Long-Range Lateral Correlation between Self-Assembled Domains of Fluorocarbon-Hydrocarbon Tetrablocks by Quantitative GISAXS

The structure and lateral correlation of fluorocarbon-hydrocarbon tetrablock di(F10Hm) domains at the air/water interface have been determined by quantitative analysis of grazing incidence small-angle X-ray scattering (GISAXS) data. The measured GISAXS signals can be well represented by the full calculation of the form and structure factors. The form factor suggests that di(F10Hm) domains take a hemiellipsoid shape. Both major and minor axes of the hemiellipsoids monotonically increased in response to the elongation of the hydrocarbon blocks, which can be explained by the concominant increase in van der Waals interaction. The structure factor calculated from the GISAXS signals suggests that the domains take an orthorhombic lattice. Remarkably, the lateral correlation can reach over a distance that is more than 14 times longer than the distance to the nearest neighbors. Our data suggest that quantitative GISAXS enables the optimal design of mesoscopic self-assemblies at the air/water interface by fine-tuning of the structures of molecular building blocks.     

A photometric method for the determination of oxalic acid

Summary A method for the quantitative determination of oxalic acid based onEegriwe's color test for glycolic acid is described. The principle of the method is the reduction of oxalic to glycolic acid by nascent hydrogen from magnesium powder and dilute sulfuric acid. By heating with a solution of 2,7-dihydroxynaphthalene in concentrated sulfuric acid formaldehyde splitt off from glycolic acid condensates with the reagent, tetrahydroxydinaphthylmethane forms and is oxidized to a deep colored dye-stuff by atmospheric oxygen.A study of interfering substances and the way of avoiding their influence was made.The color system, under the conditions of the method, follows theLambert-Beer's law. With the exception of a photoelectric colorimeter, no special equipment is required. The procedure is very simple, possesses great sensitivity, and may be applied with minor variations to a wide variety of materials.

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Zusammenfassung Es wird ein Verfahren zur quantitativen Bestimmung der Oxalsäure beschrieben, das auf der Farbreaktion nachEegriwe für Glykolsäure beruht. Das Prinzip der Methode beruht auf der Reduktion der Oxalsäure zu Glykolsäure durch nascierenden Wasserstoff aus Magnesiumpulver und verd. Schwefelsäure. Durch Erhitzen mit einer Lösung von 2,7-Dioxynaphthalin in konz. Schwefelsäure wird der abgespaltene Formaldehyd mit dem Reagens kondensiert. Es bildet sich Tetraoxydinaphthylmethan, welches durch den Luftsauerstoff zu einem intensiv gefärbten Produkt oxydiert wird. Der Einfluß störender Substanzen und dessen Vermeidung werden untersucht. Die Farbreaktion folgt unter den geschilderten Versuchsbedingungen demLambert-Beerschen Gesetz. Mit Ausnahme eines photoelektrischen Kolorimeters ist kein besonderer Aufwand erforderlich. Die Methode ist sehr einfach und von großer Empfindlichkeit. Sie kann mit geringfügigen Abänderungen für verschiedenartiges Untersuchungsmaterial angewendet werden.

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Résumé On décrit une méthode pour le dosage quantitatif de l'acide oxalique, basé sur le test coloré d'Eegriwe pour l'acide glycolique. Le principe de la méthode repose sur la réduction de l'acide oxalique en acide glycolique par l'hydrogène naissant produit avec le magnésium en poudre et l'acide sulfurique dilué. En chauffant avec une solution de dihydroxy-2,7 naphtalène dans l'acide sulfurique concentré, le formaldéhyde se libère du produit de condensation entre l'acide glycolique et le réactif; le tétrahydroxydinaphtylméthane se forme et s'oxyde en une matière colorante foncée sous l'action de l'oxygène atmosphérique.On a fait une étude des substances interférentes et de la manière d'éviter leur influence.Le système coloré, dans les conditions de la méthode, suit la loi deLambert-Beer. A l'exception d'un colorimètre photoélectrique, aucun équipement spécial n'est nécessaire. Le mode opératoire est très simple, possède une grande sensibilité et peut être appliqué avec de minimes variations à un grand nombre de substances.

     

Modulating the electronic properties of porphyrinoids: a voyage from the violet to the infrared regions of the electromagnetic spectrum

This paper examines the preparation of tailor-made azaporphyrins and analogues exhibiting their Q-bands in several particular and predetermined regions of the electromagnetic spectrum. The applications of phthalocyanines, the possibility of preparing novel related porphyrinoids with different colour properties and, consequently, new emerging applications, are discussed.     

Anticancer β-hairpin peptides: membrane-induced folding triggers activity

Several cationic antimicrobial peptides (AMPs) have recently been shown to display anticancer activity via a mechanism that usually entails the disruption of cancer cell membranes. In this work, we designed an 18-residue anticancer peptide, SVS-1, whose mechanism of action is designed to take advantage of the aberrant lipid composition presented on the outer leaflet of cancer cell membranes, which makes the surface of these cells electronegative relative to the surface of noncancerous cells. SVS-1 is designed to remain unfolded and inactive in aqueous solution but to preferentially fold at the surface of cancer cells, adopting an amphiphilic β-hairpin structure capable of membrane disruption. Membrane-induced folding is driven by electrostatic interaction between the peptide and the negatively charged membrane surface of cancer cells. SVS-1 is active against a variety of cancer cell lines such as A549 (lung carcinoma), KB (epidermal carcinoma), MCF-7 (breast carcinoma), and MDA-MB-436 (breast carcinoma). However, the cytotoxicity toward noncancerous cells having typical membrane compositions, such as HUVEC and erythrocytes, is low. CD spectroscopy, appropriately designed peptide controls, cell-based studies, liposome leakage assays, and electron microscopy support the intended mechanism of action, which leads to preferential killing of cancerous cells.     

Cure kinetics of epoxy resin and thermoplastic polymer

The cure kinetics and morphology of diglycidyl ether of bisphenol A (DGEBA) modified with polyvinyl acetate (PVAc) using diaminodiphenylmethane (DDM) as hardener were investigated through differential scanning calorimetry (DSC) and environmental scanning electron microscopy (ESEM). Isothermal curing measurements were carried out at 150, 120 and 80°C. The kinetic parameters were obtained using the general autocatalytic chemically controlled model. The comparison of the kinetic data indicates that the presence of PVAc does not change the autocatalytic nature of the cure reaction. Two T _g’s were observed in the fully cured samples of the modified systems. ESEM micrographies confirm the biphasic morphology.     

Gold(I)-catalyzed intramolecular cyclopropanation of dienynes

Gold(I) complexes are the most active catalysts for the biscyclopropanation of dienynes to form tetracyclic compounds. PtII and ZnII are also able to promote the biscyclopropanation, although less efficiently. The configurations obtained in all cases with the use of gold(I) catalysts can be explained by the pathway proceeding through anti cyclopropyl gold carbenes. Similar intermediates are most probably involved in reactions catalyzed by RuII and PtII. Two different cyclopropanation pathways have been found; they depend on the structures of the cyclopropyl gold carbenes (anti or syn) and the relative arrangements of the metal carbenes and the alkenes.     

Kinetic parameters of unsaturated polyester resin modified with poly(ε -caprolactone)

The mineral sabugalite (HAl)_0.5[(UO₂)₂(PO₄)]₂⋅8H₂O, has been studied using a combination of energy dispersive X-ray analysis, X-ray diffraction, dynamic and controlled rate thermal analysis techniques. X-ray diffraction shows that the starting material in the thermal decomposition is sabugalite and the product of the thermal treatment is a mixture of aluminium and uranyl phosphates. Four mass loss steps are observed for the dehydration of sabugalite at 48°C (temperature range 39 to 59°C), 84°C (temperature range 59 to 109°C), 127°C (temperature range 109 to 165°C) and around 270°C (temperature range 175 to 525°C) with mass losses of 2.8, 6.5, 2.3 and 4.4%, respectively, making a total mass loss of water of 16.0%. In the CRTA experiment mass loss stages were found at 60, 97, 140 and 270°C which correspond to four dehydration steps involving the loss of 2, 6, 6 and 2 moles of water. These mass losses result in the formation of four phases namely meta(I)sabugalite, meta(II)sabugalite, meta(III)sabugalite and finally uranyl phosphate and alumina phosphates. The use of a combination of dynamic and controlled rate thermal analysis techniques enabled a definitive study of the thermal decomposition of sabugalite. While the temperature ranges and the mass losses vary due to the different experimental conditions, the results of the CRTA analysis should be considered as standard data due to the quasi-equilibrium nature of the thermal decomposition process. The online version of the original article can be found at     

Isotope dilution GC-MS routine method for the determination of butyltin compounds in water

A standard GC-MS instrument with electron impact ionisation has been used to develop a fast, simple and reliable method for the simultaneous determination of monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) in water samples. Isotope dilution analysis (IDA) is used for the determination of species, taking advantage of a commercially available spike solution containing a mixture of MBT, DBT and TBT enriched in ¹¹⁹Sn. Method detection limits for 100-mL samples were between 0.18 and 0.25 ng L⁻¹ for the three butyltin compounds with typical RSD between 2 and 4% at levels between 100 and 10 ng L⁻¹, respectively. Recovery of tin species in spiked samples (natural water, wastewater and seawater) was quantitative. The stability of butyltin compounds in collected seawater samples was also studied. The addition of a 1% (v/v) glacial acetic acid preserved tin species in the samples for at least 5 days at room temperature. The IDA method was finally implemented in a routine testing laboratory and it was subsequently accredited by the Spanish National Accreditation Body according to the requirements of UNE-EN ISO/IEC 17025.