The Marine Living Resources of the Southern Ocean

The author suggests that the abundance of marine life in Antarctica presents ample opportunity both for scientific study and for exploitation. The author provides a survey of the distinct ecological system of the Southern Ocean through his discussion of the main marine species-from the simple organisms involved in primary production to the large marine mammals which have been subject to exploitation in the past. His primary emphasis is on krill, the small, shrimp-like crustacean which serves as the pivotal link in the Antarctic food chain. The abundance of krill, its high nutritive value and its ease of harvesting are factors which the author perceives as according krill significant potential for exploitation. At the same time, he identifies economic and technical obstacles which must be overcome if commercial krill harvesting is to develop

The Marine Living Resources of the Southern Ocean

The author suggests that the abundance of marine life in Antarctica presents ample opportunity both for scientific study and for exploitation. The author provides a survey of the distinct ecological system of the Southern Ocean through his discussion of the main marine species-from the simple organisms involved in primary production to the large marine mammals which have been subject to exploitation in the past. His primary emphasis is on krill, the small, shrimp-like crustacean which serves as the pivotal link in the Antarctic food chain. The abundance of krill, its high nutritive value and its ease of harvesting are factors which the author perceives as according krill significant potential for exploitation. At the same time, he identifies economic and technical obstacles which must be overcome if commercial krill harvesting is to develop

Will the Public's Health Fall Victim to the Home Foreclosure Epidemic?

Gary Bennett and colleagues discuss the ways in which the dramatic rise in home foreclosures, particularly in the US, may have health consequences

Cell-Autonomous Requirement for Rx Function in the Mammalian Retina and Posterior Pituitary

Rx is a paired-like homeobox gene that is required for vertebrate eye formation. Mice lacking Rx function do not develop eyes or the posterior pituitary. To determine whether Rx is required cell autonomously in these tissues, we generated embryonic chimeras consisting of wild type and Rx−/− cells. We found that in the eye, Rx-deficient cells cannot participate in the formation of the neuroretina, retina pigment epithelium and the distal part of the optic stalk. In addition, in the ventral forebrain, Rx function is required cell autonomously for the formation of the posterior pituitary. Interestingly, Rx−/− and wild type cells segregate before the morphogenesis of these two tissues begins. Our observations suggest that Rx function is not only required for the morphogenesis of the retina and posterior pituitary, but also prior to morphogenesis, for the sorting out of cells to form distinct fields of retinal/pituitary cells

QUBIC VI: cryogenic half wave plate rotator, design and performances

Inflation Gravity Waves B-Modes polarization detection is the ultimate goal of modern large angular scale cosmic microwave background (CMB) experiments around the world. A big effort is undergoing with the deployment of many ground-based, balloon-borne and satellite experiments using different methods to separate this faint polarized component from the incoming radiation. One of the largely used technique is the Stokes Polarimetry that uses a rotating half-wave plate (HWP) and a linear polarizer to separate and modulate the polarization components with low residual cross-polarization. This paper describes the QUBIC Stokes Polarimeter highlighting its design features and its performances. A common systematic with these devices is the generation of large spurious signals synchronous with the rotation and proportional to the emissivity of the optical elements. A key feature of the QUBIC Stokes Polarimeter is to operate at cryogenic temperature in order to minimize this unwanted component. Moving efficiently this large optical element at low temperature constitutes a big engineering challenge in order to reduce friction power dissipation. Big attention has been given during the designing phase to minimize the differential thermal contractions between parts. The rotation is driven by a stepper motor placed outside the cryostat to avoid thermal load dissipation at cryogenic temperature. The tests and the results presented in this work show that the QUBIC polarimeter can easily achieve a precision below 0.1{\deg} in positioning simply using the stepper motor precision and the optical absolute encoder. The rotation induces only few mK of extra power load on the second cryogenic stage (~ 8 K).Comment: Part of a series of 8 papers on QUBIC to be submitted to a special issue of JCA