Ordering of ruthenium cluster carbonyls in mesoporous silica     

W Zhou  JM Thomas  DS Shephard  BFG Johnson  D Ozkaya  T Maschmeyer  RG Bell  Q Ge 《Science (New York, N.Y.)》1998,280(5364):705-708

The anionic ruthenium cluster carbonylates [Ru6C(CO)16]2- or [H2Ru10(CO)25]2- interspersed with bis(triphenylphosphino)iminium counterions (PPN+) are incorporated from solution into the pores of MCM-41 mesoporous silica (3 nanometers in diameter), where they form tightly packed arrays. These arrays were shown by high-resolution transmission electron microscopy, Fourier transform optical diffraction, and computer simulations to be well ordered both along and perpendicular to the axis of the cylindrical pores. In their denuded state produced by gentle thermolysis, the cluster carbonylates yield nanoparticles of ruthenium that are less well ordered than their assimilated precursors but show good activity as hydrogenation catalysts for hexene and cyclooctene. In both their as-prepared and denuded states, these encapsulated clusters are likely to exhibit interesting electronic and other properties.  相似文献   

Near extinction of a large, widely distributed fish     

JM Casey  RA Myers 《Science (New York, N.Y.)》1998,281(5377):690-692

Are extinctions of marine vertebrates as rare and unlikely as current data indicate? Long-term research surveys on the continental shelf between the Grand Banks of Newfoundland and southern New England reveal that one of the largest skates in the northwest Atlantic, the barndoor skate (Raja laevis), is close to extinction. Forty-five years ago, research surveys on St. Pierre Bank (off southern Newfoundland) recorded barndoor skates in 10% of their tows; in the last 20 years, none has been caught, and this pattern of decline is similar throughout the range of the species.  相似文献   

Low-voltage organic transistors on plastic comprising high-dielectric constant gate insulators   总被引：1，自引：0，他引：1  

CD Dimitrakopoulos  S Purushothaman  J Kymissis  A Callegari  JM Shaw 《Science (New York, N.Y.)》1999,283(5403):822-824

The gate bias dependence of the field-effect mobility in pentacene-based insulated gate field-effect transistors (IGFETs) was interpreted on the basis of the interaction of charge carriers with localized trap levels in the band gap. This understanding was used to design and fabricate IGFETs with mobility of more than 0.3 square centimeter per volt per second and current modulation of 10(5), with the use of amorphous metal oxide gate insulators. These values were obtained at operating voltage ranges as low as 5 volts, which are much smaller than previously reported results. An all-room-temperature fabrication process sequence was used, which enabled the demonstration of high-performance organic IGFETs on transparent plastic substrates, at low operating voltages for organic devices.  相似文献   

Equine Nasal and Paranasal Sinus Tumours. Part 1: Review of the Literature and Tumour Classification     

K. W. HEAD  P. M. DIXON 《Veterinary journal (London, England : 1997)》1999,157(3):261-278

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Scrub-itch mite infestation in the endangered bridled nailtail wallaby   总被引：1，自引：1，他引：0  

JM Old  J Lowry  LJ Young 《Australian veterinary journal》2009,87(8):338-341

Skin lesions on the ears and inguinal and axillary regions of a number of adult animals within a captive population of the endangered bridled nailtail wallaby ( Onychogalea fraenata ) were associated with the trombiculid mite, Eutrombicula hirsti . The local inflammatory response of these Australian marsupials is described.  相似文献   

Three years of banning neonicotinoid insecticides based on sub‐lethal effects: can we expect to see effects on bees?          下载免费PDF全文

Tjeerd Blacquière  Jozef JM van der Steen 《Pest management science》2017,73(7):1299-1304

The 2013 EU ban of three neonicotinoids used in seed coating of pollinator attractive crops was put in place because of concern about declining wild pollinator populations and numbers of honeybee colonies. It was also concluded that there is an urgent need for good field data to fill knowledge gaps. In the meantime such data have been generated. Based on recent literature we question the existence of recent pollinator declines and their possible link with the use of neonicotinoids. Because of temporal non‐coincidence we conclude that declines of wild pollinators and of honeybees are not likely caused by neonicotinoids. Even if bee decline does occur and if there is a causal relationship with the use of neonicotinoids, we argue that it is not possible on such short term to evaluate the effects of the 2013 ban. In order to supply future debate with realistic (field) data and to discourage extrapolating the effects of studies using overdoses that are not of environmental relevance, we propose – in addition to field studies performed by the chemical industry – to use the ‘semi‐field worst case’ treated artificial diet studies approach to free flying colonies in the field. This kind of study may provide realistic estimates for risk and be useful to study realistic interactions with non‐pesticide stressors. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.  相似文献   

Organogenesis and foetal haemodynamics during the normal gestation of healthy black‐rumped agoutis (Dasyprocta prymnolopha,Wagler, 1831) bred in captivity          下载免费PDF全文

FCA Sousa  GT Pessoa  LS Moura  JR Araújo  RPS Rodrigues  MAPS Barbosa  AN Diniz  AB Souza  EG Silva  LU Lucena  MP Sanches  OF Silva‐Filho  PC Guerra  JM Sousa  WC Neves  FR Alves 《Reproduction in domestic animals》2017,52(1):60-66

The objective of this study was to define the patterns of organogenesis and foetal haemodynamics during the normal gestation of healthy agoutis (Dasyprocta prymnolopha) kept in captivity. Thirty pregnant agoutis that ranged in size from small to medium and weighed between 2.5 and 3 kg underwent B‐mode and Doppler ultrasonography for the biometric evaluation of the foetal organs. The foetal aortic blood flow proved to be predominantly systolic, and the measured flow velocity was 78.89 ± 2.95 cm/s, with a maximum pressure gradient of 2.12 ± 0.27 mmHg. The liver was characterized by its large volume, occupying the entire cranial aspect of the abdominal cavity, and it was associated cranially with the diaphragm and caudally with the stomach. The flow velocity in the portal vein was estimated to equal 12.17 ± 2.37 cm/s, with a resistivity index of 0.82 ± 0.05. The gallbladder was centrally located and protruded cranially towards the diaphragm. The spleen was visualized as an elongated structure with tapered cranial and caudal extremities, and the foetal kidneys were visualized bilaterally in the retroperitoneal region, with the right kidney positioned slightly more cranially than the left. The morphological characterization and hemodynamic analysis of the foetal organs of black‐rumped agoutis via B‐mode and Doppler ultrasonography allow determination of the vascular network and of reference values for the blood flow required for perfusing the anatomical elements essential for maintaining the viability of foetuses at different gestational ages.  相似文献   

Effects of single layer centrifugation (SLC) on bull spermatozoa prior to freezing on post‐thaw semen characteristics          下载免费PDF全文

T Nongbua  A Johannisson  A Edman  JM Morrell 《Reproduction in domestic animals》2017,52(4):596-602

Single layer centrifugation (SLC) has been shown to select the most robust spermatozoa from the ejaculate in several species. Here the effects of SLC prior to freezing on various parameters of frozen‐thawed bovine sperm quality are reported. Semen from 8 bulls was layered on top of a species‐specific colloid, Bovicoll. After centrifugation for 20 min at 300 g, the resulting sperm pellet was resuspended in OPTIXcell^® (IMV Technologies, l′Aigle, France); the SLC‐selected sperm samples and uncentrifuged controls were frozen. On thawing, all sperm samples were analysed for membrane integrity, production of reactive oxygen species, mitochondrial membrane potential (MMP) and chromatin integrity. The SLC‐treated samples had a higher percentage of live, superoxide‐positive spermatozoa than uncentrifuged samples (27.9 ± 5.1% versus 21.7 ± 6.7%; p = .03). They had a higher proportion of spermatozoa with high mitochondrial membrane potential than uncentrifuged samples (55.9 ± 8.2% versus 40.5 ± 15.1%; p = .03) and also a lower proportion of spermatozoa with low mitochondrial membrane potential than non‐treated samples (42.0 ± 8.5% versus 55.9 ± 14.4%; p = .04). No significant effects of treatment were found for membrane integrity or chromatin integrity. The effect of bull was significant on the proportions of dead, superoxide‐positive spermatozoa and live, hydrogen peroxide‐negative spermatozoa, as well as on membrane integrity, but it was not significant for mitochondrial membrane potential or chromatin integrity. These results suggest that SLC selects the most metabolically active bull spermatozoa from the rest of the population in normal ejaculates; the pattern of reactive oxygen species production may be different in SLC‐selected spermatozoa compared to unselected samples.  相似文献   

Post mortem survey of peripheral dental caries in 510 Swedish horses     

I. GERE  P. M. DIXON 《Equine veterinary journal》2010,42(4):310-315

Reasons for performing study: Peripheral caries (PC) of equine teeth is a poorly described disorder that can cause serious clinical problems if it progresses. Objectives: To assess the prevalence, sites and severity of PC in a population of Swedish horses. Methods: A post mortem study of 510 equine skulls was performed in 2 Swedish equine abattoirs. Results: PC only affected the cheek teeth (CT) and was present in 6.1% (31/510) of skulls. It affected mainly the peripheral cementum, and 87% of PC in the 29 affected mature horses occurred in the 3 caudal CT (Triadan 09‐11). Concurrent infundibular caries involving most maxillary CT (mean 9.7/skull) was present in 32% of skulls affected with PC. Trotting horses (mean age 8.1 years) believed to be on a high concentrate and silage diet were preferentially affected with PC in this population. Food was usually tightly adherent to the PC lesions and this feature may have promoted the progression of the disease. Significantly increased levels of diastemata were present in PC‐affected horses, and periodontal disease was present in areas adjacent to some PC lesions. Conclusions: PC is a relatively common disorder of horses under certain management conditions that can progress to cause serious dental disorders, especially if concurrent, widespread infundibular caries is present. Potential relevance: Equine clinicians should be aware of this significant dental disorder and research into its aetiopathogenesis, possible prevention and treatment are required.  相似文献   

The effect of high correlated colour temperature office lighting on employee wellbeing and work performance     

Peter R Mills  Susannah C Tomkins  Luc JM Schlangen 《Journal of circadian rhythms》2007,5(1):2-9

Background  

The effects of lighting on the human circadian system are well-established. The recent discovery of 'non-visual' retinal receptors has confirmed an anatomical basis for the non-image forming, biological effects of light and has stimulated interest in the use of light to enhance wellbeing in the corporate setting.  相似文献