Compression of Ice to 210 Gigapascals: Infrared Evidence for a Symmetric Hydrogen-Bonded Phase     

AF Goncharov  VV Struzhkin  MS Somayazulu  RJ Hemley  HK Mao 《Science (New York, N.Y.)》1996,273(5272):218-220

Protonated and deuterated ices (H2O and D2O) compressed to a maximum pressure of 210 gigapascals at 85 to 300 kelvin exhibit a phase transition at 60 gigapascals in H2O ice (70 gigapascals in D2O ice) on the basis of their infrared reflectance spectra determined with synchrotron radiation. The transition is characterized by soft-mode behavior of the nu3 O-H or O-D stretch below the transition, followed by a hardening (positive pressure shift) above it. This behavior is interpreted as the transformation of ice phase VII to a structure with symmetric hydrogen bonds. The spectroscopic features of the phase persisted to the maximum pressures (210 gigapascals) of the measurements, although changes in vibrational mode coupling were observed at 150 to 160 gigapascals.  相似文献   

Smart engineering in the mid-carboniferous: how well could palaeozoic dragonflies Fly?     

RJ Wootton  J Kukalova-Peck  DJS Newman  J Muzon 《Science (New York, N.Y.)》1998,282(5389):749-751

The wings of archaic Odonatoidea from the mid-Carboniferous of Argentina show features analogous to "smart" mechanisms in modern dragonflies that are associated with the agile, versatile flight necessary to catch prey in flight. These mechanisms act automatically in flight to depress the trailing edge and to facilitate wing twisting, in response to aerodynamic loading. The presence of similar features suggests that the earliest known odonatoids were already becoming adapted for high-performance flight in association with a predatory habit.  相似文献   

Scanning Single-Electron Transistor Microscopy: Imaging Individual Charges     

MJ Yoo  TA Fulton  HF Hess  RL Willett  LN Dunkleberger  RJ Chichester  LN Pfeiffer  KW West 《Science (New York, N.Y.)》1997,276(5312):579-582

A single-electron transistor scanning electrometer (SETSE)-a scanned probe microscope capable of mapping static electric fields and charges with 100-nanometer spatial resolution and a charge sensitivity of a small fraction of an electron-has been developed. The active sensing element of the SETSE, a single-electron transistor fabricated at the end of a sharp glass tip, is scanned in close proximity across the sample surface. Images of the surface electric fields of a GaAs/AlxGa1-xAs heterostructure sample show individual photo-ionized charge sites and fluctuations in the dopant and surface-charge distribution on a length scale of 100 nanometers. The SETSE has been used to image and measure depleted regions, local capacitance, band bending, and contact potentials at submicrometer length scales on the surface of this semiconductor sample.  相似文献   

The susceptibility of agricultural grasses to pre-emergence damage caused by Fusarium culmorum and its control by fungicidal seed treatment     

S. J. I. HOLMES 《Grass and Forage Science》1983,38(3):209-214

A total of 104 cultivars of six agricultural grass species were compared under controlled conditions for their relative susceptibility to the common soil-borne fungus Fusarium culmorum (W.G.Sm.) Sacc. A number of the perennial ryegrass ( Lolium perenne ) cultivars showed a high degree of resistance, their emergence being little reduced under the stringent test conditions. The emergence of others was, however, severely affected. Italian ryegrass ( L. multiflorum ) cultivars generally had a high level of resistance, the outstanding exception being cv. Leda Daehnfeldt which proved very sensitive. None of the cultivars of cocksfoot ( Dactylis glomerata ), timothy ( Phleum pratense ), meadow fescue ( Festuca pratensis ) or tall fescue ( F. arundinaceae ) which were tested had more than a moderate level of resistance and most were highly susceptible.
The vigour of ryegrass seedlings was, in most cases, closely correlated with percentage emergence but was less closely correlated in the more susceptible species. These often had a very low emergence but those seedlings which did establish were frequently of a size similar to that of healthy plants.
Treatment of grass seed with a fungicide mixture of benomyl (15% a.i.) plus captan (60% a.i.) provided excellent protection against F. culmorum on even the most susceptible cultivars.
Drazoxolon (40% a.i.) was, however, much less effective.  相似文献   

Prevalence of exon 11 internal tandem duplications in the C‐KIT proto‐oncogene in Australian canine mast cell tumours          下载免费PDF全文

VS Tamlin  AE Kessell  RJ Mccoy  EC Dobson  TS Smith  M Hebart  L Brown  D Mitrovic  AE Peaston 《Australian veterinary journal》2017,95(10):386-391

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Nonsurgical management of type II fractures of the distal phalanx in 48 Standardbred horses     

CB O''SULLIVAN  AJ DART  N MALIKIDES  RJ RAWLINSON  DR HUTCHINS  DR HODGSON 《Australian veterinary journal》1999,77(8):501-503

OBJECTIVE: To evaluate nonsurgical management of type II fractures of the distal phalanx in Standardbred horses. DESIGN: Retrospective study of 48 affected horses. RESULTS: Most fractures occurred on the lateral palmar process of the left forelimb or the medial palmar process of the right forelimb; 81% of horses were considered sound enough to return to training and 63% raced. Of those returning to racing, 41% competed in > 10 races, 37% in 2 to 10 races and 22% in only 1 race. There was no difference in performance before and after fracture. Twenty-four of 25 horses had a bar shoe fitted for > 50% of the treatment phase. Of those horses returning to training without a bar shoe, 89% refractured at the same site. Sixty percent of horses returning to training with a bar shoe raced successfully. The total convalescent time, the time rested in a box and the time spelled in a paddock were similar for horses returning to racing and those that did not. The age of the horse had no effect on the ability to return to racing. CONCLUSION: The prognosis for type II fractures of the distal phalanx is guarded. It is advisable to fit a bar shoe on the horse during convalescence. Horses returning to training and racing with a bar shoe appear less likely to refracture the distal phalanx. Those horses that return to racing can perform at a level similar to that prior to fracture.  相似文献   

Distribution of thiobacillus ferrooxidans and leptospirillum ferrooxidans: implications for generation of acid mine drainage   总被引：1，自引：0，他引：1  

MO Schrenk  KJ Edwards  RM Goodman  RJ Hamers  JF Banfield 《Science (New York, N.Y.)》1998,279(5356):1519-1522

Although Thiobacillus ferrooxidans and Leptospirillum ferrooxidans are widely considered to be the microorganisms that control the rate of generation of acid mine drainage, little is known about their natural distribution and abundance. Fluorescence in situ hybridization studies showed that at Iron Mountain, California, T. ferrooxidans occurs in peripheral slime-based communities (at pH over 1.3 and temperature under 30 degreesC) but not in important subsurface acid-forming environments (pH 0.3 to 0.7, temperature 30 degrees to 50 degreesC). Leptospirillum ferrooxidans is abundant in slimes and as a planktonic organism in environments with lower pH. Thiobacillus ferrooxidans affects the precipitation of ferric iron solids but plays a limited role in acid generation, and neither species controls direct catalysis at low pH at this site.  相似文献   

Design and fabrication of topologically complex, three-dimensional microstructures     

RJ Jackman  ST Brittain  A Adams  MG Prentiss  GM Whitesides 《Science (New York, N.Y.)》1998,280(5372):2089-2091

Two concepts for use in the fabrication of three-dimensional (3D) microstructures with complex topologies are described. Both routes begin with a two-dimensional (2D) pattern and transform it into a 3D microstructure. The concepts are illustrated by use of soft lithographic techniques to transfer 2D patterns to cylindrical (pseudo-3D) substrates. Subsequent steps-application of uniaxial strain, connection of patterns on intersecting surfaces-transform these patterns into free-standing, 3D, noncylindrically symmetrical microstructures. Microelectrodeposition provides an additive method that strengthens thin metal designs produced by patterning, welds nonconnected structures, and enables the high-strain deformations required in one method to be carried out successfully.  相似文献   

Supplementary feeding of grazing beef cattle     

J. VADIVELOO  W. HOLMES 《Grass and Forage Science》1979,34(3):173-179

The effects of cereal and protein supplements on feed intake and liveweight gain were studied. In 1975, steers were continuously stocked on autumn pasture and fed no supplement or 8 g dry matter (DM) per kg liveweight (LW) per d as rolled barley (crude protein (CP) concentration 120 g kg^-1), lucerne cobs (CP concentration 190 g kg^-1) or a mixed concentrate (CP concentration 300 g kg^-1). In 1976, steers were continuously stocked or rotationally grazed in summer and fed no supplement or 7 g DM per kg LW per d as either rolled barley (CP concentration 130 g kg^-1) or a mixture of rolled barley and groundnut meal (CP concentration 210 g kg^-1). Herbage organic matter (OM) intakes in 1975 and 1976 were depressed on average by 22 and 15% respectively with supplementation, but total OM intakes were increased by 9 and 15% respectively. Daily liveweight gain was not significantly increased by supplementation in 1975 when herbage allowance was ample but was significantly increased in 1976 when herbage allowance was limited and herbage digestibility was lower. Protein concentration of the concentrate did not significantly affect daily gain in either year nor was there any difference in gain between rotational grazing and continuous stocking.  相似文献