16,476 research outputs found
Distinguishing coherent atomic processes using wave mixing
We are able to clearly distinguish the processes responsible for enhanced
low-intensity atomic Kerr nonlinearity, namely coherent population trapping and
coherent population oscillations in experiments performed on the Rb D1 line,
where one or the other process dominates under appropriate conditions. The
potential of this new approach based on wave mixing for probing coherent atomic
media is discussed. It allows the new spectral components to be detected with
sub-kHz resolution, which is well below the laser linewidth limit. Spatial
selectivity and enhanced sensitivity make this method useful for testing dilute
cold atomic samples.Comment: 9 pages, 5 figure
Near-Infrared Observations of the Environments of Radio Quiet QSOs at z >~ 1
We present the results of an infrared survey of QSO fields at z=0.95, 0.995
and 1.5. Each z<1 field was imaged to typical continuum limits of J=20.5,
Kprime=19 (5 sigma), and line fluxes of 1.3E10{-16}ergs/cm^2/s (1 sigma)in a 1%
interference filter. 16 fields were chosen with z~0.95 targets, 14 with z~0.995
and 6 with z~1.5. A total area of 0.05 square degrees was surveyed, and two
emission-line objects were found. We present the infrared and optical
photometry of these objects. Optical spectroscopy has confirmed the redshift of
one object (at z=0.989) and is consistent with the other object having a
similar redshift. We discuss the density of such objects across a range of
redshifts from this survey and others in the literature. We also present
number-magnitude counts for galaxies in the fields of radio quiet QSOs,
supporting the interpretation that they exist in lower density environments
than their radio loud counterparts. The J-band number counts are among the
first to be published in the J=16--20.Comment: 34 pages, including 12 figures; accepted for publication in the Ap
Peace Through Prayer
As far back as he could remember he had been afraid of storms. Back there in the early years, some member of the family had set the pace of fear when a storm came. There was an old belief - probably a superstition - that if one sat on a feather bed, lightning wouldn\u27t strike. Anyway, there was a general migration to the bedrooms during a storm. Mother became nervous if the storm was severe, and sister would have a fit of trembling. Brother made a vain show of bravery, which only intensified the uneasiness. All through his seventeen years the boy had had a dread of storms. Perhaps the psychologists would say it was conditioned by those early experiences.
So that night he lay huddled among the covers, as the storm raged. The room was dungeon-black, lighted only by the vivid flashes of lightning. All other sound was swallowed up in the crash and rumble of the thunder. He could feel the house shake as the wind dashed against it, seemingly in a mad effort to tear it apart. The rain beat against the window pane in a solid phalanx. And he was scared a pointless, unreasoning, foolish fear
The Case of the Pearl Necklace
I had been teaching a class in psychology at Turner College for four years, when an incident occurred that threatened to bring the taint of scandal on the whole school. A member of one of the sororities reported the loss of a valuable pearl necklace, which, she thought, had been stolen during the dinner hour. The college officials made every attempt to discover the thief with little success. Suspicion\u27s finger pointed to a young man by the name of Henry Stewart, but there was no tangible evidence upon which to make an accusation. Then Dr. Klinger, the president, asked me to see what I could do.. He urged me to prevent the matter from getting into the newspapers
The well-coordinated linkage between acidogenicity and aciduricity via insoluble glucans on the surface of Streptococcus mutans.
Streptococcus mutans is considered the principal cariogenic bacterium for dental caries. Despite the recognition of their importance for cariogenesis, the possible coordination among S. mutans' main virulence factors, including glucan production, acidogenicity and aciduricity, has been less well studied. In the present study, using S. mutans strains with surface-displayed pH-sensitive pHluorin, we revealed sucrose availability- and Gtf functionality-dependent proton accumulation on S. mutans surface. Consistent with this, using a pH-sensitive dye, we demonstrated that both in vivo cell-produced and in vitro enzymatically synthesized insoluble glucans displayed proton-concentrating ability. Global transcriptomics revealed proton accumulation triggers the up-regulation of genes encoding functions involved in acid tolerance response in a glucan-dependent manner. Our data suggested that this proton enrichment around S. mutans could pre-condition the bacterium for acid-stress. Consistent with this hypothesis, we found S. mutans strains defective in glucan production were more acid sensitive. Our study revealed for the first time that insoluble glucans is likely an essential factor linking acidogenicity with aciduricity. The coordination of these key virulence factors could provide new insights on how S. mutans may have become a major cariogenic pathogen
An expert system for scheduling requests for communications Links between TDRSS and ERBS
An ERBS-TDRSS Contact Planning System (ERBS-TDRSS CPS) is described which uses a graphics interface and the NASA Transportable Interference Engine. The procedure involves transfer of the ERBS-TDRSS Ground Track Orbit Prediction data to the ERBS flight operations area, where the ERBS-TDRSS CPS automatically generates requests for TDRSS service. As requested events are rejected, alternative context sensitive strategies are employed to generate new requested events until a schedule is completed. A report generator builds schedule requests for separate ERBS-TDRSS contacts
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