Synthesis of cyclic norspermidine derivative of protohemin IX

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Quantum chemical calculations of hydration electrostatics and electrochemical oxidation potential of cyclic nitroxide radicals

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Hierarchical structure of SERS substrates possessing the silver ring morphology

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New nanomolar negative modulators of AMPA receptors

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A novel clipping technique for filtering FM signals embedded in intensive noise

A novel adaptive clipping technique for filtering a constant amplitude frequency modulated (FM) signal embedded in non-Gaussian noise is proposed. It is based on the analysis and processing of the estimate of probability density function of a FM signal realization. As a result, modifications of two robust estimators of FM signal amplitude are proposed. It is shown that these estimators can be used for Gaussian and non-Gaussian heavy-tail environments. The proposed clipping technique can exploit one or another obtained robust estimate of the signal amplitude for adaptive setting a threshold. Analysis of signal estimate accuracy for different noise environments is carried out. Comparative analysis of the obtained methods and known approaches based on scanning window nonlinear filtering and optimal robust L-DFT form is performed. It is demonstrated that the usage of clipping-based technique leads to the considerable improvement of the FM signal filtering efficiency in comparison to the aforementioned known approaches for different noise environments and a wide range of input SNR values.     

Ultrastructure of the Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) midgut

The insect midgut has ultimately been the focus of researches tempting to control insect pests because alterations in the insect gut may affect not only its development, but also physiological events such as nutrient absorption and transformation. The objective of the present work was to describe morphologically, histochemically, and ultrastructurally the larva midgut of Alabama argillacea (Hübner) (Lepidoptera: Noctuidae), a cotton key pest in Brazil. Light and electronic transmission microscopy was used to obtain images from midgut sections of late fourth-instar larvae of A. argillacea. In general, the morphology, histochemistry, and ultrastructure characteristics of A. argillacea midgut follow that described in the literature for other lepidopteran species. However, the results showed a mitochondrial polymorphism and branched microvilli, which suggest an ultrastrucutural and physiological modification possibly associated with a high absorption and secretion activity by the columnar cells of this species. This intense activity may favor a faster response related to the action of ingested microbial agents and/or toxins, and can explain the high susceptibility of A. argillacea to the agents of control such as the toxin of Bacillus thuringiensis.     

Synthesis and Spatial Structure of the Derivatives of 2,5-Dioxo-3,3-Bis(Trifluoromethyl)-6,7-Benzo-1,4,2-and 2,5-Dioxo-4,4-Bis(Trifluoromethyl)-6,7-Benzo-1,3,2-Oxazaphosphepines

Abstract

Hexafluoroacetone imine easily interacts with compounds (I, R = OMe, OCH₂CF₂CHF₂, NEt₂, Ph) in two directions unlike hexafluoroacttone and gives 1,4,2-oxazaphosphepines (II) (pathway I) or 1,3,2-oxszaphosphepines (III) (pathway 2). The compound (II) (R = NEt₂) lightly hydrolyzes to yield the salt (IV). The structure of heterocycles II-IV) has been confirmed by X-ray analysis (see fig. I, II, R = OMe; fig. 2, IV). The detail structural peculiarities of the compounds am discussed.     

Phosphate anion chelation and base-pairing. Design of receptors and carriers for nucleotides and nucleotide analogues

Abstract

A rational approach to the development of effective carriers for the through-membrane transport of GMP (guanosine 5′-monophosphate) at neutral pH is described. The approach detailed is a ditopic one predicated on the use of nucleic acid-base ‘nucleobase’ subunits to provide stabilizing hydrogen bonding interactions and the use of expanded porphyrin anion binding subunits to provide phosphate chelation. Appropriate background studies along with the synthesis of a functioning state-of-the-art system are reported. In addition, the reasons for preparing such GMP transport systems are presented in full.