Synthesis and Reactivity of Tricoordinate Organoberyllium Azides

A series of terminal mono- and disubstituted beryllium azides of the form [(CAAC)Be(N3)R] (R=CAACH, Dur; CAACH/CAAC=1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-yl/idene, Dur=2,3,5,6-tetramethylphenyl) and [L2Be(N3)2] (L=CAACNH=1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-imine, IiPrMe=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene), respectively, were synthesized and characterized by NMR spectroscopy and X-ray crystallography. Thermolysis and photolysis products of these first examples of tricoordinate azidoberyllium complexes evidence extensive ligand scrambling and the formal insertion of nitrenes into the CAAC-Be bond, generating cyclic alkyl(amino)imine (CAAI) ligands. Furthermore, the reaction with a small N-heterocyclic carbene (NHC) leads to unexpected CAAC-NHC ligand exchange, while the reaction with pentaphenylborole yields the first γ-azide adduct of a borole, long postulated to be the first step in the synthesis of 1,2-azaborinines from boroles and azides.

Tracking heart surface features to determine myocardial contrast agent enrichment

Fluorescent cardiac imaging can be applied for intraoperative quality control after a coronary bypass grafting surgery to ensure the myocardial perfusion by evaluating the increasing contrast agent enrichment in the heart. The motion due to the beating heart impedes the interpretation of the contrast agent enrichment in the vessels and leads to noisy enrichment curves. We propose tracking of the heart surface features to compensate for the motion of the beating heart and thereby improve the analysis of the contrast agent enrichment. Furthermore, we propose a vessel segmentation pipeline for a local evaluation of contrast agent enrichment directly in the vessels.

Determinants of Judgments of Explanatory Power: Credibility, Generality, and Statistical Relevance

Explanation is a central concept in human psychology. Drawing upon philosophical theories of explanation, psychologists have recently begun to examine the relationship between explanation, probability and causality. Our study advances this growing literature at the intersection of psychology and philosophy of science by systematically investigating how judgments of explanatory power are affected by (i) the prior credibility of an explanatory hypothesis, (ii) the causal framing of the hypothesis, (iii) the perceived generalizability of the explanation, and (iv) the relation of statistical relevance between hypothesis and evidence. Collectively, the results of our five experiments support the hypothesis that the prior credibility of a causal explanation plays a central role in explanatory reasoning: first, because of the presence of strong main effects on judgments of explanatory power, and second, because of the gate-keeping role it has for other factors. Highly credible explanations are not susceptible to causal framing effects, but they are sensitive to the effects of normatively relevant factors: the generalizability of an explanation, and its statistical relevance for the evidence. These results advance current literature in the philosophy and psychology of explanation in three ways. First, they yield a more nuanced understanding of the determinants of judgments of explanatory power, and the interaction between these factors. Second, they show the close relationship between prior beliefs and explanatory power. Third, they elucidate the nature of abductive reasoning.

The probabilistic no miracles argument

This paper develops a probabilistic reconstruction of the No Miracles Argument (NMA) in the debate between scientific realists and anti-realists. The goal of the paper is to clarify and to sharpen the NMA by means of a probabilistic formalization. In particular, I demonstrate that the persuasive force of the NMA depends on the particular disciplinary context where it is applied, and the stability of theories in that discipline. Assessments and critiques of "the" NMA, without reference to a particular context, are misleading and should be relinquished. This result has repercussions for recent anti-realist arguments, such as the claim that the NMA commits the base rate fallacy (Howson (2000), Magnus and Callender (Philosophy of Science, 71:320-338, 2004)). It also helps to explain the persistent disagreement between realists and anti-realists.

[Maturation of the autonomic nervous system: differences in heart rate variability at different gestational weeks]

AIMS

Heart rate variability (HRV) reveals information on the functional state of the autonomic nervous system (ANS). This study was initiated to assess the physiological and maturational development of the ANS by comparing HRV data of a large number healthy foetus of different gestational ages from the 24(th) to the 42(nd) week.

METHODS

Cardiotocogram (CTG) recordings of HRV of 172 healthy foetus (24-42 weeks' gestation) were performed to establish normative data. Frequency domain HRV parameters were computed in three frequency bands.

RESULTS

The gestational ages of the foetuses correlate with HRV. Lower gestational age in weeks showed lower frequency domain parameters than higher gestational age in weeks. The most significant differences were discerned for HRV parameters reflecting sympathetic activity in LF (low frequency) and VLF (very low frequency), due to the adrenergic system.

CONCLUSIONS

Maturation of the ANS is accompanied by increasing HRV with a pronounced increase of sympathetic activity. These changes are measurable by CTG recordings with a computer algorithm which can calculate short-term variability on the basis of CTG data. Problems of the CTG signal, as shown before, were the parameters of the time domain, which could only be well detected by ECG or foetal magnetocardiography (FMCG).

Larva-adult relationships in an ancestral dipteran: A re-examination of sensillar pathways across the antenna and leg anlagen of Chaoborus crystallinus (DeGeer, 1776; Chaoboridae)

In one of his classical studies on insect metamorphosis, Weismann compared the imaginal anlagen of the ancestral phantom midge, Chaoborus, with those of advanced brachycerans. We have expanded his findings on the relationships between larval and imaginal organs using electron microscopy and cobalt backfilling of the antenna and leg anlagen and the axonal trajectories of corresponding larval sensilla. We show that both primordia are confluent with the larval antennae and "leg" sensilla (an ancestral Keilin organ), respectively. These fully developed larval organs represent the distal tips of the imaginal anlagen rather than separate cell clusters. The axons of the larval antenna and leg sensilla project across the corresponding anlagen to their target neuromeres within the central nervous system (CNS). Within the discs, nerves composed of these larval axons, developing afferent fibres and efferences ascending from the CNS are found. Both the structure of the primordia and the axonal trajectories thus relate the situation found in advanced brachycerans with that seen in more ancestral insects. In addition, the larval antennae, legs, wings and even the eyes possess very similar afferent pioneer trajectories supporting the idea that the described pattern is generally used in the ontogeny of sensory systems.