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This press release is copyright Nature.
VOL.445 NO.7127 DATED 1 FEBRUARY 2007
This press release contains:
* Summaries of newsworthy papers:
Hydrology: The tropical water cycle
Ecology: Bacteria get into films
Thermodynamics: Maxwell's demon reincarnated?
* Mention of papers to be published at the same time with the same embargo
* Geographical listing of authors
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[1] Hydrology: The tropical water cycle (pp 528-532; N&V)
Rain evaporation and continental convection have been found to have an important part in the tropical water cycle, according to a report in this week’s Nature. John Worden and colleagues analyse global measurements of the isotopic composition of water vapour from NASA’s Tropospheric Emission Spectrometer (TES) to disclose the processes driving the tropical hydrological cycle.
The cycling of atmospheric moisture is a key aspect of the Earth’s climate system, both for understanding weather and climate and for managing freshwater resources. Isotopic measurements of water vapour can identify the pathways of atmospheric moisture, because lighter isotopes tend to evaporate and heavier isotopes condense. The isotopic composition can therefore be used to track water vapour as it is recycled within the system.
The TES data for water vapour near tropical clouds reveal that rainfall evaporation significantly replenishes the humidity of the lower troposphere with typically 20% and up to 50% of rainfall being evaporated near convective clouds. Over tropical continents, however, the isotopic signature of water vapour differs significantly compared with that of rainfall, suggesting that the dominant moisture sources are convection of vapour from oceanic sources and evapotranspiration (a combination of evaporation and plant transpiration). These observations provide unprecedented new information about hydrological processes that are critical for understanding the global climate system.
CONTACT
John Worden (Jet Propulsion Laboratory, Pasadena, CA, USA)
Tel: +1 818 393 7122; E-mail: [email protected]
David Noone (University of Colorado, Boulder, CO, USA) Co-author
Tel: +1 303 735 6073; E-mail: [email protected]
Thom Rahn (Los Alamos National Laboratory, NM, USA) N&V author
Tel: +1 505 667 1812; E-mail: [email protected]
[2] Ecology: Bacteria get into films (pp 533-536)
Researchers have witnessed the development of the species inter-relationships that underpin complex microbial communities called biofilms, which although not as visually impressive as rainforests, can be every bit as complex in ecological terms. By studying an artificially simple biofilm of just two species, Paul Rainey and colleagues showed how these communities can grow more stable over time as the relationship between the species evolves.
The principle is the same as that which underpins the exponentially more complex biofilms found in the natural world, say the researchers in this week’s Nature. They studied two bacterial species called Acinetobacter and Pseudomonas putida and found that, if given the opportunity to coexist as a biofilm, they could exploit scarcer nutrients than if the two species were simply mixed together in an unstructured way.
The relationship works because P. putida relies on Acinetobacter to convert benzyl alcohol, the ‘food’ supplied by the researchers, into benzoate. Thus, if the two species are growing in a biofilm, concentrations of benzoate will rise within the film as Acinetobacter pumps it out, allowing the two species to feed on lower overall concentrations of nutrients.
CONTACT
Paul Rainey (University of Auckland, New Zealand)
Tel: + 64 9 373 7599; E-mail: [email protected]
[3] Thermodynamics: Maxwell's demon reincarnated? (pp 523-527)
Researchers have made a molecular ‘machine’ that mimics some of the skills of Maxwell's ‘demon’, a hypothetical creature capable of moving systems away from equilibrium without using energy.
The molecular incarnation of the demon, made by David A. Leigh and colleagues, is a rotaxane - a molecular ring threaded onto a central axle containing binding sites where the ring can attach. Previous rotaxane machines were activated by disturbing their original ring-binding pattern, and the ensuing shuttling of the ring between possible binding sites moves the system back towards equilibrium.
In his classic thought experiment of 1867, physicist James Clerk Maxwell conjured up a little demon guarding a trapdoor between two separate gas-filled compartments. The creature only lets fast-moving molecules pass from left to right, and slow-moving molecules from right to left. Over time, one compartment fills with fast-moving molecules and becomes hot, while the other contains slower-moving molecules and is cooler. Such spontaneous changes in temperature, or movement away from equilibrium, violate the second law of thermodynamics.
In the new rotaxane machine, described in this week's Nature, information about the location of the molecular ring is used to move the system away from equilibrium. But gathering and then implementing this information costs energy - so in the real world, the second law of thermodynamics lives to see another day.
CONTACT
David A. Leigh (University of Edinburgh, UK)
Tel: +44 131 650 4721; E-mail: [email protected]
ALSO IN THIS ISSUE…
[4] The signature of hot hydrogen in the atmosphere of the extrasolar planet HD 209458b (pp 511-514)
[5] Resolving photon number states in a superconducting circuit (pp 515-518; N&V)
[6] Label-free immunodetection with CMOS-compatible semiconducting nanowires (pp 519-522)
[7] bicoid RNA localization requires specific binding of an endosomal sorting complex (pp 554-558; N&V)
ADVANCE ONLINE PUBLICATION
***These papers will be published electronically on Nature's website on 31 January at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included them on this release to avoid multiple mailings they will not appear in print on 1 February, but at a later date.***
[8] Gadd45a promotes epigenetic gene activation by repair-mediated DNA demethylation
DOI: 10.1038/nature05515
[9] In vivo imaging of germinal centres reveals a dynamic open structure
DOI: 10.1038/nature05573
GEOGRAPHICAL LISTING OF AUTHORS…
The following list of places refers to the whereabouts of authors on the papers numbered in this release. For example, London: 4 - this means that on paper number four, there will be at least one author affiliated to an institute or company in London. The listing may be for an author's main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details.
CANADA
Sherbrooke: 5
CHINA
Beijing: 8
FRANCE
Paris: 4
GERMANY
Heidelberg: 8
Tubingen: 7
ISRAEL
Rehovot: 9
NEW ZEALAND
Auckland: 2
SWITZERLAND
Geneva: 9
Zurich: 5
UNITED KINGDOM
Cambridge: 7
Edinburgh: 3
Oxford: 1
UNITED STATES OF AMERICA
Arizona
Tucson: 4
California
Pasadena: 1
Colorado
Boulder: 1
Denver: 1
Massachusetts
Lexington: 1
New Haven
Connecticut: 5, 6
New York
New York: 9
Virginia
Hampton: 6
PRESS CONTACTS…
For North America and Canada
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Tel: +1 202 737 2355; E-mail: [email protected]
For Japan, Korea, China, Singapore and Taiwan
Mika Nakano, Nature Tokyo
Tel: +81 3 3267 8751; E-mail: [email protected]
For the UK/Europe/other countries not listed above
Helen Jamison, Nature London
Tel: +44 20 7843 4658; E-mail [email protected]
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