Thoracic juxtafacet cyst (JFC) as a rare cause of myelopathy – An additional reference to support the instability theory

2010 ◽  
Vol 77 (2) ◽  
pp. 178-180 ◽  
Author(s):  
Dorothea Daentzer ◽  
Doris Stüder
2020 ◽  
pp. 1-22
Author(s):  
Peter Schauer ◽  
Stephen Shennan ◽  
Andrew Bevan ◽  
Sue College ◽  
Kevan Edinborough ◽  
...  

The authors of this article consider the relationship in European prehistory between the procurement of high-quality stones (for axeheads, daggers, and other tools) on the one hand, and the early mining, crafting, and deposition of copper on the other. The data consist of radiocarbon dates for the exploitation of stone quarries, flint mines, and copper mines, and of information regarding the frequency through time of jade axeheads and copper artefacts. By adopting a broad perspective, spanning much of central-western Europe from 5500 to 2000 bc, they identify a general pattern in which the circulation of the first copper artefacts was associated with a decline in specialized stone quarrying. The latter re-emerged in certain regions when copper use decreased, before declining more permanently in the Bell Beaker phase, once copper became more generally available. Regional variations reflect the degrees of connectivity among overlapping copper exchange networks. The patterns revealed are in keeping with previous understandings, refine them through quantification and demonstrate their cyclical nature, with additional reference to likely local demographic trajectories.


1986 ◽  
Vol 108 (2) ◽  
pp. 418-424 ◽  
Author(s):  
D. Frost ◽  
B. Sturtevant

The effect of ambient pressure on the intrinsic instability of rapid vaporization in single droplets boiling explosively at the limit of superheat has been studied experimentally and theoretically. The instability that distorts the evaporating interface and substantially enhances the mass flux at atmospheric pressure is suppressed at high pressure. The radiated pressure field is two orders of magnitude smaller from stabilized bubbles than from unstable. At intermediate pressures bubble growth occurs in two stages, first stable, then unstable. The Landau–Darrieus instability theory predicts absolute stability at atmospheric pressure for a spherical bubble, whereas the theory for planar interfaces yields results in general agreement with observation. The sensitivity of the instability to temperature suggests that small temperature nonuniformities may be responsible for quantitative departures of the behavior from predictions.


2010 ◽  
Vol 23 (1) ◽  
pp. 34-42 ◽  
Author(s):  
Katharine R. Hendry ◽  
Melanie J. Leng ◽  
Laura F. Robinson ◽  
Hilary J. Sloane ◽  
Jerzy Blusztjan ◽  
...  

AbstractCycling of deepwater silicon (Si) within the Southern Ocean, and its transport into other ocean basins, may be an important player in the uptake of atmospheric carbon, and global climate. Recent work has shown that the Si isotope (denoted by δ29Si or δ30Si) composition of deep sea sponges reflects the availability of dissolved Si during growth, and is a potential proxy for past deep and intermediate water silicic acid concentrations. As with any geochemical tool, it is essential to ensure analytical precision and accuracy, and consistency between methodologies and laboratories. Analytical bias may exist between laboratories, and sponge material may have matrix effects leading to offsets between samples and standards. Here, we report an interlaboratory evaluation of Si isotopes in Antarctic and sub-Antarctic sponges. We review independent methods for measuring Si isotopes in sponge spicules. Our results show that separate subsamples of non-homogenized sponges measured by three methods yield isotopic values within analytical error for over 80% of specimens. The relationship between δ29Si and δ30Si in sponges is consistent with kinetic fractionation during biomineralization. Sponge Si isotope analyses show potential as palaeoceaongraphic archives, and we suggest Southern Ocean sponge material would form a useful additional reference standard for future spicule analyses.


1967 ◽  
Vol 25 (2) ◽  
pp. 421-436
Author(s):  
Rayman W. Bortner

When statements of formal eligibility requirements fail to account for the characteristics of institutional populations, there is a tendency to resort to speculative explanations. This study examined some methods for empirical evaluations of these speculative notions. Univariate and step-down analyses did not aid in conceptualizing informal selection processes in this study; a discriminant function analysis seemed to provide an adequate approach to a synthesis. The method was illustrated by examining definable subsamples in a VA domiciliary which were compared with a non-institutional, community sample; means of the standardization samples for the tests used provided additional reference points for comparison. For these particular subsamples from this institution, alterations in self concept appeared to provide the single unifying theme which best integrated the diverse differences among the groups.


2021 ◽  
Vol 18 (2) ◽  
pp. 1-26
Author(s):  
Robert Klosinski ◽  
Andrew D. Hoffman

Abstract This article investigates the notion of complexity as it applies to two phonological characteristics of Heritage Bernese Swiss German, namely /l/-vocalization and /nd/-velarization. We survey literature on the role of complexity in language change generally, as well as how it applies to heritage languages specifically. We then present findings from our study of two groups of Heritage Bernese speakers, one in the United States and one in Argentina, with additional reference to the local contact languages. Our findings suggest that the loss of /nd/-velarization in Misiones, Argentina is most likely the result of an internally-driven reduction of complexity. For both the Ohio and Misiones communities, however, /l/-vocalization has been maintained. We conclude by discussing the importance of research into language dyads beyond those in the United States as well as pursuing research on lesser-studied heritage languages.


2003 ◽  
Vol 41 (7) ◽  
pp. 380-380
Author(s):  
Thomas B. Greenslade
Keyword(s):  

2017 ◽  
Vol 47 (1) ◽  
pp. 49-68 ◽  
Author(s):  
Robert D. Hetland

AbstractBaroclinic instabilities are ubiquitous in many types of geostrophic flow; however, they are seldom observed in river plumes despite strong lateral density gradients within the plume front. Supported by results from a realistic numerical simulation of the Mississippi–Atchafalaya River plume, idealized numerical simulations of buoyancy-driven flow are used to investigate baroclinic instabilities in buoyancy-driven flow over a sloping bottom. The parameter space is defined by the slope Burger number S = Nf−1α, where N is the buoyancy frequency, f is the Coriolis parameter, and α is the bottom slope, and the Richardson number Ri = N2f2M−4, where M2 = |∇Hb| is the magnitude of the lateral buoyancy gradients. Instabilities only form in a subset of the simulations, with the criterion that SH ≡ SRi−1/2 = Uf−1W−1 = M2f−2α 0.2, where U is a horizontal velocity scale and SH is a new parameter named the horizontal slope Burger number. Suppression of instability formation for certain flow conditions contrasts linear stability theory, which predicts that all flow configurations will be subject to instabilities. The instability growth rate estimated in the nonlinear 3D model is proportional to ωImaxS−1/2, where ωImax is the dimensional growth rate predicted by linear instability theory, indicating that bottom slope inhibits instability growth beyond that predicted by linear theory. The constraint SH 0.2 implies a relationship between the inertial radius Li = Uf−1 and the plume width W. Instabilities may not form when 5Li > W; that is, the plume is too narrow for the eddies to fit.


2001 ◽  
Vol 37 (4) ◽  
pp. 2380-2382 ◽  
Author(s):  
A.V. Nazarov ◽  
R.G. Cox ◽  
C.E. Patton

Sign in / Sign up

Export Citation Format

Share Document