On the enhanced X-ray emission from SGR 1900+14 after the August 27th giant flare

We show that the giant flares of soft gamma ray repeaters (E similar to 10(44) erg) can push the inner regions of a fall-back disk out to larger radii by radiation pressure, while matter remains bound to the system for plausible parameters. The subsequent relaxation of this pushed-back matter can account for the observed enhanced X-ray emission after the August 27(th) giant flare of SGR 1900+14

On the Outbursts of Soft X-ray Transients

We suggest a new scenario to explain the outburst light curves of black hole soft X-ray transients together with the secondary maximum and the bump seen on their decay phases. Our explanations are based on the disk instability models considering the effect of X-ray irradiation. The scenario is consistent with the observed X-ray delays by a few days with respect to the optical rise for both the main outburst and the later maxima. We test our scenario by numerically solving the disk diffusion equation. The obtained model curve fits well to the observed X-ray outburst photon flux curve of the black hole soft X-ray transient GS/GRS 1124-68, a typical representative of the four BH SXTs with very similar light curves.Comment: 11 pages, 8 figures, accepted for publication in A&

X-ray and infrared enhancement of anomalous x-ray pulsar 1E 2259+586

The long-term ( 1.5 yr) X-ray enhancement and the accompanying infrared enhancement light curves of the anomalous X-ray pulsar 1E 2259+586 following the major bursting epoch can be accounted for by the relaxation of a fallback disk that has been pushed back by a gamma-ray flare. The required burst energy estimated from the results of our model fits is low enough for such a burst to have remained below the detection limits. We find that an irradiated disk model with a low irradiation efficiency is in good agreement with both X-ray and infrared data. Nonirradiated disk models also give a good fit to the X-ray light curve, but are not consistent with the infrared data for the first week of the enhancement

Anatomical landmark based registration of contrast enhanced T1-weighted MR images

In many problems involving multiple image analysis, an im- age registration step is required. One such problem appears in brain tumor imaging, where baseline and follow-up image volumes from a tu- mor patient are often to-be compared. Nature of the registration for a change detection problem in brain tumor growth analysis is usually rigid or affine. Contrast enhanced T1-weighted MR images are widely used in clinical practice for monitoring brain tumors. Over this modality, con- tours of the active tumor cells and whole tumor borders and margins are visually enhanced. In this study, a new technique to register serial contrast enhanced T1 weighted MR images is presented. The proposed fully-automated method is based on five anatomical landmarks: eye balls, nose, confluence of sagittal sinus, and apex of superior sagittal sinus. Af- ter extraction of anatomical landmarks from fixed and moving volumes, an affine transformation is estimated by minimizing the sum of squared distances between the landmark coordinates. Final result is refined with a surface registration, which is based on head masks confined to the sur- face of the scalp, as well as to a plane constructed from three of the extracted features. The overall registration is not intensity based, and it depends only on the invariant structures. Validation studies using both synthetically transformed MRI data, and real MRI scans, which included several markers over the head of the patient were performed. In addition, comparison studies against manual landmarks marked by a radiologist, as well as against the results obtained from a typical mutual information based method were carried out to demonstrate the effectiveness of the proposed method

Osmanlı İmparatorluğunda Vakıf ve 16. Yüzyılda Harput'taki Vakıflar

[No Abstract Available

Sonlu Viskoplastisite Üzerine Düşünceler

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2008Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2008Sonlu Plastisite Teorisinde serbest enerji yoğunluğu genellikle iki parçalı olarak tanımlanmakta olup birinci kısım, deforme olmuş maddesel noktada depolanmış olan elastik enerji yoğunluğunu,ikinci kısım da dislokasyonlarda bloke edilmiş olan plastik enerji yoğunluğunu temsil etmektedir. İkinci kısım yalnızca saklı (dahili) değişkenlerin , birinci kısım ise gözlenebilen değişkenlerin fonksiyonu olarak ifade edilmektedir. Daha sonra serbest enerjinin maddesel türevi uygun tarzda hesaplanarak Calusius-Duhem eşitsizliğine yerleştirilip bilinen matematiksel işlemler yapılmaktadır. Bu çalışmada ise ,serbest enerji yoğunluğu fonksiyonu ayrıştırılmadan kullanılmakta ve aynen sürekli-ortam yaklaşımındaki format izlenmektedir.Ancak plastik deformasyon etkileri ,daha sonra bahsedeceğimiz Lee ayrışımıyla işlemlere dahil edilmekte, viskozite etkisi ise Kelvin-Voigt benzeşimi ile toplam deformasyon tansörünün maddesel türevi şeklinde ithal edilmektedir.Ayrıca genel formülasyon, gerilme-uzayı yerine deformasyon-uzayı üzerinden yapılmaktadır. Total deformasyon gradyanı C FTF (FeFp )T(FeFp ) Fp CeFp T ≡ = = şeklinde Lee ayrıştırması tarzında dikkate alınmakta, Şek.1, daha sonraki işlemlerde ise plastik akma şartı, tutarlılık şartı ve evolüsyon denklemleri kullanılmaktadır. Bu noktada Fe ve Fp nin birer nokta fonksiyonu olduğunu ve gerçek deplasman gradyanlarını göstermediğini hatırlamak gerekir [4], [8], [10].Sonuç olarak genel formülasyonla deformasyon uzayında hem serbest enerjinin ayrıştırılmaksızın kullanılmasının mümkün olduğu gösterilmiş ve hem de maddesel gerilme tansörü için bünye denklemi elde edilmiştir.In finite plasticity, free energy is usually decomposed into two portions with the first part representing elastically stored energy, while the second part representing plastic energy which is blocked in the dislocations. The second part is a function of internal variables [6] only ,while the first part is a function of observable variables. Material time derivative of the free energy density, ψ& , is then evaluated properly and then substituted into the Clausius396 Duhem inequality by usual operations. In this study we do not decompose the free energy ; instead we take the total deformation tensor C into general consideration, as in continuum formulation format. Plasticity is taken into account by Lee decomposition of the deformation gradient while vicosity is incorporated into the formulation as in Kelvin-Voigt materials. namely, we take C FTF (FeFp )T(FeFp ) Fp CeFp T ≡ = = and employ yield condition and consistency relation along with the evolution equations. At this point it is worth to remember that Fe and Fp are not true deformation gradient, they are Paff forms [4], [8] [10]. As a result, we have not only shown that the free energy can be employed without decomposing it into two parts , but also we have obtained constitutive equation for the material stress tensor

Streamflow and sediment load prediction using linear genetic programming

Daily flow and suspended sediment discharge are two major hydrological variables that affect rivers’ morphology and ecosystem, particularly during flood events. Artificial neural networks (ANNs) have been successfully used to model and predict these variables in recent studies. However, these are implicit and cannot be simply used in practice. In this paper, linear genetic programming (LGP) approach has been suggested to develop explicit models to predict these variables in two rivers in Iran. The explicit relationships (prediction rules) evolved by LGP take the form of equations or program codes, which can be checked for its physical consistency. The results showed that the LGP outperforms ANNs to get global maximum and minimum discharges providing lowest root mean squared error and higher coefficient of efficiency both for training and validation periods.Nehirlerin morfolojisini, ekosistemi ve özellikle taşkın olaylarını etkileyen iki ana değişken askıdaki sediment ve günlük akımlardır. Yapay sinir ağları (YSA), bu değişkenleri modellemek ve tahmin etmek için yakın zamanda yapılmış çalışmalarda başarıyla kullanılmıştır. Bununla birlikte, bunlar kapalı yöntemlerdir ve pratik uygulamalarda kolaylıkla kullanılamazlar. Bu makalede, İran'daki iki nehirde bu değişkenleri tahmin etmek üzere açık modeller geliştirmek için doğrusal genetik programlama (DGP) yaklaşımı önerilmiştir. DGP tarafından geliştirilen açık ilişkiler (tahmin kuralları), fiziksel tutarlılığı açısından kontrol edilebilen denklemler veya program kodları şeklindedir. Sonuçlar, global maksimum ve minimum akımları elde etme noktasında, DGP’nin YSA’ya göre daha başarılı olduğunu gerek kalibrasyon gerekse doğrulama aşamalarında hataların karelerinin ortalamasının karekökünün en düşük, verimlilik katsayısının ise daha yüksek olmasını sağlayarak göstermiştir.No sponso

Roman Annelerin Çocuklarının Okullarıyla İlgili Deneyimleri

This study revealed the meaning of the experiences of Roma mothers, having children studying at the primary education level, regarding their children's schools to contribute to the determination and solution of the educational problems faced by Romas in Turkey. This study uses a phenomenological design, which is a qualitative research method. The participants were 11 Roma mothers living in a Roma neighborhood in Istanbul. The participants were selected using the criterion sampling technique. Research data were collected through face-to-face and focus group interviews and analyzed using content analysis. The results revealed that Romani mothers experienced symbolic violence, discrimination, and microassault behaviors in their children's schools. Symbolic violence is institutionally practiced. School administrators and teachers as well as non-Roma parents and students practice discriminatory and microassault behaviors. Roma mothers, perhaps out of desperation, continue to see education as a means to escape from their poor lives.Bu araştırmada Türkiye’de Romanların yaşadıkları eğitim sorunlarının tespiti ve çözümüne katkıda bulunabilmek için ilköğretim kademesinde çocuğu bulunan Roman annelerin veli olarak çocuklarının okullarıyla ilgili deneyimlerinin anlamını ortaya koymak amaçlanmıştır. Araştırmada nitel araştırma yöntemlerinden olan fenomenolojik desen kullanılmıştır. Katılımcılar İstanbul’da bir Roman mahallesinde yaşayan on bir Roman annedir. Katılımcılar ölçüt örnekleme tekniği kullanılarak belirlenmiştir. Araştırma verileri yüz yüze ve odak grup görüşmeler ile toplanmış ve içerik analizi ile analiz edilmiştir. Araştırma sonucunda Roman annelerin, çocuklarının okulunda sembolik şiddet, ayrımcı ve mikro saldırgan davranışları deneyimledikleri sonucuna ulaşılmıştır. Sembolik şiddet kurumsal olarak, ayrımcı ve mikro saldırgan davranışlar hem okul yönetimi ve öğretmenler hem de Roman olmayan veli ve öğrenciler tarafından uygulanmaktadır. Roman anneler belki de çaresizlikten, eğitimi yaşadıkları yoksul hayattan kurtulmanın yolu olarak görmeye umutsuzca devam etmektedirler

Fallback disks, magnetars and other neutron stars

The presence of matter with angular momentum, in the form of a fallback disk around a young isolated neutron star will determine its evolution. This leads to an understanding of many properties of different classes of young neutron stars, in particular a natural explanation for the period clustering of AXPs, SGRs and XDINs. The spindown or spinup properties of a neutron star are determined by the dipole component of the magnetic field. The natural possibility that magnetars and other neutron stars may have different strengths of the dipole and higher multipole components of the magnetic field is now actually required by observations on the spindown rates of some magnetars. This talk gives a broad overview and some applications of the fallback disk model to particular neutron stars. Salient points are: (i) A fallback disk has already been observed around the AXP 4U 0142+61 some years ago. (ii) The low observed spindown rate of the SGR 0418+5729 provides direct evidence that the dipole component of the field is in the 1012G range. All properties of the SGR 0418+5729 at its present age can be explained by spindown under torques from a fallback disk. (iii) The anomalous braking index of PSR J1734-3333 can also be explained by the fallback disk model which gives the luminosity, period, period derivative and the period second derivative at the present age. (iv) These and all applications to a variety of other sources employ the same disk physics and evolution, differing only in the initial conditions of the disk

On the Enhanced X-ray Emission from SGR 1900+14 after the August 27 Giant Flare

We show that the giant flares of soft-gamma ray repeaters (E~10^44 ergs) can push the inner regions of a fall-back disk out to larger radii by radiation pressure, while matter remains bound to the system for plausible parameters. The subsequent relaxation of this pushed-back matter can account for the observed enhanced X-ray emission after the August 27 giant flare of SGR 1900+14. Based on the results of our models, we estimate that the ratio of the fluences of the enhanced X-ray emissions to that of the preceding bursts remains constant for a particular SGR with similar preburst inner disk conditions, which is consistent with the four different burst observations of SGR 1900+14.Comment: 13 pages, 3 figures, accepted for publication in ApJ