Multiple phase transitions in an agent-based evolutionary model with neutral fitness

Null models are crucial for understanding evolutionary processes such as speciation and adaptive radiation. We analyse an agent-based null model, considering a case without selection—neutral evolution—in which organisms are defined only by phenotype. Universal dynamics has previously been demonstrated in a related model on a neutral fitness landscape, showing that this system belongs to the directed percolation (DP) universality class. The traditional null condition of neutral fitness (where fitness is defined as the number of offspring each organism produces) is extended here to include equal probability of death among organisms. We identify two types of phase transition: (i) a non-equilibrium DP transition through generational time (i.e. survival), and (ii) an equilibrium ordinary percolation transition through the phenotype space (based on links between mating organisms). Owing to the dynamical rules of the DP reaction–diffusion process, organisms can only sparsely fill the phenotype space, resulting in significant phenotypic diversity within a cluster of mating organisms. This highlights the necessity of understanding hierarchical evolutionary relationships, rather than merely developing taxonomies based on phenotypic similarity, in order to develop models that can explain phylogenetic patterns found in the fossil record or to make hypotheses for the incomplete fossil record of deep time

Determining the Initial Content Validity of the Clinical Competency Assessment Tool (CAT) for Occupational Therapists Treating Patients with Neurodegenerative Disease

The provision of occupational therapy (OT) interventions for people with neurodegenerative disorder (NDD) requires advanced clinical competency; therefore, a means to evaluate that competency is needed. The Clinical Competency Assessment Tool for Occupational Therapists Treating Patients with Neurodegenerative Disease (CAT) was recently developed as a self-report assessment that aims to identify gaps in clinical competence and measure outcomes of professional development programs specific to occupational therapists treating patients with NDD. The purpose of this study is to explore preliminary content validity of the CAT. Classical test theory was used to test for content validity. A panel of 10 expert occupational therapists, who met specific inclusion criteria, rated the 24 items on the CAT. The number of participants who rated each item as essential was used to quantify each item’s content validity using the content validity ratio (CVR). A CVR of .62 was sought for each item on the CAT, based on the size of the panel of expert occupational therapists. At least half of the expert clinicians rated 16 of the 24 items on the CAT as essential, resulting in a 0 or positive CVR. Six items met the researchers’ criteria of a .62 CVR. Three items on the CAT were rated as essential by all members of the expert panel. This study demonstrates some degree of content validity that supports the CAT in its initial form and provides direction for further development as a tool to inform and measure outcomes of OT educational programs focused on increasing the clinical competence of occupational therapists who treat patients with NDD

OncoLog Volume 47, Number 06, June 2002

Drug Development Program Paves the Way for FDA Approval of New Agents Pediatric New Agents Working Group Advances the Study of Novel Treatments in Young Patients DiaLog: Patients and Physicians: Partners in Health Care, by Shellie M. Scott, BS, Physician Assistant, Department of Urology House Call: Taking a More Active Role in Your Own Health Care As Population of Cancer Survivors Grows, Studies of Long-Term Health Effects Become More Critical, Researchers Sayhttps://openworks.mdanderson.org/oncolog/1107/thumbnail.jp

Time out for sibling aggression: An analysis of effective durations in a natural setting

Time-out is a ubiquitous strategy to reduce problem behaviors. The current study sought to find the shortest effective duration(s) of time-out for sibling aggression in a community sample of girls ages 3–7. All participants reached a minimum reduction in sibling aggression of 60% after experiencing a 1-minute time-out. The majority (75%) of participants also demonstrated clear reversals of behavior when returned to the baseline condition. The current findings suggest that a 1-minute time-out may be sufficient for low-level sibling aggression in children as old as seven. Limitations include the presence of a graduate assistant during sibling play and unclear generalizability

Crustal Fissuring on the Crest of the Southern East Pacific Rise at 17˚15\u27-40\u27S

Fissure densities and widths have been mapped along the axial zone of the superfast spreading southern East Pacific Rise (EPR) at 17_150–400S with the near-bottom DSL-120 and Argo II imaging systems. We observe that the youngest lava flows (on a relative age scale) are sparsely fissured and that there is a cumulative increase in fissure abundance with time that produces a strong positive correlation between fissure density and relative age of lava flows. Average fissure widths were used to estimate fissure depths. In the 17_150–400S area, calculated fissure depths are estimated to extend below the seismic layer 2A/2B boundary, and fissures are widest/deepest where lava flows are youngest. We interpret these wide fissures in relatively young flows to be eruptive fissures. Relatively young lava flows combined with high average fissure widths south of 17_250S suggest that there may have been recent dike propagation along the ridge crest in this area. In comparison to the northern EPR at 9_–10_N the density of fissuring on the southern EPR is significantly higher, due in part to the higher occurrence of relatively older, more areally restricted pillow lava flows

Dynamic association between perfusion and white matter integrity across time since injury in Veterans with history of TBI.

ObjectiveCerebral blood flow (CBF) plays a critical role in the maintenance of neuronal integrity, and CBF alterations have been linked to deleterious white matter changes. Although both CBF and white matter microstructural alterations have been observed within the context of traumatic brain injury (TBI), the degree to which these pathological changes relate to one another and whether this association is altered by time since injury have not been examined. The current study therefore sought to clarify associations between resting CBF and white matter microstructure post-TBI.Methods37 veterans with history of mild or moderate TBI (mmTBI) underwent neuroimaging and completed health and psychiatric symptom questionnaires. Resting CBF was measured with multiphase pseudocontinuous arterial spin labeling (MPPCASL), and white matter microstructural integrity was measured with diffusion tensor imaging (DTI). The cingulate cortex and cingulum bundle were selected as a priori regions of interest for the ASL and DTI data, respectively, given the known vulnerability of these regions to TBI.ResultsRegression analyses controlling for age, sex, and posttraumatic stress disorder (PTSD) symptoms revealed a significant time since injury × resting CBF interaction for the left cingulum (p < 0.005). Decreased CBF was significantly associated with reduced cingulum fractional anisotropy (FA) in the chronic phase; however, no such association was observed for participants with less remote TBI.ConclusionsOur results showed that reduced CBF was associated with poorer white matter integrity in those who were further removed from their brain injury. Findings provide preliminary evidence of a possible dynamic association between CBF and white matter microstructure that warrants additional consideration within the context of the negative long-term clinical outcomes frequently observed in those with history of TBI. Additional cross-disciplinary studies integrating multiple imaging modalities (e.g., DTI, ASL) and refined neuropsychiatric assessment are needed to better understand the nature, temporal course, and dynamic association between brain changes and clinical outcomes post-injury

Quantitative sensory testing in children with sickle cell disease: additional insights and future possibilities.

Quantitative sensory testing (QST) is used in a variety of pain disorders to characterize pain and predict prognosis and response to specific therapies. In this study, we aimed to confirm results in the literature documenting altered QST thresholds in sickle cell disease (SCD) and assess the test-retest reliability of results over time. Fifty-seven SCD and 60 control subjects aged 8-20 years underwent heat and cold detection and pain threshold testing using a Medoc TSAII. Participants were tested at baseline and 3 months; SCD subjects were additionally tested at 6 months. An important facet of our study was the development and use of a novel QST modelling approach, allowing us to model all data together across modalities. We have not demonstrated significant differences in thermal thresholds between subjects with SCD and controls. Thermal thresholds were consistent over a 3- to 6-month period. Subjects on whom hydroxycarbamide (HC) was initiated shortly before or after baseline testing (new HC users) exhibited progressive decreases in thermal sensitivity from baseline to 6 months, suggesting that thermal testing may be sensitive to effective therapy to prevent vasoocclusive pain. These findings inform the use of QST as an endpoint in the evaluation of preventative pain therapies