bluuebunny/crossref_metadata_2025 huggingface dataset:
Duodenal phytohaemagglutinin (red kidney bean lectin) stimulates gallbladder contraction in humans
Authors: Purhonen A. K. , Herzig K. H. , Gabius H. J. , André S. , Ketterer S. , Matzinger D. , Beglinger C. , Hildebrand P.
Published: February 2008

Aim:  Lectins, carbohydrate‐specific proteins without enzymatic activity on the ligand, are daily ingested plant proteins which survive the passage through the gastrointestinal tract in a biologically active form. Their binding to glycan determinants of natural glycoconjugates can trigger biological effects. The lectin phytohaemagglutinin (PHA) is abundantly present in red kidney beans and induces cholecystokinin (CCK) release in rats. The aim of the study was to investigate the effect of intraduodenal administration of PHA on plasma CCK levels and gallbladder contraction in humans and to elucidate potential mechanisms of action.

Methods:  Five healthy volunteers underwent four studies. After a basal intraduodenal saline infusion for 30 min, PHA or heat‐inactivated PHA was infused in increasing doses: 150 μg, 1.5 mg and 15 mg for 30 min each. Intravenous saline, CCK1 receptor antagonist dexloxiglumide or atropine were administered in random order. Gallbladder volumes were measured by ultrasonography and plasma CCK levels by radioimmunoassay.

Results:  Intraduodenal PHA induced gallbladder contraction in a dose‐dependent fashion starting with the lowest dose. The highest dose reduced the gallbladder volume to 65.3 ± 9.4% of basal volume (P < 0.001) whereas heat‐inactivated PHA did not have any effect. Blocking CCK1 or muscarinic receptors completely abolished PHA‐stimulated gallbladder contraction (dexloxiglumide 208.7 ± 23.7%; atropine 104 ± 7.0% of basal volume) while none of the treatments affected CCK levels.

Conclusion:  Duodenal administration of PHA potently stimulates gallbladder contraction in humans. This contraction is mediated via cholinergic pathway.
To both be like a captain and fellow worker of the caring team: the meaning of Nurse Assistants’ expectations of Registered Nurses in Swedish residential care homes
Authors: Karlsson Inger , Ekman Sirkka‐Liisa , Fagerberg Ingegerd
Published: February 2008

Aim.  To describe the expectations of and to illuminate the meaning of the Nurse Assistants’ (NA) expectations of Registered Nurses (RN) who are responsible for the care of older people living in residential care homes in Sweden.

Background.  Older people in Sweden who are provided with residential care are extremely frail and incapable of independent living. Therefore, when providing care, RN and NA encounter older people who require a great deal of care. An important precondition for the provision of satisfactory care is to have adequate collaboration between NAs and RNs and their expectations of each other. In this paper, the focus is on the NAs expectations of the RNs.

Method.  The study is based on a qualitative approach and a phenomenological‐hermeneutical method. Ten NAs were interviewed and asked to narrate as freely as possible, about their expectations of RNs. The narratives were audio taped and transcribed verbatim. The analytical process includes the following steps; naïve reading, structural analysis, comprehensive understanding and reflection.

Results.  The RNs were expected to take responsibility for being fellow human beings and experts in providing care as well as always available to participate in caring. The RNs were expected to make stand‐alone decisions and create a sense of safety for both older people and the NAs and have the courage to work alone and create a safe environment for both the older people and the NAs. The meaning of these expectations was that the RNs are like a captain in providing care, but at the same time, fellow workers.

Conclusion.  When the RNs do not meet the NAs expectations, there is a risk of conflict and therefore also a risk that an unsafe environment being created when caring for older people.
Engaging older people with dementia in research: myth or possibility
Authors: Cowdell Fiona
Published: February 2008

Aim.  The aim of this paper was to explore a range of strategies that were used to enable older people with dementia to become actively engaged in research ‘with’ rather than ‘on’ them.

Background.  It is well recognized that the prevalence of dementia in older adults is increasing. This increase is reflected by a huge rise in the amount of research in this area. The biomedical model continues to dominate dementia research; however, the last two decades have seen an increased interest in studies that seek the views of people with dementia. A review of literature that has actively engaged people with dementia suggests that research can be conducted in such ways that are both ethical and meaningful. These studies demonstrate that this group has a valuable contribution to research studies.

Discussion.  This literature establishes that it is possible to engage people with dementia in research, the majority of studies have tended to focus on those in the earlier stages of the disease. This paper demonstrates, through the use of a set of criteria which were specifically developed to evaluate this type of work, how people even with advanced dementia were engaged in research about their experience of acute hospital care in ways that were both meaningful and ethical.

Conclusion.  This paper demonstrates that it is possible to actively engage older people with dementia, even those in the more advanced stages of the disease, in research. It is essential that researchers understand ethical principles and are able to apply these sensitively and flexibly.
Personhood and dementia: revisiting Tom Kitwood’s ideas
Authors: Dewing Jan
Published: February 2008

Person‐centred care is often cited as an aim of gerontological nursing and promotion of personhood is said to be the basis for person‐centred care. As such, it forms a cornerstone value for many gerontological nurses, particularly those working in dementia care. Tom Kitwood’s ideas and definition of personhood are widely referred to in the literature and used in the dementia care field. More recently, there is a move to critique and partially reject Kitwood’s ideas on personhood. This paper has three aims: (i) to explore some central ideas around key theories of personhood (ii) to critique Kitwood’s work on personhood. (iii) To summarize current critiques of Kitwood’s ideas and provide a response that outlines why Kitwoods’ ideas are still relevant. It is suggested many critiques ignore Kitwoods’ ultimate purpose; that of moral concern for ‘others’. However, the main criticism put forward in this paper is that, rather than completely rejecting personhood theories, Kitwood locates his work on what it means to be a person within a traditional Cartesian personhood framework, albeit from a revised or pragmatic viewpoint. Finally, it is suggested that definitions of persons and personhood need to take account of the body and time (corporeality and temporality) and gerontological nursing may want to reassess how much allegiance is given to basing nursing frameworks on the concept of personhood.
Still going strong: perceptions of the body among 85‐year‐old people in Sweden
Authors: Santamäki Fischer Regina , Altin Elisabeth , Ragnarsson Carina , Lundman Berit
Published: February 2008

Background. Studies on the lived experience of an aging body are scarce.

Aim and objectives. The aim of this study was to illuminate the experiences of the body among elderly people.

Design. This study is part of the Umeå 85+ Study, a cross‐sectional investigation into successful aging and threats against successful aging. The present study has an explorative design.

Methods. The text from 40 thematic interviews with 85‐year‐olds was analysed using qualitative content analysis.

Results. Two themes and seven subthemes were developed. The theme:Still going strongencompassed the subthemes of Exercising and being active, Caring for one’s body, Standing on one’s own two feet and Feeling healthy. The theme:Adapting to a failing bodyencompassed the subthemes of Not being able to perform activities and manage by oneself, Feeling fatigued and Compensating for bodily decline.

Conclusions. The participants felt that the body was still a source of pleasure, in spite of its defects. Assistive devices were important for the maintenance of independence when the body declined.

Relevance to clinical practice. When caring for elderly people with declining bodily function, it is important to have appropriate and well‐tested equipment in readiness.
Older people maintaining well‐being: discussion of key literature
Authors: Reed Jan
Published: February 2008

This paper describes the process of initial searching for publications on older people and well‐being, and discusses some of the difficulties in doing this is a field where key terms are diverse. The paper selects some publications which were judged to be particularly significant or interesting, rather than an inclusive and fully comprehensive literature report.
Older people maintaining well‐being: an International Appreciative Inquiry study
Authors: Reed Jan , Richardson Elsie , Marais Sandra , Moyle Wendy
Published: February 2008

This paper reports on the progress of an international study investigating older people's strategies for maintaining well‐being in the UK, Germany, South Africa and Australia. It uses an Appreciative Inquiry framework for investigation.
Older people maintaining well‐being: implications for future developments
Authors: Reed Jan
Published: February 2008

This paper indicates the ways in which the strategies which older people have developed for maintaining well‐being could be explored further. This exploration, it is argued, is necessary given the scarcity of research in this field, which reduces the impact that these strategies might have for practice.
Cyclooxygenase‐2 Inhibitor Nimesulide Blocks Ultraviolet B‐induced Photocarcinogenesis in SKH‐1 Hairless Mice†
Authors: Tang Xiuwei , Kim Arianna L. , Kopelovich Levy , Bickers David R. , Athar Mohammad
Published: February 2008

Cyclooxygenase‐2 (COX‐2) inhibition can inhibit UVB‐induced carcinogenesis in the skin. We have shown that COX‐2 is overexpressed in UVB‐induced squamous cell carcinomas (SCCs). Celecoxib, a specific inhibitor of COX‐2, blocks UVB‐induced papillomas and carcinomas in murine skin. However, as COX‐2 inhibitors of this type are associated with an increased risk of adverse cardiovascular events, we decided to study nimesulide, a different class of COX‐2 inhibitor, an N‐arylmethanesulfonamide derivative not known to have these untoward effects. To assess the antitumor‐promoting effects of nimesulide, 90 mice were equally divided into three groups. Group I animals received no test agent or UVB and served as age‐matched controls; group II animals were irradiated with UVB (180 mJ cm−2, twice weekly for 35 weeks) and group III animals received 300 p.p.m. nimesulide in drinking water and were irradiated with UVB as described for group‐II. Nimesulide treatment reduced the growth of UVB‐induced tumors both in terms of tumor number and tumor volume. By weeks 25, 30 and 35, the tumor numbers in the nimesulide‐treated group were 79%, 49% and 53% less than the number occurring in UVB‐treated animals whereas tumor volume was reduced 69%, 54% and 53%, respectively, compared to the UVB‐irradiated control group. Nimesulide also inhibited the malignant progression of SCCs. The reduction in tumorigenesis was paralleled by a decrease in cell cycle regulatory proteins (cyclins A, B1, D1, E, CDK2/4/6) and the antiapoptotic protein (Bcl2); concomitantly there was an increase in proapoptotic markers, poly (ADP‐ribose) polymerase (PARP) and caspase‐3. Nimesulide also decreased ornithine decarboxylase expression and the nuclear accumulation of nuclear factor kappa B transcriptionally active protein complexes. These results show that alternative classes of COX‐2 inhibitors may likely be efficacious as cancer chemopreventive agents and may have an improved therapeutic index.
Estimating space‐use and habitat preference from wildlife telemetry data
Authors: Aarts Geert , MacKenzie Monique , McConnell Bernie , Fedak Mike , Matthiopoulos Jason
Published: February 2008

Management and conservation of populations of animals requires information on where they are, why they are there, and where else they could be. These objectives are typically approached by collecting data on the animals' use of space, relating these positional data to prevailing environmental conditions and employing the resulting statistical models to predict usage at other geographical regions. Technical advances in wildlife telemetry have accomplished manifold increases in the amount and quality of available data, creating the need for a statistical framework that can use them to make population‐level inferences for habitat preference and space‐use. This has been slow‐in‐coming because wildlife telemetry data are spatio‐temporally autocorrelated, often unbalanced, presence‐only observations of behaviourally complex animals, responding to a multitude of cross‐correlated environmental variables.

We review the evolution of regression models for the analysis of space‐use and habitat preference and outline the essential features of a framework that emerges naturally from these foundations. This allows us to derive a relationship between usage of points in geographical space and preference of habitats in environmental space. Within this framework, we discuss eight challenges, inherent in the spatial analysis of telemetry data and, for each, we propose solutions that can work in tandem. Specifically, we propose a logistic, mixed‐effects approach that uses generalized additive transformations of the environmental covariates and is fitted to a response data‐set comprising the telemetry and simulated observations, under a case‐control design.

We apply this framework to a non‐trivial case‐study using satellite‐tagged grey seals Halichoerus grypus from the east coast of Scotland. We perform model selection by cross‐validation and confront our final model's predictions with telemetry data from the same, as well as different, geographical regions. We conclude that, despite the complex behaviour of the study species, flexible empirical models can capture the environmental relationships that shape population distributions.
Effects of topographic variability on the scaling of plant species richness in gradient dominated landscapes
Authors: Hofer Gabriela , Wagner Helene H. , Herzog Felix , Edwards Peter J.
Published: February 2008

It is commonly assumed that variation in abiotic site conditions influences the number of niches, which in turn affects the potential species richness in an area. Based on theoretical considerations, abiotic variation is often used as an estimator of species richness at broad scales, while at finer landscape scales the diversity of habitat types is used. However, habitat estimators assume the landscape to be composed of discrete, homogeneous patches with sharp boundaries, and such a concept is hard to apply in gradient‐dominated landscapes. The aim of this study was therefore to investigate the influence of topographic variability (TV) on species richness at the landscape level (gamma (γ) diversity) and on its components (alpha (α) and beta (β) diversity) at microsite and habitat group levels. Using floristic data from 12 “landscapes” of 1 km2 we investigated the influence on diversity components of two simple and one complex measures of TV. While the standard deviation (SD) of altitude explained a high proportion of the variation in γ diversity (linear regression model, R2=0.63), the complex measure, SD of solar radiation explained it even better (R2=0.82). There were strong effects of TV on α and β diversity components at the microsite level, but only marginal increases of the diversity components at the habitat level. Further analyses revealed that the missing increase of the habitat level components was caused by differences between habitat groups and that only grassland diversity components increased significantly with TV. We conclude that TV at a landscape scale has strong effects on niche or microsite diversity and is an appropriate estimator of relative species richness in landscapes that are topographically heterogeneous and gradient dominated.
An Adaptive One-Factor-at-a-Time Method for Robust Parameter Design: Comparison With Crossed Arrays via Case Studies
Authors: Frey Daniel D. , Sudarsanam Nandan
Published: February 2008

This paper presents a conceptually simple and resource efficient method for robust parameter design. The proposed method varies control factors according to an adaptive one-factor-at-a-time plan while varying noise factors using a two-level resolution III fractional factorial array. This method is compared with crossed arrays by analyzing a set of four case studies to which both approaches were applied. The proposed method improves system robustness effectively, attaining more than 80% of the potential improvement on average if experimental error is low. This figure improves to about 90% if prior knowledge of the system is used to define a promising starting point for the search. The results vary across the case studies, but, in general, both the average amount of improvement and the consistency of the results are better than those provided by crossed arrays if experimental error is low or if the system contains some large interactions involving two or more control factors. This is true despite the fact that the proposed method generally uses fewer experiments than crossed arrays. The case studies reveal that the proposed method provides these benefits by exploiting, with high probability, both control by noise interactions and also higher order effects involving two control factors and a noise factor. The overall conclusion is that adaptive one-factor-at-a-time, used in concert with factorial outer arrays, is demonstrated to be an effective approach to robust parameter design providing significant practical advantages as compared to commonly used alternatives.
Counterweight Balancing for Vibration Reduction of Elastically Mounted Machine Frames: A Second-Order Cone Programming Approach
Authors: Verschuure M. , Demeulenaere B. , Swevers J. , Schutter J. De
Published: February 2008

A moving linkage exerts fluctuating forces and moments on its supporting frame. One strategy to suppress the resulting frame vibration is to reduce the exciting forces and moments by adding counterweights to the linkage links. This paper develops a generic methodology to design such counterweights for planar linkages, based on formulating counterweight design as a second-order cone program. Second-order cone programs are convex, which implies that these nonlinear optimization problems have a global optimum that is guaranteed to be found in a numerically efficient manner. Two optimization criteria are considered: the frame vibration itself and the dynamic force transmitted to the machine floor. While the methodology is valid regardless of the complexity of the considered linkage, it is developed here for a literature benchmark consisting of a crank-rocker four-bar linkage supported by a rigid, elastically mounted frame with three degrees of freedom. For this particular benchmark, the second-order cone program slightly improves the previously known optimum. Moreover, numerical comparison with current state-of-the-art algorithms for nonlinear optimization shows that our approach results in a substantial reduction of the required computational time.
A Geometric Approach for Determining Inner and Exterior Boundaries of Workspaces of Planar Manipulators
Authors: Sen Dibakar , Singh B. Nagesh
Published: February 2008

In this paper, a method to determine the internal and external boundaries of planar workspaces, represented with an ordered set of points, is presented. The sequence of points are grouped and can be interpreted to form a sequence of curves. Three successive curves are used for determining the instantaneous center of rotation for the second one of them. The two extremal points on the curve with respect to the instantaneous center are recognized as singular points. The chronological ordering of these singular points is used to generate the two envelope curves, which are potentially intersecting. Methods have been presented in the paper for the determination of the workspace boundary from the envelope curves. Strategies to deal with the manipulators with joint limits and various degenerate situations have also been discussed. The computational steps being completely geometric, the method does not require the knowledge about the manipulator’s kinematics. Hence, it can be used for the workspace of arbitrary planar manipulators. A number of illustrative examples demonstrate the efficacy of the proposed method.
A Building Block Approach to the Conceptual Synthesis of Compliant Mechanisms Utilizing Compliance and Stiffness Ellipsoids
Authors: Kim Charles J. , Moon Yong-Mo , Kota Sridhar
Published: February 2008

In this paper, we investigate a methodology for the conceptual synthesis of compliant mechanisms based on a building block approach. The building block approach is intuitive and provides key insight into how individual building blocks contribute to the overall function. We investigate the basic kinematic behavior of individual building blocks and relate this to the behavior of a design composed of building blocks. This serves to not only generate viable solutions but also to augment the understanding of the designer. Once a feasible concept is thus generated, known methods for size and geometry optimization may be employed to fine-tune performance. The key enabler of the building block synthesis is the method of capturing kinematic behavior using compliance ellipsoids. The mathematical model of the compliance ellipsoids facilitates the characterization of the building blocks, transformation of problem specifications, decomposition into subproblems, and the ability to search for alternate solutions. The compliance ellipsoids also give insight into how individual building blocks contribute to the overall kinematic function. The effectiveness and generality of the methodology are demonstrated through two synthesis examples. Using only a limited set of building blocks, the methodology is capable of addressing generic kinematic problem specifications for compliance at a single point and for a single-input, single-output compliant mechanism. A rapid prototype of the latter demonstrates the validity of the conceptual solution.
Green’s function estimation in speckle using the decomposition of the time reversal operator: Application to aberration correction in medical imaging
Authors: Robert Jean-Luc , Fink Mathias
Published: February 2008

The FDORT method (French acronym for decomposition of the time reversal operator using focused beams) is a time reversal based method that can detect point scatterers in a heterogeneous medium and extract their Green’s function. It is particularly useful when focusing in a heterogeneous medium. This paper generalizes the theory of the FDORT method to random media (speckle), and shows that it is possible to extract Green’s functions from the speckle signal using this method. Therefore it is possible to achieve a good focusing even if no point scatterers are present. Moreover, a link is made between FDORT and the Van Cittert–Zernike theorem. It is deduced from this interpretation that the normalized first eigenvalue of the focused time reversal operator is a well-known focusing criterion. The concept of an equivalent virtual object is introduced that allows the random problem to be replaced by an equivalent deterministic problem and leads to an intuitive understanding of FDORT in speckle. Applications to aberration correction are presented. The reduction of the variance of the Green’s function estimate is discussed. Finally, it is shown that the method works well in the presence of strong interfering scatterers.
Phoneme representation and classification in primary auditory cortex
Authors: Mesgarani Nima , David Stephen V. , Fritz Jonathan B. , Shamma Shihab A.
Published: February 2008

A controversial issue in neurolinguistics is whether basic neural auditory representations found in many animals can account for human perception of speech. This question was addressed by examining how a population of neurons in the primary auditory cortex (A1) of the naïve awake ferret encodes phonemes and whether this representation could account for the human ability to discriminate them. When neural responses were characterized and ordered by spectral tuning and dynamics, perceptually significant features including formant patterns in vowels and place and manner of articulation in consonants, were readily visualized by activity in distinct neural subpopulations. Furthermore, these responses faithfully encoded the similarity between the acoustic features of these phonemes. A simple classifier trained on the neural representation was able to simulate human phoneme confusion when tested with novel exemplars. These results suggest that A1 responses are sufficiently rich to encode and discriminate phoneme classes and that humans and animals may build upon the same general acoustic representations to learn boundaries for categorical and robust sound classification.
The influence of spread of excitation on the detection of amplitude modulation imposed on sinusoidal carriers at high levels
Authors: Millman Rebecca E. , Bacon Sid P.
Published: February 2008

The improvement in amplitude modulation (AM) detection thresholds with increasing level of a sinusoidal carrier has been attributed to listening on the high-frequency side of the excitation pattern, where the growth of excitation is more linear, or to an increase in the number of “channels” via spread of excitation. In the present study, AM detection thresholds were measured using a 1000-Hz sinusoidal carrier. Thresholds for modulation frequencies of 4–64Hz improved by about 10–20dB as the carrier level increased from 10dB SL (14.5dB SPL on average) to 80dB SPL. To minimize the use of spread of excitation with an 80-dB carrier, tonal “restrictors” with frequencies of 501, 801, 1210, and 1510Hz were used alone and in combination. High-frequency restrictors elevated AM detection thresholds, whereas low-frequency restrictors did not, indicating that excitation on the high side is more important for detecting AM. Results of modeling suggest that the improvement in AM detection thresholds at high levels is likely due to the use of a relatively linear growth of response on the high-frequency side of the excitation pattern.
Comment on “Mutual suppression in the 6kHz region of sensitive chinchilla cochleae” [J. Acoust. Soc. Am. 121, 2805–2818 (2007)]
Authors: Cheatham M. A.
Published: February 2008

Rhode [J. Acoust. Soc. Am. 121, 2805–2818 (2007)] acknowledges that two-tone neural rate responses for low-side suppression differ from those measured in basilar membrane mechanics, making one question whether this aspect of suppression has a mechanical correlate. It is suggested here that signal coding between mechanical and neural processing stages may be responsible for the fact that the total rate response (but not the basilar membrane response) for low-frequency suppressors is smaller than that for the probe-alone condition. For example, the velocity dependence of inner hair cell (IHC) transduction, membrane/synaptic filtering and the sensitivity difference between ac and dc components of the IHC receptor potential all serve to reduce excitability for low-side suppressors at the single-unit level. Hence, basilar membrane mechanics may well be the source of low-side suppression measured in the auditory nerve.
Binaural processing of modulated interaural level differences
Authors: Thompson Eric R. , Dau Torsten
Published: February 2008

Two experiments are presented that measure the acuity of binaural processing of modulated interaural level differences (ILDs) using psychoacoustic methods. In both experiments, dynamic ILDs were created by imposing an interaurally antiphasic sinusoidal amplitude modulation (AM) signal on high-frequency carriers, which were presented over headphones. In the first experiment, the sensitivity to dynamic ILDs was measured as a function of the modulation frequency using puretone, and interaurally correlated and uncorrelated narrow-band noise carriers. The intrinsic interaural level fluctuations of the uncorrelated noise carriers raised the ILD modulation detection thresholds with respect to the pure-tone carriers. The diotic fluctuations of the correlated noise carriers also caused a small increase in the thresholds over the pure-tone carriers, particularly with low ILD modulation frequencies. The second experiment investigated the modulation frequency selectivity in dynamic ILD processing by imposing an interaurally uncorrelated bandpass noise AM masker in series with the interaurally antiphasic AM signal on a pure-tone carrier. By varying the masker center frequencies relative to the signal modulation frequency, broadly tuned, bandpass-shaped patterns were obtained. Simulations with an existing binaural model show that a low-pass filter to limit the binaural temporal resolution is not sufficient to predict the results of the experiments.
Effects of social, demographical and behavioral factors on the sound level evaluation in urban open spaces
Authors: Yu Lei , Kang Jian
Published: February 2008

The aim of this study is to analyze the effects of social, demographical and behavioral factors as well as long-term sound experience on the subjective evaluation of sound level in urban open public spaces. This is based on a series of large scale surveys in 19 urban open spaces in Europe and China. The results suggest that the effects of social/demographical factors, including age, gender, occupation, education and residential status, on the sound level evaluation are generally insignificant, although occupation and education are two related factors and both correlate to the sound level evaluation more than other factors. The effects of some behavioral factors, including wearing earphones, reading/writing and moving activities, are also insignificant on the sound level evaluation, but the watching behavior is highly related to the sound level evaluation. Compared to the social, demographical and behavioral factors, the long-term sound experience, i.e. the acoustic environment at home, significantly affect the sound level evaluation in urban open spaces. It is important to note that between the social/demographical factors, there are generally significant correlations, although the correlation coefficients may not be high. It is also noted that there are considerable variations between different urban open spaces.
The effect of hearing impairment on the identification of speech that is modulated synchronously or asynchronously across frequency
Authors: Hall Joseph W. , Buss Emily , Grose John H.
Published: February 2008

This study investigated the effect of mild-to-moderate sensorineural hearing loss on the ability to identify speech in noise for vowel-consonant-vowel tokens that were either unprocessed, amplitude modulated synchronously across frequency, or amplitude modulated asynchronously across frequency. One goal of the study was to determine whether hearing-impaired listeners have a particular deficit in the ability to integrate asynchronous spectral information in the perception of speech. Speech tokens were presented at a high, fixed sound level and the level of a speech-shaped noise was changed adaptively to estimate the masked speech identification threshold. The performance of the hearing-impaired listeners was generally worse than that of the normal-hearing listeners, but the impaired listeners showed particularly poor performance in the synchronous modulation condition. This finding suggests that integration of asynchronous spectral information does not pose a particular difficulty for hearing-impaired listeners with mild/moderate hearing losses. Results are discussed in terms of common mechanisms that might account for poor speech identification performance of hearing-impaired listeners when either the masking noise or the speech is synchronously modulated.
An improved acoustical wave propagator method and its application to a duct structure
Authors: Peng S. Z. , Cheng L.
Published: February 2008

The pseudospectral time-domain method has long been used to describe the acoustical wave propagation. However, due to the limitation and difficulties of the fast Fourier transform (FFT) in dealing with nonperiodic problems, the dispersion error is inevitable and the numerical accuracy greatly decreases after the waves arrive at the boundary. To resolve this problem, the Lagrange–Chebyshev interpolation polynomials were used to replace the previous FFT, which, however, brings in an additional restriction on the time step. In this paper, a mapped Chebyshev method is introduced, providing the dual benefit of preserving the spectral accuracy and overcoming the time step restriction at the same time. Three main issues are addressed to assess the proposed technique: (a) Spatial derivatives in the system operator and the boundary treatment; (b) parameter selections; and (c) the maximum time step in the temporal operator. Furthermore, a numerical example involving the time-domain evolution of wave propagation in a duct structure is carried out, with comparisons to those obtained by Euler method, the fourth-order Runge–Kutta method, and the exact analytical solution, to demonstrate the numerical performance of the proposed technique.
Noise in the operating rooms of Greek hospitals
Authors: Tsiou Chrisoula , Efthymiatos Gerasimos , Katostaras Theophanis
Published: February 2008

This study is an evaluation of the problem of noise pollution in operating rooms. The high sound pressure level of noise in the operating theatre has a negative impact on communication between operating room personnel. The research took place at nine Greek public hospitals with more than 400 beds. The objective evaluation consisted of sound pressure level measurements in terms of Leq, as well as peak sound pressure levels in recordings during 43 surgeries in order to identify sources of noise. The subjective evaluation consisted of a questionnaire answered by 684 operating room personnel. The views of operating room personnel were studied using Pearson’s X2 Test and Fisher’s Exact Test (SPSS Version 10.00), a t-test comparison was made of mean sound pressure levels, and the relationship of measurement duration and sound pressure level was examined using linear regression analysis (SPSS Version 13.00). The sound pressure levels of noise per operation and the sources of noise varied. The maximum measured level of noise during the main procedure of an operation was measured at Leq=71.9dB(A), L1=84.7dB(A), L10=76.2dB(A), and L99=56.7dB(A). The hospital building, machinery, tools, and people in the operating room were the main noise factors. In order to eliminate excess noise in the operating room it may be necessary to adopt a multidisciplinary approach. An improvement in environment (background noise levels), the implementation of effective standards, and the focusing of the surgical team on noise matters are considered necessary changes.
Finite element model for waves guided along solid systems of arbitrary section coupled to infinite solid media
Authors: Castaings Michel , Lowe Michael
Published: February 2008

The Semi-Analytical Finite Element (SAFE) method is becoming established as a convenient method to calculate the properties of waves which may propagate in a waveguide which has arbitrary cross-sectional shape but which is invariant in the propagation direction. A number of researchers have reported work relating to lossless elastic waves, and recently the solutions for nonpropagating waves in elastic guides and for complex waves in viscoelastic guides have been presented. This paper presents a further development, addressing the problem of attenuating waves in which the attenuation is caused by leakage from the waveguide into a surrounding material. This has broad relevance to many practical problems in which a waveguide is immersed in a fluid or embedded in a solid. The paper presents the principles of a procedure and then validates and illustrates its use on some examples. The procedure makes use of absorbing regions of material at the exterior bounds of the discretized domain.
Determining tomographic arrival times based on matched filter processing: Considering the impact of ocean waves
Authors: Lewis James K.
Published: February 2008

Reflection of high-frequency acoustic signals from an air-sea interface with waves is considered in terms of determining travel times for acoustic tomography. Wave-induced, multi-path rays are investigated to determine how they influence the assumption that the time of the largest matched filter magnitude between the source and receiver signals is the best estimate of the arrival time of the flat-surface specular ray path. A simple reflection model is developed to consider the impact of in-plane, multi-path arrivals on the signal detected by a receiver. It is found that the number of multi-path rays between a source and receiver increases significantly with the number of times the ray paths strike the ocean surface. In test cases, there was always one of the multi-path rays that closely followed the flat-surface specular ray path. But all the multi-path rays arrive at the receiver almost simultaneously, resulting in interference with the signal from the flat-surface specular ray path. As a result, multi-path arrivals due to open ocean surface waves often distort the received signal such that maxima of matched filtering magnitudes will not always be a reliable indicator of the arrival time of flat-surface specular ray paths.
The impact of water column variability on horizontal wave number estimation and mode based geoacoustic inversion results
Authors: Becker Kyle M. , Frisk George V.
Published: February 2008

The influence of water column variability on low-frequency, shallow water geoacoustic inversion results is considered. The data are estimates of modal eigenvalues obtained from measurements of a point source acoustic field using a horizontal aperture array in the water column. The inversion algorithm is based on perturbations to a background waveguide model with seabed properties consistent with the measured eigenvalues. Water column properties in the background model are assumed to be known, as would be obtained from conductivity, temperature, and depth measurements. The scope of this work in addressing the impact of water column variability on inversion is twofold. Range-dependent propagation effects as they pertain to eigenvalue estimation are first considered. It is shown that mode coupling is important even for weak internal waves and can enhance modal eigenvalue estimates. Second, the effect of the choice of background sound speed profile in the water column is considered for its impact on the estimated bottom acoustic properties. It is shown that a range-averaged sound velocity profile yields the best geoacoustic parameter estimates.
The relationship between precursor level and the temporal effect
Authors: Strickland Elizabeth A.
Published: February 2008

Previous studies have suggested that temporal effects in masking may be consistent with a decrease in cochlear gain. One paradigm used to show this is to measure the level of a long-duration masker required to just mask a short-duration tone that occurs near masker onset. The temporal effect is revealed when the signal is detected at a lower signal-to-noise ratio following preceding stimulation (either an extension of the masker or a separate precursor). The present study examined whether this effect depends on precursor level. The signal was a 10-ms, 4-kHz tone. The masker was 200ms. A fixed-level precursor had the same frequency characteristics as the masker, and was 205ms. The masker and precursor had either no notch or a wide notch about the signal frequency. For a given precursor level, the growth of masker level with signal level was determined. These data were used to estimate input–output functions. The results are consistent with a graded decrease in gain at the signal frequency when there is no notch in the masker and precursor, and a graded decrease in suppression when there is a large notch. These results could be consistent with the action of the medial olivocochlear reflex.
On the influence of interaural differences on temporal perception of noise bursts of different durations
Authors: Schimmel Othmar , Kohlrausch Armin
Published: February 2008

The perception of a composite sound’s temporal cues, like synchronous onsets, is considered essential to correct perceptual grouping of its constituent components. The processing of a single sound’s spatial cues, already present at its onset, may interact with temporal perception of the onset. The current study investigated the influence of interaural differences on temporal perception of a sound’s onset. As a measure of temporal perception, the ability to position the onset of a temporally displaced target sound to the regular meter of diotic reference marker sound onsets was measured for various target sound lateralizations, sensation levels, and target and marker sound durations. For target sounds presented in quiet, no influence of interaural differences on temporal positioning of the onset was found. However, increasing a sound’s duration systematically shifted the perceived onset position into its “interior.” For target sounds presented at low sensation levels in a noise masker, the precision of temporally positioning the onset generally degraded, though faster for dichotic conditions and for longer durations. The level below which temporal perception precision starts to degrade was found to depend on signal-to-noise ratio rather than on sensation level or duration, and is influenced by the presence of interaural differences.
Effect of background noise levels on community annoyance from aircraft noise
Authors: Lim Changwoo , Kim Jaehwan , Hong Jiyoung , Lee Soogab
Published: February 2008

A study of community annoyance caused by exposures to civil aircraft noise was carried out in 20 sites around Gimpo and Gimhae international airports to investigate the effect of background noise in terms of dose-effect relationships between aircraft noise levels and annoyance responses under real conditions. Aircraft noise levels were mainly measured using airport noise monitoring systems, B&K type 3597. Social surveys were administered to people living within 100m of noise measurement sites. The question relating to the annoyance of aircraft noise was answered on an 11-point numerical scale. The randomly selected respondents, who were aged between 18 and 70years, completed the questionnaire independently. In total, 753 respondents participated in social surveys. The result shows that annoyance responses in low background noise regions are much higher than those in high background noise regions, even though aircraft noise levels are the same. It can be concluded that the background noise level is one of the important factors on the estimation of community annoyance from aircraft noise exposure.
Behavioral and physiological correlates of temporal pitch perception in electric and acoustic hearing
Authors: Carlyon Robert P. , Mahendran Suresh , Deeks John M. , Long Christopher J. , Axon Patrick , Baguley David , Bleeck Stefan , Winter Ian M.
Published: February 2008

In the “4–6” condition of experiment 1, normal-hearing (NH) listeners compared the pitch of a bandpass-filtered pulse train, whose inter-pulse intervals (IPIs) alternated between 4 and 6ms, to that of isochronous pulse trains. Consistent with previous results obtained at a lower signal level, the pitch of the 4–6 stimulus corresponded to that of an isochronous pulse train having a period of 5.7ms—longer than the mean IPI of 5ms. In other conditions the IPI alternated between 3.5–5.5 and 4.5–6.5ms. Experiment 2 was similar but presented electric pulse trains to one channel of a cochlear implant. In both cases, as overall IPI increased, the pitch of the alternating-interval stimulus approached that of an isochronous train having a period equal to the mean IPI. Experiment 3 measured compound action potentials (CAPs) to alternating-interval stimuli in guinea pigs and in NH listeners. The CAPs to pulses occurring after 4-ms intervals were smaller than responses to pulses occurring after 6-ms intervals, resulting in a modulated pattern that was independent of overall level. The results are compared to the predictions of a simple model incorporating auditory-nerve (AN) refractoriness, and where pitch is estimated from first-order intervals in the AN response.
Spectral loudness summation for sequences of short noise bursts
Authors: Verhey Jesko L. , Uhlemann Michael
Published: February 2008

Recent loudness data of single noise bursts indicate that spectral loudness summation depends on signal duration. To gain insight into the mechanisms underlying this duration effect, loudness was measured as a function of signal bandwidth centered around 2kHz for sequences of 10-ms noise bursts at various repetition rates and, for comparison, for single noise bursts of either 10- or 1000-ms duration. The test-signal bandwidth was varied from 200 to 6400Hz. For the repeated noise bursts, the reference signal had a bandwidth of 400Hz. For the single noise bursts, data were obtained for two reference bandwidths: 400 and 3200Hz. In agreement with previous results, the magnitude of spectral loudness summation was larger for the 10-ms than for the 1000-ms noise bursts. The reference bandwidth had no significant effect on the results for the single noise bursts. Up to repetition rates of 50Hz, the magnitude of spectral loudness summation for the sequences of noise bursts was the same as for the single short noise burst. The data indicate that the mechanism underlying the duration effect in spectral loudness is considerably faster than the time constant of about 100ms commonly associated with the temporal integration of loudness.
Extended three-dimensional impedance map methods for identifying ultrasonic scattering sites
Authors: Mamou Jonathan , Oelze Michael L. , O’Brien William D. , Zachary James F.
Published: February 2008

The frequency-dependent ultrasound backscatter from tissues contains information about the microstructure that can be quantified. In many cases, the anatomic microstructure details responsible for ultrasonic scattering remain unidentified. However, their identification would lead to potentially improved methodologies for characterizing tissue and diagnosing disease from ultrasonic backscatter measurements. Recently, three-dimensional (3D) acoustic models of tissue microstructure, termed 3D impedance maps (3DZMs), were introduced to help to identify scattering sources [J. Mamou, M. L. Oelze, W. D. O’Brien, Jr., and J. F. Zachary, “Identifying ultrasonic scattering sites from 3D impedance maps,” J. Acoust. Soc. Am. 117, 413–423 (2005)]. In the current study, new 3DZM methodologies are used to model and identify scattering structures. New processing procedures (e.g., registration, interpolations) are presented that allow more accurate 3DZMs to be constructed from histology. New strategies are proposed to construct scattering models [i.e., form factor (FF)] from 3DZMs. These new methods are tested on simulated 3DZMs, and then used to evaluate 3DZMs from three different rodent tumor models. Simulation results demonstrate the ability of the extended strategies to accurately predict FFs and estimate scatterer properties. Using the 3DZM methods, distinct FFs and scatterer properties were obtained for each tumor examined.