484 research outputs found
Applying a Dynamical Systems Model and Network Theory to Major Depressive Disorder
Mental disorders like major depressive disorder can be seen as complex
dynamical systems. In this study we investigate the dynamic behaviour of
individuals to see whether or not we can expect a transition to another mood
state. We introduce a mean field model to a binomial process, where we reduce a
dynamic multidimensional system (stochastic cellular automaton) to a
one-dimensional system to analyse the dynamics. Using maximum likelihood
estimation, we can estimate the parameter of interest which, in combination
with a bifurcation diagram, reflects the expectancy that someone has to
transition to another mood state. After validating the proposed method with
simulated data, we apply this method to two empirical examples, where we show
its use in a clinical sample consisting of patients diagnosed with major
depressive disorder, and a general population sample. Results showed that the
majority of the clinical sample was categorized as having an expectancy for a
transition, while the majority of the general population sample did not have
this expectancy. We conclude that the mean field model has great potential in
assessing the expectancy for a transition between mood states. With some
extensions it could, in the future, aid clinical therapists in the treatment of
depressed patients.Comment: arXiv admin note: text overlap with arXiv:1610.0504
Elliptical orbits in the Bloch sphere
As is well known, when an SU(2) operation acts on a two-level system, its
Bloch vector rotates without change of magnitude. Considering a system composed
of two two-level systems, it is proven that for a class of nonlocal
interactions of the two subsystems including \sigma_i\otimes\sigma_j (with i,j
\in {x,y,z}) and the Heisenberg interaction, the geometric description of the
motion is particularly simple: each of the two Bloch vectors follows an
elliptical orbit within the Bloch sphere. The utility of this result is
demonstrated in two applications, the first of which bears on quantum control
via quantum interfaces. By employing nonunitary control operations, we extend
the idea of controllability to a set of points which are not necessarily
connected by unitary transformations. The second application shows how the
orbit of the coherence vector can be used to assess the entangling power of
Heisenberg exchange interaction.Comment: 9 pages, 4 figures, few corrections, J. Opt. B: Quantum Semiclass.
Opt. 7 (2005) S1-S
Unbounded-Error Classical and Quantum Communication Complexity
Since the seminal work of Paturi and Simon \cite[FOCS'84 & JCSS'86]{PS86},
the unbounded-error classical communication complexity of a Boolean function
has been studied based on the arrangement of points and hyperplanes. Recently,
\cite[ICALP'07]{INRY07} found that the unbounded-error {\em quantum}
communication complexity in the {\em one-way communication} model can also be
investigated using the arrangement, and showed that it is exactly (without a
difference of even one qubit) half of the classical one-way communication
complexity. In this paper, we extend the arrangement argument to the {\em
two-way} and {\em simultaneous message passing} (SMP) models. As a result, we
show similarly tight bounds of the unbounded-error two-way/one-way/SMP
quantum/classical communication complexities for {\em any} partial/total
Boolean function, implying that all of them are equivalent up to a
multiplicative constant of four. Moreover, the arrangement argument is also
used to show that the gap between {\em weakly} unbounded-error quantum and
classical communication complexities is at most a factor of three.Comment: 11 pages. To appear at Proc. ISAAC 200
Global and local relaxation of a spin-chain under exact Schroedinger and master-equation dynamics
We solve the Schroedinger equation for an interacting spin-chain locally
coupled to a quantum environment with a specific degeneracy structure. The
reduced dynamics of the whole spin-chain as well as of single spins is
analyzed. We show, that the total spin-chain relaxes to a thermal equilibrium
state independently of the internal interaction strength. In contrast, the
asymptotic states of each individual spin are thermal for weak but non-thermal
for stronger spin-spin coupling. The transition between both scenarios is found
for couplings of the order of , with denoting
the Zeeman-splitting. We compare these results with a master equation
treatment; when time averaged, both approaches lead to the same asymptotic
state and finally with analytical results.Comment: RevTeX, 8 pages, 14 figures, added DOI and forgotten reference
Exploring the interrelatedness of risk factors for child maltreatment: A network approach
Background: Theories on the etiology of child maltreatment generally focus on the interaction between multiple risk and protective factors. Moreover, the quadratic model of cumulative risk describes a threshold at which the risk of child maltreatment increases exponentially, suggesting a synergistic effect between risk factors. Objective: This study explored the interrelatedness of risk factors for child maltreatment. Participants and Setting: The sample consisted of risk assessments performed for both high-risk families (n = 2,399; child protection services) and lower risk families (n = 1,904; community outreach services). Methods : Network analyses were performed on parental risk factors. Three networks were constructed: a cross-sample network, a high-risk network, and a lower risk network. The relations between risk factors were examined, as well as the centrality of each risk factor in these networks. Additionally, the networks of the two samples were compared. Results : The networks revealed that risk factors for child maltreatment were highly interrelated, which is consistent with Belsky’s multi-dimensional perspective on child maltreatment. As expected, risk factors were generally stronger related to each other in the high-risk sample than in the lower risk sample. Centrality analyses showed that the following risk factors play an important role in the development of child maltreatment: “Caregiver was maltreated as a child”, “History of domestic violence”, and “Caregiver is emotionally absent”. Conclusions : We conclude that studying the interrelatedness of risk factors contributes to knowledge on the etiology of child maltreatment and the improvement of both risk assessment procedures and interventions for child maltreatment
Электропривод насоса перекачки золошлаковой пульпы
Объектом исследования является система автоматического управления насоса перекачки золошлаковой пульпы. Цель работы – разработка и исследование электропривода насоса перекачки золошлаковой пульпы.
В выпускной квалификационной работе произведён расчет и выбор приводного двигателя преобразователя частоты для управления электроприводами. Обоснован выбор способа управления, рассчитаны механические и электромеханические характеристики.The object of study is an automatic control system for the pump for transferring ash and slag pulp. The purpose of the work is the development and study of the electric drive of the pump for transferring ash and slag pulp.
In the final qualification work, the calculation and selection of the drive motor of the frequency converter for controlling electric drives were made. The choice of control method is justified, mechanical and electromechanical characteristics are calculated
Metastability in the BCS model
We discuss metastable states in the mean-field version of the strong coupling
BCS-model and study the evolution of a superconducting equilibrium state
subjected to a dynamical semi-group with Lindblad generator in detailed balance
w.r.t. another equilibrium state. The intermediate states are explicitly
constructed and their stability properties are derived. The notion of
metastability in this genuine quantum system, is expressed by means of
energy-entropy balance inequalities and canonical coordinates of observables
Quantum response of dephasing open systems
We develop a theory of adiabatic response for open systems governed by
Lindblad evolutions. The theory determines the dependence of the response
coefficients on the dephasing rates and allows for residual dissipation even
when the ground state is protected by a spectral gap. We give quantum response
a geometric interpretation in terms of Hilbert space projections: For a two
level system and, more generally, for systems with suitable functional form of
the dephasing, the dissipative and non-dissipative parts of the response are
linked to a metric and to a symplectic form. The metric is the Fubini-Study
metric and the symplectic form is the adiabatic curvature. When the metric and
symplectic structures are compatible the non-dissipative part of the inverse
matrix of response coefficients turns out to be immune to dephasing. We give
three examples of physical systems whose quantum states induce compatible
metric and symplectic structures on control space: The qubit, coherent states
and a model of the integer quantum Hall effect.Comment: Article rewritten, two appendices added. 16 pages, 2 figure
Radiokomunikacja ruchoma. Przegląd Zagadnień Łączności, 1966, nr 1 (52)
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