Multiple melt bodies fed the AD 2011 eruption of Puyehue-Cordón Caulle, Chile.

Within the volcanological community there is a growing awareness that many large- to small-scale, point-source eruptive events can be fed by multiple melt bodies rather than from a single magma reservoir. In this study, glass shard major- and trace-element compositions were determined from tephra systematically sampled from the outset of the Puyehue-Cordón Caulle (PCC) eruption (~1 km(3)) in southern Chile which commenced on June 4(th), 2011. Three distinct but cogenetic magma bodies were simultaneously tapped during the paroxysmal phase of this eruption. These are readily identified by clear compositional gaps in CaO, and by Sr/Zr and Sr/Y ratios, resulting from dominantly plagioclase extraction at slightly different pressures, with incompatible elements controlled by zircon crystallisation. Our results clearly demonstrate the utility of glass shard major- and trace-element data in defining the contribution of multiple magma bodies to an explosive eruption. The complex spatial association of the PCC fissure zone with the Liquiñe-Ofqui Fault zone was likely an influential factor that impeded the ascent of the parent magma and allowed the formation of discrete melt bodies within the sub-volcanic system that continued to independently fractionate.

Effect of pCPA on nicotine-induced analgesia.

This study investigated the effect of para-chlorophenylalanine (pCPA), on nicotine-induced analgesia. pCPA reduces physiological levels of 5-HT, a neurotransmitter that has been linked to pain. The effects of naloxone HCl and mecamylamine HCl on this analgesia were also assessed. Subjects were 24 albino rats. Each group of eight rats was injected subcutaneously (SC) with nicotine sulphate, followed by an intraperitoneal (IP) injection of one of the potential antagonists. Behavioral analgesia was assessed using the tail-flick test. Data analysis revealed that pCPA did not affect nicotine-induced analgesia. Consistent with past research, naloxone also had no effect, and mecamylamine effectively eliminated this analgesia. The results are interpreted in light of current knowledge of this behavioral analgesia and pain perception, in general.

Masticatory muscle activity as a function of parafunctional, active and passive oral behavioural patterns.

Oral behavioural patterns have received limited empirical support for their causal role in the development of head and facial pain. The present study was designed to assess electromyographic (EMG) variations in six muscle groups (i.e., bilateral masseter, temporalis and orbicularis oris) as a function of various oral behavioural patterns. A second purpose was to determine whether mandibular movement patterns and specific oral behaviours could be predicted by EMG patterns. Eleven non-pain subjects followed each of twenty oral behavioural patterns while EMG was recorded. Electromyographic change scores were computed for each behaviour relative to baseline measures. Initial analyses were performed using factorial repeated measures ANOVAS. Using post hoc analyses as general guides, specific EMG criteria were developed for classifying mandibular movements. For most subjects, EMG patterns accurately classified teeth clenching, protrusive/retrusive movements, right movements, left movements and lip movement patterns. Wide individual variations were found among muscle groups for identical behaviours. The association between particular oral behaviours and EMG patterns may explain 'sinus' headaches and certain types of facial pain.

Oral habits and TMJ dysfunction in facial pain and non-pain subjects.

Multifactorial theories for facial pain aetiology have been proposed in the past, although little research has been produced to support a multifactorial aetiology. The present study assessed self-rated oral habits over a 7 day period for facial pain and non-pain subjects with and without a clinical symptom of TMJ dysfunction. The results indicate a significant effect for TMJ dysfunction and teeth clenching and an interaction between TMJ dysfunction and facial pain for biting of the lips and mouth. A significant chi-square test showed that most non-pain controls with TMJ dysfunction reported that they never clenched. The results are discussed in terms of support for a multifactorial aetiology in some facial pain patients and the need for future research to delineate subgroups of facial pain and non-pain subjects.