1,193 research outputs found
Exact relativistic models of thin disks around static black holes in a magnetic field
The exact superposition of a central static black hole with surrounding thin
disk in presence of a magnetic field is investigated. We consider two models of
disk, one of infinite extension based on a Kuzmin-Chazy-Curzon metric and other
finite based on the first Morgan-Morgan disk. We also analyze a simple model of
active galactic nuclei consisting of black hole, a Kuzmin-Chazy-Curzon disk and
two rods representing jets, in presence of magnetic field. To explain the
stability of the disks we consider the matter of the disk made of two
pressureless streams of counterrotating charged particles (counterrotating
model) moving along electrogeodesic. Using the Rayleigh criterion we derivate
for circular orbits the stability conditions of the particles of the streams.
The influence of the magnetic field on the matter properties of the disk and on
its stability are also analyzed.Comment: 17 pages, 14 figures. arXiv admin note: text overlap with
arXiv:gr-qc/0409109 by other author
Experimental study of a gas-loquid cylindrical cyclone separator performance
New data of the experimental performance of a Gas-Liquid Cylindrical Cyclone (GLCC) separator are presented. The data were collected using a 2 3/4” (0.07m) ID GLCC model working with an air-glycerin mixture. The inlet liquid flow rate, the inlet gas flow rate, the tangential liquid velocity inside the separator body and the gas carry under were measured for an operation regime without liquid carry over. The influence of the first
three parameters over the gas carry under was established. Results show the separator efficiency is mainly affected by the inlet gas flow rate for the explored conditions with slug flow at the GLCC entrance
Experimental study of a gas-loquid cylindrical cyclone separator performance
New data of the experimental performance of a Gas-Liquid Cylindrical Cyclone (GLCC) separator are presented. The data were collected using a 2 3/4” (0.07m) ID GLCC model working with an air-glycerin mixture. The inlet liquid flow rate, the inlet gas flow rate, the tangential liquid velocity inside the separator body and the gas carry under were measured for an operation regime without liquid carry over. The influence of the first
three parameters over the gas carry under was established. Results show the separator efficiency is mainly affected by the inlet gas flow rate for the explored conditions with slug flow at the GLCC entrance
Middle Ordovician harknessellid brachiopods (Dalmanellidina) from the Mediterranean margin of Gondwana
The family Harknessellidae Bancroft, 1928 (Orthida, Dalmanellidina) was designed to embrace an assemblage of species referred previously to Harknessella Reed, 1917, and included five genera known mainly from the Middle and Upper Ordovician of England. Herein, we suggest reassigning to this family the genus Cacemia Mitchell, 1974, widespread in the middle Darriwilian (upper Middle Ordovician) of the Iberian and Armorican massifs. Since its designation, Cacemia was placed among the dalmanellidin heterorthids, in spite of its strongly mucronate hinge line, which is totally unknown within this Mediterranean family. A new harknessellid has been identified from the upper Darriwilian beds of the Central Iberian Zone (Central Spain): Isabelella fascicostellata Reyes-Abril Villas gen. et sp. nov. It is similar to Horderleyella Bancroft, 1928 for its coarsely fascicostellate radial ornamentation and obtuse cardinal angles, although its convexoplane to convexoconcave profile allows discrimination from the typically dorsibiconvex Horderleyella. A phylogenetic analysis of the family places both Cacemia and Isabelella in basal positions of their clades, which fits with their early stratigraphic record. Based on our study, the family Harknessellidae appears to have originated in the high latitude Mediterranean margins of Gondwana during pre-Darriwilian times, before the detachment of Avalonia from Gondwana. The family reached its highest diversification in Avalonia throughout the Late Ordovician, keeping connections with the Mediterranean and Proto-Andean margins of Gondwana, as well as with the mid-latitude palaeocontinents of Baltica and South China
Middle Ordovician harknessellid brachiopods (Dalmanellidina) from the Mediterranean margin of Gondwana
The family Harknessellidae Bancroft, 1928 (Orthida, Dalmanellidina) was designed to embrace an assemblage of species referred previously to Harknessella Reed, 1917, and included five genera known mainly from the Middle and Upper Ordovician of England. Herein, we suggest reassigning to this family the genus Cacemia Mitchell, 1974, widespread in the middle Darriwilian (upper Middle Ordovician) of the Iberian and Armorican massifs. Since its designation, Cacemia was placed among the dalmanellidin heterorthids, in spite of its strongly mucronate hinge line, which is totally unknown within this Mediterranean family. A new harknessellid has been identified from the upper Darriwilian beds of the Central Iberian Zone (Central Spain): Isabelella fascicostellata Reyes-Abril Villas gen. et sp. nov. It is similar to Horderleyella Bancroft, 1928 for its coarsely fascicostellate radial ornamentation and obtuse cardinal angles, although its convexoplane to convexoconcave profile allows discrimination from the typically dorsibiconvex Horderleyella. A phylogenetic analysis of the family places both Cacemia and Isabelella in basal positions of their clades, which fits with their early stratigraphic record. Based on our study, the family Harknessellidae appears to have originated in the high latitude Mediterranean margins of Gondwana during pre-Darriwilian times, before the detachment of Avalonia from Gondwana. The family reached its highest diversification in Avalonia throughout the Late Ordovician, keeping connections with the Mediterranean and Proto-Andean margins of Gondwana, as well as with the mid-latitude palaeocontinents of Baltica and South China.Peer Reviewe
Finite axisymmetric charged dust disks in conformastatic spacetimes
An infinite family of axisymmetric charged dust disks of finite extension is
presented. The disks are obtained by solving the vacuum Einstein-Maxwell
equations for conformastatic spacetimes, which are characterized by only one
metric function. In order to obtain the solutions, it is assumed that the
metric function and the electric potential are functionally related and that
the metric function is functionally dependent of another auxiliary function,
which is taken as a solution of Laplace equation. The solutions for the
auxiliary function are then taken as given by the infinite family of
generalized Kalnajs disks recently obtained by Gonz\'alez and Reina (MNRAS 371,
1873, 2006), which is expressed in terms of the oblate spheroidal coordinates
and represents a well behaved family of finite axisymmetric flat galaxy models.
The so obtained relativistic thin disks have then a charge density that is
equal, except maybe by a sign, to their mass density, in such a way that the
electric and gravitational forces are in exact balance. The energy density of
the disks is everywhere positive and well behaved, vanishing at the edge.
Accordingly, as the disks are made of dust, their energy-momentum tensor it
agrees with all the energy conditions.Comment: Submitted to PR
Weather at Sierra Negra: 7.3-year statistics and a new method to estimate the temporal fraction of cloud cover
Sierra Negra, one of the highest peaks in central Mexico, is the site of the
Large Millimeter Telescope. We describe the first results of a comprehensive
analysis of the weather data measured in situ from October 2000 to February
2008 to be used as a reference for future activity in the site. We compare the
data from two different stations at the summit considering the accuracy of both
instruments. We analysed the diurnal, seasonal and annual cycles for all the
parameters. The thermal stability is remarkably good, crucial for a good
performance of the telescopes. From the solar radiation data we developed a new
method to estimate the fraction of time when the sky is clear of clouds. We
show that our measurements are consistent with a warm standard atmosphere
model. The conditions at the site are benign and stable given its altitude,
showing that Sierra Negra is a extremely good site for millimeter and high
energy observations.Comment: Accepted, MNRAS, 17 pages, 26 figure file
Agro-industrial evaluation of new sugarcane (Saccaharum spp.) hybrids in the dry tropic under no watering conditions
Objetive: The objective of this research was to select new sugarcane hybrids with better adaptation and performance in the field and industrial within the supply area of ??the Quesería sugar mill of the Beta San Miguel group (BSM).
Design/methodology/approach: A group of 11 new hybrids were established in the agroindustrial phase, in order to compare their adaptation and field and the industrial performance using the commercial hybrid Mex 69-290 as control.
Results: The results obtained indicated that during the soca cycle and under local soil conditions, the hybrids ColMex 05-484, ColMex 05-38 (c9) and ColMex 05-627, demonstrated the highest estimated field yields, with values ??of 154, 149 and 143 t / ha-1 respectively. Regarding the highest values ??of percentage of sucrose in cane (Pol), at 12 months of age of the plant, it was obtained by the hybrids ColMex 05-147 (16.8%), ColMex 08-38 (C8) (16.5%) and ColMex 05-897 (16.1%), considered by its intermediate cycle maturation curve.
Limitations on study/implications: The limitations that could affect the results of the investigation were; the abundance of stones on the topsoil and the poor distribution of rainfall during the development of the crop (1203 mm).
Findings/conclusions: It can be concluded that after analyzing the agricultural and industrial performance that, the best hybrid was: ColMex 05-484, surpassing the commercial control Mex 69-290.Objective: To select new sugarcane (Saccaharum spp.) hybrids with better adaptability and higher field and industrial performance, within the supply area of the Quesería Sugar Mill of the Beta San Miguel group (BSM).
Design/methodology/approach: We set up a group of 11 new hybrids in the agro-industrial phase in order to compare their adaptability and their field and industrial performance, using the Mex 69-290 commercial hybrid as control.
Results: The obtained results indicated that during the soca cycle and under local soil conditions, the ColMex 05-484, ColMex 05-38 (C9), and ColMex 05-627 hybrids produced the highest estimated field yields, with values of 154, 149, and 143 t/ha-1, respectively. The highest percentages of sucrose in cane (Pol) in 12-month-old plants were observed in the ColMex 05-147 (16.8%), ColMex 08-38 (C8) (16.5%), and ColMex 05-897 (16.1%) hybrids, according to their intermediate stage maturity curve.
Study limitations/implications: The limitations that could affect the results of the research were the abundance of stones on the topsoil and the poor distribution of rainfall during crop development (1,203 mm).
Findings/conclusions: After analyzing the agricultural and industrial performance of several hybrids, we can conclude that ColMex 05-484 was the best, surpassing the Mex 69-290 commercial control
An infinite family of magnetized Morgan-Morgan relativistic thin disks
Applying the Horsk\'y-Mitskievitch conjecture to the empty space solutions of
Morgan and Morgan due to the gravitational field of a finite disk, we have
obtained the corresponding solutions of the Einstein-Maxwell equations. The
resulting expressions are simply written in terms of oblate spheroidal
coordinates and the solutions represent fields due to magnetized static thin
disk of finite extension. Now, although the solutions are not asymptotically
flat, the masses of the disks are finite and the energy-momentum tensor agrees
with the energy conditions. Furthermore, the magnetic field and the circular
velocity show an acceptable physical behavior.Comment: Submitted to IJTP. This paper is a revised and extended version of a
paper that was presented at arXiv:1006.203
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