bluuebunny/crossref_metadata_2025 huggingface dataset:
Extended speech intelligibility index for the prediction of the speech reception threshold in fluctuating noise
Authors: Rhebergen Koenraad S. , Versfeld Niek J. , Dreschler Wouter. A.
Published: December 2006

The extension to the speech intelligibility index (SII; ANSI S3.5-1997 (1997)) proposed by Rhebergen and Versfeld [Rhebergen, K.S., and Versfeld, N.J. (2005). J. Acoust. Soc. Am. 117(4), 2181–2192] is able to predict for normal-hearing listeners the speech intelligibility in both stationary and fluctuating noise maskers with reasonable accuracy. The extended SII model was validated with speech reception threshold (SRT) data from the literature. However, further validation is required and the present paper describes SRT experiments with nonstationary noise conditions that are critical to the extended model. From these data, it can be concluded that the extended SII model is able to predict the SRTs for the majority of conditions, but that predictions are better when the extended SII model includes a function to account for forward masking.
Perceptual adaptation by normally hearing listeners to a simulated “hole” in hearing
Authors: Smith Matthew W. , Faulkner Andrew
Published: December 2006

Simulations of cochlear implants have demonstrated that the deleterious effects of a frequency misalignment between analysis bands and characteristic frequencies at basally shifted simulated electrode locations are significantly reduced with training. However, a distortion of frequency-to-place mapping may also arise due to a region of dysfunctional neurons that creates a “hole” in the tonotopic representation. This study simulated a 10mm hole in the mid-frequency region. Noise-band processors were created with six output bands (three apical and three basal to the hole). The spectral information that would have been represented in the hole was either dropped or reassigned to bands on either side. Such reassignment preserves information but warps the place code, which may in itself impair performance. Normally hearing subjects received three hours of training in two reassignment conditions. Speech recognition improved considerably with training. Scores were much lower in a baseline (untrained) condition where information from the hole region was dropped. A second group of subjects trained in this dropped condition did show some improvement; however, scores after training were significantly lower than in the reassignment conditions. These results are consistent with the view that speech processors should present the most informative frequency range irrespective of frequency misalignment.
Effects of middle-ear immaturity on distortion product otoacoustic emission suppression tuning in infant ears
Authors: Abdala Carolina , Keefe Douglas H.
Published: December 2006

Distortion product otoacoustic emission (DPOAE) measures of cochlear function, including DPOAE suppression tuning curves and input/output (I/O) functions, are not adultlike in human infants. These findings suggest the cochlear amplifier might be functionally immature in newborns. However, many noncochlear factors influence DPOAEs and must be considered. This study examines whether age differences in DPOAE I/O functions recorded from infant and adult ears reflect maturation of ear-canal/middle-ear function or cochlear mechanics. A model based on linear middle-ear transmission and nonlinear cochlear generation was developed to fit the adult DPOAE I/O data. By varying only those model parameters related to middle-ear transmission (and holding cochlear parameters at adult values), the model successfully fitted I/O data from infants at birth through age 6months. This suggests that cochlear mechanics are mature at birth. The model predicted an attenuation of stimulus energy through the immature ear canal and middle ear, and evaluated whether immaturities in forward transmission could explain the differences consistently observed between infant and adult DPOAE suppression. Results show that once the immaturity was compensated for by providing infants with a relative increase in primary tone level, DPOAE suppression tuning at f2=6000Hz was similar in adults and infants.
Modeling acoustic propagation of airgun array pulses recorded on tagged sperm whales (Physeter macrocephalus)
Authors: DeRuiter Stacy L. , Tyack Peter L. , Lin Ying-Tsong , Newhall Arthur E. , Lynch James F. , Miller Patrick J. O.
Published: December 2006

In 2002 and 2003, tagged sperm whales (Physeter macrocephalus) were experimentally exposed to airgun pulses in the Gulf of Mexico, with the tags providing acoustic recordings at measured ranges and depths. Ray trace and parabolic equation (PE) models provided information about sound propagation paths and accurately predicted time of arrival differences between multipath arrivals. With adequate environmental information, a broadband acoustic PE model predicted the relative levels of multipath arrivals recorded on the tagged whales. However, lack of array source signature data limited modeling of absolute received levels. Airguns produce energy primarily below 250Hz, with spectrum levels about 20–40dB lower at 1kHz. Some arrivals recorded near the surface in 2002 had energy predominantly above 500Hz; a surface duct in the 2002 sound speed profile helps explain this effect, and the beampattern of the source array also indicates an increased proportion of high-frequency sound at near-horizontal launch angles. These findings indicate that airguns sometimes expose animals to measurable sound energy above 250Hz, and demonstrate the influences of source and environmental parameters on characteristics of received airgun pulses. The study also illustrates that on-axis source levels and simple geometric spreading inadequately describe airgun pulse propagation and the extent of exposure zones.
Role of suppression and retro-cochlear processes in comodulation masking release
Authors: Ernst Stephan M. A. , Verhey Jesko L.
Published: December 2006

Recent physiological studies suggest that comodulation masking release (CMR) could be a consequence of wideband inhibition at the level of the cochlear nucleus. The present study investigates whether the existence region of psychophysical CMR is comparable to the inhibitory areas of units showing a physiological correlate of CMR. Since the inhibitory areas are similar to suppressive regions at the level of the basilar membrane, the amount of CMR that can be accounted for by suppression was determined by predicting the data with a model incorporating a peripheral nonlinearity. A CMR of up to 6dB could still be experimentally observed for a flanking band (FB) four octaves below the on-frequency masker (OFM). For FB frequencies below the OFM, the suggested model predicts CMR equal to the measured CMR for high levels of the FB. The model underestimates the magnitude of CMR for midlevels of the FB, indicating that suppression alone cannot account for CMR. The data are consistent with the hypothesis that wideband inhibition plays a role in CMR.
Effect of intonation on Cantonese lexical tones
Authors: Ma Joan K-Y , Ciocca Valter , Whitehill Tara L.
Published: December 2006

In tonal languages, there are potential conflicts between the F0-based changes due to the coexistence of intonation and lexical tones. In the present study, the interaction of tone and intonation in Cantonese was examined using acoustic and perceptual analyses. The acoustic patterns of tones at the initial, medial, and final positions of questions and statements were measured. Results showed that intonation affects both the F0 level and contour, while the duration of the six tones varied as a function of positions within intonation contexts. All six tones at the final position of questions showed rising F0 contour, regardless of their canonical form. Listeners were overall more accurate in the identification of tones presented within the original carrier than of the same tones in isolation. However, a large proportion of tones 33, 21, 23, and 22 at the final position of questions were misperceived as tone 25 both within the original carrier and as isolated words. These results suggest that although the intonation context provided cues for correct tone identification, the intonation-induced changes in F0 contour cannot always be perceptually compensated for, resulting in some erroneous perception of the identity of Cantonese tone.
Isolating the energetic component of speech-on-speech masking with ideal time-frequency segregation
Authors: Brungart Douglas S. , Chang Peter S. , Simpson Brian D. , Wang DeLiang
Published: December 2006

When a target speech signal is obscured by an interfering speech wave form, comprehension of the target message depends both on the successful detection of the energy from the target speech wave form and on the successful extraction and recognition of the spectro-temporal energy pattern of the target out of a background of acoustically similar masker sounds. This study attempted to isolate the effects that energetic masking, defined as the loss of detectable target information due to the spectral overlap of the target and masking signals, has on multitalker speech perception. This was achieved through the use of ideal time-frequency binary masks that retained those spectro-temporal regions of the acoustic mixture that were dominated by the target speech but eliminated those regions that were dominated by the interfering speech. The results suggest that energetic masking plays a relatively small role in the overall masking that occurs when speech is masked by interfering speech but a much more significant role when speech is masked by interfering noise.
Evaluation of decay times in coupled spaces: An efficient search algorithm within the Bayesian framework
Authors: Xiang Ning , Jasa Tomislav
Published: December 2006

This paper discusses an efficient method for evaluating multiple decay times within the Bayesian framework. Previous works [N. Xiang and P. M. Goggans, J. Acoust. Soc. Am. 110, 1415–1424 (2001); 113, 2685–2697 (2003); N. Xiang, P. M. Goggans, T. Jasa, and M. Kleiner, 117, 3707–3715 (2005)] have applied the Bayesian inference to cope with demanding tasks in estimating multiple decay times from Schroeder decay functions measured or calculated in acoustically coupled spaces. Since then a number of recent works call for efficient estimation methods within the Bayesian framework. An efficient analysis is of practical significance for better understanding and modeling the sound energy decay process in acoustically coupled spaces or even in single spaces for reverberation time estimation. This paper will first formulate the Bayesian posterior probability distribution function (PPDF) in a matrix form to reduce the dimensionality as applied to the decay time evaluation. Based on existence of only global extremes of PPDFs as observed from extensive experimental data, this paper describes a dedicated search algorithm for an efficient estimation of decay times.
A note on the low-frequency noise reduction of cylindrical capsules
Authors: Ungar Eric E.
Published: December 2006

The noise reductions provided by capsules consisting of uniform cylindrical shells whose two ends are closed off by like circular plates are analyzed for the low-frequency regime in which a capsule acts quasi-statically, much like a pressure vessel. The change in the confined volume is determined from the structural deflections produced by a net pressure difference, taking account of the interactions of the shell and end plates. Expressions for the noise reduction of a single capsule and of two nested capsules are derived. Some insights into the noise reduction effects of interaction between the shell and end plates are discussed, as are the contributions of these components.
A nonlinear finite-element model of the newborn ear canal
Authors: Qi Li , Liu Hengjin , Lutfy Justyn , Funnell W. Robert J. , Daniel Sam J.
Published: December 2006

A three-dimensional nonlinear finite-element model of a 22-day-old newborn ear canal is presented. The geometry is based on a clinical x-ray CT scan. A nonlinear hyperelastic constitutive law is applied to model large deformations. The Young’s modulus of the soft tissue is found to have a significant effect on the ear-canal volume change, which ranges from approximately 27% to 75% over the static-pressure range of ±3kPa. The effects of Poisson’s ratio and of the ratio C10:C01 in the hyperelastic model are found to be small. The volume changes do not reach a plateau at high pressures, which implies that the newborn ear-canal wall would not be rigid in tympanometric measurements. The displacements and volume changes calculated from the model are compared with available experimental data.
Stability of self-similar plane shocks with Hertzian nonlinearity
Authors: McDonald B. Edward
Published: December 2006

The nonlinear progressive wave equation [McDonald and Kuperman, J. Acoust. Soc. Am. 81, 1406–1417 (1987)] is expressed in a form to accommodate Hertzian nonlinearity of order n=3∕2 typical of granular media. Stability of self-similar plane weak shocks against perturbations in three dimensions is demonstrated for arbitrary order nonlinearity with 1<n<3. Investigation of stability in the presence of Hertzian nonlinearity is motivated by the nonlinearity coefficient being arbitrarily large in the unstressed state. Energy in the perturbation field is shown to fall off at least as fast as 1∕t, while energy in the self-similar wave falls off slower than 1∕t. For an initial wave profile increasing in the direction of propagation, it is shown that where the quadratic nonlinearity coefficient diverges, the slope of the wave goes to zero.
The relationship between frequency selectivity and pitch discrimination: Effects of stimulus level
Authors: Bernstein Joshua G. W. , Oxenham Andrew J.
Published: December 2006

Three experiments tested the hypothesis that fundamental frequency (f0) discrimination depends on the resolvability of harmonics within a tone complex. Fundamental frequency difference limens (f0 DLs) were measured for random-phase harmonic complexes with eight f0’s between 75 and 400Hz, bandpass filtered between 1.5 and 3.5kHz, and presented at 12.5-dB∕component average sensation level in threshold equalizing noise with levels of 10, 40, and 65dB SPL per equivalent rectangular auditory filter bandwidth. With increasing level, the transition from large (poor) to small (good) f0 DLs shifted to a higher f0. This shift corresponded to a decrease in harmonic resolvability, as estimated in the same listeners with excitation patterns derived from measures of auditory filter shape and with a more direct measure that involved hearing out individual harmonics. The results are consistent with the idea that resolved harmonics are necessary for good f0 discrimination. Additionally, f0 DLs for high f0’s increased with stimulus level in the same way as pure-tone frequency DLs, suggesting that for this frequency range, the frequencies of harmonics are more poorly encoded at higher levels, even when harmonics are well resolved.
Lateralization of sine tones–interaural time vs phase
Authors: Zhang Peter Xinya , Hartmann William M.
Published: December 2006

Listeners estimated the lateral positions of 50 sine tones with interaural phase differences ranging from −150° to +150° and with different frequencies, all in the range where signal fine structure supports lateralization. The estimates indicated that listeners lateralize sine tones on the basis of interaural time differences and not interaural phase differences.
The influence of later-arriving sounds on the ability of listeners to judge the lateral position of a source
Authors: Dye Raymond H. , Brown Christopher A. , Gallegos José A. , Yost William A. , Stellmack Mark A.
Published: December 2006

This study examined the deleterious effects of a later-arriving sound on the processing of interaural differences of time (IDTs) from a preceding sound. A correlational analysis assessed the relative weight given to IDTs of source and echo clicks for echo delays of 1–64ms when the echo click was attenuated relative to the source click (0–36dB). Also measured were proportion correct and the proportion of responses predicted from the weights. The IDTs of source and echo clicks were selected independently from Gaussian distributions (μ=0μs, σ=100μs). Listeners were instructed to indicate the laterality of the source click. Equal weight was given to the source and echo clicks for echo delays of 64ms with no echo attenuation. For echo delays of 16–64ms, attenuating the echo had no substantial effect on source weight or proportion correct until the echo was attenuated by 18–30dB. At echo delays ≤4ms, source weights and proportions correct remained high regardless of echo attenuation. The proportions of responses predicted from the weights were lower at echo delays ≥16ms. Results were discussed in terms of backward recognition masking and binaural sluggishness and compared to measurements of echo disturbance.
Generalization of the rotated parabolic equation to variable slopes
Authors: Outing Donald A. , Siegmann William L. , Collins Michael D. , Westwood Evan K.
Published: December 2006

The rotated parabolic equation [J. Acoust. Soc. Am. 87, 1035–1037 (1990)] is generalized to problems involving ocean-sediment interfaces of variable slope. The approach is based on approximating a variable slope in terms of a series of constant slope regions. The original rotated parabolic equation algorithm is used to march the field through each region. An interpolation-extrapolation approach is used to generate a starting field at the beginning of each region beyond the one containing the source. For the elastic case, a series of operators is applied to rotate the dependent variable vector along with the coordinate system. The variable rotated parabolic equation should provide accurate solutions to a large class of range-dependent seismo-acoustics problems. For the fluid case, the accuracy of the approach is confirmed through comparisons with reference solutions. For the elastic case, variable rotated parabolic equation solutions are compared with energy-conserving and mapping solutions.
A laboratory investigation of noise reduction by riblike structures on the ground
Authors: Bougdah Hocine , Ekici Inan , Kang Jian
Published: December 2006

This paper investigates the use of periodically spaced edges or wells for the control of road traffic noise. The wells have uniform height and width and are placed on the ground. Physical scale modeling is used to assess the acoustic performance of these structures under laboratory conditions. It is shown that, in certain situations where the use of conventional barriers would not be appropriate, strategically designed riblike structures can provide insertion losses of typically 10–15dB. The findings are explained in terms of acoustic scattering with the approaches used in the study of resonators and diffraction/interference gratings.
Virtual pitch in a computational physiological model
Authors: Meddis Ray , O’Mard Lowel P.
Published: December 2006

A computational model of nervous activity in the auditory nerve, cochlear nucleus, and inferior colliculus is presented and evaluated in terms of its ability to simulate psychophysically-measured pitch perception. The model has a similar architecture to previous autocorrelation models except that the mathematical operations of autocorrelation are replaced by the combined action of thousands of physiologically plausible neuronal components. The evaluation employs pitch stimuli including complex tones with a missing fundamental frequency, tones with alternating phase, inharmonic tones with equally spaced frequencies and iterated rippled noise. Particular attention is paid to differences in response to resolved and unresolved component harmonics. The results indicate that the model is able to simulate qualitatively the related pitch-perceptions. This physiological model is similar in many respects to autocorrelation models of pitch and the success of the evaluations suggests that autocorrelation models may, after all, be physiologically plausible.
A Spontaneous Joint Infection with
Corynebacterium striatum
Authors: Scholle David
Published: December 2006

Corynebacterium striatum
is a ubiquitous saprophyte with the potential to cause bacteremia in immunocompromised patients. Until now, spontaneous infection of a natural joint has not been reported. When phenotyping failed, gene sequencing was used to identify the species. The isolate demonstrated high-level resistance to most antibiotics.
Relationship between Cytomegalovirus DNA Load in Epithelial Lining Fluid and Plasma of Lung Transplant Recipients and Analysis of Coinfection with Epstein-Barr Virus and Human Herpesvirus 6 in the Lung Compartment
Authors: Bauer Claudia C. , Jaksch Peter , Aberle Stephan W. , Haber Heinrich , Lang Gyoergy , Klepetko Walter , Hofmann Hanns , Puchhammer-Stöckl Elisabeth
Published: December 2006

Cytomegalovirus (CMV) is a significant cause of morbidity and mortality in lung transplant recipients (LTRs). The aim of the present study was to elucidate the relationship between the CMV DNA load in the lung compartment and that in plasma. For CMV load determination, the level of CMV DNA in plasma and bronchoalveolar lavage (BAL) samples was measured in a total of 97 paired BAL and plasma samples obtained from 25 LTRs. The original virus concentration in the epithelial lining fluid (ELF) was calculated from the BAL samples by correcting for dilution using the urea dilution method. In addition, the load of Epstein-Barr virus (EBV) and that of human herpesvirus 6 (HHV-6) DNA also were determined in BAL samples, recalculated for their concentrations in the ELF, and compared with the CMV DNA load. CMV DNA was found more frequently and at significantly higher levels in the lung compartment than in plasma (
P
< 0.001, Wilcoxon test), and the CMV load in the ELF was associated with symptomatic CMV disease. EBV and HHV-6 were detected in 43.6% and 21.7% of the ELF samples, respectively. A statistically significant association was found between the CMV and EBV DNA loads in the ELF (
P
< 0.001; Spearman's rho = 0.651). Thus, in LTRs, determination of the CMV DNA load in the lung compartment may be advantageous compared to monitoring only viremia. The significant relationship between EBV and CMV DNA loads in the ELF of LTRs and its clinical impact require further investigation.
Strategy To Characterize the Number and Type of Repeating EPIYA Phosphorylation Motifs in the Carboxyl Terminus of CagA Protein inHelicobacter pyloriClinical Isolates
Authors: Panayotopoulou Effrosini G. , Sgouras Dionyssios N. , Papadakos Konstantinos , Kalliaropoulos Antonios , Papatheodoridis George , Mentis Andreas F. , Archimandritis Athanasios J.
Published: December 2006

Cytotoxin-associated gene A (CagA) diversity with regard to EPIYA-A, -B, -C, or -D phosphorylation motifs may play an important role inHelicobacter pyloripathogenesis, and therefore determination of these motifs inH. pyloriclinical isolates can become a useful prognostic tool. We propose a strategy for the accurate determination of CagA EPIYA motifs in clinical strains, based upon one-step PCR amplification using primers that flank the EPIYA coding region. We thus analyzed 135H. pyloriisolates derived from 75 adults and 60 children Greek patients. A total of 34 cases were found to be EPIYA PCR negative and were consequently verified ascagAnegative bycagA-specific PCR, empty-sitecagAPCR, and Western blotting. Sequencing of the remaining 101 PCR-positive amplicons confirmed that an accurate prediction of the number of EPIYA motifs on the basis of size distribution of the PCR products was feasible in all cases. Furthermore, our assay could identify closely relatedH. pylorisubclones within the same patient, harboring different numbers of EPIYA repeats. The prevalence of CagA proteins with three EPIYA motifs (ABC) or four EPIYA motifs (ABCC) was the same within the adult and children groups. However, CagA species with more than four EPIYA motifs were observed exclusively within adults (8.6%), suggesting that CagA-positive strains may acquire additional EPIYA-C motifs throughout adulthood. Our strategy requires no initialcagAscreening of the clinical isolates and can accurately predict the number of EPIYA repeats in single or multiple closely related subclones bearing different numbers of EPIYA motifs in their CagA, which may coexist within the same patient.
Use of Enzyme-Linked Immunosorbent Assay and Dipstick Assay for Detection of
Strongyloides stercoralis
Infection in Humans
Authors: van Doorn H. Rogier , Koelewijn Rob , Hofwegen Henk , Gilis Henk , Wetsteyn Jose C. F. M. , Wismans Pieter J. , Sarfati Claudine , Vervoort Tony , van Gool Tom
Published: December 2006

A homemade enzyme-linked immunosorbent assay (ELISA) (Academic Medical Center ELISA [AMC-ELISA]) and a dipstick assay for the detection of anti-
Strongyloides stercoralis
antibodies in serum were developed and evaluated together with two commercially available ELISAs (IVD-ELISA [IVD Research, Inc.] and Bordier-ELISA [Bordier Affinity Products SA]) for their use in the serodiagnosis of imported strongyloidiasis. Both commercially available ELISAs have not been evaluated previously. The sensitivities of the assays were evaluated using sera from 90 patients with parasitologically proven intestinal strongyloidiasis and from 9 patients with clinical larva currens. The sensitivities of the AMC-ELISA, dipstick assay, IVD-ELISA, and Bordier-ELISA were 93, 91, 89, and 83%, respectively, for intestinal strongyloidiasis. In all tests, eight of nine sera from patients with larva currens were positive. The specificity was assessed using a large serum bank of 220 sera from patients with various parasitic, bacterial, viral, and fungal infectious diseases; sera containing autoimmune antibodies; and sera from healthy blood donors. The specificities of AMC-ELISA, dipstick assay, IVD-ELISA, and Bordier-ELISA were 95.0, 97.7, 97.2, and 97.2%, respectively. Our data suggest that all four assays are sensitive and specific tests for the diagnosis of both intestinal and cutaneous strongyloidiasis.
Human Immunodeficiency Virus (HIV) Antibody Avidity Testing To Identify Recent Infection in Newly Diagnosed HIV Type 1 (HIV-1)-Seropositive Persons Infected with Diverse HIV-1 Subtypes
Authors: Chawla A. , Murphy G. , Donnelly C. , Booth C. L. , Johnson M. , Parry J. V. , Phillips A. , Geretti A. M.
Published: December 2006

A guanidine-based antibody avidity assay for the identification of recently acquired human immunodeficiency virus type 1 (HIV-1) infection was evaluated. The kinetics of maturation of antibody avidity were determined prospectively in 23 persons undergoing acute seroconversion followed for up to 1,075 days. Avidity indices (AI) of ≤0.75 and ≤0.80 reproducibly identified seroconversion within the previous 125 (95% confidence interval [CI], 85 to 164) and 142 (95% CI, 101 to 183) days, respectively. To validate the assay, 432 serum samples from newly diagnosed patients were tested by both the avidity assay and the detuned assay. Results were highly concordant (kappa value for agreement, 0.85). The avidity assay was subsequently used to screen 134 consecutive newly diagnosed patients, including 55/134 (41%) infected with non-B subtypes (A, C, D, G, CRF01, CRF02, CRF06, CRF13, and CRF16). In this cohort, 25/79 (32%) persons with the B subtype and 7/55 (13%) with non-B subtypes showed an AI of ≤0.75, and there were 16/25 (64%) and 3/7 (43%) persons, respectively, with a documented history of acute seroconversion illness within the predicted seroconversion interval. An AI of ≤0.75 was also observed for four patients (three with the B subtype and one with a non-B subtype) who presented with AIDS-defining conditions. In multivariate analysis, an AI of ≤0.75 was associated with younger age, higher HIV-1 plasma RNA load, and being born in the United Kingdom or Ireland rather than in Africa but not with gender, ethnicity, risk group, HIV-1 subtype, or CD4 counts. In conclusion, HIV antibody avidity testing provides a reliable method for identifying recently acquired HIV-1 infection. Results are affected by advanced disease and should therefore be interpreted in the context of other clinical parameters.
Human T-Cell Leukemia Virus Type 1 (HTLV-1) bZIP Protein Interacts with the Cellular Transcription Factor CREB To Inhibit HTLV-1 Transcription
Authors: Lemasson Isabelle , Lewis Matthew R. , Polakowski Nicholas , Hivin Patrick , Cavanagh Marie-Hélène , Thébault Sabine , Barbeau Benoit , Nyborg Jennifer K. , Mesnard Jean-Michel
Published: December 2006

The complex human T-cell leukemia virus type 1 (HTLV-1) retrovirus encodes several proteins that are unique to the virus within its 3′-end region. Among them, the viral transactivator Tax and posttranscriptional regulator Rex are well characterized, and both positively regulate HTLV-1 viral expression. Less is known about the other regulatory proteins encoded in this region of the provirus, including the recently discovered HBZ protein. HBZ has been shown to negatively regulate basal and Tax-dependent HTLV-1 transcription through its ability to interact with specific basic-leucine zipper (bZIP) proteins. In the present study, we found that HBZ reduces HTLV-1 transcription and virion production. We then characterized the interaction between HBZ and the cellular transcription factor CREB. CREB plays a critical role in Tax-mediated HTLV-1 transcription by forming a complex with Tax that binds to viral cyclic AMP-response elements (CREs) located within the viral promoter. We found that HBZ and CREB interact in vivo and directly in vitro, and this interaction occurs through the bZIP domain of each protein. We also found that CREM-Ia and ATF-1, which share significant homology in their bZIP domains with the bZIP domain of CREB, interact with HBZ-bZIP. The interaction between CREB and HBZ prevents CREB binding to the viral CRE elements in vitro and in vivo, suggesting that the reduction in HTLV-1 transcription by HBZ is partly due to the loss of CREB at the promoter. We also found that HBZ displaces CREB from a cellular CRE, suggesting that HBZ may deregulate CREB-dependent cellular gene expression.
Quantitating the Magnitude of the Lymphocytic Choriomeningitis Virus-Specific CD8 T-Cell Response: It Is Even Bigger than We Thought
Authors: Masopust David , Murali-Krishna Kaja , Ahmed Rafi
Published: December 2006

Measuring the magnitudes and specificities of antiviral CD8 T-cell responses is critical for understanding the dynamics and regulation of adaptive immunity. Despite many excellent studies, the accurate measurement of the total CD8 T-cell response directed against a particular infection has been hampered by an incomplete knowledge of all CD8 T-cell epitopes and also by potential contributions of bystander expansion among CD8 T cells of irrelevant specificities. Here, we use several techniques to provide a more complete accounting of the CD8 T-cell response generated upon infection of C57BL/6 mice with lymphocytic choriomeningitis virus (LCMV). Eight days following infection, we found that 85 to 95% of CD8 T cells exhibit an effector phenotype as indicated by granzyme B, 1B11, CD62L, CD11a, and CD127 expression. We demonstrate that CD8 T-cell expansion is due to cells that divide >7 times, whereas heterologous viral infections only elicited <3 divisions among bystander memory CD8 T cells. Furthermore, we found that approximately 80% of CD8 T cells in spleen were specific for ten different LCMV-derived epitopes at the peak of primary infection. These data suggest that following a single LCMV infection, effector CD8 T cells divide ≥15 times and account for at least 80%, and possibly as much as 95%, of the CD8 T-cell pool. Moreover, the response targeted a very broad array of peptide major histocompatibility complexes (MHCs), even though we examined epitopes derived from only two of the four proteins encoded by the LCMV genome and C57BL/6 mice only have two MHC class I alleles. These data illustrate the potential enormity, specificity, and breadth of CD8 T-cell responses to viral infection and demonstrate that bystander activation does not contribute to CD8 T-cell expansion.
Foot-and-Mouth Disease Virus Mutant with Decreased Sensitivity to Ribavirin: Implications for Error Catastrophe
Authors: Sierra Macarena , Airaksinen Antero , González-López Claudia , Agudo Rubén , Arias Armando , Domingo Esteban
Published: December 2006

The nucleoside analogue ribavirin (R) is mutagenic for foot-and-mouth disease virus (FMDV). Passage of FMDV in the presence of increasing concentrations of R resulted in the selection of FMDV with the amino acid substitution M296I in the viral polymerase (3D). Measurements of progeny production and viral fitness with chimeric viruses in the presence and absence of R documented that the 3D substitution M296I conferred on FMDV a selective replicative advantage in the presence of R but not in the absence of R. In polymerization assays, a purified mutant polymerase with I296 showed a decreased capacity to use ribavirin triphosphate as a substrate in the place of GTP and ATP, compared with the wild-type enzyme. The results suggest that M296I has been selected because it attenuates the mutagenic activity of R with FMDV. Replacement M296I is located within a highly conserved stretch in picornaviral polymerases which includes residues that interact with the template-primer complex and probably also with the incoming nucleotide, according to the three-dimensional structure of FMDV 3D. Given that a 3D substitution, distant from M296I, was associated with resistance to R in poliovirus, the results indicate that picornaviral polymerases include different domains that can alter the interaction of the enzyme with mutagenic nucleoside analogues. Implications for lethal mutagenesis are discussed.
Influences of Glycosylation on Antigenicity, Immunogenicity, and Protective Efficacy of Ebola Virus GP DNA Vaccines
Authors: Dowling William , Thompson Elizabeth , Badger Catherine , Mellquist Jenny L. , Garrison Aura R. , Smith Jeffery M. , Paragas Jason , Hogan Robert J. , Schmaljohn Connie
Published: December 2006

The Ebola virus (EBOV) envelope glycoprotein (GP) is the primary target of protective immunity. Mature GP consists of two disulfide-linked subunits, GP1 and membrane-bound GP2. GP is highly glycosylated with both N- and O-linked carbohydrates. We measured the influences of GP glycosylation on antigenicity, immunogenicity, and protection by testing DNA vaccines comprised of GP genes with deleted N-linked glycosylation sites or with deletions in the central hypervariable mucin region. We showed that mutation of one of the two N-linked GP2 glycosylation sites was highly detrimental to the antigenicity and immunogenicity of GP. Our data indicate that this is likely due to the inability of GP2 and GP1 to dimerize at the cell surface and suggest that glycosylation at this site is required for achieving the conformational integrity of GP2 and GP1. In contrast, mutation of two N-linked sites on GP1, which flank previously defined protective antibody epitopes on GP, may enhance immunogenicity, possibly by unmasking epitopes. We further showed that although deleting the mucin region apparently had no effect on antigenicity in vitro, it negatively impacted the elicitation of protective immunity in mice. In addition, we confirmed the presence of previously identified B-cell and T-cell epitopes in GP but show that when analyzed individually none of them were neither absolutely required nor sufficient for protective immunity to EBOV. Finally, we identified other potential regions of GP that may contain relevant antibody or T-cell epitopes.
High-Temperature Superconductivity
Authors: Tanaka Shoji
Published: December 2006

A general review on high-temperature superconductivity was made. After prehistoric view and the process of discovery were stated, the special features of high-temperature superconductors were explained from the materials side and the physical properties side. The present status on applications of high-temperature superconductors were explained on superconducting tapes, electric power cables, magnets for maglev trains, electric motors, superconducting quantum interference device (SQUID) and single flux quantum (SFQ) devices and circuits.
Effect of Additional Oxygen on Formation of Silicon Oxynitride Using Nitrogen Plasma Generated near Atmospheric Pressure
Authors: Hayakawa Ryoma , Nakae Mari , Yoshimura Takeshi , Ashida Atsushi , Fujimura Norifumi , Uehara Tsuyoshi
Published: December 2006

We report that ultrathin silicon nitride films can be fabricated using N2plasma near atmospheric pressure. In this paper, we describe the effect of additional oxygen on the formation of oxynitride films. Silicon oxynitride films were formed at an oxygen flow rate as low as 2.5 mL/min with a nitrogen flow rate of 10 L/min, in which the introduction of such a small amount of additional oxygen into the nitrogen plasma generated near atmospheric pressure enhances the oxidation reaction. X-ray photoemission spectroscopy analysis revealed that with increasing oxygen flow rate, the composition of the oxynitride films changed from Si3N3.5O0.7to Si3N0.8O4.6. Optical emission spectroscopy showed emission peaks attributed to NO-γ transition as well as to the N2second-positive system in the plasma discharge space. Emissions from the NO-γ transition show the dissociation of additional oxygen molecules, and active species such as oxygen atoms as well as NO and N2O molecules were generated by collisions between the N2(A3Σu+) and the O2(X3Σg-) states, resulting in the enhancement of Si oxidation near atmospheric pressure. Leakage current density decreases with increasing in the oxygen concentration. The 2.1-nm-thick silicon oxynitride film composed of Si3N0.8O4.6showed a leakage current density as low as 3.5×10-4A/cm2at 5 MV/cm.
New Cu/Mo/Ge/Pd Ohmic Contacts on Highly Doped n-GaAs for InGaP/GaAs Heterojunction Bipolar Transistors
Authors: Chang Chun-Wei , Hsieh Tung-Ling , Chang Edward Yi
Published: December 2006

The feasibility of using novel Cu/Mo/Ge/Pd ohmic contacts on n+-GaAs for heterojunction bipolar transistors (HBTs) is investigated. The electrical and material characteristics of the Cu/Mo/Ge/Pd/n+-GaAs structure were studied. After thermal annealing at 350 °C, the specific contact resistances of the copper ohmic contacts Cu/Mo/Ge/Pd were measured to be 2.8×10-7 Ω cm2. Judging from the data of sheet resistance, X-ray diffraction analysis, Auger electron spectroscopy, and transmission electron microscopy, the Cu/Mo/Ge/Pd contact structure was very stable after annealing at 350 °C. However, after 400 °C annealing, the reaction of copper with the underneath layers started to occur and formed MoGe2, Cu3Ga and Ge3Cu phases. An InGaP/GaAs HBT with Cu/Mo/Ge/Pd contact metals was fabricated and compared with an HBT fabricated with traditional Au/Ni/Ge/Au contact metals. These two kinds of HBTs showed similar device characteristics. After reaching thermal stability and performing a high current-accelerated stress test at a current density of 120 kA/cm2 for 24 h, the device with the Cu/Mo/Ge/Pd ohmic contacts still exhibits excellent electrical characteristics.
Analysis of Low Metallic Contamination on Silicon Wafer Surfaces by Vapor-Phase Treatment and Total Reflection X-ray Fluorescence Analysis
Authors: Shimazaki Ayako , Miyazaki Kunihiro , Matsumura Tsuyoshi , Ito Shoko
Published: December 2006

We have developed a new practical method for quantifying metallic contaminants with concentrations as low as 109 atoms/cm2 on silicon wafer surfaces. It is named “VPT-TXRF” and uses vapor-phase treatment (VPT) with a total reflection X-ray fluorescence analysis (TXRF) system. VPT can change the form of metallic impurities on the surface from thin-film type to particulate type and thus the detected X-ray intensity is increased because of the inherent nature of TXRF, namely, the angular dependence of fluorescence yield. By this method, high sensitivity was achieved within a practical measuring time of 500 s, while maintaining the original surface contamination distribution of the wafers. We are convinced that this method will become the most useful monitoring method for the critical process contamination of the future ultra-large-scale-integration (ULSI) manufacturing line.
Mechanism for Fermi Level Pinning at Electrode/Hf-Based Dielectric Interface: Systematic Study of Dependence of Effective Work Functions for Polycrystalline Silicon and Fully Silicided NiSi Electrodes on Hf Density at Interface
Authors: Manabe Kenzo , Hase Takashi , Tatsumi Toru , Watanabe Heiji , Yasutake Kiyoshi
Published: December 2006

We systematically investigated the dependence of the effective work functions (Φeff) for polycrystalline silicon (poly-Si) and fully silicided NiSi electrodes on Hf density at the electrode/dielectric interface in terms of Fermi level pinning (FLP). We found that the Φeff values agree with the values calculated using the interface gap states model with an extrinsic contribution, assuming that the interface gap state density is proportional to the product of Hf density in the dielectric and Si density in the electrode at the electrode/dielectric interface. On the basis of our results, we discuss the origins of FLP at the electrode/Hf-based dielectric interface.
Reduction in Escape Times of Photogenerated Charge Carriers with Asymmetric Intrastep Quantum Wells and Subsequent Improvement in Saturation Optical Intensity
Authors: Shin Dong-Soo
Published: December 2006

Escape times of photogenerated charge carriers from an InGaAsP intrastep quantum well (IQW) are calculated and compared with those from a conventional quantum well (QW). Since the red shift of the IQW is initiated at a higher electric field, the escape times from the IQW are smaller than those from the conventional QW at given values in modulator transmission. From the reduction in escape times, improvements in the exciton saturation intensity are estimated to be a factor of ∼5 for both high and low modulator-transmission points.
High-Performance Polycrystalline Silicon Thin-Film Transistors with Low Trap Density at the Gate-SiO2/Si Interface Fabricated by Low-Temperature Process
Authors: Abe Daisuke , Inoue Satoshi , Shimoda Tatsuya
Published: December 2006

High-performance polycrystalline silicon thin-film transistors with a low trap density at the gate-SiO2/Si interface have been developed using a low-temperature process. It was found that high-performance thin-film transistors with a very low subthreshold swing could be achieved by applying postmetallization annealing at the end of the transistor fabrication. The subthreshold swing and electron mobility of the transistors were 143 mV/dec and 262 cm2 V-1 s-1, respectively, when the thickness of the gate-SiO2 was 114 nm. The ability to fabricate such high-performance thin-film transistors on a glass substrate will be very useful for realizing system-on-panel devices.
Characteristics of Single-Mode InGaAs Submonolayer Quantum-Dot Photonic-Crystal Vertical-Cavity Surface-Emitting Lasers
Authors: Yang Hung-Pin D. , Hsu I-Chen , Lai Fang-I , Lin Gray , Hsiao Ru-Shang , Maleev Nikolai A. , Blokhin Sergej A. , Kuo Hao-Chung , Chi Jim Y.
Published: December 2006

An InGaAs submonolayer (SML) quantum-dot photonic-crystal vertical-cavity surface-emitting laser (QD PhC-VCSEL) for fiber-optic applications is demonstrated for the first time. The active region of the device contains three InGaAs SML QD layers. Each of the InGaAs SML QD layers is formed by alternate depositions of InAs (<1 ML) and GaAs. A single-fundamental-mode CW output power of 3.8 mW at 28 mA has been achieved in the 990 nm range, with a threshold current of 0.9 mA. A side-mode suppression ratio (SMSR) larger than 35 dB has been demonstrated over the entire current operation range. The beam profile and near-field image study of the PhC-VCSEL indicates that the laser beam is well confined by the photonic crystal structure of the device.
Effect of Boric Acid Flux and Drying Control Chemical Additive on the Characteristics of Y2O3:Eu Phosphor Particles Prepared by Spray Pyrolysis
Authors: Koo Hye Young , Ju Seo Hee , Hong Seung Kwon , Jung Dae Soo , Kang Yun Chan , Jung Kyeong Youl
Published: December 2006

Y2O3:Eu phosphor particles with a spherical shape, a fine size, and high brightness under vacuum ultraviolet (VUV) illumination were prepared by spray pyrolysis. The polymeric precursors were needed to modify the spray solution to prepare spherical particles. The use of only flux with the polymeric precursors did not produce dense and spherical Y2O3:Eu particles; that is, the produced particles were very porous. The addition of both a drying control chemical additive (DCCA) and boric acid to a spray solution containing polymeric precursors was found to produce Y2O3:Eu phosphor particles with a dense structure while maintaining the spherical morphology. According to X-ray diffraction (XRD) analysis, the DCCA induced an enhancement of crystallinity. The use of boric acid flux improved the photoluminescence (PL) intensity under VUV illumination. In addition, the use of both boric acid flux and a DCCA with polymeric precursors further improved the PL intensity owing to the enhancement of the morphology and the crystallinity.
Micromachined Silicon Submount for Optical Communication Devices
Authors: Ishii Yorishige , Matsuo Toshihisa , Fujita Hideaki , Iwaki Tetsuo , Sekimoto Yoshihiro , Kurata Yukio
Published: December 2006

In this paper, we report the development of a new surface mount structure for optical communication devices using micro-electro-mechanical system (MEMS) technologies. We have designed and fabricated a silicon submount by wet anisotropic micromachining techniques. We have surveyed the main design parameters of this submount as an example against optical and thermal effects by computer simulations and experiments. We have mounted a light-emitting diode (LED) for plastic optical fiber (POF)-based optical communication systems on the silicon submount and evaluated the optical and thermal properties of this submount, indicating that the radiation half width at full maximum (HWFM) angle of the LED decreased from 60 to 40°. Additionally, we have observed a 60% reduction in the thermal resistance of the LED while keeping its thermal reliability.
Effect of Palladium Overlayer on Samarium Hydride Thin Film Switchable Mirror: Electrochemical and Topographical Study
Authors: Kumar Pushpendra , Malhotra Lalit Kumar
Published: December 2006

Samarium films with a typical thickness of 55 nm deposited by vacuum evaporation and covered with Pd overlayers with thicknesses of 5, 8, 11, and 15 nm were loaded with hydrogen and deloaded in a 1 M KOH solution galvanostatically at room temperature. Our study showed that palladium overlayer thickness plays the most crucial role in observing the fast transition between an as-deposited metallic state and a semiconducting nearly samarium trihydride state as well as in obtaining a very high optical contrast. The desorption of hydrogen from palladium-capped SmH3-δ films was studied by in situ transmission measurement during the electrochemical loading/unloading of hydrogen. It was shown that palladium cap layer thickness affects the deloading of hydrogen from the hydrided films. The effect of a palladium overlayer on the surface morphology of metallic and hydrogen-desorbed samarium films showed the sequence of nucleation and growth.
Apodization Method Owing to the Finite Length of UV Laser Coherence in Fabricating Fiber Bragg Gratings
Authors: Suzaki Yoshifumi , Iwata Hiromu , Nakayama Keisuke , Mizutami Yasuo , Yamauchi Makoto , Izumikawa Eiji , Yokouchi Takashi , Ejima Seiki
Published: December 2006

A very effective apodization, in which side lobes are suppressed to below a particular noise level, is found to operate automatically in a two-beam interference device for fabricating fiber Bragg gratings when a pair of mirrors deflecting two beams are off parallel to each other. This is considered to be a consequence of the short temporal coherence length of the KrF excimer laser used.