2,644 research outputs found
BUILDING SOCIAL NORMS ON THE INTERNET
This Note examines how architecture, and particularly the design and coding of software on the Internet, helps shape social norms. The Note makes two points about architecture and norms. First, architectural decisions affect what norms evolve and how they evolve. By allowing or facilitating certain types of behavior and preventing others, architecture can promote the growth of norms. On the flip side, architecture not tailored to promote certain positive norms of cooperation or compliance with the wishes of the designer (or in some cases the law) may allow the growth of antisocial norms. Second, because design decisions affect behavior directly as well as indirectly through norms, software engineers must recognize the regulatory function of the code they create. Although online architecture can promote productive social norms, design decisions can also create a backlash by fostering the development of norms that work against the sort of behavior the code is written to promote. The Note begins by describing how architecture works to regulate behavior in the physical world, examines the leading theories of social norm development, and explores the intersection of architecture and norms. The latter part of the Note transposes the general theory of architecture and norms to the Internet world, first describing the particular features of the Internet-anonymity, dispersion, and the free flow of information-that make the process of norm development different in cyberspace than in physical space, and then turning to two examples, online auctions and digital music, to show how software engineers have effectively and ineffectively used code to promote the development of social norms
Evolutionary Dynamics Within and Among Competing Groups
Biological and social systems are structured at multiple scales, and the
incentives of individuals who interact in a group may diverge from the
collective incentive of the group as a whole. Mechanisms to resolve this
tension are responsible for profound transitions in evolutionary history,
including the origin of cellular life, multi-cellular life, and even societies.
Here we synthesize a growing literature that extends evolutionary game theory
to describe multilevel evolutionary dynamics, using nested birth-death
processes and partial differential equations to model natural selection acting
on competition within and among groups of individuals. We apply this theory to
analyze how mechanisms known to promote cooperation within a single group --
including assortment, reciprocity, and population structure -- alter
evolutionary outcomes in the presence of competition among groups. We find that
population structures most conducive to cooperation in multi-scale systems may
differ from those most conducive within a single group. Likewise, for
competitive interactions with a continuous range of strategies we find that
among-group selection may fail to produce socially optimal outcomes, but it can
nonetheless produce second-best solutions that balance individual incentives to
defect with the collective incentives for cooperation. We conclude by
describing the broad applicability of multi-scale evolutionary models to
problems ranging from the production of diffusible metabolites in microbes to
the management of common-pool resources in human societies.Comment: 48 pages, 8 figure
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Effect of frequent hemodialysis on residual kidney function.
Frequent hemodialysis can alter volume status, blood pressure, and the concentration of osmotically active solutes, each of which might affect residual kidney function (RKF). In the Frequent Hemodialysis Network Daily and Nocturnal Trials, we examined the effects of assignment to six compared with three-times-per-week hemodialysis on follow-up RKF. In both trials, baseline RKF was inversely correlated with number of years since onset of ESRD. In the Nocturnal Trial, 63 participants had non-zero RKF at baseline (mean urine volume 0.76 liter/day, urea clearance 2.3 ml/min, and creatinine clearance 4.7 ml/min). In those assigned to frequent nocturnal dialysis, these indices were all significantly lower at month 4 and were mostly so at month 12 compared with controls. In the frequent dialysis group, urine volume had declined to zero in 52% and 67% of patients at months 4 and 12, respectively, compared with 18% and 36% in controls. In the Daily Trial, 83 patients had non-zero RKF at baseline (mean urine volume 0.43 liter/day, urea clearance 1.2 ml/min, and creatinine clearance 2.7 ml/min). Here, treatment assignment did not significantly influence follow-up levels of the measured indices, although the range in baseline RKF was narrower, potentially limiting power to detect differences. Thus, frequent nocturnal hemodialysis appears to promote a more rapid loss of RKF, the mechanism of which remains to be determined. Whether RKF also declines with frequent daily treatment could not be determined
Local Parasite Lineage Sharing In Temperate Grassland Birds Provides Clues About Potential Origins Of Galapagos Avian Plasmodium
Oceanic archipelagos are vulnerable to natural introduction of parasites via migratory birds. Our aim was to characterize the geographic origins of two Plasmodium parasite lineages detected in the Galapagos Islands and in North American breeding bobolinks (Dolichonyx oryzivorus) that regularly stop in Galapagos during migration to their South American overwintering sites. We used samples from a grassland breeding bird assemblage in Nebraska, United States, and parasite DNA sequences from the Galapagos Islands, Ecuador, to compare to global data in a DNA sequence registry. Homologous DNA sequences from parasites detected in bobolinks and more sedentary birds (e.g., brown-headed cowbirds Molothrus ater, and other co-occurring bird species resident on the North American breeding grounds) were compared to those recovered in previous studies from global sites. One parasite lineage that matched between Galapagos birds and the migratory bobolink, Plasmodium lineage B, was the most common lineage detected in the global MalAvi database, matching 49 sequences from unique host/site combinations, 41 of which were of South American origin. We did not detect lineage B in brown-headed cowbirds. The other Galapagos-bobolink match, Plasmodium lineage C, was identical to two other sequences from birds sampled in California. We detected a close variant of lineage C in brown-headed cowbirds. Taken together, this pattern suggests that bobolinks became infected with lineage B on the South American end of their migratory range, and with lineage C on the North American breeding grounds. Overall, we detected more parasite lineages in bobolinks than in cowbirds. Galapagos Plasmodium had similar host breadth compared to the non-Galapagos haemosporidian lineages detected in bobolinks, brown-headed cowbirds, and other grassland species. This study highlights the utility of global haemosporidian data in the context of migratory bird–parasite connectivity. It is possible that migratory bobolinks bring parasites to the Galapagos and that these parasites originate from different biogeographic regions representing both their breeding and overwintering sites
Brain Model State Space Reconstruction Using an LSTM Neural Network
Objective
Kalman filtering has previously been applied to track neural model states and
parameters, particularly at the scale relevant to EEG. However, this approach
lacks a reliable method to determine the initial filter conditions and assumes
that the distribution of states remains Gaussian. This study presents an
alternative, data-driven method to track the states and parameters of neural
mass models (NMMs) from EEG recordings using deep learning techniques,
specifically an LSTM neural network.
Approach
An LSTM filter was trained on simulated EEG data generated by a neural mass
model using a wide range of parameters. With an appropriately customised loss
function, the LSTM filter can learn the behaviour of NMMs. As a result, it can
output the state vector and parameters of NMMs given observation data as the
input.
Main Results
Test results using simulated data yielded correlations with R squared of
around 0.99 and verified that the method is robust to noise and can be more
accurate than a nonlinear Kalman filter when the initial conditions of the
Kalman filter are not accurate. As an example of real-world application, the
LSTM filter was also applied to real EEG data that included epileptic seizures,
and revealed changes in connectivity strength parameters at the beginnings of
seizures.
Significance
Tracking the state vector and parameters of mathematical brain models is of
great importance in the area of brain modelling, monitoring, imaging and
control. This approach has no need to specify the initial state vector and
parameters, which is very difficult to do in practice because many of the
variables being estimated cannot be measured directly in physiological
experiments. This method may be applied using any neural mass model and,
therefore, provides a general, novel, efficient approach to estimate brain
model variables that are often difficult to measure
Two-Center Interference in p-H2 Electron-Transfer Collisions
We report on measurements of transfer excitation in collisions of 0.3-1.3 MeV protons with spatially oriented H2 molecules. Evidences of two center interference are found in the angular distribution of the molecule after a transfer excitation process and directly in the projectile angular scattering distributions. These features can be explained in a way which is analogous to that for the interferences in Young\u27s classical double slit experiment: The fast projectiles preferentially capture electrons close to either of the molecular nuclei, and thereby they change their momenta and de Broglie wavelengths. The waves emerging from the two \u27slits\u27 of the molecule interfere yielding the observed interference structure
Deficits in Analogical Reasoning in Adolescents with Traumatic Brain Injury
Individuals with traumatic brain injury (TBI) exhibit deficits in executive control, which may impact their reasoning abilities. Analogical reasoning requires working memory and inhibitory abilities. In this study, we tested adolescents with moderate to severe TBI and typically developing (TD) controls on a set of picture analogy problems. Three factors were varied: complexity (number of relations in the problems), distraction (distractor item present or absent), and animacy (living or non-living items in the problems). We found that TD adolescents performed significantly better overall than TBI adolescents. There was also an age effect present in the TBI group where older participants performed better than younger ones. This age effect was not observed in the TD group. Performance was affected by complexity and distraction. Further, TBI participants exhibited lower performance with distractors present than TD participants. The reasoning deficits exhibited by the TBI participants were correlated with measures of executive function that required working memory updating, attention, and attentional screening. Using MRI-derived measures of cortical thickness, correlations were carried out between task accuracy and cortical thickness. The TD adolescents showed negative correlations between thickness and task accuracy in frontal and temporal regions consistent with cortical maturation in these regions. This study demonstrates that adolescent TBI results in impairments in analogical reasoning ability. Further, TBI youth have difficulty effectively screening out distraction, which may lead to failures in comprehension of the relations among items in visual scenes. Lastly, TBI youth fail to show robust cortical–behavior correlations as observed in TD individuals
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