Aysen Yilmaz

An Overview on Preparation and TL Characterization of Lithium Borates for Dosimetric Use

Boron that appears in borate form in nature is an essential additive to a variety of industrial products. Recently, certain boron compounds have attracted attention in high technology utilization areas owing to their special crystal and optical characteristics. Thermoluminescent (TL) dosimetry that is used to record amount of radiation exposure is one of such areas. Two borates searched for candidacy in TL dosimetry are lithium tetraborate and lithium triborate. These materials are synthesized and metal doped by numerous researchers to be tested for thermoluminescence response. Lithium tetraborate has aroused interest of scientists since 1960s by the courtesy of the thermoluminescence (TL) property. However, lithium triborate is rather new in this area. This study compromises a broad overview including synthesis methods employed for the production of these two materials. Furthermore, the TL properties that have significant effect on the TL dosimetry potential of a compound are noted along with the detailed information on TL measurement procedure specifications.

An integrated process for partial oxidation of alkanes

The partial oxidation of alkanes via bromination followed by the reaction with solid metal oxide mixtures (MO) is shown to give an array of products that can be tuned by varying the MO and the reaction conditions.

Synthesis and thermoluminescence properties of rare earth oxides (Y, Ce-Lu) doped lithium triborate

Abstract Lithium triborate (LiB 3 O 5 ) was synthesized by high temperature solid-state reaction method, and then rare earth oxides were doped into LiB 3 O 5 to enhance its thermoluminescent (TL) properties. The identification and characteristics of the obtained compounds were determined by X-ray diffraction (XRD), Fourier transform infrared (FTIR) analyses, differential thermal analyses (DTA) and scanning electron microscopy (SEM). The glow curves were obtained using a thermoluminescent (TL) reader. The results revealed that all the rare earth oxides were not good activators for lithium triborate and the obtained compounds could not be used for dosimetric applications.

A van der Waals density functional investigation of carboranethiol self-assembled monolayers on Au(111)

Isolated and full monolayer adsorption of various carboranethiol (C2B10H12S) isomers on the gold(111) surface has been investigated using both the standard and van der Waals density functional theory calculations. The effect of different molecular dipole moment orientations on the low energy adlayer geometries, the binding characteristics and the electronic properties of the self-assembled monolayers of these isomers has been studied. Specifically, the binding energy and work function changes associated with different molecules show a correlation with their dipole moments. The adsorption is favored for the isomers with dipole moments parallel to the surface. Of the two possible unit cell structures, (5 × 5) was found to be more stable than .

Investigation of neutron sensitivity of un-doped and Dy-doped CaB 4 O 7 for thermoluminescence applications

In this study, thermoluminescence characteristics of un-doped and Dy-doped calcium tetraborate (CaB4O7) compounds are reported. The polycrystalline powder samples of un-doped and Dy-doped CaB4O7 were prepared by a solid-state reaction at high-temperature method. The identification and characteristics of the obtained compounds were determined by X-ray diffraction, Fourier transform infrared analysis, differential thermal analysis, thermogravimetric analysis, and scanning electron microscopy. The glow curves were obtained using a thermoluminescent reader. Neutron sensitivity, dose–response, and heating rate of CaB4O7 compounds were determined by using a bare 252Cf mixed neutron + gamma (n + γ) source, and dose response results are compared to those of Harshaw TLD-600 and TLD-700 neutron dosimeters (6LiF:Mg,Ti and 7LiF:Mg,Ti). The sensitivity of CaB4O7:Dy (0.5%) sample is approximately 4.35 and 3.36 times higher than that of TLD-600 and TLD-700, respectively.

Assessing different sources of uncertainty in hydrological projections of high and low flows: case study for Omerli Basin, Istanbul, Turkey

This study investigates the assessment of uncertainty contribution in projected changes of high and low flows from parameterization of a hydrological model and inputs of ensemble regional climate models (RCM). An ensemble of climate projections including 15 global circulation model (GCM)/RCM combinations and two bias corrections (change factor (CF) and bias correction in mean (BC)) was used to generate streamflow series for a reference and future period using the Hydrologiska Byråns Vattenbalansavdelning (HBV) model with the 25 best-fit parameter sets based on four objective functions. The occurrence time of high flows is also assessed through seasonality index calculation. Results indicated that the inputs of hydrological model from ensemble climate models accounts for greater contribution to the uncertainty related to projected changes in high flows comparing to the contribution from hydrological model parameterization. However, the uncertainty contribution is opposite for low flows, particularly for CF method. Both CF and BC increases the total mean variance of high and low flows. The variability in the occurrence time of high flows through RCMs is greater than the variability resulted from hydrological model parameters with and without statistical downscaling. The CF provides more accurate timing than BC and it shows the most pronounced changes in flood seasonality.