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An aerial vehicle rotating in gyroscopic fashion about one of its axes has an optical system which scans an area below the vehicle in determined relation to vehicle rotation. A sensing device is provided to sense the physical condition of the area of scan and optical means are associated to direct the physical intelligence received from the scan area to the sensing means. Means are provided to incrementally move the optical means through a series of steps to effect sequential line scan of the area being viewed keyed to the rotational rate of the vehicle

Alteration and Oxidiation of an Olivine Lamprophyre Dike from Southern Utah, USA: An Analog for Mars

We report on oxidized basaltic dike intrusions on the Colorado Plateau as analog for Martian basalt oxidation

Measuring the energy landscape roughness and the transition state location of biomolecules using single molecule mechanical unfolding experiments

Single molecule mechanical unfolding experiments are beginning to provide profiles of the complex energy landscape of biomolecules. In order to obtain reliable estimates of the energy landscape characteristics it is necessary to combine the experimental measurements with sound theoretical models and simulations. Here, we show how by using temperature as a variable in mechanical unfolding of biomolecules in laser optical tweezer or AFM experiments the roughness of the energy landscape can be measured without making any assumptions about the underlying reaction oordinate. The efficacy of the formalism is illustrated by reviewing experimental results that have directly measured roughness in a protein-protein complex. The roughness model can also be used to interpret experiments on forced-unfolding of proteins in which temperature is varied. Estimates of other aspects of the energy landscape such as free energy barriers or the transition state (TS) locations could depend on the precise model used to analyze the experimental data. We illustrate the inherent difficulties in obtaining the transition state location from loading rate or force-dependent unfolding rates. Because the transition state moves as the force or the loading rate is varied it is in general difficult to invert the experimental data unless the curvature at the top of the one dimensional free energy profile is large, i.e the barrier is sharp. The independence of the TS location on force holds good only for brittle or hard biomolecules whereas the TS location changes considerably if the molecule is soft or plastic. We also comment on the usefulness of extension of the molecule as a surrogate reaction coordinate especially in the context of force-quench refolding of proteins and RNA.Comment: 44 pages, 7 figure

The hydration state of HO−^-(aq)

The HO$^-$(aq) ion participates in myriad aqueous phase chemical processes of biological and chemical interest. A molecularly valid description of its hydration state, currently poorly understood, is a natural prerequisite to modeling chemical transformations involving HO$^-$(aq). Here it is shown that the statistical mechanical quasi-chemical theory of solutions predicts that $\mathrm{HO\cdot[H_2O]_3{}^-}$ is the dominant inner shell coordination structure for HO$^-$(aq) under standard conditions. Experimental observations and other theoretical calculations are adduced to support this conclusion. Hydration free energies of neutral combinations of simple cations with HO$^-$(aq) are evaluated and agree well with experimental values.Comment: 10 pages, 1 figur

The 21cm Signature of the First Stars

We predict the 21-cm signature of the first metal-free stars. The soft X-rays emitted by these stars penetrate the atomic medium around their host halos, generating Lyman alpha photons that couple the spin and kinetic temperatures. These creates a region we call the Lyman alpha sphere, visible in 21-cm against the CMB, which is much larger than the HII region produced by the same star. The spin and kinetic temperatures are strongly coupled before the X-rays can substantially heat the medium, implying that a strong 21-cm absorption signal from the adiabatically cooled gas in Hubble expansion around the star is expected when the medium has not been heated previously. A central region of emission from the gas heated by the soft X-rays is also present although with a weaker signal than the absorption. The Lyman alpha sphere is a universal signature that should be observed around any first star illuminating its vicinity for the first time. The 21-cm radial profile of the Lyman alpha sphere can be calculated as a function of the luminosity, spectrum and age of the star. For a star of a few hundred solar masses and zero metallicity (as expected for the first stars), the physical radius of the Lyman alpha sphere can reach tens of kiloparsecs. The first metal-free stars should be strongly clustered because of high cosmic biasing; this implies that the regions producing a 21-cm absorption signal may contain more than one star and will generally be irregular and not spherical, because of the complex distribution of the gas. We discuss the feasiblity of detecting these Lyman alpha spheres, which would be present at redshifts $z\sim 30$ in the Cold Dark Matter model. Their observation would represent a direct proof of the detection of a first star.Comment: replaced with ApJ accepted version. Many minor revisions and additional references, major results unchange

The first detection of near-infrared CN bands in active galactic nuclei: signature of star formation

We present the first detection of the near-infrared CN absorption band in the nuclear spectra of active galactic nuclei (AGN). This feature is a recent star formation tracer, being particularly strong in carbon stars. The equivalent width of the CN line correlates with that of the CO at 2.3 microns, as expected in stellar populations (SP) with ages between ~ 0.2 and ~ 2 Gyr. The presence of the 1.1 microns CN band in the spectra of the sources is taken as an unambiguous evidence of the presence of young/intermediate SP close to the central source of the AGN. Near-infrared bands can be powerful age indicators for star formation connected to AGN, the understanding of which is crucial in the context of galaxy formation and AGN feedback.Comment: Accepted for publication in The Astrophysical Journal Letters. 4 pages, 3 figure

Formation of Primordial Protostars

The evolution of collapsing metal free protostellar clouds is investigated for various masses and initial conditions. We perform hydrodynamical calculations for spherically symmetric clouds taking account of radiative transfer of the molecular hydrogen lines and the continuum, as well as of chemistry of the molecular hydrogen. The collapse is found to proceed almost self-similarly like Larson-Penston similarity solution. In the course of the collapse, efficient three-body processes transform atomic hydrogen in an inner region of \sim 1 M_{\sun} entirely into molecular form. However, hydrogen in the outer part remains totally atomic although there is an intervening transitional layer of several solar masses, where hydrogen is in partially molecular form. No opaque transient core is formed although clouds become optically thick to H$_{2}$ collision-induced absorption continuum, since H$_{2}$ dissociation follows successively. When the central part of the cloud reaches stellar densities ($\sim 10^{-2} {\rm g cm^{-3}}$), a very small hydrostatic core (\sim 5 \times 10^{-3} M_{\sun}) is formed and subsequently grows in mass as the ambient gas accretes onto it. The mass accretion rate is estimated to be 3.7 \times 10^{-2} M_{\sun} {\rm yr^{-1}} (M_{\ast}/M_{\sun})^{-0.37}, where $M_{\ast}$ is instantaneous mass of the central core, by using a similarity solution which reproduces the evolution of the cloud before the core formation.Comment: 20 pages, 5 Postscript figures, uses AAS LaTe

Recent star formation in clusters of galaxies: extreme compact starbursts in A539 and A634

We report on the detection of two Halpha-emitting extreme compact objects from deep images of the Abell 634 and Abell 539 clusters of galaxies at z ~ 0.03. Follow up long slit spectroscopy of these two unresolved sources revealed that they are members of their respective clusters showing HII type spectra. The luminosity and the extreme equivalent width of Halpha+[NII] measured for these sources, together with their very compact appearance, has raised the question about the origin of these intense starbursts in the cluster environment. We propose the compact starburst in Abell 539 resulted from the compression of the interstellar gas of a dwarf galaxy when entering the cluster core; while the starburst galaxy in Abell 634 is likely to be the result of a galaxy-galaxy interaction, illustrating the preprocessing of galaxies during their infall towards the central regions of clusters. The contribution of these compact star-forming dwarf galaxies to the star formation history of galaxy clusters is discussed, as well as a possible link with the recently discovered early-type ultra-compact dwarf galaxies. We note that these extreme objects will be rarely detected in normal magnitude-limited optical or NIR surveys, mainly due to their low stellar masses (of the order of 10^6 solar masses), whereas they will easily show up in dedicated Halpha surveys given the high equivalent width of their emission lines.Comment: Accepted for publication in the Astronomical Journal. 31 pages, 10 fig

Signatures of the Youngest Starbursts: Optically-thick Thermal Bremsstrahlung Radio Sources in Henize 2-10

VLA radio continuum imaging reveals compact (<8 pc) ~1 mJy radio sources in the central 5" starburst region of the blue compact galaxy Henize 2-10. We interpret these radio knots as extremely young, ultra-dense HII regions. We model their luminosities and spectral energy distributions, finding that they are consistent with unusually dense HII regions having electron densities, 1500 cm^-3 < n_e < 5000 cm^-3, and sizes of 3-8 pc. Since these H II regions are not visible in optical images, we propose that the radio data preferentially reveal the youngest, densest, and most highly obscured starforming events. Energy considerations imply that each of the five \HII regions contains ~750 O7V equivalent stars, greater than the number found in 30 Doradus in the LMC. The high densities imply an over-pressure compared to the typical interstellar medium so that such objects must be short-lived (<0.5 Myr expansion timescales). We conclude that the radio continuum maps reveal the very young (<0.5 Myr) precursors of ``super starclusters'' or ``proto globular clusters'' which are prominent at optical and UV wavelengths in He 2-10. If the ultra-dense HII regions are typical of those which we predict will be found in other starbursting systems, then super starclusters spend 15% of their lifetime in heavily-obscured environments, similar to Galactic ultra-compact HII regions. This body of work leads us to propose that massive extragalactic star clusters (i.e. proto globular clusters) with ages <10^6 yr may be most easily identified by finding compact radio sources with optically-thick thermal bremsstrahlung spectral signatures.Comment: AASTeX, 8 figures 2 included with psfig in text; other 6 in jpeg format; Postscript versions of figures may be found at http://zem.ucolick.org/chip/Research/young_clusters.html -- Accepted for publication in the Astrophysical Journa