The effect of the quasar H1821+643 on the surrounding intracluster medium: revealing the underlying cooling flow

We present a detailed study of the thermodynamic properties of the intracluster medium of the only low redshift galaxy cluster to contain a highly luminous quasar, H1821+643. The cluster is a highly massive, strong cool core cluster. We find that the ICM entropy around the quasar is significantly lower than that of other similarly massive strong cool core clusters within the central 80 kpc, and that the entropy lies significantly below the extrapolated baseline entropy profile from hierarchical structure formation. By comparing the scaled temperature profile with those of other strong cool core clusters of similar total mass, we see that the entropy deficiency is due to the central temperature being significantly lower. This suggests that the presence of the quasar in the core of H1821+643 has had a dramatic cooling effect on the intracluster medium around it. We find that, if the quasar was brighter in the past, Compton cooling by radiation from the quasar may have caused the low entropy and temperature levels in the ICM around the quasar. Curiously, the gradients of the steep central temperature and entropy decline are in reasonable agreement with the profiles expected for a constant pressure cooling flow. It is possible that the system has been locked into a Compton cooled feedback cycle which prevents energy release from the black hole heating the gas sufficiently to switch it off, leading to the formation of a huge (~3x10^10 solar mass) supermassive black hole.Comment: 8 pages, 10 figures. Accepted for publication in MNRA

Ca2+ transients are not required as signals for long-term neurite outgrowth from cultured sympathetic neurons

A method for clamping cytosolic free Ca2+ ([Ca2+]i) in cultures of rat sympathetic neurons at or below resting levels for several days was devised to determine whether Ca2+ signals are required for neurite outgrowth from neurons that depend on Nerve Growth Factor (NGF) for their growth and survival. To control [Ca2+]i, normal Ca2+ influx was eliminated by titration of extracellular Ca2+ with EGTA and reinstated through voltage-sensitive Ca2+ channels. The rate of neurite outgrowth and the number of neurites thus became dependent on the extent of depolarization by KCl, and withdrawal of KCl caused an immediate cessation of growth. Neurite outgrowth was completely blocked by the L type Ca2+ channel antagonists nifedipine, nitrendipine, D600, or diltiazem at sub- or micromolar concentrations. Measurement of [Ca2+]i in cell bodies using the fluorescent Ca2+ indicator fura-2 established that optimal growth, similar to that seen in normal medium, was obtained when [Ca2+]i was clamped at resting levels. These levels of [Ca2+]i were set by serum, which elevated [Ca2+]i by integral of 30 nM, whereas the addition of NGF had no effect on [Ca2+]i. The reduction of [Ca2+]o prevented neurite fasciculation but this had no effect on the rate of neurite elongation or on the number of extending neurites. These results show that neurite outgrowth from NGF-dependent neurons occurs over long periods in the complete absence of Ca2+ signals, suggesting that Ca2+ signals are not necessary for operating the basic machinery of neurite outgrowth

Three water sites in upper mantle olivine and the role of titanium in the water weakening mechanism

Infrared spectroscopy on synthetic olivines has established that there are at least four different mechanisms by which hydrogen is incorporated into the crystal structure. Two mechanisms occur in the system MgO-SiO2-H2O associated with silicon and magnesium vacancies, respectively. A third mechanism is associated with trivalent cation substitution, commonly Fe3+ in natural olivine, while the fourth mechanism, which is the one most prevalent in natural olivines from the spinel-peridotite facies of the Earth’s upper mantle, is associated with Ti4+ [Berry et al., 2005]. Here first principles calculations based on density functional theory are used to derive the structure and relative energies of the two defects in the pure MgO-SiO2-H2O system, and possible hydrogen-bearing and hydrogen-free point defects in Ti4+-doped forsterite. Calculated structures are used to compare the predicted orientation of the O-H bonds with the experimentally determined polarization. The energies are used to discuss how different regimes of chemical environment, temperature (T), pressure (P), and both water content and water fugacity ( fH2O), impact on which of the different hydroxyl substitution mechanisms are thermodynamically stable. We find that given the presence of Ti impurities, the most stable mechanism involves the formation of silicon vacancies containing two protons charge balanced by a Ti4+ cation occupying an adjacent octahedral site. This mechanism leads to the water-mediated formation of silicon vacancies. As silicon is known to be the most slowly diffusing species in olivine, this provides a credible explanation of the observed water weakening effect in olivine

EEG–fMRI mapping of asymmetrical delta activity in a patient with refractory epilepsy is concordant with the epileptogenic region determined by intracranial EEG

We studied a patient with refractory focal epilepsy using continuous EEG-correlated fMRI. Seizures were characterized by head turning to the left and clonic jerking of the left arm, suggesting a right frontal epileptogenic region. Interictal EEG showed occasional runs of independent nonlateralized slow activity in the delta band with right frontocentral dominance and had no lateralizing value. Ictal scalp EEG had no lateralizing value. Ictal scalp EEG suggested right-sided central slow activity preceding some seizures. Structural 3-T MRI showed no abnormality. There was no clear epileptiform abnormality during simultaneous EEG–fMRI. We therefore modeled asymmetrical EEG delta activity at 1–3 Hz near frontocentral electrode positions. Significant blood oxygen level-dependent (BOLD) signal changes in the right superior frontal gyrus correlated with right frontal oscillations at 1–3 Hz but not at 4–7 Hz and with neither of the two frequency bands when derived from contralateral or posterior electrode positions, which served as controls. Motor fMRI activations with a finger-tapping paradigm were asymmetrical: they were more anterior for the left hand compared with the right and were near the aforementioned EEG-correlated signal changes. A right frontocentral perirolandic seizure onset was identified with a subdural grid recording, and electric stimulation of the adjacent contact produced motor responses in the left arm and after discharges. The fMRI localization of the left hand motor and the detected BOLD activation associated with modeled slow activity suggest a role for localization of the epileptogenic region with EEG–fMRI even in the absence of clear interictal discharges

Effect of Transporting an Evidence-Based, Violence Prevention Intervention to Jamaican Preschools on Teacher and Class-wide Child Behaviour:A Cluster Randomised Trial

Introduction.Based on extensive piloting work, we adapted the Incredible Years (IY) teacher-training programme to the Jamaican preschool setting and evaluated this adapted version through a cluster-randomised trial.Methods.Twenty-four community preschools in Kingston, Jamaica were randomly assigned to intervention (12 schools, 37 teachers) or control (12 schools, 36 teachers). The intervention involved training teachers in classroom management through eight full-day training workshops and four individual 1-h in-class support sessions. Outcome measurements included direct observation of teachers’ positive and negative behaviours to the whole class and to high-risk children and four observer ratings: two measures of class-wide child behaviour and two measures of classroom atmosphere. Measures were repeated at a six-month follow-up.Results.Significant benefits of intervention were found for teachers’ positive [effect size (ES) = 3.35] and negative (ES = 1.29) behaviours to the whole class and to high-risk children (positive: ES = 0.83; negative: ES = 0.50) and for observer ratings of class-wide child behaviour (ES = 0.73), child interest and enthusiasm (ES = 0.98), teacher warmth (ES = 2.03) and opportunities provided to share and help (ES = 5.72). At 6-month follow-up, significant benefits of intervention were sustained: positive behaviours (ES = 2.70), negative behaviours (ES = 0.98), child behaviour (ES = 0.50), child interest and enthusiasm (ES = 0.78), teacher warmth (ES = 0.91), opportunities to share and help (ES = 1.42).Conclusions.The adapted IY teacher-training programme produced large benefits to teacher's behaviour and to class-wide measures of children's behaviour, which were sustained at 6-month follow-up. Benefits were of a similar magnitude to those found in a pilot study of the minimally adapted version that required significantly more in-class support for teachers.</jats:sec

A human factors approach to analysing military command and control

This paper applies the Event Analysis for Systemic Teamwork (EAST) method to an example of military command and control. EAST offers a way to describe system level 'emergent properties' that arise from the complex interactions of system components (human and technical). These are described using an integrated methods approach and modelled using Task, Social and Knowledge networks. The current article is divided into three parts: a brief description of the military command and control context, a brief description of the EAST method, and a more in depth presentation of the analysis outcomes. Numerous findings emerge from the application of the method. These findings are compared with similar analyses undertaken in civilian domains, where Network Enabled Capability (NEC) is already in place. The emergent properties of the military scenario relate to the degree of system reconfigurability, systems level Situational Awareness (SA), team-working and the role of mediating technology. It is argued that the EAST method can be used to offer several interesting perspectives on designing and specifying NEC capability in military context