U_eff at x=0.5 is attributed to an enhanced magnetic anisotropy induced by the crossover between two spatial arrangements of spins in the A and B sub-lattices of the ferrimagnetic inverse spinel. PACS 75.50.Bb; 75.50.Gg; 75.30.Et     

Values for particle-scale properties of biomass briquettes made from agroforestry residues

The production of biomass pellets and briquettes from agroforestry residues has increased rapidly in recent years. The design of machines, equipment and the infrastructure necessary for the handling, transport and storage of these products has been an engineering challenge since, when moving, biomass does not usually flow as easily as other granular materials. The discrete element method(DEM) provides a means of studying the handling and silo discharge behaviour of granular solids as well as the distribution of the pressures exerted by such materials in silos. However, the development of such models requires certain properties of the particles in question to be known. The present work experimentally determines the true density, Young's modulus of elasticity(axial and radial), the particle–particle restitution coefficient and the particle–wall friction coefficient—all variables that must be known in the construction of DEM models—for briquettes made from maize stalk, maize stalk plus pine wood chips, rice husk, vine shoots, rape straw, cereal straw and sawdust plus cereal straw.     

Role of pH in the stabilization of two types of silver clusters

Conditions for stabilization of silver clusters peaking at 320 nm are fond. Role of pH in stabilization of two types of silver clusters peaking at 320 and 290 nm is discussed.     

Probe calibration of the scanning thermal microscope in the AC mode

Scanning thermal microscope based DC measurements of local thermal conductivity are relevant to insulating (<20 W m⁻¹ K⁻¹) materials only. We aim at using the 3ω method to enhance the sensitivity of the device to a larger range. In this paper we present both a thermal model and experimental results from the calibration procedure to study the thermal behaviour of stand-alone probes. The two approaches provide data in very good agreement on the full measured frequency domain. Several geometric and thermal parameters are deduced from the comparison. Those quantities are key inputs for future heat transfer modeling of the tip–sample contact.     

Bentonitic earth catalyzed rearrangement of aryl 1,1-dimethylpropargyl ethers. Synthesis of 2,2-dimethyl-2H-1-benzopyrans

Mexican Bentonitic earth (Tonsil) catalyzed the Claisen rearrangement of aryl 1,1-dimethylpropargyl ethers under mild conditions to provide 2,2-dimethyl-2H-1-benzopyrans. The synthesis of encecalin 2f and desmethoxyencecalin 2i , two biologically active products among other natural products ( 2b, 2e ) was performed by this procedure.     

Functional Features of Alginates Recovered from Himanthalia elongata Using Subcritical Water Extraction

Subcritical water extraction of Himanthalia elongata and the subsequent acetone fractionation to precipitate crude fucoidans generated a liquid phase which was used to recover alginates with a wide range of viscoelastic features and other soluble extracts with potential biological activities. The precipitated alginate was converted to sodium alginate using an environmentally friendly treatment before being characterized by Fourier transform infrared attenuated total reflectance, nuclear magnetic resonance, high performance size exclusion chromatography and rheological measurements. The cell viability of three human cell lines (A549, HCT-116, T98G) in the presence of the extracts obtained before and after acetone fractionation was assessed. Fractionation with different acetone volumes showed a slight effect in the behavior of the different tested cell lines. Results also indicated a notable effect of the processing conditions on the block structure and molar mass of the extracted biopolymer, with the subsequent impact on the rheological properties of the corresponding gelled matrices.