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In this article, a new type of metal–insulator–semiconductor (MIS) tunnel diode (TD), trench MIS TD, was investigated. From the current–voltage characteristics, memory retention, and memory endurance measurements, we found that the trench MIS TDs not only have lower reverse bias current, but also show stronger transient current compared to traditional planar structure MIS TDs. For example, in the 1000-cycle memory endurance test, we observed a 25 times larger current window (CW) in trench devices than the CW of planar devices. We attribute the lower reverse bias current to the fewer minority carriers (electrons) in trench MIS TDs, which is supported by the high-frequency capacitance–voltage ( C–V ) measurement. As for the enhanced transient behavior of trench MIS TDs, we proposed a mechanism based on the understanding of fewer minority carriers in trench devices to explain our observation. Eventually, we examined the effect of different equivalent oxide thicknesses (EOTs) on the CW and found that the trench devices have better CW in a wide EOT range. Because of the enhanced transient behavior leading to better memory CW, trench MIS TDs have the potential to serve as memory devices.

BACKGROUND Intestinal barrier breakdown, a frequent complication of intestinal ischemia-reperfusion (I/R) including dysfunction and the structure changes of the intestine, is characterized by a loss of tight junction and enhanced permeability of the intestinal barrier and increased mortality. To develop effective and novel therapeutics is important for the improvement of outcome of patients with intestinal barrier deterioration. Recombinant human angiopoietin-like protein 4 (rhANGPTL4) is reported to protect the blood-brain barrier when administered exogenously, and endogenous ANGPTL4 deficiency deteriorates radiation-induced intestinal injury. AIM To identify whether rhANGPTL4 may protect intestinal barrier breakdown induced by I/R. METHODS Intestinal I/R injury was elicited through clamping the superior mesenteric artery for 60 min followed by 240 min reperfusion. Intestinal epithelial (Caco-2) cells and human umbilical vein endothelial cells were challenged by hypoxia/ reoxygenation to mimic I/R in vitro. RESULTS Indicators including fluorescein isothiocyanate-conjugated dextran (4 kilodaltons; FD-4) clearance, ratio of phosphorylated myosin light chain/total myosin light chain, myosin light chain kinase and loss of zonula occludens-1, claudin-2 and VE-cadherin were significantly increased after intestinal I/R or cell hypoxia/reoxygenation. rhANGPTL4 treatment significantly reversed these indicators, which were associated with inhibiting the inflammatory and oxidative cascade, excessive activation of cellular autophagy and apoptosis and improvement of survival rate. Similar results were observed in vitro when cells were challenged by hypoxia/reoxygenation, whereas rhANGPTL4 reversed the indicators close to normal level in Caco-2 cells and human umbilical vein endothelial cells significantly. CONCLUSION rhANGPTL4 can function as a protective agent against intestinal injury induced by intestinal I/R and improve survival via maintenance of intestinal barrier structure and functions.

Fibrotic diseases cause annually more than 800,000 deaths worldwide, where of the majority accounts for cardiovascular fibrosis, which is characterized by endothelial dysfunction, myocardial stiffening and reduced dispensability. MicroRNAs (miRs), small noncoding RNAs, play critical roles in cardiovascular dysfunction and related disorders. Intriguingly, there is a critical link among miR-122, cardiovascular fibrosis, sirtuin 6 (SIRT6) and angiotensin-converting enzyme 2 (ACE2), which was recently identified as a coreceptor for SARS-CoV2 and a negative regulator of the rennin-angiotensin system. MiR-122 overexpression appears to exacerbate the angiotensin II-mediated loss of autophagy and increased inflammation, apoptosis, extracellular matrix deposition, cardiovascular fibrosis and dysfunction by modulating the SIRT6-Elabela-ACE2, LGR4-β-catenin, TGFβ-CTGF and PTEN-PI3K-Akt signaling pathways. More importantly, the inhibition of miR-122 has proautophagic, antioxidant, anti-inflammatory, anti-apoptotic and antifibrotic effects. Clinical and experimental studies clearly demonstrate that miR-122 functions as a crucial hallmark of fibrogenesis, cardiovascular injury and dysfunction. Additionally, the miR-122 level is related to the severity of hypertension, atherosclerosis, atrial fibrillation, acute myocardial infarction and heart failure, and miR-122 expression is a risk factor for these diseases. The miR-122 level has emerged as an early-warning biomarker cardiovascular fibrosis, and targeting miR-122 is a novel therapeutic approach against progression of cardiovascular dysfunction. Therefore, an increased understanding of the cardiovascular roles of miR-122 will help the development of effective interventions. This review summarizes the biogenesis of miR-122; regulatory effects and underlying mechanisms of miR-122 on cardiovascular fibrosis and related diseases; and its function as a potential specific biomarker for cardiovascular dysfunction.

This paper proposes a deep learning-based intelligent anti-collision system, which can avoid an accident caused by the improper opening of the car door. The proposed system consists of an intelligent rearview mirror, an on-board diagnostics-II (OBD-II) bridge, and an in-vehicle infotainment (IVI) platform. The proposed system can recognize the rear approaching motorcycles and prevent the car from opening the car door improperly to avoid a collision accident between a motorcycle and the car door.

A deep learning-based intelligent scalp diagnosis system will be demonstrated. This live demonstration system is composed of a scalp detector, a mobile device app, an AI computing server, and a cloud-based service platform. During the live demonstration, this system can inference five scalp symptoms based on deep-learning technology for helping the treatment of hair salon or therapy services to achieve the purpose of scalp healthcare.

In this article a comparison study of the numerical methods for compressible two-phase flows is presented. Although many numerical methods have been developed in recent years to deal with the jump conditions at the fluid-fluid interfaces in compressible multiphase flows, there is a lack of a detailed comparison of these methods. With this regard, the transport five equation model, the modified ghost fluid method and the cut-cell method are investigated here as the typical methods in this field. A variety of numerical experiments are conducted to examine their performance in simulating inviscid compressible two-phase flows. Numerical experiments include Richtmyer-Meshkov instability, interaction between a shock and a rectangle SF6 bubble, Rayleigh collapse of a cylindrical gas bubble in water and shock-induced bubble collapse, involving fluids with small or large density difference. Based on the numerical results, the performance of the method is assessed by the convergence order of the method with respect to interface position, mass conservation, interface resolution and computational efficiency.

We develop a robust cut-cell method for numerical simulation of compressible two-phase flows with topology change of the fluid-fluid interface. In cut cell methods the flows can be solved in the finite volume framework and the jump conditions at the interface are resolved by solving a local Riemann problem. Therefore, cut cell methods can obtain interface evolution with high resolution, and at the same time satisfactorily maintain the conservation of flow quantities. However, it remains a challenge for the cut cell methods to handle interfaces with topology change or very high curvature, where the mesh is not sufficiently fine to resolve the interface. Inappropriate treatment could give rise to either distorted interface advection or unphysical oscillation of flow variables, especially when the regularization process (e.g. reinitialization in the level set methods) is implemented. A robust cut-cell method is proposed here, with the interface being tracked by a level set function. The local unphysical oscillation of flow variables in the presence of topology change is shown to be greatly suppressed by using a delayed reinitialization. The method can achieve second-order accuracy with respect to the interface position in the absence of topology changes of interface, while locally degrading to first-order at the interface region where topology change occurs. Its performance is examined through a variety of numerical tests, such as Rayleigh collapse, shock-bubble interaction, and shock-induced bubble collapse in water. Numerical results are compared against either benchmark solutions or experimental observations, and good agreement has been achieved qualitatively and/or quantitatively. Finally, we apply the method to investigating the collapse process of two tandem bubbles in water.

In this study, we propose a novel speech enhancement scenario that applies a low-pass filter to the spectrogram of a noise-corrupted signal along the temporal axis. According to our recently developed method, modulation-domain wavelet denoising (ModWD), the speech quality of noisy utterances can be promoted by alleviating the temporal-domain detail component of the respective spectrogram created by discrete wavelet transform (DWT), which implies the high (modulation) frequency part has little to do with speech quality and is relatively vulnerable to noise. For this reason, this study presents employing the conventional low-pass filter structure, including a moving-average (MV) filter and a median filter, to diminish the aforementioned high modulation frequency components in noise- corrupted spectrogram to see whether the speech quality can be improved. The preliminary experiments conducted on a subset of the Aurora-2 connected digit database show that the presented scenario can provide noisy signals with moderate improvement in speech quality, and the corresponding results are superior to those obtained by ModWD.

In this study, we investigate and extend the capability of the method of modulation-domain wavelet denoising (ModWD) in speech enhancement primarily analyzing the unequal importance of different sub-band signals. The recently developed ModWD is shown to improve the speech quality in adverse noise environment by processing the magnitude spectrogram of a noisy speech signal with a one-level discrete wavelet transform (DWT) and then alleviating the obtained detailed portion, which is shown more vulnerable to noise. This study follows the idea of ModWD and use a wavelet packet decomposition (WPD) to decompose the magnitude spectral time series into four sub-band sequences at first. Then any of these four subband sequences is zeroed out while the other three ones are kept unchanged. Finally, these four sub-band sequences are used to construct the updated spectrogram. The main purpose of the aforementioned procedure is to evaluate the noise-robust capability of the magnitude series at different sub-bands which possess twice (modulation) frequency resolution compared with those used in ModWD. The presented method is conducted on a subset of the Aurora-2 connected digit database, and the speech quality evaluation results in terms of Perceptual Evaluation of Speech Quality (PESQ) scores reveal that diminishing the second highest frequency band (roughly within the range [25 Hz, 37.5 Hz]) gives rise to the optimal performance.

This study was designed to investigate the relationship between prognosis of pancreatic head cancer and status of para‐aortic lymph node (PALN). A total of 233 patients with pancreatic head cancer who underwent surgical resection between February 2008 and October 2015 were enrolled in this study. Univariate and multivariate analyses were used to reveal the prognostic factors. Prognostic factors for patients with and without metastasis of PALN were analyzed, respectively. The 5‐year overall survival (OS) rate was 19.0% for all patients, and the positive rate of PALN metastasis was 18.9% (44/233). The 1‐, 2‐, 3‐, and 5‐year OS rates in patients without metastasis of PALN were 79.4%, 54.8%, 36.4%, and 22.9%, respectively, whereas the 1‐, 2‐, and 3‐year survival rates were 54.0%, 14.8%, and 0%, respectively, in patients with metastasis of PALN. Preoperative CA19‐9 level, tumor size, T status, N status, and adjuvant therapy were independent prognostic factors for all patients confirmed by multivariate analysis. For patients without PALN metastasis, back pain, tumor size, T status, N status, portal or superior mesenteric vein invasion, and adjuvant therapy were independent prognostic factors, while the only one influence factor for 2‐year OS was adjuvant therapy for patients with metastasis of PALN. Metastasis of PALN was associated with poor prognosis for patients with pancreatic head cancer. Patients with and without metastasis of PALN had different prognostic factors, and adjuvant therapy was the only prognostic factor for patients with metastasis of PALN.

To develop the numerical control program of mill-turn machine, the traditional method is to apply the computer-aided design and manufacture software to construct the geometric model, then to generate tool path and convert the path to NC program. For complex numerical control program of mill-turn machine, such as the multiple turret synchronized motion machining, because of the need to control time sequence, the NC program is highly required on using of dedicated software system. The objective of this paper is to establish a mill-turn machining system with window interface of via the language of Borland C++ Builder. The developed system can plan the machining path of simple mill-turn features, including turning shape, axial slot milling, and radial packet milling, and generate the corresponding NC program. For the milling functions, after the offset coordinates are calculated along the polygonal angle vector in the center point of cutters, the NC program is generated. For the turning functions, through importing the 2D DXF (Drawing Exchange Format) file and inputting related configurations, the entity coordinates can be retrieved and the corresponding NC program is then converted. By means of the solid cutting simulation software and practical cutting experiment for the generated numerical control program, the accuracy of the tool path generation algorithm is confirmed. Hence, the cost of purchasing commercial software can be saved and the time of generating program can also be decreased so that the working efficiency can be enhanced.

Huntington's disease (HD) is a genetic and neurodegenerative disease, leading to motor and cognitive dysfunction in HD patients. At cellular level, this disease is caused by the accumulation of mutant huntingtin (HTT) in different cells, and finally results in the dysfunction of different cells. To clean these mutant proteins, ubiquitin-proteasome system (UPS) and autophagy system are two critical pathways in the brain; however, little is known in other peripheral tissues. As mutant HTT affects different tissues progressively and might influence the UPS and autophagy pathways at early stages, we attempted to examine two clearance systems in HD models before the onset. Here, in vitro results showed that the accumulation of UPS signals with time was observed obviously in neuroblastoma and kidney cells, not in other cells. In HD transgenic mice, we observed the impairment of UPS, but not autophagy, over time in the cortex and striatum. In heart and muscle tissues, disturbance of autophagy was observed, whereas dysfunction of UPS was displayed in liver and lung. These results suggest that two protein clearance pathways are disturbed differentially in different tissues before the onset of HD, and enhancement of protein clearance at early stages might provide a potential stratagem to alleviate the progression of HD.

Chlorinated solvents such as tetrachloroethylene (PCE) in aquifers should be remediated due to their toxicity that limited the use of groundwater resources. Nanoscale zero-valent iron (NZVI) and palladized/iron (Pd/Fe) bimetallic particles were synthesized and employed to react with PCE in water to investigate its degradation behaviors. Batch tests were conducted in a 1 L serum bottle under airtight and anaerobic conditions with parameters of Pd mass contents, temperature, pH, and dispersant. The results showed that specific reaction rate constants (kSA) of 5 mg L−1 PCE degraded by metal particles at 30°C in the absence of dispersant enhanced with higher Pd mass contents on the Pd/Fe particles. Degradation rates of PCE increased as the reaction temperature was raised from 20 to 40°C. Carboxymethyl cellulose (CMC), a dispersant, enhanced the kSA values of NZVI and 1:100 Pd/Fe particles by a factor of about 33 and 4 at 30°C, respectively. The tests of pH control with buffer solution indicated that P...

Astaxanthin is a natural carotenoid with strong antioxidant activity that has been used for decades as a nutrient/color additive and it has recently been marketed as a health supplement. Astaxanthin can be synthesized in a wide range of microalgae, yeast, and bacteria. As genes directing astaxanthin biosynthesis in various organisms have been cloned, this study assessed the safety of astaxanthin crystal produced by Escherichia coli K-12 harboring plasmids carrying astaxanthin biosynthetic genes. The astaxanthin crystal contains a total carotenoid content of 950 mg/g and an astaxanthin content of 795 mg/g. Subchronic oral toxicity and prenatal developmental toxicity of the astaxanthin in rats were conducted in accordance with the Guidelines of Health Food Safety Assessment promulgated by Food and Drug Administration of Taiwan which is based on OECD guidelines 408 and 414. Both male and female Sprague-Dawley (SD) rats (12 for each gender) receiving the astaxanthin crystal at 1.2, 240.0, or 750.0 mg/kg/day in olive oil via oral gavage for 90 days showed no changes in body weight gains, hematology and serum chemistry values and hepatic enzyme stability, organ integrity and organ weight. Except the higher food consumption observed in rats receiving 750.0 mg/g astaxanthin crystal, administration of the astaxanthin crystal to 25-27 pregnant female rats in each group throughout the period of organogenesis (G6-G15) produced no adverse effects on fetal organogenesis. Based on the results, we propose that the no-observable-adverse-effect level (NOAEL) of the astaxanthin crystal extracted from genetically modified E. coli K-12 is 750.0 mg/kg bw/day.

The object of this study is to stabilize spent alkaline batteries and to recover useful metals. A blend of dolomite, limestone, and cullet was added to act as a reductant and a glass matrix former in vitrification. Specimens were vitrified using an electrical heating furnace at 1400 °C and the output products included slag, ingot, flue gas, and fly ash. The major constituents of the slag were Ca, Mn, and Si, and the results of the toxicity leaching characteristics met the standards in Taiwan. The ingot was a good material for use in production of stainless steel, due to being mainly composed of Fe and Mn. For the fly ash, the high level of Zn makes it economical to recover. The distribution of metals indicated that most of Co, Cr, Cu, Fe, Mn, and Ni moved to the ingot, while Al, Ca, Mg, and Si stayed in the slag; Hg vaporized as gas phase into the flue gas; and Cd, Pb, and Zn were predominately in the fly ash. Recovery efficiency for Fe and Zn was >90% and the results show that vitrification is a promising technology for reclaiming spent alkaline batteries.

The immunogenicity of HLA-A*0201-restricted cytotoxic T lymphocyte (CTL) peptide in severe acute respiratory syndrome coronavirus (SARS-CoV) nuclear capsid (N) and spike (S) proteins was determined by testing the proteins' ability to elicit a specific cellular immune response after immunization of HLA-A2.1 transgenic mice and in vitro vaccination of HLA-A2.1 positive human peripheral blood mononuclearcytes (PBMCs). First, we screened SARS N and S amino acid sequences for allele-specific motif matching those in human HLA-A2.1 MHC-I molecules. From HLA peptide binding predictions (http://thr.cit.nih.gov/molbio/hla_bind/), ten each potential N- and S-specific HLA-A2.1-binding peptides were synthesized. The high affinity HLA-A2.1 peptides were validated by T2-cell stabilization assays, with immunogenicity assays revealing peptides N223-231, N227-235, and N317-325 to be the first identified HLA-A*0201-restricted CTL epitopes of SARS-CoV N protein. In addition, previous reports identified three HLA-A*0201-restricted CTL epitopes of S protein (S978-986, S1203-1211, and S1167-1175), here we found two novel peptides S787-795 and S1042-1050 as S-specific CTL epitopes. Moreover, our identified N317-325 and S1042-1050 CTL epitopes could induce recall responses when IFN-gamma stimulation of blood CD8+ T-cells revealed significant difference between normal healthy donors and SARS-recovered patients after those PBMCs were in vitro vaccinated with their cognate antigen. Our results would provide a new insight into the development of therapeutic vaccine in SARS.

A harmonic of a periodic complex tone can be heard out as a separate entity if the harmonic is slightly mistuned from its correct frequency. Pitch matching experiments show that the pitch of such a mistuned harmonic differs systematically from its frequency. The shift in pitch is found to be an exaggeration of the frequency mistuning. This article considers two classes of model for the pitch shift. In the first class are tonotopically local interaction models which attribute the pitch shift to interactions between the mistuned harmonic and neighboring harmonics, where the neighborhood is established by peripheral filtering. The second class of model attributes the pitch shift to a contrast between the mistuned harmonic and a broadband harmonic template. This article describes six pitch matching experiments using complex tones having spectral gaps, strategically chosen to compare local interaction and template models. The results show that when a competition is set up between local interactions and a template, the template proves to be dominant. A parallel between the pitch shifts of mistuned harmonics and periodicity pitch, also attributed to a harmonic template, is seen as the frequency range of the mistuned harmonic is changed. Tonotopically local influences are evident in several experiments, but they are of secondary importance.

An effect discovered by Duifhuis [J. Acoust. Soc. Am. 48, 888-893 (1970)], wherein an omitted high harmonic of a periodic complex tone is found to have an audible pitch, is extended to a variety of new broadband signal conditions. The effect is found to exist for flat spectra and spectra decreasing at 6 dB/octave, independent of phases as long as they are constant. The effect exists for alternating phases and Schroeder phases. It can generate a missing-fundamental pitch. Pitch and loudness matching experiments support the status of the omitted harmonic as an objective tone in the signal. Further experiments using narrower bands challenge the traditional explanation for the effect, which attributes it to short-term frequency analysis by peripheral auditory filters. Instead, the experiments suggest that different peripheral channels must be combined, maintaining some phase information, to generate the effect.

A simple and powerful method of designing entropy constrained scalar quantizer is presented in this paper. The method is based upon numerical minimization of the distortion function D instead of solving non-linear equations. Compared to the existing algorithms, this algorithm can be used to a variety of distribution functions including real world statistically found ones, and it converges very fast.

The chimes of contemporary 7‐foot grandfather clocks are made from steel rods, tapered at their clamped ends so that modal frequencies are stretched compared to thin‐rod theory. Melody rods, 39–56 cm in length, lead to matchable pitches, nominally in the octave from 220 to 440 Hz. Hour‐strike rods, 59 and 67 cm in length, produce pitches that are less stable. Chime tones were digitally synthesized according to both measured and idealized frequencies, amplitudes, and decay rates. Pitch matching results were compared with the pitch model of Terhardt et al. [J. Acoust. Soc. Am. 71, 679–688 (1982)]. Both experiment and model show competition between spectral and virtual pitch and between cues at the nominal strike tone and the minor third. Generally the experiment finds the range of virtual pitch to be higher than predicted by the model. [Research supported by the Sligh Clock Company, Zeeland, Michigan, by the NIDCD, and by the NSF Research Participation for Undergraduates Program.]

If a single harmonic of a complex tone is mistuned it can be heard as a separate entity. Pitch matching experiments show that the pitch of a mistuned harmonic does not agree with its frequency. The shift in pitch, caused by the complex context, is an exaggeration of the frequency mistuning. The differential pitch shift, for positive versus negative mistuning, is called the ‘‘split.’’ Splits for complex tones with simple spectra were measured by Hartmann and Smith [J. Acoust. Soc. Am. Suppl. 1 85, S109 (1989)]. Experiments reported here, measure splits for complex tones having spectral gaps and other anomalies. Experiments show that splits depend upon partial masking: Components below the mistuned harmonic create large splits; splits increase with increasing stimulus level. Experiments show that splits also depend upon the overall periodicity of the complex: Splits are larger for mistuned harmonics than for nonharmonic interstitials, given identical local spectral environments. Splits are larger for mistuned harmonics with low harmonic number or low fundamental frequency. These observations require revision of the neural timing model for the pitches of mistuned harmonics. [Work supported by the NIDCD, DC00181.]

In budgerigars, as in humans, the detection of amplitude modulation (AM) remains relatively constant as modulation frequency increases while detection of frequency modulation (FM) improves. The point at which FM and AM are equal defines the critical modulation frequency (CMF). The CMF is approximately half the size of the critical band in humans because phase information is lost outside the critical band. At small modulation indices, the power spectrum of FM is almost identical to the power spectrum of AM with the difference being the relative phase of the components. The power spectrum of quasifreqeuncy modulation (QFM) is exactly the same as AM even at high‐modulation indices. In this experiment, two budgerigars were trained by operant conditioning to detect AM, FM, and QFM at several modulation rates at three carrier frequencies. Budgerigars show nearly identical thresholds for detecting modulation in FM and QFM tones at low‐modulation rates and similar thresholds for detecting modulation in FM, AM, an...

Estimates of the filter bandwidths in the avian auditory system have traditionally come from either single‐unit tuning curves or psychophysical masking studies using broad (critical ratio) or narrow (critical band) noises—procedures that are known to have certain limitations. The experiment reported here used the notched‐noise method for determining the size and shape of the auditory filter at 2.86 kHz—the center of the budgerigar’s range of hearing. Three budgerigars were trained by operant conditioning to detect a pure tone in a background of continuous noise and tested daily until thresholds stabilized. Masked thresholds were then obtained for noises of eleven different notch widths (five symmetric, six asymmetric) surrounding 2.86 kHz. Relative equivalent rectangular bandwidths were evaluated using several procedures and these bandwidths were compared to other estimates of filter bandwidths in the budgerigar auditory system from critical ratios, directly measured critical bands, critical modulation fr...

‘‘Anomaly pitches’’ are tonal sensations caused by anomalies in the spectrum of a low‐frequency periodic wave, for example, by a missing harmonic [Duifhuis, J. Acoust. Soc. Am. 48, 888 (1970)]. They are immediately heard in the steady state and do not require any reference signal. This paper reports anomaly pitches for both missing harmonics and inverted harmonics. They occur in pulse waves (for any constant phase), in sawtooth waves, in waves with alternating sine and cosine phases, and in waves with Schroeder phase. With a series of missing upper harmonics it is possible to make a virtual anomaly pitch with a missing fundamental. The observations can be compared with the original explanation of the effect by Duifhuis based upon detection of the anomalous harmonic during gaps. Some of the conditions press this explanation to the limit but none has proved fatal. [Research supported by the NIDCD of the NIH.]

A plausible model represents the sensation of roughness as the product of three factors, a speed factor that increases with increasing modulation rate, a temporal modulation transfer function (TMTF), and a spectral window that is determined by auditory filter widths. At high signal frequency, where critical bands are broad, the TMTF is the controlling factor. At low signal frequency the auditory filters dominate. Therefore, roughness experiments can serve to measure the critical bandwidth at low frequency. To implement this idea, listeners adjusted both the modulation rate for AM signals and the beat rate of beating sine pairs in order to achieve maximum roughness. The center frequency varied from 2000 to 70 Hz, and SPLs were 60 and 80 dB. The data could be fitted with a model in which roughness is summed over all auditory filters. The data require the critical bandwidth parameter to continue to decrease with decreasing frequency below 500 Hz so that it becomes considerably narrower than critical bands fr...