Detrimental adsorbate fields in experiments with cold Rydberg gases near surfaces

We observe the shift of Rydberg levels of rubidium close to a copper surface when atomic clouds are repeatedly deposited on it. We measure transition frequencies of rubidium to S and D Rydberg states with principal quantum numbers n between 31 and 48 using the technique of electromagnetically induced transparency. The spectroscopic measurement shows a strong increase of electric fields towards the surface that evolves with the deposition of atoms. Starting with a clean surface, we measure the evolution of electrostatic fields in the range between 30 and 300 \mum from the surface. We find that after the deposition of a few hundred atomic clouds, each containing ~10^6 atoms, the field of adsorbates reaches 1 V/cm for a distance of 30 \mum from the surface. This evolution of the electrostatic field sets serious limitations on cavity QED experiments proposed for Rydberg atoms on atom chips.Comment: 4 pages, 3 figures Submitted to Phys. Rev.

Hydrographic and Acoustic Doppler Current Profiler (ADCP) data from the ONR Eastern Boundary Current Accelerated Research Iniative - June 9-16, 1992

This data report presents hydrographic (CTD) and Acoustic Doppler Current Profiler (ADCP) data from a cruise to the continental slope region near Point Arena, California during 9-16 June 1992. The study area encompassed a region from about 38 deg 0.0' N. to 39 deg 0.0' N. from 20 to 90 km offshore. The sampling grid consisted of five along-shore transects 15 km apart, with five CTD stations 15 km apart in each transect. A total of 28 CTD casts were made. ADCP data were collected throughout the cruise. The data are presented as vertical sections, property distributions on horizontal surfaces, and waterfall plots. Eastern boundary current, CTD Data, Hydrographic data, ADCP Data, Coastal eddiesThis data report presents hydrographic (CTD) and Acoustic Doppler Current Profiler (ADCP) data from a cruise to the continental slope region near Point Arena, California during 9-16 June 1992. The study area encompassed a region from about 38 deg 0.0' N. to 39 deg 0.0' N. from 20 to 90 km offshore. The sampling grid consisted of five along-shore transects 15 km apart, with five CTD stations 15 km apart in each transect. A total of 28 CTD casts were made. ADCP data were collected throughout the cruise. The data are presented as vertical sections, property distributions on horizontal surfaces, and waterfall plots.http://archive.org/details/hydrographicacou59jessApproved for public release; distribution is unlimited

Relation between TMAOase activity and content of formaldehyde in fillet minces and bellyflap minces from gadoid fishes

Minced fish is a significant component of a number of frozen fishery products like fish fingers, cakes and patties. Predominately minced fish is produced from gadoid species (Alaska pollack, cod, saithe, hake and others) possessing the enzyme trimethylamine oxide demethylase (TMAOase, E.C. 4.1.2.32) (Rehbein and Schreiber 1984). TMAOase catalyses the degradation of trimethylamine oxide (TMAO) to formaldehyde (FA) and dimethylamine (DMA), preferentially during frozen storage of products (Hultin 1992). In most gadoid species light muscle contains only low activity of TMAOase, the activity of red muscle and bellyflaps being somewhat higher. In contrast, the TMAOase activity in blood, kidney and other tissues, residues of which may contaminate minced fish flesh, may be higher for several orders of magnitude (Rehbein and Schreiber 1984)

The structural and functional integrity of peripheral nerves depends on the glial-derived signal desert hedgehog

We show that desert hedgehog ( dhh), a signaling molecule expressed by Schwann cells, is essential for the structural and functional integrity of the peripheral nerve. Dhh-null nerves display multiple abnormalities that affect myelinating and nonmyelinating Schwann cells, axons, and vasculature and immune cells. Myelinated fibers of these mice have a significantly increased ( more than two times) number of Schmidt-Lanterman incisures ( SLIs), and connexin 29, a molecular component of SLIs, is strongly upregulated. Crossing dhh-null mice with myelin basic protein ( MBP)-deficient shiverer mice, which also have increased SLI numbers, results in further increased SLIs, suggesting that Dhh and MBP control SLIs by different mechanisms. Unmyelinated fibers are also affected, containing many fewer axons per Schwann cell in transverse profiles, whereas the total number of unmyelinated axons is reduced by approximately one-third. In dhh-null mice, the blood-nerve barrier is permeable and neutrophils and macrophage numbers are elevated, even in uninjured nerves. Dhh-null nerves also lack the largest-diameter myelinated fibers, have elevated numbers of degenerating myelinated axons, and contain regenerating fibers. Transected dhh nerves degenerate faster than wild-type controls. This demonstrates that a single identified glial signal, Dhh, plays a critical role in controlling the integrity of peripheral nervous tissue, in line with its critical role in nerve sheath development ( Parmantier et al., 1999). The complexity of the defects raises a number of important questions about the Dhh-dependent cell-cell signaling network in peripheral nerves

Million years of Greenland Ice Sheet history recorded in ocean sediments

Geological records from Tertiary and Quaternary terrestrial and oceanic sections have documented the presence of ice caps and sea ice covers both in the Southern and the Northern hemispheres since Eocene times, approximately since 45 Ma. In this paper focussing on Greenland we mainly use the occurrences of coarse ice-rafted debris (IRD) in Quaternary and Tertiary ocean sediment cores to conclude on age and origin of the glaciers/ice sheets, which once produced the icebergs transporting this material into the adjacent ocean. Deep-sea sediment cores with their records of ice-rafting from off NE Greenland, Fram Strait and to the south of Greenland suggest the more or less continuous existence of the Greenland ice sheet since 18 Ma, maybe much longer, and hence far beyond the stratigraphic extent of the Greenland ice cores. The timing of onset of glaciation on Greenland and whether it has been glaciated continuously since, are wide open questions of its long-term history. We also urgently need new scientific drilling programs in the waters around Greenland, in particular in the segment of the Arctic Ocean to the north of Greenland

Math Pathways Reforms in Maine

This study of the math pathways movement is designed as a mini-case study to document the status of the reform in progress

Bottom waters of the Gulf of Maine, 1978-1983

The properties of the bottom waters (\u3e100 m) of the Gulf of Maine are described using hydrographic data from 26 surveys between May 1978 and December 1983. The average temperature and salinity of the bottom water are presented from the different surveys for four regions of the Gulf—Wilkinson, Jordan, and Georges Basins and the Northeast Channel. The spatial variability across the Gulf was larger than the temporal variability in any region. The bottom water originates from Slope Water that enters the Gulf through the Northeast Channel. It is modified within the Gulf by vertical mixing with the near-surface waters of Scotian Shelf origin. A box model for the property changes during the summer-fall period indicates that the advection and mixing processes are of approximately equal importance in determining the bottom water properties. A winter convective input to the bottom layers is shown to occur only from the coastal areas around Wilkinson Basin in years when the surface salinity there was relatively high (\u3e33.0‰). Advection and mixing rates calculated by the box model are in agreement with direct measurements of the inflow to the Gulf (Ramp et al., 1985) and mixing estimates from a budget for the intermediate layer waters in the Gulf (Hopkins and Garfield, 1979)

Math Pathways Reforms in Maine

For the past several years, attention has turned toward reviewing and reframing the curricular pathways in math for students, particularly at the postsecondary level. Focus has shifted not only to math preparedness, but also to redefining the curricular pathways that lead to academic and career success. In higher education, the central principle involves redefining and reorganizing coursework around defined pathways, based on academic and career interests of students. For K-12 institutions, the math pathways reforms have less clear implications. One key organization working in this area--both nationally and in Maine--is the Dana Center at the University of Texas at Austin. The Dana Center has been partnering with the Maine Community College System (MCCS) for several years now, and has supported their progress toward implementing math pathways reforms. For this project, Maine Education Policy Research Institute (MEPRI) researchers in the Center for Education Policy, Applied Research, and Evaluation (CEPARE) were asked to describe and summarize the mathematics pathways movement which is currently underway in the state of Maine, as well as in other states across the country. This study of the math pathways movement is designed as a mini-case study to document the status of the reform in progress. Findings review math pathways as a potential means of promoting individualized student learning and career readiness, of clarifying math expectations, and of reducing the need for remedial coursework at the post-secondary level. The successes of and challenges facing individual institutions--from MCCS, to the state universities, to K-12 institutions--are also reviewed. Other challenges, including mitigating issues with tracking and ownership of the reforms, are discussed. The report concludes with recommendations for policymakers

Measurement of absolute transition frequencies of 87Rb to nS and nD Rydberg states by means of electromagnetically induced transparency

We report the measurement of absolute excitation frequencies of 87Rb to nS and nD Rydberg states. The Rydberg transition frequencies are obtained by observing electromagnetically induced transparency on a rubidium vapor cell. The accuracy of the measurement of each state is < 1 MHz, which is achieved by frequency stabilizing the two diode lasers employed for the spectroscopy to a frequency comb and a frequency comb calibrated wavelength meter, respectively. Based on the spectroscopic data we determine the quantum defects of 87Rb, and compare it with previous measurements on 85Rb. We determine the ionization frequency from the 5S1/2(F=1) ground state of 87Rb to 1010.0291646(3) THz, providing the binding energy of the ground state with an accuracy improved by two orders of magnitude

Effect of finite detection efficiency on the observation of the dipole-dipole interaction of a few Rydberg atoms

We have developed a simple analytical model describing multi-atom signals that are measured in experiments on dipole-dipole interaction at resonant collisions of a few Rydberg atoms. It has been shown that finite efficiency of the selective field-ionization detector leads to the mixing up of the spectra of resonant collisions registered for various numbers of Rydberg atoms. The formulas which help to estimate an appropriate mean Rydberg atom number for a given detection efficiency are presented. We have found that a measurement of the relation between the amplitudes of collisional resonances observed in the one- and two-atom signals provides a straightforward determination of the absolute detection efficiency and mean Rydberg atom number. We also performed a testing experiment on resonant collisions in a small excitation volume of a sodium atomic beam. The resonances observed for 1 to 4 detected Rydberg atoms have been analyzed and compared with theory.Comment: 10 pages, 4 figures; equations 8,9,18,19,23,26-31, figures 3 and 4(d), and measurements revised in version