Axial behaviour of concrete filled steel tube stub columns: a review

[EN] Concrete-filled steel tubular (CFST) columns are widely used in construction of high-rise buildings and peers of bridges to increase the lateral stiffness of the buildings, the axial load capacity, ductility, toughness, and resistance of corrosion of the columns. The CFST columns have much superior characteristics compared with traditionally reinforced concrete columns. The position of the concrete and steel tube in the cross-section of the CFST column is the most appropriate solution in terms of the strength and ductility. The steel tube, which is placed outside of the cross-section of the column, withstand the bending moment effectively. The concrete that is placed into the steel tube delay the local buckling of the steel tube and increase the axial load capacity of the column due to continually lateral confining. This paper presents a review on experimental results of the axial behavior of CFST columns performed by various researchers.Güler, S.; Korkut, F.; Yaltay, N.; Yavuz, D. (2018). Axial behaviour of concrete filled steel tube stub columns: a review. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 359-364. https://doi.org/10.4995/ASCCS2018.2018.7602OCS35936

REE geochemistry and fluid-inclusion studies of fluorite deposits from the Yaylagözü area (Yıldızeli-Sivas) in central Turkey

Skarn- and vein-type fluorite deposits in the vicinity of Yaylagözü, Yıldızeli-Sivas, are found within the syenites and their skarn zones that are located in the Central Anatolia Massif. Mining was activite on several fluorite mineralizations during the early 1950 s, but is presently inactive. The goal of this study, on the basis of REE geochemistry and fluid inclusion investigations, is to explain the genesis and physicochemical conditions of fluorite mineralization hosted by calc-alkaline to alkaline syenites of Upper Cretaceous age. The rare-earth element content of the Yaylagözü fluorite is quite variable. Fluorites have moderate to high total REE contents ranging from 68 ppm to 5288 ppm, with a mean of 907, compared with the fluorite occurrences elsewhere both in hydrothermal and sedimentary origin. Light rare-earth elements (LREE) are enriched in all the studied fluorite samples. Chondrite-normalized La/Lu ratios range from 13.7 to 364, regardless of color variation in fluorites. This, as well as low Tb/La ratio, is the indicative of early crystallization of fluorite from the mineralizing solution. The Tb/La and Tb/Ca ratios of fluorites in the present study indicate that they plot mainly in the “pegmatitic” or “high-hydrothermal” field of the diagram of Möller et al. (1976) with the characteristics of primary crystallization and remobilization trends. Fluid inclusion microthermometry indicates that the fluorite in most of the veins was formed from the fluids at temperatures between 161 ° and 243 °C. Primary fluid inclusions for samples plotting into the “pegmatitic” field of the Möller et al. diagram (1976) has the highest homogenization temperatures

Interpretation of isotope values of sulfate produced from pyrite oxidation

Pirit (FeS2) doğada en yaygın bulunan metal sülfür mineralidir ve oksidasyonu, Asit Maden Sahaları(AMS) olarak bilinen çevre problemlerine neden olmaktadır. Bakterilerin bu ortamlarda yaygın olması, piritin oksitlenmesinde bakteriyel reaksiyonların gelişebileceğini göstermektedir. Bu çalışmanın ana hedefi,  piritin asit koşullar altında baskın oksidasyon mekanizmasının (biyolojik ve/veya kimyasal) izotoplar yardımıyla ortaya konmasıdır. Bu amaçla, pirit asit koşullar altında (pH<3) biyolojik ve kimyasal olarak oksitlenmiş, oluşan sülfatın oksijen ve sülfür izotop analizleri yapılmıştır. Biyolojik deneyler için Acidithiolacillus Ferrooxidans bakteri türü kullanılmıştır. Deney sonuçları, piritin biyolojik olarak, kimyasal deneylere oranla daha hızlı oksitlendiğini ortaya koymuştur. Sülfatın oksijen izotop değerlerinin oksidasyon mekanizması ile uyumlu olduğu ancak biyolojik izleri taşımadığı tespit edilmiştir.  Anahtar Kelimeler: Acidithiobacillus Ferrooxidans, izotop, pirit, sülfat. Pyrite is the most common sulfur mineral in nature and its oxidation causes environmental problems known as Acid Mine Drainage sites (AMD). Due to their high metal concentration and harmful effects to ecological life, the rehabilitation of these environments is inevitable. Common occurrences of bacterium in these environments indicate that pyrite oxidation can be largely mediated by biological reactions. The purpose of this study is to elucidate pyrite oxidation mechanisms (biotic vs. abiotic) under acidic conditions (pH 3) by means of oxygen and sulfur isotope composition of sulfate produced during pyrite oxidation. For this purpose, pyrite was oxidized as biologically and chemically at pH 3 and oxygen and sulfur isotope composition of the product sulfate was analyzed. For biological experiments, Acidithiolacillus Ferrooxidans, which has ability to oxidize Fe (II) and reduced sulfur compounds, was used. Biotic and abiotic experiments were carried out under aerobic and anaerobic conditions. In addition, biotic and abiotic aerobic experiments were designed as short and long-term and pH was used as proxy for these experiments. Experimental results showed that bacteria accelerated pyrite oxidation over chemical reactions, and Fe (III) ions produced by bacteria was also dominant oxidizing agent for pyrite. The oxygen isotopes composition of sulfate are consistent with oxidizing mechanisms but do not carry biological signature.  Keywords: Acidithiobacillus Ferrooxidans, isotope, pyrite, sulfate.

Geochemical patterns of the Akdagmadeni (Yozgat, Central Turkey) fluorite deposits and implications

Fluorite and fluorite-bearing Pb–Zn–Ag (Cu) deposits are quite common in granitoids and associated skarn formations that are products of Late Cretaceous–Early Paleocene magmatic intrusions into Paleozoic metamorphic rocks of the so called Central Anatolian massif. This study investigates the geochemical features, mainly REE distributions, of fluorites from the Akdagmadeni fluorite and fluorite bearing Pb–Zn–Ag (Cu) deposits. These include the vein type Tad Dere, epidote-skarn hosted Bu¨yu¨kc¸al Tepe and the skarn and granite hosted Akc¸akisla deposits. The REE contents of these deposits are 20.6–48.5 ðx ¼ 36:0Þ, 61.3–149.3 ðx ¼ 113:0Þ and 279.2–4222.4 ðx ¼ 1280:0Þ ppm for the Tad D., Bu¨yu¨kc¸al T. and Akc¸akisla, respectively. In general, theREE contents are intermediate to high and decrease in abundance with increasing distance from the granitic bodies. The LREE contents are dominantly higher than HREE contents and REE normalized patterns indicate decreasing abundances with increasing atomic number. These indicate that all the fluorites are early stage mineralizations. However, Tb/Ca–Tb/La ratios show distinct differences in the nature of the mineralizing fluids. The high ratios of Akc¸akisla fluorites are evidence of mineralizing fluids rich in late-stage differentiates from a felsic magma, while intermediate to high ratios of the Bu¨yu¨kc¸al T. fluorites are products of late-stage differentiates from hydrothermal fluids. Tad D. fluorites were mineralized under hydrothermal conditions. Decreasing SREE contents in the order of Akc¸akisla, Bu¨yu¨kc¸al T., and Tad D., and Sc/Eu vs Sr distribution (Sr increases with increasing distance from the magmatic rocks) also supports this order of formation. Each of the three types of fluorite deposits plot in well-defined areas in the Sc/Eu vs Sr diagram. Eu and Ce anomalies give a mixed pattern; the Tad D. fluorites have strong negative Eu anomalies indicating low T and low f o2 mineralizing fluids. Strong positive Eu anomalies for the Akc¸akisla fluorites are probably due to high f o2: The Ce anomalies are strongly negative for the Akc¸akisla, negative for the Bu¨yu¨kc¸al T. and weakly negative for the Tad D. fluorites. These indicate high f o2 conditions for the Akc¸akisla, intermediate for the Bu¨yu¨kc¸al T. and low for the Tad D. fluorites. Because of distinguishable differences in REE patterns, the fluorite deposits plot in well-defined areas in Sc/Eu vs Sr, (La/Yb)n– (Eu/Eup)n, Sr–(Eu/Eup)n, Sc–SREE, (Tb/Yb)n–(La/Yb)n, Tb/Ca–Tb/La diagrams, and indicate different origins and depositional histories. The homogenization temperatures ðTHÞ range from 156 to 185 8C with the corresponding salinities between 12 and 23 wt% NaCl for the Tad Dere ores, 390 to 430 8C with the corresponding salinities 8 and 12 wt% NaCl for the Akc¸akisla and Bu¨yu¨kc¸al Tere ores. Consequently, the field, fluid inclusion data and REE geochemistry indicate that the composition of mineralizing fluids, the locations of ore formations relative to the plutons, the mineralizing mechanisms and the prevailing physicochemical conditions of the depositional environments for the fluorite deposits of Akdagmadeni, were different

A Rare Complication of Chronic Otitis Media: Cerebellar Abscess

Chronic otitis media (COM) and its associated complications are currently less common because of the popularity of imaging modalities such as computed tomography and magnetic resonance imaging and the increased use of antibiotics. Patients can be treated without any complications owing to early diagnosis. Despite all these new developments and opportunities, complications of autogenous cerebellar abscess may develop and be fatal. In this case report, we present our own clinical experience regarding a patient with cerebellar abscess as a complication of COM

Predicting Severe Sleep Apnea in Patients with Complaints: Pulse Oximetry and Body Mass Index

Objective:An adequate evaluation combined with an easily accessible test would be a useful way to direct the appropriate patients to sleep centers in circumstances with a limited opportunity for polysomnography (PSG). For this reason, it is necessary to use a screening method prior to PSG evaluation. The aim of the present study was to investigate whether the use of body mass index (BMI) and pulse oximetry is sufficient to predict the severity of obstructive sleep apnea syndrome (OSAS) without PSG.Methods:A total of 956 patients who were admitted to a tertiary referral center with complaints of witnessed apnea, excessive daytime sleepiness, and previously performed PSG were included in the study. Data of PSG (included pulse oximetry) and BMI were investigated for the determination of cut-off points for parameters in the patients.Results:Based on the presence of severe OSAS, the cut-off points were ≥31.7 kg/m2 for BMI, <81% for minimum oxygen saturation (Min O2), and ≥14.1 min for sleep time with oxygen saturation <90% (ST90). Severe OSAS risk was found to be higher in patients with BMI ≥31.7 kg/m2, ST90 ≥14.1 min, and Min O2 ≤81% than in those without (OR: 37.173; 95% CI: 22.465–61.510, p=0.001). Specificity and accuracy were 94.85% and 72.49%, respectively, when all three cut-off scores were provided.Conclusion:The appropriate cut-off values obtained from combining BMI and pulse oximetry data can provide accurate results for predicting the severity of OSAS

Comparison of CT and PET-CT based planning of radiation therapy in locally advanced pancreatic carcinoma

Abstract Background To compare computed tomography (CT) with co-registered positron emission tomography-computed tomography (PET-CT) as the basis for delineating gross tumor volume (GTV) in unresectable, locally advanced pancreatic carcinoma (LAPC). Methods Fourteen patients with unresectable LAPC had both CT and PET images acquired. For each patient, two three-dimensional conformal plans were made using the CT and PET-CT fusion data sets. We analyzed differences in treatment plans and doses of radiation to primary tumors and critical organs. Results Changes in GTV delineation were necessary in 5 patients based on PET-CT information. In these patients, the average increase in GTV was 29.7%, due to the incorporation of additional lymph node metastases and extension of the primary tumor beyond that defined by CT. For all patients, the GTVCT versus GTVPET-CT was 92.5 ± 32.3 cm3 versus 104.5 ± 32.6 cm3 (p = 0.009). Toxicity analysis revealed no clinically significant differences between two plans with regard to doses to critical organs. Conclusion Co-registration of PET and CT information in unresectable LAPC may improve the delineation of GTV and theoretically reduce the likelihood of geographic misses.</p

WinClastour—a Visual Basic program for tourmaline formula calculation and classification

WinClastour is a Microsofts Visual Basic 6.0 program that enables the user to enter and calculate structural formulae of tourmaline analyses obtained both by the electron-microprobe or wet-chemical analyses. It is developed to predict cation site-allocations at the different structural positions, as well as to estimate mole percent of the end-members of the calcic-, alkali-, and X-site vacant group tourmalines. Using the different normalization schemes, such as 24.5 oxygens, 31 anions, 15 cations (T+Z+Y), and 6 silicons, the present program classifies tourmaline data based on the classification scheme proposed by Hawthorne and Henry [1999. Classification of the minerals of the tourmaline group. European Journal of Mineralogy 11, 201–215]. The present program also enables the user Al–Mg disorder between Y and Z sites. WinClastour stores all the calculated results in a comma-delimited ASCII file format. Hence, output of the program can be displayed and processed by any other software for general data manipulation and graphing purposes. The compiled program code together with a test data file and related graphic files, which are designed to produce a high-quality printout from the Grapher program of Golden Software, is approximately 3Mb as a self-extracting setup file