Alignment of the ALICE Inner Tracking System with cosmic-ray tracks

37 pages, 15 figures, revised version, accepted by JINSTALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 micron in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10^5 charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.Peer reviewe

Wide-area low-energy surface stimulation of large mammalian ventricular tissue

The epicardial and endocardial surfaces of the heart are attractive targets to administer antiarrhythmic electrotherapies. Electrically stimulating wide areas of the surfaces of small mammalian ventricles is straightforward given the relatively small scale of their myocardial dimensions compared to the tissue space constant and electrical field. However, it has yet to be proven for larger mammalian hearts with tissue properties and ventricular dimensions closer to humans. Our goal was to address the feasibility and impact of wide-area electrical stimulation on the ventricular surfaces of large mammalian hearts at different stimulus strengths. This was accomplished by placing long line electrodes on the ventricular surfaces of pig hearts that span wide areas, and activating them individually. Stimulus efficacy was assessed and compared between surfaces, and tissue viability was evaluated. Activation time was dependent on stimulation strength and location, achieving uniform linear stimulation at 9x threshold strength. Endocardial stimulation activated more tissue transmurally than epicardial stimulation, which could be considered a potential target for future cardiac electrotherapies. Overall, our results indicate that electrically stimulating wide areas of the ventricular surfaces of large mammals is achievable with line electrodes, minimal tissue damage, and energies under the human pain threshold (100 mJ)

Functional outcome of very preterm-born and small-for-gestational-age children at school age

BACKGROUND: Our aim was to determine functional outcome of very preterm-born and small-for-gestational-age (SGA) children as compared with matched controls at school age. METHODS: We included 28 very preterm SGA children (GA <32 wk, birth weight (BW) <10th percentile), born in 2000-2001. We also included 28 very preterm but appropriate-for-gestational-age (AGA) children, matched for GA, gender, and birth year, as controls. We assessed motor skills, intelligence quotient (IQ), attention, verbal memory, visual perception, visuomotor integration, executive functioning, and behavior of both sets of children at school age. RESULTS: The SGA children had a median GA of 29.7 wk and BW of 888 g, whereas the controls had a median GA of 29.4 wk and BW of 1,163 g. At 8.6 y, the median total IQ of the SGA children was 94 as compared with 95 in the controls (not significant). Performance IQ was significantly lower in SGA children (89 vs. 95, P = 0.043), whereas verbal IQ was not (95 vs. 95). Total motor skills (P = 0.048) and fine motor skills (P = 0.021) were worse in SGA children. Furthermore, SGA children scored lower on selective attention (P = 0.026) and visual perception (P = 0.025). Other scores did not differ significantly between groups. CONCLUSION: The differences we found between the groups were small. This suggests that the impaired functioning of very preterm-born SGA children is attributable to their having been born very preterm rather than to being SGA

Imaging of Ventricular Fibrillation and Defibrillation: The Virtual Electrode Hypothesis

Ventricular fibrillation is the major underlying cause of sudden cardiac death. Understanding the complex activation patterns that give rise to ventricular fibrillation requires high resolution mapping of localized activation. The use of multi-electrode mapping unraveled re-entrant activation patterns that underlie ventricular fibrillation. However, optical mapping contributed critically to understanding the mechanism of defibrillation, where multi-electrode recordings could not measure activation patterns during and immediately after a shock. In addition, optical mapping visualizes the virtual electrodes that are generated during stimulation and defibrillation pulses, which contributed to the formulation of the virtual electrode hypothesis. The generation of virtual electrode induced phase singularities during defibrillation is arrhythmogenic and may lead to the induction of fibrillation subsequent to defibrillation. Defibrillating with low energy may circumvent this problem. Therefore, the current challenge is to use the knowledge provided by optical mapping to develop a low energy approach of defibrillation, which may lead to more successful defibrillation