Solar‐tracking PV plants in Navarra: A 10 MW assessment

Currently, the know‐how and experience concerning the behavior and reliability of large tracking photovoltaic (PV) plants is scarce. Information such as the availability rate is rarely known. Acciona Solar PV plants installed in Navarra (Spain) in the frame of the Spanish utility grid constitute a representative source of information. The scope of this study is to analyze in detail the behavior along 2006 of six of these plants, located in Arguedas (two plants of a rated nominal power of 940 kWp and 2·1 MWp, respectively), Sesma (1·12 MWp), Cintruénigo (1·44 MWp), Rada (1·78 MWp), and Castejón (2·64 MWp). In our analysis, the influence of each type of energy loss affecting the plants has been quantified; and the advantages of dedicating human resources to the surveillance and maintenance of a limited number of generators have been stated. Thanks to the work of the operators, the plants registered mean availability rates above 99·7%. Copyright © 2009 John Wiley & Sons, Ltd.     

Endogenous Enzymatic Activity in Dentin Treated with a Chitosan Primer

The aim of this study was to evaluate the effect of different concentrations of chitosan polymer on dentinal enzymatic activity by means of gelatin and in situ zymography. Human dentin was frozen and ground in a miller. Dentin powder aliquots were demineralized with phosphoric acid and treated with three different concentrations of lyophilized chitosan polymer (1, 0.5 and 0.1 wt%) dissolved in distilled water. Dentin proteins were extracted from each experimental group and electrophoresed under non-reducing conditions in 10% SDS-PAGE containing fluorescein-labeled gelatin. After 48 h in the incubation buffer at 37 °C, proteolytic activity was registered under long-wave UV light scanner and quantified by using Image J software. Furthermore, additional teeth (n = 4) were prepared for the in situ zymographic analysis in unrestored as well as restored dentin pretreated with the same chitosan primers. The registered enzymatic activity was directly proportional to the chitosan concentration and higher in the restored dentin groups (p < 0.05), except for the 0.1% chitosan primer. Chitosan 0.1% only showed faint expression of enzymatic activity compared to 1% and 0.5% concentrations. Chitosan 0.1% dissolved in water can produce significant reduction in MMPs activity and could possibly contribute to bond strength preservation over time.     

Optical characterizations of ZnO, SnO2, and TiO2 thin films for butane detection

The optogeometric properties of various sensitive thin films involved in gas sensing applications are investigated by using the m-line technique and atomic force microscopy. Variations of these optical properties are studied under butane and ozone exposure.     

Cationic photocured epoxy nanocomposites filled with different carbon fillers

In this work, the effect of several carbon fillers, exfoliated graphite (EG), functionalized graphene sheets (FGS), multi-walled carbon nanotubes (MWCNTs), and oxidized multi-walled carbon nanotubes (f-MWCNTs), were compared on the curing process and physical properties of a cationically photocurable epoxy resin. The extent of the photopolymerization was monitored by Real-Time FTIR spectroscopy. It was found that all the nanofillers delayed the curing reaction probably due to a shielding effect as well as to an increase of the resin viscosity. All the systems showed an electrical percolation threshold, but with MWCNTs was attained at a lower concentration (<0.1 wt.%). In addition, FGS showed the best response in terms of the dynamic mechanical and microindentation performances. An increase of more than 20 °C in the glass transition temperature was observed with the addition of 1 wt.% of FGS.     

L carnitine in hemodialysis patients

Carnitine, 3-hydroxy-4-trimethylaminobutyrate, a small, water soluble molecule that is essential for mitochondrial fatty acid oxidation, is significantly reduced in hemodialysis patients. Uremia-induced carnitine deficiency, which is magnified by dialysis, is associated with symptoms or clinical problems such as anemia hyporesponsive to erythropoietin, cardiovascular diseases, and muscle weakness. This review examines studies dealing with the different clinical aspects of chronic renal failure patients in which carnitine deficiency may play a role and has also examined the studies, which have evaluated the effect of carnitine deficiency treatment. The reports reviewed in this study, including those more recent from our laboratory, have provided data suggesting that chronic renal failure and particularly hemodialysis patients can benefit from carnitine treatment in particular for renal anemia, insulin sensitivity, and protein catabolism. On the other hand, the heterogeneous clinical response to carnitine therapy in dialysis patients, reported by other studies, and the lack of large-scale randomized trials are the rationale for the reluctance regarding a widespread use of carnitine supplements in dialysis patients. Well-designed randomized clinical trials are therefore required to fully address the potentially important carnitine treatment in dialysis patients.     

Mechanism of co-nanoprecipitation of organic actives and block copolymers in a microfluidic environment

Microreactors have been shown to be a powerful tool for the production of nanoparticles (NPs); however, there is still a lack of understanding of the role that the microfluidic environment plays in directing the nanoprecipitation process. Here we investigate the mechanism of nanoprecipitation of block copolymer stabilized organic NPs using a microfluidic-based reactor in combination with computational fluid dynamics (CFD) modelling of the microfluidic implementation. The latter also accounts for the complex interplay between molecular and hydrodynamic phenomena during the nanoprecipitation process, in order to understand the hydrodynamics and its influence on the NP formation process. It is demonstrated that the competitive reactions result in the formation of two types of NPs, i.e., either with or without loading organic actives. The obtained results are interpreted by taking into consideration a new parameter representing the mismatching between the aggregations of the polymers and actives, which plays a decisive role in determining the size and polydispersity of the prepared hybrid NPs. These results expand the current understanding of the co-nanoprecipitation mechanism of active and block copolymer stabilizer, and on the role exerted by the microfluidic environment, giving information that could be translated to the emerging fields of microfluidic formation of NPs and nanomedicine.     

High‐Efficiency and Low Distortion Photoacoustic Effect in 3D Graphene Sponge

The conversion of light in sound plays a crucial role in spectroscopy, applied physics, and technology. In this paper, light‐sound conversion in 3D graphene sponge through a photo‐thermoacoustic mechanism is reported. It is shown that the unique combination of mechanical, optical, and thermodynamic properties of graphene assembled in a 3D sponge structure allows an unprecedented high efficiency conversion independent of light wavelength from infrared to ultraviolet. As a first application of this effect, a photothermal based graphene sponge loudspeaker is demonstrated, providing a full digital operation for frequencies from acoustic to ultrasound. The present results suggest a new pathway for light generation and control of sound and ultrasound signals potentially usable in a variety of new technological applications from high‐fidelity loudspeaker and radiation detectors to medical devices.     

Hemocompatibility of pyrolytic carbon in comparison with other biomaterials

The present generation of mechanical heart-valves prostheses offers significantly improved blood compatibility, combined with appropriate physical and mechanical properties and durability; however, thromboembolism persists as a crucial clinical complication because of the key role played by adsorbed plasma proteins and adherent platelets in determining hemocompatibility. In the present work human plasma protein adsorption and platelet adhesion and activation were evaluated on four materials, selected according to their different physico-chemical and morphological properties: pyrolytic carbon (PyC), titanium alloy Ti–6Al–4V (Ti), tissue culture polystyrene (TCPS) and polystyrene sterilized by γ-irradiation (StPS). Morphological and chemical properties of surfaces were assessed by Time of Flight Secondary Ion Mass Spectrometry (Tof-SIMS), X-ray Photoemission Spectroscopy (XPS), Atomic Force Microscopy (AFM) and Contact Angle (CA) analysis, while protein adsorption and platelet adhesion and activation were evaluated by colorimetric and immunofluorescence tests and Scanning Electron Microscopy (SEM), respectively. Among the analyzed materials, PyC induced the lowest level of protein adsorption and platelet adhesion and activation. In particular, immunofluorescence analysis of fibronectin (FN), fibrinogen (FG), von Willebrand factor (vWF), Hageman factor (FXII) and albumin (ALB) showed that PyC surface was characterized by high levels of FG adsorption, low levels of FN, ALB and vWF and the absence of FXII. Finally, when analyzing the biological response as a function of surface properties, it was found that protein adhesiveness increased with increasing contact angle values. To the contrary, platelet activation related to the total amount of adherent proteins was poor while cell activation was possibly dependent on the detailed composition of the underlying protein layer. Furthermore, differences in surface roughness of the examined materials did not seem to influence the biological response in terms of platelet activation and protein adsorption.     

Closed-Curve Path Tracking for Decentralized Systems of Multiple Mobile Robots

In this paper we address the problem of making a group of mobile robots cooperatively track an assigned path. We consider paths described by completely arbitrarily shaped closed curves. The proposed control strategy is a fully decentralized algorithm and it does not require any global synchronization. The desired behavior is obtained by means of some properly designed artificial potential functions. Analytical proofs are provided to show the asymptotic convergence of the system to the desired behavior. Matlab simulations and experiments on real robots are described as well for validation purposes.