bluuebunny/crossref_metadata_2025 huggingface dataset:
Models for predicting objective function weights in prostate cancer IMRT
Authors: Boutilier Justin J. , Lee Taewoo , Craig Tim , Sharpe Michael B. , Chan Timothy C. Y.
Published: March 2015

Purpose:

To develop and evaluate the clinical applicability of advanced machine learning models that simultaneously predict multiple optimization objective function weights from patient geometry for intensity‐modulated radiation therapy of prostate cancer.

Methods:

A previously developed inverse optimization method was applied retrospectively to determine optimal objective function weights for 315 treated patients. The authors used an overlap volume ratio (OV) of bladder and rectum for different PTV expansions and overlap volume histogram slopes (OVSR and OVSB for the rectum and bladder, respectively) as explanatory variables that quantify patient geometry. Using the optimal weights as ground truth, the authors trained and applied three prediction models: logistic regression (LR), multinomial logistic regression (MLR), and weighted K‐nearest neighbor (KNN). The population average of the optimal objective function weights was also calculated.

Results:

The OV at 0.4 cm and OVSR at 0.1 cm features were found to be the most predictive of the weights. The authors observed comparable performance (i.e., no statistically significant difference) between LR, MLR, and KNN methodologies, with LR appearing to perform the best. All three machine learning models outperformed the population average by a statistically significant amount over a range of clinical metrics including bladder/rectum V53Gy, bladder/rectum V70Gy, and dose to the bladder, rectum, CTV, and PTV. When comparing the weights directly, the LR model predicted bladder and rectum weights that had, on average, a 73% and 74% relative improvement over the population average weights, respectively. The treatment plans resulting from the LR weights had, on average, a rectum V70Gy that was 35% closer to the clinical plan and a bladder V70Gy that was 29% closer, compared to the population average weights. Similar results were observed for all other clinical metrics.

Conclusions:

The authors demonstrated that the KNN and MLR weight prediction methodologies perform comparably to the LR model and can produce clinical quality treatment plans by simultaneously predicting multiple weights that capture trade‐offs associated with sparing multiple OARs.
Patch‐based generation of a pseudo CT from conventional MRI sequences for MRI‐only radiotherapy of the brain
Authors: Andreasen Daniel , Van Leemput Koen , Hansen Rasmus H. , Andersen Jon A. L. , Edmund Jens M.
Published: March 2015

Purpose:

In radiotherapy (RT) based on magnetic resonance imaging (MRI) as the only modality, the information on electron density must be derived from the MRI scan by creating a so‐called pseudo computed tomography (pCT). This is a nontrivial task, since the voxel‐intensities in an MRI scan are not uniquely related to electron density. To solve the task, voxel‐based or atlas‐based models have typically been used. The voxel‐based models require a specialized dual ultrashort echo time MRI sequence for bone visualization and the atlas‐based models require deformable registrations of conventional MRI scans. In this study, we investigate the potential of a patch‐based method for creating a pCT based on conventional T1‐weighted MRI scans without using deformable registrations. We compare this method against two state‐of‐the‐art methods within the voxel‐based and atlas‐based categories.

Methods:

The data consisted of CT and MRI scans of five cranial RT patients. To compare the performance of the different methods, a nested cross validation was done to find optimal model parameters for all the methods. Voxel‐wise and geometric evaluations of the pCTs were done. Furthermore, a radiologic evaluation based on water equivalent path lengths was carried out, comparing the upper hemisphere of the head in the pCT and the real CT. Finally, the dosimetric accuracy was tested and compared for a photon treatment plan.

Results:

The pCTs produced with the patch‐based method had the best voxel‐wise, geometric, and radiologic agreement with the real CT, closely followed by the atlas‐based method. In terms of the dosimetric accuracy, the patch‐based method had average deviations of less than 0.5% in measures related to target coverage.

Conclusions:

We showed that a patch‐based method could generate an accurate pCT based on conventional T1‐weighted MRI sequences and without deformable registrations. In our evaluations, the method performed better than existing voxel‐based and atlas‐based methods and showed a promising potential for RT of the brain based only on MRI.
X‐ray computed tomography using curvelet sparse regularization
Authors: Wieczorek Matthias , Frikel Jürgen , Vogel Jakob , Eggl Elena , Kopp Felix , Noël Peter B. , Pfeiffer Franz , Demaret Laurent , Lasser Tobias
Published: March 2015

Purpose:

Reconstruction of x‐ray computed tomography (CT) data remains a mathematically challenging problem in medical imaging. Complementing the standard analytical reconstruction methods, sparse regularization is growing in importance, as it allows inclusion of prior knowledge. The paper presents a method for sparse regularization based on the curvelet frame for the application to iterative reconstruction in x‐ray computed tomography.

Methods:

In this work, the authors present an iterative reconstruction approach based on the alternating direction method of multipliers using curvelet sparse regularization.

Results:

Evaluation of the method is performed on a specifically crafted numerical phantom dataset to highlight the method's strengths. Additional evaluation is performed on two real datasets from commercial scanners with different noise characteristics, a clinical bone sample acquired in a micro‐CT and a human abdomen scanned in a diagnostic CT. The results clearly illustrate that curvelet sparse regularization has characteristic strengths. In particular, it improves the restoration and resolution of highly directional, high contrast features with smooth contrast variations. The authors also compare this approach to the popular technique of total variation and to traditional filtered backprojection.

Conclusions:

The authors conclude that curvelet sparse regularization is able to improve reconstruction quality by reducing noise while preserving highly directional features.
Noninvasive differential diagnosis of dental periapical lesions in cone‐beam CT scans
Authors: Okada Kazunori , Rysavy Steven , Flores Arturo , Linguraru Marius George
Published: March 2015

Purpose:

This paper proposes a novel application of computer‐aided diagnosis (CAD) to an everyday clinical dental challenge: the noninvasive differential diagnosis of periapical lesions between periapical cysts and granulomas. A histological biopsy is the most reliable method currently available for this differential diagnosis; however, this invasive procedure prevents the lesions from healing noninvasively despite a report that they may heal without surgical treatment. A CAD using cone‐beam computed tomography (CBCT) offers an alternative noninvasive diagnostic tool which helps to avoid potentially unnecessary surgery and to investigate the unknown healing process and rate for the lesions.

Methods:

The proposed semiautomatic solution combines graph‐based random walks segmentation with machine learning‐based boosted classifiers and offers a robust clinical tool with minimal user interaction. As part of this CAD framework, the authors provide two novel technical contributions: (1) probabilistic extension of the random walks segmentation with likelihood ratio test and (2) LDA‐AdaBoost: a new integration of weighted linear discriminant analysis to AdaBoost.

Results:

A dataset of 28 CBCT scans is used to validate the approach and compare it with other popular segmentation and classification methods. The results show the effectiveness of the proposed method with 94.1% correct classification rate and an improvement of the performance by comparison with the Simon's state‐of‐the‐art method by 17.6%. The authors also compare classification performances with two independent ground‐truth sets from the histopathology and CBCT diagnoses provided by endodontic experts.

Conclusions:

Experimental results of the authors show that the proposed CAD system behaves in clearer agreement with the CBCT ground‐truth than with histopathology, supporting the Simon's conjecture that CBCT diagnosis can be as accurate as histopathology for differentiating the periapical lesions.
Incorporating multislice imaging into x‐ray CT polymer gel dosimetry
Authors: Johnston H. , Hilts M. , Jirasek A.
Published: March 2015

Purpose:

To evaluate multislice computed tomography (CT) scanning for fast and reliable readout of radiation therapy (RT) dose distributions using CT polymer gel dosimetry (PGD) and to establish a baseline assessment of image noise and uniformity in an unirradiated gel dosimeter.

Methods:

A 16‐slice CT scanner was used to acquire images through a 1 L cylinder filled with water. Additional images were collected using a single slice machine. The variability in CT number (NCT) associated with the anode heel effect was evaluated and used to define a new slice‐by‐slice background subtraction artifact removal technique for CT PGD. Image quality was assessed for the multislice system by evaluating image noise and uniformity. The agreement in NCT for slices acquired simultaneously using the multislice detector array was also examined. Further study was performed to assess the effects of increasing x‐ray tube load on the constancy of measured NCT and overall scan time. In all cases, results were compared to the single slice machine. Finally, images were collected throughout the volume of an unirradiated gel dosimeter to quantify image noise and uniformity before radiation is delivered.

Results:

Slice‐by‐slice background subtraction effectively removes the variability in NCT observed across images acquired simultaneously using the multislice scanner and is the recommended background subtraction method when using a multislice CT system. Image noise was higher for the multislice system compared to the single slice scanner, but overall image quality was comparable between the two systems. Further study showed NCT was consistent across image slices acquired simultaneously using the multislice detector array for each detector configuration of the slice thicknesses examined. In addition, the multislice system was found to eliminate variations in NCT due to increasing x‐ray tube load and reduce scanning time by a factor of 4 when compared to imaging a large volume using a single slice scanner. Images acquired through an unirradiated, active gel revealed NCT varies between the top and bottom of the 1 L cylinder as well as across the diameter of the cylinder by up to 7 HU.

Conclusions:

Multislice CT imaging has been evaluated for CT PGD and found to be the superior technique compared to single slice imaging in terms of the time required to complete a scan and the tube load characteristics associated with each scanning method. The implementation of multislice scanning is straightforward and expected to facilitate routine gel dosimetry measurements for complex dose distributions in modern RT centers.
Enhanced correlation between quantitative ultrasound and structural and mechanical properties of bone using combined transmission-reflection measurement
Authors: Lin Liangjun , Lin Wei , Qin Yi-Xian
Published: March 2015

Quantitative ultrasound (QUS) is capable of predicting the principal structural orientation of trabecular bone; this orientation is highly correlated with the mechanical strength of trabecular bone. Irregular shape of bone, however, would increase variation in such a prediction, especially under human in vivo measurement. This study was designed to combine transmission and reflection modes of QUS measurement to improve the prediction for the structural and mechanical properties of trabecular bone. QUS, mechanical testing, and micro computed tomography (μCT) scanning were performed on 24 trabecular bone cubes harvested from a bovine distal femur to obtain the mechanical and structural parameters. Transmission and reflection modes of QUS measurement in the transverse and frontal planes were performed in a confined 60° angle range with 5° increment. The QUS parameters, attenuation (ATT) and velocity (UV), obtained from transmission mode, were normalized to the specimen thickness acquired from reflection mode. Analysis of covariance showed that the combined transmission-reflection modes improved prediction for the structural and Young's modulus of bone in comparison to the traditional QUS measurement performed only in the medial-lateral orientation. In the transverse plane, significant improvement between QUS and μCT was found in ATT vs bone surface density (BS/BV) (p < 0.05), ATT vs trabecular thickness (Tb.Th) (p < 0.01), ATT vs degree of anisotropy (DA) (p < 0.05), UV vs trabecular bone number (Tb.N) (p < 0.05), and UV vs Tb.Th (p < 0.001). In the frontal plane, significant improvement was found in ATT vs structural model index (SMI) (p < 0.01), ATT vs bone volume fraction (BV/TV) (p < 0.01), ATT vs BS/BV (p < 0.001), ATT vs Tb.Th (p < 0.001), ATT vs DA (p < 0.001), and ATT vs modulus (p < 0.001), UV vs SMI (p < 0.01), UV vs BV/TV (p < 0.05), UV vs BS/BV (p < 0.05), UV vs Tb.Th (p < 0.01), UV vs trabecular spacing (p < 0.05), and UV vs modulus (p < 0.01). These data suggested that the combined transmission-reflection QUS method is capable of providing information more relevant to the structural and mechanical properties of trabecular bone.
Two-compartment passive frequency domain cochlea model allowing independent fluid coupling to the tectorial and basilar membranes
Authors: Cormack John , Liu Yanju , Nam Jong-Hoon , Gracewski Sheryl M.
Published: March 2015

The cochlea is a spiral-shaped, liquid-filled organ in the inner ear that converts sound with high frequency selectivity over a wide pressure range to neurological signals that are eventually interpreted by the brain. The cochlear partition, consisting of the organ of Corti supported below by the basilar membrane and attached above to the tectorial membrane, plays a major role in the frequency analysis. In early fluid-structure interaction models of the cochlea, the mechanics of the cochlear partition were approximated by a series of single-degree-of-freedom systems representing the distributed stiffness and mass of the basilar membrane. Recent experiments suggest that the mechanical properties of the tectorial membrane may also be important for the cochlea frequency response and that separate waves may propagate along the basilar and tectorial membranes. Therefore, a two-dimensional two-compartment finite difference model of the cochlea was developed to investigate the independent coupling of the basilar and tectorial membranes to the surrounding liquid. Responses are presented for models using two- or three-degree-of-freedom stiffness, damping, and mass parameters derived from a physiologically based finite element model of the cochlear partition. Effects of changes in membrane and organ of Corti stiffnesses on the individual membrane responses are investigated.
Factors limiting vocal-tract length discrimination in cochlear implant simulations
Authors: Gaudrain Etienne , Başkent Deniz
Published: March 2015

Perception of voice characteristics allows normal hearing listeners to identify the gender of a speaker, and to better segregate speakers from each other in cocktail party situations. This benefit is largely driven by the perception of two vocal characteristics of the speaker: The fundamental frequency (F0) and the vocal-tract length (VTL). Previous studies have suggested that cochlear implant (CI) users have difficulties in perceiving these cues. The aim of the present study was to investigate possible causes for limited sensitivity to VTL differences in CI users. Different acoustic simulations of CI stimulation were implemented to characterize the role of spectral resolution on VTL, both in terms of number of channels and amount of channel interaction. The results indicate that with 12 channels, channel interaction caused by current spread is likely to prevent CI users from perceiving VTL differences typically found between male and female speakers.
Relationships between pressure, flow, lip motion, and upstream and downstream impedances for the trombone
Authors: Boutin Henri , Fletcher Neville , Smith John , Wolfe Joe
Published: March 2015

This experimental study investigates ten subjects playing the trombone in the lower and mid-high range of the instrument, B♭2 to F4. Several techniques are combined to show the pressures and the impedance spectra upstream and downstream of the lips, the acoustic and total flows into the instrument, the component of the acoustic flow due to the sweeping motion of the lips, and high speed video images of the lip motion and aperture. The waveforms confirm that the inertance of the air in the channel between the lips is usually negligible. For lower notes, the flow caused by the sweeping motion of the lips contributes substantially to the total flow into the mouthpiece. The phase relations among the waveforms are qualitatively similar across the range studied, with no discontinuous behavior. The players normally played at frequencies about 1.1% above that of the impedance peak of the bore, but could play below as well as above this frequency and bend from above to below without discontinuity. The observed lip motion is consistent with two-degree-of-freedom models having varying effective lengths. These provide insight into why lips can auto-oscillate with an inertive or compliant load, or without a downstream resonator.
Nonlinear guided wave propagation in prestressed plates
Authors: Pau Annamaria , Lanza di Scalea Francesco
Published: March 2015

The measurement of stress in a structure presents considerable interest in many fields of engineering. In this paper, the diagnostic potential of nonlinear elastic guided waves in a prestressed plate is investigated. To do so, an analytical model is formulated accounting for different aspects involved in the phenomenon. The fact that the initial strains can be finite is considered using the Green Lagrange strain tensor, and initial and final configurations are not merged, as it would be assumed in the infinitesimal strain theory. Moreover, an appropriate third-order expression of the strain energy of the hyperelastic body is adopted to account for the material nonlinearities. The model obtained enables to investigate both the linearized case, which gives the variation of phase and group velocity as a function of the initial stress, and the nonlinear case, involving second-harmonic generation as a function of the initial state of stress. The analysis is limited to Rayleigh-Lamb waves propagating in a plate. Three cases of initial prestress are considered, including prestress in the direction of the wave propagation, prestress orthogonal to the direction of wave propagation, and plane isotropic stress.
Strong localization of an acoustic wave in a sub-wavelength slot between two plates
Authors: Cai Feiyan , Li Fei , Meng Long , Wu Junru , Zheng Hairong
Published: March 2015

The dispersion relation of the acoustic field in a sub-wavelength slot (its width is smaller than the acoustic wavelength) between two identical plates immersed in an inviscid liquid is theoretically analyzed. Each plate has a phononic crystal structure consisting of periodical grooves drilled in one of outer sides of each plate. It is found that highly localization of acoustic energy can be achieved in the sub-wavelength slot when a traveling acoustic wave is incident upon the slots. The associate physical principle is as follows: The lowest anti-symmetric non-leaky A0 mode of the Lamb wave of each individual thin plate propagating as an evanescent wave extends to the liquid from opposite direction; when the width of the slot is much smaller than the characteristic decay length of the evanescent wave in the liquid, the constructive interference of evanescent waves of the both plates takes place, leading to a strong acoustic field in the slot. This system has potential to serve as an excellent candidate for the ultrasensitive microscopic chemical/biological stimulators and sensors.
Comparing methods of modeling near field fluid coupling in the cochlea
Authors: Ni Guangjian , Elliott Stephen J.
Published: March 2015

As well as generating the far field pressure, which allows wave propagation in the cochlea, the vibration of an individual element of the basilar membrane (BM) will also generate a near field pressure, which increases its mass and gives rise to local longitudinal coupling. This paper compares the efficiency and accuracy of a number of different methods of calculating the near field pressure distribution, and explores the connections between them. In particular it is shown that a common approximation to the wavenumber description of the near field pressure is equivalent, in the spatial domain, to an exponential decay away from the point of excitation. Two important properties of the near field pressure are its maximum amplitude, which is finite if the vibrating element has a finite length, and the value of its spatial integral, which determines the added mass on the BM due to the fluid loading. These properties are calculated as a function of the BM width relative to the width of the fluid chamber. By parameterizing the near field pressure variation in this way, it can be readily incorporated into coupled models of the cochlea, without the considerable computational expense of calculating the full three dimensional pressure field.
A kinematic study of critical and non-critical articulators in emotional speech production
Authors: Kim Jangwon , Toutios Asterios , Lee Sungbok , Narayanan Shrikanth S.
Published: March 2015

This study explores one aspect of the articulatory mechanism that underlies emotional speech production, namely, the behavior of linguistically critical and non-critical articulators in the encoding of emotional information. The hypothesis is that the possible larger kinematic variability in the behavior of non-critical articulators enables revealing underlying emotional expression goal more explicitly than that of the critical articulators; the critical articulators are strictly controlled in service of achieving linguistic goals and exhibit smaller kinematic variability. This hypothesis is examined by kinematic analysis of the movements of critical and non-critical speech articulators gathered using eletromagnetic articulography during spoken expressions of five categorical emotions. Analysis results at the level of consonant-vowel-consonant segments reveal that critical articulators for the consonants show more (less) peripheral articulations during production of the consonant-vowel-consonant syllables for high (low) arousal emotions, while non-critical articulators show less sensitive emotional variation of articulatory position to the linguistic gestures. Analysis results at the individual phonetic targets show that overall, between- and within-emotion variability in articulatory positions is larger for non-critical cases than for critical cases. Finally, the results of simulation experiments suggest that the postural variation of non-critical articulators depending on emotion is significantly associated with the controls of critical articulators.
Tailoring the excitation of fundamental flexural guide waves in coated bone by phase-delayed array: Two-dimensional simulations
Authors: Kilappa Vantte , Moilanen Petro , Salmi Ari , Haeggström Edward , Zhao Zuomin , Myllylä Risto , Timonen Jussi
Published: March 2015

The fundamental flexural guided wave (FFGW) enables ultrasonic assessment of cortical bone thickness. In vivo, it is challenging to detect this mode, as its power ratio with respect to disturbing ultrasound is reduced by soft tissue covering the bone. A phase-delayed ultrasound source is proposed to tailor the FFGW excitation in order to improve its power ratio. This situation is analyzed by 2D finite-element simulations. The soft tissue coating (7-mm thick) was simulated as a fluid covering an elastic plate (bone, 2–6 mm thick). A six-element array of emitters on top of the coating was excited by 50-kHz tone bursts so that each emitter was appropriately delayed from the previous one. Response was recorded by an array of receivers on top of the coating, 20–50 mm away from the closest emitter. Simulations predicted that such tailored/phase-delayed excitations should improve the power ratio of FFGW by 23 ± 5 dB, independent of the number of emitters (N). On the other hand, the FFGW magnitude should increase by 5.8 ± 0.5 dB for each doubling of N. This suggests that mode tailoring based on phase-delayed excitation may play a key role in the development of an in vivo FFGW assessment.
Effects of inherent envelope fluctuations in forward maskers for listeners with normal and impaired hearing
Authors: Svec Adam , Dubno Judy R. , Nelson Peggy B.
Published: March 2015

Gaussian noise simultaneous maskers yield higher masked thresholds for pure tones than low-fluctuation noise simultaneous maskers for listeners with normal hearing. This increased masking effectiveness is thought to be due to inherent fluctuations in the temporal envelope of Gaussian noise, but effects of fluctuating forward maskers are unknown. Because differences in forward masking due to age and hearing loss are known, the current study assessed effects of masker envelope fluctuations for forward maskers in younger and older adults with normal hearing and older adults with hearing loss. Detection thresholds were measured in these three participant groups for a pure-tone probe in quiet and in Gaussian and low-fluctuation noise forward maskers with either 1 or 1/3 equivalent rectangular bandwidths. Higher masked thresholds were obtained for forward maskers with greater inherent envelope fluctuations for younger adults with normal hearing. This increased effectiveness of highly fluctuating forward maskers was similar for older adults with normal and impaired hearing. Because differences in recovery from forward masking between listeners with normal and impaired hearing may relate to differences in cochlear nonlinearities, these results suggest that mechanisms other than cochlear nonlinearities may be responsible for recovery from rapid masker envelope fluctuations.
Wind fence enclosures for infrasonic wind noise reduction
Authors: Abbott JohnPaul , Raspet Richard , Webster Jeremy
Published: March 2015

A large porous wind fence enclosure has been built and tested to optimize wind noise reduction at infrasonic frequencies between 0.01 and 10 Hz to develop a technology that is simple and cost effective and improves upon the limitations of spatial filter arrays for detecting nuclear explosions, wind turbine infrasound, and other sources of infrasound. Wind noise is reduced by minimizing the sum of the wind noise generated by the turbulence and velocity gradients inside the fence and by the area-averaging the decorrelated pressure fluctuations generated at the surface of the fence. The effects of varying the enclosure porosity, top condition, bottom gap, height, and diameter and adding a secondary windscreen were investigated. The wind fence enclosure achieved best reductions when the surface porosity was between 40% and 55% and was supplemented by a secondary windscreen. The most effective wind fence enclosure tested in this study achieved wind noise reductions of 20–27 dB over the 2–4 Hz frequency band, a minimum of 5 dB noise reduction for frequencies from 0.1 to 20 Hz, constant 3–6 dB noise reduction for frequencies with turbulence wavelengths larger than the fence, and sufficient wind noise reduction at high wind speeds (3–6 m/s) to detect microbaroms.
Subjective and objective rating of spectrally different pseudorandom noises—Implications for speech masking design
Authors: Hongisto Valtteri , Oliva David , Rekola Laura
Published: March 2015

Artificial sound masking is increasingly used in open-plan offices to improve speech privacy and to reduce distraction caused by speech sounds. Most of the masking sounds are based on pseudorandom continuous noise filtered to a specific spectrum that should be optimized in respect with speech masking efficiency and comfort. The aim of this study was to increase basic understanding regarding the comfort. The second aim was to determine how well objective rating methods (15 different noise indices) predict the subjective ratings. Twenty-three subjects rated the loudness, disturbance, pleasantness, and six other subjective measures of 11 spectrally different noises in laboratory conditions. Speech was not present during the experiment. All sounds were presented at 42 dB LAeq within 50–10 000 Hz. Unexpectedly, the subjects were most satisfied with sounds having emphasis on low frequencies. A sound having a slope of −7 dB per octave increment resulted in the highest satisfaction. Changes in subjective ratings were reasonably well predicted by five noise indices, while many well-known noise indices frequently used in building design underperformed in this task. The results are expected to benefit in the design of masking sounds and other appliances.
An integrated analysis-synthesis array system for spatial sound fields
Authors: Bai Mingsian R. , Hua Yi-Hsin , Kuo Chia-Hao , Hsieh Yu-Hao
Published: March 2015

An integrated recording and reproduction array system for spatial audio is presented within a generic framework akin to the analysis-synthesis filterbanks in discrete time signal processing. In the analysis stage, a microphone array “encodes” the sound field by using the plane-wave decomposition. Direction of arrival of plane-wave components that comprise the sound field of interest are estimated by multiple signal classification. Next, the source signals are extracted by using a deconvolution procedure. In the synthesis stage, a loudspeaker array “decodes” the sound field by reconstructing the plane-wave components obtained in the analysis stage. This synthesis stage is carried out by pressure matching in the interior domain of the loudspeaker array. The deconvolution problem is solved by truncated singular value decomposition or convex optimization algorithms. For high-frequency reproduction that suffers from the spatial aliasing problem, vector panning is utilized. Listening tests are undertaken to evaluate the deconvolution method, vector panning, and a hybrid approach that combines both methods to cover frequency ranges below and above the spatial aliasing frequency. Localization and timbral attributes are considered in the subjective evaluation. The results show that the hybrid approach performs the best in overall preference. In addition, there is a trade-off between reproduction performance and the external radiation.
A violin shell model: Vibrational modes and acoustics
Authors: Gough Colin E.
Published: March 2015

A generic physical model for the vibro-acoustic modes of the violin is described treating the body shell as a shallow, thin-walled, guitar-shaped, box structure with doubly arched top and back plates. comsol finite element, shell structure, software is used to identify and understand the vibrational modes of a simply modeled violin. This identifies the relationship between the freely supported plate modes when coupled together by the ribs and the modes of the assembled body shell. Such coupling results in a relatively small number of eigenmodes or component shell modes, of which a single volume-changing breathing mode is shown to be responsible for almost all the sound radiated in the monopole signature mode regime below ∼1 kHz for the violin, whether directly or by excitation of the Helmholtz f-hole resonance. The computations describe the influence on such modes of material properties, arching, plate thickness, elastic anisotropy, f-holes cut into the top plate, the bass-bar, coupling to internal air modes, the rigid neck-fingerboard assembly, and, most importantly, the soundpost. Because the shell modes are largely determined by the symmetry of the guitar-shaped body, the model is applicable to all instruments of the violin family.
Spectral and modulation indices for annoyance-relevant features of urban road single-vehicle pass-by noises
Authors: Klein A. , Marquis-Favre C. , Weber R. , Trollé A.
Published: March 2015

The models that relate noise annoyance assessments to noise signal parameters are mainly based on energy-related indices (e.g., LDEN). However, various studies have shown that sound characteristics of environmental noises linked to temporal and spectral signal features also influence noise annoyance responses. In order to enhance noise annoyance models, an adequate perception-related characterization of these influential acoustical features is essential. On the basis of urban road single-vehicle pass-by noises, this study will show the identification of noise characteristics that rely on spectral and temporal signal properties and that are related to noise annoyance. Based on a semantic differential test with a verbalization task, it will be shown that the sensation dull/shrill, related to the spectral content of the noises and the modulation-related sensations sputtering and nasal are linked to annoyance. The sensation dull/shrill could be characterized using the index TETC (Total Energy of Tonal Components within critical bands from 16 to 24 barks). The correlation of sputtering and nasal sensations with psychoacoustic indices was unsatisfactory. Two alternative indices are proposed to improve the characterization of these specific sensations. It is shown that noise annoyance assessment benefits from taking the TETC index and the sputtering and nasal indices into account.
The effects of stage absorption on reverberation times in opera house seating areas
Authors: Jeon Jin Yong , Kim Jae Ho , Ryu Jong Kwan
Published: March 2015

The effects of stage absorption on reverberation times in opera houses were investigated using computer simulations and scale model measurements. The reverberation time (RT) was measured in stalls seating with and without variable stage elements (e.g., fly curtains, side curtains, cycloramas, and stage sets). The absorption coefficients of the walls and ceiling of the stage houses were varied accordingly. It was found that variable stage elements have a significant influence on reverberation times in seating areas, particularly for a reverberant stage house, due to the low absorption of the walls and ceiling in the stage house. It was also found that the absorption coefficients of the walls and ceiling should be over 0.5 to avoid RT decreases of over 10% due to the absorption of the variable stage elements. In addition, coupled room effects were investigated both with and without variable stage elements and the results show that double slope was not found in the opera houses investigated in this study.
A theory to explain some physiological effects of the infrasonic emissions at some wind farm sites
Authors: Schomer Paul D. , Erdreich John , Pamidighantam Pranav K. , Boyle James H.
Published: March 2015

For at least four decades, there have been reports in scientific literature of people experiencing motion sickness-like symptoms attributed to low-frequency sound and infrasound. In the last several years, there have been an increasing number of such reports with respect to wind turbines; this corresponds to wind turbines becoming more prevalent. A study in Shirley, WI, has led to interesting findings that include: (1) To induce major effects, it appears that the source must be at a very low frequency, about 0.8 Hz and below with maximum effects at about 0.2 Hz; (2) the largest, newest wind turbines are moving down in frequency into this range; (3) the symptoms of motion sickness and wind turbine acoustic emissions “sickness” are very similar; (4) and it appears that the same organs in the inner ear, the otoliths may be central to both conditions. Given that the same organs may produce the same symptoms, one explanation is that the wind turbine acoustic emissions may, in fact, induce motion sickness in those prone to this affliction.
Scattering by single physically large and weak scatterers in the beam of a single-element transducer
Authors: Kemmerer Jeremy P. , Oelze Michael L. , Gyöngy Miklós
Published: March 2015

Quantitative ultrasound techniques are generally applied to characterize media whose scattering sites are considered to be small compared to a wavelength. In this study, the backscattered response of single weakly scattering spheres and cylinders with diameters comparable to the beam width of a 2.25 MHz single-element transducer were simulated and measured in the transducer focal plane to investigate the impact of physically large scatterers. The responses from large single spherical scatterers at the focus were found to closely match the plane-wave response. The responses from large cylindrical scatterers at the focus were found to differ from the plane-wave response by a factor of f−1. Normalized spectra from simulations and measurements were in close agreement: the fall-off of the responses as a function of lateral position agreed to within 2 dB for spherical scatterers and to within 3.5 dB for cylindrical scatterers. In both measurement and simulation, single scatterer diameter estimates were biased by less than 3% for a more highly focused transducer compared to estimates for a more weakly focused transducer. The results suggest that quantitative ultrasound techniques may produce physically meaningful size estimates for media whose response is dominated by scatterers comparable in size to the transducer beam.
Combined Effects of Drop Height and Fatigue on Landing Mechanics in Active Females
Authors: Dickin D. Clark , Johann Emily , Wang He , Popp Jennifer K.
Published: March 2015

Drop height and fatigue have been shown in isolation to affect landing mechanics and increase the risk of sustaining an anterior cruciate ligament injury. The purpose of this study was to identify the combined effects of drop height and fatigue on landing mechanics in recreationally active females. To assess this, 11 healthy, young adult females performed a series of drop jumps from randomized heights before and following a lower extremity fatiguing protocol. Findings for kinematic results demonstrated that hip flexion decreased at initial contact (P = .003) and maximum hip (P = .005) and knee flexion (P = .001) angles increased with increases in drop height. Kinetic results demonstrated that vertical ground reaction forces and joint moments and powers increased as height increased. Ground reaction forces and maximum knee valgus increased from pre- to postfatigue with interactive effects observed in frontal plane hip angle at impact and peak ankle moment. These results confirm the effects of drop height and fatigue and highlighted interactions between these factors. The differential effect of fatigue as a function of drop heights helps to illustrate potentially risky situations that should be addressed in training and injury prevention programs.
Achieving Target Voriconazole Concentrations More Accurately in Children and Adolescents
Authors: Neely Michael , Margol Ashley , Fu Xiaowei , van Guilder Michael , Bayard David , Schumitzky Alan , Orbach Regina , Liu Siyu , Louie Stan , Hope William
Published: March 2015

Despite the documented benefit of voriconazole therapeutic drug monitoring, nonlinear pharmacokinetics make the timing of steady-state trough sampling and appropriate dose adjustments unpredictable by conventional methods. We developed a nonparametric population model with data from 141 previously richly sampled children and adults. We then used it in our multiple-model Bayesian adaptive control algorithm to predict measured concentrations and doses in a separate cohort of 33 pediatric patients aged 8 months to 17 years who were receiving voriconazole and enrolled in a pharmacokinetic study. Using all available samples to estimate the individual Bayesian posterior parameter values, the median percent prediction bias relative to a measured target trough concentration in the patients was 1.1% (interquartile range, −17.1 to 10%). Compared to the actual dose that resulted in the target concentration, the percent bias of the predicted dose was −0.7% (interquartile range, −7 to 20%). Using only trough concentrations to generate the Bayesian posterior parameter values, the target bias was 6.4% (interquartile range, −1.4 to 14.7%;
P
= 0.16 versus the full posterior parameter value) and the dose bias was −6.7% (interquartile range, −18.7 to 2.4%;
P
= 0.15). Use of a sample collected at an optimal time of 4 h after a dose, in addition to the trough concentration, resulted in a nonsignificantly improved target bias of 3.8% (interquartile range, −13.1 to 18%;
P
= 0.32) and a dose bias of −3.5% (interquartile range, −18 to 14%;
P
= 0.33). With the nonparametric population model and trough concentrations, our control algorithm can accurately manage voriconazole therapy in children independently of steady-state conditions, and it is generalizable to any drug with a nonparametric pharmacokinetic model. (This study has been registered at ClinicalTrials.gov under registration no. NCT01976078.)
Tenofovir versus Entecavir in Treatment of Chronic Hepatitis B Virus with Severe Acute Exacerbation
Authors: Hung Chao-Hung , Hu Tsung-Hui , Lu Sheng-Nan , Lee Chuan-Mo , Chen Chih-Hung , Kee Kwong-Ming , Wang Jing-Houng , Tsai Ming-Chao , Kuo Yuan-Hung , Chang Kuo-Chin , Chiu Yi-Chun , Chen Chien-Hung
Published: March 2015

Tenofovir disoproxil fumarate (TDF) and entecavir (ETV) are effective antivirals recommended as first-line monotherapies for treatment of chronic hepatitis B (CHB) infection. This study aimed to compare the short-term efficacies of TDF and ETV in the treatment of CHB with severe acute exacerbation. From 2008 to 2013, 189 consecutive treatment-naive CHB patients receiving TDF (n= 41) or ETV (n= 148) for severe acute exacerbation were enrolled. The primary endpoint was overall mortality or receipt of liver transplantation by week 24. The baseline characteristics were comparable between these two groups. By week 24, 8 (19% [95% confidence interval {CI}, 7% to 32%]) patients in the TDF group and 26 (18% [95% CI, 11 to 24%]) patients in the ETV group died (n= 30) or received liver transplantation (n= 4) (P= 0.749). The two groups of patients developed similar rates of liver-related complications and achieved comparable biochemical and virological responses at week 24. Cox regression analysis showed that baseline viral DNA level (P= 0.002), hypertension (P= 0.002), model for end-stage liver disease (MELD) score (P= 0.01), platelet count (P= 0.005), early presence (within 4 weeks) of ascites (P= 0.005), hepatic encephalopathy (P= 0.002), and hepatorenal syndrome (P< 0.001) were independent factors for mortality or liver transplantation. Among the patients who survived by week 24, there was no difference between the two groups in the percentage of patients who had a serum creatinine increase of ≥0.5 mg/dl from baseline (6.7% [95% CI, 0% to 16%] versus 2.0% [95% CI, 0% to 4.8%] in the TDF and ETV groups, respectively;P= 0.231), whereas a significant reduction in the estimated glomerular filtration rate (eGFR) was found in the two groups (P= 0.001 for both). In conclusion, TDF and ETV produce a similar treatment response and clinical outcome in patients with severe acute exacerbation of CHB.
In Vitro
Antimalarial Activity of Novel Semisynthetic Nocathiacin I Antibiotics
Authors: Sharma Indu , Sullivan Margery , McCutchan Thomas F.
Published: March 2015

Presently, the arsenal of antimalarial drugs is limited and needs to be replenished. We evaluated the potential antimalarial activity of two water-soluble derivatives of nocathiacin (BMS461996 and BMS411886) against the asexual blood stages of
Plasmodium falciparum
. Nocathiacins are a thiazolyl peptide group of antibiotics, are structurally related to thiostrepton, have potent activity against a wide spectrum of multidrug-resistant Gram-positive bacteria, and inhibit protein synthesis. The
in vitro
growth inhibition assay was done using three laboratory strains of
P. falciparum
displaying various levels of chloroquine (CQ) susceptibility. Our results indicate that BMS461996 has potent antimalarial activity and inhibits parasite growth with mean 50% inhibitory concentrations (IC
50
s) of 51.55 nM for
P. falciparum
3D7 (CQ susceptible), 85.67 nM for
P. falciparum
Dd2 (accelerated resistance to multiple drugs [ARMD]), and 99.44 nM for
P. falciparum
K1 (resistant to CQ, pyrimethamine, and sulfadoxine). Similar results at approximately 7-fold higher IC
50
s were obtained with BMS411886 than with BMS461996. We also tested the effect of BMS491996 on gametocytes; our results show that at a 20-fold excess of the mean IC
50
, gametocytes were deformed with a pyknotic nucleus and growth of stage I to IV gametocytes was arrested. This preliminary study shows a significant potential for nocathiacin analogues to be developed as antimalarial drug candidates and to warrant further investigation.
Squalestatin Is an Inhibitor of Carotenoid Biosynthesis in Plasmodium falciparum
Authors: Gabriel Heloisa B. , Silva Marcia F. , Kimura Emília A. , Wunderlich Gerhard , Katzin Alejandro M. , Azevedo Mauro F.
Published: March 2015

The increasing resistance of malaria parasites to almost all available drugs calls for the characterization of novel targets and the identification of new compounds. Carotenoids are polyisoprenoids from plants, algae, and some bacteria, and they are biosynthesized by
Plasmodium falciparum
but not by mammalian cells. Biochemical and reverse genetics approaches were applied to demonstrate that phytoene synthase (PSY) is a key enzyme for carotenoid biosynthesis in
P. falciparum
and is essential for intraerythrocytic growth. The known PSY inhibitor squalestatin reduces biosynthesis of phytoene and kills parasites during the intraerythrocytic cycle. PSY-overexpressing parasites showed increased biosynthesis of phytoene and its derived product phytofluene and presented a squalestatin-resistant phenotype, suggesting that this enzyme is the primary target of action of this drug in the parasite.