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<jats:p>Gravitational lensing, now taken as an important astrophysical consequence of the general theory of relativity, was found even before this theory was formulated but was discarded as a speculative idea without any chance of empirical confirmation. Reconstruction of some of Einstein's research notes dating back to 1912 reveals that he explored the possibility of gravitational lensing 3 years before completing his general theory of relativity. On the basis of preliminary insights into this theory, Einstein had already derived the basic features of the lensing effect. When he finally published the very same results 24 years later, it was only in response to prodding by an amateur scientist.</jats:p>

<jats:p> Single wall carbon nanotubes (SWNTs) that are found as close-packed arrays in crystalline ropes have been studied by using Raman scattering techniques with laser excitation wavelengths in the range from 514.5 to 1320 nanometers. Numerous Raman peaks were observed and identified with vibrational modes of armchair symmetry ( <jats:italic>n</jats:italic> , <jats:italic>n</jats:italic> ) SWNTs. The Raman spectra are in good agreement with lattice dynamics calculations based on C-C force constants used to fit the two-dimensional, experimental phonon dispersion of a single graphene sheet. Calculated intensities from a nonresonant, bond polarizability model optimized for <jats:italic>sp</jats:italic> <jats:sup>2</jats:sup> carbon are also in qualitative agreement with the Raman data, although a resonant Raman scattering process is also taking place. This resonance results from the one-dimensional quantum confinement of the electrons in the nanotube. </jats:p>

<jats:p> Maleic anhydride, a precursor to polyester resins, is made by oxidation of <jats:italic>n</jats:italic> -butane over vanadium phosphate catalysts. This system is of general interest because it is the only heterogeneously catalyzed, alkane-selective oxidation reaction in commercial use. Time-resolved in situ x-ray absorption spectroscopy shows that when either α <jats:sub>I</jats:sub> -VOPO <jats:sub>4</jats:sub> /SiO <jats:sub>2</jats:sub> or (VO) <jats:sub>2</jats:sub> P <jats:sub>2</jats:sub> O <jats:sub>7</jats:sub> /SiO <jats:sub>2</jats:sub> catalysts are exposed to <jats:italic>n</jats:italic> -butane, the rate of maleic anhydride formation is proportional to the rate of decay of V <jats:sup>5+</jats:sup> species in the catalyst. Thus V <jats:sup>5+</jats:sup> species are kinetically significant for the production of maleic anhydride and not just for the production of by-products. The results also suggest that V <jats:sup>5+</jats:sup> species may play a role in the initial hydrogen abstraction from <jats:italic>n</jats:italic> -butane, the rate-determining step in the reaction sequence. V <jats:sup>4+</jats:sup> sites appear to be responsible for by-product formation. </jats:p>

<jats:p>Satellite radar interferometry observations of the Reykjanes Peninsula oblique rift in southwest Iceland show that the Reykjanes central volcano subsided at an average rate of up to 13 millimeters per year from 1992 to 1995 in response to use of its geothermal field. Interferograms spanning up to 3.12 years also include signatures of plate spreading and indicate that the plate boundary is locked at a depth of about 5 kilometers. Below that depth, the plate movements are accommodated by continuous ductile deformation, which is not fully balanced by inflow of magma from depth, causing subsidence of the plate boundary of about 6.5 millimeters per year.</jats:p>

<jats:p>Recalibration of Mariner 10 color image data allows the identification of distinct color units on the mercurian surface. We analyze these data in terms of opaque mineral abundance, iron content, and soil maturity and find color units consistent with the presence of volcanic deposits on Mercury's surface. Additionally, materials associated with some impact craters have been excavated from a layer interpreted to be deficient in opaque minerals within the crust, possibly analogous to the lunar anorthosite crust. These observations suggest that Mercury has undergone complex differentiation like the other terrestrial planets and the Earth's moon.</jats:p>

<jats:p>Interaction of the p55 tumor necrosis factor receptor 1 (TNF-R1)-associated signal transducer TRADD with FADD signals apoptosis, whereas the TNF receptor-associated factor 2 protein (TRAF2) is required for activation of the nuclear transcription factor nuclear factor kappa B. TNF-induced activation of the stress-activated protein kinase (SAPK) was shown to occur through a noncytotoxic TRAF2-dependent pathway. TRAF2 was both sufficient and necessary for activation of SAPK by TNF-R1; conversely, expression of a dominant-negative FADD mutant, which blocks apoptosis, did not interfere with SAPK activation. Therefore, SAPK activation occurs through a pathway that is not required for TNF-R1-induced apoptosis.</jats:p>

<jats:p> In the developing <jats:italic>Drosophila</jats:italic> eye, differentiation is coordinated with synchronized progression through the cell cycle. Signaling mediated by the transforming growth factor-β-related gene <jats:italic>decapentaplegic</jats:italic> ( <jats:italic>dpp</jats:italic> ) was required for the synchronization of the cell cycle but not for cell fate specification. DPP may affect cell cycle synchronization by promoting cell cycle progression through the G <jats:sub>2</jats:sub> -M phases. This synchronization is critical for the precise assembly of the eye. </jats:p>

<jats:p> The interleukin-1β (IL-1β) converting enzyme (ICE) processes the inactive IL-1β precursor to the proinflammatory cytokine. ICE was also shown to cleave the precursor of interferon-γ inducing factor (IGIF) at the authentic processing site with high efficiency, thereby activating IGIF and facilitating its export. Lipopolysaccharide-activated ICE-deficient (ICE <jats:sup>−/−</jats:sup> ) Kupffer cells synthesized the IGIF precursor but failed to process it into the active form. Interferon-γ and IGIF were diminished in the sera of ICE <jats:sup>−/−</jats:sup> mice exposed to <jats:italic>Propionibacterium acnes</jats:italic> and lipopolysaccharide. The lack of multiple proinflammatory cytokines in ICE <jats:sup>−/−</jats:sup> mice may account for their protection from septic shock. </jats:p>

<jats:p>The role of back-propagating dendritic action potentials in the induction of long-term potentiation (LTP) was investigated in CA1 neurons by means of dendritic patch recordings and simultaneous calcium imaging. Pairing of subthreshold excitatory postsynaptic potentials (EPSPs) with back-propagating action potentials resulted in an amplification of dendritic action potentials and evoked calcium influx near the site of synaptic input. This pairing also induced a robust LTP, which was reduced when EPSPs were paired with non-back-propagating action potentials or when stimuli were unpaired. Action potentials thus provide a synaptically controlled, associative signal to the dendrites for Hebbian modifications of synaptic strength.</jats:p>

<jats:p>Activity-driven modifications in synaptic connections between neurons in the neocortex may occur during development and learning. In dual whole-cell voltage recordings from pyramidal neurons, the coincidence of postsynaptic action potentials (APs) and unitary excitatory postsynaptic potentials (EPSPs) was found to induce changes in EPSPs. Their average amplitudes were differentially up- or down-regulated, depending on the precise timing of postsynaptic APs relative to EPSPs. These observations suggest that APs propagating back into dendrites serve to modify single active synaptic connections, depending on the pattern of electrical activity in the pre- and postsynaptic neurons.</jats:p>