Solvent effects on extractant conformational energetics in liquid-liquid extraction: a simulation study of molecular solvents and ionic liquids.

Extractant design in liquid-liquid extraction (LLE) is a research frontier of metal ion separations that typically focuses on the direct extractant-metal interactions. However, a more detailed understanding of energetic drivers of separations beyond primary metal coordination is often lacking, including the role of solvent in the extractant phase. In this work, we propose a new mechanism for enhancing metal-complexant energetics with nanostructured solvents. Using molecular dynamics simulations with umbrella sampling, we find that the organic solvent can reshape the energetics of the extractant's intramolecular conformational landscape. We calculate free energy profiles of different conformations of a representative bidentate extractant, n-octyl(phenyl)-N,N-diisobutyl carbamoyl methyl phosphinoxide (CMPO), in four different solvents: dodecane, tributyl phosphate (TBP), and dry and wet ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf2N]). By promoting reorganization of the extractant molecule into its binding conformation, our findings reveal how particular solvents can ameliorate this unfavorable step of the metal separation process. In particular, the charge alternating nanodomains formed in ILs substantially reduce the free energy penalty associated with extractant reorganization. Importantly, using alchemical free energy calculations, we find that this stabilization persists even when we explicitly include the extracted cation. These findings provide insight into the energetic drivers of metal ion separations and potentially suggest a new approach to designing effective separations using a molecular-level understanding of solvent effects.

Critical fluctuations in liquid-liquid extraction organic phases controlled by extractant and diluent molecular structure.

Extractant aggregation in liquid-liquid extraction organic phases impacts extraction energetics and is related to the deleterious efficiency-limiting liquid-liquid phase transition known as third phase formation. Using small angle X-ray scattering, we find that structural heterogeneities across a wide range of compositions in binary mixtures of malonamide extractants and alkane diluents are well described by Ornstein-Zernike scattering. This suggests that structure in these simplified organic phases originates from the critical point associated with the liquid-liquid phase transition. To confirm this, we measure the temperature dependence of the organic phase structure, finding critical exponents consistent with the 3D Ising model. Molecular dynamics simulations were also consistent with this mechanism for extractant aggregation. Due to the absence of water or any other polar solutes required to form reverse-micellar-like nanostructures, these fluctuations are inherent to the binary extractant/diluent mixture. We also show how the molecular structure of the extractant and diluent modulate these critical concentration fluctuations by shifting the critical temperature: critical fluctuations are suppressed by increasing extractant alkyl tail lengths or decreasing diluent alkyl chain lengths. This is consistent with how extractant and diluent molecular structure are known to impact metal and acid loading capacity in many-component LLE organic phases, suggesting phase behavior of practical systems may be effectively studied in simplified organic phases. Overall, the explicit connection between molecular structure, aggregation and phase behavior demonstrated here will enable the design of more efficient separations processes.

Efficacy and Effectiveness of Wireless Binaural Beamforming Technology of Hearing Aids in Improving Speech Perception in Noise: A Systematic Review.

OBJECTIVES: To conduct a systematic review to address the following research questions: Q1. Does wireless binaural beamforming technology perform better than conventional microphone technologies in improving the speech perception in noise abilities of individuals with hearing aids bilaterally? and Q2. Do the subjective rating scores of hearing aid benefits suggest that wireless binaural beamforming technology is better than other microphone technologies? DESIGN: Two independent authors performed a comprehensive search utilizing electronic databases like PubMed, Embase, Web of Science, and Scopus. Aside from these databases, course transcripts, white papers, evidence, and field study articles from various manufacturer websites were also included. The certainty of the evidence for each outcome was determined using Grading of Recommendations Assessment, Development, and Evaluation (GRADE) guidelines. RESULTS: Eleven studies were included for the qualitative synthesis. The available data were categorized into three groups (bilateral omnidirectional, bilateral directional, and bilateral asymmetric directional microphone processing) and compared against wireless binaural beamformers. The results of the Sign test revealed that for Q1, the wireless binaural beamformer significantly outperformed the bilateral omnidirectional microphone processing. However, no significant differences were observed when compared with other groups. Results for Q2 showed no significant improvement in wireless binaural beamformers compared to other groups. CONCLUSION: The superior performance of the wireless binaural beamformers over conventional microphone technologies was demonstrated by the speech perception in noise tasks but not by the self-reported subjective ratings. Nevertheless, the evidence for both speech perception noise and subjective ratings was weak.

Spontaneous and Ion-Specific Formation of Inverted Bilayers at Air/Aqueous Interface.

Developing better separation technologies for rare earth metals, an important aspect of a sustainable materials economy, is challenging due to their chemical similarities. Identifying molecular-scale interactions that amplify the subtle differences between the rare earths can be useful in developing new separation technologies. Here, we describe the ion-dependent monolayer to inverted bilayer transformation of extractant molecules at the air/aqueous interface. The inverted bilayers form with Lu3+ ions but not with Nd3+. By introducing Lu3+ ions to preformed monolayers, we extract kinetic parameters corresponding to the monolayer to inverted bilayer conversion. Temperature-dependent studies show Arrhenius behavior with an energy barrier of 40 kcal/mol. The kinetics of monolayer to inverted bilayer conversion is also affected by the character of the background anion, although anions are expected to be repelled from the interface. Our results show the outsized importance of ion-specific effects on interfacial structure and kinetics, pointing to their role in chemical separation methods.

The pervasive impact of critical fluctuations in liquid-liquid extraction organic phases.

Liquid-liquid extraction is an essential chemical separation technique where polar solutes are extracted from an aqueous phase into a nonpolar organic solvent by amphiphilic extractant molecules. A fundamental limitation to the efficiency of this important technology is third phase formation, wherein the organic phase splits upon sufficient loading of polar solutes. The nanoscale drivers of phase splitting are challenging to understand in the complex hierarchically structured organic phases. In this study, we demonstrate that the organic phase structure and phase behavior are fundamentally connected in a way than can be understood with critical phenomena theory. For a series of binary mixtures of trialkyl phosphate extractants with linear alkane diluents, we combine small angle x-ray scattering and molecular dynamics simulations to demonstrate how the organic phase mesostructure over a wide range of compositions is dominated by critical concentration fluctuations associated with the critical point of the third phase formation phase transition. These findings reconcile many longstanding inconsistencies in the literature where small angle scattering features, also consistent with such critical fluctuations, were interpreted as reverse micellar-like particles. Overall, this study shows how the organic phase mesostructure and phase behavior are intrinsically linked, deepening our understanding of both and providing a new framework for using molecular structure and thermodynamic variables to control mesostructure and phase behavior in liquid-liquid extraction.

A systematic review on the effect of low-dose radiation on hearing.

Numerous studies have documented the adverse effects of high-dose radiation on hearing in patients. On the other hand, radiographers are exposed to a low dose of ionizing radiation, and the effect of a low dose of radiation on hearing is quite abstruse. Therefore, the present systematic review aimed to elucidate the effect of low-dose ionizing radiation on hearing. Two authors independently carried out a comprehensive data search in three electronic databases, including PUBMED/MEDLINE, CINAHL, and SCOPUS. Eligible articles were independently assessed for quality by two authors. Cochrane Risk of Bias tool was used assess quality of the included studies. Two articles met the low-dose radiation exposure criteria given by Atomic Energy Regulatory Board (AERB) and National Council on Radiation Protection (NCRP) guidelines. Both studies observed the behavioral symptoms, pure-tone hearing sensitivity at the standard, extended high frequencies, and the middle ear functioning in low-dose radiation-exposed individuals and compared with age and gender-matched controls. One study assessed the cochlear function using transient-evoked otoacoustic emissions (TEOAE). Both studies reported that behavioral symptoms of auditory dysfunction and hearing thresholds at extended high frequencies were higher in radiation-exposed individuals than in the controls. The current systematic review concludes that the low-dose ionizing radiation may affect the hearing adversely. Nevertheless, further studies with robust research design are required to explicate the cause and effect relationship between the occupational low-dose ionizing radiation exposure and hearing.

A survey of vocal health in church choir singers.

PURPOSE: Choir singing is an important tradition of Christian worship across India. However, vocal health issues related to the church choir singers are less addressed in the literature. Hence, this study aimed to investigate the prevalence of vocal symptoms, identify the variables associated with increased risk of voice problems and knowledge of factors influencing vocal health in church choir singers. METHOD: One hundred and forty-eight church choir singers (61 males and 85 females) between the age range of 18 and 70 years participated in the study. They completed a self-reported questionnaire addressing demographic and singing-related details, vocal symptoms, variables associated with increased risk reporting voice problems and knowledge about factors influencing vocal health. RESULT: Eighty-four percent of the choir singers reported two or more vocal symptoms sometimes or more frequently while or after singing. More than half of the church choir singers had experienced vocal symptoms such as accessing notes in the upper range, loss of vocal endurance, pitch breaks, hoarseness, dryness in the throat, and discomfort in the throat. Among the different variables, systemic hydration found to have a significant association with reporting of voice problems in church choir singers. The overall knowledge regarding the factors influencing vocal health was found to be limited among the choir singers. CONCLUSION: Choir singers like other professional singers experienced a higher prevalence of vocal symptoms during or after singing and exhibited limited knowledge about factors that negatively influence vocal health. Hence, there is a need to look into these singer's vocal requirements, who usually go unnoticed.

Effect of (Poly)electrolytes on the Interfacial Assembly of Poly(ethylene glycol)-Functionalized Gold Nanoparticles.

We report on the effect of interpolymer complexes (IPCs) of poly(acrylic acid) (PAA) with poly(ethylene glycol)-functionalized Au nanoparticles (PEG-AuNPs) as they assemble at the vapor-liquid interface, using surface-sensitive synchrotron X-ray scattering techniques. Depending on the suspension pH, PAA functions both as a weak polyelectrolyte and a hydrogen bond donor, and these two roles affect the interfacial assembly of PEG-AuNPs differently. Above its isoelectric point, we find that PAA leads to the formation of a PEG-AuNP monolayer at the interface with a hexagonal structure. In the presence of high concentration of HCl (i.e., below the isoelectric point), at which PAA forms IPCs with PEG, the hexagonal structure at the interface appears to deteriorate, concurrent with aggregation in the bulk. Thus, while the electrolytic behavior of PAA induces interfacial assembly, the hydrogen bonding behavior, as PAA becomes neutral, favors the formation of 3D assemblies. For comparison, we also report on the formation of PEG-AuNP monolayers (in the absence of PAA) with strong electrolytes such as HCl, H2SO4, and NaOH that lead to a high degree of crystallinity.

Superlattice assembly by interpolymer complexation.

We present a coarse grained model for a system where nanocrystals are functionalized with a polymer that is a hydrogen bond acceptor, such as polyethylene glycol (PEG), and are dispersed in a solution with a polymer whose monomers consist of a hydrogen bond donor, such as polyacrylic acid (PAA) at low pH (interpolymer complexation). We determine the minimum concentration of the polymer donor to induce aggregation and the structure and dynamics of the induced (fcc) superlattice. Our results are compared to previous and new experiments.

Interfacial Self-Assembly of Polyelectrolyte-Capped Gold Nanoparticles.

We report on pH- and salt-responsive assembly of nanoparticles capped with polyelectrolytes at vapor-liquid interfaces. Two types of alkylthiol-terminated poly(acrylic acid) (PAAs, varying in length) are synthesized and used to functionalize gold nanoparticles (AuNPs) to mimic similar assembly effects of single-stranded DNA-capped AuNPs using synthetic polyelectrolytes. Using surface-sensitive X-ray scattering techniques, including grazing incidence small-angle X-ray scattering (GISAXS) and X-ray reflectivity (XRR), we demonstrate that PAA-AuNPs spontaneously migrate to the vapor-liquid interfaces and form Gibbs monolayers by decreasing the pH of the suspension. The Gibbs monoalyers show chainlike structures of monoparticle thickness. The pH-induced self-assembly is attributed to the protonation of carboxyl groups and to hydrogen bonding between the neighboring PAA-AuNPs. In addition, we show that adding MgCl2 to PAA-AuNP suspensions also induces adsorption at the interface and that the high affinity between magnesium ions and carboxyl groups leads to two- and three-dimensional clusters that yield partial surface coverage and poorer ordering of NPs at the interface. We also examine the assembly of PAA-AuNPs in the presence of a positively charged Langmuir monolayer that promotes the attraction of the negatively charged capped NPs by electrostatic forces. Our results show that synthetic polyelectrolyte-functionalized nanoparticles exhibit interfacial self-assembly behavior similar to that of DNA-functionalized nanoparticles, providing a pathway for nanoparticle assembly in general.

Prevalence of oropharyngeal dysphagia symptoms in community-dwelling older adults: A community survey.

BACKGROUND: Dysphagia is a common clinical condition in older adults with significant implications for health and quality of life (QOL). However, its prevalence and associated factors in the Indian community-dwelling older adults remain understudied. The present study aims at identifying the prevalence of oropharyngeal dysphagia symptoms in Indian community-dwelling older adults and identifying the age-related comorbid variables associated with an increased risk of oropharyngeal dysphagia in this population. METHODS: Total 384 community-dwelling older adults (60 years of age or older) who were independent in performing daily activities were included in the present study. The Malayalam version of the Eating Assessment Tool-10 (EAT-10) questionnaire was used to assess individuals at risk for dysphagia. Additionally, they also completed a self-report questionnaire addressing age-related comorbid variables associated with an increased risk of oropharyngeal dysphagia. RESULT: Using the Malayalam version of the EAT-10, the present study identified the prevalence of oropharyngeal dysphagia symptoms in 9.9% of community-dwelling older adults. Among the EAT-10 symptoms, cough while/after swallowing, difficulty swallowing solids and difficulty swallowing liquids were the most prevalent symptoms reported by participants. Increase in age and age-related comorbidities such as tooth loss, history of heart failure and digestive diseases were found to be significantly associated with the reporting of risk for dysphagia symptoms. CONCLUSION: As dysphagia symptoms significantly impact the social, psychological and QOL of community-dwelling older adults, it is important to develop awareness about these symptoms among older adults, caretakers and physicians. Early detection and appropriate management of community-dwelling older adults at risk for dysphagia can contribute to better health outcomes and improved QOL.

Speciation and Organic Phase Structure in Nitric Acid Extraction with Trioctylamine.

Understanding chemical speciation and intermolecular interactions in multicomponent liquids is essential to understanding their phase and chemical equilibria, which underpin chemical separation processes, including solvent extraction. Here we report on the extraction of nitric acid from its aqueous solutions into organic solutions of trioctylamine (TOA) in toluene, investigated with spectroscopic, X-ray scattering, and computational tools to understand molecular speciation in the organic phase and its relationship with the nanoscale structure of the organic phase. Trends in acid and water extraction clearly show two and three regimes, respectively, indicating different stoichiometric relationships, but speciation of HNO3, water, and amine in these regimes is not apparent. 1H NMR of the organic phase shows that there are at least two distinct acidic protons in the organic phase while ATR-FTIR results show that the organic phase with excess acid extraction is a mixture of trioctylammonium-nitrate ion pairs (TOAH·NO3), and undissociated HNO3 molecules. Comparison with DFT-computed IR spectra show that the chain-like configurations of TOAH·NO3·HNO3·H2O are favored over TOAH·NO3·H2O·HNO3, i.e., direct interaction between the nitrate and HNO3 molecules is more favored compared to a water-mediated interaction. SAXS of the organic phases were modeled as sums of Ornstein-Zernike (O-Z) scattering and a prepeak feature in the higher Q region that corresponds to extractant packing. The extraction of undissociated HNO3 by the ion pairs leads to an increased X-ray scattering contrast in the organic phase without any significant change in the correlation length. These results show that the organic phase nanostructure is more sensitive to the concentration of TOAH·NO3 and is relatively unaffected by excess acid extraction. These findings will enable a molecular understanding of the mechanisms behind metal extraction from acidic media with basic extractants.

Does bilateral hearing aid fitting improve spatial hearing ability: a systematic review and meta-analysis.

Objectives: The ability to localize sound sources is crucial for everyday listening, as it contributes to spatial awareness and the detection of warning signs. Individuals with hearing impairment have poorer localization abilities, which further deteriorate when they are fitted with a hearing aid. Although numerous studies have addressed this phenomenon, there is a lack of systematic evidence. The aim of the current systematic review is to address the following research question, "Do behavioural measures of spatial hearing ability improve with bilateral hearing aid fitting compared to the unaided hearing condition?"Design: A comprehensive search was conducted by two independent authors utilizing electronic databases, using various electronic databases, covering the period of 1965 to 2022. The inclusion and exclusion criteria were formulated using the Population, Intervention, Compression, Outcome, and Study design (PICOS) format, and the certainty of evidence was determined using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) guidelines.Results: The comprehensive search resulted in 2199 studies, 17 studies for qualitative synthesis and 15 studies for quantitative synthesis. The collected data was divided into two groups, namely vertical and horizontal localization. The results of the quantitative analysis indicate that the localization performance was significantly better in the unaided condition for both vertical and horizontal planes. The certainty of our evidence was judged to be moderate, meaning that "we are moderately confident in the effect estimate. The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different".Conclusion: The review findings demonstrate that the bilateral fitting of the hearing aid did not effectively preserve spatial cues, which resulted in poorer localization performance irrespective of the plane of assessment.Review Registration: Prospective Register of Systematic Reviews (PROSPERO); CRD42022358164.

Hearing aids are a widely used rehabilitative method to compensate for the loss of audibility in individuals with hearing impairment. The current review highlights that, even though hearing aids can enhance audibility, they often fail to preserve spatial cues.This review paper provides a comprehensive summary of the existing literature, focusing on the preservation of spatial cues by hearing aids and the technologies that can enhance localization performance to a certain degree.The findings of the current study encourage both researchers and hearing aid manufacturers to advance their research methods pertaining to the preservation of spatial cues. This advancement has the potential to improve spatial awareness and possibly improve speech perception in the presence of noise in hearing aid users.

A Survey of Vocal Health in Carnatic Singing Students.

OBJECTIVE: Vocal health and hygiene are well addressed for professional singers, but less attention has been paid to singing trainees/students whose vocal demands vary significantly from trained singers. Studies conducted in the literature on singing trainees have reported a higher prevalence of voice problems in them; however, no such information is available from Indian classical singing trainees. Hence, the present study explored the frequency and nature of voice problems, self-reported vocal health and awareness of vocal hygiene and its practices in Carnatic singing trainees. METHOD: This cross-sectional study was conducted using a purposive sampling method. The data were gathered from 135 Carnatic classical singing trainees. The participants completed a self-reported questionnaire addressing demographic and singing-related details, vocal symptoms, variables associated with increased risk reporting voice problems and knowledge about factors influencing vocal health. RESULTS: The experience of past and point prevalence of voice problems in Carnatic singing students were found to be 29% and 15%, respectively. Difficulty singing higher notes, hoarseness, tired voice, loss of ability to sing/speak loudly, and breathiness in higher pitch range were the most prevalent vocal symptom reported by Carnatic singing trainees. Nasal allergies, dry mouth/throat, and excessive stress in daily routine activities raising voice many times a day, dry mouth/throat and excessive talking in social situations was found to have a significant association with singing trainees reporting voice problems. However, availing medical assistance for voice problems was found to be poor in this group of singing students. CONCLUSION: Similar to trainees of other form of singing, Carnatic singing trainees also found to have a higher frequency of voice problems. Most of the singing trainees were found to be in their adolescent age period, and they face instability in their voice and are more vulnerable to develop voice problems. This indicates the need for in-depth understanding of voice problems experienced by Carnatic singing trainees aiming to promote their vocal health and prevent injury and be successful in their singing career.

Elucidating Trivalent Ion Adsorption at Floating Carboxylic Acid Monolayers: Charge Reversal or Water Reorganization?

We study the adsorption of trivalent neodymium on floating arachidic acid films at the air-water interface by two complementary surface specific probes, sum frequency generation spectroscopy and X-ray fluorescence near total reflection. In the absence of background ions, neodymium ions compensate for the surface charge of the arachidic acid film at a bulk concentration of 50 µM without any charge reversal. Increasing the bulk concentration to 1 mM does not change the neodymium surface coverage but affects the interfacial water structure significantly. In the presence of a high concentration of NaCl, there is overcharging at 1 mM Nd3+, i.e., 30% more Nd3+ than needed to compensate for the surface charge. These results show that the total coverage of neodymium ions is not enough to describe the complete picture at the interface, and interfacial water and ion coverage needs to be considered together to understand more complex ion adsorption and transport processes.

Assembling PNIPAM-Capped Gold Nanoparticles in Aqueous Solutions.

Employing small-angle X-ray scattering (SAXS), we explore the conditions under which assembly of gold nanoparticles (AuNPs) grafted with the thermosensitive polymer poly(N-isopropylacrylamide) (PNIPAM) emerges. We find that short-range order assembly emerges by combining the addition of electrolytes or polyelectrolytes with raising the temperature of the suspensions above the lower-critical solution temperature (LCST) of PNIPAM. Our results show that the longer the PNIPAM chain is, the better organization in the assembled clusters. Interestingly, without added electrolytes, there is no evidence of AuNPs assembly as a function of temperature, although untethered PNIPAM is known to undergo a coil-to-globule transition above its LCST. This study demonstrates another approach to assembling potential thermosensitive nanostructures for devices by leveraging the unique properties of PNIPAM.

Perception of Primary School Teachers Towards Voice Problems and Vocal Health-Seeking Behaviors: A qualitative study.

OBJECTIVE: Teachers are the most common occupational group reporting to the voice clinics with dysphonia across the globe. However, less is known about teachers' perceptions about their voice and voice problems. Hence the present study aimed to explore teachers' perception about their teaching voice, voice problems and vocal health-seeking behaviors. METHOD: A qualitative phenomenological research design using semi-structured interviews were conducted with fifteen female primary school teachers. Participants were asked to express their perception of teaching voice, vocal health care knowledge, and vocal hygiene practices. Using inductive analysis, the researchers converted the raw data into concepts or themes and discussed. RESULT: The present study results showed that teachers perceive voice as the primary tool for their profession. However, teachers consider voice problems as part of their professional commitments. Despite knowing the harmful effects of voice problems, teachers' pay less attention to their voice problems and perceive them as usual, unavoidable and part of their profession. Due to their demanding work schedule and not getting enough support from the management, they hesitate to consult medical professionals unless it severely affects them. CONCLUSIONS: The data obtained from this study can be used to improve the teachers' knowledge regarding vocal health and convince the school management to extend their support for the successful implementation of the vocal health training programs for teachers.

Origins of Clustering of Metalate-Extractant Complexes in Liquid-Liquid Extraction.

Effective and energy-efficient separation of precious and rare metals is very important for a variety of advanced technologies. Liquid-liquid extraction (LLE) is a relatively less energy intensive separation technique, widely used in separation of lanthanides, actinides, and platinum group metals (PGMs). In LLE, the distribution of an ion between an aqueous phase and an organic phase is determined by enthalpic (coordination interactions) and entropic (fluid reorganization) contributions. The molecular scale details of these contributions are not well understood. Preferential extraction of an ion from the aqueous phase is usually correlated with the resulting fluid organization in the organic phase, as the longer-range organization increases with metal loading. However, it is difficult to determine the extent to which organic phase fluid organization causes, or is caused by, metal loading. In this study, we demonstrate that two systems with the same metal loading may impart very different organic phase organizations and investigate the underlying molecular scale mechanism. Small-angle X-ray scattering shows that the structure of a quaternary ammonium extractant solution in toluene is affected differently by the extraction of two metalates (octahedral PtCl62- and square-planar PdCl42-), although both are completely transferred into the organic phase. The aggregates formed by the metalate-extractant complexes (approximated as reverse micelles) exhibit a more long-range order (clustering) with PtCl62- compared to that with PdCl42-. Vibrational sum frequency generation spectroscopy and complementary atomistic molecular dynamics simulations on model Langmuir monolayers indicate that the two metalates affect the interfacial hydration structures differently. Furthermore, the interfacial hydration is correlated with water extraction into the organic phase. These results support a strong relationship between the organic phase organizational structure and the different local hydration present within the aggregates of metalate-extractant complexes, which is independent of metalate concentration.

Prevalence of Voice Problems, Self-Reported Vocal Symptoms and Associated Risk Factors in Call Center Operators (CCOs): A Systematic Review.

OBJECTIVE: The purpose of this study was to systematically review the available literature on the prevalence, self-reported voice symptoms, and associated risk factors for the development of voice problems in call center operators (CCO). STUDY DESIGN: a systematic review METHODS: An electronic search from five databases based on the guidance of preferred reporting of items for systematic reviews and meta-analysis (PRISMA) yielded 15 articles that reported the different aspects of voice problems in CCOs. The methodological quality of the studies was analyzed using the National Institute of Health (NIH) questionnaire. RESULTS: The career prevalence of voice problems in CCOs varied from 33% to 68%, whereas point prevalence was at 27%. Hoarse/rough voice was the most prominent symptom reported by most of the studies. Vocal fatigue, effortful voice, and breaks/cracks in voice were the other reported vocal symptoms. Long working hours, short breaks between calls, noisy working environment, dry work environment, work stress, stressful calls, limited breaks, prolonged use of voice, insufficient vocal rest, throat clearing, and more caffeinated beverage intake were different risk factors having significant association with telemarketers reporting vocal symptoms. CONCLUSION: The present study results suggest that CCOs are at higher risk of developing voice problems. Further, the different vocal symptoms reported by CCOs are suggestive of vocal fatigue. In addition, multiple risk factors may be associated with the development of voice problems. However, the available literature is limited, and further studies with a larger sample size are required to corroborate the current findings.

Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces.

Anions are expected to be repelled from negatively charged surfaces. At aqueous interfaces, however, ion-specific effects can dominate over direct electrostatic interactions. Using multiple in situ surface sensitive experimental techniques, we show that surface affinities of SCN- anions are so strong that they can adsorb at a negatively charged floating monolayer at the air-aqueous interface. This extreme example of ion-specific effects may be very important for understanding complex processes at aqueous interfaces, such as chemical separations of rare earth metals. Adsorbed SCN- ions at the floating monolayer increase the overall negative charge density, leading to enhanced trivalent rare earth adsorption. Surface sensitive X-ray fluorescence measurements show that the surface coverage of Lu3+ ions can be triple the apparent surface charge of the floating monolayer in the presence of SCN-. Comparison to NO3- samples shows that the effects are strongly dependent on the character of the anion, providing further evidence of ion-specific effects dominating over electrostatics.