Science management training     

Keller EC 《Science (New York, N.Y.)》1974,184(4144):1331

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Advances in Neurochemistry: Monitoring Neurotransmitter Release during Behavior     

Keller RW  Zigmond MJ 《Science (New York, N.Y.)》1987,238(4832):1448-1449

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Phenotypic basis of reproductive success in a social insect: genetic and social determinants     

Keller L  Ross KG 《Science (New York, N.Y.)》1993,260(5111):1107-1110

Social insects live in societies that include both reproductive and nonreproductive adults. Understanding the factors that determine which individuals become successful reproductives is necessary to explain the evolution of these societies. The phenotypic effects of the gene Pgm-3 (or a closely linked gene) that may cause workers of the fire ant Solenopsis invicta to selectively execute all queens of a specific genotype were investigated. These effects, which involve differences in queen reproductive development, are expressed only in colonies exhibiting a particular type of social organization (multiple-queen colonies), and it is only in such colonies that selective execution on the basis of genotype occurs. This is an unusual example of genotype-environment interaction in gene expression in which the environmental component is the social environment. The queens executed are, surprisingly, those with the greatest reproductive development. Thus, there is a counterintuitive relation between the potential and realized reproductive success of queens in multiple-queen societies of this ant.  相似文献   

Deep Impact observations by OSIRIS onboard the Rosetta spacecraft   总被引：1，自引：0，他引：1  

Keller HU  Jorda L  Küppers M  Gutierrez PJ  Hviid SF  Knollenberg J  Lara LM  Sierks H  Barbieri C  Lamy P  Rickman H  Rodrigo R 《Science (New York, N.Y.)》2005,310(5746):281-283

The OSIRIS cameras (optical, spectroscopic, and infrared remote imaging system) onboard the European Space Agency's Rosetta spacecraft observed comet 9P/Tempel 1 for 17 days continuously around the time of NASA's Deep Impact mission. The cyanide-to-water production ratio was slightly enhanced in the impact cloud, compared with that of normal comet activity. Dust particles were flowing outward in the coma at >160 meters per second, accelerated by the gas. The slope of the brightness increase showed a dip about 200 seconds after the impact. Dust Afrho values before and long after the impact confirm the slight decrease of cometary activity. The dust-to-water mass ratio was much larger than 1.  相似文献   

The three-dimensional structure of canine parvovirus and its functional implications   总被引：59，自引：0，他引：59  

J Tsao  M S Chapman  M Agbandje  W Keller  K Smith  H Wu  M Luo  T J Smith  M G Rossmann  R W Compans 《Science (New York, N.Y.)》1991,251(5000):1456-1464

The three-dimensional atomic structure of a single-stranded DNA virus has been determined. Infectious virions of canine parvovirus contain 60 protein subunits that are predominantly VP-2. The central structural motif of VP-2 has the same topology (an eight-stranded antiparallel beta barrel) as has been found in many other icosahedral viruses but represents only about one-third of the capsid protein. There is a 22 angstrom (A) long protrusion on the threefold axes, a 15 A deep canyon circulating about each of the five cylindrical structures at the fivefold axes, and a 15 A deep depression at the twofold axes. By analogy with rhinoviruses, the canyon may be the site of receptor attachment. Residues related to the antigenic properties of the virus are found on the threefold protrusions. Some of the amino termini of VP-2 run to the exterior in full but not empty virions, which is consistent with the observation that some VP-2 polypeptides in full particles can be cleaved by trypsin. Eleven nucleotides are seen in each of 60 symmetry-related pockets on the interior surface of the capsid and together account for 13 percent of the genome.  相似文献   

Porphyrins are not present in feline ocular tissues or corneal sequestra     

Newkirk KM  Hendrix DV  Keller RL 《Veterinary ophthalmology》2011,14(Z1):2-4

Objective To determine if feline lacrimal glands, glands of the third eyelid, corneas, and corneal sequestra contain porphyrins, which could be responsible for the brown/amber discoloration of corneal sequestra and tears in affected cats. Procedures Samples of grossly normal cornea, lacrimal gland, gland of the third eyelid, and sequestra obtained via keratectomy were collected. Porphyrin concentrations of the homogenate were determined by spectrofluorometry with protoporphyrin IX and coproporphyrin III dihydrochloride used as standards. A hamster harderian gland was used as a positive control. Results Normal tissues were harvested from one eye each of 14 nonclient owned, adult, mixed‐breed, short‐hair cats euthanized for reasons not associated with this study. Eighteen sequestra were acquired from cats undergoing unilateral lamellar keratectomies. Breeds of the affected cats included eight Himalayan, five domestic shorthair, and one each of four other breeds. Only the positive control and standards contained levels of porphyrins above background. All feline samples examined were histologically normal with no evidence of porphyrins. Conclusions Porphyrins are absent in normal feline lacrimal glands, corneas, and corneal sequestra. Porphyrins do not appear to be the cause of the brown/amber color of feline corneal sequestra.  相似文献   

Disseminated histoplasmosis in a Bengal tiger (Panthera tigris)     

Keller DL  Steinberg H  Sladky KK 《Journal of zoo and wildlife medicine》2011,42(4):727-731

Disseminated infection with Histoplasma capsulatum was diagnosed in a 7-yr-old female Bengal tiger (Panthera tigris). Clinical signs were nonspecific with the exception of brief periods of tachypnea for 5 days prior to death. H. capsulatum organisms were found in the lungs, tracheobronchial lymph nodes, and liver. Diagnosis was confirmed by tracheal wash, urine H. capsulatum enzyme immunoassay, and necropsy results. This report represents the first published account of disseminated histoplasmosis in a tiger.  相似文献   

Short-term nitrous oxide profile dynamics and emissions response to water, nitrogen and carbon additions in two tropical soils     

A. Nobre  M. Keller  P. Crill  R. Harriss 《Biology and Fertility of Soils》2001,34(5):363-373

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Volumeter test—A valuable auxiliary for the determination of the stability of soil aggregates     

G. Srzednicki  E.R. Keller 《Soil & Tillage Research》1984,4(5):445-457

Two methods for the determination of aggregate stability, wet-sieving and the volumeter test (based on forced consolidation of an aggregate sample), were compared. The aim of this work was to find out whether results obtained with both methods were comparable and, if so, which one was less time-consuming for the same degree of accuracy.Optimum levels of soil moisture for obtaining reliable results were determined during preliminary tests. At these levels, results obtained with both methods showed close agreement. The results of wet-sieving were mainly correlated with the proportion of aggregates between 2 and 5 mm and organic matter content, whereas the results of the volumeter tests correlated with the clay-, silt-, organic matter- and calcium-content of the soil. The time necessary for the accomplishment of the volumeter test was about half that of the wet-sieving method.  相似文献   

Phytoextraction of Cd and Zn with Salix viminalis in field trials   总被引：3，自引：0，他引：3  

D. Hammer  A. Kayser  C. Keller 《Soil Use and Management》2003,19(3):187-192

Abstract. Use of high biomass crops such as the willow Salix viminalis to extract metals for soil remediation has been proposed as an alternative to the low biomass-producing hyperaccumulating plants. High yields compensate for the moderate heavy-metal concentrations in the shoots of such species. We report the first long-term trials using Salix viminalis to extract heavy metals from two contaminated soils, one calcareous (5 years) and one acidic (2 years). Total metals extracted by the plants were 170 g Cd ha⁻¹ and 13.4 kg Zn ha⁻¹ from the calcareous soil after 5 years, and 47 g Cd ha⁻¹ and 14.5 kg Zn ha⁻¹ from the acidic soil after 2 years; in the first year outputs were negligible. After 2 years, Salix had performed better on the acidic soil because of larger biomass production and higher metal concentrations in shoots. Addition of elemental sulphur to the soil did not yield any additional benefit in the long term, but application of an Fe chelate improved the biomass production. Cd and Zn concentrations were significantly higher in leaves than stems, highlighting the necessity to collect leaves as well as shoots. On both soils, concentration in shoots decreased with time, indicating a decrease in extraction efficiency.  相似文献