Photochemie von Bis-2H-tetrazolen. III. Nachweis von Bisnitriliminen durch Tieftemperatur-UV-Spektroskopie und thermische Folgereaktionen durch Photolyse von Bis-2H-tetrazolen

Photochemistry of Bis-2H-tetrazoles. III. Detection of Bisnitrilimines through Low-Temperature-UV-Spectroscopy and Thermic Consecutive Reactions through Photolysis of Bis-2H-tetrazoles The photolysis of 2H-tetrazoles ( 1 ) leads to nitrilimines. Bis-2H-tetrazoles form correspondingly bisnitrilimines 2 . They were detected directly by the photolysis of bis-2H-tetrazoles ( 1 ) in an ethanol/ether glass at 95 K. The absorption maxima are depend in an expected manner on the substituents. In the presence of dipolarophiles the reaction of bis-2H-tetrazoles ( 1 ) at room temperature gives bis-Δ²-pyrazolines ( 3 ). These reactions can also be explained by a photoreaction of bis-2H-tetrazoles ( 1 ) to bisnitrilimines 2 at 95 K and subsequent cycloaddition above 150 K. Some bis-Δ²-pyrazolines ( 3 ) are described. The photolyses of bis-2H-tetrazoles ( 1 ) to the bisnitrilimines 2 proceed as one step eliminations of two molecules of nitrogen.     

Field-Emission Cathodes Based on Microchannel Plates

Semiconductors - The existing methods of fabricating low-field cathodes do not permit the development of device structures that comply with the requirements of developers of systems. In this work,...     

Holzeigenschaften von Buchen aus immissionsgeschädigten Beständen

In 48 trees from two immission-damaged beech stands in the Hils, Lower Saxonia, both over 100 years old, the anatomical wood properties at breast height (1,30 m) were investigated. From 24 trees out of each stand 12 trees belonged to damage class 0 and the others to damage class 2. On samples of the annual ring sequence 1975–85 and the undamaged annual ring sequence 1945–1955 fibre length, the water conducting tissue and the percentage of cell species were investigated. No abnormal variations of the anatomical wood properties due to immissions could be found.     

Influence of the zeolite structure and acidity on the hydroisomerization of n-heptane

Different acid solids loaded with 1 wt.% of Pt have been studied in n-heptane hydroisomerization in order to determine the influence of porosity and acidity (considered measured by the activity) on selectivities. The open solids like Y and β zeolites and a pillared clay present different activities towards n-C₇ conversion but similar selectivities. Consequently, acidity seems to be a less important parameter in n-C₇ isomerization than porosity. Very different results were obtained as a function of the solid structure and so n-heptane hydroconversion appears to be a simple and rapid method to obtain data concerning the porosity of unknown zeolite structures. The highest content of multibranched isomers was obtained on open solids but the value predicted by the thermodynamic was never reached due to the fact that cracking of multibranched isomers is initiated quickly.     

Anodic oxidation of phenol for waste water treatment

The electrochemical oxidation of phenol for waste water treatment was studied at a platinum anode. Analysis of reaction intermediates and a carbon balance has shown that the reaction occurs by two parallel pathways; chemical oxidation with electrogenerated hydroxyl radicals and direct combustion of adsorbed phenol or/and its aromatic intermediates to CO₂.     

A rechargeable battery of the type polyaniline/propylene carbonate-LiClO4/Li-Al

A secondary battery of the type polyaniline/propylene carbonate-LiClO₄/Li–Al is described. The polymer is made by aniline oxidation with ammonium persulphate in NH₄F, 2.3 HF as solvent. The discharge capacity of the polymer is 100 Ah kg^–1 at 25°C and 140 Ah kg^–1 at 40°C for current densities of 0.5 mA cm^–2 and for an amount of material giving a capacity of 10 mAh. The voltage in open circuit for the fully charged battery is 3.6 V. The average usable potential is 2.8–3 V. The energy density for the polymer lies between 280 and 420 Wh kg^–1. The ratio of the amounts of electricity in discharge and charge is one for several hundred deep cycles. The behaviour with regard to self discharge and to constant applied voltage (floating life) is excellent.     

Effect of a mixture of steam-flaked corn and soybeans on health, growth, and selected blood metabolism of Holstein calves

The objective of the experiment was to evaluate the effects of steam-flaked corn grains and soybeans on calf health, growth, and selected blood parameters. Holstein bull calves (n = 30, approximately 7 ± 3 d of age) were purchased from local dairy farms and offered milk, starter diets, and hay, and were then assigned to the experiment at 21 ± 3 d of age. Calves were blocked into 3 treatments by birth date and body weight and randomly assigned to receive fresh milk and a commercial pelleted starter containing extruded corn and soybeans (ECS), steam-flaked corn and soybeans (SFCS), or ground corn and soybeans (GCS). The experiment was conducted with calves from 3 to 13 wk of age. Body weight, calf starter intake, milk intake, total dry matter intake, and body structural growth were not significantly influenced by corn and soybean processing during the study; however, feed efficiency was significantly improved by the SFCS treatment. Average daily gain generally decreased during the weaning week for all treatments, but did not differ significantly among treatments. Health incidences for calves fed the SFCS starter were lower than those fed the other 2 treatments. The blood hematocrit was higher for calves fed the SFCS starter than for those fed the GCS and ECS starters during wk 6 to 11. The concentration of plasma β-hydroxybutyrate was higher for the calves fed the GCS and SFCS treatments than for those fed the ECS treatment during wk 6 to 13, but lower during wk 4 and 5. Plasma glucose concentrations decreased remarkably with increasing calf age but were not affected by corn and soybean processing. Plasma nonesterified fatty acids were influenced by calf age, and higher NEFA concentration was observed in the SFCS treatment than in the other 2 treatments during wk 5 to 9. Calves consuming the SFCS starter had similar average daily gain, milk intake, starter intake, total dry matter intake, and body structure, but had improved feed efficiency when compared with animals consuming the GCS and ECS starters. The SFCS starter decreased incidence of diarrhea during the postweaning period and required less veterinary treatment. These data suggest that the steam-flaking of corn and soybeans can influence the growth performance and the selected blood parameters of calves and that, in this study, the extrusion of corn and soybeans had no beneficial effect on the growth performance of calves.     

Physisorption of hydrogen in single-walled carbon nanotubes

The interaction of hydrogen with single-walled carbon nanotubes (SWNTs) was analysed. A SWNT sample was exposed to D₂ or H₂ at a pressure of 2 MPa for 1 h at 298 or 873 K. The desorption spectra were measured by thermal desorption spectroscopy (TDS). A main reversible desorption site was observed throughout the range 77 to 320 K. The activation energy of this peak at about 90 K was calculated assuming first-order desorption. This corresponds to physisorption on the surface of the SWNTs (19.2±1.2 kJ/mol). A desorption peak was also found for multi-walled carbon nanotubes (MWNTs), and also for graphite samples. The hydrogen desorption spectrum showed other small shoulders, but only for the SWNT sample. They are assumed to originate from hydrogen physisorbed at sites on the internal surface of the tubes and on various other forms of carbon in the sample. The nanosized metallic particles (Co:Ni) used for nanotube growth did not play any role in the physisorption of molecular hydrogen on the SWNT sample. Therefore, it is concluded that the desorption of hydrogen from nanotubes is related to the specific surface area of the sample.