Constraining Radiatively Inefficient Accretion Flows with Polarization

The low-luminosity black hole Sgr A* provides a testbed for models of Radiatively Inefficient Accretion Flows (RIAFs). Recent sub-millimeter linear polarization measurements of Sgr A* have provided evidence that the electrons in the accretion flow are relativistic over a large range of radii. Here, we show that these high temperatures result in elliptical plasma normal modes. Thus, polarized millimeter and sub-millimeter radiation emitted within RIAFs will undergo generalized Faraday rotation, a cyclic conversion between linear and circular polarization. This effect will not depolarize the radiation even if the rotation measure is extremely high. Rather, the beam will take on the linear and circular polarization properties of the plasma normal modes. As a result, polarization measurements of Sgr A* in this frequency regime will constrain the temperature, density and magnetic profiles of RIAF models.Comment: 4 pages, 3 figures, accepted by ApJ Letter

Toward a better understanding of tool wear effect through a comparison between experiments and SPH numerical modelling of machining hard materials

The aim of this study is to improve the general understanding of tungsten carbide (WC–Co) tool wear under dry machining of the hard-to-cut titanium alloy Ti6Al4V. The chosen approach includes experimental and numerical tests. The experimental part is designed to identify wear mechanisms using cutting force measurements, scanning electron microscope observations and optical profilometer analysis. Machining tests were conducted in the orthogonal cutting framework and showed a strong evolution of the cutting forces and the chip profiles with tool wear. Then, a numerical method has been used in order to model the machining process with both new and worn tools. The use of smoothed particle hydrodynamics model (SPH model) as a numerical tool for a better understanding of the chip formation with worn tools is a key aspect of this work. The redicted chip morphology and the cutting force evolution with respect to the tool wear are qualitatively compared with experimental trends. The chip formation mechanisms during dry cutting process are shown to be quite dependent from the worn tool geometry. These mechanisms explain the high variation of the experimental and numerical feed force between new and worn tools

2-(1H-Benzimidazol-1-yl)-1-(2-fur­yl)ethanone O-ethyl­oxime

In the mol­ecule of the title compound, C15H15N3O2, the planar benzimidazole ring system [maximum deviation = 0.023 (2) Å] is oriented at a dihedral angle of 74.21 (5)° with respect to the furan ring. In the crystal structure, inter­molecular C—H⋯N inter­actions link the mol­ecules into centrosymmetric R 2 2(18) dimers. In addition, the structure is stabilized by π–π contacts between parallel imidazole rings [centroid–centroid distance = 3.726 (1) Å] and a weak C—H⋯π inter­action

Chandra and RXTE Observations of 1E 1547.0-5408: Comparing the 2008 and 2009 Outbursts

We present results from observations of the magnetar 1E 1547.0-5408 (SGR J1550-5418) taken with the Chandra X-ray Observatory and the Rossi X-ray Timing Explorer (RXTE) following the source's outbursts in 2008 October and 2009 January. During the time span of the Chandra observations, which covers days 4 through 23 and days 2 through 16 after the 2008 and 2009 events, respectively, the source spectral shape remained stable, while the pulsar's spin-down rate in the same span in 2008 increased by a factor of 2.2 as measured by RXTE. The lack of spectral variation suggests decoupling between magnetar spin-down and radiative changes, hence between the spin-down-inferred magnetic field strength and that inferred spectrally. We also found a strong anti-correlation between the phase-averaged flux and the pulsed fraction in the 2008 and 2009 Chandra data, but not in the pre-2008 measurements. We discuss these results in the context of the magnetar model.Comment: 4 figures, accepted for publication in Ap

Computational Simulation of Thermal and Spattering Phenomena and Microstructure in Selective Laser Melting of Inconel 625

AbstractComputational modelling of Laser Powder Bed Fusion (L-PBF) processes such as Selective laser Melting (SLM) can reveal information that is hard to obtain or unobtainable by in-situ experimental measurements. A 3D thermal field that is not visible by the thermal camera can be obtained by solving the 3D heat transfer problem. Furthermore, microstructural modelling can be used to predict the quality and mechanical properties of the product. In this paper, a nonlinear 3D Finite Element Method based computational code is developed to simulate the SLM process with different process parameters such as laser power and scan velocity. The code is further improved by utilizing an in-situ thermal camera recording to predict spattering which is in turn included as a stochastic heat loss. Then, thermal gradients extracted from the simulations applied to predict growth directions in the resulting microstructure

Models of hydrostatic magnetar atmospheres at high luminosities

We investigate the possibility of Photospheric Radius Expansion (PRE) during magnetar bursts. Identification of PRE would enable a determination of the magnetic Eddington limit (which depends on field strength and neutron star mass and radius), and shed light on the burst mechanism. To do this we model hydrostatic atmospheres in a strong radial magnetic field, determining both their maximum extent and photospheric temperatures. We find that spatially-extended atmospheres cannot exist in such a field configuration: typical maximum extent for magnetar-strength fields is ~10 m (as compared to 200 km in the non-magnetic case). Achieving balance of gravitational and radiative forces over a large range of radii, which is critical to the existence of extended atmospheres, is rendered impossible in strong fields due to the dependence of opacities on temperature and field strength. We conclude that high luminosity bursts in magnetars do not lead to expansion and cooling of the photosphere, as in the non-magnetic case. We also find the maximum luminosity that can propagate through a hydrostatic magnetar atmosphere to be lower than previous estimates. The proximity and small extent of the photospheres associated with the two different polarization modes also calls into question the interpretation of two blackbody fits to magnetar burst spectra as being due to extended photospheres.Comment: Accepted for publication in MNRAS. 14 pages, 6 figures, 2 table

Ambassadors, spies, captives, merchants and travelers : Ottoman information networks in the East, 1736-1747

This thesis sheds light on the Ottoman information networks in the East during the reign of Nadir Shah in Iran. It emphasizes singular cases of agencies who convey (and process) information, such as ambassadors, spies, captives, merchants, couriers, and travelers, but with due effort to depict the clear and implicit connections and links among them. The study is limited to the period when Nadir Shah reigned in Iran from 1736 to 1747, because the intensity of the developments and contacts in this interesting period provides an opportunity to investigate the sources and agents of information with due attention to detail. The study emphasizes Ottoman agents but it makes room for the voices, views and actions of Iranian and other actors as well. The thesis is based mainly on Ottoman sources but benefits from other sources as well. Its main focus is on Anatolia, Iraq, the Hedjaz, Iran, and India, and on individuals who were in contact with the Ottoman central and local officials. The research combines descriptive and analytical approaches. The descriptive side of the study aims to show how and when intelligence arrived in Istanbul. In the process, it introduces new or hitherto neglected Ottoman sources and agents as well. Münif’s ambassadorial report on Iran and Müteferrika’s Zeyl-i Tarih-i Seyyah are cases in point. Careful assessment of the available information helps correct some chronological and geographical mistakes in the current literature and draw attention to incoherent narratives in the primary sources. At the analytical level, this research points to the tensions and complexities of policy making. It points to friendly or hostile relations among certain Ottoman agents and how two political factions, led by Ahmed Paşa and Hacı Beşir Ağa, respectively, influenced the making of the Ottoman government’s Iran policy in the 1730s and 1740s.CONTENTS: Abstract ................................................................................................................... iv Öz ............................................................................................................................ vi Dedication ............................................................................................................. viii Acknowledgements ................................................................................................. ix Table of Contents ..................................................................................................... xi List of Tables .......................................................................................................... xiv List of Diagrams ................................................................................................... xviii List of Maps ........................................................................................................... xix List of Figures .......................................................................................................... xx Abbreviations......................................................................................................... xxi Notes on Dates and Transliteration ....................................................................... xxv CHAPTERS 1. Introduction ......................................................................................................... 1 1.1. Significance of Ottoman-Iran Relations during the Reign of Nadir Shah ..................... 4 1.2. Significance of Information Network and Agencies ................................................... 5 1.3. The Framework of the Study ..................................................................................... 6 1.4. An Overview of Ottoman-Iranian Relations in 1736-1747.......................................... 8 2. Review on Sources, Agents and Literature.......................................................... 21 2.1. Locating the Sources ................................................................................................21 2.2. Classifying the Agents ..............................................................................................28 2.2.1. Official Missions and Their Hosts .......................................................................29 2.2.2. Spies and Captives ............................................................................................35 2.2.3. Travelers ...........................................................................................................36 2.2.4. Merchants ........................................................................................................38 2.2.5. Couriers ............................................................................................................38 2.3. A Review of Literature .............................................................................................39 2.3.1. Chronological Mistakes .....................................................................................41 2.3.2. Mistakes in Names and Location .......................................................................48 2.3.3. The Kurdan Treaty of 1746 ................................................................................55 3. Factions of Ahmed Paşa and Hacı Beşir Ağa in Making Ottoman Foreign Policy of Iran ........................................................................................................................ 62 3.1. The Faction of Ahmed Paşa ......................................................................................67 3.1.1. Ahmed Paşa ......................................................................................................67 3.1.2. Other Members ................................................................................................86 3.2. The Faction of Hacı Beşir Ağa ...................................................................................94 3.2.1. Hacı Beşir Ağa ...................................................................................................94 3.2.2. Other Members ................................................................................................99 4. Official Source of Information: Official Missions ................................................104 4.1. Journeys of the Official Missions ............................................................................113 4.2. Durations of Official Missions ................................................................................128 4.3. Official Correspondence ........................................................................................136 5. Unofficial Sources of Information: Spies, Captives, Merchants, Couriers, and Travelers ...............................................................................................................151 5.1. Spies ......................................................................................................................154 5.1.1. Karakulak Ali Bey ............................................................................................154 5.1.2. Two Ottoman Spies in Tabriz ...........................................................................156 5.1.3. A Spy from Yerevan.........................................................................................157 5.1.4. Another Ottoman Spy in Tabriz .......................................................................160 5.1.5. Molla Veli .......................................................................................................161 5.1.6. Two Documents about Payment to Ottoman Spies .........................................162 5.1.7. Iranian Spies in the Ottoman Empire ...............................................................163 5.2. Captives.................................................................................................................164 5.2.1. Ottoman Captives in Iran ................................................................................164 5.2.1.1. Feyzullah Bey ..........................................................................................165 5.2.1.2. Ahmed Ağa .............................................................................................166 5.2.1.3. Camuş Hasan Ağa ....................................................................................167 5.2.2. Uzbek Fugitives from Nadir’s Army .................................................................168 5.3. Travelers ...............................................................................................................170 5.3.1. Jean Otter .......................................................................................................171 5.3.2. Tanburi Küçük Arutin Efendi ............................................................................175 5.3.3. Khwaja Abd-ul Karim Kashmiri ........................................................................177 5.4. Couriers .................................................................................................................179 5.5. Nadir Shah’s Indian Campaign as a Case Study .......................................................184 5.5.1. The First News on the Campaign .....................................................................187 5.5.2. A Detailed Report on the Campaign ................................................................191 5.5.3. Müteferrika’s Second Work on Iran: Zeyl-i Tarih-i Seyyah ................................194 6. Conclusion ........................................................................................................200 Bibliography ..........................................................................................................205 Appendices A. Routes and Distances ........................................................................................242 A.1. Sources and Assumptions ......................................................................................242 A.2. The Return Journeys of Münif Mustafa Efendi and Nazif Mustafa Efendi ...............245 A.3. The Distances in the Sources .................................................................................247 A.4. The Routes ............................................................................................................254 B. A New Ottoman Ambassadorial Report on Iran: Münif Mustafa Efendi’s İran Sefaretnamesi .......................................................................................................264 B.1. Münif Mustafa Efendi: An Ottoman Poet and Ambassador ....................................264 B.2. The Lists of Münif’s Works in Manuscript Libraries ................................................268 B.3. Münif Mustafa Efendi’s İran Sefaretnamesi ...........................................................273 B.4. Nazif Mustafa Efendi’s Report on Münif’s Mission in 1742 .....................................282 C. Selected Turkish Poems on Nadir Shah..............................................................286 C.1. Poems on Mahmud I .............................................................................................288 C.2. Poems on the Ottoman Elites ................................................................................289 C.3. Poems on the Fifth Madhhab, Baghdad and the Diplomatic Interactions ...............292 C.4. Poems on Nadir Shah and His Death ......................................................................296 D. Selected Paintings of Certain Actors .................................................................30

Spectroscopic Constraints on the Surface Magnetic Field of the Accreting Neutron Star EXO 0748-676

Gravitationally redshifted absorption lines of Fe XXVI, Fe XXV, and O VIII were inferred recently in the X-ray spectrum of the bursting neutron star EXO 0748-676. We place an upper limit on the stellar magnetic field based on the iron lines. The oxygen absorption feature shows a multiple component profile that is consistent with Zeeman splitting in a magnetic field of ~(1-2)x10^9 gauss, and for which the corresponding Zeeman components of the iron lines are expected to be blended together. In other systems, a field strength >5x10^{10} gauss could induce a blueshift of the line centroids that would counteract gravitational redshift and complicate the derivation of constraints on the equation of state of the neutron star.Comment: 5 pages, submitted to Phys. Rev. Let

1-[2-(2,4-Dichloro­benz­yloxy)-2-phenyl­ethyl]-1H-1,2,4-triazole

In the mol­ecule of the title compound, C17H15Cl2N3O, the triazole ring is oriented at dihedral angles of 9.24 (6) and 82.49 (6)°, respectively, with respect to the phenyl and dichloro­benzene rings. The dihedral angle between the dichloro­benzene and phenyl rings is 88.57 (5)°. An intra­molecular C—H⋯O contact results in the formation of a planar five-membered ring

Innovative approaches to nisin production

Nisin is a bacteriocin produced by Lactococcus lactis that has been approved by the Food Drug Administration for utilization as a GRAS status food additive. Nisin can inhibit spore germination and demonstrates antimicrobial activity against Listeria, Clostridium, Staphylococcus, and Bacillus species. Under some circumstances, it plays an immune modulator role and has a selective cytotoxic effect against cancer cells, although it is notable that the high production cost of nisin-a result of the low nisin production yield of producer strains-is an important factor restricting intensive use. In recent years, production of nisin has been significantly improved through genetic modifications to nisin producer strains and through innovative applications in the fermentation process. Recently, 15,400 IU ml-1 nisin production has been achieved in L. lactis cells following genetic modifications by eliminating the factors that negatively affect nisin biosynthesis or by increasing the cell density of the producing strains in the fermentation medium. In this review, innovative approaches related to cell and fermentation systems aimed at increasing nisin production are discussed and interpreted, with a view to increasing industrial nisin production.Peer reviewe