Energy and information in Hodgkin-Huxley neurons

[EN]The generation of spikes by neurons is energetically a costly process and the evaluation of the metabolic energy required to maintain the signaling activity of neurons a challenge of practical interest. Neuron models are frequently used to represent the dynamics of real neurons but hardly ever to evaluate the electrochemical energy required to maintain that dynamics. This paper discusses the interpretation of a Hodgkin-Huxley circuit as an energy model for real biological neurons and uses it to evaluate the consumption of metabolic energy in the transmission of information between neurons coupled by electrical synapses, i.e., gap junctions. We show that for a single postsynaptic neuron maximum energy efficiency, measured in bits of mutual information per molecule of adenosine triphosphate (ATP) consumed, requires maximum energy consumption. For groups of parallel postsynaptic neurons we determine values of the synaptic conductance at which the energy efficiency of the transmission presents clear maxima at relatively very low values of metabolic energy consumption. Contrary to what could be expected, the best performance occurs at a low energy cost.

Annotation of orthologous genes in Tunnus thynnus and T.albacore species

Albacore and Atlantic Bluefin tuna are two pelagic fish. Atlantic Bluefin tuna is included in the IUCN red list of threatened species and albacore is considered to be near threatened, so conservation plans are needed. However, no genomic resources are available for any of them. In this study, to better understand their transcriptome we functionally annotated orthologous genes. In all, 159 SNPs distributed in 120 contigs of the muscle transcriptome were analyzed. Genes were predicted for 98 contigs (81.2%) using the bioinformatics tool BLAST. In addition, another bioinformatics tool, BLAST2GO was used in order to achieve GO terms for the genes, in which 41 sequences were given a biological process, and 39 sequences were given a molecular process. The most repeated biological process was metabolism and it is important that no cellular process was given in any of the sequences. The most abundant molecular process was binding and very few catalytic activity processes were given. From the initial 159 SNPs, 40 were aligned with a sequence in the database after BLAST2GO was run, and were polymorphic in Atlantic Bluefin tuna and monomorphic in albacore. From these 40 SNPs, 24 were located in an open reading frame of which four were non-synonymous and 20 were synonymous and 16 were not located in a known open reading frame,. This study provides information for better understanding the ecology and evolution of these species and this is important in order to establish a proper conservation plan and an appropriate management.

Structural capital, innovation capability, and company performance in technology-based colombian firms

[EN] In today s economy, innovation is considered to be one of the main driving forces behind business competitiveness, if not the most relevant one. Traditionally, the study of innovation has been addressed from different perspectives. Recently, literature on knowledge management and intellectual capital has provided new insights. Considering this, the aim of this paper is to analyze the impact of different organizational conditions i.e. structural capital on innovation capability and innovation performance, from an intellectual capital (IC) perspective. As regards innovation capability, two dimensions are considered: new idea generation and innovation project management. The population subject to study is made up of technology-based Colombian firms. In order to gather information about the relevant variables involved in the research, a questionnaire was designed and addressed to the CEOs of the companies making up the target population. The sample analyzed is made up of 69 companies and is large enough to carry out a statistical study based on structural equation modelling (partial least squares approach) using PLS-Graph software (Chin and Frye, 2003). The results obtained show that structural capital explains to a great extent both the effectiveness of the new idea generation process and of innovation project management. However, the influence of each specific organizational component making up structural capital (organizational design, organizational culture, hiring and professional development policies, innovation strategy, technological capital, and external structure) varies. Moreover, successful innovation project management is the only innovation capability dimension that exerts a significant impact on company performance.

Quantum ricochets: surface capture, release and energy loss of fast ions hitting a polar surface at grazing incidence

A diffraction mechanism is proposed for the capture, multiple bouncing and final escape of a fast ion (keV) impinging on the surface of a polarizable material at grazing incidence. Capture and escape are effected by elastic quantum diffraction consisting of the exchange of a parallel surface wave vector G= 2p/ a between the ion parallel momentum and the surface periodic potential of period a. Diffraction- assisted capture becomes possible for glancing angles F smaller than a critical value given by Fc 2- 2./ a-| Vim|/ E, where E is the kinetic energy of the ion,. = h/ Mv its de Broglie wavelength and Vim its average electronic image potential at the distance from the surface where diffraction takes place. For F< Fc, the ion can fall into a selected capture state in the quasi- continuous spectrum of its image potential and execute one or several ricochets before being released by the time reversed diffraction process. The capture, ricochet and escape are accompanied by a large, periodic energy loss of several tens of eV in the forward motion caused by the coherent emission of a giant number of quanta h. of Fuchs- Kliewer surface phonons characteristic of the polar material. An analytical calculation of the energy loss spectrum, based on the proposed diffraction process and using a model ion-phonon coupling developed earlier (Lucas et al 2013 J. Phys.: Condens. Matter 25 355009), is presented, which fully explains the experimental spectrum of Villette et al (2000 Phys. Rev. Lett. 85 3137) for Ne+ ions ricocheting on a LiF(001) surface.