The magnetic properties of maghemite (gamma-Fe2O3) cubic and spherical nanoparticles of similar sizes have been experimentally and theoretically studied. The blocking temperature, T(B), of the nanoparticles depends on their shape, with the spherical ones exhibiting larger T(B). Other low temperature properties such as saturation magnetization, coercivity, loop shift or spin canting are rather similar. The experimental effective anisotropy and the Monte Carlo simulations indicate that the different random surface anisotropy of the two morphologies combined with the low magnetocrystalline anisotropy of gamma-Fe2O3 is the origin of these effects.

Nickel ferrite (NiFe2O4) nanoparticles with an average crystallite size of about 8.6 nm were prepared by mechanochemical synthesis (mechanosynthesis). In-field Mössbauer spectroscopy and high-resolution TEM studies revealed a nonuniform structure of mechanosynthesized NiFe2O4 nanoparticles consisting of an ordered core surrounded by a disordered grain boundary (surface) region. The inner core of a NiFe2O4 nanoparticle is considered to possess a fully inverse spinel structure with a Néel-type collinear spin alignment, whereas the surface shell is found to be structurally and magnetically disordered due to the nearly random distribution of cations and the canted spin arrangement. As a consequence of frustrated superexchange interactions in the surface shell, the mechanosynthesized NiFe2O4 exhibits a reduced nonsaturating magnetization, an enhanced coercivity, and a shifted hysteresis loop. The study also demonstrates that one can tailor the magnetic properties of mechanosynthesized NiFe2O4 particles by suitably controlling their size. The thickness of the surface shell of about 1 nm estimated from size-dependent magnetization measurements is found to be in good agreement with that obtained from high-resolution TEM and Mössbauer experiments. On heating above 673 K, the mechanosynthesized NiFe2O4 relaxes to a structural and magnetic state that is similar to the bulk one.

Adjusting the remifentanil dosage according to the SPI in outpatient anaesthesia reduced the consumption of both remifentanil and propofol and resulted in faster recovery.

A single-step synthesis of magnesium ferrite (MgFe 2 O 4 ) nanoparticles with an average crystallite size of about 8.5 nm synthesized via mechanochemical processing of binary oxide precursors at room temperature is reported. The study highlights the nature of the cation disorder and of the spin arrangement in mechanosynthesized MgFe 2 O 4 as well as its response to changes in temperature. An unusual property of the magnetization enhancement in nanoscale mechanosynthesized MgFe 2 O 4 is reported. Whereas the inner core of a MgFe 2 O 4 nanoparticle exhibits a partly inverse spinel structure with a Ne ´el type collinear spin alignment, the major features of the ionic and spin configurations in the grain boundary (surface) region are a nonequilibrium cation distribution and a canted spin arrangement. Although the spin-canting effect tends to reduce the magnetic moment, the magnetization enhancement exhibited by mechanosynthesized MgFe 2 O 4 is attributed to the nearly random distribution of magnetic cations in the surface regions of nanoparticles. On heating above 623 K, the mechanosynthesized MgFe 2 O 4 relaxes to a structural and magnetic state that is similar to the bulk one.

Knowledge of the microbial consortia participating in the generation of biogas, especially in methane formation, is still limited. To overcome this limitation, the methanogenic archaeal communities in six full-scale biogas plants supplied with different liquid manures and renewable raw materials as substrates were analyzed by a polyphasic approach. Fluorescence in situ hybridization (FISH) was carried out to quantify the methanogenic Archaea in the reactor samples. In addition, quantitative real-time PCR (Q-PCR) was used to support and complete the FISH analysis. Five of the six biogas reactors were dominated by hydrogenotrophic Methanomicrobiales. The average values were between 60 to 63% of archaeal cell counts (FISH) and 61 to 99% of archaeal 16S rRNA gene copies (Q-PCR). Within this order, Methanoculleus was found to be the predominant genus as determined by amplified rRNA gene restriction analysis. The aceticlastic family Methanosaetaceae was determined to be the dominant methanogenic group in only one biogas reactor, with average values for Q-PCR and FISH between 64% and 72%. Additionally, in three biogas reactors hitherto uncharacterized but potentially methanogenic species were detected. They showed closest accordance with nucleotide sequences of the hitherto unclassified CA-11 (85%) and ARC-I (98%) clusters. These results point to hydrogenotrophic methanogenesis as a predominant pathway for methane synthesis in five of the six analyzed biogas plants. In addition, a correlation between the absence of Methanosaetaceae in the biogas reactors and high concentrations of total ammonia (sum of NH 3 and NH 4 ؉ ) was observed.During the last decade the production of biogas from organic materials and residues has increased continuously in order to reduce the greenhouse gas emission resulting from the use of fossil energy sources. The energy-bearing substance of biogas is methane, which is produced as an end product of microbial anaerobic degradation of organic substrates, such as energy crops like maize, grains, grasses, or beets. Research for optimization of biogas production from renewable materials was initially focused on the evaluation of substrate eligibility and on the development and optimization of technical systems. However, biogas formation primarily depends on the structure and activity of the microbial community (28).The key microorganisms in the biogas formation process are the methane-generating microorganisms (methanogens). The capacity for methanogenesis is limited to members of the domain Archaea and, within this domain, on the phylum Euryarchaeota. With respect to the main metabolic precursors used, methanogens are usually divided into two groups: the aceticlastic methanogens that strictly metabolize acetate and the hydrogenotrophic methanogens that use H 2 or formate as an electron donor and CO 2 as a carbon source for their metabolism. Besides these major groups, certain methanogens are also able to convert methyl groups, methylamines, or methanol to methane (23,40). The substrates for the me...