Efficient Gate-tunable light-emitting device made of defective boron nitride nanotubes: from ultraviolet to the visible

Boron nitride is a promising material for nanotechnology applications due to its two-dimensional graphene-like, insulating, and highly-resistant structure. Recently it has received a lot of attention as a substrate to grow and isolate graphene as well as for its intrinsic UV lasing response. Similar to carbon, one-dimensional boron nitride nanotubes (BNNTs) have been theoretically predicted and later synthesised. Here we use first principles simulations to unambiguously demonstrate that i) BN nanotubes inherit the highly efficient UV luminescence of hexagonal BN; ii) the application of an external perpendicular field closes the electronic gap keeping the UV lasing with lower yield; iii) defects in BNNTS are responsible for tunable light emission from the UV to the visible controlled by a transverse electric field (TEF). Our present findings pave the road towards optoelectronic applications of BN-nanotube-based devices that are simple to implement because they do not require any special doping or complex growth

Metaphysics in the Work of Charles Darwin

It is not hard to see how two visions of nature are intertwined in Darwin’s Journal of Researches: one vision, the province of romantic authors depicting the sentiments awakened by certain landscapes, the other, the domain of natural scientists describing the world without reference to the aesthetic qualities of the scenery. Nevertheless, analyses of this double perspective in Darwin’s work are relatively rare. Most scholars focus on Darwin, the scientist, and more or less ignore the aesthetic aspects of his work. Perceiving the gradual transformation of Darwin’s world view, however, depends on analyzing the two different modes in which Darwin approached and perceived the world. While one can, on occasion, find commentaries on the beauty of the natural world in Darwin’s early work, the passage of time produces a modification in the naturalist’s manner of perceiving nature. This does not, however, mean that Darwin ceases to find beauty in nature; on the contrary, the disenchantment, in Max Weber’s words, that Darwin’s theory produces should not be understood in a pejorative, but rather in a literal sense. The theory of evolution, in effect, divests nature of its magical character and begins to explain it in terms of natural selection, according it, in the process a new and more intense attraction. In the present work, the metaphysical implications of this new vision of the world are analyzed through the eyes of its discoverer.

The propagation of nerve pulses: From the Hodgkin-Huxley model to the soliton theory

The present project aims to describe and study the nature and transmission of nerve pulses. First we review a classical model by Hodgkin-Huxley which describes the nerve pulse as a pure electric signal which propagates due to the opening of some time- and voltage-dependent ion channels. Although this model was quite successful when introduced, it fails to provide a satisfactory explanation to other phenomena that occur in the transmission of nerve pulses, therefore a new theory seems to be necessary. The soliton theory is one such theory, which we explain after introducing two topics that are important for its understanding: (i) the lipid melting of membranes, which are found to display nonlinearity and dispersion during the melting transition, and (ii) the discovery and the conditions required for the existence of solitons. In the soliton theory, the pulse is presented as an electromechanical soliton which forces the membrane through the transition while propagating. The action of anesthesia is also explained in the new framework by the melting point depression caused by anesthetics. Finally, we present a comparison between the two models.

Effect of the A cation size disorder and synthesis conditions on the properties of an iron perovskite series

Póster presentado en The Energy and Materials Research Conference - EMR2015 celebrado en Madrid (España) entre el 25-27 de febrero de 2015

Osteometric analysis of the scapula and humerus of Rangifer tarandus and Cervus elaphus : A contribution to the discrimination of Late Pleistocene cervids

Fossil remains of reindeer (Rangifer tarandus) occurring outside their present range are an important indicator of formerly cold climatic conditions, but are easily confused with those of the red deer (Cervus elaphus). The locality of Kiputz IX has yielded one of the best-preserved Late Pleistocene reindeer populations of the southern Pyrenees, occurring in association with Bison priscus and the much more abundant Cervus elaphus. Fossil remains from this site are mostly complete and not affected by human intervention, thus creating the perfect conditions for reliable osteometric analyses. Here, we quantify diagnostic morphological features of the scapula and the humerus of Cervus elaphus and Rangifer tarandus to establish the potential of these bones to aid in interspecific discrimination. In the case of the scapula, the best species discriminator is the ratio of the minimum anteroposterior diameter of the scapular neck and the development of the articular process, while the breadth of the trochlea is the best discriminator in the case of the humerus.

Application of Entropy and Fractal Dimension Analyses to the Pattern Recognition of Contaminated Fish Responses in Aquaculture

The objective of the work was to develop a non-invasive methodology for image acquisition, processing and nonlinear trajectory analysis of the collective fish response to a stochastic event. Object detection and motion estimation were performed by an optical flow algorithm in order to detect moving fish and simultaneously eliminate background, noise and artifacts. The Entropy and the Fractal Dimension (FD) of the trajectory followed by the centroids of the groups of fish were calculated using Shannon and permutation Entropy and the Katz, Higuchi and Katz-Castiglioni's FD algorithms respectively. The methodology was tested on three case groups of European sea bass (Dicentrarchus labrax), two of which were similar (C1 control and C2 tagged fish) and very different from the third (C3, tagged fish submerged in methylmercury contaminated water). The results indicate that Shannon entropy and Katz-Castiglioni were the most sensitive algorithms and proved to be promising tools for the non-invasive identification and quantification of differences in fish responses. In conclusion, we believe that this methodology has the potential to be embedded in online/real time architecture for contaminant monitoring programs in the aquaculture industry.

Mother structures related to the hexagonal and cubic close packing in Cu24 clusters: solvent-influenced derivatives

Artículo científico CrystEngComm

Research on operating conditions at the catalytic reactor for the combined removal of NOx and PCDD/PCDFs from MWI plants

The management of municipal solid waste (MSW), particularly the role of incineration, is currently a subject of public debate. Incineration shows to be a good alternative of reducing the volume of waste and eliminating certain infectious components. Moreover, Municipal Waste Incinerators (MWI), are reported to be highly hygienic and apart from that MWIs are immediately effective in terms of transport (incinerators can be built close to the waste sources) and incineration's nature. Nevertheless, the emissions of many hazardous substances make the Municipal Waste Incineration (MWI) plants to be unpopular. Metals (especially lead, manganese, cadmium, chromium and mercury) are concentrated in fly and bottom ashes. Furthermore, incomplete combustion produces a wide variety of potentially hazardous organic compounds, such as aldehydes, polycyclic aromatic hydrocarbons (PAH), chlorinated hydrocarbons including polychlorinated dibenzodioxins (PCDD) and dibenzofurans (PCDF), and even acid gases, including NOx. Many of these hazardous substances are carcinogenic and some have direct systemic toxicity.

From the Cajal alumni Achucarro and Rio-Hortega to the rediscovery of never-resting microglia

Under the guidance of Ramon y Cajal, a plethora of students flourished and began to apply his silver impregnation methods to study brain cells other than neurons: the neuroglia. In the first decades of the twentieth century, Nicolas Achucarro was one of the first researchers to visualize the brain cells with phagocytic capacity that we know today as microglia. Later, his pupil Pio del Rio-Hortega developed modifications of Achucarro's methods and was able to specifically observe the fine morphological intricacies of microglia. These findings contradicted Cajal's own views on cells that he thought belonged to the same class as oligodendroglia (the so called "third element" of the nervous system), leading to a long-standing discussion. It was only in 1924 that Rio-Hortega's observations prevailed worldwide, thus recognizing microglia as a unique cell type. This late landing in the Neuroscience arena still has repercussions in the twenty first century, as microglia remain one of the least understood cell populations of the healthy brain. For decades, microglia in normal, physiological conditions in the adult brain were considered to be merely "resting," and their contribution as "activated" cells to the neuroinflammatory response in pathological conditions mostly detrimental. It was not until microglia were imaged in real time in the intact brain using two-photon in vivo imaging that the extreme motility of their fine processes was revealed. These findings led to a conceptual revolution in the field: "resting" microglia are constantly surveying the brain parenchyma in normal physiological conditions. Today, following Cajal's school of thought, structural and functional investigations of microglial morphology, dynamics, and relationships with neurons and other glial cells are experiencing a renaissance and we stand at the brink of discovering new roles for these unique immune cells in the healthy brain, an essential step to understand their causal relationship to diseases.

Analysis of multivariate stochastic signals sampled by on-line particle analyzers: Application to the quantitative assessment of occupational exposure to NOAA in multisource industrial scenarios (MSIS)

In multisource industrial scenarios (MSIS) coexist NOAA generating activities with other productive sources of airborne particles, such as parallel processes of manufacturing or electrical and diesel machinery. A distinctive characteristic of MSIS is the spatially complex distribution of aerosol sources, as well as their potential differences in dynamics, due to the feasibility of multi-task configuration at a given time. Thus, the background signal is expected to challenge the aerosol analyzers at a probably wide range of concentrations and size distributions, depending of the multisource configuration at a given time. Monitoring and prediction by using statistical analysis of time series captured by on-line particle analyzers in industrial scenarios, have been proven to be feasible in predicting PNC evolution provided a given quality of net signals (difference between signal at source and background). However the analysis and modelling of non-consistent time series, influenced by low levels of SNR (Signal-Noise Ratio) could build a misleading basis for decision making. In this context, this work explores the use of stochastic models based on ARIMA methodology to monitor and predict exposure values (PNC). The study was carried out in a MSIS where an case study focused on the manufacture of perforated tablets of nano-TiO2 by cold pressing was performed