773 research outputs found
On the origins of scaling corrections in ballistic growth models
We study the ballistic deposition and the grain deposition models on
two-dimensional substrates. Using the Kardar-Parisi-Zhang (KPZ) ansatz for
height fluctuations, we show that the main contribution to the intrinsic width,
which causes strong corrections to the scaling, comes from the fluctuations in
the height increments along deposition events. Accounting for this correction
in the scaling analysis, we obtained scaling exponents in excellent agreement
with the KPZ class. We also propose a method to suppress these corrections,
which consists in divide the surface in bins of size and use only
the maximal height inside each bin to do the statistics. Again, scaling
exponents in remarkable agreement with the KPZ class were found. The binning
method allowed the accurate determination of the height distributions of the
ballistic models in both growth and steady state regimes, providing the
universal underlying fluctuations foreseen for KPZ class in 2+1 dimensions. Our
results provide complete and conclusive evidences that the ballistic model
belongs to the KPZ universality class in dimensions. Potential
applications of the methods developed here, in both numerics and experiments,
are discussed.Comment: 8 pages, 7 figure
Solution of a model of SAW's with multiple monomers per site on the Husimi lattice
We solve a model of self-avoiding walks which allows for a site to be visited
up to two times by the walk on the Husimi lattice. This model is inspired in
the Domb-Joyce model and was proposed to describe the collapse transition of
polymers with one-site interactions only. We consider the version in which
immediate self-reversals of the walk are forbidden (RF model). The phase
diagram we obtain for the grand-canonical version of the model is similar to
the one found in the solution of the Bethe lattice, with two distinct
polymerized phases, a tricritical point and a critical endpoint.Comment: 16 pages, including 6 figure
Beliefs About Psychological Problems Inventory (BAPPI) : development and psychometric properties
Correspondence concerning this article should be addressed to Prof. Paulo Moreira, Instituto de Psicologia e de Ciências da Educação, Universidade LusÃada, Rua de Moçambique 21 e 71, Porto 4100-348, Portugal. Email: [email protected] clients’ belief systems are components of Effective Therapy Relationships. Thus, it is desirable to include clients’ beliefs about their psychological problems on systematic assessment protocols underlying the process of systematic treatment selection and of tailoring the treatment to the person. However, assessment instruments which specifically capture clients’ beliefs about their psychological problems are scarce. The objective of the studies presented was to evaluate the psychometric properties of the Beliefs About Psychological Problems Inventory (BAPPI), an assessment instrument of the clients’ beliefs about their psychological problems. Study 1 (Exploratory Factor Analysis) involved 200 participants, and Study 2 (Confirmatory Factor Analysis and other validity studies), involved 545 participants. Results revealed that the BAPPI presents a stable factorial structure of six dimensions (Psychodynamic, Humanistic, Biomedical, Cognitive-Behavioral, Systemic, and Eclectic/Integrative). Altogether, analyses of items, internal consistency, reliability, and external validity revealed that the BAPPI is a valid assessment instrument for use in mental health research and practice, especially in the process of systematic treatment selection and, therefore, of matching/tailoring the treatment to the client’s characteristics
Grand canonical and canonical solution of self-avoiding walks with up to three monomers per site on the Bethe lattice
We solve a model of polymers represented by self-avoiding walks on a lattice
which may visit the same site up to three times in the grand-canonical
formalism on the Bethe lattice. This may be a model for the collapse transition
of polymers where only interactions between monomers at the same site are
considered. The phase diagram of the model is very rich, displaying coexistence
and critical surfaces, critical, critical endpoint and tricritical lines, as
well as a multicritical point. From the grand-canonical results, we present an
argument to obtain the properties of the model in the canonical ensemble, and
compare our results with simulations in the literature. We do actually find
extended and collapsed phases, but the transition between them, composed by a
line of critical endpoints and a line of tricritical points, separated by the
multicritical point, is always continuous. This result is at variance with the
simulations for the model, which suggest that part of the line should be a
discontinuous transition. Finally, we discuss the connection of the present
model with the standard model for the collapse of polymers (self-avoiding
self-attracting walks), where the transition between the extended and collapsed
phases is a tricritical point.Comment: 34 pages, including 10 figure
Bethe lattice solution of a model of SAW's with up to 3 monomers per site and no restriction
In the multiple monomers per site (MMS) model, polymeric chains are
represented by walks on a lattice which may visit each site up to K times. We
have solved the unrestricted version of this model, where immediate reversals
of the walks are allowed (RA) for K = 3 on a Bethe lattice with arbitrary
coordination number in the grand-canonical formalism. We found transitions
between a non-polymerized and two polymerized phases, which may be continuous
or discontinuous. In the canonical situation, the transitions between the
extended and the collapsed polymeric phases are always continuous. The
transition line is partly composed by tricritical points and partially by
critical endpoints, both lines meeting at a multicritical point. In the
subspace of the parameter space where the model is related to SASAW's
(self-attracting self-avoiding walks), the collapse transition is tricritical.
We discuss the relation of our results with simulations and previous Bethe and
Husimi lattice calculations for the MMS model found in the literature.Comment: 25 pages, 9 figure
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