Synthesis of 2,6-disubstituted piperidine alkaloids from ladybird beetles Calvia 10-guttata and Calvia 14-guttata

Optically pure (+)-calvine, (+)-2-epicalvine, (2S,6S)-(6-pentylpiperidin-2-yl)acetic acid methyl ester and (2R,6S)-(6-pentylpiperidin-2-yl)acetic acid methyl ester, four piperidine alkaloids isolated from ladybird beetles of the genus Calvia (Coccinellidae), were synthesised from a common precursor using cyclisative Pd(II)/Cu(II)-catalysed carboamination-(methoxy)carbonylation tandem reaction of alkenylamines as a key step. The first single-crystal X-ray analysis of (+)-calvine confirmed its proposed absolute configuration to be (2S,6S) corresponding to that of natural product.     

High-gain amplification in Yb:CaF2 crystals pumped by a high-brightness Yb-doped 976 nm fiber laser

We report on high single-pass gain in Yb:CaF₂ crystal longitudinally pumped with a 40 W high-brightness fiber laser source based on an ytterbium-doped ultra-large core photonic crystal rod-type fiber operating at 976 nm. A single-pass small-signal gain of 3.2 has been achieved in a 6 % Yb-doped 10-mm-long CaF₂ crystal at room temperature, outperforming any CW-diode-pumped scheme and paving the way towards very promising innovative lasers and amplifiers schemes merging the Yb-doped solid-state and fiber technologies.     

Enantiopure Aminopyrans by a Lewis Acid Promoted Rearrangement of 1,2‐Oxazines: Versatile Building Blocks for Oligosaccharide and Sugar Amino Acid Mimetics

1,3‐Dioxolanyl‐substituted 1,2‐oxazines, such as syn‐ 1 and anti‐ 1 , rearrange under Lewis acidic conditions to provide bicyclic products 2 – 5 . Subsequent reductive transformations afforded enantiopure 3‐aminopyran derivatives such as 7 and 9 or their protected diastereomers 16 and 18 , which can be regarded as carbohydrate mimetics. An alternative sequence of transformations including selective oxidation of the primary hydroxyl groups in 21 and 24 led to two protected β‐amino acid derivatives with carbohydrate‐like backbone (sugar amino acids). Treatment of bicyclic ester 23 with samarium diiodide cleaved the N? O bond and furnished the unusual β‐lactam 27 in excellent yield. Alternatively, γ‐amino acid derivative 29 was efficiently prepared in a few steps. Fairly simple transformations gave azides 32 and 35 or alkyne 30 which are suitable substrates for the construction of oligosaccharide mimetics such as 34 by copper iodide catalyzed cycloadditions. With this report we demonstrate that enantiopure rearrangement products 2 – 5 are protected precursors of a variety of polyfunctionalized pyran derivatives with great potential for chemical biology.     

Effect of parameters of square-wave pulsating current on copper electrodeposition in the hydrogen co-deposition range

Copper electrodeposition processes in the hydrogen co-deposition range by the pulsating current (PC) regime were examined by the determination of the average current efficiency of hydrogen evolution and by the scanning electron microscopic (SEM) analysis of the morphology of the formed deposits. The two sets of the square-wave PC of the same pause to pulse ratios, but with different duration of deposition pulses and pauses were analyzed. The one set of square-wave PC was with the constant pause duration and different deposition pulses. In the other set, the deposition pulse was constant while the pause duration was varied. The obtained results were compared with those obtained by electrodeposition at the constant overpotential from solutions of different CuSO₄ and H₂SO₄ concentrations. It was found that the effect of the increasing deposition pulse was equivalent to the decreasing CuSO₄ concentration, while the effect of the decreasing pause duration was equivalent to the increasing H₂SO₄ concentration. It is shown that it is possible to achieve a substitution of more solutions of different CuSO₄ and H₂SO₄ concentartions by the use of the only one solution if the appropriate PC parameters were applied, what can be of high technological significance.     

Asymptotics of variance of the lattice point count

The variance of the number of lattice points inside the dilated bounded set rD with random position in ℝ ^d has asymptotics ∼ r ^d−1 if the rotational average of the squared modulus of the Fourier transform of the set is O(ϰ ^−d−1). The asymptotics follow from Wiener’s Tauberian theorem.     

Influence of Copper from the Kuprikol 50 Fungicide on Colorado Potato Beetle Adults Studied by Radionuclide X-Ray Fluorescence Analysis

The influence of copper on adults of the Colorado potato beetle (Leptinotarsa decemlineata Say) was studied. The adults were treated by the contact fungicide Kuprikol 50, which is used to control down powder mildew (Phytophtora infestans de Bary). Copper content was determined by radio-nuclide X-ray fluorescence analysis using a ²³⁸Pu exciting source. The obtained results contribute to the control measures against the Colorado potato beetle and to the question of the resistance of Colorado potato beetle towards pyrethroide insecticides.     

Chaos in the fractional-order Volta’s system: modeling and simulation

This paper deals with a new fractional-order chaotic system. It is based on the concept of Volta’s system, where the mathematical model of Volta’s system contains fractional-order derivatives. This system has simple structure and can display a double-scroll attractor. The behavior of the integer-order and the fractional-order Volta’s system with total order less than three which exhibits chaos is presented as well. Computer simulations are cross-verified by the numerical calculation and the Matlab/Simulink models.     

Thermal properties of poly-ε-caprolactam and copolyamides based on ε-caprolactam

The copolyamides consisting of ε-caprolactam and 6.1–24.5 wt.% of nylon salt prepared from adipic acid and 1-(2-aminoethyl) piperazine were synthesized. Physical and thermal characteristics of polyamide 6 and the copolyamides were compared. Nylon salt does not influence the polyreaction equilibrium so it is possible to prepare the copolyamides with high molecular weight and with the content of low-molecular compounds comparable with that of pure PA 6. Melting temperatures of the copolyamides are lower in comparison with PA 6 and decrease proportionally to the amount of the nylon salt. The thermal stability of the copolyamides is good and equal to that of PA 6. The melting enthalpies indicate that the process of crystallization of the copolyamides is influenced by the time of crystallization and the amount of comonomer present. Longer time of the crystallization assures higher degree of crystallization. The kinetics and the level of crystallization are positively influenced by the mobility of copolyamide segments mainly up to 10 wt.% of comonomer.     

Kinetic Analysis of Non-isothermal DSC Data. Computer-aided test of its applicability

The applicability of the kinetic analysis of data obtained by non-isothermal differential scanning calorimetry (DSC) is discussed. The Johnson-Mehl-Avrami (JMA) model was used for the computer simulation of DSC traces subsequently analysed by common methods of kinetic analysis of non-isothermal data. For the temperature-independent kinetic exponent n of the JMA equation, the kinetic analysis was shown to provide correct results, e.g. a correct kinetic model and apparent activation energy. On the other hand, for the temperature-dependent kinetic exponent, there is a great possibility of erroneous determination of the correct kinetic model and apparent activation energy, especially at higher heating rates. Since the temperature dependence of n cannot be determined on the basis of non-isothermal DSC experiments, conclusions must be drawn with appropriate caution. This revised version was published online in August 2006 with corrections to the Cover Date.     

On the Development of the Temperature Concept

A brief outline of the history of development of the temperature concept in physics is given. Simultaneously, some persisting imperfections in the conceptual basis of classical thermodynamics closely related to the first and the second law of thermodynamics are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.