Comparison of Spatial Visualization Skills in Courses with Either Graphics or Solid Modeling Content

This paper presents a comparison made between visualization skills in a group of students that take a course with graphics topics, and those that take a course with solid modeling. The graphics course (2D) is in the context of manual drafting and a drafting software, while the solid modeling course (3D) in based on the utilization of concepts and software for solid modeling. The objective pursued is to identify any possible benefit, from the point of view of improved spatial visualization skills, from either of these two approaches. The visualization aptitude of the students was measured by administering the standard PSVT:R test before and after the respective topics were covered. This evaluation was done at two different academic institutions, with each one of the institutions using either a graphics or a solid modeling approach. Results from this study have relevance when defining course content, particularly with the current trend of including 2D and 3D topics in one single course. The result of the comparison indicates that although there are numeric differences between the two groups, particularly with standard deviations, they are not statistically significant to make a claim about the visualization skills of courses with 2D or 3D approach

VLA Observations of H I in the Helix Nebula (NGC 7293)

We report the detection of 21-cm line emission from H I in the planetary nebula NGC 7293 (the Helix). The observations, made with the Very Large Array, show the presence of a ring of atomic hydrogen that is associated with the outer portion of the ionized nebula. This ring is most probably gas ejected in the AGB phase that has been subsequently photodissociated by radiation from the central star. The H I emission spreads over about 50 km/s in radial velocity. The mass in H I is approximately 0.07 solar masses, about three times larger than the mass in molecular hydrogen and comparable with the mass in ionized hydrogen.Comment: 19 pages, 9 figure

Multiplicity in Early Stellar Evolution

Observations from optical to centimeter wavelengths have demonstrated that multiple systems of two or more bodies is the norm at all stellar evolutionary stages. Multiple systems are widely agreed to result from the collapse and fragmentation of cloud cores, despite the inhibiting influence of magnetic fields. Surveys of Class 0 protostars with mm interferometers have revealed a very high multiplicity frequency of about 2/3, even though there are observational difficulties in resolving close protobinaries, thus supporting the possibility that all stars could be born in multiple systems. Near-infrared adaptive optics observations of Class I protostars show a lower binary frequency relative to the Class 0 phase, a declining trend that continues through the Class II/III stages to the field population. This loss of companions is a natural consequence of dynamical interplay in small multiple systems, leading to ejection of members. We discuss observational consequences of this dynamical evolution, and its influence on circumstellar disks, and we review the evolution of circumbinary disks and their role in defining binary mass ratios. Special attention is paid to eclipsing PMS binaries, which allow for observational tests of evolutionary models of early stellar evolution. Many stars are born in clusters and small groups, and we discuss how interactions in dense stellar environments can significantly alter the distribution of binary separations through dissolution of wider binaries. The binaries and multiples we find in the field are the survivors of these internal and external destructive processes, and we provide a detailed overview of the multiplicity statistics of the field, which form a boundary condition for all models of binary evolution. Finally we discuss various formation mechanisms for massive binaries, and the properties of massive trapezia.Comment: Accepted for publication as a chapter in Protostars and Planets VI, University of Arizona Press (2014), eds. H. Beuther, R. Klessen, C. Dullemond, Th. Hennin

Assembly of Matted Panels with Guadua Cane (Angustifolia Kunth), for Construction of Houses in Manabi Province

In some regions of Ecuador, mainly in the rural areas, the bamboo cane (Angustifolia Kunth), is presented as a renewable natural resource par excellence, which has ecological importance, the wood obtained from this plant is used since very ancient times in the construction of Housing, its technology has not changed in several years. Its industrialization is restricted, due to different factors, mainly because the natural characteristics of the material are unknown, such as age, moisture content, soil nutrients, and treatment after cutting, among others. Knowing these elements can be implemented technologies for the cutting and sterilization of the wood obtained from these plantations and develops a national technology for the construction of housing for social use, thereby achieving an impact on society by having more comfortable, safe and economic facilities

A Cluster of Compact Radio Sources in NGC 2024 (Orion B)

We present deep 3.6 cm radio continuum observations of the H II region NGC 2024 in Orion B obtained using the Very Large Array in its A-configuration, with $0\rlap.{''}2$ angular resolution. We detect a total of 25 compact radio sources in a region of $4' \times 4'$. We discuss the nature of these sources and its relation with the infrared and X-ray objects in the region. At least two of the radio sources are obscured proplyds whose morphology can be used to restrict the location of the main ionizing source of the region. This cluster of radio sources is compared with others that have been found in regions of recent star formation.Comment: 21 pages, 7 figure