Formation and breakdown of a protective layer of chromium sesquioxide on L-605 alloy at 1100° C

The formation and breakdown of a protective layer of Cr₂O₃ on L-605 during oxidation at 1100° C was investigated. The effects of surface deformation, pressure, and water vapor on the breakdown time were evaluated. It was found that increasing surface deformation, increased the time to breakdown. Decreasing pressure below 1 atm to 0.13 N/m² increased time of breakdown as did decreasing water content from 25,000 to 2.5 ppm. By metallographic and microprobe examinations of samples during breakdown a model was deduced. Surface deformation promotes Cr₂O₃ formation, while increasing pressure and moisture increases the volatility of Cr₂O₃. Thus, the Cr₂O₃ grows for a time determined by these three factors. At the end of this time the growth stresses cause the oxide to crack, exposing a chromium-depleted metal surface to the oxidizing gas. The resultant rapid oxidation of this surface lifts the remaining Cr₂O₃, exposing more depleted metal. When the depletion zone is consumed and a very thick oxide has formed, the rate of oxidation slows and no further disruption is noted.     

Optics clustered to output unique solutions: a multi-laser facility for combined single molecule and ensemble microscopy

Optics clustered to output unique solutions (OCTOPUS) is a microscopy platform that combines single molecule and ensemble imaging methodologies. A novel aspect of OCTOPUS is its laser excitation system, which consists of a central core of interlocked continuous wave and pulsed laser sources, launched into optical fibres and linked via laser combiners. Fibres are plugged into wall-mounted patch panels that reach microscopy end-stations in adjacent rooms. This allows multiple tailor-made combinations of laser colours and time characteristics to be shared by different end-stations minimising the need for laser duplications. This setup brings significant benefits in terms of cost effectiveness, ease of operation, and user safety. The modular nature of OCTOPUS also facilitates the addition of new techniques as required, allowing the use of existing lasers in new microscopes while retaining the ability to run the established parts of the facility. To date, techniques interlinked are multi-photon/multicolour confocal fluorescence lifetime imaging for several modalities of fluorescence resonance energy transfer (FRET) and time-resolved anisotropy, total internal reflection fluorescence, single molecule imaging of single pair FRET, single molecule fluorescence polarisation, particle tracking, and optical tweezers. Here, we use a well-studied system, the epidermal growth factor receptor network, to illustrate how OCTOPUS can aid in the investigation of complex biological phenomena.     

An apparatus for in situ spectroscopy of radiation damage of polymers by bombardment with high-energy heavy ions

A new target station providing Fourier transform infrared (FT-IR) spectroscopy and residual gas analysis (RGA) for in situ observation of ion-induced changes in polymers has been installed at the GSI Helmholtz Centre for Heavy Ion Research. The installations as well as first in situ measurements at room temperature are presented here. A foil of polyimide Kapton HN(?) was irradiated with 1.1 GeV Au ions. During irradiation several in situ FT-IR spectra were recorded. Simultaneously outgassing degradation products were detected with the RGA. In the IR spectra nearly all bands decrease due to the degradation of the molecular structure. In the region from 3000 to 2700 cm(-1) vibration bands of saturated hydrocarbons not reported in literature so far became visible. The outgassing experiments show a mixture of C(2)H(4), CO, and N(2) as the main outgassing components of polyimide. The ability to combine both analytical methods and the opportunity to measure a whole fluence series within a single experiment show the efficiency of the new setup.     

Multipurpose modular experimental station for the DiProI beamline of Fermi@Elettra free electron laser

We present a compact modular apparatus with a flexible design that will be operated at the DiProI beamline of the Fermi@Elettra free electron laser (FEL) for performing static and time-resolved coherent diffraction imaging experiments, taking advantage of the full coherence and variable polarization of the short seeded FEL pulses. The apparatus has been assembled and the potential of the experimental setup is demonstrated by commissioning tests with coherent synchrotron radiation. This multipurpose experimental station will be open to general users after installation at the Fermi@Elettra free electron laser in 2011.     

Description of the immatures of workers of the ant Linepithema micans forel (Hymenoptera: Formicidae)

Linepithema micans Forel is a poorly studied species that is now considered a pest in vineyards in South Brazil. Larval characters have been used in a few phylogenetic studies, and their importance greatly depends in the amount of available information on different species. This study presents a complete panorama on the external morphology of the immatures of L. micans based on observations by light and scanning electron microscopy. The number of larval instars was estimated as three based on the frequency distribution of head widths of 965 larvae. Larvae of L. micans were similar to other Linepithema Mayr in the general format of body and mandibles, presenting a dorsal abdominal protuberance, nine pairs of spiracle, and unbranched hairs. On the other hand, L. micans was unique for having shorter hairs, predominantly denticulate, intraspecific variation in the number of antennal sensilla and in the types of sensilla on the labial palps were reported. Microsc. Res. Tech., 2011. © 2010 Wiley‐Liss, Inc.     

Conversion of allylic hydroxy oleate to conjugated linoleic acid and methoxy oleate by acid-catalyzed methylation procedures

Conjugated linoleic acid (CLA), a term describing a group of conjugated octadecadienoic acids that are both naturally occurring and formed during food processing, is the subject of considerable current research because of the recently reported antioxidant and anticarcinogenic properties of these compounds. Allylic hydroxy oleates (AHOs), secondary products of lipid autoxidation, have also been found in foods. By means of high-performance liquid chromatography with ultraviolet detection, gas chromatography/mass spectrometry and gas chromatography/matrix isolation/Fourier transform infrared spectroscopy, we determined that currently used acid-catalyzed methylation procedures convert AHOs to CLA and other products that potentially yield high values in determination of CLA in foods. A mixture of AHOs, containing mainly (8- and 11-)hydroxy-9-octadecadecenoates, was synthesized and tested by methylation procedures with the following catalysts: BF₃, HCl, NaOMe and tetramethylguanidine. Both the BF₃ and the HCl procedures converted AHOs to CLA. The base-catalyzed procedures did not convert AHOs to CLA.     

Modulation of the enzymatic activity of papain by interdomain residues remote from the active site

The two main catalytic residues Cys25 and Hisl59 of the monomericcysteine protease papain are located on different walls of acleft formed by two domains. This topology suggests a possiblerelationship between relative domain organization and catalyticmechanism. The effect on enzymatic parameters of structuralmodifications at various locations of the twodomain interfaceof papain was examined by individual or double replacementsby Ala of pairs of interacting residues. Most modificationshad no effect on enzyme activity. However, the enzyme's substrateturnover (k_cat) decreased following simultaneous alterationof the two most conserved residues, forming an apolar contactlocated 15 Å away from the active site. The pH activityprofile of the double mutant was unchanged, indicating a conservedionization state of the active site thiolate-imidazolium ionpair. This state is strongly dependent on the distance separatingthe two residues, thus suggesting that the active site geometryhas not been significantly altered. Efficient enzymatic activityin papain requires more than a correct active site geometryand is influenced by domain packing properties in a region remotefrom the active site.     

橡胶添加剂苯并呋咱-1-氧化物

普遍称为Ｂｅｎｚｏｆｕｒｏｘａｎ（ＢＦＯ）的苯并呋咱－１－氧化物已证明能降低填充炭黑的硫化胶的滞后损失３０％以上。ＢＦＯ大概能促进弹性体和炭黑之间的键合，导致硫化胶“佩恩效应”降低。ＢＦＯ在母炼胶混炼期间于不同温度下加入。为了最大限度地降低滞后损失，需要高温混炼，而且采用高比表面积的炭黑会更有效。镍盐会改善ＢＦＯ和弹性体／炭黑间的反应。     

Towards processible poly(pyrrol-2-ylsquaraines)

Summary In an attempt to produce a processible poly(pyrrol-2-ylsquaraine) by forming a copolymer of poly(pyrrol-2-ylsquaraine) with polymethylmethacrylate, two synthetic routes were utilised. The first included forming the polysquaraine and then polymerising the attached methacrylate groups to form the desired product and the second proceeded via the preformed methacrylate polymer, containing N-alkylpyrrole side chains, which was then condensed with squaric acid. Difficulties arose in the first route when the polysquaraine product was found to be insoluble, hence preventing any further polymerisation but partial solubility during the second procedure did allow bissquaraines to be formed and, as a consequence, the resultant product exhibited fluorescent properties. Yet the desired processible poly(pyrrol-2-ylsquaraine) was not achieved. Received: 30 October 1997/Revised version: 22 January 1998/Accepted: 23 January 1998