Silent Conditions Research Articles

Air leak detection in a pressurized containment building mock-up using elastic guided waves

This article reports an experimental study of the vibrations induced by air leaks in realistic conditions reproducing a leak test of a containment building, such as those routinely conducted to probe the safety of nuclear power plants. The purpose of this work is to assess the effectiveness of a passive acoustic detection method that could assist and accelerate other scanning inspections. Using piezoelectric accelerometers, detection of leak signatures is demonstrated in the 0–20 kHz range. Noise correlation techniques are applied to obtain spectral power densities, maps of amplitudes and beamforming localization which correlate very well with the pressure applied inside the building and with the known locations and flow rates of the main leaks. At applied pressures of 4.2 bars and for concentrated leaks such as point breaks and decimeter long cracks, detection thresholds of about 500–600 L/h flow rates are reached at up to 4–5 m distance by accumulating data during 2 min under silent ambient noise conditions.

Preventing sudden cardiac death in young athletes – A perspective from the United States

Sudden cardiac death in young athletes is a rare, but devastating complication of several clinically silent conditions which can become unmasked during periods of intense physical activity. Prevention of sudden cardiac death starts with robust screening to allow the early identification of at risk individuals and the implementation of preventive strategies. The specific approach to screening (history and physical, with or without pre-participation electrocardiograms) varies across the globe with some notable differences between that used in Europe and the United States. The rationale for this variation is complex, but can be linked to the differences in risk factor prevalence, the healthcare infrastructure, and the capacity to identify and triage at risk individuals in a cost-effective manner. Beyond knowing the differences in the approaches to screening, establishing strategies that work (including novel techniques) and those that can be implemented in a successful and sustainable manner are key.

Ultrasonic-assisted extraction and automated determination of catalase and lipase activities in bovine and poultry livers using a digital movie-based flow-batch analyzer

An ultrasonic reactor (UR) was developed and coupled to a digital movie-based flow-batch analyzer (DM-FBA) for the ultrasonic-assisted extraction (UAE) and fast determination of catalase and lipase activities in bovine and poultry livers. The lab-made UR mainly consisted of a borosilicate glass container and a piezoelectric disc. The DM-FBA mainly consisted of a webcam, an ultrasonic actuator controller, a peristaltic pump, six solenoid valves, a valve driver, a mixing chamber, a magnetic stirrer, an Arduino Mega 2560, and a personal computer. This setup, named UR-DM-FBA, was controlled by custom software. Ultrasound (US) frequency, US power, sonication time, and concentration of extraction agent were optimized using the Taguchi method. Experiments at silent conditions (mechanical stirring at 1500 rpm) were carried out to evaluate extraction efficiency. Optimized parameters for the UAE of catalase were US frequency of 30 kHz, 2.0 mL of Triton X-100, sonication time of 270 s, and US power of 10.8 W. For the UAE of lipase, the optimized parameters were US frequency of 20 kHz, 0.30 mL of triethanolamine, sonication time of 270 s, and US power of 18 W. Catalase and lipase activities obtained with the UR were, on average, 1.9 × 103% and 2.0 × 103% higher than those obtained at silent conditions, respectively, which indicates that that the lab-made UR was capable of extracting these enzymes more efficiently. Determinations using the UR-DM-FBA were highly accurate (relative error ranging from −1.98% to 1.96% for bovine catalase, −0.65% to 0.76% for bovine lipase, −2.03 to 2.08% for poultry catalase, and −0.55% to 0.64% for poultry lipase) and precise (overall coefficient of variation <0.02% for bovine and poultry catalase and <0.2% for bovine and poultry lipase). Results obtained with the proposed system and reference methods were in good agreement according to the paired t-test (95% confidence level). High sampling rates (>69 h−1) and low sample/reagent consumption (<1.6 mL) were also obtained. Due to the highly efficient UAE, the proposed system can be applied for fast and accurate quantification of lipase and catalase in biological samples with low waste generation.

A TICKING TIMEBOMB: FLOATING AORTIC ARCH THROMBUS IN A PATIENT WITH METASTATIC SQUAMOUS CELL CARCINOMA OF THE LUNG

TOPIC: Lung Cancer TYPE: Medical Student/Resident Case Reports INTRODUCTION: Thoracic aortic mural thrombi are a rare clinical entity and most patients are asymptomatic before significant embolic events occur(1). There are only a few reported cases and are mostly in patients who presented with complications of peripheral thromboembolism. We report the case of a patient who presented with symptoms of congestive heart failure and was found to have a large floating thoracic aortic thrombus. CASE PRESENTATION: The patient is a 61-year-old female with no prior medical history who presented with shortness of breath on exertion and dry cough of three weeks duration. The patient has an extensive 40 pack-year smoking history. On evaluation, the patient was tachypneic, hypertensive, and was saturating well on room air. Crackles could be heard at the bases of the lungs and there was pitting edema of bilateral lower extremities. Laboratory studies showed a b-type natriuretic peptide level of 1741 pg/mL. A chest X-ray revealed pulmonary edema and bilateral pleural effusions. With a diagnosis of heart failure, gentle diuresis with intravenous furosemide was initiated. An echocardiogram showed global hypokinesis of the left ventricle with a reduced ejection fraction of 25-30%. CT scan of the chest revealed a large 6 x 7 cm necrotic mass in the left lower lung field with mediastinal adenopathy. There was a pulmonary embolus in the posterior basal segment of the left pulmonary artery, originating from the location of the mass. The CT was also significant for an intraluminal polypoid filling defect in the aortic arch with multiple small splenic and left renal infarcts, suggestive of a peripherally embolizing aortic thrombus. The patient was started on anticoagulation with low molecular weight heparin and was recommended to have an aortic arch stent placed to prevent further embolization of the thrombus. However, the patient decided against the procedure. Further biopsy and staging workup of the left lung mass revealed metastatic squamous cell carcinoma. The patient decided against palliative chemotherapy and opted for hospice care. DISCUSSION: Thoracic aortic mural thrombus is the result of disturbances in the Virchow's triad, ie, stasis, hypercoagulability, and endothelial dysfunction. The patient's smoking history, extensive atherosclerosis, malignancy, and left ventricular dysfunction were likely contributing factors. Aortic thrombi are prone to peripheral embolization to sites such as the spleen, kidneys, small bowel, and lower extremities(2). Early diagnosis and prompt management with anticoagulation are key. Endovascular repair with endograft stents is a novel modality of treatment with higher safety, patient acceptability, and a lower rate of peripheral embolization(3). CONCLUSIONS: Thoracic aortic thrombi are an initially silent rare disease condition with potentially fatal complications. Prompt management with anticoagulation and possible endovascular treatment is warranted. REFERENCE #1: Yang P, Li Y, Huang Y, Lu C, Liang W, Hu J. A giant floating thrombus in the ascending aorta: a case report. BMC Surg. 2020 Dec 9;20(1):321 REFERENCE #2: Bukharovich IF, Wever-Pinzon O, Shah A, Todd G, Chaudhry FA, Sherrid MV. Arterial Embolism Caused by Large Mobile Aortic Thrombus in the Absence of Atherosclerosis, Associated with Iron Deficiency Anemia. Echocardiogr Mt Kisco N. 2012 Mar;29(3):369–72. REFERENCE #3: Jamjoom R, Zagzoog MM, Sait S. Outcome of Endovascular Approach for Management of Thoracic Aortic Thrombus. Ann Vasc Surg. 2019 Aug 1;59:307.e7-307.e12. DISCLOSURES: No relevant relationships by Amjad Basheer, source=Web Response No relevant relationships by Rana Prathap Padappayil, source=Web Response No relevant relationships by DISHANT SHAH, source=Web Response No relevant relationships by vinit singh, source=Web Response No relevant relationships by Raghu Tiperneni, source=Web Response

Effect of Efferent Stimulation on the Differential Sensitivity in Individuals with Normal Hearing.

The aim of the article was to compare the conditions of silent and contralateral noise on Differential sensitivity in normal hearing individuals. A total of 40 participants (20 males and 20 females) were enrolled in the study with a mean age of 21.7years, participants with normal hearing thresholds and no history of middle ear pathology were enrolled for the study. Difference limen tests such as difference limen for intensity (DLI), difference limen for frequency (DLF), and difference limen for time (DLT) were carried out in these 40 individuals in the two conditions of silent and contralateral noise using MATLAB. Statistical analysis was carried out using the SPSS version 25.0 were descriptive and inferential statistics were carried out. Data was normally distributed on the Shapiro-Wilk's test of normality due to which a paired t test was carried out to establish the nature of significance between the silent and contralateral noise condition. Results reveal the presence of significant difference (P < 0.01) between the groups for DLF and DLT with contralateral noise condition performing better than silent condition for the parameters. However, no significant difference was obtained for DLI. There is a positive effect of the efferent auditory pathway on the Differential sensitivity thus implying that speech perception in noise is improved in the presence of background noise for normal hearing individuals due to this effect. But in case of DLI, the reduced spread of excitation could be the reason why there were no significant differences between silent and contralateral noise condition.

Electrochemical production of cobalt powder by using a modified hydrocyclone with ultrasonic assistance

The effect of ultrasound on the production of cobalt powder was analysed. The experiments were carried out with a standardised hydrocyclone, whose internal cylindrical stainless-steel wall acted as a cathode and the vortex finder as an anode, made of Pb-0.75%Ag alloy. The electrolyte was a synthetic solution containing 1.9–3.8 g dm−3 Co in 36.7 g dm−3 (NH4)2SO4 and 30 g dm−3 H3BO3 at pH 5.5 as the supporting electrolyte. Ultrasound application was very effective to detach the dendritic deposits from the cathode surface and also to improve the reactor performance in comparison with a silent system. The best working conditions were achieved at a current of 15 A and 60 °C, where the partial current of hydrogen evolution is acceptably low. Under these conditions, the current efficiency was 58.3%, 11.7 kW h kg−1 the specific energy consumption, 63.7 kg m−3 h−1 the space time yield and 61% the cobalt fraction obtained from the spigot. The volumetric kinetic constants under ultrasound or silent conditions were calculated from the experimental data, corroborating the beneficial effect of ultrasound for the production of cobalt powder. The particles have a globular shape with a dendritic characteristic featuring an average length of 31.7 μm.

Sonocrystallisation of ZIF-8 in water with high excess of ligand: Effects of frequency, power and sonication time

A systematic study on the sonocrystallisation of ZIF-8 (zeolitic imidazolate framework-8) in a water-based system was investigated under different mixing speeds, ultrasound frequencies, calorimetric powers and sonication time. Regardless of the synthesis technique, pure crystals of ZIF-8 with high BET (Brunauer, Emmett and Teller) specific surface area (SSA) can be obtained in water after only 5 s. Furthermore, 5 s sonication produced even smaller crystals (~0.08 µm). The type of technique applied for producing the ZIF-8 crystals did not have any significant impact on crystallinity, purity and yield. Crystal morphology and size were affected by the use of ultrasound and mixing, obtaining nanoparticles with a more spherical shape than in silent condition (no ultrasound and mixing). However, no specific trends were observed with varying frequency, calorimetric power and mixing speed. Ultrasound and mixing may have an effect on the nucleation step, causing the fast production of nucleation centres. Furthermore, the BET SSA increased with increasing mixing speed. With ultrasound, the BET SSA is between the values obtained under silent condition and with mixing. A competition between micromixing and shockwaves has been proposed when sonication is used for ZIF-8 production. The former increases the BET SSA, while the latter could be responsible for porosity damage, causing a decrease of the surface area.

Ultrasound-Engineered fabrication of immobilized molybdenum complex on Cross-Linked poly (Ionic Liquid) as a new acidic catalyst for the regioselective synthesis of pharmaceutical polysubstituted spiro compounds

A novel supported molybdenum complex on cross-linked poly (1-Aminopropyl-3-vinylimidazolium bromide) entrapped cobalt oxide nanoparticles has been successfully fabricated through two different procedures, i.e. ultrasound (US) irradiations (100 W, 40 kHz) and reflux. The efficiency of the two different methods was comparatively investigated on the fundamental properties of proposed catalyst using diverse characterization techniques. Based on the obtained results, the ultrasonication method provides controlled polymerization process; as a result, well connected polymeric network is formed. In addition, the use of ultrasound waves turned out to be able to increase the particles uniformity, specific surface area (from 79.19 to 223.83 m2/g), and the onset thermal degradation temperature (Td) value (from 248 to 400 °C) of the prepared catalyst which intensifies the catalytic efficiency. Besides, US-treated catalyst demonstrated high chemical stability and maintained its cross-linked network after eight cycles recovery, while the cross-linked network of catalyst obtained under silent condition was completely disrupted. Furthermore, the ultrafast multi-step fabrication procedure was performed in less than 6 h under ultrasonic condition while a similar process promoted by a mechanical stirring method came to a conclusion after 5–6 days. Accordingly, the utility of the ultrasound irradiation was proved, and US-treated catalyst was applied for improved synthetic methodology of spiro 1,4-dihydropyridines and spiro pyranopyrazoles through different acidic active sites. Due to the significant synergistic influence between the proposed catalyst and US irradiation, a variety of novel and recognized mono-spiro compounds were fabricated at room temperature in high regioselectivity.

Does rhythmic priming improve grammatical processing in Hungarian-speaking children with and without developmental language disorder?

Research has described several features shared between musical rhythm and speech or language, and experimental studies consistently show associations between performance on tasks in the two domains as well as impaired rhythm processing in children with language disorders. Motivated by these results, in the current study our first aim was to explore whether a short exposure to a regular musical rhythm (i.e., rhythmic priming) can improve subsequent grammatical processing in preschool‐aged Hungarian‐speaking children with and without developmental language disorder (DLD). Second, we investigated whether rhythmic priming is specific to grammar processing by assessing priming in two additional domains: a linguistic but non‐grammatical task (picture naming) and a non‐linguistic task (nonverbal Stroop task). Third, to confirm that the rhythmic priming effect originates from the facilitating effect of the regular rhythm and not the negative effect of the control condition, we added a third condition, silence, for all the three tasks. Both groups of children showed better performance on the grammaticality judgment task in the regular compared to both the irregular and the silent conditions but no such effect appeared in the non‐grammatical and non‐linguistic tasks. These results suggest that (1) rhythmic priming can improve grammatical processing in Hungarian, a language with complex morphosyntax, both in children with and without DLD, (2) the effect is specific to grammar and (3) is a result of the facilitating effect of the regular rhythm. These results could motivate further research about integrating rhythmic priming into traditional speech‐language therapy. A video abstract of this article can be viewed at https://youtu.be/zKzGuIjZyvU.

Constant Resting Frequency and Auditory Midbrain Neuronal Frequency Analysis of Hipposideros pratti in Background White Noise.

Acoustic communication signals are inevitably challenged by ambient noise. In response to noise, many animals adjust their calls to maintain signal detectability. However, the mechanisms by which the auditory system adapts to the adjusted pulses are unclear. Our previous study revealed that the echolocating bat, Hipposideros pratti, increased its pulse intensity in the presence of background white noise. In vivo single-neuron recording demonstrated that the auditory midbrain neurons tuned to the second harmonic (H2 neurons) increased their minimal threshold (MT) to a similar degree as the increment of pulse intensity in the presence of the background noise. Furthermore, the H2 neurons exhibited consistent spike rates at their best amplitudes and sharper intensity tuning with background white noise compared with silent conditions. The previous data indicated that sound intensity analysis by auditory midbrain neurons was adapted to the increased pulse intensity in the same noise condition. This study further examined the echolocation pulse frequency and frequency analysis of auditory midbrain neurons with noise conditions. The data revealed that H. pratti did not shift the resting frequency in the presence of background noise. The auditory midbrain neuronal frequency analysis highly linked to processing the resting frequency with the presence of noise by presenting the constant best frequency (BF), frequency sensitivity, and frequency selectivity. Thus, our results suggested that auditory midbrain neuronal responses in background white noise are adapted to process echolocation pulses in the noise conditions.

The Role of Visibility in Silent Speech Tongue Movements: A Kinematic Study of Consonants.

Purpose To better understand the role of tongue visibility in speech, this study compared the spatiotemporal patterns of silent versus audible speech for lingual consonants of American English. Kinematic data were obtained for articulatory features assumed to be visually salient, including tongue movement (anterior displacement and midsagittal area), lip aperture, and consonant duration. Method Electromagnetic articulography was used to measure 11 native speakers' productions of five consonants (/ɡ/, /w/, /ɹ/, /l/, and /ð/), selected to represent a continuum of tongue visibility. Nonword consonant-vowel syllables were elicited during a procedure designed to convey a dyadic communication environment. A method of kinematic-based consonant segmentation was developed for data processing, and results were analyzed with repeated-measures analysis of variance. Results Findings indicated increased consonant duration and lip aperture in the silent condition (vs. audible) for all five consonants. Tongue forward displacement was slightly greater in the silent condition, compared to audible, for all consonants except /ɡ/, the only consonant without a visible tongue component. In addition, the extent of tongue forwarding in silent speech corresponded with the degree of tongue visibility. Conclusion During silent speech, talkers increased their lip aperture and consonant duration and tended to shift their tongues forward for the most visible lingual consonants, suggesting that talkers may be aware at some level of the need to increase articulatory visibility of the tongue in the presence of an interlocutor during adverse speech conditions.

Silent hypoxia in COVID-19: pathomechanism and possible management strategy.

The novel coronavirus disease 2019 (COVID-19) has become a severe health issue, especially to the patients who develop silent hypoxia condition after SARS-CoV-2 infection. Due to the lack of dyspnoea and extremely low oxygen saturation level, these patients are at exceptionally higher risk. Although the prevalence of silent hypoxia in COVID-19 patients has been evident in several cases, the underlying pathomechanism behind this condition is still unclear. Silent hypoxia in SARS-CoV-2 infected patients can be diagnosed with the help of a pulse oximeter, blood gas levels, and a 6-min walking test. While the clinicians and researchers figure out the exact reason for this phenomenon, the patients must be under strict day-to-day monitoring. In this article, we aim to provide comprehensive insights into the underlying symptoms, mechanism, and possible factors behind the occurrence of silent hypoxia among COVID-19 patients.

Cavitation-assisted decontamination of yttria from graphite of different densities

Yttria coated graphite crucibles are widely used to handle molten refractory and radioactive metals like uranium and plutonium. However, the coated layer suffers damages like cracking and peeling off owing to thermal cycles. As a result, removal of the yttria layer from the graphite surface is essential to ensure reuse of the crucible and minimization of radioactive waste. The present work investigates intensified dissolution of yttria from the coated graphite samples using ultrasound as a non-destructive decontamination technique to recycle the graphite substrate. The optimum conditions established for maximum dissolution were 8 M as acid strength, frequency of 30 kHz, temperature of 45 °C and power density of 8 W cm−2 that resulted in maximum dissolution of 52% in 30 min. Use of an oxidant H2O2 to the acid, did not yield any improvement in the dissolution kinetics, instead, increased oxidation of the graphite substrate was observed, leading to the anomalous weight gain of the graphite substrate despite surface erosion. Effect of ultrasound on the dissolution was pronounced, with almost a threefold increase compared to dissolution performed under silent conditions. Rates of dissolution of yttria from the substrate of different densities and pore size distribution were also studied. The dissolution was slowest from graphite of density 1.82 g cm−3 as the pore size distribution was conducive to accommodate the yttria particles. The dissolution in nitric acid followed ash layer diffusion controlled kinetics. The study has demonstrated the efficacy of application of ultrasound for accelerated decontamination of graphite substrates.

Prilezhaev epoxidation of oleic acid in the presence and absence of ultrasound irradiation

AbstractBACKGROUNDEpoxidation of double bonds in vegetable oils provide valuable green intermediates for the chemical industry. The epoxidation of oleic acid with hydrogen peroxide according to the Prilezhaev principle was studied experimentally in a multiphase laboratory‐scale batch reactor operated isothermally at 50 °C and atmospheric pressure. A solid cation exchanger (Amberlite IR‐120) was used as the solid catalyst to enhance the slow step in the Prilezhaev process: the in situ formation of the epoxidation agent, peracetic acid, from hydrogen peroxide and acetic acid. A rotating basket stirrer was used to suppress the external mass transfer limitations and to guarantee a turbulent random flow in the vicinity of the catalyst particles. Kinetic experiments demonstrated the catalytic effect of the cation exchanger. Several experiments were performed in the presence and absence of ultrasound irradiation at different amplitudes.RESULTSThe exposure of ultrasound irradiation on the multiphase reaction mixture impaired the conversion of the double bonds and the yield of the epoxide, compared to a reference experiment conducted under silent conditions. Catalyst characterization by scanning electron microscopy and the determination of the acid sites in recycled catalyst samples confirmed that the main reason for deactivation was leaching and/or neutralization of the sulfonic acid groups from the solid catalyst matrix.CONCLUSIONSThe application of ultrasound at different input powers resulted in lower reaction yields compared to the silent reference experiment. This observation was attributed to deactivation of the catalyst caused by leaching and/or neutralization of the sulfonic groups promoted by ultrasound exposure. © 2021 Society of Chemical Industry (SCI).

Intensification of precipitation process by means of ultrasound-assisted methods and the selection of reactor type

The presented study is focused on the possibilities of precipitation process intensification by means of processing conditions and the selection of a crystallizer construction. The main goal was to consciously intensify the precipitation and to obtain crystals with the defined characteristics. The research took into account the CaF2 precipitation. The process was carried out in a tank reactor placed in an ultrasonic bath to increase the turbulence intensity (PUS = 150 W, f = 40 kHz). The results were compared with the previous tests, provided in silent conditions in a stirred tank reactor, Koflo, and Kenics static mixers. For the comparison of measurement data obtained under different operating conditions, a new method was proposed. The method correlates with the results very well. It has been also shown that the use of ultrasounds does not contribute to the increase of the precipitation efficiency but allows to obtain a product with a decreased particle size together with a significant reduction of agglomerates number. Moreover, the advantages and disadvantages of the studied equipment and methods have been explained. The general guidance for the selection of the proper working equipment and operating conditions to consciously stimulate the process has been presented as well.

Functional Gait Can Be Affected by Noise: Effects of Age and Cognitive Function: A Pilot Study.

Background: The ageing process may degrade an individual's balance control, hearing capacity, and cognitive function. Older adults perform worse on simultaneously executed balance and secondary tasks (i.e., dual-task performance) than younger adults and may be more vulnerable to auditory distraction.Aim: The purpose of this study was to determine the effect of passive listening on functional gait in healthy older vs. younger adults, and to investigate the effect of age, functional gait, hearing ability and cognitive functioning on dual-task performance.Methods: Twenty young and 20 older healthy adults were recruited. Functional gait (Functional Gait Assessment in silent and noisy condition), hearing function (audiogram; Speech in Babble test), and cognitive ability (Cambridge Neuropsychological Test Automated Battery) were measured.Results: Overall, a significant difference between functional gait performance in silent vs. noisy conditions was found (p = 0.022), with no significant difference in dual-task cost between the two groups (p = 0.11). Correlations were found between increasing age, worse functional gait performance, poorer hearing capacity and lower performance on cognitive function tasks. Interestingly, worse performance on attention tasks appeared to be associated with a worse functional gait performance in the noisy condition.Conclusion: Passive listening to multi-talker babble noise can affect functional gait in both young and older adults. This effect could result from the cognitive load of the babble noise, due to the engagement of attention networks by the unattended speech.

Degradation of Antibiotics in Wastewater: New Advances in Cavitational Treatments.

Over the past few decades, antibiotics have been considered emerging pollutants due to their persistence in aquatic ecosystems. Even at low concentrations, these pollutants contribute to the phenomenon of antibiotic resistance, while their degradation is still a longstanding challenge for wastewater treatment. In the present literature survey, we review the recent advances in synergistic techniques for antibiotic degradation in wastewater that combine either ultrasound (US) or hydrodynamic cavitation (HC) and oxidative, photo-catalytic, and enzymatic strategies. The degradation of sulfadiazine by HC/persulfate (PS)/H2O2/α-Fe2O3, US/PS/Fe0, and sono-photocatalysis with MgO@CNT nanocomposites processes; the degradation of tetracycline by US/H2O2/Fe3O4, US/O3/goethite, and HC/photocatalysis with TiO2 (P25) sono-photocatalysis with rGO/CdWO4 protocols; and the degradation of amoxicillin by US/Oxone®/Co2+ are discussed. In general, a higher efficiency of antibiotics removal and a faster structure degradation rate are reported under US or HC conditions as compared with the corresponding silent conditions. However, the removal of ciprofloxacin hydrochloride reached only 51% with US-assisted laccase-catalysis, though it was higher than those using US or enzymatic treatment alone. Moreover, a COD removal higher than 85% in several effluents of the pharmaceutical industry (500–7500 mg/L COD) was achieved by the US/O3/CuO process.

Interacting effects of short-term and long-term noise exposure on antipredator behaviour in sand gobies

In today's marine habitats, anthropogenic noise is widespread in space and time, affecting aquatic animal communities. Short-term exposure to noise is known to affect vital behaviours, such as the ability to evade predators. However, long-term noise pollution may lead to differences in short-term responses between naïve and experienced animals. We investigated the interaction between short-term and long-term sound exposure on the antipredator response of free-ranging sand gobies, Pomatoschistus minutus. We tested the effects of short-term boat noise playback on the response to a simulated predator strike in areas across a range of low to high long-term noise disturbance levels. Exposure to boat noise did not affect the startle response, time frozen or response latency of gobies to a predator stimulus. However, individuals exposed to short-term boat noise playback were absent from the experimental area for shorter periods after the predator strike than gobies exposed to the silent control. Moreover, gobies in long-term noisy habitats also stopped avoiding the area after the predator strike under silent control conditions. These changes point to a decreased magnitude in antipredator response, as a function of interacting short- and longer-term levels of disturbance. Thus, prey species alter their antipredator behaviour in ways that can potentially lead to higher mortality for individual prey. This could ultimately have implications at the level of the food web.

An Optimal Envelope-Based Noise Reduction Method for Cochlear Implants: An Upper Bound Performance Investigation

Cochlear implants (CI) are surgically implanted auditory prostheses for partially compensating severe to profound sensorineural hearing losses. Despite providing significant intelligibility levels under silent conditions, their performance is highly affected by additive noise. Time-frequency masks, such as the binary mask, the Wiener filter (WF) and their variations, have been widely employed for noise reduction. However, they were not originally designed for CI applications, which have very particular characteristics. In this work, we propose a new method for noise reduction, especially designed for CI. It is based on the minimization of the mean square error between the squared envelopes of the estimated and target speech. The theoretical derivation of the proposed time-frequency mask is presented and a closed-form for the one-coefficient optimal solution is obtained. Numerical simulations with objective criteria indicate that the proposed method results in higher intelligibility scores as compared to the time-domain implementation of the WF time-frequency mask. Psychoacoustic experiments with normal hearing volunteers and vocoded signals, as well as CI users, corroborate simulation results, showing significant increases in intelligibility, especially for SNR < −5 dB. The proposed method may result in an intelligibility increase of up to 70%, for SNR = −25 dB, as compared to the WF. These findings were obtained considering an ideal signal-to-noise ratio estimator.

A single step ultrasound-assisted nitrocellulose synthesis from microcrystalline cellulose

Nitrocellulose is a nitrated cellulose polymer with a broad application in industry. Depending on the nitrogen content, this polymer can be used for manufacturing explosives, varnishes, clothes, and films, being considered a product of high value-added. In this work, the use of ultrasound was investigated for the intensification of nitrocellulose synthesis from microcrystalline cellulose. The ultrasound-assisted nitrocellulose synthesis (UANS) was carried out using several ultrasound systems, such as baths and cup horns, allowing the evaluation of the frequency (from 20 to 130 kHz) and delivered power (from 23 to 134 W dm−3) to the reaction medium. The following parameters were evaluated: acid mixture (H2SO4, H3PO4, CH2O2 or CH3COOH with HNO3, 2 to 14.4 mol L−1), ultrasound amplitude (10 to 70%) and reaction time (5 to 50 min). Better nitrocellulose yield (nitrogen content of 12.5% was obtained from 1 g of microcrystalline cellulose employing a cup horn system operating at 20 kHz, 750 W of nominal power with 60% of amplitude, 25 mL of acid solution (13.6 mL of 18.4 mol L−1 H2SO4 + 9.2 mL of 14.4 mol L−1 HNO3 + 2.2 mL H2O), at 30 °C for 30 min. At silent conditions (mechanical stirring ranging from 100 to 500 rpm), the nitrogen content was lower than 11.8% which demonstrate the ultrasound effects for nitrocellulose synthesis.