Mechanical properties of lightweight concrete made with cold bonded fly ash pellets

In this paper, compressive and splitting tensile strengths, modulus of elasticity and steel rebar-concrete bond strength of lightweight aggregate concretes (LWAC) produced at 0.40 w/c with sand and mixture of crushed stone and lightweight fly ash coarse aggregates are presented. Lightweight fly ash aggregates (LWA), plain (LC) and reinforced with 0.1% (L1P) and 0.5% (L5P) crumb rubber and0.1% (L1F) polypropylene fiber are utilized. Test results revealed that the compressive strength of all LWAC conformed to the limitation for structural use whereas a reduction in density up to 20% was achieved. Whereas the mechanical properties decreased with the use of lightweight aggregates, some increases were observed for the steel-concrete bond strength

Polar olmayan ZnO/BeMgZnO kuantum kuyularında altbantlar arası geçişler: Fiziksel boyut, konsantrasyon ve donör seviyesinin etkileri

Polar ve semipolar yönlerde büyütülen BeMgZnO bariyer tabakaları üzerindeki ZnO kuyu katmanlarının polarizasyon özellikleri araştırıldı. Gevşemiş ve gerilmiş bariyer katmanların durumları göz önünde bulunduruldu. Arayüzlerdeki polarizasyon farkının, kuyu tabakası içinde 8 MV cm^(-1) büyüklüğünde yerleşik bir elektrik alanına yol açtığı bulundu. Polar olmayan ZnO/BeMgZnO kuantum kuyuları, altbantlar arası geçişler açısından incelendi. Hesaplamalar Be ve Mg konsantrasyonlarını sırasıyla 0.18 ve 0.5'e kadar kapsamaktadır. 50 ila 700 meV arasında değişen altbantlar arası geçiş (ISBT) enerjilerinin mümkün olduğu bulundu. Bariyer kalınlığının ISBT enerjileri üzerindeki etkisi incelendi. Sonuçlar, enerjilere kıyasla ISBT enerjilerinde önemsiz değişiklikler olduğunu göstermektedir.Polarizaton properties of ZnO well layers on BeMgZnO barrier layers grown in polar and semipolar orientations have been investigated. Cases of relaxed and strained barrier layers are considered. It is found that the polarizaton difference at the interfaces leads to a built-in electric field inside the well layer as much as 8 MV cm^(-1) in magnitude. Nonpolar ZnO/BeMgZnO quantum wells have been studied in terms of intersubband transitions. The calculations have covered Be and Mg concentrations up 0.18 and 0.5, respectively. It has been found that intersubband transition (ISBT) energies ranging from 50 to 700 meV are possible. The effect of barrier thickness on the ISBT energies has been studied. The results indicate insignificant changes in ISBT energies compared to the energies

ON NEW GENERALIZED FRACTIONAL MIDPOINT-TYPE INEQUALITIES FOR CO-ORDINATED CONVEX AND CO-ORDINATED CONCAVE FUNCTIONS

In this paper, we firstly obtain a new generalized identity for twice partially differentiable functions Riemann–Liouville fractional integrals. Then, using this equality, we obtain some midpoint-type inequalities for co-ordinated convex and co-ordinated concave functions. We also show that our result generalizes the give several inequalities obtained in earlier works

A comparative anatomical study of the genus Puschkinia Adams in Turkey

In the study, Puschkinia scilloides Adams, P. bilgineri Yıldırım, and P. peshmenii Rix et B. Mathew were compared anatomically. Although the stem vascular bundles were arranged in two rows in P. peshmenii, they can observed in three rows in P. scilloides and P. bilgineri. In addition, some differences were found, such as the metaxylem number in the root, number of vascular bundles in the scape, presence of raphide crystals, and number of protruding epidermis cells at the tip of the leaf. These differences have been found to be taxonomically useful for distinguishing these species. Moreover, similarities and differences between Puschkinia Adams and the taxonomically closely related Scilla L. section Chionodoxa Boiss. and Scilla bifolia L. taxa were also discussed

Impact of the COVID-19 pandemic on return and risk transmission between oil and precious metals: Evidence from DCC-GARCH model

It is frequently discussed in the literature that the correlation between low-correlation assets under ordinary market conditions may increase during crisis periods. To contribute to the ongoing debates, this paper empirically examines risk transmission between oil and precious metal markets induced by the COVID-19 pandemic using the DCC-GARCH model. The findings reveal evidence of a significant risk transmission between oil prices and precious metal prices, particularly during the onset of the COVID-19 pandemic. The findings point out that the negative relationship between oil and all precious metals returns in the pre-COVID-19 period has changed with the effect of the pandemic. In this process, it is revealed that the negative relationship between oil and gold has strengthened, but the negative relationship between oil and silver has weakened. In addition, the correlations between oil and platinum and palladium turn positive. The empirical findings imply that investors and portfolio managers seeking portfolio diversification and hedging opportunities in a high-risk environment such as the COVID-19 pandemic should consider gold and silver assets for investment

Optimización de las propiedades de durabilidad del hormigón que contiene ceniza, utilizando el enfoque Taguchi y análisis Anova]

In this study, optimization of durability properties of the concretes was performed by using Taguchi method and Anova analysis. The durability performance of the concretes was evaluated using measurements of rapid chloride ion permeability, freezing-thawing resistance and sorptivity tests. The degree of freezing-thawing resistance was assessed the change of weight, ultrasonic pulse velocity (UPV) and flexural strength after 300 cycles. The use of fly ash improved the rapid chloride ion permeability and sorptivity of concrete. The best resistance to chloride ion permeability was obtained from a combination of type of class C fly ash content of 102 kg/m(3) with PC content of 332 kg/m(3). There was a remarkable reduction in the UPV after the specimens are subjected to freezing-thawing cycles. The amounts of flexural strength loss have been measured in the range of 6.70 - 29.83%. The use of type of class C fly ash positively affected freezing-thawing resistance of concrete. The Anova analysis indicated that the cement dosage has an utmost importance on the sorptivity level, chloride ion permeability and ultrasonic pulse velocity loss. Furthermore, the fly ash percentage has an utmost importance on the weight loss and flexural strength loss

Green synthesis of silver nanoparticles using Lathyrus brachypterus extract for efficient catalytic reduction of methylene blue, methyl orange, methyl red and investigation of a kinetic model

A facile, green, and an efficient method for the synthesis of AgNPs (silver nanoparticles) using Lathyrus brachypterus var. brachypterus extract is reported. AgNPs was characterized by UV-Vis, XRD, TEM and FTIR. The UV-Vis spectra of the AgNPs revealed a characteristic surface plasmon resonance peak at 452 nm. The synthesized AgNPs reacted as a heterogeneous catalyst for the reduction of dyes (methylene blue, methyl red and methyl orange) both in unary and ternary mixture (TM) with and without NaBH4 (sodium borohydride). The kinetic parameter (k) for the degradation reactions and half-life (t(1/2)) of dyes has been calculated according to Michaelis-Menten kinetics. Green synthesized of AgNPs effectively degraded the dyes at approximately 4-6 min. In addition, oxidation studies of methyl orange with H2O2 (hydrogen peroxide) have been also carried out and it has been reported that AgNPs can be reused as heterogeneous catalysts. The oxidation of MO was monitored with a UV-Vis spectrometer. AgNPs was separated using a filter paper after the oxidation of MO. The separated AgNPs were reused without important loss of its activity with a conversion efficiency of around 98%

Türkiye çövenlerinin (Gypsophila L. ve Ankyropetalum Fenzl spp.) ekonomik önemi, kullanım olanakları ve korunması üzerine düşünceler

Ülkemizde bir çok bitki ekonomik amaçlarla kullanılmaktadır. Bu makalede, Gypsophila L. ve Ankyropetalum Fenzl (Caryophyllaceae) cinslerine ait ekonomik açıdan önemli olan taksonlarının kullanım olanakları anlatılmaktadır. Bulguların bir kısmı yerel halkın tecrübelerine dayanarak geleneksel kullanımına ait olup tarafımızdan kaydedilmiş; bir kısmı da literatür bilgilerine dayanarak derlenmiştir. Gypsophila L. ve Ankyropetalum Fenzl cinslerine ait bazı türler ekonomik bakımdan oldukça önemlidir. Bu cinslerin saponin bakımından zengin ve ekonomik önemi olan taksonları halk arasında “Çöven” adıyla bilinmektedir. Bu taksonlardan tahin helvası, köpük helvası, lokum, otlu peynir ve çöven ekmeği yapımında; fabrikasyon olarak kimyasal temizleyici imalatı, yangın söndürücü imalatı, likör imalatı, sabun imalatı ve ticari saponin elde etmede yararlanılmaktadır. Tıbbi açıdan idrar söktürücü, balgam söktürücü, sivilce giderici etkileri olduğu belirtilen bu bitkiler kuyumculuk sektöründe temizleyici ve altın parlatmada amacıyla kullanılmakta ve yurt dışına ihraç edilmektedir. Bu kadar geniş kullanım alanına ve ticari öneme sahip olan bu taksonların büyük ölçüde doğadan toplanıyor olması, bu bitkiler için yok olma tehlikesini de beraberinde getirmektedir. Anahtar kelimeler: Çöven, Gypsophila L., Ankyropetalum Fenzl, Caryophyllaceae, Türkiy

Betahistin dihidroklorür kullanımı pozisyonel nistagmusu etkiler mi?

Aim: In this study, we aimed to investigate the effect of betahistine dihydrochloride (BD) use on positional nystagmus as an objective criterion for the diagnosis of benign paroxysmal positional vertigo (BPPV). Methods: The retrospective study included 59 patients (15 males, 44 females) who were aged between 18 and 80 years and referred with suspected BPPV to the otorhinolaryngology clinic of the Istanbul Training and Research Hospital. Only patients who had no central pathology on oculomotor tests were included. Of the patients included, those not using BD were classified as Group I and those using BD medication (24 mg/day) within the last 48 hours as Group II. The positional nystagmus latency, duration, and slow-phase velocity (SPV) values were compared using videonystagmography. Results: There was no significant difference between the two groups in terms of oculomotor gains (p>0.05). While there was no difference between the two groups in terms of positional nystagmus latency and SPV values, nystagmus duration was found to be significantly longer in Group II. Conclusion: Although the BD use appears to prolong the duration of nystagmus in BPPV, it does not affect the other parameters of nystagmus, including SPV, and the prolonged duration is still within normal limits. Positional nystagmus can be investigated in patients with a history of suspected BPPV and BD prescription.Amaç: Bu çalışmada betahistin dihidroklorür (BD) kullanımının benign paroksismal pozisyonel vertigo (BPPV) tanısında objektif kriter olan pozisyonel nistagmus üzerine etkisini incelemek amaçlanmıştır. Yöntem: Retrospektif çalışmamız yaşları 18–80 yıl aralığında değişen ve BPPV şüphesiyle İstanbul Eğitim ve Araştırma Hastanesi’nin kulak–burun–boğaz polikliniğine yönlendirilen 59 (15 erkek, 44 kadın) hasta içerdi. Çalışmaya yalnızca okülomotor testlerde santral patoloji görülmeyen hastalar dahil edildi. Dahil edilen hastalardan BD kullanmayanlar Grup I, son 48 saat içinde BD grubu ilaç (24 mg/gün) kullananlar ise Grup II olarak tasnif edildi. Pozisyonel nistagmus latans, süre ve yavaş faz hızı (YFH) değerleri videonistagmografi kullanılarak karşılaştırıldı. Bulgular: İki grup arasında okülomotor kazançlar bakımından anlamlı bir fark bulunmadı (p>0,05). Yine iki grup arasında pozisyonel nistagmus latans ve YFH değerleri açısından fark saptanmazken nistagmus süresi Grup II’de anlamlı olarak daha uzun bulundu. Sonuç: BD kullanımı BPPV’de pozisyonel nistagmus süresini uzatıyor gibi görünse de YFH dahil diğer nistagmus parametrelerini etkilememektedir ve süredeki uzama halen normal sınırlar içindedir. BPPV şüphesi ve BD reçeteleme öyküsü olan hastalarda pozisyonel nistagmus araştırılabilir

3-Phenyl­pyridinium tetra­chlorido­aurate(III)

In the title mol­ecular salt, (C11H10N)[AuCl4], the AuIII atom adopts an almost regular square-planar coordination geometry and the dihedral angle between the aromatic rings of the 3-phenyl­pyridinium cation is 23.1 (3)°. In the crystal, the ions inter­act by way of N—H⋯Cl and C—H⋯Cl hydrogen bonds