The origin of volatile elements in the Earth–Moon system

The origin of volatile species such as water in the Earth–Moon system is a subject of intense debate but is obfuscated by the potential for volatile loss during the Giant Impact that resulted in the formation of these bodies. One way to address these topics and place constraints on the temporal evolution of volatile components in planetary bodies is by using the observed decay of ⁸⁷Rb to ⁸⁷Sr because Rb is a moderately volatile element, whereas Sr is much more refractory. Here, we show that lunar highland rocks that crystallized ∼4.35 billion years ago exhibit very limited ingrowth of ⁸⁷Sr, indicating that prior to the Moon-forming impact, the impactor commonly referred to as “Theia” and the proto-Earth both must have already been strongly depleted in volatile elements relative to primitive meteorites. These results imply that 1) the volatile element depletion of the Moon did not arise from the Giant Impact, 2) volatile element distributions on the Moon and Earth were principally inherited from their precursors, 3) both Theia and the proto-Earth probably formed in the inner solar system, and 4) the Giant Impact occurred relatively late in solar system history.

Understanding the formation of the Moon has long been a topic of intense interest, although hard constraints on this event only developed after the Apollo program returned lunar samples to Earth. Based on the thousands of lunar rocks that have been studied to date, arguably one of the most stringent of these constraints is that the Moon is strongly depleted in volatile elements relative to the solar photosphere, primitive meteorites, and Earth. Recognition of such a depletion of volatile elements, combined with the orbital mechanics of the Moon and geochemical evidence that it differentiated from a mostly molten state, led to the now widely accepted “Giant Impact” hypothesis, in which the Moon accreted from a volatile element–depleted debris disk produced by an impact between a Mars-sized body (Theia) and the proto-Earth (1). Yet, the formation of the Moon through such an impact scenario raises questions about the composition of the proto-Earth and Theia and their respective contributions to the makeup and subsequent evolution of the Earth–Moon system. Of particular interest is how and when the Moon and Earth obtained their present allotments of volatile components, including, and most importantly, water. Did the Moon and Earth form with their current allotments of volatile elements, or were these elements lost during the Giant Impact and reintroduced to Earth by later accretion of volatile element–laden materials? Here, we address this issue using the Rb–Sr isotopic systematics of lunar samples to provide time constraints on the history and distribution of volatile elements in the Earth–Moon system.     

Protection against noise trauma by pre-exposure to a low level acoustic stimulus

Guinea pigs were pre-exposed to a low level acoustic stimulus prior to exposure to a stimulus known to yield a permanent threshold shift. This pre-treatment resulted in: 1) approximately a 20 dB reduction in the threshold shift relative to animals not pre-exposed, and 2) complete recovery from the threshold shift after 2 months.     

Importance of radiation time and dose factors on outcome for childhood medulloblastoma

The purpose of this study was to investigate the relationship of posterior fossa radiation therapy duration (PFRTD) and relapse-free survival (RFS) following adjuvant craniospinal RT for childhood medulloblastoma. A retrospective audit was performed assessing all children aged <18 years managed with adjuvant craniospinal RT for medulloblastoma in Australia and New Zealand in 1980-1993. Children receiving prolonged (>180 days) pre-RT chemotherapy were excluded. Data were obtained for potential prognostic factors in domains of patient, tumour and treatment factors. Radiation therapy time factors assessed were PFRTD and time interval from surgery to commencement of RT (SRTD). The end-point assessed was RFS and analysis was performed using Cox regression and Kaplan-Meier survival. One hundred and eighty-nine children were identified from 10 oncology units, with data available from 182 children for analysis. Median follow up was 5.3 years. Seventy-three per cent of children presented with disease confined to the cerebellum; 13% had initial neuraxis disease. Macroscopic resection was described in 54%; 42% received adjuvant chemotherapy. Median RT dose and RT duration to PF was 55 Gy and 45 days, respectively. Seventy-eight relapses occurred with a 10-year actuarial RFS of 58.2% (standard error +/- 4%). On univariate analysis, increasing PF dose (P = 0.002), age >5 years (P = 0.006), and more thorough extent of surgical resection (P = 0.043) were associated with improved RFS; PFRTD (P = 0.20) and SRTD (P = 0.51) were not associated with RFS. On multivariate analysis, although both PF dose (P = 0.004) and extent of surgery (P = 0.045) remained strongly significant, RT duration was now associated with RFS (P = 0.049). Other factors assessed that did not reach significance were patient age, local tumour extent, presence of internal shunt and use of chemotherapy. The importance of local treatment factors was confirmed in this audit with established prognostic factors such as primary tumour macroscopic resection and adequate PF RT dose being associated with RFS. A treatment time effect is weakly suggested, although less significant than RT dose delivered.     

Autonomic cardiovascular responses in antecedent poliomyelitis

Autonomically mediated cardiovascular responses were evaluated in 20 subjects with antecedent poliomyelitis and compared to data from an age- and sex-matched control group. The polio subjects had a lower heart rate response to the Valsalva manoeuvre but the same respiratory sinus arrhythmia as the controls. From this it is concluded that the polio subjects had a normal vagal function. The polio subjects had a greater initial heart rate increase but the same blood pressure response to the orthostatic position as the controls. This indicates a normal function of the sympathetic nerves. The greater heart rate increase is most likely caused by a displacement of blood to the legs because of muscle atrophy. The polio subjects had a smaller blood flow increase as an initial response to an isometric handgrip than the controls. This might be attributed to a reduced beta-adrenergic vasodilation, possibly due to a reduced central vasomotor drive. It is concluded that subjects with antecedent poliomyelitis have no significant dysfunction of the peripheral autonomic nerves. Thus, there is no deterioration of the peripheral autonomic nerve function in parallel with the progressive muscle atrophy and paralysis earlier described in post-polio subjects.     

The allatotropic activity of the larval brain of Galleria mellonella cultured in vitro

The brains of last instar larvae of Galleria mellonella can be successfully cultured in vitro. The high allatotropic activity of 0–8 hr brains, as measured by their ability to elicit supernumerary larval molts upon implantation into 0–8 hr last instar larval hosts, remains constant through 4 days in vitro. The allatotropic activity of 120 hr brains increases during in vitro culture. The number of supernumerary larvae resulting from the implantations of 120 hr brains rises from 20 to 30% of the hosts implanted with fresh brains, to 90% of the hosts supplied with brains maintained in vitro for 24 hr prior to implantation. There is a progressive loss of paraldehyde-fuchsin-stainable neurosecretory material over 72 hr of in vitro culture from the three groups of neurosecretory cells visible in whole mounts of the brains. Nevertheless, the ultrastructural picture of the medial neurosecretory cells, which are the probable source of the allatotropic factor, indicates synthetic activity after 72 hr of culture. In 0–8 hr last instar brains which are cultured for 48 hr as complexes with attached corpora cardiaca and corpora allata, stainable neurosecretory material accumulates in all three groups of cerebral neurosecretorycells. The brains from the cultured complexes have low allatotropic activity. It is concluded on the basis of the bioassay and ultrastructural observations that under our conditions of in vitro culture, the neurosecretory cells of the last instar larval brain not only survive but also maintain synthetic activity through at least 72 hr in vitro. The relationship between stainable neurosecretory material and neurosecretory activity in this system is discussed, as are possible feedback interactions involving the corpora cardiaca-corpora allata and the brain.     

Detection of autoantibodies to ribonucleoproteins by counter-immunoelectropheresis, immunoblotting and RNA-immunoprecipitation: comparison of results.

Counterimmunoelectropheresis (CIE), immunoblotting (IB) and RNA-immunoprecipitation (RNA-IP) were compared for their potential to detect antibodies to U1RNP, Sm and SS-B in sera from 50 patients with SLE and 18 with MCTD. Anti-SS-B were detected in 6 SLE-sera (12%) and one MCTD-serum (6%) by all three techniques. Anti-Sm were present in 7 SLE-sera (14%) by RNA-IP and IB; 3 of these sera showed identity with a-Sm and 4 with a-U1RNP by CIE. Antibodies precipitating U1RNA were present in 8 SLE sera (16%); 4 of these sera were positive for anti-U1RNP by CIE (8%) and 4 sera recognized one or more of the U1RNA-associated proteins by IB (8%). All MCTD-sera were positive for anti-U1RNP by RNA-IP including one serum negative by IB and CIE. RNA-IP allowed the detection of antibodies precipitating U1-U2RNA in 4 sera; in IB, the U2RNA specific protein B" was recognized by 3 sera. RNA-IP appears to be a sensitive method for detecting anti-URNP's.     

The importance of transformational leadership style for the well-being of employees working with older people

Title.  The importance of transformational leadership style for the well-being of employees working with older people.
Aim.  This paper is a report of a study to explore the relationships between transformational leadership, followers' perceived working conditions and employee well-being and job satisfaction.
Background.  There is some evidence that transformational leadership style is linked to employee job satisfaction and well-being. However, it is not clear whether this is due to (i) a direct relationship between leadership and job satisfaction and well-being outcomes or (ii) whether followers' perceived working conditions mediate this relationship.
Methods.  A cross-sectional design was applied to data from a questionnaire study of 447 staff caring for older people in Denmark. Data were collected in 2005. A theory-driven model of the relationships between leadership, working conditions, job satisfaction and well-being was tested using structural equation modelling.
Results.  The transformational leadership style was closely associated with followers' working conditions, namely involvement, influence and meaningfulness. Involvement was associated with job satisfaction and meaningfulness was associated with well-being. However, working conditions were closely correlated with each other, and thus the mediating mechanisms may operate through several different working conditions. A direct path between leadership behaviour and employee well-being was also found.
Conclusion.  Considering working conditions in the absence of studying leadership behaviour (or vice versa) may reveal an incomplete picture of the impact of work and work relationships on well-being. Work re-design interventions focused on influence may benefit from the consideration of training managers to exert transformational leadership behaviours.