Resumption of mass accretion in RS Oph

The latest outburst of the recurrent nova RS Oph occurred in 2006 February. Photometric data presented here show evidence of the resumption of optical flickering, indicating re-establishment of accretion by day 241 of the outburst. Magnitude variations of up to 0.32 mag in V band and 0.14 mag in B band on time-scales of 600–7000 s are detected. Over the two-week observational period, we also detect a 0.5 mag decline in the mean brightness, from V≈ 11.4 to 11.9, and record B≈ 12.9 mag. Limits on the mass accretion rate of [inline image] are calculated, which span the range of accretion rates modelled for direct wind accretion and Roche lobe overflow mechanisms. The current accretion rates make it difficult for thermonuclear runaway models to explain the observed recurrence interval, and this implies average accretion rates are typically higher than seen immediately post-outburst

Streamflow and velocity as determinants of aquatic insect distribution and benthic community structure in Illinois

Stream flow characteristics, in particular velocity and depth, control channel substrates and directly or indirectly determine how aquatic insects are distributed and benthic communities are structured. A three year laboratory and field research program has been completed evaluating how streamflow affects aquatic insects in Illinois. Field studies related benthic community structure and species composition with boundary layer Reynolds number (R*) and evaluated microhabitat selection of several insect species on hydraulically defined artificial substrates. Hydraulic calibration of substrates was completed in laboratory flume studies using a thermistor based microprobe. A laboratory artificial stream was also used to determine habitat selection of net spinning caddisflies. Results indicated selection for defined microhabitats in several aquatic insect taxa. The artificial substrates proved to be a valuable tool in defining microhabitat characteristics occupied by aquatic insects. In studies to determine instream flow requirements, measures of mean column velocity were shown to be inadequate, determination of R* was preferred. The results of this research provide water resources managers with better tools to assess microhabitat modifications produced by changes in streamflow.U.S. Department of the InteriorU.S. Geological SurveyOpe

Control elements for an unmanned Martian roving vehicle Annual Progress report, 1 Jul. 1969 - 30 Jun. 1970

Design of control equipment for unmanned Martian roving vehicl

Fate of Captive-Reared and Released Mallards on Eastern Long Island, New York

We studied captive-reared mallards (Anas platyrhynchos; CRMs) released on eastern Long Island, New York, in 2006 to 2007 and 2007 to 2008 to determine: (1) survival rates of CRMs; (2) contribution to hunter harvest; (3) local movements; and (4) pair status, reproductive behavior, and production of CRMs. We banded and released 100 CRMs in November 2006 of which 20 were radio-marked. In November 2007, we banded and released 299 CRMs of which 60 were radio-marked. We used Program MARK to determine weekly survival estimates (0.53 to 1.00) up to 24 weeks after release; cumulative survival from November to May was 0.25. Seventeen percent (n = 17) of CRMs were reported harvested from 2006 to 2007, and 5% (n = 15) were reported harvested during 2007 to 2008. The median distance between harvest locations and release sites in both years was 3 km. CRMs intermingled with free-ranging waterfowl at town parks but tended to stay together in groups of 10 to 30 birds. We observed 22 pairs of CRMs, 2 pairs of CRMs with unmarked mallards, and 1 CRM with a brood. Overall, our data indicated that after some initial losses, many CRMs survived and settled in park settings where waterfowl were commonly fed by humans. Thus, CRMs appeared to contribute to feral waterfowl populations, which are a source of human–wildlife conflicts in many areas. Occurrence of CRMs in such settings also provides a means for disease transmission to free-ranging waterfowl