Dynamic deuteron polarization in irradiated D-Ammonia (ND3 and its first use in a high energy photon beam

We have dynamically polarized the deutorons in deuterated ammonia (ND₃) at 1 K, 0.5 K and at about 200 mK in a magnetic field of 2.5 T. The paramagnetic radicals were created by irradiating the material under liquid argon at 90 K (‘high temperature’ irradiation) with electrons from the 20 MeV injection linac of the Bonn synchrotron. Electron paramagnetic resonance (EPR) measurements identified the radicals as ?D₂.First target asymmetry measurements of the reaction γd ↑ → pn with ND₃ as target material in a dilution refrigerator were performed at the Bonn 2.5 GeV electron synchrotron. Starting with a deuteron polarization of 31% (using‘ high temperature’ irradiated material) the polarization went up to 44% after additional irradiation at about 200 mK with the photon beam. This polarization value corresponds to an overall polarization of 13.2% of all nucleons in ND₃. The increase of the polarization could be observed up to a dose of 8 × 10¹⁴ equivalent quanta/cm². The subsequent resistance of the polarization to radiation damage is more than one order of magnitude higher than that of butanol. These results mean a considerable improvement with respect to the deuterated alcohol materials which are currently used in high energy physics experiments with polarized deuteron targets.The dependence on the microwave frequency of the polarizations of deuterons and unsubstituted protons was examined at 1 K in order to gain insight into the prevailing mechanism of dynamic nuclear polarization (DNP). These measurements disagree with the equal spin temperature (EST)-hypothesis. They rather give evidence for a more complex behaviour apparently involving more than one polarization mechanism. It is attempted to explain these observations at 1 K with a differential solid state model.Furthermore, we present a series of DNP-signals as measured with our deuteron magnetic resonance (DMR)-system at various microwave frequencies. An unusual change of the DMR-signal shape was observed.     

Arbutin in marjoram and oregano

Arbutin is a hydroquinone derivative that has been found in species of several plant families. Within the genus Origanum the formation of arbutin is polymorphic, with arbutin present in considerable amounts (O. dubium 20.8 ± 15.3 mg/g; wild O. majorana 51.3 ± 15.4 mg/g, cultivated O. majorana 40.6 ± 11.2 mg/g), minor amounts (O. microphyllum 0.1 ± 0.1 mg/g, wild O. onites 0.3 ± 0.1 mg/g, cultivated O. onites 0.1 ± 0.1 mg/g, O. saccatum 0.1 ± 0.1 mg/g, O. solymicum 0.4 ± 1.0 mg/g) or completely absent (O. husnucan-baseri, O. syriacum, O. vulgare). Whereas the most important commercial oregano species (O. onites and O. vulgare) contain no or only minor amounts of arbutin, marjoram (O. majorana) has considerably high amounts. The high variability of arbutin in O. majorana would allow a selection into cultivars with high arbutin content and low arbutin varieties. In a segregating F₂-generation of a species crossing between O. majorana (high content of arbutin) and O. vulgare ssp. vulgare (free of arbutin), the presence of arbutin followed a Mendelian segregation of 3:1, indicating that only one gene is responsible for the polymorphism of arbutin in the genus Origanum. The absence of arbutin in O. vulgare ssp. vulgare or O. syriacum would even enable the breeding of marjoram with no arbutin at all.     

PrimePACK^TM封装优化集成模块内的IGBT叠层可提高功率密度

本文讨论了最新PrimePACK^TM模块如何集成到现有的逆变器平台中,描述了包括控制和保护在内的逆变器模块的架构概念。该模块的机械特性允许对热管理进行优化,进而充分发挥IGBT输出电流能力,分析并比较了IGBT驱动的不同方案。最后,给出逆变器的测试结果。     

Chronologie des EHEC O104:H4 Ausbruchsgeschehens bis zur Gründung der l?nderübergreifenden Task Force EHEC aus Sicht der Lebensmittelüberwachung in Schleswig-Holstein am Beispiel des Kreises Schleswig-Flensburg

Im Folgenden wird über die Chronologie der Ereignisse im Rahmen des EHEC O104:H4 Ausbruchsgeschehen aus Sicht der Lebensmittelüberwachung in Schleswig-Holstein bis zur Gründung der nationalen Task Force EHEC berichtet. Am Beispiel des Kreises Schleswig-Flensburg wird die Zusammenarbeit und der Informationsaustausch zwischen Gesundheitsbeh?rde und Lebensmittelüberwachung dargestellt. Die erste Information über einen Anstieg an Erkrankungen mit blutigem Durchfall und HUS-Symptomatik in den Kreisen anliegend an und aus Hamburg erhielt das Ministerium für Landwirtschaft, Umwelt und l?ndliche R?ume des Landes Schleswig-Holstein am 19. Mai 2011. Der Fachdienst Veterin?rmedizin und Verbraucherschutz des Kreises Schleswig-Flensburg wurde ebenfalls am 19. Mai 2011 über eine solche H?ufung im Kreis Schleswig-Flensburg in Kenntnis gesetzt. Daraufhin wurden auf Landes- und Kreisebene Ma?nahmen eingeleitet, um zusammen mit den Gesundheitsbeh?rden diesen lebensmittelassoziierten Ausbruch aufzukl?ren. Am 01. Juni 2011 fand erstmalig in Schleswig-Holstein eine Telefonkonferenz zwischen den betroffenen Ministerien und allen Lebensmittelüberwachungs- und Gesundheitsbeh?rden der Kreise und kreisfreien St?dte statt, um das weitere Vorgehen gemeinsam zu koordinieren. Am 03. Juni 2011 wurde in Berlin am Bundesamt für Verbraucherschutz und Lebensmittelsicherheit (BVL) die nationale Task Force EHEC gegründet. Zwei Wochen nachdem die Gesundheitsbeh?rden von geh?uften und l?nderübergreifenden Erkrankungsf?llen Kenntnis hatten, geht damit die Koordinierung der Aufkl?rung von den Gesundheitsbeh?rden auf das BVL über. Am 07. Juni 2011 wurde durch das MLUR ein Mitarbeiter des Kreises Schleswig-Flensburg als Vertreter für Schleswig-Holstein in die Task-Force EHEC nach Berlin entsandt. Als Ergebnis ist aus diesem Erkrankungsgeschehen auch die Lehre zu ziehen, dass vermehrt pflanzliche Lebensmittel zu den „gef?hrlichen Lebensmitteln“ geh?ren. Diese müssen in Zukunft viel st?rker in den Fokus genommen werden.     

Low-temperature differential-thermal analysis to measure variations in entropy

We describe how we can precisely measure variations in the entropy S of small solid samples below room temperature, as a function the temperature T or the external magnetic field H, respectively. A simple differential-thermal analysis technique allows, in principle, for the measurement of variations in S without any instrumental broadening of the data. The method is particularly well suited for the detection of sharp phase transitions in samples of milligram size.     

Environmental stress cracking of polyethylene high density (PE‐HD) induced by liquid media – Validation and verification of the full‐notch creep test (FNCT)

The full‐notch creep test (FNCT) is widely used to characterize the slow crack growth (SCG) behavior of polyolefin materials in “inert” media as well as effects of environmental stress cracking (ESC) in which the medium has decisive influence on damage mechanism and time to failure. The test is of greatest importance for pipe and blow molding types of polyethylene, high density (PE‐HD). Usually the full‐notch creep test is applied as a standardized testing method (ISO 16770) using a few universal liquid media, such as solutions of Arkopal N 100. In our study, selected relevant polyethylene, high density materials are investigated also in real media – practical formulations as well as representative pure chemicals – and influences of temperature and geometry of specimen and notch are explicitly addressed. Furthermore, the investigations comprise also the environmental stress cracking behavior of polyethylene, high density in media that are sorbed to a significant extent – examples are diesel and biodiesel – based on comparison with samples previously saturated with those media. Thus, also the underlying diffusion controlled sorption process has to be assessed before. The investigations were performed using a full‐notch creep testing device with 12 individual sub‐stations, each equipped with individual electronic stress and temperature control and continuous online monitoring of the specimen elongation.     

Autonomous Ultrafast Self‐Healing Hydrogels by pH‐Responsive Functional Nanofiber Gelators as Cell Matrices

The synthesis of hybrid hydrogels by pH‐controlled structural transition with exceptional rheological properties as cellular matrix is reported. “Depsi” peptide sequences are grafted onto a polypeptide backbone that undergo a pH‐induced intramolecular O–N–acyl migration at physiological conditions affording peptide nanofibers (PNFs) as supramolecular gelators. The polypeptide–PNF hydrogels are mechanically remarkably robust. They reveal exciting thixotropic behavior with immediate in situ recovery after exposure to various high strains over long periods and self‐repair of defects by instantaneous reassembly. High cytocompatibility, convenient functionalization by coassembly, and controlled enzymatic degradation but stability in 2D and 3D cell culture as demonstrated by the encapsulation of primary human umbilical vein endothelial cells and neuronal cells open many attractive opportunities for 3D tissue engineering and other biomedical applications.