Elizabeth A. Taylor

Contractile and Vasorelaxant Effects of Hydrogen Sulfide and Its Biosynthesis in the Human Internal Mammary Artery

This study aimed to test these hypotheses: cystathionine γ-lyase (CSE) is expressed in a human artery, it generates hydrogen sulfide (H2S), and H2S relaxes a human artery. H2S is produced endogenously in rat arteries from cysteine by CSE. Endogenously produced H2S dilates rat resistance arteries. Although CSE is expressed in rat arteries, its presence in human blood vessels has not been described. In this study, we showed that both CSE mRNA, determined by reverse transcription-polymerase chain reaction, and CSE protein, determined by Western blotting, apparently occur in the human internal mammary artery (internal thoracic artery). Artery homogenates converted cysteine to H2S, and the H2S production was inhibited by dl-propargylglycine, an inhibitor of CSE. We also showed that H2S relaxes phenylephrine-precontracted human internal mammary artery at higher concentrations but produces contraction at low concentrations. The latter contractions are stronger in acetylcholine-prerelaxed arteries, suggesting inhibition of nitric oxide action. The relaxation is partially blocked by glibenclamide, an inhibitor of KATP channels. The present results indicate that CSE protein is expressed in human arteries, that human arteries synthesize H2S, and that higher concentrations of H2S relax human arteries, in part by opening KATP channels. Low concentrations of H2S contract the human internal mammary artery, possibly by reacting with nitric oxide to form an inactive nitrosothiol. The possibility that CSE, and the H2S it generates, together play a physiological role in regulating the diameter of arteries in humans, as has been demonstrated in rats, should be considered.

Spectrogram denoising and automated extraction of the fundamental frequency variation of dolphin whistles

Marine mammal vocalizations are often analyzed using time-frequency representations (TFRs) which highlight their nonstationarities. One commonly used TFR is the spectrogram. The characteristic spectrogram time-frequency (TF) contours of marine mammal vocalizations play a significant role in whistle classification and individual or group identification. A major hurdle in the robust automated extraction of TF contours from spectrograms is underwater noise. An image-based algorithm has been developed for denoising and extraction of TF contours from noisy underwater recordings. An objective procedure for measuring the accuracy of extracted spectrogram contours is also proposed. This method is shown to perform well when dealing with the challenging problem of denoising broadband transients commonly encountered in warm shallow waters inhabited by snapping shrimp. Furthermore, it would also be useful with other types of broadband transient noise.

Evoked-potential audiogram of an Indo-Pacific humpback dolphin ( Sousa chinensis )

SUMMARY An evoked-potential audiogram was measured for an Indo-Pacific humpback dolphin (Sousa chinensis) living in the dolphinarium of Nanning Zoo, China. Rhythmic 20 ms pip trains composed of cosine-enveloped 0.25 ms tone pips at a pip rate of 1 kHz were presented as sound stimuli. The dolphin was trained to remain still at the water surface and to wear soft latex suction-cup EEG electrodes used to measure the animals envelope-following evoked potentials to the sound stimuli. Responses to 1000 rhythmic 20 ms pip trains for each amplitude/frequency combination were averaged and analysed using a fast Fourier transform to obtain an evoked auditory response. The hearing threshold was defined as the zero crossing point of the response input–output function using linear regression. Fourteen frequencies ranging from 5.6 to 152 kHz were studied. The results showed that most of the thresholds were lower than 90 dB re. 1 μPa (r.m.s.), covering a frequency range from 11.2 to 128 kHz, and the lowest threshold of 47 dB was measured at 45 kHz. The audiogram, which is a function of hearing threshold versus stimulus carrier frequency, presented a U-shape with a region of high hearing sensitivity (within 20 dB of the lowest threshold) between approximately 20 and 120 kHz. At frequencies lower than this high-sensitivity region, thresholds increased at a rate of approximately 11 dB octave–1 up to 93 dB at 5.6 kHz. The thresholds at high frequencies above 108 kHz increased steeply at a rate of 130 dB octave–1 up to 127 dB at 152 kHz.

Possible age-related hearing loss (presbycusis) and corresponding change in echolocation parameters in a stranded Indo-Pacific humpback dolphin

SUMMARY The hearing and echolocation clicks of a stranded Indo-Pacific humpback dolphin (Sousa chinensis) in Zhuhai, China, were studied. This animal had been repeatedly observed in the wild before it was stranded and its age was estimated to be ~40 years. The animals hearing was measured using a non-invasive auditory evoked potential (AEP) method. Echolocation clicks produced by the dolphin were recorded when the animal was freely swimming in a 7.5 m (width)×22 m (length)×4.8 m (structural depth) pool with a water depth of ~2.5 m. The hearing and echolocation clicks of the studied dolphin were compared with those of a conspecific younger individual, ~13 years of age. The results suggested that the cut-off frequency of the high-frequency hearing of the studied dolphin was ~30–40 kHz lower than that of the younger individual. The peak and centre frequencies of the clicks produced by the older dolphin were ~16 kHz lower than those of the clicks produced by the younger animal. Considering that the older dolphin was ~40 years old, its lower high-frequency hearing range with lower click peak and centre frequencies could probably be explained by age-related hearing loss (presbycusis).

Enhancing Musical Experience for the Hearing-Impaired Using Visual and Haptic Displays

This article addresses the broad question of understanding whether and how a combination of tactile and visual information could be used to enhance the experience of music by the hearing impaired. Initially, a background survey was conducted with hearing-impaired people to find out the techniques they used to “listen” to music and how their listening experience might be enhanced. Information obtained from this survey and feedback received from two profoundly deaf musicians were used to guide the initial concept of exploring haptic and visual channels to augment a musical experience. The proposed solution consisted of a vibrating “Haptic Chair” and a computer display of informative visual effects. The Haptic Chair provided sensory input of vibrations via touch by amplifying vibrations produced by music. The visual display transcoded sequences of information about a piece of music into various visual sequences in real time. These visual sequences initially consisted of abstract animations corresponding to specific features of music such as beat, note onset, tonal context, and so forth. In addition, because most people with impaired hearing place emphasis on lip reading and body gestures to help understand speech and other social interactions, their experiences were explored when they were exposed to human gestures corresponding to musical input. Rigorous user studies with hearing-impaired participants suggested that musical representation for the hearing impaired should focus on staying as close to the original as possible and is best accompanied by conveying the physics of the representation via an alternate channel of perception. All the hearing-impaired users preferred either the Haptic Chair alone or the Haptic Chair accompanied by a visual display. These results were further strengthened by the fact that user satisfaction was maintained even after continuous use of the system over a period of 3 weeks. One of the comments received from a profoundly deaf user when the Haptic Chair was no longer available (“I am going to be deaf again”), poignantly expressed the level of impact it had made. The system described in this article has the potential to be a valuable aid in speech therapy, and a user study is being carried out to explore the effectiveness of the Haptic Chair for this purpose. It is also expected that the concepts presented in this paper would be useful in converting other types of environmental sounds into a visual display and/or a tactile input device that might, for example, enable a deaf person to hear a doorbell ring, footsteps approaching from behind, or a person calling him or her, or to make understanding conversations or watching television less stressful. Moreover, the prototype system could be used as an aid in learning to play a musical instrument or to sing in tune. This research work has shown considerable potential in using existing technology to significantly change the way the deaf community experiences music. We believe the findings presented here will add to the knowledge base of researchers in the field of human–computer interaction interested in developing systems for the hearing impaired.

Genetic Algorithm based route planner for large urban street networks

Finding the shortest path from a given source to a given destination is a well known and widely applicable problem. Most of the work done in the area have used static route planning algorithms such as A*, Dijkstras, Bellman-Ford algorithm etc. Although these algorithms are said to be optimum, they are not capable of dealing with certain real life scenarios. For example, most of these single objective optimizations fails to find the equally good solutions when there is more than one optimum (shortest distance path, least congested path). We believe that the genetic algorithm (GA) based route planning algorithm proposed in this paper has the ability to tackle the above problems. In this paper, the proposed GA based route planning algorithm is successfully tested on the entire Singapore map with more than 10,000 nodes. Performance of the proposed GA is compared with an ant based path planning algorithm. Simulation results demonstrate the effectiveness of the proposed algorithm over ant based algorithm. Moreover, the proposed GA may be used as a basis for developing an intelligent route planning system.

Sodium pump numbers and cation transport of lymphocytes in pregnancy-induced hypertension.

Pregnancy-induced hypertension may be linked with sodium pump inhibition and an increase in vascular myocytic tone and, hence, flow impedance. All of the findings of studies on circulating plasma and blood cells are not, however, consistent with this hypothesis. We therefore assessed sodium pump numbers and cation transport in lymphocytes from 23 women with untreated pregnancy-induced hypertension, 28 normotensive pregnant women and 28 healthy non-pregnant women. We measured the maximum 3H-ouabain binding capacity to determine the sodium pump activity and the apparent dissociation constant (the reciprocal of which estimates binding affinity) by Scatchard analysis, ouabain-sensitive (pump-mediated) 86rubidium influx and ouabain-resistant (pump-independent) influx in lymphocytes in vitro. Pregnant women, whether normotensive or hypertensive, had significantly more sodium pump activity and a higher pump-mediated and pump-independent 86rubidium influx than non-pregnant women. Sodium pump activity and the pump-mediated and pump-independent 86rubidium influx all reached normal, non-pregnant levels in normotensive pregnant women 6 weeks after delivery, but remained high in women with pregnancy-induced hypertension. The normotensive and hypertensive pregnant women and non-pregnant women all had similar ouabain binding affinity. The results of our study do not support the circulating sodium pump inhibitor hypothesis in pregnancy-induced hypertension.

Towards building an experiential music visualizer

There have been many attempts to represent music using a wide variety of different music visualisation schemes. In this paper, we propose a novel system architecture which combines Max/MSPtrade with Flashtrade that can be used to build real-time music visualisations rapidly. In addition, we have used this proposed architecture to develop a music visualisation scheme that uses individual notes from a MIDI keyboard or from a standard MIDI file and creates novel displays that reflect pitch, note duration, characteristics such as how hard a key is struck, and which instruments are playing at any one time. The proposed music visualization scheme is a first step towards developing a music visualization that alone can provide a sense of musical experience to the user.

Automatic Classification of Whistles Produced by Indo-Pacific Humpback Dolphins (Sousa chinensis)

A fast, robust technique is needed to facilitate studies of vocalisations by dolphins and other marine mammals such as whales in which large quantities of acoustic data are commonly generated. It is sometimes necessary to be able to describe whistle contours quantitatively, rather than simply looking at descriptors such as start frequency, maximum frequency, number of inflection points, etc. This is important when whistles are to be compared using an automated classification system, and is an essential component of a real-time, automated classification system for use with a raw data stream. In this paper we describe a rapid and robust high order polynomial curve fitting technique which extracts features in preparation for automated classification. We applied this method to classify natural vocalizations of Indo-Pacific humpback dolphins (Sousa chinensis). We believe the method will be widely applicable to bioacoustic studies involving FM acoustic signals in both underwater and in-air environments.

Classification of marine organisms in underwater images using CQ-HMAX biologically inspired color approach

In many coastal environments, particularly in tropical zones, coral reef ecosystems have exceptional biodiversity, contribute to coastal defense, provide unique and important habitats and valuable commercial resources. Assessment of environmental impacts on biodiversity in such areas are increasingly important to mitigate potential adverse effects on specific ecosystems. Visual classification of marine organisms is necessary for population estimates of individual species of corals or other benthic organisms. In this paper, we introduce a new image dataset of benthic organisms that are of different colors, shapes, scales, visibility and are taken from different viewpoints. We evaluate several different classification approaches on this dataset, and show that CQ-HMAX, our new biologically inspired approach to utilizing color information for object and scene recognition, that is inspired by the characteristics of color- and object-selective neurons in the high-level inferotemporal (IT) cortex of the primate visual system, results in better classification results in comparison with existing computational models such as support vectors machines, SIFT based approaches and the HMAX biologically inspired approach. We show that concatenating our model which encodes color information with the HMAX model which encodes grayscale shape information results in the highest classification accuracy.