New horizons mapping of Europa and Ganymede

The New Horizons spacecraft observed Jupiter's icy satellites Europa and Ganymede during its flyby in February and March 2007 at visible and infrared wavelengths. Infrared spectral images map H2O ice absorption and hydrated contaminants, bolstering the case for an exogenous source of Europa's "non-ice" surface material and filling large gaps in compositional maps of Ganymede's Jupiter-facing hemisphere. Visual wavelength images of Europa extend knowledge of its global pattern of arcuate troughs and show that its surface scatters light more isotropically than other icy satellites.     

THE RHESUS GENE AND THE EFFECT OF CONSANGUINITY

It is pointed out that consanguinity among the parents of children affected by erythroblastosis foetalis should be less than in the general population, unless other loci than the R locus are involved in the disease.     

Mantle phase changes and deep-earthquake faulting in subducting lithosphere

Inclined zones of earthquakes are the primary expression of lithosphere subduction. A distinct deep population of subduction-zone earthquakes occurs at depths of 350 to 690 kilometers. At those depths ordinary brittle fracture and frictional sliding, the faulting processes of shallow earthquakes, are not expected. A fresh understanding of these deep earthquakes comes from developments in several areas of experimental and theoretical geophysics, including the discovery and characterization of transformational faulting, a shear instability connected with localized phase transformations under nonhydrostatic stress. These developments support the hypothesis that deep earthquakes represent transformational faulting in a wedge of olivine-rich peridotite that is likely to persist metastably in coldest plate interiors to depths as great as 690 km. Predictions based on this deep structure of mantle phase changes are consistent with the global depth distribution of deep earthquakes, the maximum depths of earthquakes in individual subductions zones, and key source characteristics of deep events.     

Io volcanism seen by new horizons: a major eruption of the Tvashtar volcano

Jupiter's moon Io is known to host active volcanoes. In February and March 2007, the New Horizons spacecraft obtained a global snapshot of Io's volcanism. A 350-kilometer-high volcanic plume was seen to emanate from the Tvashtar volcano (62 degrees N, 122 degrees W), and its motion was observed. The plume's morphology and dynamics support nonballistic models of large Io plumes and also suggest that most visible plume particles condensed within the plume rather than being ejected from the source. In images taken in Jupiter eclipse, nonthermal visible-wavelength emission was seen from individual volcanoes near Io's sub-Jupiter and anti-Jupiter points. Near-infrared emission from the brightest volcanoes indicates minimum magma temperatures in the 1150- to 1335-kelvin range, consistent with basaltic composition.     

1 alpha, 25-Dihydroxyvitamin D3 nuclear receptors in pituitary

Specific binding of 1 alpha,25-dihydroxyvitamin D(3) was found in nuclear and cytosol fractions of the bovine pituitary. For nuclear binding. the dissociation constant was 0.1 namomole per liter, and maximum binding was 104 femtomoles per milligram of protein. In competition studies, 25-hydroxyvitamin D(3) was 300 times weaker than 1 alpha,25-dihydroxyvitamin D(3). The existence of high-affinity sites supports a physiologic role for 1 alpha,25-dihydroxyvitamin D(3) in the pituitary.     

The Origin of the Great Bend of the Nile from SIR-C/X-SAR Imagery

The course of the Nile in northern Sudan follows a contorted path through Precambrian bedrock. Radar imagery shows that basement structures control the river's course in this region. Northward-flowing segments follow Precambrian fabrics, whereas east-west segments follow faults of much younger age. These faults may reflect recent uplift of the Nubian Swell and deflection of the river to the southwest to form the great bend of the Nile.     

The struggle to govern the commons

Human institutions--ways of organizing activities--affect the resilience of the environment. Locally evolved institutional arrangements governed by stable communities and buffered from outside forces have sustained resources successfully for centuries, although they often fail when rapid change occurs. Ideal conditions for governance are increasingly rare. Critical problems, such as transboundary pollution, tropical deforestation, and climate change, are at larger scales and involve nonlocal influences. Promising strategies for addressing these problems include dialogue among interested parties, officials, and scientists; complex, redundant, and layered institutions; a mix of institutional types; and designs that facilitate experimentation, learning, and change.     

Divalent cations directly affect the conductance of excised patches of rod photoreceptor membrane

Phototransduction in rod cells is likely to involve an intracellular messenger system that links the absorption of light by rhodopsin to a change in membrane conductance. The direct effect of guanosine 3',5'-monophosphate (cGMP) on excised patches of rod outer segment membrane strongly supports a role for cGMP as an intracellular messenger in phototransduction. It is reported here that magnesium and calcium directly affect the conductance of excised patches of rod membrane in the absence of cGMP and that magnesium, applied to intact rod cells, blocks a component of the cellular light response. The divalent cation-suppressed conductance in excised patches showed outward rectification and cation-selective permeability resembling those of the light-suppressed conductance measured from the intact rod cell. The divalent cation-suppressed conductance was partly blocked by a concentration of the pharmacological agent L-cis-diltiazem that blocked all of the cGMP-activated conductance. Divalent cations may act, together with cGMP, as an intracellular messenger system that mediates the light response of the rod photoreceptor cell.     

Modulation of hematopoietic stem cell homing and engraftment by CD26

Hematopoietic stem cell homing and engraftment are crucial to transplantation efficiency, and clinical engraftment is severely compromised when donor-cell numbers are limiting. The peptidase CD26 (DPPIV/dipeptidylpeptidase IV) removes dipeptides from the amino terminus of proteins. We present evidence that endogenous CD26 expression on donor cells negatively regulates homing and engraftment. By inhibition or deletion of CD26, it was possible to increase greatly the efficiency of transplantation. These results suggest that hematopoietic stem cell engraftment is not absolute, as previously suggested, and indicate that improvement of bone marrow transplant efficiency may be possible in the clinic.