Family Therapy in the Heart of Europe

The article introduces the situation of family therapy and systemic practice in the Czech Republic. It gives an overview of family therapy history and development in the country. Both historical and political background including major transformation events in the last couple of decades are presented so as to explain the contextual frame for major challenges, which Czech family and systemic therapists have been facing in this part of Europe. The current situation of family therapy in the Czech Republic is described in detail with regard to leading figures, major schools, training issues, international exchange and clinical practice in various settings.     

Team Perceived Trustworthiness in a Complex Military Peacekeeping Simulation

Antecedents to trust (propensity to trust, perceived trustworthiness) and trust behaviors were examined in relation to team performance in a complex eight-mission military peacekeeping simulation. Teams were colocated or distributed and stayed in the same or transferred to a different context at task transfer. In Experiment 1, an ability and competence factor accounted for most of the variance in perceived trustworthiness and greater perceptions of teammates' abilities/competences predicted posttransfer performance. One's perception of how others perceived one's ability/competence increased over missions. In Experiment 2, propensity to trust did not predict performance; however, trust in others' and one's own ability/competence and trust behaviors predicted performance. At task and/or context transfer, teams produced more monitoring and less cooperating language in their communication.     

Parenting and the dysregulation profile predict executive functioning in children with acquired brain injury

Background: Children with acquired brain injury (ABI) present with high rates of psychological disorders commonly accompanied by deficits in hot and cold executive functions (EFs). Impairments in EFs have been reported to precede mental health problems. Moreover, children who are vulnerable to developing mental health problems in adulthood frequently present with a dysregulation profile in childhood, characterized by impairments in cognitive, behavioral and emotional regulation. Objective: To identify profiles of behaviors associated with impairment in hot and cold EFs and compare injury factors, environmental stressors and dysregulation profile between them. Methods: A latent profile analysis was conducted with 77 children with ABI aged between 6 and 12. Injury factors, child IQ, environmental stressors and the dysregulation profile were compared between these behavioral profiles. Logistic regressions were conducted to predict profile membership. Results: Two profiles were identified: Profile M, with mild deficits (1–2 SD above the mean) in working memory and social skills, and profile C, presenting clinically significant deficits (2–3 SD above the mean) in shift, initiate, working memory, planning and social skills and mild deficits in inhibit, emotional control and task monitor. Proximal environmental stressors (dysfunctional parenting practices, parental stress, parent’s executive dysfunction, anxiety-trait, and depressive symptoms) and dysregulation symptoms predicted profile membership, whereas injury factors, child IQ and distal environmental stressors did not. Conclusion: Following ABI, children with profile C are at risk of mental health problems and present with more proximal stressors. The dysregulation profile may be useful as a proxy for risk for later mental health problems in children with ABI.     

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.     

Experimental determination of trapping efficiency of optical tweezers

We report an experimental determination of trapping efficiency of optical fields acting on spherical particles diluted in viscous fluids. This parameter was derived from experimentally calculated trap stiffness for micron-sized silica beads with particle radii of 1.5 and 4.8 microns, respectively. In order to obtain the trap stiffness, we used the equipartition theorem, and introduced an experimental procedure to calibrate the optical tweezers set-up. The method consists of the calculation of the trapping efficiency by using the curves of the trap stiffness vs. the incident power. Using this approach we measured the efficiency for different values of displacements of the beads in the optical trap, and compared these results with numerical and theoretical calculations reported in the literature, and an excellent agreement was found. We have shown that the ratio of efficiencies is very close to the ratio of the particle radii.     

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.