Thermoelectric properties of stannite-phase CuZn2AS4 (CZAS; A=Al,Ga and In) nanocrystals for solar energy conversion applications

The current study aimed to comprehensively investigate structural, electronic, optical and transport properties of quaternary semiconductor CuZn₂AS₄ (CZAS; A=Al, Ga and In) nanocrystals (NCs). Based on energy considerations, the stannite structure (I-42m; No. 121) is found to be more stable than the kesterite (I-4; No.82) and wurtzite (P6₃mc; No.186) type structures. By means of hybrid functional calculations, these nanocrystals have direct band gap of 0.81–1.71 eV with a high absorption coefficient of >10⁴ cm^?1, which are well-suited for use in solar energy-conversion applications. Some of the latest advances in applications of these nanocrystals in thermoelectric applications are also highlighted in the current study. It is observed that transport coefficients of these materials are found to be nearly direction independent and isotropic. All three samples are p-type conductors at room temperature. Especially, the Seebeck coefficient of CuZn₂AlS₄ is even larger than that of CuZn₂GaS₄ and CuZn₂InS₄ under the studied carrier concentration and temperature region. The maximum figure of merit (ZT) reaches 0.982 (0.977), 0.984 (0.974) and 0.53 (0.955) for p-type (n-type) CuZn₂AlS₄, CuZn₂GaS₄, and CuZn₂InS₄, respectively, at 300 K. The high Seebeck coefficients, high figure of merit and low thermal conductivities make these systems good candidates for high-efficiency thermoelectric conversion applications.     

Corrigendum to: on the inheritance of the strongly π-extending property

In this corrigendum, we provide correct versions of Theorem 2.8 and Corollary 3.2, retract two consequences of the previous form of the Theorem 2.8. To this end, the main results of the article remain after the aforementioned changes.     

Comparison of Penta and Tetra-pyridyl Cobalt-based Catalysts for Water Reduction: H2 Production Cycle,Solvent Response and Reduction Free Energy

Understanding water reduction towards H₂ generation is crucial to overcome today's renewable energy obstacles. Previous studies have shown the superior H₂ production performances of Cobalt based penta-pyridyl (CoaPPy) and tetra-pyridyl (CoaTPy) complexes in solution. We investigate H₂ production cycles of CoaPPy and CoaTPy complexes immersed in water solution by means of Ab-initio Molecular Dynamics and Density Functional Theory. We monitor dynamic properties of the systems, solvent response and structural changes occurring in the catalysts, by simulating all intermediate steps of the H₂ production cycle. Reduction free energies and reorganization energies are calculated. Our results show that, following the first electron injection, H₂ production proceeds with the singlet spin state. Following the first electron insertion, we observe a significant rearrangement of the hydrogen bonding network in the first solvation shell. The cobalt center turns out to be more accessible for the surrounding water molecules in the case of CoaTPy at all the intermediate steps, which explains its higher catalytic performance over CoaPPy. Following the first reduction reaction, a larger gain in reduction free energy is estimated for CoaTPy with respect to CoaPPy, with a difference of 0.14 eV, in line with the experiments. For the second reduction, instead, CoaPPy shows more negative reduction potential, by 0.41 eV.     

Radiation induced copolymerization reactivity of different allyl monomers with styrene

Radiation induced copolymerizations of electron donating such as allyl phenol (AP) and electron withdrawing such as allyl isothiocyanate (AITC) monomers with styrene (Sty) as a comonomer were studied in order to correlate the electronic behavior with copolymerization yield and molecular weight. The allyl monomers and comonomer were mixed in the same mol ratios under Ar atmosphere and copolymerized by using gamma radiation in various absorbed doses (55, 110, 165 kGy) obtained from a Co-60 source. Poly(AP-co-Sty), and poly(AITC-co-Sty) could have been prepared at all of the absorbed doses. The maximum copolymerization yields were calculated as a 16.35 and 6.52 percent for poly(AP-co-Sty) and poly(AITC-co-Sty), respectively. The molecular weights of poly(AP-co-Sty) copolymers are found to be higher in comparison to those of poly(AITC-co-Sty). Both results indicate that, under the same irradiation conditions, AP is more reactive on styrene than AITC is. Thus, the monomers having electron withdrawing (EW) substituents attached to allyl group may result in better copolymerization yield and molecular weight than those with electron donating (ED) substituents. Thermal stabilities of the poly(AP-co-Sty) copolymers are also higher than those of poly(AITC-co-Sty).     

Protonated Dipeptide Losses from b 5 and b 4 Ions of Side Chain Hydroxyl Group Containing Pentapeptides

In this study, C-terminal protonated dipeptide eliminations were reported for both b ₅ and b ₄ ions of side chain hydroxyl group (–OH) containing pentapeptides. The study utilized the model C-terminal amidated pentapeptides having sequences of XGGFL and AXVYI, where X represents serine (S), threonine (T), glutamic acid (E), aspartic acid (D), or tyrosine (Y) residue. Upon low-energy collision-induced dissociation (CID) of XGGFL (where X?=?S, T, E, D, and Y) model peptide series, the ions at m/z 279 and 223 were observed as common fragments in all b ₅ and b ₄ ion (except b ₄ ion of YGGFL) mass spectra, respectively. By contrast, peptides, namely S_MeGGFL-NH₂ and E_OMeGGFL-NH₂, did not show either the ion at m/z 279 or the ion at m/z 223. It is shown that the side chain hydroxyl group is required for the possible mechanism to take place that furnishes the protonated dipeptide loss from b ₅ and b ₄ ions. In addition, the ions at m/z 295 and 281 were detected as common fragments in all b ₅ and b ₄ ion (except b ₄ ion of AYVYI) mass spectra, respectively, for AXVYI model peptide series. The MS⁴ experiments exhibited that the fragment ions at m/z 279, 223, 295, and 281 entirely reflect the same fragmentation behavior of [M?+?H]⁺ ion generated from commercial dipeptides FL-OH, GF-OH, YI-OH, and VY-OH. These novel eliminations reported here for b ₅ and b ₄ ions can be useful in assigning the correct and reliable peptide sequences for high-throughput proteomic studies.

Non-Direct Sequence Ions in the Tandem Mass Spectrometry of Protonated Peptide Amides—an Energy-Resolved Study

The fragmentation reactions of the MH⁺ ions of Leu-enkephalin amide and a variety of heptapeptide amides have been studied in detail as a function of collision energy using a QqToF beam type mass spectrometer. The initial fragmentation of the protonated amides involves primarily formation of b_n ions, including significant loss of NH₃ from the MH⁺ ions. Further fragmentation of these b_n ions occurs following macrocyclization/ring opening leading in many cases to b_n ions with permuted sequences and, thus, to formation of non-direct sequence ions. The importance of these non-direct sequence ions increases markedly with increasing collision energy, making peptide sequence determination difficult, if not impossible, at higher collision energies.

Determination of radiological hazard parameters and radioactivity concentrations in bauxite samples: the case of the Sutlegen Mine Region (Antalya,Turkey)

Journal of Radioanalytical and Nuclear Chemistry - Iron phosphate glasses with melting temperatures of?~?1300 °C were developed to immobilize spent nuclear fuels. The...     

Measurements of radon concentration in drinking water samples from Kastamonu (Turkey)

Concentration of (222)Rn was determined in selected natural spring and tap water samples collected during spring and summer seasons from Kastamonu, Turkey. The aim of this work was to produce a map of the radon concentrations in water sources of the province and to determine any potential radiological risk for the local population. Radon measurements were performed by an AlphaGUARD radon gas analyser. The average radon concentrations were found to vary from 0.39±0.02 to 12.73±0.39?Bq?l(-1) for natural springs and from 0.36±0.04 to 9.29±0.45?Bq?l(-1) for tap water in spring, from 0.50±0.09 to 19.21±1.00?Bq?l(-1) for natural springs and from 0.31±0.03 to 13.14±0.38?Bq?l(-1) for tap water in summer. Furthermore, the results are compared with international recommendations and concentrations reported for other countries. Doses resulting from the consumption of these waters were calculated. The effective dose equivalents due to the intake of the (222)Rn present in these waters are expected to range from 0.93 to 32.54?μSv?y(-1) in summer and from 0.80 to 49.09?μSv?y(-1) in spring.     

On the inheritance of the strongly π-extending property

In this article, we focus on modules with the property that every projection invariant submodule is essential in a fully invariant direct summand. In contrast to π-extending condition, it is shown that the former property is inherited by direct summands and Morita invariant. An application of our results yields that the endomorphism ring of a free module enjoys the property. Moreover, we characterize generalized triangular matrix rings with the aforementioned property and apply to somewhat special cases.     

Two-dimensional transient dynamic response of orthotropic layered media

In this study, two-dimensional transient dynamic response of orthotropic plane layered media is investigated. The plane multilayered media consist of N different generally orthotropic, homogeneous and linearly elastic layers with different ply angles. In the generally orthotropic layer, representing a ply reinforced by unidirectional fibers with an arbitrary orientation angle, the principal material directions do not coincide with body coordinate axes. The solution is obtained by employing a numerical technique which combines the use of Fourier transform with the method of characteristics. The numerical results are displayed in curves denoting the variations of stress and displacement components with time at different locations. These curves clearly reveal, in wave profiles, the scattering effects caused by the reflections and refractions of waves at the boundaries and at the interfaces of the layers, and also the effects of anisotropy caused by fiber orientation angle. The curves properly predict the sharp variations in the response at the neighborhood of the wave fronts, which shows the power of the numerical technique employed in the study. By suitably adjusting the elastic constants, the results for multilayered media with transversely isotropic layers, or layers with cubic symmetry, or isotropic layers can easily be obtained from the general formulation. Furthermore, solutions for some special cases, including Lamb’s problem for an elastic half-space, are obtained and compared with the available solutions in the literature and very good agreement is found. Preliminary version presented at the Second International Congress on Mechatronics (MECH2K3), Graz, Austria, July 14-17, 2003.