Fantastic Patterns and Where Not to Find Them

Interesting patterns are everywhere we look, but what happens when we try to avoid patterns? A permutation is a list of numbers in a specific order. When we avoid a pattern, we try not to order those numbers in certain ways. For example, the permutation 45312 avoids the 123 pattern because no three elements in the permutation are in an increasing order. In our work, we studied the permutations that avoid two different patterns of length three. We focused on the distribution of peaks, valleys, double ascents, and double descents over these sets of permutations

Fantastic Patterns and Where Not to Find Them

Interesting patterns are everywhere we look, but what happens when we try to avoid patterns? A permutation is a list of numbers in a specific order. When we avoid a pattern, we try not to order those numbers in certain ways. For example, the permutation 45312 avoids the 123 pattern because no three elements in the permutation are in an increasing order. In our work, we studied the permutations that avoid two different patterns of length three. We focused on the distribution of peaks, valleys, double ascents, and double descents over these sets of permutations

Effect of minor Co additions on the crystallization and magnetic properties of Fe(Co)NbBCu alloys

The effect of partial replacement of Fe by Co (up to 8 %) on thermal stability, structure and magnetic properties of FeNbBCu alloys has been explored in this paper. The results indicate that Co reduces the stability against crystallization of the amorphous alloy and stabilizes the nanocrystalline phase prior to the further precipitation of metastable boride phases. Transmission Mössbauer spectroscopy reveals differences in the hyperfine interactions between the alloys: Co raises the mean hyperfine field of the amorphous state and differences in the nanocrystalline bcc-Fe(Co) environments between the alloys occur depending on the amount of Co near-neighbours in the bcc-Fe structure. The addition of Co has also a notable effect on the magnetic properties of both amorphous and nanocrystalline alloys increasing the Curie temperature, which shows a linear dependence with the Co composition, and the saturation polarization.Peer ReviewedPostprint (author’s final draft

The interstellar extinction in the open clusters Tr 14, Tr 15, Tr 16/Cr 232 and Cr 228 in NGC 3372 : New near-infrared photometry

Near-infrared JHKL photometry of more than 200 stars, members of the open clusters Tr 14, Tr 15, Tr 16, Cr 228 and Cr 232 in the Carina Nebula are presented. From comparing these results with the available visual photometry and spectroscopy, it is found that, except in Tr 15, the intracluster reddening is characterized by a ‘normal’ extinction law at λ>0.5μm but is highly anomalous and variable in the U- and B-bands. This behaviour may be explained by the presence of intracluster interstellar grains ‘processed’ by shock waves presumably associated with the explosive history of ƞ Carinae. All clusters are found to be at the same distance from the Sun at d=2.4±0.2kpcorV0−Mv=11.9±0.2⁠. The total amount of reddening, though, differs significantly from cluster to cluster.Facultad de Ciencias Astronómicas y Geofísica

Converse Flexoelectricity of Low-Dimensional Bismuth Selenite (Bi2Se3) Revealed by Piezoresponse Force Microscopy (PFM)

Many kinds of two-dimensional (2D) van der Waals (vdW) have been demonstrated to exhibit electromechanical coupling effects, which makes them promising candidates for next-generation devices, such as piezotronics and nanogenerators. Recently, flexoelectricity was found to account for the out-of-plane electromechanical coupling in many 2D transition metal dichalcogenides (TMDs) who only exhibit in-plane piezoelectricity. However, low dimensional vdW three-dimensional (3D) topological insulators (TIs) have been overlooked regarding their electromechanical properties. In this study, for the first time, we experimentally investigate the electromechanical coupling of low dimensional 3D TIs with a centrosymmetric crystal structure, where a binary compound, bismuth selenite (Bi2Se3), is taken as an example. The results of piezoresponse force microscope (PFM) tests on the Bi2Se3 nanoflakes show that the material exhibits both out-of-plane and in-plane electromechanical responses. The Bi2Se3 nanoflake with a thickness of 37 nm possesses an effective out-of-plane piezoelectric coefficient of ~0.65 pm V-1. With careful analyses, the electromechanical responses are verified to arise from the converse flexoelectricity. The measured effective out-of-plane piezoelectric coefficient is mainly contributed by flexoelectric coefficient, {\mu}_39, which is estimated to be approximately 0.13 nC m-1. However, it is rather difficult to obtain the in-plane component of the flexoelectric tensor from the in-plane PFM measurements since the direction of the in-plane stress is always not normal to the AFM cantilever axis. The results provide useful guidance for understanding the flexoelectric effect of low dimensional vdW materials with centrosymmetric crystal structures. Moreover, the work can pave to way to explore the electromechanical devices based on the flexoelectricity of vdW TIs.Comment: 6 figure

The Evolution of the Kinematics of Nebular Shells in Planetary Nebulae in the Milky Way Bulge

We study the line widths in the [\ion{O}{3}]$\lambda$5007 and H$\alpha$ lines for two groups of planetary nebulae in the Milky Way bulge based upon spectroscopy obtained at the Observatorio Astron\'omico Nacional in the Sierra San Pedro M\'artir (OAN-SPM) using the Manchester Echelle Spectrograph. The first sample includes objects early in their evolution, having high H$\beta$ luminosities, but [\ion{O}{3}]$\lambda 5007/\mathrm H\beta < 3$. The second sample comprises objects late in their evolution, with \ion{He}{2} $\lambda 4686/\mathrm H\beta > 0.5$. These planetary nebulae represent evolutionary phases preceeding and following those of the objects studied by Richer et al. (2008). Our sample of planetary nebulae with weak [\ion{O}{3}]$\lambda$5007 has a line width distribution similar to that of the expansion velocities of the envelopes of AGB stars, and shifted to systematically lower values as compared to the less evolved objects studied by Richer et al. (2008). The sample with strong \ion{He}{2} $\lambda 4686$ has a line width distribution indistinguishable from that of the more evolved objects from Richer et al. (2008), but a distribution in angular size that is systematically larger and so they are clearly more evolved. These data and those of Richer et al. (2008) form a homogeneous sample from a single Galactic population of planetary nebulae, from the earliest evolutionary stages until the cessation of nuclear burning in the central star. They confirm the long-standing predictions of hydrodynamical models of planetary nebulae, where the kinematics of the nebular shell are driven by the evolution of the central star.Comment: accepted for publication in the Astrophysical Journa

Measurement of the lateral distribution function of UHECR air showers with the Pierre Auger Observatory

We describe how the lateral distribution function (LDF) is measured using the large sample of events recorded with the surface detector (SD) array and with a small sample observed with the fluorescence detectors (FD). For hybrid events, in which SD and FD measurements of the same shower are available, the core position is much better constrained than for SD-onlyevents, thus providing an important cross-check on the LDF determined from SD measurements alone. [Segmento extraído de la ponencia]Facultad de Ciencias Exacta

Prioritizing causal disease genes using unbiased genomic features

Background: Cardiovascular disease (CVD) is the leading cause of death in the developed world. Human genetic studies, including genome-wide sequencing and SNP-array approaches, promise to reveal disease genes and mechanisms representing new therapeutic targets. In practice, however, identification of the actual genes contributing to disease pathogenesis has lagged behind identification of associated loci, thus limiting the clinical benefits. Results: To aid in localizing causal genes, we develop a machine learning approach, Objective Prioritization for Enhanced Novelty (OPEN), which quantitatively prioritizes gene-disease associations based on a diverse group of genomic features. This approach uses only unbiased predictive features and thus is not hampered by a preference towards previously well-characterized genes. We demonstrate success in identifying genetic determinants for CVD-related traits, including cholesterol levels, blood pressure, and conduction system and cardiomyopathy phenotypes. Using OPEN, we prioritize genes, including FLNC, for association with increased left ventricular diameter, which is a defining feature of a prevalent cardiovascular disorder, dilated cardiomyopathy or DCM. Using a zebrafish model, we experimentally validate FLNC and identify a novel FLNC splice-site mutation in a patient with severe DCM. Conclusion: Our approach stands to assist interpretation of large-scale genetic studies without compromising their fundamentally unbiased nature. Electronic supplementary material The online version of this article (doi:10.1186/s13059-014-0534-8) contains supplementary material, which is available to authorized users