bluuebunny/crossref_metadata_2025 huggingface dataset:
Directional sensitivity of auditory neurons in the superior colliculus of the bat (Myotis lucifugus)
Authors: Wong Donald
Published: January 2006

The directional sensitivity of auditory neurons in the deep layers of the superior colliculus was examined in unanesthetized bats stimulated in the free field with frequency-modulated (FM) sounds (100 to 40 kHz) mimicking their natural orientation sounds. The minimum threshold of a unit was first measured when the sound was presented directly in front of the animal. Sounds 10, 30, and 50 dB above threshold were then delivered at every 10° azimuth from a hoop-mounted speaker that rotated along the horizontal plane from 80° ipsilateral to 80° contralateral. Many units exhibited spatial selectivity to a sound source that was restricted between 10° ipsilateral to 20° contralateral and had an intensity 10 dB above threshold. Sound of higher intensity was effective throughout the contralateral side in driving these neurons, although the relative response magnitude differed at the individual angles. Mapping experiments did not reveal any systematic representation of best azimuth in this midbrain structure. Nevertheless, faint echoes returning from a target along a line near the bat's flight path provide directional cues necessary for accurate target localization. [Work supported by NIH.]
Structure-property relationships of some RIM polyurethanes for potential sound damping applications
Authors: Capps Rodger , Martin Linda M. , Rustin Eric D.
Published: January 2006

Polyurethane elastomers are block copolymers made up of relatively short urethane hard block segments separating longer flexible polyether or polyester soft blocks. Polyurethanes often exhibit mechanical properties superior to conventional elastomers. They also frequently display considerable damping. When combined with other types of semi-compatible or incompatible polymers in polymeric networks known as interpenetrating network polymers (IPN's), they have the potential for high damping over a broad range of temperatures and frequencies. In an effort to understand how chemical composition and physical morphology affect the damping of these materials, a series of experiments involving varying weight ratios of hard block to soft block segments, molecular weight of the soft block, different chain extenders, and catalyst were carried out. The reaction-injection molded (RIM) urethanes were based upon poly(capro-lactone) glycols, modified 4,4′-diphenyl methane diisocyanate (MDI), 1,4 butane diol or trimethyl propanol, and dibutyl tin dilaurate. The dynamic Young's modulus was measured by a resonance technique for each group of samples over a range of temperatures and frequencies. The observed viscoelastic properties were correlated with thermomechanical transitions observed in differential scanning calorimetry analysis. The potential of these materials for use in IPN's in sound damping applications is discussed.
The effect of reduced headband force on the attenuation of muff-type protectors
Authors: Johnson Daniel L. , Nixon Charles W. , Skelton Mike
Published: January 2006

The headband force of five different protectors was decreased in one-half pound increments until the force was less than one pound. Using a dummy head, the attenuation was measured for each value of headband force. The results indicated that four of the muffs were relatively insensitive to a decrease in headband force and loss of 50% of the original force resulted in less than a 3-dB reduction in the value of the Noise Reduction Rating (NRR). One muff, however, was very sensitive and a 50% loss in headband force resulted in roughly a 50% loss in attenuation. To verify the dummy head results, attenuation was measured at selected forces on three human subjects. Although the attenuations measured were somewhat less than those measured for the dummy heads, the effect of changing headband force produced similar results. While all protectors were unaffected by a reduction of one-half pound in force, the effect of greater reductions varied dramatically with the make and model of the protector. Apparently, manufacturers need to set guidelines tailored to their specific models.
Matrix method for numerically solving the inhomogeneous wave equation
Authors: Grimm R. E. , Gilbert K. E. , Kuperman W. A.
Published: January 2006

In recent years, matrix methods (e.g., finite elements, finite differences) have been successfully used to numerically solve the parabolic wave equation. This paper discusses the application of such methods to the solution of the elliptic wave equation for a general vertical source distribution. In particular, it is shown that one-dimensional finite elements are a convenient way to accurately reduce the depth-separated inhomogeneous wave equation to an easily solved system of linear equations. The advantages of this method over methods which use special functions are that it accepts arbitrary numerical profiles and that it can be simply applied to compute a range-dependent “fast field” solution. In addition, for realistic environments with complex stratification, the computation speed should be competitive with methods based on special functions.
Propagation in a one-dimensional random medium
Authors: McDaniel Suzanne T.
Published: January 2006

Acoustic propagation in a one-dimensional random inhomogeneous medium is considered. Exact solutions of the Dyson equation for the coherent field are examined to determine constraints on the correlation function of the random inhomogeneities to insure finite results. The long range behavior of the coherent field is predicted, yielding an attenuation due to scattering and a modification of the real part of the propagation constant. Approximate solutions for the coherent field are then applied to determine the incoherent field. In contrast to results obtained using a straightforward perturbation approach, the predicted incoherent field is, in this case, finite in the absence of attenuation. [Research supported by ONR.]
Sample effective sound velocity profiles
Authors: Floyd Edward R.
Published: January 2006

Various sample effective sound velocity profiles [E. R. Floyd, J. Acoust. Soc. Am. 60, 801–809 (1976)] for representative hypothetical sound velocity profiles are generated exactly albeit numerically. These various effective sound velocity profiles exhibit their dependence upon the constant of the motion (i.e., the vertex velocity), source frequency, and the source depth. Even for isotropic sound velocity profiles, the existance of a finite velocity gradient is sufficient to induce a constant-of-the-motion dependence in the effective sound velocity profile. Any dependence upon the constant of the motion represents an anisotropic effective sound velocity profile. All effective sound velocity profiles exhibit the vertex point receding to infinite depth (flat-earth assumption) which manifests the nodal characteristic of the singularity of the nonlinear differential equation that specifies the effective sound velocity profile. The behavior of the frequency dependence manifests an asymptotic approach to geometric acoustics in the high-frequency limit. The source depth determines the initial values for the effective sound velocity profile and its derivative with respect to depth.
Measurements of transmission fluctuations in the Florida Straits
Authors: DeFerrari H. A. , Ko D. , Gruber P.
Published: January 2006

Experiments are underway on the acoustic remote sensing of transport and average temperature of the Florida current. The experiments employ a reciprocal transmission geometry to separate transport and temperature effects. Preliminary results give information on the acoustic variability and coherence of transmission between a fixed bottom mounted source and moored receivers at ranges of 8, 16, and 24 km. Statistics of fluctuations for broadband pulse-like transmissions are presented. Environmental data are used as inputs to ray and P.E. models to intepret results. [Work supported by ONR and NOAA.]
Measuring the acoustic effects of compression amplification on speech in noise
Authors: Souza Pamela E. , Jenstad Lorienne M. , Boike Kumiko T.
Published: January 2006

This letter contains a description of an inversion technique that allows for separation of speech and noise and its application to quantifying the acoustic effects of wide-dynamic-range compression (WDRC) on speech in background noise. Three main findings are reported: that fast-acting WDRC further degrades signal-to-noise ratio; that the effective compression ratio is lower for speech in noise than speech in quiet; and that in contrast to speech in quiet, the amplitude envelope of speech is mostly unaffected when compressed in background noise.
In vitro ultrasonic characterization of human cancellous femoral bone using transmission and backscatter measurements: Relationships to bone mineral density
Authors: Jenson F. , Padilla F. , Bousson V. , Bergot C. , Laredo J -D. , Laugier P.
Published: January 2006

Thirty-eight slices of pure trabecular bone 1-cm thickness were extracted from human proximal femurs. A pair of 1-MHz central frequency transducers was used to measure quantitative ultrasound (QUS) parameters in transmission [normalized broadband ultrasound attenuation (nBUA), speed of sound (SOS)] and in backscatter [broadband ultrasound backscatter (BUB)]. Bone mineral density (BMD) was measured using clinical x-ray quantitative computed tomography. Site-matched identical region of interest (ROIs) of 7×7mm2 were positioned on QUS and QCT images. This procedure resulted in 605 ROIs for all the specimens data pooled together. The short-term precision of the technique expressed in terms of CV was found to be 2.3% for nBUA, 0.3% for SOS and 4.5% for BUB. Significant linear correlation between QUS and BMD were found for all the 605 ROIs pooled, with r2 values of 0.73, 0.77, and 0.58 for nBUA, SOS, and BUB, respectively (all p<0.05). For the BUB, the best regression was obtained with a polynomial fit of second order (r2=0.63). An analysis of measurements errors was developed. It showed that the residual variability of SOS is almost completely predicted by measurements errors, which is not the case for BUA and BUB, suggesting a role for micro-architecture in the determination of BUA and BUB.
Algorithms for computing the time-corrected instantaneous frequency (reassigned) spectrogram, with applications
Authors: Fulop Sean A. , Fitz Kelly
Published: January 2006

A modification of the spectrogram (log magnitude of the short-time Fourier transform) to more accurately show the instantaneous frequencies of signal components was first proposed in 1976 [Kodera et al., Phys. Earth Planet. Inter. 12, 142–150 (1976)], and has been considered or reinvented a few times since but never widely adopted. This paper presents a unified theoretical picture of this time-frequency analysis method, the time-corrected instantaneous frequency spectrogram, together with detailed implementable algorithms comparing three published techniques for its computation. The new representation is evaluated against the conventional spectrogram for its superior ability to track signal components. The lack of a uniform framework for either mathematics or implementation details which has characterized the disparate literature on the schemes has been remedied here. Fruitful application of the method is shown in the realms of speech phonation analysis, whale song pitch tracking, and additive sound modeling.
Effects of porous covering on sound attenuation by periodic arrays of cylinders
Authors: Umnova Olga , Attenborough Keith , Linton Chris M.
Published: January 2006

The acoustic transmission loss of a finite periodic array of long rigid cylinders, without and with porous absorbent covering, is studied both theoretically and in the laboratory. A multiple scattering model is extended to allow for the covering and its acoustical properties are described by a single parameter semi-empirical model. Data from laboratory measurements and numerical results are found to be in reasonable agreement. These data and predictions show that porous covering reduces the variation of transmission loss with frequency due to the stop∕pass band structure observed with an array of rigid cylinders with similar overall radius and improves the overall attenuation in the higher frequency range. The predicted sensitivities to covering thickness and effective flow resistivity are explored. It is predicted that a random covered array also gives better attenuation than a random array of rigid cylinders with the same overall radius and volume fraction.
Rainforests as concert halls for birds: Are reverberations improving sound transmission of long song elements?
Authors: Nemeth Erwin , Dabelsteen Torben , Pedersen Simon Boel , Winkler Hans
Published: January 2006

In forests reverberations have probably detrimental and beneficial effects on avian communication. They constrain signal discrimination by masking fast repetitive sounds and they improve signal detection by elongating sounds. This ambivalence of reflections for animal signals in forests is similar to the influence of reverberations on speech or music in indoor sound transmission. Since comparisons of sound fields of forests and concert halls have demonstrated that reflections can contribute in both environments a considerable part to the energy of a received sound, it is here assumed that reverberations enforce also birdsong in forests. Song elements have to be long enough to be superimposed by reflections and therefore longer signals should be louder than shorter ones. An analysis of the influence of signal length on pure tones and on song elements of two sympatric rainforest thrush species demonstrates that longer sounds are less attenuated. The results indicate that higher sound pressure level is caused by superimposing reflections. It is suggested that this beneficial effect of reverberations explains interspecific birdsong differences in element length. Transmission paths with stronger reverberations in relation to direct sound should favor the use of longer signals for better propagation.
The array invariant
Authors: Lee Sunwoong , Makris Nicholas C.
Published: January 2006

A method is derived for instantaneous source-range estimation in a horizontally stratified ocean waveguide from passive beam-time intensity data obtained after conventional plane-wave beamforming of acoustic array measurements. The method has advantages over existing source localization methods, such as matched field processing or the waveguide invariant. First, no knowledge of the environment is required except that the received field should not be dominated by purely waterborne propagation. Second, range can be estimated in real time with little computational effort beyond plane-wave beamforming. Third, array gain is fully exploited. The method is applied to data from the Main Acoustic Clutter Experiment of 2003 for source ranges between 1to8km, where it is shown that simple, accurate, and computationally efficient source range estimates can be made.
Uncertainty analysis in matched-field geoacoustic inversions
Authors: Huang Chen-Fen , Gerstoft Peter , Hodgkiss William S.
Published: January 2006

Quantifying uncertainty for parameter estimates obtained from matched-field geoacoustic inversions using a Bayesian approach requires estimation of the uncertainties in the data due to ambient noise as well as modeling errors. In this study, the variance parameter of the Gaussian error model, hereafter called error variance, is assumed to describe the data uncertainty. In practice, this parameter is not known a priori, and choosing a particular value is often difficult. Hence, to account for the uncertainty in error variance, several methods are introduced for implementing both the full and empirical Bayesian approaches. A full Bayesian approach that permits uncertainty of the error variance to propagate through the parameter estimation processes is a natural way of incorporating the uncertainty of error variance. Due to the large number of unknown parameters in the full Bayesian uncertainty analysis, an alternative, the empirical Bayesian approach, is developed, in which the posterior distributions of model parameters are conditioned on a point estimate of the error variance. Comparisons between the full and empirical Bayesian inferences of model parameters are presented using both synthetic and experimental data.
An ultrasonic method for dynamic monitoring of fatigue crack initiation and growth
Authors: Mi Bao , Michaels Jennifer E. , Michaels Thomas E.
Published: January 2006

Attached ultrasonic sensors can detect changes caused by crack initiation and growth if the wave path is directed through the area of critical crack formation. Dynamics of cracks opening and closing under load cause nonlinear modulation of received ultrasonic signals, enabling small cracks to be detected by stationary sensors. A methodology is presented based upon the behavior of ultrasonic signals versus applied load to detect and monitor formation and growth of cracks originating from fastener holes. Shear wave angle beam transducers operating in through transmission mode are mounted on either side of the hole such that the transmitted wave travels through the area of expected cracking. Time shift is linear with respect to load, and is well explained by path changes due to strain combined with wave speed changes due to acoustoelasticity. During subsequent in situ monitoring with unknown loads, the measured time of flight is used to estimate the load, and behavior of the received energy as a function of load is the basis for crack detection. Results are presented from low cycle fatigue tests of several aluminum specimens and illustrate the efficacy of the method in both determining the applied load and monitoring crack initiation and growth.
Acoustic waves generated by a laser point pulse in a transversely isotropic cylinder
Authors: Pan Y. , Perton M. , Audoin B. , Rossignol C.
Published: January 2006

A three-dimensional (3D) model is presented to predict the acoustic waves generated by a laser point pulse in a transversely isotropic cylinder. The Fourier series expansion and the two-dimensional Fourier transform are introduced to calculate the 3D transient response under either the ablation or the thermoelastic generation. The presented physical model and the numerical inverse scheme are applied to a fiber reinforced composite cylinder with a strong anisotropy. Experimental radial displacements of the cylinder surface are detected by the laser ultrasonic technique and analyzed by the ray trajectories for both generation regimes. Corresponding theoretical displacements are obtained numerically and compared to the experimental signals. Good agreement is found between theoretical and experimental results. The focusing effects that anisotropy gives rise to are observed in both theory and experiment under either regime.
Singular meshless method using double layer potentials for exterior acoustics
Authors: Young D. L. , Chen K. H. , Lee C. W.
Published: January 2006

Time-harmonic exterior acoustic problems are solved by using a singular meshless method in this paper. It is well known that the source points cannot be located on the real boundary, when the method of fundamental solutions (MFS) is used due to the singularity of the adopted kernel functions. Hence, if the source points are right on the boundary the diagonal terms of the influence matrices cannot be derived. Herein we present an approach to obtain the diagonal terms of the influence matrices of the MFS for the numerical treatment of exterior acoustics. By using the regularization technique to regularize the singularity and hypersingularity of the proposed kernel functions, the source points can be located on the real boundary and therefore the diagonal terms of influence matrices are determined. We also maintain the prominent features of the MFS, that it is free from mesh, singularity, and numerical integration. The normal derivative of the fundamental solution of the Helmholtz equation is composed of a two-point function, which is one of the radial basis functions. The solution of the problem is expressed in terms of a double-layer potential representation on the physical boundary based on the potential theory. The solutions of three selected examples are used to compare with the results of the exact solution, conventional MFS, boundary element method, and Dirichlet-to-Neumann finite element method. Good numerical performance is demonstrated by close agreement with other solutions.
On the acoustic field in a Pekeris waveguide with attenuation in the bottom half-space
Authors: Buckingham Michael J. , Giddens Eric M.
Published: January 2006

The acoustic field in a Pekeris channel with an attenuating basement is critically examined, based on contour integrations of the wave number integrals for the two domains. In both regions, the field consists of a finite sum of proper (square integrable) normal modes plus a branch line integral around a hyperbolic cut. For low bottom attenuation, only “trapped” modes exist but as the loss increases additional “dissipation” modes contribute to the mode sum. A Newton-Raphson iterative procedure is introduced for finding the complex eigenvalues of the modes and a new expression is derived which shows that the total number of proper (trapped plus dissipation) modes supported by the waveguide increases essentially linearly with rising bottom attenuation. Approximations for the complex shape functions of the modes in the water column and the basement are developed and compared with the exact shape functions determined from the Newton-Raphson procedure. An expression derived for the modal attenuation coefficient scales in proportion to the square of the mode number and inversely with the square of the frequency. Stationary-phase approximations for the branch line integrals for both domains are developed, which serve to illustrate the asymptotic range dependence of the lateral wave but otherwise have little utility.
A miniaturized adaptive microphone array under directional constraint utilizing aggregated microphones
Authors: Matsumoto Mitsuharu , Hashimoto Shuji
Published: January 2006

This paper introduces a miniaturized microphone array using the Directionally Constrained Minimization of Power (DCMP) method, which utilizes the transfer functions of microphones located at the same place, namely aggregated microphones. The phased microphone array realizes a noise reduction and direction of arrival (DOA) estimation system according to differences in the arrival time, phase shift, and/or the level of the sound wave for each microphone. Hence it is difficult to miniaturize the microphone array. The objective of our research is to miniaturize the system size using aggregated microphones. In this paper, we first show that the phased microphone array system and the proposed aggregated microphone system can be described within the same framework. We then apply a microphone array under directional constraint to the aggregated microphones and compare the proposed method with the microphone array. We show the directional pattern of the aggregated microphones. We also show the experimental results regarding DOA estimation.
Fishing, Trophic Cascades, and the Process of Grazing on Coral Reefs
Authors: Mumby Peter J. , Dahlgren Craig P. , Harborne Alastair R. , Kappel Carrie V. , Micheli Fiorenza , Brumbaugh Daniel R. , Holmes Katherine E. , Mendes Judith M. , Broad Kenneth , Sanchirico James N. , Buch Kevin , Box Steve , Stoffle Richard W. , Gill Andrew B.
Published: January 2006

Since the mass mortality of the urchin Diadema antillarum in 1983, parrotfishes have become the dominant grazer on Caribbean reefs. The grazing capacity of these fishes could be impaired if marine reserves achieve their long-term goal of restoring large consumers, several of which prey on parrotfishes. Here we compare the negative impacts of enhanced predation with the positive impacts of reduced fishing mortality on parrotfishes inside reserves. Because large-bodied parrotfishes escape the risk of predation from a large piscivore (the Nassau grouper), the predation effect reduced grazing by only 4 to 8%. This impact was overwhelmed by the increase in density of large parrotfishes, resulting in a net doubling of grazing. Increased grazing caused a fourfold reduction in the cover of macroalgae, which, because they are the principal competitors of corals, highlights the potential importance of reserves for coral reef resilience.
Bringing Hidden Dimensions into View
Authors: Wells James D.
Published: January 2006

Warped Passages
. Unraveling the Mysteries of the Universe's Hidden Dimensions / Unravelling the Universe's Hidden Dimensions.
By Lisa Randall
. Ecco, New York, 2005. 512 pp. $27.95, C$37.95. ISBN 0-06-053108-8. / Allen Lane, London. £25, C$40. ISBN 0-713-99699-4.

A researcher known for her argument as to how extra dimensions could be large and still hidden discusses the possibilities of proving their existence and explores their implications.
Current difficulties in the diagnosis and management of spinal tuberculosis
Authors: Cormican L , Hammal R , Messenger J , Milburn H J
Published: January 2006

Background

The diagnosis of spinal tuberculosis (ST) is difficult and it commonly presents at an advanced stage. The management and follow up is complicated by a lack of guidance on the appropriate use and interpretation of spinal magnetic resonance studies (MR).

Aims

A retrospective study was performed at a UK centre to identify the demographic and presenting features of a spinal TB population, their response to treatment, and the value of follow up MR studies.

Patients and Results

Twenty one patients were identified with mean symptom duration of 11 (1.5–36) months having been assessed by a health practitioner on 3.2 (0–10) occasions before referral for investigation for ST. Twenty were born outside the UK. Their mean duration of residence in the UK was 6.67 (0.75–20) years, and six (32%) were resident for more than 10 years. Most (85.7%) did not have a medical history and one was HIV positive. Back pain, neurological, and constitutional symptoms were found in 100%, 29%, and 38% respectively. Musculoskeletal and neurological signs were found in 29% and 19% respectively. Spinal MR performed between 6 and 12 months suggests that six months of chemotherapy (for a fully sensitive organism) may not be sufficient to achieve disease resolution.

Conclusions

Awareness of the demographic, clinical, and laboratory features of an ST population may facilitate earlier diagnosis. Guidance is required on the appropriate use and interpretation of MRI in the follow up of these patients.
Does endoscopy diagnose early gastrointestinal cancer in patients with uncomplicated dyspepsia?
Authors: Sundar N , Muraleedharan V , Pandit J , Green J T , Crimmins R , Swift G L
Published: January 2006

Background

Recent guidelines from NICE have proposed that open access gastroscopy is largely limited to patients with “alarm” symptoms.

Aims and methods

This study reviewed the outcome of all our patients with verified oesophageal or gastric carcinoma who presented with uncomplicated dyspepsia to see if endoscopic investigation is warranted in this group. All patients with histologically verified upper gastrointestinal (GI) cancers who presented over a period from 1998 to 2002 were identified. Their presenting symptoms, treatment, and outcome were analysed.

Results

228 upper GI cancers (119 oesophageal, 109 gastric; mean age 72 years (29–99 years); 130 male, 82 female) were identified in 11 145 endoscopies performed. Only 14 patients (6.2%) presented without alarm symptoms; three patients were under 55 years of age and all had gastric carcinoma—one of these had chronic diarrhoea only. Eleven had dyspepsia or reflux symptoms only, and two were under surveillance for Barrett's oesophagus. Only five patients had a curative surgical resection and are still alive two—six years from diagnosis. A sixth patient had a curative operation but died of a cerebrovascular accident one year later. The remaining eight patients unfortunately had either metastatic disease or comorbidity, which precluded surgery. All of these died within two years of diagnosis, mean survival 10 months.

Conclusion

Only five patients with dyspepsia and no alarm symptoms had resectable upper GI malignancies over a four year period. Limiting open access gastroscopy to those with alarm features only would “miss” a small number of patients who have curable upper GI malignancy.
Conflict management: a primer for doctors in training
Authors: Saltman D C , O'Dea N A , Kidd M R
Published: January 2006

Conflict in the health arena is a growing concern and is well recognised for doctors in training. Its most extreme expression, workplace violence is on the increase. There is evidence that many conflicts remain unsatisfactorily resolved or unresolved, and result in ongoing issues for staff morale. This paper describes the nature of conflict in the health care system and identifies the difference between conflict and disagreement. Using a conflict resolution model, strategies for dealing with conflict as it arises are explored and tips are provided on how to effectively manage conflict to a satisfactory resolution for all parties.
Role of cognitive function in assessing informed consent for endoscopy
Authors: Yeoman A D , Dew M J , Das L , Rajapaksa S
Published: January 2006

Background

Patient understanding of the consent process is often suboptimal and the reasons for this are poorly understood. In particular the role of cognitive function in assessing the level of understanding of consent has not been evaluated.

Aims

This study aims to assess the level of patient understanding of the informed consent process and the role of cognitive function in those with low levels of understanding.

Methods

The study was prospective, interviewing patients immediately after they had given consent but before undergoing their procedure. Understanding of the reason for the procedure, the risks attendant upon it, details of the procedure itself and post procedure care was scored with the total representing overall level of understanding. A mini mental state examination (MMSE) was then performed with the score recorded.

Results

100 patients were interviewed. A low level of understanding was shown in 36%. Ninety two patients had a MMSE score greater than 24. All patients with a high level of understanding had MMSE scores greater then 24 compared with 78% of those with a low level of understanding. All patients (n = 8) who displayed a MMSE score less than 24 had a low level of understanding. Men displayed poorer levels of understanding than women. A subnormal MMSE only identified 22% of those with low levels of understanding.

Conclusions

Understanding of the consent process is suboptimal. Adequate cognitive function does not predict a high level of understanding of the informed consent process while cognitive impairment precludes it. It is evident, however that factors other than cognitive dysfunction are at play when attempting to explain low levels of understanding.
Growth hormone and its disorders
Authors: Ayuk J , Sheppard M C
Published: January 2006

Growth hormone (GH) is synthesised and secreted by the somatotroph cells of the anterior lobe of the pituitary gland. Its actions involve multiple organs and systems, affecting postnatal longitudinal growth as well as protein, lipid, and carbohydrate metabolism. GH hypersecretion results in gigantism or acromegaly, a condition associated with significant morbidity and mortality, while GH deficiency results in growth retardation in children and the GH deficiency syndrome in adults. This article, aimed at non-paediatric physicians, examines the clinical features, diagnosis, and current concepts in the management of these conditions.
Clinical and diagnostic findings of an echovirus meningitis outbreak in the north west of England
Authors: Carrol E D , Beadsworth M B J , Jenkins N , Ratcliffe L , Ashton I , Crowley B , Nye F J , Beeching N J
Published: January 2006

Introduction

An outbreak of echovirus meningitis occurred in the north west of England in 2001. This paper reviewed the clinical features and the role of different diagnostic methods.

Methods

This was a prospective study of adults admitted to a regional infectious disease unit with a probable diagnosis of meningitis, March to August 2001.

Results

Half the 40 cases were male; median age was 28 (range 16–51) years. Fifteen of 38 (39.5%) were smokers, and 20 of 24 (83.3%) had close contact with children. Median (range) duration of symptoms was 1.1 (0.25–7) days. Symptoms included headache (100%), photophobia (87.5%), and nausea (67.5%), and severity ranged from minimal signs to those consistent with a meningoencephalitis. The diagnosis was confirmed virologically in 29 of 40 (72%); echovirus 30 was isolated from six. Cerebrospinal fluid (CSF) enterovirus polymerase chain reaction (PCR) was positive in 26 of 32 (81%), and CSF virus culture in 3 of 16 (19%). Thirty one per cent of CSF samples had a neutrophil predominance, and 3 of 29 (10%) virologically confirmed cases had normal CSF microscopy and biochemistry.

Conclusion

CSF microscopy may be normal or suggest bacterial meningitis in a substantial minority of cases of echovirus meningitis. CSF PCR for enterovirus seems to be more sensitive than virus culture of CSF, although PCR does not yield information on circulating virus type. Early and accurate diagnosis could reduce both use of parenteral antibiotics and length of hospital stay with both morbidity and cost implications. Close contact with children may be a risk factor, particularly if good hygiene measures are not practised.
TREE-WREATHING APPLIED TO GENERATION OF GROUPS BY FINITE AUTOMATA
Authors: SIDKI SAID
Published: January 2006

We extend the tree-wreath product of groups introduced by Brunner and the author, as a generalization of the restricted wreath product, thus enlarging the class of groups known to be generated by finite synchronous automata. In particular, we prove that given a countable abelian residually finite 2 -group H and B = B(n,ℤ), a canonical subgroup of finite index in GL(n,ℤ), then the restricted wreath product H wr B can be generated by finite synchronous automata on 0,1. This is obtained by producing a representation of B as a group of automorphisms of the binary tree such that the stabilizer of the infinite sequence of 0's is trivial. The uni-triangular group U = U(n,ℤ) is a subgroup of B(n,ℤ) and so, H wr U also can be generated by finite synchronous automata on 0,1.
A NOTE ON THE NORMS OF TRANSITION OPERATORS ON LAMPLIGHTER GRAPHS AND GROUPS
Authors: WOESS WOLFGANG
Published: January 2006

Let L≀X be a lamplighter graph, i.e., the graph-analogue of a wreath product of groups, and let P be the transition operator (matrix) of a random walk on that structure. We explain how methods developed by Saloff-Coste and the author can be applied for determining the ℓp-norms and spectral radii of P, if one has an amenable (not necessarily discrete or unimodular) locally compact group of isometries that acts transitively on L. This applies, in particular, to wreath products K≀G of finitely-generated groups, where K is amenable. As a special case, this comprises a result of Żuk regarding the ℓ2-spectral radius of symmetric random walks on such groups.
CONJUGATELY DENSE SUBGROUPS OF 3-DIMENSIONAL LINEAR GROUPS OVER LOCALLY FINITE FIELD
Authors: ZYUBIN S. A.
Published: January 2006

A subgroup of any group is called conjugately dense if it has nonempty intersection with each class of conjugate elements of the group. The aim of this paper is to prove the following. Let K be a locally finite field and H be an irreducible conjugately dense subgroup of the intermediate group SL 3(K) ≤ G ≤ GL 3(K); then H = G. This result confirms part of P. Neumann's conjecture from problem 6.38 in "Kourovka Notebook" for the group GL 3(K) over locally finite field K.
FROM WALL SPACES TO CAT(0) CUBE COMPLEXES
Authors: CHATTERJI INDIRA , NIBLO GRAHAM
Published: January 2006

We explain how to adapt a construction due to M. Sageev in order to construct a proper action of a group on a CAT(0) cube complex starting from a proper action of the group on a wall space.
A FUZZY DATA MINING ALGORITHM FOR INCREMENTAL MINING OF QUANTITATIVE SEQUENTIAL PATTERNS
Authors: SUBRAMANYAM R. B. V. , GOSWAMI A.
Published: January 2006

In real world applications, the databases are constantly added with a large number of transactions and hence maintaining latest sequential patterns valid on the updated database is crucial. Existing data mining algorithms can incrementally mine the sequential patterns from databases with binary values. Temporal transactions with quantitative values are commonly seen in real world applications. In addition, several methods have been proposed for representing uncertain data in a database. In this paper, a fuzzy data mining algorithm for incremental mining of sequential patterns from quantitative databases is proposed. Proposed algorithm called IQSP algorithm uses the fuzzy grid notion to generate fuzzy sequential patterns validated on the updated database containing the transactions in the original database and in the incremental database. It uses the information about sequential patterns that are already mined from original database and avoids start-from-scratch process. Also, it minimizes the number of candidates to check as well as number of scans to original database by identifying the potential sequences in incremental database.
INTERVAL METHODS IN KNOWLEDGE REPRESENTATION
Authors: KREINOVICH VLADIK
Published: January 2006

This section is maintained by Vladik Kreinovich. Please send your abstracts (or copies of papers that you want to see reviewed here) to vladik@utep.edu, or by regular mail to: VLADIK KREINOVICH, Department of Computer Science, University of Texas at El Paso, El Paso, TX 79968, USA.
Encoding of Three-Dimensional Surface Slant in Cat Visual Areas 17 and 18
Authors: Sanada Takahisa M. , Ohzawa Izumi
Published: January 2006

How are surface orientations of three-dimensional objects and scenes represented in the visual system? We have examined an idea that these surface orientations are encoded by neurons with a variety of tilts in their binocular receptive field (RF) structure. To examine whether neurons in the early visual areas are capable of encoding surface orientations, we have recorded from single neurons extracellularly in areas 17 and 18 of the cat using standard electrophysiological methods. Binocular RF structures are obtained using a binocular version of the reverse correlation technique. About 30% of binocularly responsive neurons have RFs with statistically significant tilts from the frontoparallel plane. The degree of tilts is sufficient for representing the range of surface slants found in typical visual environments. For a subset of neurons having significant RF tilts, the degrees of tilt are correlated with the preferred spatial frequency difference between the two eyes, indicating that a modified disparity energy model can account for the selectivity, at least partially. However, not all cases could be explained by this model, suggesting that multiple mechanisms may be responsible. Therefore an alternative hypothesis is also examined, where the tilt is generated by pooling of multiple disparity detectors whose preferred disparities progressively shift over space. Although there is evidence for extensive spatial pooling, this hypothesis was not satisfactory either, in that the neurons with extensive pooling tended to prefer an untilted surface. Our results suggest that encoding of surface orientations may begin with the binocular neurons in the early visual cortex.
Olfactory Nerve–Evoked, Metabotropic Glutamate Receptor–Mediated Synaptic Responses in Rat Olfactory Bulb Mitral Cells
Authors: Ennis Matthew , Zhu Mingyan , Heinbockel Thomas , Hayar Abdallah
Published: January 2006

The group I metabotropic glutamate receptor (mGluR) subtype, mGluR1, is highly expressed on the apical dendrites of olfactory bulb mitral cells and thus may be activated by glutamate released from olfactory nerve (ON) terminals. Previous studies have shown that mGluR1 agonists directly excite mitral cells. In the present study, we investigated the involvement of mGluR1 in ON-evoked responses in mitral cells in rat olfactory bulb slices using patch-clamp electrophysiology. In voltage-clamp recordings, the average EPSC evoked by single ON shocks or brief trains of ON stimulation (six pulses at 50 Hz) in normal physiological conditions were not significantly affected by the nonselective mGluR antagonist LY341495 (50–100 μΜ) or the mGluR1-specific antagonist LY367385 (100 μM); ON-evoked responses were attenuated, however, in a subset (36%) of cells. In the presence of blockers of ionotropic glutamate and GABA receptors, application of the glutamate uptake inhibitors THA (300 μM) and TBOA (100 μM) revealed large-amplitude, long-duration responses to ON stimulation, whereas responses elicited by antidromic activation of mitral/tufted cells were unaffected. Magnitudes of the ON-evoked responses elicited in the presence of THA–TBOA were dependent on stimulation intensity and frequency, and were maximal during high-frequency (50-Hz) bursts of ON spikes, which occur during odor stimulation. ON-evoked responses elicited in the presence of THA–TBOA were significantly reduced or completely blocked by LY341495 or LY367385 (100 μM). These results demonstrate that glutamate transporters tightly regulate access of synaptically evoked glutamate from ON terminals to postsynaptic mGluR1s on mitral cell apical dendrites. Taken together with other findings, the present results suggest that mGluR1s may not play a major role in phasic responses to ON input, but instead may play an important role in shaping slow oscillatory activity in mitral cells and/or activity-dependent regulation of plasticity at ON–mitral cell synapses.
Responses of Neurons in the Rat's Ventral Nucleus of the Lateral Lemniscus to Monaural and Binaural Tone Bursts
Authors: Zhang Huiming , Kelly Jack B.
Published: January 2006

Responses to monaural and binaural tone bursts were recorded from neurons in the rat's ventral nucleus of the lateral lemniscus (VNLL). Most of the neurons (55%) had V- or U-shaped frequency-tuning curves with a single clearly defined characteristic frequency (CF). However, many neurons had more complex, multipeaked tuning curves (37%), or other patterns (8%). Temporal firing patterns included both onset and sustained responses to contralateral tone bursts. Onset and sustained responses were distributed along the dorsoventral length of VNLL with no indication of segregation into different regions. Onset neurons had shorter average first-spike latencies than neurons with sustained responses (means, 8.3 vs. 14.8 ms). They also had less jitter, as reflected in the SD of first-spike latencies, than neurons with sustained responses (means, 0.59 and 4.2 ms, respectively). The extent of jitter decreased with an increase in stimulus intensity for neurons with sustained responses, but remained unchanged for onset neurons tested over the same range. Many neurons had binaural responses, primarily of the excitatory/inhibitory (EI) type, widely distributed along the dorsoventral extent of VNLL. Local application of the AMPA receptor antagonist NBQX reduced excitatory responses, indicating that responses were dependent on synaptic activity and not recorded from passing fibers. The results show that many neurons in VNLL have a precision of timing that is well suited for processing auditory temporal information. In the rat, these neurons are intermingled among cells with less precise temporal response features and include cells with binaural as well as monaural responses.
Norepinephrine Differentially Modulates Different Types of Respiratory Pacemaker and Nonpacemaker Neurons
Authors: Viemari Jean-Charles , Ramirez Jan-Marino
Published: January 2006

Pacemakers are found throughout the mammalian CNS. Yet, it remains largely unknown how these neurons contribute to network activity. Here we show that for the respiratory network isolated in transverse slices of mice, different functions can be assigned to different types of pacemakers and nonpacemakers. This difference becomes evident in response to norepinephrine (NE). Although NE depolarized 88% of synaptically isolated inspiratory neurons, this neuromodulator had differential effects on different neuron types. NE increased in cadmium-insensitive pacemakers burst frequency, not burst area and duration, and it increased in cadmium-sensitive pacemakers burst duration and area, but not frequency. NE also differentially modulated nonpacemakers. Two types of nonpacemakers were identified: “silent nonpacemakers” stop spiking, whereas “active nonpacemakers” spontaneously spike when isolated from the network. NE selectively induced cadmium-sensitive pacemaker properties in active, but not silent, nonpacemakers. Flufenamic acid (FFA), a blocker of ICAN, blocked the induction as well as modulation of cadmium-sensitive pacemaker activity, and blocked at the network level the NE-induced increase in burst area and duration of inspiratory network activity; the frequency modulation (FM) was unaffected. We therefore propose that modulation of cadmium-sensitive pacemaker activity contributes at the network level to changes in burst shape, not frequency. Riluzole blocked the FM of isolated cadmium-insensitive pacemakers. In the presence of riluzole, NE caused disorganized network activity, suggesting that cadmium-insensitive pacemakers are critical for rhythm generation. We conclude that different types of nonpacemaker and pacemaker neurons differentially control different aspects of the respiratory rhythm.
Rhabdomyosarcoma Lysis by T Cells Expressing a Human Autoantibody-Based Chimeric Receptor Targeting the Fetal Acetylcholine Receptor
Authors: Gattenlöhner Stefan , Marx Alexander , Markfort Birgit , Pscherer Sibylle , Landmeier Silke , Juergens Heribert , Müller-Hermelink Hans-Konrad , Matthews Ian , Beeson David , Vincent Angela , Rossig Claudia
Published: January 2006

Rhabdomyosarcomas are the most frequent malignant soft tissue tumors of childhood; however, because current multimodality treatments fail to improve the poor survival rate of children with metastatic rhabdomyosarcoma, new treatments are required. We previously identified the γ-subunit of the fetal acetylcholine receptor (fAChR) as a specific cell surface target in rhabdomyosarcoma. Here, we engineered human T lymphocytes to express chimeric receptors composed of the antigen-binding domain of a human anti-fAChR antibody joined to the signaling domain of the human T-cell receptor ζ-chain. The interaction of fAChRζ-transduced T cells with fAChR-positive rhabdomyosarcoma cell lines, but not with fAChR-negative control cells, induced T-cell activation characterized by strong secretion of IFN-γ and delayed lysis of tumor cells. Importantly, we found that in six of six rhabdomyosarcoma patients, chemotherapy increased fAChR expression on residual tumor cells in vivo. Our observations suggest that these fully human chimeric fAChRζ-transduced T cells, which should be well tolerated by the patient, have potential use in vivo both as a primary treatment for rhabdomyosarcoma and as a complementary approach to eradicate residual tumor cells after chemotherapy. (Cancer Res 2006; 66(1): 24-28)