The effect of mechanical vibration and drift on the reconstruction of exit waves from a through focus series of HREM images

Experimental HREM images can show a limited resolution as a result of mechanical vibration and drift. In this paper the effect of such mechanical vibrations on the accuracy of the through focus exit wave reconstruction method is investigated for different thicknesses of a test structure of La₃Ni₂B₂N₃. A through-focus series of HREM images for this structure is simulated for different kinds of mechanical vibration corresponding to an information limit g of about 7 nm⁻¹: (1) no mechanical vibration, (2) isotropic mechanical vibration, and (3) several anisotropic mechanical vibrations. From these through-focus series the reconstructed exit wave is calculated (Ultramicroscopy 64 (1996) 109). The above isotropic and anisotropic mechanical vibrations have a large effect on the reconstructed exit waves when compared with the reconstructed exit wave without mechanical vibration, i.e. the range of amplitudes and phases in a reconstructed exit wave decreases and the background intensity increases. The initial thickness and orientation can be obtained using a least-squares refinement procedure (Acta Crystallogr. A 54 (1998) 91) when there is no mechanical vibration present. In the case of isotropic or anisotropic vibration, the refined thickness and orientation are likely to give wrong results depending on the size of the vibrations and on the number of significant reflections (which is related to the size of the unit cell, the thickness and the misorientation).     

Intercalating Electron Dyes for TEM Visualization of DNA at the Single-Molecule Level

Staining compounds containing heavy elements (electron dyes) can facilitate the visualization of DNA and related biomolecules by using TEM. However, research into the synthesis and utilization of alternative electron dyes has been limited. Here, we report the synthesis of a novel DNA intercalator molecule, bis-acridine uranyl (BAU). NMR spectroscopy and MS confirmed the validity of the synthetic strategy and gel electrophoresis verified the binding of BAU to DNA. For TEM imaging of DNA, two-dimensional DNA origami nanostructures were used as a robust microscopy test object. By using scanning transmission electron microscopy (STEM) imaging, which is favored over conventional wide-field TEM for improved contrast, and therefore, quantitative image analysis, it is found that the synthesized BAU intercalator can render DNA visible, even at the single-molecule scale. For comparison, other staining compounds with a purported affinity towards DNA, such as dichloroplatinum, cisplatin, osmium tetroxide, and uranyl acetate, have been evaluated. The STEM contrast is discussed in terms of the DNA–dye association constants, number of dye molecules bound per base pair, and the electron-scattering capacity of the metal-containing ligands. These findings pave the way for the future development of electron dyes with specific DNA-binding motifs for high-resolution TEM imaging.     

Periodic capacity management under a lead-time performance constraint

In this paper, we study a production system that operates under a lead-time performance constraint which guarantees the completion of an order before a pre-determined lead-time with a certain probability. The demand arrival times and the service requirements for the orders are random. To reduce the capacity-related operational costs, the production system under study has the option to use flexible capacity. We focus on periodic capacity policies and model the production system as a queuing system that can change its capacity periodically and choose to operate in one of the two levels: a permanent capacity level and a permanent plus contingent capacity level. Contingent capacity is supplied if needed at the start of a period, and is available during that period, at a cost rate that is decreasing in period length in different functional forms. Next, we propose a search algorithm that finds the capacity levels and the switching point that minimizes the capacity-related costs for a given period length. The behaviour of the capacity-related costs changes drastically under different period lengths and cost structures. In our computational study, we observe that the periodic capacity flexibility can reduce the capacity-related operational costs significantly (up to 35%). However, in order to achieve these savings, the period length must be chosen carefully depending on ambition level and capacity-related costs. We also observe that the percentage savings are higher for more ambitious lead-time performance constraints. Moreover, we observe that the use of contingent capacity makes the total system costs more insensitive to the lead-time performance requirements.     

Effect of Growth-Induced Linear Defects on High Frequency Properties of Pulse-Laser Deposited YBa2Cu3O7?δ Films

Growth-induced linear defects are shown to strongly affect the microwave surface resistance, R_s, of highly biaxially oriented high temperature superconductor (HTS) YBa₂Cu₃O_7– (YBCO) films. Measured R_s(77 K) turned out to be 4–5 times higher than in single crystals. The films were deposited by modified pulse-laser technique, J_c(77 K) = (3-6) × 10⁶ A/cm², onto LaAlO₃ substrates. R_s(T) was measured at 134 GHz and 20–100 K. TEM/HREM study of YBCO films deposited at T_s = 750°C–780°C revealed a reduction of edge dislocation density with T_s increase (from 2 · 10¹¹ to 10¹⁰ lines/cm²). YBCO films deposited at T_s = 780°C exhibited the smallest R_s(77 K, 134 GHz) < 120 m and the lowest density of dislocations detected by HREM and X-ray analysis. A nature of the dislocation effect is discussed within a model of local anisotropic elastic deformation in a vicinity of dislocation cores, where T_c variation and an enhancement of normal quasiparticle density are significant.     

The optimisation of solid–liquid extraction of antioxidants from apple pomace by response surface methodology

Response surface methodology using two food grade solvents, acetone and ethanol, was used to optimise antioxidant extraction from industrially generated apple pomace. Efficiency of extraction was optimised by measuring antioxidant activity, phenol content and three individual polyphenol groups. Conditions for optimal antioxidant activity as measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay were 56% ethanol, 80 °C and 31 min. Using these conditions an antioxidant value of 444 mg Trolox/100 g DW was obtained. For acetone extraction the optimal conditions were 65% acetone, 25 °C and 60 min, resulting in an antioxidant value of 436 mg Trolox/100 g DW. Both ethanol and acetone would be suitable to replace methanol for a food grade and more environmental friendly solid–liquid extraction of antioxidants.     

Removal of two waterborne pathogenic bacterial strains by activated carbon particles prior to and after charge modification

Waterborne diseases constitute a threat to public health despite costly treatment measures aimed at removing pathogenic microorganisms from potable water supplies. This paper compared the removal of Raoultella terrigena ATCC 33257 and Escherichia coli ATCC 25922 by negatively and positively charged types of activated carbon particles. Both strains display bimodal negative zeta-potential distributions in stabilized water. Carbon particles were suspended to an equivalent external geometric surface area of 700 cm2 in 250 mL of a bacterial suspension, with shaking. Samples were taken after different durations for plate counting. Initial removal rates were less elevated for the positively charged carbon particle than expected, yielding the conclusion that bacterial adhesion under shaking is mass-transport limited. After 360 min, however, the log-reduction of the more negatively charged R. terrigena in suspension was largest for the positively charged carbon particles as compared with the negatively charged ones, although conditioning in ultrapure or tap water of positively charged carbon particles for 21 days eliminated the favorable effect of the positive charge due to counterion adsorption from the water. Removal of the less negatively charged E. coli was less affected by aging of the (positively charged) carbon particles, confirming the role of electrostatic interactions in bacterial removal by activated carbon particles. The microporous, negatively charged coconut carbon performed less than the mesoporous, positively charged carbon particle prior to conditioning but did not suffer from loss of effect after conditioning in ultrapure or tap water.     

Determination of vitamin A in liver and liver-containing products using narrow-bore normal, phase HPLC

Vitamin A concentrations in livers of fattening animals and liver-containing products may reach much higher values than was assumed up to now. This effect may be caused by animal feed, which is usually supplemented with vitamins. To support this supposition, 57 liver samples of different species of animals, 97 liver sausages and 106 samples of liver-containing infant food were analysed. For isolation of retinol from the sample matrix the sample was saponified for 16 h under a nitrogen atmosphere at room temperature. Retinol was extracted from the saponification solution by using disposable cartridges. For Chromatographic determination a normalphase HPLC system using a narrow-bore analytical column and a photodiode array detector was used. It was possible to separate all-trans-retinol from other isomers. The identity of the peaks could be confirmed by recording the UV spectra. —The results of the retinol contents found in the analysed samples ranged from 11.6 to 160.7 mg/100 g in liver, from 1.4 to 31.1 mg/100 g in liver sausages and from 0.5 to 3.8 mg/100 g in infant food containing between 5 and 11% liver. By consuming liver-containing meals frequently a multiple amount of the recommended dietary intake ranging from 0.375 mg for infants to 0.8 mg for adults may be taken up. Also the recommended daily intakes of the Deutsche Gesellschaft für Ernährung can be exceeded. —The carry-over effect of daily vitamin A consumption of pigs and their liver vitamin A was investigated by parallel determination of the retinol content in the liver after slaughtering and the vitamin A content in the pig-feed during the fattening period. A clear correlation between their daily vitamin A intake and the resulting retinol content in the livers was found.

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Vitamin-A-Bestimmung in Leber und leberhaltigen Lebensmitteln unter Anwendung von Narrow-Bore-Normalphasen-HPLC

Zusammenfassung Die Vitamin-A-Gehalte in Lebern von Schlachttieren können höhere Werte annehmen als man bisher vermutete, u. a.,weil in der Tiermast verwendete Futtermittel mit Vitaminen supplementiert werden. Um den aktuellen Status aufzuzeigen, wurden 57 Leberproben unterschiedlicher Tierarten, 97 Leberwürste und 106 Gläschen vorgefertigter Kleinkindernahrung mit Lebergehalten zwischen 5 und 11% untersucht. Die Proben wurden kalt unter Stickstoffatmosphäre verseift und das Unverseifbare mit Hilfe von Kieselgurkartuschen extrahiert. Zur chromatographischen Bestimmung wurde ein Normalphasen-HPLC-System mit einer Narrow-Bore-Säule verwendet. Detektiert wurde mit einem Photodiodenarray-Detektor. Das all-trans-Retinol konnte von anderen Isomeren getrennt werden. Die gefundenen Retinolkonzentrationen bewegten sich in Bereichen zwischen 11,6 und 160,7 mg/100 g in Leber, zwischen 1,4 und 31,1 mg/100 g in Leberwurst und zwischen 0,5 und 3,8 mg/100 g in Kindernahrung. Bei häufigem Konsum von leberhaltigen Mahlzeiten kann ein Vielfaches des RDI (Recommended dietary intake), der zwischen 0,375 mg für Kleinkinder und 0,8 mg für Heranwachsende liegt, bzw. der von der DGE empfohlenen täglichen Zufuhr, die sich zwischen 0,5 und 1,1 mg bewegt, an Vitamin A zugeführt werden. —Der Zusammenhang zwischen dem täglich aufgenommenen Vitamin A von Mastschweinen und dem Retinol-Gehalt in ihren Lebern wurde untersucht. Hierzu wurde sowohl der Vitamin-A-Gehalt der Schweinelebern nach Schlachtung der Tiere als auch der Gehalt in den Futtermitteln, mit denen sie während der Mastperiode gefüttert wurden, untersucht. Eine deutliche Korrelation wurde festgestellt.

     

Changes in self-schema structure in cognitive therapy for major depressive disorder: A randomized clinical trial.

Negative cognitive structure (particularly for interpersonal content) has been shown in some research to persist past a current episode of depression and potentially to be a stable marker of vulnerability for depression (D. J. A. Dozois, 2007; D. J. A. Dozois & K. S. Dobson, 2001a). Given that cognitive therapy (CT) is highly effective for treating the acute phase of a depressive episode and that this treatment also reduces the risk of relapse and recurrence, it is possible that CT may alter these stable cognitive structures. In the current study, patients were randomly assigned to CT+ pharmacotherapy (n = 21) or to pharmacotherapy alone (n = 21). Both groups evidenced significant and similar reductions in level of depression (as measured with the Beck Depression Inventory–II and the Hamilton Rating Scale for Depression), as well as automatic thoughts and dysfunctional attitudes. However, group differences were found on cognitive organization in favor of individuals who received the combination of CT+ pharmacotherapy. The implications of these results for understanding mechanisms of change in therapy and the prophylactic nature of CT are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Constructing invariants for hybrid systems

We present a new method for generating algebraic invariants of hybrid systems. The method reduces the invariant generation problem to a constraint solving problem using techniques from the theory of ideals over polynomial rings. Starting with a template invariant—a polynomial equality over the system variables with unknown coefficients—constraints are generated on the coefficients guaranteeing that the solutions are inductive invariants. To control the complexity of the constraint solving, several stronger conditions that imply inductiveness are proposed, thus allowing a trade-off between the complexity of the invariant generation process and the strength of the resulting invariants. This research was supported in part by NSF grants CCR-01-21403, CCR-02-20134 and CCR-02-09237, by ARO grant DAAD19-01-1-0723, by ARPA/AF contracts F33615-00-C-1693 and F33615-99-C-3014, and by NAVY/ONR contract N00014-03-1-0939.