José Trinidad Elizalde Galindo

Magnetic field effect on growth, arsenic uptake, and total amylolytic activity on mesquite (Prosopis juliflora x P. velutina) seeds

Magnetic field is closely related to the cell metabolism of plants [N. A. Belyavskaya, Adv. Space Res. 34, 1566 (2004)]. In order to see the effect of magnetic field on the plant growth, arsenic uptake, and total amylolytic activity of mesquite (Prosopis juliflora x P. velutina) seeds, ten sets of 80 seeds were selected to be oriented with the long axis parallel or randomly oriented to an external magnetic field. The external magnetic field magnitude was 1 T, and the exposition time t = 30 min. Then, the seeds were stored for three days in a plastic bag and then sown on paper towels in a modified Hoagland’s nutrient solution. After three days of germination in the dark and three days in light, seedlings were grown hydroponically in modified Hoagland’s nutrient solution (high PO42−) containing 0, 10, or 20 ppm of arsenic as As (III) and (V). The results show that the germination ratios, growth, elongation, arsenic uptake, and total amylolytic activity of the long axis oriented mesquite seeds were much high...

Fuzzy Database Languages Integration Using Expressive Power

Most widely known fuzzy set based extension of SQL are FSQL and SQLf. This work is an effort for integrating them in a sole standard as a step to the diffusion of fuzzy sets using in DBMS and real world applications. We apply criteria taken from programming language design area, such as the expressive power, and we provide new results: a fuzzy SQL standard and the definition of the evaluation of GROUP BY operator and nested queries over fuzzy tables with fuzzy attributes.

Nanocrystalline Sm0.5Y0.5Co5 Alloys with Enhanced Magnetic Properties

Nanocrystalline Sm0.5Y0.5Co5 powders (average crystal size d = 12 nm) were produced by arc melting pure metals followed by mechanical milling and annealing. Different milling/annealing times and annealing temperatures were used to optimize the hard magnetic properties of these nanopowders. A noticeably enhanced coercivity and remanence (coercivity of 2.1 MA/m, and σr/σmax = 0.7 respectively) were observed in samples milled for 240 minutes and then annealed for 1 minute at Temperatures ~1200K. Such remarkable magnetic properties stem from the high magnetocrystalline anisotropy field and the homogeneous grain size of the Sm0.5Y0.5Co5 nanocrystals.

Design and construction of a desktop AC susceptometer using an Arduino and Bluetooth for serial interface

We designed and developed a desktop ac susceptometer for the characterization of materials. The system consists of a lock-in amplifier, an ac function generator, a couple of coils, a sample holder, a computer system with a designed software in freeware C++ code, and an Arduino card coupled to a bluetooth module. The Arduino/bluetooth serial interface allows the user to have a connection to almost any computer and thus avoids the problem of connectivity between the computer and the peripherals such as the lock-in amplifier and the function generator. The bluetooth transmitter/receiver used is a commercial device which is robust and fast. These new features reduce the size and increment the versatility of the susceptometer for it can be used with a simple laptop. To test our instrument we performed measurements on magnetic materials and show that the system is reliable at both room temperature and cryogenic temperatures (77 K). The instrument is suitable for any physics or engineering laboratory either for research or academic purposes.

Characterization of Magnetic Particles Using a Wavelet Function

The second derivative of the remission function of several magnetic materials is calculated for the parameterization of the position and intensity of the absorption bands of diffuse reflectance spectroscopy. The reflectance spectra are obtained by ultraviolet-visible spectroscopy (UV-VIS) from 400 to 1100 nm at increments of 1nm. The noise of the remission function results on errors after calculating the second derivative. Therefore, filtering of the remission function is needed before taking any action on this signal. Several methods are tested in order to calculate the second derivative. The best polynomial resulted on a second order wavelet function which is applied to the filtered remission function. Light scattering Mie theory is used to prove the behaviour of the reflected light. This research provides a method to identify and quantify magnetic particles, as well as the crystal size.

Annealing Effect on Microstructure and Coercivity of YCo5 Nanoparticles Obtained by Mechanical Milling

Nanocrystalline YCo5 powders with high coercivity were prepared by mechanical milling and subsequent heat treatment at 820 °C for different annealing times, ta = 2.5, 3.0, 3.5 and 4.5 min, obtaining average crystallite sizes of  17, 19, 32 and 39 nm., respectively. The coercivity values were determined from the hysteresis loops measured at maxima fields of Hm = 5 and 20 T. The highest coercivity was obtained for the sample exhibiting  19 nm, where at room temperature and Hm = 5 T, the coercivity value is of 9.0 kOe. At 77 K and Hm = 5 T, the coercivity increase to 11.8 kOe and for Hm = 20 T, a higher value such as 13.1 kOe was found. The Ms/Mr ratio is enhanced to 0.62 indicating the occurrence of exchange interaction among nanocrystalline magnets.