Synthesis of polycyclic polyfunctionalized carbocycles by a cobalt(I)-initiated tandem diels–alder reaction sequence

The cobalt(I)-catalyzed neutral Diels–Alder reaction of acyclic 1,3-dienes with conjugated enynes can be used to generate secondary dihydroaromatic 1,4,8-trienes containing a 1,3-diene substructure, in good yields under mild reaction conditions. These 1,3-dienes can be converted, with reactive dienophiles in a tandem normal Diels–Alder reaction, into polycyclic compounds. In a similar tandem Diels–Alder sequence, the cobalt-catalyzed neutral homo Diels–Alder reaction of 2,5-norbornadiene can be used to generate polycyclic cycloaddition adducts. A sequential triple Diels–Alder reaction sequence can be realized when norbornadiene is reacted with the excess of the conjugated enynes under cobalt(I) catalysis. In a homo Diels–Alder, neutral Diels–Alder, normal Diels–Alder reaction sequence, the intermediately formed adducts are reacted with activated dienophiles to yield polycyclic compounds in a short sequence. The structures of several products were established by X-ray analysis. This showed that predominantly endo-products are formed in the tandem reaction sequences, while the exo-product becomes predominant in the triple Diels–Alder reaction sequence.     

Effect of dowels and adhesive types on withdrawal strength in particleboard and MDF

Composite materials and wooden dowels are being used increasingly in the construction of furniture frames and inner decoration. However, there is little information available concerning the withdrawal strength of various fasteners and in particular, dowels in these materials. The aim of this study was to determine the withdrawal strengths of 6, 8, and 10?mm diameter dowels produced from different wood species bonded parallel or vertical to the surfaces of a medium-density fiberboard (MDF) or particleboard with poly vinylacetate or Desmodur (D-VTKA). According to TS 4539 standard, the effect of dowel species, direction of withdrawal, board type and the type of adhesive on the withdrawal strength were determined. The highest (8.35?N/mm²) withdrawal strength was obtained for oak dowels bonded with D-VTKA adhesive vertically to the surface of MDF. This value is higher than the predictive expression that allows designers to estimate the withdrawal strength of dowels.     

Validating modelled NPP using statistical yield data

The German Remote Sensing Data Center operates the Biosphere Energy Transfer Hydrology Model, a process model that estimates the net primary productivity of agricultural areas. The model is driven by remote sensing data and meteorological data. Remotely sensed datasets including a time series of the leaf area index, which describes vegetation condition, and a land cover classification, which provides information about land use, are needed. Currently leaf area indices and land cover data derived from the sensor vegetation are used. Both datasets have spatial resolutions of about 1 km × 1 km and are freely available for the area of investigation (Germany and Austria). The meteorological input parameters are air temperature (at 2 m height), precipitation, cloud cover, wind speed (at 10 m height) and soil water content (in the four uppermost soil layers); these are obtained from the European Centre for Medium-Range Weather Forecasts, with a spatial resolution of about 0.25° × 0.25° and a temporal resolution up to four times daily. The output of the model, the gross primary productivity, is calculated at daily resolution. By subtracting the cumulative plant maintenance and growth respiration, the net primary productivity is then determined. In order to validate the modelled net primary productivity, crop yield estimates derived from the national statistics of Germany and Austria are used. After estimating above-ground biomass using plant-specific above- to below-ground ratios, conversion factors (corn-to-straw and leaf-to-beet relations) are applied to estimate total biomass. Finally the carbon content of dry matter is estimated. To correlate model results with these statistical data, the modelled data are aggregated to net primary productivity per administrative district. The results show that a process model using remote sensing data as input can deliver reliable estimates of agricultural biomass potential which are highly correlated with statistically derived estimates of actual biomass produced.     

用心铸造文化与友谊的桥梁——访泰国国际航空大众有限公司成都办事处总经理安南先生

创立于1960年的泰国国际航空大众有限公司，到今年已经走过了五十个年头。并又一次在全球航空业评选调查中获得“最佳头等舱贵宾室第一名”、“最佳机场服务第一名”的荣誉。在7月还被美国著名旅游休闲杂志（Travel＋Leisure）评选为全球十佳国际航空公司之一。     

Induktivitäten in Gleichrichterschaltungen

Zusammenfassung Eine einphasige Drossel mit herausgeführtem Mittelpunkt, die über einen Zweiweggleichrichter in Nullpunktschaltung einen Gleichstromverbraucher speist, kann durch entsprechende Bemessung der Kopplung zwischen ihren beiden Wicklungshälften zur Glättung des Gleichstromes herangezogen werden. Der Aufwand wird dabei zwar größer als bei besonderer Gleichstromdrossel, aber die Aufteilung auf zwei getrennte Einrichtungen, nämlich Transformator und Drossel, wird vermieden. Die Glättung ist mit dem Auftreten eines magnetischen Gleichstromfeldes in der Drossel verknüpft, und die Schaltung ist vorteilhaft verwendbar, wenn nicht der Gleichstrom sondern ein solches Magnetfeld erzeugt werden soll. Außer dem Magneten, der also mit zwei Wicklungen versehen ist und einem Zweiweggleichrichter sind dazu keine weiteren Einrichtungen notwendig. Eine solche Anordnung wurde durch Rechnung und Messung untersucht. Es zeigt sich, daß der Magnet nur um wenige Prozente größer zu bemessen ist, als wenn er mit reinem Gleichstrom erregt wäre und daß das erzeugte Feld nur ganz geringe Oberwellen hat. Der Versuch, bei dem der zeitliche Feldverlauf dadurch bestimmt wurde, daß die vom Feld in einen fremd angetriebenen Kommutatoranker induzierte Ankerspannung gemessen wurde, zeigt weitgehende Übereinstimmung mit der Rechnung.     

Chemical,physical and biological properties of alginates and their biomedical implications

Alginates are binary, linear copolymers of (1 → 4) linked ß-d-mannuronic acid (M) and α-l-guluronic acid (G) residues of widely different composition and sequence. The monomers do not occur randomly but rather in a block-like fashion, where the G-blocks are responsible for the specific ion binding and hence also the gelling properties of alginates. Alginates have for decades been used as medical devices in various products, and research has been conducted on alginate gel beads as entrapment devices for the transplantation of e.g. insulin producing cells. Until recently, no pharmaceutical activity of the alginate molecule itself had been claimed. The fact that alginates high in mannuronate residues are able to induce cytokine production and may stimulate Toll-like receptors has changed this picture. Furthermore, it has quite recently also been shown that oligoguluronates are able to transiently modify mucin network structures to such an extent that it opens up possibilities for the treatment of pathological respiratory diseases as well as a general increased drug bioavailability due to increased mucosal uptake. This review presents a summary of the physicochemical properties of alginates and their entry into biotechnology and biomedicine.     

OCRE Domains of Splicing Factors RBM5 and RBM10: Tyrosine Ring-Flip Frequencies Determined by Integrated Use of 1H NMR Spectroscopy and Molecular Dynamics Simulations

The 55-residue OCRE domains of the splicing factors RBM5 and RBM10 contain 15 tyrosines in compact, globular folds. At 25 °C, all 15 tyrosines show symmetric ¹H NMR spectra, with averaged signals for the pairs of δ- and ϵ-ring hydrogens. At 4 °C, two tyrosines were identified as showing ¹H NMR line-broadening due to lowered frequency of the ring-flipping. For the other 13 tyrosine rings, it was not evident, from the ¹H NMR data alone, whether they were either all flipping at high frequencies, or whether slowed flipping went undetected due to small chemical-shift differences between pairs of exchanging ring hydrogen atoms. Here, we integrate ¹H NMR spectroscopy and molecular dynamics (MD) simulations to determine the tyrosine ring-flip frequencies. In the RBM10-OCRE domain, we found that, for 11 of the 15 tyrosines, these frequencies are in the range 2.0×10⁶ to 1.3×10⁸ s⁻¹, and we established an upper limit of <1.0×10⁶ s⁻¹ for the remaining four residues. The experimental data and the MD simulation are mutually supportive, and their combined use extends the analysis of aromatic ring-flip events beyond the limitations of routine ¹H NMR line-shape analysis into the nanosecond frequency range.