Domain Wall Dynamics in Annealed GaMnAs Epilayers

We study magnetic field-driven domain wall motion in a GaMnAs thin film. The velocity is measured as function of the applied field. It varies over 6 orders of magnitude in a field range of 2.5 mT. Two regimes are identified. At low field, the domain wall motion follows a creep regime: it is controlled by defects and the domain wall velocity increases exponentially with the applied field. At higher fields, the domain wall motion follows a depinning regime: pinning defects are less efficient and the wall velocity increases linearly with the field. The highest measured domain wall velocity is 14 m s⁻¹.     

Selection of variables using factorial discriminant analysis for the state identification of an anaerobic UASB-UAF hybrid pilot plant, fed with winery effluents.

Anaerobic wastewater treatment has become a widely used method for wastewater depuration, and has been applied in a wide range of situations, from urban wastewater to highly toxic industrial wastewater. Particularly it has been successfully applied to the treatment of the beverage industries effluents. To avoid the destabilization of the system a monitoring diagnosis and control system of the depuration processes is necessary. The cost of this system is an important issue, that depends on the number of parameters that must be controlled for an adequate performance of a wastewater plant control system. This work shows how the classic statistical classification techniques can be applied to determine the number variables that must be monitored to achieve an adequate performance of anaerobic UASB-UAF hybrid Pilot Plant monitoring and control system. The obtained results had not been unique, so different combinations of variables can be selected for a good wastewater treatment process control. Economic or technical criteria may be considered to determine the final variables set in each particular situation.     

Application of the Voronoï tessellation to study transport and segregation of grains inside 2D and 3D packings of spheres

This article provides a simple method to simulate the transport of a small bead through a static granular medium as a random walk on a network. This kind of displacement is strongly related to the geometry of the porous structure. A way to map the interparticle space is to calculate the Voronoï tessellation of the packing whose edges describe the network of pores of the medium. Then, the calculation of the probabilities to use each bond and a Monte-Carlo method for the choice of them, can simulate the displacement of the sphere. We introduce this technique for the inter-particle percolation of a fine particle through a packing of monosize spheres. We compare our numerical simulation with experiments performed in our laboratory. Then this technique is extended to the surface segregation. For the two kinds of segregation, we study the transverse diffusion and obtain a good agreement with experimental results. That our numerical simulation based on a rigorous geometric analysis of the medium is in agreement with inter-particle percolation and surface segregation experiments shows the importance of the study of the geometry of granular materials.     

Automatic Start-Up of UASB Reactors

A control system to automate the start-up of anaerobic wastewater treatment reactors is presented. The system controls the feedflow rate, using the biogas production or the biogas flow rate as the only on-line variable. Furthermore, other off-line parameters, such as methane content in the biogas and COD of influent are also necessary to calculate the COD balance in the reactor. Two different start-up strategies were applied: fed batch and continuous operation. In the fed-batch operation the frequency of feeding is automatically set depending on the efficiency in COD removal. The residual organic load fraction (the fraction of influent COD not degraded to methane), is the key parameter enabling the controller the modification of feeding frequency. In order to improve reliability of the system, a second parameter k representing the gas flow rate, was introduced. By using this strategy, starting from an organic loading rate (OLR) lower than 0.5 kg COD∕(m3?day), a load higher than 8 kg COD∕(m3?day) was achieved in only 33 days, with an efficiency, in terms of COD removal, higher than 90%. When the system was operated in continuous mode, the key parameter applied is again the residual organic loading rate fraction, expressed as the percentage of COD that remained undegraded in methane. Two extreme values—“minimum” and “maximum”—have to be defined. Once the system reaches the minimum, the controller increases the feeding pump speed automatically, and when it attains the maximum value, the feeding flow is decreased proportionally. In order to ensure stable operation, a further parameter, the waiting time between the moment at which the threshold value is reached and the modification of the feeding flow rate, was introduced. 24 h has proven to be an excellent value for this purpose. By means of this strategy, starting from an influent OLR lower than 0.5 kg COD∕(m3?day), an OLR of 9–12 kg COD∕(m3?day) was achieved in 40 days, with COD removal efficiency higher than 95%.     

Immunomodulatory Effect of Human Lactoferrin on Toll-like Receptors 2 Expression as Therapeutic Approach for Keratoconus

Keratoconus (KC) is a corneal disorder whose etiology shares a close relationship with Lactoferrin (LTF) dysregulation and Toll-like Receptors 2 (TLR2) overexpression. This study shows how these two important biomarkers are clinically and molecularly interrelated, increasing knowledge about KC pathophysiology, and opening the door to future therapies. In this prospective clinical study, serum and tear LTF concentrations were quantified in 90 KC patients and 60 controls. A correlation analysis with multiple blood and tear immunoinflammatory mediators, and KC-associated tomographic parameters, was performed. An in vitro study using HEK-Blue^TMhTLR2 cell cultures was also conducted to determine the expression and functionality of TLR2 under the influence of LTF treatment. As a result, a LTF decreased was observed in KC patients compared to controls (p < 0.0001), evidencing the strong correlation with TLR2 overexpression at systemic and ocular surface level, with inflammatory mediator upregulation and with KC severity. In stimulated cell cultures, TLR2 expression was decreased using 2 mg/mL of LTF. The levels of secreted embryonic alkaline phosphatase (SEAP) and interleukin-8 (IL-8) were also reduced in supernatants after LTF treatment. As conclusions, the dysregulation of LTF and TLR2 in the ocular surface of KC patients contributes to KC severity by maintaining a detrimental chronic immune–inflammatory state. The immunomodulatory properties of LTF on TLR2 expression suggest its potential as a therapeutic approach for KC.     

Fetal Bovine Serum Concentration Affects Δ<Superscript>9</Superscript> Desaturase Activity of <Emphasis Type="Italic">Trypanosoma cruzi</Emphasis>

Fetal bovine serum (FBS) is an important factor in the culture of Trypanosoma cruzi, since this parasite obtains and metabolizes fatty acids (FAs) from the culture medium, and changes in FBS concentration reduce the degree of unsaturation of FAs in phosphoinositides. When T. cruzi epimastigotes were cultured with 5% instead of 10% FBS, and stearic acid was used as the substrate, ∆⁹ desaturase activity decreased by 50%. Apparent K _m and V _m values for stearic acid, determined from Lineaweaver–Burk plots, were 2 μM and 219 pmol/min/mg of protein, respectively. In studies of the requirement for reduced pyridine nucleotide, ∆⁹ desaturase activity reached a maximum with 8 μM NADH and then remained constant; the apparent K _m and V _m were 4.3 μM and 46.8 pmol/min/mg of protein, respectively. The effect of FBS was observed only for ∆⁹ desaturase activity; ∆¹² desaturase activity was not affected. The results suggest that decreased FBS in culture medium is a signal that modulates ∆⁹ desaturase activity in T. cruzi epimastigotes.     

Development of a semi-analytical model to predict the pressure drop of clean pleated high-efficiency particulate air filters

The present article outlines the development of a semi-analytical model devoted to predict the pressure drop induced by clean pleated high-efficiency particulate air (HEPA) filters. Both experimental measurements and numerical simulations are used to characterize the velocity field in the pleat channel. On this basis, a semi-analytical model is derived to determine the gas flow within the pleat channel. This analytical formulation is used to predict the air pressure evolution according to filtration velocity in the pleat. This model is then validated on the basis of comparisons with measurements found in the scientific literature for different kinds of HEPA filters with different pleat geometries. This model is easy to use, fast to run compared to standard computational fluid dynamics (CFD) approaches, and is in good agreement with the experimental results.     

Environmental engineering education in Spain.

There is a growing demand for engineers and technologists who show multidisciplinary expertise to deal with environmental issues. As a result of this demand, most countries are adapting their old university programs on environmental engineering education. In Spain an official environmental engineering degree does not yet exist, but the Council of Universities is working to present a proposal, based on Bologna agreement concepts. The paper summarizes not only the future perspectives of environmental engineering education in Spain, but also the evolution of the approach during the last decades, which includes the role of the private initiative, the environmental sciences degree, and the intensification in different traditional engineering degrees. Finally, the paper briefly details and compares the syllabus developed in the only four Spanish universities where environmental engineering is offered as a non-official post-graduate course lasting two years.     

Characterization of anaerobic granular sludge developed in UASB reactors that treat ethanol, carbohydrates and hydrolyzed protein based wastewaters.

In this work, granules developed from UASB reactors that treat different types of wastewaters (ethanol, carbohydrates and protein-based synthetic wastewaters) were studied. Granule parameters (size distribution; density; settlement characteristics; elemental composition; acidogenic and methanogenic activities) were analyzed along with micro-organisms identified by FISH to better understand granule behavior and its formation process. Micro-organisms distributions in anaerobic granules are highly dependent on the type of treated wastewater. Granules developed in a UASB reactor that treats wastewater with a high content of carbohydrates presented high acidogenic bacteria colonization. Members of Methanosaetaceae were the dominant methanogens in the studied granules, and Methanobacteriales appear to be co-dominant in the granules developed with carbohydrates and protein-based wastewaters.     

Sodium bicarbonate or multielement buffer via diet or rumen: effects on performance and acid-base status of lactating cows.

Our objective was to compare the influence of dietary NaHCO3 and a multielement buffer on ruminal acid-base status and lactation performance of dairy cows. Five ruminally fistulated, primiparous and multiparous lactating Holstein cows averaging 123 +/- 21 d postpartum were assigned randomly to treatments in a 5 x 5 Latin square with 3-wk experimental periods. Treatments were a basal diet without supplemental buffers, with 1.5% NaHCO3 or 1.5% multielement buffer, or with NaHCO3 or multielement buffer solutions poured into the rumen via cannula at 2 h postfeeding. Addition of either buffer to the diet reduced ruminal fluid hydrogen ion concentration from 0 to 6 h postfeeding; only NaHCO3 reduced ruminal fluid acidity when dosed via the cannula. Addition of buffers via ruminal cannula appeared to retard the reduction in ruminal fluid acidity that normally occurs from 6 to 12 h postfeeding; this may have been related to a feedback mechanism inhibiting salivary buffer secretion. Buffering capacity of ruminal fluid tended to increase with buffer addition; the increase was greatest during infusion of NaHCO3. The ruminal fluid buffer value index increased by 4 units for control cows from early (0 to 6 h) to late (6 to 12) postfeeding; smaller increases were noted for addition of multielement buffer. This index was not different for NaHCO3 during these two intervals. Milk yield and DMI were not affected by buffer addition. Although milk fat content tended to be higher with the multielement buffer than with NaHCO3, it was not accompanied by the expected alterations in ruminal acid-base status. Therefore, this increase may be related to systemic effects of specific minerals in the multielement buffer rather than to a more stable ruminal environment. Based on the ruminal fluid buffer value index, NaHCO3 tended to maintain the most stable ruminal acid-base status.