Physico-thermal and mechanical properties of Sanliurfa limestone,Turkey

Sanliurfa limestone is becoming increasingly popular for both interior and exterior building applications in the local area in south east Turkey, being easy to cut and shape and suitable for many purposes. Although these limestones are low cost construction materials, they are not widely used elsewhere due to the lack of data regarding their chemical, physico-thermal and mechanical properties and the requirement for highly skilled labour. A total of 264 samples of Sanliurfa limestone from four quarries were tested to determine their physico-thermal and mechanical properties. The data obtained confirmed they satisfy the main international standards for the use of limestone in the construction industry.     

Thermal-Diffusivity Measurements of Conductive Composites Based on EVA Copolymer Filled With Expanded and Unexpanded Graphite

In this research, the thermal diffusivity of composites based on ethylene- vinyl acetate (EVA) copolymer filled with two kinds of reinforcement graphite materials was investigated. The reinforcement graphite fillers were untreated natural graphite (UG) and expanded graphite (EG). Composite samples up to 29.3 % graphite particle volumetric concentrations (50 % mass concentration) were prepared by the melt- mixing process in a Brabender Plasticorder. Upon mixing, the EG exfoliates in these films having nanosized thicknesses as evidenced by TEM micrographs. Thus, the thermal diffusivity and electrical conductivity of composites based on the ethylene-vinyl acetate matrix filled with nanostructuralized expanded graphite and standard, micro-sized graphite were investigated. From the experimental results it was deduced that the electrical conductivity was not only a function of filler concentration, but also strongly dependent on the graphite structure. The percolation concentration of the filler was found to be (15 to 17) vol% for micro-sized natural graphite, whereas the percolation concentration of the filler in nanocomposites filled with expanded graphite was much lower, about (5 to 6) vol%. The electrical conductivity of nanocomposites was also much higher than the electrical conductivity of composites filled with micro-sized filler at similar concentrations. Similarly, the values of the thermal diffusivity for the nanocomposites, EG-filled EVA, were significantly higher than the thermal diffusivity of the composites filled with micro-sized filler, UG-filled EVA, at similar concentrations. For 29.3 % graphite particle volumetric concentrations, the thermal diffusivity was 8.23 × 10^?7 m² · s^?1 for EG-filled EVA and 6.14 × 10^?7 m² · s^?1 for UG-filled EVA. The thermal diffusivity was measured by the flash method.     

Strength and failure analysis of inverse Z joints bonded with Vinylester Atlac 580 and Flexo Tix adhesives

In this study, the tensile strength and failure loads of the inverse Z joints were analyzed both experimentally and numerically by using two adhesives with different properties under a tensile load. Vinylester Atlac 580 and Flexo Tix were used as adhesives and the joints were prepared with two different composite materials. Initially, the mechanical properties of the adhesives were specified using bulk specimens. Then, the stress analyses were performed using three-dimensional finite element method (3-D FEM) via Ansys (V.10.0.1). The experimental results were compared with the numerical results and they were found quite reasonable. According to the test results, it can be seen that when the adherend thickness is increased, the stress increases as well. The most appropriate value of the adherend thickness is identified as t = 5 mm. Furthermore, it was observed that the lowest failure load was obtained at t = 3 mm the thickness for each specimen.     

Decolorization of textile basic dye in aqueous solution by ozone

In this study, the factors affecting the rate of chemical oxygen demand (COD) of a synthetic waste solution containing a water soluble basic dye [Methylene Blue] were investigated. Decolorization of the dye was achieved by ozonation. The research was conducted using a batch bubble column to take the advantage of the intensive back-mixing that prevails in bubble columns. As a result, the COD of basic dyestuff wastewater was reduced to 64.96% and decolorization was observed under basic conditions (pH 12), complete MB degradation occurring in 12 min. Ozone consumption continued for a further 16 min after which time most of the degradation reactions were complete. Kinetic studies showed that direct ozonation of the aqueous dyes represented a pseudo-first-order reaction with respect to the dye. The apparent rate constant, which increased with both the applied ozone dose and higher pH values, declined logarithmically with the initial dye concentration.     

Cerebrovascular occlusive disease: hydatidosis

We reviewed six patients with cerebral hydatid embolism from the heart. Although hydatid disease is becoming less common in the world as a whole, it should be considered in the differential diagnosis of embolic stroke in children, especially in the infested areas where hydatidosis is endemic.     

Huge ossified crust-like subdural hematoma covering the hemisphere and causing acute signs of increased intracranial pressure

We report the successful removal of an ossified crust-like chronic subdural hematoma (SDH) covering the hemisphere in a 16-year-old boy. In this article, the importance of the surgical approach is stressed, and the rarity of this condition in the neurosurgical literature is also outlined.     

Secondary extradural spinal tumours in children

Secondary extradural spinal tumours are very rare, but they comprise most of the extradural neoplasms seen in infancy and childhood. Thirty-nine patients with this type of secondary tumour were treated in our hospital between 1965 and 1991. The diagnosis was proved by biopsy in every case. Following surgical decompression, all 35 survivors had radiotherapy and/or chemotherapy. Their outcome is reported.     

Role of surgical treatment in 70 patients with vertebral metastasis causing cord or root compression

Spinal metastasis plays an important role in the survival rate and general condition of cancer patients. In this paper, we present 70 patients with metastatic spinal tumors, diagnosed and surgically treated in the Departments of Neurosurgery and Orthopedics of Ankara Numune State Hospital between 1984 and 1993. Our clinical observations suggest that the survival rate is influenced by the type of the primary lesion, pathology, and the patient's preoperative physical and neurological status.     

Room-Temperature Synthesis of 2D Janus Crystals and their Heterostructures

Janus crystals represent an exciting class of 2D materials with different atomic species on their upper and lower facets. Theories have predicted that this symmetry breaking induces an electric field and leads to a wealth of novel properties, such as large Rashba spin–orbit coupling and formation of strongly correlated electronic states. Monolayer MoSSe Janus crystals have been synthesized by two methods, via controlled sulfurization of monolayer MoSe₂ and via plasma stripping followed thermal annealing of MoS₂. However, the high processing temperatures prevent growth of other Janus materials and their heterostructures. Here, a room-temperature technique for the synthesis of a variety of Janus monolayers with high structural and optical quality is reported. This process involves low-energy reactive radical precursors, which enables selective removal and replacement of the uppermost chalcogen layer, thus transforming classical transition metal dichalcogenides into a Janus structure. The resulting materials show clear mixed character for their excitonic transitions, and more importantly, the presented room-temperature method enables the demonstration of first vertical and lateral heterojunctions of 2D Janus TMDs. The results present significant and pioneering advances in the synthesis of new classes of 2D materials, and pave the way for the creation of heterostructures from 2D Janus layers.     

A simple dynamic measurement technique for comparing thermal insulation performances of anisotropic building materials

Measuring or estimating thermal properties of anisotropic building materials can be key obtaining the optimum performance for a particular application. The intensive researches on development of new building materials have necessitated in situ thermal testing apparatuses in most research laboratories. Only few standardized techniques are available for accurate thermal testing of anisotropic materials, and they are generally expensive. In the present study, common thermal testing methods are reviewed in brief. A simple and inexpensive thermal testing technique is proposed. The measurement is based on analysis of transient data, which is suitable for comparing effective thermal transmittances of both isotropic and anisotropic building materials. Sample measurements with ordinary concrete and rubberized concretes are performed. The effective thermal transmittances of rubberized concretes are found to be considerably lower than that of the ordinary one.