ARA PACIS AVGVSTAE: AN ASTRO-ARCHAEOLOGICAL ANALYSIS

The Ara Pacis Augustae (Altar of Augustan Peace) is examined as a shrine of light consistent with the astroorientation principles of Roman architect Vitruvius (c.25 BC). Italian archaeologists excavated (1937-38) and relocated the altar along Rome"s Tiber River – rotating it 75º counter- clockwise from the original orientation. While its magnificent marble sculpture may be viewed at the Museo dell’Ara Pacis, a key astronomical component of the altar"s architectural design has until now remained encoded on a paper site map. The author calculated the horizon declination (+11.3º decl.) of the altar"s original northeast opening with Program STONEHENGE (Hawkins 1983, 328-330), Guglielmo Gatti"s 1938 site map, and Google Earth satellite imagery: True Azimuth ≈ 75º; Latitude/Longitude = 41° 54" 10.47” N/12° 28" 44.60” E; Elevation ≈ 10 meters ASL; and Horizon Altitude ≈ +1.1º. The Ara Pacis was dedicated in 9 BC (Moretti 1947,7). Analysis shows that the axis of the Ara Pacis enclosure"s northeast opening originally was oriented to the rising Sun (+11.0º decl.) on both April 21st and August 27th. However, the iconography of the Ara Pacis supports an interpretation that only the April 21st sunrise orientation was intended, because each sculptural element of the Tellus frieze (young woman, flowing amphora, pair of fishes, ram, bull, infant twins) uniquely mirrors the astronomy: Venus (Morning Star phase) and the Zodiac constellations Aquarius-Pisces-Aries-Taurus- Gemini at dawn on the festival of Par ilia (Pales, goddess of shepherds), 21 April 9 BC. This month and day coincide with the founding of Rome on 21 April 1 ab urbe condita (a.u.c) as recorded by Roman historian Marcus Terentius Varro. The dedication year of 9 BC coincides with the 93rd iteration of the eight-year Earth-Venus Synodic Period when Venus also appeared as Morning Star on the first Dies Natalis Romae, 21 April 753 BC

Distances to Populous Clusters in the LMC via the K-Band Luminosity of the Red Clump

We present results from a study of the distances and distribution of a sample of intermediate-age clusters in the Large Magellanic Cloud. Using deep near-infrared photometry obtained with ISPI on the CTIO 4m, we have measured the apparent K-band magnitude of the core helium burning red clump stars in 17 LMC clusters. We combine cluster ages and metallicities with the work of Grocholski & Sarajedini to predict each cluster's absolute K-band red clump magnitude, and thereby calculate absolute cluster distances. An analysis of these data shows that the cluster distribution is in good agreement with the thick, inclined disk geometry of the LMC, as defined by its field stars. We also find that the old globular clusters follow the same distribution, suggesting that the LMC's disk formed at about the same time as the globular clusters, ~ 13 Gyr ago. Finally, we have used our cluster distances in conjunction with the disk geometry to calculate the distance to the LMC center, for which we find (m-M)o = 18.40 +/- 0.04_{ran} +/- 0.08_{sys}, or Do = 47.9 +/- 0.9 +/- 1.8 kpc.Comment: 31 pages including 5 figures and 7 tables. Accepted for publication in the August 2007 issue of A

Spinodal decomposition in alkali feldspar studied by atom probe tomography

We used atom probe tomography to complement electron microscopy for the investigation of spinodal decomposition in alkali feldspar. To this end, gem-quality alkali feldspar of intermediate composition with a mole fraction of aK=0.43 of the K end-member was prepared from Madagascar orthoclase by ion-exchange with (NaK)Cl molten salt. During subsequent annealing at 550∘C and close to ambient pressure the ion-exchanged orthoclase unmixed producing a coherent lamellar intergrowth of Na-rich and K-rich lamellae. The chemical separation was completed, and equilibrium Na–K partitioning between the different lamellae was attained within four days, which was followed by microstructural coarsening. After annealing for 4 days, the wavelength of the lamellar microstructure was ≈17nm and it increased to ≈30nm after annealing for 16 days. The observed equilibrium compositions of the Na-rich and K-rich lamellae are in reasonable agreement with an earlier experimental determination of the coherent solvus. The excess energy associated with compositional gradients at the lamellar interfaces was quantified from the initial wavelength of the lamellar microstructure and the lamellar compositions as obtained from atom probe tomography using the Cahn–Hilliard theory. The capability of atom probe tomography to deliver quantitative chemical compositions at nm resolution opens new perspectives for studying the early stages of exsolution. In particular, it helps to shed light on the phase relations in nm scaled coherent intergrowth

From Stars to Super-planets: the Low-Mass IMF in the Young Cluster IC348

We investigate the low-mass population of the young cluster IC348 down to the deuterium-burning limit, a fiducial boundary between brown dwarf and planetary mass objects, using a new and innovative method for the spectral classification of late-type objects. Using photometric indices, constructed from HST/NICMOS narrow-band imaging, that measure the strength of the 1.9 micron water band, we determine the spectral type and reddening for every M-type star in the field, thereby separating cluster members from the interloper population. Due to the efficiency of our spectral classification technique, our study is complete from approx 0.7 Msun to 0.015 Msun. The mass function derived for the cluster in this interval, dN/dlogM \propto M^{0.5}, is similar to that obtained for the Pleiades, but appears significantly more abundant in brown dwarfs than the mass function for companions to nearby sun-like stars. This provides compelling observational evidence for different formation and evolutionary histories for substellar objects formed in isolation vs. as companions. Because our determination of the IMF is complete to very low masses, we can place interesting constraints on the role of physical processes such as fragmentation in the star and planet formation process and the fraction of dark matter in the Galactic halo that resides in substellar objects.Comment: 37 pages, 16 figs, 6 tables (Table 4 is a separate LaTeX file) Accepted for publication in Astrophysical Journal (Oct 1, 2000 issue

Antibody mimetic receptor proteins for label-free biosensors

The development of high sensitivity biosensors, for example for clinical diagnostics, requires the identification of suitable receptor molecules which offer high stability, specificity and affinity, even when embedded into solid-state biosensor transducers. Here, we present an electrochemical biosensor employing small synthetic receptor proteins (Mw < 15 kDa) which emulate antibodies but with improved stability, sensitivity and molecular recognition properties, in particular when immobilized on a solid sensor surface. The synthetic receptor protein is a non-antibody-based protein scaffold with variable peptide regions inserted to provide the specific binding, and was designed to bind anti-myc tag antibody (Mw � 150 kDa), as a proof-of-principle exemplar. Both the scaffold and the selected receptor protein were found to have high thermostability with melting temperatures of 101 �C and 85 �C, respectively. Furthermore, the secondary structures of the receptor protein were found to be very similar to that of the original native scaffold, despite the insertion of variable peptide loops that create the binding sites. A label-free electrochemical sensor was fabricated by functionalising a microfabricated gold electrode with the receptor protein. A change in the phase of the electrochemical impedance was observed when the biosensor was subjected to anti-myc tag antibodies at concentrations between 6.7 pM and 6.7 nM. These findings demonstrate that these non-antibody receptor proteins are excellent candidates for recognition molecules in label-free biosensors