2,089 research outputs found
A Method for 21cm Power Spectrum Estimation in the Presence of Foregrounds
21cm tomography promises to be a powerful tool for estimating cosmological
parameters, constraining the epoch of reionization, and probing the so-called
dark ages. However, realizing this promise will require the extraction of a
cosmological power spectrum from beneath overwhelmingly large sources of
foreground contamination. In this paper, we develop a unified matrix-based
framework for foreground subtraction and power spectrum estimation, which
allows us to quantify the errors and biases that arise in the power spectrum as
a result of foreground subtraction. We find that existing line-of-sight
foreground subtraction proposals can lead to substantial mode-mixing as well as
residual noise and foreground biases, whereas our proposed inverse variance
foreground subtraction eliminates noise and foreground biases, gives smaller
error bars, and produces less correlated measurements of the power spectrum. We
also numerically confirm the intuitive belief in the literature that 21cm
foreground subtraction is best done using frequency rather than angular
information.Comment: 24 pages, 11 figures; replaced with accepted PRD version (minor
editorial changes to text; methods, results, and conclusions unchanged
The Implications for Christology of the Idenity of the Poor Man in the Teaching of Jesus
Studies have been carried out in times past on the poor man motif in the Old Testament. The results of these have varied and few have deemed it necessary to suggest any implications their conclusions might have for the Gospels. Consequently, investigations of the motif in the New Testament area have been negligible and generally disappointing. For this reason, I have undertaken this study of the poor man motif, particularly as it appertains to the Messianic role as Jesus himself understood it
The Satanic in St. Paul\u27s Letters with Special Reference to False Teachers
A vital and practical demonology is certainly necessary to sharpen our awareness of evil and the distinction between right and wrong. Our understanding of the satanic not only puts us on guard but also brings into sharp emphasis the real greatness or God\u27s grace and deepens our trust in our Saviour. For this reason I have undertaken to investigate what St. Paul says about Satan and his followers in order to find a vital and practical demonology for our day. The reason St. Paul is chosen rather than the other New Testament writers is that he more than the other writers is dealing directly with and writing explicitly about the problems that continually confronted the congregations, Christians, and teachers of his time and which still confront us today
Precision Calibration of Radio Interferometers Using Redundant Baselines
Growing interest in 21 cm tomography has led to the design and construction
of broadband radio interferometers with low noise, moderate angular resolution,
high spectral resolution, and wide fields of view. With characteristics
somewhat different from traditional radio instruments, these interferometers
may require new calibration techniques in order to reach their design
sensitivities. Self-calibration or redundant calibration techniques that allow
an instrument to be calibrated off complicated sky emission structures are
ideal. In particular, the large number of redundant baselines possessed by
these new instruments makes redundant calibration an especially attractive
option. In this paper, we explore the errors and biases in existing redundant
calibration schemes through simulations, and show how statistical biases can be
eliminated. We also develop a general calibration formalism that includes both
redundant baseline methods and basic point source calibration methods as
special cases, and show how slight deviations from perfect redundancy and
coplanarity can be taken into account.Comment: 18 pages, 13 figures; Replaced to match accepted MNRAS versio
Die SRG-Medienstudie 1996-2000 : Archivierung und Erschliessung ; Mediennutzung im Tagesablauf : öffentlich-rechtliche, regionale und private Medien
Die Studie wurde mit Mitteln der BAKOM-Forschungsförderung unterstützt.Das Projekt „Die SRG-Medienstudie 1996-2000: Archivierung und Erschliessung. Mediennutzung im Tagesablauf: Öffentlich-rechtliche, regionale und private Medien“ bezweckt die Sicherung und Aufbereitung der SRG-Medienstudiendaten der Jahre 1996-2000 für Sekundäranalysen. Diese Daten enthalten eine äusserst breite Palette von Informationen zur individuellen Mediennutzung im tageszeitlichen Verlauf der gesamtschweizerischen Bevölkerung.
In einem ersten Schritt werden alle vorhandenen analogen sowie digitalen Daten erschlossen und ihrem Entwicklungszusammenhang entsprechend dokumentiert und analysiert. Die Tauglichkeit des so gewonnenen Datensatzes wird in einem zweiten Schritt anhand ausgewählter Tagesablauf-Auswertungen überprüft.
Das Gesamtprojekt erstreckt sich ĂĽber einen Zeitraum von 15 Monaten. Die Hauptergebnisse lassen sich wie folgt zusammenfassen:
- GĂĽtesiegel jeder Informations- oder Datenaufbereitung bildet eine präzise Dokumentation des Vorhandenen. Anhand der SRG-MS 1996-2000 wurde dies exemplarisch durchexerziert, wobei auf verschiedene Probleme bei der Rekonstruktion der Studie und der Datensicherung gestossen wurde. Einerseits sind die analogen Daten nirgends – weder im Archiv des AufÂtragÂgebers, noch in den Archiven des Umfragebetreibers – vollständig vorhanden, geschweige denn in geordneter Form archiviert. Andererseits sind Informationen teilweise in digitalisierten Speichern noch greifbar, wenn auch wiederum in unsystematischer Ordnung und angesichts neuer Software-Systeme fĂĽr die Langzeitaufbewahrung gefährdet. Das Nebeneinander von analogen und digitalen Daten erschwert zudem die Forschungsarbeit in unzweckmässiger Art. Ăśberdies sind nicht dokumentierte, aber aufschlussreiche Informationen lediglich ĂĽber die Befragung der damals Beteiligten (z.B. Studienleiter, Produktionsverantwortliche, Statistiker, Programmierer), die in SchlĂĽsselpositionen tätig waren oder sind, möglich. In Hinblick auf LangÂzeitarchivierung sind diese Problempunkte zu ĂĽberdenken und vorausschauende BetriebsÂÂstrategien durch die Auftraggeber zu ĂĽberlegen.
- Die Datensammlung zur SRG-Medienstudie entpuppt sich ungeordneter als anÂgeÂnommen und präsentiert sich in einer kritischen Situation. Während einzelne Dokumentationen (Berichte, Akten usw.) nicht mehr vorhanden und auch in elektronischer Form nicht mehr rekonstruierbar sind, konnten wichtige andere Daten gesichert werden. DarĂĽber hinaus wurden zuhanden der betreffenden Archive Empfehlungen fĂĽr die Langzeitaufbewahrung gemacht.
- Das differenzierte Untersuchungsdesign der SRG-Medienstudie und die Vielzahl der Variablen fĂĽhren zu grossen Datenmengen, die nicht mehr in einer Struktur darstellbar sind. Trotz den BemĂĽhungen um Einheitlichkeit (und damit Vergleichbarkeit) bei der jährlichen DurchÂfĂĽhrung der Erhebungen in der deutschen, französischen und italienischen Schweiz resultieren – infolge der dynamischen Medienwelt – Abweichungen bei der Harmonisierung der 60 Fragebogenversionen. Diese Diskongruenzen bzw. Inkompatibilitäten werden in transÂpaÂrenter Form ausgeleuchtet.
- Die elektronischen Daten der Jahre 1996-2000 sind in ein Austauschformat konvertiert worden. Zusammen mit der Differenzierung in die drei Landesregionen, den vier quotierten JahresÂquartalen und den fĂĽnf UnterÂsuchungsjahren werden 45 Rohdatenfiles erstellt. Diese Rohdatensätze sind in zwei Auswertungsdatensätze zusammengefasst worden und stehen der Wissenschaft und dem wissenschaftlichen Nachwuchs als erster Medien-Längsschnittdatensatz der Schweiz fĂĽr Sekundäranalysen zu VerfĂĽgung.
- Das fĂĽr die Medienforschung interessante Ergebnis dieser Studie resultiert in der Disposition der Medienstudiendaten in den Auswertungsdatensätzen. Durch die vertikale Anordnung der DatenÂreihen werden neue und innovative Auswertungsmöglichkeiten erschlossen, um die komplexe, dreidimensionale Datenstruktur der statistischen Analyse zugänglich zu machen.
- Exemplarische Sekundäranalysen prĂĽfen die Frage, ob (und wie) mit den vorliegenden Datenfiles statistische Auswertungen ĂĽber drei Auswertungsdimensionen (Zeit, MedienÂnutzung, Personenmerkmale) erstellt werden können. Durch einen Methodenvergleich wird aufÂgezeigt, dass in drei ausgewählten sprachregionalen Gebieten keine homogenen AblaufÂmuster zwischen Tagesablauf, Mediennutzung und Personenmerkmalen feststellbar sind, sondern in jedem der Untersuchungsgebiete spezifische sprachregionale Besonderheiten gelten, die auch sozio-ökonomisch beschreibbar sind
Analysis of recreational psychedelic substance use experiences classified by substance
RATIONALE AND OBJECTIVES
Differences among psychedelic substances regarding their subjective experiences are clinically and scientifically interesting. Quantitative linguistic analysis is a powerful tool to examine such differences. This study compared five psychedelic substance report groups and a non-psychedelic report group on quantitative linguistic markers of psychological states and processes derived from recreational use-based online experience reports.
METHODS
Using 2947 publicly available online reports, we compared Ayahuasca and N,N-dimethyltryptamine (DMT, analyzed together), ketamine, lysergic acid diethylamide (LSD), 3,4-methylenedioxymethamphetamine (MDMA), psilocybin (mushroom), and antidepressant drug use experiences. We examined word frequencies related to various psychological states and processes and semantic proximity to psychedelic and mystical experience scales.
RESULTS
Linguistic markers of psychological function indicated distinct effect profiles. For example, MDMA experience reports featured an emotionally intensifying profile accompanied by many cognitive process words and dynamic-personal language. In contrast, Ayahuasca and DMT experience reports involved relatively little emotional language, few cognitive process words, increased analytical thinking-associated language, and the most semantic similarity with psychedelic and mystical experience descriptions. LSD, psilocybin mushroom, and ketamine reports showed only small differences on the emotion-, analytical thinking-, psychedelic, and mystical experience-related language outcomes. Antidepressant reports featured more negative emotional and cognitive process-related words, fewer positive emotional and analytical thinking-related words, and were generally not similar to mystical and psychedelic language.
CONCLUSION
This article addresses an existing research gap regarding the comparison of different psychedelic drugs on linguistic profiles of psychological states, processes, and experiences. The large sample of experience reports involving multiple psychedelic drugs provides valuable information that would otherwise be difficult to obtain. The results could inform experimental research into psychedelic drug effects in healthy populations and clinical trials for psychedelic treatments of psychiatric problems
Global 21cm signal experiments: a designer's guide
[Abridged] The spatially averaged global spectrum of the redshifted 21cm line
has generated much experimental interest, for it is potentially a direct probe
of the Epoch of Reionization and the Dark Ages. Since the cosmological signal
here has a purely spectral signature, most proposed experiments have little
angular sensitivity. This is worrisome because with only spectra, the global
21cm signal can be difficult to distinguish from foregrounds such as Galactic
synchrotron radiation, as both are spectrally smooth and the latter is orders
of magnitude brighter. We establish a mathematical framework for global signal
data analysis in a way that removes foregrounds optimally, complementing
spectra with angular information. We explore various experimental design
trade-offs, and find that 1) with spectral-only methods, it is impossible to
mitigate errors that arise from uncertainties in foreground modeling; 2)
foreground contamination can be significantly reduced for experiments with fine
angular resolution; 3) most of the statistical significance in a positive
detection during the Dark Ages comes from a characteristic high-redshift trough
in the 21cm brightness temperature; and 4) Measurement errors decrease more
rapidly with integration time for instruments with fine angular resolution. We
show that if observations and algorithms are optimized based on these findings,
an instrument with a 5 degree beam can achieve highly significant detections
(greater than 5-sigma) of even extended (high Delta-z) reionization scenarios
after integrating for 500 hrs. This is in contrast to instruments without
angular resolution, which cannot detect gradual reionization. Abrupt ionization
histories can be detected at the level of 10-100's of sigma. The expected
errors are also low during the Dark Ages, with a 25-sigma detection of the
expected cosmological signal after only 100 hrs of integration.Comment: 34 pages, 30 figures. Replaced (v2) to match accepted PRD version
(minor pedagogical additions to text; methods, results, and conclusions
unchanged). Fixed two typos (v3); text, results, conclusions etc. completely
unchange
The effect of passive base ventilation on the aerodynamic drag of a generic SUV vehicle
Sports Utility Vehicles (SUVs) typically have a blunt rear end shape (for design and practicality), however this is not beneficial for aerodynamic drag. Drag can be reduced by a number of passive and active methods such as tapering and blowing into the base. In an effort to combine these effects and to reduce the drag of a visually square geometry slots have been introduced in the upper side and roof trailing edges of a squareback geometry, to take air from the freestream and passively injects it into the base of the vehicle to effectively create a tapered body. This investigation has been conducted in the Loughborough University’s Large Wind Tunnel with the ¼ scale generic SUV model. The basic aerodynamic effect of a range of body tapers and straight slots have been assessed for 0° yaw. This includes force and pressure measurements for most configurations. The slots generate useful, but small, drag reductions with the best configurations giving reductions in drag coefficient (Cd) of approximately 0.01, whereas the best taper configurations reduce Cd by close to 0.035. The slots also have a tendency to modify the lift
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