共查询到20条相似文献,搜索用时 15 毫秒
1.
An alternative scheme for selective water excitation is proposed. The pulse sequence saturates the resonances from the solute, allowing the observation of water-solute NOEs with low artifact levels. The water resonance is subsequently excited by a relatively non-selective 90° pulse. The scheme is compared to other selective water excitation schemes. 2D NOE-NOESY and ROE-NOESY pulse sequences are proposed which afford high sensitivity by efficient water excitation and flip-back by radiation damping, yet allow the use of short mixing times for the buildup of water-solute NOEs. 相似文献
2.
Gradient-tailored excitation for single-quantum NMR spectroscopy of aqueous solutions 总被引:76,自引:6,他引:70
Summary A novel approach to tailored selective excitation for the measurement of NMR spectra in non-deuterated aqueous solutions (WATERGATE, WATER suppression by GraAdient-Tailored Excitation) is described. The gradient echo sequence, which effectively combines one selective 180° radiofrequency pulse and two field gradient pulses, achieves highly selective and effective water suppression. This technique is ideally suited for the rapid collection of multi-dimensional data since a single-scan acquisition produces a pure phase NMR spectrum with a perfectly flat baseline, at the highest possible sensitivity. Application to the fast measurement of 2D NOE data of a 2.2. mM solution of a double-stranded DNA fragment in 90% H2O at 5 °C is presented. 相似文献
3.
Summary An improved version of the constant-time HSQC experiment is presented that gives uniform sensitivity over the complete 13C bandwidth in 13C−1H correlation experiments without creating artifacts in the methyl and aromatic regions of the spectra. The improvement is
achieved by replacing the refocussing 13C 180° pulse in the evolution time by a combination of a full-power (22 kHz) hyperbolic secant 180° pulse that inverts and
refocusses the entire 13C window, immediately followed by a selective 180° pulse on the CO region. Further improvement in signal-to-noise in the aromatic
and methyl regions, although less spectacular, is obtained by replacing the other two 180° 13C pulses in the INEPT parts of the pulse sequence by full-power hyperbolic secant pulses. Results of simulations and experimental
data are presented that demonstrate the excellent performance of the hyperbolic secant pulse for broadband inversion and show
that refocussing of transverse magnetization occurs over the same bandwidth, albeit with a 13C signal phase that depends quadratically on offset. A further modification, in which one of the selective pulses on the CO
region is omitted, is also presented. Implications for other 2D and 3D experiments performed at high fields, where uniform
13C inversion and refocussing is desirable, are discussed. 相似文献
4.
García VP 《Journal of biomolecular NMR》2011,50(1):91-97
Carbohydrates influence many essential biological events such as apoptosis, differentiation, tumor metastasis, cancer, neurobiology,
immunology, development, host-pathogen interactions, diabetes, signal transduction, protein folding, and many other contexts.
We now report on the structure determination of pregnane glycosides isolated from the aerial parts of Ceropegia fusca Bolle (Asclepiadaceae). The observation of cicatrizant, vulnerary and cytostatic activities in some humans and animals of
Ceropegia fusca Bolle, a species endemic to the Canary Islands, encouraged us to begin a pharmacological study to determine their exact therapeutic
properties. High resolution 1H-NMR spectra of pregnane glycosides very often display well-resolved signals that can be used as starting points in several
selective NMR experiments to study scalar (J coupling), and dipolar (NOE) interactions. ROESY is especially suited for molecules
such that ωτc ~ 1, where τc are the motional correlation times and ω is the angular frequency. In these cases the NOE is nearly zero, while the rotating-frame
Overhauser effect spectroscopy (ROESY) is always positive and increases monotonically for increasing values of τc. The ROESY shows dipolar interactions cross peaks even in medium-sized molecules which are helpful in unambiguous assignment
of all the interglycosidic linkages. Selective excitation was carried out using a double pulsed-field gradient spin-echo sequence
(DPFGSE) in which 180° Gaussian pulses are sandwiched between sine shaped z-gradients. Scalar interactions were studied by
homonuclear DPFGSE-COSY and DPFGSE-TOCSY experiments, while DPFGSE-ROESY was used to monitor the spatial environment of the
selectively excited proton. Dipolar interactions between nuclei close in space can be detected by the 1D GROESY experiment,
which is a one-dimensional counterpart of the 2D ROESY method. The C-12 and C-17 configurations were determined by ROESY experiments. 相似文献
5.
InDrosophila montana andD. littoralis (species of theD. virilis group), females use male courtship song in their mate choice in wild preferring males which produce short and dense sound
pulses (Aspi and Hoikkala, 1995). In the present study these song characters were found to be repeatable among overwintered
males. Male progenies of wild-caught flies reared in the laboratory, and inD. montana also the males collected in wild before overwintering, exhibited very little variation between males in these characters.
Contrary to pulse characters, pulse train characters measured forD. montana song varied significantly between laboratory-reared males. Our findings suggest that inD. montana andD. littoralis song characters playing a part in sexual selection in the wild are more condition dependent than song characters which are
not the direct targets of female choice. 相似文献
6.
A new 1H NMR pulse sequence is described that combines water suppression with the selective observation of signals from coupled spin systems. The pulse sequence is easy to set up and compensates for pulse width inhomogeneity in the biological sample. Suppression of the water signal is achieved by pulses that return the water spins to their equilibrium position; spectral editing is based on the J modulation present in spin-echo spectra and its inhibition by coherent decoupling at one of the resonances of the spin system of interest. The pulse sequence, which was designed for 1H NMR spectroscopy of tissue, was tested at 470 MHz on excised frog muscle and rat brain. The lactate methyl resonance of caffeine-treated frog sartorius muscle was observed selectively by irradiation at the position of its alcoholic proton. The terminal methyl signal of linolenic acid, along with other fatty acids of the linolenic series (first double bond in the omega-3 position), was observed selectively by irradiation at the position of its omega-1 methylene group. 1H NMR spectra of rat brain were edited to reveal the terminal methyl of either linolenic series or all other fatty acids. The results suggest that the terminal methyl groups of fatty acids of the linolenic series (mostly docosahexaenoic acid, 22:6) have higher mobility than those of all other fatty acids. 相似文献
7.
Summary Two alternative, general methods are presented that lead to enhanced signal intensity of rapidly exchanging protons. Both methods work by avoiding saturation of the water resonance, and are convenient to implement since they do not use any selective pulses. One method carefully chooses proton pulse phases and gradient strength and position in such a way that the water is realigned along the +z axis at the beginning of the acquisition time. An alternative method is proposed for cases where the pulse sequence does not allow such phase cycling. The latter uses radiation damping to bring water back to the +z axis 20–30 ms after acquisition. The methods are applied to the triple-resonance experiments HNCA, HNCO and HN(CO)CA. Both methods require pulsed B0 field gradients and can result in higher signal intensity by a factor of two or more. 相似文献
8.
Modifying the ‘pulse–reserve’ paradigm for deserts of North America: precipitation pulses,soil water,and plant responses 总被引:5,自引:0,他引:5
The ‘pulse–reserve’ conceptual model—arguably one of the most-cited paradigms in aridland ecology—depicts a simple, direct relationship between rainfall, which triggers pulses of plant growth, and reserves of carbon and energy. While the heuristics of ‘pulses’, ‘triggers’ and ‘reserves’ are intuitive and thus appealing, the value of the paradigm is limited, both as a conceptual model of how pulsed water inputs are translated into primary production and as a framework for developing quantitative models. To overcome these limitations, we propose a revision of the pulse–reserve model that emphasizes the following: (1) what explicitly constitutes a biologically significant ‘rainfall pulse’, (2) how do rainfall pulses translate into usable ‘soil moisture pulses’, and (3) how are soil moisture pulses differentially utilized by various plant functional types (FTs) in terms of growth? We explore these questions using the patch arid lands simulation (PALS) model for sites in the Mojave, Sonoran, and Chihuahuan deserts of North America. Our analyses indicate that rainfall variability is best understood in terms of sequences of rainfall events that produce biologically-significant ‘pulses’ of soil moisture recharge, as opposed to individual rain events. In the desert regions investigated, biologically significant pulses of soil moisture occur in either winter (October–March) or summer (July–September), as determined by the period of activity of the plant FTs. Nevertheless, it is difficult to make generalizations regarding specific growth responses to moisture pulses, because of the strong effects of and interactions between precipitation, antecedent soil moisture, and plant FT responses, all of which vary among deserts and seasons. Our results further suggest that, in most soil types and in most seasons, there is little separation of soil water with depth. Thus, coexistence of plant FTs in a single patch as examined in this PALS study is likely to be fostered by factors that promote: (1) separation of water use over time (seasonal differences in growth), (2) relative differences in the utilization of water in the upper soil layers, or (3) separation in the responses of plant FTs as a function of preceding conditions, i.e., the physiological and morphological readiness of the plant for water-uptake and growth. Finally, the high seasonal and annual variability in soil water recharge and plant growth, which result from the complex interactions that occur as a result of rainfall variability, antecedent soil moisture conditions, nutrient availability, and plant FT composition and cover, call into question the use of simplified vegetation models in forecasting potential impacts of climate change in the arid zones in North America. 相似文献
9.
The transpiration response of excised primary Avena leaves was studied when pulse perturbations were given to the water regulatory system. Repeated light pulses given to the leaf caused regularly alternating transpiration responses, i.e. the magnitude alternated regularly between a high and a low value. This effect, denoted alternating pulse response, could be recorded under quite different light pulse conditions but was not found when the pulse interval was too long or too short (longer than about 60 min. shorter than about 15 min). Sodium chloride given to the transpiration stream induced and increased the effect. Alternating pulse response could also be recorded when mannitol pulses were given to the root system of intact plants. 相似文献
10.
Precipitation pulse use by an invasive woody legume: the role of soil texture and pulse size 总被引:9,自引:0,他引:9
Plant metabolic activity in arid and semi-arid environments is largely tied to episodic precipitation events or “pulses”.
The ability of plants to take up and utilize rain pulses during the growing season in these water-limited ecosystems is determined
in part by pulse timing, intensity and amount, and by hydrological properties of the soil that translate precipitation into
plant-available soil moisture. We assessed the sensitivity of an invasive woody plant, velvet mesquite (Prosopis velutina Woot.), to large (35 mm) and small (10 mm) isotopically labeled irrigation pulses on two contrasting soil textures (sandy-loam
vs. loamy-clay) in semi-desert grassland in southeastern Arizona, USA. Predawn leaf water potential (Ψpd), the isotopic abundance of deuterium in stem water (δD), the abundance of 13C in soluble leaf sugar (δ13C), and percent volumetric soil water content (θv) were measured prior to irrigation and repeatedly for 2 weeks following irrigation. Plant water potential and the percent
of pulse water present in the stem xylem indicated that although mesquite trees on both coarse- and fine-textured soils quickly
responded to the large irrigation pulse, the magnitude and duration of this response substantially differed between soil textures.
After reaching a maximum 4 days after the irrigation, the fraction of pulse water in stem xylem decreased more rapidly on
the loamy-clay soil than the sandy-loam soil. Similarly, on both soil textures mesquite significantly responded to the 10-mm
pulse. However, the magnitude of this response was substantially greater for mesquite on the sandy-loam soil compared to loamy-clay
soil. The relationship between Ψpd and δ13C of leaf-soluble carbohydrates over the pulse period did not differ between plants at the two sites, indicating that differences
in photosynthetic response of mesquite trees to the moisture pulses was a function of soil water availability within the rooting
zone rather than differences in plant biochemical or physiological constraints. Patterns of resource acquisition by mesquite
during the dynamic wetting–drying cycle following rainfall pulses is controlled by a complex interaction between pulse size
and soil hydraulic properties. A better understanding of how this interaction affects plant water availability and photosynthetic
response is needed to predict how grassland structure and function will respond to climate change. 相似文献
11.
Michael E. Loik 《Plant Ecology》2007,191(1):95-108
For much of the western USA, precipitation occurs in pulses, the nature of which determine soil water potential and plant
physiological performance. This research utilized three experiments to examine the sensitivity of photosynthesis and water
relations for two widespread Great Basin Desert shrub species, Artemisia tridentata (which has both deep and shallow roots) and Purshia tridentata (which reportedly has only deep roots), to (1) variation in pulse magnitude size, (2) the kinetics of responses to pulses,
and (3) the relationship between pulse-size and antecedent soil water content. At the study site in the southwestern Great
Basin Desert, USA, summer rainfall exhibits a greater frequency of larger-sized events, and longer inter-pulse intervals,
compared to annual patterns. Compared to pre-watering values, stem water potential initially increased by about 2.00 MPa for
A. tridentata and 1.00 MPa for P. tridentata following watering to simulate an 11.5 mm rainfall pulse. For the same water addition, stomatal conductance increased by
0.3 mol m−2 s−1 and photosynthetic CO2 assimilation increased 8-fold for A. tridentata and 6-fold for P. tridentata. Water potential and photosynthetic gas exchange were maximal for both species 2–3 days following a pulse addition. In comparison
to P. tridentata, the increase in photosynthesis for A. tridentata was more pronounced for plants treated incrementally with several small pulses compared to plants treated with one pulse
of an equivalent total volume. The results indicate that both species can respond to a range of summer rainfall pulse magnitudes
within about 2 days, with A. tridentata generally exhibiting larger responses in comparison to the co-dominant shrub species P. tridentata, which at this study site does indeed have shallow roots. In a future climate, the timing and magnitude of summer rainfall
pulses will determine the extent to which these two species undergo changes in water status and photosynthetic carbon uptake,
with implications for their fitness. 相似文献
12.
Anneli Hoikkala Jaakko Lumme 《Evolution; international journal of organic evolution》1987,41(4):827-845
When courting, males of the Drosophila virilis group vibrate their wings and emit species-specific courtship sounds consisting of trains of polycyclic sound pulses. To analyze the genetic basis of evolutionary changes in the sounds we made an F1 diallel set of reciprocal crosses between the members of the virilis phylad of the group (two stocks of D. virilis and one of D. americana americana, D. a. texana, D. novamexicana, and D. lummei). We also crossed the D. virilis stocks with the members of the montana phylad of the same group (D. kanekoi, D. littoralis, D. borealis, D. flavomontana, D. lacicola, and D. montana) and made a backcross (D. virilis x D. littoralis) x D. virilis using a D. virilis marker stock (b; sv t tb gp; cd; pe). The sounds of the hybrids were analyzed using the following parameters: the length of a pulse train (PTL), the number of pulses in a train (PN), the interpulse interval (IPI), the length of a pulse (PL), the number of cycles in a pulse (CN), and the length of a cycle (CL). In the virilis phylad, the differences between species appeared to be determined mainly by autosomal genes in each sound trait. The heritabilities (narrow-/broad-sense) obtained from the diallel tables were the following: PTL 0.662/0.817, PN 0.651/0.841, IPI 0.193/0.546, PL 0.408/0.552, CN 0.425/0.719, and CL 0.361/0.764. The direction of dominance is for longer PTL, higher PN and CN, and shorter IPI and CL. PL shows ambidirectional dominance. In the sounds of the virilis phylad species, PTL and PL seem to be phenotypically the most important parameters, since their components (PN and IPI for PTL, CN and CL for PL) are negatively correlated. In crosses between D. virilis and D. littoralis or D. flavomontana reciprocal hybrids differed from each other in PTL, IPI, PL, and CN indicating X-chromosomal or cytoplasmic inheritance. In the backcrosses between D. virilis and D. littoralis the role of the X chromosome was ascertained to be decisive. We conclude that an X-chromosomal major change allowing variation in IPI has occurred during the separation of the two D. virilis group phylads, the long IPI allowing variation also in PL (and CN). The evolution of the sounds in the virilis phylad has probably gone towards longer and denser pulse trains, while in the montana phylad the sounds have evolved in different directions. 相似文献
13.
Melanie Zeppel Catriona M. O. Macinnis-Ng Chelcy R. Ford Derek Eamus 《Plant and Soil》2008,305(1-2):121-130
In water-limited systems, pulses of rainfall can trigger a cascade of plant physiological responses. However, the timing and
size of the physiological response can vary depending on plant and environmental characteristics, such as rooting depth, plant
size, rainfall amount, or antecedent soil moisture. We investigated the influence of pulses of rainfall on the response of
sap flow of two dominant evergreen tree species, Eucalyptus crebra (a broadleaf) and Callitris glaucophylla (a needle leaved tree), in a remnant open woodland in eastern Australia. Sap flow data were collected using heat-pulse sensors
installed in six trees of each species over a 2 year period which encompassed the tail-end of a widespread drought. Our objectives
were to estimate the magnitude that a rainfall pulse had to exceed to increase tree water use (i.e., define the threshold
response), and to determine how tree and environmental factors influenced the increase in tree water use following a rainfall
pulse. We used data filtering techniques to isolate rainfall pulses, and analysed the resulting data with multivariate statistical
analysis. We found that rainfall pulses less than 20 mm did not significantly increase tree water use (P > 0.05). Using partial regression analysis to hold all other variables constant, we determined that the size of the rain
event (P < 0.05, R
2 = 0.59), antecedent soil moisture (P < 0.05, R
2 = 0.29), and tree size (DBH, cm, P < 0.05, R
2 = 0.15), all significantly affected the response to rainfall. Our results suggest that the conceptual Threshold-Delay model
describing physiological responses to rainfall pulses could be modified to include these factors. We further conclude that
modelling of stand water use over an annual cycle could be improved by incorporating the T-D behaviour of tree transpiration.
Responsible Editor: Stephen S.O. Burgess 相似文献
14.
Soultana Maria Valamoti Aikaterini Moniaki Angeliki Karathanou 《Vegetation History and Archaeobotany》2011,20(5):381-396
Pulses have constituted an important food source for prehistoric communities in the Old World, yet little is known as regards
their processing for consumption through the archaeobotanical record. This paper provides an overview of archaeobotanical
evidence for the use of pulses in prehistoric Greece based on two case studies from the north, and explores (a) their preparation
for consumption, in particular their detoxification and (b) the consumption of pulses as a component of ordinary daily meals
in prehistoric times, as well as those for special occasions, within a context of feasting and ritual. The paper examines
charred remains of Vicia ervilia (bitter vetch) and Lathyrus sativus (grass pea) from early Bronze Age Agios Athanasios and late Neolithic Kremasti Koiladas, respectively, as the former provides
a basis for a pilot exploration of pulse detoxification and the latter, due to its origin, offers a rare opportunity to discuss
the context of consumption. In the pilot exploration of pulse seed preparation for consumption, the inner cotyledon morphology
of modern V. ervilia seeds which were experimentally processed with water and pounding was examined macroscopically and through SEM micrographs.
Preliminary observations suggest that intentional splitting of pulse seeds as part of processing for consumption as food may
be recognisable in the archaeobotanical record. Processing with water may also be detected. The particular context of the
Kremasti finds suggests that pulses, in this particular case L. sativus, may have constituted special foods for particular occasions, loaded with symbolic meaning. 相似文献
15.
Temporal analyses were applied to the tone pulses within the courtship songs of Drosophila melanogaster, D. simulans,their interspecific hybrid, and behavioral mutants of D. melanogaster.Linear regression was performed on various parameters of the song pulses (cycles per pulse, absolute peak amplitude, intrapulse frequency, number of peaks in fast Fourier transform, width of the primary frequency peak, and interpulse interval), as a function of their positions within pulse trains. Significant differences in the slope values of these two species and of the mutant genotypes allowed for discriminative quantification of temporal changes within trains. These results are discussed in relation to previous kinds of temporal analyses of Drosophilacourtship songs and also with regard to the mechanisms of song production. 相似文献
16.
Plant N capture from pulses: effects of pulse size,growth rate,and other soil resources 总被引:8,自引:0,他引:8
In arid ecosystems, the ability to rapidly capture nitrogen (N) from brief pulses is expected to influence plant growth, survival,
and competitive ability. Theory and data suggest that N capture from pulses should depend on plant growth rate and availability
of other limiting resources. Theory also predicts trade-offs in plant stress tolerance and ability to capture N from different
size pulses. We injected K15NO3, to simulate small and large N pulses at three different times during the growing season into soil around the co-dominant
Great Basin species Sarcobatus vermiculatus, Chrysothamnus nauseosus ssp. consimilis, and Distichlis spicata. Soils were amended with water and P in a partial factorial design. As predicted, all study species showed a comparable decline
in N capture from large pulses through the season as growth rates slowed. Surprisingly, however, water and P availability
differentially influenced the ability of these species to capture N from pulses. Distichlis N capture increased up to tenfold with water addition while Chrysothamnus N capture increased up to threefold with P addition. Sarcobatus N capture was not affected by water or P availability. Opposite to our prediction, Sarcobatus, the most stress tolerant species, captured less N from small pulses but more N from large pulses relative to the other species.
These observations suggest that variation in N pulse timing and size can interact with variable soil water and P supply to
determine how N is partitioned among co-existing Great Basin species. 相似文献
17.
Objective: Recent studies have shown that free fatty acid (FFA) release is pulsatile and that this pattern is controlled by the sympathetic nervous system. It is, then, necessary to understand and characterize adipose tissue lipolysis to elucidate its effect on metabolism. In this study, we introduce deconvolution as a method to detect and quantify pulsatile FFA release. Research Methods and Procedures: Octanoate, a medium‐chain fatty acid, was infused in male mongrel dogs (n = 7) to mimic the pulsatile appearance of plasma FFAs. Deconvolution analysis was used to reconstruct the number and timing of infused octanoate pulses from plasma FFA concentrations. Results: Deconvolution analysis was able to reconstruct the exogenously infused pulses of octanoate used to mimic pulsatile appearance of FFAs (pulse frequency, 8 per hour; interpulse interval, 7 minutes). However, determination of pulse mass was less accurate (1.0 ± 0.0 vs. 0.54 ± 0.1 mM). The addition of varying levels of Gaussian noise to non‐oscillatory FFA time series did not lead to detection of extraneous FFA pulses. However, goodness of fit declined with increasing variability. Discussion: These results support the use of deconvolution as an accurate approach to determine the temporal sequence of endogenous FFA release. 相似文献
18.
Acoustic signals from the bird wrasse Gomphosus varius and saddle wrasse Thalassoma duperrey were recorded on coral reefs in Hawaii. Terminal phase males in both species emit two types of pulse trains (type I and type II). Type I pulses were produced during spawning and courtship, while type II pulses were associated only with courtship behaviours. Gomphosus varius type I pulses were of lower frequency than T. duperrey type I pulses (271 v. 840 Hz) and were of narrower band. Discriminant function analyses revealed interspecific differences between type I pulse trains and individual pulses of both types. This study is the first documentation of courtship and spawning sounds in sympatric labrids and shows divergence in acoustic signals. 相似文献
19.
Andrea L. Joyce Martin Aluja John Sivinski S. Bradleigh Vinson Ricardo Ramirez-Romero Julio S. Bernal Larissa Guillen 《BioControl》2010,55(5):573-582
The courtship acoustics of five species of parasitoid wasps (Hymenoptera: Braconidae), potential candidates for augmentative
biological control of Anastrepha (Schiner) species (Diptera: Tephritidae), were compared between recently colonized individuals and those continuously reared
70–148 generations. During courtship, males of these parasitoid species fan their wings and produce a series of low amplitude
pulses. The first series of 15 or more continuous courtship pulses was used to measure the pulse duration, frequency, and
interpulse interval (IPI) from the beginning, middle, and end of the pulse series. Each parameter was compared between young
and old colonies, and among species. Several differences in courtship acoustics were detected in colonies that had been continuously
reared. The pulse duration at the end of the pulse series was longer in old colonies for Doryctobracon crawfordi (Viereck) (Hymenoptera: Braconidae), but shorter for old colonies of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae). The IPI of the middle pulse was shorter in old colonies of Opius hirtus (Fischer) (Hymenoptera: Braconidae), and was also shorter at the last pulse for old colonies of both Utetes anastrephae (Viereck) (Hymenoptera: Braconidae) and D. longicaudata. The duration of the middle pulse distinguished the three native species, and separated the two introduced species from each
other. We discuss our findings in light of their biological and applied implications, particularly those dealing with quality
control of mass-reared parasitoids. 相似文献
20.
A nine-day acoustic and visual survey was conducted off the West Indies in March 1994 to study the pulse trains that were detected on SOSUS arrays throughout winter in deep water between the West Indies and Bermuda. During the survey, pulse train sounds were consistently recorded in an area 190–350 km northeast of Puerto Rico. Vocalizing animals were never visually observed, but visual sighting conditions were often poor and observation height was low. Pulse trains occurred in two basic forms. The "speed-up" pulse train was characterized by an accelerating series of pulses with energy in the 200–400 Hz band, with individual pulses lasting 40-60 msec. Speedup pulse trains started with average pulse rates of 1.5 pulses/sec, lasted 43.7 ± 6.0 sec, and ended with average pulse rates of 2.8 pulses/sec. The less common "slow-down" pulse train was characterized by a decelerating series of pulses with energy in the 250-350 Hz band. Slow-down pulse trains started at pulse rates averaging 4.5 pulses/sec, lasted 60.9 ± 5.8 sec, and ended with average pulse rates of 2.9 pulses/sec. We believe the recorded pulse trains are from minke whales based on careful reanalysis of, and comparison to, minke whale pulse-train sounds recorded in the Caribbean by Winn and Perkins (1976). 相似文献