Spectral slicing X-ray telescope with variable magnification

A telescope for viewing high frequency radiation (soft X-ray, extreme ultraviolet) is described. This telescope has a long focal length with a selection of magnifications despite a short housing. Light enters the telescope and is reflected by the telescope's primary optical system to one of several secondary mirrors at different locations on a movable frame. The secondary mirrors have varying degrees of magnification and select narrow spectral slices of the incident radiation. Thus, both the magnification and effective focal length field of view and wavelength can be altered by repositioning the moving frame. Configurations for spaceborne applications are discussed

Evidence linking coronal mass ejections with interplanetary magnetic clouds

Using proxy data for the occurrence of those mass ejections from the solar corona which are directed earthward, we investigate the association between the post-1970 interplanetary magnetic clouds of Klein and Burlaga and coronal mass ejections. The evidence linking magnetic clouds following shocks with coronal mass ejections is striking; six of nine clouds observed at Earth were preceded an appropriate time earlier by meter-wave type II radio bursts indicative of coronal shock waves and coronal mass ejections occurring near central meridian. During the selected periods when no clouds were detected near Earth, the only type II bursts reported were associated with solar activity near the limbs. Where the proxy solar data to be sought are not so clearly suggested, that is, for clouds preceding interaction regions and clouds within cold magnetic enhancements, the evidence linking the clouds and coronal mass ejections is not as clear; proxy data usually suggest many candidate mass-ejection events for each cloud. Overall, the data are consistent with and support the hypothesis suggested by Klein and Burlaga that magnetic clouds observed with spacecraft at 1 AU are manifestations of solar coronal mass ejection transients

The Writing of Architecture: Mnemosyne and the Wax Tablet

In the search for nature - for the true origin and order of things - we will find in architecture the origins of memory and the invention of culture. Architecture is the resistance to forgetfulness..

Magma storage and ascent of historic and prehistoric eruptions of Fogo, Cape Verde Islands: A barometric, petrologic and geochemical approach

Fogo is one of the most active oceanic intra-plate volcanoes in the world and the only island of the Cape Verde Archipelago showing historic activity. This study has been conducted to shed light on the magma plumbing systems of the island. In particular it aims to gain information on the depths of magma stagnation and differentiation, and on the ascent dynamics. Fogo was affected by a giant prehistoric lateral collapse that led to the removal of the summit and the eastern flank of the former Monte Amarelo volcano. The scar was partly refilled by intensive subsequent volcanic activity that is represented by the present-day Cha das Caldeiras plain and the young Pico do Fogo stratovolcano. During the 20th century Fogo experienced two eruptions in 1951 and 1995 that were both fed from fissures on the flanks of Pico do Fogo. The 1995 eruption differed from earlier eruptions in a distinct chemical and mineralogical bimodality with phonotephrites (2.4-2.8 wt% MgO) being erupted in the first days and basanites (5.2-6.7 wt% MgO) in the later phase, the uncommon southwest orientation of the eruption fissure, and pre-eruptive seismicity between Fogo and the adjacent island of Brava. Geochemical modeling of major and trace elements shows that the phonotephrites formed out of the basanites by crystal fractionation. Clinopyroxene-melt barometry of phenocrysts yields overlapping pressure ranges for final crystal growth before eruption of 460-680 MPa for the basanites and 460-520 MPa for the phonotephrites, corresponding to 16-24 km depth in the lithospheric mantle. Microthermometry of CO2-dominated fluid inclusions in basanites yield pressures of 270-440 MPa for olivine-hosted and 240-270 MPa for clinopyroxene hosted ones. Inclusions in phenocrysts of the phonotephrites yield a pressure range of 320-470 MPa for olivine-hosted and 200-310 MPa for clinopyroxene-hosted fluid inclusions. Fluid inclusions in olivine, especially of phonotephrites show overlapping pressures with the data of clinopyroxene-melt barometry. The lower pressures derived for clinopyroxene-hosted inclusions are interpreted to reflect a level of syn-eruptive short-term magma stagnation in the lower crust at 8-11 km depth. Chemical zonations of olivine phenocrysts indicate a rapid final magma ascent during eruption in 100 ka, which includes the Monte Amarelo collapse, indicate that magma storage and differentiation occurred in the lithospheric mantle at pressures of 420-870 MPa (15-30 km depth) presumably throughout the subaerial evolution of Fogo. The fractionation depths decreased through time, though this trend was temporarily interrupted by the giant collapse because the oldest post-collapse eruption shows a deeper stagnation level than the youngest pre-collapse one. The petrologic data indicate that large flank collapses may significantly influence deep-seated magma plumbing systems beneath ocean islands. Historic eruptions show shallower and broader pressure ranges and more complexly zoned clinopyroxene phenocrysts, suggesting an increase in complexity of the magma storage system. The lack of shallow persistent magma chambers, however, may be a consequence of the cool Mesozoic crust and thick lithosphere beneath Fogo

Tailoring the excited-state energy landscape in supramolecular nanostructures

Nature's photosynthetic machinery uses precisely arranged pigment-protein complexes, often representing superstructures, for efficient light-harvesting and transport of excitation energy (excitons) during the initial steps of photosynthesis. This function is achieved by defined electronic Coulomb interactions between the conjugated molecules resulting in tailored excited-state energy landscapes. While such complex natural structures are synthetically difficult to achieve, supramolecular chemistry is now on its advent to realize defined artificial supramolecular nanostructures with tailored functionalities via controlled self-assembly processes of small molecules. In this review, we focus on recent work reporting photophysical studies on self-assembled and hierarchical nanostructures as well as complex superstructures. We discuss how the resulting excited-state energy landscapes influence energy transport. Progress in the field of supramolecular chemistry allows for the realization of distinct kinds of H- or J-aggregates with well-defined morphologies on the mesoscale. Advances in the field of optical spectroscopy and microscopy have permitted to resolve the incoherent/coherent dynamics of exciton transport in such systems down to the level of single nanostructures. Although outstanding diffusion lengths of up to several mu m were found in selected nanostructures, a full understanding of the underlying principles is still missing. In particular, the unavoidable structural and electronic disorder in these systems influences the excited-state energy landscapes and thus the transport characteristics, which can be exploited to refine the molecular design criteria of supramolecular nanostructures and complex superstructures. Despite the rapid progress in the field of functional supramolecular nanostructures, we believe that revealing the full potential of such systems is far from complete. In particular, criteria for tailored and optimized (hierarchical) supramolecular nanostructures in view of applications are not yet established. Finally, we outline current challenges and future perspectives for optical and optoelectronic applications of supramolecular nanostructures

The Extended Range X-Ray Telescope center director's discretionary fund report

An Extended Range X-Ray Telescope (ERXRT) of high sensitivity and spatial resolution capable of functioning over a broad region of the X-ray/XUV portion of the spectrum has been designed and analyzed. This system has been configured around the glancing-incidence Wolter Type I X-ray mirror system which was flown on the Skylab Apollo Telescope Mount as ATM Experiment S-056. Enhanced sensitivity over a vastly broader spectral range can be realized by the utilization of a thinned, back-illuminated, buried-channel Charge Coupled Device (CCD) as the X-ray/XUV detector rather than photographic film. However, to maintain the high spatial resolution inherent in the X-ray optics when a CCD of 30 micron pixel size is used, it is necessary to increase the telescope plate scale. This can be accomplished by use of a glancing-incidence X-ray microscope to enlarge and re-focus the primary image onto the focal surface of the CCD

Unusual Photophysical Properties of Porphyrin-Based Supramolecular Polymers Unveiled:The Role of Metal Ligands and Side Group Amide Connectivity

Supramolecular polymers based on porphyrins are an interesting model system, since the self-assembly and thus the photophysics can be modified by the chemical structure of the porphyrins, e.g., by a metal inserted in the ligand or by different (solubilizing) side groups. Here, we investigate the photophysical properties of supramolecular polymers based on free-base and Zn-centered porphyrins, each with different amide connectivity in the side chains, by absorption and (time-resolved) photoluminescence spectroscopy on solutions. We find that for all porphyrin derivatives the B-band absorption of supramolecular polymers is a superposition of H- and J-type aggregate spectra, while the Q-band absorption indicates only J-type aggregation. The emission of supramolecular polymers stems exclusively from the Q-band and shows only J-type behavior. For supramolecular polymers based on the free-base porphyrins, we identify only a single aggregate species, whereas for Zn-centered porphyrins, two distinct species coexist in solution, each with a (slightly) different arrangement of monomers. We rationalize this complex behavior by a slip-stacking of porphyrins along the direction of one of the two B-band transition dipole moments, resulting in simultaneous H- and J-type intermolecular coupling in the B-band. In the Q-band, with its transition dipole moments oriented 45° relative to the corresponding B-band moments, only J-type coupling is thus present. Our results demonstrate that the self-assembly and the photophysics of supramolecular polymers based on porphyrins can only be fully understood if spectral information from all bands is considered.</p

Conditional quantum nonlocality in dimeric and trimeric arrays of organic molecules

Arrays of covalently bound organic molecules possess potential for light-harvesting and energy transfer applications due to the strong coherent dipole-dipole coupling between the transition dipole moments of the molecules involved. Here, we show that such molecular systems, based on perylene-molecules, can be considered as arrays of qubits that are amenable for laser-driven quantum coherent control. The perylene monomers exhibit dephasing times longer than four orders of magnitude a typical gating time, thus allowing for the execution of a large number of gate operations on the sub-picosecond timescale. Specifically, we demonstrate quantum logic gates and entanglement in bipartite (dimer) and tripartite (trimer) systems of perylene-based arrays. In dimers, naturally entangled states with a tailored degree of entanglement can be produced. The nonlocality of the molecular trimer entanglement is demonstrated by testing Mermin's (Bell-like) inequality violation.Comment: 14 pages, 8 figures, comments are welcom