722 research outputs found
Healing of simulated fault gouges aided by pressure solution: results from rock analogue experiments
see Abstract Volum
A comparison between rate-and-state friction and microphysical models, based on numerical simulations of fault slip
Rate-and-state friction (RSF) is commonly used for the characterisation of laboratory friction experiments, such as velocity-step tests. However, the RSF framework provides little physical basis for the extrapolation of these results to the scales and conditions of natural fault systems, and so open questions remain regarding the applicability of the experimentally obtained RSF parameters for predicting seismic cycle transients. As an alternative to classical RSF, microphysics-based models offer means for interpreting laboratory and field observations, but are generally over-simplified with respect to heterogeneous natural systems. In order to bridge the temporal and spatial gap between the laboratory and nature, we have implemented existing microphysical model formulations into an earthquake cycle simulator. Through this numerical framework, we make a direct comparison between simulations exhibiting RSF-controlled fault rheology, and simulations in which the fault rheology is dictated by the microphysical model. Even though the input parameters for the RSF simulation are directly derived from the microphysical model, the microphysics-based simulations produce significantly smaller seismic event sizes than the RSF-based simulation, and suggest a more stable fault slip behaviour. Our results reveal fundamental limitations in using classical rate-and-state friction for the extrapolation of laboratory results. The microphysics-based approach offers a more complete framework in this respect, and may be used for a more detailed study of the seismic cycle in relation to material properties and fault zone pressure-temperature conditions
Phase diagram of self-assembled rigid rods on two-dimensional lattices: Theory and Monte Carlo simulations
Monte Carlo simulations and finite-size scaling analysis have been carried
out to study the critical behavior in a two-dimensional system of particles
with two bonding sites that, by decreasing temperature or increasing density,
polymerize reversibly into chains with discrete orientational degrees of
freedom and, at the same time, undergo a continuous isotropic-nematic (IN)
transition. A complete phase diagram was obtained as a function of temperature
and density. The numerical results were compared with mean field (MF) and real
space renormalization group (RSRG) analytical predictions about the IN
transformation. While the RSRG approach supports the continuous nature of the
transition, the MF solution predicts a first-order transition line and a
tricritical point, at variance with the simulation results.Comment: 12 pages, 10 figures, supplementary informatio
An instrument for dimensional diagnosis of a child’s constitution (ICC)
Developmental disorders present themselves with complex problems that may threaten a child’s development. In every child a disorder shows itself in a unique way, which makes it necessary to individualize. The objective of this preliminary study is to develop an instrument that provides a dimensional diagnosis by mapping the degree of (dis)balance in three domains of child development. The instrument is based on anthroposophic anthropology and typology. The instrument will be usable in all kinds of care for children with developmental disorders.The typology of a child’s constitution was operationalized using concept mapping and consensus building with experts. Preliminary tests of the psychometric properties of the instrument were applied on children with developmental disorders in a pilot study in Dutch healthcare. The Instrument for diagnosis of a Child’s Constitution (ICC) developed in this study consists of two parts. Part I contains 36 polar formulated items in three subscales of 12 items and is to be completed by healthcare professionals. Part II consists of three VAS scales (Visual analogue scales) and is to be completed y a practitioner. The outcome (the scores of Part I and II) forms a profile of the child’s constitution, showing the (dis) balance in three domains of child development. A pilot study with 38 children shows positive face validity, and moderate internal consistency and inter-rater reliability of the ICC. The ICC has been developed as a diagnostic instrument to assess individualized dimensional diagnosis of children with a developmental disorder. Future studies will focus on validation of the instrument
Thermal transport of the XXZ chain in a magnetic field
We study the heat conduction of the spin-1/2 XXZ chain in finite magnetic
fields where magnetothermal effects arise. Due to the integrability of this
model, all transport coefficients diverge, signaled by finite Drude weights.
Using exact diagonalization and mean-field theory, we analyze the temperature
and field dependence of the thermal Drude weight for various exchange
anisotropies under the condition of zero magnetization-current flow. First, we
find a strong magnetic field dependence of the Drude weight, including a
suppression of its magnitude with increasing field strength and a non-monotonic
field-dependence of the peak position. Second, for small exchange anisotropies
and magnetic fields in the massless as well as in the fully polarized regime
the mean-field approach is in excellent agreement with the exact
diagonalization data. Third, at the field-induced quantum critical line between
the para- and ferromagnetic region we propose a universal low-temperature
behavior of the thermal Drude weight.Comment: 9 pages REVTeX4 including 5 figures, revised version, refs. added,
typos correcte
Exact two-spinon dynamical correlation function of the Heisenberg model
We derive the exact contribution of two spinons to the dynamical correlation
function of the spin-1/2 Heisenberg model. For this, we use the isotropic
limits of the exact form factors that have been recently computed through the
quantum affine symmetry of the anisotropic Heisenberg model Comment: 9 pages, Latex, 2 corrections of coefficient
Effectiveness of Neuromotor Task Training for Children with Developmental Coordination Disorder: A Pilot Study
The aim of this pilot study was to evaluate
the effectiveness of a Neuromotor Task
Training (NTT), recently developed for the
treatment of children with Developmental
Coordination Disorder (DCD) by pediatric
physical therapists in the Netherlands. NTT is
a task-oriented treatment program based
upon recent insights from motor control and
motor learning research. Ten children with
DCD (intervention group) were tested before
and after 9 and 18 treatment sessions on the
Movement ABC and a dysgraphia scale in
order to measure the effectiveness of
treatment on gross and fine motor skills in
general and handwriting in particular. Five
children (no-treatment control group) were
tested twice with a time lag of nine weeks on
the Movement ABC in order to measure
spontaneous improvement. No improvement
was measured for the children in the notreatment
control group, whereas a significant
improvement was found for children in the
intervention group for both quality of
handwriting and performance on the
Movement ABC after 18 treatment sessions
Psychedelic Treatments for Psychiatric Disorders:A Systematic Review and Thematic Synthesis of Patient Experiences in Qualitative Studies
Introduction Interest in the use of psychedelic substances for the treatment of mental disorders is increasing. Processes that may affect therapeutic change are not yet fully understood. Qualitative research methods are increasingly used to examine patient accounts; however, currently, no systematic review exists that synthesizes these findings in relation to the use of psychedelics for the treatment of mental disorders. Objective To provide an overview of salient themes in patient experiences of psychedelic treatments for mental disorders, presenting both common and diverging elements in patients' accounts, and elucidating how these affect the treatment process. Methods We systematically searched the PubMed, MEDLINE, PsycINFO, and Embase databases for English-language qualitative literature without time limitations. Inclusion criteria were qualitative research design; peer-reviewed studies; based on verbalized patient utterances; and a level of abstraction or analysis of the results. Thematic synthesis was used to analyze and synthesize results across studies. A critical appraisal of study quality and methodological rigor was conducted using the Critical Appraisal Skills Programme (CASP). Results Fifteen research articles, comprising 178 patient experiences, were included. Studies exhibited a broad heterogeneity in terms of substance, mental disorder, treatment context, and qualitative methodology. Substances included psilocybin, lysergic acid diethylamide (LSD), ibogaine, ayahuasca, ketamine and 3,4-methylenedioxymethamphetamine (MDMA). Disorders included anxiety, depression, eating disorders, post-traumatic stress disorder, and substance use disorders. While the included compounds were heterogeneous in pharmacology and treatment contexts, patients reported largely comparable experiences across disorders, which included phenomenological analogous effects, perspectives on the intervention, therapeutic processes and treatment outcomes. Comparable therapeutic processes included insights, altered self-perception, increased connectedness, transcendental experiences, and an expanded emotional spectrum, which patients reported contributed to clinically and personally relevant responses. Conclusions This review demonstrates how qualitative research of psychedelic treatments can contribute to distinguishing specific features of specific substances, and carry otherwise undiscovered implications for the treatment of specific psychiatric disorders
Wanneer is goed veilig?
In de jaren negentig bleek de bosbouw- en groenvoorzieningsector een van de onveiligste sectoren te zijn in Nederland. Verbetering van de werkomstandigheden was dus hard nodig. Hierbij is de beschikbaarheid van goedgekeurde apparatuur en middelen een belangrijk aandachtspunt. Logo's (als kwaliteitsaanduiding) kunnen de aspirant-koper helpen om iets goeds te kope
- …