826 research outputs found
On the origin of the mitochondrial genetic code: Towards a unified mathematical framework for the management of genetic information
The origin of the genetic code represents one of the most challenging problems in molecular evolution. The genetic code is an important universal feature of extant organisms and indicates a common ancestry of different forms of life on earth. Known variants of the genetic code can be mainly divided in mitochondrial and nuclear classes. Here we provide a new insight on the origin of the mitochondrial genetic code: we found that its degeneracy distribution can be explained by using a mathematical approach recently developed for the description of the Euplotes nuclear variant of the genetic code. The results point to a primeval mitochondrial genetic code composed of four base codons, which we call tesserae, that, among other features, exhibit outstanding error detection capabilities. The theoretical description suggests also a formulation of a plausible biological theory about the origin of protein coding. Such theory is based on the symmetry properties of hypothetical primeval chemical adaptors between nucleic acids and amino acids (ancient tRNA’s). Our paper provides a unified mathematical framework for different hypotheses on the origin of genetic coding. Also, it contributes to revisit our present view about the evolutionary steps that led to extant genetic codes by giving a new first-principles perspective on the difficult problem of the origin of the genetic code, and consequently, on the origin of life on earth
Prediction in Photovoltaic Power by Neural Networks
The ability to forecast the power produced by renewable energy plants in the short and middle term is a key issue to allow a high-level penetration of the distributed generation into the grid infrastructure. Forecasting energy production is mandatory for dispatching and distribution issues, at the transmission system operator level, as well as the electrical distributor and power system operator levels. In this paper, we present three techniques based on neural and fuzzy neural networks, namely the radial basis function, the adaptive neuro-fuzzy inference system and the higher-order neuro-fuzzy inference system, which are well suited to predict data sequences stemming from real-world applications. The preliminary results concerning the prediction of the power generated by a large-scale photovoltaic plant in Italy confirm the reliability and accuracy of the proposed approaches
A Comparison of the SAO-Hipparcos reference frames
The reference systems defined by the SAO and Hipparcos catalogues are compared using vector spherical harmonic analysis. The differences between astrometric data in both catalogues have been grouped into different data sets and separate harmonic analysis performed on them. The Fourier coefficients yield estimates of systematic errors in SAO catalogue.Fil: Arias, E. F.. Universidad Nacional de la Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas; ArgentinaFil: Cionco, Rodolfo Gustavo. Universidad Nacional de la Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica la Plata; ArgentinaFil: Orellana, Rosa Beatriz. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de AstrofĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas. Instituto de AstrofĂsica la Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas; ArgentinaFil: Vucetich, Hector. Universidad Nacional de la Plata. Facultad de Ciencias AstronĂłmicas y GeofĂsicas; Argentin
The banking crisis of 2007-2008, and contemporary responses
Until 2006, the financial system prospered and was stable, and Basel II rules were viewed as contributing to that stability. The financial crisis of 2007-2008 forced a change in those beliefs, as imbalances spread and risks materialized, affecting banks and other financial institutions, and impairing economic growth. We discuss the causes of the financial crisis, the response measures that were applied by governments, central banks and the changes in supervision and regulation that are being prepared under Basel III, to increase the resilience of banks, and to reduce the risks of future crisis.info:eu-repo/semantics/publishedVersio
Dynamical characterization of the last prolonged solar minima
The planetary hypothesis of the solar cycle is an old idea in which the
gravitational influence of the planets has a non-negligible effect on the
causes of the solar magnetic cycle. In this work we looked for a possible
causal link in relation with solar barycentric dynamics and prolonged minima
events. We searched for particular changes in the Sun's acceleration and
concentrated on long-term variations of the solar cycle. We show how the
orbital angular momentum of the Sun evolves and how the inclination of the
solar barycentric orbit varies during the epochs of orbital retrogressions. In
particular, at these moments, the radial component of the Sun's acceleration
(i.e., in the barycentre-Sun direction) had an exceptional magnitude. These
radial impulses occurred at the very beginning of the Maunder Minimum, during
the Dalton Minimum and also at the maximum of cycle 22 before the present
extended minimum. We also found a strong correlation between the planetary
torque and the observed sunspots international number around that maximum. We
apply our results in a novel theory of Sun-planets interaction that it is
sensitive to Sun barycentric dynamics and found a very important effect on the
Sun's capability of storing hypothetical reservoirs of potential energy that
could be released by internal flows and might be related to the solar cycle.
This process begins about 40 years before the solar angular momentum
inversions, i.e., before Maunder Minimum, Dalton Minimum, and before the
present extended minimum. Our conclusions suggest a dynamical characterization
of peculiar prolonged solar minima. We discuss the possible implications of
these results for the solar cycle including the present extended minimum.
(Please read the complete Abstract in the paper)Comment: 17 pages, 6 figures, ACCEPTED in Advances in Space Researc
ModelaciĂłn de una estructura de pavimento utilizando los mĂłdulos dinámicos obtenidos en laboratorio aplicando las metodologĂas Marshall y Superpave
El programa SHRP (Strategic Higway Research Program) a través del nuevo método de diseño de mezclas asfálticas en caliente 'Superpave', ha impulsado el desarrollo de investigaciones con el fin de obtener mezclas asfálticas más durables, resistentes y en general, que muestren un comportamiento superior como su nombre lo indica. Entonces, es importante conocer los estados de esfuerzos y deformaciones que se producen al modelar una estructura de pavimento con capas de rodadura, compuestas con mezclas asfálticas diseñadas por métodos distintos (Marshall y Superpave) y, por supuesto, con una caracterización dinámica diferente (leyes de fatiga, módulos dinámicos y respuesta al ahuellamiento). Esta modelación permite tener una idea general de la capacidad estructural para soportar el tránsito durante su vida útil representada en el valor de N (Número de ejes equivalentes de carga) y quizá obtener algunos indicios de posibles ahorros en costos de conservación de los pavimentos, razones fundamentales para apoyar e incentivar la implementación del método Superpave como nuevo diseño de las mezclas asfálticas en caliente
Comparación de módulos dinámicos de probetas elaboradas por el método Marshall y por el método Superpave
En el mundo se han emprendido grandes campañas para mejorar el comportamiento de las mezclas asfálticas; entre ellas, está la liderada por los Estados Unidos denominado 'Programa estratĂ©gico de investigaciĂłn en carreteras (SHRP)' en la que se desarrollan nuevos ensayos para medir las propiedades de los materiales que constituyen las mezclas y para las mezclas como material de construcciĂłn. Uno de los productos finales de SHRP es el sistema Superpave (pavimentos asfálticos con comportamiento superior). En Colombia, en 1996, se modificaron las especificaciones de construcciĂłn de carreteras, introduciendo exigencias en el control de los procesos constructivos, pero sin modificar de manera apreciable lo que al diseño de mezclas en caliente se refiere. En este artĂculo se muestran los resultados de una investigaciĂłn donde se pretendiĂł profundizar en uno de los tantos aspectos que intervienen en el desempeño de las mezclas asfálticas que se fabrican en Colombia, y es precisamente el de diseño de la mezcla, porque se considera que en esta etapa se pueden analizar de forma más completa los materiales constitutivos y las mezclas mismas para predecir con mayor certeza el desempeño en obra, bajo unas condiciones determinadas de tránsito, clima y apoyo estructural. Es asĂ como se realiza la comparaciĂłn de los mĂłdulos dinámicos obtenidos de probetas de mezcla asfáltica elaborados por dos metodologĂas distintas, la Marshall y la Superpave; la primera, tradicional en Colombia, y la segunda, una propuesta innovadora en el mundo sin tener acogida aĂşn en nuestro paĂs
Twitter in Mexican Politics: Messages to People or Candidates?
Twitter has reached Mexican politics in the presidential election. Despite the fact candidates have a twitter account to send messages; we propose the question how they use it to communicate with citizens? This exploratory research provides evidence that Mexican presidential candidates are only sending messages for politicians and not for citizens. We collected and analyzed 618 tweets from the three most important political parties: PRI, PAN and PRD, from November 2011 to February 2012. Using a five category framework, we found that most candidates sent thank and regret messages, but very few messages to their militancy and citizens. We found that the lack of information about this technological tool has disabled Mexican politicians to take advantage of this tool. Finally we hope this research contributes to analyze the impact of social media in Mexican Politics in a more systematic way
Hunting wino and higgsino dark matter at the muon collider with disappearing tracks
We study the capabilities of a muon collider experiment to detect
disappearing tracks originating when a heavy and electrically charged
long-lived particle decays via , where and are two
almost mass degenerate new states and is a charged Standard Model
particle. The backgrounds induced by the in-flight decays of the muon beams
(BIB) can create detector hit combinations that mimic long-lived particle
signatures, making the search a daunting task. We design a simple strategy to
tame the BIB, based on a detector-hit-level selection exploiting timing
information and hit-to-hit correlations, followed by simple requirements on the
quality of reconstructed tracks. Our strategy allows us to reduce the number of
tracks from BIB to an average of 0.08 per event, hence being able to design a
cut-and-count analysis that shows that it is possible to cover weak doublets
and triplets with masses close to in the 0.1-10 ns range. In
particular, this implies that a 10 TeV muon collider is able to probe thermal
MSSM higgsinos and thermal MSSM winos, thus rivaling the FCC-hh in that
respect, and further enlarging the physics program of the muon collider into
the territory of WIMP dark matter and long-lived signatures. We also provide
parton-to-reconstructed level efficiency maps, allowing an estimation of the
coverage of disappearing tracks at muon colliders for arbitrary models.Comment: 32 pages, 17 figures, 3 table
On the origin of the mitochondrial genetic code: Towards a unified mathematical framework for the management of genetic information
The origin of the genetic code represents one of the most challenging problems in molecular evolution. The genetic code is an important universal feature of extant organisms and indicates a common ancestry of different forms of life on earth. Known variants of the genetic code can be mainly divided in mitochondrial and nuclear classes. Here we provide a new insight on the origin of the mitochondrial genetic code: we found that its degeneracy distribution can be explained by using a mathematical approach recently developed for the description of the Euplotes nuclear variant of the genetic code. The results point to a primeval mitochondrial genetic code composed of four base codons, which we call tesserae, that, among other features, exhibit outstanding error detection capabilities. The theoretical description suggests also a formulation of a plausible biological theory about the origin of protein coding. Such theory is based on the symmetry properties of hypothetical primeval chemical adaptors between nucleic acids and amino acids (ancient tRNA's). Our paper provides a unified mathematical framework for different hypotheses on the origin of genetic coding. Also, it contributes to revisit our present view about the evolutionary steps that led to extant genetic codes by giving a new first-principles perspective on the difficult problem of the origin of the genetic code, and consequently, on the origin of life on earth
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