Coordination and Critical Mass in a Network Market: An Experimental Investigation

A network market is a market in which the benefit each consumer derives from a good is an increasing function of the number of consumers who own the same or similar goods. A major obstacle that plagues the introduction of a network good is the ability to reach critical mass, namely, the minimum number of buyers required to render purchase worthwhile. This can be likened to a coordination game with multiple Pareto-ranked equilibria. We introduce an experimental paradigm to study consumers' ability to coordinate on purchasing the network good. Our results highlight the central importance of the level of the critical mass.Experimental economics, network goods, coordination game, critical mass

Coordination and Critical Mass in a Network Market: An Experimental Investigation

A network market is a market in which the benefit each consumer derives from a good is an increasing function of the number of consumers who own the same or similar goods. A major obstacle that plagues the introduction of a network good is the ability to reach critical mass, namely, the minimum number of buyers required to render purchase worthwhile. This can be likened to a coordination game with multiple Pareto-ranked equilibria. We introduce an experimental paradigm to study consumers' ability to coordinate on purchasing the network good. Our results highlight the central importance of the level of the critical mass.experimental economics, network goods, coordination game, critical mass

Do unbalanced data have a negative effect on LDA?

For two-class discrimination, Xie and Qiu [The effect of imbalanced data sets on LDA: a theoretical and empirical analysis, Pattern Recognition 40 (2) (2007) 557–562] claimed that, when covariance matrices of the two classes were unequal, a (class) unbalanced data set had a negative effect on the performance of linear discriminant analysis (LDA). Through re-balancing 10 real-world data sets, Xie and Qiu [The effect of imbalanced data sets on LDA: a theoretical and empirical analysis, Pattern Recognition 40 (2) (2007) 557–562] provided empirical evidence to support the claim using AUC (Area Under the receiver operating characteristic Curve) as the performance metric. We suggest that such a claim is vague if not misleading, there is no solid theoretical analysis presented in Xie and Qiu [The effect of imbalanced data sets on LDA: a theoretical and empirical analysis, Pattern Recognition 40 (2) (2007) 557–562], and AUC can lead to a quite different conclusion from that led to by misclassification error rate (ER) on the discrimination performance of LDA for unbalanced data sets. Our empirical and simulation studies suggest that, for LDA, the increase of the median of AUC (and thus the improvement of performance of LDA) from re-balancing is relatively small, while, in contrast, the increase of the median of ER (and thus the decline in performance of LDA) from re-balancing is relatively large. Therefore, from our study, there is no reliable empirical evidence to support the claim that a (class) unbalanced data set has a negative effect on the performance of LDA. In addition, re-balancing affects the performance of LDA for data sets with either equal or unequal covariance matrices, indicating that having unequal covariance matrices is not a key reason for the difference in performance between original and re-balanced data

A little less conversation, a little more texting please - a blended learning model of using mobiles in the classroom

This paper reports on three case studies of use of the TxtTools Mobile phone texting system by lecturers in different subject disciplines: Business Studies, Computing and Sports Science. The lecturers were seeking to have a richer blend of technologies to support their students, and the mobile technology is combined within traditional student lectures and seminars as well as some interesting developmental uses outside the classroom. The findings show that there has been a very positive response from students, and that the system can be effective in a number of ways, including engaging more students within lectures. This blended learning approach has given a voice to a large number of students intimidated by a classroom or group environment, enabling them to ask questions, put forth an opinion and interact with fellow group members in a dynamically technological manner

A re-assessesment of the shallow paleomagnetic inclinations of the Western Cyclades, Greece

Στις Μεσο-Μειοκαινικές λιμναίες αποθέσεις και τα δακιτικά ηφαιστειακά πετρώματα της λεκάνης Κύμης-Αλιβερίου έχουν παρατηρηθεί σταθερά μικρές εγκλίσεις σε παλαιομαγνητικές μετρήσεις οι οποίες έχουν αναφερθεί ως αποδεικτικό στοιχείο είτε για τοπική γεωμαγνητική ανωμαλία είτε για μετατόπιση προς βορρά της περιοχής του Αιγαίου. Παρουσιάζονται νέα δεδομένα μετρήσεων παλαιομαγνητισμού σε λιμναία στρώματα τα οποία δεν παρουσιάζουν μικρές εγκλίσεις και είναι συμβατά με απόθεση κοντά στο σημερινό γεωγραφικό πλάτος τους. Οι ιδιαίτερα μικρές εγκλίσεις και αποκλίσεις προς τα ανατολικά που έχουν αναφερθεί στις ηφαιστειακές διεισδύσεις του Οξύλιθου είναι αποτελέσματα ακατάλληλης διόρθωσης ως προς οριζόντιο άξονα. Οι υπερβολικά μικρές παλαιομαγνητικές εγκλίσεις που έχουν αναφερθεί στα πλουτώνια σώματα της Μυκόνου και τη Νάξου, Μέσο-Μειοκαινικής ηλικίας παραμόρφωσης, είναι συμβατές με επαναπροσανατολισμό μιας αρχικής θερμο-παραμένουσας μαγνήτισης που προέκυψε κατά την ψύξη τους κάτω από 580°C την οποία ακολούθησε ιξωδοελαστική παραμόρφωση σε θερμοκρασίες 400-500°C. Δευτερεύουσες μαγνητίσεις που παρατηρήθηκαν στα πετρώματα αυτά αντικατοπτρίζουν, πιθανότατα, τη διαδικασία μίας σταθερής -χημικής προέλευσης- παραμένουσας μαγνήτισης, παράλληλα με την προϋπάρχουσα μαγνήτιση υψηλής θερμοκρασίας, ως αποτέλεσμα της δημιουργίας μαγκεμίτη σε χαμηλή θερμοκρασία (<350°C). Κατά συνέπεια δεν μπορούμε να βρούμε ικανοποιητικές αποδείξεις είτε για τοπική μαγνητική ανωμαλία ή μετακίνηση του Αιγαίου προς βορρά είτε για περιστροφή των μικρής κλίσης κανονικών ρηγμάτων που συνθέτουν το σύστημα αποκόλλησης των Βορείων Κυκλάδων.Consistently shallow paleomagnetic inclinations measured in Early to Middle Miocene lacustrine and dacitic volcanic rocks of the Kymi-Aliveri basin have been cited as evidence for an anomalous geomagnetic field geometry or northward drift of the Aegean Sea region. We present new paleomagnetic data from the lacustrine beds that are instead not anomalously shallow and consistent with deposition near their present-day latitude as predicted by global apparent polar wander paths. Anomalously shallow inclinations and easterly declinations reported from the Oxylithos volcanics are an artifact of an inappropriate tilt correction. The excessively shallow paleomagnetic inclinations reported from the deformed Middle Miocene plutons on Mykonos and Naxos are consistent with reorientation of an original thermoremanent magnetization acquired during cooling below 580°C by subsequent ductile strain at temperatures of 400-500°C. Magnetization overprints observed in these rocks may reflect the acquisition of a stable chemical remanent magnetization lying parallel to the transposed high-temperature magnetization as the result of low-temperature (<350°C) maghemitization. We therefore find no convincing evidence for an anomalous Middle Miocene field geometry, northward drift of the Aegean, or back-tilting of the low-angle normal faults that constitute the North Cycladic Detachment System

The Role of Interferon Antagonist, Non-Structural Proteins in the Pathogenesis and Emergence of Arboviruses

A myriad of factors favor the emergence and re-emergence of arthropod-borne viruses (arboviruses), including migration, climate change, intensified livestock production, an increasing volume of international trade and transportation, and changes to ecosystems (e.g., deforestation and loss of biodiversity). Consequently, arboviruses are distributed worldwide and represent over 30% of all emerging infectious diseases identified in the past decade. Although some arboviral infections go undetected or are associated with mild, flu-like symptoms, many are important human and veterinary pathogens causing serious illnesses such as arthritis, gastroenteritis, encephalitis and hemorrhagic fever and devastating economic loss as a consequence of lost productivity and high mortality rates among livestock. One of the most consistent molecular features of emerging arboviruses, in addition to their near exclusive use of RNA genomes, is the inclusion of viral, non-structural proteins that act as interferon antagonists. In this review, we describe these interferon antagonists and common strategies that arboviruses use to counter the host innate immune response. In addition, we discuss the complex interplay between host factors and viral determinants that are associated with virus emergence and re-emergence, and identify potential targets for vaccine and anti-viral therapies

A Review of Emergency Visits made by Youth and Adults with Autism Spectrum Disorder from the Parent Perspective

Purpose: Past research has shown individuals with autism spectrum disorder (ASD) visit hospital emergency departments (ED) at high rates. In order to assist individuals with ASD, their families and health care providers to improve ED care, it is important to understand these encounters in greater detail. This study aimed to provide a descriptive summary of the ED experiences of adolescents and adults with ASD, from the perspective of their families. Design/Methodology/Approach: A subset of data from a larger prospective cohort study was used. Specifically, 46 parents of adolescents and adults with ASD provided details concerning 49 ED visits over a 12-month period. Findings: Results suggest a range of presentations requiring ED use, and also diverse profiles of those with ASD who visited the ED, in terms of age, gender, and ASD severity. While overall degree of satisfaction with care received in the ED was high, parents provided recommendations to improve the ED experiences for their family members with ASD. Originality/value: This is the first study to provide detailed accounts of ED visits from the perspective of parents of adolescents and adults with ASD. Families play an important role in the lives of individuals with ASD across the lifespan and it is important to include their perspective to improve hospital- based care for those with ASD

Intra- and interspecies interactions between prion proteins and effects of mutations and polymorphisms

Recently, crystallization of the prion protein in a dimeric form was reported. Here we show that native soluble homogenous FLAG-tagged prion proteins from hamster, man and cattle expressed in the baculovirus system are predominantly dimeric. The PrP/PrP interaction was confirmed in Semliki Forest virus-RNA transfected BHK cells co-expressing FLAG- and oligohistidine-tagged human PrP. The yeast two-hybrid system identified the octarepeat region and the C-terminal structured domain (aa90-aa230) of PrP as PrP/PrP interaction domains. Additional octarepeats identified in patients suffering from fCJD reduced (wtPrP versus PrP+90R) and completely abolished (PrP+90R versus PrP+90R) the PrP/PrP interaction in the yeast two-hybrid system. In contrast, the Met/Val polymorphism (aa129), the GSS mutation Pro102Leu and the FFI mutation Asp178Asn did not affect PrP/PrP interactions. Proof of interactions between human or sheep and bovine PrP, and sheep and human PrP, as well as lack of interactions between human or bovine PrP and hamster PrP suggest that interspecies PrP interaction studies in the yeast two-hybrid system may serve as a rapid pre-assay to investigate species barriers in prion diseases