Control of near-field radiative heat transfer via surface phonon–polariton coupling in thin films

The possibility of controlling near-field radiative heat transfer with the use of silicon carbide thin films supporting surface phonon–polaritons in the infrared spectrum is explored. For this purpose, the local density of electromagnetic states is calculated and analyzed within the nanometric gap formed between two SiC films as well as the radiative heat flux exchanged between the thin layers.     

Performance of birnessite-type manganese oxide in the thermal-catalytic degradation of polyamide 6

Birnessite-type manganese oxide (BMO) was prepared by oxidation of Mn(NO₃)₂ with H₂O₂ in KOH solution. The nature and the extent of degradation of polyamide 6 (PA6) in the presence of samples were analysed by thermogravimetric analysis under static air atmosphere at several heating rates between 5 and 30 °C min^?1. The surface and structure of BMO were characterized using infrared (IR) spectroscopy, X-ray diffraction, and thermal analysis techniques. The acid sites of BMO were investigated by IR using pyridine as a molecular probe. The activation energy for degradation estimated by Kissinger method for PA6 and BMO/PA6 system containing 10 mass% of BMO was found to be 212 and 144 kJ mol^?1 under air, respectively. The catalytic activity observed in BMP catalyst was associated to a high lattice oxygen mobility.     

Synthesis of ferrocenyl pyrazoles by the reaction of 3-ferrocenylpropynal with hydrazinium salts

Synthesis of ferrocenyl-substituted pyrazoles via the reaction between 3-ferrocenylpropynal and hydrazinium salts is described. Depending upon the substitution pattern of hydrazine derivative, the reaction affords 1-alkyl/aryl-5-ferrocenylpyrazoles and/or 1-alkyl/aryl-3-ferrocenylpyrazoles. Structures of 5-ferrocenyl-1-phenyl-1H-pyrazole, 1-benzyl-5-ferrocenyl-1H-pyrazole and 2-(3-ferrocenylpyrazol-1-yl)ethanol were identified by X-ray crystallography.     

Diiodinated Mono- and Dipyridylvinyl BODIPY Dyes: Photophysicochemical Properties,in vitro Antibacterial Studies,Molecular Docking and Theoretical Calculations

In this study, novel mono- and dipyridylvinyl boron dipyrromethene dyes are prepared to compare their photodynamic antimicrobial chemotherapy (PACT) activities against Staphylococcus aureus to the corresponding core dyes. Pyridylvinyl substitution at the 3- or 3,5-positions of a meso-4-bromophenylBODIPY core dye via a Knoevenagel reaction with an aromatic 2-bromopyridinecarboxaldehyde shifts the major BODIPY spectral band to longer wavelength. The extended π-conjugation red shifts the main spectral band into the 602–618 nm region in CHCl₃, THF, ethanol and DMSO after monopyridylvinyl substitution and to 685–704 nm after dipyridylvinyl substitution. An enhancement of the population of the T₁ state through the incorporation of iodine atoms at the 2,6-positions results in moderately high singlet oxygen quantum yields in DMSO. The π-extended dyes were found to have significantly lower PACT activities than the diiodinated core dye.     

Metal-organic framework functionalized with deep eutectic solvent for solid-phase extraction of Rhodamine 6G in water and cosmetic products

An NH₂-MIL-53(Al)-DES(ChCl-Urea) nanocomposite was synthesized for extraction and determination of Rhodamine (Rh) 6G from environmental and cosmetic samples. The deep eutectic solvent (DES) was prepared by mixing choline chloride and urea in a mole ratio of 1:2. NH₂-MIL-53(Al)-DES(ChCl-Urea) nanocomposite was synthesized using the impregnation method at a ratio of 60:40 (w/w). The optimum conditions were determined after NH₂-MIL-53(Al)-DES(ChCl-Urea) characterization was performed. The optimum conditions were determined as pH 8, adsorbent amount of 15 mg, total adsorption-desorption time of 6 min, and enrichment factor of 20. The recovery values of the solid-phase extraction method for water and cosmetic samples under optimum conditions were between 95% and 106%. NH₂-MIL-53(Al)-DES(ChCl-Urea) nanocomposite was an economically advantageous adsorbent because of its reusability of 15 times. All analyses were performed using the ultraviolet-visible spectrophotometer. The linear range, limit of detection, and limit of quantification of the method were 100–1000, 9.80, and 32.68 μg/L, respectively. The obtained results showed that the synthesized nanocomposite is a suitable adsorbent for the determination of Rh 6G in water and cosmetic samples. The real sample applications were verified with the high-performance liquid chromatography system.     

The effects of top management team composition on SME export performance: an upper echelons perspective

Survival of small and medium-sized enterprises (SMEs) increasingly depends on their ability to exploit opportunities in foreign markets. Given their limited resources, exporting is one of the most viable modes of entry into foreign markets for SMEs. The present study is an attempt to contribute to the research that identifies the factors associated with SME export performance. Specifically, the association between top management team demographic composition and SME export performance was examined in an emerging market context and drawing from upper echelons perspective. Focusing on such commonly examined upper echelons attributes as age, education level, and tenure, the present research assessed whether top management team composition distinguished between SMEs in terms of their export levels. Data were collected from 128 SMEs operating in Ankara and Bursa regions of Turkey. Results obtained by a hierarchical regression analysis indicated that SMEs with lower mean industry tenure and higher age separation diversity had higher levels of export performance.     

Monitoring radiation induced alterations in biological systems,from molecules to tissues,through infrared spectroscopy

Humans can be exposed to non-ionizing and ionizing radiation for diagnostic, therapeutic, accidental, and occupational reasons. Consequently, the effect of radiation on biological systems has attracted the attention of researchers for a rather long time. This review is about the mid-infrared Fourier Transform Infrared (FTIR) spectroscopic characterization of non-ionizing and ionizing radiation-induced changes in DNA, lipids, and proteins, as isolated or synthetic macromolecules, and in biological membranes, cells, and tissues. Here, the context of radiation was limited with electromagnetic radiation including gamma rays. The review first outlines introductory information about non-ionizing and ionizing radiation and their interaction with biological systems. Afterwards, FTIR spectroscopy and spectroscopic analysis are briefly discussed. Finally, FTIR spectroscopic analysis of DNA, lipids, proteins, membranes, cells, and tissues that were exposed to radiation are presented. The findings show that FTIR spectroscopy can be successfully used as a novel method to monitor radiation-induced alteratios in biological systems.     

Influence of halogen substituents on the self-assembly of oligothiophenes--a combined STM and theoretical approach

Iodinated quaterthiophenes 2-3 have been synthesized and their self-assembling behavior investigated at the liquid-solid interface by means of high-resolution scanning tunneling microscopy in comparison to parent oligothiophene 1. All three compounds spontaneously give well-ordered 2D crystalline monolayers at the graphite surface and order in a lamella-type arrangement of the conjugated backbones concomitant with an interlocking of the alkyl side chains. Symmetrically substituted oligothiophenes 1 and 3 without a relevant dipole moment self-assemble in a similar fashion, exhibiting comparable unit cells, whereas monoiodo derivative 2 arranges as pairs along the lamella axis due to the presence of a permanent dipole moment induced by the polarizable halogen group. Corroborated by quantum chemical calculations, novel head-to-head (iodo-iodo) intermolecular interactions were found to take place for this unsymmetrical derivative. The investigation of mixed solutions clearly reveals that at the solid-liquid interface a homogeneous layer of this compound is formed, which comprises the highest packing density leading to a separation process at the interface.     

Minimal split completions

We study the problem of adding an inclusion minimal set of edges to a given arbitrary graph so that the resulting graph is a split graph, called a minimal split completion of the input graph. Minimal completions of arbitrary graphs into chordal and interval graphs have been studied previously, and new results have been added recently. We extend these previous results to split graphs by giving a linear-time algorithm for computing minimal split completions. We also give two characterizations of minimal split completions, which lead to a linear time algorithm for extracting a minimal split completion from any given split completion.We prove new properties of split graph that are both useful for our algorithms and interesting on their own. First, we present a new way of partitioning the vertices of a split graph uniquely into three subsets. Second, we prove that split graphs have the following property: given two split graphs on the same vertex set where one is a subgraph of the other, there is a sequence of edges that can be removed from the larger to obtain the smaller such that after each edge removal the modified graph is split.     

Uncovering a CF3 Effect on X-ray Absorption Energies of [Cu(CF3)4]− and Related Copper Compounds by Using Resonant Diffraction Anomalous Fine Structure (DAFS) Measurements**

Understanding the electronic structures of high-valent metal complexes aids the advancement of metal-catalyzed cross coupling methodologies. A prototypical complex with formally high valency is [Cu(CF₃)₄]⁻ ( 1 ), which has a formal Cu(III) oxidation state but whose physical analysis has led some to a Cu(I) assignment in an inverted ligand field model. Recent examinations of 1 by X-ray spectroscopies have led previous authors to contradictory conclusions, motivating the re-examination of its X-ray absorption profile here by a complementary method, resonant diffraction anomalous fine structure (DAFS). From analysis of DAFS measurements for a series of seven mononuclear Cu complexes including 1 , here it is shown that there is a systematic trifluoromethyl effect on X-ray absorption that blue shifts the resonant Cu K-edge energy by 2–3 eV per CF₃, completely accounting for observed changes in DAFS profiles between formally Cu(III) complexes like 1 and formally Cu(I) complexes like (Ph₃P)₃CuCF₃ ( 3 ). Thus, in agreement with the inverted ligand field model, the data presented herein imply that 1 is best described as containing a Cu(I) ion with dⁿ count approaching 10.