ScienceWeek

SCIENCEWEEK

September 8, 2006

Vol. 10 - Number 36

-------------------------------

Back issues of ScienceWeek can be searched for subjects, names, terms, etc. at: http://scienceweek.com/swfr.htm

--------------------------------

What is the path? There is no path.

-- Niels Bohr (1885-1962)

--------------------------------

Contents (full reports below):

1. Behavior: On Social Psychological Interventions. Some readers may be surprised, or even incredulous, that a 15-min intervention can reduce the racial achievement gap by 40%. Yet this is precisely what new work reports. African American seventh graders randomly assigned to write about their most important values achieved significantly better end-of-semester grades than students in a control condition...

2. Chemistry: On Controlling Biological Functions. Can biological functions, such as vision or photosynthesis, that are driven by incoherent phenomena, have anything to do with quantum mechanics, where the wave properties of matter play a key role? The answer is yes, and new work shows that biological processes can be manipulated by means of coherent control...

3. Cosmology: On a Theory of Everything. Hamlet's existential agony has always been, in a variant form, part of the mindset of those researching quantum gravity. In this field, a large faction has deemed itself to be in the outrageously fortunate position of being close to a unique theory of how the Universe is as it is. This theory would not only put descriptions of all forms of matter and their interactions...

4. Astrophysics: Cosmic Gamma Rays and Stellar Explosions. New work presents the first sightings of a remarkable cosmic event: the evolution of a hugely energetic gamma-ray burst into a fully fledged stellar explosion -- a supernova. It's the first time these two phenomena have been observed with the same telescope, NASA's satellite-based Swift telescope, and the implication of a common origin for both is intriguing...

--------------------------------

Also Noted:

The Best American Science Writing 2006. Atul Gawande, Ed. Ecco (HarperCollins), New York, 2006. Paperback: 379 pp. $14.95, C$19.50. ISBN 006072644X. More information at: http://www.amazon.com/exec/obidos/ASIN/006072644X/scienceweek

Exposing Men: The Science and Politics of Male Reproduction. Cynthia R. Daniels. Oxford University Press, New York, 2006. Hardback: 272 pp. $29.95. ISBN 019514841X. More information at: http://www.amazon.com/exec/obidos/ASIN/019514841X/scienceweek

The Ideas of Particle Physics: An Introduction for Scientists. 3rd ed. G. D. Coughlan, J. E. Dodd, and B. M. Gripaios. Cambridge University Press, Cambridge, 2006. Paperback: 266 pp., illus. $50. ISBN 0521677750. More information at: http://www.amazon.com/exec/obidos/ASIN/0521677750/scienceweek

Rescuing Science from Politics: Regulation and the Distortion of Scientific Research. Wendy Wagner and Rena Steinzor, Eds. Cambridge University Press, New York, 2006. Paperback: 328 pp. $29.99. ISBN 0521540097. More information at: http://www.amazon.com/exec/obidos/ASIN/0521540097/scienceweek

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

1. BEHAVIOR: ON SOCIAL PSYCHOLOGICAL INTERVENTIONS

The following points are made by Timothy D. Wilson (Science 2006 313:1251):

1) Some readers may be surprised, or even incredulous, that a 15-min intervention can reduce the racial achievement gap by 40%. Yet this is precisely what new work reports. African American seventh graders randomly assigned to write about their most important values achieved significantly better end-of-semester grades than students in a control condition. How can this be?

2) As the authors note, these results are not unprecedented. Previous studies have found results of similar magnitude in samples of United States college students (2-4). These studies share important features: Each drew on social psychological theories to change people's self- and social perceptions (i.e., people's explanations for their poor performance, their views of the malleability of their own intelligence, or their sense of social connectedness). Each did so with brief, inexpensive interventions. In each study, people in the treatment conditions achieved better grades than people in the control conditions. These increases were modest, averaging .29 on a grade-point average (GPA) scale (where A = 4, B = 3, and so on). Nonetheless, these gains are impressive, given that grades were assessed from several weeks to several months after the interventions.

3) The Cohen et al (1) study adds substantially to this earlier work. They used an intervention tailored to help African Americans, a group that has underperformed in American educational settings (5). Students in the treatment condition spent 15 min writing about why certain values, such as relationships with other people, were important to them. Students in the control condition wrote about why specific values were important to other people. African American students in the treatment condition achieved better end-of-semester grades than did African American students in the control condition. These results are especially encouraging given how intractable a problem the racial achievement gap has appeared to be.

4) The Cohen et al. study and the others like it illustrate key social psychological points. It can be as important to change people's "construals" -- their interpretations of the social world and their place in it -- as it is to change the objective environment. In none of the studies, for example, was there an effort to change the quality of the instruction students received, the clarity of the texts they read, or any other objective feature of the educational environment. Instead, the researchers attempted to change students' construals of themselves or how other people viewed them, with promising results. The objective environment is obviously important as well; as Cohen et al (1) note, the success of their intervention depended on students being in a supportive environment. How people perceive that environment, however, can be key to bringing about lasting change.

References (abridged):

1. G. L. Cohen, J. Garcia, N. Apfel, A. Master, Science 313, 1307 (2006)

2. T. D. Wilson, P. W. Linville. J. Pers. Soc. Psychol. 49, 287 (1985)

3. J. Aronson, C. B. Fried, C. Good. J. Exper. Soc. Psychol. 38, 113 (2002)

4. G. M. Walton, G. L. Cohen J. Pers. Soc. Psychol., in press.

5. C. M. Steele, Amer. Psych. 52, 613 (1997)

Science http://www.sciencemag.org

ScienceWeek http://scienceweek.com

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

2. CHEMISTRY: ON CONTROLLING BIOLOGICAL FUNCTIONS

The following points are made by Majed Chergui (Science 2006 313:1246):

1) Can biological functions, such as vision or photosynthesis, that are driven by incoherent phenomena, have anything to do with quantum mechanics, where the wave properties of matter play a key role? The answer is yes, and new work (1) shows that biological processes can be manipulated by means of coherent control (2).

2) Coherent control refers to experiments that make explicit use of the wavelike nature of matter to direct the behavior of atomic and molecular systems, often to alter the likelihood of a particular chemical reaction. An analogy with Young's double-slit experiment is useful: Light passes through both slits at the same time and interferes with itself at a distant screen to produce dark and bright fringes. To achieve complex interference patterns, however, one needs to control the number, widths, and positions of the slits.

3) For a quantum mechanical object, one can arrange interference of several "paths" to create constructive interference that selects one state and destructive interference that blocks the others. This is achieved with a pulse of light whose spectral components are controlled in phase and amplitude. This is accomplished by dispersing the different frequency components of the pulse spatially with a diffraction grating, manipulating their phase and amplitude with a spatial mask, and then recombining them to produce a short pulse of well-defined shape. Because adjustment of the relative phases of the components modifies the pulse temporal structure, coherent control can be seen in the time domain as control over a quantum system through manipulation of the temporal structure of the laser field.

4) The ideal pulse shape is not known a priori, however. In their experiment, Prokhorenko et al (1) used a well-established genetic algorithm inside a feedback loop (2). Successful control schemes have previously been demonstrated for specific molecular product channels and states in the gas phase. But most chemical and biological reactions and important physical processes occur in the condensed phase, where interactions of the system with the fluctuating environment may lead to the destruction of the coherence imparted to the system. Although coherent control has been demonstrated in a variety of condensed-phase systems, including proteins (3,4), the work of Prokhorenko et al (1) on bacteriorhodopsin contains important novel aspects. First, in all previous coherent control experiments, the shaped laser pulse suppressed unwanted pathways and therefore merely acted as a filter. Examples where the desired target is reached with higher efficiency than with symmetrically shaped pulses are lacking, but Prokhorenko et al (1) were able to increase or decrease the absolute quantum yield of isomerization of the 13-cis retinal isomer in bacteriorhodopsin by as much as 20%, as compared to excitation with symmetric pulses. Second, they used intensities of the exciting light comparable to that of sunshine, relevant to photobiological processes. This is important for controlling the actual reaction coordinate rather than the excited-state population (4), and in interpreting the correlation of the shaped pulses to the molecular processes. And third, at the end of the optimization (or antioptimization) control loop, their pulse shapes capture the underlying molecular dynamics driving the process, and show a selective coherent excitation of precisely those torsional modes responsible for isomerization.

References (abridged):

1. V. I. Prokhorenko et al., Science 313, 1257 (2006)

2. H. Rabitz, R. de Vivie-Riedle, M. Motzkus, K. Kompa, Science 288, [824] (2000)

3. C. J. Bardeen, V. V. Yakovlev, J. A. Squier, K. R. Wilson, J. Am. Chem. Soc. 120, 13023 (1998)

4. J. L. Herek, W. Wohlleben, R. J. Cogdell, D. Zeidler, M. Motzkus, Nature 417, 533 (2002)

5. G. Hummer, F. Schotte, P. A. Anfinrud, Proc. Natl. Acad. Sci. U.S.A. 101, 15330 (2004)

Science http://www.sciencemag.org

ScienceWeek http://scienceweek.com

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

3. COSMOLOGY: ON A THEORY OF EVERYTHING

The following points are made by Martin Bojowald (Nature 2006 442:988):

1) Hamlet's existential agony has always been, in a variant form, part of the mindset of those researching quantum gravity. In this field, a large faction has deemed itself to be in the outrageously fortunate position of being close to a unique theory of how the Universe is as it is. This theory would not only put descriptions of all forms of matter and their interactions on the same footing, but also reconcile the two seemingly inharmonious pillars of modern physics: general relativity, which describes gravity, and quantum theory. The belief in such an all-encompassing theory has been the driving force for the various models known as string theories, grouped under the umbrella of 'M-theory', that have been developed in the past decades.

2) But there is an alternative concept. This holds that solutions, rather than models, are unique. Solutions are generally more important for physics than theories: observations are compared with properties that emerge from a theory, not with the construct itself. But finding realistic solutions to theories -- solutions that reproduce the features of the Universe that we observe now -- has proved much harder and messier than constructing the theories themselves. That applies even with a modest interpretation of "realistic", such as merely requiring the solution to undergo the kind of accelerated late expansion that our Universe appears to be going through now. Once such solutions were finally uncovered (1), myriads of them turned up in various corners of the string landscape (2). Thus, as there is currently no selection criterion by which to choose among this vast range of solutions, it does not seem particularly useful to claim that any one string theory is unique.

3) Stephen Hawking and Thomas Hertog (3) now propose arms to be taken against this sea of troubles. The arms they propose are admittedly not new, having been developed (4) in the 1980s by Hawking, James Hartle and others. Then, too, the motivation was uniqueness of solutions: specifically, if a quantum-cosmological model explains properties of our Universe (of which, by definition, we see only one), then it should also explain why this, and only this, solution emerges. Such a model can be compared with observations, making the whole framework testable and thus predictive.

4) Hartle and Hawking (4) called their condition for establishing uniqueness the "no-boundary proposal", because it removed the boundaries of space-time. According to this view, the Universe is a closed surface -- rather like a surface of an inflating balloon -- and has no beginning in time. Such a closure of space-time is not meaningful in classical general relativity, and thus requires the introduction of aspects of quantum theory. This in turn serves to establish uniqueness: although there are several possible closures, quantum theory can, unlike classical theory, deal with all of them at once as a probabilistic superposition. Alternatives to the Hartle-Hawking proposals include Alexander Vilenkin's proposal that the Universe initially tunnels out of a quantum state where space and time are not defined (5), and more recent models based on new formulations of quantum gravity.

5) In their recent paper (3), Hawking and Hertog refresh the no-boundary proposal, adding new insight and giving it a new name: top-down cosmology. Looking at a space-time diagram where time runs in the upward direction, the conventional approach to cosmology is "bottom-up": one starts with initial conditions in the past and calculates forward to aim at properties seen now. This process usually requires very specific, fine-tuned initial values. The top-down approach avoids this problem by taking the properties of the Universe as it appears now and calculating its history backwards. This process is applied to a quantum superposition of different Universe states, with "final", rather than initial, conditions being set to select one history in the super-position relevant for our observations. In this way, the non-intuitive quantum superposition is reduced to a classical Universe as we observe it.

References (abridged):

1. Kachru, S. , Kallosh, R. , Linde, A. & Trivedi, S. P. Phys. Rev. D 68, 046005 (2003)

2. Susskind, L. preprint available at www.arxiv.org/hep-th/0302219 (2003)

3. Hawking, S. W. & Hertog, T. Phys. Rev. D 73, 123527 (2006)

4. Hartle, J. B. & Hawking, S. W. Phys. Rev. D 28, 2960-2975 (1983)

5. Vilenkin, A. Phys. Rev. D 30, 509-511 (1984)

Nature http://www.nature.com/nature

ScienceWeek http://scienceweek.com

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

4. ASTROPHYSICS: COSMIC GAMMA RAYS AND STELLAR EXPLOSIONS

The following points are made by Timothy R. Young (Nature 2006 442:992):

1) New work (1-4) presents the first sightings of a remarkable cosmic event: the evolution of a hugely energetic gamma-ray burst into a fully fledged stellar explosion -- a supernova. It's the first time these two phenomena have been observed with the same telescope, NASA's satellite-based Swift telescope, and the implication of a common origin for both is intriguing.

2) Supernovae most commonly occur when a mature star ceases to generate enough energy from thermonuclear fusion to counter its own gravity. A catastrophic, explosive collapse ensues, during which material from over-lying stellar layers falls inwards. This creates a shockwave that rebounds outwards, fuelled by energy gained probably from internal magnetic fields and rotation. At "shock breakout", when the shockwave emerges from the surface of the collapsing star, its energy is unleashed. It is sent out into space as radiation of all frequencies over a period of days to months -- the classic signal of a supernova.

3) The idea that the comparatively short, sharp blast of a gamma-ray burst (GRB) is perhaps some form of supernova early-warning signal had been around for some time, and over the past seven years, three candidate GRB-supernova pairings have been identified (5). But no one had ever obtained the clinching evidence of a connection: witnessing the evolution of a gamma-ray burst to the all-frequency display of a supernova. In fact, no supernova had ever been observed at the moment of shock breakout. That changes now, with observations at several wavelengths (1-4) of an object -- variously known as supernova SN 2006aj and gamma-ray burst GRB060218 -- that flared up on 18 February 2006. All four papers make clear that the exploding object sent out both a slightly aspherical shockwave, typical of a supernova, and a jet-like stream of material characteristic of a GRB.

4) Using, respectively, X-ray data and optical light curves, Campana et al (1) and Pian et al (2) show that the star concerned is a "Wolf-Rayet" star that exploded while in a compact state, in which it contained no hydrogen or helium. That identification is supported by computer modelling presented by Mazzali et al (3). Estimates, based on the X-ray data, of how a shell of gas at 2 million degrees expands, constrained the radius of the progenitor to 1.2 times 10^(7) km, much smaller than typical exploding stars (1). The optical light curve and spectra are characteristic of the explosion of a bare carbon-oxygen stellar core (2).

References (abridged):

1. Campana, S. et al. Nature 442, 1008-1010 (2006)

2. Pian, E. et al. Nature 442, 1011-1013 (2006)

3. Mazzali, P. A. et al. Nature 442, 1018-1020 (2006)

4. Soderberg, A. M. et al. Nature 442, 1014-1017 (2006)

5. Galama, T. J. et al. Nature 395, 670-672 (1998)

Nature http://www.nature.com/nature

ScienceWeek http://scienceweek.com

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=