Geological archive of the onset of plate tectonics

© 2018 The Author(s) Published by the Royal Society. All rights reserved. Plate tectonics, involving a globally linked system of lateral motion of rigid surface plates, is a characteristic feature of our planet, but estimates of how long it has been the modus operandi of lithospheric formation and interactions range from the Hadean to the Neoproterozoic. In this paper, we review sedimentary, igneous and metamorphic proxies along with palaeomagnetic data to infer both the development of rigid lithospheric plates and their independent relative motion, and conclude that significant changes in Earth behaviour occurred in the mid- to late Archaean, between 3.2 Ga and 2.5 Ga. These data include: sedimentary rock associations inferred to have accumulated in passive continental margin settings, marking the onset of seafloor spreading; the oldest foreland basin deposits associated with lithospheric convergence; a change from thin, new continental crust of mafic composition to thicker crust of intermediate composition, increased crustal reworking and the emplacement of potassic and peraluminous granites, indicating stabilization of the lithosphere; replacement of dome and keel structures in granite-greenstone terranes, which relate to vertical tectonics, by linear thrust imbricated belts; the commencement of temporally paired systems of intermediate and high dT/dP gradients, with the former interpreted to represent subduction to collisional settings and the latter representing possible hinterland back-arc settings or ocean plateau environments. Palaeomagnetic data from the Kaapvaal and Pilbara cratons for the interval 2780-2710Ma and from the Superior, Kaapvaal and Kola-Karelia cratons for 2700-2440Ma suggest significant relative movements. We consider these changes in the behaviour and character of the lithosphere to be consistent with a gestational transition from a non-plate tectonic mode, arguably with localized subduction, to the onset of sustained plate tectonics

The determinants and consequences of adult nursing staff turnover: a systematic review of systematic reviews.

BACKGROUND: Nurses leaving their jobs and the profession are an issue of international concern, with supply-demand gaps for nurses reported to be widening. There is a large body of existing literature, much of which is already in review form. In order to advance the usefulness of the literature for nurse and human resource managers, we undertook an overview (review of systematic reviews). The aim of the overview was to identify high quality evidence of the determinants and consequences of turnover in adult nursing. METHODS: Reviews were identified which were published between 1990 and January 2015 in English using electronic databases (the Cochrane Database of Systematic Reviews, MEDLINE, EMBASE, Applied Social Sciences Index and Abstracts, CINAHL plus and SCOPUS) and forward searching. All stages of the review were conducted in parallel by two reviewers. Reviews were quality appraised using the Assessment of Multiple Systematic Reviews and their findings narratively synthesised. RESULTS: Nine reviews were included. We found that the current evidence is incomplete and has a number of important limitations. However, a body of moderate quality review evidence does exist giving a picture of multiple determinants of turnover in adult nursing, with - at the individual level - nurse stress and dissatisfaction being important factors and -at the organisational level - managerial style and supervisory support factors holding most weight. The consequences of turnover are only described in economic terms, but are considered significant. CONCLUSIONS: In making a quality assessment of the review as well as considering the quality of the included primary studies and specificity in the outcomes they measure, the overview found that the evidence is not as definitive as previously presented from individual reviews. Further research is required, of rigorous research design, whether quantitative or qualitative, particularly against the outcome of actual turnover as opposed to intention to leave. TRIAL REGISTRATION: PROSPERO Registration 17 March 2015: CRD42015017613

A theory of organizational readiness for change

<p>Abstract</p> <p>Background</p> <p>Change management experts have emphasized the importance of establishing organizational readiness for change and recommended various strategies for creating it. Although the advice seems reasonable, the scientific basis for it is limited. Unlike individual readiness for change, organizational readiness for change has not been subject to extensive theoretical development or empirical study. In this article, I conceptually define organizational readiness for change and develop a theory of its determinants and outcomes. I focus on the organizational level of analysis because many promising approaches to improving healthcare delivery entail collective behavior change in the form of systems redesign--that is, multiple, simultaneous changes in staffing, work flow, decision making, communication, and reward systems.</p> <p>Discussion</p> <p>Organizational readiness for change is a multi-level, multi-faceted construct. As an organization-level construct, readiness for change refers to organizational members' shared resolve to implement a change (change commitment) and shared belief in their collective capability to do so (change efficacy). Organizational readiness for change varies as a function of how much organizational members value the change and how favorably they appraise three key determinants of implementation capability: task demands, resource availability, and situational factors. When organizational readiness for change is high, organizational members are more likely to initiate change, exert greater effort, exhibit greater persistence, and display more cooperative behavior. The result is more effective implementation.</p> <p>Summary</p> <p>The theory described in this article treats organizational readiness as a shared psychological state in which organizational members feel committed to implementing an organizational change and confident in their collective abilities to do so. This way of thinking about organizational readiness is best suited for examining organizational changes where collective behavior change is necessary in order to effectively implement the change and, in some instances, for the change to produce anticipated benefits. Testing the theory would require further measurement development and careful sampling decisions. The theory offers a means of reconciling the structural and psychological views of organizational readiness found in the literature. Further, the theory suggests the possibility that the strategies that change management experts recommend are equifinal. That is, there is no 'one best way' to increase organizational readiness for change.</p

Dynamics of Jupiter's Atmosphere

Results from the Galileo probe and orbiter arc compared with Voyager and ground-based results. The probe made measurements to the 20-bar level, well below the nominal cloud base at 5 bars and well below the level where sunlight is absorbed. The winds increased with depth within the clouds and then remained constant below cloud base. This rules out most "thin weather layer" models of Jovian meteorology. Water, H_2S, and NH_3 were depleted relative to "solar" abundances at the nominal cloud base but increased with depth below 10 bars. Apparently the probe entered a dry downdraft that penetrated to 20 bars. Consistent with this result, the orbiter found water varying by factors of 100 from place to place, with the lowest values at the sites that resemble the one where the probe went in. The orbiter also revealed that these sites are regions of horizontal convergence of the cloud top winds, which is consistent with the downdraft hypothesis

Saturn's rotation period from its atmospheric planetary-wave configuration

The rotation period of a gas giant's magnetic field (called the System III reference frame) is commonly used to infer its bulk rotation. Saturn's dipole magnetic field is not tilted relative to its rotation axis (unlike Jupiter, Uranus and Neptune), so the surrogate measure of its long-wavelength (kilometric) radiation is currently used to fix the System III rotation period. The period as measured now by the Cassini spacecraft is up to 7 min longer than the value of 10 h 39 min 24 s measured 28 years ago by Voyager. Here we report a determination of Saturn's rotation period based on an analysis of potential vorticity. The resulting reference frame (which we call System IIIw) rotates with a period of 10 h 34 min 13 20 s. This shifted reference frame is consistent with a pattern of alternating jets on Saturn that is more symmetrical between eastward and westward flow. This suggests that Saturn's winds are much more like those of Jupiter than hitherto believed. © 2009 Macmillan Publishers Limited