Frequency Overlap Research Articles

Echolocation, flight morphology and foraging strategies of some West African hipposiderid bats

We studied echolocation call structure, flight morphology and feeding behaviour of three hipposiderid bats (Asellia tridens, Hipposideros caffer and H. ruber: Chiroptera: Hipposideridae) in The Gambia during the wet season (July‐August). All three species emitted brief CF/FM echolocation calls. In A. tridens CF (constant frequency) frequencies between 108 and 122 kHz were recorded. This variation was caused mainly by sex and age difference in call frequencies: juveniles used lower frequencies than did adults, and males were lower in frequency than females. Among adults, CF frequency was related to forearm length in a polynomial manner. Asellia tridens is unusual for a microchiropteran in that males are larger than females: nevertheless this species follows the typical trend for bats using CF components in their calls in that males call at lower frequencies than do females. The spread in frequencies noted for A. tridens in group flight was not caused primarily by individual shifting their frequencies when flying in a group compared with when flying alone. Three bats were flown separately and then together in a small room. The hypothesis that bats shift emitted frequencies in group flight to minimize confusing their own echoes with those from conspecifies was not supported. Rather, we suggest each bat has a personal CF frequency determined by sex, age and size, and that the variation created by these factors reduces confusion with other bats' echoes during group flight. Bats of the genus Hipposideros were separated into two groups by discriminant analysis on flight morphology. The two groups showed little overlap of CF frequencies used in echolocation. Bats identified as H. ruber called with CF resting frequencies between 121 and 136 kHz, while H. caffer used 128–153 kHz. Our results support the classification of these bats into two sibling species. We compared the flight performance of A. tridens and H. ruber by flying bats through obstacle courses: H. ruber had a lower wing loading and was able to negotiate more complex arrays of obstacles than could A. tridens. In the wild, H. ruber fed in more cluttered situations than did A. tridens. Both species were feeding mainly on Coleoptera during the study period, and in H. ruber individuals with higher aspect ratios and longer wingspans tended to eat more months than did bats with broader and shorter wings.

Real-time synthetic aperture radar (SAR) processing with a new subaperture approach

A time-domain subaperture approach that is suitable for real-time synthetic aperture radar (SAR) processing and that produces high-quality, full-resolution images is presented. The real-time subaperture algorithm is based on an approximation of the phase history correction in each subaperture with a simple linear correction, which can be carried out by an up/down-conversion of the received signal followed by a moving average operation. The characteristics of the impulse response function are improved considerably by means of a frequency overlap of the subapertures and become comparable to a conventional matched filter response. Special algorithms for high-quality SAR processing, such as autofocus, Doppler centroid estimation, and range migration correction, can be efficiently implemented. High flexibility is achieved for multilook processing and no secondary range compression is needed, even for high squint angles.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Young Stutterers’ Nonspeech Behaviors During Stuttering

The purpose of this study was to assess the nonspeech behaviors associated with young stutterers' stuttering and normally fluent children's comparable fluent utterances. Subjects were 28 boys and 2 girls who stutter (mean age = 54 months) and 28 boys and 2 girls who do not stutter (mean age = 54 months). Each child and his or her mother were audio-video recorded during a loosely structured, 30-min conversation. Sixty-six different nonspeech behaviors associated with 10 randomly selected stutterings per stutterer and 10 comparable fluent utterances per normally fluent child were assessed by means of frame-by-frame analysis of the audio-video recordings. Results indicate that (a) young stutterers produce significantly more nonspeech behaviors during stuttered words than do normally fluent children during comparable fluent words, (b) young stutters produce significantly more head turns left, blinks, and upper lip raising during stuttered words than do normally fluent children during comparable fluent words, and (c) talker group membership could be significantly determined on the basis of certain types of nonspeech behaviors despite considerable overlap in frequency and type of nonspeech behavior between the two talker groups. Findings suggest that children can be classified as stutterers on the basis of their nonspeech behaviors and that these behaviors may reflect a variety of cognitive, emotional, linguistic, and physical events associated with childhood stuttering.

Specificity and frequency of primary anti-HLA cytotoxic T lymphocytes in normal and HLA-B27.2-, HLA-B27.5-, and HLA-Cw3-transgenic mice. A transgenic model for MHC xenoantigen recognition.

Abstract Previous studies have shown that the lymphocytes of naive mice produce a strong primary CTL responses in vitro to human MHC class I Ag presented by HLA-transgenic mouse (TGM) cells. A limiting dilution (LD) assay was used to analyze this xenoreactive CTL repertoire in mice. Frequencies of HLA class I-specific CTL precursors (CTLp) were estimated in naive normal and HLA-B27.2-, -B27.5- and HLA-Cw3-double TGM (i.e., mice expressing HLA and human beta 2-microglobulin (hu beta 2m]. The xenoreactive CTLp frequencies were compared to frequencies of CTLp to H-2 alloantigens estimated in naive normal mice. The results showed that the frequencies of HLA class I-specific CTLp are comparable with those of alloreactive CTLp. This overlap in CTLp frequencies suggests that HLA class I xenoantigens are recognized by primary mouse CTL as allelic variants of H-2K and H-2D. This was confirmed in split well analysis by the observation that the xenoreactive response was not restricted by self-MHC of the responding mouse. Thus, primary HLA class I-specific mouse CTL clones recognized their target Ag regardless of whether they were expressed on H-2-mismatched mouse cells or on human cells. The frequencies of HLA class I-specific CTLp in HLA-TGM were comparable to those in normal mice. We propose that MHC allo- and xenoreactive CTL responses are not caused by the activation of CTLp specific for self-MHC plus peptide but to the activation of CTLp recognizing MHC allo- and xenoantigens directly or as peptides presented by their native MHC molecules.

An Analysis of the Vibrational Characteristics of Zeolites Using Factor Group Methods

The complete group theoretical representations for the normal modes of twelve high-symmetry zeolite crystal structures (including sodalite, offretite, and zeolite rho, as well as A, X, Y, and L-type zeolites) have been determined by factor group analysis. Comparisons of the predicted number of Raman and infrared active vibrations were made with existing experimental data in cases where such data were available. The prospects for conducting detailed analyses of the vibrational dynamics of zeolite framework structures based on the factor-group-derived representations were also examined. Much of the accepted intuitive understanding of zeolite vibrational spectra is confirmed by the findings of this work: e.g., that the number of predicted Raman and infrared frquencies (1) is consistently far greater than the number actually observed and (2) depends more on the level of symmetry of the zeolite crystal than on the number of atoms in the Bravais unit cell. Tight overlapping of frequencies, particularly those that are primarily bond stretching in nature, is to be expected.

Electromagnetic basis of acoustic perception. II. Physical mechanisms

A study of physical parameters leads to the conclusion that the human skull, with brain tissue included, is a cavity that will support electromagnetic standing wave fields in the frequency range between 200 MHz and 3 GHz. This frequency range coincides with allowable transitions in the rotational energy states of integral proteins that are embedded in nerve membranes. This frequency overlap permits the integral proteins to couple energy between propagating action potentials and standing electromagnetic fields within the skull. This is a crucial physical mechanism in a full theory of brain functioning which accords standing EM fields a central role in acoustic perception. All physical mechanisms will be discussed and related to biological structures in the brain. A key prediction of the theory is that the frequency of the lowest EM standing wave mode for any individual can be predicted simply with knowledge of the cephalic index. Recent measurements made on seven individuals confirm the theory. [Work sponsored by Mentec, Inc.]

Enzyme variation in some mosquito species related to Aedes (Ochlerotatus) stimulans (Diptera: Culicidae).

Isozyme patterns were studied by polyacrylamide gel electrophoresis in 7 North American mosquito populations comprising 4 species of the Aedes stimulans group of the subgenus Ochlerotatus. Seventeen enzyme loci were examined. All 4 species could be separated on the basis of differences in allelic frequencies for 5 loci [fumarate hydratase, hydroxybutyrate dehydrogenase, isocitrate dehydrogenase (2 forms), and octanol dehydrogenase]. Although no single locus was diagnostic for all 4 species (i.e., no overlap in allele frequency with other species), the use of 2 loci in combination permitted the correct identification of nearly all individuals of even the 2 most closely related species. Cluster analysis of gene frequencies was consistent with affinities previously described by conventional morphological characters. On the basis of enzyme phenotypes, Ae. euedes appeared more closely related to Ae. fitchii than to Ae. excrucians, a species with which Ae. euedes has been synonymized in the past.

Interspecific acoustic interactions of the neotropical treefrog Hyla ebraccata

Hyla ebraccata, H. microcephala and H. phlebodes commonly occur together in Panama. The three species have calls exhibiting broad frequency overlap and call during the same season and time of day from similar microhabitats, frequently in close proximity. The vocal repertoires of the three species are structurally and functionally similar. All employ multi-part advertisement and aggressive calls which consist of a primary note followed by a variable number of clicks. H. ebraccata males often responded to heterospecific calls with multi-note synchronized responses, and calls with primary notes greater than 150–200 ms were most effective in eliciting synchrony. Playback experiments with synthetic 1-note advertisement calls of different durations and both synthetic 1-note advertisement calls and 200 ms tones of different frequencies demonstrated that H. ebraccata males will synchronize with stimuli which are similar in frequency and duration to conspecific calls. Data from a two-choice experiment with female H. ebraccata demonstrate that calls of individual H. microcephala can reduce the attractiveness of a H. ebraccata male's calls if primary notes overlap. By synchronizing response calls to those of H. microcephala, a H. ebraccata may reduce the chances that his calls are rendered less attractive to potential mates.

Raman studies of the orientational motions of small diatomics dissolved in argon

We report a study of the orientational motions of oxygen and nitrogen dissolved in argon, using Raman spectroscopy. First, second, and fourth moments are reported for the rotation and vibration–rotation bands of these molecules at various concentrations along the liquid–vapor coexistence curve. It was found that less mean square torque is exerted on an oxygen molecule in argon solution than in the pure liquid at similar temperatures. The nitrogen data are probably in accord with this, although the experimental uncertainty is greater. Experimental values of the second moments are significantly in excess of the predicted classical values, even including important quantum corrections. This is probably due to ’’collision-induced’’ effects which were not accounted for in the moment analysis. Molecular dynamics simulations of rigid rotor ’’nitrogen’’ were made and the first order DID contributions to the collision-induced vibration–rotation spectrum were calculated. Even leaving out any high frequency overlap mechanism, the effect on the second moment was suprisingly large.

Some figural properties of auditory patterns.

Listeners identified one of six permutations of three frequencies, presented as brief three-note melodies. Identification performance remained high in spite of transposition of the original three frequencies throughout a two-octave range, so long as the musical intervals or frequency ratios between the adjacent pairs of frequencies remained constant. Even when those intervals were compressed or expanded, while remaining about equal to each other, identification was quite good for the range between the lowest and highest frequency of no more than approximately 1/3 octave. Performance decreased sharply when the span was much wider. Unequal intervals, where the low and middle frequencies were closer together or farther apart than the middle and high frequencies, did not retain good identification performance. When the three-tone patterns were embedded in longer sequences of seven or eight tones, the identification performance was best when the pattern occurred at the beginning or the end of the sequence, and when the range of frequencies from which the irrelevant background tones were chosen lay outside the range of pattern frequencies. Under conditions where the background frequencies were fixed and the pattern frequencies were moved, thus combining the manipulation of embedding with that of transposition of the pattern, overlap of pattern and background frequencies was still the principal cause of deterioration in performance. The findings are related to some analogies to the perceptual rules of Gestalt theory, as well as to certain aspects of musical practice.

Representation of the cochlea in the neocortex of guinea pigs.

By recording unit clusters and local evoked responses in the auditory cortex of guinea pigs the cortical representation of best frequencies was studied. In penetrations vertical to the cortical surface best frequencies were similar. Parallel to the cortical surface, however, different frequencies were found in the antero-posterior direction, whereas medio-laterally best frequencies usually remained in the same range (isofrequency stripes). Two auditory cortical fields could be distinguished, which are tonotopically organized. With increasing sound intensity the cortical response field for a given frequency and thus the frequency overlap increased. All along the isofrequency stripes in the medio-lateral direction, the stimulation of the contralateral ear produces larger responses than the same stimulus delivered to the ipsilateral ear.

On vocal registers

For a considerable length of time, the concept of vocal registers has been the subject of controversy. Various authors have argued that there are as few as one or as many as seven registers and a considerable number of contradictory and confusing names have been used to identify them. Moreover, to date, agreement cannot be obtained even with respect to a reasonable definition of the nature of registers themselves. Accordingly, this paper first provides a definition of vocal registers, viz. a vocal register is totally a laryngeal event; it consists of a series or range of consecutive voice frequencies which can be produced with nearly identical phonatory quality; that there will be little overlap in fundamental frequency between adjacent registers, and that the operational definition of a register must depend on supporting perceptual, acoustic, physiologic and aerodynamic evidence. On the basis of this definition, it is postulated that three major registers exist; they are the pulse, modal and loft registers. It is contended that these registers can be experimentally defined and demonstrated and, while other registers could exist (at least for some individuals), they cannot be identified and described at levels approaching the precision and understanding of the three proposed. Perceptual, acoustical, physiological and aerodynamic data are presented to support postulations relevant to these three registers, and to differentiate among them.

Wave packet formulation of nonlinear plasma wave kinetics

A theory of nonlinear plasma wave propagation is presented which contains, as particular cases, both the nonlinear Schrödinger equation for coherent waves and the kinetic wave equation for weak plasma turbulence. Fluctuations are represented as a superposition of “micro” wave packets, with finite spread but negligible overlap in wavenumber and frequency. For the case of coherent wave propagation a nonlinear Schrödinger equation is derived, generalized over precious versions in that linear Landau damping nonlinear frequency shift, nonlinear damping, and three-dimensional effects are all included, as well as the non-local, non-Markovian interaction characteristic of this equation. In the case of weak plasma turbulence, the kinetic wave equation is generalized to include self-interaction of the micro packets, which, just as in the coherent case, results in non-local, non-Markovian terms, not heretofore considered in weak turbulence formulations.

Relationships between channels for colour and spatial frequency in human vision.

Five forms of relationships and four types of channels are possible between two systems of sensory channels. The relationships between channels for colour and spatial frequency were studied in three adaptation experiments. In the first, a new colour-specific spatial aftereffect was found, which indicates the existence of channels that are specific both to colour and to spatial frequency. The second showed that the spatial-frequency aftereffect of Blakemore and Sutton is not colour specific, which indicates that there are channels for spatial frequency that are not colour specific. The third demonstrated that coloured afterimages are not spatial-frequency specific immediately after adaptation, although they become so later. This indicates that there are channels for colour that are not spatial-frequency specific. The existence of these three types of channels implies that the channel systems for colour and spatial frequency overlap partially and mutually in the human visual system. This kind of organisation of channel systems, if it exists, may form the psychophysical structure that is required for the capacity of simultaneous integration and differentiation in the perception of colour and size of visual objects.

A study of distress calls of song, swamp, and white-throated sparrows (Aves: Fringillidae). II. Interspecific responses and properties used in recognition

Recorded distress calls of each species were played to territorial males of the other two, in successive stages of the breeding cycle. Responses were like those given to intraspecific calls and showed a similar peak of intensity in the late nestling and fledgling stage.Song and swamp sparrows (Melospiza spp.) responded strongly to each other's calls, which are alike in length, carrier frequency, and frequency range and overlap broadly in rate of frequency modulation. However, responses were generally weak between Melospiza spp. and the white-throated sparrow (Zonotrichia), whose calls differ in these properties.Song and swamp sparrows responded strongly to artificial sounds that simulated their natural distress calls, but white-throated sparrows responded weakly to sounds that resembled their natural calls in some but not all properties.Song sparrows were exposed to artificial sounds that were varied in length, carrier frequency, and frequency modulation rate. With respect to each property, they responded strongly if the value fell within the range found in natural calls, but weakly if it fell outside this range. Evidently, all three properties are used in call recognition.We conclude that interspecific responses among these sympatric species resulted from similarities in their distress calls. Possible advantages of this behavior are discussed.

Seed characters and organ size in the cytotaxonomy of Rumex acetosella L.

Summary Angiocarpic seeds occur in diploid, tetraploid and hexaploid populations of Rumex acetosella s.l.- gymnocarpic seeds occur in tetraploids and hexaploids only, and among the hexaploids in populations from northern and central Europe. Cell and organ sizes do not rigorously correspond with the various levels of ploidy, and the overlap in range and frequency results in monomodal distributions. All New Zealand populations are hexaploid and angiocarpic and are unlikely to have been introduced from northern and central Europe.

Distribution of the group specific (Gc) serum component in the populations of the Markham Valley, New Guinea.

AbstractThe distribution of the Gc phenotypes was determined by immunoelectrophoresis amongst 486 inhabitants of nine villages of the Markham River Valley of New Guinea. The overall gene frequencies were Gc1, 0.538; Gc2, 0.351; GcAborigine, 0.112. GcAborigine occurred in all the villages, its frequency ranging from 0.041 to 0.187. The Gc2 gene frequency also varied widely ranging from 0.167 to 0.491. No correlation could be found between altitude and the Gc distribution and there was an overlap in the gene frequencies between the Austronesian and non‐Austronesian‐speaking villages.

Spectroscopic Technique for Probing an Ionized Gas

Ionized strontium is studied by the method of resonant absorption of optical radiation. Because of an accidental frequency overlap, normal rubidium can be used in a lamp as the source of resonant light. Spectral profiles of absorption were made with a scanning Fabry-Perot interferometer. The 5s½−6p½ line of Rb and the 5s½−5p½ line of Sr+ are found to differ by 0.014 Å. Optical and Langmuir probe measurements of density compare favorably. Ion temperatures in a steady-state and a decaying plasma were determined from the Doppler width. Two different sources of ionized strontium plasma are described. Negative results were obtained in an attempt to optically pump strontium ions in a plasma.

A 6-gigacycle propagation study to evaluate system engineering considerations in traversing difficult terrain

The engineering of microwave systems traversing extensive water surfaces and flat terrain has always presented a challenging problem. The new and more sophisticated 6-gc (gigacycle) equipments present new and interesting variations to the problem. The TH system, utilizing cross-polarized channels and some frequency overlap to effect a large message load capacity, is such a system. A new study was required to evaluate the particular factors in engineering such a system across the Great Salt Lake desert in Utah.