Atomistic potential for graphene and other sp2^2 carbon systems

We introduce a torsional force field for sp$^2$ carbon to augment an in-plane atomistic potential of a previous work (Kalosakas et al, J. Appl. Phys. {\bf 113}, 134307 (2013)) so that it is applicable to out-of-plane deformations of graphene and related carbon materials. The introduced force field is fit to reproduce DFT calculation data of appropriately chosen structures. The aim is to create a force field that is as simple as possible so it can be efficient for large scale atomistic simulations of various sp$^2$ carbon structures without significant loss of accuracy. We show that the complete proposed potential reproduces characteristic properties of fullerenes and carbon nanotubes. In addition, it reproduces very accurately the out-of-plane ZA and ZO modes of graphene's phonon dispersion as well as all phonons with frequencies up to 1000~cm$^{-1}$.Comment: 9 pages, 6 figure

Literature Review of the Generalised Additive Model for location, scale and shape

Το βασικό αντικείμενο αυτής της μελέτης είναι να παρουσιάσει διαφορετικά στατιστικά μοντέλα και να συζητήσει την συνεισφορά τους στην ερμηνεία των δεδομένων. Το πρώτο μοντέλο που αναλύεται είναι το Γενικευμένο Γραμμικό Μοντέλο (ΓΓΜ) το οποίο είναι μία γενίκευση του γραμμικού μοντέλου θεωρώντας η κατανομή της επεξηγηματικής μεταβλητής να είναι μέλος της εκθετικής οικογένειας κατανομών. Η φύση των δεδομένων καθορίζει σε μεγάλο βαθμό την μορφή του γενικευμένου γραμμικού μοντέλου που θα εφαρμοστεί, μέσω της επιλογής της συνάρτησης συνδέσμου του μοντέλου. Οι επαναληπτικές μέθοδοι που επιτρέπουν την πρακτική εφαρμογή του κάθε μοντέλου καθώς και οι αντίστοιχες μέθοδοι στατιστικής συμπερασματολογίας αναλύονται. Η υπόθεση της εκθετικής οικογένειας κατανομών για την εξαρτημένη μεταβλητή ισχύει και για το Γενικευμένο Προσθετικό Μοντέλο (ΓΠΜ). Για την εξαρτημένη μεταβλητή θεωρείται μία κατανομή που ανήκει στην εκθετική οικογένεια κατανομών μαζί με την εισαγωγή μη παραμετρικών συναρτήσεων που αναμιγνύουν τις εγγενείς ιδιότητες των ΓΓΜ και των προσθετικών μοντέλων. Η απαντητική μεταβλητή εξαρτάται γραμμικώς από γνωστές μη παραμετρικές συναρτήσεις ορισμένων εκ των ανεξάρτητων μεταβλητών, η συμπερασματολογία επικεντρώνεται στις μη παραμετρικές συναρτήσεις. Μία γενική κατηγορία στατιστικών μοντέλων για μία απαντητική μεταβλητή παρουσιάζεται, η οποία ονομάζεται Γενικευμένο Προσθετικό Μοντέλο ως προς τις τέσσερις ροπές. Η επιλογή της κατανομής της επεξηγηματικής μεταβλητής στο ΓΠΜ ως προς τις τέσσερις ροπές γίνεται μέσα από μία ευρεία οικογένεια κατανομών συμπεριλαμβάνοντας έντονα ασύμμετρες ή κυρτωμένες συνεχείς και διακριτές κατανομές. Το συστηματικό κομμάτι των ΓΠΜ ως προς τις τέσσερις ροπές διευρύνεται ώστε να επιτρέπει τη μοντελοποίηση του μέσου και άλλων παραμέτρων της κατανομής της επεξηγηματικής μεταβλητής, είτε ως παραμετρικές είτε ως προσθετικές μη παραμετρικές συναρτήσεις είτε ως όροι τυχαίων γεγονότων.The main objective of this study is to present different statistical models and discuss their contribution to data fit. The first model that is analysed is the Generalised Linear Model(GLM) which is a generalisation of the linear model assuming some member of the exponential family of distributions for the response variable. The nature of the data determines to a great extent the form of the generalised linear model that will be applied, through the choice of the link function of the model. The iterative methods which allow for the practical implementation of each particular model and the respective statistical inference procedures are discussed, as well. The assumption of the exponential family distribution for the response is relaxed in the Generalised Additive Model(GAM). A general distribution is assumed for the dependent variable, with the introduction of smoothing functions that blend the inherent properties of the GLM with the additive models. The response variable depends linearly on unknown smooth functions of some predictor variables, and the inference is focused on these smoothers. A general class of statistical models for a univariate response variable is presented, which is called the Generalized Additive Model for Location, Scale and Shape (GAMLSS). The choice of the distribution for the response variable in GAMLSS is made from a very general family of distributions including highly skewed or kurtotic continuous and discrete distributions. The GAMLSS systematic part is expanded to permit modelling of the mean (or location) and other distributional parameters of the response, as parametric and/or additive nonparametric (smooth) functions of explanatory variables and/or random-effects terms

Economic impact and policy implications from urban shared transportation: The case of Pittsburgh’s shared bike system

During the last years the number of cities that have installed and started operating shared bike systems has significantly increased. These systems provide an alternative and sustainable mean of transportation to the city dwellers. Apart from the energy sustainability benefits, shared bike systems can have a positive effect on residents' health, air quality and the overall condition of the currently crumbling road network infrastructure. Anecdotal stories and survey studies have also identified that bike lanes have a positive impact on local businesses. In this study, driven by the rapid adoption of shared bike systems by city governments and their potential positive effects on a number of urban life facets we opt to study and quantify the value of these systems. We focus on a specific aspect of this value and use evidence from the real estate market in the city of Pittsburgh to analyze the effect on dwellers' properties of the shared bike system installed in the city in June 2015. We use quasi-experimental techniques and find that the shared bike system led to an increase in the housing prices (both sales and rental prices) in the zip codes where shared bike stations were installed. We further bring into the light potential negative consequences of this impact (i.e., gentrification) and discuss/propose two public policies that can exploit the impact of the system for the benefit of both the local government as well as the city dwellers

Fabrication of Metasurfaces on Building Construction Materials for Potential Electromagnetic Applications in the Microwave Band

Energy self sufficiency, as well as optimal management of power in buildings is gaining importance, while obtaining power from traditional fossil energy sources is becoming more and more expensive. In this context, millimeter scale metasurfaces can be employed to harvest energy from microwave sources. They can also be used as sensors in the microwave regime for efficient power management solutions. In the current study, a simple spray printing method is proposed to develop metasurfaces in construction materials, i.e., plasterboard and wood. Such materials are used in the interior design of buildings; therefore, the implementation of metasurfaces in large areas, such as walls, doors and floors, is realized. The fabricated metasurfaces were characterized regarding their electromagnetic performance. It is hereby shown that the investigated metasurfaces exhibit an efficient electromagnetic response in the frequency range 4 to 7 GHz, depending on the MS. Thus, spray printed metasurfaces integrated on construction materials can potentially be used for electromagnetic applications, for buildings power self efficiency and management.Comment: 14pages, 8 figure

Location Decisions of Competing Platforms

There are examples of entry in two-sided markets, where first entrants occupy a 'central location' and serve agents with 'intermediate tastes', while later entrants are niche players. Why would the first entrant choose to become a 'general' platform, given that later entrants will not have enough room for differentiation, resulting in an intense price competition? This one-sided market logic may not apply in a two-sided market. A key difference in a two-sided market, stemming from the presence of cross-group network externalities, is stronger demand creation. We develop a model which can deliver the above mentioned empirical observation, when the network externalities are intermediate. On the other hand, when externalities are low, our model predicts that differentiation will be maximum, as it would be in a one-sided market. Finally, for strong externalities only one platform is active and locates at the center

Adult trkB signaling in parvalbumin interneurons is essential to prefrontal network dynamics

Inhibitory interneurons expressing parvalbumin (PV) are central to cortical network dynamics, generation of c oscillations, and cognition. Dysfunction of PV interneurons disrupts cortical information processing and cognitive behavior. Brain-derived neurotrophic factor (BDNF)/tyrosine receptor kinase B (trkB) signaling regulates the maturation of cortical PV interneurons but is also implicated in their adult multidimensional functions. Using a novel viral strategy for cell-type-specific and spatially restricted expression of a dominant-negative trkB (trkB.DN), we show that BDNF/trkB signaling is essential to the integrity and maintenance of prefrontal PV interneurons in adult male and female mice. Reduced BDNF/trkB signaling in PV interneurons in the medial prefrontal cortex (mPFC) resulted in deficient PV inhibition and increased baseline local field potential (LFP) activity in a broad frequency band. The altered network activity was particularly pronounced during increased activation of the prefrontal network and was associated with changed dynamics of local excitatory neurons, as well as decreased modulation of the LFP, abnormalities that appeared to generalize across stimuli and brain states. In addition, our findings link reduced BDNF/trkB signaling in prefrontal PV interneurons to increased aggression. Together our investigations demonstrate that BDNF/trkB signaling in PV interneurons in the adult mPFC is essential to local network dynamics and cognitive behavior. Our data provide direct support for the suggested association between decreased trkB signaling, deficient PV inhibition, and altered prefrontal circuitry.ERCSwedish Research CouncilCAPES-STINT Program GrantKarolinska InstitutetKnut and Alice Wallenberg FoundationSTINT Program Joint Brazilian-Swedish Research Collaboration GrantPublishe

Structural dynamics in the evolution of a bilobed protein scaffold

Novel biophysical tools allow the structural dynamics of proteins and the regulation of such dynamics by binding partners to be explored in unprecedented detail. Although this has provided critical insights into protein function, the means by which structural dynamics direct protein evolution remain poorly understood. Here, we investigated how proteins with a bilobed structure, composed of two related domains from the periplasmic-binding protein–like II domain family, have undergone divergent evolution, leading to adaptation of their structural dynamics. We performed a structural analysis on ∼600 bilobed proteins with a common primordial structural core, which we complemented with biophysical studies to explore the structural dynamics of selected examples by single-molecule Förster resonance energy transfer and Hydrogen–Deuterium exchange mass spectrometry. We show that evolutionary modifications of the structural core, largely at its termini, enable distinct structural dynamics, allowing the diversification of these proteins into transcription factors, enzymes, and extracytoplasmic transport-related proteins. Structural embellishments of the core created interdomain interactions that stabilized structural states, reshaping the active site geometry, and ultimately altered substrate specificity. Our findings reveal an as-yet-unrecognized mechanism for the emergence of functional promiscuity during long periods of evolution and are applicable to a large number of domain architectures

Screening chest radiography: results from a Greek cross-sectional survey

BACKGROUND: Public health authorities worldwide discourage the use of chest radiography as a screening modality, as the diagnostic performance of chest radiography does not justify its application for screening and may even be harmful, since people with false positive results may experience anxiety and concern. Despite the accumulated evidence, various reports suggest that primary care physicians throughout the world still prescribe chest radiography for screening. We therefore set out to index the use of chest radiography for screening purposes among the healthy adult population and to analyze its relationship with possible trigger factors. METHODS: The study was designed as a cross-sectional survey. Five thousand four hundred and ninety-nine healthy adults, coming from 26 Greek provinces were surveyed for screening practice habits in the nationwide anticancer study. Data were obtained for the use of screening chest radiography. Impact of age, gender, tobacco exposure, family history positive for malignancies and professional-risk for lung diseases was further analyzed. RESULTS: we found that 20% (n = 1099) of the surveyed individuals underwent chest radiography for screening purposes for at least one time during the previous three years. Among those, 24% do so with a frequency equal or higher than once yearly, and 48% with a frequency equal or higher than every three years. Screening for chest radiography was more commonly adopted among males (OR 1.130, 95% CI 0.988–1.292), pensioners (OR 1.319, CI 1.093–1.593) and individuals with a positive family history for lung cancer (OR 1.251, CI 0.988–1.583). Multivariate analysis confirmed these results. CONCLUSION: Despite formal recommendations, chest radiography for screening purposes was a common practice among the analyzed sample of Greek adults. This practice is of questionable value since the positive predictive value of chest radiography is low. The implementation of even a relatively inexpensive imaging study on a national scale would greatly burden health economics and the workload of radiology departments

Colorectal cancer screening awareness among physicians in Greece

BACKGROUND: Data comparison between SEER and EUROCARE database provided evidence that colorectal cancer survival in USA is higher than in European countries. Since adjustment for stage at diagnosis markedly reduces the survival differences, a screening bias was hypothesized. Considering the important role of primary care in screening activities, the purpose of the study was to investigate the colorectal cancer screening awareness among Hellenic physicians. METHODS: 211 primary care physicians were surveyed by mean of a self-reported prescription-habits questionnaire. Both physicians' colorectal cancer screening behaviors and colorectal cancer screening recommendations during usual check-up visits were analyzed. RESULTS: Only 50% of physicians were found to recommend screening for colorectal cancer during usual check-up visits, and only 25% prescribed cost-effective procedures. The percentage of physicians recommending stool occult blood test and sigmoidoscopy was 24% and 4% respectively. Only 48% and 23% of physicians recognized a cancer screening value for stool occult blood test and sigmoidoscopy. Colorectal screening recommendations were statistically lower among physicians aged 30 or less (p = 0.012). No differences were found when gender, level and type of specialization were analyzed, even though specialists in general practice showed a trend for better prescription (p = 0.054). CONCLUSION: Contemporary recommendations for colorectal cancer screening are not followed by implementation in primary care setting. Education on presymptomatic control and screening practice monitoring are required if primary care is to make a major impact on colorectal cancer mortality