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<jats:p> During the last glacial period, Earth's climate underwent frequent large and abrupt global changes. This behavior appears to reflect the ability of the ocean's thermohaline circulation to assume more than one mode of operation. The record in ancient sedimentary rocks suggests that similar abrupt changes plagued the Earth at other times. The trigger mechanism for these reorganizations may have been the antiphasing of polar insolation associated with orbital cycles. Were the ongoing increase in atmospheric CO <jats:sub>2</jats:sub> levels to trigger another such reorganization, it would be bad news for a world striving to feed 11 to 16 billion people. </jats:p>

<jats:p>Analysis of a large sample of well-dated fossil mammals from localities in the Turkana Basin of Kenya and Ethiopia revealed sampling biases that affect patterns of faunal turnover during the late Pliocene. When these biases were accounted for, results indicated that 58 to 77 percent of the mammal species were replaced between 3.0 and 1.8 million years ago (Ma). Overall diversity increased from 3.0 to 2.0 Ma but then declined. No distinct turnover pulse is seen between 2.8 and 2.5 Ma; instead, the most significant period of faunal change began after 2.5 Ma and continued through 1.8 Ma.</jats:p>

<jats:p>Mantle-derived xenoliths from the Cameroon Line and northern Tanzania display differences in their platinum-group element (PGE) abundance patterns. The Cameroon Line lherzolites have uniform PGE patterns indicating a homogeneous upper mantle over several hundreds of kilometers, with approximately chondritic PGE ratios. The PGE patterns of the Tanzanian peridotites are similar to the PGE systematics of ultramafic rocks from ophiolites. The differences can be explained if the northern Tanzanian lithosphere developed in a fluid-rich suprasubduction zone environment, whereas the Cameroon Line lithosphere only experienced melt extraction from anhydrous peridotites.</jats:p>

<jats:p>The mid-latitude atmosphere is dominated by westerly, nearly zonal flow. Occasionally, this flow is deflected poleward by blocking anticyclones that persist for 10 days or longer. Experiments in a rotating annulus used radial pumping to generate a zonal jet under the action of the Coriolis force. In the presence of two symmetric ridges at the bottom of the annulus, the resulting flows were nearly zonal at high forcing or blocked at low forcing. Intermittent switching between blocked and zonal patterns occurs because of the jet's interaction with the topography. These results shed further light on previous atmospheric observations and numerical simulations.</jats:p>

<jats:p>Units of 2-ureido-4-pyrimidone that dimerize strongly in a self-complementary array of four cooperative hydrogen bonds were used as the associating end group in reversible self-assembling polymer systems. The unidirectional design of the binding sites prevents uncontrolled multidirectional association or gelation. Linear polymers and reversible networks were formed from monomers with two and three binding sites, respectively. The thermal and environmental control over lifetime and bond strength makes many properties, such as viscosity, chain length, and composition, tunable in a way not accessible to traditional polymers. Hence, polymer networks with thermodynamically controlled architectures can be formed, for use in, for example, coatings and hot melts, where a reversible, strongly temperature-dependent rheology is highly advantageous.</jats:p>

<jats:p>A distinctive two-dimensional (2D) melting transition occurring at nearly 100 degrees Celsius (°C) has been observed in Langmuir-Blodgett films by in situ atomic force microscopy (AFM). A 2D orthorhombic crystal phase melted to a 2D smectic phase at about 91°C. The smectic phase was characterized by 1D molecular periodicity with short-range correlations (about 40 angstroms). At 95°C, the smectic order melted to form a hexatic phase. Infrared spectroscopy measurements were consistent with the AFM observations. These observations support the dislocation-mediated melting scenario for an anisotropic 2D crystal predicted by Ostlund and Halperin. A longer wavelength height modulation was also observed in the smectic and hexatic phases.</jats:p>

<jats:p> Low-field tunneling magnetoresistance was observed in films of half-metallic CrO <jats:sub>2</jats:sub> that were grown by high-pressure thermal decomposition of CrO <jats:sub>3</jats:sub> . High-temperature annealing treatments modified the intergrain barriers of the as-grown films through surface decomposition of CrO <jats:sub>2</jats:sub> into insulating Cr <jats:sub>2</jats:sub> O <jats:sub>3</jats:sub> , which led to a threefold enhancement of the low-field magnetoresistance. This enhancement indicates the potential of this simple method to directly control the interface barrier characteristics that determine the magnetotransport properties. </jats:p>

<jats:p>The dynamics of a fluid surface filled with high-amplitude ripples were studied with a technique (diffusing light photography) that resolves the height at all locations instantaneously. Even when nonlinearities are strong enough to generate a (Kolmogorov) cascade from long wavelength (where energy is input) to shorter wavelength, the resulting turbulent state contains large coherent spatial structures. The appearance of these structures in a thermal equilibrium state (with the same average energy) would be highly improbable.</jats:p>

<jats:p> The interleukin-1 receptor (IL-1R) signaling pathway leads to nuclear factor kappa B (NF-κB) activation in mammals and is similar to the Toll pathway in <jats:italic>Drosophila</jats:italic> : the IL-1R–associated kinase (IRAK) is homologous to Pelle. Two additional proximal mediators were identified that are required for IL-1R–induced NF-κB activation: IRAK-2, a Pelle family member, and MyD88, a death domain–containing adapter molecule. Both associate with the IL-1R signaling complex. Dominant negative forms of either attenuate IL-1R–mediated NF-κB activation. Therefore, IRAK-2 and MyD88 may provide additional therapeutic targets for inhibiting IL-1–induced inflammation. </jats:p>

<jats:p>Lavie's theory of attention proposes that the processing load in a relevant task determines the extent to which irrelevant distractors are processed. This theory was tested by asking participants in a study to perform linguistic tasks of low or high load while ignoring irrelevant visual motion in the periphery of the display. Although task and distractor were unrelated, both functional imaging of motion-related activity in cortical area V5 and psychophysical measures of the motion aftereffect showed reduced motion processing during high load in the linguistic task. These findings fulfill the prediction that perception of irrelevant distractors depends on the relevant processing load.</jats:p>