Bubble Growth From First Principles

We consider the simplest relevant problem in the foaming of molten plastics, the growth of a single bubble in a sea of highly viscous Newtonian fluid, and without interference from other bubbles. This simplest problem has defied accurate solution from first principles. Despite plenty of research on foaming, classical approaches from first principles have neglected the temperature rise in the surrounding fluid, and we find that this oversimplification greatly accelerates bubble growth prediction. We use a transport phenomena approach to analyze the growth of a solitary bubble, expanding under its own pressure. We consider a bubble of ideal gas growing without the accelerating contribution from mass transfer into the bubble. We explore the roles of viscous forces, fluid inertia, and viscous dissipation. We find that bubble growth depends upon the nucleus radius and nucleus pressure. We begin with a detailed examination of the classical approaches (thermodynamics without viscous heating). Our failure to fit experimental data with these classical approaches, sets up the second part of our paper, a novel exploration of the essential decelerating role of viscous heating. We explore both isothermal and adiabatic bubble expansion, and also the decelerating role of surface tension. The adiabatic analysis accounts for the slight deceleration due to the cooling of the expanding gas, which depends on gas polyatomicity. We also explore the pressure profile, and the components of the extra stress tensor, in the fluid surrounding the growing bubble. These stresses can eventually be frozen into foamed plastics. We find that our new theory compares well with measured bubble behavior.

The future imagined: Exploring fiction as a means of reflecting on today’s Grand Societal Challenges and tomorrow’s options

European science policy (so-called Horizon 2020) is guided by Grand Societal Challenges (GSCs) with the explicit aim of shaping the future. In this paper we propose an innovative approach to the analysis and critique of Europe’s GSCs. The aim is to explore how speculative and creative fiction offer ways of embodying, telling, imagining, and symbolising ‘futures’, that can provide alternative frames and understandings to enrich the grand challenges of the 21st century, and the related rationale and agendas for ERA and H2020. We identify six ways in which filmic and literary representations can be considered creative foresight methods (i.e. through: creative input, detail, warning, reflection, critique, involvement) and can provide alternative perspectives on these central challenges, and warning signals for the science policy they inform. The inquiry involved the selection of 64 novels and movies engaging with notions of the future, produced over the last 150 years. Content analysis based on a standardised matrix of major themes and sub-domains, allows to build a hierarchy of themes and to identify major patterns of long-lasting concerns about humanity’s future. The study highlights how fiction sees oppression, inequality and a range of ethical issues linked to human and nature’s dignity as central to, and inseparable from innovation, technology and science. It concludes identifying warning signals in four major domains, arguing that these signals are compelling, and ought to be heard, not least because elements of such future have already escaped the imaginary world to make part of today’s experience. It identifies areas poorly defined or absent from Europe's science agenda, and argues for the need to increase research into human, social, political and cultural processes involved in techno-science endeavours.

Household debt and the European crisis. ECRI Research Report No. 13, June 2013

The fall in economic output all over Europe since 2008 has had important consequences for household liabilities. Major growth in demand and supply for household credit products has generated an increase in household debt, which contributed to growth rates during the pre-crisis period but – in some countries – became household-debt overhangs and helped inflate asset bubbles. In the run-up to the crisis, long-term economic lessons and theories were often overlooked and signs that the economic situation could worsen were ignored. Although not at the core of the crisis, household debt had important consequences for macroeconomic stability, robustness of growth and the depth of recessions. The last ten years in Europe have demonstrated the typical final stage of a household debt cycle: rapid increase and abrupt retrenchment. Widely varying outcomes across Europe enable us to consider the causes of the rapid growth in household debt and draw theoretical lessons that can help policy-makers and academics devise a coherent regulatory response to avoid extremes of the debt cycle in future.

Russia in Crisis: Year One. OSW Report, January 2010

Economic conditions which had favoured Russia’s development suddenly changed in mid-2008. The Russian economy was hit, on the one hand, by a drastic slump in oil prices (which fell from nearly US$150 to US$50 between July 2008 and January 2009), and on the other by the outflow of investors (a net of US$130 billion of capital left Russia in the fourth quarter of 2008). Within several months, the financial crisis became an economic crisis affecting the entire economy. The financial reserves accumulated in times of prosperity (more than US$162 billion in the stabilisation funds and nearly US$598 billion in the currency and gold reserve) alleviated the negative impact of the crisis, although this failed to prevent the deep declines in macroeconomic indicators. Russia is one of the states most severely affected by the crisis. In the first half of 2009, its GDP fell by 10.4% compared to the same period in the previous year, while industrial production dropped by nearly 15%, and a decrease in investments of over 18% was reported. The poor economic performance has strongly affected the Russian budget, which reported a deficit for the first time in ten years in 2009. During the first year of the crisis (August 2008 – September 2009), Russia’s financial reserves were seriously reduced as a result of the government’s anti-crisis policy and interventions from the central bank: the reserve fund decreased by nearly 45% to US$76 billion, and the central bank’s reserves shrunk by nearly US$200 billion to US$409 billion. Meanwhile, however, the money in the National Welfare Fund, which had been intended almost entirely to subsidise the Pensions Fund between 2010 and 2015, rose almost three-fold (to US$90 billion). According to government forecasts, the money from the reserve fund is also supposed to be spent fully in 2010. The financial crisis has triggered a dynamic outflow of capital from the Russian market. So-called speculative capital was the first to demonstrate the lack of confidence in the Russian market. In the first half of 2009, the growth rate of long-term investments also decreased noticeably, although no spectacular withdrawal of direct investments from Russia has been observed. The economic crisis has also halted the foreign expansion of Russian private capital, while state-owned capital strengthened its position as an investor. Russia’s raw materials companies continue to be the main category of foreign investors; however, new technologies are gaining prominence as the second main direction of Russian investments.

The end of an overlooked European currency war. CEPS Commentary, 21 January 2015

On January 15th the Swiss National Bank (SNB) abandoned the efforts it had taken since September 2011 to ensure that the Swiss franc/euro exchange rate would not fall below 1.2 Swiss francs per euro. The Swiss franc appreciated immediately by almost 20% (after a temporary overshot of an even larger amount).The justification was that speculative capital flows induced by the euro crisis were driving the Swiss franc above its equilibrium value. Daniel Gros draws some important general lessons in this Commentary from the Swiss case and finds that the move by the SNB to stop its interventions will have an important impact on the euro-area economy.

(Table 2) Picked maximum velocities from 3 radars (RAY, SHK, and SUM), showing 10 explosions at Erebus volcano, Antarctica, and their respective directivity vectors

We used a novel system of three continuous wave Doppler radars to successfully record the directivity of i) Strombolian explosions from the active lava lake of Erebus volcano, Antarctica, ii) eruptions at Stromboli volcano, Italy, and iii) a man-made explosion in a quarry. Erebus volcano contains a convecting phonolite lava lake, presumably connected to a magma chamber at depth. It is one of the few open vent volcanoes that allow a direct observation of source processes during explosions. Its lava lake is the source of frequent violent Strombolian explosions, caused by large gas bubbles bursting at the lake surface. The exact mechanism of these bubble bursts is unclear, as is the mechanism of the creation of the infrasound signal accompanying the explosions. We use the Doppler radar data to calculate the directivity of Strombolian eruptions at Erebus. This allows us to derive information about the expected type of infrasound source pattern (i.e. the role of a dipole in addition to the monopole signature) and the physical structure of the volcano. We recorded 10 large explosions simultaneously with three radars, enabling us to calculate time series of 3D directivity vectors (i.e. effectively 4D), which describe the direction of preferred expansion of the gas bubble during an explosion. Such directivity information allows a comparison to dipole infrasound radiation patterns recorded during similar explosions only a few weeks later. Video observations of explosions support our interpretation of the measurements. We conclude that at Erebus, the directivity of explosions is mainly controlled by random processes. Since the geometry of the uppermost conduit is assumed to have a large effect on the directivity of explosions, the results suggest a largely symmetrical uppermost conduit with a vertical axis of symmetry. For infrasound recordings, a significant dipole signature can be expected in addition to the predominant monopole signature.

Clay and smectite content in sediment core CRP-3

The Cenozoic sediments of the CRP-3 drill core from the continental shelf of McMurdo Sound in Ross Sea, Pacific sector of the Southern Ocean, have been investigated for their clay mineral assemblages, especially for the smectite abundances, concentrations and crystallinities. The assemblages of CRP-3 are very different from those of the CRP-1 and CRP-2/2A drill cores. Thus, an almost monomineralic assemblage characterizes the sequence below 330 mbsf. This assemblage is made of well-crystallized smectite with probably authigenic origin between 800 mbsf and 625 mbsf. From 625 mbsf to 330 mbsf the assemblage consists of moderately crystallized smectite that, at least in part, seems to be of detrital origin and thus indicates weathering under a relatively warm and wet climate. In the interval 330-145 mbsf, smectite concentrations fluctuate between 50% and 100% and probably document alternating phases of chemical weathering under a warm and wet climate and physical weathering under a relatively cool and dry climate. Above 145 mbsf the smectite decreases dramatically to concentrations of about 20% and becomes poorly crystalline. In contrast, illite and chlorite become more abundant. Such an assemblage is typical for early Oligocene and younger sediments in McMurdo Sound and reflects physical weathering conditions under a cool climate on a glaciated Antarctic continent. Correlations of the changes in the clay mineral spectrum of CRP-3 with other cores from McMurdo Sound and from other parts of the Southern Ocean has to remain speculative at this stage, because of the poor age control.

Bubble sizes in waters of the Atlantic Ocean

Typical size of bubbles obtained from cavitation inception pressure measured in the surface layer of the Atlantic Ocean in situ aboard R/V Professor Vize in 1971 and Nerey in 1973 are reported. These results do not contradict ones of bubble size measurements using optical or acoustical techniques. Variability of bubble size is discovered and described. This variability is related to passing from one geographical region to another (from 68°55'S to 61°52'N), to changes in depth (from 5 to 100 m) and in day time, as well as to spatial fluctuations within an aquatic area. It is suggested that, in addition to wave breaking, there is another source of bubbles at depth 10-20 m that associates with hydrobiological processes.

The little keepsake, or, Easy lessons, in words of one syllable.

Includes publisher's advertisement, p. [4] of wrapper.

Effect of gas entrainment on the heat transfer characteristics of mercury under turbulent flow conditions : final report /

"Gas entrainment, indicated by visual bubbles in the mercury, led to low heat transfer rates which were increased by increasing the static pressure. Suitable changes in the flow system resulted in a reduction of this entrainment effect and an increase in heat transfer performance."--Page iii.

The progress of the intellect : as exemplified in the religious development of the Greeks and Hebrews /

Includes bibliographical references.

Die italienische philosophie des neunzehnten jahrhunderts /

Each volume has also special t.-p.

Report of the Workshop on Magnetic Information Technology (MINT), Washington, D.C., June 22-24, 1983 /

Mode of access: Internet.

The collected writings of Thomas De Quincey,

Title within ornamental borders.

Philosophie des Geistes : oder Encyklopädie der gesammten Geisteslehre.

1. abth. Ontologische und psychologische betrachtung des geistes.--2. abth. Pragmatologie des geistes, philosophie der geschichte und speculative theologie.