O Aksu

Publications (7)12.99 Total impact

• Source

  Available from: usyd.edu.au

  Article: Light curve solution and orbital period analysis of the contact binary V842 Herculis

  S. O. Selam, B. Albayrak, H. V. Şenavci, O. Aksu
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  ABSTRACT: New photoelectric BV light curves were obtained for the neglected eclipsing binary V842 Her at the TÜBİTAK National Observatory (TUG) and studied for the first time in detail to determine the orbital parameters and geometry of the system. The solutions obtained simultaneously for the new light curves and the radial velocity curves in the literature by using the Wilson-Devinney code reveal a typical W-type contact system. The light curves exhibit the so-called O'Connell effect which the level of the primary maxima being higher than that of the secondary ones in both pass-bands. The O'Connell effect in the light curves is explained in terms of a dark-spot located on the more massive component which makes the more massive larger component slightly cooler than the less massive smaller one. The O – C diagram constructed for all available times of minima of V842 Her exhibits a cyclic character superimposed on a quadratic variation. The quadratic character yields a orbital period increase with a rate of dP /dt = 7.76 × 10–7 days yr–1 which can be attributed to the mass exchange/loss mechanism in the system. By assuming the presence of a gravitationally bound third body in the system, the analysis of the cyclic nature in the O – C diagram revealed a third body with mass of 0.4M⊙ orbiting around the eclipsing pair. The possibility of magnetic activity cycle effect as a cause for the observed cyclic variation in the O – C diagram was also discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
  Astronomische Nachrichten 09/2005; 326(8):746 - 753. · 1.01 Impact Factor
• Source

  Available from: belsurg.org

  Article: Giant ancient schwannoma of the posterior mediastinum cytologically misdiagnosed as a malignant tumour. A case report.

  M Kara, M Ozkan, S Dizbay Sak, O Aksu, S Kavukçu
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  ABSTRACT: We report a case of a 45-year old woman who was found to have a giant mediastinal tumour with radiological degenerative changes. She underwent thoracotomy to remove the mass, which was eventually diagnosed histologically as an ancient schwannoma, whereas cytological interpretation of the accompanying pleural fluid was malignant. Ancient schwannoma is a rare variant of schwannoma, histologically showing atypical features that may result in erroneous diagnosis of a malignant tumour. Clinical and radiological findings are important aids for further consideration of surgical removal of these potentially resectable tumours.
  Acta chirurgica Belgica 01/2003; 102(6):464-6. · 0.43 Impact Factor
• Article: Cytologic diagnosis and subtyping of rhabdomyosarcoma.

  S Atahan, O Aksu, C Ekinci
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  ABSTRACT: We reviewed the cytological findings of 38 cases of rhabdomyosarcoma (RMS) with histological confirmation performed during a period of 15 years and proposed a morphological subtyping based on the most prominent cytologic features. Seventeen of these cases were alveolar, 14 cases embryonal, and seven botryoid subtypes. From these cases, a total of 43 samples, of which 37 were fine needle aspiration (FNA) biopsies and six were touch imprints, were evaluated. Detailed cellular features were identified which enabled differentiation into histological subtypes. In the alveolar RMSs, most tumour cells were small and lymphocyte-like, having finely granular chromatin. The finding of cells with more abundant cytoplasm, eccentrically located nuclei and bi/multinucleated tumour cells in a background of mucosubstance helped in the differential diagnosis. Two cell types, including large, tadpole or ribbon-shaped tumour cells and small, round cells with scant cytoplasm, were seen in embryonal RMSs. In botryoid RMSs, a cell type with tightly grouped nuclei within elongated cytoplasm similar to a myotubular structure was observed in addition to the two cell types of embryonal RMSs. We conclude that with experience it will be possible to subtype these tumours by cytologic examination alone.
  Cytopathology 01/1999; 9(6):389-97. · 1.59 Impact Factor
• Article: A case of Lenz microphthalmia syndrome.

  F F Ozkinay, C Ozkinay, H Yüksel, A Yenigun, G Sapmaz, O Aksu
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  ABSTRACT: Lenz microphthalmia syndrome was first described by Lenz et al in 1955. The cardinal features of the syndrome are microphthalmia or anophthalmos, narrow shoulders, other skeletal anomalies, and dental and urogenital malformations. Here we present a case of Lenz microphthalmia syndrome who shows the typical characteristics and, additionally, dysgenesis of the corpus callosum associated with dilatation of the lateral ventricles. The patient, a 13 year old male, was referred to our hospital by a dental hospital for genetic counselling. On physical examination, height, weight, and head circumference were below the 3rd centile and he had brachymicrocephaly, a preauricular tag, microphthalmia, missing teeth, narrow shoulders, long, proximally placed thumbs, hypospadias, cryptorchidism, and a normal IQ. Ophthalmological examination showed microcornea, sclerocornea, absence of the pupil, no vision in the left eye and decreased vision and a small pupil in the right eye in addition to his bilateral microphthalmia. Cranial MRI showed dilatation of the lateral ventricles and dysgenesis of the corpus callosum.
  Journal of Medical Genetics 08/1997; 34(7):604-6. · 6.36 Impact Factor
• Article: Primary mediastinal liposarcoma. A report of a case and review of the literature.

  R Doğan, K Ayrancioğlu, O Aksu
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  ABSTRACT: A case of primary liposarcoma of the mediastinum with a review of the literature is presented. Liposarcomas may attain a large mass and exhibit various kinds of clinical symptoms according to their localisation. Histological typing is very important in determining the type and extent of therapy. Surgical excision of the tumour is the therapy of choice in all cases. Radiotherapy may be of value for the palliation of unresectable cases.
  European Journal of Cardio-Thoracic Surgery 02/1989; 3(4):367-70. · 2.55 Impact Factor
• Article: The effect of montelukast on eosinophil apoptosis: induced sputum findings of patients with mild persistent asthma.

  O Abadoglu, D Mungan, O Aksu, S Erekul, Z Misirligil
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  ABSTRACT: Apoptosis may be important in limiting airway eosinophilia. Treatment with leukotriene antagonists decreases the number of eosinophils in both peripheral blood and sputum. To assess the effect of montelukast on eosinophil apoptosis in a group of patients with mild persistent asthma (MPA) and to compare this effect with the apoptotic effect of fluticasone propionate (FP). Randomly selected patients with MPA (n = 22) who had not taken anti-inflammatory therapy within the preceding 12 months were included in the study. The sputum induction procedure was performed and the patients were divided into two groups: group 1 (n = 10) received FP 250 microg/day and group 2 (n = 22) received montelukast 10 mg/day orally for 4 weeks. Sputum induction was repeated after the treatment period. The resulting cytospin slides were stained by Wright's stain and morphologic changes in apoptotic eosinophils were assessed by the use of light microscopy by two blinded expert pathologists. Serum soluble Fas ligand (sFasL) concentrations were measured by an ELISA method at baseline and after treatment in both groups, as well as in a group of healthy subjects. In within-group comparisons, the apoptotic ratio (AR) increased at the end of the study period in group 1 (p = 0.05). In the group treated with FP the ratio of sputum eosinophils significantly decreased (p = 0.02), and the AR significantly increased (p < 0.005). No differences were found in the two study groups in serum sFasL levels at the end of the treatment period compared with baseline values (p > 0.05). Our findings demonstrate that 4 weeks' treatment with a CysLT receptor antagonist (montelukast) resulted in an increase in eosinophil apoptosis comparable to that produced by FP, suggesting that induction of apoptosis may be a potential mechanism for the mode of action of CysLT receptor antagonists in asthma.
  Allergologia et Immunopathologia 33(2):105-11. · 1.04 Impact Factor
• Article: The Blazhko effect of RR Lyrae in 2003-2004

  K. Kolenberg, H. A. Smith, K. D. Gazeas, A. Elmaslı, M. Breger, E. Guggenberger, P. Van Cauteren, P. Lampens, P. Reegen, P. G. Niarchos, B. Albayrak, S. O. Selam, İ. Özavcı, O. Aksu
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  ABSTRACT: Aims.Extensive photometry of RR Lyr was obtained over a 421-day interval in 2003–2004, covering more than 10 Blazhko cycles in a multisite campaign. The length and density of this data set allow for a detailed analysis.Methods.We used Fourier techniques to study RR Lyr's behavior over the pulsation and the Blazhko cycle. We propose a two-frequency model for decomposing the frequency spectrum.Results.The light variations were fitted with the main radial frequency, its harmonics up to 11${\rm th}$ order, and the detected triplet frequencies. No significant quintuplet components were found in the frequency spectrum. Given the total time span of the measurements, we can now unambiguously conclude that the Blazhko period has become notably shorter than the previously known value of 40.8 days, whereas the main pulsation period remained roughly the same. Changes in the modulation period have been reported for other well-studied Blazhko variables. They challenge the explanations for the Blazhko effect which link the modulation period directly to the rotation period. The new photometry reveals an interval in the pulsation cycle of RR Lyr during which the star's intensity barely changes over the Blazhko cycle. This interval occurs during the infalling motion and between the supposed phases of the early and the main shock. The data also permit a more detailed study of the light curve shape at different phases in the Blazhko period through Fourier parameters.
  http://dx.doi.org/10.1051/0004-6361:20054415.