9,612 research outputs found
Identifying Student Difficulties with Entropy, Heat Engines, and the Carnot Cycle
We report on several specific student difficulties regarding the Second Law
of Thermodynamics in the context of heat engines within upper-division
undergraduates thermal physics courses. Data come from ungraded written
surveys, graded homework assignments, and videotaped classroom observations of
tutorial activities. Written data show that students in these courses do not
clearly articulate the connection between the Carnot cycle and the Second Law
after lecture instruction. This result is consistent both within and across
student populations. Observation data provide evidence for myriad difficulties
related to entropy and heat engines, including students' struggles in reasoning
about situations that are physically impossible and failures to differentiate
between differential and net changes of state properties of a system. Results
herein may be seen as the application of previously documented difficulties in
the context of heat engines, but others are novel and emphasize the subtle and
complex nature of cyclic processes and heat engines, which are central to the
teaching and learning of thermodynamics and its applications. Moreover, the
sophistication of these difficulties is indicative of the more advanced
thinking required of students at the upper division, whose developing knowledge
and understanding give rise to questions and struggles that are inaccessible to
novices
Pairwise Ising model analysis of human cortical neuron recordings
During wakefulness and deep sleep brain states, cortical neural networks show
a different behavior, with the second characterized by transients of high
network activity. To investigate their impact on neuronal behavior, we apply a
pairwise Ising model analysis by inferring the maximum entropy model that
reproduces single and pairwise moments of the neuron's spiking activity. In
this work we first review the inference algorithm introduced in Ferrari,Phys.
Rev. E (2016). We then succeed in applying the algorithm to infer the model
from a large ensemble of neurons recorded by multi-electrode array in human
temporal cortex. We compare the Ising model performance in capturing the
statistical properties of the network activity during wakefulness and deep
sleep. For the latter, the pairwise model misses relevant transients of high
network activity, suggesting that additional constraints are necessary to
accurately model the data.Comment: 8 pages, 3 figures, Geometric Science of Information 2017 conferenc
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