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J Schulenburg

Publications and source records attributed to J Schulenburg.

7 recordsLinked to original sources
PubMed2006

Quantum J1-J2 antiferromagnet on a stacked square lattice: influence of the interlayer coupling on the ground-state magnetic ordering.

Using the coupled-cluster method and the rotation-invariant Green's function method, we study the influence of the interlayer coupling Jperpendicular on the magnetic ordering in the ground state of the spin-1/2 J1-J2 frustrated Heisenberg antiferromagnet (J1-J2 model) on the stacked square lattice. In agreement with known results for the J1-J2 model on the strictly two-dimensional square lattice (Jperpendicular=0), we find that the phases with magnetic long-range order at small J2 Jc2 are separated by a magnetically disordered (quantum paramagnetic) ground-state phase. Increasing the interlayer coupling Jperpendicular >0, the parameter region of this phase decreases, and, finally, the quantum paramagnetic phase disappears for quite small Jperpendicular approximately (0.2-0.3)J1.

Journal Article↗
PubMed2006

Efficacy of amphoteric surfactant- and peracetic acid-based disinfectants on spores of bacillus cereus in vitro and on food premises of the German armed forces.

In mass catering facilities of the German Armed Forces, foodborne outbreaks are commonly attributed to Bacillus cereus, and spores of this organism are regularly found on equipment surfaces. B. cereus is the causative agent of foodborne emetic or diarrheic disease. Hence, the use of sporicidal disinfectants may provide a starting point for successful risk mitigation of diseases associated with B. cereus. In this study, the amphoteric surfactant-based disinfectant (product A) that has been routinely used in catering facilities of the German Armed Forces and a peracetic acid-based disinfectant (product B) were compared for their efficacy against B. cereus spores in laboratory tests and under field conditions. In a carrier test for B. cereus spores, product A displayed no efficacy against spores of the test strain. In contrast, a substantial reduction in spore concentration (>5-log reduction) was achieved with product B. In a controlled trial conducted in seven Army catering facilities, the reduction in the number of B. cereus-positive samples was significantly greater (P < 0.001) for product B (from 28% initial contamination to 3% after application) than for product A (from 33 to 21%). Product B was estimated to be 6.25 times more efficacious than product A. Field trials confirmed the higher efficacy of the peracetic acid-based disinfectant to reduce B. cereus contamination on surfaces as found for the in vitro experiments. The tests used to assess the sporicidal effects of disinfectants were adequate under practice conditions and could be used for sporicidal testing of disinfectants for catering and food production establishments.

Bacillus cereus↗
PubMed2002

Macroscopic magnetization jumps due to independent magnons in frustrated quantum spin lattices.

For a class of frustrated spin lattices including the Kagomé lattice we construct exact eigenstates consisting of several independent, localized one-magnon states and argue that they are ground states for high magnetic fields. If the maximal number of local magnons scales with the number of spins in the system, which is the case for the Kagomé lattice, the effect persists in the thermodynamic limit and gives rise to a macroscopic jump in the zero-temperature magnetization curve just below the saturation field. The effect decreases with increasing spin quantum number and vanishes in the classical limit. Thus it is a true macroscopic quantum effect.

Journal Article↗
PubMed1998

[Model investigations of the impedance effectiveness conerning bacterial relevant to food hygiene].

The impedance technique mostly meets today's requirements of microbiological rapid methods. At relatively high prime cost for the equipment the advantages are marked by low personnel and material costs as well as swiftness combined with highly flexible usage. The method is applicable for both quantitative and qualitative examinations but can fail occasionally in total count determination, especially if the sample material contains heterogeneous microbes. In model investigations with 53 strains of 17 different genera Enterobacteriaceae strains, Aeromonads and Enterococcus strains proved to be highly impedance effective. Lactobacillus strains and Pseudomonads as well as Staphylococcus aureus strains showed a low impedance effectiveness. Several strains, for example of the genera Micrococcus, Acinetobacter and Brochothrix, did not show any changes of the medium impedance under the chosen conditions. Criterion for characterization of impedance effectiveness was the impedance detection time starting with identical initial counts (10(3) cfu/ml). Impedance effectiveness of microbes was determined at highly varying degree by the parameters of generation time, lag-phase duration and relative activity. This can lead either to wrong negative (underestimations) or wrong positive (overestimations) results of bacterial count.

Bacteria↗
PubMed1997

[Early functional treatment of a 5th metatarsal fracture using an orthopedic boot].

The fracture of the base of the fifth metatarsal bone is a common fracture of the foot. We differentiate avulsion fractures of the apophysis from meta-diaphysial of the Jones-Type. In the literature you find many different methods of treatment extending from simple immobilization through functional strapping to osteosynthesis of the fracture. Depending on the method of treatment the results are quite different especially in the period of immobilization and the period of sick-leave. From March 1988 to September 1991 52 patients of the orthopedic clinic Kantonsspital Liestal/Switzerland with a fracture of the base of their fifth metatarsal bone were treated functionally with a special orthopedic shoe and were studied prospectively. This treatment allowed them full weightbearing after approx. 9 days, the average time of sick-leave was 19 days. Longterm results showed no complications. The majority of patients (92%) were satisfied with this treatment. We consider the early functional treatment of a fracture of the base of the fifth metatarsal bone with an orthopedic boot as a reliable and cost effective treatment.

Adolescent↗