79 research outputs found
C IV broad absorption line disappearance in a large SDSS QSO sample
No full textContext. Broad absorption lines (BALs) in the spectra of quasi-stellar objects (QSOs) originate from outflowing winds along our line of sight; winds are thought to originate from the inner regions of the QSO accretion disk, close to the central supermassive black hole (SMBH). These winds likely play a role in galaxy evolution and are responsible for aiding the accretion mechanism onto the SMBH. Several works have shown that BAL equivalent widths can change on typical timescales from months to years; such variability is generally attributed to changes in the covering factor (due to rotation and/or changes in the wind structure) and/or in the ionization level of the gas.Context. Broad absorption lines (BALs) in the spectra of quasi-stellar objects (QSOs) originate from outflowing winds along our line of sight; winds are thought to originate from the inner regions of the QSO accretion disk, close to the central supermassive black hole (SMBH). These winds likely play a role in galaxy evolution and are responsible for aiding the accretion mechanism onto the SMBH. Several works have shown that BAL equivalent widths can change on typical timescales from months to years; such variability is generally attributed to changes in the covering factor (due to rotation and/or changes in the wind structure) and/or in the ionization level of the gas. Aims. We investigate BAL variability, focusing on BAL disappearance. Methods. We analyze multi-epoch spectra of more than 1500 QSOs - the largest sample ever used for such a study - observed by different programs from the Sloan Digital Sky Survey-I/II/III (SDSS-I/II/III), and search for disappearing C IV BALs. The spectra cover a rest-frame time baseline ranging from 0.28 to 4.9 yr; the source redshifts range from 1.68 to 4.27. Results. We detect 73 disappearing BALs in the spectra of 67 unique sources. This corresponds to 3.9% of BALs disappearing within 4.9 yr (rest frame), and 5.1% of our BAL QSOs exhibit at least one disappearing BAL within 4.9 yr (rest frame). We estimate the average lifetime of a BAL along our line of sight (approximate to 80-100 yr), which appears consistent with the accretion disk orbital time at distances where winds are thought to originate. We inspect various properties of the disappearing BAL sample and compare them to the corresponding properties of our main sample. We also investigate the existence of a correlation in the variability of multiple troughs in the same spectrum, and find it persistent at large velocity off sets between BAL pairs, suggesting that a mechanism extending on a global scale is necessary to explain the phenomenon. We select a more reliable sample of disappearing BALs on the basis of some criteria adopted in a previous publication, where a subset of our current sample was analyzed, and compare the findings from the two works, obtaining generally consistent results.</p
Author Attribution of Turkish Texts by Feature Mining
No full textAbstractThe aim of this study is to identify the author of an unauthorized document. Ten different feature vectors are obtained from authorship attributes, n-grams and various combinations of these feature vectors that are extracted from documents, which the authors are intended to be identified. Comparative performance of every feature vector is analyzed by applying Naïve Bayes, SVM, k-NN, RF and MLP classification methods. The most successful classifiers are MLP and SVM. In document classification process, it is observed that n-grams give higher accuracy rates than authorship attributes. Nevertheless, using n-gram and authorship attributes together, gives better results than when each is used alone.KeywordsAuthor attribution n-grams Text classification Feature extraction Turkish documents </p
Solar and stellar rotation
No full textWorkshop on Solar and Stellar Physics through Eclipses -- MAR 27-29, 2006 -- Ankara Univ, ORSEM Campus, Side, Antalya, TURKEYThe secular evolution of the stellar rotation through angular momentum loss, driven by the stellar wind, and the consequences of the angular momentum transfers between orbit and spinning components in binary star systems will be reviewed with the special emphasis on the Solar rotation. A large co-rotating distance (Alfven radius) of the magnetically driven wind around single stars will be introduced to explain the large angular momentum loss from close binary star systems
High Resolution Coude Echelle Spectroscopy of IX Per
No full text15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun -- JUL 21-25, 2008 -- St Andrews, SCOTLANDHigh resolution (R=45033) Coude - Echelle spectra of IX Per has been obtained at TUBITAK National Observatory (TUG) of Turkey. IX Per has been known to be a single lined (SBI) spectroscopic binary having chromospheric activity. However, analyzed spectra of IX Per by KOREL disentangling method indicated that the system is a double lined (SB2) spectroscopic binary. Weaker lines from the secondary arc discovered on the decomposed spectra. A preliminary orbit indicates that the mass ratio of the system is 0.64. The light contribution of the secondary is tip to 10% in investigated spectral region. Circular orbit is sufficient to explain radial velocity variations.Royal Astron Soc,Scottish Univ Phys Alliance,European Space Agcy,NASA Astrobiol Ins
Biological aspects of two coexisting indigenous and non-indigenous fish species in the Aegean Sea: Pagellus erythrinus vs. Nemipterus randalli
No full textYapici, Sercan/0000-0003-2288-5084WOS: 000504749700013Nowadays, the Mediterranean is a hotspot of biodiversity, characterized by changes in fish communities due to invasions. These invasions, mainly occurring through the entrance of species through the Suez Canal, a process called Lessepsian migration, has been increasing in the last 40 years. It is reported that, in Turkish seas, where 512 fish species are found, are 75 Lessepsian species. However, knowledge about the impact of Lessepsian species on native species is insufficient. This study aims to determine the bio-ecological characteristics and food interactions of a native Pagellus erythrinus and non-native Nemipterus randalli distributed in the Gokova Bay. In the monthly sampling survey, carried out between January 2016 and December 2016, 1698 N. randalli and 945 P. erythrinus individuals were collected. Length, weight, age, sex distributions and ratios, length-age, weight-age, length-weight relationships, condition factors, stomach contents and reproduction periods were examined to determine the interaction between species. According to results, the life span of P. erythrinus is longer than N. randalli in the Gokova Bay. Nevertheless, N. randalli grows faster than P. erythrinus. Reproduction periods of both two species show similarities. Food competition between species is found to be significantly high. Results of condition factors exhibit that N. randalli shows an increased ability to exploit the available food sources. Pagellus erythrinus displays strategies such as: early maturation, short reproduction period, reproduction in the deeper waters and batch spawning, to compete with N. randalli. With the invasive characteristics of N. randalli established a successful population in the Gokova Bay.Mugla Sitki Kocman University Scientific Research FundMugla Sitki Kocman University [BAP 13/120]This research is based on Ph.D. thesis of the corresponding author and was supported by Mugla Sitki Kocman University Scientific Research Fund (BAP 13/120). The authors would like to thank the anonymous reviewers for their suggestions and comments. Also, corresponding author is grateful to Mr. Rifat Tezel, Dr. Umit Acar, Mr. Murat Celik, Mr. Umut Uyan for their valuable contributions and efforts during the study
Evaluation of new silica‐based humic acid stationary phase for the separation of tocopherols in cold‐pressed oils by normal‐phase high‐performance liquid chromatography
No full textA new humic acid stationary phase was prepared by immobilizing humic acid onto aminopropyl silica via an amide linkage formation and used, for the first time, for the separation and quantification of the tocopherol compounds in cold-pressed oil samples under normalphase high-performance liquid chromatography conditions. Parameters affecting the chromatographic separation such as mobile phase composition and flow rate were optimized. By evaluating the calculations of capacity factor, asymmetry factor, resolution, selectivity factor, and theoretical plate number, the best separation was obtained with isocratic elution of n-hexane and isopropyl alcohol (99:1% v/v) at a flow rate of 1.0 mL/min. The effluent was monitored by a fluorescence detector set at excitation and emission wavelengths 295 and 330 nm, respectively. All compounds were separated in 20 min. The method was validated according to international guidelines and found to be linear in a wide concentration range, also the mean recovery of the compounds ranged from 97.9 to 99.2%, with a CV less than 2.7% in all cases. The results showed that the developed stationary phase is suitable for the separation and quantification of the tocopherol compounds in real oil samples.Selcuk University Coordination of Scientific ResearchSelcuk University [SU-BAP 14401096]The author would like to thank Selcuk University Coordination of Scientific Research for supporting research with SU-BAP 14401096 project number
Orbits of six late-type active-chromosphere binaries
No full textWe present spectroscopic orbits for the active stars HD 82159 (GS Leo), HD 89959, BD +39A degrees 2587 (a visual companion to HD 112733), HD 138157 (OX Ser), HD 143705, and HD 160934. This paper is a sequel to one published in this journal in 2006, with similar avowed intention, by Galvez et al. They showed only graphs, and gave no data, and no orbital elements apart from the periods (only two of which were correct) and in some cases the eccentricities. Here we provide full information and reliable orbital elements for all the stars apart from HD 160934, which has not completed a cycle since it was first observed for radial velocity.We present spectroscopic orbits for the active stars HD 82159 (GS Leo), HD 89959, BD +39° 2587 (a visual companion to HD 112733), HD 138157 (OX Ser), HD 143705, and HD 160934. This paper is a sequel to one published in this journal in 2006, with similar avowed intention, by Gálvez et al. They showed only graphs, and gave no data, and no orbital elements apart from the periods (only two of which were correct) and in some cases the eccentricities. Here we provide full information and reliable orbital elements for all the stars apart from HD 160934, which has not completed a cycle since it was first observed for radial velocity.</p
Emergence and Variability of Broad Absorption Line Quasar Outflows
No full textWe isolate a set of quasars that exhibit emergent C IV broad absorption lines (BALs) in their spectra by comparing spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 and the SDSS/BOSS Data Releases 9 and 10. After visually defining a set of emergent BALs, follow-up observations were obtained with the Gemini Observatory for 105 quasars. We find an emergence rate consistent with the previously reported disappearance rate of BAL quasars given the relative numbers of non-BAL and BAL quasars in the SDSS. We find that candidate newly emerged BALs are preferentially drawn from among BALs with smaller balnicity indices, shallower depths, larger velocities, and smaller widths. Within two rest-frame years (average) after a BAL has emerged, we find it equally likely to continue increasing in equivalent width in an observation 6 months later (average) as it is to start decreasing. From the time separations between our observations, we conclude that the coherence timescale of BALs is less than 100 rest-frame days. We observe coordinated variability among pairs of troughs in the same quasar, likely due to clouds at different velocities responding to the same changes in ionizing flux, and the coordination is stronger if the velocity separation between the two troughs is smaller. We speculate that the latter effect may be due to clouds having on average lower densities at higher velocities owing to mass conservation in an accelerating flow, causing the absorbing gas in those clouds to respond on different timescales to the same ionizing flux variations.We isolate a set of quasars that exhibit emergent C IV broad absorption lines (BALs) in their spectra by comparing spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 and the SDSS/BOSS Data Releases 9 and 10. After visually defining a set of emergent BALs, follow-up observations were obtained with the Gemini Observatory for 105 quasars. We find an emergence rate consistent with the previously reported disappearance rate of BAL quasars given the relative numbers of non-BAL and BAL quasars in the SDSS. We find that candidate newly emerged BALs are preferentially drawn from among BALs with smaller balnicity indices, shallower depths, larger velocities, and smaller widths. Within two rest-frame years (average) after a BAL has emerged, we find it equally likely to continue increasing in equivalent width in an observation 6 months later (average) as it is to start decreasing. From the time separations between our observations, we conclude that the coherence timescale of BALs is less than 100 rest-frame days. We observe coordinated variability among pairs of troughs in the same quasar, likely due to clouds at different velocities responding to the same changes in ionizing flux, and the coordination is stronger if the velocity separation between the two troughs is smaller. We speculate that the latter effect may be due to clouds having on average lower densities at higher velocities owing to mass conservation in an accelerating flow, causing the absorbing gas in those clouds to respond on different timescales to the same ionizing flux variations.</p
The mystical symbolism of İbn al-Arabi
No full textİbn Arabû'de Mistik Sembolizm Endülüslü ünlü sufi düşünür Muhyiddûn İbn Arabû'nin (1165-1240) eserleri ve fikirleri kendi çağından günümüze kadar İslamû düşüncenin merkezinde kalmıştır. Onun sevenleri ve tâbileri onun fikirlerini anlamak, açıklamak ve yaymak için uğraşırken, karşıtları fikirlerini çürütmek ve İslam-dışı olduğunu ispatlamaya çalışmışlardır. Yine onun taraftarları ona `Şeyh-i Ekber' (En Büyük Şeyh) unvanını verirken düşmanları `Şeyh-i Ekfer' (En Büyük Kâfir) yaftasını vurmuşlardır. Şeyh'in şahsiyetini ve fikirlerini algılamak ve fikirlerini anlamak yönünden sevenleri ve düşmanları arasındaki bu büyük farklılık Şeyh'in öğretisini ifade biçimine, yani yazım stratejisine râcidir. Çalışmamız giriş, üç bölüm ve sonuçtan oluşmaktadır. Girişte, sonraki bölümlerde sıkça kullanacağımız temel terimleri ele almaya çalıştık. `Mistisizm' sözcüğünün literal ve terminolojik anlamı, tarihsel gelişimi, mistik tecrübenin ifadesi sorunu ve mistisizm-tasavvuf ilişkisi üzerinde durmaya çalıştık. Daha sonra `sembol' terimini ve sembolle ilişkili olan işaret, metafor ve alegori terimlerini ele almaya çalıştık. İbn Arabû'nin mistik şahsiyetinin belirginleşmesi için onun birkaç tasavvufû tecrübesinden bahsettik. Bu tecrübelerin, eserlerinde kullandığı dil ve üslup üzerindeki etkisini göstermeye gayret ettik. İbn Arabû'nin `işaret ilmi' olarak isimlendirdiği fenomenle sembolizm arasındaki ilişkiyi göstermeye çalıştık. Son olarak İbn Arabû'nin felsefesinden ana hatlarıyla bahsettik. Birinci bölümde `ayna sembolizmi'ni incelemeye çalıştık. İbn Arabû'ye gelinceye kadar aynanın dinû ve mistik geleneklerdeki kullanım seyrinden bahsettik. Daha sonra İbn Arabû'nin yaratma, Tanrı-âlem ilişkisi, mümkünlerin statüsü ve insân-ı kâmil gibi ayna sembolüne dayanarak anlattığı konuları inceledik. kinci bölümde `harf sembolizm'ini incelenmeye, harflerin dinû ve mistik geleneklerde taşıdığı anlamlardan bahsetmeye çalıştık. Sonra İbn Arabû'nin, harflerin ve kelimelerin oluşumu ile varlıkların oluşumu arasında kurduğu ilişkiyi incelemeye çalıştık. Son olarak varoluşsal mertebelerle harfler arasında kurulan benzerlik üzerinde durmaya çalıştık. Üçüncü bölümde `ışık sembolizmi'ni tahlil etmeye, ışığın felsefû ve tasavvufû gelenekteki kullanımını ele almaya çalıştık. Sonra İbn Arabû'nin ışıkla varoluş arasında kurduğu ilişki üzerinde durduk. Işık sembolizminin Tanrı-âlem ilişkisi, sudûr nazariyesi, mümkünlerin statüsü ve psikoloji konularındaki kullanımlarını incelemeye çalıştık. Sonuç bölümünde, İbn Arabû'nin düşüncesi ile dili arasındaki ilişkiye dair genel bir değerlendirme yaptık.The Mystical Symbolism of Ibn al-`ArabÄ« The works and ideas of the celebrated Andalusian Sufi-thinker MuhyiddÄ«n Ibn al- `ArabÄ« (1165-1240) have remained at the heart of Islamic intellectuality from his own age up to the modern times. As his lovers and followers have endeavored to understand, explain as well as disseminate his ideas, his detractors have tried to refute and ?de-Islamize? his views; whereas his proponents called him ?the Greatest Sheikh? or ?Doctor Maximus?, his opponents labeled him ?the Greatest Nonbeliever.? This huge discrepancy as to the perception of the Sheikh?s personality and the understanding and explanation of his ideas on the part of his lovers and detractors goes largely back to the way the Sheikh expressed his doctrine, i.e., to his writing strategy. This study consists of an introduction, three chapters, and a conclusion. In the introduction, I tried to treat the terms which I will make a frequent use in the following chapters. I addressed the literal and terminological senses of the word ?mysticism?, its rise and development, the problem of the ineffability of mystical experience, and finally the relationship between mysticism and Sufism. Afterwards, I discussed the term ?symbol? and such related terms as sign, metaphor, and allegory. To further clarify Ibn al-`ArabÄ«?s mystical personality, I spoke of some of his mystical experiences. Then, I attempted to show the impact such Sufi experiences had on his language. I also tried to explain the relationship between what the author calls ?`ilm al-ishÄ rat, (the science of signs or semiotics). Lastly, I outlined Ibn al-`ArabÄ«?s teaching of Oneness of Being. In first chapter, I focused on the ?mirror symbolism.? I delineated the usage of the mirror symbolism in religious and mystical heritage preceding Ibn al-`ArabÄ«?s age. Then, I examined the topics, which the author explained relying on this symbol, such as the creation of the cosmos, the relationship between God and the cosmos, the status of possible things, and the Perfect Man. In second chapter, I examined the ?letter symbolism.? I discussed the meanings attributed to the letters in different religious and mystical traditions. Afterwards, I tried to address the relationship that the author establishes between the formation of words and that of creatures. Lastly, I treated the comparison which the Sheikh makes between the levels of being and letters from the perspective of the latter?s places of articulation. In third chapter, I tried to analyze the ?light symbolism.? I investigated the use of light in philosophical and Sufi literature. I also concentrated on the relationship established by the author between the Being and light. Furthermore, I examined a number of contexts, in which the author resorted to the light symbol, such as the God- cosmos relationship, the theory of emanation, the existential status of possible things, and the reality of soul. In conclusion, I tried to make a general assessment of the strong relationship between the thought and language of Ibn al-`Arabi
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