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Search Results: 1 - 10 of 461728 matches for " A. Andic "
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Umbral Dynamics in the Near Infrared Continuum
A. Andic,W. Cao,P. R. Goode
Physics , 2011, DOI: 10.1088/0004-637X/736/2/79
Abstract: We detected peaks of oscillatory power at 3 and ~6.5 minutes in the umbra of the central sunspot of the active region NOAA AR 10707 in data obtained in the near infrared (NIR) continuum at 1565.7 nm. The NIR dataset captured umbral dynamics around 50 km below the photospheric level. The umbra does not oscillate as a whole, but rather in distinct parts that are distributed over the umbral surface. The most powerful oscillations, close to a period of ~ 6.5, do not propagate upward. We noted a plethora of large umbral dots that persisted for more than 30 minutes and stayed in the same locations. The peaks of oscillatory power above the detected umbral dots are located at 3 and 5 minutes oscillations, but are very weak in comparison with the oscillations of ~ 6.5 minutes.
Newly Observed Small-Scale Structures in the Quiet Sun and Their Connection to Solar Oscillations
Aleksandra Andic
Physics , 2009,
Abstract: Our observations of the quiet Sun with the NST have yielded unanticipated results on smal-scale solar dynamic. Althought small-scale solar dynamic have been well-studied, the NST is enabling us to probe finer scale dynamic exploiting higher spatial resolution. We discuss NST resutls from data taken 29th July 2009 using an broadband filter centered on TiO 705.7nm spectral line. Data are from the center of the solar disk where we observed quiet Sun. We registered bright-point like structures in most of the intergranular lanes. They vary in behaviour and evolution. Co-registered solar oscillations tend to congregate near certain types of bright-point like structures. The oscillations with maximum power tend to appear only above or near these structures.
Signature of Collision of Magnetic Flux Tubes in the Quiet Solar Photosphere
Aleksandra Andic
Physics , 2010, DOI: 10.1017/S1743921311015638
Abstract: Collision of the magnetic flux tubes in the Quiet Sun was proposed as one of the possible sources for the heating of the solar atmosphere (Furusawa and Sakai, 2000). The solar photosphere was observed using the New Solar Telescope ad Big Bear Solar Observatory. In TiO spectral line at 705.68 nm we approached resolution of 0.1". The horizontal plasma wave was observed spreading from the larger bright point. Shorty after this wave an increase in the oscillatory power appeared at the same location as the observed bright point. This behavior matches some of the results from the simulation of the collision of the two flux tubes with a weak current.
Oscillatory behavior in the quiet Sun observed with the New Solar Telescope
A. ~Andic,P. R. Goode,J. Chae,W. Cao,K. Ahn,V. Yurchyshyn,V. Abramenko
Physics , 2010, DOI: 10.1088/2041-8205/717/2/L79
Abstract: Surface photometry of the quiet Sun has achieved an angular resolution of $0".1$ with the New Solar Telescope at Big Bear Solar Observatory revealing that a disproportionate fraction of the oscillatory events appear above observed bright point-like structures. During the tracking of these structures, we noted that the more powerful oscillatory events are cospatial with them, indicating that observed flux tubes may be the source of many observed oscillatory events.
Migration and Transfer of Knowledge: Refugees from Nazism and Turkish legal Reform
Fuat Andic,Arnold Reisman
Forum Historiae Iuris , 2007,
Abstract: Starting in 1933, Turkey reformed its judicial system as well as its higher education system by giving refugees fleeing the Nazis a safe haven through formal government invitations and employing them in reform its institutions. For them America was out of reach because of restrictive immigration laws and widespread anti-Semitic hiring bias at its universities. Among the invited were several German legal scholars and economists who played a large role to further westernize the new Turkish Republic’s legal code and tax legislation. This paper discusses that epoch, its legacy, and perceptions thereof in Turkey today.
Chromospheric signatures of small-scale flux emergence as observed with NST and Hinode instruments
V. B. Yurchyshyn,P. R. Goode,V. I. Abramenko,J. Chae,W. Cao,A. Andic,K. Ahn
Physics , 2011, DOI: 10.1088/0004-637X/722/2/1970
Abstract: With the ever increasing influx of high resolution images of the solar surface obtained at a multitude of wavelengths, various processes occurring at small spatial scales have become a greater focus of our attention. Complex small-scale magnetic fields have been reported that appear to have enough stored to heat the chromosphere. While significant progress has been made in understanding small-scale phenomena, many specifics remain elusive. We present here a detailed study of a single event of disappearance of a magnetic dipole and associated chromospheric activity. Based on New Solar Telescope H$\alpha$ data and {\it Hinode} photospheric line-of-sight magnetograms and Ca II H images we report the following. 1) Our analysis indicates that even very small dipoles (elements separated by about 0\arcsec.5 or less) may reach the chromosphere and trigger non-negligible chromospheric activity. 2) Careful consideration of the magnetic environment where the new flux is deposited may shed light on the details of magnetic flux removal from the solar surface. We argue that the apparent collision and disappearance of two opposite polarity elements may not necessarily indicate their cancellation (i.e., reconnection, emergence of a "U" tube or submergence of $ \Omega $ loops). In our case, the magnetic dipole disappeared by reconnecting with overlying large-scale inclined plage fields. 3) Bright points seen in off-band H$\alpha$ images are very well-correlated with the Ca II H bright points, which in turn are co-spatial with G-band bright points. We further speculate that, in general, H$\alpha$ bright points are expected be co-spatial with photospheric BPs, however, a direct comparison is needed to refine their relationship.
Remote Oscillatory responses to a solar flare
Aleksandra Andic,R. T. James McAteer
Physics , 2013,
Abstract: The processes governing energy storage and release in the Sun are both related to the solar magnetic field. We demonstrate the existence of a magnetic connection between energy released caused by a flare and increased oscillatory power in the lower solar atmosphere. The oscillatory power in active regions tends to increase in response to explosive events at a different location, but not in the region itself. We carry out timing studies and show that this is probably caused by a large scale magnetic connection between the regions, and not a globally propagating wave. We show that oscillations tend to exist in longer lived wave trains at short periods (P< 200s) at the time of a flare. This may be a mechanism by which flare energy can be redistributed throughout the solar atmosphere.
Substructure of Quiet Sun Bright Points
Aleksandra Andic,Jongchul Chae,Phillip R. Goode
Physics , 2010, DOI: 10.1017/S174392131101550X
Abstract: Since photospheric bright points (BPs) were first observed, there has been a question as to how are they structured. Are they just single flux tubes or a bundle of the flux-tubes? Surface photometry of the quiet Sun (QS) has achieved resolution close to 0.1" with the New Solar Telescope at Big Bear Solar Observatory. This resolution allowed us to detect a richer spectrum of BPs in the QS. The smallest BPs we observed with TiO 705.68 nm were 0.13", and we were able to resolve individual components in some of the BPs clusters and ribbons observed in the QS, showing that they are composed of the individual BPs. Average size of observed BPs was 0.22".
Transcatheter Embolization for the Treatment of Both Vaginal and Lower Intestinal Bleeding Due to Advanced Pelvic Malignancy
Bulent Karaman,Nisa Cem Oren,Cagatay Andic,Bahri Ustunsoz
Eurasian Journal of Medicine , 2010,
Abstract: We report a 31-year-old woman with end-stage cervical carcinoma who suffers both lower intestinal and vaginal bleeding. A selective internal iliac arteriogram demonstrated pseudoaneurysm formation in the vaginal branch of the left internal iliac artery. There was also a fistula between the pseudoaneurysm and the lower intestinal segments. Selective transcatheter coil embolization was performed, and the bleeding was treated successfully. We conclude that the internal iliac artery should be evaluated first in patients with advanced pelvic malignancy when searching for the source of lower gastrointestinal (GI) bleeding. Additionally, transcatheter arterial embolization is a safe and effective treatment technique.
A dosimetric comparison of different treatment plans of palliative spinal bone irradiation: analysis of dose coverage with respect to ICRU 50 report
Fundagul Andic, Sule Baz Cifci, Yasemin Ors, Umar Niang, Ahmet Dirier, Mustafa Adli
Journal of Experimental & Clinical Cancer Research , 2009, DOI: 10.1186/1756-9966-28-2
Abstract: Forty-five simulation CT scans of 39 patients previously treated for thoraco-lumbar spinal bone metastases were used. Three different treatment plans were created: (1) single posterior field plans using the ICRU reference points (ICRUrps); (2) single posterior field plans using the International Bone Metastasis Consensus Working Party reference points (IBMCrps); (3) two opposed anterior-posterior (AP-PA) field plans using the ICRUrps. The intended dose range for planning target volume (PTV) was 90% to 110% of the prescribed dose for AP-PA field plans. Cumulative dose-volume histograms were generated for each plan, and minimum, maximum and mean doses to the PTV, medulla spinalis, esophagus and intestines were analyzed.The mean percentages of minimum, maximum and mean PTV doses ± standard deviation were, respectively, 91 ± 1.3%, 108.8 ± 1.3% and 99.7 ± 1.3% in AP-PA field plans; 77.3 ± 2.6%, 122.2 ± 4.3% and 99.8 ± 2.6% in ICRUrp single field plans; and 83.7 ± 3.3%, 133.9 ± 7.1% and 108.8 ± 3.3% in IBMCrp single field plans. Minimum doses of both single field plans were significantly lower (p < 0.001) while maximum doses were significantly higher (p < 0.001) than AP-PA field plans. Minimum, maximum and mean doses were higher in IBMCrp single field plans than in ICRUrp single field plans (p < 0.001). The mean medulla spinalis doses were lower in AP-PA field plans than single posterior field plans (p < 0.001). Maximum doses for medulla spinalis were higher than 120% of the prescribed dose in 22 of 45 (49%) IBMCrp single field plans. Mean esophagus and intestinal doses were higher (p < 0.001) in AP-PA field plans than single field plans, however, less than 95% of the prescribed dose.In palliative spinal bone irradiation, 2D conventional single posterior field radiotherapy did not accomplish the ICRU Report 50 recommendations for PTV dose distribution, while the AP-PA field plans did achieve the intended dose ranges with a homogenous distribution and reasonable doses to t
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