Investigation on a “tentacle-like” corrosion feature on Bronze Age tin-bronze objects

Studying the micro-structure of Austrian, Bosnian and Croatian Bronze Age objects made of tin bronze, a rare kind of corrosion feature, called in the following “tentacle-like” according to its specific way of penetrating the metallic matrix, was noted and investigated. Differing from the more classical intergranular, pitting, or crevice corrosion features, the “tentacle-like” corrosion is not following the grain boundaries, nor precisely positioned under the etching area, but penetrates mainly the crystal matrix without any apparent order. This paper discusses the first results achieved and the following hypotheses formulated in respect of the typology of this corrosion. The analyses were carried out by optical microscopy, Raman microspectroscopy, and scanning electron microscopy equipped with EDX spectroscopy for quantitative analyses.     

Spontaneous Edge Currents for the Dirac Equation in Two Space Dimensions

Spontaneous edge currents are known to occur in systems of two space dimensions in a strong magnetic field. The latter creates chirality and determines the direction of the currents. Here we show that an analogous effect occurs in a field-free situation when time reversal symmetry is broken by the mass term of the Dirac equation in two space dimensions. On a half plane, one sees explicitly that the strength of the edge current is proportional to the difference between the chemical potentials at the edge and in the bulk, so that the effect is analogous to the Hall effect, but with an internal potential. The edge conductivity differs from the bulk (Hall) conductivity on the whole plane. This results from the dependence of the edge conductivity on the choice of a selfadjoint extension of the Dirac Hamiltonian. The invariance of the edge conductivity with respect to small perturbations is studied in this example by topological techniques Mathematics Subject Classification (2000). 81Q10, 58J32     

Sense and nonsense of laboratory accreditation

 An open mind is essential for the implementation and improvement of total quality management. Leadership, as such, is of no value without a vision concerning corporate culture and human resources. Therefore, constant communication between partners within a corporate body is the cornerstone for empowerment. The evaluation of ideas and complaints is considered to be essential for the identification of strengths and weaknesses of a system, whereas, competition and benchmarking may reveal surprising opportunities for improvement. We discuss the idea that customer-oriented efficiency in a hospital environment may be classified as a critical success factor.     

Starch‐graft‐(synthetic copolymer) latexes initiated with Ce4+ and stabilized by amylopectin

A method is presented for synthesizing surfactant‐free latexes comprising starch‐graft‐(vinyl polymer) starting with a suspension of amylopectin, either native or modified, then using cerium(IV) with either potassium persulfate or glucose to create grafting sites on the starch. Latex particles comprising polystyrene, poly(styrene‐co‐(n‐butyl acrylate)) and poly(vinyl acetate) grafted onto high molecular weight amylopectin were developed, with up to 80% of the starch effectively grafted to the particles. These latexes were colloidally stable against electrolyte (several months in 4 M NaCl). Reaction rates of Ce⁴⁺ with simple sugars and polysaccharides were investigated, as well as the gelation mechanism of the latex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4185–4192, 2007     

X-ray diffraction study of the structure of carboxymethylcellulose-cationic surfactant complexes.

We have investigated dilute aqueous solutions of an anionic polymer (carboxymethylcellulose) mixed with cationic surfactants of different chain lengths (dodecyl to octadecyl trimethylammonium bromides: DTAB, TTAB, CTAB and OTAB). The structures of the concentrated phases formed above the precipitation threshold were studied by X-ray diffraction. Different body-centred cubic structures with space groups Pm3n were observed in the presence of surfactant with a short aliphatic chain (DTAB), despite the fact that the polymer persistence length is comparable to the repeat distance of the structure (5 nm). For larger surfactant chain lengths (TTAB and CTAB), the structure of the precipitates can be either cubic (Pm3n) or 2D hexagonal depending on the initial surfactant and polymer concentrations. For still larger chain length (OTAB), the structure becomes lamellar. This structural evolution from micellar cubic towards 2D hexagonal and lamellar is attributed to the decrease of the local curvature of the surfactant aggregates, as observed for flexible synthetic polymers and short DNA fragments under similar conditions. Furthermore, the structure of the bulk complexes formed just below the precipitation threshold anticipates the structure seen in the precipitated phases.     

Lipopolysaccharide identification with functionalized polydiacetylene liposome sensors

The outer membrane of Gram negative bacteria contains lipopolysaccharides, which are glycolipids with carbohydrate sequences that are unique for each bacterial species and serotype. In this communication, we report a method for identifying LPS from different bacteria using an electronic tongue approach. Two functionalized polydiacetylene liposomes were used as colorimetric sensors for detecting various types of LPS. These liposomes were assayed under four different experimental conditions to generate a data set of eight colorimetric responses. This data set constitutes a unique fingerprint for each analyte and permits identification of each LPS type.     

Glyconothio-O-lactones Part II. Cycloaddition to Dienes,Diazomethane, and Carbenoids

The addition of dienes, diazomethane, and carbenoids to the manno- and ribo-configurated thio-γ-O-lactones 1 and 2 was investigated. Thus, 1 (Scheme 1) reacted with 2,3-dimethylbutadiene (→ 4 , 73%), cyclopentadiene (→ 5a/b 1:1, 70%), cyclohexa- 1,3-diene (→ 9a/b 2:3, 92%), and the electron-rich butadiene 6 (→ 7a/b 3:1, 82%). Wheras 5a/b was separated by flash chromatography, 7a/b was desilylated leading to the thiapyranone 8 . Selective hydrolysis of one isopropylidene group of 9a/b and flash chromatography gave 10a and 10b . The structures of the adducts were elucidated by X-ray analysis ( 4 ), by NOE experiments ( 4 , 5a , 5b , 7a/b , 10a , and 10b ), and on the basis of a homoallylic coupling ( 7a/b ). The additions occurred selectively from the ‘exo’ -side of 1 . Only a weak preference for the ‘endo’-adducts was observed. Hydrogenation of 9a/b with Raney-Ni (EtOH, room temperature) gave the thiabicyclo [2.2.2]octane 11 . Under harsher conditions (dioxane, 110°), 9a/b was reduced to the cyclohexyl ß-D C-glycoside 12 which was deprotected to 13 . X-Ray analysis of 13 proved that the desulfuration occurred with inversion of the anomeric configuration. The regioselective addition of the dihydropyridine 14 to 1 (Scheme 2) and the methanolysis of the crude adduct 15 gave the lactams 16a (32%) and 16b (38%). Desilylation of 15 with Bu₄NF · 3H₂O, however, gave the unsaturated piperidinedione 17 (92%) which was deprotected to the tetrol 18 (65%). Similarly, 2 was transformed via 19 (62%) into the triol 20 (74%). The cycloaddition of 1 with CH₂N₂ (Scheme 3) gave a 35:65 mixture of the 2,5-dihydro- 1,3,4-triazole 21 and the crystalline 4,5-dihydro 1,2,3-triazole 22 . Treatment of 21 and 22 with base gave the hydroxytriazoles 23 and 24 , respectively. The structure of 24 was established by X-ray analysis. The triazole mixture 21/22 was separated by prep. HPLC at 5°. At room temperature, 21 already decomposed (half-life 21.6 h) leading in CDCI₃ solution to a complex mixture (containing ca. 20–25% of the spirothiirane 27 and ca. 7–10% of its anomer) and in MeOH solution exclusively to the O,O,S-ortholactone 26 . Crystals of 22 proved be stable at 105°. Upon heating in petroleum ether at 100°, 22 was transformed into a ca. 1:1 mixture of 27 and the enol ether 28 . The reaction of 1 with ethyl diazoacetate (Scheme 4) in the presence of Rh₂(OAc)₄. 2H₂O gave the unsaturated esters 29 (33%) and 30 (26%), whereas the analogous reaction with diethyl diazomalonate afforded the spirothiirane 31 (68%) and the enol ether 32 (29%). Complete transformation of 31 into 32 was achieved by the treatment with P(NEt₂)₃. Similary, 33 (69%) was prepared from 2 .     

Liquid chromatographic separation of 2,4,6-trinitrotoluene and its principal reduction products

A liquid chromatographic method is described for the baseline separation of 2,4,6-trinitrotoluene (TNT) and its main reduction products. Two analytical columns (LC-18 and LC-CN) are connected in series and eluted isocratically at 1.5 ml min^?1 with water-methanol-tetrahydrofuran (60.5 + 25 + 14.5). The capacity factors (k′) are 1.4, 1.6, 5.1, 6.4 and 7.0 for 2,6-diamino-4-nitroluene, 2,4-diamino-6-nitrotoluene, TNT, 4-amino-2,6-dinitrotoluene and 2-amino-4,6-dinitrotoluene, respectively.