Shallow structure beneath the Central Volcanic Complex of Tenerife from new gravity data: implications for its evolution and recent reactivation

We present a new local Bouguer anomaly map of the Central Volcanic Complex (CVC) of Tenerife, Spain, constructed from the amalgamation of 323 new high precision gravity measurements with existing gravity data from 361 observations. The new anomaly map images the high-density core of the CVC and the pronounced gravity low centred in the Las Cañadas caldera in greater detail than previously available. Mathematical construction of a sub-surface model from the local anomaly data, employing a 3D inversion based on 'growing' the sub-surface density distribution via the aggregation of cells, enables mapping of the shallow structure beneath the complex, giving unprecedented insights into the sub-surface architecture. We find the resultant density distribution in agreement with geological and other geophysical data. The modelled sub-surface structure supports a vertical collapse origin of the caldera, and maps the headwall of the ca. 180 ka Icod landslide, which appears to lie buried beneath the Pico Viejo–Pico Teide stratovolcanic complex. The results allow us to put into context the recorded ground deformation and gravity changes at the CVC during its reactivation in spring 2004 in relation to its dominant structural building blocks. For example, the areas undergoing the most significant changes at depth in recent years are underlain by low-density material and are aligned along long-standing structural entities, which have shaped this volcanic ocean island over the past few million years

Hadis Mecmualarında Yer Alan Kıraate Dair Hadislerin Değerlendirilmesi ve Bu Hadislerin Kıraat İlmindeki Yeri

Kur’ân-ı Kerîm, İslâm dininin birinci, hadisler ise ikinci kaynağı kabul edilmektedir. Hadis mecmualarında kıraat ilmine dair birtakım rivâyetler mevcuttur. İlgili rivâyetler; Kur’ân’daki bir ayetin veya bir kelimenin eda keyfiyetine dair olduğu gibi Kur’ân okuma adabı, Kur’ân’ı öğretmek ve öğrenmeye dair de olabilmektedir. Bu rivâyetlerde geçen kıraat farklılıkları, hadis ilminin kaidelerine göre sahih, hasen veya zayıf olabilmektedir. Sahih kabul edilen bir hadis rivâyetindeki kıraat farklılığı, kıraat ilmi literatüründe de sahih kabul görülür. Ancak bazı rivâyetler hadis ilmi açısından sahih kabul edilmesine rağmen resm-i mushafa ters düştüğü için şâz kıraat kabul edilmektedir. Öte yandan hadislerde zayıf kabul edilen bir kıraat rivâyeti, kıraat ilmi açısından sahih kabul edilebilmektedir. Bu çalışmamızda kıraat ilmi usulüne göre sahih olan bir veçhin neden hadis kaynaklarında zayıf görüldüğü, hadis ilmi literatüründe sahih görülen bir hadisteki kıraat veçhinin kıraat ilmi literatüründe neden şâz veya merdut görüldüğü hususları üzerinde durulacaktır

Hafif silahlarda kullanılan namlu malzemesinin geliştirilmesi ve işleme parametrelerinin incelenmesi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Namlu, hafif silahlardan tabancanın en önemli parçası olup silahın kullanım ömrü namlu parçasının ömrü ile ilişkilidir. Namlu parçasının ömrü silah tasarımlarındaki en önemli parametrelerden biridir. Namlu ömrünü belirlemek zor bir iştir. Namlunun ömrünü belirlemek için saha testlerinden ve silaha özgü laboratuvar testlerinden yararlanılır. Silah üreticileri namlu ömrünü geliştirmek adına farklı yiv-set geometrilerine sahip namlu tasarımları geliştirirken diğer bir yandan namlu malzemesiyle ilgili çalışmalar yapmaktadırlar. Bu çalışmada, hafif silahların en önemli parçası olan namlu parçasına alternatif malzeme geliştirilmesiyle beraber saha ve laboratuvar testlerinin yapılması üzerine çalışmalar yapılmıştır. Günümüz hafif silah sektöründe namlu malzemesi olarak genel anlamıyla 4140 ve türevi malzemeler kullanılırken bu çalışmada 1.2340 sıcak iş takım çeliğinin özellikleri incelenmiş olup, namlu üretimine uygun olduğu görülmüştür. 1.2340 sıcak iş takım çeliğinden üretilen namlu parçasının kullanıldığı hafif polimer gövdeli silah müşteri kabul şartnamesinde istenen "soğuk hava testi, sıcak hava testi, boya (tuz) testi, düşme testi, hız testi, dağılım atış testi, düşme testi, yüksek basınç atış testi, ömür mukavemet testi, kum ve çamur testi gibi saha ve laboratuvar testlerinden başarı ile geçmiştir. Namlu malzemesi olarak belirlenen 1.2340 sıcak iş takım çeliğinden üretilen namlular için ömür değerleri de incelenmiştir. Namlu malzemesi olarak mevcutta kullanılan AISI 4140 malzemesinden yapılan polimer gövdeli tabancaların namlu ömürleri 30.000 atım olarak belirlenmiş iken yapılan malzeme çalışmasıyla yeni ömür değeri 50.000 atım olarak artırılmıştır. Böylece kullanılan yeni namlu malzemesiyle ömür değeri yaklaşık %66 oranında artırılmıştır. Ayrıca kullanılan malzeme ile atış dağılım performansı iyileştirilmiştir. Bunların dışında kullanılan 1.2340 sıcak iş takım çeliği ile de namlu malzemesinin aşınmaya dayanımı artmıştır. Böylece namlu malzemesinin aşınma ömrü artırılmıştır. Yapılan geliştirmeler ve testlerin sonucunda namlu malzemesi olarak 1.2340 çeliği kullanılmaya başlanmıştır.Barrel is the most significant polymer pistol component that is directly related to pistols usage life. Barrel fatigue life is a critical design parameter of light weapon as pistols. There are so many variables involved (gunpowder type, bore diameter, bullet coatings, types and geometry of rifling etc.) that it's hard to predict barrel fatigue life. To determine the barrel fatigue life, light weapon field test and weapon-specific laboratory tests are performed. In order to improve the barrel fatigue life, barrel designs with different rifling geometries have developed. In the meanwhile material improvement studies have investigated. In this study, it has been studied on the development and testing of alternative material for gun barrel which is the most important part of light weapons in this respect. In general, modern gun barrels are manufactured from low alloy steel forgings as AISI 4140. However 1.2340 hot work tool steel is investigated instead of AISI 4140 alloy steel in this study. As a result of material studies, 1.2340 hot work tool steel is more suitable than AISI 4140 alloy steel. According to customer acceptance specification, barrel which was produced from 1.2340 hot work steel has passed weapon field test and weapon-specific laboratory tests like as cold weather test, hot weather test, drop test, velocity test, firing dispersal test, high-pressure shooting test, endurance test, sand and mud tests successfully. The barrel fatigue life of polymeric body guns made of AISI 4140 alloy steel used as barrel material has been determined as 30,000 cyclic rate of fire. Fatigue life cycle of barrel that is made of 1.2340 hot work tool steel has been increased by 50,000 cyclic rate of fire. It ıs seen that cyclic rate of fire has been increased by about %66. In addition, firing dispersal test performance has been improved with new steel. Also the wear resistance of the barrel has increased because of using 1.2340 hot work tool steel. According to material improvement studies, 1.2340 hot work tool steel has been started to use for new generations gun barrels

New evidence for the reawakening of Teide volcano

Geophysical signals accompanying the reactivation of a volcano after a period of quiescence must be evaluated as potential precursors to impending eruption. Here we report on the reactivation of the central volcanic complex of Tenerife, Spain, in spring 2004 and present gravity change maps constructed by time-lapse microgravity measurements taken between May 2004 and July 2005. The gravity changes indicate that the recent reactivation after almost a century of inactivity was accompanied by a sub-surface mass addition, yet we did not detect widespread surface deformation. We find that the causative source was evolving in space and time and infer fluid migration at depth as the most likely cause for mass increase. Our results demonstrate that, even in the absence of previous baseline data and ground deformation, microgravity measurements early in developing crises provide crucial insight into the dynamic changes beneath a volcano

New Insight on the Increasing Seismicity during Tenerife's 2004 Volcanic Reactivation

Starting in April 2004, unusual seismic activity was observed in the interior of the island of Tenerife (Canary Islands, Spain) with much evidence pointing to a reawakening of volcanic activity. This seismicity is now analyzed with techniques unprecedented in previous studies of this crisis. The 200 earthquakes located onshore during 2004 and 2005 have been classified by cross-correlation, resulting in a small number of significant families. The application of a relative location algorithm (hypoDD) revealed important features about the spatial distribution of the earthquakes. The seismic catalogue has been enhanced with more than 800 additional events, detected only by the closest seismic station. These events were assigned to families by correlation and as a consequence their hypocentral location and magnitude were estimated by comparing them to the earthquakes of each family. The new catalogue obtained by these methods identifies two major seismogenic zones, one to the northwest and the other to the southwest of the Teide-Pico Viejo complex and having a separation of at least 10 km between them. These regions alternate their activity starting in January 2004, i.e., three months earlier than previously thought. We propose a simple model based on the results of this work which will also concur with all previous geophysical and geochemical studies of the 2004 crisis. The model proposes a single magma intrusion affecting the central part of the island with lateral dikes driven by the rifts to the northwest and southwest.Comment: 20 pages, 15 figure

Building Scientific Capability and Reducing Biological Threats: The Effect of Three Cooperative Bio-Research Programs in Kazakhstan.

Cooperative research programs aimed at reducing biological threats have increased scientific capabilities and capacities in Kazakhstan. The German Federal Foreign Office's German Biosecurity Programme, the United Kingdom's International Biological Security Programme and the United States Defense Threat Reduction Agency's Biological Threat Reduction Program provide funding for partner countries, like Kazakhstan. The mutual goals of the programs are to reduce biological threats and enhance global health security. Our investigation examined these cooperative research programs, summarizing major impacts they have made, as well as common successes and challenges. By mapping various projects across the three programs, research networks are highlighted which demonstrate best communication practices to share results and reinforce conclusions. Our team performed a survey to collect results from Kazakhstani partner scientists on their experiences that help gain insights into enhancing day-to-day approaches to conducting cooperative scientific research. This analysis will serve as a basis for a capability maturity model as used in industry, and in addition builds synergy for future collaborations that will be essential for quality and sustainment

Volcanic and geochemical evolution of the Teno massif, Tenerife, Canary Islands: some repercussions of giant landslides on ocean island magmatism

Large-scale, catastrophic mass wasting is a major process contributing to the dismantling of oceanic intraplate volcanoes. Recent studies, however, have highlighted a possible feedback relationship between flank collapse, or incipient instability, and subsequent episodes of structural rearrangement and/or renewed volcano growth. The Teno massif, located in northwestern Tenerife (Canary Islands), is a deeply eroded Miocene shield volcano that was built in four major eruptive phases punctuated by two lateral collapses, each removing >20–25 km3 of the volcano's north flank. In this paper, we use detailed field observations and petrological and geochemical data to evaluate possible links between large-scale landslides and subsequent volcanism/magmatism during Teno's evolution. Inspection of key stratigraphic sequences reveals that steep angular unconformities, relics of paleolandslide scars, are marked by polymict breccias. Near their base, these deposits typically include abundant juvenile pyroclastic material, otherwise scarce in the region. While some of Teno's most evolved, low-density magmas were produced just before flank collapses, early postlandslide lava sequences are characterized by anomalously high proportions of dense ankaramite flows, extremely rich in clinopyroxene and olivine crystals. A detailed sampling profile shows transitions from low-Mg # lavas relatively rich in SiO2 to lavas with low silica content and comparatively high Mg # after both landslides. Long-term variations in Zr/Nb, normative nepheline, and La/Lu are coupled but do not show a systematic correlation with stratigraphic boundaries. We propose that whereas loading of the growing precollapse volcano promoted magma stagnation and differentiation, the successive giant landslides modified the shallow volcano-tectonic stress field at Teno, resulting in widespread pyroclastic eruptions and shallow magma reservoir drainage. This rapid unloading of several tens of km3 of near-surface rocks appears to have upset magma differentiation processes, while facilitating the remobilization and tapping of denser ankaramite magmas that were stored in the uppermost mantle. Degrees of mantle melting coincidently reached a maximum in the short time interval between the two landslides and declined shortly after, probably reflecting intrinsic plume processes rather than a collapse-induced influence on mantle melting. Our study of Teno volcano bears implications for other oceanic volcanoes where short-term compositional variations may also directly relate to major flank collapse events

Upper mantle magma storage and transport under a Canarian shield-volcano, Teno, Tenerife (Spain)

We use clinopyroxene-liquid thermobarometry, aided by petrography and mineral major element chemistry, to reconstruct the magma plumbing system of the late Miocene, largely mafic Teno shield-volcano on the island of Tenerife. Outer rims of clinopyroxene and olivine phenocrysts show patterns best explained by decompression-induced crystallization upon rapid ascent of magmas from depth. The last equilibrium crystallization of clinopyroxene occurred in the uppermost mantle, from ∼20 to 45 km depth. We propose that flexural stresses or, alternatively, thermomechanical contrasts create a magma trap that largely confines magma storage to an interval roughly coinciding with the Moho at ∼15 km and the base of the long-term elastic lithosphere at ∼40 km below sea level. Evidence for shallow magma storage is restricted to the occurrence of a thick vitric tuff of trachytic composition emplaced before the Teno shield-volcano suffered large-scale flank collapses. The scenario developed in this study may help shed light on some unresolved issues of magma supply to intraplate oceanic volcanoes characterized by relatively low magma fluxes, such as those of the Canary, Madeira and Cape Verde archipelagoes, as well as Hawaiian volcanoes in their postshield stage. The data presented also support the importance of progressive magmatic underplating in the Canary Islands