The relaxation of the structure of RADP in an electric field

X-ray scattering measurements have been made to study the behaviour of the ferroelectric glass of Rb_1–x(NH₄)_xH₂PO₄ withx0.22 in the presence of an electric field. The results showed that the system has very long relaxation times, characteristic of competing interactions. The change in the intensity of the x-ray scattering from the incommensurate modulation and the ferroelectric phase have a roughly linear relationship with time.     

The Condensation Phase Transition in Random Graph Coloring

Based on a non-rigorous formalism called the “cavity method”, physicists have put forward intriguing predictions on phase transitions in diluted mean-field models, in which the geometry of interactions is induced by a sparse random graph or hypergraph. One example of such a model is the graph coloring problem on the Erd?s–Renyi random graph G(n, d/n), which can be viewed as the zero temperature case of the Potts antiferromagnet. The cavity method predicts that in addition to the k-colorability phase transition studied intensively in combinatorics, there exists a second phase transition called the condensation phase transition (Krzakala et al. in Proc Natl Acad Sci 104:10318–10323, 2007). In fact, there is a conjecture as to the precise location of this phase transition in terms of a certain distributional fixed point problem. In this paper we prove this conjecture for k exceeding a certain constant k₀.     

Synthesis of modified multi-walled carbon nanotube poly(benzimidazole-imide) composites: assessment of morphological and thermo-mechanical properties

A fully aromatic poly(benzimidazole-imide) (PBI) containing triazole side units and amine-modified multi-wall carbon nanotube (MWCNT)/PBI composites were fabricated via a polymerization process of monomer reactants and solution mixing with ultrasonication excitation. The polymer and composites were characterized by field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. According to the microscopic characterizations, the MWCNTs homogeneously dispersed in the composites. The mechanical properties of the composite films were also measured by tensile test. The test results evidently indicated that the Young’s modulus increased by about 60.0% at 1 wt% CNT loading, and further modulus growth was observed at higher filler loading. The composite films hold preferable thermal stability the same as the pure PBI. The improvement of the mechanical and thermal properties was attributed to the incorporation of the surface modified CNTs. For CNT-reinforced polymer composites, strong interfacial adhesion and uniform dispersion of CNTs are more crucial factors for improving such properties.     

Simple chromatogaphic method for the separation and estimation of gibberellic acid in crude products

Summary The estimation of gibberellic acid by a direct spectrophotometric method is described. For the separation a paper-chromatographic technique is used with a modified solvent and with a colour reaction of alkaline permanganate. Comparative data proved that the new method is superior to other techniques and can be applied to pure gibberellic acid or crude preparations as no interference occurs after chromatographic separation.

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Zusammenfassung Zur Bestimmung der Gibberellinsäure wird eine spektralphotometrische Methode angegeben. Dabei wird zunächst papierchromatographisch abgetrennt und dann eine Farbreaktion mit alkalischem Permanganat ausgewertet. Die Methode, die früheren überlegen ist, kann zur Bestimmung von Gibberellinsäure in reinen Produkten sowie in Rohprodukten verwendet werden.

     

Röntgenographische Kristallstrukturbestimmung des Additionsproduktes von Fluorsulfonylisocyanat an Tetraschwefeltetranitrid (S4N4 · FSO2NCO)

X-Ray Structure Analysis of the Addition Product of Fluorosulfonylisocyanate and Tetrasulfurtetranitride (S₄N₄ · FSO₂NCO) In order to determine the structure of the addition product of tetrasulfurtetranitride with fluorosulfonylisocyanate an X-ray structure analysis was performed. The structure analysis shows a nucleophilic attack of a nitrogen atom of the S₄N₄ ring at the carbonyl carbon atom of the isocyanate forming an N? C single bond. The dipolar compound is very similar to the structures of S₄N₄ · SO₃, S₄N₄ · BF₃ and S₄N₄ · SbCl₅. The conformation of the S₄N₄ ring deviates significantly from a planar environment. The packing of the molecules int the crystal structure of the triclinic space group P1 is comparable with the arrangement of molecules in the crystal structure of S₄N₄ · SO₃.     

Chemical constituents of Genista numidica Spach aerial parts and their antimicrobial,antioxidant and antityrosinase activities

A previously undescribed triterpenoid saponin, 3-O-[α-l-rhamnopyranosyl-(1→2)-{β-d-glucopyranosyl-(1→6)-}β-d-galactopyranosyl-(1→2)-β-d-glucuronopyranosyl]-sophoradiol (1), in addition to twenty-nine known constituents (2–30) were isolated from the aerial parts of Genista numidica Spach. Structures elucidation was performed by comprehensive 1D- and 2D-NMR analyses and HRESIMS. The extracts, fractions and isolated compounds were evaluated for their antibacterial, antioxidant and tyrosinase inhibitory activities. The experimental findings indicated that genistin (16), isosalipurpol (27), and koaburaside (29) have moderate to low antibacterial activity against E. faecalis, S. aureus, S. epidermidis and P. aeruginosa bacteria with MICs ranging from 31.2 to 125 μg/mL. Compounds 19 and 27 exhibited a good antiradical activity potential (IC₅₀ 11.8 and 11.1 μg/mL, respectively). Only compounds 23, 27 and 28 exhibited low inhibitory effect against mushroom tyrosinase (IC₅₀ from 90.2 to 225.6 μg/mL).     

PVC-supported ethylenediamine-copper(II) complex: a heterogeneous,efficient, and eco-friendly catalyst for multi-component synthesis of 1,2,3-triazoles by reaction of propargyl bromide,aromatic azides,and amines in water

Research on Chemical Intermediates - The PVC-supported ethylenediamine-copper(II) complex (PVC–EDA–Cu+2) has provided a highly efficient, active, and reusable heterogeneous catalyst for...     

Exploring in house glutamate inhibitors of matrix metalloproteinase-2 through validated robust chemico-biological quantitative approaches

Structural Chemistry - Matrix metalloproteinase-2 (MMP-2) is established as one of the most important metalloenzymes for targeting cancer. However, homologous MMP-9 of the gelatinase family is...