Sampling and local models for multivariate image analysis

Local models are a very important concept for microscopic and macroscopic imaging. Different methods of sub-sampling a multivariate image are described both in general and for three examples. The need for sub-sampling and its influence on multivariate image analysis and visualization are studied. Examples from MRI (256 × 256), satellite imaging (7 × 512 × 512) and biofuel studies (6 × 512 × 512) are used to illustrate some of the principles involved.     

Binding Ensembles of p53-MDM2 Peptide Inhibitors by Combining Bayesian Inference and Atomistic Simulations

Designing peptide inhibitors of the p53-MDM2 interaction against cancer is of wide interest. Computational modeling and virtual screening are a well established step in the rational design of small molecules. But they face challenges for binding flexible peptide molecules that fold upon binding. We look at the ability of five different peptides, three of which are intrinsically disordered, to bind to MDM2 with a new Bayesian inference approach (MELD × MD). The method is able to capture the folding upon binding mechanism and differentiate binding preferences between the five peptides. Processing the ensembles with statistical mechanics tools depicts the most likely bound conformations and hints at differences in the binding mechanism. Finally, the study shows the importance of capturing two driving forces to binding in this system: the ability of peptides to adopt bound conformations (ΔGconformation) and the interaction between interface residues (ΔGinteraction).     

Sol-gel polyimide-silica composite membrane: gas transport properties

The effect of introduction of silica particles prepared by the sol-gel technique on the gas transport properties of a polyimide film was studied. The sorption and permeation of N₂, O₂, CO₂, H₂ and CH₄ were studied and correlated with morphological changes in the polymer structure. From sorption isotherms, we observed that the composite membrane presents higher solubility coefficients than the polyimide one. The solubility coefficient ratio between the composite and the polyimide is about 1.5–2.0. The isotherms were analyzed in terms of the dual mode sorption. The Henry's coefficient and the Langmuir's affinity and saturation constants were obtained allowing to calculate the Langmuir to Henry concentration ratios as function of the gas pressure. These ratios decrease until zero within a certain pressure range as long as the Langmuir's mode is acting and they are higher for the polyimide membrane when compared with the composite one. This study was completed with calorimetric measurements during the sorption. The gas interaction energy in kJ/mol decreases within the same pressure range as previously described. The measured energies are higher for the polyimide film when compared with the composite one because the polyimide membrane presents a stronger energetic effect caused by a higher Langmuir's contribution. From permeation studies at 3.15⁵ Pa, the composite membrane showed higher permeability coefficients and permselectivities than the polyimide one. All these results were explained, taking into account the difference on the imidization degree of both membranes and the morphological changes which may be induced by the silica nodules in the organic/inorganic interphases.     

Physico-chemical studies on the chelation behaviour of biologically active 2-hydroxy-1-naphthaldehyde semicarbazone (HNAS) with some lanthanons

Summary The chelation behaviour of the complexes of La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Y³⁺, Tb³⁺, Dy³⁺, Ho³⁺ with biologically active 2-Hydroxy-1-naphthaldehyde semicarbazone (HNAS) has been studied potentiometrically in 75% (v/v) dioxane-water medium at various ionic strengths. The method of Bjerrum and Calvin, as modified by Irving and Rossotti has been used to find out the values of n andpL. The formation constants of metal chelates and the values ofS _min have been calculated. The order of formation constants of chelates was found to be: La³⁺3+3+3+3+3+3+3+3+3+3+.

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Physikochemische Untersuchungen zur Komplexierung von biologisch aktivem 2-Hydroxy-1-naphthaldehyd-Semicarbazon (HNAS) mit Lanthanoiden

Zusammenfassung Das Chelierungsverhalten von La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Y³⁺, Tb³⁺, Dy³⁺ und Ho³⁺ mit 2-Hydroxy-1-naphthaldehydsemicarbazon (HNAS) wurde potentiometrisch in 75% (v/v) Dioxan-Wasser bei verschiedenen Ionenstärken untersucht. Die Werte für n undpL wurden nach der Methode von Bjerrum und Calvin in der Modifikation von Irving und Rossotti bestimmt. Die Komplexbildungskonstanten der Metallchelate und die WerteS _min wurden ermittelt. Die Reihung der Komplexbildungskonstanten war La³⁺3+3+3+3+3+3+3+3+33+.

     

Solid sampling Fourier transform infrared determination of Mancozeb in pesticide formulations

A series of approaches have been assayed for FTIR determination of Mancozeb in several solid commercial fungicides using different calibration strategies. The simplest procedure was based on the use of the ratio between the absorbance of a characteristic band of Mancozeb and that of a KSCN internal standard measured in the FTIR spectra obtained from KBr pellets. It was employed the quotient between peak height absorbance values at 1525 cm⁻¹ for Mancozeb and 2070 cm⁻¹ for KSCN. In these conditions a precision as relative standard deviation (RSD) of 0.6% and a relative accuracy error of 0.8% (w/w) were found. For complex formulations, containing other compounds with characteristic absorption bands at different wavenumbers than Mancozeb, one of them was used as internal reference being employed the standard addition approach. In this case, the Mancozeb bands at 1525 cm⁻¹ or at 1289 cm⁻¹ were employed, being used the ferrocyanide band at 2075 cm⁻¹ as internal reference. RSD values between 0.7-1.4% and a relative accuracy error of 3% (w/w) were found. A third strategy was based on the use of partial least squares (PLS) calibration. A reference set was prepared mixing Mancozeb, Kaolin, Cymoxanil and KBr, being predicted the Mancozeb concentration in pesticide formulations by using the quotient between absorbance bands of Mancozeb and those of Cymoxanil. In these conditions a relative accuracy error of 0.6% (w/w) and a relative standard deviation of 1.3% were found.     

Lithium bromide in acetonitrile: Thermodynamics,theory, and simulation

A variety of methods has been used for the study of lithium bromide solutions in acetonitrile yielding by their combination reliable information on different levels of approximation. Osmotic coefficients based on precise vapor pressure measurements are reproduced by CM (chemical model) and HNC (hypernetted chain) calculations and by BD (brownian dynamics) simulations. The results of neutron scattering experiments are treated with the help of HNC and BD methods. Hartree-Fock calculations on isolated LiBr pairs and solvated lithium ions yield reliable particle distances and reveal the geometry of the lithium solvation sphere.     

互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体，水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂），制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD），热重分析（TGA）对其结构进行表征；采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面，形成多层次结构，并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构；MnO₂纳米片具有典型的K-Birnessite 型晶体结构；复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1；随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极，活性炭（AC）为负极，1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器，发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V，容量可达86F·g^-1，且表现出良好的电容特性和大电流放电性能.     

Reduced parabolic model for radical addition reactions

The transition state of addition of free radicals and atoms to multiple bonds is considered as a result of intersecting of two parabolic potential curves. One of them characterizes the stretching vibration of the attacked multiple bond, and another curve characterizes the stretching vibration of the bond formed in the transition state. The force constant of the latter is calculated by an empirical equation that correlates the force constant with the bond dissociation energy. In the framework of this model, the thermally neutral activation energy (E _e0) and the elongation of the attacked and formed bonds (r _e) in the transition state were calculated from the experimental data (activation energy (E _e) and enthalpy of reaction (H _e)) for the addition of an H atom and methyl, alkoxyl, aminyl, triethylsilyl, and peroxyl radicals to the C=C bond and the addition of H and CH₃ to the C=O and CC bonds. Analysis of the data obtained showed that E _e0 depends linearly on the |H _e| + E_e sum, i.e., E_e0/kJ mol^–1 = 14.2 + 0.61 · (E_e – H _e), and the bond elongation in the transition state for addition of the most part of radicals to ethylene and acetylene vary within (0.65–0.87)·10_–10 m. The factors affecting the activation energy of the radical addition reactions are discussed.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1542–August, 2004.     

Calorimeters for biotechnology

The isothermal and temperature scanning calorimeters manufactured by Calorimetry Sciences Corporation are briefly described. Applications of calorimetry to determine thermodynamics and kinetics of reactions of interest in biotechnology are described with illustrative examples.     

Thermal properties of sodium acetylacetonate

Sodium acetylacetonate was prepared by the interaction of acetyl acetone with sodium hydroxide. The thermal conductivity, phonon velocity, mean free path, Yong's modulus, and the thermal expansion coefficient were studied. The thermal conductivity of the material decreases with increasing temperature due to the thermal lattice scattering of phonons. The velocity of phonons is also decreased due to the perturbation of thermal phonons. The linear thermal expansion coefficient increases with temperature due to the weakness of the attractive forces between the small Na⁺ cations and bulkier acetylacetonate anions in the lattice.

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Zusammenfassung Natriumacetylacetonat wurde durch die Wechselwirkung zwischen Acetylaceton und Natriumhydroxid gewonnen. Es wurde die Wärmeleitfähigkeit, die Phononengeschwindigkeit, die mittlere freie Wegstrecke, das Elastizitätsmodul und der Wärmeausdehnungskoeffizient untersucht. Die Wärmeleitfähigkeit der Substanz nimmt wegen der thermischen Gitterstreuung der Phononen mit steigender Temparatur ab. Die Geschwindigkeit der Phononen nimmt auf Grund der Perturbierung der thermischen Phononen ebenfalls ab. Der lineare Wärmeausdehnungskoeffizient steigt mit zunehmender Temperatur an, was auf die schwachen Anziehungskräfte zwischen den kleinen Na⁺ Ionen und den massigen Acetylacetonat-Anionen im Gitter zurückzuführen ist.