Time filter

Source Type

Hernandez-Velez M.,Autonomous University of Madrid | Hernandez-Velez M.,CSIC - Institute of Materials Science | Sanz R.,Campus Universitario Of Cantoblanco | Manso M.,Autonomous University of Madrid | And 6 more authors.
Materials Research Society Symposium Proceedings | Year: 2010

Nanoporous Anodic Alumina Films (NAAF) have been used for growing a lot of nanostructure functional materials. Of particular interest is the NAAF conversion into membranes (NAAM) with different highly controlled pore diameter and distribution to be used as templates and masks to grow a wide variety of nanomaterials. This work constitutes an approach to a review of our latest results regarding the use of NAAF and NAAM as templates in which II-VI semiconductor, functional oxides, hard materials and magnetic nanowires have been grown. The growth techniques and methods used include Isothermal Close Space Sublimation (ICSS), Magnetron Sputtering, electroplating and sol-gel. Ion Beam Irradiation (IBI) combined with different NAAM as masks has been also used for Titania substrates functionalization. © 2010 Materials Research Society.

Rice R.H.,Kansas State University | Gnecco E.,Campus Universitario Of Cantoblanco | King W.P.,University of Illinois at Urbana - Champaign | Szoszkiewicz R.,Kansas State University
Materials Chemistry and Physics | Year: 2013

We report on spiral wear patterns produced at constant angular velocity by hot tip atomic force microscopy (HT-AFM) on surfaces of two common amorphous polymers: polystyrene (PS) and polymethylmethacrylate (PMMA). Topography of these patterns is obtained with regular AFM cantilevers. Topography cross-sections taken from a center of each spiral at a given azimuthal angle Θ relate changes of surface corrugation hcorr with tangential velocity v of a thermal cantilever. Polymer wear is characterized by a power law hcorr(v) = α(v/vmax)-β, which yields a pre-factor α and an exponent β. Below the glass transition temperature Tg, α is polymer specific and β varies weakly between similar conditions and samples. Variations of β are hypothesized to reflect polymer relaxation processes, which are expected to vary only weakly between amorphous polymers. At and above Tg, α approaches initial thermal tip indentation depth within a polymer, β plummets, and a power law relation of hcorr with v diverges. These results are explained by heterogeneous wear around Tg due to a local nature of glass transition. At all studied temperatures, additional wear heterogeneities are found as due to position on the polymer and Θ. Variations of α and β with position on the polymer are found to be only marginally larger then uncertainties of the thermal tip-polymer interface temperature. Variations of α and β with Θ are found to be largely influenced by buckling of thermal cantilevers traveling in a spiral pattern© 2013 Elsevier B.V. All rights reserved.

Kubickova S.,ASCR Institute of Physics Prague | Niznansky D.,Charles University | Morales Herrero M.P.,CSIC - Institute of Materials Science | Salas G.,CSIC - Institute of Materials Science | And 2 more authors.
Applied Physics Letters | Year: 2014

Monodisperse maghemite nanoparticles with diameter ranging from 7 to 20 nm were examined by the In-field Mössbauer Spectroscopy (IFMS) in varying external magnetic field up to 6 T. Surprisingly, the small-sized particles (7 nm) exhibit nearly no spin canting in contrast to the larger particles with lower surface-to-volume ratio. We demonstrate that the observed phenomenon is originated by lower relative crystallinity of the larger particles with different internal structure. Hence, the persistence of the 2nd and 5th absorption lines in the IFMS cannot be unambiguously assigned to the surface spins. © 2014 AIP Publishing LLC.

Betancor L.,Campus Universitario Of Cantoblanco | Luckarift H.R.,Air Force Research Lab | Luckarift H.R.,Universal Technology Corporation
Biotechnology and Genetic Engineering Reviews | Year: 2010

The development of coimmobilized multi-enzymatic systems is increasingly driven by economic and environmental constraints that provide an impetus to develop alternatives to conventional multistep synthetic methods. As in nature, enzyme-based systems work cooperatively to direct the formation of desired products within the defined compartmentalization of a cell. In an attempt to mimic biology, coimmobilization is intended to immobilize a number of sequential or cooperating biocatalysts on the same support to impart stability and enhance reaction kinetics by optimizing catalytic turnover. There are three primary reasons for the utilization of coimmobilized enzymes: to enhance the efficiency of one of the enzymes by the in-situ generation of its substrate, to simplify a process that is conventionally carried out in several steps and/or to eliminate undesired by-products of an enzymatic reaction. As such, coimmobilization provides benefits that span numerous biotechnological applications, from biosensing of molecules to cofactor recycling and to combination of multiple biocatalysts for the synthesis of valuable products.

Pineiro A.,Campus Universitario Of Cantoblanco | Barja I.,Campus Universitario Of Cantoblanco
Naturwissenschaften | Year: 2012

The chemical signals of solitary and territorial felid species are essential for their intraspecific communication. We studied the selection of plant substrates during the fecal marking behavior of the European wildcat Felis silvestris from September 2008 to June 2009 in a protected area in Northwest Spain. The aim of the study was to examine the selection of plants as signal posts with respect to their physical characteristics. We hypothesized that wildcats deposit their fecal marks on plants with physical characteristics (e.g., size, species, and visual conspicuousness) that enhance the olfactory and visual effectiveness of the signal. Our results indicate that diameter, plant group, visual conspicuousness, and interaction between the diameter and plant group influence the decision of wildcats to deposit their fecal marks on plants. The wildcats chose plants with greater diameters and greater visual conspicuousness as scent-marking posts. Moreover, the wildcats chose woody and herbaceous plants, and certain plant species were marked more frequently than expected at random. Indeed, our results indicate that the fecal marks were not randomly distributed on the plants: the wildcats chose to place their marks on plants with certain physical characteristics that maximized the detectability of the signal by intruders and potential mates, thus facilitating the spatial distribution of the species. © Springer-Verlag 2012.

Discover hidden collaborations