A comparison of traditional and geometric morphometric techniques for the study of basicranial morphology in horses: a case study of the Araucanian horse from Colombia

Skull size and shape have been widely used to study domestic animal populations and breeds. Although several techniques have been proposed to quantify cranial form, few attempts have been made to compare the results obtained by di erent techniques. While linear morphometrics has traditionally been used in breed characterization, recent advances in geometric morphometrics have created new techniques for specifically quantifying shape and size. The objective of this study was to compare two morphometric methods for their ability to describe external morphology. For this purpose, 20 skull specimens of adult male Araucanian horses were examined. Two age categories were established (the 'mature group',M3 not fully erupted to moderately worn, n = 7; and the 'senile group', M3 totally erupted and highly worn, n = 13). Both methods showed that there were statistical di erences between generations, but discrimination rates were di erent between methods with the geometric morphometric analysis obtaining a rate of 97.5%. Although linear morphometrics was found to be compatible with geometric morphometrics, the latter was better able to discriminate the two groups and it also provides more information on shape.This research was funded by Cooperative University of Colombia, project 2378

Photonic realization of the relativistic Dirac oscillator

A photonic realization of the Dirac oscillator (DO), i.e. of the relativistic extension of the quantum harmonic oscillator, is proposed for light propagation in fiber Bragg gratings. Transmission spectra clearly show the existence of electron and positron bound states of the DO, corresponding to resonance modes above and below the Bragg frequency, as well as the asymmetry of the energy spectrum for electron and positron branches

Energy spectrum of the relativistic Dirac-Morse problem

We derive an elegant analytic formula for the energy spectrum of the relativistic Dirac-Morse problem, which has been solved recently. The new formula displays the properties of the spectrum more vividly.Comment: Replaced with a more potrable PDF versio

Efectos No Genéticos sobre la Reproducción en Vacas Mestizas con Predominio Bos indicus en el Municipio de Arauca, Colombia

The aim of this study was to determine some non-genetic factors that affect age at first calving (AFC) and the interval between calving (CI) in dual purpose cows in the municipality of Arauca, Colombia. Records related to AFC (n=110) and CI (n=168) of cows with Bos indicus predominance were analyzed. The effect of fixed factors that were considered for EPP were: Farm (FAR: 1,2,3), season of first calving (FCS: dry, rainy), year of first calving (FCY: 1992...2011), sex of calf (CS: M,F) and for CI: FAR, season of calving interval (SCI), year of calving interval (CIY), CS and parity number (PN: 1...5). Data was analyzed using the SAS GLM procedures and for the averages comparison was used the Duncan test with a significance level of 5%. The estimated average for AFC was 1 243.6 ± 160.3 days and for CI was 608.0 ± 165.4 days. FAR and FCY were significant factors of variation (p<0.05) for CY, while NP and CIY were significant factors of variation (p<0.05) for CI. It is concluded that the influence of farm, year of birth, year of calving interval and parity on reproductive parameters in crossbred cows reared under the tropical conditions of Cauca, Colombia is related to technical and productive management characteristics of each farm. Besides, age at first calving and calving interval on farms under study are within the ranges considered acceptable for the production system in flooded savanna.Los factores no genéticos o ambientales son la principal causa de variación de los parámetros reproductivos en vacas mestizas en regiones tropicales. El objetivo fue determinar algunos factores no genéticos que afectan la edad al primer parto (EPP) y el intervalo entre partos (IEP) en vacas doble propósito en el municipio de Arauca, Colombia. Se analizó la información de 176 y 110 datos de EPP e IEP de vacas con predominio de razas indicus. Se consideró el efecto de los factores fijos para EPP: Finca (FIN: 1, 2, 3), época de primer parto (EPPP: seca, lluviosa), año de primer parto (APP: 1992….2011), sexo de la cría (SCR: M, H). Para IEP: finca (FIN), época de intervalo entre partos (EIP), año de intervalo entre partos (AIEP), sexo de la cría (SCR) y numero de parto (NP: 1…5). Los datos  se analizaron utilizando los procedimientos GLM de SAS y para la comparación de medias se usó el test Duncan con un nivel de significancia 5%. La media estimada para la EPP fue de 1243,56±160,3 días y para el IEP fue de 608,03 ±165,4 días. La FIN y el APP fue un factor de variación significativo (p<0,05) para la EPP, mientras que El NP y el AIEP fue un factor de variación significativo (p<0,05) para el IEP. Los demás factores no fueron significativos (p>0,05) para los parámetros analizados. Se concluye que la influencia ambiental sobre los parámetros reproductivos depende de la región donde se localice el sistema de producción y se relaciona con el manejo técnico y productivo propio de cada finca. Los valores encontrados se consideran adecuados para el sistema de producción dada las condiciones de manejo en la sabana inundable y está dentro del rango establecido para los grupos raciales con predominio de las razas cebuinas

No Morphological Integration of Dorsal Profiles in the Araucanian Horse (Colombia)

The aim of this research was to determine if the division between the cervical, dorsal, and croup profiles (three regions commonly assessed for descriptive profile purposes) has a modular basis as well as a morphological integration. For this, a total of 135 digital photographs were obtained, in a lateral view, of adult horses (14 females and 121 geldings; age range: 2–20 years), of the Araucanian breed, an equine population typical of the flooded savannah of Arauca, NE Colombia. From each image, 25 reference points (semi-landmarks) were obtained at the dorsal level of the neck, back, and croup. The hypothesis of the modularity of different body profiles based on differentiated regions was tested using the RV coefficient, and an analysis of two blocks of partial least-squares allowed the evaluation of the level of morphological integration. The results showed that each alloidic group reflected high integration but low modularity. The covariation between the modules was centered mainly on the withers, the loin, and the croup. For the studied profile blocks, no module can be considered. The absence of the fragmentation of the alloidic sets would promote the adaptive capacity of the breed by linking coordinated functional responses to similar selection pressures, e.g., field work. Although the integration between the neck, back, and croup profiles was proven, their modular covariation was low.https://scienti.minciencias.gov.co/cvlac/visualizador/generarCurriculoCv.do?cod_rh=0001022903https://scholar.google.com/citations?hl=es&user=EqGLQZUAAAAJhttps://scienti.minciencias.gov.co/gruplac/jsp/visualiza/visualizagr.jsp?nro=00000000009387https://orcid.org/0000-0002-5416-590

ACS Observations of a Strongly Lensed Arc in a Field Elliptical

We report the discovery of a strongly lensed arc system around a field elliptical galaxy in Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) images of a parallel field observed during NICMOS observations of the HST Ultra-Deep Field. The ACS parallel data comprise deep imaging in the F435W, F606W, F775W, and F850LP bandpasses. The main arc is at a radius of 1.6 arcsec from the galaxy center and subtends about 120 deg. Spectroscopic follow-up at Magellan Observatory yields a redshift z=0.6174 for the lensing galaxy, and we photometrically estimate z_phot = 2.4\pm0.3 for the arc. We also identify a likely counter-arc at a radius of 0.6 arcsec, which shows structure similar to that seen in the main arc. We model this system and find a good fit to an elliptical isothermal potential of velocity dispersion $\sigma \approx 300$ \kms, the value expected from the fundamental plane, and some external shear. Several other galaxies in the field have colors similar to the lensing galaxy and likely make up a small group.Comment: Accepted for publication in ApJ Letters. 10 pages, 3 figures. Figures have been degraded to meet size limit; a higher resolution version and addtional pictures available at http://acs.pha.jhu.edu/~jpb/UDFparc

Componentes ponderales en la cachama blanca (Piaractus brachypomus) (Cuvier, 1818) (Teleostei: Characidae) en la sabana inundable de Arauca, Colombia

The aim of this study was to estimate the allometric parameters of different parts of pirapitinga (Piaractus brachypomus), as well as to establish if the growth of these components is allometric or isometric. In total, 60 specimens collected at random from a farm in Arauca (Colombia) were used. Live weights, carcass weights and weights of scales, viscera and gills were determined. Three algorithms were tested to quantify the relationships between live body weight and each of the components: Ordinary Least Squares, Reduced Major Axis, and Major Axis. The data were logarithmically transformed in order to fit the equations to the allometric function y=10bxa, where y represents the body component in question and x is the independent associated variable. The three methods provided regression coefficients that are, from a theoretical point of view, different, thus providing different estimates of the same quantity. The Ordinary Least Squares algorithm, with the minimum slope, would appear to be the model that best fits the real allometric behavior of this species.El objetivo del presente estudio fue estimar los parámetros alométricos de distintas partes de la cachama blanca (Piaractus brachypomus), así como establecer si el crecimiento de estos componentes son alométricos o isométricos. Se utilizaron 60 ejemplares colectados al azar en una granja en Arauca (Colombia). Se determinaron los pesos vivos, peso de canal y pesos de escamas, vísceras y branquias. Se testearon tres algoritmos para cuantificar las relaciones entre el peso corporal vivo y cada uno de los componentes: Cuadrados mínimos ordinarios (Ordinary Least Squares), Eje Mayor Reducido (Reduced Major Axis) y Eje Mayor (Major Axis). Los datos fueron transformados logarítmicamente a fin de ajustar las ecuaciones a la función alométrica y=10bxa, donde y representa el componente corporal en cuestión y x es la variable independiente relacionada con ese componente en cuestión. Los tres métodos proporcionaron coeficientes de regresión que son, desde un punto de vista teórico, distintos, por lo que proporcionan estimaciones diferentes de una misma cantidad. El algoritmo de Cuadrados mínimos ordinarios, con la mínima pendiente, parecería ser el modelo que más se ajusta al comportamiento alométrico real de esta especie

Error analysis of the photometric redshift tecnique

We present a calculation of the systematic component of the error budget in the photometric redshift technique. We make use of it to describe a simple technique that allows for the assignation of confidence limits to redshift measurements obtained through photometric methods. We show that our technique, through the calculation of a redshift probability function, gives complete information on the probable redshift of an object and its associated confidence intervals. This information can and must be used in the calculation of any observable quantity which makes use of the redshift.Comment: 6 pages, 5 figures, MNRAS style. Accepted for publication in MNRA

Discovery of Globular Clusters in the Proto-Spiral NGC2915: Implications for Hierarchical Galaxy Evolution

We have discovered three globular clusters beyond the Holmberg radius in Hubble Space Telescope Advanced Camera for Surveys images of the gas-rich dark matter dominated blue compact dwarf galaxy NGC2915. The clusters, all of which start to resolve into stars, have M_{V606} = -8.9 to -9.8 mag, significantly brighter than the peak of the luminosity function of Milky Way globular clusters. Their colors suggest a metallicity [Fe/H] ~ -1.9 dex, typical of metal-poor Galactic globular clusters. The specific frequency of clusters is at a minimum normal, compared to spiral galaxies. However, since only a small portion of the system has been surveyed it is more likely that the luminosity and mass normalized cluster content is higher, like that seen in elliptical galaxies and galaxy clusters. This suggests that NGC2915 resembles a key phase in the early hierarchical assembly of galaxies - the epoch when much of the old stellar population has formed, but little of the stellar disk. Depending on the subsequent interaction history, such systems could go on to build-up larger elliptical galaxies, evolve into normal spirals, or in rare circumstances remain suspended in their development to become systems like NGC2915.Comment: ApJ Letters accepted; 6 pages, 2 figures, 3 table