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A non-contacting displacement measuring system utilizing focussed x-rays is being developed for use in hostile environments. Ultimately, this method will be used to measure mechnical strain under adverse conditions such as high temperatures, flame, cutting fluids, and gases with high velocity and pressure gradients. The foundation of the technique is the use of xrays, which are immune to the various environmental factors mentioned above. The proposed system uses a highly focussed, intense x-ray line which is scanned across markers that fluoresce secondary radiation. This secondary radiation level is then monitored using a photon detector and marker-focussed line overlap can be discerned. These targets can be used as fiducial markers demarcating a gage length, and the change in pointing angle of the focussed beam at target overlap is used as a measure of relative displacement. The present experimental systemcan consistently resolve 1.27 microns at ambient conditions, and 2.54 microns have been measured at a target temperature of 1900 de-grees F through an open flame. Given the performance of the current apparatus, equipment improvements should permit increases in resolution by a least a factor of 10 and measurements at much higher temperatures are possible.
Emerging evidence in the 1980s of a link between infants positioned to sleep on their front (prone) and sudden infant death syndrome (SIDS) eventually led to a national “Back to Sleep” campaign in England and Wales in November 1991 (1-6). The SIDS rate dramatically fell by two-thirds (67%) in just four years, from a peak of 1,597 SIDS deaths in 1988 to 531 deaths by 1992 (7). To monitor the characteristic profile of this reduced number of deaths, and identify further potential risk factors associated with SIDS, a case-control study was commissioned as part of a Confidential Enquiry into Stillbirths and Deaths in Infancy (CESDI) and conducted via the University of Bristol between 1993 and 1996 across a third of England (8, 9). A similar study in a smaller geographical area, the South West Infant Sleep Scene Study (SWISS), collecting additional details surrounding the infant sleeping environment, was conducted 10 years later between 2003 and 2006 by the same team (10). Both studies have been instrumental in providing the evidence base for SIDS risk reduction campaigns worldwide and reducing these deaths nationally by a further 60% to 212 SIDS deaths in 2014. This is a review of the main findings, the changes in risk profile over time, and what can be learnt from combining the data from these two studies.
The Optimal Study Design
Despite SIDS being one of the leading causes of post-neonatal infant death, it is a relatively rare event and thus the optimal study design is the observational case-control study. With this design, rare events can be captured as they happen (cases) and compared to suitable controls, although it is often difficult to establish whether significant associations are causal or whether the observations collected are subject to bias. With SIDS investigations in particular, the importance of the final sleeping environment and lack of an immediate causal explanation means recall and misclassification bias can be problematic.
Sudden infant death syndrome (SIDS) is still a leading cause for infant mortality in the United Kingdom (UK) despite the significant reduction in cases since the 1990s. Currently, there are ongoing public health campaigns aimed at promoting safer sleep, as the majority of SIDS cases in the UK occur in unsafe sleep environments. There is little uniformity of practice nationally about which deaths should be classified as SIDS or “unascertained”, with very few deaths recognized as being due to accidental asphyxia. The investigation of sudden and unexpected death in infancy (SUDI) has changed considerably since the early 2000s. Joint agency investigation by police, healthcare, and social care is now standard, with local review of all child deaths mandatory.
SIDS is a prominent cause of death for infants in the UK (1). There were 247 unexplained deaths of children under 2 years of age in 2014; of these, 230 were unexplained infant deaths, giving a rate of 0.30 deaths per 1,000 live births, the lowest on record (2). There were 17 unexplained deaths of children aged between 12 and 24 months, accounting for 6.9% of all unexplained deaths of children younger than 2 years. Much higher rates of deaths in the 1970s and 1980s (2.30 deaths per 1,000 live births, or 1,593 deaths in 1988) (3) led to a concerted effort to identify modifiable risk factors and translate these into advice for parents. As in other countries, associations between unexplained infant deaths and the prone sleeping position, smoking during pregnancy, and overwrapping led to educational campaigns for parents, the successful implementation of which has led to a rapid decline in these deaths in the last 25 years.
The UK “Back to Sleep” campaign
The introduction of the “Back to Sleep” campaign in the UK in 1991 (see Figure 18.1) led to a dramatic fall in the number of infants dying (see Figures 18.2 and 18.3). The campaign in the UK was promoted at a national level and included a strong media element, as well as guidance for health professionals, to change their recommendations to parents. Anne Diamond, who was a popular TV presenter at the time, had a son, Sebastian, who died of SIDS in 1991. She campaigned strongly for the changes to advice (4), which eventually included a television advertisement in collaboration with the Department of Health (5).
Detrital zircon U–Pb ages from samples of the Neoproterozoic Visingsö Group, Sweden, yield a maximum depositional age of ≤ 886±9 Ma (2σ). A minimum depositional age is established biochronologically using organic-walled and vase-shaped microfossils present in the upper formation of the Visingsö Group; the upper formation correlates with the Kwagunt Formation of the 780–740 Ma Chuar Group in Arizona, USA, and the lower Mount Harper Group, Yukon, Canada, that is older than 740 Ma. Mineralized scale microfossils of the type recorded from the upper Fifteenmile Group, Yukon, Canada, where they occur in a narrow stratigraphic range and are younger than 788 Ma, are recognized for the first time outside Laurentia. The mineralized scale microfossils in the upper formation of the Visingsö Group seem to have a wider stratigraphic range, and are older than c. 740 Ma. The inferred age range of mineralized scale microfossils is 788–740 Ma. This time interval coincides with the vase-shaped microfossil range because both microfossil groups co-occur. The combined isotopic and biochronologic ages constrain the Visingsö Group to between ≤ 886 and 740 Ma, thus Tonian in age. This is the first robust age determination for the Visingsö Group, which preserves a rich microfossil assemblage of worldwide distribution. The organic and mineralized microorganisms preserved in the Visingsö Group and coeval successions elsewhere document global evolutionary events of auto- and heterotrophic protist radiations that are crucial to the reconstruction of eukaryotic phylogeny based on the fossil record and are useful for the Neoproterozoic chronostratigraphic subdivision.
From 1918 to 1939, a diplomatic partnership between the Holy See and Poland appeared extremely likely. Since 1870 the Vatican had sought to restore the temporal status it had lost during Italian unification. The Lateran accords of 1929 resolved the Roman question and confirmed the disputed sovereignty of the papal enclave. This achievement, however, was only part of the Apostolic See's determined efforts to fortify its international standing in a continent dominated by Protestant, anticlerical, or atheist states. The Vatican seemed to be a natural match for revived Poland, a nation renowned for its fealty to Rome and menaced by Germany and Russia, traditional antagonists of the papacy and champions of totalitarian doctrines that the church regarded as inimical.
Oceanographic, meteorological and sea-ice data were obtained from the northern Bering Sea and Chukchi Sea during the autumns of 1987 and 1988. Ice-edge location was observed from ships and via AVHRR satellite data, and ice-drift information was obtained from ARGOS-tracked drift buoys. Meteorological data were obtained from ships, from an ARGOS-tracked meteorological station and from synoptic charts. The ice edge was significantly farther south in 1988 than during other years and impacted the Alaskan coastline. In 1987, the ice edge was, conversely, anomalously far north. Ice melt-back in certain regions, such as along the Alaskan coast and in Herald Canyon, was due to input from warm ocean currents. The larger-scale interannual differences in ice extent were, however, due to interannual differences in the regional winds. In particular, the anomalous and extreme southward extent of the ice edge during 1988 was due to northerly to northwesterly winds, which held the summer pack ice against the the beach. Meltwater from this ice salt-stratified the upper water column, so that the ice eventually became effectively insulated against vertical flux of heat from the underlying warm water in the coastal current.
A free-drift sea-ice model for advection is described which includes an interactive wind-driven ocean for closure. A reduced system of equations is solved economically by a simple iteration on the water stress. The performance of the model is examined through a sensitivity study considering ice thickness, Ekman-layer scaling, wind speed, and drag coefficients. A case study is also presented where the model is driven by measured winds and the resulting drift rate compared to measured ice-drift rate for a three-day period during March 1981 at about 80 km inside the boundary of the open pack ice in the Bering Sea.
The advective model is shown to be sensitive to certain assumptions. Increasing the scaling parameter A for the Ekman depth in the ocean model from 0.3 to 0.4 causes a 10 to 15% reduction in ice speed but only a slight decrease in rotation angle (α) with respect to the wind. Modeled α is strongly a function of ice thickness, while speed is not very sensitive to thickness. Ice speed is sensitive to assumptions about drag coefficients for the upper (CA) and lower (CW) surfaces of the ice. Specifying CA and the ratio of CA to CW are important to the calculations.
Standard formulae for the electrical resistance and for the radiating properties of a fully ionized gas have been combined with pinch effect relations to obtain the stationary state radial distribution functions and current—voltage characteristics of a filamentary current. The calculations suggest that the radiation cooling permits a pinched discharge to exist, with a maximum current of about one or two million amperes.
Matériaux. La fabrication de grands disques de quartz a été poursuivie aux États-Unis; mais aucun résultat n’a encore été communiqué à la Commission.
Mlle Clavier, de l’Observatoire de Paris, a étudié des miroirs en acier inoxydable, taillés, polis optiquement et argentés. Deux points d’ordre chimique restaient à élucider pour rendre pratique l’emploi de cette matière: (a) l’argenture, qui ne donnait jamais de couches bien régulières et adhérentes; (b) l’enlèvement de l’argent terni, en vue d’une argenture nouvelle.
La Commission n’a pas été informée de travaux particuliers importants concernant les matières d’optique. Il convient toutefois de mentionner dans cet ordre d’idées les résultats intéressants obtenus par application d’une pellicule d’aluminium comme surface réfléchissante, pour les miroirs astronomiques.
Le dépôt est fait par évaporation dans le vide et s’applique immédiatement aux miroirs en verre de petites dimensions. Pour les grandes surfaces, l’installation capable de résister à la pression atmosphérique peut présenter de grandes difficultés. Cependant, il a été possible de traiter ainsi, par exemple, le miroir de 90 cm. de diamètre de l’Observatoire de Lick. Plusieurs observatoires américains ont mis en service des miroirs aluminisés.
The mean taxon duration, , and the 50 percent point of the Lyellian curve, T50, are directly proportional to one another: . However, there is a disagreement in the literature over the correct value of the proportionality constant, C. Various authors have claimed that C ≈ 1.44, C = 2.00 and C ≈ 2.89. I critically examine the assumptions underlying these three choices of C and argue that C ≈ 1.44, which is based on an exponential model of survivorship, is more widely applicable than the other values of C.