Editors' Choice

Science  14 Jul 2006:
Vol. 313, Issue 5784, pp. 148
  1. ECOLOGY/EVOLUTION

    Subsidy from the Sea

    1. Andrew M. Sugden

    Migratory species, by virtue of their movements, can be agents of nutrient transport between ecosystems. For example, stable isotope studies have shown that the carcasses of salmon can be a rich source of nutrients not only for the mountain streams in which they die but also for adjacent terrestrial habitats. Merz and Moyle have quantified the nutrient subsidy of Pacific salmon to Californian grape growers. They show that cultivated vines as well as native streamside vegetation bordering on salmon spawning grounds derive about 20% of their foliar nitrogen from marine sources via returning salmon. This is a classic example of what has become known as an ecosystem service—in this case, one of substantial economic and oenological value. — AMS

    Ecol. Appl. 16, 999 (2006).

  2. CHEMISTRY

    Tiny MOFs that Glow

    1. Jake Yeston

    The structural tunability of metal organic framework (MOF) solids, in which bridging organic ligands form a scaffold by coordinating to metal ions, has proven useful in bulk applications such as gas sorption. Pushing toward the opposite end of the size spectrum, Rieter et al. present a controlled approach to the synthesis of discrete nanometer-scale MOF assemblies. They combined trivalent gadolinium ions with a benzenedicarboxylate (BDC) salt in a microemulsion, created through surfactant addition to an isooctane/hexanol/water mixture. By modifying the water-to-surfactant ratio, the authors could tune the size of the resultant Gd(BDC)1.5(H2O)2 rods from ∼100 nm to ∼1 μm in length, and ∼40 to ∼100 nm in diameter. The high gadolinium density in the rods is advantageous for contrast enhancement in magnetic resonance imaging; the rods evidenced remarkably high relaxivities (>107/s/mmol) during test runs using aqueous xanthan gum suspensions. Doping with alternative metals increased the versatility of potential imaging applications: addition of 5 mole % of either europium or terbium during the synthesis respectively induced red or green luminescence on ultraviolet irradiation of the rods in solution. — JSY

    J. Am. Chem. Soc. 128, 10.1021/ja0627444 (2006).

  3. PSYCHOLOGY

    Close Encounters

    1. Gilbert J. Chin

    The effect of contact between groups on prejudice has been a topic of research at least as far back as the middle of the 20th century. Since then, there have been a very large number of studies and many reviews of this literature. Pettigrew and Tropp have conducted a meta-analysis of what has become known as intergroup contact theory. They (and their dedicated research assistants) have combed through published papers and unpublished dissertations, using a methodological (rather than topical) basis for inclusion; the final data set covers 515 studies, containing over 700 independent samples representing a quarter million individuals spread over 38 countries. The summary finding is that intergroup contact reduces prejudice.

    Their statistical analyses reveal that this cannot be ascribed to self-selection by the participants, or to a publication bias toward positive results, or to the rigor of the research (methodologically stronger studies yielded larger effect sizes). Roughly half of the studies focused on nonracial and nonethnic groups (as described by sexual orientation or physical or mental disability, for example), and the effect sizes seen within this subset were the same as that for the racial/ethnic targets that stimulated the historical development of intergroup contact theory. Furthermore, it appears that the effects on individual attitudes can generalize to other members of the outgroup and even to other outgroups.

    How is this mediated? They find that Allport's four features (common goals, intergroup cooperation, equal status, and official sanction) contribute significantly to the reduction of prejudice but are not essential, and that the last of the four conditions may be the most important one. Greater contact may reduce feelings of uncertainty or discomfort that might otherwise coalesce into anxiety or perceived threat, which might in turn harden into prejudice. Yet these ameliorative shifts may not survive in the absence of normative or authoritarian support, and studies of why contact fails to curb prejudice are needed. — GJC

    J. Pers. Soc. Psychol. 90, 751 (2006).

  4. PHYSICS

    Quark Plasma Reexamined

    1. David Voss

    A fraction of a second after the Big Bang, the universe is thought to have consisted of a hot primordial soup of fundamental particles: a quark-gluon plasma. Researchers have sought to recreate this early matter by smashing heavy ions together. Because the quark soup lasts only for a short time and quarks cannot exist in free form, the formation of the plasma is diagnosed by what other kinds of particles emerge from the collision. Analysis of this collision process is predicated on important assumptions about the fluid dynamic properties of the quark plasma and the strength of interactions among the particles. One view has been that the data support the existence of a strongly coupled quark-gluon plasma.

    Asakawa et al. propose an alternative picture to explain the fluid dynamics. Their analysis reaches back to theories from the 1960s that were developed to understand particle transport in turbulent magnetically confined plasmas. In this environment, excited oscillations of the plasma can scatter particles and strongly reduce the plasma viscosity, a phenomenon that came to be called anomalous transport. The authors find that a similar process, with quark-gluon forces replacing electromagnetic waves, could give rise to an anomalous viscosity in a weakly coupled plasma and thereby explain the fluid dynamic behavior revealed in recent experimental heavy-ion collision data. — DV

    Phys. Rev. Lett. 96, 252301 (2006).

  5. CHEMISTRY

    Warped Simulations

    1. Phil D. Szuromi

    Aromatic molecules such as benzene and naphthalene are planar, but several electron-correlated ab initio computational methods (such as CISD, configuration interactions with single and double excitations), when used with certain commonly available basis sets, predict nonplanar structures and yield imaginary values for at least one vibrational frequency. Inherently one-electron methods such as Hartree-Fock predict the correct planar structures and real vibrational frequencies when the same basis sets are used.

    Moran et al. analyzed the problem at the MP2 level (Møller-Plesset perturbation theory with two-electron correlations). After clearly ruling out numerical precision error, they found that basis sets lacking higher angular momentum functions (that is, too rich in s-, p-, and even d-orbital character) create artificially large correlation energies between σ and π electrons. This effect in turn leads to the distortions from planarity and imaginary vibrational frequencies. The authors also indicate the types of basis sets that minimize such errors. — PDS

    J Am. Chem. Soc. 128, 10.1021/ja0630285 (2006).

  6. STKE

    Inhibiting the Restocking of the Store

    1. Elizabeth M. Adler

    Golli proteins, which are generated by alternative splicing from the gene that encodes myelin basic proteins (which are found only in the nervous system), are expressed not only in the nervous system but also in immune system tissues. Feng et al., who previously showed that golli negatively regulates T cell activation, establish that this occurs via the inhibition of calcium influx. When stimulated with antibody directed against CD3 (anti-CD3) or with anti-CD3 plus anti-CD28, golli-deficient T cells proliferated more vigorously than did wild-type cells. Similarly, golli-deficient cells stimulated with anti-CD3 plus anti-CD20 produced more interleukin-2 (a T cell growth factor) than did wild-type cells. No differences between golli-deficient and wild-type T cells in extracellular receptor-activated kinase (ERK) or Jun N-terminal kinase (JNK) activation in response to anti-CD3 stimulation were apparent. On the other hand, the increase in intracellular calcium upon stimulation was enhanced. Calcium imaging in the presence or absence of extracellular calcium and thapsigargin suggested that golli inhibited calcium influx through store-operated calcium channels (these plasma membrane conduits open in response to a signal that calcium levels in internal compartments need replenishing). Moreover, patch-clamp analysis of golli-deficient cells revealed increased inward calcium current in response to store depletion. A portion of T cell golli protein was associated with the plasma membrane, and experiments in which cells were transfected with either wild-type golli protein or a myristoylation-deficient mutant indicated that membrane association was required for golli to inhibit calcium influx. Thus, the authors conclude that golli acts as a negative regulator of T cell activation by means of a mechanism completely distinct from that of other regulators of T cells. — EMA

    Immunity 24, 717 (2006).

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