Dietary exogenous and endogenous abrasives and tooth wear in African buffalo

The potential contribution of exogenous dust and grit and endogenous plant silica to tooth wear of the African buffalo in Kruger National Park was examined. Endogenous silica as percent dry matter on basalt soils (6.58%) was significantly higher than on granite soils (4.41%), and significantly higher in dry season grasses (6.64%) than in wet season grasses (4.41%). Exogenous grit on granite grasses (0.43%) had significantly higher loads than basalt grasses (0.16%) and wet season loads significantly higher (0.50%) than dry season (0.09%) loads. Grasses on granite soils were significantly tougher (0.266 J m-1) than those on basalt soils (0.215 J m-1). Adult buffalo were estimated to consume 10–28 kg per year of exogenous grit and 300–400 kg per year of endogenous silica. First lower buffalo molars are estimated to wear at an average rate of 1.94 mm per year with no significant difference between wear on the different soil types or between sexes. The high silica intake with no observable differences in tooth wear questions the role of silica in tooth wear. It is proposed that there is an interaction between exogenous and endogenous abrasives and that abrasion must be considered more holistically

Does tree size influence timing of flowering in Cerberiopsis candelabra (Apocynaceae), a long-lived monocarpic rain-forest tree?

Cerberiopsis candelabra is a long-lived monocarpic rain-forest tree endemic to New Caledonia that shows mass flowering across a substantial proportion of a population, and across a substantial number of populations. We investigated the relationship between tree size and flowering (and subsequent dying) across 18 populations from the flowering event of 2003 in order to understand the role of possible size thresholds for flowering in the life history and regeneration ecology of this monocarpic species. There was a strong positive correlation between trunk diameter and the incidence of flowering when population data were combined. However, the relationship between size and flowering was complex in that flowering occurred across a wide range of tree sizes, with almost complete overlap in size between flowering (5-79 cm dbh) and non-flowering trees (5-64 cm dbh), and with large trees in both the flowering and nonflowering state in the same population. In about half the populations studied there was no significant difference in mean trunk diameter of flowering and non-flowering trees. Nonetheless, we suggest that tree size may play a fundamental role in the life history and regeneration ecology of this species. The seedlings appear to be relatively shade-intolerant and dependent on large canopy gaps for recruitment. A significant effect of mass flowering and subsequent death of multiple large trees is the potential to form large canopy gaps and enhance seedling survival, as the gap is temporally linked with seed germination. However, it is unclear why there is such a large size range of flowering trees, i.e. whether this is just a consequence of the proximate cue, or whether the optimal size for flowering does indeed vary among individuals

Impact of ‘synchronous’ and ‘asynchronous’ CPR modality on quality bundles and outcome in out-of-hospital cardiac arrest patients

During cardiopulmonary resuscitation (CPR), the need to interrupt chest compressions to provide synchronous ventilations prevents blood flow continuity, reducing the possibility to ensure high-quality CPR bundles of care and, thus, having a potentially negative impact on perfusion and patient outcome. Contemporaneous asynchronous chest compressions and ventilations may avoid these potentially negative effects. Only a few studies measured the CPR quality metrics during synchronous and asynchronous CPR modality and its relation to patient outcome. A prospective observational study was conducted on 285 consecutive adult patients with out-of-hospital cardiac arrest treated by EMS teams over a 30-month period. Ventilation rate, chest compression fraction (i.e. cardiac arrest time spent delivering uninterrupted chest compressions compared to total cardiac arrest time) and chest compression rate per minute were collected in real time by defibrillators and analysed through a dedicated software (electrical cardiac activity through the ECG, chest compression and ventilations through the transthoracic impedance) during synchronous and asynchronous CPR modalities. During asynchronous CPR modality, higher ventilation rate and chest compression fraction (p < 0.001), and lower chest compression rate per minute (p < 0.001) were ensured, being all cited metrics more adherent to the high-quality CPR bundles. Ventilation rate provided during the whole CPR was an independent predictor for a good neurological outcome (OR 3.795, p = 0.005). Asynchronous chest compression and ventilation ensured the most adequate chest compression fraction, uninterrupted chest compression rate and ventilation rate