Using Robust PCA to estimate regional characteristics of language use from geo-tagged Twitter messages

Principal component analysis (PCA) and related techniques have been successfully employed in natural language processing. Text mining applications in the age of the online social media (OSM) face new challenges due to properties specific to these use cases (e.g. spelling issues specific to texts posted by users, the presence of spammers and bots, service announcements, etc.). In this paper, we employ a Robust PCA technique to separate typical outliers and highly localized topics from the low-dimensional structure present in language use in online social networks. Our focus is on identifying geospatial features among the messages posted by the users of the Twitter microblogging service. Using a dataset which consists of over 200 million geolocated tweets collected over the course of a year, we investigate whether the information present in word usage frequencies can be used to identify regional features of language use and topics of interest. Using the PCA pursuit method, we are able to identify important low-dimensional features, which constitute smoothly varying functions of the geographic location

The First Post-Kepler Brightness Dips of KIC 8462852

We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in October 2015, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and "Angkor", which persist on timescales from several days to weeks. Our main results so far are: (i) there are no apparent changes of the stellar spectrum or polarization during the dips; (ii) the multiband photometry of the dips shows differential reddening favoring non-grey extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale <<1um, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process

Miscellanea. Folyóirat-referátumok, Sajtóközlemények, Kvíz = Miscellaneous

Folyóirat-referátumok: 1. M. J. Babcock [et al.]: A nikotinsav okozta tartós erythema nem jelent aszpirinrezisztenciát (Persistent erythema with niacin is not attributable to aspirin resistance) 2. S. Arif [et al.]: Anti-tumornekrózis-faktor-α-terápia – két madarat megölni egy kővel? (Anti-TNF α therapy – killing two birds with one stone?) 3. J. Mehilli - R. A. Byrne - K. Tiroch [et al.]: A paclitaxel-versus sirolimuskibocsátó stentek randomizált vizsgálata a sirolimuskibocsátó coronariastentek in stent restenosisának (ISR) kezelésében: ISAR-DESIRE 2 vizsgálat (Randomized trial of paclitaxel-versus sirolimus-eluting stents for teatment of coronary restenosis in sirolimus-eluting stents. The ISAR-DESIRE 2 [Intracoronary Stenting and Angiographic Results: Drug Eluting Stents for In-Stent Restenosis 2] 4. F. Alfonso: A gyógyszerkibocsátó stentek restenosisának (újra beszűkülésének) kezelése: merrefelé tartunk? (Szerkesztőségi kommentár) (Treatment of drug-eluting stent restenosis. The new pilgrimage: Quo vadis? [Editorial comment]) 5. I. B. Barsoum - H. H. C. Yao: A magzati Leydig-sejtek: az őssejtek fenntartása és differenciációja (Fetal Leydig cells: Progenitor cell maintenance and differentiation) Sajtóközlemények: 1. Az agyi pacemaker korszerűsíti az epilepsziakezelés