Single-Electron Transport in Ropes of Carbon Nanotubes     

M Bockrath  DH Cobden  PL McEuen  NG Chopra  A Zettl  A Thess  RE Smalley 《Science (New York, N.Y.)》1997,275(5308):1922-1925

The electrical properties of individual bundles, or "ropes," of single-walled carbon nanotubes have been measured. Below about 10 kelvin, the low-bias conductance was suppressed for voltages less than a few millivolts. In addition, dramatic peaks were observed in the conductance as a function of a gate voltage that modulated the number of electrons in the rope. These results are interpreted in terms of single-electron charging and resonant tunneling through the quantized energy levels of the nanotubes composing the rope.  相似文献   

Silurian trilete spores and spore tetrads from gotland: their implications for land plant evolution     

Gray J  Laufeld S  Boucot AJ 《Science (New York, N.Y.)》1974,185(4147):260-263

Land-plant type spores occur in argillaceous limestones and platform graptolitic mudstones of Wenlock-Ludlow age in Sweden. Analysis of the stratal sequence demonstrates that occurrence of abundant spores is a function of depositional ecology, particularly water depth and shoreline proximity. This ecological analysis and the seeming absence of any correlation between the first appearances of abundant spores and megafossils of land-plant type raise the possibility that land plants evolved far earlier than the megafossil record suggests.  相似文献   

Antiproliferative activity of a hybrid protein between interferon-gamma and tumor necrosis factor-beta   总被引：2，自引：0，他引：2  

G S Feng  P W Gray  H M Shepard  M W Taylor 《Science (New York, N.Y.)》1988,241(4872):1501-1503

A hybrid protein between interferon-gamma and tumor necrosis factor-beta was made by ligating the respective genes and expressing the fused genes under the control of the trp promoter in Escherichia coli. The antiproliferative activity of the hybrid protein in vitro was greatly increased compared with either interferon-gamma or tumor necrosis factor-beta alone, and both antiviral activity and cytotoxic effect were retained in the hybrid protein. The hybrid protein may have potential clinical application.  相似文献   

Gaussian free-energy dependence of electron-transfer rates in iridium complexes     

Fox LS  Kozik M  Winkler JR  Gray HB 《Science (New York, N.Y.)》1990,247(4946):1069-1071

The kinetics of photoinduced electron-transfer (ET) reactions have been measured in a series of synthetic donor-acceptor complexes. The electron donors are singlet or triplet excited iridium(I) dimers (Ir(2)), and the acceptors are N-alkylpyridinium groups covalently bound to phosphinite ligands on the Ir(2) core. Rate constants for excited-state ET range from 3.5 x 10(6) to 1.1 x 10(11) per second, and thermal back ET (pyridinium radical to Ir(2)(+)) rates vary from 2.0 x 10(10) to 6.7 x 10(7) per second. The variation of these rates with driving force is in remarkably good agreement with the Marcus theory prediction of a Gaussian free-energy dependence.  相似文献   

Intravenous anaesthesia using detomidine, ketamine and guaiphenesin for laparotomy in pregnant pony mares     

Polly M Taylor  MA  VetMB  PhD  DVA  MRCVS  Stelio PL Luna  DVM  PhD  Kate L White MA  Vet MB  CertVA  MRCVS  Malcolm Bloomfield  Abigail L Fowden MA  PhD 《Veterinary anaesthesia and analgesia》2001,28(3):119-125

Objective To characterize intravenous anaesthesia with detomidine, ketamine and guaiphenesin in pregnant ponies. Animals Twelve pony mares, at 260–320 days gestation undergoing abdominal surgery to implant fetal and maternal vascular catheters. Materials and methods Pre‐anaesthetic medication with intravenous (IV) acepromazine (30 µg kg^?1), butorphanol (20 µg kg^?1) and detomidine (10 µg kg^?1) preceded induction of anaesthesia with detomidine (10 µg kg^?1) and ketamine (2 mg kg^?1) IV Maternal arterial blood pressure was measured directly throughout anaesthesia and arterial blood samples were taken at 20‐minute intervals for measurement of blood gases and plasma concentrations of cortisol, glucose and lactate. Anaesthesia was maintained with an IV infusion of detomidine (0.04 mg mL^?1), ketamine (4 mg mL^?1) and guaiphenesin (100 mg mL^?1) (DKG) for 140 minutes. Oxygen was supplied by intermittent positive pressure ventilation (IPPV) adjusted to maintain PaCO₂ between 5.0 and 6.0 kPa (38 and 45 mm Hg), while PaO₂ was kept close to 20.0 kPa (150 mm Hg) by adding nitrous oxide. Simultaneous fetal and maternal blood samples were withdrawn at 90 minutes. Recovery quality was assessed. Results DKG was infused at 0.67 ± 0.17 mL kg^?1 hour^?1 for 1 hour then reduced, reaching 0.28 ± 0.14 mL kg^?1 hour^?1 at 140 minutes. Arterial blood gas values and pH remained within intended limits. During anaesthesia there was no change in heart rate, but arterial blood pressure decreased by 10%. Plasma glucose and lactate increased (10‐fold and 2‐fold, respectively) and cortisol decreased by 50% during anaesthesia. Fetal umbilical venous pH, PO₂ and PCO₂ were 7.34 ± 0.06, 5.8 ± 0.9 kPa (44 ± 7 mm Hg) and 6.7 ± 0.8 kPa (50 ± 6 mm Hg); and fetal arterial pH, PO₂ and PCO₂ were 7.29 ± 0.06, 4.0 ± 0.7 kPa (30 ± 5 mm Hg) and 7.8 ± 1.7 kPa (59 ± 13 mm Hg), respectively. Surgical conditions were good but four ponies required a single additional dose of ketamine. Ponies took 60 ± 28 minutes to stand and recovery was good. Conclusions and clinical relevance Anaesthesia produced with DKG was smooth while cardiovascular function in mare and fetus was well preserved. This indicates that DKG infusion is suitable for maintenance of anaesthesia in pregnant equidae.  相似文献   

Modelling the oceanic habitats of two pelagic species using recreational fisheries data          下载免费PDF全文

Stephanie Brodie  Alistair J. Hobday  James A. Smith  Jason D. Everett  Matt D. Taylor  Charles A. Gray  Iain M. Suthers 《Fisheries Oceanography》2015,24(5):463-477

Defining the oceanic habitats of migratory marine species is important for both single species and ecosystem‐based fisheries management, particularly when the distribution of these habitats vary temporally. This can be achieved using species distribution models that include physical environmental predictors. In the present study, species distribution models that describe the seasonal habitats of two pelagic fish (dolphinfish, Coryphaena hippurus and yellowtail kingfish, Seriola lalandi), are developed using 19 yr of presence‐only data from a recreational angler‐based catch‐and‐release fishing programme. A Poisson point process model within a generalized additive modelling framework was used to determine the species distributions off the east coast of Australia as a function of several oceanographic covariates. This modelling framework uses presence‐only data to determine the intensity of fish (fish km^?2), rather than a probability of fish presence. Sea surface temperature (SST), sea level anomaly, SST frontal index and eddy kinetic energy were significant environmental predictors for both dolphinfish and kingfish distributions. Models for both species indicate a greater fish intensity off the east Australian coast during summer and autumn in response to the regional oceanography, namely shelf incursions by the East Australian Current. This study provides a framework for using presence‐only recreational fisheries data to create species distribution models that can contribute to the future dynamic spatial management of pelagic fisheries.  相似文献   

Epizootics in Industrial Livestock Production: Preventable Gaps in Biosecurity and Biocontainment          下载免费PDF全文

J. H. Leibler  K. Dalton  A. Pekosz  G. C. Gray  E. K. Silbergeld 《Zoonoses and public health》2017,64(2):137-145

While technological advances in animal husbandry have facilitated increases in global meat production, the high density and geographic concentration of food animal production facilities pose risks of infectious disease transmission. The scale of the 2014–2015 highly pathogenic avian influenza H5N2 outbreak in the United States demonstrates the challenges in achieving pathogen control within and around industrial animal facilities using existing technologies. We discuss gaps in current practice in two specific systems within these facilities – ventilation and waste management – which are under‐recognized as important drivers of microbial porosity. The development of innovative ventilation systems to reduce influx and efflux of pathogens is critically needed, and cross‐sectoral partnerships should be incentivized to do so. Adapting current human biosolid treatment technologies for farm applications, reducing animal stocking density and shifting waste management responsibility from farmer to corporation would reduce risk from current manure management systems. While innovative approaches to functionally altering the industrial food animal production system remain important priorities to promote sustainability, our intention here is to identify gaps within the current system that allow for pathogen emergence and transmission and address specific areas in which technological, administrative or policy changes are necessary to mitigate these risks.  相似文献