There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth system. Here, we revise and update the planetary boundary framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries—climate change and biosphere integrity—have been identified, each of which has the potential on its own to drive the Earth system into a new state should they be substantially and persistently transgressed.

/pdf/planetary-boundaries-guiding-human-development-on-a-changing-5gmf909etg.pdf

Planetary boundaries: Guiding human development on a changing planet

THE major active ingredient of marijuana, Δ9-tetrahydrocannabi-nol (Δ9-THC), has been used as a psychoactive agent for thousands of years. Marijuana, and Δ9-THC, also exert a wide range of other effects including analgesia, anti-inflammation, immunosuppression, anticonvulsion, alleviation of intraocular pressure in glaucoma, and attenuation of vomiting1. The clinical application of cannabinoids has, however, been limited by their psychoactive effects, and this has led to interest in the biochemical bases of their action. Progress stemmed initially from the synthesis of potent derivatives of δ9-THC4,5, and more recently from the cloning of a gene encoding a G-protein-coupled receptor for cannabinoids6. This receptor is expressed in the brain but not in the periphery, except for a low level in testes. It has been proposed that the non-psychoactive effects of cannabinoids are either mediated centrally or through direct interaction with other, non-receptor proteins1,7,8. Here we report the cloning of a receptor for cannabinoids that is not expressed in the brain but rather in macrophages in the marginal zone of spleen.

Molecular characterization of a peripheral receptor for cannabinoids

This paper contrasts the natural and anthropogenic controls on the conversion of unreactive N2 to more reactive forms of nitrogen (Nr). A variety of data sets are used to construct global N budgets for 1860 and the early 1990s and to make projections for the global N budget in 2050. Regional N budgets for Asia, North America, and other major regions for the early 1990s, as well as the marine N budget, are presented to highlight the dominant fluxes of nitrogen in each region. Important findings are that human activities increasingly dominate the N budget at the global and at most regional scales, the terrestrial and open ocean N budgets are essentially dis- connected, and the fixed forms of N are accumulating in most environmental reservoirs. The largest uncertainties in our understanding of the N budget at most scales are the rates of natural biological nitrogen fixation, the amount of Nr storage in most environmental reservoirs, and the production rates of N2 by denitrification.

/pdf/nitrogen-cycles-past-present-and-future-1zdbw0976r.pdf

Nitrogen cycles: past, present, and future

Relationships between wind speed and gas transfer, combined with knowledge of the partial pressure difference of CO2 across the air-sea interface are frequently used to determine the CO2 flux between the ocean and the atmosphere. Little attention has been paid to the influence of variability in wind speed on the calculated gas transfer velocities and the possibility of chemical enhancement of CO2 exchange at low wind speeds over the ocean. The effect of these parameters is illustrated using a quadratic dependence of gas exchange on wind speed which is fit through gas transfer velocities over the ocean determined by the natural-14C disequilibrium and the bomb-14C inventory methods. Some of the variability between different data sets can be accounted for by the suggested mechanisms, but much of the variation appears due to other causes. Possible causes for the large difference between two frequently used relationships between gas transfer and wind speed are discussed. To determine fluxes of gases other than CO2 across the air-water interface, the relevant expressions for gas transfer, and the temperature and salinity dependence of the Schmidt number and solubility of several gases of environmental interest are included in an appendix.

Relationship between wind speed and gas exchange over the ocean

A new biogeochemcial Earth system model for the Phanerozoic Eon

This lecture will present novel simulation techniques for lightweight deployable structures consisting of very thin sheets of fibre-reinforced composite materials. These structures are folded elastically and are able to self-deploy (dynamically) when they are released. Novel structural concepts of this kind were recently introduced on missions requiring parabolic reflector dishes for telecommunications and tubular deployable booms supporting sensors. A variety of related concepts are currently under consideration for future missions. Designing these structures requires detailed predictions that capture both the overall, large displacement deformation of the structure, including the effects of contact and friction at the interfaces between parts of the structure that come into contact, and also the localised deformation of the most heavily deformed regions of the structure, in order to verify that no damage will occur in these regions. Achieving this poses a number of novel challenges. First, the constitutive behaviour of thin composite materials differs fundamentally from that of standard composites and hence needs to be approached with suitable homogenization theories. Second, contact between heavily deformed (but still elastic) surfaces plays a key role in the tight packaging of these structures and the interaction between local and global instabilities that are encountered, even for the simplest configurations of current interest, is such that implicit solution schemes that attempt to capture the complexity of the physical situation become overwhelmed. Third, folding aids, such as jigs, straps, etc. are often used to facilitate the actual folding of a real structure without causing any damage and, although modelling this process in full detail is not necessary, any simulation needs to be steered through a maze of instabilities. The engineer must have confidence in the final predictions, because a fully detailed model of the folded configuration is required, to provide the initial conditions for any study of deployment. Proceedings of the 6th International Conference on Computation of Shell and Spatial Structures IASS-IACM 2008: “Spanning Nano to Mega” 28-31 May 2008, Cornell University, Ithaca, NY, USA John F. ABEL and J. Robert COOKE (eds.) 1 Unfolding of potato flower as a deployable structure Hidetoshi KOBAYASHI*, Keitaro HORIKAWA and Yoshinori MORITA *Dept. of Mech. Sci. and Bioeng., Osaka University, 1-3, Machikaneyama, Toyonaka, 560-8531, Japan. hkoba@me.es.osaka-u.ac.jp Abstract A potato flower has triangle gussets between individual petals and five or six petals almost make a flat plane when they are fully unfolded. In this research, therefore, the folding and unfolding manners of a number of regular polygon paper models as the petals and gussets of a potato flower fully unfolded were investigated by vector analysis. It was found that the bud volume depends on the petal number, N, and the bud with N = 5 has the largest volume. On the total kinetic energy during unfolding, however, the model with N = 5 or 6 became smaller than other models. Therefore, the energy about unfolding is more important for potato flower.

Deployable Structures and Biological Morphology

The Runaway Greenhouse: New Model Results and Implications for Planets and Anthropogenic Global Change

. We present new estimates of the regional North Atlantic
(15–80 ∘  N) CO 2 flux for the 2000–2017 period
using atmospheric CO 2 measurements from the NOAA long-term surface site
network in combination with an atmospheric carbon cycle data assimilation
system (GEOS-Chem–LETKF, Local Ensemble Transform Kalman Filter). We assess the sensitivity of flux estimates to
alternative ocean CO 2 prior flux distributions and to the
specification of uncertainties associated with ocean fluxes. We present a
new scheme to characterize uncertainty in ocean prior fluxes, derived from a
set of eight surface p CO 2 -based ocean flux products, and which
reflects uncertainties associated with measurement density and
 p CO 2 -interpolation methods. This scheme provides improved model
performance in comparison to fixed prior uncertainty schemes, based on
metrics of model–observation differences at the network of surface sites.
Long-term average posterior flux estimates for the 2000–2017
period from our GEOS-Chem–LETKF analyses are − 0.255  ±  0.037 PgC yr −1 for the subtropical basin (15–50 ∘  N) and
 − 0.203  ±  0.037 PgC yr −1 for the subpolar region (50–80 ∘  N, eastern boundary at 20 ∘  E). Our basin-scale
estimates of interannual variability (IAV) are 0.036  ±  0.006 and 0.034  ±  0.009 PgC yr −1 for subtropical and subpolar
regions, respectively. We find statistically significant trends in carbon
uptake for the subtropical and subpolar North Atlantic of − 0.064  ±  0.007 and − 0.063  ±  0.008 PgC yr −1  decade −1 ; these trends are
of comparable magnitude to estimates from surface ocean p CO 2 -based
flux products, but they are larger, by a factor of 3–4, than trends estimated from
global ocean biogeochemistry models.

/pdf/variability-of-north-atlantic-co2-fluxes-for-the-2000-2017-1xbwtpsd29.pdf

Andrew J. Watson

Papers

A new biogeochemcial Earth system model for the Phanerozoic Eon

Deployable Structures and Biological Morphology

The Runaway Greenhouse: New Model Results and Implications for Planets and Anthropogenic Global Change

Variability of North Atlantic CO2 fluxes for the 2000–2017 period estimated from atmospheric inverse analyses

Prospects for improved pregnancy outcomes by assisted reproductive technologies