Incommensurate antiferromagnetic fluctuations in the two-dimensional Hubbard model

Commensurate and incommensurate antiferromagnetic fluctuations in the two-dimensional repulsive t-t'-Hubbard model are investigated using functional renormalization group equations. For a sufficient deviation from half filling we establish the existence of local incommensurate order below a pseudocritical temperature T_{pc}. Fluctuations not accounted for in the mean field approximation are important--they lower T_{pc} by a factor \approx2.5.Comment: 7 pages, 8 figures, some changes due to referees' comments, equivalent to published versio

Fermionic functional renormalization group for first-order phase transitions: a mean-field model

First-order phase transitions in many-fermion systems are not detected in the susceptibility analysis of common renormalization-group (RG) approaches. Here we introduce a counterterm technique within the functional renormalization-group (fRG) formalism which allows access to all stable and metastable configurations. It becomes possible to study symmetry-broken states which occur through first-order transitions as well as hysteresis phenomena. For continuous transitions, the standard results are reproduced. As an example, we study discrete-symmetry breaking in a mean-field model for a commensurate charge-density wave. An additional benefit of the approach is that away from the critical temperature for the breaking of discrete symmetries large interactions can be avoided at all RG scales.Comment: 17 pages, 8 figures. v2 corrects typos, adds references and a discussion of the literatur

Nanocrystalline and stacking-disordered β-cristobalite AlPO4: the now deciphered main constituent of a municipal sewage sludge ash from a full-scale incineration facility

This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.For the first time evidence is provided that a nanocrystalline and stacking-disordered, chemically stabilized β-cristobalite form of AlPO4 occurs in a sewage sludge ash (SSA). This proof is based on a combined X-ray powder diffraction and X-ray fluorescence investigation of an SSA produced at a large-scale fluidized bed incineration facility serving a catching area with a population of 2 million. The structural and chemical characterization was carried out on ‘as received’ SSA samples as well as on solid residues remaining after leaching this SSA in sodium hydroxide solution. Thus, it was ascertained that the observed nanocrystalline and stacking-disordered cristobalite-like component belongs to the aluminum phosphate component of this SSA, rather than to its silicon dioxide component. In addition, a direct proof is presented that the chemically stabilized β-cristobalite form of AlPO4 does crystallize from X-ray amorphous precursors under conditions that mimic the huge heating rate and short retention time (just seconds at T ≈ 850°C), typical for fluidized bed incinerators.Peer Reviewe

ARE MUSCLE FORCES RELEVANT IN THE AGE RELATED RISE OF INJURIES IN ADOLESCENT SOCCER PLAYERS?

The purpose of this study was the comparison of the kinematics and kinetics in soccer inside passes between three age groups (U12, U16, U23). Using 3D movement analysis and inverse dynamics, hip joint kinematics and adductor muscle forces were calculated. SPM analysis showed significant differences in adduction angle and velocity and in muscle forces of adductor longus and gracilis. Comparison of the muscle forces shows a rapid increase in muscle forces from the youngest children to the adolescents while the difference between the adolescents and adults is only minor. It seems reasonable, that the fast development of muscle forces in adolescents compared to the slower development of the tendons is a factor in the sudden rise in injury incidence at the beginning of puberty. Therefore, adolescent players should be trained with caution to avoid early injuries

HIP JOINT LOAD AND MUSCLE STRESS IN SOCCER INSIDE PASSlNG

Studies investigating the mechanisms of adductor injuries in soccer have concentrated on full effort kicks. Purpose of this study was a kinetic analysis of the inside pass. Using infrared cameras and inverse dynamics, hip joint moments and adductor muscle stress was calculated during the swing phase of the pass. Moments in the transverse plane were nearly as high as in full effort kicks reported previously. Muscle stress in the m. gracilis reached up to 450 kPa. Considering the repetitive nature of inside passes in modern sot; cer, adductor muscles undergo high loads in matches and training. This might contribute to the explanation of the high incidences of adductor injuries. Practitioners should therefore consider the load-recovery-relation even in inside pass training. Specific strength training programs for the adductor and abductor muscle groups should be developed

Pastagem de missioneira-gigante submetida a alturas de corte e severidades de desfolha em pleno sol e com restrição de luminosidade.

A ampliação das áreas em sistemas integrados de produção agropecuária, aliado a necessidade do aumento de produtividade, gera uma demanda de conhecimento que norteie a implantação e o manejo dos sistemas como um todo. Neste contexto, objetivou-se com este trabalho a avaliação das características morfológicas e estruturais da pastagem de Missioneira-gigante submetida a diferentes alturas de corte, severidades de desfolha em pleno sol e com restrição de luminosidade. A missioneira-gigante foi cultivada em vasos de 0,30 m2 (1,0 x 0,3 m), com profundidade de 0,5 m. A sombra foi reproduzida por ripados de madeira, com 50% de redução da luminosidade. Os tratamentos consistiram na combinação de quatro alturas de corte (15, 25, 35 e 45 cm), quatro severidades de desfolha (20, 40, 60 e 80%), em dois ambientes luminosos (sol e sombra), avaliados em esquema fatorial 4 x 4 x 3, em delineamento inteiramente casualizado, com 3 repetições, totalizando 96 unidades experimentais. Em ambiente com restrição de luminosidade as plantas apresentaram 7,0 cm a mais na altura do dossel para atingir o mesmo nível de interceptação luminosa, quando comparado ao pleno sol. A missioneira-gigante submetida a maior severidade de desfolha apresenta menor densidade populacional de perfilhos vegetativos e totais, independente da condição luminosa