bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions between overstorey and understorey vegetation along an overstorey compositional gradient
Authors: Bartels Samuel F. , Chen Han Y.H.
Published: October 2012

Questions

What is the nature of the interactions between higher vegetation strata (overstorey) and lower strata (understorey vegetation) and among understorey vegetation layers in closed canopy forests? How does the abundance or richness of one vegetation layer affect the abundance or richness of the other?

Location

Boreal mixed‐wood forests ofOntario andQuebec,Canada.

Methods

We sampled fire‐origin stands of varying overstorey composition from broad‐leaf‐dominated to mixed to conifer‐dominated stands on mesic sites inOntario and subhydric sites inQuebec. Overstorey tree species composition and understorey shrub, herb, bryophyte and lichen species cover and richness were estimated within 400‐m2circular plots. In addition, soil nutrients, coarse woody debris and light conditions were measured. Overstorey composition was expressed as the percentage basal area of broad‐leaf tree species. Path analysis was used to examine interactions among the forest layers.

Results

Overstorey broad‐leaf composition had positive effects on shrub and herb layer cover and herb layer richness, and negative effects on bryophyte and lichen species cover and richness. Shrub layer cover had no effect on herb layer cover, but shrub layer richness had a positive effect on herb layer richness. Herb layer cover and richness had negative effects on bryophyte species cover and richness. Bryophyte cover had no effect on lichen cover, but its richness was positively related to lichen richness. In both regions, soil pH, total nitrogen, total phosphorus and cation exchange capacity of the forest floor were positively correlated with overstorey broad‐leaf composition and with shrub layer cover and herb layer cover.

Conclusions

Increasing overstorey broad‐leaf composition, through its influence on soil nutrients, promotes shrub and herb layer species, but limits bryophyte and lichen species. In the overstorey‐controlled understorey resource environment, cover and richness of shrub and herb layers increase with resource availability, whereas bryophytes and lichens show positive associations with abundance of coarse woody debris.
Limits to State‐Led Nation‐Building? An Eritrean Village Responds Selectively to the Plans of the Eritrean Government
Authors: O'Kane David
Published: October 2012

Since independence in the early 1990s, the east African state of Eritrea has been ruled by a self‐consciously nationalist and modernising authoritarian regime, which seeks to build an Eritrean national consciousness among the country's 3.5 million people via top‐down strategies of intervention in rural communities. These are not limited to the use of cultural interventions intended to revise people's identities. They also take the form of state‐led development strategies, including land nationalisation. In a village in highland Eritrea, the residents oppose some of the projects of the state while adopting parts of the national identity proffered to them by the state. The author argues that this case suggests a new way of thinking about the ways in which national identities and nation‐states are constructed – one that reconsiders the relationship between nationalism and resistance, and between nation‐building elites and communities in resistance.
Narrow Irregular QRS Tachycardia with AV Dissociation: What Is the Mechanism?
Authors: CASTILLO CASTILLO JESÚS , PEÑAFIEL VERDÚ PABLO , MARTÍNEZ SÁNCHEZ JUAN , GARCÍA ALBEROLA ARCADI
Published: October 2012

Arrhythmia Rounds. A 39‐year‐old woman with no structural heart disease and frequent episodes of sudden onset palpitations was referred for the electrophysiological study. During the study, a slightly irregular narrow QRS tachycardia with AV dissociation was repeatedly induced and spontaneously terminated. Apparently, irregular cycles and termination of the tachycardia were related to the dissociated sinus rhythm: atrial depolarizations timed when the AV junction was refractory were able to reset the tachycardia, while early atrial depolarizations caused its termination. This observation was enough to diagnose the tachycardia mechanism in our case. (J Cardiovasc Electrophysiol, Vol. 24, pp. 364‐366, March 2013)
Response to Atrial Extrastimulus During Supraventricular Tachycardia: What Is the Mechanism?
Authors: PHILIPS BINU , BERGER RONALD D. , MARINE JOSEPH E.
Published: October 2012

Arrhythmia Rounds. We describe a case illustrating the potential challenges in distinguishing AV nodal reentry tachycardia (AVNRT) from automatic junctional tachycardia (JT). While an early atrial extrastimulus advanced the next His and ventricular depolarization without tachycardia termination, suggesting JT, other features indicated the correct diagnosis of AVNRT. This teaching case demonstrates a novel exception to a recently reported diagnostic pacing maneuver and illustrates the importance of considering response to multiple maneuvers in reaching a diagnosis of SVT mechanism. (J Cardiovasc Electrophysiol, Vol. 24, pp. 359‐363, March 2013)
Cost‐Effectiveness Evaluation of a Collaborative Patient Education Hypertension Intervention in Utah
Authors: Trogdon Justin G. , Larsen Barbara , Larsen David , Salas Wendy , Snell Matt
Published: October 2012

J Clin Hypertens (Greenwich). 2012;14:760–766. ©2012 Wiley Periodicals, Inc.

This study analyzed the cost‐effectiveness of a patient hypertension education intervention that provided patient education through interactive voice response technology and distribution of automated blood pressure monitors to high‐risk plan members with uncontrolled hypertension. A total of 17,318 members were identified with hypertension in an administrative database. The study sample consisted of all 534 high‐risk hypertensive plan members who received blood pressure monitors. Using data on activity‐based program costs and changes in hypertension control, this study modeled the intervention’s cost‐effectiveness relative to no intervention. The intervention was estimated to have brought hypertension under control in 151 patients during the study year. Across all 534 participants in 1 year, 0.3 events (acute myocardial infarction, stroke, congestive heart failure, and renal failure) were avoided and 2.77 life‐years were gained (LYG). The incremental cost‐effectiveness ratio (ICER) for the intervention compared with no intervention was $767 per person brought under control or $41,927 per LYG. If the gains in hypertension control from 1 year’s investment were assumed to last 10 years, the 10‐year ICER relative to no intervention was $1857 per LYG. The intervention is a cost‐effective strategy to address hypertension and can serve as a model for future innovations.
Recurrent Hypertensive Cerebral Hemorrhages in a Boy Caused by a Reninoma: Rare Manifestations and Distinctive Electron Microscopy Findings
Authors: Mao Jiangfeng , Wang Zhixin , Wu Xingcheng , Dai Wei , Tong Anli
Published: October 2012

J Clin Hypertens (Greenwich). 2012;14:802–805. ©2012 Wiley Periodicals, Inc.

Recurrent cerebral hemorrhages caused by hypertension secondary to reninoma are extremely rare in children. Because of its detrimental effects on children’s health, the importance of early diagnosis of and treatment for reninoma should be emphasized. Here, the authors present a 10‐year‐old boy with intermittent headaches and neurologic deficiency symptoms caused by hypertension. A reninoma in the right kidney was detected and successfully treated with laparoscopic partial nephrectomy. Two cell types were revealed in the tumor tissue under electron microscopy: renin secreting tumor cells and mast cells. This rare case expands our knowledge of hypertension in children and provides direct evidence that mast cells may infiltrate reninoma.
Characterization and analysis of migration patterns of dentospheres derived from periodontal tissue and the palate
Authors: Keeve P. L. , Dittmar T. , Gassmann G. , Grimm W. ‐D. , Niggemann B. , Friedmann A.
Published: October 2012

Background and Objective

Stem cells derived from periodontal and palatal tissues may be useful for regenerative therapies of periodontal tissues. In addition to the use of single periodontium‐derived stem cells (pdSCs) and palatal‐derived stem cells (paldSCs), the application of pdSC and paldSC dentospheres, providing a pool of vital stem cells, may be a useful approach.

As cell migration is a prerequisite for stem cells to regenerate a three‐dimensional tissue environment, we characterized pdSCs and paldSCs and investigated the migratory activity of dentospheres within a three‐dimensional environment. We also investigated the capacity of the dentospheres to grow on zirconium dioxide surfaces.

Material and Methods

The capacity of pdSCs and paldSCs to differentiate into the neuronal and osteogenic lineages was proved by RT‐PCR and immunohistochemistry through the detection of specific lineage markers, such as alkaline phosphatase, glutamate decarboxylase 1 (also known as GAD67, the 67‐kDa isoform of glutamate decarboxylase), neurofilament‐M and β‐III‐tubulin. The expression profile of surface molecules on pdSCs and paldSCs was analyzed by flow cytometry. Adhesion and growth of pdSC/paldSC dentospheres on zirconium dioxide surfaces were determined using confocal laser‐scanning microscopy. The migratory behavior of the cells was analyzed using a three‐dimensional collagen matrix migration assay.

Results

Both pdSCs and paldSCs were positive for epidermal growth factor receptor, CC chemokine receptor 2 and CXC chemokine receptor 4 expression and were able to grow on zirconium dioxide surfaces. Cell‐migration experiments revealed that both stem‐cell populations responded similarly to epidermal growth factor (EGF), monocyte chemotactic protein 1 (MCP‐1) and stromal cell‐derived factor 1alpha (SDF‐1α). Stimulation with EGF resulted in an increased migratory activity of both stem‐cell types, whereas the locomotory behavior of the cells was impaired by both MCP‐1 and SDF‐1α.

Conclusion

Dentospheres represent a pool of vital pdSCs/paldSCs. As a result of the migratory activity demonstrated, along with the capacity to grow on zirconium dioxide surfaces, dentospheres may be useful for regenerative purposes in periodontal tissues.
Transgenic rice with inducible ethylene production exhibits broad‐spectrum disease resistance to the fungal pathogens Magnaporthe oryzae and Rhizoctonia solani
Authors: Helliwell Emily E. , Wang Qin , Yang Yinong
Published: October 2012

Rice blast (Magnaporthe oryzae) and sheath blight (Rhizoctonia solani) are the two most devastating diseases of rice (Oryza sativa), and have severe impacts on crop yield and grain quality. Recent evidence suggests that ethylene (ET) may play a more prominent role than salicylic acid and jasmonic acid in mediating rice disease resistance. In this study, we attempt to genetically manipulate endogenous ET levels in rice for enhancing resistance to rice blast and sheath blight diseases. Transgenic lines with inducible production of ET were generated by expressing the rice ACS2 (1‐aminocyclopropane‐1‐carboxylic acid synthase, a key enzyme of ET biosynthesis) transgene under control of a strong pathogen‐inducible promoter. In comparison with the wild‐type plant, the OsACS2‐overexpression lines showed significantly increased levels of the OsACS2 transcripts, endogenous ET and defence gene expression, especially in response to pathogen infection. More importantly, the transgenic lines exhibited increased resistance to a field isolate of R. solani, as well as different races of M. oryzae. Assessment of the growth rate, generational time and seed production revealed little or no differences between wild type and transgenic lines. These results suggest that pathogen‐inducible production of ET in transgenic rice can enhance resistance to necrotrophic and hemibiotrophic fungal pathogens without negatively impacting crop productivity.
Comparison endpoint study of process plasma and secondary electron beam exciter optical emission spectroscopy
Authors: Stephan Thamban P. L. , Yun Stuart , Padron-Wells Gabriel , Hosch Jimmy W. , Goeckner Matthew J.
Published: October 2012

Traditionally process plasmas are often studied and monitored by optical emission spectroscopy. Here, the authors compare experimental measurements from a secondary electron beam excitation and direct process plasma excitation to discuss and illustrate its distinctiveness in the study of process plasmas. They present results that show excitations of etch process effluents in a SF6 discharge and endpoint detection capabilities in dark plasma process conditions. In SF6 discharges, a band around 300 nm, not visible in process emission, is observed and it can serve as a good indicator of etch product emission during polysilicon etches. Based on prior work reported in literature the authors believe this band is due to SiF4 gas phase species.
PACS and Digital Medicine: Essential Principles and Modern Practice.
Authors: Langer Steve G.
Published: October 2012

PACS and Digital Medicine: Essential Principles and Modern Practice. Y. Liu J. Wang CRC, Taylor & Francis Group, Boca Raton, FL, 2011. Hardcover, 367 pp. Price: $135.95. ISBN: 978‐1‐4200‐83651.
Nuclear Medicine Physics: The Basics. 7th ed.
Authors: Mihailidis Dimitris
Published: October 2012

Nuclear Medicine Physics: The Basics. 7th ed. Ramesh Chandra, Lippincott Williams and Wilkins, a Wolters Kluwer Business. Philadelphia, 2012. Softbound, 224 pp. Price: $69.99. ISBN: 9781451109412.
The use of exit detector sinograms to detect anatomical variations for patients extending beyond the TomoTherapy field of view: A feasibility study
Authors: Wooten H. Omar , Goddu S. Murty , Rodriguez Vivian , Cates Jeremy , Grigsby Perry , Low Daniel A.
Published: October 2012

Purpose:

This work describes an independent method to use the TomoTherapy Hi‐ART megavoltage CT imaging system for daily monitoring of anatomical changes of cancer patients whose anatomy extends beyond the imaging field of view.

Methods:

The imaging detector response to changes in attenuating media was measured using water‐equivalent plastic. Weight loss was simulated using an anthropomorphic phantom and determining the systemˈs ability to detect the weight loss. Layers of tissue‐equivalent bolus were added to an anthropomorphic pelvis phantom and CT simulations of the phantom were conducted, one in which the phantom and bolus were both within the TomoTherapy imaging field of view, and another in which the couch was raised so that the bolus was outside the field of view. Gynecological treatment plans were developed using the TomoTherapy treatment planning system, and successive fractions of the plan were then delivered to the phantom. Weight loss was simulated by removing a 0.5 cm layer of bolus following each fraction. The exit detector sinograms were obtained from each fraction, and ratios of sinograms were calculated relative to a reference sinogram for which all bolus was in place. Histograms of ratio sinograms were determined and used to correlate with simulated weight loss. Exit detector sinograms and ratio histograms were also retrospectively analyzed for five patients all of whose anatomies extended beyond the imaging field of view and all of whom experienced weight variations exceeding 10% during treatment.

Results:

Exit detector signal is well correlated to changes in attenuator thickness as demonstrated in both slab and anthropomorphic phantom geometries. Measured and expected signal increases agreed to within less than 2% for simulated weight loss on the anthropomorphic phantom. Exit detector signals for pelvic patients with significant weight loss variations were consistent with phantom measurements.

Conclusions:

The analysis of the ratio sinograms for the phantom measurements and real patients indicated that exit detector sinograms can be used to detect relative changes in patient anatomy for each fraction as a means ofin vivo quality assurance.
MR/PET quantification tools: Registration, segmentation, classification, and MR‐based attenuation correction
Authors: Fei Baowei , Yang Xiaofeng , Nye Jonathon A. , Aarsvold John N. , Raghunath Nivedita , Cervo Morgan , Stark Rebecca , Meltzer Carolyn C. , Votaw John R.
Published: October 2012

Purpose:

Combined MR/PET is a relatively new, hybrid imaging modality. A human MR/PET prototype system consisting of a Siemens 3T Trio MR and brain PET insert was installed and tested at our institution. Its present design does not offer measured attenuation correction (AC) using traditional transmission imaging. This study is the development of quantification tools including MR‐based AC for quantification in combined MR/PET for brain imaging.

Methods:

The developed quantification tools include image registration, segmentation, classification, and MR‐based AC. These components were integrated into a single scheme for processing MR/PET data. The segmentation method is multiscale and based on the Radon transform of brain MR images. It was developed to segment the skull on T1‐weighted MR images. A modified fuzzy C‐means classification scheme was developed to classify brain tissue into gray matter, white matter, and cerebrospinal fluid. Classified tissue is assigned an attenuation coefficient so that AC factors can be generated. PET emission data are then reconstructed using a three‐dimensional ordered sets expectation maximization method with the MR‐based AC map. Ten subjects had separate MR and PET scans. The PET with [11C]PIB was acquired using a high‐resolution research tomography (HRRT) PET. MR‐based AC was compared with transmission (TX)‐based AC on the HRRT. Seventeen volumes of interest were drawn manually on each subject image to compare the PET activities between the MR‐based and TX‐based AC methods.

Results:

For skull segmentation, the overlap ratio between our segmented results and the ground truth is 85.2 ± 2.6%. Attenuation correction results from the ten subjects show that the difference between the MR and TX‐based methods was <6.5%.

Conclusions:

MR‐based AC compared favorably with conventional transmission‐based AC. Quantitative tools including registration, segmentation, classification, and MR‐based AC have been developed for use in combined MR/PET.
Analysis of a homemade Edison tinfoil phonograph
Authors: Sagers Jason D. , McNeese Andrew R. , Lenhart Richard D. , Wilson Preston S.
Published: October 2012

Thomas Edison’s phonograph was a landmark acoustic invention. In this paper, the phonograph is presented as a tool for education in acoustics. A brief history of the phonograph is outlined and an analogous circuit model that describes its dynamic response is discussed. Microphone and scanning laser Doppler vibrometer (SLDV) measurements were made on a homemade phonograph for model validation and inversion for unknown model parameters. SLDV measurements also conclusively illustrate where model assumptions are violated. The model elements which dominate the dynamic response are discussed.
Absorption and impedance boundary conditions for phased geometrical-acoustics methods
Authors: Jeong Cheol-Ho
Published: October 2012

Defining accurate acoustical boundary conditions is of crucial importance for room acoustic simulations. In predicting sound fields using phased geometrical acoustics methods, both absorption coefficients and surface impedances of the boundary surfaces can be used, but no guideline has been developed on which boundary condition produces accurate results. In this study, various boundary conditions in terms of normal, random, and field incidence absorption coefficients and normal incidence surface impedance are used in a phased beam tracing model, and the simulated results are validated with boundary element solutions. Two rectangular rooms with uniform and non-uniform absorption distributions are tested. Effects of the neglect of reflection phase shift are also investigated. It is concluded that the impedance, random incidence, and field incidence absorption boundary conditions produce reasonable results with some exceptions at low frequencies for acoustically soft materials.
Special transformations for pentamode acoustic cloaking
Authors: Gokhale Nachiket H. , Cipolla Jeffrey L. , Norris Andrew N.
Published: October 2012

The acoustic cloaking theory of Norris [Proc. R. Soc. London, Ser. A 464, 2411–2434 (2008)] permits considerable freedom in choosing the transformation f from physical to virtual space. The standard process for defining cloak materials is to first define f and then evaluate whether the materials are practically realizable. In this paper, this process is inverted by defining desirable material properties and then deriving the appropriate transformations which guarantee the cloaking effect. Transformations are derived which result in acoustic cloaks with special properties such as (1) constant density, (2) constant radial stiffness, (3) constant tangential stiffness, (4) power-law density, (5) power-law radial stiffness, (6) power-law tangential stiffness, and (7) minimal elastic anisotropy.
Resonant coupling of Rayleigh waves through a narrow fluid channel causing extraordinary low acoustic transmission
Authors: Garcia-Chocano Victor M. , Nagaraj  , Lòpez-Rios Tomàs , Gumen Lyudmila , Sànchez-Dehesa Josè , Krokhin Arkadii
Published: October 2012

Coupling of Rayleigh waves propagating along two metal surfaces separated by a narrow fluid channel is predicted and experimentally observed. Although the coupling through a fluid (water) is weak, a strong synchronization in propagation of Rayleigh waves even for the metals with sufficiently high elastic contrast (brass and aluminum) is observed. Dispersion equation for two polarizations of the coupled Rayleigh waves is derived and experimentally confirmed. Excitation of coupled Rayleigh waves in a channel of finite length leads to anomalously low transmission of acoustic energy at discrete set of resonant frequencies. This effect may find useful applications in the design of acoustic metamaterial screens and reflectors.
Transformation ray method: Controlling high frequency elastic waves (L)
Authors: Chang Zheng , Liu Xiaoning , Hu Gengkai , Hu Jin
Published: October 2012

Elastic ray theory is a high frequency asymptotic approximation of solution of elastodynamic equation, and is widely used in seismology. In this paper, the form invariance under a general spatial mapping and high frequency wave control have been examined by transformation method. It is showed that with the constraint of major and minor symmetry of the transformed elastic tensor, the eikonal equation keeps its form under a general mapping, however, the transport equation loses its form except for conformal mapping. Therefore, the elastic ray path can be controlled in an exact manner by a transformation method, whereas energy distribution along the ray is only approximately controlled. An elastic rotator based on ray tracing method is also provided to illustrate the method and to access the approximation.
Root locus analysis and design of the adaptation process in active noise control
Authors: Tabatabaei Ardekani Iman , Abdulla Waleed H.
Published: October 2012

This paper applies root locus theory to develop a graphical tool for the analysis and design of adaptive active noise control systems. It is shown that the poles of the adaptation process performed in these systems move on typical trajectories in the z-plane as the adaptation step-size varies. Based on this finding, the dominant root of the adaptation process and its trajectory can be determined. The first contribution of this paper is formulating parameters of the adaptation process root locus. The next contribution is introducing a mechanism for modifying the trajectory of the dominant root in the root locus. This mechanism creates a single open loop zero in the original root locus. It is shown that appropriate localization of this zero can cause the dominant root of the locus to be pushed toward the origin, and thereby the adaptation process becomes faster. The validity of the theoretical findings is confirmed in an experimental setup which is implemented using real-time multi-threading and multi-core processing techniques.
Set-size procedures for controlling variations in speech-reception performance with a fluctuating masker
Authors: Bernstein Joshua G. W. , Summers Van , Iyer Nandini , Brungart Douglas S.
Published: October 2012

Adaptive signal-to-noise ratio (SNR) tracking is often used to measure speech reception in noise. Because SNR varies with performance using this method, data interpretation can be confounded when measuring an SNR-dependent effect such as the fluctuating-masker benefit (FMB) (the intelligibility improvement afforded by brief dips in the masker level). One way to overcome this confound, and allow FMB comparisons across listener groups with different stationary-noise performance, is to adjust the response set size to equalize performance across groups at a fixed SNR. However, this technique is only valid under the assumption that changes in set size have the same effect on percentage-correct performance for different masker types. This assumption was tested by measuring nonsense-syllable identification for normal-hearing listeners as a function of SNR, set size and masker (stationary noise, 4- and 32-Hz modulated noise and an interfering talker). Set-size adjustment had the same impact on performance scores for all maskers, confirming the independence of FMB (at matched SNRs) and set size. These results, along with those of a second experiment evaluating an adaptive set-size algorithm to adjust performance levels, establish set size as an efficient and effective tool to adjust baseline performance when comparing effects of masker fluctuations between listener groups.
Eigenvalues of the sample covariance matrix for a towed array
Authors: Gerstoft Peter , Menon Ravishankar , Hodgkiss William S. , Mecklenbräuker Christoph F.
Published: October 2012

It is well known that observations of the spatial sample covariance matrix (SCM, also called the cross-spectral matrix) reveal that the ordered noise eigenvalues of the SCM decay steadily, but common models predict equal noise eigenvalues. Random matrix theory (RMT) is used to derive and discuss properties of the eigenvalue spectrum of the data SCM for linear arrays, with an application to ocean acoustic data. Noise on the array is considered either incoherent or propagating acoustic noise that is coherent across the array. Using conventional three-dimensional or two-dimensional isotropic noise models with full or snapshot-deficient observations, realizations of the SCM eigenvalues are explained using RMT. Deep-water towed-array data are analyzed and it is shown that the eigenvalues of the SCM compare well with theory. It is demonstrated how RMT can be applied to study eigenvalue spectrum estimation as dependent on array properties (element spacing to wavelength ratio) and data sampling (snapshots). Apart from explaining the observed noise eigenvalue spectrum, the improved model of the eigenvalue spectrum has important applications in array signal processing.
Auditory filter tuning inferred with short sinusoidal and notched-noise maskers
Authors: Jennings Skyler G. , Strickland Elizabeth A.
Published: October 2012

The physiology of the medial olivocochlear reflex suggests that a sufficiently long stimulus (>100 ms) may reduce cochlear gain and result in broadened frequency selectivity. The current study attempted to avoid gain reduction by using short maskers (20 ms) to measure psychophysical tuning curves (PTCs) and notched-noise tuning characteristics, with a 4-kHz signal. The influence of off-frequency listening on PTCs was evaluated using two types of background noise. Iso-level curves were derived using an estimate of the cochlear input/output (I/O) function, which was obtained using an off-frequency masker as a linear reference. The influence of masker duration on PTCs was assessed using a model that assumed long maskers (>20 ms) evoked gain reduction. The results suggested that the off-frequency masker was a valid linear reference when deriving I/O functions and that off-frequency listening may have occurred in auditory filters apical to the signal place. The iso-level curves from this growth-of-masking study were consistent with those from a temporal-masking-curve study by Eustaquio-Martin and Lopez-Poveda [J. Assoc. Res. Otolaryngol. 12, 281–299. (2011)], suggesting that either approach may be used to derive iso-level curves. Finally, model simulations suggested that masker duration may not influence estimates of frequency selectivity.
Evidence for a common scale O(0.1) m that controls seabed scattering and reverberation in shallow water
Authors: Holland Charles W.
Published: October 2012

Analysis of the spectral content of long-range reverberation yields two observations. First, there is a remarkably similar scale, O(0.1) m, between three diverse continental shelf regions. This is surprising given the complexity and diversity of geologic processes. Second, there is strong evidence that the scale is associated with heterogeneities within the sediment. Thus, sediment volume scattering, not interface scattering, controls long-range reverberation from a few hundred hertz to several kilohertz. This is also unexpected given that at long ranges the vertical grazing angles are less than the critical angle, and hence the penetration of the acoustic field into the sub-bottom is expected to be modest. The consistency of the scale, O(0.1) m, suggests an underlying feature or mechanism that is consistent across many ostensibly diverse geological settings. Neither the feature nor mechanism is known at this time.
Approximate theory of reverberation in rectangular rooms with specular and diffuse reflections
Authors: Sakuma Tetsuya
Published: October 2012

First, an approximate theory of reverberation in rectangular rooms is formulated as a specular reflection field based on the image source method. In the formulation, image sources are divided into axial, tangential, and oblique groups, which chiefly contribute to the corresponding groups of normal modes in wave acoustics. Consequently, the total energy decay consists of seven kinds of exponential decay curves. Second, considering surface scattering on walls with scattering coefficients, an integrated reverberation theory for nondiffuse field is developed, where the total field is divided into specular and diffuse reflection fields. The specular reflection field is simply formulated by substituting specular absorption coefficients, while the diffuse reflection field is assumed to be a perfectly diffuse field, of which energy is supplied from the specular reflection field at each reflection. Finally, a theoretical case study demonstrates how surface scattering affects the energy decay in rectangular rooms with changing the aspect ratio and the absorption distribution.
Perceptual effects of noise reduction by time-frequency masking of noisy speech
Authors: Brons Inge , Houben Rolph , Dreschler Wouter A.
Published: October 2012

Time-frequency masking is a method for noise reduction that is based on the time-frequency representation of a speech in noise signal. Depending on the estimated signal-to-noise ratio (SNR), each time-frequency unit is either attenuated or not. A special type of a time-frequency mask is the ideal binary mask (IBM), which has access to the real SNR (ideal). The IBM either retains or removes each time-frequency unit (binary mask). The IBM provides large improvements in speech intelligibility and is a valuable tool for investigating how different factors influence intelligibility. This study extends the standard outcome measure (speech intelligibility) with additional perceptual measures relevant for noise reduction: listening effort, noise annoyance, speech naturalness, and overall preference. Four types of time-frequency masking were evaluated: the original IBM, a tempered version of the IBM (called ITM) which applies limited and non-binary attenuation, and non-ideal masking (also tempered) with two different types of noise-estimation algorithms. The results from ideal masking imply that there is a trade-off between intelligibility and sound quality, which depends on the attenuation strength. Additionally, the results for non-ideal masking suggest that subjective measures can show effects of noise reduction even if noise reduction does not lead to differences in intelligibility.
Comment on plate modal wavenumber transforms in Sound and Structural Vibration [Academic Press (1987, 2007)] (L)
Authors: Shepherd Micah R. , Hambric Stephen A.
Published: October 2012

The wavenumber transform for rectangular, simply supported, isotropic thin plates has been rederived to correct a technical error found in the text Sound and Structural Vibration (Academic Press, 1985/2007) by Fahy/Fahy and Gardonio. The text states that the modal wavenumber corresponds to the peak of the wavenumber spectrum. While this is approximately true for higher-order modes, it does not hold for lower-order modes due to coupling between positive and negative wavenumber energy. The modal wavenumber is shown to be related to the zeros in the wavenumber spectrum by an integer multiple of 2π normalized by the plate length.
Hearing threshold shifts and recovery in harbor seals (Phoca vitulina) after octave-band noise exposure at 4 kHz
Authors: Kastelein Ronald A. , Gransier Robin , Hoek Lean , Macleod Amy , Terhune John M.
Published: October 2012

Safety criteria for underwater sounds from offshore pile driving are needed to protect marine mammals. As a first step toward understanding effects of impulsive sounds, two harbor seals were exposed to octave-band white noise centered at 4 kHz at three mean received sound pressure levels (SPLs; 124, 136, and 148 dB re 1 μPa) at up to six durations (7.5, 15, 30, 60, 120, and 240 min); mean received sound exposure level (SEL) range was 166–190 dB re 1 μPa2 s. Hearing thresholds were determined before and after exposure. Temporary hearing threshold shifts (TTS) and subsequent recovery were quantified as changes in hearing thresholds at 1–4, 4–8, 8–12, 48, and 96 min after noise exposure in seal 01, and at 12–16, 16–20, 20–24, 60, and 108 min after exposure in seal 02. Maximum TTS (1–4 min after 120 min exposure to 148 dB re 1 μPa; 187 dB SEL) was 10 dB. Recovery occurred within ∼60 min. Statistically significant TTSs (>2.5 dB) began to occur at SELs of ∼170 (136 SPL, 60 min) and 178 dB re 1 μPa2 s (148 SPL, 15 min). However, SEL is not an optimal predictor of TTS for long duration, low SPL continuous noise, as duration and SPL play unequal roles in determining induced TTS.
Characterizing the low strain complex modulus of asphalt concrete specimens through optimization of frequency response functions
Authors: Gudmarsson Anders , Ryden Nils , Birgisson Björn
Published: October 2012

Measured and finite element simulated frequency response functions are used to characterize the low strain (∼10−7) complex moduli of an asphalt concrete specimen. The frequency response functions of the specimen are measured at different temperatures by using an instrumented hammer to apply a load and an accelerometer to measure the dynamic response. Theoretical frequency response functions are determined by modeling the specimen as a three-dimensional (3D) linear isotropic viscoelastic material in a finite element program. The complex moduli are characterized by optimizing the theoretical frequency response functions against the measured ones. The method is shown to provide a good fit between the frequency response functions, giving an estimation of the complex modulus between minimum 500 Hz and maximum 18|000 Hz depending on the temperature. Furthermore, the optimization method is shown to give a good estimation of the complex modulus master curve.
Tracking fin whales in the northeast Pacific Ocean with a seafloor seismic network
Authors: Wilcock William S. D.
Published: October 2012

Ocean bottom seismometer (OBS) networks represent a tool of opportunity to study fin and blue whales. A small OBS network on the Juan de Fuca Ridge in the northeast Pacific Ocean in ∼2.3 km of water recorded an extensive data set of 20-Hz fin whale calls. An automated method has been developed to identify arrival times based on instantaneous frequency and amplitude and to locate calls using a grid search even in the presence of a few bad arrival times. When only one whale is calling near the network, tracks can generally be obtained up to distances of ∼15 km from the network. When the calls from multiple whales overlap, user supervision is required to identify tracks. The absolute and relative amplitudes of arrivals and their three-component particle motions provide additional constraints on call location but are not useful for extending the distance to which calls can be located. The double-difference method inverts for changes in relative call locations using differences in residuals for pairs of nearby calls recorded on a common station. The method significantly reduces the unsystematic component of the location error, especially when inconsistencies in arrival time observations are minimized by cross-correlation.
Restoration of loudness summation and differential loudness growth in hearing-impaired listeners
Authors: Strelcyk Olaf , Nooraei Nazanin , Kalluri Sridhar , Edwards Brent
Published: October 2012

When normal-hearing (NH) listeners compare the loudness of narrowband and wideband sounds presented at identical sound pressure levels, the wideband sound will most often be perceived as louder than the narrowband sound, a phenomenon referred to as loudness summation. Hearing-impaired (HI) listeners typically show less-than-normal loudness summation, due to reduced cochlear compressive gain and degraded frequency selectivity. In the present study, loudness summation at 1 and 3 kHz was estimated monaurally for five NH and eight HI listeners by matching the loudness of narrowband and wideband noise stimuli. The loudness summation was measured as a function both of noise bandwidth and level. The HI listeners were tested unaided and aided using three different compression systems to investigate the possibility of restoring loudness summation in these listeners. A compression system employing level-dependent compression channels yielded the most promising outcome. The present results inform the development of future loudness models and advanced compensation strategies for the hearing impaired.
Unified modeling of turbulence effects on sound propagation
Authors: Cheinet Sylvain , Ehrhardt Loic , Juvé Daniel , Blanc-Benon Philippe
Published: October 2012

Many aspects of outdoor sound propagation depend on the scattering effects induced by atmospheric turbulence. Standard analytical and numerical assessments of these effects make an a priori distinction between the scattering effects at large versus small angles. The present study evaluates the ability of a numerical model in overcoming this distinction. The model solves a set of two coupled equations for the sound pressure and vector acoustic velocity, with the finite-difference time domain approach. It is first introduced and evaluated. The numerical predictions are compared to well-known analytical solutions in the case of two-dimensional plane wave propagation through turbulence. They are found to agree in the investigated scenarios. Hence, the finite-difference, time domain solution of the two coupled equations provides a unified, versatile numerical approach to investigating the effects of atmospheric turbulence on sound propagation. The comparison also provides original insights on the applicability and limitations of various methods used to investigate sound propagation through turbulence.
Chinchilla middle-ear admittance and sound power: High-frequency estimates and effects of inner-ear modifications
Authors: Ravicz Michael E. , Rosowski John J.
Published: October 2012

The middle-ear input admittance relates sound power into the middle ear (ME) and sound pressure at the tympanic membrane (TM). ME input admittance was measured in the chinchilla ear canal as part of a larger study of sound power transmission through the ME into the inner ear. The middle ear was open, and the inner ear was intact or modified with small sensors inserted into the vestibule near the cochlear base. A simple model of the chinchilla ear canal, based on ear canal sound pressure measurements at two points along the canal and an assumption of plane-wave propagation, enables reliable estimates of YTM, the ME input admittance at the TM, from the admittance measured relatively far from the TM. YTM appears valid at frequencies as high as 17 kHz, a much higher frequency than previously reported. The real part of YTM decreases with frequency above 2 kHz. Effects of the inner-ear sensors (necessary for inner ear power computation) were small and generally limited to frequencies below 3 kHz. Computed power reflectance was ∼0.1 below 3.5 kHz, lower than with an intact ME below 2.5 kHz, and nearly 1 above 16 kHz.
Sound texture recognition through dynamical systems modeling of empirical mode decomposition
Authors: Van Nort Doug , Braasch Jonas , Oliveros Pauline
Published: October 2012

This paper describes a system for modeling, recognizing, and classifying sound textures. The described system translates contemporary approaches from video texture analysis, creating a unique approach in the realm of audio and music. The signal is first represented as a set of mode functions by way of the Empirical Mode Decomposition technique for time/frequency analysis, before expressing the dynamics of these modes as a linear dynamical system (LDS). Both linear and nonlinear techniques are utilized in order to learn the system dynamics, which leads to a successful distinction between unique classes of textures. Five classes of sounds comprised a data set, consisting of crackling fire, typewriter action, rainstorms, carbonated beverages, and crowd applause, drawing on a variety of source recordings. Based on this data set the system achieved a classification accuracy of 90%, which outperformed both a Mel-Frequency Cepstral Coefficient based LDS-modeling approach from the literature, as well as one based on a standard Gaussian Mixture Model classifier.
Differences between psychoacoustic and frequency following response measures of distortion tone level and masking
Authors: Gockel Hedwig E. , Farooq Redwan , Muhammed Louwai , Plack Christopher J. , Carlyon Robert P.
Published: October 2012

The scalp-recorded frequency following response (FFR) in humans was measured for a 244-Hz pure tone at a range of input levels and for complex tones containing harmonics 2-4 of a 300-Hz fundamental, but shifted by ±56 Hz. The effective magnitude of the cubic difference tone (CDT) and the quadratic difference tone (QDT, at F2-F1) in the FFR for the complex was estimated by comparing the magnitude spectrum of the FFR at the distortion product (DP) frequency with that for the pure tone. The effective DP levels in the FFR were higher than those commonly estimated in psychophysical experiments, indicating contributions to the DP in the FFR in addition to the audible propagated component. A low-frequency narrowband noise masker reduced the magnitude of FFR responses to the CDT but also to primary components over a wide range of frequencies. The results indicate that audible DPs may contribute very little to the DPs observed in the FFR and that using a narrowband noise for the purpose of masking audible DPs can have undesired effects on the FFR over a wide frequency range. The results are consistent with the notion that broadly tuned mechanisms central to the auditory nerve strongly influence the FFR.
Tuberculosis Vaccine Conundrum
Authors: Mueller Kristen L.
Published: October 2012

A mutation that accounts for adverse reactions to the Bacille Calmette-Guérin vaccine against tuberculosis is identified.
A Mechanism of Interest as We Grow Older
Authors: Skarke Carsten
Published: October 2012

The mineralocorticoid receptor expressed in vascular smooth muscle cells helps regulate blood pressure.
Role of
CTR4
in the Virulence of Cryptococcus neoformans
Authors: Waterman Scott R. , Park Yoon-Dong , Raja Meera , Qiu Jin , Hammoud Dima A. , O’Halloran Thomas V. , Williamson Peter R.
Published: October 2012

While research has identified an important contribution for metals, such as iron, in microbial pathogenesis, the roles of other transition metals, such as copper, remain mostly unknown. Recent evidence points to a requirement for copper homeostasis in the virulence of
Cryptococcus neoformans
based on a role for a
CUF1
copper regulatory factor in mouse models and in a human patient cohort.
C. neoformans
is an important fungal pathogen that results in an estimated 600,000 AIDS-related deaths yearly. In the present studies, we found that a
C. neoformans
mutant lacking the
CUF1
-dependent copper transporter,
CTR4
, grows normally in rich medium at 37°C but has reduced survival in macrophages and attenuated virulence in a mouse model. This reduced survival and virulence were traced to a growth defect under nutrient-restricted conditions. Expression studies using a full-length
CTR4
-fluorescent fusion reporter construct demonstrated robust expression in macrophages, brain, and lung, the latter shown by
ex vivo
fluorescent imaging. Inductively coupled mass spectroscopy (ICP-MS) was used to probe the copper quota of fungal cells grown in defined medium and recovered from brain, which suggested a role for a copper-protective function of
CTR4
in combination with cell metallothioneins under copper-replete conditions. In summary, these data suggest a role for
CTR4
in copper-related homeostasis and subsequently in fungal virulence.

IMPORTANCE
Crytococcus neoformans
is a significant global fungal pathogen, and copper homeostasis is a relatively unexplored aspect of microbial pathogenesis that could lead to novel therapeutics. Previous studies correlated expression levels of a Ctr4 copper transporter to development of meningoencephalitis in a patient cohort of solid-organ transplants, but a direct role for Ctr4 in mammalian pathogenesis has not been demonstrated. The present studies utilize a Δ
ctr4
mutant strain which revealed an important role for
CTR4
in
C. neoformans
infections in mice and relate the gene product to homeostatic control of copper and growth under nutrient-restricted conditions. Robust expression levels of
CTR4
during fungal infection were exploited to demonstrate expression and lung cryptococcal disease using
ex vivo
fluorescence imaging. In summary, these studies are the first to directly demonstrate a role for a copper transporter in fungal disease and provide an
ex vivo
imaging tool for further study of cryptococcal gene expression and pathogenesis.