Small Frequency Differences Research Articles

Stimulus uncertainty and insensitivity to pitch-change direction

In a series of experiments, Semal and Demany [(2006). J. Acoust. Soc. Am. 120, 3907-3915] demonstrated that some normally hearing listeners are unable to determine the direction of small but detectable differences in frequency between pure tones. Unlike studies demonstrating similar effects in patients with brain damage, the authors used stimuli in which the standard frequency of the tones was highly uncertain (roved) over trials. In Experiment 1, listeners were identified as insensitive to the direction of pitch changes using stimuli with frequency roving. When listeners were retested using stimuli without roving in Experiment 2, impairments in pitch-direction identification were generally much less profound. In Experiment 3, frequency-roving range had a systematic effect on listeners' thresholds, and impairments in pitch-direction identification tended to occur only when the roving range was widest. In Experiment 4, the influence of frequency roving was similar for continuous frequency changes as for discrete changes. Possible explanations for the influence of roving on listeners' insensitivity to pitch-change direction are discussed.

Vocal communication in African Elephants (Loxodonta africana)

Research on vocal communication in African elephants has increased in recent years, both in the wild and in captivity, providing an opportunity to present a comprehensive review of research related to their vocal behavior. Current data indicate that the vocal repertoire consists of perhaps nine acoustically distinct call types, "rumbles" being the most common and acoustically variable. Large vocal production anatomy is responsible for the low-frequency nature of rumbles, with fundamental frequencies in the infrasonic range. Additionally, resonant frequencies of rumbles implicate the trunk in addition to the oral cavity in shaping the acoustic structure of rumbles. Long-distance communication is thought possible because low-frequency sounds propagate more faithfully than high-frequency sounds, and elephants respond to rumbles at distances of up to 2.5 km. Elephant ear anatomy appears designed for detecting low frequencies, and experiments demonstrate that elephants can detect infrasonic tones and discriminate small frequency differences. Two vocal communication functions in the African elephant now have reasonable empirical support. First, closely bonded but spatially separated females engage in rumble exchanges, or "contact calls," that function to coordinate movement or reunite animals. Second, both males and females produce "mate attraction" rumbles that may advertise reproductive states to the opposite sex. Additionally, there is evidence that the structural variation in rumbles reflects the individual identity, reproductive state, and emotional state of callers. Growth in knowledge about the communication system of the African elephant has occurred from a rich combination of research on wild elephants in national parks and captive elephants in zoological parks.

Properties of gamma frequency oscillatory activity induced in hippocampal slices from the adult GAD67-GFP (Δneo) mouse

The green fluorescent protein (GFP)-linked expression of protein in transgenic mice provides an ideal tool for the correlation of structure and function in the CNS. An important target of study is the role of GABAergic neurons in oscillatory activity in the hippocampus, and this would be facilitated with transgenic mice in which GFP is linked to the expression of GABA markers. One such mouse is the GAD67-GFP (Δneo), and here we compare the properties of kainate- and carbachol-induced oscillatory activity generated in CA3 of hippocampal slices from heterozygous GAD67-GFP (Δneo) mice and wild type litter mates. For both paradigms and in both mouse preparations oscillations were generated in the 20–30 Hz range, and for the kainate-, but not the carbachol-induced oscillations, there was a small but significant difference in peak frequency of the oscillations between GAD67-GFP (Δneo) mice (28.4 ± 2.2 Hz) and wild type mice (25 ± 1.6 Hz). For both oscillatory paradigms there was no significant difference between mouse strains in area power of the oscillatory activity in the stratum oriens lamina of CA3, but for the kainate-induced oscillations, area power became significantly diminished in the stratum radiatum lamina of the GAD67-GFP (Δneo) mouse compared with the wild type mouse after prolonged exposure to kainate. This gradual reduction in area power in CA3 of the transgenic mouse was rescued by inclusion of Guvacine, a GABA uptake inhibitor, suggesting that the reported lower levels of GABA in the GAD67-GFP (Δneo) mouse brain during development and in the adult may contribute to a reduction in the efficiency of GABA neurotransmission after prolonged stimulation of the GABAergic circuitry.

Population transfer to theE Σ1gexcited electronic state ofLi2by femtosecond laser pulses with all possible interstate radiative couplings

Population transfer to the excited electronic state $E\text{ }{^{1}\ensuremath{\Sigma}}_{\text{g}}$ of ${\text{Li}}_{2}$ by transform limited delayed femtosecond pulses has been investigated. The validity of the usual neglect of some field-molecule coupling terms in such transfers, accomplished using counterintuitively ordered pulses through ``adiabatic passage on light-induced potentials,'' has been reexamined. It has been found that such an approximation cannot be justified in the case of the ladder system $X\text{ }^{1}\ensuremath{\Sigma}^{+}_{\text{g}}\text{\ensuremath{-}}A\text{ }^{1}\ensuremath{\Sigma}^{+}_{\text{u}}\text{\ensuremath{-}}E\text{ }^{1}\ensuremath{\Sigma}^{+}_{\text{g}}$ of ${\text{Li}}_{2}$. However, the transfer can be successfully accomplished over a range of pulse parameters, which is more restricted than those obtained with the usual approximation. In this scheme, when two pulses with a small frequency difference between them are used, the lower-frequency pulse must precede the higher-frequency pulse for a successful transfer. We introduce an adiabatic representation, appropriate to this full coupling case, for examining the mechanism of transfer. In our representation the initial wave packet may be prepared on more than one adiabatic state, and at an early stage it is transferred to a single adiabatic surface after which the evolution mostly proceeds adiabatically. The vibrational analysis of the final wave packet shows that for short pulses high vibrational states are generally excited, while for pulses with larger width low-lying vibrational states are preferred in cases where successful transfer occurs. These results can be understood in terms of the motion of the wave packet on the time-dependent adiabatic potentials.

The Actual Role of CT and Ventilation–Perfusion Scanning in Workup for Suspected Pulmonary Embolism: Evidence From Hospitals

Over the past two decades, CT has been found valuable in the diagnosis of pulmonary embolism (PE). We sought to ascertain the relative roles of CT and ventilation-perfusion (V/Q) scanning, the previously preferred technique, in the diagnosis of PE in recent practice and whether there is variation among hospital types. Using the Medicare anonymized 5% of beneficiaries complete claims file for 2005, we studied the use of relevant CT and V/Q scanning in the evaluation of patients with a diagnosis of PE and of patients with symptoms that might have been due to PE (chest pain, syncope, difficulty breathing). In 2008, we surveyed the radiology departments of Pennsylvania hospitals about the use of CT and V/Q scanning for PE, service availability hours, and what equipment was used. In all data, we found that CT was used approximately six times as frequently as V/Q scanning. In the Medicare data, only small differences in frequency of use of CT and V/Q scanning were associated with hospital characteristics. Academic hospitals did not differ in a major way from other hospitals, nor did small or rural hospitals. In the survey, 97% of radiology departments reported that CT was available for evaluation of PE 24 hours a day 7 days a week. Ninety-three percent of departments reported V/Q scanning was available at some times; 77% reported V/Q available at all times. CT was a fully disseminated and dominant technique for the diagnosis of PE by 2005, and it was readily available at small and rural hospitals. The lack of availability of off-hours V/Q scanning at a substantial fraction of hospitals may be a problem for patients with contraindications to CT.

Theoretical Analysis of a New Technique for Inertial Rotation Sensing Using a Semiconductor Ring Laser

We introduce a new technique for the measurement of inertial rotations using a semiconductor ring laser. Inertial rotation introduces a frequency deviation of the optical frequency of the two counterpropagating waves in the laser cavity, whereas mode coupling causes frequency attraction (frequency pushing) and finally locking at low rotation rates, washing out the small Sagnac frequency difference to be measured. Here we propose to measure inertial rotation whitin the so-called locking band using the phase/amplitude dependence on detuning found for the oscillating modes under the gain line. The dephasing accumulated by the two counterpropagating waves unbalances the fields' amplitudes within the locking region. We analytically derive the responsivity function quantifying the two-mode power unbalance versus rotation rate, by means of a two-mode rate equations model. Noise performance of a possible rotations sensor are also discussed by calculating the noise equivalent rotation rate.

Investigation of DNA polymorphisms in SMAD genes for genetic predisposition to diabetic nephropathy in patients with type 1 diabetes mellitus

SMAD proteins are involved in multiple signalling pathways and are key modulators of gene expression. We hypothesised that genetic variation in selected SMAD genes contributes to susceptibility to diabetic nephropathy. We selected 13 haplotype tag (ht) single nucleotide polymorphisms (SNPs) from 67 variants identified by resequencing the SMAD2 and SMAD3 genes. For SMAD1, SMAD4 and SMAD5 genes, genotype data were downloaded for 217 SNPs from Phase II of the International HapMap project. Of these, 85 SNPs met our inclusion criteria, resulting in the selection of 13 tag SNPs for further investigation. A case-control approach was employed, using 267 nephropathic patients and 442 controls with type 1 diabetes from Ireland. Two further populations (totalling 1,407 patients, 2,238 controls) were genotyped to validate initial findings. Genotyping was conducted using iPLEX, TaqMan and gel electrophoresis. The distribution of genotypes was in Hardy-Weinberg equilibrium. Analysis by the chi(2) test of genotype and allele frequencies in patients versus controls in the Irish population (n = 709) revealed evidence for the association of one allele at 5% level of significance (rs10515478, p(uncorrected) = 0.006; p(corrected) = 0.04). This finding represents a relatively small difference in allele frequency of 6.4% in the patient group compared with 10.7% in the control group; this difference was not supported in subsequent investigations using DNA from European individuals with similar phenotypic characteristics. We selected an appropriate subset of variants for the investigation of common genetic risk factors and assessed SMAD1 to SMAD5 genes for association with diabetic nephropathy. We conclude that common polymorphisms in these genes do not strongly influence genetic susceptibility to diabetic nephropathy in white individuals with type 1 diabetes mellitus.

Sensitivity of feedback‐enhanced MRI contrast to macroscopic and microscopic field variations

Nonlinear feedback interactions have been shown to amplify contrast due to small differences in resonance frequency arising from microscopic susceptibility variations. Determining whether the selectivity of feedback-based contrast enhancement for small resonance frequency variations remains valid even in the presence of macroscopic field inhomogeneity is important for transitioning this new methodology into in vivo applications in imaging systems with lower field strengths and poorer homogeneity. This work shows that contrast enhancement under the radiation damping (RD) feedback field is sensitive to microscopic intravoxel frequency variations. Feedback-enhanced contrast provides superior signal differentiation from voxels with distinct microscopic frequency distributions compared with T(2)*-weighted imaging, while remaining robust to macroscopic field gradients, which frequently give rise to artifacts by other frequency-sensitive methods. Applying multiple RF pulses during evolution under RD and actively adjusting the phase and amplitude of the feedback field are shown to further improve signal differentiation. Experimental results reveal that feedback-enhanced contrast can generate positive contrast, reflecting microscopic field variations induced by strong local dipole fields, such as those created by blood vessels and superparamagnetic iron oxide nanoparticles. Extensions to in vivo imaging at lower field strengths are discussed in the context of amplifying the RD field via active electronic feedback.

Two high-performance and low-power serial communication interfaces for on-chip interconnects

This paper presents two novel methods for on-chip serial communication in which the clocks of the transmitter and the receiver are generated with two separate ring oscillators. These oscillators are identical, although they can have a small frequency difference. In the first method, a strobe line that toggles exactly once with every frame of n-bit data is used to activate the oscillators. Local counters are used to count the number of bits in the data frame and to stop the local oscillators when the frame has been processed. In the second method, a single physical line is used to transmit both data and (in-band) control information, further reducing the power dissipation. The data transmission is controlled by the output of a starter flip-flop that indicates the empty/full state of an input buffer, whereas the data reception is controlled by the decoding of a 1 start bit and a 0 end bit, both of which are added to the n-bit data word to form a frame. Circuit simulation results demonstrate that both communication methods have high bandwidth and low power dissipation.

A Genome-wide Analysis of Admixture in Uyghurs and a High-Density Admixture Map for Disease-Gene Discovery

Following up on our previous study, we conducted a genome-wide analysis of admixture for two Uyghur population samples (HGDP-UG and PanAsia-UG), collected from the northern and southern regions of Xinjiang in China, respectively. Both HGDP-UG and PanAsia-UG showed a substantial admixture of East-Asian (EAS) and European (EUR) ancestries, with an empirical estimation of ancestry contribution of 53:47 (EAS:EUR) and 48:52 for HGDP-UG and PanAsia-UG, respectively. The effective admixture time under a model with a single pulse of admixture was estimated as 110 generations and 129 generations, or admixture events occurred about 2200 and 2580 years ago for HGDP-UG and PanAsia-UG, respectively, assuming an average of 20 yr per generation. Despite Uyghurs' earlier history compared to other admixture populations, admixture mapping, holds promise for this population, because of its large size and its mixture of ancestry from different continents. We screened multiple databases and identified a genome-wide single-nucleotide polymorphism panel that can distinguish EAS and EUR ancestry of chromosomal segments in Uyghurs. The panel contains 8150 ancestry-informative markers (AIMs) showing large frequency differences between EAS and EUR populations (F(ST) > 0.25, mean F(ST) = 0.43) but small frequency differences (7999 AIMs validated) within both populations (F(ST) < 0.05, mean F(ST) < 0.01). We evaluated the effectiveness of this admixture map for localizing disease genes in two Uyghur populations. To our knowledge, our map constitutes the first practical resource for admixture mapping in Uyghurs, and it will enable studies of diseases showing differences in genetic risk between EUR and EAS populations.

Concluding remarks and perspectives on the evolution and seismic tools activity (ESTA) of the CoRoT community

A first part gives a summary of the main conclusions stemmed from the different comparisons reported in this book. One main conclusion is: with some care in the computations, one is able to obtain frequency differences between different computations which are smaller than required by Corot challenges. This is true for high frequency modes. Small frequency differences are much less easily obtained for low frequencies around the fundamental radial mode frequency. Care here means: having the same physics, same constants of physics, same input stellar parameters, computing models and oscillations with enough self numerical consistent accuracy. The ESTA group has built reference grids of models and associated oscillation frequencies and made them available to the community. In a second part of the present paper, a study case is considered in order to show the need and the use of such reference grids. Finally some perspectives concerning the remaining tasks are suggested.

Control of light speed: From slow light to superluminal light

A scheme for controlling light speed from slower-than-$c$ to faster-than-$c$ in an atomic system is presented in this paper. The scheme is based on far detuning Raman effect. Two far detuning coupling fields with small frequency difference will produce two absorptive peaks for the probe field in a $\ensuremath{\Lambda}$ structure, and an optical pump between the two ground states can change the absorptive peaks into enhanced peaks, which makes the normal dispersion between the two peaks change into anomalous dispersion, so the probe field can change from slow light to superluminal propagation.

Herbicide effect on the hydrogen-bonding interaction of the primary quinone electron acceptor QA in photosystem II as studied by Fourier transform infrared spectroscopy

The redox potential of Q(A) in photosystem II (PSII) is known to be lower by approximately 100 mV in the presence of phenolic herbicides compared with the presence of DCMU-type herbicides. In this study, the structural basis underlying the herbicide effects on the Q(A) redox potential was studied using Fourier transform infrared (FTIR) spectroscopy. Light-induced Q(A)(-)/Q(A) FTIR difference spectra of Mn-depleted PSII membranes in the presence of DCMU, atrazine, terbutryn, and bromacil showed a strong CO stretching peak of Q(A)(-) at 1,479 cm(-1), while binding of phenolic herbicides, bromoxynil and ioxynil, induced a small but clear downshift by approximately 1 cm(-1). The CO peak positions and the small frequency difference were reproduced in the S(2)Q(A)(-)/S(1)Q(A) spectra of oxygen-evolving PSII membranes with DCMU and bromoxynil. The relationship of the CO frequency with herbicide species correlated well with that of the peak temperatures of thermoluminescence due to S(2)Q(A)(-) recombination. Density functional theory calculations of model hydrogen-bonded complexes of plastoquinone radical anion showed that the small shift of the CO frequency is consistent with a change in the hydrogen-bond structure most likely as a change in its strength. The Q(A)(-)/Q(A) spectra in the presence of bromoxynil, and ioxynil, which bear a nitrile group in the phenolic ring, also showed CN stretching bands around 2,210 cm(-1). Comparison with the CN frequencies of bromoxynil in solutions suggested that the phenolic herbicides take a phenotate anion form in the Q(B) pocket. It was proposed that interaction of the phenolic C-O(-) with D1-His215 changes the strength of the hydrogen bond between the CO of Q(A) with D2-His214 via the iron-histidine bridge, causing the decrease in the Q(A) redox potential.

Vibration mechanism of a mistuned bladed-disk

For coupling vibration of the mistuned bladed-disk in aeroengine, the vibration differential equation of the system is established using component-mode synthesis methods. Experimental mode analysis and mode correction are used to calculate some low-order modes of tuned blade and the disk with cone-flange. The models of actual mistuned bladed-disk is constructed by exerting some small perturbation on the mode stiffness of blades. The forced vibration experimentation of an actual mistuned bladed-disk in non-rotating status is carried out to verify the vibration model and calculation formulae. The results show that excessive vibration response of a single blade is caused by blade mistuning, and the random mistuning distribution of a small frequency difference is more profitable than other arrangements for depressing the maximal vibration level of the hapless blade. In this study, the better natural frequency difference amplitude of blades and the right working frequency range of aeroengine are also suggested according to the result analysis of several numerical calculations.

Entanglement-preserving frequency conversion in cold atoms

We propose a method that enables efficient frequency conversion of quantum information based on recently demonstrated strong parametric coupling between two single-photon pulses propagating in a slow-light atomic medium at different group velocities. We show that an incoming single-photon state is efficiently converted into another optical mode in a lossless and shape-conserving manner. The persistence of initial quantum coherence and entanglement within frequency conversion is also demonstrated. We first illustrate this result for the case of small frequency difference of converted photons, and then discuss the modified scheme for conversion of photon wavelengths in different spectral ranges. Finally we analyze the generation of a narrow-band single-photon frequency-entangled state.

Auditory Scene Analysis: the interaction of stimulation rate and frequency separation on pre‐attentive grouping

Segregation of auditory inputs into meaningful acoustic groups is a key element of auditory scene analysis. Previously, we showed that two interwoven sets of tones differing widely along multiple feature dimensions (duration, pitch and location) were pre-attentively separated into different groups, and that tones separated in this manner did not elicit the mismatch negativity component with respect to each other. Grouping was studied with human subjects using a stimulus rate too slow to induce streaming. Here, we varied the separation of tone sequences along a single feature dimension, i.e. frequency. Frequency differences were either 24 Hz (small) or 1054 Hz (large). Two relatively slow stimulus rates were used (2.7 or 1 tone/s) to explicitly investigate grouping outside the so-called 'streaming effect', which requires rates of about 4 tones/s or faster. Two tones were presented in a quasi-random manner with embedded trains of one to four identical tones in a row. Deviants were defined as frequency switches after trains of four identical tones. Mismatch negativity was only elicited for small frequency switches at the slower stimulation rate. The data indicate that pre-attentive grouping of tones occurred when the frequency difference that separated them was large, regardless of stimulation rate. For small frequency differences, inputs were only grouped separately when the stimulation rate was relatively fast.

Optical microwave generation based on DFB lasers

A new device of two parallel distributed feedback (DFB) lasers integrated monolithically with Y-branch waveguide coupler was fabricated by means of quantum well intermixing. Optical microwave signal was generated in the Y-branch waveguide coupler through frequency beating of the two laser modes coming from two DFB lasers in parallel, which had a small difference in frequency. Continuous rapidly tunable optical microwave signals from 13 GHz to 42 GHz were realized by adjusting independently the driving currents injected into the two DFB lasers.

A Genomewide Admixture Mapping Panel for Hispanic/Latino Populations

Admixture mapping (AM) is a promising method for the identification of genetic risk factors for complex traits and diseases showing prevalence differences among populations. Efficient application of this method requires the use of a genomewide panel of ancestry-informative markers (AIMs) to infer the population of origin of chromosomal regions in admixed individuals. Genomewide AM panels with markers showing high frequency differences between West African and European populations are already available for disease-gene discovery in African Americans. However, no such a map is yet available for Hispanic/Latino populations, which are the result of two-way admixture between Native American and European populations or of three-way admixture of Native American, European, and West African populations. Here, we report a genomewide AM panel with 2,120 AIMs showing high frequency differences between Native American and European populations. The average intermarker genetic distance is ~1.7 cM. The panel was identified by genotyping, with the Affymetrix GeneChip Human Mapping 500K array, a population sample with European ancestry, a Mesoamerican sample comprising Maya and Nahua from Mexico, and a South American sample comprising Aymara/Quechua from Bolivia and Quechua from Peru. The main criteria for marker selection were both high information content for Native American/European ancestry (measured as the standardized variance of the allele frequencies, also known as "f value") and small frequency differences between the Mesoamerican and South American samples. This genomewide AM panel will make it possible to apply AM approaches in many admixed populations throughout the Americas.

Optical microwave generation using two parallel DFB lasers integrated with Y-branch waveguide coupler

A new device of two parallel distributed feedback (DFB) lasers integrated monolithically with Y-branch waveguide coupler was fabricated by means of quantum well intermixing. Optical microwave signal was generated in the Y-branch waveguide coupler through frequency beating of the two laser modes coming from two DFB laser in parallel, which had a small difference in frequency. Continuous rapid tuning of optical microwave signal from 13 to 42 GHz were realized by adjusting independently the driving currents injected into the two DFB lasers.

Female preferences for multiple attributes in the acoustic signals of the Italian treefrog, Hyla intermedia

The advertisement call of frogs and toads is an example of multiple message signal because different acoustic properties encode different kinds of biologically significant information. In the Italian treefrog, Hyla intermedia, pulse rate and frequency have been found to be under stabilizing female preferences and to encode information important for mate recognition, whereas the number of calls per call group have been found to be under directional preferences and, thus, to be important for mate quality assessment. In this study, we investigate preferences for calls that differ simultaneously in frequency, pulse rate, and number of calls per call group, and we ask how these properties interact with each other in influencing female mating decisions. Results of two-choice phonotaxis experiments provide no evidence to support the hypothesis that females process multi-attribute signals in a hierarchical way. In contrast, the pattern of preferences is consistent with the ‘preference function’ hypothesis, that is, with the hypothesis that females rank signals along an ordinal scale of values and choose accordingly. Pulse rate and frequency influence mating preferences more than does the number of calls per call group. The interaction between pulse rate and frequency is not additive but multiplicative: small differences in either pulse rate or frequency that, alone, have no effects on female choice, interact synergistically so that their combination has strong influence on female preferences. A preference repeatability test shows strong among-female differences in preference for multi-attribute signals. We suggest that this result reveals not only a variation in attribute values among females, but also a variation in the way females weight and combine attribute values into a single preference score.