7,396 research outputs found
Theory of pixel lensing towards M31 I: the density contribution and mass of MACHOs
POINT-AGAPE is an Anglo-French collaboration which is employing the Isaac
Newton Telescope (INT) to conduct a pixel-lensing survey towards M31. In this
paper we investigate what we can learn from pixel-lensing observables about the
MACHO mass and fractional contribution in M31 and the Galaxy for the case of
spherically-symmetric near-isothermal haloes. We employ detailed pixel-lensing
simulations which include many of the factors which affect the observables. For
a maximum MACHO halo we predict an event rate in V of up to 100 per season for
M31 and 40 per season for the Galaxy. However, the Einstein radius crossing
time is generally not measurable and the observed full-width half-maximum
duration provides only a weak tracer of lens mass. Nonetheless, we find that
the near-far asymmetry in the spatial distribution of M31 MACHOs provides
significant information on their mass and density contribution. We present a
likelihood estimator for measuring the fractional contribution and mass of both
M31 and Galaxy MACHOs which permits an unbiased determination to be made of
MACHO parameters, even from data-sets strongly contaminated by variable stars.
If M31 does not have a significant population of MACHOs in the mass range
0.001-1 Solar masses strong limits will result from the first season of INT
observations. Simulations based on currently favoured density and mass values
indicate that, after three seasons, the M31 MACHO parameters should be
constrained to within a factor four uncertainty in halo fraction and an order
of magnitude uncertainty in mass (90% confidence). Interesting constraints on
Galaxy MACHOs may also be possible. For a campaign lasting ten years,
comparable to the lifetime of current LMC surveys, reliable estimates of MACHO
parameters in both galaxies should be possible. (Abridged)Comment: 21 pages, 14 figures. Submitted to MNRA
Analytical model for large-scale design of sidewalk delivery robot systems
With the rise in demand for local deliveries and e-commerce, robotic
deliveries are being considered as efficient and sustainable solutions.
However, the deployment of such systems can be highly complex due to numerous
factors involving stochastic demand, stochastic charging and maintenance needs,
complex routing, etc. We propose a model that uses continuous approximation
methods for evaluating service trade-offs that consider the unique
characteristics of large-scale sidewalk delivery robot systems used to serve
online food deliveries. The model captures both the initial cost and the
operation cost of the delivery system and evaluates the impact of constraints
and operation strategies on the deployment. By minimizing the system cost,
variables related to the system design can be determined. First, the
minimization problem is formulated based on a homogeneous area, and the optimal
system cost can be derived as a closed-form expression. By evaluating the
expression, relationships between variables and the system cost can be directly
obtained. We then apply the model in neighborhoods in New York City to evaluate
the cost of deploying the sidewalk delivery robot system in a real-world
scenario. The results shed light on the potential of deploying such a system in
the future
AgapeZ1: a Large Amplification Microlensing Event or an Odd Variable Star Towards the Inner Bulge of M31
AgapeZ1 is the brightest and the shortest duration microlensing candidate
event found in the Agape data. It occured only 42" from the center of M31. Our
photometry shows that the half intensity duration of the event6 is 4.8 days and
at maximum brightness we measure a stellar magnitude of R=18.0 with B-R=0.80
mag color. A search on HST archives produced a single resolved star within the
projected event position error box. Its magnitude is R=22.Comment: 4 pages with 5 figure
Star formation histories and evolution of 35 brightest E+A galaxies from SDSS DR5
We pick out the 35 brightest galaxies from Goto's E+A galaxies catalogue
which are selected from the Sloan Digital Sky Survey Data Release 5. The
spectra of E+As are prominently characterized by the strong Balmer absorption
lines but little [Oii] or H_alpha emission lines. In this work we study the
stellar populations of the sample galaxies by fitting their spectra using
ULySS, which is a robust full spectrum fitting method. We fit each of the
sample with 1-population (a single stellar population-a SSP) and 3-population
(3 SSPs) models, separately. By 1-population fits, we obtain SSP-equivalent
ages and metallicities which correspond to the `luminosity-weighted' averages.
By 3-population fits, we divide components into three groups in age (old
stellar population-OSP, intermediate-age stellar population-ISP, and young
stellar population-YSP), and then get the optimal age, metallicity and
population fractions in both mass and light for OSP, ISP and YSP. During the
fits, both Pegase.HR/Elodie3.1 and Vazdekis/Miles are used as two independent
population models. The two models result in generally consistent conclusions as
follows: for all the sample galaxies, YSPs (< 1Gyr) make important
contributions to the light. However, the dominant contributors to mass are
OSPs. We also reconstruct the smoothing star formation histories (SFHs) by
giving star formation rate (SFR) versus evolutionary age. In addition, we fit
the E+A sample and 34 randomly selected elliptical galaxies with 2-population
(2 SSPs) model. We obtain the equivalent age of old components for each of the
E+A sample and elliptical galaxies. By comparison, the old components of E+As
are statistically much younger than those of ellipticals. From the standpoint
of the stellar population age, this probably provides an evidence for the
proposed evolutionary link from E+As to early-types (E/S0s).Comment: 16 pages, 9 figures, Accepted for publication on MNRA
Ontology based Approach for Precision Agriculture
In this paper, we propose a framework of knowledge for an agriculture
ontology which can be used for the purpose of smart agriculture systems. This
ontology not only includes basic concepts in the agricultural domain but also
contains geographical, IoT, business subdomains, and other knowledge extracted
from various datasets. With this ontology, any users can easily understand
agricultural data links between them collected from many different data
resources. In our experiment, we also import country, sub-country and disease
entities into this ontology as basic entities for building agricultural linked
datasets later
Critical and Non-Critical Einstein-Weyl Supergravity
We construct N=1 supersymmetrisations of some recently-proposed theories of
critical gravity, conformal gravity, and extensions of critical gravity in four
dimensions. The total action consists of the sum of three separately off-shell
supersymmetric actions containing Einstein gravity, a cosmological term and the
square of the Weyl tensor. For generic choices of the coefficients for these
terms, the excitations of the resulting theory around an AdS_4 background
describe massive spin-2 and massless spin-2 modes coming from the metric;
massive spin-1 modes coming from a vector field in the theory; and massless and
massive spin-3/2 modes (with two unequal masses) coming from the gravitino.
These assemble into a massless and a massive N=1 spin-2 multiplet. In critical
supergravity, the coefficients are tuned so that the spin-2 mode in the massive
multiplet becomes massless. In the supersymmetrised extensions of critical
gravity, the coefficients are chosen so that the massive modes lie in a
"window" of lowest energies E_0 such that these ghostlike fields can be
truncated by imposing appropriate boundary conditions at infinity, thus leaving
just positive-norm massless supergravity modes.Comment: 29 page
AGAPE: a microlensing search in the direction of M31
A status report of the microlensing search by the pixel method in the direction of M31, on the 2 meter telescope at Pic du Midi is given. Pixels are stable to a level better than 0.5%. Pixel variations as small as 0.02 magnitude can clearly be detected
Neo/adjuvant chemotherapy does not improve outcome in resected primary synovial sarcoma: a study of the French Sarcoma Group
Background: There are only scarce data about the benefit of adjunctive chemotherapy in patients with localized synovial sarcoma (SS). Patients and methods: Data from 237 SS patients recorded in the database of the French Sarcoma Group were retrospectively analyzed. The respective impact of radiotherapy, neo-adjuvant chemotherapy and adjuvant chemotherapy on overall survival (OS), local recurrence-free survival (LRFS) and distant recurrence-free survival (DRFS) were assessed after adjustment to prognostic factors. Results: The median follow-up was 58 months (range 1-321). Adjuvant, neo-adjuvant chemotherapy and postoperative radiotherapy were administered in 112, 45 and 181 cases, respectively. In all, 59% of patients treated with chemotherapy received an ifosfamide-containing regimen. The 5-year OS, LRFS and DRFS rates were 64.0%, 70% and 57%, respectively. On multivariate analysis, age >35 years old, grade 3 and not-R0 margins were highly significant independent predictors of worse OS. After adjustment to prognostic factors, radiotherapy significantly improved LRFS but not DRFS or OS. Neither neo-adjuvant nor adjuvant chemotherapy had significant impact on OS, LRFS or DRFS. Conclusion: As for other high-grade soft-tissue sarcomas, well-planned wide surgical excision with adjuvant radiotherapy remains the cornerstone of treatment for SS. Neo-adjuvant or adjuvant chemotherapy should not be delivered outside a clinical trial settin
Predicting the solar maximum with the rising rate
The growth rate of solar activity in the early phase of a solar cycle has
been known to be well correlated with the subsequent amplitude (solar maximum).
It provides very useful information for a new solar cycle as its variation
reflects the temporal evolution of the dynamic process of solar magnetic
activities from the initial phase to the peak phase of the cycle. The
correlation coefficient between the solar maximum (Rmax) and the rising rate
({\beta}a) at {\Delta}m months after the solar minimum (Rmin) is studied and
shown to increase as the cycle progresses with an inflection point (r = 0.83)
at about {\Delta}m = 20 months. The prediction error of Rmax based on {\beta}a
is found within estimation at the 90% level of confidence and the relative
prediction error will be less than 20% when {\Delta}m \geq 20. From the above
relationship, the current cycle (24) is preliminarily predicted to peak around
October 2013 with a size of Rmax =84 \pm 33 at the 90% level of confidence.Comment: 7 pages, 3 figures, accepted for publication in SCIENCE CHINA
Physics,Mechanics & Astronom
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