A decade into Facebook: where is psychiatry in the digital age?

Social networking sites are a part of everyday life for over a billion people worldwide. They show no sign of declining popularity, with social media use increasing at 3 times the rate of other Internet use. Despite this proliferation, mental healthcare has yet to embrace this unprecedented resource. We argue that social networking site data should become a high priority for psychiatry research and mental healthcare delivery. We illustrate our views using the world’s largest social networking site, Facebook, which currently has over 1 billion daily users (1 in 7 people worldwide). Facebook users can create personal profiles, socialize, express feelings, and share content, which Facebook stores as time-stamped digital records dating back to when the user first joined. Evidence suggests that 92% of adolescents go online daily and disclose considerably more about themselves online than offline. Thus, working with Facebook data could further our understanding of the onset and early years of mental illness, a crucial period of interpersonal development. Furthermore, a diminishing ‘digital divide’ has allowed for a broader sociodemographic to access Facebook, including homeless youth, young veterans, immigrants, patients with mental health problems, and seniors, enabling greater contact with traditionally harder-to-reach populations

Invertible Dirac operators and handle attachments on manifolds with boundary

For spin manifolds with boundary we consider Riemannian metrics which are product near the boundary and are such that the corresponding Dirac operator is invertible when half-infinite cylinders are attached at the boundary. The main result of this paper is that these properties of a metric can be preserved when the metric is extended over a handle of codimension at least two attached at the boundary. Applications of this result include the construction of non-isotopic metrics with invertible Dirac operator, and a concordance existence and classification theorem.Comment: Accepted for publication in Journal of Topology and Analysi

Can restenosis after coronary angioplasty be predicted from clinical variables?

AbstractObjectives. The purpose of this study was to determine whether variables shown to correlate with restenosis in one group (learning group) could be shown to predict recurrent stenosis in a second group (validation group).Background. Restenosis remains a critical limitation after percutaneous transluminal coronary angioplasty. Although several clinical variables have been shown to correlate with restenosis, there are few data concerning attempts to predict recurrent stenosis.Methods. The source of data was the clinical data bese at Emory University. Patients who had had previous coronary surgery and patients who underwent coronary angioplasty in the setting of acute myocardial Infarction were excluded. A total of 4,006 patients with angiographic restudy after successful angioplisty were identified. They were classified into a learning group of 2,500 patients and a validation group of 1,506 patients. The correlates of restenosis in the learning group were determined by stepwise logistic regression, and a model was developed to predict the probability of restenosis and was tested in the validation group. By using various cut points for the predicted probability of restenosis, a receiver operating characteristic curve was created. Goodness of fit of the model was evaluated by comparing average predicted probabilities with average observed probabilities within subgroups on the basis of risk level determined by linear regression analysis.Results. In the learning group 1,145 patients had restenosis and 1,355 did not. Correlates of restenosis were severe angina, severe diameter stenosis before angioplasty, left anterior descending coronary artery dilation, diabetes, greater diameter stenosis after angioplasty, hypertension, absence of an intimal tear, eccentric morphology and older patient age. The model derived from the learing group was used to predict restenosis in the validation group. By varying the cut point for the predicted probability of restenosis above which restenosis is diagnosed and below which it is not, a receiver operating characteristic curve was created. The curve was close to the line of identity, reflecting a poor predictive ability. However, the model was shown to fit well with the predicted probability of restenosis correlating well with the observed probability (r = 0.98, p = 0.0001).Conclusions. Clinical variables provide limited ability to predict definitively whether a particular patient will have restenosis. However, the current model may be used to predict the probability of restenosis, with some uncertainty, at least in well characterized patients who have already had angioplasy

Hemodynamic effects of intravenous amiodarone

Amiodarone is a potent antiarrhythmic agent that is effective in controlling both atrial and ventricular arrhythmias. Recently, intravenous administration was demonstrated to be effective in the acute management of rhythm disorders and, in addition, appeared to shorten the loading period normally required for oral drug administration. This investigation examined the hemodynamic effects of amiodarone after both acute intravenous bolus and continuous intravenous administration. Patients with a left ventricular ejection fraction greater than 0.35 experienced improved cardiac performance due to both acute and chronic peripheral vasodilation. However, patients with a lower ejection fraction developed a 20% decrease in cardiac index and clinically significant elevation of right heart pressures after acute bolus administration; these changes were variably compensated for by peripheral vasodilation when the drug was administered intravenously over 3 to 5 days continuously. Therefore, intravenous amiodarone can result in significant impairment of left ventricular performance in patients with preexisting left ventricular dysfunction

Two Coupled Harmonic Oscillators on Non-commutative Plane

We investigate a system of two coupled harmonic oscillators on the non-commutative plane \RR^2_{\theta} by requiring that the spatial coordinates do not commute. We show that the system can be diagonalized by a suitable transformation, i.e. a rotation with a mixing angle \alpha. The obtained eigenstates as well as the eigenvalues depend on the non-commutativity parameter \theta. Focusing on the ground state wave function before the transformation, we calculate the density matrix \rho_0(\theta) and find that its traces {\rm Tr}(\rho_{0}(\theta)) and {\rm Tr}(\rho_0^2(\theta)) are not affected by the non-commutativity. Evaluating the Wigner function on \RR^2_{\theta} confirms this. The uncertainty relation is explicitly determined and found to depend on \theta. For small values of \theta, the relation is shifted by a \theta^2 term, which can be interpreted as a quantum correction. The calculated entropy does not change with respect to the normal case. We consider the limits \alpha=1 and \alpha={\pi\over 2}. In first case, by identifying \theta to the squared magnetic length, one can recover basic features of the Hall system.Comment: 15 pages, 1 figur

A Path Integral Approach To Noncommutative Superspace

A path integral formula for the associative star-product of two superfields is proposed. It is a generalization of the Kontsevich-Cattaneo-Felder's formula for the star-product of functions of bosonic coordinates. The associativity of the star-product imposes certain conditions on the background of our sigma model. For generic background the action is not supersymmetric. The supersymmetry invariance of the action constrains the background and leads to a simple formula for the star-product.Comment: Latex 13 pages. v2: references and footnotes adde

Computational personality recognition in social media

A variety of approaches have been recently proposed to automatically infer users' personality from their user generated content in social media. Approaches differ in terms of the machine learning algorithms and the feature sets used, type of utilized footprint, and the social media environment used to collect the data. In this paper, we perform a comparative analysis of state-of-the-art computational personality recognition methods on a varied set of social media ground truth data from Facebook, Twitter and YouTube. We answer three questions: (1) Should personality prediction be treated as a multi-label prediction task (i.e., all personality traits of a given user are predicted at once), or should each trait be identified separately? (2) Which predictive features work well across different on-line environments? (3) What is the decay in accuracy when porting models trained in one social media environment to another

Adaptive Equalization and Capacity Analysis for Amplify-and-Forward Relays

Recent research has shown that multiple-input multiple-output (MIMO) systems provide high spectral efficiencies and error performance gains. However, the use of multiple antennas in mobile terminals may not be very practical. Certainly there is limited space and other implementation issues which make this a challenging problem. Therefore, to harness the diversity gains afforded by MIMO transmitter diversity techniques, while maintaining a minimal number of antennas on each handset, cooperative diversity techniques have been proposed. In addition, attention has also been given to combining wireless relaying systems with MIMO techniques to improve capacity, coverage, and obtain better diversity at the expense of increased node complexity. This thesis considers the design and analysis of cooperative diversity systems and MIMO amplify-and-forward relaying systems. In particular, we investigate adaptive time- and frequency-domain equalization techniques for cooperative diversity systems using space-time block codes (STBC). For MIMO relaying systems, we analyze the ergodic capacity of various systems and compare different amplify-and-forward methods in terms of system capacity performance. We propose a new block time-domain adaptive equalization structure for time reversal-space time block coding (TR-STBC) systems, which eliminates the separate decoder and also the need for explicit channel state information (CSI) estimation at the receiver. Our simulation results show that the time-domain adaptive block equalizer performs better than the frequency-domain counterpart but at the cost of increased complexity. Then, we extend this time-domain adaptive equalization scheme to distributed TR-STBC systems. We also develop a frequency-domain counterpart for the distributed systems. Our simulation results show that the adaptive algorithms work well for Protocols I and III proposed by Nabar et al. The time-domain adaptive algorithms perform better than the frequency-domain algorithms, and overall the Protocol I receivers outperform the Protocol III receivers. We also show that, if only the Protocol III receiver is used, it can be susceptible to noise amplification due to a weaker source-to-relay link compared to the relay-to-destination link. This problem can be mitigated by using the Protocol I receivers with some extra complexity but much superior diversity performance. We also present an ergodic capacity analysis of an amplify-and-forward (AF) MIMO two-hop system including the direct link and validate the analysis with simulations. We show that having the direct link improves the capacity due to diversity and quantify this improvement. We also present an ergodic capacity analysis of an AF MIMO two-hop, two relay system. Our results verify the capacity gain of relaying systems with two relays due to the extra diversity compared to a single relaying system. However, the results also show that when one of the source-to-relay links has a markedly higher SNR compared to the other, a single relay system has better capacity than a two relay system. Finally, we compare three types of relay amplification methods: a) average amplification, b) instantaneous channel amplification, and c) instantaneous power amplification. The instantaneous power amplification method has a higher mean capacity but with a higher variance. Also, it requires additional information at the destination and would create enormous overheads compared to the other methods. We also find that the instantaneous channel amplification method has almost no advantage in terms of the mean capacity but its capacity is less variable than the average amplification method. On the other hand, the average amplification method is simpler to implement as it does not require channel estimation at the relaying terminal

Braided algebras and the kappa-deformed oscillators

Recently there were presented several proposals how to formulate the binary relations describing kappa-deformed oscillator algebras. In this paper we shall consider multilinear products of kappa-deformed oscillators consistent with the axioms of braided algebras. In general case the braided triple products are quasi-associative and satisfy the hexagon condition depending on the coassociator $Phi \in A\otimes A\otimes A$. We shall consider only the products of kappa-oscillators consistent with co-associative braided algebra, with Phi =1. We shall consider three explicite examples of binary kappa-deformed oscillator algebra relations and describe briefly their multilinear coassociative extensions satisfying the postulates of braided algebras. The third example, describing kappa-deformed oscillators in group manifold approach to kappa-deformed fourmomenta, is a new result.Comment: v2, 13 pages; Proc. of 2-nd Corfu School on Quantum Gravity and Quantum Geometry, September 2009, Corfu; Gen. Rel. Grav. (2011),special Proceedings issue; version in pres