Mars Express measurements of surface albedo changes over 2004 - 2010

The pervasive Mars dust is continually transported between the surface and the atmosphere. When on the surface, dust increases the albedo of darker underlying rocks and regolith, which modifies climate energy balance and must be quantified. Remote observation of surface albedo absolute value and albedo change is however complicated by dust itself when lifted in the atmosphere. Here we present a method to calculate and map the bolometric solar hemispherical albedo of the Martian surface using the 2004 - 2010 OMEGA imaging spectrometer dataset. This method takes into account aerosols radiative transfer, surface photometry, and instrumental issues such as registration differences between visible and near-IR detectors. Resulting albedos are on average 17% higher than previous estimates for bright surfaces while similar for dark surfaces. We observed that surface albedo changes occur mostly during the storm season due to isolated events. The main variations are observed during the 2007 global dust storm and during the following year. A wide variety of change timings are detected such as dust deposited and then cleaned over a Martian year, areas modified only during successive global dust storms, and perennial changes over decades. Both similarities and differences with previous global dust storms are observed. While an optically thin layer of bright dust is involved in most changes, this coating turns out to be sufficient to mask underlying mineralogical near-IR spectral signatures. Overall, changes result from apparently erratic events; however, a cyclic evolution emerges for some (but not all) areas over long timescales

Astrophysical jets: observations, numerical simulations, and laboratory experiments

This paper provides summaries of ten talks on astrophysical jets given at the HEDP/HEDLA-08 International Conference in St. Louis. The talks are topically divided into the areas of observation, numerical modeling, and laboratory experiment. One essential feature of jets, namely, their filamentary (i.e., collimated) nature, can be reproduced in both numerical models and laboratory experiments. Another essential feature of jets, their scalability, is evident from the large number of astrophysical situations where jets occur. This scalability is the reason why laboratory experiments simulating jets are possible and why the same theoretical models can be used for both observed astrophysical jets and laboratory simulations

Equilibrium in the Catalytic Condensation of Carboxylic Acids with Methyl Ketones to 1,3-Diketones and the Origin of the Reketonization Effect

Acetone is the expected ketone product of an acetic acid decarboxylative ketonization reaction with metal oxide catalysts used in the industrial production of ketones and for biofuel upgrade. Decarboxylative cross-ketonization of a mixture of acetic and isobutyric acids yields highly valued unsymmetrical methyl isopropyl ketone (MIPK) along with two less valuable symmetrical ketones, acetone and diisopropyl ketone (DIPK). We describe a side reaction of isobutyric acid with acetone yielding the cross-ketone MIPK with monoclinic zirconia and anatase titania catalysts in the absence of acetic acid. We call it a reketonization reaction because acetone is deconstructed and used for the construction of MIPK. Isotopic labeling of the isobutyric acid’s carboxyl group shows that it is the exclusive supplier of the carbonyl group of MIPK, while acetone provides only methyl group for MIPK construction. More branched ketones, MIPK or DIPK, are less reactive in their reketonization with carboxylic acids. The proposed mechanism of reketonization supported by density functional theory (DFT) computations starts with acetone enolization and proceeds via its condensation with surface isobutyrate to a β-diketone similar to β-keto acid formation in the decarboxylative ketonization of acids. Decomposition of unsymmetrical β-diketones with water (or methanol) by the retrocondensation reaction under the same conditions over metal oxides yields two pairs of ketones and acids (or esters in the case of methanol) and proceeds much faster compared to their formation. The major direction yields thermodynamically more stable products—more substituted ketones. DFT calculations predict even a larger fraction of the thermodynamically preferred pair of products. The difference is explained by some degree of a kinetic control in the opposite direction. Reketonization has lower reaction rates compared to regular ketonization. Still, a high extent of reketonization occurs unnoticeably during the decarboxylative ketonization of acetic acid as the result of the acetone reaction with acetic acid. This degenerate reaction is the major cause of the inhibition by acetone of its own rate of formation from acetic acid at high conversions

Passive control of viscous flow via elastic snap-through

We demonstrate the passive control of viscous flow in a channel by using an elastic arch embedded in the flow. Depending on the fluid flux, the arch may `snap' between two states --- constricting and unconstricting --- that differ in hydraulic conductivity by up to an order of magnitude. We use a combination of experiments at a macroscopic scale and theory to study the constricting and unconstricting states, and determine the critical flux required to transition between them. We show that such a device may be precisely tuned for use in a range of applications, and in particular has potential as a passive microfluidic fuse to prevent excessive fluxes in rigid-walled channels.Comment: Main text 5 pages, Supplementary Information 14 page

Precise Coulomb wave functions for a wide range of complex l, eta and z

A new algorithm to calculate Coulomb wave functions with all of its arguments complex is proposed. For that purpose, standard methods such as continued fractions and power/asymptotic series are combined with direct integrations of the Schrodinger equation in order to provide very stable calculations, even for large values of |eta| or |Im(l)|. Moreover, a simple analytic continuation for Re(z) < 0 is introduced, so that this zone of the complex z-plane does not pose any problem. This code is particularly well suited for low-energy calculations and the calculation of resonances with extremely small widths. Numerical instabilities appear, however, when both |eta| and |Im(l)| are large and |Re(l)| comparable or smaller than |Im(l)|

Exploring the NRO Opportunity for a Hubble-sized Wide-field Near-IR Space Telescope -- NEW WFIRST

We discuss scientific, technical and programmatic issues related to the use of an NRO 2.4m telescope for the WFIRST initiative of the 2010 Decadal Survey. We show that this implementation of WFIRST, which we call "NEW WFIRST," would achieve the goals of the NWNH Decadal Survey for the WFIRST core programs of Dark Energy and Microlensing Planet Finding, with the crucial benefit of deeper and/or wider near-IR surveys for GO science and a potentially Hubble-like Guest Observer program. NEW WFIRST could also include a coronagraphic imager for direct detection of dust disks and planets around neighboring stars, a high-priority science and technology precursor for future ambitious programs to image Earth-like planets around neighboring stars.Comment: 76 pages, 26 figures -- associated with the Princeton "New Telescope Meeting