1,883 research outputs found
Forehead Skin Blood Flow in Normal Neonates during Active and Quiet Sleep, Measured with a Diode Laser Doppler Instrument
Changes in forehead skin blood flow during active and quiet sleep were determined in 16 healthy neonates using a recently developed semi-conductor laser Doppler flow meter without light conducting fibres. Measurements were carried out at a postnatal age varying from 5 hours to 7 days. The two sleep states could be distinguished in 17 recordings. The mean skin blood flow values during active sleep were significantly higher (p<0.01) than those during quiet sleep, the mean increase being 28.1%. The variability of the flow signal, expressed as the coefficient of variation, changed significantly from 23.1% during active sleep to 18.2% during quiet sleep
Social interactions through the eyes of macaques and humans
Group-living primates frequently interact with each other to maintain social bonds as well as to compete for valuable resources. Observing such social interactions between group members provides individuals with essential information (e.g. on the fighting ability or altruistic attitude of group companions) to guide their social tactics and choice of social partners. This process requires individuals to selectively attend to the most informative content within a social scene. It is unclear how non-human primates allocate attention to social interactions in different contexts, and whether they share similar patterns of social attention to humans. Here we compared the gaze behaviour of rhesus macaques and humans when free-viewing the same set of naturalistic images. The images contained positive or negative social interactions between two conspecifics of different phylogenetic distance from the observer; i.e. affiliation or aggression exchanged by two humans, rhesus macaques, Barbary macaques, baboons or lions. Monkeys directed a variable amount of gaze at the two conspecific individuals in the images according to their roles in the interaction (i.e. giver or receiver of affiliation/aggression). Their gaze distribution to non-conspecific individuals was systematically varied according to the viewed species and the nature of interactions, suggesting a contribution of both prior experience and innate bias in guiding social attention. Furthermore, the monkeysβ gaze behavior was qualitatively similar to that of humans, especially when viewing negative interactions. Detailed analysis revealed that both species directed more gaze at the face than the body region when inspecting individuals, and attended more to the body region in negative than in positive social interactions. Our study suggests that monkeys and humans share a similar pattern of role-sensitive, species- and context-dependent social attention, implying a homologous cognitive mechanism of social attention between rhesus macaques and humans
Star Routing: Between Vehicle Routing and Vertex Cover
We consider an optimization problem posed by an actual newspaper company,
which consists of computing a minimum length route for a delivery truck, such
that the driver only stops at street crossings, each time delivering copies to
all customers adjacent to the crossing. This can be modeled as an abstract
problem that takes an unweighted simple graph and a subset of
edges and asks for a shortest cycle, not necessarily simple, such that
every edge of has an endpoint in the cycle.
We show that the decision version of the problem is strongly NP-complete,
even if is a grid graph. Regarding approximate solutions, we show that the
general case of the problem is APX-hard, and thus no PTAS is possible unless P
NP. Despite the hardness of approximation, we show that given any
-approximation algorithm for metric TSP, we can build a
-approximation algorithm for our optimization problem, yielding a
concrete -approximation algorithm.
The grid case is of particular importance, because it models a city map or
some part of it. A usual scenario is having some neighborhood full of
customers, which translates as an instance of the abstract problem where almost
every edge of is in . We model this property as , and
for these instances we give a -approximation algorithm,
for any , provided that the grid is sufficiently big.Comment: Accepted to the 12th Annual International Conference on Combinatorial
Optimization and Applications (COCOA'18
Statistical Inference for Valued-Edge Networks: Generalized Exponential Random Graph Models
Across the sciences, the statistical analysis of networks is central to the
production of knowledge on relational phenomena. Because of their ability to
model the structural generation of networks, exponential random graph models
are a ubiquitous means of analysis. However, they are limited by an inability
to model networks with valued edges. We solve this problem by introducing a
class of generalized exponential random graph models capable of modeling
networks whose edges are valued, thus greatly expanding the scope of networks
applied researchers can subject to statistical analysis
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