The Onset of Chaos in Pulsating Variable Stars

Random changes in pulsation period occur in cool pulsating Mira variables, Type A, B, and C semiregular variables, RV Tauri variables, and in most classical Cepheids. The physical processes responsible for such fluctuations are uncertain, but presumably originate in temporal modifications of the envelope convection in such stars. Such fluctuations are seemingly random over a few pulsation cycles of the stars, but are dominated by the regularity of the primary pulsation over the long term. The magnitude of stochasticity in pulsating stars appears to be linked directly to their dimensions, although not in simple fashion. It is relatively larger in M supergiants, for example, than in short-period Cepheids, but is common enough that it can be detected in visual observations for many types of pulsating stars. Although chaos was discovered in such stars 80 years ago, detection of its general presence in the group has only been possible in recent studies.Comment: To appear in the proceedings of the Odessa Variable Stars 2010 Conference (see http://uavso.org.ua/?page=vs2010&lang=en), edited by I. Andronov and V. Kovtyuk

The common ground for sustainable urbanism in the case of Doha

Doha, like most of the Gulf States' cities, has evolved dramatically to the global city model due to the oil economy, thereby experiencing a massive urban evolution and creating mega urban development projects that are inattentive to sustainability. Creating mega projects reflects different urban trends to fulfill the sustainable agenda. Sustainability, as a definition, is still vague, but the term survived the test of time. A large number of studies have conducted research on cities and how to change the development path to a more sustainable one. But sustainable urbanism cannot be reached if there is no standard definition of sustainability between different key players involved in the urbanization process. Between strategy and implementation, there is an apparent gap because there is no standard definition for sustainable urbanism. Recently, in Doha, some urban development has taken place, which claims to be viable. This study aims to evaluate these models through critical observation and analysis of the urban form and characteristic of these developments. It questions the level of applicability of such models to the context of Doha, and its urban revitalization process. First, the study documents the milestones of the sustainable urbanism strategy of Doha. Second, it analyzes key projects and how sustainable urbanism was implemented. In this study, four projects are used to compare the sustainable urbanism definition about strategy and implementation process. The aim of this paper is to highlight a common definition of sustainable urbanism for Doha, highlighting the challenges of policy and implementation. Finally, it compares the policy with the application to a more standard definition of sustainable urbanism appropriate to the Doha context. The paper argues that creating a common urban sustainability definition will narrow the gap between implementation and strategy. It concludes with recommendation guidelines to repost sustainable urbanism in the case of Doha.qscienc

Upper Paleocene-Lower Eocene biostratigraphy of Darb Gaga, Southeastern Kharga Oasis Western Desert, Egypt

© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of African Earth Sciences 118 (2016): 12-23, doi:10.1016/j.jafrearsci.2016.02.016.Paleontological studies on the Upper Paleocene-Lower Eocene succession at Darb Gaga, southeastern Kharga Oasis, Western Desert, Egypt document the changes associated with the Paleocene-Eocene Thermal Maximum (PETM), such as 1) a radical alteration of the relative and absolute abundance of planktonic foraminifera; 2) a massive occurrence of the excursion planktonic foraminiferal taxa; 3) a widespread deposition of calcarenite yielding atypical (extremely high) faunal abundance associated with the younger phase of warming; and 4) a concentration of coprolites associated with the middle phase of warming. We also document the Lowest Occurrence (LO) of dimorphic larger benthic and excursion foraminifera during the earlier phase of warming at Darb Gaga, as recorded in Bed 1 of the Dababiya Quarry Member. The absence of these faunas in Bed 1 at Dababiya (the GSSP for the P/E Boundary) is likely to be due to both intense deficiency in dissolved oxygen and massive carbonate dissolution. Only remains (fish remains) of faunas that can tolerate the toxicity produced by low oxygen conditions are found in the stratigraphic record of this (oldest) phase at Dababiya. The Dababiya Quarry Member (DQM) at Darb Gaga reflects the unfolding of the sedimentary and biotic changes associated with the PETM global warming at, and following, the Paleocene/Eocene boundary on the southern Tethys platform. The changes began with a rapid increase in bottom and “intermediate” water temperature. The temperature increase was accompanied by removal of oxygen during the early and middle stages of warming. This led to the absence of both subbotinids and calcareous benthic foraminifera in the early and second coprolite-bearing phases (Beds 2 and 3 of the DQM). Dissolution seems to have no role during these stages as shown by the unusual abundance and good preservation of the warm-tolerant Ac. sibaiyaensis. This species reaches its maximum abundance in Bed 2 where it exhibits a broad range of size (63-250 μm) and shape that probably reflect optimal growth under the warmest water conditions. Thus, we infer that temperature and dissolved oxygen content of the sea-water were the main factors controlling the distribution pattern(s) of the microplankton and microbenthos during the PETM.2017-02-2

Palynological analysis of the holocene section of a new core from Tswaing Crater, South Africa

Palynological data from a new core from Tswaing Crater Lake within the savanna biome of South Africa contributes to a better understanding of vegetation and climate dynamics during the Holocene. A 650cm sediment core section TSW1, with 65 samples and fourteen AMS 14C dates, covers a time period between ca 10000-2000 cal yrs BP. No pollen data are available from the lower part of the profile (600-800cm) due to palynomorph destruction, but a single sample with a low number of pollen grains gives a glimpse into a presumably very dry time period at ca11300 cal yrs BP. A warm and dry early Holocene (ca 9000-7500 cal yrs BP) is evidenced by high pollen percentages of Asteraceae, Tarchonanthus and Dichrostachys. The mid Holocene phase from ca 7500-4000 cal yrs BP is characterised by an increase of Burkea, Combretaceae and Podocarpus as well as aquatics and swamp plant pollen. This suggests warm sub-humid conditions and local moisture during this time interval. A short-term dry period occurred ca 4000 -3600 cal yrs BP characterized by a significant decline of most tree pollen including Podocarpus, whereas Poaceae pollen increased slightly. From ca 3600 - 2000 cal yrs BP tree pollen percentages gradually increased and the presence of Spirostachys pollen suggests a return to warm sub-humid conditions. The upper part of the profile above a depth of 150cm shows disturbances due to salt mining and was therefore not sampled. The palaeoclimatic interpretation of the pollen fluctuations was supported by PCA (Principal Components Analysis). From around ca 1800 cal yrs BP additional samples were studied in this project in comparison to the previous study of Scott to improve the resolution. The climatic investigation from the Tswaing pollen record of the current study supports the climatic interpretations which were inferred from the biomarker analysis by Kristen et al., 2009. A regional comparison between the current Tswaing pollen profile and pollen records from Wonderkrater and Lake Eteza was done in the frame of the current study. The general palaeoclimatic changes recorded from Tswaing pollen sequence are consistent with the pollen evidence inferred from Wonderkrater which can attributed to regional changes in eastern South Africa. These trends differ from those in lake Eteza, especially during the early Holocene, which might be explained as a consequence of the generally more humid climate in the coastal plain of KwaZulu-Natal

Stochastic Processes in Yellow and Red Pulsating Variables

Random changes in pulsation period are well established in cool pulsating stars, in particular the red giant variables: Miras, semi-regulars of types A and B, and RV Tau variables. Such effects are also observed in a handful of Cepheids, the SX Phe variable XX Cyg, and, most recently, the red supergiant variable, BC Cyg, a type C semi-regular. The nature of such fluctuations is seemingly random over a few pulsation cycles of the stars, yet the regularity of the primary pulsation mechanism dominates over the long term. The degree of stochasticity is linked to the dimensions of the stars, the randomness parameter 'e' appearing to correlate closely with mean stellar radius through the period 'P', with an average value of e/P = 0.0136+-0.0005. The physical processes responsible for such fluctuations are uncertain, but presumably originate in temporal modifications of envelope convection in such stars.Comment: Poster given at the "Stellar Pulsation: Challenges for Theory and Observation" conference in Santa Fe, New Mexico (2009

How to improve sustainability inside higher educational institutions: A strategic plan for Qatar University

Designing and implementing sustainable solutions means to take responsibility for the welfare of future generations as well as for our environment and planet. Positive approach towards sustainability should be an essential part of the ethical base of our lifestyle and actions. Moreover, sustainable development is a vital aspect of the educational agenda at all levels. Universities and higher education institutions have a great responsibility in promoting sustainable development, not only through the educational programs they offer, but also through the involvement of students and staff in the sustainability issues, by encouraging interaction with them. Universities should implement sustainable solutions and adopt sustainability in their future plans, and ultimatel they should have an impact on the society and lead the way by offering knowledge, solutions through influential individuals. Indeed, most universities understood the responsibility and the extreme importance of shifting to more sustainable policies and plans, and most of them have started investing in green buildings future that includes, green building, greener practices and green products along with less environmental impact, and ways of engaging its faculty and students.In the last few years the need for sustainable solutions for universities has rapidly increased. Many efforts have been dedicated to this issue, and now many universities have realized and implemented different plans that suit their needs and nature. These plans have achieved sustainable transport, energy, procurement, food services and many other issues.In this research, a review of other universities' sustainability plans is used to derive a strategy aimed to improve sustainability inside Qatar University by introducing new solutions, evaluating current implemented methods, and assessing or promoting the use of services already in place. The sustainability plan is designed to deliver a strategic blue print to meet the future development at Qatar University campus via converting its operations, education and research activities towards more sustainable practices. The proposed plan is designed based on the collaboration of three university bodies (students, academics and administrative staff), and it is outlined in three main branches: operational; planning and administration; education and research. The plan identifies and maps the required action to build the initiative to achieve sustainable goals at QU, and proposes new ways to face the challenge of sustainability in academic campuses. The plan also helps in offering a benchmark model for peer higher education organizations inside Qatar, and for other institutions outside Qatar with similar conditions.qscienc

Photometric and Spectroscopic Analysis of the SX Phe Star BL Cam

In the present paper, we report the photometric and spectroscopic observations obtained by the 1.88 m telescope at the Kottamia astronomical observatory of the pulsating star BL Cam. Fourier analysis of the light curves reveals that the fundamental mode has two harmonics. The O-C method is used to establish the period changes. So far, the analysis has been very successful in mapping the pulsation amplitude of the star across the instability strip. By using the formalism of Eddington and Plakidis (1929), we found significant results and strong indications of the evolutionary period change. A total of 55 new maximum light timings are reported. New values of (1/P) dP/dt are estimated using the O-C diagram based on all newly obtained times of maximum light combined with those taken from the literature, assuming the periods are decreasing and changing smoothly. To compute the effective temperature and surface gravity of the star, we performed model atmosphere analysis on its spectra. The physical parameters of the star are calculated and compared with the evolutionary models

The Dababiya corehole, Upper Nile Valley, Egypt : preliminary results

Author Posting. © Austrian Geological Society, 2012. This article is posted here by permission of Austrian Geological Society for personal use, not for redistribution. The definitive version was published in Austrian Journal of Earth Sciences 105, no. 1 (2012): 161-168.The Dababiya corehole was drilled in the Dababiya Quarry (Upper Nile Valley, Egypt), adjacent to the GSSP for the Paleocene/ Eocene boundary, to a total depth of 140 m and bottomed in the lower Maastrichtian Globotruncana aegyptiaca Zone of the Dakhla Shale Formation. Preliminary integrated studies on calcareous plankton (foraminifera, nannoplankton), benthic foraminifera, dinoflagellates, ammonites, geochemistry, clay mineralogy and geophysical logging indicate that: 1) The K/P boundary lies between 80.4 and 80.2 m, the Danian/Selandian boundary between ~ 41 and 43 m, the Selandian/Thanetian boundary at ~ 30 m (within the mid-part of the Tarawan Chalk) and the Paleocene/Eocene boundary at 11.75 m (base [planktonic foraminifera] Zone E1 and [calcareous nannoplankton] Zone NP9b); 2) the Dababiya Quarry Member (=Paleocene/Eocene Thermal Maximum interval) extends from 11.75 to 9.5 m, which is ~1 m less than in the adjacent GSSP outcrop.; 3) the Late Cretaceous (Maastrichtian) depositional environment was nearshore, tropical-sub tropical and nutrient rich; the latest Maastrichtian somewhat more restricted (coastal); and the early Danian cooler, low(er) salinity with increasing warmth and depth of water (i.e., more open water); 4) the Paleocene is further characterized by outer shelf (~ 200 m), warm water environments as supported by foraminifera P/B ratios > 85% (~79-28 m), whereas benthic foraminifera dominate (>70%) from ~27-12 m (Tarawan Chalk and Hanadi Member) due, perhaps, in part to increased dissolution (as observed in nearby outcrop samples over this interval); 5) during the PETM, enhanced hydrodynamic conditions are inferred to have occurred on the sea-floor with increased river discharge (in agreement with sedimentologic evidence), itself a likely cause for very high enhanced biological productivity on the epicontinental shelf of Egypt; 6) correlation of in situ measured geophysical logs of Natural Gamma Ray (GR), Single-Point Resistance (PR), Self-Potential (SP), magnetic susceptibility (MS), and Resistivity, and Short Normal (SN) and Long Normal (LN) showed correspondence to the lithologic units. The Dababiya Quarry Member, in particular, is characterized by very high Gamma Ray and Resistivity Short Normal values.The Dababiya corehole was made possible by the financial support of the National Geographic Society