Synergistic Activation of Inert Iron Oxide Basal Planes through Heterostructure Formation and Doping for Efficient Hydrogen Evolution.

Iron oxides have emerged as a very promising and cost-effective alternative to precious metal catalysts for hydrogen production. However, the inert basal plane of iron oxides needs to be activated to enhance their catalytic efficiency. In this study, we employed heterostructure engineering and doped nickel to cooperatively activate the basal planes of iron oxide (Ni-Fe2 O3 /CeO2 HSs) to achieve high hydrogen evolution reaction (HER) activity. The Ni-Fe2 O3 /CeO2 HSs electrocatalyst demonstrates excellent basic HER activity and stability, such as an extremely low overpotential of 43 mV at 10 mA cm-2 current density and corresponding Tafel slope of 58.6 mV dec-1 . The increase in electrocatalyst activity and acceleration of hydrogen precipitation kinetics arises from the dual modulation of Ni doping and heterostructure, which not only modulates the electrocatalyst's electronic structure, but also increases the number and exposure of active sites. Remarkably, the generation of heterogeneous structure makes the catalyst se. The Ni-doped catalyst has not only increased HER activity but also low-temperature resistance. These results suggest that the synergistic activation of inert iron oxide basal planes through heterostructure formation and doping is a feasible strategy. Furthermore, for efficient electrocatalytic water splitting, this technique can be extended to other non-noble metal oxides.

Linolenic Acid-Metronidazole: a Compound Relieving Drug Resistance and Inhibiting Helicobacter pylori.

Metronidazole (Met) is the first choice for treating Helicobacter pylori (Hp). However, Hp is easy to resistant, making Met unable to be widely used. How to overcome Hp's Met resistance is still an issue. In this study, Met was used as the primary raw material with linolenic acid to prepare a novel compound-linolenic acid-metronidazole (Lla-Met). The MIC, minimum bactericidal concentration (MBC), colonization amount of Hp in gastric mucosa, etc., were evaluated, respectively. Lla-Met was successfully prepared by the detection of nuclear magnetic resonance, etc., and its MIC and MBC to Hp were 2~4 µg/mL, 8~16 µg/mL. Moreover, in vivo experiments, Lla-Met significantly reduced the colonization of drug-resistant Hp in gastric mucosa. In the toxicity test, Lla-Met inhibited rate to GES-1 and BGC823 cells were 15% at 128 µg/mL; the mice were administered 10 times treatment Lla-Met treatment (240 mg/kg), have no difference significant injuries were found in their stomach, liver, spleen, kidney, and weight. In addition, Hp G27 continued for 18 days in vitro with sub-Lla-Met concentration, G27 did not show drug resistance to Lla-Met; Lla-Met did not exert an effect on non-Hp species with 128 µg/mL; Compared with a neutral environment, when the acid concentration is 3.0, Lla-Met is not decomposed and has better stability. Conclusion: Lla-Met, a newly prepared compound, has relatively well antibacterial of Met-resistant and sensitive Hp, with a capability of overcoming the metronidazole resistance of Hp.

Three-Dimensional Finite Element Modeling of Blast Wave Transmission From the External Ear to a Spiral Cochlea.

Blast-induced injuries affect the health of veterans, in which the auditory system is often damaged, and blast-induced auditory damage to the cochlea is difficult to quantify. A recent study modeled blast overpressure (BOP) transmission throughout the ear utilizing a straight, two-chambered cochlea, but the spiral cochlea's response to blast exposure has yet to be investigated. In this study, we utilized a human ear finite element (FE) model with a spiraled, two-chambered cochlea to simulate the response of the anatomical structural cochlea to BOP exposure. The FE model included an ear canal, middle ear, and two and half turns of two-chambered cochlea and simulated a BOP from the ear canal entrance to the spiral cochlea in a transient analysis utilizing fluid-structure interfaces. The model's middle ear was validated with experimental pressure measurements from the outer and middle ear of human temporal bones. The results showed high stapes footplate (SFP) displacements up to 28.5 µm resulting in high intracochlear pressures and basilar membrane (BM) displacements up to 43.2 µm from a BOP input of 30.7 kPa. The cochlea's spiral shape caused asymmetric pressure distributions as high as 4 kPa across the cochlea's width and higher BM transverse motion than that observed in a similar straight cochlea model. The developed spiral cochlea model provides an advancement from the straight cochlea model to increase the understanding of cochlear mechanics during blast and progresses toward a model able to predict potential hearing loss after blast.

Production of bioactive metabolites by submerged fermentation of the medicinal mushroom Antrodia cinnamomea: recent advances and future development.

Edible and medicinal mushrooms have usually been considered as a sustainable source of unique bioactive metabolites, which are valued as promising provisions for human health. Antrodia cinnamomea is a unique edible and medicinal fungus widespread in Taiwan, which has attracted much attention in recent years for its high value in both scientific research and commercial applications owing to its potent therapeutic effects, especially for its hepatic protection and anticancer activity. Due to the scarcity of the fruiting bodies, the cultivation of A. cinnamomea by submerged fermentation appears to be a promising substitute which possesses some unique advantages, such as short culture time period and its high feasibility for scale-up production. However, the amount of fungal bioactive metabolites derived from the cultured mycelia of A. cinnamomea grown by submerged fermentation is much less than those obtained from the wild fruiting bodies. Hence, there is an urgent need to bridge such a discrepancy on bioactive metabolites between the wild fruiting bodies and the cultured mycelia. The objective of this article is to review recent advances and the future development of the mycelial submerged fermentation of A. cinnamomea in terms of enhancement for the production of fungal bioactive components by the optimization of culture conditions and the regulation of fungal metabolism. This review provides valuable information for further biotechnological applications of A. cinnamomea as well as other mushrooms being the source of bioactive ingredients by submerged fermentation.

Surface Motion Changes of Tympanic Membrane Damaged by Blast Waves.

Eardrum or tympanic membrane (TM) is a multilayer soft tissue membrane located at the end of the ear canal to receive sound pressure and transport the sound into the middle ear and cochlea. Recent studies reported that the TM microstructure and mechanical properties varied after the ear was exposed to blast overpressure. However, the impact of such biomechanical changes of the TM on its movement for sound transmission has not been investigated. This paper reports the full-field surface motion of the human TM using the scanning laser Doppler vibrometry in human temporal bones under normal and postblast conditions. An increase of the TM displacement after blast exposure was observed in the posterior region of the TM in four temporal bone samples at the frequencies between 3 and 4 kHz. A finite element model of human TM with multilayer microstructure and orthogonal fiber network was created to simulate the TM damaged by blast waves. The consistency between the experimental data and the model-derived TM surface motion suggests that the tissue injuries were resulted from a combination of mechanical property change and regional discontinuity of collagen fibers. This study provides the evidences of surface motion changes of the TM damaged by blast waves and possible fiber damage locations.

TREM2 modulates microglia phenotypes in the neuroinflammation of Parkinson's disease.

Neuroinflammation and overactivated microglia underlies the pathogenesis of Parkinson's disease (PD). Furthermore, microglia could polarize into classic inflammatory M1 and immunosuppressive M2 phenotype. Thus, inhibiting the overactivated inflammatory M1 microglia by promoting the transformation of microglia to the protective M2 phenotype provides potential therapy for PD, but the mechanism that modulates microglia polarization remains unknown. Triggering receptor expressed on myeloid cells-2 (TREM2) is a recently identified immune receptor expressed by the microglia in the brain. Emerging evidence indicates that TREM2 enhances the phagocytosis function of microglia and suppress inflammation. Based on these evidence, we hypothesized that TREM2 might play a protective role through regulating microglia polarization. Here, we employ a lentiviral strategy to overexpress or suppress TREM2 on microglia and found that TREM2 was essential for M2 microglia polarization. Knockdown of TREM2 in BV2 microglia inhibited M2 polarization and lead to exaggeration of M1 microglial inflammatory responses, whereas overexpression of TREM2 promoted M2 polarization and alleviated microglial inflammation. We also observed that the TREM2 level was higher in the midbrain of PD mice, which was accompanied by an elevated level of Arginase-1 and increased proinflammatory cytokines, suggesting that TREM2 is an important factor in switching the microglia phenotypes. Taken together, these findings indicate that TREM2 plays a crucial role in altering the proinflammatory M1 microglia to M2 phenotype and has beneficial effects in the immune pathogenesis of PD.

Biomechanical Changes of Tympanic Membrane to Blast Waves.

Eardrum or tympanic membrane (TM) is a multilayer soft tissue membrane located at the end of the ear canal to receive sound pressure and transport the sound into the middle ear and cochlea. Rupture of the TM is one of the most frequent injuries of the ear after blast exposure in military service members. The TM mechanical property changes induced by blast waves also affect progressive hearing loss in veterans. This chapter describes the biomechanical measurements and modeling of blast wave transduction through the ear and the TM mechanical property changes after blast exposure. The human TM rupture thresholds were determined with a relationship to blast wave direction. It is found that the sensitivity of TM stress change with respect to the pressure reaching on TM surface characterizes the mechanical damage of the TM in relation to blast waves. Mechanical properties of the human TM after exposure to blasts were measured using acoustic loading and laser Doppler vibrometry with the inverse problem-solving method. The complex modulus of the TM exposed to blast waves had significant reduction compared to normal tissue. The SEM images of post-blast TM showed obvious microstructural changes from the normal TM which indicate the tissue damage caused by blast exposures. This chapter provides important data on human TM damage and mechanical changes induced by blast overpressure waves.

Changes in theta activities in the left posterior temporal region, left occipital region and right frontal region related to mild cognitive impairment in Parkinson's disease patients.

The aim of this study was to investigate changes in brain activity associated with mild cognitive impairment (MCI) in a large sample of nondemented Parkinson's disease (PD) patients and its relationship with specific neuropsychological deficits. Electroencephalography (EEG) and neuropsychological assessment were performed in a sample of 135 nondemented PD patients and 44 healthy controls. All patients underwent a neuropsychological battery to assess global cognitive function. Patients were classified according to their cognitive status as PD patients with MCI (n = 61) and without MCI (n = 74). EEG data were used to analyze the relative band power parameters for the following frequency bands: delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-13 Hz) and beta (13-30 Hz). In addition, relative band power parameters were compared between groups and examined for correlations with neuropsychological performance. The relative theta band powers in three regions (O1, T5 and F4) exhibited statistically significant increases in PD patients with MCI. Beta band powers also exhibited obvious decreases in five regions (T5, T6, P3, P4 and C3) in the PD-MCI group compared with the normal control group. Furthermore, correlation analyses revealed that attention, visuospatial and executive functions were associated with theta power in local regions, mainly in the frontal region (F4). The present study demonstrated that changes in brain activities limited to distinct cognitive domains, especially the theta power in the frontal region, could serve as an electrophysiological marker of cognitive impairment in nondemented PD patients.

The patterns of EEG changes in early-onset Parkinson's disease patients.

The aim of this study was to investigate the patterns of brain activity changes in early-onset Parkinson's disease (EOPD) patients and its relationship with the severity of disease and motor deterioration. Electroencephalography (EEG) was performed in a sample of 52 nondemented EOPD patients and 20 healthy controls with similar age. All patients underwent a battery to assess PD severity and motor deterioration. The EEG data were rated by visual and quantitative analyses with the grant total EEG (GTE) score and NicoletOne Software. The parameters of relative band power and coherences for various frequency bands were calculated. In addition, all parameters were compared between groups and examined for correlations with the severity of disease and motor deterioration. The GTE score and two subscores including "Diffuse Slow Waves" and "Frequency of Rhythmic Background Activity" of EOPD increased comparing to control group. The relative beta band powers in seven regions (O1,O2,T5,T6,P3,P4 and C3) indicated significant decreases in EOPD patients and obvious increases in interhemispheric beta coherences were observed in the midtemporal area and frontal area (T3T4 and F3F4). Furthermore, correlation analyses revealed that longer duration was associated with the subscore of "background wave frequency". The beta frequency bands in the right posterior temporal (T6) showed negative relationship with the modified Hoehn-Yahr grading scores. This study is the first to depict the patterns of EEG changes in EOPD patients without dementia and offer a better understanding of the pathophysiological mechanisms underlying and prognostic purposes in EOPD. Some of these changes could serve as useful biomarkers in the study of EOPD.

Measurement of thickness and profile of a transparent material using fluorescent stereo microscopy.

Full-field thickness measurement for a thin transparent film is of interest for biological, medical, electronic, and packaging materials. It is a challenging task when the film is curvy, delicate and its thickness varies with location. We report herein a method to measure the thickness of a transparent (flat or curved) material and its topography using a stereo fluorescent profilometry technique. In this technique, two different types of fluorescent particles are deposited to both sides of the transparent film. Selected fluorescent excitation and emission are used to allow the observation of each one surface of the film at a time to determine the surface profile using stereo-based digital image correlation techniques. After the surface profiles for both surfaces are determined, subtraction of one surface profile from the other provides accurate thickness distribution of the film. Validation experiments were conducted using transparent films with known thickness. As an application, a measurement on a contact lens was conducted. The technique is appropriate for measurement of the full-field thickness of objects at other scales, such as soft transparent or translucent biofilms, with which thickness can hardly be measured accurately with other techniques.

Stimulating the biosynthesis of antroquinonol by addition of effectors and soybean oil in submerged fermentation of Antrodia camphorata.

Antrodia camphorata is a precious medicinal mushroom that has attracted increasing attentions. Antroquinonol has been considered as being among the most biologically active components of A. camphorata. However, it was hardly biosynthesized via conventional submerged fermentation. Two approaches were applied to stimulate the biosynthesis of antroquinonol in submerged fermentation. On one hand, different kinds of effectors that may involve in the antroquinonol biosynthesis were investigated. Among the tested effectors, camphorwood leach liquor was the most effective for stimulating the antroquinonol production. On the other hand, because of the hydrophobic characteristics of antroquinonol, soybean oil was added to establish an extractive fermentation system for alleviating the product inhibition and resulting in enhanced productivity. The highest antroquinonol concentration could be achieved at 89.06 ± 0.14 mg/L when 10% (v/v) soybean oil was added at the beginning of the fermentation. This study will be of great significance for the study of A. camphorata and the bioprocess regulation of antroquinonol production.

Predictions of middle-ear and passive cochlear mechanics using a finite element model of the pediatric ear.

A finite element (FE) model was developed based on histological sections of a temporal bone of a 4-year-old child to simulate middle-ear and cochlear function in ears with normal hearing and otitis media. This pediatric model of the normal ear, consisting of an ear canal, middle ear, and spiral cochlea, was first validated with published energy absorbance (EA) measurements in young children with normal ears. The model was used to simulate EA in an ear with middle-ear effusion, whose results were compared to clinical EA measurements. The spiral cochlea component of the model was constructed under the assumption that the mechanics were passive. The FE model predicted middle-ear transfer functions between the ear canal and cochlea. Effects of ear structure and mechanical properties of soft tissues were compared in model predictions for the pediatric and adult ears. EA responses are predicted to differ between adult and pediatric ears due to differences in the stiffness and damping of soft tissues within the ear, and any residual geometrical differences between the adult ear and pediatric ear at age 4 years. The results have significance for predicting effects of otitis media in children.

Cognitive profile of Parkinson's disease patients: a comparative study between early-onset and late-onset Parkinson's disease.

AIM: To investigate the influence of onset age on the occurrence and progression of cognitive dysfunction using neuropsychological tests and the electrophysiological component P300 in both early-onset Parkinson's disease (EOPD) and late-onset Parkinson's disease (LOPD) patients. METHODS: A cohort of 76 EOPD patients and 166 LOPD patients was recruited for this study. Demographic information and clinical features, including age, disease duration, education level, family history, the Unified Parkinson's Disease Rating Scale, the Hoehn and Yahr stage, and depression scores were documented for each patient. The Mini-Mental State Examination, Montreal Cognitive Assessment (MoCA), Wechsler Adult Intelligence Scale - Revised, Chinese version (WAIS-RC) and Wechsler Memory Scale - Revised, Chinese version (WMS-RC) were used. In addition, P300 was also examined to assess cognitive function. RESULTS: Although EOPD patients had longer disease duration, their cognitive dysfunction progressed more slowly. The MoCA tests revealed that EOPD patients had higher scores in visuospatial function, attention, delayed recall, and orientation than the LOPD patients. The difference between the two groups on the WMS-RC test did not reach significance, whereas the scores in executive function, visuospatial function and attention as measured on the WAIS-RC test were significantly lower in the LOPD group. In addition, P300 latencies were markedly delayed and P300 amplitudes were reduced in the LOPD group. CONCLUSIONS: The current findings demonstrated that cognitive dysfunction progressed more slowly in the EOPD group. Although the LOPD patients exhibited shorter disease durations, their cognitive abilities, including executive function, visuospatial function and attention, may have been impaired.

MCP-1 and CCR2 gene polymorphisms in Parkinson's disease in a Han Chinese cohort.

Monocyte chemoattractant protein-1 (MCP-1) and its receptor CC chemokine receptor-2 (CCR2) play important roles in neuroinflammation and they have been shown to be involved in Parkinson's disease (PD) pathogenesis. In addition, several studies have suggested a role for the MCP-1 and CCR2 genotypes in cognitive impairment and depression, which are common non-motor symptoms in PD patients. In this study, a cohort of 521 PD patients and 556 cases of healthy controls were recruited to investigate the association between the MCP-1 2518A/G (rs1064211) and CCR2 V64I (rs1799864) gene polymorphisms and PD risk in the Chinese population. We also analyze the influence of these genotypes on the cognitive function and depression in PD patients by comparing Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Wechsler Adult Intelligence Scale-Chinese Revision (WAIS-RC), Wechsler Memory Scale-Chinese Revision (WMS-RC) and Hamilton Depression Rating Scale (HAMD) ratings in 217 PD patients. Our results showed no significant differences in the genotype frequency between the PD group and the control group (P > 0.05). In addition, we also failed to find an influence of the MCP-1 and CCR2 genotypes on MMSE scores, MoCA scores, WAIS-RC scores, WMS-RC scores and HAMD scores in PD patients (P > 0.05). The MCP-1 and CCR2 gene polymorphisms may not be genetic risk factors for PD in the Han Chinese population, and they do not appear to influence cognitive function and depression in PD patients.

Dynamic Properties of Tympanic Membrane in a Chinchilla Otitis Media Model Measured With Acoustic Loading.

Otitis media is the most common infectious disease in young children, which results in changes in the thickness and mechanical properties of the tympanic membrane (TM) and induces hearing loss. However, there are no published data for the dynamic properties of the TM in otitis media ears, and it is unclear how the mechanical property changes are related to TM thickness variation. This paper reports a study of the measurement of the dynamic properties of the TM in a chinchilla acute otitis media (AOM) model using acoustic loading and laser Doppler vibrometry (LDV). AOM was created through transbullar injection of Haemophilus influenzae into the middle ear, and AOM samples were prepared 4 days after inoculation. Vibration of the TM specimen induced by acoustic loading was measured via LDV over a frequency range of 0.1-8 kHz. The experiment was then simulated in a finite element (FE) model, and the inverse-problem solving method was used to determine the complex modulus in the frequency domain. Results from 12 ears (six control and six AOM) show that the storage modulus of the TM from AOM ears was on average 53% higher than that of control ears, while the loss factor was 17.3% higher in control ears than in AOM ears at low-frequency (f < 1 kHz). At high-frequency (e.g., 8000 Hz), there was a mean 40% increase in storage modulus of the TM from AOM compared to control samples. At peak frequency (e.g., 3 kHz), there was a 19.5% increase in loss factor in control samples compared to AOM samples. These findings quantify the changes induced by AOM in the chinchilla TM, namely, a significant increase in both the storage and loss moduli.

Cerebrospinal fluid alpha-synuclein as a biomarker for Parkinson's disease diagnosis: a systematic review and meta-analysis.

To date, there are no definitive biomarkers for Parkinson's disease (PD) diagnosis. The detection of cerebrospinal fluid (CSF) alpha (α)-synuclein in PD patients has yielded promising but inconclusive results. To determine the performance of CSF α-synuclein as a diagnostic biomarker of PD and whether CSF α-synuclein can discriminate PD from other neurodegenerative diseases, a systematic search of all relevant studies investigating reproducible CSF α-synuclein quantification methods was conducted in electronic databases. A total of 17 studies that included 3311 patients were included in this systemic review and meta-analysis. The mean CSF α-synuclein concentration was significantly lower in PD patients compared to normal/neurological controls [weighted mean difference (WMD) -0.31; 95% CI, -0.45, -0.16; p < 0.0001] and patients with Alzheimer's disease (AD) [WMD -0.15; 95% CI, -0.26, -0.04; p < 0.0001]. There was no significant difference between PD patients and dementia with Lewy bodies (DLB) patients [WMD -0.03; 95% CI, -0.16, 0.09; p = 0.58] or patients with multiple system atrophy (MSA) [WMD 0.05; 95% CI, -0.04, 0.13; p = 0.25]. Sensitivity and specificity of CSF α-synuclein in the diagnosis of PD was 0.88 (95% CI, 0.84-0.91) and 0.40 (95% CI, 0.35-0.45), respectively. The positive and negative likelihood ratios of CSF α-synuclein in the diagnosis of PD were 1.41 (95% CI, 1.24-1.60), and 0.29 (95% CI, 0.15-0.56), respectively. The corresponding summary receiver operating characteristic (SROC) curve showed an area under the curve (AUC) of 0.73. The concentration of CSF α-synuclein may be a biomarker for the diagnosis of PD. The use of α-synuclein alone however is not sufficient as a single biomarker and it must therefore be used in conjunction with other documented and reliable biomarkers.

Enhanced production of Monacolin K by addition of precursors and surfactants in submerged fermentation of Monascus purpureus 9901.

The main problem in Monacolin K (MK) production by submerged fermentation of Monascus purpureus is low productivity. In this study, on one hand, addition of precursors was used to activate the biosynthesis of MK. When 4.0 g/L of sodium citrate was supplemented at the 48th H of the fermentation, the final MK production reached to 1,658.9 ± 28.5 mg/L after 20 day of fermentation, which was improved by 52.6% compared with that of the control. On the other hand, addition of surfactants could increase the permeability of cell membrane, thus driving more intracellular metabolites secreted into the fermentation broth and alleviating the product inhibition. When 40.0 g/L of Triton X-100 was added at the beginning of the fermentation, the final MK production reached to 2,026.0 ± 30.4 mg/L after 20 day of fermentation, which was improved by 84.9% compared with that of the control. These results are helpful to provide some new insights into the biosynthetic regulation on MK production; the approach can be applied to other fungal fermentation processes for enhancing production of useful metabolites.

Integrated strategy of pH-shift and glucose feeding for enhanced production of bioactive Antrodin C in submerged fermentation of Antrodia camphorata.

Antrodin C is one of the most potent bioactive components produced by the medicinal mushroom Antrodia camphorata. However, almost all studies in this field have focused on the biological activity of Antrodin C and relatively rare information has been reported regarding the biosynthetic process of Antrodin C. In this study, the strategies of pH-shift and glucose feeding for enhanced production of Antrodin C in submerged fermentation of A. camphorata were successfully applied in stirred bioreactors. The critical parameters for pH-shift and glucose feeding were systematically investigated. On one hand, the optimal culture pH for cell growth was distinct with Antrodin C biosynthesis and the maximum Antrodin C production was obtained by maintaining the first-stage culture at initial pH 4.5 and adjusted to 6.0 at day 8. On the other hand, it was beneficial for the Antrodin C accumulation with the initial glucose concentration of 40 g/L and feeding glucose to keep the residual sugar above 10 g/L. The maximum Antrodin C production (1,549.06 mg/L) was about 2.1-fold higher than that of control in 15-L stirred bioreactors by taking advantage of the integrated strategy of pH-shift and glucose feeding. These results would be helpful for the design of a highly efficient Antrodin C biosynthesis process.

Dynamic properties of human stapedial annular ligament measured with frequency-temperature superposition.

Stapedial annular ligament (SAL) is located at the end of human ear ossicular chain and provides a sealed but mobile boundary between the stapes footplate and cochlear fluid. Mechanical properties of the SAL directly affect the acoustic-mechanical transmission of the middle ear and the changes of SAL mechanical properties in diseases (e.g., otosclerosis) may cause severe conductive hearing loss. However, the mechanical properties of SAL have only been reported once in the literature, which were obtained under quasi-static condition (Gan, R. Z., Yang, F., Zhang, X., and Nakmali, D., 2011, "Mechanical Properties of Stapedial Annular Ligament," Med. Eng. Phys., 33, pp. 330-339). Recently, the dynamic properties of human SAL were measured in our lab using dynamic-mechanical analyzer (DMA). The test was conducted at the frequency range from 1 to 40 Hz at three different temperatures: 5 °C, 25 °C, and 37 °C. The frequency-temperature superposition (FTS) principle was applied to extend the testing frequency range to a much higher level. The generalized Maxwell model was employed to describe the constitutive relation of the SAL. The storage shear modulus G' and the loss shear modulus G" were obtained from seven specimens. The mean storage shear modulus was 31.7 kPa at 1 Hz and 61.9 kPa at 3760 Hz. The mean loss shear modulus was 1.1 kPa at 1 Hz and 6.5 kPa at 3760 Hz. The dynamic properties of human SAL obtained in this study provide a better description of the damping behavior of soft tissues than the classic Rayleigh type damping, which was widely used in the published ear models. The data reported in this study contribute to ear biomechanics and will improve the accuracy of finite element (FE) model of the human ear.

3D finite element modeling of earplug-induced occlusion effect in the human ear.

Poor utilization of earplugs among military personnel may be due to discomfort caused by the occlusion effect (OE). The OE occurs when an earplug occludes the ear canal, thereby changing bone conduction (BC) hearing and amplifying physiological noises from the wearer. There is a need to understand and reduce the OE in the human ear. A 3D finite element model of the human ear including a 3-chambered spiral cochlea was employed to simulate the OE caused by foam and aerogel earplugs. 90 dB sound pressure was applied at the ear canal entrance and BC sound was applied as vibration of the canal bony wall. The model reported the ear canal pressure and the displacements of the stapes footplate and cochlear basilar membrane with and without earplugs. Without BC stimulation, the foam earplug showed a greater pressure attenuation than the aerogel earplug. However, the foam earplug results were more affected by BC stimulation, with a maximum sound pressure increase of 34 dB, compared to the 21.0 dB increase with the aerogel earplug. The aerogel earplug's lower OE demonstrates its promise as an earplug material. Future work with this model will examine BC sound transmission in the cochlea.