Bend it like dark matter!

Dark matter is one of the most intriguing scientific mysteries of our time and offers exciting instructional opportunities for physics education in high schools. The topic is likely to engage and motivate students in the classroom and allows addressing open questions of the Standard Model of particle physics. Although the empirical evidence of dark matter links nicely to many standard topics of physics curricula, teachers may find it challenging to introduce the topic in their classrooms. In this article, we present a fun new approach to teach about dark matter using jelly lenses as an instructional analogy of gravitational lenses. We provide a brief overview of the history of dark matter to contextualise our presentation and discuss the instructional potential as well as limitations of the jelly lens analogy.Comment: 17 pages, 4 figure

Untersuchungen zur postglazialen Landschaftsentwicklung in der Niederlausitz

Ziel der Arbeit war es, die holozäne Landschaftsentwicklung dreier Untersuchungsgebiete in der Niederlausitz zu rekonstruieren und dabei das kausale Wirkungsgefüge zwischen Landnutzung und Landschaftsentwicklung zu erfassen. Es wurden bodenkundlich-feinstratigraphische Boden- und Sedimentaufnahmen durchgeführt und durch laboranalytische Untersuchungen, Archivrecherchen sowie die Verknüpfung mit aktuellen archäologischen Forschungen ergänzt. Für die Untersuchungsgebiete wurden die relevanten Phasen geomorphodynamischer Teilaktivität herausgearbeitet und mit Phasen intensiverer Landnutzung korreliert (späte Bronzezeit, Römische Kaiserzeit, Hoch- und Spätmittelalter). Nach jeder Phase intensiver Landnutzung, die mit einer Destabilisierung der Landschaft verbunden war, folgten Phasen geringerer Bevölkerungsdichte, in denen die Landschaft nicht oder nur in geringer Intensität genutzt wurde und eine Restabilisierung des Landschaftshaushaltes stattfand (vorrömische Eisenzeit, Völkerwanderungszeit). Der Übergang von stabilen Landschaftsverhältnissen zur Destabilisierung der Landschaft erfolgte meist schnell durch ein rasches Bevölkerungswachstum, durch die Erhöhung des Nutzungsdruckes auf die Landschaft und / oder durch die Einführung neuer Agrartechniken aus anderen Gebieten. Anhand detaillierter bodenchemischer Analysen der Organikfraktion von fossilen und rezenten Oberböden ließen sich Zusammenhänge zwischen Zusammensetzung der organischen Bodensubstanz mit dem Alter und der (vor)geschichtlichen Nutzung der Böden korrelieren

Optical studies of the mesospheric region

A three-field photometer has been employed at the University of Adelaide's Buckland Park field site to collect optical observations of the 557.7nm OI and 730nm OH airglow emissions. Data have been collected on an almost continuous basis since May 1995 through to May 2000, with observations made whenever the moon was not up. Techniques and analysis procedures have been developed which allow routine extraction of the parameters of gravity waves observed each night. A cross-spectral analysis was performed on processed data from the photometer to identify short period (less than 3 hours) wave activity on nights where the impact of clouds on the data was minimal. The resulting wave parameters are analysed for seasonal variability and used to build up a climatology of wave parameters over the 5 years of observation. No consistent seasonal variation was observed, although there was a strong eastward perference to the wave's propagation direction. Implications of this finding are discussed. A co-located MF radar has been operating in spaced antenna mode providing wind data concurrent with the optical observations for most of the acquisition period. When available the wind data allowed calculation of the intrinsic parameters for waves identified in the optical data. The seasonal variablility of these parameters was investigated. An evaluation of energy and momentum fluxes estimated using the method of Swenson et al (1998b) was carried out. Approximations made in this method were found to be inappropriate for the waves detected by the photometer, and a refined procedure was therefore developed. This gave more realistic results, although large number of physically unreasonable momentum flux measurements were reported. Possible reasons for these were explored, and the need for further investigations emphasised. The five year dataset also allowed investigation of the long-term behaviour of the airglow. Both the intensity and variance were analysed using the Lomb-Scargle method across the complete dataset to identify the dominant periods present. Following similar treatment, the MF spaced antenna winds were compared with the optical results; this utilised a complex spectrum extension to the basic Lomb algorithm. Seasonally related periodicities of two years, one year, one half of a year and one third of a year were observed in the optical data, along with a possible signature of a five and a half year period potentially linked to the eleven year solar cycle. The radar data did not have stong signatures of the one third of a year periodicity although the presence of an five and a half year periodicity could not be ruled out. Gravity wave activity, as measured by the optical intensity variance, reached a maximum during autumn with a secondary maximum occurring in spring. The annual variability of the wave spectrum detected by the photometer was also studied which showed a falloff in the wave energy at short periods (less than thirty minutes) during autumn and spring. This suggested that the enhanced wave activity at these times consisted mainly of waves with periods greater than thirty minutes.Thesis (Ph.D.) -- University of Adelaide, Dept. of Physics and Mathematical Physics, 2000

Seasonal MLT-region nightglow intensities, temperatures, and emission heights at a Southern Hemisphere midlatitude site

We consider 5 years of spectrometer measurements of OH(6–2) and O2(0–1) airglow emission intensities and temperatures made near Adelaide, Australia (35° S, 138° E), between September 2001 and August 2006 and compare them with measurements of the same parameters from at the same site using an airglow imager, with the intensities of the OH(8–3) and O(1S) emissions made with a filter photometer, and with 2 years of Aura MLS (Microwave Limb Sounder) v3.3 temperatures and 4.5 years of TIMED SABER (Thermosphere Ionosphere Mesosphere Energetics and Dynamics Sounding of the Atmosphere using Broadband Emission Radiometry) v2.0 temperatures for the same site. We also consider whether we can recover the actual emission heights from the intercomparison of the ground-based and satellite observations. We find a significant improvement in the correlation between the spectrometer OH and SABER temperatures by interpolating the latter to constant density surfaces determined using a meteor radar.Iain M. Reid, Andrew J. Spargo, Jonathan M. Woithe, Andrew R. Klekociuk, Joel P. Younger and Gulamabas G. Sivje

Comparison of Guidance Modes for the AUV “Slocum Glider ” in Time-Varying Ocean Flows

Abstract — This paper presents possibilities for the reliable guidance of an AUV “Slocum Glider ” in a time-varying oceans flows. The presented guidance modes consider the restricted information during a real mission about the actual position and ocean current conditions as well as the available control modes of a glider. A faster-than-real-time, full software stack simulator for the Slocum glider will be described in order to test the developed guidance modes under real mission conditions. Keywords—component; AUV “Slocum Glider”; Path Planning; Glider Simulator; Time-Varying Ocean Flows; Dead Reckonin

Imaging of atmospheric gravity waves in the stratosphere and upper mesosphere using satellite and ground-based observations over Australia during the TWPICE campaign

Extent: 20p.During the Tropical Warm Pool International Cloud Experiment (TWPICE) an intense tropical low was situated between Darwin and Alice Springs, Australia. Observations made on 31 January 2006 by the Atmospheric Infrared Sounder instrument on the NASA Aqua satellite imaged the presence of atmospheric gravity waves (AGWs), at approximately 40 km altitude, with horizontal wavelengths between 200 and 400 km that were originating from the region of the storm. Airglow images obtained from Alice Springs (about 600 km from the center of the low) showed the presence of similar waves with observed periods of 1 to 2 h. The images also revealed the presence of 30- to 45-km-horizontal-wavelength AGWs with shorter observed periods of near 15 to 25 min. Ray tracing calculations show that (1) some of the long wavelength waves traveled on rays, without ducting, to the altitudes where the observations were obtained, and (2) shorter-period waves rapidly reached 85 km altitude at a horizontal distance close to the storm, thus occurring over Alice Springs only if they were trapped or ducted. The mesospheric inversion layer seen in the measured temperature data almost forms such a trapped region. The winds therefore critically control the formation of the trapped region. Wind profiles deduced from the available data show the plausibility for the formation of such a trapped region. Variations in the wind, however, would make ideal trapped region conditions short-lived, and this may account for the sporadic nature of the short-period wave observations.J. H. Hecht, M. J. Alexander, R. L. Walterscheid, L. J. Gelinas, R. A. Vincent, A. D. MacKinnon, J. M. Woithe, P. T. May, W. R. Skinner, M. G. Mlynczak, and J. M. Russell II

BISCOITOS ADICIONADOS DE FARINHA DE CASCA DE COCO, SEM LACTOSE E ENRIQUECIDO COM VITAMINA D

No processamento dos alimentos ocorre um grande desperdício das cascas, sementes e folhas de vegetais. A utilização destas partes do produto geram menos desperdício e mais empregos quando beneficiadas. Entre eles, destaca-se a casca do coco, rica em fibras, sais minerais, com efeito anti-inflamatório, que é descartada pelas indústrias alimentícias. Deve-se salientar que 80 a 85% do peso bruto do coco é considerado resíduo orgânico. A vitamina D regula a quantidade de cálcio e fósforo no organismo, já o licor de banana contém a mesma quantia de vitamina C equivalente a maçã, além de razoáveis quantidades de vitamina A, B1, B2, pequenas quantidades de vitaminas D e E, e menor porcentagem de potássio, fósforo e cálcio do que uma maçã ou laranja. Sendo assim, o objetivo deste trabalho foi desenvolver um biscoito utilizando farinha de casca de coco, vitamina D e licor de banana, bem como realizar a análise sensorial e microbiológica dos produtos desenvolvidos. Devido a composição descrita acima, tem-se como público alvo mulheres, idosos, atletas e intolerantes à lactose. Desta forma, elaborou-se duas formulações. Sendo uma com o subproduto (farinha de casca de coco) e a outra constituída de uma formulação controle, sem a adição da farinha de casca de coco. Ambas formulações continham vitamina D e licor de banana. A vida de prateleira foi estimada em 56 dias, agregando valor ao produto no que tange o seu consumo diário. Vislumbrando-se a aceitação pelo consumidor, realizou-se um painel sensorial, utilizando-se o Teste de Comparação Pareada Bilateral e uma análise microbiológica de contagem de bolores e leveduras. Através do teste sensorial obteve-se como resultado a ausência da preferência entre um biscoito específico, de tal forma que o subproduto adicionado não gerou interferência na escolha dos julgadores. Os resultados das análises microbiológicas mostraram que houve crescimento de bolores e leveduras, sendo que pode ser considerado baixo o valor de contaminação (5x10¹ UFC/g estimado e 5x10² UFC/g estimado), o que indicou qualidade microbiológica na matéria prima, no processamento e sem risco ao consumidor. No geral é um produto adequado para consumo e traz enriquecimento na dieta alimentar

Observations of the phase-locked 2 day wave over the Australian sector using medium-frequency radar and airglow data

Extent: 22p.The quasi 2 day wave, with a nominal mean period just above 50 h, is a significant feature of the 80–100 km altitude region in both hemispheres. It becomes particularly prominent in the Southern Hemisphere summer at midlatitudes where, a short time after summer solstice, its amplitude rapidly increases and its mean period is found to be approximately 48 h, producing an oscillation phase locked in local time. This lasts for a few weeks. Presented here are observations of the meridional winds and airglow over two sites in Australia, for 4 years during the austral summers of 2003–2006. We show that during those times when the large-amplitude phase-locked 2 day wave (PL-TDW) is present the diurnal tide greatly decreases. This is consistent with the Walterscheid and Vincent (1996) model in which the PL-TDW derives its energy from a parametric excitation by the diurnal tide. These data also show that the diurnal tide is more suppressed and the PL-TDW amplitude is larger in odd-numbered years, suggesting a biannual effect. The airglow data indicated that, for the PL-TDW, the winds and temperature are nearly out of phase. When the PL-TDW is present airglow amplitudes can become quite large, a result dependent on the local time of the PL-TDW maximum. The airglow intensity response was, in general, much larger than what would be expected from the airglow temperature response, suggesting that the PL-TDW is causing a significant composition change possibly due to minor constituent transport.J. H. Hecht, R. L. Walterscheid, L. J. Gelinas, R. A. Vincent, I. M. Reid, and J. M. Woith