Nature as historical protagonist: environment and society in pre-industrial England

This article compares chronologies reconstructed from historical records of prices, wages, grain harvests, and population with corresponding chronologies of growing conditions and climatic variations derived from dendrochronology and Greenland ice-cores. It demonstrates that in pre-industrial, and especially late medieval, England, short-term environmental shocks and more enduring shifts in environmental conditions (sometimes acting in concert with biological agencies) exercised a powerful influence upon the balance struck between population and available resources via their effects upon the reproduction, health and life expectancy of humans, crops, and livestock. Prevailing socio-economic conditions and institutions, in turn, shaped society's susceptibility to these environmental shocks and shifts.

Gender differences, responsiveness and memory of a potentially painful event in hermit crabs

Nonreflexive responses to a noxious event and prolonged memory are key criteria of a pain experience. In a previous study, hermit crabs, Pagurus bernhardus, that received a small electric shock within their shell often temporarily evacuated the shell and some groomed their abdomen and/or moved away from their vital resource. Most, however, returned to the shell. When offered a new shell 20 s later, shocked crabs were more likely than nonshocked crabs to approach and move into a new shell and did so more quickly (Elwood & Appel 2009, Animal Behaviour, 77, 1243-1246). Here we examined how increasing the time between the shock and the offering of a new shell influences the response. There was evidence of a memory of the aversive shock that lasted at least 1 day. Crabs tested after 30 min and 1 day were more likely to approach the shell and new shells were more likely to be taken 30 min after the shock. Shocked crabs approached the new shell more quickly and used fewer probes of the chelipeds prior to moving in and these results were stable over time and significant for specific times up to 1 day. Females were more likely than males to evacuate shells and did so after fewer shocks. These results extend previous work and demonstrate an extended memory of having been shocked. The findings are consistent with respect to criteria for pain that are accepted for vertebrates.

Motivational trade-offs and potential pain experience in hermit crabs

One criterion of pain experience is that the emotional response to pain may be traded-off against other motivational requirements. This was tested in hermit crabs, housed in either preferred or unpreferred species of shells, by subjecting their abdomens to electric shocks of gradually increasing intensity. The first observable response was not affected by shell species but those in preferred shells evacuated at a higher shock level than those in poor quality shells. Thus, they seem to trade-off the requirement to retain a high quality shell with that of avoidance of the noxious stimulus. Some crabs returned to their shells and those that got back into the preferred species did so with less probing of the aperture before getting in and subsequently thrust their abdomen in and out less often in further investigation, thus confirming their shell species preference. Not all crabs returned to the vicinity of the shell and some attempted to climb the wall of the experimental chamber. Others engaged in shell rapping as if in a fight and grooming of the abdomen was noted. These findings are consistent with the idea of a pain experience rather than a nociceptive reflex. (C) 2009 Elsevier B.V. All rights reserved.

Pain experience in hermit crabs?

Pain may be inferred when the responses to a noxious stimulus are not reflexive but are traded off against other motivational requirements, the experience is remembered and the situation is avoided in the future. To investigate whether decapods feel pain we gave hermit crabs, Pagurus bernhardus, small electric shocks within their shells. Only crabs given shocks evacuated their shells indicating the aversive nature of the stimulus, but fewer crabs evacuated from a preferred species of shell indicating a motivational trade-off. Some crabs that evacuated attacked the shell in the manner seen in a shell fight. Most crabs, however, did not evacuate at the stimulus level we used, but when these were subsequently offered a new shell, shocked crabs were more likely to approach and enter the new shell. Furthermore, they approached that shell more quickly, investigated it for a shorter time and used fewer cheliped probes within the aperture prior to moving in. Thus the experience of the shock altered future behaviour in a manner consistent with a marked shift in motivation to get a new shell to replace the one occupied. The results are consistent with the idea of pain in these animals. (C) 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Uncertainty, learning and growth

The paper extends Blackburn and Galindev's (Economics Letters, Vol. 79 (2003), pp. 417-421) stochastic growth model in which productivity growth entails both external and internal learning behaviour with a constant relative risk aversion utility function and productivity shocks. Consequently, the relationship between long-term growth and short-term volatility depends not only on the relative importance of each learning mechanism but also on a parameter measuring individuals' attitude towards risk.

Nonlinear theory of solitary waves associated with longitudinal particle motion in lattices - Application to longitudinal grain oscillations in a dust crystal

The nonlinear aspects of longitudinal motion of interacting point masses in a lattice are revisited, with emphasis on the paradigm of charged dust grains in a dusty plasma (DP) crystal. Different types of localized excitations, predicted by nonlinear wave theories, are reviewed and conditions for their occurrence (and characteristics) in DP crystals are discussed. Making use of a general formulation, allowing for an arbitrary (e.g. the Debye electrostatic or else) analytic potential form phi(r) and arbitrarily long site-to-site range of interactions, it is shown that dust-crystals support nonlinear kink-shaped localized excitations propagating at velocities above the characteristic DP lattice sound speed v(0). Both compressive and rarefactive kink-type excitations are predicted, depending on the physical parameter values, which represent pulse- (shock-)like coherent structures for the dust grain relative displacement. Furthermore, the existence of breather-type localized oscillations, envelope-modulated wavepackets and shocks is established. The relation to previous results on atomic chains as well as to experimental results on strongly-coupled dust layers in gas discharge plasmas is discussed.

Electron-impact rotational excitation of the carbon monosulphide (CS) molecule

Rotational excitation of the carbon monosulphide (CS) molecule by thermal electron-impact is studied using the molecular R-matrix method combined with the adiabatic-nuclei-rotation (ANR) approximation. Rate coefficients are obtained for electron temperatures in the range 5-5000 K and for transitions involving levels up to J = 40. It is confirmed that dipole allowed transitions (Delta J = 1) are dominant and that the corresponding rate coefficients exceed those for excitation by neutrals by at least five orders of magnitude. As a result, the present rates should be included in any detailed population model of CS in sources where the electron fraction is larger than similar to 10(-5), in particular in diffuse molecular clouds and interstellar shocks.

Ascending Out of Poverty: An analysis of family histories in Kenya

This paper looks at inheritance through minimally-structured interviews with several generations of Kenyan families, seeking to explain that the how and why of poverty can be understood in the wider family context. Five main routes for ascending out of poverty were identified: (1) the gradual accumulation of resources due to income deriving from cash crops; (2) the gradual accumulation of resources due to income from non-farm work, including remittances from family member who have moved away for work; (3) the role of education, particularly skills training opposed to academic qualification, in helping provide employment; (4) accessing financial assets through support both from extended family members and from informal support mechanisms; (5) stability and benefits accruing from long-term strategic planning, including entrepreneurial activity. Both the ascent out of and the descent into poverty can be better conceived as processes, rather than due to chains of discrete events or specific ‘shocks’.

DENSE GAS IN NEARBY GALAXIES .9. A SURVEY FOR HNC

Ten detections and five tentative detections of hydrogen isocyanide (HNC) J=1-0 emission are reported from a survey including sixteen galaxies. Full maps are presented for the nuclear regions of NGC 253 and IC 342, partial maps for Maffei 2, M 82, and M 83. Toward IC 342, the HNC and HCO+ distributions differ from those observed in 12CO, 13CO, HCN, CS, and NH3. This is likely a consequence of the density structure. Relative HNC abundances are with 10(-10)-10(-9) much smaller than those measured in nearby dark clouds and appear to be slightly smaller than those in regions of massive star formation of the Galactic disk. This is consistent with the presence of dense warm gas or a frequent occurrence of shocks in the nuclear regions of the galaxies observed. As in prominent Galactic star forming regions, 3 mm HNC line emission tends to be weaker than the corresponding emission from HCN and HCO+. Toward Arp 220, however, the 3 mm HNC/HCN line intensity ratio is > 1. HNC/HCO+, HNC/CO, and HNC to 20 cm radio continuum luminosity ratios are also particularly large. A possible interpretation is the presence of cool quiescent gas outside the central region which contains the starburst. In the other ultraluminous galaxy observed, NGC 6240, X(HNC) 10 smaller than in Arp 220, demonstrating that the molecular composition in ultraluminous galaxies is far from being uniform.

Electrostatic shock dynamics in superthermal plasmas

The propagation of ion acoustic shocks in nonthermal plasmas is investigated, both analytically and numerically. An unmagnetized collisionless electron-ion plasma is considered, featuring a superthermal (non-Maxwellian) electron distribution, which is modeled by a ?-(kappa) distribution function. Adopting a multiscale approach, it is shown that the dynamics of low-amplitude shocks is modeled by a hybrid Korteweg-de Vries-Burgers (KdVB) equation, in which the nonlinear and dispersion coefficients are functions of the ? parameter, while the dissipative coefficient is a linear function of the ion viscosity. All relevant shock parameters are shown to depend on ?: higher deviations from a pure Maxwellian behavior induce shocks which are narrower, faster, and of larger amplitude. The stability profile of the kink-shaped solutions of the KdVB equation against external perturbations is investigated. The spatial profile of the shocks is found to depend upon the dispersion and the dissipation term, and the role of the interplay between dispersion and dissipation is elucidated.

Note on the single-shock solutions of the Korteweg-de Vries-Burgers equation

The well-known shock solutions of the Korteweg-de Vries-Burgers equation are revisited, together with their limitations in the context of plasma (astro)physical applications. Although available in the literature for a long time, it seems to have been forgotten in recent papers that such shocks are monotonic and unique, for a given plasma configuration, and cannot show oscillatory or bell-shaped features. This uniqueness is contrasted to solitary wave solutions of the two parent equations (Korteweg-de Vries and Burgers), which form a family of curves parameterized by the excess velocity over the linear phase speed.

Magnetic instability in a dilute circular rarefaction wave

The growth of magnetic fields in the density gradient of a rarefaction wave has been observed in simulations and in laboratory experiments. The thermal anisotropy of the electrons, which gives rise to the magnetic instability, is maintained by the ambipolar electric field. This simple mechanism could be important for the magnetic field amplification in astrophysical jets or in the interstellar medium ahead of supernova remnant shocks. The acceleration of protons and the generation of a magnetic field by the rarefaction wave, which is fed by an expanding circular plasma cloud, is examined here in form of a 2D particle-in-cell simulation. The core of the plasma cloud is modeled by immobile charges, and the mobile protons form a small ring close to the cloud's surface. The number density of mobile protons is thus less than that of the electrons. The protons of the rarefaction wave are accelerated to 1/10 of the electron thermal speed, and the acceleration results in a thermal anisotropy of the electron distribution in the entire plasma cloud. The instability in the rarefaction wave is outrun by a TM wave, which grows in the dense core distribution, and its magnetic field expands into the rarefaction wave. This expansion drives a secondary TE wave. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769128]

Simulation of relativistically colliding laser-generated electron flows

The plasma dynamics resulting from the simultaneous impact, of two equal, ultra-intense laser pulses, in two spatially separated spots, onto a dense target is studied via particle-in-cell simulations. The simulations show that electrons accelerated to relativistic speeds cross the target and exit at its rear surface. Most energetic electrons are bound to the rear surface by the ambipolar electric field and expand along it. Their current is closed by a return current in the target, and this current configuration generates strong surface magnetic fields. The two electron sheaths collide at the midplane between the laser impact points. The magnetic repulsion between the counter-streaming electron beams separates them along the surface normal direction, before they can thermalize through other beam instabilities. This magnetic repulsion is also the driving mechanism for the beam-Weibel (filamentation) instability, which is thought to be responsible for magnetic field growth close to the internal shocks of gamma-ray burst jets. The relative strength of this repulsion compared to the competing electrostatic interactions, which is evidenced by the simulations, suggests that the filamentation instability can be examined in an experimental setting. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768426]

A new method for estimating liquidity risk: Insights from a liquidity-adjusted CAPM framework

This paper proposes a new non-parametric method for estimating model-free, time-varying liquidity betas which builds on realized covariance and volatility theory. Working under a liquidity-adjusted CAPM framework we provide evidence that liquidity risk is a factor priced in the Greek stock market, mainly arising from the covariation of individual liquidity with local market liquidity, however, the level of liquidity seems to be an irrelevant variable in asset pricing. Our findings provide support to the notion that liquidity shocks transmitted across securities can cause market-wide effects and can have important implications for portfolio diversification strategies. ©2012 Elsevier B.V. All rights reserved.

Generation of scaled protogalactic seed magnetic fields in laser-produced shock waves

The standard model for the origin of galactic magnetic fields is through the amplification of seed fields via dynamo or turbulent processes to the level consistent with present observations. Although other mechanisms may also operate, currents from misaligned pressure and temperature gradients (the Biermann battery process) inevitably accompany the formation of galaxies in the absence of a primordial field. Driven by geometrical asymmetries in shocks associated with the collapse of protogalactic structures, the Biermann battery is believed to generate tiny seed fields to a level of about 10 gauss (refs 7, 8). With the advent of high-power laser systems in the past two decades, a new area of research has opened in which, using simple scaling relations, astrophysical environments can effectively be reproduced in the laboratory. Here we report the results of an experiment that produced seed magnetic fields by the Biermann battery effect. We show that these results can be scaled to the intergalactic medium, where turbulence, acting on timescales of around 700 million years, can amplify the seed fields sufficiently to affect galaxy evolution.