20,556 research outputs found
Detailed and GlobalAnalysis of a Remedial Course's Impact on Incoming Students' Marks
Engineering incoming students are facing great difficulties to overcome first course subjects. To tackle that situation and increase the students’ success a Remedial course in Mathematics was offered to Informatics Engineering freshmen. This study presents a statistical analysis of their results comparing the marks obtained by those joining the course (studio group) versus those who did not participate (control group). ANOVA tests are performed over the students’ marks averages as well as over each subject students marks. These tests show statistically significant differences between both groups, with the studio group consistently outperforming the control group at 99% confidence level in most cases and at more than 92% confidence level in every case
Near-IR internetwork spectro-polarimetry at different heliocentric angles
The analysis of near infrared spectropolarimetric data at the internetwork at
different regions on the solar surface could offer constraints to reject
current modeling of these quiet areas.
We present spectro-polarimetric observations of very quiet regions for
different values of the heliocentric angle for the Fe I lines at 1.56 micron,
from disc centre to positions close to the limb. The spatial resolution of the
data is 0.7-1". We analyze direct observable properties of the Stokes profiles
as the amplitude of circular and linear polarization as well as the total
degree of polarization. Also the area and amplitude asymmetries are studied.
We do not find any significant variation of the properties of the
polarimetric signals with the heliocentric angle. This means that the magnetism
of the solar internetwork remains the same regardless of the position on the
solar disc. This observational fact discards the possibility of modeling the
internetwork as a Network-like scenario. The magnetic elements of internetwork
areas seem to be isotropically distributed when observed at our spatial
resolution.Comment: Sorry, this is the version with the correct bibliography. Some
figures had to be compressed. Accepted for publication in A&
Time as a limited resource: Communication Strategy in Mobile Phone Networks
We used a large database of 9 billion calls from 20 million mobile users to
examine the relationships between aggregated time spent on the phone, personal
network size, tie strength and the way in which users distributed their limited
time across their network (disparity). Compared to those with smaller networks,
those with large networks did not devote proportionally more time to
communication and had on average weaker ties (as measured by time spent
communicating). Further, there were not substantially different levels of
disparity between individuals, in that mobile users tend to distribute their
time very unevenly across their network, with a large proportion of calls going
to a small number of individuals. Together, these results suggest that there
are time constraints which limit tie strength in large personal networks, and
that even high levels of mobile communication do not fundamentally alter the
disparity of time allocation across networks.Comment: 10 pages, 3 figures. Accepted for publication in Social Network
Analysis of Swine Movements in a Province in Northern Vietnam and Application in the Design of Surveillance Strategies for Infectious Diseases
While swine production is rapidly growing in South-East Asia, the structure of the swine industry and the dynamic of pig movements have not been well-studied. However, this knowledge is a prerequisite for understanding the dynamic of disease transmission in swine populations and designing cost-effective surveillance strategies for infectious diseases. In this study, we assessed the farming and trading practices in the Vietnamese swine familial farming sector, which accounts for most pigs in Vietnam, and for which disease surveillance is a major challenge. Farmers from two communes of a Red River Delta Province (northern Vietnam) were interviewed, along with traders involved in pig transactions. Major differences in the trade structure were observed between the two communes. One commune had mainly transversal trades, that is between farms of equivalent sizes, whereas the other had pyramidal trades, that is from larger to smaller farms. Companies and large familial farrow-to-finish farms were likely to act as major sources of disease spread through pig sales, demonstrating their importance for disease control. Familial fattening farms with high pig purchases were at greater risk of disease introduction and should be targeted for disease detection as part of a risk-based surveillance. In contrast, many other familial farms were isolated or weakly connected to the swine trade network limiting their relevance for surveillance activities. However, some of these farms used boar hiring for breeding, increasing the risk of disease spread. Most familial farms were slaughtering pigs at the farm or in small local slaughterhouses, making the surveillance at the slaughterhouse inefficient. In terms of spatial distribution of the trades, the results suggested that northern provinces were highly connected and showed some connection with central and southern provinces. These results are useful to develop risk-based surveillance protocols for disease detection in the swine familial sector and to make recommendations for disease control. (Résumé d'auteur
Monitoring the influence of marine aquaculture on wild fish communities: benefits and limitations of fatty acid profiles
Fatty acids (FA) have been applied as indicators of the influence of coastal sea-cage fish farming on wild fish communities in several recent scientific publications. Due to the relatively high conservation of FA composition throughout the food web, they are useful for characterizing trophic relationships. The increasing utilization of vegetable or alternative animal oils in the production of aquafeeds results in cultivated fish exhibiting higher levels of terrestrial FAs in their tissues. As previously reported, wild fish ubiquitously aggregate around fish farms as a consequence of the introduction of new habitat and the easy availability of food—fish farms act as enhanced fish aggregation devices (FADs). The influence of food pellets on the composition of wild fish has been detected in recent studies on salmon, sea bass and sea bream aquaculture, with increased levels of linoleic acid (18:2n-6) and a low n-3/n-6 ratio as clear indicators of the consumption of food pellets from the farms. The potential ecological and physiological effects on wild fish are presently unknown. In the present article, guidelines are proposed for the investigation and use of terrestrial FAs to track the effects of coastal aquaculture on wild fish communities and local fisheries, as well as the benefits or limitations of this technique
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