Physics of Nonthermal Radio Sources

On December 3 and 4, 1962, the Goddard Institute for Space Studies, an office of the National Aeronautics and Space Administration, was host to an international group of astronomers and physicists who met to discuss the physics of nonthermal radio sources. This was the third in a continuing series of interdisciplinary meetings held at the Institute on topics which have a special bearing on the main lines of inquiry in the space program. The conference was organized by G. R. Burbidge of the University of California at San Diego and by L. Woltjer, then of the University of Leiden but temporarily at the Massachusetts Institute of Technology, and now of Columbia University

Online neurostimulation of Broca's area does not interfere with syntactic predictions: A combined TMS-EEG approach to basic linguistic combination

Categorical predictions have been proposed as the key mechanism supporting the fast pace of syntactic composition in human language. Accordingly, grammar-based expectations facilitate the analysis of incoming syntactic information—e.g., hearing the determiner “the” enhances the prediction of a noun—which is then checked against a single or few other word categories. Previous functional neuroimaging studies point towards Broca’s area in the left inferior frontal gyrus (IFG) as one fundamental cortical region involved in categorical prediction during on-line language processing. Causal evidence for this hypothesis is however still missing. In this study, we combined Electroencephalography (EEG) and Transcranial Magnetic Stimulation (TMS) to test whether Broca’s area is functionally relevant in predictive mechanisms for language. Specifically, we transiently perturbed Broca’s area during the categorical prediction phase in two-word constructions, while simultaneously measuring the Event-Related Potential (ERP) correlates of syntactic composition. We reasoned that if Broca’s area is involved in predictive mechanisms for syntax, disruptive TMS during the processing of the first word (determiner/pronoun) would mitigate the difference in ERP responses for predicted and unpredicted categories when composing basic phrases and sentences. Contrary to our hypothesis, perturbation of Broca’s area at the predictive stage did not affect the ERP correlates of basic composition. The correlation strength between the electrical field induced by TMS and the magnitude of the EEG response on the scalp further confirmed this pattern. We discuss the present results in light of an alternative account of the role of Broca’s area in syntactic composition, namely the bottom-up integration of words into constituents

Relating Spin Foams and Canonical Quantum Gravity: A Discrete Step Evolution Formulation of Spin Foams

This article has been replaced by gr-qc/0412011Comment: This article has been replaced by gr-qc/041201

Towards a causal role of Broca's area in language: A TMS-EEG study on syntactic prediction

Introduction: In language comprehension, the analysis of the grammatical category of words occurs during the very early phase of processing (Friederici, 2011). When the category of incoming words violates syntactic rules, increased negativities are observed compared to grammatical constructions (Early Left Anterior Negativity – ELAN, Friederici et al., 1993); Early Syntactic Negativity – ESN, Hasting & Kotz, 2008). The early latencies of these components have been attributed to the presence of structural predictions (Lau et al., 2006). For example, after hearing “The”, a noun, alone or with an adjective, is expected to build a phrase. Accordingly, the ELAN and ESN effects would reflect a mismatch between the predicted category and the observed ungrammatical one. Functional studies implicated Broca’s area in syntactic categorical prediction (Bonhage et al., 2015), but causal evidence for this claim is still missing. We tested this hypothesis by simultaneously combining Transcranial Magnetic Stimulation (TMS) and Electroencephalography (EEG) in a two-word ESN paradigm. With TMS, we transiently perturbed activity in Broca’s area at the stage of prediction (e.g., “the”) and measured the negativity elicited by predicted (e.g., noun) and unpredicted (e.g., verb) categories. We hypothesized that disruption of Broca’s area during the processing of the first word would prevent an ESN effect (ungrammatical vs. grammatical) on the second word, as no prediction is initiated. Therefore, categorical effects on the second word would be similar for both grammatical and ungrammatical items. Methods: We employed a German version of the auditory two-word ESN paradigm. The first word could either be the determiner “Ein” (a, predicting a noun) or the pronoun “Er” (he, predicting a verb). The second word could either be a noun or a verb. Two types of two-word constructions were therefore included: grammatical (“Ein” and a noun, “Er” and a verb) and ungrammatical (“Ein” and a verb, “Er” and a noun). To selectively interfere with the predictive stage, we transiently perturbed activity in Broca’s area by means of a 10 Hz train of five TMS pulses starting at the onset of the first word. Three stimulation conditions were included: Broca’s area (target site) and two control conditions (superior parietal lobe and sham stimulation), with the order counterbalanced across subjects. Data from twenty-nine German speakers entered the final analysis (fifteen female; mean age: 27.1 years, standard deviation: 4.1 years). The statistical analysis focused on the second word. We analyzed the main effect of grammaticality (ESN effect) and its modulation by TMS (grammaticality*TMS interaction) with cluster-based permutation tests (Maris & Oostenveld, 2007). By employing state-of-the-art electrical field modelling (Weise et al., 2020), we further correlated the TMS-induced electrical field in Broca’s area with changes in the ESN effect relative to the sham condition. Results: The cluster-based permutation test revealed a main effect of grammaticality, with the presence of a significant early negative cluster (approximately from 190 to 430ms, P .5, cluster-corrected). No significant correlation was found between changes in the ESN effect and the TMS-induced electrical field in Broca’s area (r = 0.142, p > 0.1, BF01 = 3.302). Conclusions: The main effect of grammaticality is consistent with an early analysis of word category, followed by late repairing processes (Friederici, 2011) in case of ungrammaticality. The lack of a significant grammaticality*TMS interaction suggests that Broca’s area may not be causally involved in categorical prediction. Our findings are compatible with functional studies proposing that this region might be involved in the bottom-up integration of words into syntactic structures (Bhattasali et al., 2019)

Private hospital workflow optimization via secure k-means clustering

Optimizing the workflow of a complex organization such as a hospital is a difficult task. An accurate option is to use a real-time locating system to track locations of both patients and staff. However, privacy regulations forbid hospital management to assess location data of their staff members. In this exploratory work, we propose a secure solution to analyze the joined location data of patients and staff, by means of an innovative cryptographic technique called Secure Multi-Party Computation, in which an additional entity that the staff members can trust, such as a labour union, takes care of the staff data. The hospital, owning location data of patients, and the labour union perform a two-party protocol, in which they securely cluster the staff members by means of the frequency of their patient facing times. We describe the secure solution in detail, and evaluate the performance of our proof-of-concept. This work thus demonstrates the feasibility of secure multi-party clustering in this setting