Electron irradiation-induced destruction of carbon nanotubes in electron microscopes

Observations of carbon nanotubes under exposure to electron beam irradiation in standard transmission electron microscope (TEM) and scanning electron microscope (SEM) systems show that such treatment in some cases can cause severe damage of the nanotube structure, even at electron energies far below the approximate 100 keV threshold for knock-on damage displacing carbon atoms in the graphene structure. We find that the damage we observe in one TEM can be avoided by use of a cold finger. This and the morphology of the damage imply that water vapour, which is present as a background gas in many vacuum chambers, can damage the nanotube structure through electron beam-induced chemical reactions. Though, the dependence on the background gas makes these observations specific for the presently used systems, the results demonstrate the importance of careful assessment of the level of subtle structural damage that the individual electron microscope system can do to nanostructures during standard use.     

Spatially dependent regularization parameter selection in total generalized variation models for image restoration

In this paper, the automated spatially dependent regularization parameter selection framework for multi-scale image restoration is applied to total generalized variation (TGV) of order 2. Well-posedness of the underlying continuous models is discussed and an algorithm for the numerical solution is developed. Experiments confirm that due to the spatially adapted regularization parameter, the method allows for a faithful and simultaneous recovery of fine structures and smooth regions in images. Moreover, because of the TGV regularization term, the adverse staircasing effect, which is a well-known drawback of the total variation regularization, is avoided.     

集成安全：有效保证安全性

安全是任何工厂的头等大事，人员伤亡更是令人无法接受。但是，安全的含义可能并不仅仅局限于对人员和设备实施必要的基本保护，如与安全相关事件的负面宣传可能会对相关企业造成极其深刻的影响，在某些情况下，甚至会影响到整个行业。随着工艺复杂性的不断增加，工厂使用不同制造商提供的不同系统，这就给保证整体安全水平提出了挑战。ABB相信，未来的安全系统不再是一个附带系统，虽然在设计和供应方面与其他系统分开在不同的工厂或工艺过程进行，但理应成为其集成的一部分。     

A Parallel Semisynthetic Approach for Structure–Activity Relationship Studies of Peptide YY

The gut hormone peptide YY (PYY) is postprandially secreted from enteroendocrine L cells and is involved in the regulation of energy homeostasis. The N‐terminal truncated version PYY(3–36) decreases food intake and has potential as an anti‐obesity agent. The anorectic effect of PYY(3–36) is mediated through Y₂ receptors in the hypothalamus, vagus, and brainstem regions, and it is well known that the C‐terminal tetrapeptide sequence of PYY(3–36) is crucial for Y₂ receptor activation. The aim of this work was to develop a semisynthetic methodology for the generation of a library of C‐terminally modified PYY(3–36) analogues. By using an intein‐based expression system, PYY(3–29) was generated as a C‐terminal peptide α‐thioester. Heptapeptides bearing an N‐terminal cysteine and modifications at one of the four C‐terminal positions were synthesized in a 96‐well plate by parallel solid‐phase synthesis. In the plate format, an array of [Ala30]PYY(3–36) analogues were generated by ligation, desulfurization, and subsequent solid‐phase extraction. The generated analogues, in which either Arg33, Gln34, Arg35, or Tyr36 had been substituted with proteinogenic or non‐proteinogenic amino acids, were tested in a functional Y₂ receptor assay. Generally, substitutions of Tyr36 were better tolerated than modifications of Arg33, Gln34, and Arg35. Two analogues showed significantly improved Y₂ receptor selectivity; therefore, these results could be used to design new drug candidates for the treatment of obesity.     

Automatic nematode detection in cod fillets (Gadus morhua L.) by hyperspectral imaging

Detection of objects embedded in tissue, using visible light, is difficult due to light scattering. The optical properties of the surrounding tissue will influence the spectral characteristics of the light interacting with the object, and the spectral signature observed from the object will be directly affected. A method for calibrating the spectral signature of small objects, embedded in translucent material, by the estimated local background spectrum is presented. The method is evaluated under industrial conditions in a new hyperspectral imaging system for automatic detection of nematodes in cod fillets. The system operates at a conveyor belt speed of 400 mm/s which meets the industrial required speed of assessing one fillet per second. The local calibration method reduces the number of spectra needed to be classified by 89.6%. For one or more false alarms in 60% of the fillets sampled after the trimming station, the Gaussian maximum likelihood classifier detects 70.8% and 60.3% of the dark and pale nematodes, respectively. This is better than what is previously reported using a higher resolution instrument on a slow moving conveyor belt, and comparable or better to what is reported for manual inspection under industrial conditions.     

Pd@Al2O3‐Catalyzed Hydrogenation of Allylbenzene to Propylbenzene in Methanol and Aqueous Micellar Solutions

The palladium on alumina (Pd@Al₂O₃)‐catalyzed hydrogenation of allylbenzene to propylbenzene was studied in methanol and aqueous micellar solutions of sodium dodecyl sulfate (SDS), decyltrimethylammonium bromide (DTAB), and t‐octylphenoxypolyethoxyethanol (TX‐100). Over Pd@Al₂O₃, propylbenzene was obtained via direct hydrogenation of allylbenzene and isomerization to β‐methylstyrene which was hydrogenated afterwards. In aqueous micellar solutions, the reaction was faster than in pure water, but slower than in methanol due to lower hydrogen solubility. In the H₂O/SDS system, a higher activation energy was obtained than in methanol. For the investigated surfactants, the initial reaction rate in the micellar systems decreased in the order SDS > TX‐100 > DTAB.     

Particle finite element analysis of the granular column collapse problem

The problem of granular column collapse is investigated by means of an axisymmetric version of the particle finite element method (PFEM). The granular medium is represented by a simple rate-independent plasticity model and the frictional contact between the granular flow and its rigid basal surface is accounted for. In the version of the PFEM developed for this study, the governing equations of the boundary value problem are cast in terms of an optimization problem and solved using mathematical programming tools. The agreement between model and experiment is generally satisfactory, quantitatively as well as qualitatively. However, the friction angle of the granular material, as well as the exact interface conditions between the base and granular material, are shown to have a relatively significant influence on the results.