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We report a female infant noted prenatally to have an umbilical cord mass. At birth, a labial strawberry haemangioma was noted. She subsequently developed an abdominal mass which was discovered to be a proliferating haemangioma, continuous with both the labial and the umbilical stump lesions. 相似文献
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Adsorption of arsenate and arsenite on ferrihydrite in the presence and absence of dissolved organic carbon 总被引:6,自引:0,他引:6
The adsorption of As(V) and As(III) on synthetic two-line ferrihydrite in the presence and absence of a peat humic acid (HAp), Suwannee River fulvic acid (FA), or citric acid (CA) was investigated. Previous work with goethite has demonstrated the ability of dissolved organic carbon (DOC) to decrease As(V) and As(III) adsorption. The results obtained demonstrate that As(V) adsorption on ferrihydrite was decreased only in the presence of CA. Arsenate decreased the adsorption of all organic acids except HAp. Both FA and CA reduced As(III) adsorption on ferrihydrite, while HAp had no effect. Fulvic and citric acid adsorption on ferrihydrite was decreased in the presence of As(III); however, FA and CA adsorption increased at lower pH, which was consistent with decreased As(III) adsorption. Peat humic acid did not decrease As(III) adsorption, and we believe that the adsorption process of HAp and As(III) and As(V) on ferrihydrite are independent of each other. Previously, we observed that As(V) adsorption on goethite decreased in the presence of HAp > FA > CA, while As(III) adsorption on goethite was decreased similarly to that on ferrihydrite in the presence of CA > FA approximately HAp, yet As(III) adsorption on ferrihydrite was greater than on goethite. The observed differences between this study and the earlier study on goethite are believed to be an intricate function of ferrihydrite's surface characteristics, which affect the mechanisms of adsorption and hence the affinity of organic acids such as HAp, FA, and CA for the ferrihydrite surface. As such, the adsorption of DOCs to ferrihydrite are assumed to be less favorable and to occur with a fewer number of ligands, resulting in lower surface coverage of weaker bond strength. 相似文献
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The function of call alternation in the African reed frog (Hyperolius marmoratus): precise call timing prevents auditory masking 总被引:3,自引:0,他引:3
T. Ulmar Grafe 《Behavioral ecology and sociobiology》1996,38(3):149-158
The function of call alternation in the African painted reed frog, Hyperolius marmoratus was studied. Males actively avoided call overlap with neighboring males in their natural habitat. Advertisement calls produced
by groups of two or three males showed less overlap than expected if they called at random. In addition, isolated males significantly
reduced their calling rate to match the periodicity of a playback of periodic tone pulses, with vocalizations given during
the silent intervals between tones. Gap-detection experiments showed that males suppressed vocalizations during playbacks
of constant-frequency tone bursts and gave more calls during silent periods than expected by chance. Females discriminated
against conspecific advertisement calls with many pulses in favor of calls with few or no pulses. This suggests that there
would be little selection pressure on males to alternate calls so that pulses are not obscured. To test if call alternation
functions to make calls more conspicuous, females were presented with identical conspecific advertisement calls from two speakers
in four different temporal patterns: simultaneous, overlapping, abutting, and alternating. Females did not discriminate when
calls were presented in a simultaneous, abutting, or alternating time pattern. When calls overlapped with the trailing call
delayed from 0.5 to 70 ms females discriminated in favor of the leading call. When the intensity of the leading call was reduced
by 6 dB the preference for the leading call was maintained when calls overlapped by 2 and 40 ms but was abolished or reversed
at 0.5 and 70 ms, respectively. These results support the notion that the second of two partially overlapping calls was acoustically
masked, rendering female painted reed frogs unwilling to approach or unable to locate such calls. It is suggested that either
simultaneous masking or the precedence effect are responsible for the observed behavior. Acoustic masking of the second call
by the first when calls overlapped was maintained even when the frequency of the first call was altered by 150 Hz above and
below the more preferred frequency of the second call.
Received: 13 April 1995/Accepted after revision: 5 November 1995 相似文献
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