Bond Behavior of Near-Surface Mounted CFRP Laminate Strips under Monotonic and Cyclic Loading

Near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) laminate strips are used to increase the load-carrying capacity of concrete structures. This is done by inserting the CFRP strips into slits made in the concrete cover of the elements to be strengthened and gluing the strips to the concrete with an epoxy adhesive. In several cases the NSM technique has substantial advantages when compared with externally bonded laminates. To assess the bond behavior between the CFRP and concrete under monotonic and cyclic loading, an experimental program was carried out based on a series of pullout-bending tests. The influence of the bond length and loading history on the bond behavior was investigated. In this work the details of the tests are described and the obtained results discussed. Using the experimental data and an analytical-numerical strategy, a local bond stress-slip relationship was determined. A finite-element analysis was performed to evaluate the influence of the adhesive on the global response observed in the pullout-bending tests.     

Thin film graphite electrodes with low stress generation during Li-intercalation

We report here the development of thin film ‘graphite’ electrodes for Li-ion batteries, with near theoretical Li-intercalation/de-intercalation capacity (∼372 mAh/g). These films, synthesized by chemical vapor deposition at a relatively low temperature of 1000 °C, exhibit strong graphitic order with the basal planes oriented parallel to the Ni current collector. During galvanostatic cycling, in-situ stress measurements show that full lithiation corresponds to the development of only modest in-plane compressive stresses of ∼ −250 MPa. These stresses are more than an order of magnitude lower than expected, which should promote long cycle life.     

Extraction of Pr(III), Nd(III), and Dy(III) from HTFSA Aqueous Solution by TODGA/Phosphonium-Based Ionic Liquids

The extraction behavior of rare earth (RE) elements using N,N,N′,N′-tetraoctyl diglycolamide (TODGA) in an ionic liquid (IL) system was investigated by slope analyses. Metallic salts of Pr(III), Nd(III), and Dy(III) with bis(trifluoromethylsulfonyl)amide (TFSA) were synthesized and studied for their extraction mechanism. The selected concentration of TODGA was diluted with triethylpentylphosphonium bis(trifluoromethylsulfonyl)amide ([P₂₂₂₅][TFSA]) to prepare an extracting phase for the slope analyses. The stoichiometry of RE(III) was determined in order to estimate the extracted species. Furthermore, the complexation state of the extracted species was evaluated by spectroscopic analyses, including Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy, and ultraviolet–visible (UV–Vis) spectroscopy. The FT-IR and Raman spectra were estimated using density functional theory (DFT) calculations. Thorough analysis of the FT-IR spectrum was carried out in order to assign the TODGA group that mainly coordinated the metal ion. The solvation of the [TFSA]^? anion in the coordination sphere of [Nd(TODGA)_(2–3)]³⁺ was investigated by Raman spectroscopic analysis. The coordination ability of TODGA was investigated from the peak shift of the hypersensitive transition (⁴I_9/2→²G_7/2) in UV–Vis spectroscopic measurements. From electrochemical analysis, the extracted [Nd(TODGA)₃]³⁺ complex in [P₂₂₂₅][TFSA] was found to be reduced as per the following reaction: [Nd(TODGA)₃]³⁺ + 3e^? → Nd(0) + 3[TODGA] at ?3.0 V, and the diffusion coefficient of [Nd(TODGA)₃]³⁺ was calculated to be 1.6 × 10^?11 m² s^?1 at 373 K. The direct electrodeposition of the extracted [Nd(TODGA)₃]³⁺ in [P₂₂₂₅][TFSA] at 373 K allowed us to conclude that the middle layer of Nd electrodeposits was the metallic state, while a part of the top surface was the oxidation state by XPS analysis.     

Curaua leaf fiber (Ananas comosus var. erectifolius) reinforcing poly(lactic acid) biocomposites: Formulation and performance

Formulations of poly(lactic acid) (PLA) reinforced by curaua leaf fibers were prepared and characterized. This biocomposite has material characteristics such as biodegradability and renewability. This work aimed to develop a PLA/curaua leaf fiber composite as a sustainable biodegradable polymer composite. The PLA and composites were thermally, mechanically, and morphologically evaluated. The critical fiber length was studied to check its influence on the mechanical properties. Predictions of the Young's modulus were done to compare with the experimental data, having a reasonable agreement. The Young's modulus increased above 70%, and the impact strength increased 20% compared with the pure PLA. Thermal analysis showed that formulations with up to 20% by weight of fibers were more thermally stable. The fiber modified the crystallinity of the PLA matrix. The best overall balance of properties was attained in composites containing 15% curaua fiber. POLYM. COMPOS., 36:1520–1530, 2015. © 2014 Society of Plastics Engineers     

The adsorption of basic dyes by poly(styrene sulphonate)

The adsorption of basic dyes (Safranine, Neutral Red, Acridine Orange and Proflavine) on poly(styrene sulphonate) has been studied by measuring the amount of free dye in solution using a photochemical method. Adsorption free energies are in the range 7.1–5.3 kcal/mol. Comparing the values of these energies as a function of the structure of the dyes, three different types of interactions can be postulated to contribute to the binding of the dyes to the polymer, viz., electrostatic (c. 4 kcal/mol), hydrophobic and charge-transfer.     

Contributions of Turkish academicians supervising PhD dissertations and their universities to economics: an evaluation of the 1990–2011 period

In this study, doctoral dissertations conducted at the Turkish Universities for the period of 1990–2011 and the scientifically indexed publications of the professors supervising these dissertations were investigated. In the evaluations, the publications scores of the Google Scholar, Web of Science, and Scopus as well as the citations belonging to the publications in these indexes were included. During the relevant period, 617 professors supervised all the 1,906 doctoral dissertations in the field of economics. The first three universities with the highest number of doctoral dissertations were determined to be Istanbul University, Marmara University, and Dokuz Eylül University whereas the first three universities with the highest scientific indexes were Ihsan Do?ramaci Bilkent University, Middle East Technical University, and Bo?aziçi University. The academicians of the last three universities also outperformed those at the other universities regarding the scientific publications they produced and the citations they received. Overall, there is a low correlation between the dissertations conducted and scientific citations. Finally, academicians with publications and/or citations in Web of Science or Scopus were researched further via logistic regressions. The results indicate that there is positive and meaningful relation with PhD degrees earned abroad and number of publication in the Web of Science.     

Adsorption of Pb(II) ions from aqueous solutions by carbon nanotubes oxidized different methods

This study investigated the heavy metal adsorption of the carbon nanotubes (CNTs) oxidized different methods. Besides the conventional ultrasonication method, the UV-light used as an oxidation agent. The two oxidation methods compared with each other by Pb(II) adsorption. The characterizations of oxidized CNTs were analyzed by FTIR, XRD, DTG, SEM and total acidity capacity analysis. The adsorption capacities of carbon nanotubes were compared with using Langmuir and Freundlich isotherms. Two different kinetic theories were applied to experimental data. These theories are pseudo-second order and intra-particle diffusion models. The adsorption results can be compared using non-linear Langmuir isotherm parameters. For single wall carbon nanotubes (SWCNTs), theoretical adsorption capacity value (Q_m) of UV-light method is 511.99 mg/g and ultrasonication method is 342.36 mg/g. The UV-light increased the surface acidity of the carbon nanotubes more than ultrasonication. After the adsorption experiments, it is apparently seen that the UV-light oxidation method is a useful method for heavy metal adsorption.     

Complement C4 Is Reduced in iPSC-Derived Astrocytes of Autism Spectrum Disorder Subjects

In recent years, accumulating evidence has shown that the innate immune complement system is involved in several aspects of normal brain development and in neurodevelopmental disorders, including autism spectrum disorder (ASD). Although abnormal expression of complement components was observed in post-mortem brain samples from individuals with ASD, little is known about the expression patterns of complement molecules in distinct cell types in the developing autistic brain. In the present study, we characterized the mRNA and protein expression profiles of a wide range of complement system components, receptors and regulators in induced pluripotent stem cell (iPSC)-derived neural progenitor cells, neurons and astrocytes of individuals with ASD and neurotypical controls, which constitute in vitro cellular models that recapitulate certain features of both human brain development and ASD pathophysiology. We observed that all the analyzed cell lines constitutively express several key complement molecules. Interestingly, using different quantification strategies, we found that complement C4 mRNA and protein are expressed in significantly lower levels by astrocytes derived from ASD individuals compared to control astrocytes. As astrocytes participate in synapse elimination, and diminished C4 levels have been linked to defective synaptic pruning, our findings may contribute to an increased understanding of the atypically enhanced brain connectivity in ASD.