Femtosecond dynamics of electron localization at interfaces     

N Ge  CM Wong  RL Lingle  JD McNeill  KJ Gaffney  CB Harris 《Science (New York, N.Y.)》1998,279(5348):202-205

The dynamics of two-dimensional small-polaron formation at ultrathin alkane layers on a silver(111) surface have been studied with femtosecond time- and angle-resolved two-photon photoemission spectroscopy. Optical excitation creates interfacial electrons in quasi-free states for motion parallel to the interface. These initially delocalized electrons self-trap as small polarons in a localized state within a few hundred femtoseconds. The localized electrons then decay back to the metal within picoseconds by tunneling through the adlayer potential barrier. The energy dependence of the self-trapping rate has been measured and modeled with a theory analogous to electron transfer theory. This analysis determines the inter- and intramolecular vibrational modes of the overlayer responsible for self-trapping as well as the relaxation energy of the overlayer molecular lattice. These results for a model interface contribute to the fundamental picture of electron behavior in weakly bonded solids and can lead to better understanding of carrier dynamics in many different systems, including organic light-emitting diodes.  相似文献   

Tracking the long-term decline and recovery of an isolated population     

RL Westemeier  JD Brawn  SA Simpson  TL Esker  RW Jansen  JW Walk  EL Kershner  JL Bouzat  KN Paige 《Science (New York, N.Y.)》1998,282(5394):1695-1698

Effects of small population size and reduced genetic variation on the viability of wild animal populations remain controversial. During a 35-year study of a remnant population of greater prairie chickens, population size decreased from 2000 individuals in 1962 to fewer than 50 by 1994. Concurrently, both fitness, as measured by fertility and hatching rates of eggs, and genetic diversity declined significantly. Conservation measures initiated in 1992 with translocations of birds from large, genetically diverse populations restored egg viability. Thus, sufficient genetic resources appear to be critical for maintaining populations of greater prairie chickens.  相似文献   

Establishment and early growth of different plant types of Corsican pine (Pinus nigra var. maritima) on four sites in Thetford Forest     

Jinks  RL; Kerr  G 《Forestry》1999,72(4):293-304

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Suppurative otitis in cattle associated with ear mites (Raillietia auris)     

TF JUBB  RL VASSALLO  RH WROTH 《Australian veterinary journal》1993,70(9):354-355

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Encephalomyocarditis virus infection in pigs     

AR MERCY  RL PEET †  TM ELLIS †  J. PARKINSON † 《Australian veterinary journal》1988,65(11):355-355

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Rhabdomyolysis in housed, fine-woolled merino sheep, associated with low plasma alphatocopherol concentrations     

RL PEET  J. DICKSON 《Australian veterinary journal》1988,65(12):398-399

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Isolation of infectious bronchitis virus from a flock of racing pigeons   总被引：6，自引：0，他引：6  

DA BARR  RL REECE  D O'ROURKE  C BUTTON  JT FARAGHER 《Australian veterinary journal》1988,65(7):228-228

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Vaginal isolation of beta‐haemolytic Streptococcus from bitches with and without neonatal deaths in the litters          下载免费PDF全文

AE Guerrero  MC Stornelli  SB Jurado  G Giacoboni  GH Sguazza  RL de la Sota  MA Stornelli 《Reproduction in domestic animals》2018,53(3):609-616

The aim of the study was to identify beta‐haemolytic streptococci in the vagina of bitches who had delivered healthy litters and bitches who had delivered litters in which neonatal deaths occurred. Fifty‐one bitches divided into two groups were used. Group 1 (G1) included 28 bitches that had delivered healthy litters and group 2 (G2) included 23 bitches that had delivered puppies who died in the neonatal period. Two vaginal samples were taken, one in proestrus and the other at the end of gestation (EG). Beta‐haemolytic Streptococcus (BS) was isolated from 16 bitches (57%) in G1 and from 21 bitches (91%) in G2. The bacteriological cultures, serological tests (Streptex^®) and PCR assay allowed identification of Streptococcus canis and Streptococcus dysgalactiae in G1 and G2. Ultramicroscopic studies allowed the observation of M Protein and capsules in strains of S. dysgalactiae and S. canis in G1 and G2. The S. canis strains isolated from G2 showed thicker capsules than S. canis strains isolated from G1 (234 ± 24.2 vs 151.23 ± 28.93 nm; p < .001.). No differences were observed in capsule thickness between strains of S. dysgalactiae isolated from G1 and G2 (210 ± 13.54 vs 211.66 ± 19.67 nm; p > .70). All strains of beta‐haemolytic Streptococcus isolated were penicillin sensitive. Penicillin was administered from EG to 5 days post‐partum in 10 G2 females with isolation of BS (G2A). Saline solution was administered in eleven G2 females with isolation of BS (G2B). Ninety per cent of the puppies survived in G2A and 25% survived in G2B. Our results suggest BS is involved in canine neonatal deaths.  相似文献   

Ban on antimicrobial growth promoters: a safety advantage for consumers?     

Althaus FR 《Schweizer Archiv für Tierheilkunde》1999,141(3):103-107

The general ban of antimicrobial growth promoters seems reasonable and desirable to consumers, but is nevertheless problematic in a veterinary medical and political perspective. Rational risk management would imply that restrictive government decisions are evidence-based and provide the consumer with a higher safety level. The recent decision of the European Commission to ban avoparcin from the market was explicitly not based on scientific evidence, and apart from temporarily reducing consumer fears, the risk balance could even turn negative. The prejudicial nature of the avoparcin ban may encourage far reaching governmental interference on the market leading to the withdrawal of therapeutically important veterinary drugs on the basis of suspected side effects alone. Rational risk management would call for balancing the elimination of risks with the risks of elimination.  相似文献   

Managing animal wellbeing: a preliminary survey of pig farmers     

RL Wilson  PK Holyoake  GM Cronin  RE Doyle 《Australian veterinary journal》2014,92(6):206-212

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