4,5‐Pyrenocyanine—Just Another Phthalocyanine? A STM and 2D WAXS Study

Pyrene‐fused tetraazaporphyrins were synthesized from pyrene‐4,5‐dicarbonitrile precursors using a recently reported procedure as the key step for the asymmetric substitution of pyrene. Metal‐free, zinc‐ and lead‐centered pyrenocyanines were obtained and their optical properties as well as their molecular assembly in the solution and bulk phases and at the liquid/solid interface were studied. The characteristic Q‐band appears broadened, most likely owing to distortion of the molecule introduced by the steric demand of the angularly extended aromatic residue. The angular annulation does not bathochromically shift the Q‐band as far as would have been expected for the linear case. Peripheral substitution with linear and branched alkoxy chains affords solubility of the compounds in organic solvents. The influence of the distinct steric demand of the substituents on aggregation was investigated for metal‐centered pyrenocyanines by using temperature‐dependent ¹H NMR and UV/Vis spectroscopy. The self‐assembly at the liquid/solid interface was studied using scanning tunneling microscopy. The alkoxy substituents facilitate the anchoring of these slightly non‐planar molecules on the surface of graphite. Pyrenocyanine molecules form well‐ordered 2D arrays in which the molecules are arranged in rows. The angular annulation of the pyrenocyanine residue leads to characteristic adsorption behavior at the liquid/solid interface, in which the molecules adsorb in two different adsorption geometries. The alkoxy side‐chains give rise to a discotic columnar superstructure and induce distinct thermotropic behavior. Dependent on the steric demand of the branched chains and the central metal atom, the molecules are rotated with respect to each other to form helical organization.     

Copper(II) mediated facile and ultra fast peptide synthesis in methanol

A novel, ultrafast, mild and scalable amide bond formation strategy in methanol using simple thioacids and amines is described. The mechanism suggests that the coupling reactions are initially mediated by CuSO(4)·5H(2)O and subsequently catalyzed by in situ generated copper sulfide. The pure peptides were isolated in satisfactory yields in less than 5 minutes.     

Structural evolution of the KTa0.6Nb0.4O3 alkoxide-based solutions: probing the transition metals local environment by X-ray absorption spectroscopy

The KTa_0.6Nb_0.4O₃ sols for chemical solution deposition of thin films were prepared from potassium acetate and transition metal ethoxides by the 2-methoxyethanol based route. The local environment of both transition metals after reflux times 1, 4, 24, and 48 h, whereby the crystallization behavior of the films was strongly affected, was monitored by extended X-ray absorption fine structure spectroscopy, at Ta L₃ and Nb K edges. The Ta species existed in the sols as monomers, remaining stable even with prolonged reflux time. The Ta–O–K correlations were confirmed in all cases. In contrast, the Nb-alkoxide formed dimers, with a gradual formation of oligomeric species with prolonged refluxing. The Nb–O–K correlations were present after all reflux times. The number of K neighbours around Nb increased upon refluxing, saturating at 24 h.     

On the existence of tori in Asada’s two-regional model

A two-regional five-dimensional model describing the development of income, capital stock and money stock, which was introduced by Asada in (2004) [2] is analysed. Sufficient conditions for the existence of two pairs of purely imaginary eigenvalues and the last one being negative in the linear approximation matrix of the model are found. Formulae for the calculation of the coefficients in the bifurcation equation of the model are derived. The theorem on the existence of invariant tori is presented. A numerical example illustrating the gained results is given.     

Rain Height in Relation to 0°C Isotherm Height Over Some Indian Tropical Locations and Rain Attenuation for an Indian South Coastal Station for Microwave and Millimeter Wave Communication Systems

There is a dearth of results on rain height over Indian tropical stations.The results on rain height in relation to 0°C isotherm height over four stations having different latitudes are presented in this paper. Four stations have been chosen in such a way that all have different latitudes and are located in different geographical regions having different local weather conditions. The seaonal variation of rain height in relation to 0°C isotherm height has been found to be appreciable over the station located in Indian east coast and Gujarat region, while seasonal variation is not significant at lower and intermediate probability levels over the stations located in Indian south-east coast and island. The prevailing local weather conditions over different stations also have been discussed. Based on observed rain heights and rain rates, the attenuation of radio wave at different frequencies lying in the range from 10 GHz to 150 GHz for different probability levels over Indian south-east coastal station have been deduced and presented in this paper.     

Multiple 3D- and 2D-quantitative structure–activity relationship models (QSAR), theoretical study and molecular modeling to identify structural requirements of imidazopyridine analogues as anti-infective agents against tuberculosis

Structural Chemistry - Tuberculosis (TB), an infectious remains a global health burden till date. Considering immense importance of theoretical tools in computer aided-drug designing, the current...     

激光二极管侧面泵浦的高效率Nd：YAG激光器

用准连续激光二极管列阵侧面泵浦Ｎｄ：ＹＡＧ固体激光器，获得３９．５ｍＪ的静态输出，器件重复频率为５０Ｈｚ，效率最高达３９．５％，对该器件进行了细致的实验研究，验证了理论计算的正确性，并对实验结果进行了分析。     

Characterization of the Penetration of the Blood–Brain Barrier by High-Performance Liquid Chromatography (HPLC) Using a Stationary Phase with an Immobilized Artificial Membrane

The biological activity of drugs on organisms is associated with the pharmacokinetic properties, such as the ability to penetrate through environments of varying polarity such as cellular organelles. In this area, particular attention is turned to the physicochemical properties that determine the potential of drugs to pass across the blood–brain barrier and thus to act on the central nervous system. In this study, special effort has been devoted to the simulation of passive diffusion of seven drugs (propranolol, ibuprofen, atenolol, promazine, chlorpromazine, imipramine, and desipramine) through the blood–brain barrier by high-performance liquid chromatography (HPLC) using a column with an immobilized artificial membrane. Gradient reverse elution was used to develop a linear correlation model for the capacity factors k_IAM and the in vivo logarithmic values of brain-to-blood drug concentration ratios (log BB) with R of 0.9851. Eleven additional pharmaceuticals were determined by the same method to predict their potential to penetrate the blood–brain barrier. The reported analytical method represents an alternative tool for rapid and noninvasive assessment of the absorption properties of chemicals, especially for the development of novel drugs. The retention of the studied compounds on the immobilized artificial membrane column was also compared with three other C18-based stationary phases. Herein, the results of the HPLC determination of drugs using an immobilized artificial membrane are briefly discussed with respect to a general application of the method for evaluating a broader spectrum of pharmaceutical compounds.