1,615 research outputs found
The Eccentric Binary Millisecond Pulsar in NGC 1851
PSR J0514-4002A is a 5-ms pulsar is located in the globular cluster NGC 1851;
it belongs to a highly eccentric (e = 0.888) binary system. It is one of the
earliest known examples of a numerous and fast-growing class of eccentric
binary MSPs recently discovered in globular clusters. Using the GBT, we have
obtained a phase-coherent timing solution for the pulsar, which includes a
measurement of the rate of advance of periastron: 0.01289(4) degrees per year,
which if due completely to general relativity, implies a total system mass of
2.453(14) solar masses. We also derive m_p 0.96
solar masses. The companion is likely to be a massive white dwarf star.Comment: 3 pages, including 2 figures. To appear in the proceedings of "40
Years of Pulsars: Millisecond Pulsars, Magnetars, and More", August 12-17,
2007, McGill University, Montreal, Canad
Liquid crystal phase and waterlike anomalies in a core-softened shoulder-dumbbells system
Using molecular dynamics we investigate the thermodynamics, dynamics and
structure of 250 diatomic molecules interacting by a core-softened potential.
This system exhibits thermodynamics, dynamics and structural anomalies: a
maximum in density-temperature plane at constante pressure and maximum and
minimum points in the diffusivity and translational order parameter against
density at constant temperature. Starting with very dense systems and
decreasing density the mobility at low temperatures first increases, reach a
maximum, then decreases, reach a minimum and finally increases. In the
pressure-temperature phase diagram the line of maximum translational order
parameter is located outside the line of diffusivity extrema that is enclosing
the temperature of maximum density line. We compare our results with the
monomeric system showing that the anisotropy due to the dumbbell leads to a
much larger solid phase and to the appearance of a liquid crystal phase. the
double ranged thermodynamic and dynamic anomalies.Comment: 14 pages, 5 figure
Urban sprawl and its impact on sustainable urban development: a combination of remote sensing and social media data
Urbanization is one of the most impactful human activities across the world today affecting the quality of urban life and its sustainable development. Urbanization in Africa is occurring at an unprecedented rate and it threatens the attainment of Sustainable Development Goals (SDGs). Urban sprawl has resulted in unsustainable urban development patterns from social, environmental, and economic perspectives. This study is among the first examples of research in Africa to combine remote sensing data with social media data to determine urban sprawl from 2011 to 2017 in Morogoro urban municipality, Tanzania. Random Forest (RF) method was applied to accomplish imagery classification and location-based social media (Twitter usage) data were obtained through a Twitter Application Programming Interface (API). Morogoro urban municipality was classified into built-up, vegetation, agriculture, and water land cover classes while the classification results were validated by the generation of 480 random points. Using the Kernel function, the study measured the location of Twitter users within a 1 km buffer from the center of the city. The results indicate that, expansion of the city (built-up land use), which is primarily driven by population expansion, has negative impacts on ecosystem services because pristine grasslands and forests which provide essential ecosystem services such as carbon sequestration and support for biodiversity have been replaced by built-up land cover. In addition, social media usage data suggest that there is the concentration of Twitter usage within the city center while Twitter usage declines away from the city center with significant spatial and numerical increase in Twitter usage in the study area. The outcome of the study suggests that the combination of remote sensing, social sensing, and population data were useful as a proxy/inference for interpreting urban sprawl and status of access to urban services and infrastructure in Morogoro, and Africa city where data for urban planning is often unavailable, inaccurate, or stale
Super-Massive Neutron Stars
We present here the results of Arecibo timing of PSR B1516+02B, a 7.95-ms
pulsar in a binary system with a ~0.17 solar mass companion and an orbital
period of 6.85 days located in the globular cluster M5. The eccentricity of the
orbit (e = 0.14) has allowed a measurement of the rate of advance of
periastron: (0.0136 +/- 0.0007) degrees per year. It is very likely that the
periastron advance is due to the effects of general relativity; the total mass
of the binary system is (2.14 +/-0.16) solar masses. The small measured mass
function implies, in a statistical sense, that a very large fraction of this
total mass is contained in the pulsar: (1.94+0.17 -0.19) solar masses
(1-sigma); there is a 5% probability that the mass of this object is below 1.59
solar masses. With the possible exception of PSR J1748-2021B, this is the
largest neutron star mass measured to date. When combined with similar
measurements made previously for Terzan 5 I and J, we can exclude, in a
statistical sense, the ``soft'' equations of state for dense neutron matter,
implying that matter at the center of a neutron star is highly incompressible.
There is also some evidence for a bimodal distribution of MSP masses, the
reasons for that are not clear.Comment: 5 pages, one table, 2 figures. To appear in the proceedings of "40
Years of Pulsars: Millisecond Pulsars, Magnetars, and More", August 12-17,
2007, McGill University, Montreal, Canad
Eight new MSPs in NGC 6440 and NGC 6441
We report the discovery of five new millisecond pulsars in the globular
cluster NGC 6440 and three new ones in NGC 6441; each cluster has one
previously known pulsar. Four of the new pulsars are found in binary systems.
One of the new pulsars, PSR J1748-2021B in NGC 6440, is notable for its
eccentric (e = 0.57) and wide (P_b = 20.5 days) orbit. If the rate of advance
of periastron is due solely to general relativity, we can estimate of the total
mass of this binary system: 2.92 +/- 0.20 solar masses. This would imply an
anomalously large mass for this pulsar, which could introduce important
constraints in the study of the equation of state for cold neutron matter.Comment: 3 pages, 3 figures. To appear in the proceedings of "40 Years of
Pulsars: Millisecond Pulsars, Magnetars, and More", August 12-17, 2007,
McGill University, Montreal, Canad
Hybrid passive optical network–free-space optic-based fronthaul architecture for ultradense small cell network
Low-dietary fiber intake as a risk factor for recurrent abdominal pain in children
Objective: To evaluate dietary fiber intake in children with recurrent abdominal pain.Design: Cross-sectional study with control group.Setting: Outpatients of the Pediatric Gastroenterology public health clinic of the Darcy Vargas Children's Hospital, Brazil.Subjects: Forty-one patients with recurrent abdominal pain were evaluated and 41 children, as a control group.Interventions: Macronutrients and fiber intake evaluation by the Daily Food Intake method. Two tables of fiber composition in foods were used.Results: According to the Brazilian table the mean intake of fiber ( g/day) by the children of the recurrent abdominal pain groups with chronic constipation or not, and the control group was, respectively, 18.2, 16.6 and 23.7 for total fiber ( P 0.001), 7.5, 6.9 and 9.5 for soluble fiber ( P 0.001) and 10.7, 9.7 and 14.1 for insoluble fiber ( P 0.002). According to the AOAC table, the recurrent abdominal pain group with chronic constipation or not ( 10.6 and 9.9 g/day) also had lower intake of total fiber than the control group ( 13.4 g/day) ( P 0.008). the intake of fiber was lower than the minimum recommended value ( age+5g) and statistically associated ( P 0.021) with the recurrent abdominal pain group ( 78%) in comparison with the control one ( 51.2%). the odds ratio was 3.39 ( 95% CI, 1.18 - 9.95).Conclusion: fiber intake below the minimum recommended value is a risk factor for recurrent abdominal pain in children.Universidade Federal de São Paulo, Dept Pediat, Paulista Sch Med, BR-04023062 São Paulo, BrazilDarcy Vargas Childrens Hosp, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Pediat, Paulista Sch Med, BR-04023062 São Paulo, BrazilWeb of Scienc
Development of a lewis-based catalytic system for biodiesel production: from a batch laboratory scale to a continuous pilot plant
The development of an industrial process or product involves different steps: (i) identify the necessity of a new product or process; (ii) research in glassware scale to find a way that leads to the desired product or process; (iii) build up and optimize a laboratory pilot plant; (iv) scale up one or more times the pilot plant; (v) build up an industrial plant and start up a commercial production. From the beginning of 2002 to the end of 2011, the Laboratory of Materials and Fuels (Institute of Chemistry, University of Brasília) has focused in the development of an alternative process to produce biodiesel. The aim of this account paper is to describe all this development in order to show the long way to achieve a laboratory pilot plant scale.O desenvolvimento de um processo ou produto industrial envolve diferentes passos: (i) identificar a necessidade de um novo produto ou processo; (ii) pesquisar no laboratório, em escala de vidraria, um caminho que leve ao produto ou processo desejado; (iii) construir uma planta piloto em escala de laboratório; (iv) scale up uma ou mais vezes a planta piloto; (v) construir e iniciar a produção industrial. Do início de 2002 até o fim de 2011, o Laboratório de Materiais e Combustíveis (Instituto de Química, Universidade de Brasília) dedicou-se ao desenvolvimento de um processo alternativo para produzir biodiesel. O objetivo deste trabalho é descrever todo este desenvolvimento, a fim de mostrar o longo caminho para se construir uma planta piloto em escala de laboratório
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