The effect of different hypertension models on active avoidance learning

This study tested the effects of different hypertension models on active avoidance learning in rats. Three-month-old male Wistar rats were divided randomly into six groups as follows: control (C), sham operated (sham), two kidney-one clip (2K-1C), one kidney-one clip (1K-1C), deoxycorticosterone-salt (DOCA), and N-omega-nitro-L-arginine-methyl ester (L-NAME) groups. Mean arterial blood pressures were significantly higher in four hypertensive groups compared with control and sham groups. The active avoidance training results indicated that hypertension state is associated with learning impairment. Thiobarbituric acid-reactive substances (TBARS) were determined as an indicator of lipid peroxidation in brain and hippocampus. Additionally, brain and hippocampus nitrite levels were studied.     

Ferromagnetism in Kondo lattice models

We report the discovery of a new ferromagnetic phase in the one-dimensional Kondo lattice model for intermediate values of the coupling constant. This new ferromagnetic phase was observed using a non-Abelian density-matrix renormalization group algorithm, which allowed us to measure directly the magnetization of the ground state with high accuracy.     

Exact ferromagnetic ground state of pentagon chains

We model conducting pentagon chains with a multi-orbital Hubbard model and prove that well below half filling, exact ferromagnetic ground states appear. The rigorous method we use is based on the transformation of original hamiltonian into positive semidefinite form. This technique is independent of the spatial dimension and does not require integrability of the model. The obtained ferromagnetism is connected to dispersionless bands but in a much broader sense than flat-band ferromagnetism requires, where on every site a Hubbard term is present. In our case, only a small percentage of, even randomly distributed, sites are only interacting.     

Effective Hamiltonian of the two-band Hubbard model: An exact result

An effective Hamiltonian for the two-band Hubbard model was derived by a canonical transformation which was calculated and summed up to infinite order . The transformed Hamiltonian contains terms with strongly renormalized interaction energies. These new interaction energies show sign reversals as a function of the hopping integral in addition to a strong reduction in the charge-transfer gap and a significant increase in the attractive oxygen Hubbard term.     

A new approach to surface photovoltage measurements on hydrogenated microcrystalline silicon layers

A new approach to the surface photovoltage method is demonstrated on thick undoped microcrystalline silicon films grown on different substrates. The model, which includes top as well as bottom space-charge regions, gives a good picture of rather complex experiments and allows good fitting of theoretical curves to experimental results. This method gives us not only the diffusion length of minority carriers but also information on the existence and properties of the space-charge regions in the sample and the results are verified by comparison with the standard procedure.     

Total spin in the density matrix renormalization group algorithm

A new density matrix renormalization group (DMRG) algorithm is presented which conserves the total spin. This is the first time that standard DMRG is extended to exploit fully the symmetries of the Hamiltonian. The obtained general procedure works for any operator, even operators that do not commute with the Hamiltonian. The new method gives substantial improvements over the standard DMRG.     

Variational solution of the one-dimensional t–J model

A new variational scheme based on a modified Bethe–Peierls method is used to study the ground state properties of the one-dimensional t–J model. Expectation values are evaluated by cutting out a four-site cluster from a correlated Fermi sea, the ground state of which is described by a variational trial wave function. We study a generalized Gutzwiller state where nearest-neighbour hole–hole correlations are controlled variationally. From the electron concentration dependence of the ground state energy, we determine the true thermodynamic boundary where segregation into an electron-rich, and purely hole phase sets in. We also determine the spinodal line and pair susceptibilities. The variational method is applied also to an extended t–J–V model, where V is the coupling constant of the charge interaction term.     

Cultural effects in emotion and gender recognition

There is evidence for cultural differences in how people respond to basic properties of faces. We examined task switching between two properties of faces, emotion and gender, for individuals drawn from Western (White UK citizens) and Asian (Pakistani) cultures. There were three main results of interest. First, there was a double dissociation between gender and emotion classification across the participant populations – Western participants were faster to make gender than emotion classifications while Asian participants were faster to make emotion than gender classifications. It is argued that the different patterns of results reflect the greater attentional weight given to contrasting face dimensions in the different cultures, and the dependence on using different attributes to make gender discriminations in individuals from varying cultures. Second, Asian participants showed smaller switch costs overall than did White British participants. This result may be attributed to effects of bilingualism in the Asian participants, which results in their having greater executive resources. Third, emotion decisions showed larger switch costs than gender decisions but essentially because emotion decisions benefited from priming on non‐switch trials. It is argued that emotion decisions benefit from the activation of a specific processing module across consecutive trials.     

Temperature dependence of the flow stress in Ir3Nb with the L12 structure

The effective s-d spin interaction is derived exactly for the one-impurity Anderson model via a unitary transformation. The unitary transformation has been calculated up to infinite order, thus an exact transformation was performed in the strict mathematical sense.