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1.
Sound stimulates the tympanic membrane (TM) of anuran amphibians through multiple, poorly understood pathways. It is conceivable
that interactions between the internal and external inputs to the TM contribute to the nonlinear effects that noise is known
to produce at higher levels of the auditory pathway. To explore this issue, we conducted measurements of TM vibration in response
to tones in the presence of noise in the frog Eupsophus calcaratus. Laser vibrometry revealed that the power spectra (n = 16) of the TM velocity in response to pure tones at a constant level of 80 dB sound-pressure level (SPL) had a maximum
centered at an average frequency of 2,344 Hz (range 1,700–2,990 Hz) and a maximum velocity of 61.1 dB re 1 μm/s (range 42.9–66.6
dB re 1 μm/s). These TM-vibration velocity response profiles in the presence of increasing levels of 4-kHz band-pass noise
were unaltered up to noise levels of 90 dB SPL. For the relatively low spectral densities of the noise used, the TM remains
in its linear range. Such vibration patterns facilitate the detection of tonal signals in noise at the tympanic membrane and
may underlie the remarkable vocal responsiveness maintained by males of E. calcaratus under noise interference. 相似文献
2.
Stephan Baumgartner Martin Wolf Peter Skrabal Felix Bangerter Peter Heusser André Thurneysen Ursula Wolf 《Die Naturwissenschaften》2009,96(9):1079-1089
Quantitative meta-analyses of randomized clinical trials investigating the specific therapeutic efficacy of homeopathic remedies
yielded statistically significant differences compared to placebo. Since the remedies used contained mostly only very low
concentrations of pharmacologically active compounds, these effects cannot be accounted for within the framework of current
pharmacology. Theories to explain clinical effects of homeopathic remedies are partially based upon changes in diluent structure.
To investigate the latter, we measured for the first time high-field (600/500 MHz) 1H T1 and T2 nuclear magnetic resonance relaxation times of H2O in homeopathic preparations with concurrent contamination control by inductively coupled plasma mass spectrometry (ICP-MS).
Homeopathic preparations of quartz (10c–30c, n = 21, corresponding to iterative dilutions of 100−10–100−30), sulfur (13x–30x, n = 18, 10−13–10−30), and copper sulfate (11c–30c, n = 20, 100−11–100−30) were compared to n = 10 independent controls each (analogously agitated dilution medium) in randomized and blinded experiments. In none of the
samples, the concentration of any element analyzed by ICP-MS exceeded 10 ppb. In the first measurement series (600 MHz), there
was a significant increase in T1 for all samples as a function of time, and there were no significant differences between homeopathic potencies and controls.
In the second measurement series (500 MHz) 1 year after preparation, we observed statistically significant increased T1 relaxation times for homeopathic sulfur preparations compared to controls. Fifteen out of 18 correlations between sample
triplicates were higher for controls than for homeopathic preparations. No conclusive explanation for these phenomena can
be given at present. Possible hypotheses involve differential leaching from the measurement vessel walls or a change in water
molecule dynamics, i.e., in rotational correlation time and/or diffusion. Homeopathic preparations thus may exhibit specific
physicochemical properties that need to be determined in detail in future investigations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
The bathymetric distribution of marine benthic invertebrates is likely governed by a combination of ecological and physiological
factors. The present study investigates oxygen consumption and heartbeat rate in response to attempted feeding at 1, 100 and
150 atm in the shallow-water spider crab, Maja brachydactyla, from temperate European waters. No significant difference was evident between the resting heartbeat rate of specimens at
1 or 100 atm, which were 56 and 65 bpm, respectively (Mann–Whitney, U = 5382.0; n = 95, 98; p = 0.079). However, at 150 atm the resting heartbeat rate was significantly higher than that observed for 100 atm at 108 bpm
(Mann–Whitney, U = 149.0; n = 45, 98; p < 0.001). At 150 atm, feeding was never observed and coupled with the elevated resting heartbeat rate; it is suggested by
150 atm continued survival is unfeasible. At 1 and 100 atm, feeding instigated a distinct increase in heartbeat rate, which
remained elevated for over 30 h. This increase peaked within 1 h at 1 atm. At 100 atm, this required 4 h and postprandial
oxygen consumption was significantly higher than at 1 atm (Kruskal–Wallis, H = 85.036; df = 2; p < 0.001). Elevated hydrostatic pressure is hypothesized to extend the duration and the total metabolic energy devoted to
specific dynamic action. The metabolic requirements of feeding under hyperbaric conditions may even reach such a critical
demand that feeding is entirely inhibited. 相似文献
4.
Reversed sex change by widowed males in polygynous and protogynous fishes: female removal experiments in the field 总被引:1,自引:0,他引:1
Sex change, either protogyny (female to male) or protandry (male to female), is well known among fishes, but evidence of bidirectional
sex change or reversed sex change in natural populations is still very limited. This is the first report on female removal
experiments for polygnous and protogynous fish species to induce reversed sex change in the widowed males in the field. We
removed all of the females and juveniles from the territories of dominant males in the cleaner wrasse Labroides dimidiatus (Labridae) and the rusty angelfish Centropyge ferrugata (Pomacanthidae) on the coral reefs of Okinawa. In both species, if new females or juveniles did not immigrate into the territories
of the widowed males, some of them emigrated to form male–male pairs. When a male–male pair formed, the smaller, subordinate
partner began to perform female sexual behaviours (n = 4 in L. dimidiatus; n = 2 in C. ferrugata) and, finally, released eggs (n = 1, respectively). Thus, the reversed sex change occurred in the widowed males according to the change of their social status.
These results suggest that such female removal experiments will contribute to the discovery of reversed sex change in the
field also in other polygnous and protogynous species. 相似文献
5.
Humin, the most recalcitrant and abundant organic fraction of soils and of sediments, is a significant contributor to the
stable carbon pool in soils and is important for the global carbon budget. It has significant resistance to transformations
by microorganisms. Based on the classical operational definition, humin can include any humic-type substance that is not soluble
in water at any pH. We demonstrate in this study how sequential exhaustive extractions with 0.1 M sodium hydroxide (NaOH) + 6 M
urea, followed by dimethylsulphoxide (DMSO) + 6% (v/v) sulphuric acid (H2SO4) solvent systems, can extract 70–80% of the residual materials remaining after prior exhaustive extractions in neutral and
aqueous basic media. Solid-state 13C NMR spectra have shown that the components isolated in the base + urea system were compositionally similar to the humic
and fulvic acid fractions isolated at pH 12.6 in the aqueous media. The NMR spectra indicated that the major components isolated
in the DMSO + H2SO4 medium had aliphatic hydrocarbon associated with carboxyl functionalities and with lesser amounts of carbohydrate and peptide
and minor amounts of lignin-derived components. The major components will have significant contributions from long-chain fatty
acids, waxes, to cuticular materials. The isolates in the DMSO + H2SO4 medium were compositionally similar to the organic components that resisted solvation and remained associated with the soil
clays. It is concluded that the base + urea system released humic and fulvic acids held by hydrogen bonding or by entrapment
within the humin matrix. The recalcitrant humin materials extracted in DMSO + H2SO4 are largely biological molecules (from plants and the soil microbial population) that are likely to be protected from degradation
by their hydrophobic moieties and by sorption on the soil clays. Thus, the major components of humin do not satisfy the classical
definitions for humic substances which emphasise that these arise from microbial or chemical transformations in soils of the
components of organic debris. 相似文献
6.
Subbaiah KC Raniprameela D Visweswari G Rajendra W Lokanatha V 《Die Naturwissenschaften》2011,98(12):1019-1026
The aim of the present study was to investigate the effect of vitamin E on pro/anti-oxidant status in the liver, brain and
heart of Newcastle disease virus (NDV) infected chickens. Activities of superoxide dismutase (SOD), catalase (CAT), glutathione
peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST) and the levels of reduced glutathione and malonaldehyde were estimated in selected tissues of uninfected,
NDV-infected and NDV + vit. E-treated chickens. A significant increase in MDA levels in brain and liver (p < 0.05) was observed in NDV-infected chickens when compared to controls. The activities of SOD, CAT, GPx, GR, GST and levels
of GSH were significantly (p < 0.05) decreased in brain and liver of NDV-infected chickens over controls. On the other hand, a significant decreased MDA
levels and enhanced antioxidant enzyme activity levels were observed in NDV + vit. E-treated animals compared to NDV-infected
chickens. Histopathological studies revealed that liver of NDV infected chicken shows focal coagulation and infiltration of
hepatocytes, whereas neuronal necrosis and degeneration of Purkinje cells were observed in brain and moderate infiltration
of inflammatory cells was observed in heart. However such histological alterations were not observed in NDV + vit. E-treated
animals. The results of the present study, thus demonstrated that antioxidant defense mechanism is impaired after the induction
of NDV, suggesting its critical role in cellular injury in brain and liver. Further, the results also suggest that vitamin
E treatment will ameliorate the antioxidant status in the infected animals. The findings could be beneficial to understand
the role of oxidative stress in the pathogenesis of NDV and therapeutic interventions of antioxidants. 相似文献
7.
We have found that giant hornets (Vespa mandarinia japonica) are killed in less than 10 min when they are trapped in a bee ball created by the Japanese honeybees Apis cerana japonica, but their death cannot be solely accounted for by the elevated temperature in the bee ball. In controlled experiments, hornets
can survive for 10 min at the temperature up to 47°C, whereas the temperature inside the bee balls does not rise higher than
45.9°C. We have found here that the CO2 concentration inside the bee ball also reaches a maximum (3.6 ± 0.2%) in the initial 0–5 min phase after bee ball formation.
The lethal temperature of the hornet (45–46°C) under conditions of CO2 concentration (3.7 ± 0.44%) produced using human expiratory air is almost the same as that in the bee ball. The lethal temperature
of the honeybee is 50–51°C under the same air conditions. We concluded that CO2 produced inside the bee ball by honeybees is a major factor together with the temperature involved in defense against giant
hornets. 相似文献
8.
During reproductive migration the electroreceptive African sharptooth catfish, Clarias gariepinus (Siluriformes), preys mainly on a weakly electric fish, the bulldog Marcusenius macrolepidotus (Mormyridae; Merron 1993). This is puzzling because the electric organ discharges of known Marcusenius species are pulses of a duration (<1 ms) too short for being detected by the catfishes' low-frequency electroreceptive system
(optimum sensitivity, 10–30 Hz; Peters and Bretschneider 1981). On the recent discovery that M. macrolepidotus males emit discharges lasting approximately ten times longer than those of females (Kramer 1997a) we determined behavioral
thresholds for discharges of both sexes, using synthetic playbacks of field-recorded discharges. C. gariepinus detected M. macrolepidotus male discharges down to a field gradient of 103 μVpeak-peak/cm and up to a distance of 1.5 m at natural field conditions. In contrast, thresholds for female discharges were not reached
with our setup, and we presume the bulldogs eaten by catfish are predominantly male.
Received: 7 October 1998 / Accepted in revised form: 29 December 1998 相似文献
9.
Light-dependent magnetoreception in birds: the effect of intensity of 565-nm green light 总被引:1,自引:0,他引:1
In a previous study, Australian silvereyes tested in autumn under monochromatic 565-nm green light at intensities of 2.1
and 7.5 mW m–2 preferred their normal northerly migratory direction, whereas they showed a significantly different tendency towards northwest
at 15.0 mW m–2. Repeating these experiments in spring with silvereyes migrating southward, we again observed well-oriented tendencies in
the migratory direction at 2.1 and 7.5 mW m–2. At 15.0 mW m–2, however, the birds once more preferred northwesterly directions, i.e. their response under this condition proved to be independent
of the migratory direction. This contradicts the interpretation that monochromatic green light of this high intensity leads
to a rotation of compass information; instead, it appears to produce sensory input that causes birds to give up their migratory
direction in favor of a fixed direction of as yet unknown origin.
Received: 3 April 2000 / Accepted in revised form: 19 June 2000 相似文献
10.
Xiaoming Xu Jie Tang Zhaoyang Li Chang Liu Weizheng Han 《Mitigation and Adaptation Strategies for Global Change》2011,16(6):721-731
In this study, paddy fields in Jilin province which are flooded parcel of arable lands used for growing rice (Oryza sativa Linn.) were selected as the object. Long-term exploitation of paddy fields led to variations of soil organic carbon (SOC) and green
house gases (GHGs) emissions which might contribute to global warming. In order to calculate the amount of global warming
potentials (GWPs) of emissions from ricepaddies and find the correlations among rice yield, SOC storage and GWP, DeNitrification-DeComposition
(DNDC) model was used to simulate SOC densities and fluxes of main GHGs emitted from paddy fields. After verification, simulation
results were used to calculate SOC storages and 100-year GWPs from 1949 to 2009. Results indicated that SOC densities in depths
of 0–10 cm, 10–20 cm and 20–30 cm all kept increasing. Average methane (CH4) and nitrous oxide (N2O) fluxes were 278.55 kg carbon (kgC) ha−1 a−1 and 2.22 kg nitrogen (kgN) ha−1 a−1. The SOC storage (0–30 cm) had increased from 3.96 × 109kgC in 1949 to 47.85 × 109kgC in 2009. In addition, GWP emission was increasing exponentially in the past 61 years, from 0.16 × 106 Mg carbon dioxide equivalents (CO2-equivalents) to 66.36 × 106 Mg CO2-equivalents. Both SOC storage and GWP presented obviously linear relation to rice yields. Overall, the research suggested
that long-term rice yields could be used to estimate the SOC storage and GWP variations. 相似文献
11.
Although turbidite deposits are classically considered to be good reservoir rocks for oil and gas, there are no reports concerning
their source rock potential in the literature. The sediments from the Vallfogona Formation in the South-Eastern Pyrenees present
numerous organic matter-rich levels interbedded in sandstones and coarse turbidite deposits. Two types of organic matter deposits
were differentiated on the basis of organic geochemistry and petrography: type A and type B. Type A was deposited in a carbonate
marine environment under hypersaline conditions as indicated mainly by even/odd n-alkane predominance, pristane and phytane ratio (Pr/Ph) < 1, presence of gammacerane, and trisnorneohopane over trisnorhopane
ratio (Ts/Tm) > 1. Type B was deposited in a more mud-rich marine environment evidenced by the predominance of odd n-alkane, Pr/Ph ≥ 1, Ts/Tm < 1, the absence of gammacerane, similar concentrations of the C27 and C29 regular steranes, and the greater abundance of C27 diasteranes. Turbidite facies can be regarded as an environment where organic matter sedimentation is heterogeneous in type
and amount. This study suggests that turbidite deposits with interbedded organic matter-rich levels may act as a combined
source–reservoir system. 相似文献
12.
Fruits of Garden Lettuce, imbibed in 0.01 M KNO3, were depleted of maternal active phytochrome B by saturating deep-red exposure and photosensitized by chilling for 1 week
at 4 °C. Twenty saturated fluence-response curves for photoinduced germination were elaborated between 300 and 800 nm, using
exposure periods from 6 to 600 s at 22.5 °C; there is linear and closely parallel regression in the logarithmic probability
net. The reciprocals of the half-response fluences obtained gave the apparent conversion spectrum of the controlling pigments
and this was corrected for the transmittance of the seed-coat. It is a phytochrome spectrum of P
r with photoconversion cross-sections of 1.2·109 and 4.5·103 m2 mol–1 at 666 and 800 nm, respectively. This means that for half-saturated germination of sensitized seed, fewer than 1 out of 200,000
phytochrome A molecules have to be photoconverted to P
fr, and no photo-reversibility by deep-red was found. Therefore, all spectral colours of nightly moon- or skylight should stimulate
the germination of sensitized weed seeds if they are exposed at the soil surface between sequential tillage operations.
Received: 28 April 2000 / Accepted in revised form: 28 July 2000 相似文献
13.
Elo H 《Die Naturwissenschaften》2007,94(9):779-780
The ionization potential of one-electron ions can be calculated from a well-known simple equation, but no such equation has
been available for calculating the ionization potential of multi-electron ions. I report here an equation that accurately
gives the ionization potential of helium-like (i.e., two-electron) ions as a function of the atomic number, the relative difference
from experimental values being below 1% for all ions for which reliable experimental data were found (Z = 3–29). The equation also predicts the stability of the negative hydrogen ion (the hydride ion), H−, although with twice too large a value for the ionization potential. 相似文献
14.
Cerumen, or propolis, is a mixture of plant resins enriched with bee secretions. In Australia, stingless bees are important
pollinators that use cerumen for nest construction and possibly for colony’s health. While extensive research attests to the
therapeutic properties of honeybee (Apis mellifera) propolis, the biological and medicinal properties of Australian stingless bee cerumen are largely unknown. In this study,
the chemical and biological properties of polar extracts of cerumen from Tetragonula carbonaria in South East Queensland, Australia were investigated using gas chromatography-mass spectrometry (GC-MS) analyses and in
vitro 5-lipoxygenase (5-LOX) cell-free assays. Extracts were tested against comparative (commercial tincture of A. mellifera propolis) and positive controls (Trolox and gallic acid). Distinct GC-MS fingerprints of a mixed diterpenic profile typical
of native bee cerumen were obtained with pimaric acid (6.31 ± 0.97%, w/w), isopimaric acid (12.23 ± 3.03%, w/w), and gallic
acid (5.79 ± 0.81%, w/w) tentatively identified as useful chemical markers. Characteristic flavonoids and prenylated phenolics
found in honeybee propolis were absent. Cerumen extracts from T. carbonaria inhibited activity of 5-LOX, an enzyme known to catalyse production of proinflammatory mediators (IC50 19.97 ± 2.67 μg/ml, mean ± SEM, n = 4). Extracts had similar potency to Trolox (IC50 12.78 ± 1.82 μg/ml), but were less potent than honeybee propolis (IC50 5.90 ± 0.62 μg/ml) or gallic acid (IC50 5.62 ± 0.35 μg/ml, P < 0.001). These findings warrant further investigation of the ecological and medicinal properties of this stingless bee cerumen,
which may herald a commercial potential for the Australian beekeeping industry. 相似文献
15.
Marcelo Perantoni Darci M. S. Esquivel Eliane Wajnberg Daniel Acosta-Avalos Geraldo Cernicchiaro Henrique Lins de Barros 《Die Naturwissenschaften》2009,96(6):685-690
Magnetotactic microorganisms use the interaction of internal biomineralized nanoparticles with the geomagnetic field to orientate.
The movement of the magnetotactic multicellular prokaryote Candidatus Magnetoglobus multicellularis under an applied magnetic field was observed. A method using digital image processing techniques
was used to track the organism trajectory to simultaneously obtain its body radius, velocity, U-turn diameter, and the reorientation
time. The magnetic moment was calculated using a self-consistent method. The distribution of magnetic moments and radii present
two well-characterized peaks at (9 ± 2) × 10−15 and (20 ± 3) × 10−15 A m2 and (3.6 ± 0.1) and (4.3 ± 0.1) μm, respectively. For the first time, simultaneous determination of the distribution of the
organism radii and magnetic moment was obtained from the U-turn method by a new digital imaging processing. The bimodal distributions
support an organism reproduction process model based on electron microscopy observations. These results corroborate the prokaryote
multicellular hypothesis for Candidatus M. multicellularis. 相似文献
16.
The phonotactic capacity of tachinid flies to acoustically detect and localize a sound source simulating their cricket host
was investigated in a large flight room. Acoustic measurements were performed to estimate the actual stimulus delivered to
the flies, revealing highly heterogeneous sound fields. When presented with a simulated cricket song in red or infrared light
conditions, the flies readily flew to the sound source and landed on it. Behavioural phonotactic thresholds were established
as a function of carrier frequency and were found to coincide well with the frequency of the host's natural song (4.5–5.2 kHz).
Experiments revealed that the same range of frequencies is preferentially attractive to the free-flying flies, and that the
reliability of signal detection in the presence of noise is best at behaviourally relevant frequencies.
Received: 23 February 2000 / Accepted in revised form: 6 June 2000 相似文献
17.
Alexander Lerchl 《Die Naturwissenschaften》1999,86(7):340-342
The relationship between average monthly air temperature and sex ratios at birth (SRB) was analyzed for children born in
Germany during the period 1946–1995. Both the absolute temperature and – more markedly – the monthly temperature deviations
from the overall mean were significantly positively correlated with the SRB (P<0.01) when temperatures were time-lagged against the SRB data by –10 or –11 months. It is concluded that the sex of the offspring
is partially determined by environmental temperatures prior to conception.
Received: 26 August 1998 / Accepted in revised form: 18 February 1999 相似文献
18.
Where clocks are redundant: weak circadian mechanisms in reindeer living under polar photic conditions 总被引:1,自引:0,他引:1
Biological rhythms are a result of interplay between endogenous clocks and the ambient light–dark (LD) cycle. Biological timing
in resident polar organisms presents a conundrum because these experience distinct daily LD cycles for only a few weeks each
year. We measured locomotor activity in reindeer, Rangifer tarandus platyrhynchus (SR, n = 5 and 6) and R. tarandus tarandus (NR, n = 6), ranging freely at 78 and 70°N, respectively, continuously throughout 1 year using data loggers. NR, but not SR, are
gregarious which enabled us to examine the integrated effects of differences in social organisation and the photic environment
at two different latitudes on the organisation of activity. In both sub-species, ultradian bouts of activity and inactivity
alternated across the 24-h day throughout the year. This pattern was modified by the LD cycle in NR but barely at all in SR.
Periodogram analysis revealed significant ultradian rhythmicity in both sub-species; the frequency of daily cycles of activity
increased from three per day in winter to nearly five in summer. We conclude that this increase, and a concomitant increase
in the level of daily activity, reflected the seasonal increase in the animals’ appetite and the quality of their forage.
Secondly, the combination, most evident in SR, of a weak photic response, weak circadian mechanisms and a weak social synchronization
reduces the constraints of biological timing in an environment which is effectively non-rhythmic most of the year and permits
expression of the basic ultradian pattern of ruminant activity. Third, the weaker 24-h rhythmicity in SR compared to NR indicates
a latitudinal decrease in circadian organization and photic responsiveness in Rangifer. 相似文献
19.
Laura Rodríguez-Loeches Alejandro Barro Martha Pérez Frank Coro 《Die Naturwissenschaften》2009,96(4):531-536
Both sexes of Phoenicoprocta capistrata have functional tymbals. The scanning electron microscopy revealed differences in the morphology of these organs in males
and females. Male tymbals have a well-developed striated band, constituted by 21 ± 2 regularly arranged striae whereas female
tymbals lack a striated band. This type of sexual dimorphism is rare in Arctiidae. The recording of the sound produced by
moths held by the wings revealed that while males produced trains of pulses organized in modulation cycles, females produced
clicks at low repetition rate following very irregular patterns. Statistically, there are differences between sexes in terms
of the duration of pulses, which were 355 ± 24 μs in the case of males and 289 ± 29 μs for females. The spectral characteristics
of the pulses also show sexual dimorphism. Male pulses are more tuned (Q
10 = 5.2 ± 0.5) than female pulses (Q
10 = 2.7 ± 0.5) and have a higher best frequency (42 ± 1 kHz vs. 29 ± 2 kHz). To our knowledge, this is the first report on
an arctiid moth showing sexual dimorphism in tymbal’s anatomy that leads to a best frequency dimorphism. Males produce sound
at mating attempts. The sounds recorded during mating are modulation cycles with the same spectral characteristics as those
recorded when males are held by the wings. The morphological and acoustic features of female tymbals could indicate a process
of degeneration and adaptation to conditions under which the emission of complex patterns is not necessary.
Frank Coro no longer works at Universidad de La Habana. 相似文献
20.
Fisher CR MacDonald IR Sassen R Young CM Macko SA Hourdez S Carney RS Joye S McMullin E 《Die Naturwissenschaften》2000,87(4):184-187
During a research cruise in July 1997 in the Gulf of Mexico we discovered a gas hydrate approximately 1 m thick and over
2 m in diameter which had recently breached the sea floor at a depth of 540 m. The hydrate surface visible from the submarine
was considerably greater than that of any other reported hydrate. Two distinct color bands of hydrate were present in the
same mound, and the entire exposed surface of the hydrate was infested (2500 individuals/m2) with 2 to 4 cm-long worms, since described as a new species, Hesiocaeca
methanicola, in the polychaete family Hesionidae (Desbruyères and Toulmond 1998). H.
methanicola tissue stable isotope values are consistent with a chemoautotrophic food source. No evidence of chemoautotrophic symbionts
was detected, but geochemical data support the presence of abundant free living bacteria on the hydrate. The activities of
the polychaetes, grazing on the hydrate bacteria and supplying oxygen to their habitats, appears to contribute to the dissolution
of hydrates in surface sediments.
Received: 16 August 1999 / Accepted in revised form: 19 January 2000 相似文献