Erratum

The width of the shell shown on the cover of the 1 July issue was given incorrectly in the caption on page 5. The shell is approximately 2 millimeters im width, not 2 micrometers.     

Corrections

In the report "Distribution and detection of positrons from an orbiting nuclear reactor" by E. W. Hones and P. R. Higbie (28 Apr., p. 448), the following corrections should be noted. The first sentence of the caption for figure 1 should have read, "Location of SMM (dots) and Cosmos 1176 (triangles) at the times of 21 of the most intense 511-keV gamma events recorded by SMM during the 29 April to 2 September 1980 operating period." The first sentence of the caption for figure 3 should have read, "Estimated differential energy spectrum positrons escaping from Cosmos 1176 per joule of fission energy." On page 450, the second sentence of the first full paragraph should have referred to event 5, not event 59.     

Electrophysiological Evidence that Abnormal Early Visual Experience Can Modify the Human Brain

In the caption of the cover photograph for 25 May 1973, the word "below" is misplaced; it should be deleted from the first sentence, and the second sentence should read: "(Below) Same view taken through a cylindrical lens . . ." Two errors occurred in the report by Freeman and Thibos in the same issue, p. 876: in column 2, line 4, "Freeman and co-workers" should be changed to "Freeman et al." in column 3, line 44, "the visual resolution" should be changed to "visual resolution"-Ed.     

Erratum

The caption for figure 1 (p. 1497) of the report "Transformation by v-sis occurs by an internal autoactivation mechanism" by B. E. Bejcek et al. (29 Sept., p. 1496) was inadvertently not printed. The caption should have read, "Fig. 1. (A) Plasmid pSEB3 (B) Mutations used."     

Clarification

In the cover caption for the issue of 6 September (p. 1069), the magnification for the image of the mite Proctlaelaps regalis was approximately 400 times its actual body size (actual length was about 500 micrometers).     

Erratum

The color photograph accompanying a ScienceScope item on computational mechanics (18 Oct., p. 365) should have been credited to the San Diego Supercomputing Center. The photograph is a graphic rendering of the brain and not a simulation of Alzheimer's disease, as the caption suggested.     

Changes in Atmospheric Circulation and Ocean Ice Cover over the North Atlantic During the Last 41,000 Years

High-resolution, continuous multivariate chemical records from a central Greenland ice core provide a sensitive measure of climate change and chemical composition of the atmosphere over the last 41,000 years. These chemical series reveal a record of change in the relative size and intensity of the circulation system that transported air masses to Greenland [defined here as the polar circulation index (PCI)] and in the extent of ocean ice cover. Massive iceberg discharge events previously defined from the marine record are correlated with notable expansions of ocean ice cover and increases in PCI. During stadials without discharge events, ocean ice cover appears to reach some common maximum level. The massive aerosol loadings and dramatic variations in ocean ice cover documented in ice cores should be included in climate modeling.     

Erratum

The first sentence of the caption for the figure on page 525 accompanying Marcia Barinaga's Research News artide "Neuroscience models the brain" (2 Feb., p. 524) should have read, "Computer simulation by Kenneth D. Miller models formation of ocular dominance columns." The photo credit fbr the figure should have been to Kenneth D. Miller.     

A high phase-space-density gas of polar molecules

A quantum gas of ultracold polar molecules, with long-range and anisotropic interactions, not only would enable explorations of a large class of many-body physics phenomena but also could be used for quantum information processing. We report on the creation of an ultracold dense gas of potassium-rubidium (40K87Rb) polar molecules. Using a single step of STIRAP (stimulated Raman adiabatic passage) with two-frequency laser irradiation, we coherently transfer extremely weakly bound KRb molecules to the rovibrational ground state of either the triplet or the singlet electronic ground molecular potential. The polar molecular gas has a peak density of 10(12) per cubic centimeter and an expansion-determined translational temperature of 350 nanokelvin. The polar molecules have a permanent electric dipole moment, which we measure with Stark spectroscopy to be 0.052(2) Debye (1 Debye = 3.336 x 10(-30) coulomb-meters) for the triplet rovibrational ground state and 0.566(17) Debye for the singlet rovibrational ground state.     

Corrections and clarifications

The caption accompanying the News article by Steve Sternberg "The emerging fungal threat" (9 Dec., p. 1632) should not have included the words "in the body." Candida albicans produces hyphae, but not chlamydospores, in the body.     

Divalent metal nanoparticles

Nanoparticles can be used as the building blocks for materials such as supracrystals or ionic liquids. However, they lack the ability to bond along specific directions as atoms and molecules do. We report a simple method to place target molecules specifically at two diametrically opposed positions in the molecular coating of metal nanoparticles. The approach is based on the functionalization of the polar singularities that must form when a curved surface is coated with ordered monolayers, such as a phase-separated mixture of ligands. The molecules placed at these polar defects have been used as chemical handles to form nanoparticle chains that in turn can generate self-standing films.     

Polar orientation of dyes in robust multilayers by zirconium phosphate-phosphonate interlayers

Polar orientation of molecules in solids leads to materials with potentially useful properties such as nonlinear optical and electrooptical activity, electrochromism, and pyroelectricity. A simple self-assembly procedure for preparing such materials is introduced that yields multiple polar dye monolayers on solid surfaces joined by zirconium phosphate-phosphonate interlayers. Second harmonic generation (SHG) shows that the multilayers have polar order that does not decrease with increasing numbers (up to a large number) of monolayers in the film. The inorganic interlayers, as determined by SHG, impart excellent orientational stability to the dye molecules, with the onset of orientational randomization above 150 degrees C.     

Erratum

The caption for the photograph accompanying the review of Neurobiology of Arachnids (28 Mar., p. 1610) should have read, "Peocilotheria regalis, an Indian bird-spider. Beneath it is a spike train recorded from a sensory neuron responding to mechanical stimuli in the spider Cupiennius salei."     

Erratum

In the article by R. Hekinian et al. (28 Mar., p. 1433), in line 3 of the caption for Fig. 7 (p. 1440), "Fe-rich clay-like material" should have read "Fe-bearing opaline material."     

Corrections and clarifications

The title of the Perspective by Christopher Miller in the issue of 24 September (p. 1692) was printed incorrectly. It should have read, "Potassium selectivity in proteins: Oxygen cage or pi in the face?" In the figure caption on the same page, "-electron" was printed incorrectly instead of "pi-electron."     

Erratum

In equation 6 of the Research Article "Effects of age on dopamine and seratonin receptors measured by positron tomography in the living human brain" by D. F. Wong et al. (21 Dec., p. 1393) C(p)(t) in the denominator of the last term should have been A(cb)(t). This does not affect the rest of the derivation. In the caption of figure 1, the first word, "Decrease," should have been "Change." The data in parts A and B of figure 3 should have been regraphed on common axes to facilitate comparison. A corrected figure 3 is shown below.     

Erratum

In line 7 of the caption for table 1 (p. 1682) of the report "Association of transfer RNA acceptor identity with a helical irregularity" by William H. McClain et al. (23 Dec., p. 1679), ">/=20%" should have been "相似文献   

Erratum

In the report "Malaria parasites adopt host cell superoxide dismutase" by A. S. Fairchild et al. (19 Aug., p. 764), the caption for figure 2 on page 765 was incorrect and should read as follows: "Comparison of host and parasite SOD's (9) by (A) polyacrylamide gel electrophoresis (8) and (B) isoelecteric focusing (7). Gels were stained for SOD activity (10), and bovine erythrocyte SOD (Sigma, type 1) was used as a reference [pI = 4.95 (13)]. Lane 1, rat-derived P. berghei SOD; lane 2, rat erythrocyte SOD (pI = 5.1); lane 3, mouse-derived P. berghei SOD; lane 4, mouse erythrocyte SOD (pl = 5.7); lane 5, bovine erythrocyte SOD." The pI's of mouse and rat erythrocyte SOD's cited in the text should also be corrected to the values given above.     

Observations of Stratospheric NO2 and O3 at Thule, Greenland

Scattered sunlight and direct light from the moon was used in two wavelength ranges to measure the total column abundances of stratospheric ozone(O(3)) and nitrogen dioxide (NO(2)) at Thule, Greenland (76.5 degrees N), during the period from 29 January to 16 February 1988. The observed O(3) column varied between about 325 and 400 Dobson units, and the lower values were observed when the center of the Arctic polar vortex was closest to Thule. This gradient probably indicates that O(3) levels decrease due to dynamical processes near the center of the Arctic vortex and should be considered in attempts to derive trends in O(3) levels. The observed NO(2) levels were also lowest in the center of the Arctic vortex and were sometimes as low as 5 x 10(14) molecules per square centimeter, which is even less than comparable values measured during Antarctic spring, suggesting that significant heterogeneous photochemistry takes place during the Arctic winter as it does in the Antarctic.