2009年03月05日

complement : The risks

from "TAKE 5 : Save handling of nanotechnoiogy".

As research leaders in our respective fields, we recognize that systematic risk research is need if emerging nano-industries are to thrive.

We cannot set the international reserch agenda on our own, but can inspire the scientific community - including government, industry, academia and other stakeholders - to move in the right direction.

So we prppose five grand callenges to stimulate research that is imaginative, innvative and avove all relevant to the safery of nanotechnology.

Fears over the possible dangers of somme nanotechnologyes may be exaggerated, but they are not necessarily unfounded.

Recent studies examiming the toxicity of engineered nanomaterials in cell cultures and animals have shown that size, surface area, surface chemistry solubility and possibly shape all play a role in determining the potential for engineerd nano-meterials to couse harm.(Oberdorster,G., Oberdorster,E. & Oberdorster, J. Environ Health Perspect. 13,823-840/2005)

This is not suprising : we have known for many years that inhaled dusts cause disease, and that their harmfulness depends on both what they are made of and their physical nature.

For instance, small particles of inhaled quartz lead to lung damage and the potential development of progressive lung disease, yet the same particles with a thin coating of clay are less harmful.(Donaldson,K. & Borm,P.J.A.Ann. Occup.Hyg. 42,287-294/1998)

Asbestos presents a far more dramatic example : thin, long fibress of the material can lead to lung disease if inhaled, but grind the fibres down to shorter particles with the same chemical make-up and the harmful ness is signficantly reduced.(Davis, J. G. et al. Br. J. Exp. Pathol. 67,415-430/1986)

It is generally accepted that, in principle, some nanomaterials may have the potential to cause harm to people and the enbironment.

But the way science is done is often ill-equipped to address novel ridks associated with emerging technologyes.

Reserch into understanding and preventing risk often has a low priority in the compertitive worlds of intellectual property, research funding and technology development.

And yet there is much at stake in how potential nano-specific riskes are understood and managed.

without strategic and targeted risk research, people producing and using nano-materials could develop unanticipated illness arising from their exposure ; public confidence in nanotechnoligies could be reduced through real or perceived dangers ; and fears of litigation may make nanotechnologies less attractive to investors and the insurance industry.


(...to be continue...)


### DataBace ###
nature Vol.444 243-400 Issue no.7117 16 November 2007
Commentary p.267 / Save handling of nanotechnoiogy / Andrew D. Maynard

posted by 0≠素子 at 02:05| Comment(0) | nanotechnology | このブログの読者になる | 更新情報をチェックする

2009年03月04日

TAKE 5 : Save handling of nanotechnoiogy

The pursuit og responsible nanotechnologies can be tackled through a series of grand challengs, argue Andrew D. Maynard and his co-authors.

When the physist and Nobel laureate Richard Feynman challenged the science community to think small in his 1959 lecture 'There's Plenty of Room at The Bottom', he planted the seeds of a new era in science and technology.

Nanotechnology, which is about controlling matter at near-atomic scals to produce unique or enhanced materials, products and devices, is now maturing rapidly with more than 300 claimed nanotechnology products already on the market.(The Nanotechnology Consumer Products Inventory / Washington DC,2006/Published online at -www.nanotechproject.org/consimerproducts)

Yet concerns have been raised that the very properties of nanostructured materials that make them so attractive could potentially lead to unforeseen health or environmental hazards.(Nsnoscience and Nanotechnologies : Opportunities and Uncertainties / The RoyalSociety and The Royal Academy of Engineering, London,2004)

The spectre of possible harm - whether real or imagined - is threatening to slow the development of nanotechnology unless sound, independent and authoritative information is developed on what the risk are, and how to aboid them.(Takling Action on Nanotech Environmental, Health and safety Risks / Lux Research, New York,2006)

In what may be unprecedented pre-emptive action in the face of a new technology, governments,industries and research organizations around the world are beginning to address how the benefits of emerging nanotechnologies can be realized while while minimizing potential risks.(Report of the OECD Workshop on the safety of Manufactured Nanomaterials : Building Co-operation and Communication / Organization for Economic Co-operation and Develoment,Paris,2006)

Yet despite a clear commitment to support risk-focused ersearch,opportunities to establish collaborative, integrated and targeted reserch programies are being missed .(Maynard,A.D Nanotechnology : A Research Strategy for Addressing Risk / Woodrw Wilson International Center for Scholars, washington DC,2006)

In september, Sherwood Boehlert, chair of the US House Sience Commitee, commented in a hearing that "we're on the right path to dealing with the problem, but we're sauntering down it when it when a sense of urgency is required".

And in October, Britain's Royal Society reised concerns that the UK government had not made enough progerss on reducing the uncertain ties surrounding the health and environmental impacts of nanomaterials.(Two-Year Review of Progress on Government Actions : Joint Academies'Response to the Council for Science and Technology's Call for Evidence / The Royal Society and the Royal Academy of Engineering, London,2006)


### DataBace ###
nature Vol.444 243-400 Issue no.7117 16 November 2007
Commentary p.267 / Save handling of nanotechnoiogy / Andrew D. Maynard

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posted by 0≠素子 at 03:37| Comment(0) | nanotechnology | このブログの読者になる | 更新情報をチェックする

2009年03月03日

Planetary gears

The Antikythera Mechaninm is an intricate bronze construction discovered damaged and fragmented in the wreck of a cargo ship pff the Greep island of Antikythera in 1900.

Made towards the end of the second century BC, it contains 30 bronza gear wheels and many astronomical isscriptions.

The mechanism is technically more complex than any known device for at least a millennium afterwords.

It acted as a lunar-solar calender, but its specific functions have remained controversial.

Now a joint British-Greek team has reconstructed the device based on surface imaging and X-ray tomography of the surviving fragments.

The reconstruction shows how the gears worked, and doubles the number of deciphered inscriptions.

The Mechanism seems to have been a sophisticated predictor for the Sun/Moon/Earth system, and can justfiably be caimed as the world's oldest known analogue computer.


### DataBace ###
nature Vol.444 519-652 Issue no.7119 30 November 2007
News Feature p.534 / Insearch of lost time / Jo Marchant reports.
News & Views p.551 / ARCHAEOGY : High thech from Ancient Greece / Francois Charette
Letter p.587 / Decoding the anciment Greek astronomical calculator known as the Antikythera Mechanism / T Freeth et al. (Cardiff University, Images First Ltd)

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Structural basis for messenger RNA movement on the ribosome

Translation initiation is a major determinant of the overall expression level of a gene.(Gold,L. Posttranscriptional regulatory mechanisms in Escherichia coli. Annu. Rev. Biochem 57,199-233/1988)(Draper,D.E. in Eschericha coli and Salmonella : Cellular and Moecular Biology 2nd edn /eds Neidhardt,F.C. et al./902-908/ASM Press, Washington,DC,1996/)(Kozak,M. Regulation of translation via mRNA structure in prokaryotes and eukaryotes. Gene 361,13-37/2005)

The translation of functionally active protein requires the messenger RNA to be positioned on the ribosome such that the syart/initiation codon will be read first and in the correct frame.

Little is Known about the molecular basis for the interaction of mRNA with the ribosome at different states of translation.

Recent crystal structures of the ribosomal subunits (Wimberly,B.T. et al. structure of the 30S ribosomal subunit. Nature 407,327-339/2000)(Ogle,J.M. et al. Recognition of cognate transfar RNA by the 30S ribosomal subunit. Scrence 292,897-902/2001)(Ban,N. et al. The complete atomic structure of the large ribosomal subunit at 2.4 Å resolution. Science 289,905-920/2000)(Schluenzen,F. et al. Structure of functionally activated samall ribosomal subunit at 3.3 Å resolution. Cell 102,615-623/2000)(Haems,J. et al. High resolution structure of the large ribosomal subunit from a mesophilic eubacterium. Cell 107,679-688/2001), the empty 70S ribosome (Schuwirth,B.S. et al. structures of the bacterial ribosome at 3.5 Å resolution. Science 310,827-834/2005) and the 70S ribosome containing functional ligands (Yusupov,M.M. et al. Crystal structure of the ribosome at 5.5 Å resolution. Science 292,883-896/2001)(Yusupova,G.Z. et al. The path of messenger RNA through the ribosome. Cell 106, 233-241/2001)(Jenner,L. et al. Translational operator of mRNA on the ribosome : how reperssor proteins exclude ribosome binding. Science 308,120-123/2005)(Petry,S. et al. Crystal structures of the ribosome in complex with release factors RF1 and RF2 bound to a cognate stop codon. Cell 123, 1255-1266/2005) have provided information about the general organization of the robosome and its functional centres.

Hare we compare the X-ray structures of eight ribosome complexes modelling the translation initiation, post-initiation and elongation states.

In the initiation and post-initiation complexes, the presence of the Shine-Dalgarno (SD) duplex causes strong anchoring of the 5'- end of mRNA onto the platform of the 30S subunit, with numerous interactions between mRNA and the ribosome.

Conversely, the 5' end of the 'elongator' mRNA lacking SD interctions is flexible, suggesting a different exit path for mRNA during elongation.

After the initiation of translation, but while an SD interaction is still present, mRNA moves in the 3'→5' direction with simultaneous clockwise rotation and lengthening of the SD duplex, bringing it into contact with robosomal protein S2.


### DataBace ###
nature Vol.444 243-400 Issue no.7117 16 November 2007
Letters p.391 / Structural basis for messenger RNA movement on the ribosome / G Yusupova et al. (IGBMC)


posted by 0≠素子 at 12:15| Comment(0) | sturacuture - biology | このブログの読者になる | 更新情報をチェックする

STURUCTUAL BIOROGY : Dangerros liaisons on newrons

Crystal structures show that botulinum toxins bind simultaneously to two sites on neurons. This dual interaction allows them to use a trojan-horse strategy to enter nerve terminals, with deadly effect.

Botulinum neurotoxins (BoNTs) are some of the most deadly substances known to mankind. By blocking nerve function, they cause botulism, a severe condition that may ultimately lead to muscular and respiratory paralysis.

These sophisticated bacterial proteins owe their toxicity to their extraordinary specificity for neurons and to their enzymatic activity.

In this issue, papers by Jin et al. and Chai et al. describe the mechanisms by which BoNT/B - a toxin that causes human botulism - recognizes the surface of neuron junctions(syn apses - * This article and the papers concerned -were published online on 13 December 2006).(Jin,R., Rummel,A. Binz,A.T. Nature 444,1092-1095/2006)(Chai,Q. et al. Nature 444,1096-1100/2006)

This work provides insight in to how other BoNTs may exert their lethal action, and describes a mode of binding that night be used by other biological compounds.

Once inside a neuron, a single molecule of BoNT is, in principle, capable of deactivating the whole synapse. NoNTs consist of two protein segments, known, as the heavy and light chains.

IT is the light chain that deactivates neuromuscular junctions - the synapses that connect muscles to their contorolling neurons - by specifically inhibiting members of the SNARE protein family.(Schiavo,G., Matteoli, M. & Montecucco,C. Physiol. Rev. 717-766/2000).

SNARE proteins are distributed over the membranes of all animal and plant cells and are also found on the membranes of synaptic vesicles, the bubble-shaped organelles that store and release neurotrans-mitter chemicals at neuron terminals.

SNARE proteins are essential for membrane fusion, during which vesicles merge with the cell membrane and release their load. Once the synapticvesicles have done this, they are recycled by the neuron for further use.


### DataBace ###
nature Vol.444 243-400 Issue no.7117 16 November 2007
News and Vews p.1019/ STURUCTUAL BIOROGY : Dangerros liaisons on newrons / Giampietro Schiavo
Letters p.1092 / Botulinum newrotoxin B recognizes its protein receptor with high affinity and specificity / R Jin et al. (Stanfoed University)
Letters p,1096 / Structural basis of cell surface receptor recognition by botulinum newrotoxin B / Q Chai et al. (Scripps Research Institute)

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posted by 0≠素子 at 06:25| Comment(0) | sturacuture - biology | このブログの読者になる | 更新情報をチェックする

CONDENSED-MATTER PHYSICS : Let's twist agein

The spins of a layer of manganese atoms on a tungusten surface from a spiral pattern with a unique truning sense.

such 'chirial maganitic order' might exist in other, similar contexts, and have many useful applications.


Objects that differ from their mirror image - fuman hands, for instance - have a turn ing sense. This phenomenon of handedness, or chirality, is found in many natural contexts, from the elementary particles participating in electroweak interactions, via organic molecules and furricanes, all the way to galaxies.

Solids with a magnetic order of unique chirality could have many useful practical applications, becouse their peculiar symmetry allows the mixing of electronic, optical, magnetic and structural properties.

On page 190 of this isse, Bode et al. present compelling evidence for chiral magnetic order in a atrikingly simple solid-state system : a single layer of manganese atoms on a tungsten substrate.(Bode,M. et al. Nature 447,190-193/2007)

The authors achieved this by combining highly sophisticated, spin-sensitive scanning tunnelling micros-copy (STM) with an equally sophisticated first-principles calculation of the electronic structure of the manganese surface.

The amount of electrical current tunnelling from the manganese sample to the authors 'STM tip, which was coated with chromium or iron, depended on the electrons' derection of spin.

What Bode et al. observed was a long-period, spiral-shaped magnetic modulation of the STM intensity distoribution, superimposed on a basic antiferromagnetic structure (one in which adjacent spins point in opposite directions) .

When a magnetic field was applied, the pattern shifted in a given direction, identifying its unique chirality.


### DataBace ###
nature Vol.447 115-230 Issue no.7141 10 May 2007
News & Views p.157 /CONDENSED-MATTER PHYSICS : Let's twist agein / Cristien Pfleiderer and Urich K Robler
Letter p.190 / Chiral magnetic order at surfaces driven by inversion asymmetry / M Bode et al. (University of Hambrg)

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posted by 0≠素子 at 00:49| Comment(0) | condensed-matter physics | このブログの読者になる | 更新情報をチェックする

2009年03月01日

SEISMLOGY : Greatness thrust upon them

The latest research seems to imply that all earthquakes are born eaual. But combining that insight with earlier, seemingly contradictory, work could help us to tell which tremors grow to become more equal than others.

In an analysis on page 358 of this issue, Steven Wesnousky provides strong evidence that the ultimate size of a seismic ruputure is largely controlled by the structure of the underlyng fault, and therebefore that big earthquakes do not differ from small earthquakes in their beginnings.(Wesnousky,S.G et Nature444,358-360/2006)

These data might seen to conflict with earlier observations implying that the size of an earthquake is determined by the dynamics of ruputure onset.

In fact, both conclusions could be true, and combining these two data sets in future analyses of seismic hazards might result in a better prediction of the eventual size of an earthquake before the shaking stops.

Many Earth scientists have long suspected that the limit of an earthquake rupture, and therefore the magnitude of an event, is largely controlled by the structure of the fault zone and variations in stress along the fault itself.(Segall,P. & Pollard,D.D.J. Geophys.Res.85,4337-4350/1980)(Sibson,R.H. Nature316,248-251/1985)(Harris,R.A & Day,S.M,Geophys. Lett.26,2089-2092/1999)

In this view, all earthquakes begin in the same way, and continue to propagate until they reach a barrier, in the from of a structural complexity or a part of the fault on which the stresses are sufficiently low to stop rupture. Bur the alternative standpoint - that large earthquakes are in some way born differenty from their smaller brethren - is attractive becouse it holds thepromise of determining the evevntual size of anearthquake during the first fewseconds of the rupture.(Ellsworth, W.L. & Beroza, G. C. Science 268,851-855/1995)(Olsen,E.L. & Allen, R.M. Nature438,212-215/2005)

That could provide the basis for an wffective eary-waring system.


### DataBace ###
nature Vol.444 243-400 Issue no.7117 16 November 2007
News & Views p.276 / SEISMLOGY : Greatness thrust upon them / James F. Dolan
posted by 0≠素子 at 02:47| Comment(0) | earth | このブログの読者になる | 更新情報をチェックする

Rotation at faults

An early finding of the San Andress Fault Ovservatory at Depth (SAFOD) project, currently drilling an inclined borehole across the San Andreas Fault Zone to a 4-km depth, is that strees is rotated in the vicinity of the fault zoone.

Why this should occur here and at other similar 'weak' faults is not yet clear. A new model to help explain the phenomenon has been developed, based on field structure date of a large fault zone, lab measurements of rock elasticity, and numerical modelling.

The model suggests that is re-oriented around faults by the change in rock elasticity resulting from microscale damage produced by the fault.

### DataBace ###
nature Vol.454 789-970 Issue no.7121 14 December 2007
Letter p.922 / Slip on 'weak' faults by the rotation of regional stress in the fracture damage zone / D R Faulkner et al.(University of Liverpool)


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posted by 0≠素子 at 01:08| Comment(0) | earth | このブログの読者になる | 更新情報をチェックする

2009年02月28日

Moving memories

The transfer of information between the entities that do the processing and memory is crucial - and problematic - for quantum computation. In classical systems, information transfer can include a copying step, where errors can be spotted and crrected, but in quantum systems copying is fundamentally precluded.

Morton et al. demonstrate a technology that could solve the problem : the coherent storage and readout of information between electron-spin processing elements and memory elemrnts based on a nuclear spin. The system utilizes phosphourus-31 spin donors in a silicon -28 crystal.

The nuclear spin acts as a memory element that can store the full state of the electron spin for over a second, then transfer it back to the electron spin at about 90% sfficiency.


### DataBace ###
nature Vol.455 1007-1148 Issue no.7216 23 October 2008
Letter p.1085 / Solid-state quantum memory using the ^31~P nuclear spin / J J L Morton et al. (Oxford Univirsity)
* refarence

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posted by 0≠素子 at 13:37| Comment(0) | quantum information | このブログの読者になる | 更新情報をチェックする

2009年02月27日

Galaxies made simple

At farst glance a galaxy looks pretty complex : each contains bilions of stars subject to many influences including gravity, rotation and radiation.

The hierarchical theory of galaxy formation - currently fashinoable - holds that they are assembled from smaller pieces, through many mergers of cold dark matter, and that the properties of individual galaxies are determinied by six independent parameters.

Now a survey of 200 individual galaxies suggests that things are simpler than that, and that galactic structure is controlled by a single parameter. Though frustratingly, it is not yet clear which parameter that is.

This lebel of organization is at odds with hierarchical galaxy formation and the predictions of cold dark matter cosmology.


### DataBace ###
nature Vol.455 1007-1148 Issue no.7216 23 October 2008
News and Vews p.1049/ ASTROPHYSICS : How do galaxies from? / Sidney van den
Letter p.1082 / Galaxies appear simpler than expected M J Disney et al. (cardiff University)

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posted by 0≠素子 at 23:10| Comment(0) | cosmos | このブログの読者になる | 更新情報をチェックする
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