Quantifying Transport Between the Tropical and Mid-Latitude Lower Stratosphere     

CM Volk  JW Elkins  DW Fahey  RJ Salawitch  GS Dutton  JM Gilligan  MH Proffitt  M Loewenstein  JR Podolske  K Minschwaner  JJ Margitan  KR Chan 《Science (New York, N.Y.)》1996,272(5269):1763-1768

Airborne in situ observations of molecules with a wide range of lifetimes (methane, nitrous oxide, reactive nitrogen, ozone, chlorinated halocarbons, and halon-1211), used in a tropical tracer model, show that mid-latitude air is entrained into the tropical lower stratosphere within about 13.5 months; transport is faster in the reverse direction. Because exchange with the tropics is slower than global photochemical models generally assume, ozone at mid-latitudes appears to be more sensitive to elevated levels of industrial chlorine than is currently predicted. Nevertheless, about 45 percent of air in the tropical ascent region at 21 kilometers is of mid-latitude origin, implying that emissions from supersonic aircraft could reach the middle stratosphere.  相似文献   

Coupled 186Os and 187Os evidence for core-mantle interaction     

AD Brandon  RJ Walker  JW Morgan  MD Norman  HM Prichard 《Science (New York, N.Y.)》1998,280(5369):1570-1573

Osmium isotopic analyses of picritic lavas from Hawaii show enrichments in the osmium-186/osmium-188 ratio (186Os/188Os) of 0. 008 to 0.018%, relative to a chondritic upper mantle, that are positively correlated with enrichments in 187Os/188Os of 5.4 to 9.0%. The most viable mechanism to produce these coupled 186Os and 187Os enrichments is by addition of 0.5 to 1 weight percent of outer core metal to a portion of the D" layer and subsequent upwelling of the mixture. These data suggest that some plumes originate at the core-mantle boundary and that Os isotopes may be used to distinguish plumes derived from shallow versus deep mantle sources.  相似文献   

A Magnetic Signature at Io: Initial Report from the Galileo Magnetometer   总被引：1，自引：0，他引：1  

MG Kivelson  KK Khurana  RJ Walker  CT Russell  JA Linker  DJ Southwood  C Polanskey 《Science (New York, N.Y.)》1996,273(5273):337-340

During the inbound pass of the Galileo spacecraft, the magnetometer acquired 1 minute averaged measurements of the magnetic field along the trajectory as the spacecraft flew by Io. A field decrease, of nearly 40 percent of the background jovian field at closest approach to Io, was recorded. Plasma sources alone appear incapable of generating perturbations as large as those observed and an induced source for the observed moment implies an amount of free iron in the mantle much greater than expected. On the other hand, an intrinsic magnetic field of amplitude consistent with dynamo action at Io would explain the observations. It seems plausible that Io, like Earth and Mercury, is a magnetized solid planet.  相似文献   

Multivariable dependence of Fe-Mg partitioning in the lower mantle     

H Mao  G Shen  RJ Hemley 《Science (New York, N.Y.)》1997,278(5346):2098-2100

High-pressure diamond-cell experiments indicate that the iron-magnesium partitioning between (Fe,Mg)SiO3-perovskite and magnesiowustite in Earth's lower mantle depends on the pressure, temperature, bulk iron/magnesium ratio, and ferric iron content. The perovskite stability field expands with increasing pressure and temperature. The ferric iron component preferentially dissolves in perovskite and raises the apparent total iron content but had little effect on the partitioning of the ferrous iron. The ferrous iron depletes in perovskite at the top of the lower mantle and gradually increases at greater depth. These changes in iron-magnesium composition should affect geochemical and geophysical properties of the deep interior.  相似文献   

The effects of season, temperature and initial gonad condition on roe enhancement of the sea urchin Evechinus chloroticus     

Philip J. James  Philip Heath  Martin J. Unwin 《Aquaculture (Amsterdam, Netherlands)》2007,270(1-4):115-131

A series of 10-week experiments were repeated during the austral autumn, winter, spring and summer to investigate the seasonal effects, independent of seasonal temperature variation, on roe development (enhancement) of Evechinus chloroticus over a 12-month period and whether this differed among urchins with different initial gonad index (GI) values. E. chloroticus collected from wild populations with high and low initial GI values were caught and held in either ambient or constant ( 14.7 °C) seawater temperatures. The study has shown that, given a suitable roe enhancement diet, it is possible to significantly increase the GI of urchins throughout the year and that a seasonal effect on both the final GI and increase in GI, is primarily caused by seasonal variation in temperature. There are also significant effects from other factors, such as the initial condition of the animals prior to the trial and the reproductive stage of the urchins, but these are not as significant as the effects of temperature. The results indicate that it would be possible to increase the productivity of sea urchins by capturing them in cooler water and enhancing them at a site with relatively warmer water. The initial condition (GI) of the urchins plays an important role in gonad production with animals taken in low initial GI condition producing significantly larger increases in GI throughout each of the four seasons, than those with a high initial GI value. The urchins from the two populations developed through the stages of the reproductive cycle at a similar rate despite different final GI values and rates of increase in GI in both the temperature and population treatments, indicating that the differences in gonad production are related to environmental effects rather than the reproductive stage of the urchins. The exception to this occurred in the autumn samples where lower GI values and increase in GI were found during this season compared to in other seasons for the constant temperature treatment.

There is an overabundance of low GI urchins in the coastal waters of New Zealand and these animals are relatively easily found and fished on snorkel compared to high GI animals for which fishing pressure is much higher. It would appear to be more economic to fish and enhance low GI animals in New Zealand due to their relative abundance, ease of access and higher productivity during enhancement.  相似文献   

Surgical removal of a fish hook from the oesophagus of a turtle     

RJ HYLAND 《Australian veterinary journal》2002,80(1):54-56

An adult male Macquarie turtle was presented for examination after swallowing a fish hook. Radiographs taken to determine the position of this foreign body within the gastrointestinal tract revealed the fish hook lodged in the turtle's oesophagus. Surgical removal of the fish hook involved an approach through the soft tissues of the lateral neck. The turtle recovered well and was returned to the wild.  相似文献   

Edwardsietla tarda septicaemia in rainbow trout (Oncorhynchus mykiss)     

GL REDDACLIFF  M. HORNITZKY  RJ WHITTINGTON 《Australian veterinary journal》1996,73(1):30-30

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Suspected traumatic rupture of the urinary bladder in an alpaca     

AL ANDREWS  RJ RAWLINSON  AL RAISIS  DR HODGSON 《Australian veterinary journal》1995,72(2):73-75

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Microbiological evaluation of dressing procedures for crocodile carcases in Queensland     

MW RICKARD  AD THOMAS†  S. BRADLEY‡  J. FORBES-FAULKNER†  RJ MAYER† 《Australian veterinary journal》1995,72(5):172-176

SUMMARY Microbiological testing of crocodiles during the dressing procedure has shown that sanitising the skin before skinning reduces the bacterial count on the skin and that dipping crocodile meat in 1.3% acetic acid solution effectively reduces bacterial levels. The total bacterial count on the processed meat sample was comparable with that obtained in the beef, pork and lamb industries. Salmonellae were isolated from 14 of the 72 carcases. Most (65%) of these isolates were in Salmonella subspecies III, formerly classified as Arizona.  相似文献   

Programs for surveillance and monitoring of antibacterial residues in Australia, 1989 to 1993   总被引：1，自引：0，他引：1  

TJ NICHOLLS  NL BLACKMAN  IB STEPHENS  RJ WILD† 《Australian veterinary journal》1994,71(12):397-399

SUMMARY The development of a State-based confirmatory testing capability for antibiotic residues in meat in Australia has allowed the rapid feedback to producers failing to comply with antibiotic maximum residue limits. The identification of problem areas in various categories of livestock, and subsequent focused surveillance programs, has reduced the prevalence of antibacterial residues in both domestic and export meat products. Failure to observe withholding periods of antibacterial drugs after treatment is the most significant cause of non-compliance. In the period July 1991 to June 1993 the compliance rate for antibacterial residues for all species was 99.9%.  相似文献