4,418 research outputs found
Direct evidence of dust growth in L183 from MIR light scattering
Theoretical arguments suggest that dust grains should grow in the dense cold
parts of molecular clouds. Evidence of larger grains has so far been gathered
in near/mid infrared extinction and millimeter observations. Interpreting the
data is, however, aggravated by the complex interplay of density and dust
properties (as well as temperature for thermal emission). We present new
Spitzer data of L183 in bands that are sensitive and insensitive to PAHs. The
visual extinction AV map derived in a former paper was fitted by a series of 3D
Gaussian distributions. For different dust models, we calculate the scattered
MIR radiation images of structures that agree agree with the AV map and compare
them to the Spitzer data. The Spitzer data of L183 show emission in the 3.6 and
4.5 micron bands, while the 5.8 micron band shows slight absorption. The
emission layer of stochastically heated particles should coincide with the
layer of strongest scattering of optical interstellar radiation, which is seen
as an outer surface on I band images different from the emission region seen in
the Spitzer images. Moreover, PAH emission is expected to strongly increase
from 4.5 to 5.8 micron, which is not seen. Hence, we interpret this emission to
be MIR cloudshine. Scattered light modeling when assuming interstellar medium
dust grains without growth does not reproduce flux measurable by Spitzer. In
contrast, models with grains growing with density yield images with a flux and
pattern comparable to the Spitzer images in the bands 3.6, 4.5, and 8.0 micron.Comment: 13 pages, 11 figures, accepted for publication in Astronomy and
Astrophysic
Towards a better Understanding of Aggression and Other Related Concepts
This special issue entitled "Towards a better understanding of aggression and other related concepts" is a product of the XXXVII CICA International Conference co-organized by two Polish universities: Kazimierz Wielki University of Bydgoszcz and the University of Zielona G?ra. It took place from the 22 to the 25 June, 2014 and was attended by about 100 participants from 16 countries [1]. The aim of the Conference was to study the phenomena of aggression and conflict resolution using a comprehensive, integrated and interdisciplinary approach which takes into account both biological and psycho-socio-cultural factors. Several communications dealing with emotions, including anger and fear, and others with behaviors such as aggression, violence and terrorism, have been selected for this issue. The discussion on aggression and other related concepts is carried out from various scientific perspectives, which include traditional experimental psychology with a special focus on the role of family relationships and cultural factors, social and political psychology with a special focus on the role of State policies, and other theoretical perspectives which try to integrate their psychological framework with contributions from western and eastern philosophy, the neurosciences, biology, quantum physics, and complexity theory
Areal surface texture parameters on surface
Additive manufacturing (AM) techniques enable
the manufacture of components with free-form
geometries and complex internal and external
features. X-ray computed tomography (CT) is
increasingly being used to inspect internal features
of AM parts. An advantage of the CT process,
compared to optical and stylus instruments
with limited acquisition slope angles, is the ability
to reconstruct reentrant features (undercuts).
Processing reentrant features provides an advantage
in the computation of surface parameters.
If the surface includes many reentrant features,
their elimination can lead to a biased estimation
of parameters related to the height or the area
of the scale limited surface. A unified framework
capable of handling free-from surfaces, with
generic form surface, reentrant features and unevenly
spaced points, such as those from CT reconstruction,
will be proposed. Standard software
instruments employed for roughness parameter
require evaluation of height data on a rectangular
grid. This allows the computation of areal parameters
based on discrete methods with good
approximation, dependent upon the sample size.
The reconstruction from CT volume to mesh allows
performance of an adaptive meshing based
on the maximum allowable distance between the
implicit function (implicit surface defined by a constant
grey value) and the final triangular mesh [1].
With irregular meshes it is not possible to perform
the integral with the discrete approximation and
a bias on the parameters computation can arise.
In this paper an approach that approximates a
generic mesh based on locally refined (LR) Bspline
is proposed [2]. The approach can be applied
to a generic form surface because the local
stretching of the surface is taken into account.
Mesh parameterisation enables to handle undercuts,
each acquired point is described as a function
of two abstract parameters. In this paper the
proposed method will be compared with the discrete
(ISO 25178-2 compliant [3]) method implemented
in standard software packages [4]. Since
filtering techniques based on a general mesh are
not yet defined in the standard, the primary surfaces,
the surface after removing the form, will be
analysed. The areal parameters of a Rubert sample
(casting plate 334, nominal Ra of 25 µm) measured
with a focus variation (FV) instrument will
be evaluated. Two form surfaces will be taken into
account: plane and cylinder. Robustness of the
discrete method will be finally evaluated with the
mesh reconstructed from two CT measurements:
the Rubert sample and an AM part
Alternative Substrates and Fertilization Routine Relationships for Bedding Pot Plants: Impatiens wallerana
This study was carried out searching for alternative substrates to traditional peat based on river waste and Sphagnum and Carex peat from Argentinean peatlands and used to grow Impatiens wallerana bedding plant. The aim of this study was i) to characterize physical and chemical effects from seven growing media on I. wallerana plants grown under different fertilization rates and ii) to describe the physiological mechanisms in plants, involved in the use of such substrates. Particle stability was lower for the six alternative substrates compared to the Canadian peat-base control substrate. However, with a high fertilization dose it is possible to reach non significant differences in plant growth compared to the control substrate. It is suggested, for future research, that nitrogen signalling associated to cytokinin synthesis by roots is involved.Fil: Thibaud, J.. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Floricultura; ArgentinaFil: Loughlin, T. Mc.. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Floricultura; ArgentinaFil: Pagani, A.. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Floricultura; ArgentinaFil: Lavado, Raul Silvio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales; ArgentinaFil: Di Benedetto, Adalberto Hugo. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Floricultura; Argentin
Curvature based sampling of curves and surfaces
Efficient sampling methods enable the reconstruction of a generic surface with a limited amount of points. The reconstructed surface can therefore be used for inspection purpose. In this paper a sampling method that enables the reconstruction of a curve or surface is proposed. The input of the proposed algorithm is the number of required samples. The method takes into account two factors: the regularity of the sampling and the complexity of the object. A higher density of samples is assigned where there are some significant features, described by the curvature. The analysed curves and surfaces are described through the B-splines spaces. The sampling of surfaces generated by two or more curves is also discussed
A study on various methods of supplying propellant to an orbit insertion rocket engine
Various types of pumps and pump drives were evaluated to determine the lightest weight system for supplying propellants to a planetary orbit insertion rocket engine. From these analyses four candidate propellant feed systems were identified. Systems Nos. 1 and 2 were both battery powered (lithium-thionyl-chloride or silver-zinc) motor driven pumps. System 3 was a monopropellant gas generator powered turbopump. System 4 was a bipropellant gas generator powered turbopump. Parameters considered were pump break horsepower, weight, reliability, transient response and system stability. Figures of merit were established and the ranking of the candidate systems was determined. Conceptual designs were prepared for typical motor driven pumps and turbopump configurations for a 1000 lbf thrust rocket engine
Host Galaxies of low z Radio-loud Quasars: A search of HST archives
We searched the HST archives for unpublished WFPC2 images of low redshift
(z<0.5) radio loud quasars (RLQ). This led to the identification of 11 objects.
We present here the results of the analysis of these images from which we
derive the properties of their host galaxies. All objects are clearly resolved
and their surrounding nebulosity is consistent with an elliptical galaxy model.
These new data, together with previous published HST observations, form a
sample of 34 sources which significantly expands all previous studies of low
redshift RLQ based on HST data. For this full sample we derive the average
absolute magnitude of the host galaxies =-24.01+/-0.48, and the effective
radius =10.5+/-3.7kpc. No significant correlation is found between the
nucleus and the host galaxy luminosity. Using the relationship between black
hole mass (M_BH) and bulge luminosity we investigate the relation between M_BH
and total radio power for RLQ and compare with other classes of radio sources.
The overall distribution of AGN in the plane M_BH-P(radio) exhibits a trend for
increasing M_BH with increasing P(radio) but with a substantial spread. RLQ
occupy the region of most powerful sources and most massive BH. The quasars
appear to emit over a wide range of power with respect to their Eddington
luminosity as deduced by the estimated M_BH.Comment: 23 pages, 8 figures, ApJ in pres
Linearized buckling analysis of isotropic and composite beam-columns by Carrera Unified Formulation and Dynamic Stiffness Method
This article introduces a one-dimensional (1D) higher-order exact formulation for linearized buckling analysis of beam-columns. The Carrera Unified Formulation (CUF) is utilized and the displacement field is expressed as a generic N-order expansion of the generalized unknown displacement field. The principle of virtual displacements is invoked along with CUF to derive the governing equations and the associated natural boundary conditions in terms of fundamental nuclei, which can be systematically expanded according to N by exploiting an extensive index notation. After the closed form solution of the N-order beamcolumn element is sought, an exact dynamic stiffness (DS) matrix is derived by relating the amplitudes of the loads to those of the responses. The global DS matrix is finally processed through the application of the Wittrick-Williams algorithm to extract the buckling loads of the structure. Isotropic solid and thin-walled
cross-section beams as well as laminated composite structures are analyzed in this article. The validity of the formulation and its broad range of applicability are demonstrated through comparisons of results from the literature and by using commercial finite element codes
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