1,515 research outputs found
An Examination of the Spectral Variability in NGC 1365 with Suzaku
We present jointly analyzed data from three deep Suzaku observations of NGC
1365. These high signal-to-noise spectra enable us to examine the nature of
this variable, obscured AGN in unprecedented detail on timescales ranging from
hours to years. We find that, in addition to the power-law continuum and
absorption from ionized gas seen in most AGN, inner disk reflection and
variable absorption from neutral gas within the Broad Emission Line Region are
both necessary components in all three observations. We confirm the clumpy
nature of the cold absorbing gas, though we note that occultations of the inner
disk and corona are much more pronounced in the high-flux state (2008) than in
the low-flux state (2010) of the source. The onset and duration of the "dips"
in the X-ray light curve in 2010 are both significantly longer than in 2008,
however, indicating that either the distance to the gas from the black hole is
larger, or that the nature of the gas has changed between epochs. We also note
significant variations in the power-law flux over timescales similar to the
cold absorber, both within and between the three observations. The warm
absorber does not vary significantly within observations, but does show
variations in column density of a factor of more than 10 on timescales less
than 2 weeks that seem unrelated to the changes in the continuum, reflection or
cold absorber. By assuming a uniform iron abundance for the reflection and
absorption, we have also established that an iron abundance of roughly 3.5
times the solar value is sufficient to model the broad-band spectrum without
invoking an additional partial-covering absorber. Such a measurement is
consistent with previous published constraints from the 2008 Suzaku observation
alone, and with results from other Seyfert AGN in the literature.Comment: 19 pages, 11 figures, accepted for publication in MNRA
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Experimental and numerical investigation on forced convection in circular tubes with nanofluids
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.In this paper an experimental and numerical study to investigate the convective heat transfer
characteristics of fully developed turbulent flow of a water–Al2O3 nanofluid in a circular tube is presented.
The numerical simulations are accomplished on the experimental test section configuration. In the analysis,
the fluid flow and the thermal field are assumed axial-symmetric, two-dimensional and steady state. The
single-phase model is employed to model the nanofluid mixture and k-ε model is used to describe the
turbulent fluid flow. Experimental and numerical results are carried out for different volumetric flow rates
and nanoparticles concentration values. Heat transfer convective coefficients as a function of flow rates and
Reynolds numbers are presented. The results indicate that the heat transfer coefficients increase for all
nanofluids concentrations compared to pure water at increasing volumetric flow rate. Heat transfer
coefficient increases are observed at assigned volumetric flow rate for nanofluid mixture with higher
concentrations whereas Nusselt numbers present lower values than the ones for pure water
On a microcanonical relation between continuous and discrete spin models
A relation between a class of stationary points of the energy landscape of
continuous spin models on a lattice and the configurations of a Ising model
defined on the same lattice suggests an approximate expression for the
microcanonical density of states. Based on this approximation we conjecture
that if a O(n) model with ferromagnetic interactions on a lattice has a phase
transition, its critical energy density is equal to that of the n = 1 case,
i.e., a system of Ising spins with the same interactions. The conjecture holds
true in the case of long-range interactions. For nearest-neighbor interactions,
numerical results are consistent with the conjecture for n=2 and n=3 in three
dimensions. For n=2 in two dimensions (XY model) the conjecture yields a
prediction for the critical energy of the Berezinskij-Kosterlitz-Thouless
transition, which would be equal to that of the two-dimensional Ising model. We
discuss available numerical data in this respect.Comment: 5 pages, no figure
Multisensory perception and decision-making with a new sensory skill
It is clear that people can learn a new sensory skill – a new way of mapping sensory inputs onto world states. It remains unclear how flexibly a new sensory skill can become embedded in multisensory perception and decision-making. To address this, we trained typically-sighted participants (N=12) to use a new echo-like auditory cue to distance in a virtual world, together with a noisy visual cue. Using model-based analyses, we tested for key markers of efficient multisensory perception and decision-making with the new skill. We found that twelve of fourteen participants learned to judge distance using the novel auditory cue. Their use of this new sensory skill showed three key features: (1) it enhanced the speed of timed decisions; (2) it largely resisted interference from a simultaneous digit span task; and (3) it integrated with vision in a Bayes-like manner to improve precision. We also show some limits following this relatively short training: precision benefits were lower than the Bayesoptimal prediction, and there was no forced fusion of signals. We conclude that people already embed new sensory skills in flexible multisensory perception and decision-making after a short training period. A key application of these insights is to the development of sensory augmentation systems that can enhance human perceptual abilities in novel ways. The limitations we reveal (sub-optimality, lack of fusion) provide a foundation for further investigations of the limits of these abilities and their brain basis
Influence of intra-articular injections of sodium hyaluronate on clinical features and synovial fluid nitric oxide levels of temporomandibular osteoarthritis
Objective: This study was designed to assess the effect of intra-articular injection of sodium hyaluronate (SH) on clinical findings of temporomandibular osteoarthritis (OA) and on synovial fluid (SF) levels of nitric oxide (NO). Methods: Twenty seven patients (7 men, 20 women, mean (SD) age 53.9 (11.8) years) with OA of the temporomandibular joint were randomly allocated to receive an injection of either SH (2ml, Hyalgan®, Fidia SpA, Abano T., P.M. 500-700.000, 20mg/2ml; once a week for 5 weeks) or a Ringer's lactate solution (once a week for 3 weeks). Clinical evaluation was done before each procedure, and at 1 week, 1, 3 and 6 months post-injection. Intensity of temporomandibular joint pain, jaw function, maximal mouth opening and lateral jaw movements were recorded at each visit. NO was measured on SF collected by rinsing the joint with saline 1 ml before the treatment. Results: Injection of SH caused significant improvement in the main clinical symptoms until the last follow-up which was carried out 6 months after last injection. Among patients who received SH injection, those who reached a good outcome showed the lowest basal levels of NO. Conclusions: The results of this study showed that intra-articular injections of SH lead to a lasting improvement in the clinical symptoms of temporomandibular OA. Furthermore, our findings suggest that low NO levels in SF are related to a better outcome of temporomandibular OA among patients treated with SH intra-articular injection
A Trnsys Simulation of a Solar-Driven Air Refrigerating System for a Low-Temperature Room of an Agro-Industry site in the Southern part of Italy
Solar cooling technologies are of great interest because the cooling load in buildings is directly correlated to the intensity of solar radiation. In this paper, a feasibility study of a solar cooling system for a cold room in the Southern part of Italy is carried out. This feasibility study can be an example for future achievements in Southern of Italy. The cold room is part of an agro-industrial structure; the set point of temperature is 10°C. The room is 11.0 m long, 9.5 m wide and 3.5 m high. Two sliding doors 3.0 m high are present and strawberries are inside mainly. Thermal loads are evaluated by means of the software TRNSYS 17. Parabolic Though Collectors (PTCs) are employed to capture the solar energy. The solar field extends for 210 m2. Two double-effect chillers (with a total installed power equal to 150 kW) for the collectors are employed. In addition, a conventional heat pump is installed to meet the demand for refrigeration during unfavorable weather conditions or during the maintenance of chillers. There are two different storage tanks: a tank with volume 10 m3 for hot water storage and a tank with volume 40 m3 for cold storage. The terminal part is constituted by dry coolers. Results are given in terms of heat transfer rates and solar fraction. Besides, an economic analysis is carried out to evaluate the payback time
Temporomandibular joint examination reviewed
The temporo-mandibular joint (TMJ) it's a joint closely related to the skull base, the spine, and the jaws; all these anatomical structures must be taken in consideration when evaluating pain involving the tmj. In order to detect patients affected by pathology or dysfunctions of the tmj, physical examination is of great value in orienting the diagnosis. Inspection must consider the symmetry of the body, the dental status and the type of occlusion. Palpation is a way to assess contractiont involving the muscles of the masticatory system and of the neck. Auscultation, based on articular noise provides means to determine whether we are dealing with degeneration of the joint or a dislocation of the intrarticular disc. In order to confirm the diagnosis obtained with the clinical evaluation, it's useful to perform imaging techniques as opt, tomography and TC of the tmj and electromyokineosiography – index of the mandibular functionality and of the muscles status. MRI and dynamic MRI are among the non invasive exams which give the greatest amount of information, regarding the disc position and the joint degeneration. Arthroscopy is an invasive technique that allows early diagnosis of degeneration and is helpful to reveal early inflammatory processes of the joint
Leaf water relation traits in typical Sicilian varieties of Vitis vinifera L.
In Italy, grapevines are extensively cultivated, with Sicily representing one of the most significant wine regions. The high number of autochthonous grapevine varieties represents an important source of genetic diversity, and the many Sicilian varieties have anatomical and physiological traits that allow them to resist to different levels of drought stress. We investigated the water relation parameters of four cultivars of Vitis vinifera L. (Catarratto, Corinto, Nero d'Avola and Zibibbo) and characterized their leaf hydraulics. Measurements were conducted during summer on plants growing in the experimental field of the IBBR-CNR near Palermo. Daily patterns of leaf water potential (Yleaf) and stomatal conductance (gs) were measured in the field. Pressure-volume curves were constructed by the bench dehydration method to obtain leaf water potential at turgor loss point (Ytlp), osmotic potential at full rehydration (p0) and bulk modulus of elasticity (εmax). Leaf samples were collected to determine vein density using ImageJ. Major vein density was measured on digitally scanned leaves, while minor vein density was measured on photomicrographs of cleared and stained leaf portions
A computer aided approach for river styles-inspired characterization of large basins: The Magdalena river (Colombia)
This paper addresses the geomorphic characterization and classification of large rivers in a framework of scarce information. This is inspired by the River Styles Framework with some modifications that make the process more straightforward and accessible to practitioners and more applicable to large basins, while reducing the subjective, expert-based inputs, as the process is now more systematic. To this aim, it utilizes innovative criteria and some computer-aided procedures and tools based on GIS, Excel and Python. This approach sheds light on the character and the behavior of rivers, which is key to informing planning, management and restoration. The application to the Magdalena River (Colombia) illustrates the characterization and classification process and the type of results, which ultimately highlight the great geomorphic diversity of that river. The process is applicable to many other rivers worldwide
Numerical solution of the two-dimensional Helmholtz equation with variable coefficients by the radial integration boundary integral and integro-differential equation methods
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2012 Taylor & Francis.This paper presents new formulations of the boundary–domain integral equation (BDIE) and the boundary–domain integro-differential equation (BDIDE) methods for the numerical solution of the two-dimensional Helmholtz equation with variable coefficients. When the material parameters are variable (with constant or variable wave number), a parametrix is adopted to reduce the Helmholtz equation to a BDIE or BDIDE. However, when material parameters are constant (with variable wave number), the standard fundamental solution for the Laplace equation is used in the formulation. The radial integration method is then employed to convert the domain integrals arising in both BDIE and BDIDE methods into equivalent boundary integrals. The resulting formulations lead to pure boundary integral and integro-differential equations with no domain integrals. Numerical examples are presented for several simple problems, for which exact solutions are available, to demonstrate the efficiency of the proposed methods
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