Pure magnetooptic diffraction and Kerr microscopy of periodic domain structures

The fabrication of a periodic domain structure in a ferromagnetic thin film is reported. This periodic domain structure is formed in a thin continuous magnetic film by coupling it to a periodic array of magnetic elements grown on top. When the array and the continuous film are exchange decoupled, magnetostatic interactions produce in the continuous layer a domain structure replica of the topographic pattern at selected field values. The present work reports a direct confirmation of this periodic domain structure in the flat continuous film by Kerr microscopy, which is responsible for the pure magnetooptic diffraction. The effect on the magnetization processes of oneand two-dimensional structures with different periodicities and dimensions is studied in detail and compared with micromagnetic simulations, for Co and Fe films.     

Microstructure, interdiffusion and magnetic properties of ZnO/MnOx multilayers grown by pulse laser deposition

ZnO/MnO_x nano-thin multilayers are fabricated by pulsed laser deposition with a sectioned target or “cake” technique. Structure and magnetic properties are measured, finding a magnetic signal that scales better with the number of interfaces than with the film volume, and an interlayer interdiffusion that happens at remarkably low film growth temperatures.     

Effect of Osmotic Pretreatment on Hot Air Drying Kinetics and Quality of Chilean Papaya (Carica pubescens)

The effect of osmotic pretreatment on the mass transfer kinetics and quality of dried rehydrated Chilean papaya was researched. Osmotic treatments were sucrose solutions of 40, 50, and 60% w/w and dried at 60°C; non-pretreated samples were dried at different temperatures (40, 60, and 80°C). Quality parameters were analyzed: proximal composition, rehydration ratio, water-holding capacity, color, vitamin C content, firmness, and microstructure. Non-pretreated samples showed a clear turgor loss, color loss. and low ascorbic acid retention when rehydrated. Osmotic pretreatment improved the quality of rehydrated papayas, showing higher ascorbic acid retention and best firmness and color. Microstructure is better preserved in the pretreated papayas than in the non-pretreated samples, although this difference is minimal.     

Structural and physical modifications of corn biscuits during baking process

Colour, crust browning and specific volume of batter is essential to the manufacture of biscuit of good quality, but these properties are rarely measured directly in fermenting batter due to lack of suitable instrumentation. The aim of this study was to systematically evaluate the changes in quality parameters and physical properties of corn biscuits during baking in real time and different oven temperatures using a computer vision system. Colour, crust browning and specific volume of corn biscuits were determined by an image analysis technique using a computerized vision system. Additional quality parameters evaluated were weight loss and firmness of corn biscuit samples. Baking experiments were performed at 190, 210, 230 and 250 °C under natural convection. Colour results showed that it is possible to distinguish two stages in the variation of lightness during the baking time of corn biscuit samples, independently of oven temperature. As a result of the drying effect, it was observed a weight loss and superficial dry layer formation in corn biscuit. The computer vision system can be useful to measure some quality parameters in food products because, among other advantages, it is easy to use, as well as faster and flexible.     

Rapid engraftment without significant graft-versus-host disease after allogeneic transplantation of CD34+ selected cells from peripheral blood

We have prospectively evaluated the feasibility and results of the biotin-avidin immunoadsorption method (Ceprate SC system) for a phase I/II study of T-cell depletion of granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood progenitor cells (PBPC) for allogeneic transplantation. Twenty consecutive patients, median age, 40 years (21 to 54) and diagnoses of chronic myeloid leukemia in chronic phase (n = 5), acute myeloblastic leukemia (n = 7), acute lymphoblastic leukemia (n = 2), chronic myelomonocytic leukemia (n = 1), refractory anemia with excess of blasts in transformation (n = 3), histiocytosis X (n = 1), and chronic lymphocytic leukemia (n = 1), were conditioned with cyclophosphamide (120 mg/kg) and total body irradiation (13 Gy; 4 fractions). HLA identical sibling donors received G-CSF at 10 microg/kg/d subcutaneously (SC); on days 5 and 6 (19 cases) and days 5 to 8 (1 case) donors underwent 10 L leukapheresis. PBPC were purified by positive selection of CD34+ cells using immunoadsorption biotin-avidin method (Ceprate SC) and were infused in the patients as the sole source of progenitor cells. No growth factors were administered posttransplant. The median recovery of CD34+ cells after the procedure was of 65%. The median number of CD34+ cells infused in the patients was 2.9 (range, 1.5 to 8.6) x 10(6)/kg. The median number of CD3+ cells administered was 0.42 x 10(6)/kg (range, 0.1 to 2). All patients engrafted. Neutrophil counts >500 and >1,000/microL were achieved at a median of 14 days (range, 10 to 18) and 15 days (range, 11 to 27), respectively. Likewise, platelet counts >20,000 and >50,000/microL were observed at a median of 10 days (range, 6 to 23) and 17 days (range, 12 to 130), respectively. Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine plus methylprednisolone. No patient developed either grade II to IV acute or extensive chronic GVHD. After a median follow-up of 7.5 months (range, 2 to 22) three patients have relapsed, and one of them is again in hematologic and cytogenetic remission after infusion of the donor lymphocytes. Two patients died in remission: one on day +109 of pulmonary aspergillosis and the other on day +251 of metastasic relapse of a previous breast cancer. Sixteen of the 20 patients are alive in remission after a median follow-up of 7.5 months (range, 2 to 22). In conclusion, despite the small number of patients and limited follow-up, it appears that this method allows a high CD34+ cell recovery from G-CSF mobilized PBPC and is associated with rapid engraftment without significant GVHD, and with low transplant related mortality.     

Assessment of different selective agar media for enumeration and isolation of Listeria from dairy products

Different selective agar media were compared for the recovery and isolation of five species of Listeria from raw milk and cheese. The selective media examined were Beerens medium, MacBride medium and that described by Dominguez et al. (1984) with 6 mg/l acriflavine, listeria selective agar medium (LSAM), and LSAM with 12 mg/l acriflavine (LSAM X 2A); a non-selective yeast glucose Lemco agar was included for comparison. When the difference between listeria and the natural microflora of raw milk and cheese was 10(2) cfu/ml, listeria could be isolated by direct plating on all media tested. When it was lower than 10(3)-10(4) cfu/ml, listeria were isolated by direct plating only on LSAM and LSAM X 2A. When the difference was greater than 10(4) cfu/ml, a previous enrichment was necessary to isolate them. LSAM and LSAM X 2A media performed better than the other media tested for isolating listeria by direct plating and improved their isolation from dairy products. This superior performance was evaluated by the ability of these media to support colony formation of different species of Listeria tested, the easy recognition of these colonies from those formed by other microorganisms and by their capacity to inhibit the natural microflora of these foods.     

The leaching of silver sulfide with the thiosulfate–ammonia–cupric ion system

In recent years, there has been renewed interest in the use of thiosulfate as a substitute for cyanide in gold and silver leaching. Copper has been recognized to act as a catalyst in the process, and ammonia to stabilize the system. However, discrepancies exist in the literature concerning the oxidizing agent and, specifically in the case of silver sulfide (argentite), whether the leaching is oxidative or by substitution. The distinct mechanisms have implications concerning the feasibility of the process. The present study elucidates the chemistry of the leach through calculation of the species distribution and experiments on pure phase argentite, and also determines the role of the ammonia/thiosulfate concentration ratio. The experimental results on the pure phase show that the cupric ion reacts with thiosulfate to form the tetrathionate ion and a cuprous thiosulfate or ammonia complex, which liberates the silver by substitution in the solid phase. The results of leaching studies from a mineral concentrate indicate that, in addition to the cuprous ion concentration, the ammonia/thiosulfate ratio influences the silver extraction velocity: silver solubility and extraction are favored at low values of this quantity. A mathematical model for silver leaching in this system, which considers redox and complex equilibria, was developed. The experimental extractions were similar to those predicted by the model for low ammonia concentrations. Divergence from the simulated behavior was probably due to the slow reduction of the cupric ion at the high ammonia concentration (1 M).     

Nanostructure and magnetic properties of the MnZnO system, a room temperature magnetic semiconductor?

The magnetic properties of the system MnZnO prepared by conventional ceramic procedures using ZnO and MnO(2) starting powders are studied and related to the nanostructure. Thermal treatment at 500?°C produces a ferromagnetic phase, although this temperature is not high enough to promote proper sintering; thus the thermally treated compact shows brittle characteristics of unreacted and poorly densified ceramic samples. Scanning electron microscopy and x-ray analysis reveal the appearance of a new phase, most probably related to the diffusion of Zn into MnO(2) oxide nanocrystals. The magnetic properties deviate considerably from what would be expected of an unreacted mixture of ZnO (diamagnetic) and MnO(2) particles (paramagnetic above 100?K and anti-ferromagnetic below that temperature), exhibiting a ferromagnetic like behaviour from 5 to 300?K and beyond mixed with a paramagnetic component. The ferromagnetic phase seems to be originated by diffusion at the nanoscale of Zn into MnO(2) grains. The Curie temperature of the ferromagnetic phase, once the paramagnetic component has been subtracted from the hysteresis loops, is measured to be 450?K. EPR resonance experiments from 100 to 600?K confirm a ferromagnetic to paramagnetic like transition above room temperature for these materials.