38 resultados para Effective medium theory
Resumo:
Traditional methods do not actually measure peoples’ risk attitude naturally and precisely. Therefore, a fuzzy risk attitude classification method is developed. Since the prospect theory is usually considered as an effective model of decision making, the personalized parameters in prospect theory are firstly fuzzified to distinguish people with different risk attitudes, and then a fuzzy classification database schema is applied to calculate the exact value of risk value attitude and risk be- havior attitude. Finally, by applying a two-hierarchical clas- sification model, the precise value of synthetical risk attitude can be acquired.
Resumo:
We review the failure of lowest order chiral SU(3)L ×SU(3)R perturbation theory χPT3 to account for amplitudes involving the f0(500) resonance and O(mK) extrapolations in momenta. We summarize our proposal to replace χPT3 with a new effective theory χPTσ based on a low-energy expansion about an infrared fixed point in 3-flavour QCD. At the fixed point, the quark condensate ⟨q̅q⟩vac ≠ 0 induces nine Nambu-Goldstone bosons: π,K,η and a QCD dilaton σ which we identify with the f0(500) resonance. We discuss the construction of the χPTσ Lagrangian and its implications for meson phenomenology at low-energies. Our main results include a simple explanation for the ΔI = 1/2 rule in K-decays and an estimate for the Drell-Yan ratio in the infrared limit.
Resumo:
We report an electrochemical gating approach with [similar]100% efficiency to tune the conductance of single-molecule 4,4′-bipyridine junctions using scanning-tunnelling-microscopy break junction technique. Density functional theory calculation suggests that electrochemical gating aligns molecular frontier orbitals relative to the electrode Fermi-level, switching the molecule from an off resonance state to “partial” resonance.
Resumo:
Overcoming a crisis situation in which the socioemotional wealth (SEW) of a family is at risk can be threatened by a lack of formal crisis procedures, which can increase the probability of organizational decline. Thus, not being prepared for a crisis situation may be a critical factor in the long-term survival of family firms. From a corporate governance perspective, supervisory boards may achieve higher levels of crisis readiness. Applying the resourced-based view and SEW theory, we analyze the relationship between family ownership and formalized crisis procedures in 150 small and medium-sized German firms. Our results show that formalized crisis procedures decrease as family ownership increases. Including supervisory boards in our analysis, we find a significant moderating effect of supervisory boards on the relationship between family ownership and formalized crisis procedures. Specifically, our results suggest that family firms with supervisory boards show similar levels of formalized crisis procedures as non-family firms with supervisory boards. In contrast, family firms without supervisory boards exhibit lower levels of formalized crisis procedures compared with non-family firms without supervisory boards. We also discuss managerial implications, limitations, and future research.
Resumo:
In this article, we present a new microscopic theoretical approach to the description of spin crossover in molecular crystals. The spin crossover crystals under consideration are composed of molecular fragments formed by the spin-crossover metal ion and its nearest ligand surrounding and exhibiting well defined localized (molecular) vibrations. As distinguished from the previous models of this phenomenon, the developed approach takes into account the interaction of spin-crossover ions not only with the phonons but also a strong coupling of the electronic shells with molecular modes. This leads to an effective coupling of the local modes with phonons which is shown to be responsible for the cooperative spin transition accompanied by the structural reorganization. The transition is characterized by the two order parameters representing the mean values of the products of electronic diagonal matrices and the coordinates of the local modes for the high- and low-spin states of the spin crossover complex. Finally, we demonstrate that the approach provides a reasonable explanation of the observed spin transition in the [Fe(ptz)6](BF4)2 crystal. The theory well reproduces the observed abrupt low-spin → high-spin transition and the temperature dependence of the high-spin fraction in a wide temperature range as well as the pronounced hysteresis loop. At the same time within the limiting approximations adopted in the developed model, the evaluated high-spin fraction vs. T shows that the cooperative spin-lattice transition proves to be incomplete in the sense that the high-spin fraction does not reach its maximum value at high temperature.
Resumo:
Background: ASSIP is a manualized brief therapy based on a model of suicide as goal-directed action, aimed at establishing a therapeutic alliance in a patient-oriented, collaborative approach. The main goals of the three-session program ASSIP are for patients to understand, from an observer’s position, patterns leading to a suicidal crisis, recognize triggers and warning signs, and to establish individual safety strategies for future suicidal crises. An ongoing therapeutic support is provided with regular letters over 24 months. Method: The study was conducted in a naturalistic setting. 120 Patients were randomly assigned to an intervention group (60 participants) treated with ASSIP combined with follow-up contact through letters, and a control group (60 participants) receiving a single session of clinical assessment. Both groups had treatment as usual. Patients completed a set of psychosocial and clinical questionnaires every six months over a period of 24 months. Results: In the ASSIP group 5 patients made a total of 5 reattempts, compared to 15 patients with 41 reattempts in the control group. The survival analysis yielded a significant difference with a Wald Chi2 of .000003. The ASSIP group had significantly lower suicidal ideation and fewer days of inpatient treatment compared to the control group. Higher scores in the Penn Helping Alliance Questionnaire were associated with lower suicidal ideation during follow-up. Conclusions: ASSIP is a highly effective brief therapy for patients with recent suicide attempts. Forming a strong therapeutic alliance is considered to be a major factor for outcome. ASSIP can be used with minimal training by experienced therapists. An English version of the manual will be published in May 2015.
Resumo:
We investigate the transition from unitary to dissipative dynamics in the relativistic O(N) vector model with the λ(φ2)2 interaction using the nonperturbative functional renormalization group in the real-time formalism. In thermal equilibrium, the theory is characterized by two scales, the interaction range for coherent scattering of particles and the mean free path determined by the rate of incoherent collisions with excitations in the thermal medium. Their competition determines the renormalization group flow and the effective dynamics of the model. Here we quantify the dynamic properties of the model in terms of the scale-dependent dynamic critical exponent z in the limit of large temperatures and in 2≤d≤4 spatial dimensions. We contrast our results to the behavior expected at vanishing temperature and address the question of the appropriate dynamic universality class for the given microscopic theory.