We have studied the concentrations of 10Be and 26Al in quartz crystals extracted from glacially polished granitic surfaces from the Sierra Nevada range. These surfaces were identified with the glacial advance during the Tioga period ∼11,000 years ago. Our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in SiO2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43.8°–44.6°N and altitudes 2.1–3.6 km. The estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0°–75° with respect to the horizontal. The principal uncertainty arises due to the lack of a precise date for the glacial retreat event, about ±10%. The 26Al/10Be ratio at production (6.0) is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides. Production rates of 10Be and 26Al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling, using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons. Knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies.

The Atacama Cosmology Telescope was designed to measure small-scale anisotropies in the Cosmic Microwave Background and detect galaxy clusters through the Sunyaev-Zel'dovich effect. The instrument is located on Cerro Toco in the Atacama Desert, at an altitude of 5190 meters. A six-meter off-axis Gregorian telescope feeds a new type of cryogenic receiver, the Millimeter Bolometer Array Camera. The receiver features three 1000-element arrays of transition-edge sensor bolometers for observations at 148 GHz, 218 GHz, and 277 GHz. Each detector array is fed by free space mm-wave optics. Each frequency band has a field of view of approximately 22 ′ × 26 ′ . The telescope was commissioned in 2007 and has completed its third year of operations. We discuss the major components of the telescope, camera, and related systems, and summarize the instrument performance.

We present results for Vela C obtained during the 2012 flight of the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol). We mapped polarized intensity across almost the entire extent of this giant molecular cloud, in bands centered at 250, 350, and 500 µm. In this initial paper, we show our 500 µm data smoothed to a resolution of 2. 5 (approximately 0.5 pc). We show that the mean level of the fractional polarization p and most of its spatial variations can be accounted for using an empirical three-parameter power-law fit, p ∝ N −0.45 S −0.60 , where N is the hydrogen column density and S is the polarization-angle dispersion on 0.5 pc scales. The decrease of p with increasing S is expected because changes in the magnetic field direction within the cloud volume sampled by each measurement will lead to cancellation of polarization signals. The decrease of p with increasing N might be caused by the same effect, if magnetic field disorder increases for high column density sightlines. Alternatively, the intrinsic polarization efficiency of the dust grain population might be lower for material along higher density sightlines. We find no significant correlation between N and S. Comparison of observed submillimeter polarization maps with synthetic polarization maps derived from numerical simulations provides a promising method for testing star formation theories. Realistic simulations should allow for the possibility of variable intrinsic polarization efficiency. The measured levels of correlation among p, N , and S provide points of comparison between observations and simulations.

Accurate terrestrial glacial chronologies are needed for comparison with the marine record to establish the dynamics of global climate change during transitions from glacial to interglacial regimes. Cosmogenic beryllium-10 measurements in the Wind River Range indicate that the last glacial maximum (marine oxygen isotope stage 2) was achieved there by 21,700 +/- 700 beryllium-10 years and lasted 5900 years. Ages of a sequence of recessional moraines and striated bedrock surfaces show that the initial deglaciation was rapid and that the entire glacial system retreated 33 kilometers to the cirque basin by 12,100 +/- 500 beryllium-10 years.

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