K-12 Writing Teachers’ Careerspan Development: Participatory Pedagogical Content Knowledge of Writing

This narrative grounded theory study examines 19 US K–12 teachers’ development of pedagogical content knowledge of writing (PCKW) across their careers. Building on writing pedagogies and career cycle theories, we invited writing teachers to tell stories of critical experiences that contributed to their development. Findings indicate that teachers’ understanding of writing, being writers, and teaching writers were propelled by various critical experiences--both personal and professional. Our model shows that these experiences prompted teachers to engage in participatory PCKW to cultivate development. Implications are that writing teachers need communities of practice, mentors, and ongoing participatory engagements to sustain process pedagogies

Comparative 3D analyses and palaeoecology of giant early amphibians (Temnospondyli: Stereospondyli)

Macroevolutionary, palaeoecological and biomechanical analyses in deep time offer the possibility to decipher the structural constraints, ecomorphological patterns and evolutionary history of extinct groups. Here, 3D comparative biomechanical analyses of the extinct giant early amphibian group of stereospondyls together with living lissamphibians and crocodiles, shows that: i) stereospondyls had peculiar palaeoecological niches with proper bites and stress patterns very different than those of giant salamanders and crocodiles; ii) their extinction may be correlated with the appearance of neosuchians, which display morphofunctional innovations. Stereospondyls weathered the end-Permian mass extinction, re-radiated, acquired gigantic sizes and dominated (semi) aquatic ecosystems during the Triassic. Because these ecosystems are today occupied by crocodilians, and stereospondyls are extinct amphibians, their palaeobiology is a matter of an intensive debate: stereospondyls were a priori compared with putative living analogous such as giant salamanders and/or crocodilians and our new results try to close this debate.Peer ReviewedPostprint (published version

Epicardial reflection as a cause of incessant ventricular bigeminy

Incessant monomorphic ventricular bigeminy was studied in a young patient with no organic heart disease. The arrhythmia could not be controlled by drug therapy. Spontaneous and artificial variation of the heart rate showed that reentry was the most likely arrhythmogenic mechanism. Peroperative epicardial and transmural mapping revealed an epicardial focal origin which was cryoablated. Reflected reentry occurring in a small area of working myocardial cells appeared to be the most likely explanation for this arrhythmi

Slow potentials in the atrioventricular junctional area of patients operated on for atrioventricular node tachycardias and in isolated porcine hearts

The purpose of this study was to 1) investigate extracellular electrograms in the atrioventricular (AV) junctional area of patients with AV node reentrant tachycardia, 2) compare them with recordings made in isolated porcine hearts, and 3) study their origin. Electrograms with slow components have been used to target the delivery of radiofrequency energy for the cure of AV node reentrant tachycardia. The origin of these electrograms is unknown. In 12 human and 19 porcine hearts, extracellular recordings were made simultaneously from 64 sites. In five other porcine hearts, intracellular recordings were made at sites at which extracellular electrograms revealed slow potentials. Histologic investigations were carried out in four of these hearts. Electrograms with slow components were recorded in five human and eight porcine hearts. These signals were found at sites up to 12 mm from the His bundle. Characteristics of the electrograms did not differ significantly among human and porcine hearts. Electrophysiologic evidence for multiple pathways was present in four hearts. Superficial impalements with microelectrodes at sites with slow potentials showed action potentials with AV node characteristics. In the majority of these recordings, the upstroke coincided with the downstroke of slow potentials. Histologic investigations of the sites of impalement revealed transitional cells directly underneath the endocardium. Slow potentials were recorded in both human and porcine hearts in similar measure. They arise from transitional cells and have action potentials similar to N cell

Dispersion of 'refractoriness' in noninfarcted myocardium of patients with ventricular tachycardia or ventricular fibrillation after myocardial infarction

Postinfarction ventricular tachycardias (VTs) may degenerate into ventricular fibrillation (VF), but this does not happen in all patients. The underlying mechanism is not exactly known, but dispersion of refractory periods is considered a major factor in both induction and persistence of reentrant arrhythmias in general. Hypertrophied, noninfarcted myocardium has altered electrophysiological characteristics. We hypothesized that noninfarcted ventricular tissue may provide the heterogeneities that cause the transition from VT into VF. Local fibrillation intervals, ie, the average interval between local activations during VF, have previously been shown to correlate well with local refractoriness in human and canine atrium and in porcine and canine ventricle and may therefore be used as an index of local refractoriness. This technique permits simultaneous assessment of refractoriness at multiple sites. We measured local fibrillation intervals at 32 to 64 sites in the noninfarcted part of the left ventricle in patients undergoing antiarrhythmic surgery for symptomatic, drug-refractory, postinfarction ventricular tachyarrhythmias. The grid of electrodes (interelectrode distance, 7 mm) was attached to the epicardium of the left ventricle remote from the infarcted tissue. Group 1 consisted of 7 patients with hemodynamically tolerable sustained VT (VT group). Group 2 consisted of 7 patients with cardiac arrest and documented VF (VF group). With the patients on cardiopulmonary bypass, VF was induced by multiple premature stimulation. The VF interval was not significantly different in the two study groups (VT group, 136 +/- 5.5 ms; VF group, 129 +/- 3.4 ms, mean +/- SEM). However, spatial dispersion of the VF intervals (remote from the infarcted area) expressed as the coefficient of variation of VF intervals (SD x 100/mean VF interval in each heart) was significantly larger in the VF group. It was 3.63 +/- 0.56 in the VF group and 1.55 +/- 0.40 in the VT group (mean +/- SEM; P < .01). Differences between the shortest and longest VF intervals in one and the same heart and the largest difference between two adjacent sites were also larger in the VF group (P < .02 and P < .05, respectively). This study shows larger dispersion in VF intervals and therefore suggests larger dispersion of refractory periods in parts of the myocardium remote from the infarction in patients with postinfarction VF than in patients with postinfarction V