bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear Dynamic Behavior of Rotor-Bearing Systems Involving Two Hydrodynamic Oil Films in Series: Prediction and Test Application to High-Speed Turbochargers
Authors: Gjika Kostandin , Groves Chris
Published: September 2008

In recent years, the desire for increased engine performance has led to technology that increasingly relies on robust and reliable turbocharging solutions. The rotor-bearing system (RBS) operates under extreme oil conditions of low viscosity, high temperatures, low HTHS (high temperature high shear) value and low pressure, while the demand for maximum turbocharger speed and variable geometry technology continues to increase. The rotordynamics instability is a potential issue and the development of RBS is becoming a challenge for design optimization at the development stage. It is further complicated by a lack of industrial standards to guide design practices related to the dynamics and the effort to combine high performance with low cost. This paper concerns the progress on nonlinear dynamic behavior modeling of turbocharger rotor-radial bearing system with fully floating bearing design. A developed fluid dynamics code predicts bearing rotational speed, operating inner and outer bearing clearances, effective oil viscosity taking into account the shear effect and hydrostatic load. The data are input to a rotordynamics code which predicts nonlinear lateral response (total shaft motion) of the rotor-bearing system. The model is validated with a high speed turbocharger RBS of 7.9 mm journal diameter running up to 160,000 rpm (maximum speed) with oil 0W30, 100 °C oil inlet temperature and 4 bar oil feed pressure. The test is conducted on a rotordynamics technology cell. An advanced data acquisition system is implanted and a powerful code is developed for automated data reduction. Prediction/test data show good correlation with the respect of synchronous response and total motion. The predictive model helps the development of high performance RBS with faster development cycle times and increased reliability.
An Investigation on the Failure Risks in a Steam Cracking Plant
Authors: Orru` P. F. , Pilloni M. T.
Published: September 2008

The paper concerns an experimental study performed at a petrochemical plant of Enichem, located in Porto Torres, in the north western area of Sardinia. The investigation performed was centred on a steam cracking plant, the output of which is mainly composed of ethylene, propylene, pyrolytic benzine, hydrogen, methane and ethane. The study was focused on the problems concerning the maintenance of the plant components and the risks associated with the plant failures. The analysis, accomplished on a time interval of five years, from 1999 to 2004, enabled the characterization of the plant components and of the whole productive system from the point of view of the risk; this allowed to determine, in each year, which components are associated to the highest values of the risk, what is the behaviour of the most critical components during the five years under exam, which parts of the plant deserve a deeper attention and more resources and what kind of failures are the worst in terms of real damage produced. At the same time, a criticality analysis was performed employing both the MAGEC method and the Fuzzy Logic approach. The listing of the plant critical components based on the two methodologies employed places in the first positions the same components identified in the risk analysis. Nevertheless, in the results obtained through the risk analysis, some basic differences mainly due to the introduction of the basic economic aspects, are registered.
Numerical Modeling of the Ventilation System for a Cooler Room
Authors: Cambuli F. , Orru` P. F. , Pilloni M. T.
Published: September 2008

The goal of the present work was to perform a thermal and fluid dynamic analysis of a refrigerated warehouse used for cheese conservation and ripening at a cheese factory close to the city of Cagliari. Air cooling is obtained by means of cooling units located under the cooler rooms ceiling, where the air distribution is realized by means of tubular pipes made of micro-porous material. An electronic control system allows keeping temperature and humidity within the desired range. As a first step, in order to verify the operation of the cooling system, an investigation was performed through a numerical simulation of the 3D and turbulent flow within the warehouse by solving the Reynolds Averaged Navier-Stokes (RANS) equations; this task was performed by employing the commercial code Fluent. The simulation allowed to represent the temperature and the velocity maps of the air flow inside the cooler room; the most relevant result mainly consists of a strong temperature gradient along the vertical direction. Some possible interventions for improving the air distribution are also suggested.
Geometry Assessment of Variable Displacement Radial Pumps
Authors: Rundo Massimo , Nervegna Nicola
Published: September 2008

The paper brings to evidence the effect that geometry of the stator ring of variable displacement radial pumps bears on performance characteristics of these units. The type of motion of the stator ring (linear or rotational), the location of the centre of rotation, the porting plate integral with the casing or with the stator ring all have remarkable effects on the pump steady state and dynamic performance. At steady state, an influence exists on the attainable minimum displacement and on the deviation of discharge pressure from the desired setting when displacement is being controlled. In turn, dynamic performance is affected by changes in port plate timing as stator position and displacement undergo transitions. Specific attention is then committed to variable displacement vane pumps for internal combustion engines lubrication where an additional and foremost effect is investigated concerning the issues entailed by internal forces distribution on the stator ring that originate from incomplete chambers filling at high rotational pump speed.
An Experimental Study on a High-Speed Rotor Supported by Air Bearings Mounted on O-Rings
Authors: Belforte G. , Raparelli T. , Viktorov V. , Colombo F.
Published: September 2008

A test bench on rotors supported on air bearings floating on O-rings has been designed in order to study the whirling phenomenon and individuate the stability threshold with the presence of damping elements mounted on the bearings. The work contains description of the test bench and the first experimental results. A rotor of 1 kg mass and 37 mm diameter is rotated up to 75000 rpm by an air turbine manufactured on the rotor. Capacitance probes, placed in two radial planes, allow to scan the orbits of both the rotor and the bushing at different rotating speeds and proper load devices make it possible to measure the static and dynamic stiffness of the rotor-bearing system. Diagrams on the rotating response using different kinds of rubber O-rings are presented and compared, with also indications on the Fourier spectra of the signals relative to the rotor displacement. The phenomenon of whirling instability is showed, with considerations on the whirling frequency and on the orbit amplitudes of the rotor and the bearings. The effect of both supply pressure and angular velocity on the stability threshold is showed.
Feeding System of Aerostatic Bearings With Porous Media
Authors: Belforte G. , Raparelli T. , Viktorov V. , Trivella A.
Published: September 2008

In porous resistances, Darcy’s law provides a good approximation of mass flow rate when the differences between upstream and downstream pressures are sufficiently small. In this range, the mass flow rates are proportional to the porous resistance’s permeability. For gas bearings, the pressure difference is normally higher, and it is known experimentally that the mass flow rates are lower than would result from Darcy’s law. Forchheimer’s law adds an inertial term to Darcy’s law and, when an appropriate coefficient is selected for this term, provides a good approximation of flow rates for the same applications even with the highest pressure differences. This paper presents an experimental and theoretical investigation of porous resistances used in gas bearing supply systems. Cylindrical sintered bronze inserts featuring lengths, diameters and particle sizes commonly used in gas bearings and thrust pads were examined. The paper describes the test set-up and experimental results obtained for: a) Mass flow rate through single porous resistances at different upstream and downstream pressures; and b) Mass flow rate and pressure distribution on a pneumatic pad featuring the same porous resistances. The theoretical permeability of the chosen porous resistances was calculated, and the results from set-up a) were then used to obtain experimental permeability and to determine the inertial coefficients. The results, which are expressed as a function of the Reynolds number, confirmed the validity of using Forchheimer’s law. The mass flow rates from set-up b) were compared with those from set-up a) at the same pressure differentials across the insert.
Seismic Analysis of a Turbine on a Spring Isolated Pedestal
Authors: Kostarev Victor V. , Petrenko Andrei V. , Vasilyev Peter S. , Lisyansky Alexander S.
Published: September 2008

Paper deals with the detailed seismic analysis of powerful high-speed Russian turbine of Nuclear Power Plant. Dozens of patterns of such turbine work reliably since 70’s worldwide. Until last decade only simplified structural analyses were available due to a complicated overall structure and internals of such turbines. The current analysis considers detail geometry of the turbine itself as well as vibration and seismic isolation system within turbine’s pedestal and full range of operational, accident and seismic loads. To solve the problem of the turbine seismic and dynamic qualification the following steps have been done. On the first step detailed finite element models of turbine’s high and low pressure parts and rotor system with bearings were created. Using such models corresponding simplified models were developed to be included into the coupled model of the system: “Building – Vibroisolation Pedestal – Turbine” (BVT). The second step was the analysis of that coupled system. Soil-structure interaction was considered using actual soil conditions. Three components of time history acceleration were used to define seismic excitation. As the result of BVT system analysis a full picture of time history displacements and loads were determined. At the same time a non-linear problem of rotor’s axial and radial bearings behavior and gaps in the system was solved. On the final step determined loads were applied to the detailed model of turbine for seismic and dynamic qualification of the whole structure.
Flow and Heat Transfer Analysis in Diverse Microchannel Geometries
Authors: Garci´a-Gonza´lez J. , Herna´ndez-Guerrero A. , Rubio-Arana C. , Solorio-Ordaz F.
Published: September 2008

In this paper an analysis of the fluid flow and the heat transfer in the next generation micro-sized heat sinks is presented. The analysis includes three different geometries for the channels of the heat sinks: rectangular, triangular and trapezoidal, with water as the cooling work flow. A constant heat flux typical of the current high-intensive computational chips (such as the current Pentium chips) is applied at the bottom of the heat sink in a small 1 cm × 1 cm area, an area also typical of the current contact area between electronic devices and the heat dissipaters. The analysis aims to determine the effect of geometry at microscopic scales. It is found that the temperature at the bottom of the dissipater increases approximately in a linear fashion and that by increasing the Reynolds number this temperature decreases. On the contrary, by having a decay in the Reynolds number the temperature of the working fluid increases, bringing a decrease in the viscosity allowing in turn a decrease in the friction losses since the friction coefficient decreases.
Real‐time tumor tracking with preprogrammed dynamic multileaf‐collimator motion and adaptive dose‐rate regulation
Authors: Yi Byong Yong , Han‐Oh Sarah , Lerma Fritz , Berman Barry L. , Yu Cedric
Published: September 2008

The authors have developed a new method for real‐time tumor tracking with dynamic multileaf‐collimator (MLC) motion under condition of free breathing. Unlike other previously proposed tumor‐tracking methods, their new method uses a preprogrammed dynamic MLC sequence in combination with real‐time dose‐rate control. This new scheme circumvents the technical challenge in MLC‐based tumor tracking of having to control the MLC motion in real time, based on real‐time detected tumor motion. With their new method, the movement of the tumor, as a function of breathing phase, amplitude, or tidal volume, is reflected in the preprogrammed MLC sequence. The irregularity of breathing during treatment is handled by real‐time regulation of the machine dose rate, which effectively speeds up or slows down the delivery of radiation as needed. This method is based on the fact that all of the parameters in dynamic radiation delivery, including MLC motion, are enslaved to the cumulative dose, which, in turn, can be accelerated or decelerated by varying the dose rate. Because commercially available MLC systems do not allow the MLC delivery sequence to be modified in real time based on the patient's breathing signal, previously proposed tumor‐tracking techniques using a MLC cannot be readily implemented in the clinic today. By using a preprogrammed MLC sequence to handle the required motion, the task for real‐time control is greatly simplified. With their new scheme, which they call dose‐rate‐regulated tracking (DRRT), it is possible to use existing linear accelerators that have dynamic MLC capability to achieve real‐time tumor tracking, provided that the beam dose rate can be controlled externally. Tracking‐error evaluation for 13 patients out of 14 resulted in a tracking error of less than , if the effect of the response time of the treatment machine on the dose‐rate modulation can be neglected. Film measurements on a moving phantom with variable breathing patterns and DRRT delivery showed that 97% of the measurement points have gamma values less than 1 (for 3% and 2‐mm criteria), while non‐DRRT delivery showed only 87%. This study shows that real‐time tracking is feasible with DRRT even when the patient breathing frequency is irregular. Effects of the variation of breathing amplitude and of base line drift on the tracking error with DRRT are discussed; pending further study, a criterion is suggested for patient selection in the application of this new technique in the clinic.
Reconstruction of a time‐averaged midposition CT scan for radiotherapy planning of lung cancer patients using deformable registrationa)
Authors: Wolthaus J. W. H. , Sonke J.‐J. , van Herk M. , Damen E. M. F.
Published: September 2008

Purpose: lower lobe lung tumors move with amplitudes of up to due to respiration. To reduce respiration imaging artifacts in planning CT scans, 4D imaging techniques are used. Currently, we use a single (midventilation) frame of the 4D data set for clinical delineation of structures and radiotherapy planning. A single frame, however, often contains artifacts due to breathing irregularities, and is noisier than a conventional CT scan since the exposure per frame is lower. Moreover, the tumor may be displaced from the mean tumor position due to hysteresis. The aim of this work is to develop a framework for the acquisition of a good quality scan representing all scanned anatomy in the mean position by averaging transformed (deformed) CT frames, i.e., canceling out motion. A nonrigid registration method is necessary since motion varies over the lung. Methods and Materials: 4D and inspiration breath‐hold (BH) CT scans were acquired for 13 patients. An iterative multiscale motion estimation technique was applied to the 4D CT scan, similar to optical flow but using image phase (gray‐value transitions from bright to dark and vice versa) instead. From the (4D) deformation vector field (DVF) derived, the local mean position in the respiratory cycle was computed and the 4D DVF was modified to deform all structures of the original 4D CT scan to this mean position. A 3D midposition (MidP) CT scan was then obtained by (arithmetic or median) averaging of the deformed 4D CT scan. Image registration accuracy, tumor shape deviation with respect to the BH CT scan, and noise were determined to evaluate the image fidelity of the MidP CT scan and the performance of the technique. Results: Accuracy of the used deformable image registration method was comparable to established automated locally rigid registration and to manual landmark registration (average difference to both methods for all directions) for the tumor region. From visual assessment, the registration was good for the clearly visible features (e.g., tumor and diaphragm). The shape of the tumor, with respect to that of the BH CT scan, was better represented by the MidP reconstructions than any of the 4D CT frames (including MidV; reduction of “shape differences” was 66%). The MidP scans contained about one‐third the noise of individual 4D CT scan frames. Conclusions: We implemented an accurate method to estimate the motion of structures in a 4D CT scan. Subsequently, a novel method to create a midposition CT scan (time‐weighted average of the anatomy) for treatment planning with reduced noise and artifacts was introduced. Tumor shape and position in the MidP CT scan represents that of the BH CT scan better than MidV CT scan and, therefore, was found to be appropriate for treatment planning.
The Hybrid Automobile and the Atkinson Cycle
Authors: Feldman Bernard J.
Published: September 2008

The hybrid automobile is a strikingly new automobile technology with a number of new technological features that dramatically improve energy efficiency. This paper will briefly describe how hybrid automobiles work; what are these new technological features; why the Toyota Prius hybrid internal combustion engine operates on the Atkinson cycle instead of the Otto cycle; and what are the advantages and disadvantages of the hybrid automobile. This is a follow-up to my two previous papers on the physics of automobile engines.1,2
Gender Differences in the High School and Affective Experiences of Introductory College Physics Students
Authors: Hazari Zahra , Sadler Philip M. , Tai Robert H.
Published: September 2008

The disparity in persistence between males and females studying physics has been a topic of concern to physics educators for decades. Overall, while female students perform as well as or better than male students,1 they continue to lag considerably in terms of persistence. The most significant drop in females studying physics occurs between high school and college.2 Since most female physicists report that they became attracted to physics and decided to study it further while in high school, according to the International Study of Women in Physics,3 it is problematic that high school is also the stage at which females begin to opt out at much higher rates than males. Although half of the students taking one year of physics in high school are female, females are less likely than males to take a second or Advanced Placement (AP) physics course.4 In addition, the percentage of females taking the first physics course in college usually falls between 30% and 40%.1 In other words, although you may see gender parity in a first high school physics course, this parity does not usually persist to the next level of physics course. In addition, even if there is parity in a high school physics course, it does not mean that males and females experience the course in the same way. It is this difference in experience that may help to explain the drop in persistence of females.
A Time-of-Flight Method To Measure the Speed of Sound Using a Stereo Sound Card
Authors: Carvalho Carlos C. , Lopes dos Santos J. M. B. , Marques M. B.
Published: September 2008

Most homes in developed countries have a sophisticated data acquisition board, namely the PC sound board. Designed to be able to reproduce CD-quality stereo sound, it must have a sampling rate of at least 44 kHz and have very accurate timing between the two stereo channels. With a very simple adaptation of a pair of regular PC microphones, a computer with a stereo sound board, and sound analysis software, we were able to implement a method of accurate measurement of the speed of sound with several attractive features: a) The most expensive equipment, the PC, the sound board, and sound analysis software, are available in many homes and almost all schools; the two microphones and the additional electronics (see below) can be acquired for less than $50. b) The concept of the experiment is sufficiently simple to be grasped by very young students, 13–14 years old. c) The experiment itself is so straightforward that in a recent Open Day at our department, every group of students passing through the experiment was able to complete, in a couple of minutes, several measurements of cs, the speed of sound in air. d) It is possible to use the same apparatus to measure the speed of sound in solids.
Experimental characterization of nonlinear rubber isolators in a multi-degree-of-freedom system configuration
Authors: Richards Christopher M. , Singh Rajendra
Published: September 2008

Experimental characterization has been investigated for three rubber isolators placed in a multi-degree-of-freedom system configuration. The configuration consisted of a rigid mass mounted to a flexible support beam via each of the rubber isolators. Random, sinusoidal, and sine sweep excitations were applied to the rigid mass and accelerations were measured. Data revealed the dependence of the isolators’ properties on amplitude and type of excitation. Modeling based on the continuous system theory resulted in quasi-linear representations of the experimental system. Discrete system models consisting of nonlinear polynomial equations for describing the nonlinearities of the isolators were also developed. In addition, sound pressure levels were measured during sine sweep excitation for one of the isolators. Increased sound levels were observed at off-resonant regions of the vibration response. Finally, single-degree-of-freedom static and dynamic experiments were conducted. Discrepancies in the isolators’ properties were found between the single- and multi-degree-of-freedom experimental results.
Clinical studies of digital wireless phone interference in hearing aids
Authors: Schlegel Robert E. , Shehab Randa L. , Fry Tamy L. , Grant Hank
Published: September 2008

Two clinical studies were conducted to evaluate the impact of electromagnetic interference from three digital wireless phone technologies on hearing aid wearers. Sixty-eight participants were tested with their own hearing aids to determine the interference detection threshold and annoyance, along with the impact on speech intelligibility. Bystander interference varied as a function of the hearing aid type and the phone technology. The interference was significant only when the digital wireless phone was within 2 ft of the hearing aid user. Significant declines in speech intelligibility were observed as a function of the specific phones used. In the second study, interference signals for three phone technologies were generated at five sound pressure levels from 35 to 75 dB and mixed with speech at 65-dB SPL to test the speech intelligibility of 24 hearing-impaired participants. Scores for the TDMA-217 Hz phone signal at low speech-to-noise ratios (less than 10 dB) were significantly lower than those for CDMA and TDMA-50 Hz at the same level. Speech intelligibility scores at speech-to-noise ratios of 20 and 30 dB were similar to those for a ‘‘no noise’’ condition. The articulation index accurately represented the impact of the wireless phone interference on speech intelligibility.
Statistical theory of peak detection for human hearing
Authors: Goldstein Julius L.
Published: September 2008

Envelope peaks and peak factors of narrow-band sounds have been found in simulation studies to explain a wide range of experiments on sound discrimination [e.g., J. L. Goldstein, J. Acoust. Soc. Am. 99, 2541(A) (1996)]. To extend understanding of peak detection, mathematical approximations were developed for the first and second moments of log (dB) envelope statistics of a tone centered in noise with duration T and bandwidth W. Noises considered are: uniform periodic noise (UPN) having uniform amplitudes and random phases, Gaussian periodic noise (GPN) having random amplitudes and phases, and true Gaussian noise (TGN). Key properties quantified include: (1) Three nearly independent causes of waveform fluctuation underlie peak variance, viz., phase noise, energy noise, and interaction of tone with common frequency noise (energy cross term). (2) The energy variances in peak detection are similar as for energy detection. (3) Peak factor variance is primarily phase noise, which, for noise alone, is ∼1 dB for T×W>2. (4) Peak and peak factor means differ by mean energy. (5) Mean peak growth for a small tone added to noise follows energy summation, while for a small noise added to a tone, the growth follows rms amplitude summation. [Work supported by NSF Grant IBN-9728383.]
The relations between auditory problems and cognitive, linguistic, and intellectual measures in first grade children
Authors: Kidd Gary R. , Eddins David A. , Watson Charles S.
Published: September 2008

The relations between hearing ability and several sensory, perceptual, and cognitive abilities were determined for all children entering first grade in the Benton County, Indiana school system for three consecutive years. This research was part of a multi-disciplinary, epidemiological, longitudinal study of the factors that influence the development of reading and language skills in the early grades. As a result of an auditory evaluation that included otoscopy, tympanometry, pure-tone screening, and speech audiometry, two groups of children with auditory problems were identified who also had lower scores on nonauditory measures. In the total sample of 459 children, 24 had hearing thresholds excess of 20 dB HL and 51 had either excessive ear wax or evidence of ear infection based on otoscopy. Scores for both groups on measures of reading, cognitive/intellectual abilities, and on the SCAN central auditory test battery were significantly lower than for children with normal auditory function. At entry into second grade, however, reading achievement for both groups was within normal limits. The association between these measures of auditory function and socio-economic status will be discussed. [Work supported by the Benton County School System and by a grant from Indiana University.]
Advantages of mapping climatic temperature changes in the ocean with mobile receivers
Authors: Spiesberger John L. , Fabrikant Anatoly L. , Silivra Anisim A. , Hurlburt Harley E.
Published: September 2008

An acoustic tomography simulation is carried out in the North Pacific ocean to assess whether climate trends are better detected and mapped with mobile or fixed receivers. Natural variability of the sound-speed field is simulated with the Naval Research Laboratory (NRL) layered-ocean model. A Kalman filter is used to estimate the sound speed field, where the a priori error covariance matrix of the parameters is estimated from the model. A spatially homogeneous climate trend is added to the NRL fluctuations, but the trend is not parametrized in the Kalman filter because, in reality, the ocean’s variability is poorly known. The effects of the unparametrized climate trend are projected onto parameters which eventually drift beyond acceptable limits, which triggers the trend’s detection. Mobile and fixed receivers detect the trend at the same time, but the maps from the mobile receivers are more accurate because they provide a synthetic aperture which better samples the variability than the fixed receivers [A. L. Fabrikant et al., IEEE Ocean. Eng. 23, 20–25 (1998)]. This simulation is one of several which motivates a program designed to show that U.S. submarines are useful for collecting tomographic signals for scientific study. [Work supported by ONR.]
Internal waves and temperature inversion in the East China Sea
Authors: Wang Tao , Gao Tian-Fu , Jiang De-Jun , Zhang Yun-Peng
Published: September 2008

Several shallow-water acoustics experiments were performed in the Zhoushan offshore area of the East China Sea from 1996 to 1998. The water depth is about 55 m at the mooring locations. Temperature chains sampling once per 6.4 s or 1 min provide the oceanographic data. One clearly sees the long-wavelength internal tides. The dominant component of the internal wave field is the semidiurnal tide of 10-m height. High-frequency internal waves with 10–15 min duration and 2-m amplitude ride on top of the internal tide. These rank-ordered waves are likely internal solitons, which is validated by recent SAR images. The asymmetry of the initial and final states indicates that the solibore description is somewhat applicable to this case, but more evidence is needed. The inversion phenomenon of temperature and salinity frequently occurs in the long and narrow East China Sea area off the coast of Jiangsu and Zhejiang. Temperature inversion is noted via the measurements and shows yearly variations. Its structure and generation mechanism are discussed. [Work supported by NSFC.]
Modal analysis of a new steelpan: The ping
Authors: Rossing Thomas D. , Hansen Uwe J. , Rohner Felix , Schärer Sabina
Published: September 2008

The ping, which has the same playing range as a tenor steelpan, is a new instrument in the steelpan family. Its playing surface is sandwich hardened steel having a uniform thickness of 0.9 mm, and its skirt is of stainless steel 1.25-mm thick. Each note area has a small elliptical dome at the center to provide stability and a durable strike point. We compare the modes of vibration of the ping to those of a tenor steelpan. In both pans, the (0,1) mode of each note is tuned an octave above the fundamental, and the (1,0) mode is tuned a twelfth (three times the frequency) above the fundamental in the lower notes. In the ping, it is possible to tune a twelfth throughout more of the range, and the frequency remains unchanged for a longer time during hard playing. Radiation of sound by the skirt is compared.
Consonant recognition in noise with temporal cues: II. Effects of temporal envelope enhancement on response times
Authors: Apoux Frederic , Crouzet Olivier , Lorenzi Christian
Published: September 2008

In an effort to evaluate the importance of envelope cues in speech recognition, response times and percentages of correct responses were measured simultaneously in normal-hearing and hearing-impaired listeners, using a forced-choice identification paradigm. Naturally produced /aCa/ disyllables presented in a white noise background (+6 dB signal-to-noise ratio) were used to create temporal-only stimuli having instantaneous amplitudes identical to the natural speech stimuli, but flat spectra. The temporal envelope of the /aCa/ disyllables was either left intact or enhanced by raising it to the power 2. In the first experiment, 13 young normal-hearing listeners (24–27 years) were tested. The results show that envelope enhancement yields a general improvement in both percent correct identification (4.75%) and response times (63 ms). In the second experiment, nine hearing-impaired listeners (53–71 years) were tested at a comfortable listening level. Overall, temporal expansion fails to show better consonant identification in terms of percentage of correct responses, but yields a significant improvement (66 ms) in terms of response time. These results suggest that: (1) the perceptual effects of speech-envelope enhancement cannot be completely accounted for by percent correct-responses measurements, and (2) response times seem to be more sensitive to the effects of envelope enhancement.
A time-variant wedge assemblage method for acoustic Doppler backscattering from 2-D sea surfaces
Authors: Keiffer Richard S. , Novarini Jorge C.
Published: September 2008

Recently, the details of a time domain model for the acoustic impulse response of static two-dimensional (2-D) sea surfaces based on wedge diffraction theory were reported [R. S. Keiffer and J. C. Novarini, J. Acoust. Soc. Am. 107, 27–39 (2000)]. That approach, which is called the wedge assemblage (WA) method, was shown to accurately predict the acoustic backscattering from static, 2-D, fully developed (U=20 m/s) sea surfaces in the low to moderate frequency range. In this presentation, concepts from linear time-variant filter theory are used to extend that modeling capability to the problem of scattering from moving surfaces. Numerical simulations of the time-variant impulse response function have been computed for backscattering from (pressure-release) moving sinusoids and standing waves. The results are shown as Doppler spectra over a broad band range of source frequencies (50 Hz to 2 kHz). Also presented are simulations of monostatic backscattering from time-evolving, fully developed seas as a function of azimuthal orientation. In the crosswind orientation, it is found that the Doppler shifts are substantially smaller than the first-order perturbation theory prediction and similar to the predictions from higher-order pertubation theory by M. Pourkaviani and J. F. Willemsen [J. Acoust. Soc. Am. 90, 426–432 (1991)].
Ultrasonic release of insulin from implantable, bio-compatable polymers coated with self-assembling membranes
Authors: Mourad Pierre D. , Crum Lawrence A. , Kwok Connie , Ratner Buddy
Published: September 2008

There has been some research in the late 1980s on the development and use of biologically compatable, drug-carrying polymers for the purpose of subcutaneous release of the drug. In those papers, ultrasound was used to release the drug. This intriguing method for temporally targeted drug release has been hampered by a large, non-ultrasonic drug release rate. In other words, even without the application of ultrasonic stimulation, an excessive amount of the drug leaches out of the drug-carrying implant. We have developed a bio-compatable, drug-carrying polymer that can release a drug of interest upon ultrasonic stimulation, but whose background leaching rate is negligible. The advance in the present study over previous work is the coating of the drug-carrying polymer with a self-assembling membrane (SAM). Before and after the application of ultrasound, the SAM acts as an effective barrier. During and shortly after the application of ultrasound, the SAM transiently disassembles—thereby releasing the drug—then reassembles, which cuts off the drug flux. We present in vitro results demonstrating this effect, with insulin and ciprofloxin as candidate drugs. [This work was supported in part by DARPA and NSF.]
The relative time course of neighborhood and lexical effects
Authors: Newman Rochelle S. , Sawusch James R. , Luce Paul A. , Aubin Amanda
Published: September 2008

We have previously demonstrated that neighborhood density can have effects similar to those of lexical status in phoneme identification tasks. In a typical task demonstrating a lexical effect, subjects might hear two series, one ranging from ‘‘bag’’ to ‘‘pag,’’ while the other varies from ‘‘pal’’ to ‘‘bal.’’ Subjects are more likely to classify ambiguous stimuli from each series as members of the category that makes a word (they would classify ambiguous items as ‘‘b’’ in the bag–pag series but as ‘‘p’’ in the pal–bal series). In a similar task where none of the four endpoints were words, subjects classified ambiguous items as members of the category that had a greater neighborhood density. The current study examines the relative time course of these effects. We created both lexical and neighborhood series using the identical initial contrast, and presented them to the same set of listeners. Neighborhood effects occurred primarily in the fastest responses, while lexical effects occurred in the medium and slower responses. That is, neighborhood effects appear earlier in processing, and dissipate quickly, whereas lexical effects take longer to build up. These results will be discussed in terms of their implications for models of word recognition.
Merging Photoredox Catalysis with Organocatalysis: The Direct Asymmetric Alkylation of Aldehydes
Authors: Nicewicz David A. , MacMillan David W. C.
Published: September 2008

Photoredox catalysis and organocatalysis represent two powerful fields of molecule activation that have found widespread application in the areas of inorganic and organic chemistry, respectively. We merged these two catalysis fields to solve problems in asymmetric chemical synthesis. Specifically, the enantioselective intermolecular α-alkylation of aldehydes has been accomplished using an interwoven activation pathway that combines both the photoredox catalyst Ru(bpy)
3
Cl
2
(where bpy is 2,2′-bipyridine) and an imidazolidinone organocatalyst. This broadly applicable, yet previously elusive, alkylation reaction is now highly enantioselective and operationally trivial.
An Integrated Genomic Analysis of Human Glioblastoma Multiforme
Authors: Parsons D. Williams , Jones Siân , Zhang Xiaosong , Lin Jimmy Cheng-Ho , Leary Rebecca J. , Angenendt Philipp , Mankoo Parminder , Carter Hannah , Siu I-Mei , Gallia Gary L. , Olivi Alessandro , McLendon Roger , Rasheed B. Ahmed , Keir Stephen , Nikolskaya Tatiana , Nikolsky Yuri , Busam Dana A. , Tekleab Hanna , Diaz Luis A. , Hartigan James , Smith Doug R. , Strausberg Robert L. , Marie Suely Kazue Nagahashi , Shinjo Sueli Mieko Oba , Yan Hai , Riggins Gregory J. , Bigner Darell D. , Karchin Rachel , Papadopoulos Nick , Parmigiani Giovanni , Vogelstein Bert , Velculescu Victor E. , Kinzler Kenneth W.
Published: September 2008

Glioblastoma multiforme (GBM) is the most common and lethal type of brain cancer. To identify the genetic alterations in GBMs, we sequenced 20,661 protein coding genes, determined the presence of amplifications and deletions using high-density oligonucleotide arrays, and performed gene expression analyses using next-generation sequencing technologies in 22 human tumor samples. This comprehensive analysis led to the discovery of a variety of genes that were not known to be altered in GBMs. Most notably, we found recurrent mutations in the active site of isocitrate dehydrogenase 1 (
IDH1
) in 12% of GBM patients. Mutations in
IDH1
occurred in a large fraction of young patients and in most patients with secondary GBMs and were associated with an increase in overall survival. These studies demonstrate the value of unbiased genomic analyses in the characterization of human brain cancer and identify a potentially useful genetic alteration for the classification and targeted therapy of GBMs.
Internally Generated Reactivation of Single Neurons in Human Hippocampus During Free Recall
Authors: Gelbard-Sagiv Hagar , Mukamel Roy , Harel Michal , Malach Rafael , Fried Itzhak
Published: September 2008

The emergence of memory, a trace of things past, into human consciousness is one of the greatest mysteries of the human mind. Whereas the neuronal basis of recognition memory can be probed experimentally in human and nonhuman primates, the study of free recall requires that the mind declare the occurrence of a recalled memory (an event intrinsic to the organism and invisible to an observer). Here, we report the activity of single neurons in the human hippocampus and surrounding areas when subjects first view cinematic episodes consisting of audiovisual sequences and again later when they freely recall these episodes. A subset of these neurons exhibited selective firing, which often persisted throughout and following specific episodes for as long as 12 seconds. Verbal reports of memories of these specific episodes at the time of free recall were preceded by selective reactivation of the same hippocampal and entorhinal cortex neurons. We suggest that this reactivation is an internally generated neuronal correlate for the subjective experience of spontaneous emergence of human recollection.
DNA from BK Virus and JC Virus and from KI, WU, and MC Polyomaviruses as Well as from Simian Virus 40 Is Not Detected in Non-UV-Light-Associated Primary Malignant Melanomas of Mucous Membranes
Authors: Giraud Géraldine , Ramqvist Torbjörn , Ragnarsson-Olding Boel , Dalianis Tina
Published: September 2008

The single most important causative factor for malignant melanomas of the skin is UV radiation. However, this is not true for melanomas on body surfaces sheltered from the sun; thus, it is important to seek new causative factors of melanoma genesis. Human papillomaviruses and gammaherpesviruses are associated with human skin cancer; for example, human papillomavirus types 5 and 8 are associated with epidermodysplasia verruciformis, and human herpesvirus 8 is associated with Kaposi's sarcoma. Recently, a newly described human polyomavirus, Merkel cell polyomavirus (MCPyV), has been associated with Merkel cell carcinoma, an unusual form of neurotropic skin cancer. Moreover, melanocytes are of neuroepithelial origin. This background impelled us to investigate if human polyomavirus DNA could play a role in the development of extracutaneous melanomas. Sixty-four extracutaneous melanomas were initially collected and dissected. Of these, 38 could be successfully used for further testing for the presence of the five human polyomaviruses known so far—BK virus (BKV), JC virus (JCV), KI polyomavirus (KIPyV), WU polyomavirus (WUPyV), and MCPyV—and of simian virus 40 (SV40). No polyomavirus DNA could be detected in any of the samples tested by use of a nested PCR detecting BKV, JCV, and SV40; a newly designed PCR detecting KIPyV and WUPyV; or a newly designed PCR for MCPyV. We conclude that since no human polyomavirus DNA was detected in primary malignant melanomas on non-sun-exposed body surfaces, these polyomaviruses presumably are not major factors for the development of extracutaneous melanomas.
Conserved Salt Bridge between the N- and C-Terminal Heptad Repeat Regions of the Human Immunodeficiency Virus Type 1 gp41 Core Structure Is Critical for Virus Entry and Inhibition
Authors: He Yuxian , Liu Shuwen , Li Jingjing , Lu Hong , Qi Zhi , Liu Zhonghua , Debnath Asim K. , Jiang Shibo
Published: September 2008

The fusogenic human immunodeficiency virus type 1 (HIV-1) gp41 core structure is a stable six-helix bundle formed by its N- and C-terminal heptad repeat sequences. Notably, the negatively charged residue Asp
632
located at the pocket-binding motif in the C-terminal heptad repeat interacts with the positively charged residue Lys
574
in the pocket formation region of the N-terminal heptad repeat to form a salt bridge. We previously demonstrated that the residue Lys
574
plays an essential role in six-helix bundle formation and virus infectivity and is a key determinant of the target for anti-HIV fusion inhibitors. In this study, the functionality of residue Asp
632
has been specifically characterized by mutational analysis and biophysical approaches. We show that Asp
632
substitutions with positively charged residues (D632K and D632R) or a hydrophobic residue (D632V) could completely abolish Env-mediated viral entry, while a protein with a conserved substitution (D632E) retained its activity. Similar to the Lys
574
mutations, nonconserved substitutions of Asp
632
also severely impaired the α-helicity, stability, and conformation of six-helix bundles as shown by N36 and C34 peptides as a model system. Furthermore, nonconserved substitutions of Asp
632
significantly reduced the potency of C34 to sequestrate six-helix bundle formation and to inhibit HIV-1-mediated cell-cell fusion and infection, suggesting its importance for designing antiviral fusion inhibitors. Taken together, these data suggest that the salt bridge between the N- and C-terminal heptad repeat regions of the fusion-active HIV-1 gp41 core structure is critical for viral entry and inhibition.
Importance of the V1/V2 Loop Region of Simian-Human Immunodeficiency Virus Envelope Glycoprotein gp120 in Determining the Strain Specificity of the Neutralizing Antibody Response
Authors: Laird Melissa E. , Igarashi Tatsuhiko , Martin Malcolm A. , Desrosiers Ronald C.
Published: September 2008

Plasma samples from individuals infected with human immunodeficiency virus type 1 (HIV-1) are known to be highly strain specific in their ability to neutralize HIV-1 infectivity. Such plasma samples exhibit significant neutralizing activity against autologous HIV-1 isolates but typically exhibit little or no activity against heterologous strains, although some cross-neutralizing activity can develop late in infection. Monkeys infected with the simian-human immunodeficiency virus (SHIV) clone DH12 generated antibodies that neutralized SHIV DH12, but not SHIV KB9. Conversely, antibodies from monkeys infected with the SHIV clone KB9 neutralized SHIV KB9, but not SHIV DH12. To investigate the role of the variable loops of the HIV-1 envelope glycoprotein gp120 in determining this strain specificity, variable loops 1 and 2 (V1/V2), V3, or V4 were exchanged individually or in combination between SHIV DH12 and SHIV KB9. Despite the fact that both parental viruses exhibited significant infectivity and good replication in the cell lines examined, 3 of the 10 variable-loop chimeras exhibited such poor infectivity that they could not be used further for neutralization assays. These results indicate that a variable loop that is functional in the context of one particular envelope background will not necessarily function within another. The remaining seven replication-competent chimeras allowed unambiguous assignment of the sequences principally responsible for the strain specificity of the neutralizing activity present in SHIV-positive plasma. Exchange of the V1/V2 loop sequences conferred a dominant loss of sensitivity to neutralization by autologous plasma and a gain of sensitivity to neutralization by heterologous plasma. Substitution of V3 or V4 had little or no effect on the sensitivity to neutralization. These data demonstrate that the V1/V2 region of HIV-1 gp120 is principally responsible for the strain specificity of the neutralizing antibody response in monkeys infected with these prototypic SHIVs.