Military Expenditure and Economic Activity: The Colombian Case

We enhance a standard RBC model to account for military expenditure and the costs of an internal conflict or war. The model captures the natural trade-off in military expenditure: crowding out of private consumption and investment but less destruction (and, therefore, higher marginal productivity) of private capital (and labor). Hence, military expenditure below (above) a certain threshold generates a positive (negative) net benefit in terms of output. The model is calibrated to an annual frequency using Colombian data. We find that an increase in military expenditure of 1% GDP (the current policy of Colombian authorities) increases investment and output above the steady state during several periods, before the shock fades away. Even though consumption falls on impact (to open up space for the additional military expenditure and private investment), it increases above its stationary trend after three periods, remains on positive grounds thereafter, and the cumulated net gain is positive.Real business cycle, stationary state, military expenditure, crowding-out, productivity shock

Tropical eigenwave and intermediate Jacobians

Tropical manifolds are polyhedral complexes enhanced with certain kind of affine structure. This structure manifests itself through a particular cohomology class which we call the eigenwave of a tropical manifold. Other wave classes of similar type are responsible for deformations of the tropical structure. If a tropical manifold is approximable by a 1-parametric family of complex manifolds then the eigenwave records the monodromy of the family around the tropical limit. With the help of tropical homology and the eigenwave we define tropical intermediate Jacobians which can be viewed as tropical analogs of classical intermediate Jacobians.Comment: 38 pages, 8 figure

Herschel-PACS observation of the 10 Myr old T Tauri disk TW Hya: Constraining the disk gas mass

Planets are formed in disks around young stars. With an age of ~10 Myr, TW Hya is one of the nearest T Tauri stars that is still surrounded by a relatively massive disk. In addition a large number of molecules has been found in the TWHya disk, making TWHya the perfect test case in a large survey of disks with Herschel–PACS to directly study their gaseous component. We aim to constrain the gas and dust mass of the circumstellar disk around TW Hya. We observed the fine-structure lines of [O_I] and [C_(II)] as part of the open-time large program GASPS. We complement this with continuum data and ground-based ^(12)CO 3–2 and ^(13)CO 3–2 observations. We simultaneously model the continuum and the line fluxes with the 3D Monte-Carlo code MCFOST and the thermo-chemical code ProDiMo to derive the gas and dust masses. We detect the [O_I] line at 63 μm. The other lines that were observed, [O_I] at 145 μm and [C_(II)] at 157 μm, are not detected. No extended emission has been found. Preliminary modeling of the photometric and line data assuming [^(12)CO]/[^(13)CO] = 69 suggests a dust mass for grains with radius <1 mm of ~1.9 × 10^(−4) M_⊙ (total solid mass of 3 × 10^(−3) M_⊙) and a gas mass of (0.5–5) ×10^(−3) M_⊙. The gas-to-dust mass may be lower than the standard interstellar value of 100

A Disk Census for Young Brown Dwarfs

Recent surveys have identified sub-stellar objects down to planetary masses in nearby star-forming regions. Reliable determination of the disk frequency in young brown dwarfs is of paramount importance to understanding their origin. Here we report the results of a systematic study of infrared L'-band (3.8-micron) disk excess in ~50 spectroscopically confirmed objects near and below the sub-stellar boundary in several young clusters. Our observations, using the ESO Very Large Telescope, Keck I and the NASA Infrared Telescope Facility, reveal that a significant fraction of brown dwarfs harbor disks at a very young age. Their inner disk lifetimes do not appear to be vastly different from those of disks around T Tauri stars. Our findings are consistent with the hypothesis that sub-stellar objects form via a mechanism similar to solar-mass stars.Comment: accepted for publication in The Astronomical Journa

Expectativas hacia el consumo de alcohol en adultos jóvenes de Bucaramanga, Colombia, 2005

Objective: To settle down in young adults of Bucaramanga if the statistical and conceptual performance of the test AEQIII is similar to the one reached in young adults from Mexico, and to describe the relationship of these expectancies with some variables of the context. Methods: Study of factorial validation and internal consistency. In Bucaramanga, Colombia, 156 young adults, answered 51 items of the alcohol expectancy questionnaire. A model of structural equation was developed to evaluate the goodness of fit of the factorial solution through the reason of verisimilitude Chi-square (X2) and the half quadratic approach error (RMSEA). The global internal consistency and intra expectancies were carried out with the alpha of Cronbach. The scores for the expectancies were calculated with base in additives scales. Results: The value reached for the X2 was 6921, with 1196 grades of freedom, p=0.000. The RMSEA was 0.18. The global internal consistency and for the factors, it was bigger in this sample with regard to the Mexican. Equally, all the scores means was bigger in each factor and the smallest variability (p<0.001). Conclusion: In young adults of Bucaramanga, the internal consistency in the eight expectancies is good. However, the statistical coherence is poor. It is necessary to adapt the questionnaire to Bucaramanga culture and in other age groups, before applying their results. Objetivos: Establecer en adultos jóvenes de Bucaramanga si el desempeño estadístico y conceptual de la prueba «Expectativas positivas hacia el consumo de alcohol -AEQ-III» es similar al alcanzado en adultos jóvenes de México, y describir la relación de estas expectativas con algunas variables del contexto. Métodos: Estudio de validación factorial y consistencia interna. En Bucaramanga 156 adultos jóvenes contestaron 51 ítems del formulario AEQ-III. Se desarrolló una ecuación estructural para evaluar la bondad de ajuste a través de la razón de verosimilitud Chi-cuadrado (X2) y el error de aproximación cuadrático medio (RMSEA). La consistencia interna global e intra expectativas se realizó con el alfa de Cronbach. Los puntajes para las expectativas se calcularon con base en escalas aditivas. Resultados: El valor alcanzado para X2 fue 6921, con 1196 grados de libertad, p=0,000. El RMSEA fue 0.18. La consistencia interna global y para los factores fue mayor en esta muestra con respecto a la mexicana. Igualmente, todos los puntajes medios alcanzados en las ocho expectativas fueron mayores y la variabilidad menor (p<0.000). Conclusión: En adultos jóvenes de Bucaramanga, la consistencia interna en las ocho expectativas es adecuada. Sin embargo, la coherencia estadística del modelo es pobre. En este grupo de edad es necesario adaptar el formato AEQ-III antes de utilizarlo en estudios epidemiológicos

GASPS—A Herschel Survey of Gas and Dust in Protoplanetary Disks: Summary and Initial Statistics

We describe a large-scale far-infrared line and continuum survey of protoplanetary disk through to young debris disk systems carried out using the ACS instrument on the Herschel Space Observatory. This Open Time Key program, known as GASPS (Gas Survey of Protoplanetary Systems), targeted ∼250 young stars in narrow wavelength regions covering the [OI] fine structure line at 63 μm the brightest far-infrared line in such objects. A subset of the brightest targets were also surveyed in [OI]145 μm, [CII] at 157 μm, as well as several transitions of H_2O and high-excitation CO lines at selected wavelengths between 78 and 180 μm. Additionally, GASPS included continuum photometry at 70, 100 and 160 μm, around the peak of the dust emission. The targets were SED Class II–III T Tauri stars and debris disks from seven nearby young associations, along with a comparable sample of isolated Herbig AeBe stars. The aim was to study the global gas and dust content in a wide sample of circumstellar disks, combining the results with models in a systematic way. In this overview paper we review the scientific aims, target selection and observing strategy of the program. We summarise some of the initial results, showing line identifications, listing the detections, and giving a first statistical study of line detectability. The [OI] line at 63 μm was the brightest line seen in almost all objects, by a factor of ∼10. Overall [OI]63 μm detection rates were 49%, with 100% of HAeBe stars and 43% of T Tauri stars detected. A comparison with published disk dust masses (derived mainly from sub-mm continuum, assuming standard values of the mm mass opacity) shows a dust mass threshold for [OI]63 μm detection of ∼10^(-5) M_⊙. Normalising to a distance of 140 pc, 84% of objects with dust masses ≥10^(-5) M_⊙ can be detected in this line in the present survey; 32% of those of mass 10^(-6)–10^(-5) M_⊙, and only a very small number of unusual objects with lower masses can be detected. This is consistent with models with a moderate UV excess and disk flaring. For a given disk mass, [OI] detectability is lower for M stars compared with earlier spectral types. Both the continuum and line emission was, in most systems, spatially and spectrally unresolved and centred on the star, suggesting that emission in most cases was from the disk. Approximately 10 objects showed resolved emission, most likely from outflows. In the GASPS sample, [OI] detection rates in T Tauri associations in the 0.3–4 Myr age range were ∼50%. For each association in the 5–20 Myr age range, ∼2 stars remain detectable in [OI]63 μm, and no systems were detected in associations with age >20 Myr. Comparing with the total number of young stars in each association, and assuming a ISM-like gas/dust ratio, this indicates that ∼18% of stars retain a gas-rich disk of total mass ∼1 M_(Jupiter) for 1–4 Myr, 1–7% keep such disks for 5–10 Myr, but none are detected beyond 10–20 Myr. The brightest [OI] objects from GASPS were also observed in [OI]145 μm, [CII]157 μm and CO J = 18 - 17, with detection rates of 20–40%. Detection of the [CII] line was not correlated with disk mass, suggesting it arises more commonly from a compact remnant envelope

Effect of Oxygen Contamination on Propionate and Caproate Formation in Anaerobic Fermentation

Mixed microbial cultures have become a preferred choice of biocatalyst for chain elongation systems due to their ability to convert complex substrates into medium-chain carboxylates. However, the complexity of the effects of process parameters on the microbial metabolic networks is a drawback that makes the task of optimizing product selectivity challenging. Here, we studied the effects of small air contaminations on the microbial community dynamics and the product formation in anaerobic bioreactors fed with lactate, acetate and H$_{2}$/CO$_{2}$. Two stirred tank reactors and two bubble column reactors were operated with H$_{2}$/CO$_{2}$ gas recirculation for 139 and 116 days, respectively, at pH 6.0 and 32°C with a hydraulic retention time of 14 days. One reactor of each type had periods with air contamination (between 97 ± 28 and 474 ± 33 mL O$_{2}$ L$^{-1}$ d$^{-1}$, lasting from 4 to 32 days), while the control reactors were kept anoxic. During air contamination, production of n-caproate and CH$_{4}$ was strongly inhibited, whereas no clear effect on n-butyrate production was observed. In a period with detectable O$_{2}$ concentrations that went up to 18%, facultative anaerobes of the genus Rummeliibacillus became predominant and only n-butyrate was produced. However, at low air contamination rates and with O$_{2}$ below the detection level, Coriobacteriia and Actinobacteria gained a competitive advantage over Clostridia and Methanobacteria, and propionate production rates increased to 0.8–1.8 mmol L$^{-1}$ d$^{-1}$ depending on the reactor (control reactors 0.1–0.8 mmol L$^{-1}$ d$^{-1}$). Moreover, i-butyrate production was observed, but only when Methanobacteria abundances were low and, consequently, H$_{2}$ availability was high. After air contamination stopped completely, production of n-caproate and CH$_{4}$ recovered, with n-caproate production rates of 1.4–1.8 mmol L$^{-1}$ d$^{-1}$ (control 0.7–2.1 mmol L$^{-1}$ d$^{-1}$). The results underline the importance of keeping strictly anaerobic conditions in fermenters when consistent n-caproate production is the goal. Beyond that, micro-aeration should be further tested as a controllable process parameter to shape the reactor microbiome. When odd-chain carboxylates are desired, further studies can develop strategies for their targeted production by applying micro-aerobic conditions

Deep Neural Networks Rival the Representation of Primate IT Cortex for Core Visual Object Recognition

The primate visual system achieves remarkable visual object recognition performance even in brief presentations and under changes to object exemplar, geometric transformations, and background variation (a.k.a. core visual object recognition). This remarkable performance is mediated by the representation formed in inferior temporal (IT) cortex. In parallel, recent advances in machine learning have led to ever higher performing models of object recognition using artificial deep neural networks (DNNs). It remains unclear, however, whether the representational performance of DNNs rivals that of the brain. To accurately produce such a comparison, a major difficulty has been a unifying metric that accounts for experimental limitations such as the amount of noise, the number of neural recording sites, and the number trials, and computational limitations such as the complexity of the decoding classifier and the number of classifier training examples. In this work we perform a direct comparison that corrects for these experimental limitations and computational considerations. As part of our methodology, we propose an extension of "kernel analysis" that measures the generalization accuracy as a function of representational complexity. Our evaluations show that, unlike previous bio-inspired models, the latest DNNs rival the representational performance of IT cortex on this visual object recognition task. Furthermore, we show that models that perform well on measures of representational performance also perform well on measures of representational similarity to IT and on measures of predicting individual IT multi-unit responses. Whether these DNNs rely on computational mechanisms similar to the primate visual system is yet to be determined, but, unlike all previous bio-inspired models, that possibility cannot be ruled out merely on representational performance grounds.Comment: 35 pages, 12 figures, extends and expands upon arXiv:1301.353

A Survey for Low-mass Stars and Brown Dwarfs in the Upper-Scorpius OB Association

The Upper-Scorpius association is the OB association nearest to the Sun (145 pc). Its young age (5 Myr) makes it an ideal place to search for low-mass stars and brown dwarfs, as these objects should be relatively bright. We have performed a photometric search for the low-mass members of the association, using the R, I, and Z filters. The completeness limit is I=18.5 and the saturation limit is I=13. We obtain 138 candidate members, covering nearly the entire M spectral type range. We find an excess of brown dwarf candidates over the number predicted by a Miller-Scalo Initial Mass Function. In addition, we have performed infrared imaging and low resolution optical spectroscopy of selected candidates. We find that the infrared observations confirm the spectral types obtained with the optical photometry. Furthermore, we find H_alpha in emission in 20 of the 22 objects observed spectroscopically. As H_alpha is an indicator of youth, we believe that these 20 objects may belong to the association. One of them, UScoCTIO 128 has a very strong and constant H_alpha line (equivalent width: -130 A), and its position in the color magnitude diagram suggests that it is a brown dwarf with mass equal to 0.02 msun. Confirmation of this and the other candidates will have to wait for higher resolution observations that can reveal spectroscopic mass indicators like Li I and gravity indicators, such as K I and the subordinate lines of Na I.Comment: 20 pages, 7 figures, 3 tables, accepted in the Astronomical Journa

Desarrollo y seudovalidación de un cuestionario de frecuencia de bebidas alcohólicas para una población Colombiana

ResumenObjetivo: Desarrollar un cuestionario de frecuencia de consumo de bebidas alcoh&oacute;licas (CFC) &uacute;til para clasificar sujetos de acuerdo con su consumo de alcohol. Lugar y fecha. Bucaramanga, Colombia. Junio de 2002-Septiembre de 2004.[Herr&aacute;n OF, Ardila MF.Desarrollo y seudovalidaci&oacute;n de un cuestionario de frecuencia de bebidas alcoh&oacute;licas para una poblaci&oacute;n Colombiana. MedUNAB 2005; 8:176-82].Palabras clave: Ingesta de alcohol. Cuestionario de frecuencia de estudio. Max_r. Estudio de validez. Tecnologia diagn&oacute;stica. Colombia